Thin film profile and interfacial temperature distribution of binary fluid sessile droplet evaporating on heated substrate

Abstract

The interfacial profile and temperature distribution in the thin film region near the triple line is important for comprehensive modelling the transport process. For fluids with multi-components, typically binary fluids, the volatilities of the components are different from pure fluids and hence the interfacial characteristics needs to be properly modeled. In this work, a numerical analysis on the thin film profile, the interfacial temperature and the conjugate heat transfer characteristics in the thin film region of binary fluid sessile droplets of 5 wt% aqueous methanol and ethanol solutions evaporating on heated glass or copper substrates is given. The concentration of the components of binary fluid in the thin film region is assumed to be uniform for the low mass fraction of alcohol solution. The results show that the fluid property, substrate wettability and wall superheat have substantial effects on these parameters. The wall superheat has the greatest effect on the thin film heat transfer followed by the substrate wettability and fluid property. It also shows that surface tension gradients play a more important role in the formation of the Marangoni convection in the thin film region than the thermal-induced density differences and inertial motion. The effects of fluid properties and substrate wettability can be efficiently utilized for superior heat removal capacity in phase-change devices involving thin film heat transfer using binary fluids.