Chemical engineering education ( Journal Site )

Material Information

Chemical engineering education
Alternate Title:
Abbreviated Title:
Chem. eng. educ.
Physical Description:
v. : ill. ; 22-28 cm.
American Society for Engineering Education -- Chemical Engineering Division
Chemical Engineering Division, American Society for Engineering Education
Place of Publication:
Storrs, Conn
Publication Date:
annual[ former 1960-1961]


Subjects / Keywords:
Chemical engineering -- Study and teaching -- Periodicals   ( lcsh )
periodical   ( marcgt )
serial   ( sobekcm )


Chemical abstracts
Additional Physical Form:
Also issued online.
Dates or Sequential Designation:
1960-June 1964 ; v. 1, no. 1 (Oct. 1965)-
Numbering Peculiarities:
Publication suspended briefly: issue designated v. 1, no. 4 (June 1966) published Nov. 1967.
General Note:
Title from cover.
General Note:
Place of publication varies: Rochester, N.Y., 1965-1967; Gainesville, Fla., 1968-

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Source Institution:
University of Florida
Rights Management:
All applicable rights reserved by the source institution and holding location.
Resource Identifier:
oclc - 01151209
lccn - 70013732
issn - 0009-2479
lcc - TP165 .C18
ddc - 660/.2/071
System ID:

Full Text

David F. 011is

Special Feature: Award Lecture


and Che at
Arizona State University

Chemical Engineering Education
Department of Chemical Engineering
University of Florida
Gainesville, FL 32611
PHONE and FAX: 904-392-0861
Ray W. Fahien
T. J. Anderson
Mack Tyner
Carole Yocum
James 0. Wilkes and Mark A. Burns
University of Michigan
William J. Koros
University of Texas, Austin

E. Dendy Sloan, Jr.
Colorado School of Mines
Gary Poehlein
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Klaus Timmerhaus
University of Colorado
George Burnet
Iowa State University
Anthony T. DiBenedetto
University of Connecticut
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University of Texas at Austin
Richard M. Felder
North Carolina State University
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University of Washington
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Purdue University
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McMaster University

Chemical Engineering Education

Volume 28

Number 3

Summer 1994

154 Arizona State University, Gene Sater, Neil Berman

158 David F. Ollis, of North Carolina State University

162 Polymer Flow Instabilities: A Picaresque Tale, Morton M. Denn

168 Teaching Thermo With the Help of Friends, Johannes M. Nitsche
184 Judging the Speed of a Reaction From Its Funny-Looking Rate
Constant, Robert R. Hudgins
188 Fun Ways to Learn Fluid Mechanics and Heat Transfer,
Bernard J. Van Wie, Joe C. Poshusta, Robert D. Greenlee,
Robert A. Brereton
198 Performance Problems, Richard C. Bailie, Joseph A. Shaeiwitz
204 A Holistic Approach to ChE Education: Part 2. Approach at the
Introductory Level,
Francesc Giralt, A. Fabregat, X. Farriol, F.X. Grau, J. Giralt, M. Medir
218 Teaching Process Analysis, Moses O. Tadd, Terence N. Smith

174 Any Questions? Richard M. Felder

176 The Third Law of Thermodynamics, B. G. Kyle

180 Magic Unveiled Through the Concept of Heat and Its Transfer,
A. R. Konak
183 A Second Look at Thermodynamics and Common Sense,
Octave Levenspiel

194 Accelerated BS/Master's Industry Program in Chemical Engineering,
Ron Darby

210 Process Systems Engineering: The Cornerstone of a Moder Chemical
Engineering Curriculum,
I.T. Cameron, P.L. Douglas, P.L. Lee

214 A Simple but Effective Fluidized-Bed Experiment, Conan J. Fee

167 Books Received
166, 187, 192, 193 Book Reviews
167 Errata

CHEMICAL ENGINEERING EDUCATION (ISSN 0009-2479) is published quarterly by the Chemical Engineering
Division, American Society for Engineering Education, and is edited at the University of Florida. Correspondence
regarding editorial matter, circulation, and changes of address should be sent to CEE, Chemical Engineering Department,
University of Florida, Gainesville, FL 32611-2022. Copyright 1994 by the Chemical Engineering Division, American
Society for Engineering Education. The statements and opinions expressed in this periodical are those of the writers and
not necessarily those of the ChE Division, ASEE, which body assumes no responsibility for them. Defective copies replaced
if notified within 120 days of publication. Write for information on subscription costs and for back copy costs and
availability. POSTMASTER: Send address changes to CEE, Chemical Engineering Department., University of Florida,
Gainesville, FL 32611.

Summer 1994






Arizona State University
Tempe, AZ 85287-6006
he institution known today as Arizona State University began in 1886 as
a small teacher's college with thirty-three students. Following World
War II, large enrollment increases and an accompanying program ex-
pansion resulted in its change from a state college to Arizona State University
in 1958. Today, with over 43,000 students, ASU is the fifth largest university in
the United States. The main campus is located in Tempe, Arizona, on the
eastern edge of Phoenix. As a leading public university in a populous urban
setting (Phoenix is the ninth largest city in the U.S., with a
metropolitan area population of over 2,300,000), a large part
of its mission focuses on problems associated with the area's
changes from a desert to a metropolitan center. The growth of
the university, as measured by enrollment and the quality of
research, has paralleled the growth of Phoenix as a major
electronics center.
The College of Engineering was established in 1956, and
chemical engineering followed in 1958 when Castle O. Reiser
was hired to build a chemical engineering program. Sam
Craig came in 1960, Gene Sater in 1962, and Neil Berman
in 1964; with these four faculty, the group was large
enough to obtain formal accreditation of the program in 1966.
The first graduate class began in 1964, the AIChE stu-
dent chapter was chartered in 1967, and the first PhD student
was Marshall Gurian.
Bill Dorson, who has a strong interest in biomedical engineering, came to
ASU in 1966 and initiated an interdisciplinary program at the BSE level in that
discipline. Jim Kuester became the sixth faculty member in 1969, and Eric
Guilbeau, another chemical engineer with a biomedical research interest, joined
the faculty in 1977. Imre Zwiebel arrived on campus as Chair in 1979, and
during his tenure the bio program saw steady growth in terms of both faculty
and students-in 1988, with Eric Guilbeau directing the program, ASU began
offering BSE, MS, and PhD degrees in bioengineering.

A familiar sight to all ASU students
is Palm Walk, above, one of the main
walkways on campus, while the En-
gineering Center offices and class-
rooms shown below are Chemical
Engineering territory.
u -

In 1986 the materials science program
moved from the Mechanical and Aero-
space Engineering Department to chemi-
cal and bioengineering, creating the present
Department of Chemical, Bio, and Materi-
als Science Engineering (CBME). The
name is lengthy, but it reflects a natural
and synergistic combination based on the
overlapping interests of the faculty in those
three areas.

Chemical Engineering Education

Copyright ChE Division of ASEE 1994

The name [Department of Chemical, Bio, and Materials Science Engineering]
is lengthy, but it reflects a natural and synergistic
combination based on the overlapping
interests of the faculty in
those three areas.

One of our students working in the Honeywell Automatic
Control Lab at ASUand its distillation column control
with the TDC 3000 system.

Joe Henry, Jr., became Chair of the department in 1988.
He stepped down last fall, and James Mayer (who is also
Director of the university's Center for Solid State Science)
has assumed the role of Interim Chair. The chemical engi-
neering program has thirteen faculty, 230 undergraduate
students, and 50 graduate students who make up about one-
half of the CBME department totals.

ASU recognizes the importance of actively encouraging
the education of underrepresented minority students. The
College of Engineering and Applied Sciences provides spe-
cial advising services and courses intended to ease the tran-
sition of minority students into university life. In addition,
tutoring sessions and minority professional organizations
have chapters on campus. Tony Garcia is a Co-Project
Director of an NSF-funded Southern Rocky Mountain Alli-
ance for Minority Participation which sponsors a special
series of academic and support activities including under-
graduate research programs.

The undergraduate engineering programs at ASU were
traditionally based on a strong engineering science core, but
in 1992, the chemical engineering faculty decided that the
curriculum should include more technical electives so that
students could better prepare themselves for careers in the
emerging technologies. At about the same time, a decision
was made at the college level to reduce the total credits
required for BSE degrees to 132. An integrated core, based
on the underlying conservation laws, has been adopted-
Summer 1994

COB-home of the undergraduate
laboratories at ASU.

patterned after the sequence of courses developed at Texas
A&M University. Lynn Bellamy and Greg Raupp were the
leaders in teaching these courses and using cooperative learn-
ing and TQM principles in the classroom. By teaching the
engineering sciences in this more efficient integrated format,
the number of elective courses was increased, even though
the total program hours were reduced.
The current curriculum consists of 132 semester hours
(math, 19 hours; chemistry, 18 hours; physics, 8 hours;
English and general studies, 19 hours; engineering core, 19
hours; chemical engineering, 31 hours; and technical elec-
tives, 18 hours). Traditional chemical engineering courses in
thermodynamics, fluids, heat and mass transfer, reactor de-
sign, and process control are followed by two design courses
at the senior level.
The undergraduate program has a heavy laboratory com-
ponent. Bob Torrest has developed a transport lab (fluids
and heat transfer) that has been highlighted by accreditation
visitors as being truly exceptional. Before leaving ASU for a
position with Setpoint, Inc., Lew Bezanson led in arranging
a cooperative venture with Honeywell that made available a
six-console TDC 3000 distributed-control system. This sys-
tem has been integrated into the undergraduate process con-
trol course, resulting in a state-of-the-art platform not nor-
mally available in a university, and Dan Rivera was added
to the faculty in 1990 to serve as its Director. A "unit opera-
tions" lab (with experiments ranging from measuring the

rate of oxide growth on silicon wa-
fers to determining tray efficiencies
in a 20-tray distillation column)
rounds out the three-lab sequence;
Jim Beckman was the main contribu-
tor to the development of this lab.
Students are encouraged to select
technical electives from areas of em-
phasis such as environmental, bio-
chemical, or semiconductor materi-
als processing in order to build on the
chemical engineering base while de-
veloping depth in some area.
ASU is a consortium participant in
an NSF-funded Engineering Educa-
tion Grant to extend the integrated
curriculum to the freshman level. A
pilot program will be in effect this
coming fall when freshmen are
enrolled as a block in calculus, phys-
ics, English, and a freshman engi-
neering course with the intent of inte-
grating the subject matter across
these four courses. Chemistry was ex-
cluded from the program because of
the different levels of freshman
chemistry required of engineering
students. Chemical engineering fac-
ulty will play an active role in the
instruction in this program.

Typical ASU desert lan
Verde dormitory in

development of and

Traditional MS and PhD degrees are offered in chemical
engineering. The MS degree requires 21-24 hours of course
work and 9 or 6 hours of thesis. Currently, students must
take four of the following courses: thermodynamics, reactor
engineering, transport phenomena I and II, and applied
math analysis. A proposal to relax this requirement to
give students greater opportunity to specialize in a given
area is in the process of being implemented. Specialized
technical electives at the graduate level include courses
in environmental and biochemical engineering, process
control, solid state and electronic materials processing, and
process engineering.
The PhD degree is research oriented and requires 84 se-
mester hours, including research and dissertation. Students
entering the program must pass a qualifying exam. The first
part of the exam is based on undergraduate material (this
part is waived for well-qualified candidates.), and the second
half is the development of a research proposal on a topic
outside of the student's intended research area. A compre-
hensive exam based on the dissertation prospectus is also
required. Once this exam is completed, the student is ex-

pected to engage in scholarly, in-
dependent research leading to a
successful dissertation defense.

Research within the department
began modestly in the late 1960s
with work in materials process-
ing, environmental dispersion, al-
ternate energy sources, and bio-
medical engineering. The estab-
lishment of a strong research com-
ponent evolved over time as fac-
ulty members with diversified in-
terests were added to the faculty.
Research funding in chemical en-
gineering has varied between
$500,000 and $1 million during
the past three years and has come
from a healthy mix of industrial
and governmental sources. The
university has just been designated
a Research I University by the
Carnegie Foundation, a significant
accomplishment for an institution
tdscaping, with Palo lacking a medical school and land
the background. grant college status.
Chemical engineering faculty
play active roles in the Centers for Energy Systems Re-
search, Computer Integrated Manufacturing Systems, and
Solid State Electronics Research; Tim Cale, a member
of the chemical engineering faculty, is Interim Director of
the latter. While the emphasis of the Centers is on
graduate research, they have also benefited undergraduate
students by serving as hosts for undergraduate research
and providing high-tech equipment that can also be used in
the teaching labs.
In addition to these Centers (based in the College of Engi-
neering and Applied Sciences), chemical engineering fac-
ulty are contributing members of the University Cancer Re-
search Institute and the Center for Solid State Science.
The department has prepared a more detailed description
of its program and facilities on a HyperCard disk, which is
available on request. We are also contributing material for
the CD-ROM on department activities being prepared in
conjunction with CACHE's Twentieth Jubilee at next fall's
annual AIChE meeting.
0- Environmental Research Neil Berman is currently
working on applications of numerical and physical modeling
to dispersion calculations in complex terrain. This interdisci-
plinary research involves faculty and students from me-
chanical engineering and geography as well as from chemi-
cal engineering. A recent example of this research is the
Chemical Engineering Education

Lynn Bellamy is shown below with some students,
engaging in cooperative learning ...

while the photograph at the right shows research being
carried out in the Clean Room in ASU's Center for
Solid State Electronics Research.

determination of the nocturnal windfield at the border be-
tween Arizona and Mexico during periods in the winter
when the windflow is controlled by heating and cooling of
the surface. A model of the surface representing a 12-kilo-
meter square area centered on amboss" Nogales (both U.S.
and Mexican cities on the border have the same name) was
constructed and used to determine the locations for the best
field study when only a few sensors would be available.
Other studies have used stratified salt solution to simulate
the atmosphere above a long mountain.
Roni Burrows is leading a study on the use of ultra-thin
films of organic semiconductors (phthalocyamines) as sen-
sors for the measurement of hazardous gas molecules. Sur-
face infrared spectroscopy, secondary ion mass spectrom-
etry and Raman spectroscopy are being used to study the
effects of Pc deposition methods. She is also developing a
spectroscopic method for identifying and quantifying atmo-
spheric dispersion onto leaves and other vegetation surfaces.
Jim Kuester has developed a process for converting re-
newable resources as well as liquid and solid wastes into
various chemicals (primarily diesel and jet fuels) through
indirect liquefaction. The current focus is on the use of
agricultural residues, but studies have been done with scrap
polymers, waste solvents, and municipal wastes. His re-
search lab includes a pilot scale fluidized bed pyrolysis unit
in series with a fluidized bed reactor to convert the pyrolysis
products into liquid fuels.
Greg Raupp has been issued a patent based on a process
for remediation of air streams contaminated with VOCs
using a combination of UV light and a titanium catalyst. The
process can also be adapted to ground water remediation by
Summer 1994

processing the VOC-laden air resulting when VOCs are air
stripped from the water. The EPA is sponsoring a demon-
stration unit to be placed in the Phoenix area to treat water
pumped from a chlorinated solvent contaminated aquifer.
Gene Sater has been investigating a process for recover-
ing a chelating agent and a buffer that are present in a liquid
used as a derusting agent by the military. The normal proce-
dure to remove heavy metals from the resulting waste stream
was to destroy the organic and then precipitate the metals as
hydroxides or sulfides. Recovery and reuse of the organic
would improve the economics of the cleaning process.
Surface Chemistry/Semiconductor Processing Tim
Cale and Greg Raupp collaborate on an integrated experi-
mental and theoretical research program aimed at improving
the scientific basis for designing, optimizing, and control-
ling microelectronic device fabrication processes. Their mod-
eling and experimental efforts at ASU, as well as their col-
laborations with a number of university and industrial groups,
focus on developing the reaction kinetic and transport mod-
els appropriate for deposition and etch processes. EVOLVE,
a 'topography simulation' package developed by Cale, uses
these transport and kinetic models to predict how surfaces
change during processing. Knowledge of topography is cen-
tral to device manufacturing, and EVOLVE is being used in
a number of companies. These efforts have led to an in-
creased understanding of the role which chemistry plays in
deposition and etch processes-particularly in: chemical va-
por deposition of tungsten, tungsten silicide, aluminum, and
silicon dioxide; plasma enhanced chemical vapor deposition
of silicon dioxide; sputter deposition of aluminum alloys,
titanium and titanium-tungsten films; and etching of tita-
nium-tungsten-nitride and aluminum films. Cale is involved
in collaborative research with faculty in HREM and engi-
neers and scientists at Motorola and the national laboratories
to study the evolution of film microstructure during process-
Continued on page 224.






of North Carolina State University

By His Friends and Colleagues

t has become fashionable to ques-
tion whether research reinforces
teaching or vice versa. In a jumble
of statistics and surveys, arguments
and counterarguments, the importance
of a personal example can be lost. In
an era where graduate education has
been criticized as overspecialized, and
where graduate students may think of
themselves as square pegs preparing
to spend their professional lives in
square holes, perhaps the message in
one individual's career is too easily
overlooked. In an environment where
professional accomplishment is often
divorced from personal satisfaction,
it is rejuvenating to see first-hand the
enjoyment that can be derived from a
successful, productive dedication to
education and scholarship.
The appearance of this article is timely, as it helps to
celebrate the tenth anniversary of David Ollis' affiliation
with North Carolina State's Department of Chemical Engi-
neering, which he joined as Distinguished Professor in the
summer of 1984. During that time, as the Department has
grown in size and stature, Dave has set a quiet example for
the faculty and students of the university. He has demon-
strated that a successful faculty member does not have to
make a choice between excellence in research and excel-
lence in teaching. He has demonstrated an exceptional scien-
tific versatility, illustrating by personal commitment the need
to master new areas of technology as the pace of scientific
change accelerates. Finally, he has demonstrated that a
successful academic career can be a source of great per-
sonal satisfaction. Being a professor can be fun! Dave has
enjoyed life at two universities besides North Carolina State:
Princeton (1969-80) and the University of California at Davis

(1980-84). He is fond of pointing out
that his academic posts have spanned
the range from "ivy" to "aggie."
Dave's twenty-five years in academe
have borne out the "teacher-scholar"
designation of a Camille Dreyfus
Award that he received in 1973. He
has taught and enjoyed most of chemi-
cal engineering's undergraduate clas-
sics and over the years has initiated
new courses in biochemical engineer-
ing, bioseparations, photochemical en-
gineering, "how to prepare and defend
a research proposition," and a fresh-
man laboratory for product and pro-
cess engineering. The last four of these
courses were developed at NCSU.
Table 1 shows that Dave's spirit of
course creation is alive and well, and
is in fact accelerating. What philosophy drives this new-
course developer? "Find a (teaching) need (that you like) ...
and fill it!" (with Dave's apologies to J. Paul Getty for the
inserts.) The last two items in Table 1 best illustrate this
point. About five years ago, the Department did a careful
study of its doctoral qualifying examinations. At that time,
doctoral candidates took three written exams (each lasting
three hours) in thermodynamics, transport and separations,
and kinetics and reaction engineering. To the (retrospective)
surprise of no one, there was an almost perfect correlation
between student scores on these exams and their grades in
"core" graduate courses in corresponding subject areas. The
qualifying exams were causing a lot of anxiety for both
students and faculty but weren't providing any new informa-
tion over and above what was contained in the course grades.
On the other hand, when the Department examined the cases
of students who were not successful in the doctoral program,

Copyright ChE Division ofASEE 1994

Chemical Engineering Education

Dave Ollis and his graduate students have contributed key papers in immobilized
enzymes and cells, hybridoma metabolism and antibody production, scanning microfluorimetry,
photocatalyst efficiencies and kinetics, and the photocatalytic and photolytic purification of contaminated
water and air streams. Over his career, Dave has graduated a total of twenty-one Master's
degree students and twenty-four doctoral students.

the problems were invariably associated with research meth-
odology: analyzing the existing literature, defining a satis-
factory research problem, planning a research program, mak-
ing oral presentations, answering difficult technical ques-
tions, etc. Dave's "research proposition" course was created
in response to this unmet need. Now in its third year, the
course is proving to be a major step toward helping doctoral
students initiate a positive, effective research experience.
The course in product and process engineering is another
example of filling an unmet need. In this case, the need was
to give freshman engineering students some practical, hands-
on experience, in counterpoint to the "trust me, someday

A Career of Course Development Dave and his lab group:

> Biochemical Engineering Fundamentals (1971-1992) back row (left to right) Julie Brown, Amy Parker, Mark
Microbiology; enzyme and microbial kinetics; bioenergetics and Marten, NCSU's "Strolling Professor," Jon Scott,
metabolism; reactor design; transport phenomena, control and Svetlona Velkovska, Dave, and Jian Chen;
instrumentation; bioseparations; process economics; wastewater front row, Michael Sauer, Kaihong Huang, Yang Luo
> Bioseparations (1986-1990) you're going to need this stuff' approach that is typical of
Physical chemistry of biomolecules and cells; solid separations many freshman-level science and mathematics courses. The
(sedimentation, filtration, centrifugation); isolation (adsorption, product and process engineering course was developed with
ion exchange, extraction); purifications (chromatographies,
crystallization, ultrafiltration); polishing and GMP operations funding from the National Science Foundation's SUCCEED
> Photochemical Engineering (1987-present) (Southeastern University and College Consortium for Engi-
Fundamentals (quanta, illumination sources andfilters, chemical neering Education). Although it is still in its trial stage and
actinometry and radiometry) andphotochemical reaction will undoubtedly undergo some refinement, the early re-
kinetics; reactor modeling and applications in gas phase (smog spouse is enthusiastic.
formation, ozone depletion and upper atmosphere chlorocarbon
transformations); polymers (grafting, crosslinking, Creating books also has been an important part of Dave's
microlithography); liquids (water purification and sterilization); philosophy of filling unmet educational needs. Upon reading
photoactive solids (photocatalysts, photovoltaics, photography,
reprographics) George Tsao's 1970 Chemical Engineering Education state-
D Research Proposition (1991-) ment that, for biochemical engineering, "There is no satis-
Frontiers in chemical engineering; the natureofresearch, factory text ," Dave's first offering of this course (at
crystallization ofa problem (hypothesis, assertion); organization Princeton) produced a 400-page draft manuscript. When
of support (presuppositions and documentation); focus of Dave visited the University of Houston for a seminar in
proposed effort (operational statement); construction of method
and proposed analysis (expected results) sections; creation and 1971, chairman Dan Luss opined that his newest faculty
oral presentation of proposition to peers and faculty committee, colleague, James Bailey, ". .. was the fastest and most fluid
(Course now offered in lieu of a previous PhD qualifying exam writer ." he'd seen. Jay agreed to work with Dave and
and is required of all PhD candidates) write a second draft of the text-and did much more, refin-
D Product and Process Engineering Laboratory (1993 -) ing the suggestion of a book into a coherently-organized,
Freshman introduction to engineering (3 units) through role
playing as product user, assembler, and analyst (neophyte carefully-proofread manuscript, Biochemical Engineering
engineer) using teams of two students each to explore six light- Fundamentals, which went, eventually and happily, into
based technologies: bar code scanners; compact discs and CD- widespread use.
ROMs, optical fiber communications, photocopiers, videocameras
and VCRs, and water purification and sterilization systems. The book's actual birth was not without surprises. McGraw-
Hill editor B.J. Clark said, upon manuscript receipt, "It's 250
Summer 1994 159

pages longer than the 500 pages stated in the contract.
Could you drop the last four chapters without too
much pain?" In an earthier vein, Elmer Gaden commented
prior to publication, "Sounds like a sex manual written by
two virgins!" Undaunted, but with their machos severely
bruised, Dave and Jay persevered, and even Elmer eventu-
ally adopted the book.
According to Michael Flickinger of the University of Min-
nesota, "This book has been used to train an entire genera-
tion of biochemical engineers, not only in the U.S. but also
around the world." What goes around, comes around, and it
was with considerable satisfaction that Dave, grandson of a

Dave's enjoyment of academic life is as evident
today as when he began his career. His deepest
professional satisfactions have included
collaborations with his graduate students and his
many faculty colleagues, as well as the freedom
to wander in both teaching and research.

Jewish emigr6 from an inhospitable Czarist Russia, saw Mir
Publishers request and publish Biochemical Engineering Fun-
damentals in Russian.
Photochemical conversions are increasingly encountered
in chemical engineering research, yet instructional materials
for graduate students are rare. A 1988 lecturing invitation at
Ecole Polytechnique Federale de Lausanne alerted Dave to
Technologie Photochimique by A. Braun (now professor at
the University of Karlsruhe), E. Oliveros, and M.-T. Maurette.
The translation of this book, in collaboration with Nick
Serpone of Concordia University (Canada), provided
Dave with a novel form of self-paced photochemistry educa-
tion. The first several chapters of Photochemical Tech-
nology (Wiley-Interscience, 1991) now serve to introduce
the fundamentals of illumination sources and filters,
actinometry, and radiometry in his NCSU photochemical
engineering course.
Dave is part of a strong departmental linguistic tradition
that includes Ruben Carbonell (Spanish, Italian, Portugese),
Rich Felder (Italian, Portugese), Benny Freeman (French),
and Hal Hopfenberg (Italian). But foreign language came
late to Dave, in keeping with a long-standing American
tradition. As a graduate student, he produced a (probably)
miserable but required translation of a French kinetics paper
for his advisor, Belgian-bor Michel Boudart, who remarked,
"It's a delight that you Americans take an interest in lan-
guage, but a pity that you begin twenty years too late!" Slow
to start indeed, but Dave has enjoyed the last laugh by being
invited twice to Ecole Polytechnique to lecture on biotech-
nology and bioseparations enfrancais, bien sur.
In Dave Ollis' world, teaching and research have always
gone together, not in a competitive but in a supportive rela-
tionship. It is Ernest Boyer's proposition that research devel-

Examples of Ollis' Pioneering Papers

"Phase Stability of Binary Alloy Crystallites," J. Catalysis,
23, 131 (1971)
This paper introduced the use of regular solution
theory to rationalize why nanometer-sized alloy
crystallites should exhibit enhanced phase stability and
component solubilities. A rash offollowing papers used
this approach for catalytic alloy surfaces.

> "Photocatalyzed Mineralization of Trichloroethylene in
Dilute Aqueous Solution," (with Anne Lorette Pruden), J.
Catalysis, 82,404 (1983)
This was the first paper to demonstrate total oxidation in
water of a chlorinated hydrocarbon by photocatalysis at
room temperature. Along with early photocatalysis
contributions by Stone (England), Teichner (France),
Bard (Texas), and Cary (Canada), this and related
photocatlysis papers from Dave's research group led to
the environmental engineering interest in photocatalytic
remediation, summarized in the recent volume
Photocatalytic Treatment and Purification of Water and
Air (Elsevier), co-edited with Hussain AI-Ekabi (1993).

0 "Scanning Microfluorimetry of Calcium-Alginate Immobi-
lized Cells of Zymomonas mobilis," (with Harold
Monbouquette), Bio/Technology, 6, 1076 (1988)
This paper contained the first announcement of a new
technique allowing quantitative spatial profiling of
immobilized cell number density and specific growth rate.

Two of the more important recent contributions from
Dave's research group are:

- "Photocatalytic Degradation of Organic Water Contami-
nants: Mechanisms Involving Hydroxyl Radical Attack,"
(with C. Turchi), J. Catalysis, 122, 178 (1990)
This paper demon iratei thru Langmur-Hmihelh od
rate expressions can arise in photocatalysis, regardless of
whether active oxidant (hydroxyl radical) and oxidizable
contaminant are both adsorbed, one adsorbed and one
dissolved, or both dissolved in solution at the time of
reaction. This analysis, indicating mechanistic ambiguity,
precipitated extensive efforts by photochemists to resolve
the true location ofphotocatalytic oxidation steps.

0 "Scanning Microfuorimetry and Modeling of Immobilized
Acid-Sensitive E. coli: A Quantitative Comparison," (with
R. Kuhn and S.W. Peretti), Appl. Biochem. BiotechnoL, 39/
40, 401 (1993)
This paper provides the first confrontation between a
reaction-diffusion model, derived a priori from suspension
culture kinetics, and experimentalfluorescence profiling
of cell specific growth rate. The results compare
satisfactorily with pH, buffer, and substrate bulk solution
variations and demonstrate development of a new
analytical tool for biochemical engineering of immobi-
lized cells. Current work pursues structured modeling of
immobilized recombinant bacteria.

Chemical Engineering Education

ops into broader themes, which in turn are transformed into
formal courses. Thus, research begets teaching, as Table 1 so
nicely illustrates, when played through a natural maturation
of personal development.
In research parallels, Dave Ollis and his graduate students
have contributed key papers in immobilized enzymes and
cells, hybridoma metabolism and antibody production, scan-
ning microfluorimetry, photocatalyst efficiencies and kinet-
ics, and the photocatalytic and photolytic purification of
contaminated water and air streams. Over his career, Dave
has graduated a total of twenty-one Master's degree students
and twenty-four doctoral stu-
dents. Many have gone on to
distinguished careers in both
academe and industrial re-
search (e.g., Pao Chau, UC-San
Diego; Hal Monbouquette,
UCLA; Eiji Suzuki, University
of Tokyo; Rathin Datta, Merck/
Exxon/CPC; Ed Wolynic,
Union Carbide; Bob Kuhn,
Synergen; Mina Dalili,
Centacor/Medarex); Craig
Turchi (NREL); and Lorette
Pruder (Mobil Chemical).
Dave's research career has
been characterized by three fea-
tures: 1) a deep intellectual cu-
riosity and a broad grasp of sci- Dave and Marcia Olli
ence and engineering which has riage, are still laugh
led to important contributions their 30th wedding
in three different topical areas: been a social work
heterogeneous catalysis, French at a
photocatalysis, and biochemi-
cal engineering; 2) early papers which have opened new
research directions; and 3) careful elucidation and character-
ization of catalysts-thermal, biological, and photochemi-
cal. Some examples of his early pioneering papers in each
field are shown in Table 2.
In his ten years at NCSU, Dave has been part of a depart-
ment with an increasing research orientation, but not at
the expense of quality instruction at the graduate and
undergraduate levels. He has contributed to the fine
teaching tradition in the spirit of Warren McCabe and col-
league Rich Felder. Dave has also helped foster the
growth of the graduate program, which now numbers over
seventy doctoral students.
Dave's colleagues share some of his scientific wanderlust
and aren't much easier to put into tidy categories than is
Dave. As a first approximation, they include:
The Biotech Bunch Ruben Carbonell (biosensors and
bioseparations, next Head); Carol Hall (statistical thermo-
dynamics; NCSU's 1993 Alcoa Distinguished Research
Summer 1994

s, af
ng a
:er a

Award winner); Bob Kelly (hyperthermophilic enzymes and
microorganisms); Peter Kilpatrick (bioseparations, surface
chemistry); Steve Peretti (applied molecular biology, PYI)
The Polymers and Materials Mafia Benny Freeman
(polymer transport, PYI); Hal Hopfenberg (polymer per-
meation, self-described university utility infielder, ex-Head,
ex-Assistant to the Dean and to the Chancellor, ex-Interim
Athletic Director, and currently Director of the Kenan Insti-
tute for Science, Engineering and Technology); Saad Khan
(polymer rheology); Henry Lamb (surface science, orga-
nometallic chemistry, PYI); John Setzer (polymer
processing, Associate Head);
Vivian Stannett (polymer
gentilhomme extraordinaire,
On Her Majesty's Service,
emeritus); Greg Parsons
(electronic materials)
The Environmental Club
Peter Fedkiw (electrochemi-
cal engineering); Rich
Felder (process synthesis
and optimization); Christine
Grant (transport, waste
minimization); P. K. Lim
synthesis, free-radical chem-
istry); Michael Overcash
(life-cycle analysis, pollution
ter fifteen years of mar- prevention); George Rob-
nd recently celebrated erts (reaction engineering,
niversary. Marcy has alternate fuels, Head); Rob-
nd currently teaches ert Thorogood (separations)
tessori school.
Dave's embrace of aca-
demic life is also evident on the homefront. With four sons,
one each in law school, graduate school, college, and el-
ementary school, and an adopted daughter yet to begin school,
the Ollis factor will likely be apparent in the academic
world for some time to come; he clearly supports higher
education in more ways than one! Marcia, Dave's wife
of thirty years, should get credit as first author for these
contributions, however.
Dave's enjoyment of academic life is as evident today as
when he began his career. His deepest professional satisfac-
tions have included collaborations with his graduate stu-
dents and his many faculty colleagues, as well as the free-
dom to wander in both teaching and research. Dave vividly
remembers a conversation he had as a young Assistant Pro-
fessor at Princeton during which his former colleague, Ernie
Johnson, told him, "There is no finer post than professor." In
Dave's hands, this post has provided a wandering license for
life and a paying permit to pause, postulate, and proceed in
just about any research or teaching direction that struck his
fancy. "Ernie, you were right: teaching is the finest post!" 0

Award Lecture...


A Picaresque Tale

The thirty-first annual Chemical Engineer-
ing Division Lectureship Award was presented
to Morton M. Denn at the June, 1993, annual
meeting of ASEE held at the University of
Illinois, Urbana-Champaign, Illinois, for his
lecture (presented here) titled "Polymer Flow
Instabilities: A Picaresque Tale." The pur-
pose of this annual award is to recognize and
encourage outstanding achievement in an im-
portant field of fundamental chemical engi-
neering theory or practice.
Morton Denn is Professor and Chairman of Chemical Engineer-
ing at the University of California at Berkeley. He earned his BSE
from Princeton University in 1961 and his PhD from the University
of Minnesota in 1964. After spending a post-doctoral year at the
University of Delaware he joined the Delaware faculty, where he
was named the Allan P. Colburn Professor in 1977. He went to
Berkeley in 1981, where he also serves as Program Leader for
Polymers and Composites in the Center for Advanced Materials of
the Lawrence Berkeley Laboratory.
Denn's PhD dissertation with Rutherford Aris, The Optimization
of Complex Processes, was the start of an interest in process optimi-
zation and control that lasted for many years; the fruits of this
period include his text Optimization by Variational Methods (1968).
His postdoctoral work with Arthur B. Metzner on rheology and
non-Newtonian fluid mechanics defined the other major focus of
his research interests. This work has included theoretical and ex-
perimental rheology of polymer solutions and melts and analytical,
computational, and experimental investigations of the flow of com-
plex liquids. Flow instabilities have been a particular concern.
Much of Denn's research has focused on modeling the steady and
dynamical behavior of processing operations. These activities are
illustrated in his book Process Modeling (1986).
Denn's interest in education is reflected in his textbooks, which in
addition to those noted above include Introduction to Chemical
Engineering Analvsis (%Iith T.W F. Russell. 19721. Stability of Re-
action and Transport Processes (1975). and Process Fluid Me-
chanics 19801. His professional acnvtide include service as Editor
of AIChE Journal from 1985 to 1991.
Denn is a member of the National Academy of Engineering and a
Fellow of the AIChE. He w as a Guggenheim Fellow and a Fulbright
Lecturer and has received the Bingham Medal of the Society of
Rheology and the Professional Progress and William H. Walker
Awards of the AIChE.

