Unraveling droplet drying kinetics under electric fields: A study on moisture content and evaporative flux profiles

Abstract

This study investigates the influence of electric fields (EF) on the drying kinetics and evaporative flux of CuSO₄.5H₂O aqueous droplets at different solid contents. The drying behavior of pendant droplets was examined under both convective and diffusive conditions with varying EF intensities. The results indicate that the EF increases the surface area of the pendant droplet during both drying scenarios. In diffusive drying, the drying kinetic is different with and without EF. Indeed, the EF reduces moisture removal and evaporative flux in the early stages for highly concentrated droplets having high response to the electric field. However, as the droplet dries, the moisture removal rate and evaporative flux increase and converges to constant values, a trend observed under no-field conditions. In convective drying, the application of an electric field maintained a constant moisture removal rate until the droplet had lost 30 % of its water content, while in the no-field conditions this rate decreased up to 25 % as the drying progresses until the same water loss. Furthermore, when the electric field is applied, the evaporative flux increases with the drying time to reach constant values with the drying time. As a conclusion, this work uniquely combines pendant droplet drying under controlled dying conditions and high electric fields with a real time mass measurement and image-based surface area and deformation tracking, providing experimental access to electrohydrodynamic evaporation fluxes not previously reported in literature.