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Chemical engineering education

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Title:
Chemical engineering education
Alternate Title:
CEE
Abbreviated Title:
Chem. eng. educ.
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American Society for Engineering Education -- Chemical Engineering Division
Publisher:
Chemical Engineering Division, American Society for Engineering Education
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Quarterly[1962-]
Annual[ FORMER 1960-1961]
quarterly
regular
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English
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v. : ill. ; 22-28 cm.

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Chemical engineering -- Study and teaching -- Periodicals ( lcsh )
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Chemical abstracts
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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.
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Title from cover.
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Place of publication varies: Rochester, N.Y., 1965-1967; Gainesville, Fla., 1968-

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7AHEMMRl9
ENAPWI196
APRIL 1966


FIRST AID
to Ailing Thermodynamics










The Prentice-Hall International Series

in the Physical and Chemical

Engineering Sciences


Edited by Neal R. Amundson, Head of the Department of Chemical
Engineering, University of Minnesota. The consulting editors are
Andreas Acrivos, Stanford University; John Dahler, University of
Minnesota; Thomas J. Hanratty, University of Illinois; David E. Lamb,
University of Delaware; John M. Prausnitz, University of California,
Berkeley; and L. E. Scriven, University of Minnesota.
PUBLICATIONS IN THIS SERIES INCLUDE:

COMPUTER CALCULATIONS FOR MULTICOMPONENT VAPOR-
liquid equilibria BY J. M. Prausnitz, C. A. Eckert, R. V. Orye, and J. P.
O'Connell. 1966, Price and publication date to be announced.
UNSTEADY STATE PROCESSES WITH APPLICATIONS IN MUL-
TI-COMPONENT DISTILLATION by Charles D. Holland. 1966,
Price and publication date to be announced.
MATHEMATICAL METHODS IN CHEMICAL ENGINEERING:
Matrices and Their Application by Neal Amundson. 1966, 270pp.,
$10.50
CHEMICAL REACTION ANALYSIS by Eugene E. Peterson. 1965,
276pp., $10.50
INTRODUCTION TO THE ANALYSIS OF CHEMICAL REAC-
TORS by Rutherford Aris. 1965, 286pp., $10.95
LOW REYNOLDS NUMBER HYDRODYNAMICS: With Special
Applications to Particulate Media by John Happel and Howard Brenner.
1965, 553 pp., $15.00
OPTIMUM SEEKING METHODS by Douglass J. Wilde. 1964,
282pp., $8.25
PRINCIPLES AND APPLICATIONS OF RHEOLOGY by A. G. Fred-
rickson. 1964, 326pp., $12.95
MULTICOMPONENT DISTILLATION by Charles D. Holland. 1963,
506 pp., $14.95
PHYSICOCHEMICAL HYDRODYNAMICS, 2nd Ed., 1962 by Venia-
min G. Levich. 1962, 700 pp., $15.00
VECTORS, TENSORS, AND THE BASIC EQUATIONS OF FLUID
MECHANICS by Rutherford Aris. 1962, 286pp., $10.50

PRICES SHOWN ARE FOR STUDENT USE:

for further information -
and approval copies,
write box 903

PRENTICE-HALL
Englewood Cliffs, New Jersey 07632








EDITORS'


Contents for Volume 1, No. 3, Apr. '66


37 First Aid To Ailing Thermodynamics
H. T. Bates

44 Shri Jyant Saraiya, Engineer
Lloyd Berg

46 Unit Operations To Transport
Phenomena
M. T. Willis

52 Evaluation Of An Approach
To Plant Design
D. R. Woods
and A. E. Hamielec


DEPARTMENTS

iii Editors' Corner


45 Speaking Out



48 What They're Using


R. L. Kenyon



K. M. Kiser


C'ORNER


To the question "What is engineering?" there are
a variety of answers given today. Some are help-
ful, many are confused, a few border on nonsense.
Their variegation is impressive, their capacity for
mutual contradiction startling. But within the
broad range of ideas about engineering there is
wide agreement that design-itself a subject of
diversified definition-is a central engineering
function and an earmark of the field. It is heart-
ening, therefore, to see a renascense of process
design courses in chemical engineering curricula.
The significantly creative efforts in process design
pedogogy at McMaster University, M.I.T., Dart-
mouth, and Michigan, to name a few, promise a
bright future for the teaching of design to chemi-
cal engineering undergraduates, graduate students,
and industrial practitioners.
Process design is as complex as it is important,
and to strive for it to yield increasingly optimum
plants is to move toward complexity and difficulty
that are orders of magnitude greater. In an
engineering world where the system seems to be
a new discovery in mechanical and electrical
realms, the chemical design engineer is an old
and calloused hand at dealing with the super
system: a chemical manufacturing process that is
a linkage of components each of which itself may
be a quite sophisticated system. It is appropriate,
then, that process design become an unparalleled
illustration of splendid systems engineering. The
challenge that it do so is matched by a remarkable
convergence of favorable conditions: necessary
knowledge was never more plentiful, technique
never more advanced, computation never more
facile, the incentive never stronger.
CHEM ENG ED commends to its readers the
significant articles on process design pedagogy
carried in this issue and in the preceding one.
Others will follow from time to time. Watch for
them.


ENGINEERING EDUCATION


Chemical Engineering Division, American Society for Engineering Education


Editor Shelby A. Miller
Consulting Editor Albert H. Cooper
Assistant Editor John W. Bartlett
Publications Committee of CED
L. Bryce Andersen Chairman
Charles E. Littlejohn
E. P. Bartkus
James H. Weber
Executive Committee of CED
Chairman John B. West
Chairman-elect J. A. Bergantz
Secretary-Treasurer William H. Honstead
Elected Committeemen J. T. Banchero
W. H. Corcoran
Past Chairman George Burnet


CHEMICAL ENGINEERING EDUCATION is pub-
lished four times during the academic year
by the Chemical Engineering Division, Ameri-
can Society of Education. Publication months:
October, January, April, June. Publication
and editorial offices: 201 Gavett Hall, Uni-
versity of Rochester, Rochester, N. Y. 14627.
Title registered U. S. Patent Office.
Subscription rates: To Chemical Engineering
Division members, $3.00 per year; to non-
members in the Western Hemisphere, $4.00
per year; to non-members' outside the West-
ern Hemisphere, $5.00 per year; single issue
price, $1.50. Advertising rates quoted upon
request.


The official journal of the


CHEMICAL


APRIL 1966









































































CHEM ENG ED







FIRST AID

to Ailing Thermodynamics


H. T. Bates
Professor of Chemical Engineering
Kansas State University, Manhattan, Kansas


Engineering educators stand accused by
those investigating the drop in engineering
enrollment, of practices that tend to dis-
courage students (2). It appears that there
may be just basis for the accusation, par-
ticularly apropos of some of the literature
with which students are forced to contend.
There is a literary form called the objec-
tive correlative. It was used extensively by
T. S. Eliot. It has been likened to beefsteak
that a burglar carries to divert the watch-
dog while he robs the safe (3). Mr. Eliot's
poetry abounds in this sort of thing; the
casual reader gets something-the beef-
steak-but it takes real digging to find the
underlying idea-the contents of the safe.
Eliot must have felt a little sorry for his
readers, because he later published foot-
notes to trace some of his ideas. His good
friend, Ezra Pound, on the contrary, felt
that it wasn't sporting to put in any foot-
notes at all.
Even some of the scientific disciplines are
producing technical literature that re-
sembles the objective correlative in the
confusion it offers the reader. (Nicholas
Vanserg's pieces "Mathmanship" and "How
to Write Geologese" are entertaining com-
mentaries on publications in two fields
(6, 7).) Engineering has not been a major
offender in this respect, although examples
of misleading prose and illogical termin-
ology can be found in our literature (1, 5).
An important instance occurs in the sub-
ject of thermodynamics. It is the purpose
of this article to propose reforms in the
subject; to rearrange the concepts into
forms that are more logical under modern
conditions; to alter some definitions and
conventions in the interest of clarity; and
to propose a unifying treatment that can
be presented immediately to beginning
scholars.
If this objective is to be successful, a
certain amount of re-education of faculty


members and research workers will be nec-
essary in advance of its introduction to
students in the classroom. It should be
emphasized at the outset that these pro-
posals represent some changes in point of
view, but they are in every respect alge-
braically compatible with the more tradi-
tional treatment. These changes, evolved
from experience with the difficulties that
learners have with the subject, were ac-
ceptable to those students who were
honestly trying to get the picture.

Improving the Terminology
A little investigation will reveal a number
of examples of confusing nomenclature in
thermodynamics. It is almost as if the
terminology had not been brought up to
date for 40 years. Surely it is time for a
reappraisal in the educational methods that
are needed today.
We may start with the word thermo-
dynamics itself, which means literally "heat
in motion," although other kinds of energy
transformation are just as important to the
subject as heat. A better term would be
energetic. It is really redundant to say
thermodynamics because any proper defi-
nition of heat must include the idea that it
is energy in motion. Heat, work, and elec-
tricity are all by definition manifesta-
tions of energy in motion. Unlike stored
energy, they are not associated with any
particular mass of material. They may flow
across the boundaries of a system and they
may flow through the interior. They are not
point functions. The quantity of energy
transferred across the boundaries of a sys-
tem as heat, work, or electricity depends
upon the path as well as upon the initial
and final values of state conditions such as
temperature, pressure, volume, and voltage.
The terms thermostatics, stored heat,
heat content, heat capacity, stored work,
and stored electricity are misnomers. They
conflict with the definitions; they confuse
students. We must stop using them if we
are to have a truly logical body of knowl-
edge. The idea of dividing all energy first


APRIL 1966









TABLE 1


THE DICHOTOMY OF ENERGY

All Energy
iI


Energy in Motion
I


Heat
(Q)

Mechanical
Work
(Ws)


Other
Potential
Energies


Work


Electric
Work
(E)


Pressure
Potential
Energy
(NPV)


al


External
Energy

I


I
Potential
Energy

I


Elevation
Potential
Energy


I
Stored Energy
I


Internal
Energy


I
Kinetic
Energy

2gc)


Potential Kinetic
Energy Energy
(NA) (NTS)


into two classes of energy in motion and
stored energy is basic to the understanding
of the subject, but we should not allow the
idea to be undermined by the use of un-
precise and contradictory terms.
Stored energy should be represented by
a number of names corresponding to all the
commonly recognized classifications. It is
worth noting that the classification is com-
plex. The early workers appear to have been
afraid that some little understood kind of
energy might be left out. As a result they
organized a dichotomy of energy. This is
outlined in Table I. Notice that the sub-
divisions are always made by dividing into
two classes-those that do and those that
do not meet some criterion. Thus stored
energy is divided into external energy and
internal energy. At the next level both of
these are divided into kinetic energy and


potential energy. Now there are clearly
several kinds of potential energies on the
external side and two of these are shown-
but one must remember that in certain
special kinds of problems magnetic poten-
tial energy, surface potential energy, or
other kinds must be included.
All stored energy terms are associated
with a mass of material. They are point
functions; differences in their values asso-
ciated with a change of state of the system
are determined solely by the initial and
final conditions and are independent of
the path.
Certain common energy terms have been
left out of Table I deliberately: non-flow
work, internal energy, enthalpy, and Gibbs
free energy. Some of these have their uses,
but none of them should be taught to
students at first. The reason for this is
CHEM ENG ED






that each of these terms represents an arbi-
trary combination of simpler terms, as can
be seen from the following equations

dW = dW, + d(PV) (1)
dU = dA + d(TS) (2)
dH = dU + d(PV) (3)
dF = dH d(TS) (4)

where A = Helmholtz free energy, F =
Gibbs free energy, H = enthalpy, P =
absolute pressure, S = entropy, T = abso-
lute temperature. U = internal energy,
V = volume, W = non-flow work, and
W- = shaft work.

A Canon for the First Law
The first law of thermodynamics is an
energy balance. Unfortunately, the litera-
ture is full of different statements of this
law. There seems to be no clearly recog-
nized, generally agreed upon, form that
could always be used as a starting point.
Students need such a statement which they
can use to avoid the possibility of leaving
out some energy terms that are important
to their problem. If they were to be given
a universal formulation or canon to begin
every problem, and it were clearly stated
that subsequent manipulations apply only
to a particular situation, it would be easier
to break the habit of formula snatching
which many of them attempt to practice.
In view of the fact that the first division
employed in the dichotomy of energy, Table
I, is that between energy in motion and
stored energy, it is suggested that an equal-
ity be used to relate the two kinds of
quantities in a system. As a matter of fact,
some textbooks do this by putting heat,
work, and electricity on the left side and
all stored energy terms on the right side.
On the stored energy side it is recom-
mended that one term be provided for each
kind of energy, all combination terms being
avoided. It is also recommended that the
standard form of the energy balance be
written with differentials, since deltas and
integral signs raise questions about datum
levels, the initial and final states, or con-
stants of integration-all matters having to
do with a particular problem. Beginning
engineering students should be able to per-
form the necessary integration.


With these recommendations in mind a
canonical statement of the first law can be
formulated as follows:

dQ dW. dE = dA + d(TS) + d(PV)
+ NgX\ NU2 (5)
+ )-+d -2)

where E = electricity, g = acceleration of
gravity, g, = gravitational conversion
factor, N = mass, Q = heat, U = velocity,
and X = absolute elevation.
What Is Work?
The so-called work terms in the energy
balance do not always satisfy the criterion
of representing energy in motion. Lectures
intended to establish the principle that
heat, work, and electricity are always
energy in motion are weakened by the
algebra in many textbooks. That which is
usually called non-flow work (W) in a
batch process is one such instance. This
can be shown by algebraic manipulation to
be:
W = W, + A(PV) (6)

The shaft work (W, ) clearly satisfies the
definition of work; i.e., it is energy in
motion. It requires a machine with a rotat-
ing shaft or a moving piston rod. The so-
called flow work or flowing energy term,
A(PV), is a different matter. It represents
stored energy, for it is a point function. For
this reason the terms flow work and flow
energy also should be avoided.
An excellent exercise to give students
early in their course work involves them in
a pressure-volume graph. They are asked
to choose points on the graph representing
arbitrary initial and final states and to draw
two arbitrary paths between these points
with a French curve. They are then asked
to evaluate graphically for each path the
quantity
PdV + f2 VdP


and to compare the two values with the
value of the function P2V2 PiV Since all
of the expressions give the same result, the
students can see readily that A(PV) is a
point function and that the individual in-
tegrals are not point functions, for they do
depend upon the path.


