Experimental investigation on heat transfer and pressure drop characteristics of confined jet impingement boiling on hybrid-structured surface

In this study, confined jet impingement boiling experiments are carried out using ammonia for the heat dissi-pation of high-heat-flux hotspot. A hybrid-structured surface with triangular prism-convex structure in the stagnation zone and microchannel structure in the wall jet zone is designed for heat transfer enhancement. Utilizing the advantages of jet impingement and microchannel flow boiling, the temperature of the heating surface is maintained below 86.5 degrees C when subjected to a hotspot heat flux of 1367 W/cm2, verifying the promising cooling performance of jet boiling on hybrid-structured surface. Effects of jet velocity (0.34-7.07 m/s), heat flux (752, 1064, and 1367 W/cm2), saturation temperature (22, 26, and 30 degrees C), and inlet condition (sub -cooled, near-saturated, and two-phase state) are also investigated. Increasing jet velocity and saturation tem-perature are beneficial to the heat transfer of jet boiling in the central stagnation zone. For high jet velocity flow (V > 2.3 m/s), the junction-to-fluid thermal resistance is the lowest at heat flux of 753 W/cm2; while for low jet velocity flow (V < 2.3 m/s), the best cooling performance is obtained at heat flux of 1367 W/cm2. The pressure drop increases with jet velocity and inlet vapor quality, and shows no significant dependence on heat flux and saturation temperature.