Partitioning measurements of convective and radiative heat flux

Abstract

New measurement techniques are presented to simultaneously determine the radiative and convective components in a mixed-mode heat transfer environment. These techniques rely on making hot surface heat flux measurements using a hybrid heat flux gage capable of measuring heat flux at surface temperatures up to 1000°C without water cooling. Experiments were performed with an apparatus where the convection and radiation heat fluxes could be independently controlled to produce convection only, radiation only, and mixed convection and radiation environments. Using these experiments two methods were compared for quantifying the heat transfer coefficient: a reference method and a slope method. These methods yielded heat transfer coefficients of 1.11kW/m2°C with a relative uncertainty of ±14.0% and 1.00kW/m2°C with a relative uncertainty of ±11.3% for the mixed-mode heat transfer environment, respectively. The calculated heat transfer coefficients were then used to separate the radiative and convective heat fluxes. The separated irradiation heat flux was 18.1% less than in the radiation only case. This was thought to be caused by error in the gas temperature measurement as well as by the uncertainty in the convective heat transfer coefficient. Sensitivity of the separated irradiation heat flux values to the gas temperature was evaluated.