Citation
Improving forced-air cooler performance

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Title:
Improving forced-air cooler performance
Series Title:
Circular Florida Cooperative Extension Service
Creator:
Talbot, Michael T ( Michael Thomas ), 1948-
Florida Cooperative Extension Service
Place of Publication:
Gainesville
Publisher:
Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida
Publication Date:
Language:
English
Physical Description:
9 p. : ill. ; 28 cm.

Subjects

Subjects / Keywords:
Precooling ( lcsh )
Crops -- Postharvest technology ( lcsh )
Food -- Cooling ( lcsh )
Crops -- Quality ( lcsh )
Genre:
bibliography ( marcgt )
non-fiction ( marcgt )

Notes

Bibliography:
Includes bibliographical references (p. 9).
General Note:
Cover title.
General Note:
"June 1992."
Statement of Responsibility:
Michael T. Talbot ... et al..

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University of Florida
Holding Location:
University of Florida
Rights Management:
All applicable rights reserved by the source institution and holding location.
Resource Identifier:
AAA6717 ( LTQF )
ALD2897 ( LTUF )
26517263 ( OCLC )
022776514 ( ALEPHBIBNUM )

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June 1992 Circular AE 108


Improving Forced-Air Cooler Performance

Michael T. Talbot, C. Direlle Baird, Steven A. Sargent and Jeffrey K. Brecht
































Florida Cooperative Extension Service
Institute of Food and Agricultural Sciences
University of Florida
John T. Woeste, Dean


Circular AE 108


June 1992















































































Associate Professor and Professor, Agricultural Engineering Department and Associate Professors, Vegetable Crops Department.








Introduction
Commercial forced-air precooling
has become an important posthar-
vest procedure in Florida for rapid
cooling and maintaining quality of
several vegetable crops, strawber-
ries, blueberries, and cut flowers.
A detailed description of forced-air
cooling and several different types
(Figures 1 and 2) are described in
several publications 11, 3, 4, 5, 6, 8,
9] (numbers in brackets refer to cited
references). One study [21 discusses
in detail the numerous variables
which affect product cooling rate
and/or overall cost of forced-air cool-
ing systems for fruits and vegeta-
bles. These variables relate to the
product, such as, size, shape, initial
product temperature, desired final
product temperature, and thermal
properties; to the product configura-
tion, such as, product packaging
(bulk or in shipping containers), car-
ton vent area, depth of product load
during cooling; to the precooling sys-
tem, such as, air-flow rate, tempera-
ture, and relative humidity, ambient
temperature; and to economics, such
as, time of operation per year, unit
costs of cooling space, heat exchang-
ers, compressors, and fans, electric
power cost, maintenance cost, labor
cost, and interest rates.

In forced-air cooling (Figure 1),
produce is air-cooled rapidly by a dif-
ference in air pressure on opposite
faces of stacks of vented containers
(pallet boxes, corrugated cartons,
flats, etc.). Fans create the pressure
difference, which is called static-
pressure difference. This pressure
difference forces air through the con-
tainers and product, removing pro-
duce heat. The product is most effi-
ciently cooled when the cooling air
flows around the individual fruits or
vegetables in the containers, rather
than by flowing around the outside
of the containers (as in room cool-
ing). In other words, the cooling me-
dium (cold air) comes into intimate
contact with the product to be cooled.


Figure 1. Forced-air tunnel with portable exhaust fan.


Figure 2. Forced-air cooler with permanent constructed air plenum.













































Figure 3. Container and pallet stacking configuration for forced-air cooling tunnel.
This publication discusses meth-
ods to evaluate and improve forced- pi 1
air cooler performance. It is in-
tended to assist those interested in 04'.i- 1
improving the performance of an i
existing forced-air cooler as well as p ,PEBS R.
those planning to install new cm
forced-air cooling systems. The in-
formation is applicable to all types
of forced-air cooling systems.

System performance can be as-
sessed by measurement of static-
pressure drop, air velocity or flow,
and cooling rate during commercial
forced-air cooling. Precoolers can be
made more efficient by several
minimal cost methods and by in- Figure 4. Opening in pallets sides
creased management. These meth- for cooling air bypass.


ods include sealing air-leak areas
to force additional air through
products, improving carton stack-
ing configurations or orientation,
modifying pallet-tunnel length and
width, and proper temperature
monitoring. Methods requiring
more time and cost include im-
provement in carton design, in-
creased fan and cooling capacity.

Seal leaks
The path of least resistance is a
key physical principle when con-
sidering forced-air cooling. Air,
like water, flows from a point of
high pressure to a point of lower
pressure by the path which pre-
sents the least resistance. The
goal for effective forced-air cooling
is to insure that the path of least
resistance is through the product
rather than around the container.

Air bypasses or short circuits
whenever the path of least resis-
tance is not through the product.
Such bypasses include openings
between stacked containers on pal-
lets (Figures 3, 4, and 5), between
adjacent pallets, side pallet entry
holes under pallets, loosely in-
stalled canvas covers or through
holes in the canvas, and at the
junction between pallets and air
plenums or ducts.


IsPI e uareI I

mkU t S'U 10I
OUE

dwLUZ Ol


and tops and gaps between adjacent pallets provide paths


OPENINGS
BETWEEN
PALLETS



-' a I I I
I I I I I I I I I I
I I I I II
I I I I ,

I OI I CARTON I I I I N
I I I I t

I I I I I I I I I

TWO-WAY OPENNGS
PALLET
PALLET
FRONT VIEW SIDE VIEW SIDES




















'M
/ I "








Figure 5. Opening in tops of pallets and misalignment of pallets forming forced-air cooling
tunnel.


Figure 6. Plastic used to seal the pallet opening in the row of pallets on the left.


Recent research on forced-air
cooling of peppers [9] has shown
that the air bypass of the openings
beneath pallets can be blocked
with plastic (Figures 4 and 5), sig-
nificantly reducing cooling time.
This study also clearly illustrates
that a large volume of cooling air
can pass through seemingly small
gaps between adjacent pallets of a
product.

Flexible materials such as plas-
tic, canvas or foam rubber should
be used to seal openings that allow


cooling air to bypass containers
(Figure 6). This material should be
placed such that the fan suction
seals the undesirable openings.
Plywood is used in some strawberry
and other forced-air cooling opera-
tions for blocking large, open areas,
and is not effective in reducing by-
passed air. In the above-mentioned
study [9], sealing pallet openings
with plastic was successful in block-
ing air bypasses while lumber
placed against the sides of the pal-
lets was not effective. Apparently
the rigid structure of the wood


could not properly seal the openings
in the pallets. Lumber and plywood
are not effective unless duct tape or
plastic seals the spaces between the
wood and containers or plenums.
Boards can be effective if 5 cm (2 in)
of polyurethane foam is glued to the
side of the boards placed against
the pallets.

A simple idea for sealing pallets
is to attach purchased or salvaged
plastic or scrap corrugated paper to
cover the top of the pallet and the
pallet side openings not normally
used for the forklift blades. This
can be accomplished inexpensively
by in-house personnel using sta-
plers or tape.

The more resistance through the
product, the more important it is to
seal leakage areas. Therefore, re-
ducing the resistance through the
product (e.g. increasing carton face-
vent area) can reduce the signifi-
cance of air leakage or bypass.

Carton face-vent area
For forced-air cooling the recom-
mendation for minimum carton
vent opening is 5% of the container
surface facing the airflow [2, 6, 9].
Many Florida packinghouses should
increase the openings of the carton
vents to achieve this recommended
value, which reduces the resistance
to airflow through the cartons (Fig-
ure 7). A few larger holes produce
less resistance than several smaller
holes of the same total area.

The percent of vent openings of a
particular carton surface or face can
be calculated by determining the
ratio of the vent openings of a par-
ticular surface to the total area of
that surface (Figures 8 and 9). Only
the surfaces perpendicular to the
air flow should be considered. To
determine the percent vent opening
for a container surface, the area of
each vent should be calculated us-
ing basic geometric equations and
the area of all vents added. Most























* *




SA- *~ --


Figure 7. Several currently used and experimental containers with vents of various sizes,
shapes, and locations.


carton venting is circular or round-
ended slots, which are combinations
of rectangles and semicircle ends.
The total vent area should then be
divided by the total face area of that
surface (length times height) and
finally multiplied by 100.

For many packinghouse opera-
tions, cartons are placed such that
the side vents align with the side
vents of the adjacent carton or the
end vents align with the end vents
of the adjacent carton, for example
standard 1-1/9 bushel containers
stacked eight containers per layer
(Figures 3 and 8). In other applica-
tions, such as 40 x 30 MUM
(Modularization, Unitization, and
Metrification) containers stacked
ten per layer, the stacking patterns
require ends of cartons to align with
the sides of adjacent cartons and the
carton vent locations must be de-
signed accordingly (Figures 9 and
10). If the vent holes on adjacent
cartons do not align, a major disrup-
tion of air flow occurs and should be
avoided. For produce cartons with
slender vertical slots commonly
used on the ends and sides, offset of
the carton by as little as 0.6 cm (1/4


in) results in vent hole misalign-
ment. This is another reason for
selecting large rather than small
vent holes, because the larger
holes would allow partial vent
alignment even when the cartons
are not aligned correctly. How-
ever, wide holes can be partially
blocked by the product more so
than narrow slots. Also, more cor-
rugate flutes are cut with a wider
hole, which reduces the strength of
the carton.

