Impingement/Effusion Cooling: The Influence of the Number of Impingement Holes and Pressure Loss on the Heat Transfer Coefficient

Abstract

Measurements of the overall heat transfer coefficient within an impingement/effusion cooled wall are presented. The FLUENT CFD computer code has been applied to the internal aerodynamics to demonstrate the importance of the internal recirculation in the impingement gap. This generates a convective heat transfer to the impingement jet and measurements of this heat transfer plate coefficient are presented that show it to be approximately a half of the impingement/effusion heat transfer coefficient. The influence of the relative pressure loss or X/D between the impingement and effusion was investigated, for an effusion X/D of 4.67 and a Z of 8 mm, and shown to be only significant at high G where a reduction in h of 20% occurred. Increasing the number of holes, N, in the impingement/effusion array at a constant Z of 8 mm reduced h by 20%, mainly due to the higher Z/D for the smaller holes at high N. Reduced numbers of impingement holes relative to the effusion holes, in a ratio of 1 to 4, were shown to have a small influence on h with a maximum reduction in h of 20% at high G and a negligible effect at low G.