Abstract

Heat transfer results are presented for a rotating disk cooled with an impinging air jet directed on its free surface. In this study, local heat transfer distribution was investigated for a disk under the combination of rotation and jet impingement. The main focus considered here was cooling by pure rotation and the effect of location of the jet center relative to the disk center. Several important factors, such as rotational Reynolds numbers, jet Reynolds numbers, and jet-to-disk spacing were considered when the jet was positioned in different distances from the center of the disk. Disk rotational speed was varied from 250 to 4,000 rpm while three jet Reynolds numbers of 6,800, 24,000, and 48,000 were used. The jet was placed perpendicular to the disk surface at four different distances from the center of the disk. These distances were, zero cm (center-to-center), 3.5 cm, 6.9 cm and 8.9 cm. The jet-to-disk diameter ratio was about 0.09. This ratio was kept constant for this study.

The heat transfer measuring technique for this study was a transient technique which employed liquid crystals. A near uniform wall temperature thermal boundary condition was achieved for the disk by constructing an enclosed insulated oven with well-controlled heating elements and a sliding door on the top for easy access. The results of this investigation reveal that, in most cases for rotating disk with jet impingement cooling, local heat transfer distribution follows a parabolic function which has a minimum at a radial distance (from the disk center) of about one half of the disk radius.

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