Humid-heat Definition

The heat capacity (specific heat) of humid air, expressed per unit mass of dry air in the mixture. The engineering symbol is c_s.

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], c_s = 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, c_s = 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.