University of California
Berkeley, CA 94720

am honored to have been chosen to deliver the 1993
ASEE Chemical Engineering Division Lecture. While
this brief written text cannot capture the mood of an
hour-long evening presentation to a relaxed and friendly
group, I hope it does convey some of my excitement over
the topic.
Extrusion instabilities are ubiquitous in polymer pro-
cessing and have commanded attention for four decades;
my students and I have been studying them off and on for
nearly three, and the entire time has been a learning
experience. I chose this subject for my lecture because I
believe the path which has been followed mirrors the
evolution of chemical engineering research over the same
time period; we have moved from the macroscopic to the
molecular level as finer-scale tools, experimental and
theoretical, have become available. This has not hap-
pened because the nature of the problems has changed,
but rather because we are better equipped to deal with
them on a fundamental level. I have commented else-
wherell' on the risks to the soul of our profession which
are inherent in too strong a research emphasis on the
underlying sciences; here I will look only at the gains.
I subtitled my lecture "a picaresque tale," which I find
descriptive of the progression of our focus from millime-
ter-sized dies to molecules. The scoundrels along the way
have only sometimes been evident, and on rare occasions
the quixotic has been clouded by the appearance of epic
triumphs; in every case (save the current one, which is
still in doubt) the Homeric landscape has faded and the
windmills have reappeared. The physical phenomenon
being studied is deceptively simple. Beyond some critical
throughput in an extrusion die, all polymer melts develop
irregularities on the surface of the extrudate, sometimes
accompanied by unsteady flow in the die. Polymer melts
are viscoelastic, and the simplest description of the stress
state requires at least two material parameters: a modulus
Copyright ChE Division ofASEE 1994
Chemical Engineering Education

and a viscosity. The modulus, which is typically of order 0.1
MPa, can be estimated from a variety of measurements with
varying degrees of rigor. A useful empiricism is that the first
visual onset of surface irregularities occurs when the wall
shear stress is comparable to the modulus. (The ratio of
stress to modulus is often called the recoverable shear.) The
empiricism is not surprising; in the absence of inertia, which
is always the case in melt extrusion, and with the dubious
assumption of fully developed flow everywhere in the die,
the critical velocity might be expected to depend primarily
on the viscosity, the die diameter, and the modulus-in
which case the idea of a critical recoverable shear follows
immediately from dimensional analysis.

Figure 1. Extrudate of linear low-density polyethylene
exhibiting sharkskin.
(Extrudate and micrograph by Stephanus Pudjijanto.)

Figure 2. Extrudate of linear low-density polyethylene in
the slip-stick regime, with alternating sharkskin and
somewhat smooth surfaces.
(Extrudate and micrograph by Stephanus Pudjijanto.)
Summer 1994

In linear polyolefins the first visual manifestation of an
extrusion instability is a high-frequency, small-amplitude
distortion known as sharkskin (Figure 1). The onset of
sharkskin appears to coincide with a change in the slope of
the flow curve (shear stress vs. shear rate). In constant
throughput processing (as opposed to constant pressure drop
or, equivalently, constant stress) there is a second critical
stress at which pressure and flow rate oscillations* occur
and the extrudate emerges with alternating "sharkskinned"
and relatively smooth sections (Figure 2). This regime is
known as slip-stick.
Finally, at still higher throughput, pressure oscillations
cease, sharkskin vanishes completely, and there is a transi-
tion to a wavy distortion which gradually becomes more
severe. A typical flow curve is shown in Figure 3, where the
slip-stick region is reminiscent of ignition-extinction phe-
nomena in combustion; in constant pressure operation the
intermediate portion of the curve is unattainable and there
are hysteretic jumps between the two branches. The slip-
stick discontinuity is absent in other polymers, such as
branched polyolefins and polystyrene, and the first instabil-
ity is often more pronounced than sharkskin. These instabili-
ties are often known collectively as melt fracture, a term
coined in 1956 by Tordella because he heard crackling noises
in the die and the extrudate had the appearance of a fractured
solid material. Elastic turbulence is another common early
term which has now largely disappeared.
Flow instabilities in viscoelastic liquids have been the
subject of several major reviews (see, for example, Petrie

< XX XXXX)A xa
g 10.1

o sharkskin
x slip-stick
A wavy

10-2 .... ... 1 w
100 10' l10 103 104
Nominal Shear Rate (s-')

Figure 3. Flow curve (shear stress as a function of shear
rate) for a Unipol linear low-density polyethylene at 155 OC.
Flow in the slip-stick region oscillates between the upper
and lower branches of the curve, with the average rate,
shown by the symbolx, determined by the constant through-
put. (Data by Stephanus Pudjijanto.)

* Flow rate oscillations are possible in constant throughput
operation because of the small degree of compressibility of the
polymer melt.

and Denn[21 and Larson[31). I have recently addressed[4,51
what I consider to be the outstanding issues of the subject at
hand, and my treatment here will be selective, rather per-
sonal, and without references. I do call attention to an excel-
lent set of data on well-characterized polybutadienes and
polyisoprenes by Vinogradov and coworkers,[61 which illus-
trate the phenomena very well and have been used to test
several theoretical formulations.

In 1966 Huseby showed that a molecular theory of poly-
mer melt rheology could lead to a maximum and minimum
in the flow curve, reminiscent of the shape in Figure 3, and
he suggested that melt fracture is a consequence of the
intrinsic rheology. The reputation theory of polymer chain
motion of De Gennes and Doi and Edwards leads naturally
to a flow curve with a maximum, and the subsequent mini-
mum may occur because of rapid molecular motions not
contained in the basic theory. The magnitude of the disconti-
nuity in the flow curve in Vinogradov's data has been pre-
dicted quite well from this theory by McLeish and Ball;
Malkus, Kolkka, and their coworkers have explored the rich
dynamics of such systems.
This constitutive mechanism does not require molecular
theories. The possibility of maxima and minima in flow
curves was apparently first noted by Oldroyd in 1950 in
the context of a rigorous formulation of continuum
theories. Oldroyd considered such behavior unphysical, and
I tend to agree. Gabriel Pomar, working with me and
Susan Muller, has recently shown that the discontinuity in
the flow curve for a series of octadecane-diluted linear
polyethylenes occurs at a constant stress, independent of
modulus, which appears to be inconsistent with the concept
of a constitutive instability.

The appearance of a highly structured distortion suggests
the use of hydrodynamic stability theory to explain the be-
havior. My students and I, as well as a number of others,
explored this avenue. In 1973 we succeeded in "predicting"
the onset of melt fracture in capillary dies with remarkable
accuracy, and we made an experimentally testable predic-
tion for slit dies which motivated at least three experimental
studies. The prediction for slits was incorrect, leading to a
reexamination of the theory with Teh Ho and the discovery
that the eigenvalue problem is so computationally sensitive
that false neutral stability curves are the rule. While this was
a triumph of the scientific method, it was a great disappoint-
ment regarding our understanding of the phenomena and
showed (as has been verified by several research groups
since) that fully-developed channel flow of model viscoelas-
tic liquids with monotonic stress curves is stable to small
disturbances. (I often wonder how a young faculty member
subject to today's critical mode of tenure evaluation would

fare in such a situation.)
There is no universally accepted equation relating the
stress to the strain rate in polymeric liquids, but certain
mathematical structures appear in many constitutive formu-
lations. It is a common feature that the full system of equa-
tions describing flow can change type; i.e., in certain regions
of the flow field they will be elliptic, while in others they
will be hyperbolic. (Non-zero inertial terms are required for
this change of type.) Hyperbolic equations admit
discontinuities, and they allow small boundary disturbances
to grow as "Hadamard instabilities." A critical transition
of this type has been suggested by Joseph and his coworkers
as a mechanism for extrusion instabilities as well as a
number of other phenomena.
The first analysis of change of type for viscoelastic liquids
was apparently done by my student Jim Ultman in the
early 1970s to explain anomalous heat transfer in dilute
polymer solutions, so I have a certain fondness for this
approach, but I doubt its general applicability. The notion of
change of type is inconsistent with explanations based on a
constitutive instability.

The standard macroscopic tools which we used in the
sixties and seventies (rheological measurement and con-
tinuum mechanics and stability theory) provided little in-
sight into the problem of extrusion instabilities, and flow
experiments were not instructive regarding mechanisms. A
dramatic turn came with the publication of a paper by
Ramamurthy in 1986 in which he demonstrated that the
stress for the onset of extrudate distortion in an alpha-brass
die was different from one made of chrome-plated steel.
(Similar observations had been made twenty years before,
but had attracted little attention.) Rather than serving as a
passive element, with the sole function of providing an an-
chor for a no-slip condition, the die wall was shown to be an
active element in the process.
Exploration of the limits of the no-slip condition is not
new-I recall writing a course paper reviewing some of the
literature when I was in graduate school-but the notion that
wall effects could influence liquid-phase processing seemed
revolutionary. Measurements in our laboratory by Doug
Kalika were consistent with the observation that the onset of
sharkskin in linear low-density polyethylene coincides with
the onset of apparent wall slip. Glenn Lipscomb, Roland
Keunings, and I estimated the stresses at a corner in the flow
(using a most inexact theory for a problem that is still un-
solved for any stress constitutive equation of interest) and
found that, while the region over which a Newtonian fluid
experiences stresses that exceed the cohesive strength of
materials is of atomic scale, for polymer melts the region is
of the order of tens of microns, casting doubt on the applica-
bility of the no-slip condition near boundary discontinuities.
Chemical Engineering Education

Davide Hill, Tomichi Hasegawa, and I showed in 1990
that the theory of the adhesion of elastomers to rigid sub-
strates could be extended to flowing polymer melts at high
levels of stress, and that adhesive failure between the melt
and the wall is predicted to occur at stresses quite close to
those where sharkskin is observed. Furthermore, the theory
provides an a priori calculation of the dependence of the slip
velocity on wall stress which is in remarkably good agree-
ment with Kalika's measurements.
What is significant is not the quantitative agreement be-
tween theory and experiment, for the theory has important
limitations which make it clear that the extent of agreement
is fortuitous, and a mechanism for the periodicities charac-
teristic of sharkskin and slip-stick seems to be missing.
Rather, the significance is in the message that progress
in understanding the instabilities is most likely to be made
by applying the tools of surface science and dynamic frac-
ture in place of the macroscopic methodologies which had
dominated the field. For me, it meant a major redirection
of my research effort.

Once we accept the principle that some flow instabilities
are governed by surface effects, molecular probes of the
surface become the logical means of study. Let me give two
examples here of our recent and ongoing work which reflect
this change in methodology.
Our theoretical treatment of adhesion at the melt/die wall
interface requires that we understand the adhesion of solid
polymers to metals under conditions where the interactions
are mostly governed by dispersive forces. In our laboratory,
Davide Hill and, more recently, Tim Person have used ion
and electron spectroscopies, primarily SIMS and XPS, to
study the adhesion of polyethylene at metal and metal-oxide
substrates. Following removal of a polymer film from the
metal substrates, Hill saw evidence of transfer of metal
atoms to the polymer. We find consistently that a 2- to 6-nm
layer of polymer is left behind on the metal, although the
metal is also clearly revealed, possibly because the crack
moves between the phase boundary and the interior of the
polymer. Surface chemistry involving the metals under ex-
trusion conditions seems to be very important to the nature
of adhesion. The question of whether the failure is adhesive,
cohesive, or a mix of the two is important to the theory of
melt slip; the energetic leading to agreement with experi-
ments assume adhesive failure, and a cohesive failure would
give different results.
Laura Dietsche and, more recently, Christophe David,
working with me and Alex Bell, have used attenuated total
reflectance Fourier transform infrared spectroscopy (ATR/
FTIR) to study the dynamics of chain exchange between the
bulk melt and the channel surface in a flow system, working
with C-16 oligomers. The dynamics of exchange are com-
Summer 1994

plex, with surprisingly long time scales. When the flow
channel is filled with one oligomer and displaced with the
other, the initial transient response is consistent with simple
flow and diffusion. Dietsche found, however, that at a
critical surface concentration, which is independent of flow
rate but very dependent on the material of construction of
the channel face, there is a transition to an apparent
first-order process with a time constant of order one minute;
the exact time constant is flow rate and surface dependent.
The time constant can be lengthened by the addition of
chains with functional groups like those used in some com-
mercial "flow modifiers."
The dynamics seem to be governed by a very slow adsorp-
tion/desorption process, which probably results from a ten-
dency of chains to extend and densify at the surface, as
predicted in somewhat different contexts by several molecu-
lar dynamics simulations. This observation is clearly rel-
evant to the behavior of chain segments in an entangled
polymer near a surface, but it is possible that entanglement-
dominated surface dynamics will be rate-limiting for macro-
molecular melts, and the relevance of this fascinating phe-
nomenon to the dynamical processes associated with extru-
sion instabilities is presently unclear and needs further study.


Following extrusion experiments in our laboratory by Hideo
Shidara, using slits as small as 34 gm in height to achieve a
large surface-to-volume ratio, I noted an interesting differ-
ence between instabilities in linear polyethylene and poly-
styrene. (As with most important observations, this one was
not new; I simply had not appreciated the significance be-
fore.) In the region of flow instabilities there was a decrease
in the polyethylene extrusion pressure, suggestive of wall
slip. With polystyrene, however, the flow became more dis-
sipative following the onset of the instability.
This behavior could be rationalized in the context of an
adhesion mechanism, but alternative ideas are possible. It
should be much easier, for example, to pull linear polyethyl-
ene out into an extended-chain conformation at high stress
than the bulky polystyrene, and the possibility of a stress-
induced phase change leading to a low-viscosity material
near the wall (perhaps a liquid-crystalline phase) had to be
considered. Several years ago, Andrew Keller claimed to
have observed a liquid-crystalline transition in high-density,
high-molecular-weight polyethylene, so the idea had some
respectability even if it seemed a bit unlikely.
While pursuing this concept, Stephanus Pudjijanto and I
recently showed that a linear low-density polyethylene can
exhibit a remarkable "stable island" in the midst of the slip-
stick region, where pressure oscillations stop, extrusion pres-
sure drops, and the extrudate becomes reasonably smooth.
At throughputs on both sides of this "island," which exists
only in a narrow temperature range, unstable oscillating

flow persists. Thus far we have found no evidence of the
existence of a liquid-crystalline phase in the near-surface
region. This experimental observation does not seem to fit
into any of the theoretical frameworks developed thus far for
the instabilities, including the surface-dominated mechanism.

What started nearly thirty years ago as a classical con-
tinuum problem has evolved into a study of molecular inter-
actions at surfaces, in my laboratory (which I have empha-
sized here) and others. We are following this path because
our ability to study real processing problems at a molecular
level is enhanced by tools which were previously unknown
or unfamiliar to us.
Our goal is unchanged from what it was when we began,
but our methodology is quite different. My students are
routinely using a variety of surface-sensitive methods (those
mentioned above and other microscopies and spectroscopies)
to study the mechanics of polymer interfaces, as are those
in other laboratories. My colleagues Arup Chakraborty
and Doros Theodorou, and their counterparts elsewhere, are
using powerful computational and theoretical methods to
study polymer chain conformations and dynamics near
surfaces because of their own interests in a variety of
practical problems.
I believe a thorough understanding of polymer surface
interactions will result in major advances in processing, not
just in problems of extrusion instability but, more impor-
tantly, in our ability to tailor surfaces for specific processing
functions. I remain convinced that many of the extrusion
instabilities which we have been studying (for I do not
believe there is just one, despite the common onset at about
the same recoverable shear) are the result of surface interac-
tions, and that this is a fruitful avenue for research. It is
likely that other mechanisms (stress-induced phase transi-
tions, for example) are also important, and the recurrent
danger is to become so focused on one idea that we miss
other possibilities. We have done this too often in the past.

My recent studies of polymer interfaces have been carried
out through a program in the Center for Advanced Materials
at the Lawrence Berkeley Laboratory, supported in part by
the Director, Office of Energy Research, Office of Basic
Energy Sciences, Materials Science Division of the U. S.
Department of Energy, under Contract No. DE-AC03-

1. Denn, M.M., "The Identity of our Profession," in C.W. Colton,
Ed., Perspectives in Chemical Engineering (Advances in
Chemical Engineering, 16), Academic Press, New York, NY,
565 (1991)
2. Petrie, C.J.S., and M.M. Denn, "Instabilities in Polymer
Processing," AIChE J., 22, 209 (1976)

3. Larson, R.G., "Instabilities in Viscoelastic Flows," Rheol.
Acta, 31, 213 (1992)
4. Denn, M.M., "Issues in Viscoelastic Fluid Mechanics," An-
nual Review of Fluid Mechanics, Vol. 22, J.L. Lumley, et al.,
eds, Ann. Rev. Inc., 13 (1990)
5. Denn, M.M., "Surface-Induced Effects in Polymer Melt Flow,"
in P. Moldenaers and R. Keunings, eds., Theoretical and
Applied Rheology (Proc. XIth Int. Cong. Rheol.), Elsevier,
Amsterdam, Holland, 45 (1992)
6. Vinogradov, G.V., A. Ya. Malkin, Yu. G. Yanovskii, E.K.
Borisenkova, B.V. Yarlykov, and G.V. Berezhnaya, "Vis-
coelastic Properties and Flow of Narrow Distribution
Polybutadienes and Polyisoprenes," J. Polym. Sci. Part A-2,
10, 1061 (1972) O

am book review

by Sangtae Kim, Seppo J. Karilla
Butterworth-Heinemann, 80 Montvale Avenue, Stone, MA 02180;
507pages, $69.95 (1991)
Reviewed by
C. Pozrikidis
University of California, San Diego
There has been a long-standing need for a comprehensive
book that discusses analytical, asymptotic, and numerical
methods for computing the motion of particles in creeping
flows and that catalogues known solutions, which can be
used as a reference by instructors, students, and researchers.
This book satisfies that need and does so in a well-
organized, meticulous, proficient, and imaginative manner.
The topics presented in the book, along with those in the
classical monograph by Happel and Brenner (Low Reynolds
Number Hydrodynamics) should be required reading for
students of fluid mechanics, colloidal science, and other
engineering disciplines involving particulate flows.
The main theme of the book concerns the question of how
to compute the structure and properties of creeping flow past
a single particle or a collection of particles of arbitrary shape
in the presence of solid boundaries, and the alternative meth-
ods for this computation. The answer is given in the various
chapters that are organized according to the geometrical
conditions surrounding the problem. In the interest of rigor
and comprehension, the mathematical developments are in-
troduced with an illuminating discussion of the general prop-
erties of creeping flow, including variational principles.
One important and pioneering contribution this book makes
is an instructive discussion of boundary integral representa-
tions in a manner that is coherent, rigorous, and accessible to
readers with a fundamental background in functional analy-
sis and integral equation theory. The application of methods
of functional analysis and operator theory to study the prop-
erties of the integral equations of Stokes flow will be a
Chemical Engineering Education

delightful treat to readers with deeper mathematical interests
and is likely to draw the attention of researchers in applied
mathematics, as it has done in the analogous fields
of elastostatics and elastodynamics. Furthermore, readers
with an interest in the field of computational science will
be intrigued by the discussion of advanced computa-
tional procedures for solving the integral equations describ-
ing flow past collections of particles with reference to
parallel computation.
The book consists of nineteen chapters and is divided into
four parts according to geometrical configuration. Each sec-
tion is followed by exercises with varying degrees of diffi-
culty, with the objective of supplementing and extending the
theory and filling in the details.
Part I, "Governing Equations and Fundamental Theorems,"
introduces the equations governing creeping flow with sus-
pended particles. It contains the first two chapters:
"Microhydrodynamic Phenomena," and "General Properties
and Fundamental Theorems." Uniqueness of solution, en-
ergy dissipation theorems and their application to estimate
the forces exerted on particles, the boundary integral repre-
sentation, and the mathematical origin of the multi-pole
expansion method are discussed.
Part II focuses on the "Dynamics of a Single Particle."
Exact and asymptotic solutions are presented via singularity
and functional expansion methods in spherical coordinates,
and the mobility and resistance problems are defined. This
part concludes with a chapter on unsteady Stokes flow or
linearized Navier-Stokes flow that contains some original
contributions and indicates avenues for further development.
Part III considers "Hydrodynamic Interactions" (that is,
flows in the presence of two or more suspended particles)
and outlines methods for computing mutual hydrodynamic
effects. The resistance and mobility problems for multi-
particle systems are formalized, an instructive discussion of
the method of reflections for well-separated particles is pre-
sented, and asymptotic methods for well-separated particles
and particles with disparate sizes are discussed. Further-
more, the two-sphere problem is analyzed in an exhaustive
manner. The last chapter in this part introduces the applica-
tion of numerical methods to compute creeping flow in the
context of the multi-pole collocation method.
Part IV is dedicated to developing and solving the integral
equations that describe flow in a container with suspended
particles. The five chapters in this part are grouped under the
general heading "Foundations of Parallel Computational
Microhydrodynamics." The properties of the integral equa-
tions arising from boundary integral representations of Stokes
flow are discussed in detail, and a proper boundary integral
formulation leading to integral equations of the second kind
(called the completed double-layer representation) is devel-
oped. Some advanced concepts of functional analysis and
operator theory are used to explain the procedures, and the
Summer 1994

book also provides adequate references for background
reading. All this discussion is geared towards developing
convergent iterative methods of solutions that can be carried
out on parallel processors: each particle is assigned to
a different processor, the problem is solved locally, and
the processors communicate every few iterations to let the
other processors know about the local behavior of the
flow. The authors are generous enough to make computer
programs available to the public (but note that there is an
update on the procedures).
I highly recommend this book as a text for an intro-
ductory or advanced course on colloidal science, low-
Reynolds-number hydrodynamics, boundary integral meth-
ods, or advanced scientific computing. Furthermore, in the
opinion of this reviewer, the book belongs on the bookshelf
of any chemical engineer who has a direct or a peripheral
interest in fluid flow. 7

books received

Electron Paramagnetic Resonance: Elementary Theory and Practical Applications,
by Weil, Bolton, and Wertz; Wiley Interscience, 605 Third Ave., New York, NY
10158; 568 pages, $79.95 (1994)
Intermediate Organic Chemistry, 2nd edition, by John Stowell; Wiley Interscience,
605 Third Ave., New York, NY 10158; 334 pages, $49.95 (1994)
Information Theory in Analytical Chemistry, by Karel Eckschlager and Klaus Danzer;
Wiley Interscience, 605 Third Ave., New York, NY 10058; 275 pages, $64.95
Low Energy Ion-Surface Interactions, Edited by J. Wayne Rabalais; Wiley & Sons,
605 Third Ave., New York, NY 10058; 594 pages, $120 (1994)
The Surface Science of Metal Oxides, by V.E. Henrich and P. A. Cox; Cambridge
University Press, 40 West 20th St., New York, NY 10011-4211; 464 pages, $84.95
Progress in Inorganic Chemistry, Vol. 41, edited by Kenneth D. Karlin; Wiley
Interscience, 605 Third Ave., New York, NY 10058; 848 pages, $125 (1994)
Chemical Dynamics at Low Temperatures, by Benderskii, Makarov, and Wight;
Wiley Interscience, 605 Third Ave., New York, NY 10158; 385 pages, $74.95
Practical NIR Spectroscopy; With Applications in Food and Beverage Analysis, 2nd
edition, by Osborne, Fearn, and Hindle; Wiley Interscience, 605 Third Ave., New
York, NY 10158; 227 pages, $89.95 (1993)
Design andAnaysis ofExperiments: Vol 1. Introduction to Experimental Design, by
Hinkelmann and Kempthore; Wiley Interscience, 605 Third Ave., New York, NY
10158; 495 pages $49.95 (1994)
Electron Paramagnetic Resonance: Elementary Theory and Practical Applications,
by Weil, Bolton, and Wertz; Wiley Interscience, 605 Third Ave., New York, NY
10158; 568 pages, $79.95 (1994)
There were several errors in the spring-issue article detailing the
history of the Corcoran Award:
> The venue for the first Corcoran Award was the Division banquet in
the University of Cincinnati ASEE meeting, not the Lake Tahoe
meeting (which was the venue for the second award to Bob Bird).
> Richard Felder's award winning paper was "The Generic Quiz" [CEE,
19(4), 176 (1985)] and not his paper on cheating which was
mistakingly cited.
> Table 1 also listed E. Dendy Sloan's affiliation as Colorado State
University when it is, in fact, the Colorado School of Mines.
We apologize both to the individuals and to our readers for the errors.





State University of New York at Buffalo
Buffalo, NY 14260

Classical equilibrium thermodynamics is unique among
the core courses in chemical engineering. It is un-
commonly pervasive, for it addresses some of the
deepest questions relating to the nature of the physical world
and it lurks in the background of all disciplines (indeed,
what but a departure from equilibrium drives transport, what
but an approach toward chemical equilibrium is kinetics?).
Yet it is also so plainly and tangibly applicable to real
systems that, with a few well-placed comments, a teacher
finds it quite unnecessary to apologize for any derivation, no
matter how long, for there is always a need to know to act as
a light at the end of the tunnel.
Most people either love or hate thermodynamics; it seems
to evoke such strong emotions that there is little room for a
middle ground. One sees people indifferent to (or mildly
interested in or irritated by) transport, kinetics, control or
design-but not so with thermo. And unlike other subjects,
it seems not to be learned per se, but rather to be acquired by
acclimation through repeated, deepening exposure in a se-
quence of courses that ostensibly cover the same material.
A teacher of thermodynamics makes a few inevitable ob-
servations. To wit: why is it that the student who professes
most strongly to have studied for the first hour exam (and, in
particular, claims to understand fully the difference between
functions of state and path-dependent quantities) proudly
recites the first law as U = AQ AW?
(Oh no!)
And why is it that at some time in every single semester
somebody uses the ideal gas law to estimate the density of
liquid water?
(NO! NO! NO!)
Actually, the purpose of these lines is not to belabor com-

Johannes M. Nitsche is an assistant professor
of chemical engineering at the State University
of New York at Buffalo. He received his BChE
and BMath degrees from the University of Min-
nnesota and his PhD in chemical engineering
from MIT (1989). His research interests are in
transport phenomena, thermodynamics, cataly-
sis with immobilized enzymes, protein and par-
ticulate separations, and applied mathematics.

mon experiences but rather to record my acquaintance with
two individuals who have profoundly affected the way in
which I teach undergraduate thermodynamics, and the ap-
plied subject that rests so heavily upon it, separations. The
first is a mysterious writer of urgent letters that always seem
to arrive just before class and make me drop whatever I was
"actually going to cover" in favor of working out his practi-
cal problem (which turns out to have considerable pedagogi-
cal value). Over time he has come to exude a real presence,
despite the fact that he has never actually been seen by any
student on or off campus. Rumor has it that he is quite
incompetent (hence the need for all the help) and drinks
copious amounts of organic liquids, apparently without ill
effect. His name is Elroy Hutch.
The second is far more capable than Elroy, but more
elusive. He is Virial Man, caped crusader against inaccura-
cies in physical property predictions.
Faster than a speeding fugacity co-
efficient! Able to leap whole phase
diagrams in a single bound! He
solves really hard thermo prob-
lems without a second's thought.
Unfortunately, his benevo-
lent duties frequently re-
quire his presence else-

Copyright ChE Division ofASEE 1994

Chemical Engineering Education

where, so he is rarely available.

I had the privilege of dining with Elroy on March 3, 1990,
and on that day he made a statement that puzzled me. He
said, "the internal energy of gases depends only upon tem-
perature." I corrected him by adding the qualification, ideal
gases, but he was quite insistent and dismissed my protesta-
tions. Our conversation then turned to other things, but I was
disturbed by his misconception, and slowly I began to real-
ize why he'd said what he said.
In most courses the ideal gas is introduced immediately
because of its key role as the simplest working fluid and a
realizable limiting case of real gas behavior. Textbooks ad-
dress all sorts of processes with ideal gases, which readily
present themselves, and the first law is easy to apply because
dU is indeed CvdT. Soon it's off to the Carnot cycle, en-
tropy, and the Maxwell relation leading to the identity

T l= T=,j P (1)

that finally allows one to ascertain the volumetric depen-
dence of internal energy for real gases. But by then all the
tough first-law problems with pistons and cylinders are for-
gotten, and they often go unrevisited because time is short
and one must move on to the Gibbs energy and phase equi-
libria and mixtures and Raoult's law. So students can easily
go on without being drilled in solving first-law problems
with real gases using equations of state, and their first im-
pulse is to write dU = CvdT always.
By next morning I had come to the conclusion that I would
have to change things. So I called Virial Man (who, thank-
fully, was available, albeit briefly for he soon had to be off to
do battle against the Redlich-Kwong Invaders in the North).
He thought for a moment and then responded with character-
istic brevity and insight: Why not give students the identity,
Eq. (1), at the start, promise them you will derive it later,
quickly discuss the reversible and irreversible, isothermal
and adiabatic processes with ideal gases (which they have
inevitably seen before), and then concentrate on real gases?
Virial Man suggested the following exercise.

- PROBLEM One mol of ethylene gas is confined
within an insulated, frictionless piston-and-cylinder assem-
bly at 300K and 60 bar by a suitable weight in vacuo (Figure
1). If half the weight is suddenly removed so that the gas
undergoes an irreversible adiabatic expansion, what will be
the gas temperature when it finally settles down to equilib-
rium again? Data: the ideal gas heat capacity of ethylene is
given bytl
Cpg(T)= A+BT+CT2 +DT3

A = 38.06 bar cm3/mol K
B = 1.566 bar cm3/mol K2
C = 8.348 x 10-4 bar cm3/mol K3
D = 1.755 x 10-7 bar cm3/mol K4
and its PVT behavior may be assumed to be described by
the Peng-Robinson[21 equation

RT aa(Tr) i Tr)=[I l-Tr/2 )
V-b V2+2bV-b2'

a = 0.45724 R2Tc2/Pc = 5.001 x 106 bar cm6/mol2
b = 0.07780 RT/Pc = 36.24 cm3/mol
K = 0.37464 + 1.54226( 0.2699202 = 0.5098*

Elroy's (ideal gas) solution Assuming the piston to have
negligible mass, the pressure has dropped by half in the final
equilibrium state. The initial and final molar volumes are
given by
RTi _RTf
Vi = -, Vf-
Pi Pf
Note that the final temperature is unknown in the second
equation. Assuming the heat capacity to be a constant, ap-
proximated by its value at 300K (Cv at 300 K = 354.3 bar
cm3/mol K), application of the first law gives


m m


.. 'J


S, .

Figure 1. Piston-and-cylinder assembly for carrying
out an irreversible adiabatic expansion.

* Critical constants and acentric factor T = 282.4K, P- = 50.4 bar,
o = 0.089, from Reid, et al.f

Summer 1994

in which Pf(Vf-V) represents the work done by the gas in lifting the
single weight remaining on the piston. It follows that

C y +R(Pf/ Pi) 2.
Tf- = Ti =271.5K
C, +R
Virial Man's solution The initial and final molar volumes are
given by

60 bar = Pi = RT aX( (2)
V,-b V2+2bVi-b2

30bar=Pf= RT a (Tf) (3) /
Vf-b V2+2bV -b2 (3)

Again, the final temperature, Tf, is unknown in Eq. (3).
Next, in applying the first law it will be necessary to ascertain the functional
dependence of the internal energy U upon temperature T and molar volume V. By
line integration from an arbitrary reference state at temperature To and effectively
infinite molar volume,

U(T,V)= U+ JC(T dT +[ +Vj (T,V )dV
To ~ T

= Uo+ C9 R dT + T P dV
= (A-R)T + T2 + -3 +T4
2 3 4
__ F ( V+Wl-V)b
+ -[a(Tr)-Tr (Tr)nV +---()b + cost.
2V2 ) + i V +(l+)b

Substitution into the first-law statement
U(Tf,Vf)- U(Ti,V,)= Q- W = 0- Pf(Vf -Vi)
gives the constraint

(A R)(T Ti)+ B(T2 Ti2+(T Ti3) + (Tf4 Ti4)

a [Trf ) -Tr ce (Tf)] fn Vf + (1 T2 )b a'(T, n Vi+ (- -i )b I
2+2bL r Vf+(l+ 2)b [ t( Tri )i + (l+ +2)bl

=-(30bar)(Vf Vi) (4)

Equations (2), (3), and (4) constitute three nonlinear equations in the three un-

knowns Vi, Vf, and Tf. (Actually, Eq.
2 can be solved first for Vi indepen-
dently of Eqs. 3 and 4.) Solution by
Newton's method (starting from Elroy's
values as initial guesses) leads to the
Vi= 210.1 cm3/mol
Vf = 367.2 cm3/mol
Tf= 251.1 K
Work must be done to separate real
molecules (which attract each other
under these conditions), and the addi-
tional energy to do this work comes at
the expense of a greater drop in tem-
perature than would be observed with
an ideal gas.
Examples where the temperature
drop (and molar volume, for that mat-
ter) are off by fifty percent or more do
wonders to convince students that the
ideal gas law really wouldn't cut it in
modeling supercritical extraction. If
students are furnished with a nonlinear
equation solver, they usually become
quite agreeable to solving such prob-
lems (although I find surprising their
initial reluctance to use the computer).

