Comparison of Heat Transfer and Thermal Performance of a Double Wall Cooling Scheme at Large Impingement Heights

Abstract

Impingement channel cooling shows great potential for removing large amounts of heat from turbine airfoils and combustor liners. 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 transfer 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 chargecoupled device (CCD) camera, and compared to available literature. Results are presented for average jet based Reynolds numbers between 7,500 and 15,000. All experiments were carried out on a large scale triple streamwise row, 15 spanwise row impingement channel, with X/D of 5, Y/D of 2, and Z/D of 8 and 10, with a channel width of Y c/D of 8. Results showed that the channel with a height of 8 diameters, and low 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, at low Reynolds number, considering constant pressure conditions.