Effects of hole spacing on spatially-resolved jet array impingement heat transfer

Data which illustrate the effects of hole spacing on spatially-resolved heat transfer from an array of jets impinging on a flat plate are presented. Considered are Reynolds numbers ranging from 8200 to 30,500, and Mach numbers from 0.1 to 0.6. The spacing of the holes used to produce the impinging jets is either 8D or 12D in both the streamwise and spanwise directions. Local and spatially-averaged Nusselt numbers show strong dependence on the impingement jet Reynolds number for both situations, with negligible variations between Ma = 0.1 and 0.2 at constant Reynolds number. Experimental data, taken at Mach numbers greater than 0.2, while maintaining constant Reynolds number, show that Mach number has a significant impact on overall heat transfer. For 8D spacing, heat transfer is augmented significantly as the Mach number increases, and for hole spacing of 12D, heat transfer also increases significantly as the Mach number increases. Also included is a new correlation, based on that of Florschuetz et al. [L.W. Florschuetz, C.R. Truman, D.E. Metzger, Streamwise flow and heat transfer distributions for jet array impingement with crossflow, ASME Trans.–J. Heat Transfer 103 (1981) 337–342], as an impingement design tool.