Pallet configurations

Pallet placement
In one type of forced-air cooler,
two rows of pallets are placed end
to end to form each side of a cool-
ing tunnel (Figures 1 and 3). It is
important that the pallets are
placed such that very little gap
exists between the cartons of adja-
cent pallets. Otherwise another
path is created for the cooling air
to bypass the cartons. Velocity
measurements [9] indicated sig-
nificant air flow through such
gaps, particularly when plastic
was installed to seal the side open-
ings of the pallets. For example, a


4.5 cm (2 in) by 1.2 m (4 ft) gap was
noted between the two pallets dur-
ing a test at a packinghouse with
plastic installed. The measured
velocity through the gap was 5 m/s
(970 fpm) and the calculated flow
rate was 0.3 m 3/s (650 cfm). The
total flow through an adjacent car-
ton was 0.01 m3/s (26 cfm). At an-
other packinghouse, a 4.5 cm (2 in)
by 28 cm (11 in) gap was noted be-
tween the two pallets with plastic
installed. The measured velocity
through the gap was 3.5 m/s (680
fpm) and the calculated flow rate
was 0.05 m3/s (104 cfm). The total
flow through an adjacent carton
was 0.006 mV/s (12 cfm).

This study [9] suggests that
additional studies should be con-
ducted to determine how varying
the number of pallets, height of the
cartons on the pallets, tunnel width
(distance between rows of pallets),
and similar factors affect the per-
formance of the air handling and
cooling systems. Limited data indi-
cates that reducing the number of
pallets in the cooling tunnel from
10 to 6 reduced the half cooling
time for the last pallet ( without
plastic) from 1.9 to 0.7 hours.
Therefore, it might be possible to
cool 36 pallets (3 groups of 12 pal-
lets cooled) with tunnels 6 pallets
long in the same length of time as
20 pallets (1 group of 20 pallets
cooled) with tunnels 10 pallets long,
if sufficient refrigeration capacity
is available (Figure 11).

In addition to the side openings
in the two-way pallet, the bottom
layer of cartons at times does not
always completely cover the surface
of the pallet. This leaves openings
between boards on the top of the
pallet, thus allowing air to bypass
the product. Significant air bypass
was noted through these open pal-
let surfaces [9]. Normally the car-
tons are stacked flush with one side
of the pallet, while the other side
exposes the surface of the pallet.











1-1/9 BU PEPPER CONTAINER


48 in
(120 cm)
PLAN VIEW


% Vent Opening

1.9 3.5*

* Hand Hole Assists
Forced-Air Cooling


SIDE VIEW

Area of Round-ended Slot

.. rhi |=L-d -

d=2r

....... L=l+d--

Area Slot = Area Rectangle + 2(Area Semi-Circle)
= Area Rectangle + Area Circle
= (L-d)d + rd2/4 = (l)d +T r

For example using the side view above (English units):
Area Slot = [(2 3/8)-(7/16)](7/16) + T (7/16)2
Area Slot = 1.00 in2
Total Vent Area = 4 Area Slot = 4.00 in2


Vent Alignment: Vents
are aligned because
containers are stacked
either side to side
or end to end.













Hand Hole,
- 1 x 3-3/8 in
(2.5 X 8.6 cm)

SVertical Slot,
15/32 x 1-15/16 in


END VIEW

Area of Container Face


T ---------- ----
T

I....... w .. ... "1

Area Face = Area Rectangle = Width x Height = WH
For example using the side view above (English units):
Area Face = (17 7/8)(12) = 214.5 in2
% Vent Opening Area

Total Vent Area
% Vent Opening 100
Area Face
For example using the side view above (English units):
% Vent Opening = (4.00/214.5)100 = 1.9 %


Figure 8. 1-1/9 bushel pepper container showing dimensions, percent vent openings, and pallet stacking configuration.


Vertical Slot.
7/16 x 2-3/8 in
(1 1 X 6.0 cm)





I-












40 X 30 cm MUM PEPPER C(

---9

15 13/16
(40cm)
i c-


11 7/8 in
(30cm)


47 1/2 .in........
(120 cm)
PLAN VIEW


CONTAINER
Vent Alignment: Vents
were designed so holes
align when ends and
sides of containers are
cross-stocked. In this
example some vents
align with the space
between adjacent
containers.


Cross-stack
plane used for
finding Effective
% Vent Opening


Hand Hole.
1 x 3.5 in
% VENT OPENINGS (2.5 X 8.9 cm)
Individual Container 3 8 in)
8. cm)
15 13/16 in 7.4 6.6(8.8)*
(40cm) Effective 11 7/8 in ij E
5.0 (7.2)* (30cm)
Hand Hole Does Not
Assist Forced Air Cooling
1-3/8 in. wide. 1-15/16 in. long semi-circular ended slot
(3.5 cm wide, 4.9 cm long semi-circular ended slot)
SIDE VIEW END VIEW


Area of Round-ended Slot

r. r l=L-r
+ ---i-r..
d=2r

... L=l+r -'

Area Slot = Area Rectangle + Area Semi-Circle
= (L-r)d +1/2(Td2/4) = Id +1/2(rrr2)
For example using the side view above (Metric units):
Area Slot = [(4.9-(3.5)/2)](3.5) +1/2[ r(3.5f/4]
Area Slot = 15.8 cm2
Total Vent Area = 6(Area Slot) = 94.8 cm2


Area of Container Face



------... -

Area Face = Area Rectangle = Width x Height = WH
For example using the side view above (Metric units):
Area Face = (40)(32) = 1280 cm2

% Vent Opening Area
Total Vent Area
% Vent Opening = 100
Area Face
For example using the side view above (Metric units):
% Vent Opening = (94.8/1280)100 = 7.4%
% Effective Vent Opening = (12)(15.8)/(3)(1280)100 = 5.0%


Figure 9. 40 x 30 cm MUM pepper container showing dimensions, percent vent openings, and pallet stacking configuration.


r t
0m


Vent Hole Alignment

t t t


3 15/16
(10 cm)


.i


II I~
II II


L
Q


- .-----.. ..

































Figure 10. Top view of 40 x 30 cm MUM container showing vent hole alignment when con-
tainers are cross-stacked (end to side).


The side with the exposed pallet
surface should be placed so that the
exposed surface is inside the forced-
air cooling tunnel. MUM-type con-
tainers can reduce this problem be-
cause they cover 90% or more of the
pallet surface [7].

For efficient precooling, packing-
house personnel must be properly
trained and supervised to insure
that pallets are tightly placed and
aligned when forming the cooling
tunnels.

Static pressure
measurement
The importance of sealing the
openings under the pallets is illus-
trated [9] by measurement of the
static pressure drop across the pal-
lets (outside to inside of the cooling
tunnel), at the center of each pallet
and at the end of the tunnel away
from the fan. With plastic added,
the pressure drop was nearly dou-
bled. Since the pressure varies with
the square of the velocity, doubling
the pressure would result in a 40%
increase (square root of 2) in the
velocity.


The packinghouse manager
should routinely check the static-
pressure drop for each cooling tun-
nel at the beginning of a cooling
cycle to insure proper fan operation.
This is particularly important when
the forced-air precoolers employ
more than one exhaust fan for each
precooling tunnel. Twice during
pressure drop checks at one pack-
inghouse [9], one tunnel's pressure
drop was much less than the others.
A check of the two fans revealed
that only one was operating because
a circuit breaker had tripped on the
other. Visual observation of the two
fans was insufficient to determine
whether one or two fans were oper-
ating since both were turning at the
same apparent speed and some suc-
tion was evident when moving the
canvas. Air was coming in through


VARYING PALLET NUMBER FOR
FORCED-AIR COOLING TUNNELS


HALF-COOLING TIME


0.7 HOURS


SIX- PALLET
COOLING TUNNEL


I


2
PA'
4 UUN
CA]

I ,- Al I


Initial Product Temperature:
Cooling Air Tenmperature:
Temperature to Achieve Half


1 .9 HOURS


TEN -PALLET
COOLING TUNNEL


IM


2
LY
4


)W -
ON 7

9


Cooling:


75 F
43F
59F


Figure 11. Example of reduced cooling time by reducing the forced-air cooling tunnel length.







the top of the off fan and pulled
back through the operating fan.
Therefore, little cooling air was
passing through the palletized
product. In addition, these fans
were not readily accessible.

A simple, homemade, U-tube
manometer [9] is adequate for pack-
inghouse personnel to quickly check
the static pressure drop at the end
of the tunnel away from the fan and
immediately correct problems (Fig-
ure 12). An additional approach is
the installation (wired to fan elec-
tric circuit) of easily observed lights
for each fan, which are on while the
fans operate. However, pressure
drop should still be checked periodi-
cally, to insure that air is not by-
passing the product.

