Nano-scale transport characteristics during thin film evaporation: Effect of liquid film thickness

Abstract

In the present study, molecular dynamics simulations have been performed to understand the characteristics of thin film evaporation with particular emphasis on the effect of initial liquid film thickness. The simulation domain consists of liquid and vapor argon atoms placed over a solid flat platinum substrate. Five different film thicknesses (2 nm ∼ 6 nm) of liquid argon with the hydrophilic wetting condition for an evaporation temperature of 150 K have been considered in this simulation work. The role of liquid film thickness in wall heat flux, evaporative mass flux, and disjoining pressure has been investigated. As found in the current study, lower film thickness results in higher evaporative mass flux and hence offers better heat transfer. For sufficiently thick liquid film, it has been observed that the transient liquid film thickness attains a state that offer local maximum heat flux prior to the formation of non-evaporative layer. The thickness of non-evaporative layer formed at the end of evaporation, increases as the liquid initial film thickness increase that in turn results in smaller disjoining pressure. The heat flux characteristics obtained herein are compared with theoretical limit of maximum heat flux (qmax, max) and reasonable consistency has been found. Eventually, results obtained from the present molecular dynamics shows good agreement with thermodynamic analysis of thin film evaporation.