A Word About the Figures...
There are cases where the manuscript review process is a wholly rewarding experience, and this paper represents one of them, owing particularly to the
input of Professor Kenneth R. Jolls, who served as one of the referees. In addition to suggesting numerous improvements now incorporated in the text, he
kindly offered to make the figures with his unique expertise in thermodynamics and its graphical representation. This is embodied, in part, in his Equations
of State (EOS) software [see K.R. Jolls, "Understanding Thermodynamics Through Interactive Computer Graphics," Chem. Eng. Prog., 85, 64 (1989)]. It
is a pleasure to acknowledge Professor Jolls as the creator of Figures 2-5 as they appear here, far better than the author could have made them. They are, in
fact, quantitative representations of the various processes discussed based on the Peng-Robinson equation, and not mere qualitative sketches.

70 Chemical Engineering Education

cubic centimeters/g-mol
degrees Kelvin


P s=o

300.0 E
-- 25.1.1 .
245.9 TEM

Figure 2. Two reversible paths between the initial state (300K, 60 bar) and the final
state (251.1K, 30 bar). One path consists of a reversible adiabatic expansion
followed by an isochoric heating step. The other consists of an isochoric
cooling step followed by a reversible isothermal expansion.

Figure 3. Final condition of the ethylene assuming the existence of only vapor (which
turns out to be supersaturated vapor with molar volume 367.2 cm3/mol at 251.1 K,
indicated by the small square box) or both vapor and liquid (with respective
molar volumes 447.9 cm3/mol and 72.3 cm3/mol at 259.9 K).
Summer 1994

For thorough practice in applying the first
law and manipulating real gas properties, I
have found it to be highly beneficial for
students to calculate the line integral


between specified initial and final states by
various reversible paths (e.g., the two paths
in Figure 2). In the process, most students
come to appreciate the following facts:
1. For a real gas, a reversible adiabatic
expansion is governed by the differen-
tial equation

dTo(,T T _
dV av s Cv(T,V)

which generally must be solved numeri-
cally. The path PVt = constant is only a
very special case. (Supplying a Runge-
Kutta routine helps with the solution.)
Of course, AS = 0 for the reversible
adiabatic expansion marked in Figure 2,
but it is necessary to perform a calcula-
tion to determine the temperature 245.9K
at the start of the subsequent isochoric
heating step for this path.
2. For a reversible isothermal expansion,
Q is generally not equal to W but rather
is given by

V2 p
Q=Tf I dV
J lT v

After a while the profound truth is driven
home, by direct detailed calculation, that
IdQ/T is invariably independent of path for
reversible processes carried out with any
working fluid (not just ideal gases). The
concept of entropy becomes downright pal-
atable. Virial Man informs me that AS for
the irreversible expansion considered above
comes out to be 6.537 bar cm3/mol K (by
either reversible path marked with arrows
in Figure 2). Unfortunately, Elroy doesn't
believe in entropy and his remarks concern-
ing AS are quite unprintable.

The astute student will observe (and this
sort of thing has happened!) that the vapor

cubic centimeters/g-mol
degrees Kelvin

LU r0

[Elroy's letters] always seem to arrive just before class and make me drop whatever I was
S"actually going to cover" in favor of working out his practical problem (which
turns out to have considerable pedagogical value). Over time he has come
to exude a real presence, despite the fact that he has never
actually been seen by any student on or off campus.

Pressure of ethylene at the final tem-
perature in our example is lower than
the prescribed final pressure of 30
bar (or, equivalently, that the final
temperature is lower than the boiling
point of ethylene at 30 bar). This cir-
cumstance furnishes an excellent opportunity to discuss meta-
stable states (for the outcome of the expansion as predicted
above is, in fact, a supersaturated vapor), and the fact that
alternatives to a single phase can exist (see Figure 3).
In the preceding problem we really ought to allow for the
presence of two phases in equilibrium at the pressure Pf = 30
bar. I mentioned this to Elroy, but his mind must have
been on other things, for he responded only with the inexpli-
cable statement, "two pints toluene, no ice," before rush-
ing off. Predictably, the point was not overlooked by
Virial Man, and it is worth considering somewhat later
in the semester.

Continuation of Virial Man's solution Allowing for
the existence of both liquid and vapor, distinguished by C
and v subscripts, the molar volumes of the final coexisting
phases must satisfy

RTf at (Trf )
V3-b V2+2bVv-b2

RT aa(Trf)
30bar =Pf = RTf a2(Tf
V,-b V,+2bV,-b2

The condition of equality of chemical potential (molar Gibbs
energy) leads to the additional constraint

-RT n[V b]

a ()Tr)F V (+ I- 2)b e V,+ (1- )bii
a22 b VV +( 1+ )b V, + (1+V2)bl

+30bar(V -V,)=0 (7)

which is an algebraic statement of the Maxwell criterion.
(This criterion will be discussed further below.) Equations
(5) through (7) constitute three nonlinear equations in the
three unknowns Tf, V,, and Vt, and one finds
Tf = 259.9 K

V, = 447.9 cm3/mol
Ve = 72.3 cm3/mol
The first law enters in ascertaining how the ethylene is
distributed between liquid and vapor phases according to the
following equation for the fraction vapor q:

qU(Tf,V,)+ (1-q)U(Tf,V)- U(Ti,Vi)
=-30bar(qV + (1- q)V Vi) (8)

By direct computation,

U(Ti,Vi) = 1.92 x104 bar cm3 / mol
U(Tf,V,) = 2.05x 104 barcm3 /mol
U(Tf, V) = -4.06 x 104 bar cm3 / mol

based on the reference value constant = 0 (i.e., Uo = 0,
To = 0) in the formula for U(T,V). With these numbers, one
finds q = 0.88. Needless to say, had the original problem not
led to a final supersaturated vapor, the solution of Eq. (8)
would not satisfy the requirement 0 < q < 1.

The reason I tolerate Elroy's antics and excursions beyond
the realm of rationality is that he has rare moments of lucid-

Figure 4. Perturbation of an isotherm in a manner that
does not affect any measurable PVT properties. The
perturbation should not have any effect, but according to
the Maxwell equal-area construction, it changes the
calculated vapor pressure.
Chemical Engineering Education


260 K

ity in which he makes remarkably insightful observation
case in point is an incident that occurred in late Augus
1992 when Elroy woke me at 2:30 AM, pounding on
front door, and began a fit of unintelligible screaming at
top of his lungs that persisted for nearly four hours witl
interruption while I watched and wrung my hands.
blaring stopped only after he turned his head skyward,
lowed the words that I shall never forget, "Maxwell
reptile!!!" and then toppled over backwards, landing
a thud, an exhausted silent heap. When Elroy came
his mood was one of resignation. He withdrew a tatt
sketch from his pocket (reproduced here as Figure 4)
asked quietly, "What do I do with that?" I stared at
figure for several minutes, and then I saw what was t
bling Elroy so deeply.
According to standard practice, all thermodynamic fi
tions (heat capacity Cv, Helmholtz energy A, etc.) are
rived from the PVT equation of state together with ideal
heat capacities by well-established integration procedu
and the formulas obtained are applied throughout the pi
space. Thus, for instance, a liquid heat capacity at temp
ture T and molar volume Ve is computed from the form

Cv(T,V,)=C'(T)+T --(T,V)dV

The trouble with Eq. (9) is that it tacitly makes use of
equation of state in the unstable interval between the spine
points where it is devoid of significance. Adding a pertu
tion to the isotherms that is negligible outside the unst
region (Figure 4) should not affect the values of any mea
able thermodynamic properties, but according to Eq. ('
does. Similarly, in using Maxwell's equal-area construct
the calculated vapor pressure would be materially affe
by the perturbation indicated in Figure 4.

Figure 5. Nonisothermal path between liquid an
vapor states both at the same temperature T.

Summer 1994

s. A
st of
is a


These types of concerns upon which Elroy stumbled
were in fact enunciated many years ago in a short but
profound article by G.D. Kahl[31 which unfortunately has
gone almost unnoticed, being cited only three times since
its publication in contexts removed from engineering VLE
calculations. The conclusion to be drawn from Kahl's work
is that calculations of thermodynamic functions must in-
volve paths restricted to stable portions of the phase space.
In particular, liquid properties at subcritical temperatures
should be related to ideal gas properties not by isothermal
integration but rather by using nonisothermal paths that go
around the two-phase region (Figure 5). Recent work
by the author[41 has shown that such a nonisothermal for-
malism offers distinct practical advantages in modeling
phase equilibria. In particular, it furnishes an extra param-
eter for fitting vapor pressure data and enables the incorpo-
ration of liquid heat capacity data into algebraic represen-
tations of the free energy.

ires, From the pedagogical perspective, the usual statement
chase that all thermodynamic properties can be derived from (i)
era- the ideal gas heat capacity and (ii) an equation of state,
ila needs to be amended. One must also be in possession of
(iii) liquid heat capacity data at subcritical temperatures.
Students should be made suspicious of isothermal integra-
(9) tion through the unstable region and be exposed to alterna-
tives to this questionable procedure. They can derive con-
the siderable practice in the logical construction of
odal nonisothermal computational paths between given initial
rba- and final states if they are forbidden to tread between the
able spinodal points.
ion, The exercise considered here, spawned by Elroy's mis-
cted conception and brought to a satisfactory resolution with
Virial Man's assistance, shows that a simple-looking first-
law problem can teach a lot about the calculation of ther-
modynamic properties with equations of state. There is
value in revisiting a pithy example several times in a se-
mester from increasingly advanced perspectives (e.g., first
law, second law, phase equilibrium), because this approach
lends continuity and saves the time that would be spent in
setting up several unrelated problems from scratch. Having
friends to help (or hinder) you makes the teaching and
learning process fun.

1. Reid, R.C., J.M. Prausnitz, and B.E. Poling, The Proper-
ties of Gases and Liquids, 4th ed., McGraw-Hill, New
York, NY (1987)
2. Peng, D.-Y., and D.B. Robinson, "A New Two-Constant
Equation of State," Ind. Eng. Chem. Fundam., 15,59 (1976)
3. Kahl, G.D., "Generalization of the Maxwell Criterion for
van der Waals Equation," Phys. Rev., 155, 78 (1967)
4. Nitsche, J.M., "New Applications of Kahl's VLE Analysis
d to Engineering Phase Behavior Calculations," Fluid Phase
Equilibria, 78, 157 (1992) 0

Random Thoughts ...


North Carolina State University
Raleigh, NC 27695

Most questions asked in engineering classes follow one of
two models:
1."If a first-order reaction A B with specific reaction
rate 3.76 min' takes place in an ideal continuous stirred-
tank reactor, what volume is required to achieve a 75.0%
reactant conversion at steady state if the throughput rate
is 286 liters/s?"
2. "Do you have any questions?"
While these may be important questions to ask, they don't
exactly stimulate deep thought. "What's the volume?" has
only one possible correct answer, obtained by mechanically
substituting values into a formula. "Do you have any ques-
tions?" is even less productive: the leaden silence that usu-
ally follows makes it clear that the answer for most students
is always "No," whether or not they understand the material.
Questions lie at the heart of the learning process. A good
question raised during class or on a homework assignment
can provoke curiosity, stimulate thought, illustrate the true
meaning of lecture material, and trigger a discussion or
some other form of student activity that leads to new or
deeper understanding. Closed (single-answer) questions that
require only rote recitation or substitution don't do much
along these lines, and questions of the "Any questions?"
variety do almost nothing.
Following are some different things we can ask our stu-
dents to do which can get them thinking in ways that "Given
this, calculate that" never can.

Define a concept in your own words
Using terms a bright high school senior (a
chemical engineering sophomore, a physics major,
your grandmother) could understand, briefly
explain the concept of vapor pressure (viscosity,
heat transfer coefficient, ideal solution).'

'Warning: Don't ask your students to give a comprehensible
definition of something like rz or entropy or temperature or mass
unless you're sure you can do it.

Richard M. Felder is Hoechst Celanese Pro-
fessor of Chemical Engineering at North Caro-
lina State University. He received his BChE from
City College of CUNY and his PhD from
Princeton. He has presented courses on chemi-
cal engineering principles, reactor design, pro-
cess optimization, and effective teaching to vari-
ous American and foreign industries and institu-
tions. He is coauthor of the text Elementary
Principles of Chemical Processes (Wiley, 1986).

Explain familiar phenomena in
terms of course concepts

Why do Ifeel comfortable in 65 F still air, cool
when a 65 F wind is blowing, freezing in 65 F
water, and even colder when I step out of the water
unless the relative humidity is close to 100%?
A kettle containing boiling water is on a stove. If
you put your finger right next to the kettle but not
touching it, you'll be fine-but if you touch the
kettle for more than a fraction of a second you'll
burn yourself Why?

Predict system behavior before
calculating it

Without using your calculator, estimate the time it
will take for half of the methanol in the vessel to
drain out (for all the water in the kettle to boil off
for half of the reactant to be converted).
> What would you expect plots of CB vs. t to look
like if you ran the reactor at two different tem-
peratures? Don't do any calculations-just use
logic. Explain the shapes of your plots.
An openflask containing an equimolar mixture of
two miscible species is slowly heated. The first

Copyright ChE Division ofASEE 1994
Chemical Engineering Education

species has a normal boiling point of 75 C and
the second boils at 125C. You periodically
measure the temperature, T, and the height of the
liquid in the flask, h, until all of the liquid is gone.
Sketch plots ofT and h vs. time, labeling the
temperatures at which abrupt changes in system
behavior occur.2

Think about what you've calculated

Find three different ways to verify that the formula
we just derived is correct.
> Suppose we build and operate the piping system
(heat exchanger, absorption column, VLE still,
tubular reactor) exactly as specified, and lo and
behold, the throughput rate (heat duty, solvent
recovery, vapor phase equilibrium composition,
product yield) is not what we predicted. What are
at least ten possible reasons for the disparity ?3

What separation processes might work for a
mixture of benzene and acetone? Which one would
you be tempted to try first? Why?
What are possible safety (environmental, quality
control) problems we might encounter with the
process unit we just designed? You get double
credit for an answer that nobody else thinks of
The longest list gets a three-point bonus on the
next test. Once a list of problems has been
generated, you might follow up by asking the
students to prioritize the problems in terms of their
potential impact and to suggest ways to minimize
or eliminate them.

Formulate questions

What are three good questions about what we
covered today?
Make up and solve a nontrivial problem about
what we covered in class this week (about what we
covered in this class and what you covered in your
organic chemistry class this month). Memory and
plug-and-chug problems won't be worth much-
forfull credit, the problem should be both creative

'You will be amazed and depressed by how many of your
students-whether they're sophomores or seniors-say the level
remains constant until T=750and then the liquid boils.
3Be sure to provide feedback the first few times you ask this
critically important question, so that the students learn to think
about both assumptions they have made and possibilities for
human error.
Summer 1994

and challenging.
A problem on the next test will begin with the
sentence, "A first-order reaction A -- B with
specific reaction rate 3.76 min-' takes place in an
ideal continuous reactor." Generate a set of
questions that might follow. Your questions should
be both qualitative and quantitative, and should
involve every topic the test covers. I guarantee
that I will use some of the questions I get on the

I could go on, but you get the idea.
Coming up with good questions is only half the battle; the
other half is asking them in a way that has the greatest
positive impact on the students. I have not had much luck
with the usual approaches. If I ask the whole class a question
and wait for someone to volunteer an answer, the students
remain silent and nervously avoid eye contact with me until
one of them (usually the same one) pipes up with an answer.
On the other hand, if I call on individual students with
questions, I am likely to provoke more fear than thought. No
matter how kindly my manner and how many eloquent
speeches I make about the value of wrong answers, most
students consider being questioned in class as a setup for
them to look ignorant in public-and if the questions require
real thought, their fear may be justified.
I find that a better way to get the students thinking actively
in class is to ask a question, have the students work in groups
of two to four to generate answers, and then call on several
of the groups to share their results. I vary the procedure
occasionally by having the students formulate answers indi-
vidually, then work in pairs to reach consensus. For more
complex problems, I might then have pairs get together to
synthesize team-of-four solutions.
Another effective strategy is to put questions like those
listed above into homework assignments and pre-test study
guides, promising the students that some of the questions
will be included on the next test, and then include them. If
such questions only show up in class, many students tend to
discount them; however, if the questions also routinely ap-
pear in homework and on tests, the students take them seri-
ously. It's a good idea to provide feedback on their initial
efforts and give examples of good responses, since this is
likely to be a new game for most of them and so at first they
won't know exactly what you are after. After a while they'll
start to get it, and some of them may even turn out to be
better at it than you are. This is not a bad problem to have.4

4For more information on helping students develop creative
problem-solving abilities, see R.M. Felder, "On Creating Creative
Engineers," Eng. Ed., 77(4), 222 (1987) and "The Generic Quiz,"
Chem. Eng. Ed., 19(4), 176 (1985), and Chapter 5 of P.C. Wankat
and F.S. Oreovicz, Teaching Engineering, McGraw-Hill, New
York (1993).

[R essay



Kansas State University Manhattan, KS 66506-5102

In sharp contrast to the first two laws, the third law of
thermodynamics can be characterized by diverse ex-
pression,111 disputed descent, and questioned authority.[21
Since it was first advanced by Nernst13 in 1906 as the Heat
Theorem, its thermodynamic status has been controversial;
its usefulness, however is unquestioned.
This essay addresses the question of why the third law of
thermodynamics requires entropy changes to approach zero
as the absolute temperature approaches zero. The putative
view that the entropy is an intrinsic physical property that
measures disorder and therefore must be zero for a perfect
crystal has the advantage of providing a simple physical
picture. Unfortunately, this view is inconsistent since it
can be shown that liquids, vapors, and glasses also exhibit
zero entropy at zero absolute temperature. Here it is
shown that the third law should be understood in logical
rather than physical terms.
The Heat Theorem was first proposed as an empirical
generalization based on the temperature dependence of the
internal energy change, DU, and the Helmholtz free energy
change, DA, for chemical reactions involving condensed
phases. As the absolute temperature, T, approaches zero, DU
and DA by definition become equal, but the Heat Theorem
stated that dDU/dT and dDA/dT also approach zero. These
derivatives are DCv and -DS, respectively. The statement
that DCv equals zero would attract little attention today in
view of the abundance of experimental and theoretical evi-
dence showing that the heat capacities of condensed phases
approach zero as zero absolute temperature is approached.
Even today, however, the controversial and enigmatic aspect

of the Heat Theorem is the equivalent statement
lim AS= 0 (1)
In 1912 Nernst offered a proof that the unattainability
of zero absolute temperature was dictated by the second law
of thermodynamics and was able to show that Eq. (1) fol-
lows from the unattainability principle. The latter result
seems undisputed, but Nernst was unable to convince his
contemporaries of the thermodynamic grounding of the
unattainability principle.
Many years of low-temperature research have firmly estab-
lished the credibility of the unattainability principle, and as a
result it has been proposed as the third law of thermodynamics.
This proposal has the merit of having all three laws expressed
in phenomenological language and, of course, it leads to the
useful result stated in Eq. (1).
As a matter of convenience, it is possible to express AS for a
process under consideration in terms of entropies of formation
of participating species because in such a calculation there is a
cancellation of the entropies of the constituent elements. For
this reason, the entropy of an element may be assigned any
value. According to Eq. (1), at zero absolute temperature
the entropy changes for formation reactions will be zero and it
is convenient to set elemental entropies equal to zero as
recommended by Lewis and Randall.[41 This results in the
familiar statement that the entropy of every perfect crystal-
line substance can be taken zero at zero absolute temperature
and is, of course, the convention employed in the determina-
tion of "absolute" entropies.

Undoubtedly the most convincing confirmation of the Heat
Theorem involved the calculation of absolute entropies from
calorimetric measurements on pure substances which were
then used to calculate entropy changes for chemical reactions.
These calculated values were in agreement with entropy changes
determined from the temperature dependence of experimen-
tally measured equilibrium constants.
Later, it was shown through the use of quantum statistical

Copyright ChE Divsion ofASEE 1994

Chemical Engineering Education

Benjamin G. Kyle is Professor of Chemical
Engineering at Kansas State University, where
he has enjoyed over thirty years of teaching.
He holds a BS from the Georgia Institute of
Technology and a PhD from the University of
Florida. He has not outgrown an early fascina-
tion with thermodynamics and is interested in
practically all aspects of the subject. He is the
author of a thermodynamics textbook published
by Prentice-Hall.

mechanics that spectroscopic data could be used to calculate
absolute entropies in excellent agreement with those calcu-
lated from calorimetric data. Quantum statistical mechanics
also provides the microscopic interpretation of zero entropy
for a perfect crystal as well as quantitative corrections for
those few errant substances exhibiting small positive entropy
values at zero absolute temperature. The statement that the
lowest energy state of the crystal is nondegenerate is easily
visualized as a perfectly ordered crystal where only a single
arrangement of atoms, molecules, or ions on the crystal lattice
is possible, Thus, in terms of Boltzmann's famous equation
S = k Cn 0 (2)
it may be stated that
Q0 = 1 at T = 0
and thus, So = 0.
Exceptions to So equal to zero are explained in terms of
"frozen-in" disorder. For example, a linear molecule such as
carbon monoxide can take two possible orientations on a
lattice site, CO, or OC. Orientations on adjacent sites such as
COOC or OCCO represent a slightly higher energy state than
ordered orientations such as COCO and are therefore favored
at higher temperatures. While the tendency is for the crystal
to move toward the low-energy ordered state on cooling, the
rate at which molecular orientations proceed slows to a
standstill and a state of "frozen-in" disorder results at zero
absolute temperature. If the orientations of the CO molecule
were completely random, there would be 2N possible configu-
rations on a lattice of N sites (two possibilities per site).
Setting Qo = 2N in Eq. (2) leads to So = Rfn2, which is
also seen to be the entropy change on forming an equi-
molar binary mixture. The value of R n 2 is extremely close
to the observed difference between calorimetric and spectro-
scopic absolute entropies.
The vast majority of substances conform to So equal to zero
and can be visualized as forming crystals of perfect order
(Q, = 1). The few exceptions can be explained in terms of
"frozen-in" disorder in a manner similar to that described for
carbon monoxide. Here there is seen to be a close cor-
respondence between entropy and disorder in a spatial sense.
Unfortunately, there are other systems conforming to the Heat
Theorem that place a strain on this interpretation. We now
examine these systems.
Measurements of phase equilibrium data for pure substances
show that the slope of the solid-vapor coexistence curve for
many substances and the slope of the liquid-vapor coexist-
ence curves for 4H and 3He approach zero as zero absolute
temperature is approached.[51 From the Clapeyron equation,
dT Av
and the fact that Av is finite, it can be concluded that Eq. (1)
applies to these phase changes. Both helium isotopes remain
liquid under their own vapor pressure down to zero Kelvin
and both require a pressure considerably higher than their
Summer 1994

vapor pressures in order to form a solid phase. The appropriate
calculations showl51 that Eq. (1) also applies to the solid-liquid
phase transition. Thus, if the Lewis and Randall convention is
used, pure liquids and vapors also have zero entropies. While it
may be possible to argue that these systems are nondegenerate
in their lowest energy state, the simple picture of zero entropy
corresponding to perfect spatial order does not seem appropri-
ate, at least in a physical sense.
The interpretation is further strained when the behavior of
glasses in the low-temperature limit is considered. The Max-
well relationship

T= (4)
together with Eq. (1) leads to

lim =0 (5)
T-o0 aT)p
Thermal coefficients of expansion for many substances have
been measured at temperatures approaching absolute zero. As
expected, Eq. (5) is obeyed by crystalline solids, but one may
be surprised to learn that it is also obeyed by glasses.161 Here, a
microscopic physical interpretation hardly seems possible.
Systems comprised of liquids, vapors, and glasses strain to
the breaking point the putative association of zero entropy with
perfect spatial order. These are the systems that prompt us to
ask, "Is there a microscopic physical interpretation of the Heat
Theorem applicable to all systems?" One could argue that the
association of entropy with spatial order is naive and that S20 =
1 only means that the system is nondegenerate (only a single
quantum state is available to it). For example, both Fermi-
Dirac and Bose-Einstein gases have been shown to be
nondegenerate[71 and therefore have So = 0. In the case of
crystalline solids, 2o = 1 can be interpreted physically as
spatial order, but no much microscopic description of the gases
in physical terms is possible. Instead, 0 can only be seen as a
logical construct that allows a mathematical treatment of the
system. The answer to the question is, "No! Only an explana-
tion in logical terms is possible." This is yet another instance
of our inability to obtain a microscopic view of entropy in
anything other than logical terms.181
If there is no physical microscopic interpretation of the Heat
Theorem, then what is the basis for its existence? As will be
shown below, the answer is that Eq. (1) is dictated by the
logical structure of thermodynamics.

The absolute temperature scale is defined in terms of the
performance of a Carnot engine

T, IQ 11
-= -(6)
T2 1Q21
where IQ21 is the input heat at T2 and IQil is rejected heat at T1.
Instrumental in the derivation of Eq. (6) is a second-law state-

ment such as, "It is impossible to completely convert heat into
work in a cyclic process." Equation 6 is therefore subject to
this constraint and would not be valid for T1= 0 where IQ11
would be zero. Therefore, the logical structure of thermody-
namics does not permit zero absolute temperature, and since
the laws of thermodynamics are based on statements from the
physical world and have proven reliable in dealing with the
physical world, it may be stated that zero absolute tempera-
ture is unattainable. Thus, it is not necessary to propose the
unattainability principle as a third law of thermodynamics.
Equation (1) can be derived from the unattainability prin-
ciple[91 by considering the arbitrary process a P, which
could be a chemical or physical transformation or a change in
a thermodynamic property (e.g., intensity of magnetization).
The entropies of the system in these states are
S" = S + dT (7)
SP = So + dT
The mathematical formalism of thermodynamics allows
these equations to be written as if T = 0 were possible. But a
more rigorous approach that uses the limit as T approaches
zero yields the same result when the heat capacity takes the

S= aT (a > 0)
C= aT (b >(8)
For a reversible adiabatic process between states a and b
occurring near zero absolute temperature, we use Eq. (7) to

S +J" dT = S+J-dT (9)
o o
If the process began in state a at T' and ended in state b at
T" = 0, we would have
S S f= dT> 0 (10)
but because T"= 0 is not possible, the following holds
S0 0 (11)
Considering the reverse process that proceeds from T" to
T' = 0, we can, in the same manner, show that it is necessary
so-So > 0 (12)
These two inequalities can be satisfied only when
cP sa
0 U0
and it is seen that Eq. (1) follows from the unattainability
principle. Thus, Eq. (1) arises from the second law and is
needed to preserve the logical structure of thermodynamics; a
third law is therefore unnecessary.

Two types of arguments found in the literature should be
addressed: those that attempt to show that the attainment of
zero absolute temperature is not prohibited by the second law,
and those that attempt to show that existence of a reservoir at
zero absolute temperature does not threaten the second law.
Using a heat capacity described by Eq. (8) and applying the
mathematical formalism of thermodynamics down to and in-
cluding zero absolute temperature, it has been shown that this
temperature can be reached in a finite number of steps1101 or
that the work required to reduce a systemll 1 to this tempera-
ture is finite.' 21 As previously noted, the mathematical formal-
ism is such that the use of T = 0 instead of T -- 0 gives the
appearance of being permissible. A similar condition probably
obtains for these arguments which, despite their apparent co-
gency, are incomplete because the possibility that the exist-
ence of a reservoir at zero absolute temperature might pose a
threat to the second law was not examined.
Nernst's proof that the unattainability principle is required
by the second law was based on the argument that if a reservoir
at zero absolute temperature existed, it would be possible to
operate a Carnot engine using this reservoir to convert heat
taken in at a higher temperature completely into work. This is
essentially the argument presented here. The two most damag-
ing objections against this position were based on possible
operating difficulties associated with the Carot cycle.113-15]
The first objection calls into question the possibility of
carrying out an isothermal process at zero absolute tem-
perature because the effects of heat leaks and frictional heat
are much more pronounced at this extreme. This is an objec-
tion of degree rather than principle and should carry no
weight when it is recognized that the logical structure consti-
tuting thermodynamics rests on such idealizations as
reversibility, isothermality, and adiabaticity. As these ideal-
izations can never be realized in the physical world, it
seems pointless to argue that they would be more difficult to
achieve at low temperature.
The second objection points to the ambiguity associated
with the isothermal step in the Carnot cycle presumed to occur
at zero absolute temperature. Because no heat is rejected, this
step would be adiabatic as well as isothermal, but it would not
necessarily be isentropic for it can only be said that the entropy
change is 0/0. It has been argued that when a system attempt-
ing to follow a Carnot cycle reaches zero absolute tempera-
ture, the second law is not threatened because there is no
assurance that the system would take the isothermal path and
complete the cycle rather than take the adiabatic path and
return to a previous state. The emphasis here is misplaced!
Because a single violation would vitiate the second law, con-
cern should be directed to the possibility, no matter how small,
that the system would take the isothermal path. There is no
assurance that this would not occur, and therefore the
unattainability principle is needed.
Chemical Engineering Education

Both of these inoperability objections seem to demand a
premature reality check. I would argue that the Carnot en-
gine is simply a concept that is part of the logical, math-
ematical formalism of thermodynamics and it is rather the
final result of the argument which should be subjected to a
reality check. In this regard, it should be noted that the
observed conformance to Eq. (5) may be taken as proof that
the concept of a Carnot engine is viable in the limit as T
approaches zero. This is because the Maxwell relation, Eq.
(4), can be derived through the agency of a Carnot cycle as
was originally shown by Maxwell himself.1161

The purpose of this essay is to demonstrate that Eq. (1) can
be understood only in a logical sense, and to that end a
derivation showing its descent from the second law has been
presented. As this derivation is essentially an elaboration of
Nernst's original derivation which was never fully accepted,
it is reasonable to expect that it could suffer the same fate.
Nevertheless, whether Eq. (1) is regarded as deriving from
the second law, or whether it is regarded as an additional
statement required to save the second law, it is still possible
to see it as a logical requirement. At the very least, it could
be stated that Eq. (1) is necessary to define the limiting
entropy change, which we have seen would otherwise have
the indeterminate form 0/0. By reversing the argument pre-
sented here, it is easily seen that the unattainability principle
follows from Eq. (1).
Although Eq. (1) has now been given thermodynamic
justification, its exceptions seem uncomfortably numerous
for a thermodynamic relationship, and it is therefore appro-
priate to examine its applicability. This problem has been
addressed by Simon117] and resolved by the following state-
At absolute zero the entropy differences vanish between all
those states of a system between which a reversible transition is
possible in principle even at the lowest temperature.
Simon's statement is completely general. In regard to the
behavior of glasses the statement of Fowler and
Guggenheim[91 is more specific:
For any isothermal process involving only phases in internal
equilibrium or, alternatively, if any phase is in frozen
metastable equilibrium, provided the process does not disturb
this frozen equilibrium, lim AS = 0
Simon assigned unquestioned thermodynamic status to
Eq. (1) and pointed out that the restrictions made explicit in
his statement are implicitly made in applying any other
thermodynamic relationship. The question is not whether
Eq. (1) is valid, but whether the application of thermody-
namics to a particular system is valid. Valid thermodynamic
systems must exist in equilibrium states and thus be capable
of undergoing reversible processes. As Eq. (1) is applied
only under the most stringent conditions where "frozen-in"
Summer 1994

nonequilibrium states are not unexpected, it is natural that it
will not seem to possess the unexceptional status accorded to
the other laws and relations of thermodynamics. This is a
problem in the application of thermodynamics, however,
and should not call the validity of Eq. (1) into question.
Because of the widespread use of the Lewis and Randall
convention leading to the convenience of "absolute" entro-
pies, and because of the remarkable success in calculating
these values via the methods of quantum statistical mechan-
ics, we are tempted to regard entropy as an intrinsic property
of matter and thereby seek a physical microscopic interpre-
tation such as So = 0 for perfect spatial order. But we
have seen for the case of liquids, gases, and glasses, that
this is not a fruitful approach.
Equation (1) is the most general statement and has been
shown to be simply a necessary logical statement. This sug-
gests the view that entropy is merely a defined state function
embedded in the logical-mathematical structure of thermo-
dynamics. Thus, it seems appropriate that quantum statisti-
cal mechanics yields a representation of entropy in logical
rather than physical terms. Because classical thermodynam-
ics neither provides nor requires physical visualization of its
functions, entropy is no less useful for want of a microscopic
physical interpretation. While this view of entropy does not
provide the insight available through a physical microscopic
interpretation, it is at least free of contradictions.

1. For a sampling of expressions, see E.M. Loebl, J. Chem. Ed.,
37, 361 (1960)
2. For extreme positions, see E.D. Eastman, Chem. Rev., 18,
257 (1936)
3. All of Nernst's work in this area is covered in W. Nernst,
The New Heat Theorem, Dutton, New York, NY (1926)
4. Lewis, G.N., and M. Randall, Thermodynamics and the Free
Energy of Chemical Substances, Chap. 31, McGraw-Hill,
New York, NY (1923)
5. Beattie, J.A., and I. Oppenheim, Principles of Thermody-
namics, Chap. 11, Elsevier, Amsterdam, Holland (1979)
6. White, G.K., Cryogenics, 4, 2 (1964)
7. Wilson, A.H., Thermodynamics and Statistical Mechanics,
Chap. 6, Cambridge University Press, Cambridge, England
8. Kyle, B.G., Chem. Eng. Ed., 23(4), 250 (1989)
9. Fowler, R., and E.A. Guggenhein, Statistical Thermody-
namics, Chap. 5, pg. 224, Cambridge University Press, Cam-
bridge, England (1956)
10. Simon, F.E., Low Temperature Physics, Chap. 1, Academic
Press, London, England (1952)
11. The heat capacity of the system was assumed to follow Eq.
12. See reference 1
13. Epstein, P.S., Textbook of Thermodynamics, Chap. 15, Wiley,
New York, NY (1937)
14. Pippard, A.B., The Elements of Classical Thermodynamics,
Chap. 5, Cambridge University Press, Cambridge, England
15. Boas, M.L.,Am. J. Phys., 28, 675 (1960)
16. Nash, L.K.,J. Chem. Ed., 41, 368 (1964)
17. Simon, F.E., Physica, 10, 1089 (1937) O

S1 class and home problems

The object of this column is to enhance our readers' collection of interesting and novel problems in
chemical engineering. Problems of the type that can be used to motivate the student by presenting a
particular principle in class, or in a new light, or that can be assigned as a novel home problem, are
requested, as well as those that are more traditional in nature and which elucidate difficult concepts. Please
submit them to Professors James O. Wilkes and Mark A. Burns, Chemical Engineering Department, Univer-
sity of Michigan, Ann Arbor, Ml 48109-2136.




