Confined Submerged Jet Impingement Boiling of Subcooled FC 72 over Micro Pin Finned Surfaces
Heat transfer characteristics of confined submerged jet impingement boiling of air dissolved FC 72 on heated micro pin finned surfaces are presented. The dimension of the silicon chips is 10 x 10 x 0.5 mm3 (length x width x thickness) on micro pin fins with the four dimensions of 30 x 30 x 60 mm3, 50 x 50 x 60 mm3, 30 x 30 x 120 mm3, and 50 x 50 x 120 mm3 fabricated by using the dry etching technique. For comparison, experiments of jet impinging on a smooth surface were also conducted. The results have shown that submerged jet impingement boiling gives a large heat transfer enhancement compared with pool boiling, and all micro pin fins showed better heat transfer performance than a smooth surface. The effects of jet Reynolds number, jet inlet subcooling, micro pin fins, and nozzle to surface distance on jet impingement boiling heat transfer were explored. For micro pin fins, the maximum allowable heat flux increases with jet Reynolds number and subcooling. The largest value of the maximum allowable heat flux of micro pin fins by submerged jet impingement boiling is 157 W/cm2, which is about 8.3 times as large as that for the smooth surface in pool boiling. Also, Nusselt number has a strong dependence on Reynolds number.