Vaisala DEWCAP DM500 User's Guide Page 133

  • Download
  • Add to my manuals
  • Print
  • Page
    / 138
  • Table of contents
  • BOOKMARKS
  • Rated. / 5. Based on customer reviews
Page view 132
Appendix A __________________________________________________________ Humidity Theory
VAISALA ______________________________________________________________________ 131
Absolute Humidity (a)
Absolute humidity (a) is the mass of water vapour present in unit
volume of moist air of a given temperature and pressure.
15.273
16679.2
+
=
T
P
a
w
(6)
where
T = temperature (ºC)
a = absolute humidity (g/m
3
)
P
w
= water vapor pressure
Absolute Humidity at NTP (aNTP)
NTP
NTP
T
Pw
P
P
a = 16679.2(7)
where
a
NTP
= absolute humidity at NTP (g/m
3
)
P
w
= water vapor pressure (Pa)
P = pressure (Pa)
Normal conditions are defined as: P
NTP
= 101 325 (Pa)
T
NTP
= 273.15 (K)
Wet Bulb Temperature
)-(000662.0-
wtotwsw
TTPPP = (8)
where
P
w
= water vapor pressure (Pa)
P
ws
= saturation water vapor pressure at temperature T
w
(Pa)
Enthalpy (h)
Enthalpy (h) is measure of the total energy in a humid gas. Enthalpy is
a function of the gas temperature and pressure, and of the moisture
content, since water absorbs energy on changing from condensed state
to vapour.
Page view 132

Comments to this Manuals

No comments