An experimental study of heat transfer from a disk rotating in an infiniteenvironment including heat transfer enhancement by jet impingement cooling

Neat transfer results are presented for a rotating disk cooled with an impi nging air jet directed on its free surface. In this study local heat transf er distribution was investigated for a disk freely rotating in space. Then, the effect of rotation and jet impingement were examined. Several importan t factors, such as rotational Reynolds numbers, jet Reynolds numbers, jet-t o-disk spacing and finally location of the jet, center relative to the disk center were considered. The disk rotational speed was varied from 250 to 4 000 rpm while three jet Reynolds number of 6800, 24000, and 48000 were used . Jet-to-disk spacings of 2 to 8 jet diameters were selected while the jet- to-disk diameter ratio was kept constant at 0.09. The jet was placed perpen dicularly to the disk surface at four different distances from the center o f the disk. These distances were, zero cm (center-to-center), 3.5 cm, 6.9 c m and 8.9 cm. The heat transfer from the disk was measured using a transien t technique which employed liquid crystals. A nearly uniform nail temperatu re thermal boundary condition was achieved for the disk by constructing an enclosed insulated oven with well-controlled heating elements.