Temperature measure-
ment/Cooling schedule

Temperature monitoring
Since the goal of forced-air cool-
ing is to rapidly reduce the tempera-
ture of the cooled product the cooler
operator must have a method of
measuring the temperature of the
product being cooled to determine
when cooling has been completed.
The important management prac-
tice of determining when precooling
has been completed to the desired
temperature has been stressed 181.
Due to daily differences in the ini-
tial product temperature, the cool-
ing time to achieve a desired final
temperature may vary. The cooling
time also varies if the cooling-air
temperature cannot be maintained
during cooling due to inadequate
refrigeration capacity. Another fac-
tor which can change the cooling
rate is the product size, since larger
products cool more slowly than
smaller products. In general, dou-
bling the diameter or thickness re-
quires 4 times as long to cool. A
precooling schedule should be devel-
oped for every precooler and modi-
fied as conditions require [8].


TOIP VIEW


FRONT VIEW


Ml: A'M,JhL MLHFi
LOCA; IHUN

1 1- M E -'A I JRI
III ) I-II J E N/





















J *UBF
v*\AN OMETFR


Figure 12. Static pressure drop and temperature measurement locations.


Recent cooling tests 11,91 investi-
gated the variation of cooling as a
function of bed effect (the effect due
to the depth of the product) and
height of the carton on the pallet.
The experimental data verified that
a bed effect does occur. The product
in cartons exposed to incoming air,
close to the air entrance cooled
more rapidly than product on the
opposite side, near the air exit from
the pallet into the cooling tunnel.
The cooling rate was found to vary
with height of the containers on the
pallet, although no criterion was
established [91. Additional work is
needed to determine the "best" loca-
tion for sampling temperature.


Temperature
measuring equipment
Dial-type thermometers are com-
monly used to measure the product
temperature during cooling, and the
pulp temperature samples are often
taken at inadequate locations. These
thermometers have a slow response
time (minutes) and limited accuracy.
Also, it is difficult to precisely locate
the probe-the probe may pass
through product and measure air
temperature inside the carton. The
sampling location suggested above
is inside the cooling tunnel and not
easily reached with a probe-type
thermometer (Figure 12). To over-







come these problems, one or more
thermocouples could be inserted
easily into product in cartons on the
inside of the last pallet before it is
positioned for cooling with the ther-
mocouple leads located outside the
canvas area. An inexpensive hand-
held thermocouple reader could be
used to measure cooling for all the
tunnels. The thermocouple reader
is accurate and has a fast response
time (seconds). The thermocouples
are durable and can be used many
times. With additional investment,
permanent thermocouple leads and
remote data loggers could be used.

Velocity and flow rate
Velocity and flow measurements
are difficult and require expensive
instruments, however the total flow
rate is an important item of infor-
mation. A cheaper and more conve-
nient method is to use the manom-
eter mentioned above to measure
the static pressure across forced-air
cooling fans and then estimate the
flow rate using fan performance
curves supplied by the fan manu-
facturer. The performance curve
estimates the flow rate for various
static pressure operating conditions.

Summary
This publication presents several
methods for increasing the efficiency
of forced-air precoolers for fresh pro-
duce. Recommendations for increas-
ing efficiency with minimal cost and
increased management include seal-


ing air bypasses (particularly
through the pallets) to force addi-
tional air through products, im-
proving carton stacking configura-
tions/orientation, and proper tem-
perature monitoring. Modifying
pallet-tunnel length and width also
show promise for improving effi-
ciency. Recommendations which
require more time and cost include
increasing carton vent opening,
increasing fan capacity, and in-
creasing refrigeration capacity.
Of these three, the design of the
carton with particular attention to
the percent vent openings should
be addressed first. Increasing the
fan and refrigeration capacity
should be considered only after all
the above-mentioned changes have
been accomplished.

Literature cited
1. Arifin, B.B. and K.V. Chau.
1988. Cooling of strawberries in
cartons with new vent hole de-
signs. Trans. ASHRAE. Vol. 94
(1): 1415-1426.

2. Baird, C.D., J.J. Gaffney, and
M.T. Talbot. 1988. Design crite-
ria for efficient and cost effective
forced-air cooling systems for
fruits and vegetables. ASHRAE
Transactions 94(1):1434-1454.

3. Gaffney, J.J. and C.D. Baird.
1977. Forced-air cooling of bell
peppers in bulk. Transactions of
the ASAE 20(6):1174-1179.


4. Kader, A.A., R.F. Kasmire, F.G.
Mitchell, M.S. Reid, N.F.
Sommer, and J.F. Thompson.
1992. Postharvest technology of
horticultural crops. California
Coop. Ext. Serv. Pub. 3311.

5. Mitchell, F.G., R. Guillou, and
R.A. Parsons. 1972. Commercial
cooling of fruits and vegetables.
California Agr. Expt. Sta. Man.
43.

6. Parsons, R.A., F.G. Mitchell,
and G. Mayer. 1970. Forced-air
cooling of palletized fresh fruit.
ASAE Paper No. 70-875.

7. Sargent, S.A., J.K. Brecht, and
J.J. Zoellner. 1990. Some physi-
cal characteristics of bell pepper
in relation to capacities of stan-
dard and potential shipping con-
tainers. Proc. Fla. State Hort.
Soc. 103:222-225.

8. Sargent, S.A., M.T. Talbot, and
J.K. Brecht. 1991. Evaluating
precooling methods for vegetable
packinghouse operations. Univ.
FL, IFAS, Vegetable Crops
Department Special Series SS-
VEC-47.

9. Talbot, M.T. and C.D. Baird.
1990. Evaluating commercial
forced-air precoolers. ASAE
Paper No. 91-6021.





















































































COOPERATIVE EXTENSION SERVICE, UNIVERSITY OF FLORIDA, INSTITUTE OF FOOD AND AGRICULTURAL SCIENCES, John T. Woeste, Director,
in cooperation with the United States Department of Agriculture, publishes this information to further the purpose of the May 8 and June 30,1914 Acts of Congress;
and is authorized to provide research, educational information and other services only to individuals and institutions that function without regard to race, color,
sex, age, handicap or national origin. Single copies of extension publications (excluding 4-H and youth publications) are available free to Florida residents from
county extension offices. Information on bulk rates or copies for out-of-state purchasers is available from C.M. Hinton, Publications Distribution Center, IFAS
Building 664, University of Florida, Gainesville, Florida 32611. Before publicizing this publication, editors should contact this address to determine availability.
Printed 6/92.




Full Text

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Associate Professor and Professor, Agricultural Engineering Department and Associate Professors, Vegetable Crops Department.



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The packinghouse manager should routinely check the staticpressure drop for each cooling tunnel at the beginning of a cooling s cycle to insure proper fan operation. Sj .This is particularly important when the forced-air precoolers employ more than one exhaust fan for each S A precooling tunnel. Twice during S DO NOT COOL pressure drop checks at one packinghouse [9], one tunnel's pressure drop was much less than the others. A check of the two fans revealed that only one was operating because a circuit breaker had tripped on the O -other. Visual observation of the two fans was insufficient to determine whether one or two fans were operSating since both were turning at the same apparent speed and some suction was evident when moving the Figure 10. Top view of 40 x 30 cm MUM container showing vent hole alignment when concanvas. Air was coming in through tainers are cross-stacked (end to side). The side with the exposed pallet VARYING PALLET NUMBER FOR surface should be placed so that the exposed surface is inside the forcedFORCED-AIR COOLING TUNNELS air cooling tunnel. MUM-type containers can reduce this problem beHALFCOOLING TIME cause they cover 90% or more of the pallet surface [7]. 0.7 HOURS 1 .9 HOURS For efficient precooling, packinghouse personnel must be properly SCOOLIXPALLET TENUNNEL COOLING T-PALLUNNELT trained and supervised to insure that pallets are tightly placed and aligned when forming the cooling PLENUM tunnels. FANS Static pressure 2 2 ci PARTIALLY measurement UNROLLEDVA The importance of sealing the 5 openings under the pallets is illus-G -AIR FLOW 6 trated [9] by measurement of the DIRECTION 7 static pressure drop across the pallets (outside to inside of the cooling tunnel), at the center of each pallet 1 0 .o and at the end of the tunnel away from the fan. With plastic added, the pressure drop was nearly douInitial Product Temperature: 75 -F bled. Since the pressure varies with Cooling Air Tern pe rat u re: 43 oF the square of the velocity, doubling Temperature to Achieve Half -Cooling: 59 F the pressure would result in a 40% increase (square root of 2) in the velocity. Figure 11. Example of reduced cooling time by reducing the forced-air cooling tunnel length. 7



