DOE-2 Engineers Manual Version 2.1A - DOE-2.com

4.6 Calculation of Wet-Bulb Temperature (subroutine WBFS)
The routine WBFS calculates the wet-bulb temperature, given the dry-bulb
temperature (T), humidity ratio (W), and the atmospheric pressure (PB).
Calculation Outline
Calculate the wet-bulb temperature in ranges for:
1. negative enthalphy,
2. atmospheric pressure within ± 5 percent of standard atmospheric
pressure, and
3. nonstandard atmospheric pressure.
Calculation Algorithm.
Step 1. Negative Enthalphy
If the enthalphy of the air is less than 1.0, the wet-bulb temperature is
set to zero. This low wet-bulb temperature is not important because the wetbulb
temperature is only used for adjusting cooling equipment capacity.
Step 2. Atmospheric Pressure Within ± 5 Percent of Standard Atmospheric
Pressure
If the atmospheric pressure is within ± 5 percent of standard atmospheric
pressure (28.5 to 31.5 in. Hg.), the following curve fit is used
where
WBFS = A + Y[B + Y(C + Y * D)], (IV.601)
Y is the logrithm of the enthalpy of the air at dry-bulb temperature
T and humidity ratio W, and
A, B, C, and 0 are from Table IV.3.
TABLE IV.3
COEFFICIENTS FOR CALCULATING THE WET-BULB TEMPERATURE IF THE ATMOSPHERIC
PRESSURE IS WITHIN ± 5 PERCENT OF STANDARD ATMOSPHERIC PRESSURE
HI < 11.758
HI > 11.758
A
0.6041
30.9185
B
3.4841
-39.682
IV.211
c
1.3601
20.5841
o
0.97307
-1.758