Mathematical modeling of concentration influence on evaporative convection in a bilayer system of binary mixtures

Abstract

A problem of evaporative buoyancy-thermocapillary convection in a two-phase system of binary media is studied. Characteristics of a joint steady flow of evaporating fluid and gas in a narrow plane horizontal channel are analyzed on the example of aqueous ethanol solution and mixture of the nitrogen with the ethanol vapor. The influence of solutal effects related to changes in the ethanol concentration in the liquid mixture is scrutinized. New exact solution of thermosolutal convection equations is constructed in the framework of a two-sided model based on the Oberbeck–Boussinesque approximation. The model used implies the presence of the liquid–gas interface admitting evaporation where surface phenomena play a key role. The testing of problem statements is performed in order to determine feasible closing relations. A correct problem statement is proposed that provides acceptable accordance with known experimental data concerning both the working liquid properties and possible pattern of the bilayer flows. Non-linear character of dependence of evaporation rate on the concentration of the aqueous solution is established. The solution predicts the decrease in evaporation rate due to the diffusion resistance effect for some compositions of the liquid mixture, thereby it is shown the possibility of control of the heat exchange parameter by means of the choice of the working fluid compound. The results obtained can be useful under developing the experimental methods for exploration of the interfacial effects in multicomponent fluids.