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40 X 30 cm MUM PEPPER CONTAINER SVent Alignment: Vents Swere designed so holes align when ends and 115 13/16 i sides of containers are "(40c) cross-stocked. In this example some vents o align with the space "ci between adjacent • -, containers. oE So Cross-stock c), Vent Hole Alignmen Cross-stack 'n O plane used for 0 _ finding Effective -% Vent Opening 11 7/8 in (30cm) _i_ _ ............4 7 1 /2 ............. ....................... (120 cm) PLAN VIEW Hand Hole. 1 x 3.5 in % VENT OPENINGS (2.5 X 8.9 cm) Individual Container -(8 3 m) 8 cm) 15 11/16 in 7.4 6.6(8.8)* (1 c)(40cm) .Effective 11: 7/8 in .E 315/16 inmji (10 c nI 5.0 (7.2)+ (30cm) S* Hand Hole Does Not Assist Forced Air Cooling 1-3/8 in. wide. 1-15/16 in. long semi-circular ended slot (3.5 cm wide. 4.9 cm long semi-circular ended slot) SIDE VIEW END VIEW Area of Round-ended Slot Area of Container Face .r--=Lr.. d=2r l--L=+r--------W ......... ...... L=I+r-Area Face = Area Rectangle = Width x Height = WH Area Slot = Area Rectangle + Area Semi-Circle For example using the side view above (Metric units): = (L-r)d +1/2(Td/4) = Id +1/2(Tr2) Area Face = (40)(32) = 1280 cm2 For example using the side view above (Metric units): % Vent Opening Area Area Slot = [(4.9-(3.5)/2)](3.5) +1/2[ T(3.5/4] Totalnt STotal Vent Area Area Slot = 15.8 cm2 % Vent Opening = 100 Total Vent Area = 6(Area Slot) = 94.8 cm Are F For example using the side view above (Metric units): % Vent Opening = (94.8/1280)100 = 7.4% % Effective Vent Opening = (12)(15.8)/(3)(1280)100 = 5.0% Figure 9. 40 x 30 cm MUM pepper container showing dimensions, percent vent openings, and pallet stacking configuration. 6



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the top of the off fan and pulled back through the operating fan. Therefore, little cooling air was A passing through the palletized AN r product. In addition, these fans were not readily accessible. A simple, homemade, U-tube LJFL manometer [9] is adequate for packLOCA O!N inghouse personnel to quickly check the static pressure drop at the end of the tunnel away from the fan and -.`E A i, immediately correct problems (Figi ure 12). An additional approach is the installation (wired to fan electric circuit) of easily observed lights for each fan, which are on while the fans operate. However, pressure drop should still be checked periodically, to insure that air is not byTO'P VIEW passing the product. Temperature measure, ment/Cooling schedule . Temperature monitoring Since the goal of forced-air cooling is to rapidly reduce the temperature of the cooled product the cooler operator must have a method of I measuring the temperature of the product being cooled to determine FRONT VIEW .A.N OVEBF when cooling has been completed. The important management practice of determining when precooling Figure 12. Static pressure drop and temperature measurement locations. has been completed to the desired temperature has been stressed 181. Recent cooling tests 11,91 investiTemperature Due to daily differences in the inigated the variation of cooling as a measurig tial product temperature, the coolfunction of bed effect (the effect due measuring equipment ing time to achieve a desired final to the depth of the product) and Dial-type thermometers are corntemperature may vary. The cooling height of the carton on the pallet. monly used to measure the product time also varies if the cooling-air The experimental data verified that temperature during cooling, and the temperature cannot be maintained a bed effect does occur. The product pulp temperature samples are often during cooling due to inadequate in cartons exposed to incoming air, taken at inadequate locations. These refrigeration capacity. Another facclose to the air entrance cooled thermometers have a slow response tor which can change the cooling more rapidly than product on the time (minutes) and limited accuracy. rate is the product size, since larger opposite side, near the air exit from Also, it is difficult to precisely locate products cool more slowly than the pallet into the cooling tunnel, the probe-the probe may pass smaller products. In general, douThe cooling rate was found to vary through product and measure air bling the diameter or thickness rewith height of the containers on the temperature inside the carton. The quires 4 times as long to cool. A pallet, although no criterion was sampling location suggested above precooling schedule should be develestablished [9]. Additional work is is inside the cooling tunnel and not oped for every precooler and modineeded to determine the "best" locaeasily reached with a probe-type fled as conditions require [8]. tion for sampling temperature. thermometer (Figure 12). To over8



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come these problems, one or more ing air bypasses (particularly 4. Kader, A.A., R.F. Kasmire, F.G. thermocouples could be inserted through the pallets) to force addiMitchell, M.S. Reid, N.F. easily into product in cartons on the tional air through products, imSommer, and J.F. Thompson. inside of the last pallet before it is proving carton stacking configura1992. Postharvest technology of positioned for cooling with the thertions/orientation, and proper terhorticultural crops. California mocouple leads located outside the perature monitoring. Modifying Coop. Ext. Serv. Pub. 3311. canvas area. An inexpensive handpallet-tunnel length and width also held thermocouple reader could be show promise for improving effi5. Mitchell, F.G., R. Guillou, and used to measure cooling for all the ciency. Recommendations which R.A. Parsons. 1972. Commercial tunnels. The thermocouple reader require more time and cost include cooling of fruits and vegetables. is accurate and has a fast response increasing carton vent opening, California Agr. Expt. Sta. Man. time (seconds). The thermocouples increasing fan capacity, and in43. are durable and can be used many creasing refrigeration capacity. times. With additional investment, Of these three, the design of the 6. Parsons, R.A., F.G. Mitchell, permanent thermocouple leads and carton with particular attention to and G. Mayer. 1970. Forced-air remote data loggers could be used. the percent vent openings should cooling of palletized fresh fruit. Velocity and flow rate be addressed first. Increasing the ASAE Paper No. 70-875. Vel ty and l rate fan and refrigeration capacity Velocity and flow measurements should be considered only after all 7. Sargent, S.A., J.K. Brecht, and are difficult and require expensive the above-mentioned changes have J.J. Zoellner. 1990. Some physiinstruments, however the total flow been accomplished, cal characteristics of bell pepper rate is an important item of inforin relation to capacities of stanmation. A cheaper and more conveLiterature cited dard and potential shipping connient method is to use the manom1. Arifin, B.B. and K.V. Chau. tainers. Proc. Fla. State Hort. eter mentioned above to measure 1988. Cooling of strawberries in Soc. 103:222-225. the static pressure across forced-air cartons with new vent hole decooling fans and then estimate the signs. Trans. ASHRAE. Vol. 94 8. Sargent, S.A., M.T. Talbot, and flow rate using fan performance (1): 1415-1426. J.K. Brecht. 1991. Evaluating curves supplied by the fan manuprecooling methods for vegetable facturer. The performance curve 2. Baird, C.D., J.J. Gaffney, and packinghouse operations. Univ. estimates the flow rate for various M.T. Talbot. 1988. Design criteFL, IFAS, Vegetable Crops static pressure operating conditions. ria for efficient and cost effective Department Special Series SSSummar forced-air cooling systems for VEC-47. fruits and vegetables. ASHRAE This publication presents several Transactions 94(1):1434-1454. 9. Talbot, M.T. and C.D. Baird. methods for increasing the efficiency 1990. Evaluating commercial of forced-air precoolers for fresh pro3. Gaffney, J.J. and C.D. Baird. forced-air precoolers. ASAE duce. Recommendations for increas1977. Forced-air cooling of bell Paper No. 91-6021. ing efficiency with minimal cost and peppers in bulk. Transactions of increased management include sealthe ASAE 20(6):1174-1179. 9



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Introduction Commercial forced-air precooling has become an important postharvest procedure in Florida for rapid cooling and maintaining quality of several vegetable crops, strawberries, blueberries, and cut flowers. A detailed description of forced-air cooling and several different types (Figures 1 and 2) are described in several publications 11, 3, 4, 5, 6, 8, 9] (numbers in brackets refer to cited references). One study [21 discusses in detail the numerous variables which affect product cooling rate and/or overall cost of forced-air cooling systems for fruits and vegetables. These variables relate to the product, such as, size, shape, initial product temperature, desired final product temperature, and thermal properties; to the product configuration, such as, product packaging (bulk or in shipping containers), carton vent area, depth of product load Figure 1. Forced-air tunnel with portable exhaust fan. during cooling; to the precooling system, such as, air-flow rate, temperature, and relative humidity, ambient temperature; and to economics, such as, time of operation per year, unit costs of cooling space, heat exchangers, compressors, and fans, electric power cost, maintenance cost, labor cost, and interest rates. In forced-air cooling (Figure 1), produce is air-cooled rapidly by a difference in air pressure on opposite faces of stacks of vented containers (pallet boxes, corrugated cartons, flats, etc.). Fans create the pressure difference, which is called staticpressure difference. This pressure difference forces air through the containers and product, removing produce heat. The product is most efficiently cooled when the cooling air -flows around the individual fruits or vegetables in the containers, rather than by flowing around the outside of the containers (as in room cooling). In other words, the cooling medium (cold air) comes into intimate contact with the product to be cooled. Figure 2. Forced-air cooler with permanent constructed air plenum. 1



