Evaporation of a Sessile Microdroplet on a Heated Hydrophobic Substrate

Abstract

We investigated evaporation of sessile water microdroplets on heated hydrophobic glass substrate. An in-house, experimentally validated finite-element numerical model was employed to simulate internal fluid flow and heat transfer during the evaporation. We also validated the non-uniform evaporative flux for water droplets having different initial wetting angles with theoretical results from literature. During evaporation, the fluid flow is radially outward due to the largest evaporative flux near the wetting line. The isotherms are almost horizontal which indicates that the conduction between the droplet and substrate dominates over internal convection during the evaporation. The evolution of wetted radius and wetting angle indicates a two-stage evaporation process:during the first stage of the evaporation, wetted radius remains constant and wetting angle decreases with time; while in the second stage, wetting angle remains constant and wetted radius decreases with time. The droplet volume shows a linear ...