Southern Alberta Institute of Technology
Calgary, Alberta, Canada T2M OL4

Everyday common experiences help us understand
the fundamentals of nature and how things func
tion. We all tend to relate our new knowledge to
what we already know and to make connections that
create a bridge between the two. When these bridges are
sound, not only do we understand the new information
better and faster, but we also retain the details in our
long-term memory.
The following are some examples I have used in my
quest to get through to the students the concept of heat
capacity and heat transfer. Since students are familiar
with these events in their everyday life, they tend to be
more interested in the relationship between the new con-
cepts being presented to them and their own experiences.
Quite often, this generates classroom discussion, another
raison d'etre to learn and retain the information.

Copyright ChE Division ofASEE 1994


1. We often hear mothers talk about their babies at length
(what mother doesn't?), and one frequent comment they
make is that babies must be well wrapped up. Is there a
good reason for this? If there is, why would babies lose
more heat compared with older children and adults?
2. Why should there be a minimum amount of wood to
light up a camp fire and sustain it?
3. Why is fire-walking possible on a red hot bed of coals
which may have a temperature of around 10000C? What
limitations can you think of to prevent severe burning?
4. Why do you not burn your hand inside an oven at
300'C, but bur it on a metal tray taken from the same
5. Why don't you bur your mouth trying to sample a hot
jam tart or slice of pizza straight from the oven until
you bite into the portion containing jam or sauce?
6. Oceanic climate of coastal areas and of islands tends to
be milder than it would otherwise be. Why does the
nearby ocean exert a moderating influence on the land's
7. Defending soldiers of castles in the middle ages used to
pour down boiling oil on the attacking enemy soldiers.
Why did the defenders go to all the trouble and expense

Chemical Engineering Education

A. Riza Konak received his BSc and PhD de-
grees in chemical engineering from the University
of Birmingham (England). He started his career
as assistant professor, and then spent fifteen years
in industry, mostly in applied research and devel-
opment and engineering with a major oil and gas
company, before returning to academia. He cur-
rently teaches unit operations, process design,
simulation, and control.

of using oil, especially when the heat capacity of oil is
less than half of that of water? You may use the follow-
ing data for illustration:


Heat capacity

Boiling Point


8. If you want to drink a very hot cup of coffee in a hurry,
do you pour the cold milk into the coffee first and then
wait a while, or do you wait first and then pour in the
milk? Explain.
9. A Chinese restaurant offers noodles which vary in di-
ameter from about 1 mm to 8 mm. Which size should a
Westerner choose if he is in a hurry during the lunch
hour and wants to avoid a burned tongue? Assume that
the food is already cooked and ready to eat.
10. Give two reasons why an increase in temperature causes
a worldwide rise in sea levels.
11. In the winter, why does an outdoor metal door handle
feel much colder than a wooden one?
12. Why is it desirable to paint steam and hot-water pipes
with aluminum paint?
13. A hen's egg of mass 50 grams requires 5 minutes to
hard boil. How long will it take to hard boil an ostrich's
egg of mass 3 kg? State your assumptions.
14. Someone recommends a cold-water diet to lose weight.
You are asked to drink ice cold water at 0C to shed
2000 calories (8.4 kJ) per day. Can you do it?
15. Why is it easy to burn toast in a toaster or oven?
16. Explain why many swimming pools are in the hot sun
all day but never get really warm. What can you sug-
gest to overcome this?
17. What would be the temperature at the bottom of a 50-m
deep freshwater lake in Canada in the winter and the


:i A baby has a larger surface area per unit mass com-
pared with adults. Since heat loss is directly propor-
tional to the area (everything else being equal, such as
body and room temperatures) the heat loss by babies is
greater and needs to be reduced by extra layers of
clothing. Incidentally, thin layers of clothing are more
effective than one thick layer since the air trapped
between the layers acts as an insulator due to poor
thermal conductivity of gases.
SThis situation is similar to that of the heat loss by

babies presented above. If the heat generated by burn-
ing wood cannot compensate for the heat lost from the
surface of the pile, then the fire will extinguish itself.
Therefore, there must be sufficient wood in the fire to
sustain the burning and to minimize the surface area of
the pile through which heat is lost. Of course, one
needs to ensure that the fire is not suffocated by a lack
of oxygen (air) as the wood pile is stacked up to reduce
its surface area per unit mass.
There are three factors to consider here:
a) In the general heat equation, Q = mCpAT, although
the temperature difference, AT, between the hot char-
coal and the surface of the feet is very large, mCp is
very small as the charcoal is very light in mass and its
specific heat capacity is about 1.01 kJ/kg.-C.
b) In the heat conduction equation, q = kA(dT/dx), the
temperature gradient is very high, but the points of
contact A between the feet and charcoal is small and so
is the conductivity, k, due to the formation of steam
under the feet; steam as a gas is a poor conductor.
c) The time of contact is important since q times the
contact time is the amount of heat transferred to the
feet. Although 1 or 2 seconds may not be long enough
to bur the feet, anything longer may cause severe
In the fire-walking scenario, the people taking part
are usually "hyped" up by pep talks. They tend to
sweat-and they also tend to walk on the wet evening
grass with bare feet. These factors may help create that
insulating layer of steam under the feet. Again, this
steam will only be there temporarily and may disappear
after the first few steps.

There are two important reasons. First, the mass of air
surrounding the hand is very small (the density of air at
3000C and 1 atm is 0.615 kg/m3), and hence its heat
content is small despite the high oven temperature.
Second, the air is a poor conductor and the relatively
still hot air will not burn.
The metal oven tray, on the other hand, has a much
larger mass and hence contains much more heat than
the air. In addition, the metals are better conductors of
heat. Therefore, a good conductor coupled to a large
reservoir of heat will relay large quantities of heat at a
faster rate than blood can take it away from the fingers.

Jam and sauce contain water, and water has the highest
specific heat among the common substances. There-
fore, the jam and sauce portions have a higher heat
content than the mostly bread portions despite their
being at the same temperature. (Now that you know the

Summer 1994

theory as well as having had the experience, you have
no excuse for burning your tongue!)
Water has a higher heat capacity. For the same tem-
perature rise, water will hold more heat than land.
When weather gets cold, water gives up heat, dropping
to a lower temperature. Land gives up the same amount
of heat in dropping to a lower temperature, however-
this results in the ocean being warmer than the neigh-
boring land in cold weather and colder than the neigh-
boring land in warm weather. The ocean, when near
by, therefore exerts a moderating influence on the
land's temperature. Land that is far from the ocean
does not enjoy the same advantage.
Taking a basis of 1 m3 of oil and 1 m3 of water, we can
estimate the heat content of each as
Q(water) = 958 kg x 4.2 kJ/kg.oC x (100-20)C = 321888kJ
Q(oil) = 800 kg x 2.0 kJ/kg.oC x (300-20) C = 448000 kJ
assuming a skin temperature of 200C. Hence, the ratio
Q(oil) to Q(water) is 1.4. This means oil has 40% more
burning power. (Those clever soldiers knew what they
were doing!)
Newton's law of cooling states that the rate of heat loss
is proportional to the temperature difference between
the hot coffee and the surrounding air. Therefore it
may be desirable to let the hot coffee cool and then add
milk for additional cooling.
There is something, however, to be said about the
option of adding milk first since this increases the
volume of liquid and hence the surface area through
which heat escapes (as well as the additional cooling
obtained from the milk).
SThe thin noodles will cool quicker because of their
larger surface area per unit mass; this will help when
eating individual noodles. On the other hand, for a
given pile of noodles, thin ones have smaller spaces
between them (small porosity), cutting off the cooling
ambient air while on the plate.
SRising temperature will melt some of the ice caps in
the poles and the sea water will thermally expand. The
thermal expansion of the land may be considered neg-
SMetals are much better conductors of heat than
wood and therefore conduct heat away from hand more
rapidly. For example, the thermal conductivity of
carbon steel is 43 W/m C and that of maple or oak is
0.17 W/m oC. This means that carbon steel will con-
duct heat at a rate 250 times faster than wood.
SThis is because of the principle that a poor absorber of

radiative heat is also a poor emitter of the same. A
brightly painted pipe radiates heat at the minimum
Assume the eggs are spherical with a radius r and are
similar chemically. The mass of each egg is propor-
tional to r3 and the surface area through which the heat
transfer takes place to r2. The rate of heat transfer by
conduction is proportional to the temperature gradient
inside the eggs, which itself is proportional to 1/r.
Therefore the cooking time is proportional to r2, or to
m(2/3) where m is the mass. If follows then that the time
to cook the larger egg is
(5 min)[(3000/50)(2/3)] = 76.6 minutes
(You have to get up early to prepare your breakfast if
you want to feast on one of these delicacies!)
The same result may be obtained by using the ana-
lytical solution to the unsteady-state heat conduction
equation for one dimension.
Water is heated from 0C to the body temperature of
370C and therefore requires
4.2 kJ/kg. C x (37-0) C = 155.4 J
of energy for each kilogram. Using up 8400 J body
energy then requires 54 kg of ice-cold water. (Good

As the toast starts to get brown it absorbs more of the
radiant heat energy falling on it and rapidly burs.
Next time your spouse burns your toast, be kind to him
or her. (Also see question 12.)

As soon as the top layer of water gets hot, it evapo-
rates and cools the remaining water. A very thin layer
of a special liquid spread over the water surface will
prevent evaporation. This liquid should have a high
heat capacity and high latent heat of evaporation.
Since the density of water is highest at 40C, the bottom
of the lake will remain at 4C irrespective of seasons.
In winter the surface water becomes colder and more
dense than the water beneath it and is replaced by the
warmer water. This continues until all the deep water
is at the temperature of maximum density (i.e., 4C).
Further cooling of the surface water forms ice, and
the water just below the ice will be at 0C. The water
at the bottom of the lake remains at 4C. It would take
many years for the bottom water to be cooled to 0C
by conduction through 50 m of water since the con-
duction process is very slow. When spring arrives, the
ice melts and the surface water warms up. The bottom
water remains undisturbed, however, being at the maxi-
mum density. 0

Chemical Engineering Education

A Second Look at...


Oregon State University
Corvallis, OR 97331-2702

On page 206 of the fall 1993 issue of CEE, I posed a little
thermo problem and asked readers to respond. The prob-
lem asked what happens to the pressure when a batch of
ideal gas is raised isothermally and reversibly from Z, to Z2. I
arrived at my answer with four equations:

AU= Q- W
AU + AE + AEk = Q- Wsh Wpv

Y+AEp +^ k= fpdV

ending up with

In P = (const.)Az (4)
which tells us that p increases with z!! I asked what, if anything,
was wrong with this solution.
I have received thirty-eight responses-from textbook writers,
from professors, from students, and even some from mechanical
engineers. The remarkable feature of these solutions is that they are
so distinctly different, one from the other. Here are examples of
what the correspondents say:
> Equations 1 and 2 don't apply when Ep is involved-so I
started the analysis incorrectly.
> Equations 1 and 2 are okay-my error comes in one of three
places in Eq. 3. Some say that I should have put Q 0; others say
that I should have put Wsh 0; still others say that I should have
used A(pV), not JpdV.
The problem is unsolvable as stated because I didn't say
anything about the surroundings. Of course, if you assume that
in(p2 /Pl) o Azfor the surroundings, that's what you'll find for the
I The assumptions I made are contradictory.
> The sign on g is wrong; just use -g and all works out well.
1 The pressure gradient cannot be obtained from thermo alone.
You must use a force or momentum balance.
Just use transport analysis, forget thermo, and the answer pops
O Since the system is in equilibrium, you must use the second
law with the Gibbs free energy concept to solve the problem.
I One responder said I was correct for the problem as stated.

Now, who is right?
When I read the first solution above I was swayed; when I read
the second I got confused; and after I read the third, I was lost.
Because of space limitations I won't present the solutions here.
But I will prepare copies of twenty-one solutions and will send them
to each of the thirty-eight responders. If other CEE readers would
like to see these solutions, send me your names and addresses and I
will also mail them to you.
The following is a list of the brave souls who dared to challenge
my curious conclusion.

J.M. Smith
UC Davis
C.T. Lira
Michigan State University
A. Patel
A.R. Konak
S. Alberta Inst. of Technology
M.A. Mathews
University of Wyoming
J. Hong
UC Irvine
J.D. Lindsay
Institute of Paper Science and
S.S. Iyengar
University of Florida
Hall and Eubank
Texas A & M University
O. Talu
Cleveland State University
J.O. Wilkes
University of Michigan
A.L. Meyers
University of Pennsylvania
D.L. Schruben
Texas A & I University
N.V. Suryanarayana
Michigan Tech. Institute
D.M. Himmelblau
University of Texas
C. Crowe
McMaster University
U. Mann
Texas Tech University
A.G. Fredrickson
University of Minnesota
R. Pal
University of Waterloo

L.L. Lee
University of Oklahoma
D. Hart, retiree
Birmingham, Alabama
M.V. Sussman
Tufts University
M. Koretsky
Oregon State University
R.B. Bird
University of Wisconsin
J.P. O'Connell
University of Florida
E. Miller
U. Simon Bolivar, Venezuela
C.M. Sliepcevich
University of Oklahoma
K.M. Khandare
West Virginia University
F.E. Haskin
University of New Mexico
A.G. and C.J. Williamson
Canterbury, New Zealand
A. Rakow
Colorado State University
Noel de Nevers
University of Utah
M. Fehr
Uberlandia, Brazil
Loureiro and Macedo
Porto, Brazil
J.C.R. Turner
Exeter, England
S.I. Sander
University of Delaware
Vincenzo Brandani
University ofL'Aquila, Italy
Stephano Brandani
University of Naples, Italy

Summer 1994 183

r B0 classroom




University of Waterloo
Waterloo, Ontario, Canada N2L 3G1

In his comprehensive, handwritten source book
on reactor design, The Chemical Reactor
Omnibook, Levenspiel[tl examines the range of
practical reaction rates. Astonishingly, it is about a
billion-fold (i.e., 109), extending from the slowest
biochemical reactions in waste water to the most
rapid ones in rocket engines.
Our sense of how rapidly reactions occur is intui-
tive. Without needing numbers, we recognize that
algae grow slowly and that fires bur rapidly. In-
deed, anyone who has worked with a particular
reaction in a chemical plant can usually state whether
that reaction occurs quickly, slowly, or something
in between. A list of such terms, describing the
speed of a number of familiar batch processes, is
suggested in Table 1. In the table, I have arbitrarily
assigned the rate of quick-setting epoxy as "moder-
ate." Related adjectives have been assigned to de-
scribe the speeds of a number of common reactions
that are easily recognized as faster or slower. As a
result, their meanings have no particular currency
beyond the context of this article.
It seems paradoxical that once a reaction rate has
been measured and modeled with a power law, the
resulting kinetic rate constant often tends to con-
ceal how fast the reaction occurs. Although sensing
the speed of a reaction by observing it may be
intuitive, deducing that speed from a rate constant
is not. Indeed, most students of chemical kinetics
cannot easily interpret a rate constant apart from
formally integrating the rate equation and examin-
ing the time taken for the limiting reactant to ap-
proach either zero or its equilibrium concentration.

Intuitive Classification of Reaction Speeds

half an hour
a few minutes
half a minute
a few seconds


Example ofBatch Process

Growth of new annulus on a tree trunk
Fermentation of cabbage to sauerkraut
Human digestion of a meal
Baking a medium-sized potato
Setting of quick epoxy
Dissolving a seltzer tablet in water
Burning a sheet of newspaper
Gasoline combustion in a car cylinder (one cycle)
Explosion of a cap in a toy pistol

adjectives Describing
Reaction Rate
extremely slow
very slow
moderately slow
moderately rapid
very rapid
extremely rapid

To a student conducting calculations with a rate constant, the time-
honored exhortation to "consider the reasonableness of your figures"
sounds ludicrous. Nor do standard textbooks on the subject come to the
rescue. Reluctantly, we must conclude that reaction kinetics tends to be
one of the least intuitive of scientific subjects; its most basic parameter
comes in a wide variety of units, often involving unusual exponents, and
its magnitude is usually difficult to grasp. To address this predicament, I
always include the following brief topic in my courses in chemical
reaction engineering.
To begin, let us consider only constant-volume, power-law kinetic
rate expressions-that is to say, only those rate expressions that exhibit
an "order" of reaction with respect to one or more concentrations. We
start by developing an intuitive interpretation of the speed of a first-
order rate constant and then relate first-order rate constants to rate
constants of other orders of reaction. Finally, we examine how to
estimate the speed of heterogeneous reaction rates from their often
peculiar-looking rate constants.

Copyright ChE Division ofASEE 1994

Chemical Engineering Education

If we consider the first-order rate expression for a reaction
dCA kCA (
which can be rearranged into the form
k- dCA (2)
CAdt At
The final quotient of Eq. (2) may be interpreted to mean
that the fractional change in the concentration in a given
time is equal to the rate constant of a first-order rate of
reaction. Thus, for a first-order constant of 0.1 min-1, the
reaction initially consumes reactant at a rate of one-tenth of
the concentration per minute.
Because the concentration driving force falls as the reac-
tant disappears, no reaction (except one of zero-order) goes
fully to completion. The time at which a reaction is deemed
"complete" is therefore arbitrary. Since the notion of comple-
tion of reaction still has intuitive appeal, let us consider a
reaction when it is "half-complete"-that is, when its con-
centration has fallen to half of its original value. The rate at
this point still reflects its initial value for practical cases, as
is discussed below. The "half-life" (the time required for the
reaction to reach 50% conversion) is related to the reaction
rate constant, the order, and initial concentration, as com-
monly found in textbooks on reaction kinetics. The half-
lives in Table 1 are obtained intuitively by estimating the
time at which they are approximately half complete.
For the first-order rate constant above, its half-life is
tl/2 = (In 2)/0.1, or about 7 min. Because we are interested in
just an approximate value of the half-life, we can simply
take the reciprocal of the first-order rate constant. Thus, we
obtain ty/ = 1/0.1, or 10 min. This result indicates that the
speed of this reaction is similar to that of fast-setting epoxy.
A first-order rate constant, the numerical value of which is
greater than unity, say 42 h-1, is not at first glance easy to
interpret as a percentage change in concentration per hour.
To consider it as 4200% change per hour obscures its mes-
sage; what, after all, is the meaning of a percentage change

Our sense of how rapidly reactions
occur is intuitive. Without needing numbers,
we recognize that algae grow slowly and that fires
burn rapidly. Indeed, anyone who has worked
with a particular reaction in a chemical plant
can usually state whether that reaction occurs
quickly, slowly, or something in between.

greater than 100? But let us choose a smaller time unit with
which to express the rate constant as a value less than unity,
i.e., 0.012 s-'. Simply interpreted, this constant suggests that
the initial rate is rapid-1.2% of the concentration being
converted each second. The reciprocal of the rate constant
provides a half-life of the order of a minute, so we may
regard it as a moderately rapid reaction, according to the
terminology of Table 1.
Before we leave the above examples, it is worth emphasiz-
ing the well-known point that a first-order rate is unique in
being independent of its starting concentration. All other
orders of reaction require such information, as will become
apparent in the following paragraphs.

If we consider the nth-order rate expression for a reaction
A B,

-dCA kC
A kC (3)

we can rearrange it into the form

k1 -dCA -ACA/CA (4)
(CA)(c-)(dt) (At)(C -I)
The final quotient may be interpreted to mean that the
fractional change in the concentration in a given time
(-DCA/CA)/(Dt), if divided by C- ', is equal to the rate
constant of an nth-order reaction. This Cn-' needs further
interpretation. For purposes of understanding the initial rate
of reaction, CA in Cn-1 should be replaced by some initial
value of CO. Then
= -ACA/CA k(
k, ~ n-1 n-I (5)
(At)(c)n- (C)n-
where kl is the "equivalent" first-order reaction rate con-
stant. Thus

ki = k(CA)n (6)

can be used to recast the nth-order rate constant as an ap-
proximately "equivalent" first-order rate constant. Further-
more, the reciprocal of k, may be interpreted as the approxi-
mate half-life of the reaction

Summer 1994

Bob Hudglns holds degrees in chemical engi-
neering from the University of Toronto and
Princeton University. He teaches courses in
stoichiometry, unit operations ,and reaction en-
gineering, and studies the periodic operation of
catalytic reactors.

tl/2 (7)

A rigorous expression for the half-life is obtained by set-
ting C/C = 0.5 in the integrated reaction rate expression for
an nth-order reaction

to form

C (/Co)n -1
t= ;
k(n 1)Co-

(0.5)'-" 1
tl/2 k -
k(n 1)CO"

for n l 1

for n 1

For a second-order reaction, Eq. (7) and Eq. (9) are
identities. For the range of practical reaction orders (i.e.,
-1 < n < 3), the half-life approximation of Eq. (7) is of the
same order of magnitude as that of the rigorous half-life
given in Eq. (9), so it is easier for a quick appraisal to use the
Let us now consider the approximate speed of the iodine-
catalyzed bromination of xylene, the rate constant for which
is 0.1 L/2/(moll/2)(min), since the reaction is 3/2-order
in bromine concentration. The initial concentration of bro-
mine was 0.3335 mol/L.[2] An approximate value of the
"equivalent" first-order reaction rate constant under these
conditions is

n-1 0.1 L2 ( mol )/2
k, =k(CA) (mo- min 0.3335 = 0.058 min-'
moll/2 minl < L

Thus, its half-life is approximately a quarter of an hour. A
first-order rate constant of this value indicates a reaction of
moderate speed, according to the examples in Table 1.
Let us now consider the power-law rate expression for a
bimolecular reaction A + B iE C, with an overall power of
2.5, and a rate law
-dCA ,k*C .5
-=k CACB
for which the rate constant k is 0.15 dm4.5/(moll.5min).
The initial concentrations, Co and Co, are 0.5 and 0.04
mol/dm3, respectively. To estimate the speed of this reaction
from its rate constant, we can rearrange it into the form of an
"equivalent" first-order reaction as follows:

k*= -dCA
CA (CAC5)dt

and thus the initial rate is approximately

-dCA = k* C fC") or k,
CAdt A B
Thus, k, is calculated to be 0.015 min-1. The reciprocal of k,

indicates that the half-life of this reaction is approximately
an hour, so it must be judged a moderately slow reaction by
the terminology of Table 1.

The speed of a heterogeneous reaction rate is often hard to
judge because of the units accompanying the rate constant.
As an example, let us consider the dehydrogenation of
ethylbenzene. Wenner and Dybdal[3] provide an analytical
expression for the rate constant of the forward reaction,
which is first-order with respect to ethylbenzene partial pres-
sure. At temperature To = 898 K, the rate constant assumes a
value of

1.68 (10- )kmol
s(kPa)kg cat.
which, clothed in these units, may not be instantly recogniz-
able as a first-order rate constant. For this reaction, the
catalyst bulk density is 1440 kg/m3 of empty reactor. Thus,
the equivalent homogeneous rate constant is found by multi-
plying these two quantities together to obtain

2.423 (10-4)kmol
khmog s(kPa)m3 empty bed

This form is still hard to recognize as a first-order rate
constant unless it is further simplified by means of the
ideal gas law. By multiplying khomog by the gas constant,
Rg = 8.309 kPa-m3/(kmol-K), and the feed temperature, To,
we obtain the product

khomog = khomogRgTo
which equals 1.81 s-1 at 898 K. In this form, the rate constant
is clearly recognizable as first-order; thus we can interpret
its half-life to be of the order of 1/1.81 s, or about half a
second. According to Table 1, the initial dehydrogenation of
ethylbenzene would be very rapid. Not surprisingly, a typi-
cal empty-tube space-time for a tubular flow reactor under
these conditions is of the order of seconds.[41
The above approach is one I use to show how to interpret
the speed of rate constants of power-law reactions. Its chief
benefit is to enable students to estimate whether their reactor
calculations are reasonable.

1. Levenspiel, O., The Chemical Reactor Omnibook, OSU Book
Stores, Inc., Corvallis, OR (1989)
2. Neyens, A., in Cinetique Chimique Appliquge, Jungers, J.C.,
et al., editions Technip, Paris, France, 88 (1958)
3. Wenner, R.R., and F.C. Dybdal, Chem. Eng. Progr., 44, 275
4. Smith, J.M., Chemical Engineering Kinetics, 3rd ed.,
McGraw-Hill, New York, NY, Example 13-3 (1981) 0

Chemical Engineering Education

BM book review

by Stephen L. Rosen
Wiley Interscience, 420 pages (1993)

Reviewed by
Kyu-Yong Choi
University of Maryland

This book is a revised version of the book with the same
title that was published in 1981. The major target audience
would be senior-level undergraduate chemical engineering
students and industrial engineers who do not have prior
background in polymers but who do have fundamental chemi-
cal engineering knowledge.
One visible change in the revised edition is that many
exercise problems have been added to each chapter. With
fully worked-out example problems, the addition of these
exercise problems makes the book attractive as a textbook.
While there are several undergraduate-level textbooks on
polymer science and engineering, this one stands out be-
cause of these examples and exercise problems. Undergradu-
ate students, in general, like textbooks with many examples.
The style of the author's writing is more like that of a
classroom lecture. Many interesting and humorous examples
and analogies are sprinkled throughout to help readers un-
derstand difficult basic concepts. I found the reading of this
book very entertaining. The materials are presented in a very
concise manner and important physical and chemical con-
cepts are presented clearly. For senior-level chemical engi-
neering students or practicing engineers with appropriate
knowledge in reaction kinetics, thermodynamics, and math-
ematics, there should be no problem in studying this book
with very little help.
The book consists of our parts: Polymer Fundamentals,
Polymer Synthesis, Polymer Properties, Polymer Technol-
ogy. The first part comprises seven chapters that cover types
of polymers, bonding in polymers, stereoisomerism, poly-
mer morphology, characterization of molecular weight, poly-
mer solubility and solutions, and transitions in polymers. It
should be noted that conceptual understanding of dif-
ficult concepts has been stressed throughout the book, and
the manner in which the subject materials are presented is
excellent. For example, in Chapter 8 ("Polymer Solu-
bility and Solutions"), the concepts of Flory-Huggins
model, solubility parameter, and its physical significance are
explained in easy-to-understand language with minimal use
of mathematical equations. This approach has an advantage
in that students are not overwhelmed by complex math-
ematical derivations.
Summer 1994

In the second part ("Polymer Synthesis"), both step growth
and chain growth polymerization kinetics are discussed. The
depth of the theoretical discussion of these topics is ad-
equate, and a few numerical examples are also presented. In
the chain growth polymerization part, heterogeneous poly-
merization systems including emulsion polymerization and
transition metal catalyzed olefin polymerization are discussed
in some detail. In particular, olefin polymerization kinetics,
which in many other textbooks are not well covered, are
presented with some recent literature on the topic.
Chapter 13 is devoted to the discussion of industrial poly-
merization processes. This chapter is somewhat short, but
descriptive, and the examples chosen by the author are good
in that the students can understand the process characteris-
tics using the knowledge gained in earlier chapters of Part 2.
This chapter offers some interesting problems for senior
students looking for problems for their design courses.
Part 3 covers rubber elasticity, viscous flow, viscometry
and tube flow, continuum mechanics, and linear visco-
elasticity. In general, senior undergraduate students take
elementary transport phenomena courses before taking the
polymer course-thus the theoretical development in poly-
mer solution or melt rheology in Part 3 looks quite reason-
able for those students. Chapter 17 ("Introduction to Con-
tinuum Mechanics") is shorter than other chapters, but it
offers enough advanced material for the book's readers to
think about. Chapter 18 on linear elasticity is quite thorough
and serves as an excellent reference for basic theories of
linear elasticity.
Finally, in Part 4, various topics related to polymer
processing, plastics, rubber, synthetic fibers, surface fin-
ishes, and adhesives are discussed in a descriptive
manner. Although many of the chapters in Part 4 are
short, each one gives a good list of pertinent literature for
more advanced study.
In summary, the book is an excellent textbook covering
almost all the basic materials for senior-level undergraduate
chemical engineering students. The strengths of the book
can be found in its coverage of a wide variety of important
topics, its well-organized presentation, its few typographical
errors, its technical accuracy, its many worked-out examples
and exercise problems, and its reader-friendly writing style.
All of the book's subjects can be easily covered in an
one-semester, three-hours/week course. As Professor Rosen
states in its preface, the book can serve successfully as a
textbook as well as a self-study guide for practicing engi-
neering and scientists. No solution manual is available for
instructors, but a two-page errata (typographical) is avail-
able from the author. O

, M. classroom





Washington State University
Pullman, WA 99164-2710

One of the greatest challenges in the university is to
get students to look beyond merely passing courses
to the actual application of principles they learn to
everyday life. For a chemical engineer this means using a set
of academic tools to design industrial processes. Further-
more, the students' horizons should extend beyond solving
traditional problems to drawing links between engineering
theory and non-conventional, yet real-world, problems.
In this paper we will present a creative project-centered

Bernie Van Wie is an associate professor of
chemical engineering at Washington State Uni-
versity. He received his BS, MS, and PhD from
the University of Oklahoma. His research is in
biotechnology and biomedical engineering.

Joe Poshusta is an honors ChE senior at Wash-
ington State University. He has been involved in
undergraduate research with gas phase catalytic
reactors and has started his master's research in
heat flow in moving particle beds.

Bob Greenlee holds a degree in education and
taught middle school English before returning for
a second degree in chemical engineering at
Washington State University. His career inter-
ests include research and development in bio-

Robert Brereton is a chemical engineering se-
nior and is currently President of the AIChE Chap-
terat Washington State University. His future plans
include graduate work in business administration.

@ Copyright ChE Division ofASEE 1994

approach that we have used successfully as part of a junior-
level fluid mechanics and heat transfer course. These projects
supplemented the traditional lecture/homework problem for-
mat of instruction; they were developed outside of class,
were presented by groups during four late-semester class
periods, and accounted for eight percent of the final grade.
To assure quality instruction on the essential aspects of the
course, the project topics were limited to subjects normally
receiving less emphasis, such as flow measurement, hin-
dered settling, and mixing. Also, students could suggest
other choices by proposing to cover some topic in greater
detail than is normally done in the classroom. The objective
of the projects was to make learning fun while also fostering
teamwork, risk-taking, and originality-all without compro-
mising quality. To develop presentation skills and to repre-
sent better the learner's viewpoint, students were also en-
couraged to volunteer as coauthors.
To begin the effort, the following assignment was given to
the class.
Groups of 3-4 will select their top three project choices ...
[from a list handed out in class or their own suggestion] ...
and come up with a group name. For the project itself a
creative approach should be devised in which you design a
makeshift process from common everyday materials to solve
some practical fluids or heat-transfer problem. The score for
a perfect job will be "91"; to get above that you must obtain
R.O. V. points for risk (3 pts), originality (3 pts), and virtuos-
ity (3 pts). You will present the idea in a 20-minute period
and give the class a problem to solve on your design. You
should hand in one short group report of 5 pages maximum
in which you discuss the problem, theory, and solution.

Table 1 summarizes the projects and how each group
sought to raise their score by introducing risk, originality,
and virtuosity (R.O.V.)* into their approach.
* The R.O.V. concept was introduced years back in gymnastics
competition and has served to greatly improve the level of
difficulty and overall flair in the sport.
Chemical Engineering Education


The following are three sample project descriptions. They
were written by the students with editorial aid from the

Practical Heat Transport (" Three Cool Guys and Ken")
* In the event of a furnace failure during a severe Northwest
winter, we designed an apartment heating alternative. Our
solution was to use a car radiator as a heat-transfer device.
These radiators are small, yet have a very large heat-transfer
area. Furthermore, we were able to obtain a slightly dam-
aged Audi radiator from an auto repair shop for only six
dollars. We sealed the unit and fitted it with garden hose
connectors. One hose connected the radiator to the kitchen
faucet while another routed radiator output to the kitchen
sink drain. The radiator was positioned in the apartment
living room directly in front of a fan which provided convec-
tive air flow for greater heat transfer and mixing of the room
air. The coauthors proudly display the unit in Figure 1.

To test our unit, we ran some experiments and performed
calculations. Water temperatures were measured at the fau-
cet and drain. We timed the filling of a half-gallon milk
bottle to determine flow rates. From these values we deter-
mined the total heat transferred to be 498 Btu/min (29,880
Btu/hr). An overall heat-transfer coefficient was found by
dividing the heat flux by the log-mean temperature differ-
ence (LMTD): U = q/A(LMTD). An outside area of 58 ft2
was estimated for the radiator. Room temperature rose from
630F to 800F in four minutes, and we calculated a LMTD of
390F after correcting for the cross-flow system of air blow-
ing perpendicular to the water stream.12:p.389] This resulted in
an overall heat-transfer coefficient based on the outside area
of 13.2 Btu/hr-ft2- F. This value is of aid in determining if

Figure 1. Coauthors with apartment heating unit con-
sisting of an Audi radiator with accompanying garden
hoses for transport of sink hot water heating fluid. The
unit is positioned on an ordinary housefold fan.

one radiator is sufficient for a given air-flow rate and desired
outlet air temperature.
To compare actual heat transferred to that received by the
room air, we modeled the apartment as a box of ideal air. We
found an error of 59% between our model and experimental
results. This was probably because the model did not include
absorption of heat by the walls of the room, the furniture,
and especially the carpet, which has a large total surface
area. In an effort to improve the model, we determined the
total heat capacity of the apartment; this was done easily and
was found to be 117 Btu/F. This value is much like a total

Summary of Projects and R.O.V. Credit

Project Selection

Risk (3 pts)

Orieinalitv (3 pts)

The Fluid Mechanics

"Cold Rock Cafe"

"3 Men & A Phares"*

"RCBB Scientific"

"Ch.Eng. Ba Da Beng"


"Three Cool Guys
& Ken"

Blending & Mixing

Circulation &
Power Consumption

Hindered Settling


Venturi Meter

First ice cream trial in class

Calculations relied on obtaining
expt'l data

85 weight oil medium first tried
in class

Handmade wooden roller
peristaltic pump

Styrofoam cup heat exchanger

Enhanced Flow Flow enhancers found by
trial/Triton x 1000

Heat Exchanger

Fans, Blowers

Assumptions in relating design
to theory

Silly Putty to attach pitot
tube and stop leaks

Tennis ball can continuous
ice cream maker

Local hardware ice cream maker

Coins separated in 3" schedule
40 PVC pipe

Pumping toilet tank water to

Candle power induced
convective flow

Super Soaker' squirt gun
payload enhancers

Apartment heating with auto
radiator and fan

Hair dryer capacity by pitot tube

Built working model

Measured ice cream

Demonstrated in class;
Scale model built to

Class demonstration with
dye to show flow
10 experiments in hallway,
each at 4 flow conditions
Heated apartment 63' to
80F in 4 minutes
Pitot tube from straw and
cardboard roll

Group Name

Virtuosity (3 nts)

* Phares is the last name of a member of the group.

