The Effect of Upstream Thermal Boundary Condition on Convective Heat Transfer Coefficient on a Film-Cooled Flat Plate

The convection heat transfer coefficient on a film-cooled flat plate with and without upstream surface heating is investigated using liquid crystal thermography. The experiments were conducted with a turbulent boundary layer and low freestream turbulence at mass flux ratios of 0.5, 1.0, and 1.5 and density ratio of unity, using cylindrical holes at a 30° injection angle. Results show that upstream surface heating produces a lower convective heat transfer coefficient as expected, and the spanwise-averaged heat transfer enhancement factor is increased by up to 5% over approximately 60% of the film-cooled region. As blowing ratio increased, this area of increased enhancement factor moved further downstream of the holes.