In this project, we perform droplet evaporation experiments and conduct numerical and CFD simulation studies to study the effect of an applied electric field on the evaporation of stationary and impacting drops on a heated surface. The objective is to develop new techniques for enhancing phase change heat transfer in industrial applications. 

Phase change processes such as evaporation, boiling, and condensation are extremely important heat transfer mechanisms in many industrial applications. Further, they automatically occur in other natural and man-made processes. The physics at the liquid-vapor interface and at the solid-liquid-vapor three-phase contact line is of primary importance in all of these processes. Although the rate of evaporation from or condensation to a liquid-vapor interface depends on the interfacial gas kinetics, it is primarily limited by the rate of heat transfer in the liquid thin film adjacent to the three-phase contact line. Further, the ultrafast transient nature of bubble (in boiling) or drop (in condensation) growth makes the dynamics of the contact line an extremely important factor in ultimately determining the values of different phase change heat transfer performance parameters. For example, the value of the critical heat flux (CHF) for liquid boiling on a hot solid surface is now widely believed to depend, among other factors, on the timely rewetting of a hot dry spot on the boiling surface by the surrounding liquid. Since this rewetting is achieved by an advancing three-phase contact line, the dynamic flow and thermal behavior of this region takes on increased importance. The phase change heat transfer performance parameters such as the critical heat flux (in boiling) and the heat transfer coefficient (in boiling and condensation) can potentially be enhanced by actively manipulating the dynamic flow and thermal behavior of the three-phase contact line and the surrounding region. In this project, we employ experimental and computational techniques to explore the effect of an applied high electric field on the behavior of a liquid drop impacting a hot solid surface. High-speed optical and infrared imaging techniques are employed for visualizing the flow and measuring the temperatures, respectively. An electromagnetic model is developed to explain the effect of the electric field on the liquid-vapor interface adjacent to the contact line. The results and insights obtained in this project can have a significant impact on several high-heat-flux heat transfer and thermal management technologies being used in industry and research.