Numerical Investigation of Impingement Heat Transfer Enhancement on a Flat Plate with an Attached Porous Medium

Abstract

The enhancement of impingement heat transfer on a flat plate covered with a thick layer of porous medium with or without a center hole was numerically investigated. The renormalization group turbulence model is selected for the fluid region while Forchheimer extended Darcy’s model is used for porous region. The numerical models were justified by comparisons with available experimental data. Computational results show that an attached porous medium with a center hole can effectively enhance jet impingement heat transfer while an attached thick porous layer without a center hole has detrimental effect. The physics of these results are supported and well explained by the detailed flow patterns. The most influential parameters in this heat transfer process include the jet Reynolds number and the center hole geometry (hole depth and jet-to-hole diameter ratio). A good hole geometry should well trap the jet and direct the coolant along the heated plate.

Impingement Cooling of a Semi-Spherical Concave Surface Covered by Porous Medium with a Jet Trapping Hole

“…4. This conclusion agrees with that of [3,4]. It should be mentioned that in the present study, a center through hole is always made whenever the target plate is covered with porous material.…”

“…The through hole is designed to trap the jet fluid so that it can reach the target plate and exchange heat which it more easily than the cases without a hole or with a shallower hole. It was shown in [3,4] that an attached porous medium with a center hole can effectively enhance jet impingement heat transfer on a flat plate when the cavity is deep enough, while an attached thick porous layer without a center hole has detrimental effect on heat transfer. When a comparison of the present results with that of a flat plate [4] (not shown for clarity of the figure) is made, it is found that for a target covered with thick porous material having a center trapping hole, the semi-spherical concave surface has about 20% -45% increase at the Defect and Diffusion Forum Vol.…”

“…As a result, less fluid is trapped to the center hole and some fluid impinges on top of porous surface. It has been shown in [3,4] that this part of fluid impinging on a porous surface helps to enhance heat transfer in the far field. This enhancement compensates the loss of heat transfer due to less fluid in the boundary-layer flow.…”

“…The Forchheimer extended Darcy's laminar model is adopted for the porous region and the renormalization group (RNG) ε − k turbulence model is selected for the fluid region. More discussions on the numerical model can be seen in [4].…”

“…For the enhancement of jet impingement heat transfer, many previous studies focused on a flat plate covered with a thin layer of porous medium which thickness is either very thin or in the order of the jet diameter [1,2]. Recent studies by Wu et al [3,4] showed that for a flat plate covered with a thick layer of porous material, the jet impingement heat transfer on the plate can be enhanced as long as a sufficiently deep trapping hole is manufactured. The stagnation Nusselt number could be increased up to 58.3% and the averaged Nusselt number increased up to 77.5% compared to that of bare plate impingement.…”