Effect of Temperature Ratio on Jet Array Impingement Heat Transfer

Abstract

This paper consider the effects of temperature ratio on the heat transfer from an array of jets impinging on a flat plate. At a constant Reynolds number of 18,000 and a constant Mach number of 0.2, different ratios of target plate temperature to jet temperature are employed. The spacing between holes in the streamwise direction X is 8D, and the spanwise spacing between holes in a given streamwise row Y is also 8D. The target plate is located 3D away from the impingement hole exits. Experimental results show that local, line-averaged, and spatially averaged Nusselt numbers decrease as the Twa∕Tj temperature ratio increases. This is believed to be due to the effects of temperature-dependent fluid properties, as they affect local and global turbulent transport in the flow field created by the array of impinging jets. The effect of temperature ratio on crossflow-to-jet mass velocity ratio and discharge coefficients is also examined.