APRIL 1966






Another approach is to write A(PV) as
N A (P/p). The mass N is the capacity
factor and P/p is the intensity factor of the
energy term. The later is readily recogniz-
able as the pressure head in Bernoulli's
equation. Therefore, A(PV) is really pres-
sure potential energy. For example: putting
work into a compressor that delivers com-
pressed air to a pressure tank at the corner
service station is analogous to putting work
into a pump that supplies water to an
elevated tank at the water works. Both the
air in the pressure tank and the water in
the elevated tank possess stored potential
energy. In order to differentiate them
Ng AX/g. should be called elevation poten-
tial energy and A(PV) should be called
pressure potential energy.
Thus W turns out to be a mixture of
work and stored energy, and it should no
longer be referred to as work. Some books
try to make W look like pure work by
attempting to show that A(PV) is work.
The explanation usually goes something like
this: "The gas that goes into the process
enclosure is pushed in by the gas that
follows it, and the gas that leaves the en-
closure pushes back the atmospheric air."
This is very confusing to students because
they cannot visualize other gas or air as
being the same as the face of a piston.
They also find it hard to follow an imagin-
ary boundary that shifts as the gas passes
through it. The educational advantage of
the new point of view should be clear, for it
does not require such explanation.
The Trouble With Enthalpy
Kammerling Onnes (4) invented the term
enthalpy as a substitute for such terms as
stored heat and heat content. Although it
was a worthwhile advance, it still gives
trouble. Some students tend to equate
enthalpy with heat without regard to the
effects of other terms in the energy balance.
Of course enthalpy is a hybrid concept con-
sisting of part internal energy and part
external pressure potential energy. Such a
mixture is quite illogical though convenient
in many practical problems. A logical alter-
native would be to discard enthalpy and
return to internal energy. Unfortunately,
this is not likely to come to pass; for the
literature is full of tables and graphs of
enthalpy, and there are comparatively few


data in the form of internal energy.
The progress of understanding would be
aided, however, if the terms heat capacity
and latent heat were abandoned. These
terms provide a misleading connection be-
tween heat and enthalpy that should be
discouraged. Students will get along with
much less trouble with the terms enthalpy
capacity instead of "heat capacity at con-
stant pressure," internal energy capacity
instead of "heat capacity at constant vol-
ume," latent enthalpy instead of "latent
heat at constant pressure," and latent in-
ternal energy instead of "latent heat at
constant volume." At first these new names
seem cumbersome to old timers, but this
is not the case with beginning learners.
Extending the First Law of Energetics
In Table I and Equation 5 internal
energy is divided into internal potential
energy and internal kinetic energy. This is
done arbitrarily, calling TS the internal
kinetic energy and A (the Helmholtz free
enery) the internal potential energy. In
view of the statistical difficulties of dealing
with the interactions of all of the molecules
and sub-atomic particles this may seem to
be questionable. However, in view of the
relationship of Equation 2, the fact that
there are only two subdivisions under inter-
nal energy (no unknown form of energy
thus being overlooked), and the convention
of a form of the first law that includes no
combination terms, it is logical to make
such a division.
Handling Irreversible Processes
For a reversible process,
dQreversible = Tds (7)


dWreversible


-VdP


The canonical statement of the energy bal-
ance for such a process results from the
substitution of Equations 7 and 8 into
Equation 5 (with electricity assumed to be
zero) :
TdS + VdP = dA + (TdS + SdT)
Ng N (v2\ (9)
+ (VdP + PdV) + dX + d
gc c I
For the reversible case the like terms on
both sides of the equation may be cancelled.
But wait! All actual processes are irrevers-


CHEM ENG ED






Table


An irreversible


t-- --o-p
Pt P2
P1 = 14.7 psia
P2= 85.0 psia
VA= 0.0255 ft3
VB= 0.850 ft3
VC = 0.2245 ft3
VD = 0.00675 ft3
Cp= 7.00 Btu/lLb mole-"R)
Cv = 5.01 Btu/(Lbmole-R)
K = 1.400
n = 1.318


Energies


ideal-gas compressor

T


-- Dc

D
I I
I I
I I
I I
AiI B
I I
I I I I


SAs
A D


S S


TA a TB = 530. OR
Tc = 808. OR
TD a 700. OR
SA = + 0.040 X 103Btu/OR
SB U + 3.91 X 10-3
Sc = + 2.377 X 10-3
So a + 0.157 X 103
NA N = 0.000,0764 Lb
N 8 Nc 0.00220 Lbmole
B C mole


Btu


Function AB BC CD DA A BCD
Q 0.00 -0.76 1.67 +0.11 2.32
Ws 0.00 -5.05 0.00 +0.15 -4.90
W +2.24 -3.82 -3.43 +0.11 4.90
A (PV) +2.24 +1.23 -3.4-3 0.04 0.00
AU 0.00 +3.05 -0.47 0.00 +2.5 8
AH +2.24 +4.28 3.90 0.04 +2.5 8
TAS +1.86 -0.76 1.67 0.09 0.66
A (T S) t 0.004 0.00 0.004 0.00 0.0 0
AA 0.004 +3.05 0.466 0.00 +2.58
A F +. 2.236 +4.28 3.896 0.04 + 2.5 8
ASxI O3 +43.510 1.155 2.22 0.1 17 0.00


APRIL 1966





Table III

A reversible diesel engine


'A VB
= 2.46
= 4.10
= 24.6
= 10.0
= 1.670
= 1.000


VD
liters
liters
liters
atmos
otmos
atmos


T, =

T2 =
SA =
SB =
SDc =
SD =


SD Sc


SB
500. K
300. OK
-4.11
-0,53
+3- .03
+ 0.46


col./K
cal./K
cal./K
col./K


Energies in Calories
Function AB BC CD DA ABCD
Q 41,400. 41,780. -1,001. -1,375. + 804.
Ws O0. +1,780. + 399. -1,375. + 804.
W + 399. +1,780. 0. -1,375. +- 804.
A (PV) +4- 399. 0. 399. 0. 0.
A U +1,003. 0. -1,003 0. 0.
A H +1,400. 0. -1,400. 0. 0.
TA S +1,400 +1,780. -1,001. -1,375. + 804.
A F 0. -1,780. 399. +1,375. 804.
AS + 3.58 + 3.56 2.57 4.57 0.


CHEM ENG ED


cycle







ible. The right side of the equation repre-
sents stored energy; all of the functions on
the right side are point functions. The left
side of the equation represents energy in
motion, namely heat and work. If the work
goes into the enclosure and heat comes out,
irreversibilities and friction increase both
heat and work beyond the limiting case.
Now either the Tds or the VdP term on
the left side will have to be integrated
(graphically or formally) over the actual
path. It is not necessary to integrate both
terms, for the energy balance can be solved
for the second term on the left side. The
right side can be evaluated with the aid of
the second law.
Many textbooks seem to place too much
emphasis on reversible cases. In engineering
the greatest emphasis should be on the ir-
reversible. A useful technique in teaching
students is to represent cycles, reversible
or irreversible, on both P-V and T-S plots.
The various steps of the cycle and the com-
plete cycle should be investigated com-
pletely. All of the terms and their compon-
ents should be calculated, and all of the
numbers should be tested in the light of the
first and second laws and the various defin-
ing equations to locate errors and reinforce
understanding. A few such exercises are the
equivalent of a much larger number of
discrete one-step, one-question, one-answer
problems. Tables II and III illustrate this
technique. Students to whom algebraic
equations are somewhat unreal achieve
quicker understanding when they are re-
quired to substitute numbers, and the
inevitable mistakes that crop up are illumi-
nated immediately.

What Sign Should the Work Term Have?
The usual convention is that heat flowing
into the system is positive and work flowing
out of the system is also positive. This
appears so illogical that teachers should
keep their eyes open for a clue showing
which of these signs can be changed the
more reasonably. Evidence appears very
quickly. Inasmuch as work input, like heat
inflow, is associated with an increase in the
value of such thermodynamic properties of
the system as enthalpy and free energy, its
sign should be positive for consistency with
the general convention. If it were, both heat
and work would be positive for flow into
APRIL 1966


the system and negative for flow out of the
system-a much more satisfactory situation.
Conclusion
Thermodynamics energeticc, that is) is
ailing-or, speaking more precisely, its
pedagogy is. The illness is neither organic
nor incurable, but it is debilitating and it
should be checked. This critique has sug-
gested some therapeutic measures. Will they
be effective? Can they help students under-
stand one of the foundation subjects of their
engineering education? The experience of
one instructor is affirmative, but in the end
each must try them himself to find out.

REFERENCES
1. Anderson, H. J., J. Eng. Education, 53, (3),
xiii, (1962).
2. Bronwell, A. B., et al., J. Eng. Education, 53,
494-500 (1963).
3. Davis, E., "The Quelle Lectures," Kansas State
Univ., Manhattan, Kansas, 1963.
4. Hougen, 0. A., Watson, K. M., and Ragatz, R.
A., "Chemical Process Principles, Part I," 2nd
ed., footnote p. 247, John Wiley and Sons, New
York, 1954.
5. Inveiss, J. H., J. Eng. Education, 53, (9), xx, xxi,
(1963).
6. Vanserg, N., Am. Scientist, 46, 94a, 96a, 98a,
(1958)
7. Vanserg, N., Econ. Geol., 47 220-3, (1952).
NOMENCLATURE
A=Helmholtz free enregy
E= Electricity
F = Gibbs free enregy
g= Acceleration of gravity
gc= Gravitational conversion factor
H= Enthalpy
N=Mass
P= Absolute pressure
Q = Heat
S = Entropy
T = Absolute temperature
U= Internal energy
U= Velocity
V= Volume
W= Non-flow work
Ws = Shaft work
X= Absolute elevation
p = Density


PffI/







Shri

Jayant

Saraiya ENGINEER


Lloyd Berg
Professor of Chemical Engineering,
Montana State University, Bozeman, Montana


At 9:30 P.M. on a cold, windy night in January,
1966, the telephone rang at the Sixth Street home
of Mr. and Mrs. Jayant Saraiya in Sinclair,
Wyoming. Jay, who was watching TV, got up
and answered. "Jay? This is Sam at the plant.
The temperature on the regenerator has been
slowly dropping all evening. Thought I better tell
you." "Thanks," said Jay. "I'll be right over."
He hung up, walked over to the kitchen window
where he could see an outside thermometer
which indicated a cool seven below zero, and pro-
ceeded to don a ski parka, boots, and leather cap
with ear flaps. "I'll be at the plant for awhile;
don't wait up for me," he called to his wife. He
stepped into his 1963 Falcon, and drove the four
blocks to the plant. The plant is Sinclair Refining
Company's refinery at Sinclair, near Rawlings,
Wyoming.
Going directly to the control house, Jay talked
with Sam Watkins, the shift supervisor. He
studied the temperature, pressure, and throughput
logs of the refinery that the recording instruments
spewed out steadily. "Sam," Jay said finally,
"Let's go down to the blower house and look
around." Donning their heavy parkas and caps,
they went out into the icy wind and across the
refinery yard to a small galvanized iron building
which housed the blower for the regenerator. This
machine gulps in the enormous quantities of air
required to burn the carbon off the catalyst and
forces it into the burning vessel, called the regen-
erator. The blower was screaming at a high pitched
roar in its usual manner and at its designed
speed. Jay had noted in the control room a
reduced air flow from the blower. Now by in-
specting the blower equipment carefully, he finally
noted that the air intake duct above the roof had
built up a ring of ice which was restricting the
flow of air to the blower. Pointing this out to Sam,
he suggested that Sam call the maintenance fore-
man and ask him to chip off the ice. "I'm sure
that will correct the trouble and I'm going home,"
he told Sam. "If the temperature doesn't start
back up after they finish knocking off the ice,
call me."
Just another common incident in the working
life of an industrial chemical engineer, with this
difference. Jay Saraiya is an Indian national
trained as a chemical engineer in the United
States who plans to spend his professional career
in the U.S. A lack of interest in chemical engi-
neering on the part of U.S. youth and a burgeon-
ing demand has created an opportunity that


foreigners are taking advantage of. Some educa-
tors have estimated that we may soon reach the
point where one fifth of all chemical engineers
being graduated by U.S. engineering schools will
be non-citizens.
Jay's experience is typical. Born and raised in
Bombay as the son of a moderately wealthy
importer, Jay went to the University of Bombay
and majored in chemistry and physics. In 1959,
by straining the family's financial resources almost
to the breaking point, he went to the United
States and enrolled as a freshman in chemical
engineering at Montana State University. Tech-
nical education in India is conducted in English,
so language was no handicap. Four years later
he was graduated as a B.S. in Chemical Engineer-
ing. Immediately upon graduation he was hired by
Sinclair. Desperately short of chemical engineers
and located in what many Americans consider
"Nowheresville," Sinclair and Rawlins welcomed
Jay with open arms. Company employees found
Jay a comfortable apartment in Rawlins for $35
per month and the local newspaper ran a feature
article on Jay and his history.
Feeling that he would be a happier and more
stable employee if he were married, Sinclair
encouraged him to take his vacation ahead of
schedule to go to India to get his bride. Accord-
ingly, in January Jay married Jayshee Asher,
a Bombay girl selected with his family's approval
according to the Indian tradition.
Jay and Jayshee returned to the high, barren,
wind-swept plains of Wyoming in February.
After having spent her entire life in steaming,
teeming, tropical Bombay, Rawlins seemed like
another planet to Jayshee. But there were com-
pensations. The apartment was warm, comfort-
able, and convenient-and then there were the
stores, particularly the supermarket with its
abundance and cleanliness like nothing she had
ever experienced in India.
Spring comes late at 6500 feet altitute but it
does ccme eventually. In summer there were trips
to the nearby Wind River and Teton mountain
ranges and to Yellowstone Park.
In November, their son Monal was born. Now
the difference between India and America really
became apparent to Jayshee. What with the
washer and drier, the canned milk and baby food,
the abundance of shots, pills and vitamins, the
baby was never sick. A major crisis was narrowly

(continued on page 51)


CHEM ENG ED







R. L. Kenyon
Director of Publications SPEAKING
American Chemical Society. Washington. D.C


ABOUT Skepticism Being Better than
Paranoia.

It could be argued that what the world
offers to this year's scientific or engineering
graduate represents the greatest promise
ever held out to his kind as individuals.
Arguments on the other side are easier to
find and they agitate and stimulate. What
historian Richard Hofstadter calls the "para-
noid style" is enjoying popularity in the
United States. We can build black worries
on all sides: Business life is enforced con-
formity; technology is dominating human-
ity instead of serving it; government for the
people is perishing; and the free intellectual
stimulation of the university has succumbed
to the scramble for federal grants.
General day-to-day progress usually is
stumbling and uneven. Worthy minds are
inspired by and aspire to the high peaks of
human works. The inclination to match this
week's failures against mankind's better
achievements-as they stood out against
the poorer levels of their times--can bring
discouragement and feelings of frustration.
We hear and see evidence that among
college students there may be greater than
usual discontent with the world. Students
are reported discontented over too few
opportunities for having a hand in making
human society better. This is admirable
insofar as the attitude is based on under-
standing. But viewing a mountain from one
position doesn't tell much about how hard
it would be to climb the unseen side. Some
skepticism and probing to learn just what
can be done should be a part of the ap-
proach of any technically trained person.
Society is changing and is likely to
change with increasing speed. Such ele-
ments as business, technology's influence,
government, and the university atmosphere
all could stand some improvement. But all
of these are likely to remain influential
elements of society and, if they are to be
improved, they will have to have the driving
efforts of able people. Therein lie challenges
to the worthiest of idealists who want to
improve the human lot.
APRIL 1966


After baccalaureate (at Illinois) and doctoral
(at North Carolina) degrees in chemistry,
Dr. Richard L. Kenyon became a research
chemist with DuPont. During four years of
research, a strong interest in people and in
professional communication persisted and
ultimately led him to join the publications
staff of the American Chemical Society. As
a field editor of Chemical and Engineering
News and Industrial and Engineering
Chemistry, as managing editor of the Jour-
nal of Agriculture and Food Chemistry, as
editor of C & E N, as editorial director of
ACS's applied journals, and finally as
Director of Publications for ACS, he has
devoted two extremely fruitful decades to
the challenging business of more accurate,
more literate, more readable, and more
exciting communication in the world of
applied chemistry and chemical engineering.
Many of our readers doubtlessly have
enjoyed Dr. Kenyon's scholarly, arresting
editorials in C & E N. The message of a
recent one was so timely a piece of mature
opinion that we wished to have it respoken
from our pages. It is reprinted from the
Career Opportunities Supplement of the
March 14, 1966, issue of Chemical and
Engineering News. CHEM ENG ED is
grateful to the American Chemical Society
for permission to reprint it.


