Study on the mechanism of sessile droplets evaporation enhanced by the electric field

Abstract

The evaporation characteristics of a sessile droplet under a direct current electric field were numerically investigated, and a numerical model was developed based on the arbitrary Lagrange-Euler method, combining the flow, heat transfer, vapour transport, and electrostatic equations. The simulations were validated to be in good agreement with previously reported experiments. The results demonstrate that the electric field can enhance the evaporation of the sessile droplet with different evaporative cooling numbers (initial electric field intensity E0 = 280 kV·m−1; 32.9% decrease in the evaporation time for water) by the following three methods: increasing the surface area of the droplet evaporation (2.6%) through the electric-field-induced deformation, improving the heat transfer efficiency between the droplet and substrate (droplet average temperature increases by 2.3 K) through the internal vortex, and by enhancing the shearing effect on the vapour layer (450.3% increase in vapour diffusion distance dc) through the external vortex. Additionally, the evaporation of a sessile water droplet undergoing thermocapillary convection is further enhanced under the electric field (E0 = 280 kV·m−1; 20.0% decrease in the evaporation time). As the inhomogeneous temperature distribution inside the droplet was eliminated by thermocapillary convection, the evaporation efficiency was dominated by the increased surface area of the droplet evaporation and the enhanced shearing effect on the vapour layer. These results will provide a better understanding of the electro-hydrodynamic enhanced droplet evaporation.