Modeling and simulation of counterflow wet-cooling towers and the accurate calculation and correlation of mass transfer coefficients for thermal performance prediction

Abstract

This work provides a detailed mathematical derivation of a steady-state one-dimensional continuous differential air-water contactor (CDAWC) model that describes the material and energy balances in a counterflow wet-cooling tower. The model consists of four ordinary differential equations that describe the changes (along the packed height) of the liquid water temperature, dry-bulb temperature of moist air, liquid water mass flowrate, and moist-air humidity mass ratio. The model is formulated for the cases of unsaturated and supersaturated air, and the model equations are compared to those of previous works. It is shown that the equations of some previous models are approximately equivalent to the equations of the CDAWC model. However, the formulation of the CDAWC model is simpler and the resulting equations have a more general form. A simulation method is proposed to determine accurate values of the volumetric mass transfer coefficient by matching the experimental thermal performance of counterflow wet-cooling towers.