y affected by bin placement and stacking patterns. Hellickson and Baskins (2003)
documented differences in air movement in a 1000 bin room equipped with one evaporator unit
that provided air movement with four 30-inch diameter fans. Empty spaces and non-symmetrical
bin placement caused major changes in airflow patterns.
Achieving the overall objective of providing the highest possible quality fruit to consumers
requires careful attention to each phase of production, storage, transportation and distribution.
One breakdown in this sequence can adversely impact product quality and profit. Establishment
and maintenance of proper storage conditions is a vital link in this chain of events. Seemingly
minor differences in room temperature, relative humidity, gas content and uniformity of air
distribution can cause significant quality and quantity losses. The longer fruit are stored,
e.g., long-term controlled atmosphere storage, the greater the impact these differences can have.
Information presented in this report was developed from visits to multiple fruit storage facilities
located in Oregon and Washington, which provided data including precise inside dimensions of
individual rooms, in addition to number, size, location, capacity and manufacturer of evaporator
units present in storage rooms. Designated bin placement schemes and actual bin stacking
patterns present at room closings were also documented.
ROOM SIZES AND CAPACITIES
Room sizes in regional storage facilities vary greatly in both width and depth. In this document,
depth is measured in the same direction as air flow from an evaporator unit. Maximum and
minimum room depths documented were 100 feet and 28 feet, respectively. Maximum and
minimum room widths documented were 100 feet and 22 feet, respectively.
Room capacities listed by various storages ranged from the largest having an average bin count
of 5000 and the smallest 810. Typically, these approximate capacities were reported for fruit
stored in wooden bins that were spaced four to six inches between rows. Bin rows are defined as
running perpendicular to room width. Some facilities differentiated listed room capacity
depending upon whether apples or pears were to be stored.
EVAPORATOR MANUFACTURERS, CAPACITIES AND LOCATIONS
Evaporator units manufactured by the following companies were present in regional storerooms
visited: Colmac, Frigid Coil, IMECO, Krack, Lewis, McCormack, Recold, and Wescold. Fan W
ASHINGTON
T
REE
F
RUIT
P
OSTHARVEST
C
ONFERENCE

December 7
th
, 2005 Wenatchee, WA
2005

P
ROCEEDINGS
, Improving Air Distribution in Fruit Storage Warehouses
page 2 of 5
WSUTFREC

P
OSTHARVEST
I
NFORMATION
N
ETWORK

http://postharvest.tfrec.wsu.edu/PC2005E.pdf

sizes varied from 18 inches to 42 inches in diameter. Fan motor horsepower varied from ½ HP
to 5 HP. Cooling capacities ranged from 6.1 to 58 tons of refrigeration per unit. These
capacities were typically determined based on a 12 ºF temperature difference across the cooling
coil.
Air movement capacity (cubic feet per minute [cfm]) of evaporator fans is affected by blade
diameter and configuration, motor speed (rpm), motor horsepower, number of evaporator fin
rows present, space between fins (fins per inch [fpi]) and air density. Manufacturer reported
values are typically for 32 ºF air temperature and zero static pressure.
Representatives from several of the coil manufacturers indicated that configuration and capacity
information of each unit installed may be available from their records. Some companies have
changed the identification nomenclature of more recent models. For example, Colmac has
renamed their APC identified coils as now being in the ICH 18 group. Current catalogs reflect
these newer designations.
BIN PLACEMENT IN ROOMS
Airflow from the evaporator units into the storage space creates the cooling environment
necessary to maintain fruit quality. The more uniformly this cooled air is circulated over, under
and through the stacked bins, the better. As in any fluid-flow system, airflow will be greatest in
the path of least resistance. Research presented by Hellickson and Baskins (2000) documented
real-time measurement of fruit cooling rates and efficiencies at 27 locations within regular-
stacked and tight-stacked rooms filled with both wooden and plastic bins. Further research
(Hellickson and Baskins, 2003) verified that nonsymmetrical bin stacking patterns and open
spaces frequently left to allow egress of forklifts adversely affected airflow in the same rooms.
Figure 1 illustrates a non-symmetrically stacked room that caused airflow patterns to be severely
unbalanced within the room.
Unless wooden bins have two-way pallets, space required for forklift movement dictates that
some bins must be cross-stacked. Cross-stacked bins are those that the pallet runner space is
perpendicular to the majority of bins in a row of bins. Regional warehouses have developed
various stacking plans for wooden bins. Some line up all runner spaces from the rear of the
room to near the exit. Then, two or three rows of bin stacks are rotated 90 degrees and spaced
approximately one foot from the previous stacks. As the stacking space directly in front of the
exit door is filled, bin stacks are frequently angled such that the forklift can exit the room without
damaging the door casing. Plastic bins are manufactured with two-way pallets which eliminates
cross-stacking. However, forklift egress near doors is still challenging and drivers often angle
the last few stacks of bins to more easily exit the room. Stacking height of bins placed directly in
front of exit doors is typically limited to five bins high. Depending upon where the door is
located in relation to the room, up to three stacks of bins may have this limitation. This creates a
sizeable empty space that may both adversely affect uniformity of air distribution in the room,
and increase unwanted air movement under evaporator units.
W
ASHINGTON
T
REE
F
RUIT
P
OSTHARVEST
C
ONFERENCE

