Heat and mass transfer during ethanol evaporation on the walls of a flat channel at forced convection of humid air

The results of numerical investigation of heat and mass transfer in the laminar flow of humid air in a plane-parallel channel with adiabatic walls from the surface of which ethanol is evaporated are presented. The main attention is paid to studying the influence of air humidity at the inlet in the entire range of its change from absolutely dry to fully saturated state (phi = 0 divided by 100%) on the heat and mass transfer intensity and cooling efficiency. It has been established that ethanol evaporation and steam condensation occur simultaneously on the channel walls. The relationship between the components of the heat and diffusion flows on the wall is determined depending on the initial air humidity. An increase in the humidity of steam at the channel inlet is accompanied by an increase in the gas temperature at the outlet of the evaporation cell and, accordingly, deterioration in the cooling efficiency. Nevertheless, even when a steam-air mixture in the saturation state (phi = 100%) with ethanol as an evaporation agent is fed to the cell inlet, the efficiency of such a cell remains high and approximately equal to the theoretical limit of water evaporation into dry air. (C) 2020 Elsevier Ltd. All rights reserved.