Supersonic Two-Phase Impinging Jet Heat Transfer

The experimental heat transfer rates from a supersonic two-phase impinging air jet with disperse droplets are presented. The experimental configuration consists of an expanding disperse mixture of air and water through a converging–diverging nozzle, designed for Mach 3.26 with a liquid to air mass flow ratio ranging from 1.28% to 3.83%, impinging upon a thin film heater constructed of nichrome. The spatially varying heat transfer coefficient is measured, and peak values are on the order of $200,000 W/m2K$⁠. Two distinct regions of heat transfer are identified, one dominated by the jet impingement flow and another dominated by thin film heat transfer. The heat transfer coefficient of an impinging jet with dry air and no droplets is measured during the investigation as well. The heat transfer results are compared, and it is demonstrated that the addition of disperse water droplets to the jet significantly increases the heat removal capability of the jet as well as smoothing the spatial temperature distribution of the heater surface. As much as an order of magnitude increase in heat transfer coefficient is observed near the centerline of the jet and a factor of 3–5 increase is seen at a distance of approximately 4 nozzle diameters from the jet. The fundamental heat transfer coefficient measurements should benefit applications involving supersonic two-phase jets for high heat flux thermal management.