The new graduates at all levels of chem-
istry and chemical engineering probably
are, on the average, the best trained ever.
The demands for excellent training prob-
ably also will be the greatest ever. And not
only will demands for high training be the
greatest, but demands for breadth also are
growing.
There appears to be exciting opportunity
for competent, well-trained and educated
chemists and chemical engineers far beyond
the numbers that will be produced. This
is true not only in the highest form of
"pure" research, but in applied research,
technology, commerce, politics, and a host
of other pursuits. Those who want a feeling
of contributing to the improvement of
society should not turn theit backs on what
appears to be a slightly tawdry mess in
comparison to one's ideal society. There lies
a very real challenge.






Unit Operations to Transport Phenomena


M. S. Willis
Assistant Professor of Chemical Engineering
University of Dayton, Dayton, Ohio

Engineering as a profession was first
identified with weaponry and military
works. The demand by the civilian populace
for structures primarily designed for com-
merce and trade led only in the last 250
years to "civil" engineering and the civil
engineer, whose job was defined in 1828 in
the charter of the Institute of Civil Engi-
neers. Civil engineering was "the art of
directing the great sources of power in
nature for the use and convenience of man,
as the means of production and of traffic in
states, both for external and internal trade,
as applied in the construction of roads,
bridges, aqueducts, canals, river navigation
and docks for internal intercourse and ex-
change, and in the construction of ports,
harmors, moles, breakwaters and light-
houses, and in the art of navigation by
artificial power for the purposes of com-
merce, and the construction and adaptation
of machinery, and in the drainage of cities
and towns (2). This early definition of
engineering is primarily concerned with
construction not design, and with art rather
than science. It is because of this latter
point, in addition to the very ambitious
nature of the defininition, that it became
necessary to divide the field of engineering.
The mechanical engineer came to be identi-
fied with "the construction and adaptation
of machinery," the naval engineer with the
"art of navigation by artificial power," and
the sanitary engineer with "the drainage
of cities and towns." Once under way, the
subdivision of engineering increased as the
demands of industry became more spe-
cialized.
The chemical engineer did not appear
until about 70 years ago. The construction
and selection of equipment for chemical
plants was once largely in the hands of
mechanical engineers who knew some chem-
istry or chemists who knew some mechani-
cal engineering. As the process industry
grew, the problems became more complex
and peculiar, until it finally appeared that


there was a need for a distinct branch of
engineering to which such problems might
be assigned. "In response we have the
development of chemical engineering, not
as a composite of chemistry and mechanical
or civil engineering, but as a separate
branch of engineering, the basis of which
is those unit operations which, in their
proper sequence and coordination, consti-
tute a chemical process as conducted on the
industrial scale" (2). The unit operations
really became the defining concept for
chemical engineering and allowed the chem-
ical engineer to use a systematic approach
to the solution of complex industrial prob-
lems. The distinction between industrial
chemistry and chemical engineering, in fact,
is that the former is concerned with indi-
vidual processes as entities in themselves,
whereas the latter focuses attention on the
unit operations common to many processes
and on the proper grouping of these unit
operations to produce a desired product.
In 1915 Arthur D. Little formally defined
the unit operations of chemical engineering,
and in 1923 the text by Walker, Lewis and
McAdams entitled "Principles of Chemical
Engineering" appeared. During the period
from 1923 until 1960, this work and its two
revisions served as models for subsequent
chemical engineering text books (1-6).
In the mid 1950's, it became apparent to
some chemical engineers that, because of
the economic demands, there had to be a
departure form the traditional approach of
multiple scale-up in the design of chemical
plants. Some chemical engineering teachers
were finding that "too often the fundamen-
tal concepts and laws have been slighted
in the haste to teach application. The result
has frequently been that a practicing engi-
neer or graduate student, faced with prob-
lems for which his empirical training has
not prepared him, has first had to learn the
fundamental principles of the transport
processes before he could proceed" (3). The
transport porcesses underlie the unit oper-
ations of chemical engineering, for "the unit
operations themselves, although carried out
CHEM ENG ED





in a wide variety of equipment types that
apparently have nothing in common are,
from the point of view of the theory in-
volved, applications of a very few funda-
mental laws. In fact, these laws are the
fundamental laws of physical sciences that
underlie practically all technology .
[They] are: first, the conservation of mat-
ter and energy; second, the relations per-
taining to the equilibria of physical and
chemical processes; and third, the laws
governing the rate of change in systems not
in equilibrium" (2). The recent innovation,
then, is not in recognizing that the unit
operations are based on a few fundamental
laws but in teaching these laws (particu-
larly those that describe process rates) in
a separate course which "should rank along
with thermodynamics, mechanics, and elec-
tromagnetism as one of the key engineering
sciences" (4).
What Is Meant by Transport Phenomena?
Courses in transport phenomena consist
of the study of the transfer of momentum,
energy, and mass. In order to transfer any
of these quantities, a non-equibibrium situ-
ation must exist. For example, if internal
energy is to be transferred, there must be
a temperature difference. The temperature
difference is the driving force and the
quantity which is moved by this tempera-
ture difference is called the heat flux. From
the observational point of view, a linear
relation is postulated between the flux and
the driving force in which the coefficient of
proportionality is a property of the sub-
stance in which the energy transfer is
occurring. In the case of heat transfer, the
coefficient of proportionality is the thermal
conductivity, k.
The observational or phenomenological
approach is not concerned with the mechan-
ism for the transfer of this energy. For the
mechanism, the kinetic theory of molecular
motion must be considered. From the sim-
plified theory, the kinetic energy of a
spherical molecule is directly related to the
temperature
-mu2= 3KT (1)
2 2
The tendency toward equilibrium of tem-
perature then is a result of the transport
of molecules with high kinetic energy to
regions where the molecules have low kin-


etic energies and vice-versa. But while a
molecule, by its change of location, is trans-
ferring kinetic energy, it must at the same
time transfer mass, m, and momentum, mu.
On a microscopic level, the mechanism for
the transport of mass, momentum, and
energy is fundamentally molecular diffu-
sion.
From the observational point of view,
the following laws for the transfer of mo-
mentum, energy, and mass under the condi-
tion of constant density and heat capacity
define the transport properties of viscosity,
M, thermal conductivity, k, and mass diffu-
sivity, DAB.

v d(pvx (2)

Newton's Law of Viscosity

___ d(PCp T) (3)
\pCp/ dy
Fourier's Law of Heat Conduction
DA dPA (4)


Fick's First Law of Diffusion

From the simplified kinetic theory, the ex-
pressions for transport properties are:


2 (mKT)1/2
3 7r3/2 d '


k = J-K3T1/2


S 2 ( K3 /2
3 -T(4


T3/2
pdA 2


where d is the molecular diameter. Experi-
ment agrees with the temperature and pres-
sure dependence of the transport properties
as shown in Equations 5-7 and therefore
verifies the molecular transport mechanism.
This is of engineering value in that for
moderate ranges, the temperature and pres-
sure dependence of the transport properties
can be predicted.
What other information of engineering
value can be obtained from these rate
equations? The dimensions of I/a= v, DAB,
and k/ocp= a are (length) 2/time.
(continued on page 49)


APRIL 1966








USN


FUNDAMENTALS OF CHEMICAL REAC-
TION ENGINEERING, by Walter Brotz;
translation from German by D. A. Diener and
J. A. Weaver; Addison-Wesley Publishing Com-
pany, Reading, Mass., 1965. 325 pages. $15.00.


It is stated in the translators' preface of
this book that the book can be used at the
senior or first-year-graduate level. Most
seniors will in fact find it to be a rather
sophisticated mathematical treatment not
only of reaction engineering but also of
some conventional unit operations as well.
Though sophisticated, the mathematics are
not beyond that to which current under-
graduates are exposed.
Much of the material contained in the
first 183 pages is not directly related to
reaction engineering and will not be new to
a fourth-year student. In the first 68 pages,
the reader is taken through stoichiometry
and thermodynamics and introduced to
chemical kinetics and catalysis, the last two
subjects in 24 succinct pages. Primarily
these 183 pages contain a wealth of design
information about fluidized beds, packed
beds, and heat exchangers. Much of this
information is very skillfully organized into
tables and graphs. The text is short on
theory but long on application.
The remaining 231 pages are concerned
with various types of reactors and their
design. The presentation is good. More
emphasis is put on the derivation of the
equations here than in the first section and
this is as it should be. In keeping with the
first part of the book, the heat and mass
transfer aspects of reactor design are em-
phasized. The book should be of value to
those wishing to bring themselves up to
date on the subject of reaction engineering.
This reviewer attempted to use the book
for a fourth-year, one-semester course cov-
ering applications of transport theories,
including reactor design. The sections cover-
ing the conventional unit operations were
well-received. Students found the charts


and graphs particularly useful. Most dis-
turbing to them was the lack of problems
and a sufficient number of illustrative ex-
amples. While the symbols in the text have
been properly "Americanized," the formu-
lation of the equations is not always that of
the more conventional texts. As a result, the
students encountered some difficulty when
problems were assigned from other texts.
One final point: few undergraduate courses
are so broadly based that this book can be
used in its entirety. With the present curri-
culum at the State University of New York
at Buffalo this reviewer probably would try
to use it again.
For a first printing there are surprisingly
few errors. To show that it is not perfect,
however, the section on multiphase reactors
(pp. 232-246) is singled out. Here signs are
lost and notation is poor. For some reason
the symbols for the mass transfer coeffi-
cients are changed from that introduced
earlier (p. 108). Concepts like conversion
are introduced for no apparent reason. More
importantly, the development of the trans-
fer coefficients on page 235 is at best mis-
leading. Does the author (or do the trans-
lators) really mean k and k G, to be the
film coefficients pertaining to the case of
absorption without chemical reaction? Since
no use is ever made of this concept the
reader never finds out.


CHEM ENG ED


Review by K. M. Kiser
Assistant Professor of Chemical Engineering
State University of New York at Buffalo





(continued from page 4 7)
By analogy with the mass diffusivity,
DAB, v is called the momentum diffusivity
and a is called the thermal diffusivity.
Since these three quantities have the same
units, dimensionless numbers can be formed
from the ratio of any two of them. For
example, the Prandtl number is given as

PCp V momentum diffusivity
Prandtl number .=
k a thermal diffusivity


and can be interpreted as a measure of
the capacity of a fluid to diffuse momentum
as compared with its capacity to diffuse
heat. The Prandtl numbers for air, water
and mercury are approximately 1.0, 5.0 and
0.01, respectively.
The next question is how do the trans-
port properties fit into the conservation
statements for mass, momentum, and en-
ergy? The conservation statements must be
applicable to all substances and, further-
more, they must be independent of any
reference frame. The transport properties
serve as parameters in the conservation
statements and permit a distinction to be
made when the same conservation state-
ment is applied to two different substances.
For the latter requirement the conservation
statements must be expressed by a mathe-
matics which is also independent of coor-
dinate system, The calculus of vectors and
tensors transforms the basic laws from re-
ference frame to reference frame with no
change in the fundamental law.
Consider now the application of the three
conservation statements to a single one-
dimensional, time-dependent system:


8 8T\ 8T
8y \y/ 8t
Conservation of Energy

8 Y 8(PVx)\ 8(P t)
8y 8y at
Conservation of Momentum

A8 ) 8PA PA
- (DA Bp 8
sy y at
Conservation of Chemical Species


These equations are all of the same form.
Consequently, under certain conditions,
there is an analogy among the conservation
statements as well as an analogy among
the mechanisms for transfer. This analogy
can be very useful in the solution of cer-
tain engineering problems. For example, the
transfer of momentum in a wire-coating
operation where the coating is applied by
pulling the wire through a die is exactly
analogous to the flux of heat in the insula-
tion on a steam pipe. Information about
the first system can be inferred by a study
of the second, since the systems are analo-
gous.
Methodology of Transport Phenomena
In order to justify the statement made
earlier that a course in the transport pro-
cess should be ranked along with thermo-
dynamics, let us compare the derivations of
the Bernoulli equation.
In most unit operations texts, the deriva-
tion is limited to a steady flow system
consisting of a pump which takes an in-
compressible liquid at one elevation and
raises it to a second elevation at mass flow
rate w. A pound of liquid at the entrance
has a potential energy gh,, a kinetic
energy < v1>2i/p, where p3 = 1 for lam-
inar flow and p = 2 for turbulent flow,
and a pressure volume work, p,/p, which
the fluid needs to enter the system. The
pump must raise the liquid and adds work
W/w to the liquid. At the exit, the fluid has
a potential energy gh2, a kinetic energy
2/f and has a pressure volume work
of p'2/p. The Bernoulli equation is simply
written then as

< v>2 PI W
gh, + ---- +-+--E,
3 p w (11)
2 P2
P P


(9) where E. is a correction factor necessary
for the equality.
In the study of transport phenomena, the
starting point in the derivation is the local
conservation statement for momentum or
Newton's second law of motion for a fluid.
(1 Dv
p-O: = E Fi -V" V p +pg (12)
Dt i


APRIL 1966






This statement says that on a unit volume
basis, the mass times acceleration of a fluid
particle is equal to the sum of the viscous
forces, the pressure forces and the gravita-
tional forces. Since mechanical energy is the
product of a force and a displacement, this
equation can be multiplied by the fluid
velocity to obtain the local time rate of
change of mechanical energy.

D (1 \ r 1
PO- -v }2=-) V pg T* pU*g\
(13)
+PV.7 +.r: Vj

The left hand term represents the accumu-
lation of kinetic energy and the term in
brackets on the right side represents pro-
ducts of forces and velocities and hence the
rate of mechanical work done by pressure,
viscous and gravity forces. In order to
explain the last two terms, the equation of
thermal energy must be examined.

