Psychrometrics

The humid heat of moist air is $c_s = c_{pa} + W c_{pv}$, where dry air specific heat is $c_{pa} = 1.005\text{ kJ/(kg}\cdot\text{K)}$, water vapor specific heat is $c_{pv} = 1.88\text{ kJ/(kg}\cdot\text{K)}$, and humidity ratio is $W = 0.020\text{ kg water/kg dry air}$. The humid heat $c_s = 1.005 + 0.020(1.88) = 1.005 + 0.0376$ in $\text{kJ/(kg}\cdot\text{K)}$ is (rounded off to three decimal places):