3. Electronic Theses and Dissertations (ETDs) - All submissions

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Stagnation heat transfer on a concave surface cooled by unconfined slot jet
(2015) Aziz, Maurel Nguepnang
Heat transfer at the stagnation point on a concave surface and on a flat plate subjected to un-confined slot jet impingement is characterized and compared at a fixed jet Reynolds number of ReB = 20000. The concave surface diameter-to-slot width ratio is fixed at 9.0 whilst the slot exit-to-target surface distance, H/B, varies from 0.5 to 20.0. In particular, the non-monotonic variation of heat transfer at the stagnation point with H/B is fluidically explained. The present results clarify that the deflection zone formed on the target surface as a result of the jet impingement leads to the upstream shift of the peak in turbulence strength that exactly coincides with the peak of heat transfer at the stagnation point. With the concave surface, the impinging jet deflected radially on the surface is re-entrained into the incoming jet due to the curvature, which causes the shortening of the potential core of the slot jet and the longitudinal upstream shift of the peak in turbulence strength compared to the flat plate. Therefore, the peak in heat transfer at the stagnation point occurs at shorter H/B on the concave surface than on the flat plate.