Enhanced controllability of droplet evaporation via DC electric field

Abstract

To enhance the controllability of droplet evaporation, this study introduces a system that integrates an electric field with a temperature field. In addition, lattice Boltzmann method (LBM) simulations were performed to examine the flow field and heat transfer within the droplet, confirming the mechanism of evaporation rate transition. The impacts of the electric field on droplet evaporation and the characteristics of heat and mass transfer were thoroughly investigated through experimental, theoretical and numerical approaches. The findings indicate that elevating the substrate temperature and intensifying the electric field can modify the evaporation rate of droplets via distinct mechanisms: the temperature field governs droplet evaporation by increasing the heat flux and changing droplet surface tension, whereas the electric field predominantly enhances or inhibits droplet evaporation by affecting the droplet’s surface tension and deformation. According to the Rayleigh limit, charge accumulation reduces the droplet’s surface tension, thereby accelerating evaporation. Conversely, greater deformation resulting from a stronger electric field increases the thermal resistance of the droplet, which dampens heat transfer and inhibits droplet evaporation. Furthermore, an excessive electric field may induce oscillation or droplet breakup. Simulations of droplet evaporation under an electric field further revealed that an increased electric field significantly influences the internal flow of the droplet. A low Peclet (Pe) number suggests that internal flow has a negligible effect on the temperature distribution compared to the impact of heat conduction. This research provides critical insights into the precise manipulation of droplet evaporation.