Vaisala HUMICAP HMP155 Guía de usuario Pagina 82

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USER'S GUIDE____________________________________________________________________
80 _______________________________________________________________ M210912EN-C
Enthalpy:
xxTh
5.2)00189.001.1(
(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
pwsi
TCT
(5)
PWS over ice:
pws
T
(6)
where:
T
pws
= temperature in K
C
i
= coefficients
C
0
= 0.4931358
C
1
= -0.46094296 * 10
-2
C
2
= 0.13746454 * 10
-4
C
3
= -0.12743214 * 10
-7
Over water:
3
0
4
1
lnln100
b
i
iwsWATER
bb
b
P
(7)
Over ice:
4
0
6
1
lnln100
b
i
iwsICE
aa
a
P
(8)
where:
b
i
= Coefficients over water
b
-1
= -0.58002206 * 10
4
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