Summer 1994 IRe

.. ( pt,


heat capacity of a calorimeter, and its usefulness is shown by
a simple example. Suppose we wanted to know how long
our heat-exchange device needs to run to heat the room from
40F to 800F: the energy required would be the product of
the heat capacity and the temperature difference (4680 Btu).
At a flow rate of 4.62 gal/min and a change in water tem-
perature of 130F, the total energy supplied is 498 Btu/min.
To deliver the 4680 Btu required, the heater must be left on
for 9 minutes and 24 seconds.
The usefulness of this study depends on how the system
can be improved or adapted to different uses and environ-
ments. For example, simply knowing the water temperature
change, apartment heat capacity, and operation time, we
could easily predict the temperature rise in the room. Also,
knowing the overall heat transfer coefficient allows us to
design heating systems with different capacities by choosing
the number of radiators in the system.
Blending and Mixing Principles in a Continuous -Flow
Ice Cream Maker (" The Fluid Mechanics") As our group
considered how best to illustrate blending and mixing, our
thought turned (naturally) to food. We decided to design a
continuous-flow process for making one of our favorites-
ice cream. In addition to demonstrating mixing times and
different types of impellers, our project demonstrates some
heat-transfer principles.
Since one of the requirements for the project was to use
readily available household items, we went on a search for
suitable containers, impellers, and connections. The hard-
ware store had the plastic fittings, paint stirrers, and styrofoam
ice chest we needed. We used an old tennis ball can with
caps at both ends for the mixing container and crushed dry
ice from the school stores for coolant. We spent a lot of time
constructing the 6-blade impeller from plastic rulers and
making the fittings and can leak-proof. A schematic of our
final design in shown in Figure 2.
We also spent a lot of time tracking down heat-transfer

Ice Cream Mix
nf- Irlr I

Figure 2. The continuous ice cream maker comprised
of a tennis ball can capped at both ends and fittings for
tubing attachment.

coefficients, ice-cream mix composition, and typical stirring
speeds as well as methods for calculating mixing time, freez-
ing time, and mass-flow rate of the ice cream mix. We used
an overall heat-transfer coefficient from the sixth edition of
Perry's Handbook[31 for an air/water tubular heat exchanger
of 4.08 x 10-3 cal/cm2-C-s and an average rotation speed of
2 r/s, as suggested in The Joy of Cooking. 41 From Ice Cream[51
we found an average mix viscosity of 175 cp, an average
density of 1.1 g/cm3, and heat capacities of unfrozen and
frozen ice cream mix of 1.1 cal/g-C and 0.82 cal/g-C.
Although our calculations involved several estimates,
they indicated that the process was feasible. The heat-
transfer rate calculations involved both latent and specific
heats and an estimate of what percentage of the mixture we
wanted to freeze. We calculated that using dry ice we could
produce about 62 g/min of ice cream flowing through the
tennis ball can.

One tennis ball can of ice cream mix:
Volume = 7t(3.75 cm)2(20.3 cm) = 896 cm3
m = mass of mix = (896 cm3)(1.1 g/cm3) = 986 g
Heat transfer to cool mix from 10C to 00C:
q = mCpAT = (986 g)(0.82 cal/g-C)(100C)
= 8.09 x 103 cal

Heat transfer to freeze 60% of water:
q = m(%H20)(60%)(AHf) = (986 g)(0.60)(0.60)(80 cal/g)
= 2.84 x 104 cal
Heat transfer to cool ice cream from 0 C to -10C:
q = mCpAT = (986 g)(0.42 cal/g-C)(100C) = 4.14 x 103 cal
Total heat transfer required:
8.90 x 103 + 2.84 x 104 + 4.14 x 103 = 4.06 x 104 cal

Rate of heat transfer:
q = AUAT = (120 cm2)(4.08 x 10-3 cal/cm2-_C-s)( 0- {-78 }C)
= 42.9 cal/s
Time to cool one can of ice cream:
t = (4.06 x 104 cal)/(42.9 cal/s) = 946 sec = 16 min
Mass flow rate:
(986 g)/(16 min) = 62 g/min

The calculation of mixing times is straightforward, and
either empirical correlations or charts can be used once the
Reynolds number is calculated. We used a Reynolds number
and Figure 9-17 (page 231) in McCabe, Smith, and Harriott:[2]
NRe = nDa2p/t
= 2(5 cm)2(1.1 g/cm3)/(1.75 g/cm-s) = 31
From Figure 9-17, f, = 50. Using Eq. (9-34) in the text, we
found that the mixing time was about 48 seconds.
To maximize our risk points, we waited until our class
presentation to test the ice cream maker. Our presentation
Chemical Engineering Education

k Ice Cream

.' i -

included a discussion of mixing-time factors versus
Reynolds numbers, power requirements, solid sus-
pensions, baffled tanks, and different kinds of agita-
tors. As we presented, we also stirred the ice cream,
using an old fashioned hand drill attached to the
paint stirrer impeller. Unfortunately, we let the ini-
tial charge of mix stay in the can a little too long
before introducing more feed, and the mix froze
solid. Nevertheless, when we opened the can we
found that we had made some pretty good ice cream!
In working on this project, we used a wide variety
of text and reference materials, and exercised both
analytical and practical problem-solving skills. We
had a lot of fun, too-improvising and carrying an
idea through from initial design to finished product.

Settling Calculations for Various Coins*

Diameter Density
(m) (kg/m 3)

Penny .011815 6760
Nickel .013332 8650
Dime .010804 9042
Quarter .014961 7529

U, Time tofall
(m/s) 1.75 m (s)

0.232 7.54
0.390 4.49
0.269 6.51
0.420 4.17

* p=910 (kg/m3); g=1.2 (kg/m-s2); .t=1.92 (kg/m-s2)

Figure 3. The hindered settling apparatus consist-
ing of a vertical 3" PVC tube filled with 85-wt. oil,
with a modified funnel catch basket at the bottom.

Hindered Settling ("Three Men and a Phares"*) Our group
designed a coin separator using readily available household items.
The purpose of the coin separator was to provide a quick and efficient
method of separating a large pile of coins into their respective groups
while demonstrating the effects of hindered settling. A schematic of
the separation process is shown in Figure 3.
The separator consisted of a 1.75-m long, 3"-diameter PVC pipe
capped at one end and filled with a highly viscous fluid-in our case,
85-wt oil. The pipe was held vertically so that after coins were added
at the top, they would separate as they sank to the bottom. A plastic
funnel served as the catch basket at the bottom which could be pulled
by fishing line to the top of the PVC pipe to retrieve the coins. The
benefit of the coin separator was that the coins can be dumped into the
top in a handful and then removed from the catch basket in their sorted
Theory: For multicomponent systems, one must introduce the effec-
tive viscosity term, is, into the Stokes' relation. From The Chemical
Engineers' Handbook[l (pages 3-247), we obtain

[I + 0.5 (1 -)]
s 4
where E = porosity.
An equation for the terminal settling velocity, Ut, is
g*D *(p -p)
Ut = g Pp-P)
18* P,

Solution: We first calculated the effective diameter for each coin
using eight different coin operations. These values were averaged to
get a characteristic diameter. We then showed that settling velocities
could be estimated by the Stokes' relation by using the following
equation (p. 43 of ref. 2):

gp( -p))3

In our study, K values ranged between 2.9 and 3.8; these are at the
lower end of the intermediate regime and near the Stokes' region. We
assumed that only small errors would result by using the Stokes'
correlation. Furthermore, since only the relative velocities were of
importance in determining coin separations, values based on Stokes'
law will predict the correct trends. Table 2 summarizes the predicted
terminal velocities and settling times for each coin based on a porosity
of 0.90.
The differences in the terminal velocities, Ut, will cause the coins to
separate as they fall through the fluid. On running an experiment with
a group of ten coins of each type, we found that the pennies and dimes
separated quite well, with only one pair switched. The nickels and
quarters were somewhat mixed, but were well separated from the
pennies and dimes. These results are in agreement with what would be
expected given the relative differences in settling velocities. To im-
prove separation, we would recommend a longer pipe, a more viscous
* Phares is the last name of a member of the group.

Summer 1994

3 in. PVC pipe

85 wt. oil

fluid, or a more dense particle suspension. All of these
factors would enlarge the difference in settling times.

The following written comments demonstrate the students'
perspectives on the projects:
> Our project provided us with a lot of good experi-
ences. One of these was simply working together to
brainstorm, research, write, and present the project.
D ... gives an appreciation for fellow colleagues'
imaginations and a change of pace by learning from
students instead of a professor.
D Finding or estimating these values on our own gave
me a better understanding of what these numbers
really mean and how useful they really are.
> The most fun and educational part of the whole
project was the freedom we had in defining our
problem and designing our solution.
> The projects were a welcome relief from the usual
homework assignments.

These team projects were an outstanding success. By choos-
ing novel designs to meet practical problems, students could
see that engineering is simply a codification to describe
mathematically what goes on everywhere around them. Be-
cause a high score absolutely depended on a creative and yet
quality design, a spirit of comraderie and excitement was
established among the groups. Each knew that others were
actively engaged in constructing hilarious prototypes, or in
obtaining quality data. Even in this eight-o-clock class, one
could feel the energy build as students arrived in lab coats
and goggles, or with some fanciful construct veiled with a
cloth. Not willing to be outdone, team members spent long
hours in preparation for "their day" as they sought to ascer-
tain that engineering principles were really at work and that
their calculations were indeed meaningful.
To assure points for originality, groups interjected such
things as candy bar intermissions or passed around cups of
ice cream. Since they were having so much fun, the students
didn't at first realize just how much they learned, nor how
much time they had really spent on their projects. Finally,
recruitment of student volunteers as coauthors encouraged
some to further reflect on what was learned and whetted
their appetite for a yet higher quality of presentation. As to
continuing in this vein of instruction, this professor will
certainly use the method again.

The authors are grateful for the work of Andrew Au (class
member) and Lance Snowhite (Columbia Basin College In-

structor) in helping to prepare the figures for this publica-

1. Chemical Engineers' Handbook, 5th ed., McGraw-Hill Book
Co., New York, NY (1973)
2. McCabe, W.L., J.C. Smith, and P. Harriott, Unit Operations
of Chemical Engineering, 4th ed., McGraw-Hill Book Co.,
New York, NY (1985)
3. Perry's Engineers' Handbook, 6th ed., McGraw-Hill Book
Company, New York, NY (1984)
4. Rombaver, IS., and M.R. Becker, The Joy of Cooking, Bobbs-
Merrill Co., Inc., Indianapolis, IN, p 758 (1975)
5. Turnbow, G.D., and L.A. Faffetto, Ice Cream, John Wiley &
Sons, New York, NY, p. 373 (1928) 0

Ma book review

by D.M. Ruthven, S. Farooq, K.S. Knaebel
VCH Publishers, New York, NY; 352 pages, $95.00 (19940
Reviewed by
Ralph T. Yang
State University of New York at Buffalo

Industrial adsorption processes employ fixed beds of sor-
bents which need to be regenerated so they can be reused.
The conventional approach for sorbent regeneration is heat-
ing to desorb the adsorbed molecules, followed by cooling to
the initial temperature to form an adsorption-desorption cycle,
referred to as temperature saving adsorption. Due to the
large sizes of the beds used in industry, however, the regen-
eration step is very time-consuming, usually adding hours to
the duration of each cycle. Desorption can also be accom-
plished by depressurization and subsequent repressurization,
which can be achieved in minutes. Such a cycle is called
pressure swing adsorption (PSA). Since the sorbent capacity
is used more frequently in PSA, it is a more efficient pro-
cess. This is the major reason that adsorption has received
renewed interest during the past two decades and has now
become a major tool for separation and purification in the
chemical and petrochemical industries.
This book provides a thorough review of the subject. It
discusses the underlying principles as well as present and
possible future applications. Modeling is an important as-
pect of PSA because it not ony guides design but it also
predicts feasibility of new applications. Nearly half the text
is devoted to mathematical modeling for this reason. The
book consists of eight chapters and three appendices:
1. Introduction
2. Fundamentals of Adsorption
3. PSA Cycles: Basic Principles
4. Equilibrium Theory of Pressure Swing Adsorption
Chemical Engineering Education

5. Dynamic Modeling of a PSA System
6. PSA Processes
7. Extension of the PSA Concept
8. Membrane processes: Comparison with PSA

Appendix A. The Method of Characteristics
Appendix B. Collocation Form of the PSA Model
Appendix C. Synopsis of PSA Literature

Several excellent monographs on adsorption processes are
already in print, covering much of the materials in pressure
swing adsorption. This new book is, however, the first one to
focus specifically on the subject of PSA. From my own
vantage point, its most notable features are the treatment
of PSA dynamics and its cyclic behavior by the method
of characteristics, and the comparison between PSA and
membrane separations.
The book is coauthored by highly accomplished research-
ers in the field who reside in three different countries. The
fine quality of the final product is an indication that the
three-way collaboration has worked well.
I would highly recommend Pressure Swing Adsorption as
a reference book for any advanced graduate course on sepa-
rations. Needless to say, anyone working on PSA should
own a copy of this book. 0

u book review

by Owen P. Ward
Van Nostrand Reinhold, 7625 Empire Drive, Florence, KY 41042;
198 pages, $52.95 (1991)

Reviewed by
Peter J. Reilly
Iowa State University

This slim book is a comprehensive treatment of the vari-
ous processes that are used to make commercial quantities of
biological materials. The author, an Irishman transplanted to
Canada, is Industrial Research Professor in Microbial Tech-
nology at the University of Waterloo.
Although advances in making formerly unknown mol-
ecules or in making known molecules, but from new sources,
by biological means has captured the attention of both scien-
tists and the general public, the scaleup of the methods to
produce these molecules is still of prime concern. Even
when achieving the lowest possible price is not the most
important consideration, as with pharmaceuticals and other
medicines, there is growing pressure to cut processing costs
and to make purer materials. This is the province of

bioprocessing, the area covered in this book.
Bioprocessing is composed of twelve chapters that range
from what is commonly considered biochemical engineering
all the way to standard food processing. Each chapter is
divided into sections of one to several pages that cover
different topics, and each ends with an extensive list of
references for further reading. A list of the chapter titles is as
good a way as any in such a wide-ranging book to described
what is covered:
* Biomaterials and Bioprocessing
* Bulk Bioprocessing Operations
* Bioreactors in Bioprocessing
* Biochemical Separations
* Sterilization and Preservation in Bioprocessing
* Bulk Bioprocessing of Animal and Plant Materials
* Purification of Fine Chemicals from Non-Microbial
Fermentation and Cell Culture Processes
Recovery of Cell Products
Enzyme Bioprocessing Applications
Waste Treatment
Good Manufacturing
The treatment of the material in Bioprocessing is entirely
descriptive; a few viscosity and heat transfer equations ap-
pear in the second chapter, but no others follow. Instead
there are many figures and some tables presenting different
pieces of equipment and process flow sheets, along with
some generalized experimental data. Given that so many
areas are covered in so few pages, there is little explan-
ation of the basic material. Facts inexorably follow facts,
making this book difficult to read in large gulps. The
difficulty is compounded by the rather stodgy appearance
of the book-it would have benefited from typefaces and
graphics with more flair.
Where does such a book find its niche? In this case,
the niche is not as a textbook. The treatment is not at all
theoretical or mathematical, prerequisites for any text used
by engineers. On the other hand, Bioprocessing is not a
review of a specific area; it spreads over too much terrain.
Although it has extensive lists of other articles and pub-
lications at the end of each chapter, it has few references to
other work within its text, so tracking down more detailed
information on any particular statement would be a hit-or-
miss proposition.
It is probably best employed as a primer-for finding the
first information about a new topic and acting as a starting
point to dig deeper. For this, Bioprocessing is admirably
suited: each topic is concisely covered, there are a great
number of topics, and the index at the end is very compre-
hensive, making each topic easy to find. 0

Summer 1994

n learning in industry

This column provides examples of cases in which students have gained knowledge, insight, and
experience in the practice of chemical engineering while in an industrial setting. Summer interns and coop
assignments typify such experiences; however, reports of more unusual cases are also welcome. Descrip-
tion of analytical tools used and the skills developed during the project should be emphasized. These
examples should stimulate innovative approaches to bring real world tools and experiences back to campus
for integration into the curriculum. Please submit manuscripts to Professor W. J Koros, Chemical Engi-
neering Department, University of Texas, Austin, Texas 78712.




Texas A&M University
College Station, TX 77843-3122

he Accelerated BS/Master's Industry Program in

Chemical Engineering was established at Texas A&M
University in the fall of 1991. The program permits
students with a GPA of 3.25 or higher to begin work toward
the Master's degree, either Master of Science (MS) or Master
of Engineering (ME), at the end of their Junior year and to
complete the requirements for the degree in one additional
year after receiving the BS degree.
A key feature of the program is an extensive research
project (for the MS degree) or engineering project (for the
ME degree) which is conducted in industry at the company
site. The project is normally done during two summer peri-
ods, before and after the Senior year, but can also be done in
two consecutive semesters.
During their Senior year, the students can take up to three
graduate-level courses and receive credit toward three re-
quired undergraduate electives as well as credit toward the
Master's degree for these courses. Since graduate credit is
also given for the summer project work, the student can

Ron Darby is Professor of Chemical Engineering at Texas A&M Univer-
sity and Director of the Accelerated BS/Master's Industry Program. He
holds a PhD in Chemical Engineering from Rice University and has been
at A&M since 1965. His primary research interests are in applied rheology
and flow behavior of viscoelastic and non-Newtonian fluids, and he has
published over fifty papers in technical joumals, a book on Viscoelastic
Fluids, and has a book on process fluid mechanics in preparation.
Copyright ChE Division ofASEE 1994

complete approximately one-half of the requirements for the
Master's degree by the time the BS degree is awarded. One
additional academic year beyond the BS degree, including
the second work period, is required to complete all require-
ments for the Master's degree, which could thus be obtained
after a total of five years of college work. Although this
schedule is the "norm," many students are out of phase with
the regular four-year undergraduate curriculum (the average
student takes closer to four and one-half years for the BS
degree), but the program is sufficiently flexible to accom-
modate these students.
To date, fifteen students have enrolled in the program-
five the first year, four the second year, and six the third
year. Two of them have completed the program (one with an
MS and the other with the ME). One student decided to take
a permanent job before finishing the program and dropped
out. A total of eleven different companies have participated
in the program, and the feedback from all participating stu-
dents and companies has been positive.

A program coordinator solicits participation in the pro-
gram from both students and companies. Brochures and
information on the program are mailed to companies, with a
follow-up phone call. Students with a GPA of 3.25 or higher
at the beginning of their Junior year may apply by submit-
ting a resume to the program coordinator. Participating com-
panies are asked to submit a brief description of a project or
project area in which the students would participate, which
Chemical Engineering Education

is given to the student applicants. Interviews are then ar-
ranged between the company representatives and the stu-
dents, and the companies subsequently select the students
they wish to work with.
Once a match between the student and company is made,
the company project supervisor is identified and the project
is defined in more detail. The student, with the help of the
program coordinator, then selects a faculty advisor who has
an interest in the project's technical area and is willing to
work with the student. A meeting at the company location is
arranged between the student, the company supervisor, the
program coordinator, and the faculty advisor. The program
requirements, project objectives and methods, report require-
ments, and scheduling are discussed and agreed upon at this
meeting, which typically occurs during the spring of the
student's Junior year.
The student is supervised jointly by the industry supervi-
sor and the faculty advisor, who normally visits the student
at the company site at least once during each summer work
period. Periodic progress reports are required of the student,
as well as a comprehensive report at the end of each summer
period. The ME degree requires one or more extensive engi-
neering reports, and the MS degree requires a research project
and thesis. Both degrees require a final oral examination,
and the student's industry supervisor participates as an ad-
junct member of the student's advisory committee. The na-
ture of the project determines whether it is appropriate for
the MS or ME degree, and it is the students' choice as to
which they wish to pursue. In practice, there are usually
more good students available than there are company projects,
so supply and demand comes into play in this decision.
The first summer work period is usually devoted primarily
to the "learning" phase of the project and its necessary pre-
paratory work. Students working toward the MS degree
concentrate entirely on the research project, which is done at
the company research laboratory site-whereas the students
working toward the ME degree may typically be working
simultaneously on several projects. The students receive
four hours of graduate credit (research for the MS or intern-
ship for the ME) for each of the two summer work periods,
based on their project reports.
The MS research projects are typically long-range, so
there is no urgency in completing them within a short time
frame, and the two-summer period is normally adequate.
From the company's perspective, the ME projects are some-
times of a more urgent nature, and in such cases it is usually
possible to identify two shorter-duration projects which can
each be completed in one summer. Excellent cooperation of
the companies involved, along with the flexibility afforded
by the two degrees, has made it easy to identify and com-
plete projects which are not only quite appropriate for the
program but also challenging.
During the Senior year the student may take up to three
Summer 1994

graduate-level courses (instead of the three elective chemi-
cal engineering courses specified in the curriculum) and
receive credit toward both the BS and Master's degree for
these courses. The elective courses are to be taken from a
prescribed list of chemical engineering electives, including
topics such as polymer engineering, bioengineering, envi-
ronmental engineering, high-tech materials engineering, pro-
cess safety engineering, etc. Most of these courses have
parallel graduate-level courses covering the same or similar
subjects, and the students in the accelerated program may
take the graduate-level course and qualify for credit by exam
for the corresponding undergraduate course. The student
therefore satisfies the requirements for the BS degree at the
end of the regular (four-year) curriculum and must then
formally apply and be accepted into the graduate program.
The second summer work period is completed following
the Senior year, and the project reports are submitted. All
reports are reviewed and approved by the company supervi-
sor before being submitted to the faculty advisor for review,
revision, and final acceptance. The remaining course re-
quirements for the Master's degree can be completed during
the following academic year. The MS degree requires a total
of thirty-two hours, including eight hours for the research
thesis. The research project is more extensive and compre-
hensive than the ME engineering report, but the ME degree
requires thirty-six hours of graduate credits, including eight
hours for the engineering project report.
About half of the required course credits for both degrees
consists of a basic core of required graduate courses, with
the remainder being tailored to the specific interests of the
student. The thesis or engineering report can be completed
during the final year, and the student must then pass a final
oral exam by the graduate advisory committee (which in-
cludes the industry supervisor).
Occasionally a project will involve proprietary company
information. When this is the case, the company determines
what information can be divulged and the student and fac-
ulty advisor execute a nondisclosure agreement. It is under-
stood at the outset, however, that the project must involve
sufficient disclosable information to form the basis of an
acceptable MS thesis or ME report. The results of the MS
work are expected to be publishable, although the ME re-
ports usually are not.

The most obvious benefit to the student might seem to be
the opportunity to obtain a Master's degree in the least pos-
sible time (a minimum of five years of college work). In
reality, however, the most significant benefit is the opportu-
nity to engage in a research or engineering project in the
industrial setting. Since the projects are proposed by the
companies, the topics are of direct and timely interest to
them-they are definitely "real world" projects. Students

have much more responsibility and independence on the
project than they would in a typical summer internship or co-
op assignment, and they get much more involved in an in-
depth technical project.
For their summer work, students are paid by the compa-
nies at a level commensurate with their ability and experi-
ence, which is higher than the rate for a typical internship
position. The companies are also asked to provide a $2500/
year fellowship stipend for the student for two years, since
Master's students do not normally receive departmental fi-
nancial support. Although this fellowship is not a mandatory
requirement of the program, the majority of the participating
companies do provide it.
Another benefit of the program is that students have
ample opportunity to "prove" themselves to the company
sponsor, and they can reasonably be assured of an offer
of permanent employment upon completing the program.
The students tend to be very enthusiastic about their projects
and are highly motivated and interested, which pro-
motes high-quality work.

In addition to the direct benefit of the work performed by
the student, the company has an opportunity to engage some
of the best chemical engineering students and to evaluate
their performance on a significant project over an extended
period of time. There is no permanent obligation on the part
of either the company or the student during this period, but a
permanent job offer is a natural consequence when a good
match of interests is achieved. Another benefit is an opportu-
nity for increased interaction between the participating com-
panies and chemical engineering faculty which often leads
to other forms of interaction, research collaboration, etc.

Table 1 shows the companies that have participated in the
program, along with a brief description of some of the projects
conducted by the students-the table also demonstrates the
wide variety of projects that have been involved in the pro-
gram. Four of the companies are presently sponsoring their
second student in the program. Two students have finished
the program-one with the MS degree and one with the
ME degree. The former presented the results of his project
("A Thermodynamic Model for Predicting Wax Deposition
from Crude Oils") at the national AIChE spring meeting
in Houston in 1993.111
Although each of the projects is unique and no one project
is truly representative of them all since they cover such a
wide range of topics, a brief summary of the study on wax
deposition from crude oils will be given here as an illustra-
tion of a sample project. The project was done at Core
Laboratories in Houston by Loganathan Narayanan under
the joint direction of Dr. Kosta J. Leontaritis of Core Labs
and Ron Darby of Texas A&M. Narayanan had already
finished his course requirements before beginning his project,
which was done during two consecutive semesters.
The motivation for the project is the fact that many crude
oils contain heavy hydrocarbon fractions which precipitate
as a wax phase at low temperatures, leading to the plugging
of pipelines and various other problems in the field. The
project objective was to develop a thermodynamic model for
predicting the liquid-solid wax phase distribution, based on
a refinement of a previous model (Scatchard-Hildebrand[21).
The Lee-Kessler correlation,131 along with the modified BWR
equation of state, was used to calculate solubility parameters
and molar volumes, and the Gibbs free energy equation was
based on polymer solution theory, including a size exclusion

Companies Participating in the Texas A&M Accelerated BS/Master's Program



Texaco Research Port Arthur, TX

The Dow Chemical Co. Freeport, TX
Brown & Root Braun Houston, TX
OXYCHEM, Chocolate Bayou, TX

Core Laboratories Houston, TX
SAIC Clear Lake, TX
ALCOA Pt. Comfort, TX

Texaco Inc./EPTD Houston, TX
FINA Technical Center Deer Park, TX

BASF Freeport, TX
Phibro Energy USA, Inc. Houston, TX

MS Experimental evaluation of a biofiltration process for removing VOCs from remediation site off-gas
ME Evaluation of factors limiting the operating efficiency of a large steam jet thermocompressor.
ME Technical and economical feasibility study of plastic recycling processes.
MS Analysis of relationship between properties and processing conditions and blown film properties for
HMW HDPE polymer blends.
MS Modeling of waxy crude oil phase behavior using polymer solution theory.
ME Optimization of procedures for Process Hazards Analysis and Process Safety Management reviews.
MS Modification of the non-Newtonian properties of bauxite mud residue for maximum solids loading and
minimum viscosity.

MS Computer modeling of crude oil phase behavior and recovery by steam flooding.

MS Experimental and theoretical modeling, initiator optimization, and scale-up for a free-radical polymeriza-
tion reaction.
MS Experimental evaluation of a fluidized bed process as a substitute for a fixed bed catalytic process.
ME Computer optimization of a catalytic cracking refinery unit for variable feedstock and product properties.

96 Chemical Engineering Education


term from the Flory-Huggins theory to account for the range
of carbon numbers. A key element of the model is a binary
interaction coefficient which is used as a tuning parameter to
fit experimental data. The model can be used to perform
flash calculations as well as to determine the onset tempera-
ture or pressure for wax crystallization. Onset temperatures,
as well as the effect of temperature and pressure on compo-
nent distribution, have been determined for various crude
oils and compared with experimental observations.

The crude oil compositions were characterized by nine
discrete "pseudocomponent" fractions, from C to C20,. The
Lee-Kessler mixing rules were applied to these components,
and the binary interaction parameters were determined by a
computer optimization routine in comparison with literature
data from Hansen, et al.[4] The predicted wax deposition
onset temperatures using this model were in excellent agree-
ment with experimental measurements and were consider-

ably better than predictions of previous models, as shown in
Figure 1. Equilibrium compositions of the liquid and solid
phases at the onset temperature were predicted, as well as
the wax solubility as a function of temperature and pressure,
as shown in Figure 2. There are insufficient data available in
the literature for confirming these predictions, however.
After finishing his MS degree, Narayanan remained with
Core Labs and is presently continuing this study. He is in the
process of acquiring additional laboratory data on waxy
crude phase behavior which will be used to further evaluate
and extend the computer model.

In summary, it is fair to say that this program has been
extremely well received by both the participating companies
and the students. It is continuing to expand, and provides an
excellent opportunity for combining an advanced chemical
engineering education
with practical industrial
experience, in a manner
which is of significant
A benefit to the student and
the company alike.

285 290 295 300 305 310 315 320
Experimental Onset Temperature
Figure 1. Comparison of experimental and calculated onset temperatures.

Figure 2. Equilibrium compositions of liquid and solid phases for mixture 1 at the onset
conditions of 308 K and 1 atm.
Summer 1994


1. Narayanan, L., K.J.
Leontaritis, and R.
Darby, "A Thermody-
namic Model for Pre-
dicting Wax Deposition
from Crude Oils," Paper
#55a, AIChE National
Meeting, Houston, TX,
March 28 (1993)

2. Hildebrand, H.J., M.J.
Prausnitz, and R.L.
Scott, Regular and Re-
lated Solutions: The
Solubility of Gases, Liq-
uids, and Solids, Van
Nostrand Reinhold Co.

3. Lee, B.I., and M.G.
Kessler, "A Generalized
Correlation Based on
a Three-Parameter
Corresponding States,"
AIChE J., 21,510 (1975)

4. Hansen, J.H., K.S.
Pedersen, and H.P.
Ronningsen, "A Ther-
modynamic Model for
Predicting Wax Forma-
tion in Crude Oils,"
AIChE J., 34, 1937
(1988) D

A Hansen etat. Model
--"-- This Model



I 310



W 295



a Oclassroom


West Virginia University
Morgantown, WV26506-6101

More BS chemical engineers join industry in posi-
tions identified with plant operations than with
the design of new plants and facilities. During
these operations, numerous modifications in process operat-
ing conditions are necessary to meet changes in the market-
place, in product mixes and specifications, in feed materials,
in costs of utilities and feed stock, in governmental regula-
tions, in the availability of improved equipment, and in
performance losses resulting from aged equipment, etc. Ex-
isting facilities serve to constrain the options that may be
considered in any solution. The strategies used in approach-
ing problems involving operating plants differ significantly
from those used in designing the plant. Performance prob-
lem solutions require an understanding of how operating
units will behave over a range of operating situations and are
contingent on data from and observation of plant operations.
Problems that consider the effect of input streams and
equipment behavior on process systems output are identified
in this paper as performance problems. They include indus-
trial applications identified as trouble shooting, retrofitting,
and debugging problems. Four examples of performance
problems which have been used in class will be presented:
one involving heat transfer, one involving fluid mechanics,
and two involving separations. We hope that this paper will
serve as a catalyst for more wide-spread use of performance
problems in chemical engineering curricula.


Problem 1
Problem Statement During the summer, production in
our allyl chloride plant has dropped as much as 20% from
normal operation. (The reactor section with the normal oper-
ating temperatures in given in Figure 1.) The reactor dis-
charge temperature is maintained at 5100C by changing the
input flow rate. We ask the students to suggest possible
causes for this behavior and to recommend changes to cor-
rect the problem.
Copyright ChE Division ofASEE 1994

Richard C. Bailie received his degrees from
Iowa State University (PhD), Wayne State
University (MSChE), and Illinois Institute of
Technology (BSChE). His interests are in flu-
idization and energy utilization, and he has
published a book and many articles in these

Joseph A. Shaeiwitz received his degrees in
chemical engineering from the University of
Delaware (BS in 1974) and Carnegie Mellon
University (MS in 1976 and PhD in 1978). His
research interests are in mass transfer, espe-
cially in pharmaceutical systems, and in design
and design education.

Information The reaction is a gas phase highly exother-
mic reaction and is carried out in a fluidized bed for easy
heat removal. The fluidized bed operates at a constant tem-
perature equal to the exit temperature (stream 2). The heat-
transfer coefficient on the hot side (fluidized bed) is constant
and unaffected by changes in flow rate through the reactor.
In the design, the heat-transfer coefficient on the cold side
(liquid coolant) was four times that of the hot side. Under
normal operations the heat released is 6 x 105 W and mC, for
the coolant is 1.2 x 104 W/C.
Discussion There are two causes that force a change in
system output:
A change in input streams
A change in unit effectiveness resulting from unit
failure leading to a step change in performance or
deterioration (such as fouling of the heat-transfer
surface or deactivation of the catalyst) leading to a
gradual change. The "summer only" loss in production
does not fit this pattern
The "summer only" loss of production focuses attention on
inputs to the system, particularly the coolant stream (stream
3). The performance of the heat exchanger under changing
coolant temperature and/or flow rate for a hot-side tempera-
Chemical Engineering Education

ture fixed at 510C and duty of 6 x 105 W must be known.
The information given on Figure 1 is sufficient to develop a
performance curve for the heat exchanger.
The overall heat-transfer coefficient, U, and the exit cool-
ant temperature can be calculated for normal operations
(hereinafter referred to as the base case). The individual
heat-transfer coefficients can be estimated from the equation
1 1 1
-l- +-- (1)
U hcoldside hhotside

and the ratio of the individual coefficients given (hcold/hhot =
4). The performance under other conditions is anchored to

Figure 1. Reaction section of ally] chloride plant.

