Surface Evaporation of Sessile Water Droplet on a Hydrophobic Surface

Abstract

Abstract In this paper, the surface evaporation of a sessile water droplet on hydrophobic solid substrates was numerically and experimentally investigated. The droplet evaporation is governed by multi-dimensional heat and mass transport and interfacial processes of three (gas, liquid, and solid) phases. A Computational Fluid Dynamics (CFD) simulation was performed to analyze the simultaneous heat and mass transfer in the surface evaporation of a sessile water droplet by considering the Marangoni and/or free convection. The results from the CFD simulation were validated using experimental results for the water droplet evaporation on a hydrophobic-coated silicon substrate. It was found that the droplet evaporation rate is greatly increased by a thermocapillary-driven flow (Marangoni convection) in the droplet with small liquid volumes of less than 2.4 μL on the hydrophobic substrate, while the contribution of the free convection is negligible. The peak mass flux of droplet evaporation was always observed along the three-phase contact line.