Wet-Air Characteristics

08/10/2024

Hideki Miki, Ph.D. (Engineering), JICA Expert

Calculation

Note1: Error handling is minimal.

Note2: Tested with Chrome. (blocks must be removed.)

Fomula

DT >= 0.01 : LogE(PWS) = - 0.58002206 x 10 ^ 4 / AT + 0.13914993 x 10 - 0.48640239 x 10 ^ -1 x AT + 0.41764768 x 10 ^ -4 x AT ^ 2 - 0.14452093 x 10 ^ -7 x AT ^ 3 + 0.65459673 x 10 x log10(AT)
DT < 0.01: LogE(PWS) = - 0.56745359 x 10 ^ 4 / AT + 0.63925247 x 10 - 0.96778430 x 10 ^ -2 x AT + 0.62215701 x 10 ^ -6 x AT ^ 2 + 0.20747825 x 10 ^ -8 x AT ^ 3 - 0.94840240 x 10 ^ -12 x AT ^ 4 + 0.41635019 x 10 x log10(AT)

DT	:	Dry-bulb temperature	[degC]
PWS	:	Saturated water vapor pressure	[Pa]
AT	:	Absolute temperature (DT + 273.15)	[degC]

PW = PWS x RH / 100

PW	:	Water vapor pressure	[Pa]
RH	:	Relative humidity	[%]

AH = (MW / MA) x PW / (PA - PW)

AH	:	Absolute humidity	[kg/kg']
MW	:	Molecular weight of water vapor (18.02)	[kg/kmol]
MA	:	Molecular weight of dry-air (28.96)	[kg/kmol]
PA	:	Atomosphere pressure (normally 101.325)	[kPa]

ET = CPA x DT + (CPW x DT + LH) x AH

ET	:	Specific enthalpy	[kJ/kg]
CPA	:	Specific heat capacity of dry air at constant pressure (1.006)	[kJ/kg degC]
CPW	:	Specific heat capacity of water vapor at constant pressure (1.86)	[kJ/kg degC]
LH	:	Latent heat of vaporization of water at 1[degC] (2501)	[kJ/kg]