A.5 Saturation Vapor Pressure Calculation
Saturation vapor pressure (P
ws
) is the equilibrium water vapor pressure in a closed chamber
containing liquid water. It is a function only of temperature, and it indicates the maximum
amount of water that can exist in the vapor state.
Water vapor saturation pressure (P
ws
) is calculated with the following 2 formulas:
=
= 0
3
ℎ
where
T Temperature in K
C
i
Coecients
C
0
0.49313580
C
1
-0.46094296 * 10
-2
C
2
0.13746454 * 10
-4
C
3
-0.12743214 * 10
-7
ln
=
= 1
3
+
4
ln
where
b
i
Coecients
b
-1
-0.58002206 * 10
4
b
0
0.13914993 * 10
1
b
1
-0.48640239 * 10
-1
b
2
0.41764768 * 10
-4
b
3
-0.14452093 * 10
-7
b
4
6.5459673
A.6 Water Vapor Pressure Calculation
Vapor pressure refers to the vapor pressure of water in air or other gas. Water vapor has a
partial pressure P
w
which is part of the total pressure of the gas.
Water vapor pressure (Pw) is calculated with the following formula:
=
100
ℎ
Appendix A – Calculation Formulas
79
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