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RB SERIES ENGINEERING GUIDE
3, 4 & 5. HP Selection:
After making our preliminary selection (RB*060 VS ECM), we enter
the tables at design water flow and water temperature and read
Total Cooling, Sens. Cooling and Heat of Rej. capacities:
Total Cooling ..............................................................54,100 Btu/h
Sensible Cooling........................................................40,500 Btu/h
Heat of Rejection .......................................................68,800 Btu/h
6 & 7. Entering Air and Airflow Corrections:
Next, we determine our correction factors. (Refer to Correction
Factor Tables - Airflow and Entering Air correction tables — using
1750 cfm. or 1,750÷2,000 nom. = 87.5%).
Corrected Total Cooling = 54,100 x 0.982 x 0.967 = 51,373
Corrected Sens Cooling = 40,500 x 0.929 x 0.881 = 33,147
Corrected Heat of Reject = 68,800 x 0.978 x 0.972 = 65,402
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 figures 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 figure is within 1,000 Btu/h of the actual indicated load.
Selection Example cont.
Antifreeze Corrections
Catalog performance can be corrected for antifreeze use. Please use the following table and note the example given.
Antifreeze Correction Example
Antifreeze 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 an RB Series RB*024-PSC.
The corrected cooling capacity at 90°F would be: 22,600 Btu/h x 0.969 = 21,899 Btu/h
The corrected heating capacity at 30°F would be: 16,800 Btu/h x 0.913 = 15,338 Btu/h
The corrected pressure drop at 30°F and 6 gpm would be: 20.8 ft. hd x 1.270 = 26.42 ft. hd.
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
should be avoided due to the extreme performance penalty they represent.
HR = 500 x gpm x (T
in
- T
out
)
HR
= (T
in
- T
out
) or ¨T Rise
500 x gpm
65,402
= 8.72 °F Rise
500 x 15
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