Arvind Pattamatta

An experimental study using Liquid crystal thermography technique is conducted to study the convective heat transfer enhancement in jet impingement cooling in the presence of porous media. Aluminium porous sample of 10 PPI with permeability 2.48e-7 and porosity 0.95 is used in the present study. Results are presented for two different Reynolds number 400 and 700 with four different configurations of jet impingement (1) without porous foams (2) over porous heat sink (3) with porous obstacle case (4) through porous passage. Jet impingement with porous heat sink showed a deterioration in average Nusselt number by 10.5% and 18.1% for Reynolds number of 400 and 700 respectively when compared with jet impingement without porous heat sink configuration. The results show that for Reynolds number 400, jet impingement through porous passage augments average Nusselt number by 30.73% whereas obstacle configuration enhances the heat transfer by 25.6% over jet impingement without porous medium. Similarly for Reynolds number 700, the porous passage configuration shows average Nusselt number enhancement by 71.09% and porous obstacle by 33.4 % over jet impingement in the absence of porous media respectively.

In this paper, an optimization study involving five variable parameters which are critical in evaluating the thermal performance of the air jet flow impingement over porous heat sinks in mixed convection regime is presented. The variable parameters include porous block height, channel height, jet width, porosity and Darcy number. The Lattice Boltzmann method for porous media is used as the numerical tool to simulate the objective functions in terms of Nusselt number and pressure drop. Kriging method combined with Genetic algorithm is used to generate the optimal Pareto plot. Three optimal cases from the pareto plot showing maximum, minimum and optimum Nusselt numbers and pressure drop are considered. The optimized results show that the porosity and Darcy number are relatively invariant along the pareto surface. Thus the geometry of the channel and porous block are the most significant parameters governing Nusselt number and pressure drop values. The results from optimization corresponding to the three optimal cases are analyzed in detail. The local variation in Nusselt number for these cases is also plotted to understand the effect of the channel and porous heat sink parameters on heat transfer.