DU
P-- V. q- (pV. v.+ T :Vv_) (14)
Dt
The term of the left represents the accu-
mulation of internal energy and the first
term on the right represents heat conduc-
tion. The last two terms in the internal
energy equation also appear in the mechan-
ical energy equation but with opposite
signs. The term p V. represents compres-
sibility effects and may be either positive
or negative. The term (-. : V v), for New-
tonian fluids, is always positive which
means that this term always causes a de-
crease in mechanical energy and an increase
in thermal energy. This term then repre-
sents the irreversible degradation of me-
chanical energy into thermal energy.
In order to obtain the Bernoulli equation,
the mechanical energy equation is inte-
grated over an arbitrary volume consisting
of three types of surfaces: inlet and exit
surfaces, fixed surfaces and moving sur-
faces. The moving surfaces provide a means
of adding or removing work from'the sys-
tem, the fixed surfaces represent the con-
fines of the system and the inlet and exit
surfaces allow mass to enter and leave the
system. After integration, the result is de-
pendent only upon the inlet and outlet con-


editions and for an unsteady state system is

- (K tot + 4b tot +A tot) =
dt

-A + + G) w + W E,
2 V W
(15)

where Ktot, D tot and Atot are respec-
tively, the total kinetic energy, potential
energy and thermodynamic work content;
W is the rate at which the surroundings
perform mechanical work on the system;
and E, is the "friction loss." This term is
given by
E, = -_ (. : v) dV (16)

JV

and represents the irreversible conversion of
mechanical energy to thermal energy.
For a steady-state liquid system, Equa-
tion 15 becomes
1 Pl W Ev
gh, + -+--
2 P w w
(17)
1 P2
= gh2 + -
2

A comparison of this equation with Equa-
tion 11 indicates that


2
/ =


This derivation proceeds from a funda-
mental law to a general equation of engi-
neering utility by logical and reasonable
steps. The scope of the equation, its rela-
tion to fundamentals, and the lack of
balancing "fudge factors" illustrates to the
student the scientific basis of engineering
and gives him confidence in the application
of this equation and others of similar origin.
ACKNOWLEDGEMENT
Permission of the McGraw-Hill Book Company
to quote and paraphrase passages from the intro-
duction and first chapter of Badger and McCabe's
"Elements of Chemical Engineering" and from
the preface of Bennett and Myers' "Momentum,
Heat, and Mass Transfer"; and of John Wiley &
Sons to quote a passage from the preface of Bird,
Stewart, and Lightfoot's "Transport Phenomena"
is gratefully acknowledged.
(continued on page 51)


CHEM ENG ED






NOMENCLATURE
Dimensions are given in terms of mass (M),
length (L), time t, and temperature (T.) Vec-
tors have a single underline and tensors have a
double underline. Force is not considered a funda-
mental dimension, but is assigned instead the
dimensions of mass-acceleration instead the
dimensions of mass-acceleration product (ML/t2).
This "absolute" system of dimensions is com-
monly used by physicists, much less commonly
by engineers.
A = thermodynamic work function, ML2/t2.
Cp = heat capacity at constant pressure per
unit mass, L2/t2T.
DAB = binary diffusivity for system of species
A-B, L2t.
d = molecular diameter, L.
E, = total rate of viscous dissipation of me-
chanical energy, ML2/t3.
G = Gibbs free-energy per unit mass,
ML2/t2.
g = gravitational acceleration, L/t2.
h,. h2 = elevation, L.
= mass flux of species A in the y-direc-
A y tion, M/tL2.
K = kinetic energy, ML2/t2.
K = Boltzmann constant, ML2/t2T.
k = thermal conductivity, ML/t3T.
m = mass of molecule, M.
p = fluid pressure, M/Lt2.
qy = y-component of the heat flux vector,
M/t3.
T = absolute temperature, T.
t = time, t.
u = mean molecular speed, L/t.
v = mass average velocity, L/t.
= space average value of velocity, L/t.
W = rate of doing work on system, ML2/t3.
w = mass flow rate, M/t.
a = thermal diffusivity, L2/t.
p = velocity function (defined in Equation
18), dimensionless.
It = viscosity, M/Lt.
v = kinematic viscosity, L2/t.
P = density, M/L3.
1 = shear stress tensor, M/t2L.
> = potential energy, ML2/t2.

REFERENCES
1. Badger, W. L., and Banchero, J. T., "Introduc-
tion to Chemical Engineering," McGraw-Hill
Book Co., New York, 1955.
2. Badger, W. L., and McCabe, W. L., "Elements
of Chemical Engineering," McGraw-Hill Book
Co., New York, 1931.
3. Bennett, C. 0., and Meyers, J. E., "Momentum,
Heat and Mass Transfer," McGraw-Hill Book
Co., New York, 1962.
4. Bird, R. B., Stewart, W. E., Lightfoot, E. N.,
"Transport Phenomena," John Wiley and Sons,
Inc., 1960.


5. Brown, G. G., and associates, "Unit Opera-
tions," John Wiley and Sons, New York, 1950.
6. Coulson, J. M., and Richardson, J. F., "Chemi-
cal Engineering," 2 volumes, McGraw-Hill Book
Co., New York, 1954.
7. McCabe, W. L., and Smith, J. C., "Unit Opera-
tions of Chemical Engineering," McGraw-Hill
Book Co., New York, 1956.
8. Walker, W. H., Lewis, W. K., McAdams, W. H.,
and Gilliland, E. R., "Principles of Chemical
Engineering," 3rd ed., McGraw-Hill Book Co.,
New York, 1937.







(continued from page 44)
averted the following spring. Jay's parents insisted
that he bring his son home for a family inspec-
tion. Jay and Jayshee realized that a six-month
old child from antiseptic America would have an
extremely difficult time in India, possibly even
dying of dysentery. They finally persuaded Jay's
family to come to Wyoming instead.
Jay has moved steadily ahead with Sinclair.
Shortly after his son was born, they asked him to
move out to the company town of Sinclair so that
he would be more readily available whenever
technical difficulties arose. For $50 per month, he
rents a two-bedroom, one-floor company-owned
house. At his present salary rate of $700 per
month, he has been able to live well and still help
his family. Until his brother completed college
last summer, he contributed $100 per month
towards his expenses. Financial help to his family
in India has been accomplished with the aid of a
favorable exchange rate which converts one dollar
into four rupees.
This true story points to one way that the
continued shortage of U.S. chemical engineers is
being met. Not an isolated example by any means,
Jay Saraiya is only one of sixteen non-citizen
chemical engineers graduated and placed in per-
manent positions in the U.S. by one educational
institution, Montana State University, in the past
six years. The employers of these men include
some of the U.S.'s leading companies at some of
their most attractive locations. Just as nature
abhors a vacuum, so good jobs are going to be
filled whether or not American boys want them.












(a


APRIL 1966







Evaluation of an Approach to Plant Design

D. R. Woods and A. E. Hamielec
Associate Professors of Chemical Engineering
McMaster University, Hamilton, Ontario, Canada


Plant Design is taught at McMaster University
in two courses. The theory and design of pieces
of equipment are discussed as part of a four
credit course called Economics and Technology.
This is taught to fourth-year students for both
the fall and spring terms for two hours a week.
In addition to this course, three credits are given
to a senior project laboratory: an 80-hour work-
shop in the spring term. This paper evaluates
a novel approach to the project laboratory. The
major novelty arose in (1) the student's respon-
sibility, (2) the time allocation, (3) the staff
supervision, (4) the outside judging committee,
and (5) the problem specification. These are
discussed, and the evaluation follows.

Project Description
The Student's Responsibility:
Each student decides how he is going to make
the quantity of specification material, designs his
own plant, submits a complete report, and verb-
ally defends his approach and design before an
outside committee.
Time Allocation:
Eighty hours and only 80 hours are to be
spent on this project. Each student draws up a
time schedule for his calculations; then the
students meet as a committee and draw up a
work schedule that will be adhered to by each.
The schedule breaks into a number of major
stages. At the end of each of these, the students
meet with the staff for an hour of constructive
criticism about how each has handled the assign-
ment.
The 80 hours are divided into a 12-hour/week
design laboratory that simulates an industrial
situation. A room is booked, a filing cabinet is
placed at the student's disposal, and the design
laboratory is not supervised; but the students are
expected to be either in the booked room or in
the library during the design laboratory time. We
emphasize that they are not to work outside of
class time.
Full marks are given for the most efficient use
of the time the student allots himself for each
calculation. Marks are deducted if he does not
have each project finished on time; if he does
a five-minute calculation for a three-hour period
or if he spends time doing unimportant and unre-
lated calculations, he loses marks.
The marking scheme for each criticism session
is based on a total of 10 marks for every hour of
design laboratory that has elapsed since the last
criticism session.
The Staff Supervision:
1. Give constructive criticism after each major


design effort. While each completed project is
fresh in the student's mind we explain how he
could have saved himself time, and suggest
reliable short cuts and good design technique.
The staff members with the most experience
in the given field criticize the effort.
2. Are prepared to present request-lectures
before each major design effort. Any staff
member will present a maximum of a one-
hour workshop or discussion session provided
such a workshop is requested by the students
at least two days in advance of the lecture
time and provided that hour is the first hour
of the allocated project for the topic under
consideration.
The staff are not consulted otherwise. All the
staff are involved in this project.
The Outside Judging Committee:
The students design their plant for three out-
side judges, and not for the staff members.
To the judges we suggest a complicated mark-
ing scheme for the oral presentation. (The four
page, typed report from each student that is
given to the judges provides background informa-
tion for the judges. We feel that it is too burden-
some to ask them to mark the written reports).
After each presentation, the judges are given as
much time as they want to finish evaluating one
speaker before the next starts.
The Problem Specification:
Little information is provided in the specifica-
tion. The quantity and quality of a given product
and the utilities available-these alone are given.
Table I is a typical specification.
The students are informed also of the emphasis
expected and the report specifications.
All calculations are to include assumptions
and limitations and estimated accuracy for each
answer. The calculations must be legible and easy
to follow.
Specifications are required for each major
piece of equipment. For heat exchangers, a stand-
ard 1-in. nominal tube is stipulated and details
required include approximate tube count, tube
length, and pitch; shell diameter; baffle spacing;
pipe connections; material of construction; work-
ing pressure; and mounting instructions. A de-
tailed calculation for the selection of one pump
is needed. The types of control required must be
indicated but not specified. The mechanical design
of the reactor and of one of the major pieces of
separation equipment is to be included.
The production and the capital investment costs
are to be calculated.
The report:
The design report must be turned in one week
before the presentation day and later is filed in

CHEM ENG ED









































the chemical engineering department library. The
report consists of two parts: the body and the
appendix.
The body is a four- to five-page, double-
spaced, typed summary report of what was done,
why it was done, how it was done, and what
conclusions were drawn from the calculations.
The purpose of the report is to convince the out-
side committee that the best possible design has
been turned out in the time available. The readers
are the outside committee, a group with chemical
engineering training who may or may not be
familiar with the subtleties of the design topic.
Four copies of the body of the report are required.
The appendix of the report is a well-indexed
collection of all of the actual calculations done,
together with appropriate summary pages inter-
spersed throughout the work. The calculations
need not be typed; but they must be legible and
indicate the calculation approach. The purpose of
the appendix is to supply a complete record of all
of the calculations done on the design project so
that anyone who had to do a more elaborate
design can go one from where each student
stopped rather than be forced to recalculate work
that has been done. The average reader of the
appendix will have a chemical engineering back-
ground, will probably know nothing about the
design topic, and will be interested in learning
what has been done and what are the limitations
APRIL 1966


and assumptions involved in the calculations.
Evaluation
The advantages and the weaknesses of this
approach to design teaching are outlined as
follows.
Advantages
We have found the following advantages:
1. The outside committee adds reality to the
project for the students. The students' em-
phasis is shifted so that they are working
against the outside committee and its evalu-
ation, rather than against a staff member for
a grade. The students feel .their reputations
are at stake. Twenty percent of the final
class mark depends on the outside commit-
tee's judgment. Our outside committee mem-
bers not only have been very learned in the
field but have asked stimulating and probing
questions. The committee for the styrene
project included a senior process designer
from Dow Chemical (who produce styrene),
a senior chemist in the petrochemicals divi-
sion from Polymer Corporation (who also
make styrene), and a University of Toronto
colleague who ran the plant project design
there.
2. The students enjoy the individual responsi-
bility. Since we do not form companies, each
student has to do his own creative design and

53


TABLE I. DESIGN PROJECT SPECIFICATION


Desired: A plant to produce

50 long tons/24 hr. of 95% pure monomeric
styrene
or

300 long tons/24 hr. of 95% pure monomeric
styrene

Utilities available:

Fuel oil
Natural gas
Electricity
Cooling water: Lake water 50C. (winter) and
20C. (summer)
City water (same average
temperature)

Steam: 200 psig, 100 psig, and 50 psig
(all saturated)







justify it on the basis of economics.
3. The students enjoy the diversity of responsi-
bility, including choice of process, design, and
cost estimation. They say they prefer to make
an overall, high-spot design of a complete
process rather than a detailed design of an
element of a process.
Twelve hours of design laboratory time are
free between the time the students hand in
their reports and the oral presentations. We
use this time to build a scale model of one
student's plant. For the degree of accuracy
required, we found that this could be done
for a styrene plant for about $10. The scale
was 1/4 in = 1 ft.
4. Lectures are given only at the students'
request. Most want to get on with the job;
few lectures are required. This pleases the
students and the staff alike because we feel
that they are asking and answering their own
questions.
5. The criticism periods after each major design
effort give rapid feed-back of suggested im-
provements and the type of assumptions to
make. Since any lectures are at the request of
the students, we want strong feed-back on
their approach as they proceed.
6. The limitation for the time spent on this
project is worthwhile. The students do not
jeopardize their standing in other courses by
devoting excessive extra time to this course;
they learn to match their designs to the time
available. The marking scheme for the criti-
cism sessions accentuates matching time with
accuracy.
7. The marking scheme specified to the judges
requires about 10 minutes per speaker.
Although the judges think the marking
scheme cumbersome, we find it very helpful
to the students.
8. It is easy to rate each student.
9. Staff load for the course is distributed among
the staff members. Furthermore, the students
gain from the background experience of staff
specialists in the criticism periods.
Weaknesses
Some weaknesses of this approach are:
1. An apparent lack of understanding of the role
of plant design in an economics analysis. The
students do not seem to realize that the pre-
liminary plant design is done to improve their
accuracy in their economic assessment of the
process. We think that the onus of this is not
upon the design course but rather on the
economics and technology course which one
of us also taught. In the future we plan to
be more specific in the students' purpose in
doing the plant design.
2. Inadequacy of decision-making theory. The
students do not fully appreciate the conse-
quences of the various decisions made. More
emphasis will be given to this topic in the
economics and technology courses in the
future. For example, not only will we crea-
tively look at process flow sheets as we do


now, but we will do exercises on getting quick
numbers for equipment cost for several dif-
ferent flow-sheets. This training in cursory
equipment costing should help them to allo-
cate their design time for any preliminary
design project itself.
3. Inadequacy of the criticism sessions. Whether
the improvement is achieved by converting
the sessions into a verbal presentation to the
combined staff after each sub-project or by
supplying more staff manpower to correct
and criticize individual efforts, the whole key
is the constructive criticism of the student's
effort at various stages along the way imme-
diately after he has completed his work.
4. Poor distribution of staff responsibility. The
staff coordinators sometimes do not call on
other staff members to help out enough.
5. Paucity of time available for the design. The
completeness of the project could be improved
either by requiring the students to do some
work outside the specified hours, by forming
companies of design engineers, or by reducing
the scope of the project. Increasing the stu-
dent's homework is easy to justify because
our fourth year, second term load is relatively
light. The formation of companies requires
careful consideration. The advantages for
individual design that both the staff and the
students have appreciated are
(a) each student is completely responsible
for all of the decisions and calculations.
(b) each sees all facets of the design rather
than working on his specialty with
figures that are handed to him by
someone else.
(c) each realizes that the individual mark
can be given at the end of the project.
It would be interesting to see if we can in-
corporate all of these advantages by forming
companies of two students and by insisting
that each student be able to defend any
part of the final design. The suggestion of
reducing the scope of the project has received
a negative reaction by the students..
6. Poor technical communication. Although the
general reaction to the student's oral presen-
tation has been favorable, the written reports
are poor. We have introduced a two-credit
course in technical communication into our
second-year program in an attempt to remedy
the situation.
Summary
' A novel approach to teaching plant design is
being developed at McMaster University. The
uniqueness of this approach lies in the method
of handling the student's responsibility, the time
allocation, the staff supervision, the judging com-
mittee, and the problem specification.
An evaluation of the approach, based on its
application to one project with a class of fourth-
year students, shows that it has many advantages
and several weaknesses. With the correction of
the latter, the approach should offer great
promise as a powerful method of teaching design.


