Recent Developments in Impingement Array Cooling, Including Consideration of the Separate Effects of Mach Number, Reynolds Number, Temperature Ratio, Hole Spacing, and Jet-to-Target-Plate Distance

Abstract

Presented are data that illustrate the effects of Mach number, Reynolds number, temperature ratio, hole spacing, and jet-to-target-plate distance on surface Nusselt numbers produced by an array of jets impinging on a fl at plate. The local and spatially averaged Nusselt numbers, and local and spatially averaged recovery factors are unique because: (i) data are obtained at constant Reynolds number as the Mach number is varied, and at constant Mach number as the Reynolds number is varied, (ii) data are obtained at constant Reynolds number and constant Mach number, as the temperature ratio is varied, (iii) data are obtained at constant temperature ratio, Mach number, and Reynolds number, as the impingement hole spacing is varied, (iv) data are obtained as the jet-to-target-plate distance is varied as Reynolds number, Mach number, hole spacing, and temperature ratio are constant, and (v) data are given for jet impingement Mach numbers up to 0.74, and for Reynolds numbers up to 60,000. Also included are crossfl ow-to-jet mass velocity ratio data and discharge coeffi cient data. Impingement hole spacings are 5D, 8D, and 12D in the streamwise and spanwise directions, with jet-to-target-plate distances of 1.5D, 3D, 5D, and 8D. Local spatially resolved and spatially averaged Nusselt numbers, measured using infrared thermography and energy balance techniques, show strong dependence on the impingement jet Reynolds number for each situation as the jet Mach number is maintained constant. Nusselt numbers show negligible variations with Mach number, between Ma = 0.1 and 0.2, however, data taken at Mach numbers greater than approximately 0.25 (as the Reynolds number is held constant)