Numerical study of evaporation by mixed convection of a binary liquid film

This paper deals with a numerical analysis of the evaporation of binary liquid film. The film is falling down on one plate of a vertical channel under mixed convection channel. The first plate of a vertical channel is externally submitted to a uniform heated flux q1 while the second one (y = d) is dry and isothermal. The liquid mixture consists of water (the more volatile component) and ethylene glycol while the gas mixture has three components: dry air, water vapour and ethylene-glycol vapour. The results concern the effects of the inlet parameters in the gas and in the liquid film on the interfacial pressure, temperature and concentration profiles. The evolutions of the heat fluxes and of the water and mixture evaporation rates have been analysed. Results obtained show, in particular, that it is possible to increase the accumulated evaporation rate of water and of the liquid mixture when the inlet liquid concentration of ethylene glycol (the less volatile component) is less than 40%. This result has been explained by the fact that an increase of the inlet liquid concentration of ethylene glycol has two antagonistic effects on the accumulated evaporation rates of water and of liquid mixture.

► The changing behaviours evolution of water and mixture evaporation rates is due to the existence of two antagonistic effects.
► The changing behaviours evolution of the heat transferred by latent mode is due to the existence of two antagonistic effects.
► It is possible to increase the water evaporation rate when the inlet film composition is less than 40%.
► It is possible to increase the mixture evaporation rate when the inlet film composition is less than 40%.
► The heat and mass transfer strongly depends on the inlet liquid concentration of ethylene glycol.