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CHEM!l@IJ!l, EJIG!/!i!!!lll/JJ!l!i!l.i (]/}@!Jlf[/{l}/i!l

PAGE 2

The Prentice-Hal/ International Series in the Physical and Chemical Engineering Sciences Edited by Neal R. Amundson, Head of the Department of Chemical Engineering, University of Minnesota The consulting editors are Andreas Acrivos, Stanford University; John Dahler, University of Minnesota; Thomas J. Hanratty, University of Illinois; David E. Lamb, University of Delaware; John M. Prausnitz, University of California, Berkeley; and L. E. Scriven, University of Minnesota PUBLICATIONS IN THIS SERIES INCLUDE: COMPUTER CALCULATIONS FOR MULTICOMPONENT VAPOR liquid equilibria BY J. M. Prausnitz, C. A Eckert, R. V. Orye, and J. P. O'Connell. 1966, Price and publication date to be announced. UNSTEADY STATE PROCESSES WITH APPLICATIONS IN MUL TI-COMPONENT DISTILLATION by Charles D. Holland. 1966, Price and publication date to be announced. MATHEMATICAL METHODS IN CHEMICAL ENGINEERING: Matrices and Their Application by Neal Amundson 1966, 270pp., $10.50 CHEMICAL REACTION ANALYSIS by Eugene E. Peterson. 1965, 276pp ., $10.50 INTRODUCTION TO THE ANALYSIS OF CHEMICAL REAC TORS by Rutherford Aris. 1965, 286pp $10 95 LOW REYNOLDS NUMBER HYDRODYNAMICS: With Special Applications to Particulate Media by John Happel and Howard Brenner. 1965, 553 pp., $15.00 OPTIMUM SEEKING METHODS by Douglass J. Wilde. 1964, 282pp., $8 25 PRINCIPLES AND APPLICATIONS OF RHEOLOGY by A G Fred rickson 1964, 326pp., $12.95 MULTICOMPONENT DISTILLATION by CharlesD. Holland. 1963, 506pp., $14.95 PHYSICOCHEMICAL HYDRODYNAMICS, 2nd Ed., 1962 by Venia min G Levich. 1962, 700pp., $15.00 VECTORS TENSORS, AND THE BASIC EQUATIONS OF FLUID MECHANICS by Rutherford Aris. 1962, 286pp., $10.50 PRICES SHOWN ARE FOR STUDENT USE: for further information and approval copies, write box 903 PRENTICE-HALL Englewood Cliffs, New Jersey 07632

PAGE 3

CHEMIJ@j{j/Z ENG!lli!!!l!llllllli!!@ ED!Jl@j{jl1/l(l}li!J Contents for Volume 1, No. 3, Apr. '66 37 First Aid To Ailing Thermodynamics H. T. Bates 44 Shri Jyant Saraiya, Engineer Lloyd Berg 46 Unit Operations To Transport Phenomena M. T. Willis 52 Evaluation Of An Approach To Plant Design DEPARTMENTS iii Editors' Corner 45 Speaking Out D.R. Woods and A. E. Hamielec R. L. Kenyon 48 What They're Using K. M. Kiser EDITORS' IJi1jJffll To th e question "What is engineering?" there are a variety of answers given today Some are help ful, many are confused, a few border on nonsense. Their variegation is impressive th eir cap acit y for mutual contradiction startling. But within the broad range of ideas about engineering there is wide agreement that design-itself a subject of di ve rsified definition-is a central engineering function and an earmark of the field It is heart ening, therefore to see a renascense of process design courses in chemical engineering curricula. The significantly creative efforts in process design pedogogy at McMaster University M.I.T., Dart mouth and Michigan, to name a few promise a bright future for the teaching of design to chemi cal engineering undergraduates, graduate students, and industrial practition e rs. Process design is as complex as it is important, and to strive for it to yield increasingly optimum plants is to mov e toward complexity and difficulty that ar e ord e rs of magnitude greater. In an engineering world where the system seems to be a new discovery in mechanical and electrical realms, the chemical design engineer is an old and callo u sed hand at dealing with the super system: a chemical manufacturing process that is a linkage of components e ach of which itself may be a quite sophisticated system. It is appropriate, then, that process design become an unparalleled illustration of splendid systems engineering The challenge that it do so is matched by a remarkable convergence of favorable conditions: necessary knowledge was never more plentiful, technique never more advanced computation never more fa c ile, th e incentive never stronger. CHEM ENG ED commends to its readers the significant articles on process design pedagogy carried in this issue and in the preceding one. Others will follow from time to time Watch for them .----------CHEMICAL ENGINEERING EDUCATION----------, The official journal of the Chemical Engineering Division, American Society for Engineering Education APRIL 1966 Editor Shelby A. Miller Consulting Editor Albert H. Cooper Assistant Ed i tor John W Bartlett Publications Committee of CED L. Bryce Andersen Chairman Charles E. Littlejohn E P. Bartkus James H. Weber Executive Committee of CED Chairman John B West Chairman-elect J. A. Bergantz Secretary-Treasurer William H Honstead Elected Committeemen J T. Banchero W. H. Corcoran Past Cha irman George Burnet CHEMICAL ENGi-NEERiNG EDUCATION is pub lished four times during the academ i c year by the Chemical Engineering Division, Ameri can Society of Education Publication months : October, January, April, June. Publication and editorial offices : 201 Gavett Hall, Uni versity of Rochester, Rochester, N. Y. 1-4627. Title registered U S. Patent Office. Subscription rates: To Chemical Engineering Division members, $3.00 per year; to non members in the Western Hemisphere, $4 00 per year; to non-members outs i de the West ern Hemisphere, $5 00 per year; single issue price, $1 5 0. Advertising rates quoted upon request. iii

PAGE 4

CHEM ENG ED

PAGE 5

FIRST AID to Ailing Thermodynamics H. T. Bates Professor of Chemical Engineering Kansas State University, Manhattan, Kansas Engineering educators stand accused by those investigating the drop in engineering enrollment, of practices that tend to dis courage students (2). It appears that there may be just basis for the accusation, par ticularly apropos of some of the literature with which students are forced to contend. There is a literary form called the objec tive correlative. It was used extensively by T. S. Eliot. It has been likened to beefsteak that a burglar carries to divert the watch dog while he robs the safe (3). Mr. Eliot's poetry abounds in this sort of thing; the casual reader gets something-the beef steak-but it takes real digging to find the underlying idea-the contents of the safe. Eliot must have felt a little sorry for his readers, because he later published foot notes to trace some of his ideas. His good friend, Ezra Pound, on the contrary, felt that it wasn't sporting to put in any foot notes at all. Even some of the scientific disciplines are producing technical literature that re sembles the objective correlative in the confusion it offers the reader. (Nicholas Vanserg's pieces "Mathmanship" and "How to Write Geologese" are entertaining com mentaries on publications in two fields (6, 7) .) Engineering has not been a major offender in this respect, although examples of misleading prose and illogical termin ology can be found in our literature (I, 5) An important instance occurs in the sub ject of thermodynamics. It is the purpose of this article to propose reforms in the subject; to rearrange the concepts into forms that are more logical under modern conditions; to alter some definitions and conventions in the interest of clarity; and to propose a unifying treatment that can be presented immediately to beginning scholars. If this objective is to be successful, a certain amount of re-education of faculty APRIL 1966 members and research workers will be nec essary in advance of its introduction to students in the classroom. It should be emphasized at the outset that these pro posals represent some changes in point of view, but they are in every respect alge braically compatible with the more tradi tional treatment. These changes, evolved from experience with the difficulties that learners have with the subject, were ac ceptable to those students who were honestly trying to get the picture. Improving the Terminology A little investigation will reveal a number of examples of confusing nomenclature in thermodynamics. It is almost as if the terminology had not been brought up to date for 40 years. Surely it is time for a reappraisal in the educational methods that are needed today We may start with the word thermo dynamics itself, which means literally "heat in motion," although other kinds of energy transformation are just as important to the subject as heat. A better term would be energetics. It is really redundant to say thermodynamics because any proper defi nition of heat must include the idea that it is energy in motion. Heat, work, and elec tricity are all by definition manifesta tions of energy in motion. Unlike stored energy, they are not associated with any particular mass of material. They may flow across the boundaries of a system and they may flow through the interior. They are not point functions. The quantity of energy transferred acros(, the boundaries of a sys tem as heat, work, or electricity depends upon the path as well as upon the initial and final values of state conditions such as temperature Pressure, volume, and voltage. The terms thermostatics, stored heat, heat content, heat capacity, stored work, and stored electricity are misnomers They conflict with the definitions; they confuse students. We must stop using them if we are to have a truly logical body of knowl edge The idea of dividing all energy first 37

PAGE 6

TABLE l THE DICHOTOMY OF ENERGY All Energy Energy in Motion f Heat Work (Q) I l External Energy I Stored Energy I J Internal Energy I Mechanical Work Electrical f Work .~----------~, (Ws) (E) Potential Kinetic Energy a Other Potential Energies I Pressure Potential Energy (NPV) I Elevation Potential Energy ir (~) into two classes of energy in motion and stored energy is basic to the understanding of the subject, but we should not allow the idea to be undermined by the use of un precise and contradictory terms. Stored energy should be represented by a number of names corresponding to all the commonly recognized classifications; It is worth noting that the classification is com plex. The early workers appear to have been afraid that some little understood kind of energy might be left out. As a result they organized a dichotomy of energy. This is outlined in Table I. Notice that the sub divisions are always made by dividing into two classes-those that do and those that do not meet some criterion. Thus stored energy is divided into external energy and internal energy. At the next level both of these are divided into kinetic energy and 38 Potential Energy (NA) Ki netic Energy (NTS) potential energy Now there are clearly several kinds of potential energies on the external side and two of these are shown but one must remember that in certain special kinds of problems magnetic poten tial energy, surface potential energy, or other kinds must be included. All stored energy terms are associated with a mass of material. They are point functions; differences in their values asso ciated with a change of state of the system are determined solely by the initial and final conditions and are independent of the path. Certain common energy terms have been left out of Table I deliberately: non-flow work internal energy, enthalpy, and Gibbs free energy. Some of these have their uses, but none of them should be taught to students at first. The reason for this is CHEM ENG ED

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that each of these terms represents an arbi trary combination of simpler terms, as can be seen from the following equations With these recommendations in mind a canonical statement of the first law can be formulated as follows: dW = dW + d(PV) dU = dA + d(TS) dH = dU + d(PV) dF = dH d(TS) (1) dQ dW dE = dA + d(TS) + d(PV) (2) (3) (4) where A = Helmholtz free energy, F = Gibbs free energy, H = enthalpy, P = absolute pressure S = entropy, T = absolute temperature. U = internal energy, V = volume, W non-flow work, and W = shaft work. A Canon for the First Law The first law of thermodynamics is an energy balance. Unfortunately, the litera ture is full of different statements of this law. There seems to be no clearly recog nized, generally agreed upon, form that could always be used as a starting point. Students need such a statement which they can use to avoid the possibility of leaving out some energy terms that are important to their problem. If they were to be given a universal formulation or canon to begin every problem, and it were clearly stated that subsequent manipulations apply only to a particular situation, it would be easier to break the habit of formula snatching which many of them attempt to practice. In view of the fact that the first division employed in the dichotomy of energy, Table I, is that between energy in motion and stored energy it is suggested that an equal ity be used to relate the two kinds of quantities in a system. As a matter of tact, some textbooks do this by putting heat, work, and electricity on the left side and all stored energy terms on the right side. On the stored energy side it is recom mended that one term be provided for each kind of energy, all combination terms being avoided. It is also recommended that the standard form of the energy balance be written with differentials, since deltas and integral signs raise questions about datum levels, the initial and final states or con stants of integration-all matters having to do with a particular problem. Beginning engineering students should be able to per form the necessary integrations. APRIL 1966 ( NgX) ( NV2) +d+d -gc 2g c (5) where E = electricity, g = acceleration of gravity, C c = gravitational conversion factor, N = mass, Q = heat, fJ = velocity, and X = absolute elevation. What Is Work? The so-called work terms in the energy balance do not always satisfy the criterion of representing energy in motion. Lectures intended to establish the principle that heat, work, and electricity are always energy in motion are weakened by' the algebra in many textbooks. That which is usually called non-flow work ( W) in a batch process is one such instance. This can be shown by algebraic manipulation to be: W = W. + A(PV) (6) The shaft work ('Wa ) clearly satisfies the definition of work; i.e., it is energy in motion. It requires a machine with a rotat ing shaft or a moving piston rod. The so called flow work or flowing energy term, A(PV), is a different matter. It represents stored energy, for it is a point function. For this reason the terms flow work and flow energy also should be avoided. An excellent exercise to give students early in their course work involves them in a pressure-volume graph. They are asked to choose points on the graph representing arbitrary initial and final states and to draw two arbitrary paths between these points with a French curve. They are then asked to evaluate graphically for each path the quantity i 2 P dV + i 2 VdP and to compare the two values with the value of the function P2 V2 P, V, Since all of the expressions give the same result, the students can see readily that A(PV) is a point function and that the individual in tegrals are not point functions, for they do depend upon the path. 39