380 1i I

370 -
360 -

M350 -

+ 340 -

S330 -
0 320

0.0 0.5 1.0 1.5 2.0 2.5
flow ratio

Figure 2. Heat transfer performance curve for allyl
chloride reactor.
Summer 1994

information on the base case. The ratio of coolant flow is
defined by R:
R H Flow rate (m)
Flow rate (base case)
For any value of R, the cold-side heat-transfer coefficient

h(cold) = h (cold, base case) R08 (3)

and the overall heat-transfer coefficient can be calculated
from Eq. (1). The basic equation for heat transfer gives

AT,, = -(4)
and energy balance over the coolant yields

AT con = cAToolant(base case) (5)
"Tcoolant = R (5)
Solving Eqs. (4) and (5) provides the coolant inlet and exit
temperatures for any value of R. The results are plotted as a
performance curve in Figure 2. The figure relates the flow
rate needed for different coolant temperatures to maintain
normal product output. Curves for other production rates
(heat duties) could also be included on this performance
curve. With the information provided in Figure 2, the erratic
behavior can be controlled by changing the coolant flow rate
to compensate for a change in coolant temperature.
Critique This simple trouble-shooting problem demon-
strates unique features of performance problems, some of
which are:

The equipment limits the range of solutions.
The solution is unique to a specific piece of equip-
Operating conditions provide a "base case" used to
predict changes.
Using operating data reduces the need for physical
property data.
Equations are importantfor "functional form" (see
Eqs. 2, 3, and 5).
Judgments are required in making assumptions (see
Eq. 1).

Students find this simple problem challenging. The major
obstacle results from a lack of physical property data and
equipment specifications. Flow rates are not known nor are
the materials that make up the streams. Students have many
design equations in their arsenal, but all require physical
property data and detailed equipment specifications. Equa-
tions 2, 3, and 5 are obtained, however, by taking the ratio of
these design equations to obtain a new case relative to the
base case. With no change of equipment and when it can be
assumed that physical properties remain essentially con-
stant, there is often no need for physical property data and
equipment specifications to develop the performance curve.



O stream number
Temperature C

Problem 2

Problem Statement The solution to the previous problem
required changing the coolant flow rate. This problem exam-
ines the limits on coolant flow rate due to existing equip-
ment. Figure 3 provides details of the coolant system pro-
vided for the allyl chloride reactor in Figure 1. The students
are asked to determine the maximum flow rates obtainable
with the existing equipment.
Information Pressure drops over various sections of the
coolant loop are provided for the base case (Figure 3). Not
shown in the figure are on/off valves that redirect the flow
in the system. Two identical pumps are installed, but only
one pump is operated at any time. Figure 4 (curve P-I)
provides a pump (performance) curve for these pumps.
It relates the pressure delivered (feet of water) as a function
of coolant flow rate (gallons/minute). The normal flow rate
is 85 gallons/minute.
Solution The pump operates only at conditions shown on
the pump curve (P-I) in Figure 4. The pressure drop over the
flow system must equal the pressure delivered by the pump.
The base case solution gives one point on this line (see point
A). Of this total pressure drop, 15 feet is from the valve. The
valve pressure drop can be independently changed. The re-
maining pressure drop (125-15 = 110 feet) is designated as
the "system pressure drop" and is dependent on the flow rate
through the system. This system pressure drop can be esti-
mated from the equation

AP- = (6)
Taking the ratio of Eq. (6) for the new case to the base case,
for constant L, D, and the assumed constant friction factor, f
(high Reynolds number), yields

AP(m)= AP(base case)R2 =110R2 (7)

where R is the ratio of flow rates in the new case to the base
case. This system pressure drop is superimposed on the
pump curve in Figure 4 (S-I).
The maximum flow rate occurs when there is no pressure
drop across the valve. This is shown as point B (89 gpm),
and it represents the highest possible flow with the existing
pump and coolant system. Thus, the flow cannot be in-
creased more than 5%. There are two approaches to obtain-
ing higher flow rates: lower the system curve (lower the
pressure drop), or raise the pump curve.
Several options are possible. They include:
1. Run both pumps in parallel. For a given pressure drop
this configuration will produce twice the flow rate. The
pump curve for this double pump combination is ob-
tained from the single pump curve and is plotted in
Figure 4 (P-III). It crosses the system curve at point C,

giving 95 gpm (a maximum increase of 7% over
the single pump).
2. Run both pumps in series. For a given flow rate, this
configuration will produce twice the pressure. The pump
curve for this double pump combination is plotted in
Figure 4 (P-II). It crosses the system curve at point D,
giving 116 gpm (a maximum increase of 29%).
3. Operate the reactor heat exchangers in parallel. In this
case, the velocity through each exchanger will drop by
half, and the distance the fluid travels through the heat
exchanger also drops by half. From Eq. (6), AP o LeqV2,
the pressure drop in the heat exchanger section drops
by a factor of 8. This provides a new system with a
lower pressure drop and is shown on Figure 4 (S-II). It
crosses the single pump performance curve at point E,
giving 127 gpm (a maximum increase of 43%). If this
change is made, however, the effect of lower velocity in
the heat exchanger on the cold-side heat-transfer coeffi-
cient must be considered.
4. Combinations (e.g., changing both pump and system).

[ E AP ftHIO
Figure 3. Heat transfer fluid circulation
system for allyl chloride plant.

Figure 4. Pump and system curves for allyl chloride
plant heat-transfer fluid-circulation system.

Chemical Engineering Education

P-4 pump curve
one pump
P-I4 pump curve
two in series
P-I4 pump curve
two in parallel
S1 original system
-11 system curve
2 X in parallel


0 40 80 120
flow rate (gallmin)

Combinations of 2 and 3 give a maximum flow of 136
gpm (point F), and combinations of 1 and 3 give a
maximum flow of 155 gpm (point G).
The pumps in parallel with the exchangers provide the
largest increase (to 155 gpm) using the existing equipment.
Additional increase is possible from increasing the pump
rpm, but this was not evaluated because of the lack of infor-
mation (e.g., a new pump curve).
Critique This problem is characteristic of a "bottleneck"
problem. The performance of this coolant loop limits
the ability of the heat exchanger to remove heat from the
reactor. The analysis showed that changes in both the
system and the pump are necessary to increase the coolant
flow rate substantially.
All of the features identified with performance problems
in the first problem apply to this new situation. Additional
features introduced in this example are

Performance curves for the pump and the system
determine the flow rate.
Several alternatives are available to increase the
coolant flow rate.
The valve provides a variable pressure drop that can
be regulated.

Typical "end of chapter" problems have as a solution
a single point on a performance curve. Examination of
the characteristics of the entire performance curve provides
insights into system behavior that are not possible from
evaluation of single points. The options presented were
identified from an analysis of the original pump and
system curves in Figure 4.

Problem 3

Problem Statement You are in charge of operating a
distillation column which has been designed to fractionate
100 lb-mole/hr of 32.1 mole % n-butane and 67.9 mole % n-
pentane fed as saturated liquid. The distillate contains 88.5%
n-butane at a rate of 30 lb-mole/hr, and the bottoms contains

F =100 Ibmoles/hr
z,= 0.321

feed on tray 4
(only feed location)

S D = 30 lbmoles/hi
x4 = 0.885
tray area

B = 70 lbmoles/hr
x4, = 0.079

Figure 5. Base case conditions for Problem 3.

Summer 1994

7.9% n-butane. You have been asked to investigate the ef-
fects of two possible changes in operating conditions for the
same feed rate.
1.You must recommend the maximum possible n-bu-
tane concentration achievable in the distillate in the
existing column. The feed, distillate, and bottoms rate
must remain constant.
2. The feed n-butane concentration will be temporarily
reduced to 25 mole % (still saturated liquid at the same
rate). How do you compensate while maintaining the
same distillate and bottoms concentration?
3. You must recommend the maximum possible butane
concentration achievable in the distillate for this case.
The feed, distillate, and bottoms rates must remain
Information Available Figure 5 illustrates the existing
distillation column.
Background This problem is an extension of Problem
39-3 in Bennett and Myers.I'l In that problem, the above
design (number of trays, reflux ratio, and internal flows)
was requested. For the given tray spacing, the flooding
and column diameter calculations are straightforward. This
problem is different in that the performance of an existing
column, designed for one feed and distillate concentra-
tion, must be predicted for different distillate and feed
concentrations. A decision on how to compensate for the
new feed or distillate concentrations must then be made. On
a McCabe-Thiele diagram, a trial-and-error solution is
required in that the operating lines must be varied until
the graphical construction yields seven equilibrium stages. It
is also possible that the feed may not be at the optimal
location in the new case.

Solution For the original feed the distillate is 30 lb-moles/
hr and the bottoms is 70 lb-moles/hr. For the reduced con-
centration feed the distillate is 21 lb-moles/hr and the bot-
toms is 79 lb-moles/hr. Less distillate at the same concentra-
tion is produced from a more dilute feed.
All calculations were done using CHEMCAD. This type
of problem presents a good opportunity to introduce students
to the advantages of process simulation software.
It is possible to prepare a performance curve, similar to the
one in Problem 2, for these problems. Since distillation
columns are limited by flooding, the vapor velocity is the
performance variable and it will be plotted versus distillate
concentration for the two feed conditions. The flooding ve-
locity curve can also be plotted, and the intersection between
the performance curve and the flooding curve predicts the
maximum possible operating conditions.
Figure 5 shows the performance curves for both feed
conditions and for flooding. The performance curve was
obtained by varying the distillate concentration and obtain-

ing the reflux ratio from the simulation. The reflux ratio
fixed all internal flows, which were used to calculate the
vapor velocity. The flooding velocity was obtained using the
internal flows and a standard flooding correlation.121 Since
the feed was saturated liquid, conditions at the bottom of
the column were assumed limiting. The intersection is
the maximum distillate concentration obtainable in the col-
umn, at 100% of flooding, which is an n-butane mole
fraction of 0.93 for the original case and 0.95 for the lower
feed concentration case. It is likely that the true maximum
is at a lower distillate concentration, and judgment should
determine how close to flooding to operate. The steep
rise in the performance curve at higher distillate con-cen-
trations suggests a conservative approach since small
errors or disturbances will have a drastic effect on the
vapor velocity. An intermediate result of these calcula-
tions is that the reflux ratio needed to maintain the dis-
tillate and bottoms concentrations for the reduced feed
condition is 2.82.
The relative position of the two performance curves is also
interesting. A higher reflux ratio is needed for the lower feed
concentration, and lower vapor velocities result. This is be-
cause the distillate flow rate is lower and the bottoms flow
rate is higher. But flooding is determined by internal flows.
In this case, even though the reflux ratio increased, the
decrease in distillate flow rate results in lower internal flows.
For example, for a distillate n-butane mole fraction of 0.885,
the base case reflux ratio is 2.12, whereas the reflux ratio for
the lower feed concentration case is 2.82, even though the
vapor velocities are 1.2 and 1.03 ft/sec, respectively.
Critique Several key points are illustrated in this prob-
lem. One is that the McCabe-Thiele (or computational) solu-
tion does not account for the physical performance of a
distillation column. Another is that the reflux ratio is the key
control variable in distillation column operation. If the per-
formance of an existing distillation column must be ad-
justed, the reflux ratio is adjusted. A distillation column is
limited by the flooding velocity, however, making the vapor
velocity the performance variable. One conclusion is appar-
ent from this problem: it is not possible to make major
changes in operation of an existing distillation column de-
signed to operate at 75% of flooding. An increase in distil-
late mole fraction of 5% requires operation at 90% of flood-
ing. Other alternatives such as changing the feed location,
changing the feed condition, and decreasing the feed rate
were not considered here.

Problem 4

Problem Statement A packed scrubber has been de-
signed to reduce the acetone concentration in 40,000 moles/
hr (fixed) of air from a mole fraction of 0.02 to 0.001.
Acetone is absorbed into a water stream at 20,000 moles/hr
(can vary). The acetone is recovered from the effluent liquid,

and the water (which is assumed pure) is recycled to the
absorption unit. After a period of successful operation, the
exit acetone mole fraction in air is 0.002. Diagnose the cause
of the problem and suggest methods for compensation.
Information Available The column is packed with
1-in Raschig rings and has a 9.6-in diameter, which is
obtained by designing for 75% of flooding. The column
operates isothermally at 26.70C and the nominal pressure
is 1 atm. Raoult's law is assumed, and the partition co-
efficient, m = y/x, is
in (m/P) = 10.92 3598/T(K)
The value of m at 26.70C is 0.337.
Background Like the distillation problem above, most
absorber problems found in textbooks are of the design type.
For a given separation, the size of the column is determined.
This problem can be solved either graphically or by using
the Colburn graph for dilute solutions.[31
Solution From the Colburn graph, the base case point for
this column can be located. The y-axis is at a value of 0.05,
and the absorption factor is 1.48. This gives NtoG = 6.2. The
case to be diagnosed has a y-axis value of 0.1. The most
obvious diagnosis is that the absorption factor has decreased,
which moves the operating point for the column vertically at
constant NtoG = 6.2 to a y-axis value of 0.1. The new absorp-
tion factor is 1.15. The problem could be in any (or all)
components of the absorption factor. L could have decreased
to 17,391 moles/hr, or G could have increased to 46,000
moles/hr. Alternatively, the value of m could have been
changed to 0.388, meaning that the temperature of the col-

-^10 |1
1 vapor velocity
z = 0.321
8 2 flooding velocity
*z = 0.321
O 3 vapor velocity
S6 0.25
4 flooding velocity
0) z 0.25
4 -
o 3

0 2

0 0
0.90 0.92 0.94 0.96 0.98 1.00
distillate mole fraction
Figure 6. Performance and flooding curves for n-butane-n-
pentane distillation column. The distillate mole fraction
and the feed mole fraction, z, are that of n-butane.
Chemical Engineering Education

umn has been increased to 30.50C or that the column pres-
sure has decreased to 0.87 atm.
For all of the above cases, the outlet concentration of
acetone in the water has also changed, which could affect a
downstream stripper or water treatment. There is an alterna-
tive diagnosis, however. The operating point can remain
fixed in the original position, but the outlet acetone concen-
tration in air was increased due to the presence of acetone in
the water fed to the column. This makes the second term
in the numerator and denominator of the y-axis non-zero.
Solution for the inlet acetone concentration in water yields
a mole fraction of 0.0031235. Therefore, there are five
possible causes for the observed increase in outlet ace-
tone concentration in air. We are not considering equipment
failure causes, such as liquid distribution, channeling,
fouling, etc., which could also contribute to the observed
performance decrease.
If the five causes of the reduced performance of the ab-
sorber are understood, then possible methods of compensa-
tion are straightforward. It is assumed that compensation
cannot be achieved by altering the cause of the disturbance,
e.g., if the cause is too high a gas rate, it cannot be lowered.
If the gas rate is too high, the liquid rate can be increased to
compensate. But flooding could be a problem--especially if
both gas and liquid rates are increased.
A better choice would be to decrease the temperature of
the absorber to 22.30C, increase the pressure in the absorber
to 1.15 atm, or combining these changes in temperature and
pressure in order to make the absorption equilibrium more
favorable. If the liquid rate is too low, the gas rate could be
reduced in order to compensate. Flooding would not be a
problem-but reducing the amount of gas treated in the
absorber is not permissible.
In this case, reducing the temperature of the absorber to
22.3C or increasing the pressure to 1.15 atm are the only
logical choices. If a temperature increase is the problem and
altering flow rates is not favored due to flooding consider-
ations, the only possible compensation is to alter the pres-
sure. Once again, it is theoretically possible to decrease the
gas rate, but it is not permissible. Increasing the liquid rate
moves the column toward flooding, but a small increase
should not be as serious a problem as increasing the gas rate,
since the liquid rate appears to the first power in the x-axis of
the flooding correlation whereas the gas rate appears as a
square in the y-axis of the flooding correlation.
Finally, if the cause of the disturbance is acetone in the
water, compensation can be accomplished by decreasing the
temperature, increasing the liquid rate, or increasing the
pressure. Of course, there can be multiple causes of the
disturbance and compensation can be achieved by adjusting
two variables by smaller amounts rather than by adjusting
only one variable.
Summer 1994

Critique One of the most important points learned from
this problem (and a similar one using a tray tower) is how all
problems involving mass separating agents can be under-
stood and solved from a thorough knowledge of the Colburn
(or Kremser) charts. It is also possible to illustrate this solu-
tion on a McCabe-Thiele diagram by adjusting the slopes of
the operating and equilibrium lines. Even though use of the
Colburn (or Kremser) charts is subject to certain assump-
tions, the qualitative understanding gained is applicable to
problems which must be solved more rigorously. Therefore,
even though this problem is more qualitative than the others
presented in this paper, it is equally instructive. It also dem-
onstrates that there can be multiple causes of disturbances
and different ways to compensate. In many ways, adjusting
the temperature or pressure is the best method of compensa-
tion since flooding is not an issue.
Data involving pressure drop changes can also be included
to differentiate between some of the causes of the distur-
bance. An increase (decrease) in pressure drop would follow
an increase (decrease) in gas or liquid rate, though the sensi-
tivity of pressure drop to gas-flow rate is more significant.
No significant change in pressure drop would follow a tem-
perature change or acetone contamination of the water.
Finally, more subtle features can be included in this prob-
lem. The effect of changing flow rates on NtoG has been
ignored since it is assumed in the derivation of the design
equation for packed beds that NtoG is a constant. This is not
precisely true and depends upon the exact relationship be-
tween KG and flow rate. The dependence of NtoG is weak,
however, and it is reasonable to ignore it. This is in contrast
to the heat-transfer performance problem (problem 1).

We believe that performance problems of the type illus-
trated here enhance students' understanding of chemical en-
gineering processes. We consider them to be as essential as
design problems are in preparing chemical engineering stu-
dents for industry and that such performance problems are
sufficiently open-ended to be considered a design activity.
Performance problems require using principles presented in
one or more classes and combining them with judgment to
obtain solutions. They are realistic because they require
students to consider constraints resulting from working with
process equipment. The required calculations also allow stu-
dents the opportunity to develop expertise on process simu-
lation and spreadsheet software.

1. Bennett, C.O., and J.E. Myers, Momentum, Heat and Mass
Transfer, 3rd ed., McGraw-Hill, New York, NY, p. 749 (1982)
2. King, C.J., Separation Processes, 2nd ed., McGraw-Hill, New
York, NY, p. 594 (1980)
3. Treybal, R.E., Mass Transfer Operations, 3rd ed., McGraw-
Hill, New York, NY, p. 310 (1980) O

, classroom



PART 2. Approach at the Introductory Level*

Universitat Rovira i Virgili
43006 Tarragona, Catalunya, Spain

he objective of this paper, the second of two parts, is

to describe the introductory chemical engineering
course taught since 1985 at the former University of
Barcelona. It follows the professional and issue-oriented
holistic or integrated approach to education described in Part
1 of this paper.11] In this type of approach, students who have
the basic background in science and mathematics begin their
more formal chemical engineering education by working
together in cooperative groups, investigating and trying to
solve real engineering problems (open questions).
The introductory course described here deals with the
preliminary design of a chemical plant, and the questions
that arise are related to the elementary principles of chemical
process engineering, unit operations, and transport phenom-
ena. The integrated class work and the laboratory simulate a
real working environment, with emphasis on decision mak-
ing in relation to issues that are of interest to students, acting
as practicing chemical engineers, and to the community in
which they live. The course is organized so that students can
Learn how to ask relevant questions when dealing with
practicing engineering and public policy issues
Assume responsibility for their own learning
Experience team responsibility in class
Work in a challenging, creative, responsible, interde-
pendent and enjoyable environment.
The advantages of adopting a cooperative learning scheme
with classroom activities designed to foster creativity and
research (the discovery process) in education have been
extensively discussed elsewhere.[2-101
Students will also be learning the concepts and basic prin-
ciples of chemical engineering that are required by profes-
sionals responsible for the analysis and design of a given
chemical plant. They will be made aware of their leading

* Part 1 of this two-part paper, "Professional and Issue-Oriented
Approach," appear in the Spring 1994 issue of CEE: Volume
28(2), page 122.


Francesc Giralt is Professor of Chemical Engineering at the University
Rovira i Virgili. He received his BCh from the Institute Quimic de Sarria, his
BChE from the University of Barcelona, his MBA from the ICT, his MASc and
PhD from the Univ. of Toronto, and his ScD from the Univ. of Barcelona.
Azael Fabregat is Associate Professor of Chemical Engineering at the
University Rovira i Virgili. He received his BCh in chemistry and his ScD from
the University of Barcelona.
Xavier Farriol is Associate Professor of Chemical Engineering at University
Rovira i Virgili. He received his BCh and his ScD from the University of
Xavier Grau is Associate Professor of Mechanical Engineering at the Uni-
versity Rovira i Virgili, He received his BCh and his ScD from the University
of Barcelona.
Jaume Giralt is Associate Professor of Chemical Engineering at the Univer-
sity Rovira i Virgili. He received his BCh in chemistry and his ScD from the
University of Barcelona.
Magda Medir is Associate Professor of Chemical Engineering and Science
Education at the University Rovira i Virgili. She received her BCh from the
Institute Quimic de Sarria, her BChE from the University of Barcelona, her
MASc from the Univ. of Toronto, and her ScD from the Univ. of Barcelona.

role in the design and operation of a new generation of chemi-
cal processes that have to be efficient and safe, with minimal
adverse environmental impact, while also being economically
feasible in a global economy. The course also introduces the
roles of and opportunities for chemical engineers and provides
a perspective for subsequent classes.[ ll
The course lasts two semesters and was originally designed
for third-year chemistry or second-year chemical engineering
majors who had already been exposed to basic mathematics,
chemistry, physics, and thermodynamics. The teaching load is
75 hours of class work plus 45 hours of laboratory or field
work per semester-about 25% larger than an equivalent ma-
jor course taught in Spain with traditional teaching approaches.
During the first semester, students learn basic macroscopic
balances for mass, heat, and momentum as well as their differ-
ential counterparts in one dimension. They work in groups to
investigate and try to solve real engineering problems (i.e.,
mostly open-ended problems, related to the design of a chemi-
cal plant). Students use the knowledge and techniques they
learned in previous years and are self-motivated to go a step
further by applying these techniques to an industrial-scale prob-
lem with larger mass flow rates and energy needs.
Copyright ChE Division ofASEE 1994
Chemical Engineering Education

In the second semester, students further investigate the
transfer mechanisms and rate equations introduced during
the first semester and apply them in the form of differential
or microscopic balances to analyze a variety of situations of
industrial and societal interest.
The course ends with a project where, in addition to the
chemical engineering principles and basic economics dealt
with during the course, students have to consider some as-
pect of environmental engineering, risk assessment, and

analysis,[12,131 as an integral part of the everyday practice of
chemical engineering. The course has also been taught in the
past to chemistry students as two, one-semester courses,
each covering macroscopic and microscopic balances, re-
spectively, and both including a final project.


As can be seen in Table 1, the course begins with an
introduction to chemical engineering and process plant de-

Course Guidelines: Blocks and Activities
Introduction Chemistry, Chemical Engin- Manufacturing a given chemical; feasibility and plant location studies (5 hrs)
eering, and Technology Searching for a process: from chemistry to chemical engineering (5 hrs)
SField work: Students visit a petrochemical site (5 hrs)
SChemical Processing Process description: Scaling up, from laboratory to industrial scale; unit operations and transport
mechanisms; choosing the best proposal (5 hrs)
Macroscopic Conservation principles. Overall and partial material balances for the plant and relevant process equipment (10 hrs)
Balances equilibrium, and rate Laboratory work: Unsteady state mass balances in stirred tanks (3 hrs)
equations Analysis of plant energy requirements; identifying donors and receptors of energy in the plant (5 hrs)
Outlet temperature in a continuous adiabatic reactor (10 hrs)
Identification of sources of momentum; momentum balances in bends and other accessories (5 hrs)
SUnit Operations Laboratory work: Batch distillation of ideal and non-ideal mixutres; design and applications (3 hrs)
Continuous distillation or alternative mass transfer operations: design hypothesis/applications (10 hrs)
Design of a tubular heat exchanger (5 hrs)
Chemical reactors; types and applications; design of the process reactors) (10 hrs)
Laboratory work: Mass and energy balances in a batch reactor with Ist-order kinetics (6 hrs)
Laboratory work: Mechanical energy balance; applications to flow in conduits (6 hrs)
Design of pumps and/or compressors (5 hrs)
Free laboratory andfield work (22 hrs)
Microscopic Introduction From unit operations to transport phenomena; identification of transport mechanisms in different
balances equipment of the plant (5 hrs)
Steady-state heat Formulation of Fourier's Law from one-dimensional heat conduction data; application to furnace
conduction design; boundary conditions (5 hrs)
Design of a furnace from real data (5 hrs)
Saving energy; application of Fourier's Law and heat transfer coefficients to pipe insulation (5 hrs)
Laboratory (computer experiments): Steady heat conduction through composite materials (3 hrs)
Steady-state mass Mass fluxes, diffusion and convection of mass; formulation of Fick's Law (5 hrs)
diffusion Laboratory work: Mass diffusion with chemical reaction (3 hrs)
Laboratory (computer experiments): Measurement of mass diffusivities in gases (Arnold's cell)
and in liquids (3 hrs)
Diffusion of momentum Formulation of Newton's Law of viscosity from one-dimensional data; vector and tensor analysis;
in steady state stress and deformation tensors (5 hrs)
Microscopic momentum balances to determine the velocity profiles in simple one-dimensional
flows of industrial or environmental interest (5 hrs)
Unsteady transport Laboratory: Unsteady heat conduction in solid bodies; formulation of Fourier's 2nd Law (3 hrs)
phenomena Laboratory: Numerical solutions of PDEs; time evolution of the velocity profiles between a fixed
and a suddenly sliding wall (9 hrs)
Transport equations Lagrangian and eulerian representations; substantial derivative; formulation of generalized transport
equations (5 hrs)
Determination of velocity, temperature, and concentration profiles in industrial and environmental
flow of interest; exact, approximate, and numerical solutions (15 hrs)
Free laboratory andfield work (24 hrs)
Project Design of a chemical Preliminary design of a chemical plant; economical feasibility, plot plan, general flowsheet,
plant equipment design, and environmental issues (20 hrs)

Summer 1994 205

sign (block 1), continues with macroscopic (block 2) and
microscopic balances (block 3), and ends with a project
(block 4) as mentioned above. Each block is developed
through a set of activities that are carried out in the class-
room or in the laboratory or field. The Table includes a list
of tentative activities with their duration. Those correspond-
ing to the first semester (blocks 1 and 2) are more profes-
sionally oriented, while those of the second semester (mainly
block 3) emphasize societal issues. Activities change each
year because student interests and the chosen chemical pro-
cess vary. The guidelines presented here correspond to the
course outline given in Table 1, which represents a syntheses
of the course content over the last eight years.
Activities generally last for 5 or 10 hours of class work,
distributed in 3 hours plus 2 hours per week. The objectives
and content of the activities are decided by the class when
relevant questions are asked at the end of the previous activ-
ity. Groups of four to five students work in the class or in the
laboratory to attain the objectives initially set for that activ-
ity, under the coordination of a group leader-a role that is
assumed in a rotary fashion by all students. Each leader also
has the responsibility of evaluating group members, prepar-
ing the group's report to the instructors, and making oral
presentations to the class. The role of the instructors,
professors, and TAs is one of facilitators of learning-
helping students learn by asking pertinent questions. When
the need arises, the instructors or invited experts in the
specific field being analyzed may also dispense knowledge
to the class. A detailed description of the organization and
procedures adopted in and applied to the present course is
given in reference 1.
Introduction to Chemical Engineering
The first block is of an introductory nature and is designed
to help students who have only a basic scientific background
to become acquainted with the chemical industry.['14151 It
also illustrates the differences between laboratory processes
and operations (which students know so well) and those
carried out on an industrial scale in a chemical plant. In the
process, the students come to appreciate the differences in
the professional profiles of a chemist and a chemical engi-
neer and become aware of the role played by science (chem-
istry), engineering (chemical), and technology.[16] It may be
convenient at this point to provide the class with reports such
as the US National Research Council's report of "Critical
Technologies: The Role of Chemistry and Chemical Engi-
neering," or some equivalent publication. Since one of the
objectives of chemical engineering is the design and opera-
tion of chemical plants, the introductory block deals with
what is needed to accomplish this objective.
The introductory block and the course usually begins with
a story concerning the interest of a group of business people
willing to invest money and resources for the purpose of

producing a given chemicals) in the geographical area where
the course takes place. The story may be summarized and
explained with a simulated letter from the investors ad-
dressed to a chemical engineering consultant firm (the class)
requesting an evaluation of the feasibility and costs of the
chemical plant suited to produce such chemicalss. If, for
example, the chemical were nitric acid, the case-study ap-
proach of Ray and Johnston l17 could be an answer to that
request and the book by Sinnott[l18 would be a helpful refer-
ence for the preliminary process design.
The first activity then becomes writing a proposal, in-
cluding all the basic and preliminary items and questions
that the class thinks should be addressed during this consult-
ing job (e.g., during at least the first semester of the course).
The proposal is in fact the preliminary description of the
course contents. The following questions are generally ad-
What are the local, regional, and world-wide needs
for the chemical, and what is its total annual produc-
tion rate?
Who are the leading producers, and how will the
actual price and possible profit margins be affected
when the new plant becomes operational?
Which of the existing chemical processes is the best
for a given plant location?
Is there room for improving any of the existing
chemical processes?
Would new regulatory actions concerning the
environment, raw materials, etc., provide room for
competitive advantages in relation to current
If the plant is not local, students also address the question
Which is the best region or country in which to locate
the new plant?
In addition to considering manufacturing an existing prod-
uct or material, students become aware of other situations
that a chemical manufacturer may face, such as how to
create and produce a new material, the convenience of inte-
grating a product purchased elsewhere, how to convert a by-
product into a valuable product, environmental issues, etc.
Other questions about incorporating new technologies and
new materials or construction may also be addressed.[191
To answer the above questions, which are strongly busi-
ness and economically oriented and less related to technol-
ogy and chemistry, it is necessary to carry out a preliminary
analysis and design of the chemical plant.[19-211 Therefore,
the content of the course follows from, and is justified by,
the criteria applied by the investors in deciding the design,
construction, and operation of the plant. The initial set of
questions could be followed by more specific questions con-
cerning factors that might affect the decision of where to
Chemical Engineering Education

locate the plant. If there is a chemical industrial site located
nearby, it could be useful if the investor's letter mentions a
chemical produced in that area. This will not only give the
students a sense of reality, but it will also help facilitate the
necessary collaboration between the university and industry.
In the second activity of the introductory block, students
begin searching for the best chemical process (e.g., treat-
ment and separation of materials and chemical reaction paths)
that could be licensed to obtain the desired chemical. In the
process of answering this question, students continue to act
as chemists or first-year chemical engineering students,
searching the literature for chemical reaction information as
well as chemical, physical, and hazardous information about
all chemicals involved. They also search for techniques to
separate and purify the products of reaction and for informa-
tion on maximum yields and energy requirements. They
should be able to propose a laboratory setup to carry out the
process at a scale familiar to them, and they should ask
themselves, "What can possibly be the differences in design
and operation between the laboratory scale and the industrial
plant?" and "How can the laboratory operations be carried
out on an industrial scale?"
The third activity of the introductory block includes pre-
paring a proposal for implementing the process on an indus-
trial scale. The students should identify the differences be-
tween the laboratory and an industrial scale, including a
comparison of the type of equipment (or unit operations), the
mode of operation (discontinuous or continuous), and the
operating conditions isothermall, adiabatic, variable tem-
perature, isobaric, etc.). The comparisons will bring atten-
tion to the difficulties involved when large amounts of chemi-
cals have to be processed at possibly high temperatures and
pressures and-thus, demonstrating the need for control strat-
egies, providing for safety, and meeting environmental stan-
dards. The basic content and principles of chemical engi-
neering will be made clear to the students.
The third activity continues with the classification of all
operations and the identification of the underlying transport
mechanisms. This, in turn, helps students identify the need
for basic macroscopic balances for mass, energy, and mo-
mentum as a necessary part of the design. The next subject
in the activities constituting the second block of the course is
thus defined. Finally, the activity and the introductory block
may conclude with an extended closing presentation, a dis-
cussion of the results, and a decision concerning the chemi-
cal process best suited to the problem-which is the process
that will be studied by the class during the rest of the course.
The first block is also used to acquaint students with the
course methodology and procedures.lI] This is the reason
why it has also been so extensively described here. Group
work and class discussion are favored from the beginning,
and the initial leading role played by the professor is pro-
gressively decreased. It should be noted that the content of
Summer 1994

the introductory activities is well established in the course
regardless of the active role played by the students in decid-
ing the topics to be considered on a yearly basis. What has
been presented above roughly reflects the content of these
activities during the past eight years.
Macroscopic Conservation Principles and Balances
The second block covers mainly macroscopic balances for
mass, energy, and momentum, for the whole or parts of the
process,[22] and some unit operations. It also may include
microscopic or differential balances in one direction if needed.
This is the case when dealing with plug-flow situations in
preliminary heat exchanger and tubular chemical reactor
designs. Transient operations are incorporated either when
batch operations take place in the process or as a generaliza-
tion of steady balances. Also, examples of loading and un-
loading tanks or equipment, and simulations of start-up situ-
ations help illustrate time dependence. Students learn how to
extend their experience on closed systems to open systems.
Whenever transfer rates occur across interfaces bounding
one-dimensional flows within a given piece of equipment,
calculations are performed using mass/heat transfer coeffi-
cients or using efficiencies provided by the professor or
found in the literature. Students generally work with a vari-
ety of books published in English or in Spanish on chemical
engineering principles, process plant design, unit operations,
and transport processes.
Some activities in the second block require knowledge
not yet acquired by the students and which is difficult for
them to learn on their own in a short period of time. In these
cases, the professor may use part of the activity time to
present and discuss these new concepts or subjects. Table 1
shows that the chemical plant under study will probably
include heat exchangers, continuous separation equipment,
pumps and compressors, etc. Other equipment not present in
the chemical plant may be introduced and studied, for ex-
ample, as possible alternatives. Also, the need to recover
valuable unreacted chemicals may lead to the study of re-
cycled material balances.
The design of any piece of equipment can be carried out in
a set of separate activities if the instructors introduce the
necessary additional material to students in seminars or lec-
tures. For example, students understand intermittent (batch)
distillation from their chemistry experience in the laborato-
ries, but they may need help in learning continuous separa-
tion processes and in formulating hypotheses to simplify the
calculation equations necessary to design the plant. These
seminars allow students to discuss specific topics with spe-
cialists in the field, other professors, or staff from industry,
and they are organized like a continuing education program
for industry or a graduate seminar in a university. After
finishing the presentations, the specialists become engaged
in group discussions or mini-lectures at the students' re-

quests.[31 Coordinating classwork and outside contributions
is complex because students' interests determine the topics
of concern, but after some experience with the course, plan-
ning these related activities becomes an easier task.

