Research On The Coupling Model Of Thin Liquid Film Considering The Transfer Of Components And The Description Of State Parameters

Heat and mass transfer at the gas-liquid interface of a multicomponent mixture is of great importance in industrial applications such as porous media,fuel cells,distillation,and extraction.At present,there is no comprehensive model that can take into account the transfer of components and the related state parameters of the mixed solution in the evaporation process of thin liquid film,so it can not reasonably and accurately describe the evaporation characteristics of the mixed solution in the thin film region.In this paper,we consider the changes of physical parameters such as surface tension,saturated vapor pressure,density,and other parameters of the actual nonideal binary mixed solution at different concentrations and temperatures.Based on these modified governing equations,Young-Laplace equations,and kinetic theory,a coupled heat transfer numerical model of flow and evaporation in the thin film region of binary mixed solution is established.The heat transfer and flow characteristics of methanol-water mixtures with different mass fractions in the evaporation thin film region were investigated,the results show that the disjoining pressure at the initial position increases with the increase of methanol mass fraction.The higher the mass fraction of methanol in the same location,the higher the disjoining pressure,the lower the temperature of the gas-liquid interface,the faster the change speed of temperature,the greater the evaporation mass flow rate of methanol,and the smaller the evaporation mass flow of water.With the increase of methanol mass fraction,the position of the maximum evaporation mass flow of water and methanol in the mixed solution gradually moves back,and the average heat transfer coefficient of low concentration methanol mixed solution is slightly larger than that of pure water.This paper further explores the influence of different mixed solution types,initial temperature and superheat on the mass and heat transfer process in the evaporation thin film region.At the same time,a multi-component coupling evaporation model of the gas-liquid interface in the presence of noncondensable gas is proposed,and the influence of noncondensable gas on the evaporation process of the binary mixed solution was also studied.The results show that the evaporation heat transfer characteristics of mixed solutions are also related to the types of mixed solutions.When the initial temperature of the mixed solution is increased,the evaporation heat and mass transfer effect at the gas-liquid interface is enhanced.When the superheat is increased,the evaporation heat transfer at the gas-liquid interface will be enhanced and the effect of disjoining pressure will be weakened.And adding noncondensable gas into the gas phase of the mixed solution will weaken the evaporation process at the gas-liquid interface.