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 internal recirculation in the impingement gap. This generates a convective heat transfer to the impingement jet. Measurements of this heat transfer plate coefficient are presented that show it to be approximately half of the impingement/effusion heat transfer coefficient. The influence of the relative pressure loss or X/D between the impingement and effusion walls 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 percent occurred. Increasing the number of holes N in the impingement/effusion array at a constant Z of 8 mm reduced h by 20 percent, 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 percent at high G and a negligible effect at low G.