Investigation of the heat-island effect for heat-flux measurements in short-duration facilities

This paper presents the results of an experimental investigation designed to determine the possible influence of a surface-temperature discontinuity on the heat-flux history inferred from the temperature history of a miniature thin-film heat-flux gage (painted on an insulator) embedded in the surface of a metallic component. The resulting surface material discontinuity has the potential of causing a heat-island effect. Simultaneous measurements of the heat-flux history at selected locations along the midspan of a representative turbine airfoil (metal) were performed using continuous strip-type contoured inserts (without temperature discontinuity) and button-type inserts (with temperature discontinuity). Measurements are reported for two Reynolds number conditions. The experimental results suggest that for the experimental conditions of interest to gas turbine research in short-duration facilities, the influence of a potential heat-island on the measured heat flux is insignificant.