SPX Cooling Technologies Recold JW Series - Manual (Page 7)

Recold / JW Series Fluid Cooler / Selection Procedure
7
Closed circuit cooler selections can easily be made by using the information on pages 6 through 11. The
examples below demonstrate proper procedures for water and ethylene glycol solutions. Other fluids can be
cooled, but since their heat transfer and flow characteristics may vary, please contact your local Recold sales
representative for assistance.
WATER SELECTION EXAMPLE
Select a unit to cool 225 GPM of water from 102°F to
90°F at 76°F wet bulb temperature.
1. Determine Range:
102°F - 90°F = 12°F Range
2. Determine Approach:
90°F - 76°F = 14°F Approach
3. Select Load Factor — Enter Unit Load Factor Table 2
for 76°F wet bulb. Select load factor based on
12°F range and 14°F approach. Load factor in this
example equals 3.3. When wet bulb temperature
is an odd number interpolate between appropriate
tables to determine the load factor.
4. Select Unit Model — Table 3, the load factor
determined in step 3 falls between 3.0 and 3.5.
Enter the 3.0 column and read down to the smallest
unit flow rating which is greater than or equal to
225 GPM. For the Model JWL35B, interpolate
between 245 and 190 GPM to determine the
flow rating at the 3.3 load factor. Interpolation
gives a rating of 212 GPM which is less than the
design requirement. Select a Model JWL35C and
again interpolate between load factor columns
to determine flow rating. The second selection
provides a flow rating of 245 GPM which exceeds
the design requirement. The correct unit size is,
therefore, a Model 35C
5. Determine Flow Limitations — Enter Table 3 at unit
size determined in Step 4 to select a JWL low flow
or JW standard flow unit. The Model 35C with 225
GPM design flow falls within the standard coil flow
limitations. The correct unit selection is, therefore,
a JW35C.
6. Determine Coil Pressure Drop — Enter the Coil
Pressure Drop Table at 225 GPM and read across
to the unit model column to select pressure drop
reading. In this example, pressure drop equals
4.8 PSI.
ETHYLENE GLYCOL EXAMPLE
Select a unit to cool 75 GPM of 40% by volume
ethylene glycol from 107°F to 85°F with 78°F wet
bulb.
1. Determine Range:
107°F - 85°F = 22°F Range
2. Determine Approach:
85°F - 78°F = 7°F Approach
3. Select Load Factor — Enter Table 2 for 78°F wet bulb
and select load factor at design range and approach.
Select 6.0 factor.
4. Select Test Unit Model — Enter the Unit Rating
Table 3 at the 6.0 load factor and read down to the
smallest unit flow rating greater than or equal to the
design 75 GPM. Select the test model JWL35C
5. Correct Flow for Ethylene Glycol — The flow correction
factor obtained from Table 1 is 1.04. 75 GPM x 1.04
= 78 GPM
6. Adjust Model Selection — Re-enter Table 3 at the 6.0
load factor and make selection based on corrected
flow of 78 GPM. The adjusted unit selection is the
Model JWL50A indicating an 80 GPM rating
7. Determine Flow Limitations — Enter Table 3 at unit
size determined in Step 6 to select a JWL low flow
or JW standard flow unit. The Model 50A with
75 GPM design flow falls within the low flow coil
limitations. The correct unit selection is, therefore,
a JWL50A.
8. Determine Coil Pressure Drop — For ethylene glycol
pressure drop calculation, the conversion factor
from Table 5 must be applied to design flow before
entering Table 4. 75 GPM x 1.05 = 79 GPM.
The coil pressure drop for 79 GPM is 2.4 PSI
DEFINITIONS
Range: the difference between the entering and
leaving water temperatures (WT in – WT out).
Approach: the difference between the leaving water
temperature and the web bulb temperature (WT out
– WB).
Load BTUH =
GPM x 500 x Sp. Gr. x Sp. Ht. x (T
1 – T 2 ) where
Sp. Gr. = specific gravity at average temperature
Sp. Ht. = specific heat at average temperature
T
1 = entering temperature
T 2 = leaving temperature