A Convection Calibration Method for Local Heat Flux Gages

An apparatus for calibrating local heat flux gages in convective air flows is described. Heat transfer from a “hot” gage to a “cold” fluid was measured using a guarded hot-plate technique. The system was used to calibrate Gardon-type circular foil heat flux gages of 1/8 in. and 1/16 in. outer diameters. The results indicate that the calibration curves are nonlinear, which is different from the linear calibration obtained using the standard radiation technique. The degree of nonlinearity matches the analysis which accounts for the effect of the temperature distribution in the gage foil. The effect of this temperature distribution can be neglected in the standard radiation calibration but is often significant in convection applications. These results emphasize the importance of calibrating heat flux gages in thermal environments similar to those in which they will be used.