Effects of Liquid Transpiration Cooling on Heat Transfer to the Diverging Region of a Porous-Walled Nozzle

This research effort investigated the effects of evaporation of water on the heat transferred to the wall of the diverging portion of a porous walled nozzle The AFIT High Pressure Shock Tube was used with a two-dimensional Mach 3 nozzle. One flat surface of the nozzle was fitted with a layer of porous stainless steel from the nozzle throat to the exit. This porous material was saturated with water to simulate liquid transpiration cooling. Surface temperature data was taken in this region using fast response coaxial thermocouple. Heat transfer was determined from the surface temperature history. Data was taken for stagnation pressures ranging from 2.0 to 5.2 MPa. The effectiveness of the cooling diminished with increasing stagnation conditions. Reduction in convection heat transfer coefficient ranged from 10% at higher stagnation pressures to 130% at the lowest stagnation pressure tested