Model of Natural Draft Cooling Tower Performance

A method is developed for analyzing the performance of counterflow and crossflow natural draft cooling towers that does not assume saturated air at the top of the packing. Types of cooling towers and the principles of operation are considered. Simplified differential equations for the heat and mass transfer relations and the methods of integrating them for both counterflow and crossflow towers are given. A large number of integration steps is shown to be unnecessary. Equations for estimating the pressure losses in the tower are also given. Simplified flow charts using these integration schemes show how the computer program is used to evaluate tower performance. The computed performance of towers of various heights operating in moist and in dry conditions is shown. The effect of inlet water temperature is shown to be significant. Finally, the computed performance of a given tower with fixed inlet water temperature is shown as a function of relative humidity and dry bulb air temperature.