Enhancement of heat transfer on micro- and macro- structural surfaces in close-loop R410A flashing spray cooling system for heat dissipation of high-power electronics

High effective spray cooling system is urgently required for the thermal management of high-power electronics in small areas. These electronic devices need to be cooled at functional operating temperature, and it is particularly lacking in current spray cooling studies. For this purpose, a hybrid structural surface that integrates micro-roughness and macro-structure is investigated in close-loop R410A flash spray cooling system. The heat transfer performance is tremendously enhanced as the increase of roughness on flat surface until it reaches the value of 3.5 mu m. Meanwhile, a novel tetrahedral fin surface is proposed and compared with modified surfaces including flat, wavy, square, and pyramid fins. It performs high heat flux of 411.2 W cm- 2, a 101.5 % enhancement over the flat surface. What's more, the hybrid structure with 3.5 mu m roughness can further improve the maximum critical heat flux and heat transfer coefficient by up to 424 W cm-2 and 814 kW K-1 m- 2, respectively, while keeping the surface temperature below 50 degrees C. Besides, correlations and energy efficiency are studied to explore the performance of structural surfaces. These findings in a wider range of roughness and macrostructure will provide insights to guide the surface modification in flash spray cooling.