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Another approach is to write A(PV) as N tl(P/p). The mass N is the capacity factor and P /p is the intensity factor of the energy term. The later is readily recogniz able as the pressure head in Bernoulli's equation. Therefore, tl(PV) is really pres sure potential energy. For example: putting work into a compressor that delivers com pressed air to a pressure tank at the corner service station is analogous to putting work into a pump that supplies water to an elevated tank at the water works. Both the air in the pressure tank and the water in the elevated tank possess stored potential energy. In order to differentiate them Ng AX/g c should be called elevation poten tial energy and A ( PV) should be called pressure potential energy Thus W turns out to be a mixture of work and stored energy, and it should no longer be referred to as work Some books try to make W look like pure work by attempting to show that A(PV) is work. The explanation usually goes something like this: "The gas that goes into the process enclosure is pushed in by the gas that follows it, and the gas that leaves the en closure pushes back the atmospheric air." This is very confusing to students because they cannot visualize other gas or air as being the same as the face of a piston. They also find it hard to follow an imagin ary boundary that shifts as the gas passes through it. The educational advantage of the new point of view should be clear, for it does not require such explanation. The Trouble With Enthalpy Kammerling Onnes ( 4) invented the term enthalpy as a substitute for such terms as stored heat and heat content Although it was a worthwhile advance, it still gives trouble. Some students tend to equate enthalpy with heat without regard to the effects of other terms in the energy balance. Of course enthalpy is a hybrid concept con sisting of part internal energy and part external pressure potential energy. Such a mixture is quite illogical though convenient in many practical Problems. A logical alter native would be to discard enthalpy and return to internal energy. Unfortunately this is not likely to come to pass; for the literature is full of tables and graphs of enthalpy, and there are comparatively few 40 data in the form of internal energy. The progress of understanding would be aided, however if the terms heat capacity and latent heat were abandoned. These terms provide a misleading connection be tween heat and enthalpy that should be discouraged. Students will get along with much less trouble with the terms enthalpy capacity instead of "heat capacity at con stant pressure," internal energy capacity fnstead of "heat capacity at constant vol ume latent enthalpy instead of "latent heat at constant pressure," and latent in ternal energy instead of "latent heat at constant volume." At first these new names seem cumbersome to old timers but this is not the case with beginning learners. Extending the First Law of Energetics In Table I and Equation 5 internal energy is divided into internal potential energy and internal kinetic energy. This is done arbitrarily calling TS the internal kinetic energy and A ( the Helmholtz free enery) the internal potential energy. In view of the statistical difficulties of dealing with the interactions of all of the molecules and sub-atomic particles this may seem to be questionable. However, in view of the relationship of Equation 2, the fact that there are only two subdivisions under inter nal energy ( no unknown form of energy thus being overlooked) and the convention of a form of the first law that includes no combination terms, it is logical to make such a division. Handling Irreversible Processes For a reversible process, dQ r eve rsibl e = Tds (7) dWr e v e rsibl e = VdP (8) The canonical statement of the energy bal ance for such a process results from the substitution of Equations 7 and 8 into Equation 5 (with electricity assumed to be zero) : TdS + V d P = dA + (TdS + SdT) Ng N d (u22) (9) + ( VdP + PdV) + dX + g c g c For the reversible case the like terms on both sides of the equation may be cancelled But wait! All actual processes are irreversCHEM ENG ED

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Table 11 An irreversible idealgas compressor V T Ve VA Vo A I -+------P, P 1 = 14,7 psio P 2 = 85.0 psio VA= 0.0255 ft 3 V 8 -= 0.850 ft 3 Ve-= 0.2245 ft 3 V 0 = 0.00675 ff 3 C D P2 p Cp= 7.00 Btu/(Lb mole 0 R) Cv= 5. O I Btu/ (Lb mole 0 R} K = 1.400 n = 1.31a Tc To TA I I I I I -~ I B I I I I I S SASO Sc SB TA Ta = 530. 0 R Tc = sos. 0 R T 0 = 100. 0 R SA : + o. 040 X 10 3 atu/ 0 R s 8 + 3.91 X 10 3 sc = + 2.377 x 10 3 s O 11 + o. 1 5 7 x I o 3 NA = No = o. 000,0764 ~bole Na NG 0.00220 Lb mole Energies in Btu Function AB BC co DA A BCD Q o.oo 0,76 1.67 + 0.11 2. 3 2 Ws o.oo 5.05 o.oo + 0,15 4, 9 0 w + 2.24 3 ,82 -3.43 + 0, 11 4,9 0 ( PV) + 2.24 + 1. 23 3,4 3 0.04 o.o 0 AU o.oo -t-3,05 0.47 o.oo + 2.5 8 ~H + 2.24 +4.28 3.90 0.04 + 2,5 8 TAS + I. 86 0.76 1,67 o.~9 o.e e A lT S) i" 0,004 0,00 0.004 o.oo o.o 0 AA .. 0,004 +3.05 0.466 o.oo + 2.5 8 AF + 2.236 +4.28 3,896 0,04 + 2.5 8 ASxl0:3 + 3,5 I 0 I, l 5 5 2.22 O. I 17 0,00 APRIL 1966 41

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Table Ill A reversible diesel cycle engine p T PA A B r, B C I I I I I I I I Pc I C I -,-I I T2 D I I I I I I I D po -----+--I I I I I I V s VA VB Vo SA Sa So Sc VA 2.46 I iters T, :::s 500. K Va 4.1 0 I iters T2 = 300. K Vo 2 4.6 I iters SA = 4.1 I col./K PA 1 o.o atmos Sa= 053 col./K Pc 1.670 atmos Sc = + 3-03 cal./K Po 1.000 atmos s 0 = + 0-46 col./K Energies in Calories Function AB BC CD DA ABCD Q -+1,400. +I, 780. -1,001. -1,375. + 804. Ws o. +1,7 80. + 399. -1,375. + 804. w + 399. +1,780. o. -1,375. + 804. A (PV) +399. o. 399. 0. 0. AU +1,003. o. -1,003 o. o. AH +l,400. o. -1,400. o. 0. TAS +1,400 +l,780. -1,001. -1,375. +804. dF o. -1,780. 399. +1,375. 804. AS + 3.58 + 3.56 257 4!,7 o. 42 CHEM ENG ED

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ible. The right side of the equation repre sents stored energy; all of the functions on the right side are point functions. The left side of the equation represents energy in motion, namely heat and work. If the work goes into the enclosure and heat comes out, irreversibilities and friction increase both heat and work beyond the limiting case. Now either the Tds or the VdP term on the left side will have to be integrated (graphically or formally) over the actual path. It is not necessary to integrate both terms, for the energy balance can be solved for the second term on the left side. The right side can be evaluated with the aid of the second law. Many textbooks seem to place too much emphasis on reversible cases. In engineering the greatest emphasis should be on the ir reversible. A useful technique in teaching students is to represent cycles, reversible or irreversible, on both P-V and T-S plots. The various steps of the cycle and the com plete cycle should be investigated com pletely. All of the terms and their compon ents should be calculated, and all of the numbers should be tested in the light of the first and second laws and the various defin ing equations to locate errors and reinforce understanding. A few such exercises are the equivalent of a much larger number of discrete one-step, one-question, one-answer problems. Tables II and III illustrate this technique. Students to whom algebraic equations are somewhat unreal achieve quicker understanding when they are re quired to substitute numbers, and the inevitable mistakes that crop up are illumi nated immediately. What Sign Should the Work Term Have? The usual convention is that heat flowing into the system is positive and work flowing out of the system is also positive. This appears so illogical that teachers should keep their eyes open for a clue showing which of these signs can be changed the more reasonably. Evidence appears very quickly. Inasmuch as work input, like heat inflow, is associated with an increase in the value of such thermodynamic properties of the system as enthalpy and free energy, its sign should be positive for consistency with the general convention. If it were, both heat and work would be positive for flow into APRIL 1966 the system and negative for flow out of the system-a much more satisfactory situation. Conclusion Thermodynamics (energetics, that is) is ailing-or, speaking more precisely, its pedagogy is. The illness is neither organic nor incurable, but it is debilitating and it should be checked. This critique has sug gested some therapeutic measures. Will they be effective? Can they help students under stand one of the foundation subjects of their engineering education? The experience of one instructor is affirmative, but in the end each must try them himself to find out. REFERENCES 1. Anderson, H. J., J. Eng Education 53 (3), xiii, (1962). 2. Bronwell, A. B., et al ., J. Eng. Education, 53, 494-500 (1963). 3. Davis, E., "The Quelle Lectures Kansas State Univ ., Manhattan, Kansas, 1963. 4 Hougen, 0. A., Watson, K M and Ragatz R. A., Chemical Process Principles, Part I," 2nd ed., footnote p, 247, John Wiley and Sons, New York 1954 5 Inveiss, J. H. J. Eng. Education 53, (9), xx, xxi, (1963) 6 Vanserg, N., Am Scientist 46 94a, 96a 98a (1958) 7. Vanserg, N., Econ. Geol., 47 220-3, (1952). NOMENCLATURE A = Helmholtz free enregy E = Electricity F = Gibbs free enregy g = Acceleration of gravit y g c =Gravitational conversion fa c tor H = Enthalpy N = Mass P=Absolute pressure Q = Heat S=Entropy T = Absolute temperature U = Internal energy U = Velocity V = Volume W = Non flow work Ws = Shaft work X = Absolute elevation p = Density 43

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Shri Jayant Saraiya ENGINEER Lloyd Berg Professor of Chemical Engineering, Montana State University, Bozeman, Montana At 9: 30 P M on a cold, windy night in January, 1966 the telephone rang at the Sixth Street home of Mr. and Mrs. Jayant Saraiya in Sinclair, Wyoming Jay, who was watching TV, got up and answered "Jay? This is Sam at the plant. The temperature on the regenerator has been slowly dropping all evening. Thought I better tell you." "Thanks," said Jay. "I' ll be right over." He hung up, walked over to the kitchen window where he could see an outside thermometer which indicated a coo l seven below zero, and pro ceeded to don a ski parka, boots, and leather cap with ear flaps. "I'll be at the plant for awhile ; don't wait up for me," he called to his wife. He stepped into his 1963 Falcon, and drov e the four blocks to the plant. The plant is Sinclair Refining Company's refin e ry at Sinclair, near Rawlings Wyoming Going directly to th e control house Jay talked with Sam Watkins, the shift supervisor. He studied the temperature pressure and throughput logs of the refinery that the recording instruments sp ewe d out steadily. "S am," Jay said finally "L et's go down to the blower house and look around." Donnin g their h e avy parkas and caps, they went out into the ic y wind and a cross the r efi n e r y yard to a small g alvaniz e d iron building which hou se d th e blower for the regenerator This machin e gulps in the enormous quantities of air required to burn the carbon off the catalyst and forces it into the burning vessel, called the regen erator. Th e blow er was screaming at a high pitch e d roar in its usual mann e r and at its design e d speed Jay had noted in the co ntrol room a reduced air flow from th e blow e r. Now by in specting the blow er equipment carefully, h e finally noted that th e air intake duct above th e roof had built up a ring of ice which was restricting the flow of air to th e blower. Pointing this out to Sam, he suggested that Sam ca ll the maintenance fore man and ask him to c hip off the ice. "I'm sure that will correct the troubl e and I'm going home," h e told Sam. "If th e t e mp e ratur e doesn't start back up after th ey finish kn oc kin g off the ic e, call me." Just anoth er common in ci dent in the working life of an indu s trial chemical e n gineer, with thi s diff e r e nc e. Jay Saraiya is an Indian national train e d as a chemical e ngin eer in the United Stat es who plans to spend his professional c ar eer in the U.S. A lack of interest in chemical engi neering on the part of U .S. youth and a burgeon ing d e mand ha s cre ated an opportunity that 44 foreigners are taking advantage of. Some educa tors have estimated that we may soon reach the point where one fifth of all chemical engineers b ei ng graduated by U.S engineering schools will be non-citizens. Jay's experience is typical. Born and raised in Bombay as the son of a moderately wealthy importer Jay went to the University of Bombay and majored in chemistry and physics In 1959, by straining the family's financial resources almost to the breaking point, he went to the United States and enrolled as a freshman in chemical engineering at Montana State University Tech ni c al e ducation in India is conducted in English, so language was no handicap. Four years later he was graduated as a B.S in Chemical Engineer ing Immediately upon graduation he was hired by Sinclair Desperately short of chemical engineers and located in what many Americans consider "Nowheresville," Sinclair and Rawlins welcomed Jay with open arms. Company employees found Ja y a comfortable apartment in Rawlins for $35 per month and the local newspaper ran a feature article on Jay and his history Feelin g that he would be a happier and more stable employee if he were married, Sinclair encouraged him to take his vacation ahead of schedule to go to India to get his brid e. Accord ingly in January Jay married Jayshee Asher, a Bombay girl selected with his family's approval ac co rding to the Indian tradition Jay and Jaysh ee returned to th e high barren, wind -s wept plains of Wyoming in February. After having spent h e r e ntire life in steaming, teeming tropical Bombay, Rawlins seemed like another planet to Jayshee. But there were com pensations. The apartm e nt was wa rm comfort abl e, and co nv e ni e nt-and th e n th e r e were th e stores, particularly the supermarket with its abundan ce and cleanliness like nothing she had ever ex p erience d in India. Spring comes late at 6500 feet altitute but it does ccme eventually. In summer there were trips to the n ea rby Wind Riv e r and Teton mountain ranges and to Yellowstone Park. In Nov em ber, their son Mona! was born. Now th e differ e nc e betwe en India and America really b ec am e apparent to Jayshee. What with th e washer and drier, the canned milk and baby food, th e abundan ce of s h o ts, pills and vitamins, th e bab y was n ever sick. A major crisis was narrowly (continued on page 51) CHEM ENG ED

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R. L. Kenyon Director of Publications American Chemical Society, Washington, D C. ABOUT Skepticism Being Better than Paranoia. It could be argued that what the world offers to this year's scientific or engineering graduate represents the greatest promise ever held out to his kind as individuals. Arguments on the other side are easier to find and they agitate and stim\llate. What historian Richard Hofstadter calls the "para noid style" is enjoying popularity in the United States. We can build black worries on all sides: Business life is enforced con formity; technology is dominating human ity instead of serving it; government for the people is perishing; and the free intellectual stimulation of the university has succumbed to the scramble for federal grants. General day-to-day progress usually is stumbling and uneven. Worthy minds are inspired by and aspire to the high peaks of human works. The inclination to match this week's failures against mankind's better achievements-as they stood out against the poorer levels of their times-can bring discouragement and i feelings of frustration. We hear and see evidence that among college students there may be greater than usual discontent with the world. Students are reported discontented over too few opportunities for having a hand in making human society better. This is admirable insofar as the attitude is based on under standing. But viewing a mountain from one position doesn't tell much about how hard it would be to climb the unseen side. Some skepticism and probing to learn just what can be done should be a part of the ap proach of any technically trained person. Society is changing and is likely to change with increasing speed. Such ele ments as business technology's influence, government, and the university atmosphere all could stand some improvement. But all of these are likely to remain influential elements of society and, if they are to be improved, they will have to have the driving efforts of able people. Therein lie challenges to the worthiest of idealists who want to improve the human lot. APRIL 1966 I SPEAKING OUT After baccalaureate (at Illinois) and doctoral (at North Carolina) degrees in chemistry Dr. Richard L. Kenyon became a research chemist with DuPont. During four years of research, a strong interest in people and in professional communication persisted and ultimately led him to join the publications staff of the American Chemical Society. As a field editor of Chemical and Engineering News and Industrial and Engineering Chemistry, as managing editor of the Jour nal of Agriculture and Food Chemistry as editor of C & E N as editorial director of ACS's applied journals, and finally as Director of Publications for ACS, he has devoted two extremely fruitful decades to the challenging business of more accurate, more literate, more readable, and more exciting communication in the world of appli e d chemistry and chemical engineering Many of our readers doubtlessly have enjoyed Dr. Kenyon s scholarly arresting editorials in C & E N The message of a recent one was so timely a piece of mature opinion that we wished to have it respoken from our pages. It is reprinted from the Career Opportunities Supplement of th e March 14 1966, issue of Chemi c al and Engin ee ring News. CHEM ENG ED is grateful to the Americar: Chemical Scciety for p e rmission to r e print it The new graduates at all levels of chem istry and chemical engineering probably are, on the average, the best trained ever. The demands for excellent training prob ably also will be the greatest ever. And not only will demands for high training be the greatest but demands for breadth also are growing. There appears to be exciting opPortunity for competent, well-trained and educated chemists and chemical engineers far beyond the numbers that will be produced. This is true not only in the highest form of "pure" research, but in applied research, technology, commerce, politics, and a host of other pursuits. Those who want a feeling of contributing to the improvement of society should not turn theit backs on what appears to be a slightly tawdry mess in comparison to one's ideal society. There lies a very real challenge. 45

