Vaisala HMP155 User Manual
Page 82
USER'S GUIDE____________________________________________________________________
80 _______________________________________________________________ M210912EN-C
Enthalpy:
x
x
T
h
5
.
2
)
00189
.
0
01
.
1
(
(4)
The water vapor saturation pressure at temperature T
pws
is calculated over
water and over ice by using four equations (5-8). These formulas are
taken from Hyland, R.,Wexler, A.:Formulations of the Thermodynamic
Properties of the Saturated Phases of H2O from 173.15 K to 473.15 K,
Ashrae transactions 1983, Part 2A. pp. 500-513.
PWS over water:
3
0
i
i
pws
i
T
C
T
(5)
PWS over ice:
pws
T
(6)
where:
T
pws
= temperature
in
K
Ci = coefficients
C0 = 0.4931358
C1 = -0.46094296 * 10-2
C2 = 0.13746454 * 10-4
C3 = -0.12743214 * 10-7
Over water:
3
0
4
1
ln
ln
100
b
i
i
wsWATER
b
b
b
P
(7)
Over ice:
4
0
6
1
ln
ln
100
b
i
i
wsICE
a
a
a
P
(8)
where:
bi = Coefficients over water
b-1 = -0.58002206 * 104