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1-1/9 BU PEPPER CONTAINER 0 -o-----,-"o u Vent Alignment: Vents cE -1i i ore aligned because "-o li containers ore stocked o 0o Io 5 either side to side "" _0 or end to end. LL 3i .il 17-7/8 in 11-3/4 in (44 cm) 29.8 cm 48 in (120 cm) Vertical Slot. PLAN VIEW Hand Hole, 7/16 x 2-3/8 in 1 x 3-3/8 in (1.1 X 6.0 cm) (2.5 X 8.6 cm) % Vent Opening -% eI Vertical Slot, .E 1.9 3.5, /-15/32 x 1-15/16 in (1.2 X 4.9 cm) S * Hand Hole Assists Forced-Air Cooling SIDE VIEW END VIEW Area of Round-ended Slot Area of Container Face .. I=L-d d=2r I-i -L I....... w ......... ........ L=l+d.. Area Face = Area Rectangle = Width x Height = WH Area Slot = Area Rectangle + 2(Area Semi-Circle) For example using the side view above (English units): = Area Rectangle + Area Circle Area Face = (17 7/8)(12) = 214.5 in2 S(L-d)d + Td2/4 = (l)d +TT % Vent Opening Area For example using the side view above (English units): Total Vent Area 2 % Vent Opening =100 Area Slot = [(2 3/8)-(7/16)](7/16) + 1T (7/16) Area Face Area Slot = 1.00 in2 For example using the side view above (English units): Total Vent Area = 4 Area Slot = 4.00 in2 % Vent Opening = (4.00/214.5)100 = 1.9 % Figure 8. 1-1/9 bushel pepper container showing dimensions, percent vent openings, and pallet stacking configuration. 5



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could not properly seal the openings P in the pallets. Lumber and plywood Si are not effective unless duct tape or wood and containers or plenums. Boards can be effective if 5 cm (2 in) of polyurethane foam is glued to the Sside of the boards placed against Sthe pallets. I ! A simple idea for sealing pallets 9 ý is to attach purchased or salvaged i plastic or scrap corrugated paper to Scover the top of the pallet and the "pallet side openings not normally used for the forklift blades. This Figure 5. Opening in tops of pallets and misalignment of pallets forming forced-air cooling can be accomplished inexpensively by in-house personnel using staplers or tape. The more resistance through the p t product, the more important it is to in ar me wile seal leakage areas. Therefore, reSducing the resistance through the SPEPPEn product (e.g. increasing carton facevent area) can reduce the signifi"UAv cance of air leakage or bypass. ls Is Carton face-vent area PEPPERS I ree For forced-air cooling the recommendation for minimum carton I vent opening is 5% of the container , surface facing the airflow [2, 6, 9]. k n ..| Many Florida packinghouses should increase the openings of the carton P.... .vents to achieve this recommended Svalue, which reduces the resistance ... .-.-. Ato airflow through the cartons (FigFigure 6. Plastic used to seal the pallet opening in the row of pallets on the left. ure 7). A few larger holes produce less resistance than several smaller Recent research on forced-air cooling air to bypass containers holes of the same total area. cooling of peppers [9] has shown (Figure 6). This material should be that the air bypass of the openings placed such that the fan suction The percent of vent openings of a beneath pallets can be blocked seals the undesirable openings. particular carton surface or face can with plastic (Figures 4 and 5), sigPlywood is used in some strawberry be calculated by determining the nificantly reducing cooling time. and other forced-air cooling operaratio of the vent openings of a parThis study also clearly illustrates tions for blocking large, open areas, ticular surface to the total area of that a large volume of cooling air and is not effective in reducing bythat surface (Figures 8 and 9). Only can pass through seemingly small passed air. In the above-mentioned the surfaces perpendicular to the gaps between adjacent pallets of a study [9], sealing pallet openings air flow should be considered. To product. with plastic was successful in blockdetermine the percent vent opening ing air bypasses while lumber for a container surface, the area of Flexible materials such as plasplaced against the sides of the paleach vent should be calculated ustic, canvas or foam rubber should lets was not effective. Apparently ing basic geometric equations and be used to seal openings that allow the rigid structure of the wood the area of all vents added. Most 3



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June 1992 Circular AE 108 Improving Forced-Air Cooler Performance Michael T. Talbot, C. Direlle Baird, Steven A. Sargent and Jeffrey K. Brecht Florida Cooperative Extension Service Institute of Food and Agricultural Sciences University of Florida John T. Woeste, Dean


xml record header identifier oai:www.uflib.ufl.edu.ufdc:UF0000845200001datestamp 2009-04-08setSpec [UFDC_OAI_SET]metadata oai_dc:dc xmlns:oai_dc http:www.openarchives.orgOAI2.0oai_dc xmlns:dc http:purl.orgdcelements1.1 xmlns:xsi http:www.w3.org2001XMLSchema-instance xsi:schemaLocation http:www.openarchives.orgOAI2.0oai_dc.xsd dc:title Improving forced-air cooler performance Circular Florida Cooperative Extension Service dc:creator Talbot, Michael T ( Michael Thomas ), 1948-Florida Cooperative Extension Servicedc:subject Precooling ( lcsh )Crops -- Postharvest technology ( lcsh )Food -- Cooling ( lcsh )Crops -- Quality ( lcsh )dc:description b Bibliography Includes bibliographical references (p. 9).Statement of Responsibility Michael T. Talbot ... et al..Cover title."June 1992."dc:publisher Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Floridadc:type Bookdc:format 9 p. : ill. ; 28 cm.dc:identifier http://www.uflib.ufl.edu/ufdc/?b=UF00008452&v=00001AAA6717 (LTQF)ALD2897 (LTUF)26517263 (OCLC)002193083 (ALEPHBIBNUM)dc:source University of Floridadc:language English



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COOPERATIVE EXTENSION SERVICE, UNIVERSITY OF FLORIDA, INSTITUTE OF FOOD AND AGRICULTURAL SCIENCES, John T. Woeste, Director, in cooperation with the United States Department of Agriculture, publishes this information tofurtherthe purposeof the May 8 and June 30,1914 Acts of Congress; and is authorized to provide research, educational information and other services only to individuals and institutions that function without regard to race, color, sex, age, handicap or national origin. Single copies of extension publications (excluding 4-H and youth publications) are available free to Florida residents from county extension offices. Information on bulk rates or copies for out-of-state purchasers is available from C.M. Hinton, Publications Distribution Center, IFAS Building 664, University of Florida, Gainesville, Florida 32611. Before publicizing this publication, editors should contact this address to determine availability. e Printed 6/92.


