Finned and unfinned thermal resistances of a metal foam under jet impingement conditions

Heat transfer in a flat plate with metal foam under impinging jet conditions is a complex combination of conduction (finned) and convection (unfinned) heat transfer. This study reports an analytical approach for the quantification of finned and unfinned heat transfer from a targeted plate with metal foam under impinging jet conditions. Along with the quantification of heat transfer modes, the interstitial heat transfer, the efficiency of metal foam as a fin, and thermal resistances are also quantified analytically. The analysis is carried out for rectangular slot jet and multiple air jet impingement conditions. The varying parameters are jet to plate spacing, metal foam thickness and Reynolds number. The results suggest that for the slot jet case, the finned and unfinned heat transfer is around 70 and 30 percent of the total heat transfer independent of the foam thickness. However, for multiple jet case, finned and unfinned heat transfer is around 50 percent each except for 12 mm thickness. The interstitial heat transfer coefficient and fin efficiency increase with a decrease in the thickness of the foam. For both slot and multiple jet impingement cases, the thermal resistance to unfinned heat transfer is more in comparison with the finned heat transfer. The presence of metal foam on the flat plate incenses the overall heat transfer by 2 times the smooth flat plate.