Impingement cooling and heat transfer measurement using transient liquid crystal technique

Abstract

A heat transfer study on jet impingement cooling is presented. The study focuses on the effect of impingement jet flow rate, jet angle, and flow exit direction on various target surface heat transfer distributions. A two-channel test section simulates a series of jets impinging on a target surface. This work is mostly experimental. The experiment is done on three configurations: orthogonal impinging jets impinge on a smooth impingement target surface, +45[] or-45[] inclined impinging jets impinge on a smooth impingement target surface, and orthogonal impinging jets impinge on a target surface with coolant extraction holes. Each configuration is based on four Reynolds numbers between 4000 and 20000 and three flow exit orientations, namely one end open in the flow forward or flow backward direction, and both ends open. The effects of the different configurations on heat transfer are experimentally studied. A transient liquid crystal technique involving a single color capturing method is used in this study to obtain the detailed heat transfer coefficient. Results show that a higher Reynolds number increases heat transfer over the entire impingement target surface. The flow exit orientation with crossflow affects the heat transfer coefficient distribution. The impingement target surface with coolant extraction holes changes the local heat transfer distribution significantly compared with the smooth impingement target surface.