Effect of Jet Reynold’s Number on Nusselt Number for Convective Impingement Air Cooling on a Hot Plate

Abstract

Studies were carried out to determine the Convective Heat Transfer Coefficient, h, under multiple jets of impinging cold air on a target heated flat plate. Tests were run with air- distribution plates with hole diameters, d, of 1.5mm, 2.0mm, 2.5mm and 3.0mm. The target plate is a carbon-steel flat plate of 6mm thickness, instrumented with a total of three Chromel-Alumel K-type thermocouples. The plate is electrically heated using a variable supply current input. Test were run at various cooling air flow rate G, between 1.0kg/m³, sec to 3.0kg/m³, sec. Distribution plate-to-target plate distance Z(mm), was varied between 100mm to 200mm. Heat input to the target plate Q Watt, was varied to give a heat flux rate between 10 to 100 watts. Results obtained were reduced and analyzed by evaluating for the dependence of h on the impingement jet diameter,Jet Reynolds Number, and the coolant mass flow rate G. Correlations were done, using the dimensionless parameters of Nusselt Number, Reynolds Number and Prandtl Number. Based on the results obtained, it is proposed that within the Reynolds Number range of 1500 to 2000, correlation may be made with:-   = 0.15Re^0.58Pr^0.33

Keywords: Reynold’s Number, Nusselt Number, Prandtl Number, Impingement, Cooling, Heat transfer Coefficient