Enhanced flow boiling heat transfer with jet impingement on micro-pin-finned surfaces

Experiments were conducted to study the performance of subcooled flow boiling heat transfer with jet impingement of FC-72 over silicon chips (10 x 10 x 0.5 mm(3)). Four kinds of micro-pin-fins with dimensions of 30 x 60, 30 x 120, 50 x 60, 50 x 120 mu m(2) (thickness tx height h) were fabricated on the chip surfaces by using the dry etching technique. The experiments were made at two different liquid subcooling (25 degrees C and 35 degrees C), three different crossflow velocities V-c(0.5, 1, 1.5 m/s) and three different jet velocities V-j (0,1, 2 m/s). A smooth surface was also tested for comparison. The results show that both the microstructure and impingement give a large enhancement on heat transfer. The maximum allowable heat flux increases with the velocity and liquid subcooling. For a fixed V-c, the enhancement degree increases with V-j especially for V-c = 0.5 m/s, V-j = 2 m/s. As V-c increases, the heat transfer enhancement of jet impingement weakens and the increase rate of CHF (the critical heat flux) also decreases. The largest value of q(max) (the maximum allowable heat flux) can reach 167 W/cm(2) for chip with the fin dimension of 50 x 120 mu m(2) at the condition of V-c = 1.5 m/s, V-j = 2 m/s and liquid subcooling of 35 degrees C. (C) 2011 Elsevier Ltd. All rights reserved.