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'2012-04-03T14:33:35-04:00'
describe
'148333' 'info:fdaE20090918_AAAATAfileF20090918_AADPCN' 'sip-files00004.jpg'
7493b3df29ce61ff0bba5be34729be49
e514ba00e2edc8345990306f29f21953686869d6
describe
'615436' 'info:fdaE20090918_AAAATAfileF20090918_AADPCO' 'sip-files00004.pdf'
26f0de6728923e56979d927beffa34a3
46a1831f279e5072a2afde341d65184631dfa6b0
describe
'info:fdaE20090918_AAAATAfileF20090918_AADPCO-norm-0' 'aip-filesF20090918_AADPCO-norm-0.pdf'
ff1a61a668d9cc4434fdd1edaf6d66da
2f3c5b0fecf7a41da25f8ed6c1af3f105d3ce63f
describe
'2015-06-08T15:56:18-04:00'
normalize
'64446' 'info:fdaE20090918_AAAATAfileF20090918_AADPCP' 'sip-files00004.pro'
c35af420c6177e61709efcd77bf12a60
90fb5b22d140626ea1cec88de8c56b07324d1280
'2012-04-03T14:33:46-04:00'
describe
'56428' 'info:fdaE20090918_AAAATAfileF20090918_AADPCQ' 'sip-files00004.QC.jpg'
580dc6b00d88fe4447f820b13f8b1bbb
1133147d8e8c712966536e524277ec35b76fcdbd
'2012-04-03T14:33:04-04:00'
describe
'7817768' 'info:fdaE20090918_AAAATAfileF20090918_AADPCR' 'sip-files00004.tif'
5d9ce9159c67a9bed040f2d7e791b42e
3c04a8bb21bc2b851b8d7b6a4758d3ca02b59368
'2012-04-03T14:33:19-04:00'
describe
'3108' 'info:fdaE20090918_AAAATAfileF20090918_AADPCS' 'sip-files00004.txt'
ff4783683178baf573b2368d6e588421
32fcb19812a21465ece50e6b0bc185a1feb9c77a
describe
WARNING CODE 'Daitss::Anomaly' Invalid character
'29719' 'info:fdaE20090918_AAAATAfileF20090918_AADPCT' 'sip-files00004thm.jpg'
9e9444d570ffcca84b2f87039315b6fc
746e056aad33ce5b377af1e03b4f9fefa5fc76ea
'2012-04-03T14:33:25-04:00'
describe
'974600' 'info:fdaE20090918_AAAATAfileF20090918_AADPCU' 'sip-files00005.jp2'
1367030f1f2f46fe37731d5b5daee4c2
090ae370f6062d242304dfed7f746511d1dabfaf
describe
'165680' 'info:fdaE20090918_AAAATAfileF20090918_AADPCV' 'sip-files00005.jpg'
cab7f9ef57f68a559c678a47704c53e1
4a0c714344c23a81db4dcc37a0e6ba78ed11e7eb
describe
'785714' 'info:fdaE20090918_AAAATAfileF20090918_AADPCW' 'sip-files00005.pdf'
7a2f7c6869b5c14c00f9eeab79dccd3d
df7a9c74ad1fb83772ffaa33c06c2578ee20a50d
describe
'info:fdaE20090918_AAAATAfileF20090918_AADPCW-norm-0' 'aip-filesF20090918_AADPCW-norm-0.pdf'
ff1a61a668d9cc4434fdd1edaf6d66da
2f3c5b0fecf7a41da25f8ed6c1af3f105d3ce63f
describe
'2015-06-08T15:56:16-04:00'
normalize
'78825' 'info:fdaE20090918_AAAATAfileF20090918_AADPCX' 'sip-files00005.pro'
93a0a042e62b6a12a2e3fa8fcb773c37
8cda11a79ba56a2955d86819c4fdb57b6253b26b
describe
'60550' 'info:fdaE20090918_AAAATAfileF20090918_AADPCY' 'sip-files00005.QC.jpg'
0964576f0566a11774a28156485effbd
82250e22db532a79962d689afe6f582cafc6f752
'2012-04-03T14:33:09-04:00'
describe
'7818776' 'info:fdaE20090918_AAAATAfileF20090918_AADPCZ' 'sip-files00005.tif'
0c829a8126a18ead99f564da84bc07dd
cfbcfc6222926bd3ef963d595ae2637a2336b0ae
'2012-04-03T14:33:26-04:00'
describe
'3110' 'info:fdaE20090918_AAAATAfileF20090918_AADPDA' 'sip-files00005.txt'
da4f2f991431fb9c4277286ae327fb63
82edc47570e94f5530ee5e5b142f528ddf49ce97
'2012-04-03T14:33:00-04:00'
describe
'31503' 'info:fdaE20090918_AAAATAfileF20090918_AADPDB' 'sip-files00005thm.jpg'
67e47c760fa132a40238297e17151ba1
2c3aa3e46eff03ea97b22efe7c1e92d0bdc64e5a
'2012-04-03T14:33:27-04:00'
describe
'974626' 'info:fdaE20090918_AAAATAfileF20090918_AADPDC' 'sip-files00006.jp2'
931383f1725257bc9086570d33041ebe
665b7ddf8f209053f523adf1e1e3a9bb435fd4e9
describe
'192782' 'info:fdaE20090918_AAAATAfileF20090918_AADPDD' 'sip-files00006.jpg'
d2f91c2580d416622ff4173306d6d958
166afd5c8aacf13cb08f2c5bf25c673d3fef5b1b
describe
'898452' 'info:fdaE20090918_AAAATAfileF20090918_AADPDE' 'sip-files00006.pdf'
0ec18d22bc75e287d4ae8114ea5d50e9
08afb1f9c1f11cd7074e1429e9367f9ff61694d0
describe
'info:fdaE20090918_AAAATAfileF20090918_AADPDE-norm-0' 'aip-filesF20090918_AADPDE-norm-0.pdf'
ff1a61a668d9cc4434fdd1edaf6d66da
2f3c5b0fecf7a41da25f8ed6c1af3f105d3ce63f
describe
'2015-06-08T15:56:13-04:00'
normalize
'107521' 'info:fdaE20090918_AAAATAfileF20090918_AADPDF' 'sip-files00006.pro'
ea5496b3cdccb78a0fc35dcb8de7967b
64804f8b29d551023d1cae0dcd509725fdfe2136
'2012-04-03T14:33:52-04:00'
describe
'65481' 'info:fdaE20090918_AAAATAfileF20090918_AADPDG' 'sip-files00006.QC.jpg'
928e5ca4de56f82b6d1152dfa1fa0d72
e4eaf3d7d2c299450aaf84ebab46671796e3c0c3
describe
'7820448' 'info:fdaE20090918_AAAATAfileF20090918_AADPDH' 'sip-files00006.tif'
a81ba981a3525a0a7b58f458134c5ce8
9e9b3e81cde27315676bdfeb36e8d314289300d7
'2012-04-03T14:33:28-04:00'
describe
'4220' 'info:fdaE20090918_AAAATAfileF20090918_AADPDI' 'sip-files00006.txt'
8e02f84170de85fbfc177b7c9d0b6d3a
d9471d0c8828da6b0f6f403b7f00c71785828ac5
'2012-04-03T14:32:59-04:00'
describe
'33564' 'info:fdaE20090918_AAAATAfileF20090918_AADPDJ' 'sip-files00006thm.jpg'
a9f89d6774b6c0263288be9695712a85
fa35a0089a7d7fef38e4452755688a88da8292f3
describe
'82020' 'info:fdaE20090918_AAAATAfileF20090918_AADPDK' 'sip-files00007.jp2'
0ff895c6586bf21a1d0438e7757f1fe0
ab156531f14284f843bc98a8434e6ba2a884a7ff
'2012-04-03T14:33:21-04:00'
describe
'98189' 'info:fdaE20090918_AAAATAfileF20090918_AADPDL' 'sip-files00007.jpg'
716302b30a2ad134426380724cb819ee
6260b360f5805b24f8466df52b06d3ebc5479ede
describe
'34422' 'info:fdaE20090918_AAAATAfileF20090918_AADPDM' 'sip-files00007.pdf'
337c0418ebf9eef636a1f4ca2239cb6b
f9b13b3d6a8ca2deaf506fc78c6178e65ba37ecc
describe
'info:fdaE20090918_AAAATAfileF20090918_AADPDM-norm-0' 'aip-filesF20090918_AADPDM-norm-0.pdf'
ff1a61a668d9cc4434fdd1edaf6d66da
2f3c5b0fecf7a41da25f8ed6c1af3f105d3ce63f
describe
'2015-06-08T15:56:08-04:00'
normalize
'34236' 'info:fdaE20090918_AAAATAfileF20090918_AADPDN' 'sip-files00007.pro'
015f9bf056c26d34bf3d2da0a1c159b6
b5a92714928f76d8681ff0fd094be8080cff9271
describe
'47130' 'info:fdaE20090918_AAAATAfileF20090918_AADPDO' 'sip-files00007.QC.jpg'
d4e9036404661012ea1c42eac2190aa3
9db1caa8e0635d4faf8c931d2e8ede0643854be7
'2012-04-03T14:33:24-04:00'
describe
'999236' 'info:fdaE20090918_AAAATAfileF20090918_AADPDP' 'sip-files00007.tif'
adac1be59bd573088bf702adae745f96
4037f15298b542e90a1290973cf400dcbde6e30d
'2012-04-03T14:33:06-04:00'
describe
'1580' 'info:fdaE20090918_AAAATAfileF20090918_AADPDQ' 'sip-files00007.txt'
9ced03045f234326a4927ff0d0f95d84
e1cfdd5c92aa0f588351af677e1e3b673b712b5b
describe
'30324' 'info:fdaE20090918_AAAATAfileF20090918_AADPDR' 'sip-files00007thm.jpg'
3c4914a3b72528e1b24c5455d5e796bb
a59267a83be5e2e189ac22666d4be9621bbc3671
describe
'98668' 'info:fdaE20090918_AAAATAfileF20090918_AADPDS' 'sip-files00008.jp2'
22e7b10b5496020581cc6600b2774c2b
0884701834ae8b069a5ba80414ae7a784acacbf3
describe
'110413' 'info:fdaE20090918_AAAATAfileF20090918_AADPDT' 'sip-files00008.jpg'
8c738197c64c6739595dcf1e9eb4501f
b6da13e0be56857925b4b798e87c52c8c83cded5
describe
'43044' 'info:fdaE20090918_AAAATAfileF20090918_AADPDU' 'sip-files00008.pdf'
d6e5f0414edd66109639001439b6d953
dd5779be0c71c91bbee796b6ece15fb881560101
describe
'info:fdaE20090918_AAAATAfileF20090918_AADPDU-norm-0' 'aip-filesF20090918_AADPDU-norm-0.pdf'
ff1a61a668d9cc4434fdd1edaf6d66da
2f3c5b0fecf7a41da25f8ed6c1af3f105d3ce63f
describe
'2015-06-08T15:56:11-04:00'
normalize
'48175' 'info:fdaE20090918_AAAATAfileF20090918_AADPDV' 'sip-files00008.pro'
b880b8ec688ac554093a40179c341cf3
7556dc5fd76e95ae14de502a6718361cf4ef9598
'2012-04-03T14:33:34-04:00'
describe
'52114' 'info:fdaE20090918_AAAATAfileF20090918_AADPDW' 'sip-files00008.QC.jpg'
ba9a8048caf5db46f0ec4c488db5ebfd
ac3a95bb1e0500bdd5f99d85ba935f656727461c
'2012-04-03T14:33:23-04:00'
describe
'1000548' 'info:fdaE20090918_AAAATAfileF20090918_AADPDX' 'sip-files00008.tif'
00bea929408ab3bdc83a4839de76a86e
b3c1fa8796f459ade5a386bbcbb08e8ef7686a76
describe
'2453' 'info:fdaE20090918_AAAATAfileF20090918_AADPDY' 'sip-files00008.txt'
9715c93fed2b62bcb1438b686f269202
a23e6c31d86ed00998633ea726dd0939d42f5df0
describe
'32421' 'info:fdaE20090918_AAAATAfileF20090918_AADPDZ' 'sip-files00008thm.jpg'
924dfdeab28b097254fcc0307a697446
02f410b17e9fe12ace656570d90507d669b86d17
'2012-04-03T14:32:54-04:00'
describe
'974609' 'info:fdaE20090918_AAAATAfileF20090918_AADPEA' 'sip-files00009.jp2'
ef0a60a8b540925d07538288b86bc209
f9ef743499a746f5f53d62ed3e1f69832fcdcc66
describe
'145477' 'info:fdaE20090918_AAAATAfileF20090918_AADPEB' 'sip-files00009.jpg'
488de2cb2907778aa7baf71d506ef993
485411fc8833b6182bf46ca560e6563399dc809d
describe
'631560' 'info:fdaE20090918_AAAATAfileF20090918_AADPEC' 'sip-files00009.pdf'
6a9276eddfb902c75da9d5c921625951
2568ffcbb6333d388f2a5a5f732587feeb160904
describe
'info:fdaE20090918_AAAATAfileF20090918_AADPEC-norm-0' 'aip-filesF20090918_AADPEC-norm-0.pdf'
ff1a61a668d9cc4434fdd1edaf6d66da
2f3c5b0fecf7a41da25f8ed6c1af3f105d3ce63f
describe
'2015-06-08T15:56:22-04:00'
normalize
'60187' 'info:fdaE20090918_AAAATAfileF20090918_AADPED' 'sip-files00009.pro'
e77a73c77d22a645869465d7ac8ccf42
9de2a0e57b57afd13ef0f5b4cf08982de43a5d95
describe
'55980' 'info:fdaE20090918_AAAATAfileF20090918_AADPEE' 'sip-files00009.QC.jpg'
d1879e82c1d6ae4236beb4d65aa74b28
e60b6abfd70af11073c67ed05194ea5782d510a8
describe
'7817540' 'info:fdaE20090918_AAAATAfileF20090918_AADPEF' 'sip-files00009.tif'
ee3c3e39fa1d2d18396b0c7c2a1123db
c3b740b0529cdae69607db04a178e7ebd53aec8e
'2012-04-03T14:33:45-04:00'
describe
'2638' 'info:fdaE20090918_AAAATAfileF20090918_AADPEG' 'sip-files00009.txt'
1a6e276eb9d88377d5d1b00e061cce46
2d209f61d5eb01c0d62dcc218c04da19580a7c19
describe
Invalid character
'29641' 'info:fdaE20090918_AAAATAfileF20090918_AADPEH' 'sip-files00009thm.jpg'
ef80fd42d63187ba6c0487d625387815
fc66479d96131c85d8b46fa5bbe5dacbef845881
describe
'193025' 'info:fdaE20090918_AAAATAfileF20090918_AADPEI' 'sip-files00010.jp2'
c2168457f1f6fe7b81708f6f6f6b7f37
33cf940140cb38e70dffe58d1eaa28e4f524383b
describe
'178938' 'info:fdaE20090918_AAAATAfileF20090918_AADPEJ' 'sip-files00010.jpg'
281665c7e56c2f3fdc852b4830c691b6
0779860f4d144b12d4f2712e0d5eeefed8ed99ba
describe
'94114' 'info:fdaE20090918_AAAATAfileF20090918_AADPEK' 'sip-files00010.pdf'
a79f6ada4488f05f34197257103370ac
dcfd3d81d3d0d33ef8ef23990cb0c08786979e65
'2012-04-03T14:33:38-04:00'
describe
'info:fdaE20090918_AAAATAfileF20090918_AADPEK-norm-0' 'aip-filesF20090918_AADPEK-norm-0.pdf'
ff1a61a668d9cc4434fdd1edaf6d66da
2f3c5b0fecf7a41da25f8ed6c1af3f105d3ce63f
describe
'2015-06-08T15:56:34-04:00'
normalize
'83315' 'info:fdaE20090918_AAAATAfileF20090918_AADPEL' 'sip-files00010.pro'
44a8dd37af4e1e6aff8f2e35aa5ef699
6308189a3d6c3c741b32d7bd2eb8714706df5b5c
describe
'67687' 'info:fdaE20090918_AAAATAfileF20090918_AADPEM' 'sip-files00010.QC.jpg'
0755504088ea6062edf718459b67091c
0a13de03c452b7a36217347fe756d7dbe21dc179
describe
'1005912' 'info:fdaE20090918_AAAATAfileF20090918_AADPEN' 'sip-files00010.tif'
f1eb9f283b6e751ff0ebcaa016394c62
a85433e39399615cf32159383517e693ff5adec2
'2012-04-03T14:33:44-04:00'
describe
'3337' 'info:fdaE20090918_AAAATAfileF20090918_AADPEO' 'sip-files00010.txt'
8d1a110b7973e51627c80f04f195f2b9
541461aa2b24b2873903143fc40a5e418aea9c2a
'2012-04-03T14:33:49-04:00'
describe
'38816' 'info:fdaE20090918_AAAATAfileF20090918_AADPEP' 'sip-files00010thm.jpg'
5fd7d9c8c5396e79fa1470eb16d84bbd
a949cb70b524dea0801e8f2371a1d38c68b17a03
describe
'166666' 'info:fdaE20090918_AAAATAfileF20090918_AADPEQ' 'sip-files00011.jp2'
6f699fe328507a1cd6a3e6392d730a93
8343244d07a0fad790139cfb621947498364f0b9
describe
'157478' 'info:fdaE20090918_AAAATAfileF20090918_AADPER' 'sip-files00011.jpg'
cd377a697255294443a3c6c89568e3ee
e12cb28b874abd4c571bdbfb951cce64167c5034
'2012-04-03T14:33:11-04:00'
describe
'75201' 'info:fdaE20090918_AAAATAfileF20090918_AADPES' 'sip-files00011.pdf'
bf9ae501403e5412eb99508a30e6d36c
259a2f5658522ff970729f031c5c6f78df111b34
describe
'info:fdaE20090918_AAAATAfileF20090918_AADPES-norm-0' 'aip-filesF20090918_AADPES-norm-0.pdf'
ff1a61a668d9cc4434fdd1edaf6d66da
2f3c5b0fecf7a41da25f8ed6c1af3f105d3ce63f
describe
'2015-06-08T15:56:36-04:00'
normalize
'90192' 'info:fdaE20090918_AAAATAfileF20090918_AADPET' 'sip-files00011.pro'
bd9af2294d33a28ef37a6c8fdfb79c55
54824cbb9ba4031d3abdbaca72950fd88a36d1f7
'2012-04-03T14:33:32-04:00'
describe
'58022' 'info:fdaE20090918_AAAATAfileF20090918_AADPEU' 'sip-files00011.QC.jpg'
7c92e6fba9b3e0e9796e6efac4f14b51
dfd676e900ad461a20009da4e30c888b709fd826
describe
'1001156' 'info:fdaE20090918_AAAATAfileF20090918_AADPEV' 'sip-files00011.tif'
2449c9da6761f63243b78ad8a7145c4b
fa2f82294ddccd1591a86c3c596cfa9089e614ac
describe
'3693' 'info:fdaE20090918_AAAATAfileF20090918_AADPEW' 'sip-files00011.txt'
36352ccb3757674cc09f8a76a5c9c62c
766c44b37e190ce26fb23846bf7e50c2e25916d0
describe
'32850' 'info:fdaE20090918_AAAATAfileF20090918_AADPEX' 'sip-files00011thm.jpg'
d1e1f0c471b3d07158283876c86d51f1
274a8c340e6e566d1875491036ecd6175d3114b9
'2012-04-03T14:33:39-04:00'
describe
'35007' 'info:fdaE20090918_AAAATAfileF20090918_AADPEY' 'sip-files00012.jp2'
439e044c759cf35c048ab238a6002cba
b2115e1dc5520c512c6d85c62266eb253265e82c
describe
'32768' 'info:fdaE20090918_AAAATAfileF20090918_AADPEZ' 'sip-files00012.jpg'
c4ae645f4413f23fe81fe4ee3fe3e29e
2e75b3e40f35e59287377989e3ae1d4fcc1bb5c3
describe
'17984' 'info:fdaE20090918_AAAATAfileF20090918_AADPFA' 'sip-files00012.pdf'
095423fe944a232a3d3bb187774a16d4
fb4f63296315ad41eb021ba5b1ff527972c7ef02
'2012-04-03T14:33:16-04:00'
describe
'info:fdaE20090918_AAAATAfileF20090918_AADPFA-norm-0' 'aip-filesF20090918_AADPFA-norm-0.pdf'
ff1a61a668d9cc4434fdd1edaf6d66da
2f3c5b0fecf7a41da25f8ed6c1af3f105d3ce63f
describe
'2015-06-08T15:56:27-04:00'
normalize
'27824' 'info:fdaE20090918_AAAATAfileF20090918_AADPFB' 'sip-files00012.pro'
42b8419a92c81febd7e1f8e1f74a6127
41934d8828431db97f40a9293eacf733832f9c38
describe
'15712' 'info:fdaE20090918_AAAATAfileF20090918_AADPFC' 'sip-files00012.QC.jpg'
b9e77c096239092d690447ce4de3bcaf
1c9c3ca3015e62efee966f30124ff9bb29cf8b0e
describe
'985572' 'info:fdaE20090918_AAAATAfileF20090918_AADPFD' 'sip-files00012.tif'
91d8e4b7d74944ed7efffb8ab7d88ef4
a7f17adc9f9825ea99b6d8aaf6cd491cf751b8fa
describe
'1128' 'info:fdaE20090918_AAAATAfileF20090918_AADPFE' 'sip-files00012.txt'
a18428ad534c4f0e02a5e4e7a9c2bf68
1fb0d1a18f46e46d742a3a1df971f7e3c11408b3
describe
'11470' 'info:fdaE20090918_AAAATAfileF20090918_AADPFF' 'sip-files00012thm.jpg'
7909fccaa20873f3736809c29c59d7d3
045ef8ec39466b30429e3b77902c020c9831a012
describe
'29210' 'info:fdaE20090918_AAAATAfileF20090918_AADPFG' 'sip-filesUF00008452_00001.mets'
32b4599ec6a8ebceaed8cc807dc8426c
7ec2e256b9ee3ec6ef5e3b6137ddf21740ac250d
'2012-04-03T14:33:51-04:00'
describe
TargetNamespace.1: Expecting namespace 'http://www.uflib.ufl.edu/digital/metadata/ufdc2/', but the target namespace of the schema document is 'http://digital.uflib.ufl.edu/metadata/ufdc2/'.
'2015-06-08T15:56:41-04:00' 'mixed'
xml resolution
http://www.uflib.ufl.edu/digital/metadata/ufdc2/ufdc2.xsd
BROKEN_LINK schema http://www.uflib.ufl.edu/digital/metadata/ufdc2/ufdc2.xsd
The element type "div" must be terminated by the matching end-tag "
".
TargetNamespace.1: Expecting namespace 'http://www.uflib.ufl.edu/digital/metadata/ufdc2/', but the target namespace of the schema document is 'http://digital.uflib.ufl.edu/metadata/ufdc2/'.
'35536' 'info:fdaE20090918_AAAATAfileF20090918_AADPFJ' 'sip-filesUF00008452_00001.xml'
7ba1cddef42d6fee19ab16f1cc1805b2
383aa7cd740c91d0c4c2f324910062875547e9f5
describe
TargetNamespace.1: Expecting namespace 'http://www.uflib.ufl.edu/digital/metadata/ufdc2/', but the target namespace of the schema document is 'http://digital.uflib.ufl.edu/metadata/ufdc2/'.
xml resolution
http://www.uflib.ufl.edu/digital/metadata/ufdc2/ufdc2.xsd
http://www.uflib.ufl.edu/digital/metadata/ufdc2/ufdc2.xsd
The element type "div" must be terminated by the matching end-tag "".
TargetNamespace.1: Expecting namespace 'http://www.uflib.ufl.edu/digital/metadata/ufdc2/', but the target namespace of the schema document is 'http://digital.uflib.ufl.edu/metadata/ufdc2/'.



