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Droplet evaporation can be used to transfer large amounts of energy since heat is transferred across a thin liquid film. Spreading the drop over a larger area can enhance this heat transfer. One method of accomplishing this is to dissolve gas into the liquid. When the drop strikes the surface, a gas bubble nucleates and can grow and merge within the liquid, resulting in an increase in the droplet diameter. In this study, time and space resolved heat transfer characteristics for a single droplet striking a heated surface were experimentally investigated. The local wall heat flux and temperature measurements were provided by a novel experimental technique in which 96 individually controlled heaters were used to map the heat transfer coefficient on the surface. A high-speed digital video camera was used to simultaneously record images of the drop from below. The measurements to date indicate that significantly smaller droplet evaporation times can be achieved.

Heat transfer by phase change is an attractive method of cooling since large amounts of heat can be removed with relatively small temperature differences. Droplet cooling is one method whereby very high heat transfer rates coupled with good temperature uniformity across surfaces can be provided, which is important in microelectronics where even small temperature gradients across the chip can cause component failure. When a droplet strikes a heated surface, it flattens into a splat whose thickness is much smaller than the diameter of the droplet, and high heat fluxes can be obtained due to the formation and evaporation of a thin liquid film on the heated surface. In this study, time and space resolved heat transfer characteristics for a single droplet striking a heated surface were experimentally measured, and the results are compared to a model of droplet evaporation.