EXPERIMENTAL INVESTIGATION OF HEAT TRANSFER IN A ROTATING LATERAL OUTFLOW TRAPEZOIDAL CHANNEL WITH PIN-FINS

In this study, the heat transfer characteristics in a rotating lateral outflow trapezoidal channel with pin-fins, which is a typical model of the internal cooling passage in a turbine blade, were experimentally investigated under the Reynolds number range of 10,000 - 80,000, rotating speed range of 0 - 1000 rpm. The tested Re and Ro ranges are considerably extended from the previous experiences. For the non-rotating condition, the heat transfer characteristics of the leading and trailing sides of the internal channel are relatively uniform due to the different construction. On the inner smooth surface, at Re=30000 of nonrotating, the leading and trailing averaged Nusselt number of the point near the inlet is about 48% higher than that at the end of the channel, but on the outer pin-fin arrayed surface, the averaged Nusselt number decreases about 20.5%. For the rotating conditions, the heat transfer of inner leading surface significantly reduced due to the rotation-induced Coriolis force and coolant discharged from the channel along the outlets. Interestingly, with Reynolds number increases, the Nusselt number ratios decreases. When the rotating speed is 1000 rpm and the Reynolds number is 10000, 3000, 50000 and 70000, the Nusselt number ratios are 2.11, 1.40, 1.19 and 1.07 respectively. Moreover, the leading side of the inner smooth area exhibit a critical rotation number, in which the rotation weakened the heat transfer before the critical point and promoted heat transfer after the critical point. However, the critical rotation number varied with X/D.