Steady‐state heat flux measurements in radiative and mixed radiative

Steady‐state heat flux measurements in radiative and mixed radiative–convective environments

Lam, Cecilia S. / Weckman, Elizabeth J.

10.1002/fam.992.abs

The steady‐state responses of four heat flux gauges (Schmidt–Boelter, Gardon, directional flame thermometer (DFT) and hemispherical heat flux gauge (HFG)) were examined under various radiative and convective heating conditions. In radiative environments, Gardon measurements were up to 8% higher than Schmidt–Boelter measurements, but in mixed radiative–convective environments, Gardon measurements were 8–18% below those of the Schmidt–Boelter gauge. This difference increased as the convective portion of the total heat transfer increased, due to discrepancies between the radiation‐based calibration environment and the application environment. The DFT data in radiative environments were comparable with the Schmidt–Boelter and Gardon values (within 12%), with the difference largely attributed to natural convection losses from the DFT. In mixed environments, the DFT values were significantly lower than those of the Schmidt–Boelter gauge due to differences in the surface temperatures of the gauges, resulting in the convective flow cooling, rather than heating, the DFT. The HFG heat flux estimates were 35–48% lower than the Schmidt–Boelter measurements under radiative conditions, influenced by large conduction losses from the sensor plate to the gauge housing. Lateral conduction due to a mismatch between the experimental convective flow outlet diameter and the gauge width also affected results from the DFT and HFG. Copyright © 2009 John Wiley & Sons, Ltd.