Comparison of Heat Transfer Coefficient and Thermal Performance of a Narrow Impingement Channel

Abstract

Impingement channel cooling shows great potential for removing large amounts of heat from turbine airfoils. This comes at the expense of a large pressure drop required across the jet plate. The consideration of both heat transfer levels and pressure losses is then important when considering the implementation of this cooling scheme. This paper examines the local and averaged effects of channel height in the presence of side walls on heat transfe r coefficients and the additional work required to achieve these levels . Local temperature distributions on target and side wall surfaces were measured using temperature sensitive paint and recorded via a scientific grade charge -coupled device (CCD) camera, and compared to available literature. Streamwise pressure distributions were recorded and used to explain heat transfer trends and determining pumping power requirements. Results are presented for average jet based Reynolds numbers between 17,000 and 45,000. All experiments were carried out on a large scale single row, 5 hole impingement channel, with X/D of 15, Yc/D of 4, and Z/D of 1, 3 and 5. Results showed that the channel with a medium channel height, and high Reynolds number yields both high heat transfer coefficients, at a minimal relative pumping power penalty. On the other hand, the smallest channel height performs best considering constant pressure conditions.