Chapter 6, Problem 6.80P

A wet-bulb thermometer consists of a mercury-in-glass thermometer covered with a wetted (water) fabric. When suspended in a stream of air, the steady-state thermometer reading indicates the wet-bulb temperature $T_{\text{wb}}.$ Obtain an expression for determining the relative humidity of the air from knowledge of the air temperature $\left(T_{\infty }\right),$ the wet-bulb temperature, and appropriate air and water vapor properties. If $T_{\infty }=45°\text{C}$ and $T_{wb}=25°\text{C,}$ what is the relative humidity of the airstream?