Mathematical modeling of a modular convection-enhanced evaporation system

Abstract

This study presents mathematical modeling of a novel convection-enhanced evaporation (CEE) system. The proposed system represents a modular brine management option for decentralized desalination plants and small-scale industries. Liquid is pumped over horizontally packed evaporation surfaces and forced convection is induced by means of a fan. The developed model of heat and mass transfer in the CEE system is solved using the finite difference method to predict the evaporation rate and the spatial distribution of humidity and temperature, based on operating condition (ambient temperature and relative humidity, air flow speed, and the spacing between the evaporation surfaces) and liquid inlet condition (temperature, flow rate and salinity). Comparison between model-predicted evaporation rates and experimental results show good agreement; for 11 out of 16 operating conditions error was within 10%, for 4 conditions error was within 20%, and for 1 condition error was within 35%. The effect of various operating conditions on the evaporation performance is also investigated. An increase in evaporation of up to 13 times is achieved by active control of liquid inlet temperature and air flow speed. Preheating the liquid was found to be a good strategy to overcome the negative effect of high relative humidity.