WINGLET-PAIR TARGET SURFACE ROUGHNESS INFLUENCES ON IMPINGEMENT JET ARRAY HEAT TRANSFER

Abstract

Vortex generator target surface roughness elements, with sizes on the same approximate scale as impingement hole diameter, are utilized within an array along target surfaces employed with impingement jet array cooling. Two different types of vortex generators are used: rectangular winglet pair and delta winglet pair, where of these is utilized with a common flow upward orientation (where the upflow region is located between the two vortices within each induced vortex pair). The impingement plate employed contains round holes, such that holes in adjacent streamwise rows are staggered with respect to each other. The vortex generator target surface results are compared to experimental data obtained with target surfaces with arrays of small triangle roughness elements. The arrays of small triangle roughness are employed with different roughness heights, both with and without the addition of large pin roughness elements. As such, new small triangle roughness data, and new vortex generator roughness data, are provided for different impingement jet Reynolds numbers (based on impingement jet hole diameter) of 9 × 102, 15 × 102 to 16 × 102, 5 × 103 to 51 × 102, and 11 × 103 to 111 × 102. Resulting variations in performance are then related to different roughness element arrangements, with different ratios of wetted surface area to flat projected area, as well as to target surface internal conduction, and to the increased three-dimensional transport and mixing produced by arrays of target surface roughness elements.