Local Heat Transfer From a Rotating Disk in an Impinging Round Jet

Abstract

The results of an experimental investigation of local convective heat transfer from the surface of a rotating disk in an impinging free round air jet, issuing from a long tube, are reported. Using a transient heat transfer method applied to the ring-shaped h-calorimeter (as a single lumped capacitance element) measurements of convective heat transfer rates were made for five impingement radius (fixed) to tube diameter ratios for a range of rotational and jet Reynolds numbers. In the pure impingement-dominated regime, where the rotation of the disk does not show an effect on heat transfer, the velocity ratio is ur/uj ≤ (1 − 2 × 10−4 Re2/3) (1 − 0.18 r/d), where ur = tangential velocity of the disk at the jet impingement radius r, uj = average exit velocity of jet, and d = jet tube diameter. In this regime, the local heat transfer on the rotating disk can be strongly enhanced by jet impingement. For ur/uj ⪞ 5, the effect of the jet impingement on heat transfer can be neglected. The discussion of the heat transfer results has been supported by smoke flow visualization.