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4.5 cm (2 in) by 1.2 m (4 ft) gap was noted between the two pallets during a test at a packinghouse with plastic installed. The measured velocity through the gap was 5 m/s (970 fpm) and the calculated flow rate was 0.3 m 3/s (650 cfm). The total flow through an adjacent carton was 0.01 m3/s (26 cfm). At another packinghouse, a 4.5 cm (2 in) by 28 cm (11 in) gap was noted between the two pallets with plastic installed. The measured velocity through the gap was 3.5 m/s (680 * * v fpm) and the calculated flow rate 0r * , was 0.05 mI/s (104 cfm). The total om flow through an adjacent carton was 0.006 mI/s (12 cfm). -This study [9] suggests that additional studies should be conFigure 7. Several currently used and experimental containers with vents of various sizes, ducted to determine how varying shapes, and locations. the number of pallets, height of the carton venting is circular or roundin) results in vent hole misaligncartons on the pallets, tunnel width ended slots, which are combinations ment. This is another reason for (distance between rows of pallets), of rectangles and semicircle ends. selecting large rather than small and similar factors affect the perThe total vent area should then be vent holes, because the larger formance of the air handling and divided by the total face area of that holes would allow partial vent cooling systems. Limited data indisurface (length times height) and alignment even when the cartons cates that reducing the number of finally multiplied by 100. are not aligned correctly. Howpallets in the cooling tunnel from ever, wide holes can be partially 10 to 6 reduced the half cooling For many packinghouse operablocked by the product more so time for the last pallet ( without tions, cartons are placed such that than narrow slots. Also, more corplastic) from 1.9 to 0.7 hours. the side vents align with the side rugate flutes are cut with a wider Therefore, it might be possible to vents of the adjacent carton or the hole, which reduces the strength of cool 36 pallets (3 groups of 12 palend vents align with the end vents the carton. lets cooled) with tunnels 6 pallets of the adjacent carton, for example long in the same length of time as standard 1-1/9 bushel containers Pallet configurations 20 pallets (1 group of 20 pallets stacked eight containes ers layer Pallet placement cooled) with tunnels 10 pallets long, (Figures 3 and 8). In other applicaif sufficient refrigeration capacity tions, such as 40 x 30 MUM In one type of forced-air cooler, is available (Figure 11). (Modularization, Unitization, and two rows of pallets are placed end Metrification) containers stacked to end to form each side of a coolIn addition to the side openings ten per layer, the stacking patterns ing tunnel (Figures 1 and 3). It is in the two-way pallet, the bottom require ends of cartons to align with important that the pallets are layer of cartons at times does not the sides of adjacent cartons and the placed such that very little gap always completely cover the surfAce carton vent locations must be deexists between the cartons of adjaof the pallet. This leaves openings signed accordingly (Figures 9 and cent pallets. Otherwise another between boards on the top of the 10). If the vent holes on adjacent path is created for the cooling air pallet, thus allowing air to bypass cartons do not align, a major disrupto bypass the cartons. Velocity the product. Significant air bypass tion of air flow occurs and should be measurements [9] indicated sigwas noted through these open palavoided. For produce cartons with nificant air flow through such let surfaces [9]. Normally the carslender vertical slots commonly gaps, particularly when plastic tons are stacked flush with one side used on the ends and sides, offset of was installed to seal the side openof the pallet, while the other side the carton by as little as 0.6 cm (1/4 ings of the pallets. For example, a exposes the surface of the pallet. 4



