- the heat capacity (specific heat) of humid air, expressed per unit mass of dry air in the mixture. The engineering symbol is cs.
For ordinary engineering calculations in the range 0 to 50°C the following expressions are used to calculate humid heat:
In [U.S. customary units], cs = 0.24 + 0.45H where 0.24 BTU/lb°F is the heat capacity of dry air, 0.45 BTU/lb°F is the heat capacity of water vapor, and H is the specific humidity in lb water vapor per lb dry air in the mixture.
In SI units, cs = 1.005 + 1.82H where 1.005 kJ/kg°C is the heat capacity of dry air, 1.82 kJ/kg°C the heat capacity of water vapor, and H is the specific humidity in kg water vapor per kg dry air in the mixture.
Perry's Handbook of Chemical Engineering, 6th edition; section 12, Psychrometry.
Çengel and Boles, Thermodynamics, an Engineering Approach, 4th edition, chapter 13, Psychrometry