Pressure of saturated water vapor 1

There is an ASME specification covering Saturated water as well as Heated Steam as well as Super Heated Steam. I will look through my reference material later and forward you the specification...that is idf it's the one that I'm thinking of. I use it in calculating designs for Safety Relief valve nozzle attachments.

There are several emperical expressions you can use to calculate vapor pressure. In college we usually used the Antoine equation:

log P(sat) = A - [B/(T+C)]

Where A, B, and C are constants, P(sat) is the vapor pressure at a temperature, T.

From Perry's:
A = 8.07131
B = 1730.630
C = 233.426
This is valid from 1 - 100ºC.
P(sat) is in torr, T is in ºC.

Another equation you can use to calculate Vapor pressure (also from Perry's) is as follows:

P(sat) = exp[C1 +(C2/T) + C3*ln(T) + C4*T^(C5)]

where:
C1 = 73.649
C2 = -7258.2
C3 = -7.3037
C4 = 4.1653E-06
C5 = 2

Temperature (T) is in Kelvin and Vapor pressure (P(sat)) is in Pa. This equation is valid from 0ºC to 373.98ºC.

There are also tables in Perry's Chemical Engineers Hanbook if you need them.

Hope this helps!

Jproj