Specifications

47
RG SERIES ENGINEERING GUIDE
Selection Example cont.
Antifreeze Type
Antifreeze
% by wt
Cooling
Capacity
Heating
Capacity
Pressure Drop
EWT - degF [DegC] 90 [32.2] 30 [-1.1] 30 [-1.1]
Water 0 1.000 1.000 1.000
10 0.991 0.973 1.075
20 0.979 0.943 1.163
Ethylene Glycol 30 0.965 0.917 1.225
40 0.955 0.890 1.324
50 0.943 0.865 1.419
10 0.981 0.958 1.130
20 0.969 0.913 1.270
Propylene Glycol 30 0.950 0.854 1.433
40 0.937 0.813 1.614
50 0.922 0.770 1.816
10 0.991 0.927 1.242
20 0.972 0.887 1.343
Ethanol 30 0.947 0.856 1.383
40 0.930 0.815 1.523
50 0.911 0.779 1.639
10 0.986 0.957 1.127
20 0.970 0.924 1.197
Methanol 30 0.951 0.895 1.235
40 0.936 0.863 1.323
50 0.920 0.833 1.399
Warning: Gray area represents antifreeze concentrations greater than 35% by weight and
s
hould be avoided due to the extreme performance penalty they represent.
3, 4
&
5. HP
S
election:
A
fter making our preliminary selection (US*060 ECM), we enter the
tables at design water fl ow and water temperature and read
Total Cooling, Sens. Cooling and Heat of Rej. capacities:
Total Cooling ..............................................................60,500 Btu/h
Sensible Cooling........................................................45,000 Btu/h
Heat of Rejection .......................................................75,500 Btu/h
6 & 7. Entering Air and Airfl ow Corrections:
Next, we determine our correction factors. (Refer to Correction
Factor Tables - Airfl ow and Entering Air correction tables — using 1,850
cfm. or 1,850÷2,000 nom. = 92.5%).
Corrected Total Cooling = 60,500 x 0.990 x 0.967 = 57,918
Corrected Sens Cooling = 45,000 x 0.956 x 0.881 = 37,900
Corrected Heat of Reject = 75,500 x 0.987 x 0.972 = 72,432
8. Water Temperature Rise Calculation & Assessment:
Note: 500 = parameters for water & 485 = parameters for antifreeze
solutions to 30% weight.
When we compare the Corrected Total Cooling and Corrected
Sensible Cooling fi gures with our load requirements stated in Step
1, we discover that our selection is within +10% of our sensible load
requirement. Further more, we see that our Corrected Total Cooling
fi gure is within 1,000 Btu/h of the actual indicated load.
Antifreeze Corrections
Catalog performance can be corrected for antifreeze use. Please use the following table and note the example given.
Antifreeze Correction Example
A
ntifreeze solution is Propylene Glycol 20% by weight. Determine the corrected heating and cooling performance at 30°F and 90°F re-
spectively as well as pressure drop at 30°F for a Model 024-PSC.
The corrected cooling capacity at 90°F would be: 24,500 Btu/h x 0.969 = 23,740 Btu/h
The corrected heating capacity at 30°F would be: 19,000 Btu/h x 0.913 = 17,347 Btu/h
The corrected pressure drop at 30°F and 6 gpm would be: 10.5 ft. hd x 1.270 = 13.34 ft. hd.
HR = 500 x gpm x (T
in
- T
out
)
HR
= (T
in
- T
out
) or ¨T Rise
500 x gpm
72,432
= 9.65 °F Rise
500 x 15