Microscopic Balances
The second semester (the third block) begins by focusing
on the use of microscopic balances to characterize transport
phenomena situations of interest in the chemical plant al-
ready designed and around the site. The conservation prin-
ciples are applied in differential form to further study some
of the activities carried out during the first semester and to
provide information for decision-making in relation to soci-
etal issues that may arise. This procedure for linking the first
and second semesters of the course not only reinforces the
learning process but also shows students how to increase
their depth of analysis by asking pertinent questions.
For example, the first activity of this third block examines
how the plant under study can be further analyzed and how
equipment design and operation can be improved. One an-
swer to these questions is to better understand and character-
ize the transport processes occurring in the plant and, thus,
moving from unit operations to transport phenomena, as
shown in Table 1. The objectives of this activity involve
finding the relationship between unit operations and trans-
port phenomena and identifying the different types of bal-
ances, their characteristics and applications. The actions un-
dertaken by students to attain these objectives include:
Analysis of the process flow sheet of the previously
designed plant
Identification of the physical, chemical, and mechani-
cal operations in that process
Determination of the type of transport present in each
operation and its classification according to the
phenomena involved
Phenomenological description of possible relation-
ships between the size of equipment and the rate of
transport phenomena present
Identification of factors affecting transfer rates at a
given location in a piece of equipment,
Phenomenological formulation of the microscopic
balances for heat, mass, and momentum, with a
preliminary analysis of the need for different bound-
ary conditions.
The rest of the activities are organized so that differential
energy balances are studied first, followed by mass and
momentum. This structure was chosen because temperature
and concentration are scalars and the corresponding bal-
ances are more easily deduced and understood by students
initially. The differential mass balances are more difficult to
introduce because of the need to define and use different
velocities to characterize the diffusion of all the species

present. Students work with different transport phenomena
The initial activities of the third block deal with steady and
unsteady pure conduction and mass diffusion situations so
that the basic transport mechanisms for energy and mass
through different media are well understood first-before
convection is introduced. These activities are supported by
computer-simulated experiments to help students who are
not familiar with differential balances to deal with non-
uniform spatial distribution of variables and fluxes within a
given domain. All computer experiments show screen im-
ages which are replicas of real equipment, forcing the stu-
dents to act as if they were in the laboratory. They may
change media, or initial and boundary conditions, and get
results in a real or compressed time scale with the same
accuracy and precision as in real experiments. This scien-
tific, analytical approach forces students to gather evidence
(information) and to use it to deduce general relationships or
laws that can be readily applied to many different problems
of engineering and related societal concerns.
The societal and business competitive issues that most
commonly interest students are related to: the minimization
of energy losses in the plant; estimation and reduction of
emissions; characterization of the movement or dispersion
of contaminants through different media, or through under-
ground water beds, after accidental leaking from the plant;
and the compliance with quality standards by obtaining a
given product distribution in a chemical reactor. In some
cases, the last issue has allowed inclusion of an activity at
the end of this third block for comparing the performance of
different types of chemical reactors. If time allows, numeri-
cal two-dimensional calculations are carried out in a tubular
reactor, and predictions are compared with the one-dimen-
sional results obtained during the first semester.
It should be noted that issue-oriented engineering educa-
tion means, in this course, that students learn how to apply
the science and available technology to provide quantitative
information (estimates) for decision making. Also, these
issues encourage them to investigate and propose new alter-
natives for better understanding of the scientific phenomena
involved. Students discuss the issues in order to comprehend
the limitations involved in setting public policies, but learn-
ing engineering is the primary goal of the course. For ex-
ample, if students become involved with the issue of volatile
organic compounds (VOCs) emissions, they will have to
identify the sources and assess the limitations of the mea-
surement techniques. They will need to focus their efforts on
setting up and solving the pertinent differential balances
(see, for example, references 13 and 26).

The purpose of the final project is to make students aware
that the concepts and techniques studied in this and in previ-
Chemical Engineering Education

ous courses are very relevant for the design of economically
feasible chemical processes. The plant they design should
operate safely and with minimal adverse environmental im-
pact. The project also makes clear the need for further knowl-
edge in the different areas that make up the chemical engi-
neering profession and provides an opportunity to evaluate
the overall student performances from a professional point
of view. Students have access to all the information and
documentation from previous years.
The organization of this last block, summarizing all past
activities and forcing students to make decisions, varies
depending on the number of students enrolled in the course.
Projects are chosen by each group from a list made avail-
able by the professor and are not generally repeated for
several years. When several groups choose the same project,
a random draw is conducted. In some instances students
are allowed to work on a project not included on the
original list but which can be defined within the conceptual
framework of the course. In the present course, different
group configurations have been successfully tried, rang-
ing from two to four students per group. That decision de-
pends on enrollment.
The duration and objectives of the project may also vary
slightly from year to year depending on how the course
develops (i.e., number of activities carried out by students).
The usual length is one month, and the class work during this
period may also include complementary seminars on
principles and applications of process control to answer stu-
dent questions on how to operate a given plant. In this
respect the project is a convenient way to end this introduc-
tory course because it justifies not only the above men-
tioned methodology, organization, and guidelines, but also
the overall curricula of chemical engineering. When the
course has been offered as two separate parts, a project of
shorter duration (e.g., two weeks) has been included at the
end of each semester.

Student Assessment Students have been assessed ac-
cording only to their performance when solving individually
or as group members real engineering problems in the class-
room and in the laboratory. An external and more global
assessment of the course using different techniques (see, for
example, reference 27) is currently being developed.
The overall grade that each individual student obtains at
the end of the term is based on the following aspects:
Quality of work carried out individually, as part of a
group effort, or when leading a group-both in the
classroom and in the laboratory. This work has been
reviewed by the professor both as oral presentations
and as the reports handed in at the end of each activity.
The quality of both results and presentation is consid-
ered. Each individual group member has also been
Summer 1994

evaluated by the group leader in each activity. The
weight of all these items is 35%.
SAbility to solve unknown problems, similar to those
considered in the activities, in several test sessions of
limited duration carried out during part of several class
periods. These tests are individual, but books and notes
are allowed-again, to reproduce a real working
environment. In some cases, students are asked to
propose test questions with the understanding that the
professor will incorporate the best ones, up to 50% of
the total. The open-book tests, three per semester,
account for 30% of the total.
SPerformance in project development with its oral cross-
examination is the final and most important element to
student evaluation. The weight of this part is 35%.
The attitude of the students during the course, their ability
to write and orally communicate, and their involvement
and enthusiasm are also considered in their final grad-
ing. This more subjective component, which is considered
during an evaluation session with all instructors present,
can modify the grade resulting from the above three
aspects by ten points.
Results On one hand, an examination of student perfor-
mance during the past eight years shows that average student
participation (attendance and involvement) were among the
highest in the college of chemistry at the Tarragona campus.
The lowest attendance has been 95% of enrollment-when
class attendance in engineering schools in Spain may be as
low as 60% of enrollment. On the other hand, failure rates
are lower than in equivalent courses-generally of the order
of 10%, with below-average students performing better than
expected. It is important to realize that the number of fail-
ures may reach 60% in some science and engineering courses.
Failure rates are also lower than when the same course was
taught following a traditional approach nine years ago.
Different surveys given by external organizations indicate
that a large majority (more than 90%) of the students had a
very favorable opinion of the course. They valued the oppor-
tunity to explore and learn on their own and suggested that
other courses be organized in a similar fashion. They stated,
however, that their initial reaction was not completely favor-
able, due to several factors: because of the extra effort the
course would require in terms of participation; because it
did not use a reference textbook; and because the students
would have to assume responsibility for their own learning
(later on, this factor became highly valued). Students also
expressed some sense of initial frustration because of the
difficulties they encountered in handling real-life problems
after their years of studying passively.
Students mentioned that this course affected their overall
performance because they tended to spend more time on it
Continued on page 213



The Cornerstone of a

Modern Chemical Engineering Curriculum

University of Queensland
Queensland, Australia 4072

oday's chemical engineering students find employ-
ment in an increasingly wide variety of industries,
many of which were not considered traditional twenty
years ago. To meet the demands of these new employers, we
are being asked by industry and accreditation boards to
incorporate more and more material into the curriculum. The
current approach by many department is to "jam" new mate-
rial into the curriculum as best they can-with the result that
while we are covering more material, we are doing a disser-
vice to the students through the disjointed and rushed man-
ner in which the material is taught.
It is evident that "something has to give," and the curricu-
lum should give before we or the students give. Process
systems engineering (PSE) is a partial, but significant, solu-
tion to the dilemma.
Process systems engineering can be defined as a system-
atic approach to the design, analysis, and operation of pro-
cesses, ensuring they are
optimal at the design and operation stage
> controllable
flexible over a range of operating conditions
> environmentally acceptable
From this definition it can be seen that PSE is a multifac-
eted approach to the design and analysis of processes which
incorporates all aspects of chemical engineering. As a result,
it is difficult to teach. There are several different philoso-
phies for teaching process engineering, and some people
have strong feelings about which approach is most appropri-
ate; some feel that process engineering should be taught via
a final-year design course, while others try to integrate it into
several courses. The use of computers is frequently even
more of a contentious issue. Some believe that the use of

' University of Waterloo, Waterloo, Ontario, Canada N2L 3G1

computers and sophisticated software (that students often
don't completely understand) prevents them from gaining
insight into chemical engineering problems. This can also
lead to the "garbage in/garbage out" syndrome. On the other
hand, others feel that process engineering can be approached
as a mathematical programming problem, and they encour-
age the use of computers.
Clearly, the solution lies somewhere in the middle. PSE
should be taught as a subject and used as a tool to aid in
teaching other subjects.

There are a number of inducements for the introduction of
PSE on a wide scale as well as resistance to it. Some of the

Peter L. Douglas is an Associate Professor of
Chemical Engineering at the University of Water-
loo. He holds a PhD degree from the University of
Waterloo. His teaching and research interests are
in process systems engineering-process model-
ing, simulation, optimization, and control.

Peter L. Lee is currently Head of the Department of
Chemical Engineering at the University of
Queensland. He has research interests in most
aspects of computer-aided process engineering,
with a particular focus on process control. He joined
the department at Queensland in 1983. He has
published over one hundred papers and two books.

lan Cameron is a Reader in Chemical Engineering
at the University of Queensland. He graduated from
the University of New South Wales and obtained his
PhD from Imperial College, London. He joined the
department after working as an UN consultant in
process engineering. His research interests are in
the areas of process systems dynamics and design.
Copyright ChE Division ofASEE 1994
Chemical Engineering Education

Process systems engineering is the cornerstone of
a modern ChE curriculum. By viewing processes
as systems, students and faculty will be able to
focus more clearly on the curriculum-thus
streamlining the material presented.

inducements are
Chemical engineering departments are continually
being asked to incorporate more material into their
Many chemical engineering students seek careers in
the process industries, and most end up working in the
analysis and operation of processes where PSE
approaches are common
The variety of career possibilities is increasing, and the
curriculum must be general enough to prepare students
to adapt to technology that they may not have encoun-
tered in their undergraduate education
Information processing has become important in all
engineering disciplines as well as in business and
The PSE approach streamlines the curriculum by
helping faculty and students to focus on the essence of
chemical engineering
The most often cited obstacles to incorporating PSE are
Lack of trained personnel
Cost of implementing PSE in the curriculum
The above reservations are important considerations. There
is a lack of competent chemical engineering faculty who can
implement and teach in a PSE-based curriculum. In addition,
the cost of the necessary software and hardware is substan-
tial. But the most significant resistance to change is the
attitude of faculty members who take a lofty pedagogical
view that PSE is simply using black-box programs that
cloud student understanding of fundamentals, resulting in
computer programmers rather than chemical engineers. The
reality is, however, that PSE, when properly taught, actually
enhances the students' understanding of the fundamentals.
Departments wishing to implement PSE will have to come
to grips with faculty who are too set in their ways to contem-
plate overhauling their courses with new material, and who
refuse to relinquish control of the curriculum to young fac-
ulty members who will change it. Only after those attitudes
are changed can a successful implementation proceed.

An outline for a PSE curriculum is presented below. It
focuses on the specific courses that should be identified as
PSE courses and that should have a high PSE content.
PSE should play a significant part throughout the freshmen-
Summer 1994

to-senior years and should be implemented in existing
courses where appropriate. The approach presented here
incorporates several lecture courses, project courses, and the
use of computers.
A good process engineering curriculum should
Encourage team work
1 Integrate various aspects of chemical engineering
Provide exposure to process engineering technology
> Provide exposure to computer software and techniques
> Provide exposure to industrial process engineering
Should not be taught in one course
Five key phases which need to be addressed in the curricu-
lum are
1. Process awareness
2. Process flowsheeting
3. Process synthesis and optimization
4. Process operations and control
5. Case studies
Each of the above phases has one or more elements that
can be addressed in one or more courses. The implementa-
tion of the elements into courses is a strong function of the
current curriculum and other constraints within the depart-
ment and the university.
The first phase, process awareness, involves an introduc-
tion to processes and unit operations. There are two elements
that should be addressed in this phase: heat and material
balances (often addressed in a single course) and qualitative
topics and activities such as
> Basic process goals (technical, economic, health,
safety, and environmental)
> The process as a system of inputs, output, recycle,
interactions, etc.
> Plant tours
> Simple lab experiments
> Reading process blueprints and drawing process flow
> Demonstrations of various unit operations
(The second element above may be taught as a separate
course or can be incorporated into the heat and material
balance course as a lab.)
The second phase, process flowsheeting, is a formalized
treatment of process flowsheets. Now that students have an
understanding of processes and heat and material balances,
they can be introduced to the structure of process flowsheets
and computer-aided process flowsheeting packages such as
Aspen or Hysim. The important elements addressed in this
phase are
> Structure of flowsheets
> Degree of freedom analysis
> Difference between manual and automatic solution

> Recycle structure
> Solution techniques (equation oriented, sequential
> Models (how they are created and used in the simulator)
> Thermodynamics
> Convergence promotion methods
This phase should be introduced through formal lectures,
together with a computer lab that will allow students to study
various flowsheeting problems. The course should be intro-
duced as early as possible in the curriculum so that students
have an opportunity to understand how process engineering
is affected by all other chemical engineering courses and so
they can use the software packages in their other courses.
Students are often introduced to the flowsheeting packages
in their final year in conjunction with a design course-it
is too late at that point for them to use the system in
courses such as thermodynamics, mass transfer, economics,
heat transfer, etc. Also, the students gain a greater apprecia-
tion and understanding of these other courses by studying
process engineering.
The third phase, process synthesis and optimization,
focuses on more advanced techniques in process flowsheeting.
The first two phases have focused on analysis of processes,
first by hand calculations and then by simulation packages.
Students are now ready to think about optimization. Concep-
tually, the optimization of process variables in a single unit
(e.g., temperature, pressure, reflux ratio) is easy for students
to visualize. A more difficult problem is the synthesis prob-
lem. Optimization software routines are available in some
flowsheeting packages as well as some stand-alone optimi-
zation software packages. There is little synthesis software
available for teaching purposes, however. This phase should
be addressed in a lecture courses) with a computer lab, and
the elements considered should include
> Single variable and multivariable optimization
> Linear, nonlinear, and mixed integer programming
> Unit optimization
> Process optimization
> Process synthesis (separation sequences, HX networks,
and flowsheets)
> Design and analysis in the face of uncertainty
> Expert systems
> Loss prevention and hazard analysis
Phase four, control and operation, focuses on the con-
tinuous operation of process plants. By this time, students
should have mastered the concepts of steady-state analysis
and design and should be ready for operational issues. The
key elements introduced here include
> Dynamics
> Process control

> Process variable interaction
> Stability
> Process planning and scheduling
> On-line optimization
> Control system synthesis

This phase involves a lecture component and a laboratory
component. In the lab, students can study the dynamics and
computer control of actual lab processes and/or work on
computer simulations of processes.
Phase five is the use of case studies. It is paramount that
the students be exposed to a variety of case-study problems
designed to illustrate the various aspects of process engi-
neering in the four preceding phases. Case studies can be
implemented in a variety of ways: multiple assignments
performed in the previous phases; research projects; a final-
year design project; industrial design projects; a combina-
tion of the foregoing.
On its own, a final-year design project is not an adequate
tool for teaching process engineering. In fact, the individual
assignments in each of the phases are more important than
the final-year design project. The ideal would be multiple
assignments in each of the phases and a final-year design
project supplied by industry since industrial design projects
are more representative of what the student will face in
industry. Often, faculty dream up large grass-roots design
projects involving all aspects of process engineering in one
design-although this may be interesting, few such projects
exist and even fewer students are likely to work on the
complete design of a large process. Process engineers are
more likely to be faced with retrofit, analysis, optimization,
or control problems involving one or two units.

The development and implementation of a comprehensive
process engineering curriculum is a strong function of the
research interests of the faculty. It is therefore difficult, if not
impossible, for all departments to implement all of the ideas
presented here. But for those departments just starting out or
those that want to make changes, the following relatively
simple steps should be considered.
Clearly identify the courses where PSE is to be
Contact local industry to give PSE lectures
Introduce a computer simulation package such as
the PC-based Hysim in an upper-year course
(migrate to early-year courses later)
Form collaborative links with other universities
to share the teaching development load
Run the same assignment in a process engineer-
ing course and a companion course, e.g.,
thermodynamics or separation processes.
Chemical Engineering Education

Process systems engineering is the cornerstone of a mod-
ern chemical engineering curriculum. Since the systems ap-
proach is fast becoming a fact of life in the worlds of busi-
ness and commerce, it is imperative that our students and
faculty become familiar with it. In addition, the use of PSE
technology will allow us to effectively incorporate more
material into the curriculum through computer-aided learn-
ing and simulation. By viewing processes as systems, stu-
dents and faculty will be able to focus more clearly on the
curriculum-thus streamlining the material presented.
A good understanding of PSE enhances student under-
standing of chemical engineering science since the PSE course
material and software are based on chemical engineering
fundamentals. Therefore, the PSE case studies actually rein-
force the traditional course material. O

Continued from page 209.
than on their other courses, and they reported that their
interest in the course was the main cause for spending extra
time. Some students (less than 10%) said that they felt
uneasy about making decisions independently. This
minority also felt they could have learned more (contents) if
the professor had assumed a more active and leading role.
Most students were surprised by the importance that presen-
tations have on the class' opinion about a given work, re-
gardless of its intrinsic quality. All of the students thought
that more time should be assigned to the project. Final
reports exceeded expectations, however. The overall rating
of the course was among the highest during its eight years
of existence, with students placing great value on the
instructor's efforts to bring the practicing world of the engi-
neer into the classroom.
The opinion of other faculty and of industry about the
performance of our students and graduating engineers after
taking this course is favorable, as reported in the first part of
this paper.[1l Also, the implementation of this introductory
course increased enrollment in chemical engineering, par-
ticularly that of women.

The collaboration of Professors J. Grifoll, F. L6pez-Bonillo,
and J.A. Ferr6 and the support given by the Chemical Manu-
facturers Association of Tarragona (AEQT) are greatly ap-
preciated. The comments and suggestions made by Dr. H.
Thier and Professor J.A.C. Humphrey of the University of
California at Berkeley are also appreciated.

1. Giralt, F., M. Medir, H. Thier, and F.X. Grau, "A Holistic
Approach to ChE Education: Part 1. Professional and Issue-

Oriented Approach," Chem. Eng. Ed., 28(2), 122 (1994)
2. Hawley, R.C., and I.L. Hawley, Human Values in the Class-
room, Hart Publishers Co., New York, NY (1975)
3. Blanks, R.F., "Fluid Mechanics Can Be Fun," Chem. Eng.
Ed., 13, 14 (1979)
4. Smith, K.A., D.W. Johnson, and R.T. Johnson, "Structuring
Learning Goals to Meet the Goals of Engineering Educa-
tion," Eng. Ed., December, 221 (1981)
5. Goldstein, H., "Learning Through Cooperative Groups," Eng.
Ed., November, 171 (1982)
6. Johnson, D.W., R.T. Johnson, and K.A. Smith,Active Learn-
ing: Cooperation in the College Classroom, Interaction Book
Co., Edina, MN (1991)
7. Wankat, P.C., and F.S. Oreovicz, Teaching Engineering,
McGraw-Hill, New York, NY (1993)
8. Rhinehart, R.R., "Experiencing Team Responsibility in
Class," Chem. Eng. Ed., 23, 38 (1989)
9. Felder, R.M., "Creativity in Engineering Education," Chem.
Eng. Ed., 22, 120 (1988)
10. Fletcher, L.S., "The Role of Research in Undergraduate
Engineering Education," presentation at Session 33, 29th
National Heat Transfer Conference, Atlanta, GA (1993)
11. Miller, W.M., and M. A. Petrich, "A Novel Freshman Class
to Introduce ChE Concepts and Opportunities," Chem. Eng.
Ed., 25, 134 (1991)
12. Cohen, Y., W. Tsai, and S. Chetty, "A Course on Multimedia
Environmental Transport, Exposure, and Risk Assessment,"
Chem. Eng. Ed., 24, 212 (1990)
13. Allen, D.T., N. Bakshani, and K. Sinclair Rosselot, "Pollu-
tion Prevention: Homework and Design Problems for Engi-
neering Curricula," University of California, Los Angeles,
CA (1992)
14. Heaton, C.A., The Chemical Industry, Blackie, London, En-
gland (1986)
15. Heaton, C.A., An Introduction to Industrial Chemistry,
Leonard Hill, London, England (1986)
16. Encyclopaedia of Science and Technology, 7th ed., McGraw-
Hill, New York, NY (1992)
17. Ray, M.S., and D.W. Johnston, Chemical Engineering De-
sign Project: A Case Study Approach, Gordon and Breach
Science Publishers, Glasgow (1989) (Topics in Chemical
Engineering, ed. by R. Hughes)
18. Sinnot, R.K., An Introduction to Chemical Engineering De-
sign, Pergamon Press, New York (1991) (Coulson, J.M., J.F.
Richardson, J.R. Backhurst, and J.H. Harker, Vol VI)
19. Douglas, J.M., Conceptual Design of Chemical Processes,
McGraw-Hill, New York, NY (1988)
20. Baasel, W.D., Preliminary Chemical Engineering Plant De-
sign, Van Nostrand Reinhold, New York, NY (1990)
21. Peters, M.S., and K.D. Timmerhaus, Plant Design and Eco-
nomics for Chemical Engineers, 4th ed., McGraw-Hill, New
York, NY (1991)
22. Felder, R.M., and R.W. Rousseau, Elementary Principles of
Chemical Processes, 2nd ed., Wiley, New York, NY (1986)
23. Geankoplis, C.J., Transport Processes and Unit Operations,
3rd ed., Prentice-Hall, Englewood Cliffs, NJ (1993)
24. Welty, J.R., C.E. Wicks, and R.E. Wilson, Fundamentals of
Momentum, Heat, and Mass Transfer, 3rd ed., Wiley, New
York, NY (1984)
25. Bird, R.B., W.E. Stewart, and E.N. Lightfoot, Transport
Phenomena, Wiley, New York, NY (1960)
26. Chemical Manufacturers Association, Improving Air Qual-
ity: A Guide to Estimating Secondary Emissions, Washing-
ton, DC (1990)
27. Cross, K.P., and T.A. Angelo, Classroom Assessment Tech-
niques: A Handbook for Faculty, Tech. Rep. No. 88-A-004.0,
University of Michigan (1988) O

Summer 1994

W laboratory



University of Waikato*
Hamilton, New Zealand

Fluidization is an aspect of chemical engineering not
usually covered in depth at the undergraduate level,
but engineers are as likely to meet with fluidization
during their careers as they are some other, more extensively
taught, unit operations. It has applications ranging from chro-
matography and fermentation through filtration, drying, and
catalysis and is likely to be encountered by non-engineering
professionals such as chemists and biologists.
The laboratory experiment described in this paper was
designed as part of a course in process technology for chem-
istry and biology majors. Often, such courses (intended to
introduce "engineering principles" to science students) are
given toward the end of the student's schooling, and it is
difficult to pitch material at an appropriate level to students
who are senior but who have little background in engineer-
ing. For obvious reasons, the mathematical demands of this
practical session are low, but it still demonstrates basic engi-
neering principles well and provides an effective, interactive
learning experience for the student. The session is loosely
structured, giving students an opportunity to test out their
investigative skills-but not so loose as to allow them to
wander off-track. This approach avoids boring senior stu-
dents without demanding an unreasonably high level of en-
gineering knowledge.
The laboratory would suit first- or second-year chemical
engineering students and may be easily modified to include
more sophisticated concepts for advanced engineering

Conan J. Fee received his BE in 1984 and his
PhD in 1989 from the University of Canterbury
(New Zealand) and was a postdoctoral fellow
at the University of Waterloo (Canada) during
1989-90. He currently holds a joint appoint-
ment as a lecturer at the University of Waikato
and as a biochemical engineer at the Meat
Industry Research Institute of New Zealand.
His research interests include bioreactors,
bioseparations, and hemodynamics.

Address: Centre for Technology, University of Waikato, Private
Bag 3105, Hamilton, New Zealand

Students are given a brief introduction to the concept of
fluidization and it's use as a processing tool, including rea-
sons why one would want to contact a fluid with a solid in
the first place. This section includes a qualitative description
of the desirability on the one hand of using small particles
that have a high surface-area-to-volume ratio, and, on the
other hand, the need to keep the pressure drop through such a
bed of particles low.
A comparison with a packed bed is made to highlight
some advantages of the fluidized bed in terms of lower
pressure drops, uniformity of temperature, a greater toler-
ance for solids in the feedstream, etc. The concepts of fric-
tional drag around a sphere and terminal settling velocities
are also qualitatively outlined, together with the notion
that bed washout can be avoided. (The students have, by
this stage, had several lectures on fluid dynamics, so
the concepts of boundary layers and viscous drag are
not new to them.)
The students are given only the following four hypotheses
to test, with the task of describing and explaining observed
bed behavior, especially noting any differences between the
two beds provided.

Hypothesis 1: That at flowrates equal to and above the
point of minimum (incipient) fluidization the bed behaves as
a "liquid" with a density between the fluid and the solid

Hypothesis 2: That the pressure drop in the bed is a
function of the superficial velocity, us (m s-1), of the bed,

where Q is the volumetric flowrate of the fluidizing medium
(m3 s-1) and Ac is the cross-sectional area of the column

Hypothesis 3: That at the point of minimum fluidization
the frictional losses over the entire bed height will equal the
Copyright ChE Division ofASEE 1994
Chemical Engineering Education

total weight of the particles in the bed. That is, at the onset of
Drag force by Upward Moving Fluid = Weight of Particles
( pressure ( cross ) (volume)(fraction)( specific

across bed of column bed solids of solids



AP A, = W = (AcLmf)(1- cmt)(ps pf)g

AP pressure drop in the bed (Pa)
W weight of particles (N)
L,,,, height of the bed at the point of minimum fluidization (m)
f,, voidage at the point of minimum fluidization (-)
p, solid density (kg m 3)
p, the fluid density (kg m 3)
g gravity (m s-)

Hypothesis 4: That above the point of minimum fluidiza-
tion the bed will expand (i.e., it's height will increase) with
increasing fluid velocity.

The amount of assistance given to the students regarding
methodology can easily be adjusted. Some will need little, if
any, help, while others will require a little more prompting.
For instance, some students can figure out on their own
how to measure emf; others might only need the hint to use
a displacement method using a measuring cylinder, while
some may need the methodology spelled out for them in
greater detail. Engineering students ought to cope with
developing the force balance expression given under Hy-
pothesis 3 by themselves.

Students are provided with two plexiglass columns (see
Figure 1). The columns can be any size, but I wanted them to
be large enough for students to be able to see what was going
on internally. The columns should be large enough to allow
the students to float or sink a few objects (such as a block of
wood) in the (fluidized) bed. The columns used in my class
are 0.45 m in height, with an inside diameter of 0.074 m.
The first column, fluidized by air, contains 0.163-mm
diameter glass beads to a height of 0.38 m (at rest), while the
second column, fluidized by water, contains 1-mm glass
beads to a height of 0.26 m. Each column has a plexiglass
support plate with 44 holes (3-mm diameter) and a fluid
distributor plate, used also to retain the bed particles, made
from 85-gm and 750-gm aperture sieve material for the air-
and water-fluidized beds respectively. Each column has a
valve and rotameter for setting and measuring volumetric
flowrates and a manometer that allows measurement of the
pressure drop between two pressure probes (Pitot tubes)
Summer 1994

located at different heights within each bed. The height of
each probe within the bed is adjustable. Bed particles are
prevented from entering the Pitot tubes by pieces of brass
sieve material held in place over the ends of the Pitot tubes
with screw-on collars. This arrangement is necessary be-
cause the sieves can block over time and it is best to replace
them regularly. Also provided is a small block of wood
which can be introduced to the air-fluidized bed via the top
of the column. Water exits the water column via a drain tube
located on the side of the column, above the bed. Air is
vented directly from the top of the air column.
Adequate flowrate ranges are 0 to 2.5 x 104m'3s- for the
air-fluidized bed, and 0 to 5 x 10-5m3s- for the water-fluid-
ized bed. The cost of the apparatus was less than NZ$2000

The students were enthusiastic, and they all remarked
positively on the fluidization laboratory when they were
asked in course appraisals to recall their most enjoyable
practical session.
The apparatus lends itself well to demonstration. It is
simple to operate, repeatable results are easy to obtain, and
there is no setting-up time required before each session.
There is no deadtime or time spent waiting for steady state,
and measurements can be repeated literally in seconds. Also,
even the most hapless students would find it difficult to harm
either themselves or the equipment.
The magical moment when the block of wood floats in
a bed of solids never fails to fascinate the students. Even
the "coolest" student in the class cannot repress a childish
amusement and the urge to repeatedly push the block of
wood into the bed and watch it bob back to the surface and
float around. If the columns are mounted so they can be
tilted, the liquid-like flow properties of the fluidized par-
ticles can be easily shown.

(Water Drain Tube
in Water-Fluidized Bed)

Air Out I- 1

Figure 1. The air-fluidized bed apparatus. A similar
column is used for water-fluidization

The following experimental results for the air-fluidized system are typical. Those for the
water-fluidized column are qualitatively similar.
For Hypothesis 1, the more mathematically literate students can derive an expression for
the effective density of the bed at minimum fluidization with little difficulty. Less quantita-
tively inclined students are satisfied with demonstrating that a block of wood with a density
between that of air and glass floats in the fluidized bed.
A plot (Figure 2) of total bed-pressure drop versus superficial velocity is sufficient to
show the existence of a relationship, as predicted by Hypothesis 2. The pressure drop in an
equivalent packed bed can be calculated using the well-known Ergun equation[']

AP 150(1-E) u, 1.75(1-e) pfu
L e3 (Odp)2 e3 sdp

Figure 2. Total bed pressure drop versus superficial velocity in the air-fluidized bed.

Bed Height vs Superficial Velocity

0.45 -


S0.41 Minimum Fluldization

o^ o
S o0o o 0

0.35I I I I I
0 0.005 0.01 0.015 0.02 0.025 0.03 0.035 0.04 0.045 0.05
Superficial Velocily [m/s]

Figure 3. Bed height versus superficial velocity in the air-fluidized bed.

where E is the bed voidage and 0
is the sphericity of the particles.
The increase in bed voidage due
to the expansion of the bed with
increasing superficial velocity
above minimum fluidization can
be calculated from measurements
of bed height. If this is taken
into account, Eq. (3) predicts
pressure-drop values which ini-
tially are close to the experimen-
tal values, but which become
higher than the experimental val-
ues as superficial velocity is in-
creased, as might be expected for
unrestrained particles. The slope
of the pressure drop versus su-
perficial velocity predicted by Eq.
(3) changes at the point of mini-
mum fluidization.

Figure 2 also illustrates that
once the particles are fluidized,
the frictional losses do not in-
crease significantly with in-
creased superficial velocities, in
contrast to the behaviour of
packed beds. This is explained
partly by the increased bed
voidage and also by the fact that
the excess air flow (above that
required for fluidization) moves
through the bed largely as
bubbles, as can be seen through
the column walls. The bubbles
bypass the solids and therefore
do not contribute significantly to
the frictional losses, similar to the
case of air bubbling through wa-
ter in which the pressure required
for air injection depends mainly
on the static pressure head and
not on the flowrate.

