LOCAL HEAT TRANSFER OF JET IMPINGEMENT COOLING WITH FILM EXTRACTION FLOW IN A ROTATING CAVITY

摘要

An experimental investigation was carried out to examine the heat transfer characteristics on impingement cooling with extraction flow in a rotating cavity. Two H/d configurations of 3.0 and 6.0 were conducted. The Reynolds number based on the inlet velocity of the jet air and the diameter of the impingement hole was fixed at 2000. The test model rotated at five different speeds, 0, 200, 400, 600, and 800 rpm, in two reversal directions, respectively. The local heat transfer coefficient on the target surface was measured by a transient method with thermochromic liquid crystal. Experimental result reveals that the jet flow could be bent by the Coriolis force and consequently the heat transfer would be weakened by rotation. The heat transfer coefficient of H/d = 3 configuration is higher than that of H/d = 6 configuration for either stationary or rotational conditions. For the structure of H/d = 6.0, the stagnation point has an offset of 1.5d due to the bending of the jet flow. Compared to the stationary results, the maximum of the local heat transfer coefficient is reduced by 38.3% and the averaged heat transfer coefficient is reduced by 44.5% at 800 rpm. For the structure of H/d = 3.0, the offset of the stagnation point is small, but the spreading rate of the jet core is enhanced by rotation. Although not as strongly as the structure of H/d = 6.0, the heat transfer is still weakened by rotation. The maximum of local heat transfer coefficient is decreased 29.2% and average heat transfer coefficient is decreased 27.8% at 800 rpm compared to those at 0 rpm.