December 7
th
, 2005 Wenatchee, WA
2005

P
ROCEEDINGS
, Improving Air Distribution in Fruit Storage Warehouses
page 3 of 5
WSUTFREC

P
OSTHARVEST
I
NFORMATION
N
ETWORK

http://postharvest.tfrec.wsu.edu/PC2005E.pdf


TIGHT-STACKING BINS
Conventional stacking of fruit bins attempts to maintain an open space of approximately six
inches between rows to facilitate airflow past the containers and presumably improve fruit
cooling. Maintaining this space between rows of wooden bins is seldom accomplished due to
wood deflections. Additionally, most wooden bins do not have ventilation slots in their vertical
sides. Therefore, the amount of heat transferred from the fruit through the solid sides of a bin is
minor compared to cooling induced by air passing over the fruit through the runner space.
A formula to determine if tight-stacking bins in a room is possible is:
N = (Room width in feet 1 foot) / bin width
This formula requires that actual inside width of the room is measured and that six inches of
space is maintained between bin stacks and sidewalls. (This is the term -1 foot in the above
equation.) Placing stacks of bins tight against the walls is not recommended. Wooden bins
typically measure 4 feet. Model 28 MacroBin bins measure 4.0725 feet.
The following example illustrates use of the above formula.
Actual inside dimensions are 42 0 wide by 61 0 deep
Normal stacking (with spaced stacks) = 9 rows of stacks wide by 14 stacks deep
Room to be filled with Model 28 MacroBin bins
N = (42 feet 1 foot) /4.0725 feet
N = 10.0675 bins
Bins 10 high
Bins 5 high due to door
Door
Bins 10 high with cross-stacked runners.
Figure 1. Illustration of a non-symmetrical bin stacking
pattern that adversely affected airflow uniformity. W
ASHINGTON
T
REE
F
RUIT
P
OSTHARVEST
C
ONFERENCE

December 7
th
, 2005 Wenatchee, WA
2005

P
ROCEEDINGS
, Improving Air Distribution in Fruit Storage Warehouses
page 4 of 5
WSUTFREC

P
OSTHARVEST
I
NFORMATION
N
ETWORK

http://postharvest.tfrec.wsu.edu/PC2005E.pdf

Since the value of N, above, is equal to, or in this case, greater than 10, one additional row of
stacked bins can be added to this room.
Research presented by Hellickson and Baskins (2000) showed that equal cooling rates were
achieved when fruit were tight-stacked or conventionally stacked. A symmetrical pattern of
tight-stacked bins eliminates space between rows of bins and results in increased airflow through
runner spaces where the majority of fruit cooling is accomplished. Research presented by
Hellickson and Baskins (2003) also documented that nonsymmetrical bin placement caused
airflow in some areas of the room to short circuit and return to the evaporator unit before
reaching the opposite end of the room. Another positive consequence of tight-stacking a room is
that additional fruit may be stored in the same space.
Providing sufficient open space at end walls is also critical to achieving uniform air movement
throughout the room. (End walls are defined as the walls opposite the evaporator units.)
Likewise, sufficient open space must be maintained so the air returning to evaporator units is not
restricted. If either or both of these spaces are less than approximately two feet, resistance to
airflow will be increased. Restricting open space at end walls will reduce the quantity and
velocity of air movement in that area of the room.