StmEng_XPS
- Last UpdatedSep 17, 2025
- 1 minute read
- PI System
- PI Server 2023
- PI Server
Calculates the steam quality (vapor fraction) as a function of pressure and entropy—all variables expressed in English units. Use only for wet steam.
Format
StmEng_XPS(P, S)
Arguments
-
P
Pressure of the steam in psia. The valid range is 0.08865 to 3200.112psia.
-
S
Specific entropy of the steam in BTU/lbm/R. The valid range is -3.691353466E-05 to 1.672077738 BTU/lbm/R or Error digital state.
Returns
Computed steam quality (vapor fraction).
Sample Values
|
Pressure |
Entropy |
Steam Quality |
|
300. |
1.4183 |
0.899 |
|
800. |
1.3458 |
0.900 |
|
1400. |
1.2923 |
0.901 |
Note: If the input entropy is greater than that of the saturated vapor, the function returns 1.0 as vapor fraction. If the input entropy is less than that of the saturated liquid, the function would compute negative vapor fraction without setting an error state.