A wet towel hangs on a clothes line under conditions for which one surface receives solar irradiation of GS = 900 W/m2 and both surfaces are exposed to atmospheric (sky) and ground radiation of Gatm = 200 W/m2 and Gg = 250 W/m2, respectively. Under moderately windy conditions, airflow at a temperature of 27°C and a relative humidity of 60% maintains a convection heat transfer coefficient of 20 W/m2· K at both surfaces. The wet towel has an emissivity of 0.96 and a solar absorptivity of 0.65. As a first approximation the properties of the atmospheric air may be evaluated at a temperature of 300 K.
Determine the temperature Ts of the towel. What is the corresponding evaporation rate for a towel that is 0.75 wide by 1.50 m long?