Enhancement of flow-jet combined boiling heat transfer of FC-72 over micro-pin-finned surfaces

For highly efficient solving of the power dissipation problem of electronic components with high heat flux, experimental study of the flow-jet combined boiling heat transfer on silicon chips was conducted. Micro-pin-fins with dimensions of 30×60 μm² and 30×120 μm² (thickness × height) were fabricated on the chip surfaces by the dry etching technique. The experiments were made at three different cross-flow velocities V_c (0.5, 1.0, 1.5 m/s) and different jet velocities V _j (0-2 m/s) with two liquid subcooling ΔTsub (25°C and 35°C). A smooth surface was also tested for comparison. The micro-pin-fins showed a considerable heat transfer enhancement due to an increase in effective heat transfer surface area caused by micro-convection around micro-pin-fins. The maximum allowable heat flux q_maxis increased and the wall superheat is decreased greatly. For a given V_c, the heat transfer enhancement is more significant as Vj increases, but the q_max increment decreases as V_c increases. The fin efficiency decreases as V_cor/and V_j increases or the heat flux q increases. The maximum q _max can reach 161 W/cm² at Vc ₌= 1.5 m/s, V_j = 2 m/s, ΔT_sub = 35°C for chip PF30-120.