Measurement of local Nusselt number and local recovery factor for impinging multiple compressible jets

Abstract

In the present study the appropriate reference temperature is identified for the compressible impinging jet. Using the measured reference temperature, local recovery factor is calculated. The steady state thin metal foil technique is used for the measurement of target plate temperature. In this study, the effect of Mach number (Ma) at a constant Reynolds number (Re) and the combined effect of Mach number and Reynolds number on the heat transfer rate are investigated. For both the cases, jet-to-plate distance is varied from z/d = 5 to 12. For the first case (effect of Mach number at a constant Re = 20,000), Ma is varied from 0.15 to 0.85. In the second case (combined effect of Mach number and Reynolds number), Ma is varied from 0.2 to 0.78 and the corresponding Re variation is 7200 to 29,000. At a constant Reynolds number, the heat transfer coefficient increases with the increase in the Mach number. For a given Mach number and Reynolds number, the heat transfer rate decreases with the increase in the jet-to-plate distance. The recovery factor remains unaffected by the Mach number and jet-to-plate distance in the case of the concurrent variation of the Mach number and Reynolds number.