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Unit Operations to Transport Phenomena M. S. Willis Assistant Professor of Chemical Engineering University of Dayton, Dayton, Ohio Engineering as a profession was first identified with weaponry and military works. The demand by the civilian populace for structures primarily designed for com merce and trade led only in the last 250 years to "civil" engineering and the civil engineer, whose job was defined in 1828 in the charter of the Institute of Civil Engi neers. Civil engineering was "the art of directing the great sources of power in nature for the use and convenience of man, as the means of production and of traffic in states, both for external and internal trade, as applied in the construction of roads, bridges, aqueducts, canals, river navigation and docks for internal intercourse and ex change, and in the construction of ports, harmors, moles, breakwaters and light houses, and in the art of navigation by artificial power for the purposes of com merce, and the construction and adaptation of machinery, and in the drainage of cities and towns (2). This early definition of engineering is primarily concerned with construction not design, and with art rather than science. It is because of this latter point, in addition to the very ambitious nature of the defininition, that it became necessary to divide the field of engineering. The mechanical engineer came to be identi fied with "the construction and adaptation of machinery," the naval engineer with the "art of navigation by artificial power," and the sanitary engineer with "the drainage of cities and towns." Once under way, the subdivision of engineering increased as the demands of industry became more spe cialized. The chemical engineer did not appear until about 70 years ago. The construction and selection of equipment for chemical plants was once largely in the hands of mechanical engineers who knew some chem istry or chemists who knew some mechani cal engineering. As the process industry grew, the problems became more complex and peculiar, until it finally appeared that 46 there was a need for a distinct branch of engineering to which such problems might be assigned. "In response ... we have the development of chemical engineering, not as a composite of chemistry and mechanical or civil engineering, but as a separate branch of engineering, the basis of which is those unit operations ... which, in their proper sequence and coordination, consti tute a chemical process as conducted on the industrial scale" (2). The unit operations really became the defining concept for chemical engineering and allowed the chem ical engineer to use a systematic approach to the solution of complex industrial prob lems. The distinction between industrial chemistry and chemical engineering, in fact, is that the former is concerned with indi vidual processes as entities in themselves, whereas the latter focuses attention on the unit operations common to many processes and on the proper grouping of these unit operations to produce a desired product. In 1915 Arthur D. Little formally defined the unit operations of chemical engineering, and in 1923 the text by Walker, Lewis and McAdams entitled "Principles of Chemical Engineering" appeared. During the period from 1923 until 1960, this work and its two revisions served as models for subsequent chemical engineering text books ( 1-6) In the mid 1950's, it became apparent to some chemical engineers that, because of the economic demands, there had to be a departure form the traditional approach of multiple scale-up in the design of chemical plants. Some chemical engineering teachers were finding that "too often the fundamen tal concepts and laws have been slighted in the haste to teach application. The result has frequently been that a practicing engi neer or graduate student, faced with prob lems for which his empirical training has not prepared him, has first had to learn the fundamental principles of the transport processes before he could proceed" ( 3). The transport porcesses underlie the unit oper ations of chemical engineering, for "the unit operations themselves, although carried out CHEM ENG ED

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in a wide variety of equipment types that apparently have nothing in common are, from the point of view of the theory in volved, applications of a very few funda mental laws. In fact, these laws are the fundamental laws of physical sciences that underlie practically all technology [They] are: first, the conservation of mat ter and energy; second, the relations per taining to the equilibria of physical and chemical processes; and third, the laws governing the rate of change in systems not in equilibrium" (2). The recent innovation, then, is not in recognizing that the unit operations are based on a few fundamental laws but in teaching these laws (particu larly those that describe process rates) in a separate course which "should rank along with thermodynamics, mechanics, and elec tromagnetism as one of the key engineering sciences" ( 4) What Is Meant by Transport Phenomena? Courses in transport phenomena consist of the study of the transfer of momentum, energy, and mass. In order to trans er any of these quantities, a non-equibibrium situ ation must exist. For example, if internal energy is to be transferred, there must be a temperature difference. The temperature difference is the driving force and the quantity which is moved by this tempera ture difference is called the heat flux. From the observational point of view, a linear relation is postulated between the flux and the driving force in which the coefficient of proportionality is a property of the sub stance in which the energy transfer is occuring In the case of heat transfer, the coefficient of proportionality is the thermal conductivity, k. The observational or phenomenological approach is not concerned with the mechan ism for the transfer of this energy. For the mechanism, the kinetic theory of molecular motion must be considered From the sim plified theory, the kinetic energy of a spherical molecule is directly related to the temperature 1 3 -mu 2 = -KT 2 2 (1) The tendency toward equilibrium of tem perature then is a result of the transport of molecules with high kinetic energy to regions where the molecules have low kinAPRIL 1966 etic energies and vice-versa. But while a molecule, by its change of location, is trans ferring kinetic energy, it must at the same time transfer mass, m, and moment1,1m, mu. On a microscopic level, the mechanism for the transport of mass, momentum, and energy is fundamentally molecular diffu sion. From the observational point of view, the following laws for the transfer of mo mentum energy, and mass under the condi tion of constant density and heat capacity define the transport properties of viscosity, thermal conductivity, k, and mass diffu sivity, DAB. T =()d(Pvx) ( 2 ) .v x p dy Newton's Law of Viscosity = (_}!_1 d(PCp T) q y PCp dy Fourier's Law of Heat Conduction dPA = DAB .v dy Fick's First Law of Diffusion (3) (4) From the simplified kinetic theory, the ex pressions for transport properties are: = _2_ (n1KT) 112 3 7!" 3/2 d 2 k = ,2_/.KlT)l/2 d2 \ 7l"3m 2 ( Kl )1/2 T3 /2 DAB-3 71" ]":4 pdA i (5) (6) (7) where d is the molecular diameter. Experi ment agrees with the temperature and pres sure dependence of the transport properties as shown in Equations 5-7 and therefore verifies the molecular transport mechanism. This is of engineering value in that for moderate ranges, the temperature and pres sure dependence of the transport properties can be predicted. What other information of engineering value can be obtained from these rate equations? The dimensions of /o:= v, DAB and k/PC p= o: are (length) 2 / time. ( continued on page 4 9) 47

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WHAT THEY'RE USING FUNDAMENTALS OF CHEMICAL REAC TION ENGINEERING, by Walter Brotz; translation from German by D. A Diener and J. A. W e aver; Addison-Wesley Publishing Com pany, Reading, Mass., 1965. 325 pages $15 00 It is stated in the translators' preface of this book that the book can be used at the senior or first-year-graduate level. Most seniors will in fact find it to be a rather sophisticated mathematical treatment not only of reaction engineering but also of some conventional unit operations as well. Though sophisticated, the mathematics are not beyond that to which current under graduates are exposed. Much of the material contained in the first 183 pages is not directly related to reaction engineering and will not be new to a fourth-year student. In the first 68 pages, the reader is taken through stoichiometry and thermodynamics and introduced to chemical kinetics and catalysis, the last two subjects in 24 succinct pages. Primarily these 183 pages contain a wealth of design infonnation about fluidized beds, packed beds, and heat exchangers. Much of this information is very skillfully organized into tables and graphs. The text is short on theory but long on application. The remaining 231 pages are concerned with various types of reactors and their design. The presentation is goo
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( continued from page 4 7) By analogy with the mass diffusivity, DAB, 11 is called the momentum diffusivity and a is called the thermal diffusivity. Since these three quantities have the same units, dimensionless numbers can be formed from the ratio of any two of them. For example, the Prandtl number is given as C P v momentum diffusivity Prandtl number = -=-=------k a th e rmal diffusivity and can be interpreted as a measure of the capacity of a fluid to diffuse momentum as compared with its capacity to diffuse heat. The Prandtl numbers for air, water and mercury are approximately 1.0, 5.0 and 0.01, respectively. The next question is how do the trans port properties fit into the conservation statements for mass, momentum, and en ergy? The conservation statements must be applicable to all substances and, further more, they must be independent of any reference frame. The transport properties serve as parameters in the conservation statements and permit a distinction to be made when the same conservation state ment is applied to two different substances. For the latter requirement the conservation statements must be expressed by a mathe matics which is also independent of coor dinate system, The calculus of vectors and tensors transforms the basic laws from re ference frame to reference frame with no change in the fundamental law. Consider now the application of the three conservation statements to a single one dimensional, time-dependent system: a l aT) aT (S) s;-\Q'"a; = at Conservation of Energ y I These equations are all of the same form. Consequently, under certain conditions, there is an analogy among the conservation statements as well as an analogy among the mechanisms for transfer. This analogy can be very useful in the solution of cer tain engineering problems. For example, the transfer of momentum in a wire-coating operation where the coating is applied by pulling the wire through a die is exactly analogous to the flux of heat in the insula tion on a steam pipe Information about the first system can be inferred by a study of the second, since the systems are analo gous Methodology of Transport Phenomena In order to justify the statement made earlier that a course in the transport pro cess should be ranked along with thermo dynamics let us compare the derivations of the Bernoulli equation. In most unit operations texts the deriva tion is limited to a steady flow system consisting of a pump which takes an in compressible liquid at one elevation and raises it to a second elevation at mass flow rate w A pound of liquid at the entrance has a potential energy gh,, a kinetic energy < u, > 2 / (3, where (3 = 1 for lam inar flow and (3 = 2 for turbulent flow, and a pressure volume work, P, / p, which the fluid needs to enter the system. The pump must raise the liquid and adds work W / w to the liquid. At the exit, the fluid has a potential energy ghz a kinetic energy < u 2 > 2 / (3 and has a pressure volume work of P 2 I P The Bernoulli equation is simply written then as P, W (3 +-+--E p w u (11) =ghz+ --+ /3 ( 11 8(P ux) ) = B(Pvx) 'f>y BY Bt ( 9 ) where E u is a correction factor necessary for the equality. Conservation o f Mom e ntum (10) Cons e r v ation of Ch e mi ca l Sp ec i es APRIL 1966 In the ~tudy of transport phenomena, the starting point in the derivation is the local conservation statement for momentum or Newton's second law of motion for a fluid. PD!!. = L .E ; Dt 'v !_ 'iJ p + pg (12) 49

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This statement says that on a unit volume basis, the mass times acceleration of a fluid particle is equal to the sum of the viscous forces, the pressure forces and the gravita tional forces. Since mechanical energy is the product of a force and a displacement, this equation can be multiplied by the fluid velocity to obtain the local time rate of change of mechanical energy. (13) The left hand term represents the accumu lation of kinetic energy and the term in brackets on the right side represents pro ducts of forces and velocities and hence the rate of mechanical work done by pressure, viscous and gravity forces. In order to explain the last two terms, the equation of thermal energy must be examined_ DU p= 'v q(p V, + ...!. :V..) (14) Dt The term of the left represents the accu mulation of internal energy and the first term on the right represents heat conduc tion. The last two terms in the internal energy equation also appear in the mechan ical energy equation but with opposite signs. The term p V .Q represents compres sibility effects and may be either positive or negative. The term ( -J;.: V JZ.), for New tonian fluids, is always positive which means that this term always causes a de crease in meGhanical energy and an increase in thermal energy. This term then repre sents the irreversible degradation of me chanical energy into thermal energy. In order to obtain the Bernoulli equation, the mechanical energy equation is inte grated over an arbitrary volume consisting of three types of surfaces: inlet and exit surfaces, fixed surfaces and moving sur faces The moving surfaces provide a means of adding or removing work from the sys tem, the fixed surfaces represent the con fines of the system and the inlet and exit surfaces allow mass to enter and leave the system. After integration, the result is de pendent only upon the inlet and outlet con50 ditions and for an unsteady state system is d (K tot + tot + A tot) = dt V + +a)w]+w-E, (15) where Ktot, cf> tot and A tot are respec tively the tota1 kinetic energy, potential energy and thermodynamic work content; W is the rate at which the surroundings perform mechanical work on the system; and E v is the "friction loss." This term is given by Eu = -Iv (J; : VJL) dV (16) and represents the irreversible conversion of mechanical energy to thermal energy. For a steady-state liquid system, Equa tion 15 becomes 1 W E u + + --p w w (17) 1 < v/ > Pz =ghz + -+ 2 p A comparison of this equation with Equa tion 11 indicates that /3 (18) This derivation proceeds from a funda mental law to a general equation of engi neering utility by logical and reasonable steps. The scope of the equation, its rela tion to fundamentals, and the lack of balancing "fudge factors" illustrates to the student the scientific basis of engineering and gives him confidence in the application of this equation and others of similar origin. ACKNOWLEDGEMENT Permission of the McGraw-Hill Book Company to quote and paraphrase passages from the intro duction and first chapter of Badger and McCabe's "Elements of Chemical Engineering" and from the preface of Benn e tt and Myers' "Momentum, Heat, and Mass Transfer"; and of John Wiley & Sons to quote a passage from the preface of Bird, Stewart, and Lightfoot's "Transport Phenomena" is gratefully acknowl edged. ( c ontinu ed on pag e s.1 ) CHEM ENG ED

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NOMENCLATURE Dimensions are given in terms of mass (M), length (L), time t, and temperature (T.) Vec tors have a single underline and tensors have a double underline. Force is not considered a funda mental dimension, but is assigned instead the dimensions of mass-acceleration instead the dimensions of mass-acceleration product (ML/t 2 ). This "absolute" system of dimensions is com monly used by physicists, much less commonly by engineers. A = thermodynamic work function, ML2 / t 2 C p = heat capacity at constant pressure per G K K k m p q y T t u [I <.!!.> w w a /3 II p unit mass, L2 / t2T = binary diffusivity for system of species A-B, Vt. = molecular diameter, L. = total rate of viscous dissipation of me chanical energy, MV/t 3 = Gibbs free-energy per unit mass, MV/tz. = gravitational acceleration L / t 2 = elevation, L. = mass flux of species A in the y-direction, M / tV = kinetic energy, ML2 / t2. = Boltzmann constant MV/t 2 T. = thermal conductivity, ML / t 3 T. = mass of molecule, M = fluid pressure, M / Lt 2 = y-component of the heat flux vector, M / tl. = absolute temperature, T. = time, t. = mean molecular speed, L / t. = mass average velocity, L / t. = space average value of velocity, L / t. = rate of doing work on system, ML 2 / t 3 = mass flow rate, M / t. = thermal diffusivity, V / t. =velocity function (defined in Equation 18), dimensionless. = viscosity, M / Lt. = kinematic viscosity, V / t. = density M / V. = shear stress tensor, M/t2L. = potential energy, MV / t 2 REFERENCES 1. Badger, W. L ., and Banchero, J. T ., "Introduc tion to Chemical Engineering," McGraw-Hill Book Co., New York, 1955. 2. Badger W. L ., and McCabe, W. L. Elements of Chemical Engineering," McGraw-Hill Book Co., New York, 1931. 3. Bennett, C. 0., and Meyers, J E., "Momentum, Heat and Mass Transfer," McGraw-Hill Book Co., New York, 1962. 4. Bird, R. B., Stewart, W. E., Lightfoot, E. N., Transport Phenomena," John Wiley and Sons, Inc ., 1960. APRIL 1966 5. Brown, G. G., and associates, "Unit Opera tions," John Wiley and Sons, New York, 1950. 6. Coulson, J M., and Richardson, J. F., "Chemi cal Engineering," 2 volumes, McGraw-Hill Book Co. New York, 1954. 7. McCabe, W. L., and Smith, J.C., "Unit Opera tions of Chemical Engineering," McGraw-Hill Book Co., New York, 1956 8. Walker, W H., Lewis, W. K., McAdams, W. H., and Gilliland, E. R., Principles of Chemical Engineering," 3rd ed ., McGraw-Hill Book Co., New York, 1937. ( continued from page 4 4) averted the following spring Jay's parents insisted that he bring his son home for a family inspec tion Jay and Jayshee realized that a six-month old child from antiseptic America would have an extremely difficult time in India, possibly even dying of dysentery. They finally persuaded Jay's family to come to Wyoming instead Jay has moved steadily ahead with Sinclair. Shortly after his son was born they asked him to move out to the company town of Sinclair so that he would be more readily available whenever technical diffi<:ulties arose. For $50 per month, he rents a two-bedroom, one-floor company-owned house. At his present salary rate of $700 per month he has been able to live well and still help his family Until his brother completed college last summer, he contributed $100 per month towards his expenses. Financial help to his family in India has been accomplished with the aid of a favorable exchange rate which converts one dollar into four rupees. This true story points to one way that the continued shortage of U.S. chemical engineers is being met. Not an isolated example by any means, Jay Saraiya is only one of sixteen non-citizen chemical engineers graduated and placed in per manent positions in the U.S. by one educational institution, Montana State University in the past six years. The employers of these men include some of the U.S.'s leading companies at some of their most attractive locations Just as nature abhors a vacuum, so good jobs are going to be filled whether or not American boys want them. (IJ 'II Ell 51

