A sample of moist air has a dry bulb temperature of 25°C and a relative humidity of 50 percent. The barometric pressure is 740 mm of Hg. Without using Psychometric chart, calculate: 1) partial pressure of water vapor and dry air; 2) Dew point temp; 3) specific humidity of air; 4) Enthalpy of air per kg of dry air.

1) Partial pressure of water vapour and dry air: Let $p_{v}=$ partial pressure of water vapour. We know that relative humidity $\phi:$ $$ \phi=\frac{p_{v}}{p_{s}} $$ From steam table, we find that the saturation pressure of vapour corresponding to dry bulb temperature of $25^{\circ} \mathrm{C}$ is $$ \begin{array}{c} p_{s}=0.031698 b a …