A NUMERICAL STUDY OF CONVECTIVE HEAT TRANSFER ENHANCEMENT WITH JET IMPINGEMENT COOLING USING POROUS OBSTACLES

Jet impingement over porous heat sinks has gained a lot of attention in the recent past, due to the convective heat transfer enhancement stated in the literature. However, it is not clear form the studies whether the reported enhancement is due to the presence of porous heat sinks alone or due to the observed inconsistencies in the geometric parameters considered for comparison. The present numerical work investigates three different configurations of jet impingement cooling with porous blocks as heat sinks in the stagnation zone, as flow obstacle along the bottom plate and as flow obstacle along the top plate in the wall jet region. The results show that the enhancement in convective heat transfer is only possible in the jet impingement configuration with porous obstacle along the top wall. The other two configurations are actually deteriorating the convective heat transfer. Jet impingement with porous blocks as flow obstacles along the top confining wall enhances the convective heat transfer by 55.5% in forced convection and 3% in mixed convection regime. The solid obstacles replacing the porous block in the same configuration shows enhancement up to 68% in forced convection and 7% in mixed convection regime. However, the heat transfer performance ratio, eta based on convective heat transfer performance with respect to pressure drop has proved jet impingement with porous obstacles is beneficial over solid obstacles, in forced convection regime. In mixed convection regime, both porous and solid obstacles do not show any appreciable enhancement in the convective heat transfer and are best suggested for localized cooling applications.