Issue
How is Enthalpy calculated in Sigma?
Environment
Programmable Object
Prog Point
Enthalpy
Cause
Customers request for this information.
Resolution
A Programmable Object calculates Enthalpy using the following formula.
I = 1.006 * t + x * (2501 + 1.8 * t) where
t is the temperature and
x = 0.62198 * (í * pdm / (p - í * pdm)) and at p = 101.325 kPa =>
x = 0.62198 * (í * pdm / (101.325 - í * pdm))
where í is relative humidity and
pdm = p` = 101325 * 10A where
A = A0 - A1/T - A2*logT - A3*10(-T/A4) + A5*10(A6/T) where
A0 = 20.82648355
A1 = 2948.997118
A2 = 5.02808
A3 = 29811.33781
A4 = 32.923061
A5 = 25.21934913
A6 = 1302.8503
T = absolute temperature = 273.15 + t