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Evaluation of an Approach to Plant Design D.R. Woods and A. E. Hamielec Associate Professors of Chemical Engineering McMaster University, Hamilton, Ontario, Canada Plant Design is taught at McMaster University in two courses. The theory and design of pieces of equipment are discussed as part of a four credit course called Economics and Technology, This is taught to fourth-year students for both the fall and spring terms for two hours a week. In addition to this course, three credits are given to a senior project laboratory: an 80-hour work shop in the spring term. This paper evaluates a novel approach to the project laboratory. The major novelty arose in (1) the student's respon sibility, (2) the time allocation, (3) the staff supervision, (4) the outside judging committee, and (5) the problem specification. These are discussed, and the evaluation follows. Project Description The Student's Responsibility: Each student decides how he is going to make the quantity of specification material, designs his own plant, submits a complete report, and verb ally defends his approach and design before an outside committee. Time Allocation: Eighty hours and only 80 hours are to be spent on this pro jec t. Each student draws up a time schedule for his calculations; then the students meet as a committee and draw up a work schedule that will be adhered to by each. The schedule breaks into a number of major stages. At the end of each of these the students meet with the staff for an hour of constructive criticism about how each has handled the assign ment. The 80 hours are divided into a 12-hour / week design laboratory that simulates an industrial situation. A room is booked, a filing cabinet is placed at the student's disposal, and the design liiboratory is not supervised; but the students are expected to be either in the booked room or in the library during the design laboratory time. We emphasize that they are not to work outside of class time. Full marks are given for the most efficient use of the time the student allots himself for each calculation. Marks are deducted if he does not have each project finished on time; if he does a five-minute calculation for a three-hour period or if he spends time doing unimportant and unre lated calculations, he loses marks The marking scheme for each criticism session is based on a total of 10 marks for every hour of design laboratory that has elapsed since the last criticism session. The Staff Supervision: 1. Give constructive criticism after each major 52 design effort While each completed project is fresh in the student's mind we explain how he could have saved himself time, and suggest reliable short cuts and good design technique The staff members with the most experience in the given field criticize the effort. 2. Are prepared to present request-lectures before each major design effort. Any staff member will present a maximum of a one hour workshop or discussion session provided such a workshop is requested by the students at least two days in advance of the lecture time and provided that hour is the first hour of the allocated project for the topic under consideration The staff are not consulted otherwise. All the staff are involved in this project. The Outside Judging Committee: The students design their plant for three out side judges, and not for the staff members. To the judges we suggest a complicated mark ing scheme for the oral presentation. (The four page, typed report from each student that is given to the judges provides background informa tion for the judges. We feel that it is too burden so me to ask them to mark the written reports). After each presentation, the judges are given as much time as they want to finish evaluating one speaker before the next starts. The Problem Specification: Little information is provided in the specifica tion. The quantity and quality of a given product and the utilities available-these alone are given. Table I is a typical specification. The students are informed also of the emphasis expected and the report specifications. All calculations are to include assumptions and limitations and estimated accuracy for each answer. The calculations must be legible and easy to follow. Specifications are required for each major piece of equipment For heat exchangers, a stand ard 1-in nominal tube is stipulated and details required include approximate tube count, tube length, and pitch; shell diameter; baffle spacing; pipe connections; material of construction; work ing pressure; and mounting instructions. A de tailed calculation for the selection of one pump is needed The types of control required must be indicated but not specified. The mechanical design of the reactor and of one of the major pieces of separation equipment is to be included. The produ c tion and the capital investment costs are to b e calculated. The report: 'I;'he d esig n r e port must be turned in one week b efo re the presentation day and later is filed in CHEM ENG ED

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TABLE I. DESIGN PROJECT SPECIFICATION .Desil:'ed: A plant to produce 50 long tons/24 hr. of 95% pure monomeric styrene or 300 long tons/24 hr. of 95% pure monomeric styrene Utilities available: Fuel oil Natural gas Electricity Cooling 20c. water: Lake water 5C. (winter) and (summer) City water (same average temperature) Steam: 200 psig, 100 psig, and 50 psig (all saturated) the chemical engineering department library The report consists of two parts: the body and the appendix. The body is a fourto five-page, double spac e d typ e d summary r e port of what was done why it was done, how it was done and what conclusions w e r e drawn from th e calculations The purpose of the report is to convinc e th e out side c ommitt ee that th e b e st possibl e d es i g n has been turned out in the time available Th e readers are th e outsid e committee, a g roup with ch e mi c al engineering training who may or ma y not be familiar with th e subtleti e s of th e d e sign topic. Four copies of the body of the report ar e r e quir e d Th e app e nd i x of th e report is a w e ll ind e x e d c ollection of all of the a c tual calculations d o n e, tog e th e r with appropriat e s ummar y pa ge s int e r sp e r se d throughout the work. Th e calculation s n ee d not b e typ e d ; but th ey must b e l egi bl e and indicate the c alculation approa c h Th e purp ose o f th e app e ndix is to s upply a compl e t e r ec ord o f all of the c alculations done on th e d e si g n proj ec t so that anyon e who had to do a mor e e laborat e design c an g o one from wh e r e each s tudent stopped rath e r than b e for ce d t o r ec al c ulat e work that has be e n done. The av e ra ge r e ader o f th e app e ndi x will hav e a c h e mi c al e n g in eer in g b ac k ground, will probabl y kn o w nothin g ab o ut t h e d es i g n topic, and will b e int eres t e d i n l e arnin g what ha s b ee n don e and what ar e th e limitat i on s APRIL 1966 and assumptions involved in the calculat i ons Evaluation The advantages and the weaknesses of this approa c h to d e sign t e achin g ar e outlin e d as fo llows. Ad v antag e s W e have found th e following advantag e s : l. Th e outsid e c ommitt ee a dds realit y to th e pro je ct for th e stud e nts. Th e stud e nts' e phasi s is shifted so that they are working a g ainst th e outsid e committe e and its e valu ation, rath e r than against a staff m e mber for a grad e. Th e stud e nts f e el their reputations ar e at stak e Tw e nty p e rcent o f th e final class mark d e p e nds on th e outsid e c ommit t ee s judgm e nt. Our o utsid e c ommit tee mem b e rs not onl y ha ve b ee n very l e arn e d in th e fi e ld but hav e a s k e d stimulating and probin g qu e stion s. Th e co mmitt ee fo r th e st y r e n e proj e ct i n cl uded a s e nior pro cess designer from Dow C h e mi c al (who produ ce s t y r e n e ), a se ni o r c h e mi s t in th e p e troch e mi c als divi s i o n fr o m Pol y m e r C orporati o n (who also ma k e st y r e n e ) and a Uni vers it y of Toronto c oll e a g u e wh o ran th e plant pro jec t d e si g n th e r e 2 Th e stud e nts e n joy th e i nd ivi dual r e sponsi bilit y Sin ce w e d o n o t form c ompani es, e a c h s tud e nt ha s to d o hi s own c r e ativ e desi g n and 53

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justify it on the basis of economics. 3. The students enjoy the diversity of responsi bility, including choice of process, design, and cost estimation. They say they prefer to make an overall, high-spot design of a complete process rather than a detailed design of an element of a process. Twelve hours of design laboratory time are free between the time the students hand in their reports and the oral presentations. We use this time to build a scale model of one student's plant. For the degree of accuracy required, we found that this could be done for a styrene plant for about $10. The scale was l / 4 in = 1 ft 4. Lectures are given only at the students' request. Most want to get on with the job; few lectures are required. This pleases the students and the staff alike because we feel that they are asking and answering their own questions. 5. The criticism periods after each major design effort give rapid feed-back of suggested im provements and the type of assumptions to make. Since any lectures are at the request of the students, we want strong feed-back on their approach as they proceed. 6 The limitation for the time spent on this project is worthwhile. The students do not jeopardize their standing in other courses by devoting excessive extra time to this course; they learn to match their designs to the time available. The marking scheme for the criti cism sessions accentuates matching time with accuracy. 7 The marking scheme specified to the judges requires about 10 minutes per speaker. Although the judges think the marking scheme cumbersome, we find it very helpful to the students 8. It is easy to rate each student. 9. Staff load for the course is distributed among the staff members. Furthermore, the students gain from the background experience of staff specialists in the criticism periods. Weaknesses Some weaknesses of this approach are: 1. An apparent lack of understanding of the role of plant design in an economics analysis. The students do not seem to realize that the pre liminary plant design is done to improve their accuracy in their economic assessment of the process. We think that the onus of this is not upon the design course but rather on the economics and technology course which one of us also taught. In the future we plan to be more specific in the students purpose in doing the plant design. 2. Inadequacy of decision-making theory. The students do not fully appreciate the conse quences of the various decisions made. More emphasis will be given to this topic in the economics and technology courses in the future. For example, not only will we crea tively look at process flow sheets as we do 54 now, but we will do exercises on getting quick numbers for equipment cost for several dif ferent flow-sheets. This training in cursory equipment costing should help them to allo cate their design time for any preliminary design project itself. 3. Inadequacy of the criticism sessions. Whether the improvement is achieved by converting the sessions into a verbal presentation to the combined staff after each sub-project or by supplying more staff manpowJr to correct and criticize individual efforts the whole key is the constructive criticism of the student's effort at various stages along the way imme diately after he has completed his work. 4. Poor distribution of staff responsibility. The staff coordinators sometimes do not call on other staff members to help out enough. 5. Paucity of time available for the design. The completeness of the project could be improved either by requiring the students to do some work outside the specified hours, by forming companies of design engineers, or by reducing the scope of the project. Incre~sing the stu dent's homework is easy to justify because our fourth year, second term load is relatively light. The formation of companies requires careful consideration. The advantages for individual design that both the staff and the students have appreciated are (a) each student is completely responsible for all of the decisions and calculations. (b) each sees all facets of the design rather than working on his specialty with figures that are handed to him by someone else. (c) each realizes that the individual mark can be given at the end of the project. It would be interesting to see if we can in corporate all of these advantages by forming companies of two students and by insisting that each student be able to defend any part of the final design The suggestion of reducing the scope of the project has received a negative reaction by the students 6. Poor technical communication. Although the general reaction to the student's oral presen tation has been favorable, the written reports are poor We have introduced a two-credit course in technical communication into our second-year program in an attempt to remedy the situation. Summary 1 A novel approach to teaching plant design is being developed at McMaster University. The uniqueness of this approach lies in the method of handling the student's responsibility, the time allocation, the staff supervision, the judging com mittee, and the problem specification An evaluation of the approach based on its application to one project with a class of fourth year students, shows that it has many advantages and several weaknesses With the correction of the latter, the approach should offer great promise as a powerful method of teaching design CHEM ENG ED

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WHY SETTLE FOR SECONH BEST? when you can get the best from these Wiley hooks. Fundamentals of Classical Thermodynamics By GORDON J. VAN WYLEN and RICHARD E. SONNTAG, both of The University of Michigan. 1965. 634 pages. $8.95. Fundamentals of Statistical Thermodynamics By RICHARD E. SONNTAG and GORDON J. VAN WYLEN. 1965. Approx. 352 pages. $7.75. Diffusional Separation Processes: Theory, Design and Evaluation By EARL D. OLIVER Universit y of New Mexico. 1966. 445 pages. Prob. $14.00. Introduction to Chemical Process Control By DANIEL D. PERLMUTTER University of P enns yl vania. 1965. 204 pages. $ 6. 95. The Discrete Maximum Principle: A Study of Mul~istage Systems Optimization By LIANG-TSENG FAN and CHIU SEN WANG both of Kansas S tate Uni versity. 1964. 158 pages. $5.75. The Continuous Maximum Principle: A Study of Complex Systems Optimization By LIANG-TSENG FAN. 1966. 411 pages. $ 16.00. Heat Exchanger Design By ARTHUR P. FRAAS Oak Ridg e National L aborator y USAEC, and M. NECATI OZISIK, North C ar ol ina Stat e University at R a l eigh. 1965. 386 pages. $ 17 .50. Boiling Heat Tran s fer and Two-Phase Flow By L. S. TONG, Westinghouse Electric Corporation Pittsburgh P ennsylvania 1965. 242 pages. $ 14.00. Technique s of Pro ce ss Control By PAGE S. BUCKLEY E I. du Pont de Nemours & Company, In c. 196 4 303 page s $ 15.00. Industrial Chemicals Third Edition By W. L. FAITH, Co nsulting Chemi cal Engineer, San Marino, California; DONALD B. KEYE S, Consulting Ch emical Engineer, N e w York; and RONALD L. CLARK, Hook e r Ch e m i cal C orporation, New York. 1965. 852 pag es $ 25.00. Principles of General Thermodynamics By GEORGE N. HATSOPO U LOS Massachusetts Institut e of Technology and Pr e sident of Thermo Electron Engi n ee ring Corporation; and JOSEPH H. KEENAN Massachus e tts Institut e of Technology 1965. 788 p ages $ 1 5. 00. JOHN WILEY & SONS, Inc. 605 Third Avenue New York N. Y. 10016

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Professors, Employers of Chemical Engineers, Graduate Students Keep itp to date in the ways of CHEM!lfll{}/1 EIG!lli!llllllllllli!lfl ED/lJ@l{Jl1!J(l}li!/ In the pages of CHEM ENG ED yoit will find reports on instru ction methods, discussions of industry's view of modern chemical engineerng, opinion of leading engineering teachers, reviews of chemical engineering textbooks. DON'T MISS AN ISSUE ... SUBSCRIBE TODAY! Only $3.00 a year for members of the Chemical Engineering Division, ABEE; $4.00 for non members ($5.00 if outside the Western Hemisphere). Prepayment is requested. CHEMICAL ENGINEERING EDUCATION 201 Gavett Hall, University of Rochester Rochester, N Y. 14627.