Heat Flux Determination from Pressure Data for a Transpiration Cooling Environment

This paper describes a new heat flux gauge for application in transpiration cooled environments. The sensor is a transpiration cooled porous element and the surface heat flux is determined from the plenum pressure trace. The sensor is characterized using the non-integer system identification method. It was calibrated at four constant mass flow rates, i.e., 15, 30, 45, and 60 mg/s, of nitrogen. Toward higher mass flow rates, stronger system response is observed. The sensor performance was determined by the analysis of a well-known Gauss function-shaped heat flux profile. The deviation is below 18%. The sensor was applied to heat flux measurements in the plasma wind tunnel PWK4 at the University of Stuttgart. The stagnation point heat flux was determined to be 20 to 395 kW/m2 for decreasing mass flow rates. From this data, the local freestream mass-specific enthalpy of 10.5 MJ/kg and uncooled surface heat flux of 1042 kW/m2 were calculated based on the stagnation point heat flux reduction over the mass flow rate increase.