Numerical investigation on effect of impingement plate covered by a porous layer in a multiple impinging jet flow

The impinging jet array is capable of enhancing heat transfer rates over the impinging surface. A sever challenge of such cooling method is that it does not transfer the heat across the target plate as uniformly as required in many applications. The main objective of the current numerical research is to study the effects of covering the impingement surface by a porous layer in order to increase the heat uniformity throughout the surface without losing the advantage of high heat transfer rates in a multiple impinging jet flow. The porosity, permeability and thickness of the porous layer are considered. The standard deviation of local Nusselt numbers compared to the average value is used as a measure to evaluate the uniformity of heat transfer along the plate. A performance evaluation factor is proposed to simultaneously account for uniformity as well as total rate of heat transfer. The results show that lowest evaluation factor of 0.137 is obtained once the flow channel is fully covered by the porous medium and the permeability and porosity are at their lowest values of k=1.76*10-12 and ԑ=0.2, respectively. The highest heat transfer performance is obtained for the case when the channel is half filled with the porous layer and the coefficient of permeability and porosity are at their lowest (k=1.76*10-12) and highest (ԑ=0.8) levels, respectively.