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S-.ods include sealing air-leak areas PLENUM FANS to force additional air through 2 products, improving carton stack3 PARTIALLY ing configurations or orientation, UNROLLED OPENINGSi CANVAS modifying pallet-tunnel length and PALLET width, and proper temperature TOP --i 6 T AIR FLOW monitoring. Methods requiring S6... DIRECTION more time and cost include im.9 provement in carton design, in.o -_I creased fan and cooling capacity. COOLING S TUNNEL Seal leaks L............... ................. _ _ J TOP VIEW FORCED-AIR TUNNEL The path of least resistance is a key physical principle when conOPENINGS sidering forced-air cooling. Air, BETWEEN PALLETS like water, flows from a point of high pressure to a point of lower " i I I -I pressure by the path which preI I I I I I I I I I I I I sents the least resistance. The S1 .goal for effective forced-air cooling I I I I I I is to insure that the path of least SI resistance is through the product -I I I I rather than around the container. SBETWEENINGS ---Air bypasses or short circuits I I I CARTONS -I I I I whenever the path of least resisI I I I I I I I I tance is not through the product. SSuch bypasses include openings SI I I I -between stacked containers on palSI I I lets (Figures 3, 4, and 5), between adjacent pallets, side pallet entry TWO-WAY OPENINGS holes under pallets, loosely inPALLETOPENINGS PALLET stalled canvas covers or through FRONT VIEW S E V W S S holes in the canvas, and at the Figure 3. Container and pallet stacking configuration for forced-air cooling tunnel. junction between pallets and air plenums or ducts. This publication discusses methods to evaluate and improve forcedpinl FAI .. air cooler performance. It is in-z a own m tended to assist those interested in 9Mp b -am= Q U I ... improving the performance of an existing forced-air cooler as well as TB iS those planning to install new E? I forced-air cooling systems. The inO . a formation is applicable to all types of forced-air cooling systems. System performance can be assessed by measurement of staticpressure drop, air velocity or flow, and cooling rate during commercial forced-air cooling. Precoolers can be made more efficient by several minimal cost methods and by inFigure 4. Opening in pallets sides and tops and gaps between adjacent pallets provide paths creased management. These methfor cooling air bypass. 2