To test Hypothesis 3, Em must
be known. The void fraction for
non-fluidized beads, measured by
water displacement, is about 0.35
for both columns. At minimum
fluidization, bed expansion over
the rest state is negligible, so Emf
is also 0.35. The density of the
glass is given by the supplier as
2.09 g cm-. The pressure drop at
minimum fluidization is 5120 Pa,
Chemical Engineering Education

Bed Pressure Drop vs Superficial Velocity

| Minimu.nm Fliason

S5000 o O o o O o O
I o

saooo -
SExpedimenal Values
2000 / O
00 -- Equalion (3)
1000 //

Superldal Velocty [nDs]

giving a value for the left-hand side of Eq. (2) of
(5120 Pa)(0.0043 m2) = 22.0 N
compared to a right-hand side value of
(0.0043 m2)(0.380 m)(l 0.36)(2090 kg m-3 1.2 kg m- )(9.81 m s) = 21.4 N
The resultant force balance of within 3% is pretty good!
Hypothesis 4 is easily tested, as shown in Figure 3-but it requires some conceptual
thought by the students to explain the observed behavior, as follows. The frictional
drag on a particle is a function of the relative velocity between the particle and the
fluid moving through the void space surrounding it. At minimum fluidization the drag
is just sufficient to support the weight of the particles, as proposed in Hypothesis 3. As
the flowrate is increased above minimum fluidization, the particles in the bed begin to
lift due to the extra drag force generated by the greater fluid velocity in the available
void space. But the void space correspondingly increases until the fluid velocity,
relative to the particle, reduces to the level at which the drag force again just balances
the particle's weight. Hence the bed expands, but the particles are not washed out with
the fluid, and the explanation for this is consistent with the observation that the
pressure drop frictionall loss) in the bed is relatively constant above minimum fluidi-
zation (at least within the limits of this experiment).
The superficial velocity at the point of minimum fluidization, umf, can be determined
from either Figure 2 or 3, and in this case it is about 0.02 m s- The experimen-
tally determined value of uf can then be compared to that calculated from packed
bed considerations by combining Eqs. (2) and (3), equating u, with umf, and using
the voidage and bed height at minimum fluidization.21 The following quadratic in
umf is obtained:

f1.75(1-emif)Pf 1 50-em } ,
5 E, fp + 15 dp2 U nf (--E mf)Ps -Pf)g= 0 (4)

Solving Eq. (4) for umt, using the data from the air-fluidized bed, yields a value for uf
of 0.02 m s Given that Eq. (3) is expected to represent data only to within 25%, this
result is in surprisingly good agreement with the values found from Figures 2 and 3.
There are numerous points for discussion and they can be stimulated by perusing
any standard fluidization text, such as the one by Kunii and Levenspiel. A few
possibilities are:
Comparisons between the gas- and liquid-fluidized beds, such as bubbling and
slugging in the fonner, can be highlighted and the consequences for scale-up
pointed out.
How does bubbling affect fluid-solid contact?
Why are particles not washed out of the bed at superficial velocities immediately
above minimum fluidization, and does this have anything to do with bed expansion?
Why not place the pitot tubes at the very bottom or top of the bed?
Would the fluid distributor at the base affect fludization ?
What would heat transfer be like in the bed?

We have developed a low-cost fluidized bed laboratory experiment, using apparatus
that is safe and simple to operate and which requires no running costs. The level of
experimental or theoretical complexity of the laboratory session can easily be adjusted
to suit the backgrounds and capabilities of the students involved.
The experimental results can be presented and analyzed in both quantitative and

Summer 1994

qualitative fashion. Students have
found the session interesting and
enjoyable, and they relate well to
the engineering principles in-
volved, such as fluid-solid con-
tacting, pressure drop and fric-
tional losses, etc. In particular, the
session is designed to stimulate
and hold the interest of relatively
senior undergraduate students
from outside of engineering,
whose limited quantitative back-
grounds often constrain their en-
gineering practical sessions to
more mundane topics.

Ac cross-sectional area of bed, m'
dp particle diameter, m
g acceleration due to gravity, m
L bed height, m
Lm, bed height at minimum
fluidization, m
AP axial pressure drop in bed, Pa
Q volumetric flowrate, m s
u, superficial velocity, m s
Umf superficial velocity at
minimum fluidization, m s'
W weight of bed material, N

Greek Symbols
E bed voidage
En,, bed voidage at minimum
) particle sphericity
I1 I
p fluid viscosity, kg mi s
p, density of solid particles, kg
p, density of fluid, kg m


I would like to thank Ms. Jijian
Lu for her technical assistance in
developing the fluidized bed appa-

1. Ergun, Chem. Eng. Prog., 48, 89
2. Kunii, D., and 0. Levenspiel, Flu-
idization Engineering, 2nd ed.,
Butterworth-Heinemann, Bos-
ton, MA (1991) O

E classroom



Curtin University of Technology
Perth 6001, Western Australia

The Chemical Engineering Department at Curtin Uni-
versity of Technology in Perth is about ten years old,
and to date 175 students have graduated from our
program. The department has excelled in its undergraduate
Chemical Engineering Plant Design Project, having won
the Student Design Award-an annual plant design compe-
tition among the nine Australian chemical engineering
departments-for three consecutive years (1990-1992). Also,
one of our students won this award in 1987, and another
placed second in 1988.
The various components of the undergraduate curriculum
have evolved over the years, and some of them are unique to
our department. The purpose of this paper is to share our
experience in the Process Analysis Units with the chemical
engineering community. We will present a brief structure of
the undergraduate curriculum, followed by a description of
the contents of the three Process Analysis (PA) units. We
will also discuss the instructional approach and the assess-
ment procedure, and the use and integration of these units in
the other units will be clearly indicated.

The chemical engineering degree program is a four-year
course following the 12th grade of high school. About 95%
of the students are in the mainstream program, and the
success or completion rate is usually around 70%. The first-
year intake averages about thirty-five students per year. The
first and second years of the course establish a general foun-
dation in engineering and science, with emphasis on chemis-
try and mathematics. Specialized units in handling of pro-
cess materials, design of reactors, transfer of heat and en-
ergy, mixing and separation, and process control make up
the mainstream of the senior years. A plant-design project
concludes the course. It is also mandatory for our students to
complete an industrial attachment for at least twelve weeks

Moses 0. Tade is a Senior Lecturer in Chemi-
cal Engineering at Curtin University of Technol-
ogy. He obtained his BSc degree in 1980 from
the University of Ife (now Obafemi Awolowo
University) in Nigeria, and his MSc and PhD
from Queen's University in Kingston, Canada
(1982 and 1986, respectively). His current re-
search interests are in process modeling and
simulation, process optimization and control, and
Applied statistics.
Terence N. Smith completed his BE degree at
the University of Sydney in 1952. He worked at
Bahrein Petroleum Company and Australian Oil
Refining before joining the University of Adelaide
in 1959. He obtained his PhD in 1965 and moved
to Curtin University in 1982 to establish its De-
partment of Chemical Engineering, which he
heads. He has special interests in fluid mechan-
ics, handling of fluids and solids, and mixing and
separation of fluids and solids.

before graduation. This is usually undertaken after comple-
tion of the second and/or third year of the program.
The first-year students undertake a general program in
common with other engineering students. Each engineering
program differs by one or two units per semester to provide
some variation to accommodate particular needs. For ex-
ample, the chemical engineering program includes a full
science-type chemistry component. The department does not
have teaching contact with the first-year students. Teaching
activities at this stage are usually coordinated by the Sub-
Dean of Engineering.
Figure 1 shows a schematic of the chemical engineering
course. The first-year units are shown in the two left-hand
column boxes under YEAR 1, where the first column boxes
show the seven first-semester units (e.g., CHEM 115 to
ENGLISH 150) and the second column boxes indicate the
seven second-semester units (e.g., CHEM 116 to WORK-
SHOP TECH 162). The units for the two semesters of YEAR
2 are shown in the next two column boxes, while those under
YEAR 3 indicate the units for the two semesters of the third
year. The fourth-year units are shown in the last two right-
hand column boxes under YEAR 4, where the units for the

Copyright ChE Division ofASEE 1994

Chemical Engineering Education

first semester are SEP PROC 441 to CE PROJ 491, and
those for the second semester are RESOURCE MAN 442 to

The vertical lines in two of the boxes for the first semester
of YEAR 4 indicate that all the YEAR 1 to YEAR 3 (six
semesters) units must be completed satisfactorily before SPE-
CIAL TOPICS 441 and CE PROJ 491 can be done. Simi-
larly, the vertical lines in the last two boxes of the second
semester of YEAR 4 (the eighth and final semester of the CE
program) indicate that all the first-semester units of YEAR 4
must be completed satisfactorily before PLANT DESIGN
442 and DESIGN PROJ 442 can be done.

Arrows are used in Figure 1 to indicate the prerequisite
units for higher level units. For simplicity, only a few of
these arrows are shown. For example, the arrows entering
the box labeled PROC ANAL 342 indicate that PROC ANAL
242, MATH 272, and PROC ENG 242 are the prerequisites
for this unit. Space limitation does not permit any further
discussion of the complete prerequisite structure.


The three Process Analysis units, PA 241, PA 242, and PA
342 are service units since some of the other units rely on
them, as shown by the arrows in Figure 1. The contents of
each of these units are summarized in Tables 1 and 2. The
first author teaches all the three PA units. The second-year
PA units (241 and 242) are 15 credit points each, with an
allocated contact time of three hours per week over a four-
teen-week semester, whereas PA 342 is 20 credit points with
a four-hour contact time per week.

These units were originally incorporated in the curriculum
in recognition of the growing importance of data modeling,
numerical analysis, and optimization. The units support CE
Project 491/492, Plant Design 442, Process Control 342/
441, and Design Project 442, as shown in Figure 1. The
rationale for locating these units in the second and third
years of the program is to develop the ability of students in
the analysis of chemical processes and plants before special-
ized chemical engineering units such as handling of process



.0 116

175 176




101 102

105 GRAPH 106


TECH 103

TECH 162



CHEM 271 CHEM 272

PRINC 241 242

MECH 242



ANAL 241 ANAL 242


341 342


PROC 341 TRANS 342 441 MAN 442


MECH 341

; ^ PROC
CONT 342

ANAL 342

MECH 241 242 PLANT 341






PROC 441

CONT 441


MAN 442


SIGN 442

PROJ 442

FIGURE 1. Chemical Engineering Course Schematic

Summer 1994


materials, design of reactors, mass and heat transfer, etc., are
covered. The tools for this analysis are applied mathematics
and applied statistics. The components of these tools are
introduced below. The content of each unit has been orga-
nized to avoid duplication of material in any of the other PA
units. Since the same person teaches all three units, it is easy
to consolidate and integrate the content of each unit from
one level to the other, thereby ensuring that the prerequisite
requirements are satisfied.
The instruction/teaching approach is a combination of lec-
tures, tutorials, computer labs, projects, and case studies.
The tutorials and projects are run in such a way as to ensure
effective student participation in the various sections of the
units during the semester. The tutorial problems are usually
assigned a week ahead of discussion and a few students may
be called to lead discussion of specific problems. Projects
are carried out in groups of two or three students. The
objective of the project is to integrate various sections of the
unit in a given problem. Consultation times are provided
outside of lecture periods to discuss various stages of the
project. Times required for each project vary from four to
eight weeks, depending on the scope of the project. Hence
only one project is usually given per unit.
An effective assessment procedure is used for each unit to
relieve students' pressure in final exam. The mark distribu-
tion for a typical unit is as follows: assignments, 15%;
projects, 20%, examination, 65%. The examination consists
of two parts: a mid-semester test, 15%, and a final exam
which constitutes 50% of the overall mark.
The contents of the three process analysis units in Tables 1
and 2 have been divided into two distinct modules: applied
mathematics and applied statistics. Further discussion of
these units is given below.


It is usual in most chemical engineering curricula that
students either teach themselves numerical methods or take
units which are available in the mathematics department.[l]
These units, however, are mostly oriented toward the theo-
retical aspects (proofs and theorems) rather than specific
engineering applications. An alternative approach is for vari-
ous engineering lecturers to either present problems having
only analytical solutions or to introduce numerical methods
themselves. This obviously has some drawbacks. Therefore,
the objective of parts of this module is to present a unified
perspective of the most commonly used methods for numeri-
cal solution of problems. Since all the units that teach funda-
mentals of chemical engineering require solution of equa-
tions, it is logical to teach the students how to solve these
equations first, before they extensively learn about how to
formulate them. During part of the second and third year, we
strive to provide students with knowledge and experience in

applying numerical methods efficiently. We also focus
on the integration of the material with other concurrent
units. The concepts of convergence, stability, and ac-
curacy are emphasized with less theoretical detail at this
level. The applied mathematics module is given in Table
I and is made up of: Part I of PA 241; Parts I and II of
PA 242; and Part II of PA 342.

Process Analysis 241, Part I
We begin this section with a brief introduction to personal
computers. Three or four years ago, work in this section
would have been curtailed in order to allow time for a formal
introduction to MS-DOS (Microsoft[21). But in the past two
years about 60% of the students have had better exposure to
using computers, and it is foreseen that this section of the

Content of the Applied Mathematics Module
Unit Title Unit Content
PA 241 Part l: Computer Applications in CE
Introduction to MS-DOS
Introduction to spreadsheet packages
FORTRAN programming language
PA 242 Part 1: Numerical Procedures for Problem Solving
Linear and nonlinear equations
Matrix operations
Approximation of functions
Ordinary differential equations
Partial differential equations
Boundary value problems
Part II: Formulation and Solution of CE Problems Using
Linear differential equations
Laplace transforms
Periodic functions and Fourier analysis
PA 342 Part l: Optimization Techniques
Problem formulation and basic concepts
Unconstrained optimization
Single variable and multivariable systems
Constrained optimization
Linear programming technique
Lagrange multipliers
Direct search methods
Gradient projection approaches

Content of the Applied Statistics Module
Unit Title Unit Content
PA 241 Part II: Applications to CE Problems in Context of
Probability models
Frequency distribution
Variability of data
Statistical treatment and evaluation
Introduction to interactive statistical packages
PA 342 Part : Applied Statistics
Analysis of variance
Correlation and regression analysis
Design of experiments

Chemical Engineering Education

module may eventually be phased out. The section involves
about three hours of lecture on the MS-DOS operating
system together with two two-hour computer laboratories.
We distributed an assignment covering various applica-
tions of MS-DOS during the first lecture to motivate and
force students to pick up the salient features of this
system and its associated editor. We do not cover the use
of Macintosh machines since all our personal computers
are IBM compatible.
A two-hour lecture is then given on the spreadsheet sec-
tion. We discuss specific application of chemical engineer-
ing, e.g., material and energy balances, fluid mechanics,
heat transfer, statistical process control, etc. The lecture is
complemented by a two-hour laboratory period where each
student is allowed to explore the various utilities available
on the spreadsheet package, Quattro (Borlandl31), which is
licensed to the department. We encourage students to use
any spreadsheet of their choice.
We devote about ten hours of lectures (two hours per
week) to FORTRAN programming. The presentation covers
the materials in Chapters 1 to 7 of Etter,[41 which is one of
the recommended textbooks for this unit. We have restruc-
tured the presentation so as to avoid duplication of content
which can be found from chapter to chapter. We em-
phasize the need to cultivate the habit of good program
documentation and introduce the students to the LP77
FORTRAN compiler[51 during the third week of this section.
We encourage them to start building their own subroutine
library using the examples in Himmelblau,[61 Gerald and
Wheatley,[7] and Press, et al.181

Process Analysis 242
We cover the material in Table 1 under PA 242 in the
second semester of the second year. It is difficult to recom-
mend a particular textbook for the material in Part I since
most numerical analysis textbooks tend to be theoretical in

Sample of Students' Experimental Design Projects, 1992

Experimental Analysis of a Sedimentation Process
Efficiency of Model Locomotives
The PJS Challence: A 2"' Fractional Factorial Experiment
in Bike Riding
The Effect of Rig Settings and Wind Speed on Sailing
How to Get the Most Thrust from a Model Aero-Engine
A 262 Fractional Factorial Experiment for the Dyeing
Bubble Maximization in Milkshakes
+ The Factors Affecting the 3-Point Shot in Basketball
Factors Affecting Sultana Moisture

Summer 1994

nature (more so for second-year students). Therefore, the
first author has written a partially completed set of notes
which adapts the content of Gerald and WheatleyT[7 and
Riggsll] in his lectures. The material is normally covered in
about eighteen lectures (two hours per week for nine weeks).
The rest of the allocated period is used for tutorials and
computer related assignments.
The lectures begin with the solution of linear equations of
the form, Ax = b. Our approach to teaching this section is
similar to that described by Zygourakis[91 except that we do
not stress the theoretical part (necessary for a first-year gradu-
ate chemical engineering unit) to as great an extent as he did.
Students already have an appreciation of how these prob-
lems arise during the first semester on material and energy
balances. We place emphasis on the computation of a solu-
tion, if it exists and briefly mention non-uniqueness issues
without theoretical details.
We introduce the idea of iterative methods of solution for
nonlinear equations by using specific examples. The use of
polynomial expansions in finite difference approximations
of derivatives, interpolation of function values, and integra-
tion of discrete valued functions are discussed. We stress the
role of the Taylor series expansion in deriving finite differ-
ence approximations for first- and second-order derivatives,
linear, quadratic, and cubic spline interpolations. We then
cover the trapezoidal rule and Simpson's rule, and put stress
on adaptive integration and the use of Romberg's integration
in specific applications.
We discuss the solution of ordinary differential equations
(ODE) and partial differential equations (PDE) for two classes
of problems: initial value problems (IVP) and boundary
value problems (BVP). More time is spent on the IVP class
since these problems constitute a large class of chemical
engineering problems. Methods that we cover include the
Euler and Modified Euler methods, the Runge-Kutta meth-
ods, and the multistep methods (Milne's method and Adams-
Moulton method). We discuss stability and accuracy consid-
erations, using specific examples, as well as the various
sources of errors and error propagation. The solution of n-
coupled first-order ODEs using any of the above methods is
described through a complete hand-calculation for two-
coupled equations. This allows easy extension of the algo-
rithms to the n-coupled system. We develop the numerical
solutions of BVP using the finite difference approximations
of the derivatives, with the focus mainly on one-dimen-
sional, two-point BVPs. Only two methods are discussed:
the shooting method and the finite difference method with
the successive over-relaxation convergence procedure.
In Part II of PA 242 (Table 1), we reinforce the necessity
for unsteady state material and energy balances and intro-
duce additional elements of mathematical models, such
as transport rate equations and reaction rate equations.
We illustrate the effect of transportation lag on process out-

puts and discuss examples to give the students an appre-
ciation for how process models can be formulated. We
cover Laplace transforms in the context of the third-year
process control unit.
The emphasis throughout PA 242 is efficient computer
implementation of the numerical procedures discussed. The
students are forced to do this through assignments and
projects. Various software packages are available to us on
both PCs and the Vax mainframe; among them are the li-
brary programs, LINPACK, and Numerical Recipes. The
collections of software in Riggsl[' and Gerald and Wheatleyl71
have also been particularly useful. We encourage the stu-
dents to write their own codes and to adapt any of the above
software for their own software library.

Process Analysis 342, Part II
The final section in the applied mathematics module is
Optimization Techniques (Part II of PA 342, Table 1), and it
is taught during the second semester of the third year. The
material is covered in about seven weeks of three one-hour
lectures per week. An additional one hour per week is spent
on tutorial related discussions. A good reference textbook
which we have used selectively over the past three years is
one by Edgar and Himmelblau.o101 About 60% of our ex-
amples and assignments are taken from this textbook.
We address the significance of problem formulation by
using examples of different types of chemical engineering
problems and feel that the examples give students an appre-
ciation for the necessity of optimization. We emphasize the
use of prior knowledge and experience in reducing the com-
plexity of any given problem and discuss the hierarchy of
optimization levels, from individual equipment design to
management decision making. We then introduce the prop-
erties of objective functions and constraints as well as the
necessary and sufficient conditions to ensure that an opti-
mum is a minimum or a maximum. We also discuss the
characteristics of the region of search. The rest of the lec-
tures cover unconstrained and constrained optimization meth-
ods for single variable and multivariable systems.

The importance of the applied statistics module in chemi-
cal engineering education cannot be overemphasized. Dur-
ing the past decade, Western management has come to real-
ize (due to the world-wide success of some Japanese indus-
tries) that their success is totally dependent on satisfying
customers by constantly improving products and services
(quality, cost, and reliability). According to Dyson,['] the
traditional approach of "design quality" (i.e., to optimally
target the features of a product to allow the customer to
achieve maximum functionality) is now being augmented
with "conformance quality" or product consistence (i.e., mini-
mizing variation about the optimum design targets of prod-

uct features). Therefore, appropriate quality and statistical
training is required to equip industrial personnel (and in
particular, engineers) to focus on conformance quality as
well as design quality throughout their careers. This is the
motivation behind the applied statistics module in our under-
graduate program.
Various statisticians (e.g., Hogg, et al.,'21 and Bisgaard[131)
have written papers on "Teaching Statistics to Engineers,"
and the content of our applied statistics module and its
presentation are adapted to some of their recommendations.
The objectives of the module are:
Plan data collection, turn data into information,
and achieve action.
Apply the methods taught in real-life situations.
Communicate statistical information in oral and
written form.
Use computer and graphical techniques.
Plan, analyze, and interpret the results of experi-
Understand the scientific method.
This module has been taught by the first author for the past
three years. The medium of instruction during this period is:
formal lectures on basic concepts (theoretical details are
minimized and emphasis is on application); use of detailed
examples, case studies, workshop, and laboratory experi-
ence (industrial practitioners are sometimes invited to give
the case studies); use of suitable computer software; tutorials
and assignments, as appropriate; requirements of the comple-
tion of a project, usually a design of an experiment and
submission of a suitable report.
The applied statistics module is presented as parts of two
units, as shown in Table 2. The first part is given over a five-
week period during the first semester of the second year.
The class meets about four hours a week for lectures,
tutorials, and computer workshops. The second part is cov-
ered during the first five weeks of the second semester of the
third year. Two hours per week are spent on lectures,
one hour for tutorials, and another hour is reserved for stu-
dents to discuss their projects which are usually started in the
third week of the semester.
The detailed content of Part II of PA 241 (Table 2) is the
same as that of modules A, B, and C of Section 6.3 of Hogg,
et al., [12 while the content of Part I of PA 342 (Table 2) is
structured to follow the material in modules D and E of their
proposed statistical course for engineering students.
We recommend a book by Walpole and Meyersl141 for
some part of the above syllabus, and one by Box, et al.,['5] is
used as a reference textbook. The first author also has a
partially completed set of notes which is easier for the stu-
dents to understand. We also emphasize the use of statistical

Chemical Engineering Education

software packagest[6-'18 for various sections of this module.
Since these packages are easy to use, students spend less
time writing codes for appropriate statistical formula and
can concentrate on thorough problem formulation. The avail-
ability of these packages has also allowed solution of more
complex problems. Space limitation does not permit more
information on these packages here.
The most interesting part of the applied statistics module
is the final project which the students do to complete the
requirements for PA 342. This idea was adapted from
Hunter[191 and Bisgaard.1131 During the third week of the
semester, each student is required to team up with one or two
other students and to design, conduct, and analyze an experi-
ment of their own choice. A proposal to conduct the experi-
ment is due within two weeks. The proposal consists of the
objective of the experiment, its motivation, the responses)
and independent variables, the necessary resources, and the
time required to carry out the experiment. A written report
is due at the end of the semester. The projects help stu-
dents to learn the practical aspects of experimental design
and puts them in good stead to apply statistical techniques in
their final-year thesis work. Table 3 gives a representative
sample of the experiments conducted on experimental de-
sign by our students in 1992.

Our process analysis units attempt to introduce students to
the basics of numerical analysis, optimization techniques,
and applied statistics which are significant in the education
of a chemical engineer. We gear the teaching style and
instructional medium toward effective student learning and
participation in class activities. We use tutorials to facilitate
student learning, assignments to force them to study, and
projects to stretch their imagination. We use practical chemi-
cal engineering problems as examples in both tutorials and
assignments, and we assign projects to integrate various
sections of the material covered with other chemical engi-
neering units. Emphasis throughout the units is on efficient
computer implementation of popular numerical algorithms
as well as use of available software packages and libraries.
We encourage students to write their own codes for some of
the assignments and projects. This is necessary because some
of the library packages require user calling programs.
An effective assessment method is used so that perfor-
mance does not rely mainly on a final examination. Student
responses to the unit evaluation questionnaire indicate that
they particularly like the project requirement for each of the
process analysis units. These projects point out some of
the real problems that a chemical engineer is required to
solve, as well as integrating various sections of the units in
problem solving. Among other things, students also learn to
get along with other group members during the execution of
the project, thus emphasizing that chemical engineering is

rarely an individual profession.
The delivery of these units is considered a dynamic
process where improvements are continually sought and
made. In particular, more chemical engineering case studies
and examples are introduced each year to enable students
to appreciate the importance of these two modules in
their careers well beyond graduation. Comments and sug-
gestions from readers on case studies in these areas will be

The authors are grateful for comments from anonymous
reviewers which helped in improving the quality of this

1. Riggs, J.B., An Introduction to Numerical Methods for Chemi-
cal Engineers, Texas Tech University Press, Lubbock, TX
2. Microsoft Corporation, MS-DOS Version 3.3 Manuals,
Redmond, WA (1988)
3. Borland International, Inc. Quattro Manuals, Scotts Valley,
CA (1990)
4. Etter, D.M., Structured Fortran 77 for Engineers and Scien-
tists, 3rd ed., The Benjamin/Cummings Pub. Co., New York,
NY (1990)
5. Lahey Computer Systems, Inc., LP77 Compiler, Incline Vil-
lage, NV (1989)
6. Himmelblau, D.M., Basic Principles and Calculations in
Chemical Engineering, 5th ed., Prentice-Hall, Inc.,
Englewood Cliffs, NJ (1989)
7. Gerald, C.F., and P.O. Wheatley, Applied Numerical Analy-
sis, 4th ed., Addison-Wesley Publ. Co., New York, NY (1989)
8. Press, W., B. Flannery, S. Teukolsky, and W. Vetterling,
Numerical Recipes: The Art of Science of Computing, Cam-
bridge University Press, New York, NY (1986)
9. Zygourakis, K., "Linear Algebra for Chemical Engineers,"
Chem. Eng. Ed., 18, 176 (1984)
10. Edgar, T.F., and D.M. Himmelblau, Optimization of Chemi-
cal Processes, McGraw-Hill Book Co., New York, NY (1988)
11. Dyson, L.A., Industrial Statistics and Quality Training for
Engineering Students, Alcoa of Australia Ltd., Private Com-
munications, March (1990)
12. Hogg, R.V., et al., "Statistical Education for Engineers: An
Initial Task Force Report," The Amer. Statistician, 39, 169
13. Bisgaard, S., "Teaching Statistics to Engineers," The Amer.
Statistician, 45, 274 (1991)
14. Walpole, R.E., and R.H. Myers, Probability and Statistics
for Engineers and Scientists, 4th ed., Macmillan Pub. Co.,
New York, NY (1989)
15. Box, G.E.P., W.G. Hunter, and J.S. Hunter, Statistics for
Experimenters: An Introduction to Design, Data Analysis,
and Model Building, Wiley & Sons, New York, NY (1978)
16. Lincoln Systems Corporation, ISP User Guide, Westford,
MA (1987)
17. SAS Institute, Inc., SAS User's Guide: Basics Version 5
Edition, Cary, NC (1985)
18. Joiner Associates, Inc., JASS Manual, Version 2.1, Madison
WI (1986)
19. Hunter, W.G., "Some Ideas About Teaching Design of Ex-
periments, and 25 Examples of Experiments Conducted by
Students," The Amer. Statistician, 31, 12 (1977) O

Summer 1994

DEPARTMENT: Arizona State University
Continued from page 157.

ing, and to relate microstructure to the reliability of the final
devices. Raupp is studying the epitaxial growth of HgCdTe
through metal organic chemical vapor deposition.
Roni Burrows is investigating the effect of the treatment
of gallium arsenide surfaces with sulfur-containing media in
order to improve the electronic properties of these surfaces.
She is using real-time surface spectroscopy, HREM, and
ion-beam analysis to study the basic surface chemistry of the
processes. She is also studying the effects of chemicals,
either contaminants or those intentionally introduced, on
semiconductor surfaces.
> Biochemical Engineering Tony Garcia is develop-
ing a novel method for bioseparations involving metal affin-
ity chromatography using Ag(I) and Pt(II) as metal supports
in the separation of sulfur containing amino acids and biopoly-
mers. He is also using scanning tunneling (STM) and scan-
ning force (SFM) microscopy in the study of how cell mor-
phology and surface chemistry influence immunomodulation.
Imre Zwiebel has used his background in adsorptive
separation processes to study the adsorption of proteins
onto various substrates. Using STM, he is looking for spe-
cific bonding points of collagen on a variety of substrates
for answers to biocompatibility, wound healing, and tissue
Joe Henry, Jr., is currently focusing on biochemical sepa-
rations with emphasis on the resolution of protein mixtures.
He has recently developed a process which permits the use
of affinity-specific ligands for highly selective protein sepa-
rations in a continuous process mode.

> Process Engineering and Control Dan Rivera is
using his expertise in system identification to develop con-
trol-relevant algorithms resulting in improvements in all fac-
ets of the identification problem (experimental design, model
structure definition, parameter estimation, and model valida-
tion). The highly fluctuating economic conditions faced by
industry place importance on another of Rivera's research
areas-the development of control systems that are robust to
changing plant conditions, yet easily implemented in distrib-
uted control systems. A third research topic is the develop-
ment of a "user-friendly" CAD package to allow the BS-
level engineer to use sophisticated control technology.
Jim Kuester has a second research focus in the area of
microwave heating of fluidized beds. This form of heating
has the advantages that the reactor walls are relatively cool
and that process streams or solids are heated rapidly. Micro-
wave heating has potential applications in semiconductor
materials processing, catalyst preparation, and thermochemi-

cal conversions. He has integrated a microwave generator
and a pilot-scale fluidized bed and has performed initial
experiments in the areas of catalyst preparation and
polysilicon production from silane.
Bob Torrest is continuing his study of gas-liquid flow
through porous media in a wide variety of applications. He is
also looking at in situ, controlled precipitation of a plugging
agent in porous media necessary for profile control in oil
reservoirs and the suspension flow of aqueous polymer solu-
tions which give the high viscosity necessary to minimize
settling of the suspended particles.
Jim Beckman collaborates with a local company on the
development of a non-freon air conditioner. The uniqueness
of the unit is based on a patented highly efficient energy
transfer process. He is also investigating the incorporation of
the idea into distillation column and desalination equipment
> Engineering Education Lynn Bellamy has taken
the initiative in introducing Cooperative Education, TQM,
and Teaming to the engineering faculty, as well as work-
ing with elementary schools, high schools, and community
colleges to implement the principles in their environ-
ments. As part of the NSF-funded Integrated Curriculum
team, Bellamy is continuing his work in developing a pilot
freshman curriculum.

During the past spring semester, faculty in the three pro-
grams within the department met to develop a Vision state-
ment of the department's future. The main outcome was
recognition of the fact that we are in an unparalleled envi-
ronment arising from our unique combination of disciplines
and our setting in an expanding major metropolitan and
manufacturing center. The population growth and the con-
tinuing movement of high-tech industries into the Southwest
will result in increasing enrollments and opportunities to
coordinate research and teaching activities with industrial
partners. Having the three programs (chemical, bio, and
materials) under one administrative umbrella has already
resulted in cooperative efforts in graduate research. We be-
lieve that we can also build on this synergism in the class-
room at both the undergraduate and graduate level.
The chemical engineering faculty intend to continuously
improve our program by building on our closeness with the
bio and the materials science programs, while at the same
time maintaining our identity as a chemical engineering
program. In summary, the future of chemical engineering at
ASU is as bright as the Arizona sunshine. O
Chemical Engineering Education


This guide is offered to aid authors in preparing manuscripts for Chemical Engineering Education
(CEE), a quarterly journal published by the Chemical Engineering Division of the American Society
for Engineering Education (ASEE).
CEE publishes papers in the broad field of chemical engineering education. Papers generally
describe a course, a laboratory, a ChE department, a ChE educator, a ChE curriculum, research
program, machine computation, special instructional programs, or give views and opinions on
various topics of interest to the profession.

Specific suggestions on preparing papers *
TITLE Use specific and informative titles. They should be as brief as possible, consistent with the
need for defining the subject area covered by the paper.

AUTHORSHIP Be consistent in authorship designation. Use first name, second initial, and
surname. Give complete mailing address of place where work was conducted. If current address is
different, include it in a footnote on title page.

TEXT We request that manuscripts not exceed twelve double-spaced typewritten pages in
length. Longer manuscripts may be returned to the authors) for revision/shortening before being
reviewed. Assume your reader is not a novice in the field. Include only as much history as is needed
to provide background for the particular material covered in your paper. Sectionalize the article and
insert brief appropriate headings.

TABLES Avoid tables and graphs which involve duplication or superfluous data. If you can use a
graph, do not include a table. If the reader needs the table, omit the graph. Substitute a few typical
results for lengthy tables when practical. Avoid computer printouts.

NOMENCLATURE Follow nomenclature style of Chemical Abstracts; avoid trivial names. If
trade names are used, define at point of first use. Trade names should carry an initial capital only,
with no accompanying footnote. Use consistent units of measurement and give dimensions for all
terms. Write all equations and formulas clearly, and number important equations consecutively.

ACKNOWLEDGMENT Include in acknowledgment only such credits as are essential.

LITERATURE CITED References should be numbered and listed on a separate sheet in the
order occurring in the text.

COPY REQUIREMENTS Send two legible copies of the typed (double-spaced) manuscript on
standard letter-size paper. Submit original drawings (or clear prints) of graphs and diagrams on
separate sheets of paper, and include clear glossy prints of any photographs that will be used. Choose
graph papers with blue cross-sectional lines; other colors interfere with good reproduction. Label
ordinates and abscissas of graphs along the axes and outside the graph proper. Figure captions and
legends will be set in type and need not be lettered on the drawings. Number all illustrations
consecutively. Supply all captions and legends typed on a separate page. State in cover letter if
drawings or photographs are to be returned. Authors should also include brief biographical sketches
and recent photographs with the manuscript.
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If your deatmn is no Sotiuo, ivteo

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