An experimental study of spray cooling using FC-72

This manuscript presents the experimental results of the spray cooling performance of a pin-finned surface and a smooth surface in a close loop spray-cooling device. Five pores of either 0.23mm or 0.56mm diameter were made on the spraying device. Dielectric fluid, FC-72, was used as the working fluid and the test section was maintained at 50°C saturation temperature. The total flow rate varied between 24.5 and 99.1 ml/min, and the heat flux varied from 60 to 800 kW/m². The pin-fin surface was made on a 2mm thick copper plate by etching to form 100 micron squared pin fins of 80 micron fin height. The smaller pores (0.23 mm diameter) of the liquid distributor created stronger impingement on the test surface, and yielded better spray evaporation performance at low heat fluxes. The larger pores (0.56 mm) provided thicker liquid layer on the surface, and resulted in higher performance at high heat fluxes. The larger pores (0.56 mm) also resulted in a greater critical heat flux than the smaller pores (0.23mm). The pin-finned surface yielded about 10∼40% enhancement as compared with the smooth surface for heat flux > 200 kW/m².