Annals of the Assembly for International Heat Transfer Conference 13

ISBN 1-56700-225-0 / CD 1-56700-226-9

Year 2006

M. Imraan
Department of Mechanical Engineering, The University of Auckland Private Bag 92019, Auckland, New Zealand

R. N. Sharma
Department of Mechanical Engineering, The University of Auckland Private Bag 92019, Auckland, New Zealand

Characteristics of heat transfer from a slot jet of air from a contoured nozzle (of width w) impinging on a circular cylinder (of diameter d = w), located between confining walls (at varying separation distance H apart) and at a range of spacing z from the jet exit, was studied experimentally and computationally for Reynolds number Re in the range of 1000 − 12000. The results reveal that for most cases, the slot jet impinging on a cylinder in confined space yields higher average heat transfer when compared with the uniform cross flow case on the basis of identical slot jet and uniform cross flow velocities. The heat transfer rates with confinement however was almost always found to be lower than the corresponding slot jet impingement without confining walls. Furthermore, in the Reynolds number range studied, it was found that a dimensionless confinement spacing H/d = 10 exists which consistently exhibits a minimum in cylinder heat transfer over all the non-dimensional jet exit to cylinder spacing z/w. It was also found that jet impingement does not always enhance heat transfer rate, but may in fact reduce it under certain conditions. A strong dependence of heat transfer on jet exit to cylinder spacing z/w was also found, and for z/w = 5 a maximum in heat transfer was consistently obtained at all the confinements and Reynolds numbers studied. Furthermore, at z/w = 4, a significant drop in heat transfer relative to those at z/w = 3 and 5 was consistently observed.

JET-28 pages DOI: 10.1615/IHTC13.p16.270 Download article

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