Radiation-corrective gas temperature measurement in a circular channel

Abstract

Gas temperature measurement by a probe-type thermometer has a large bias because of the thermal radiation effect on the measured surface. In the gas flow, the convective heat transfer coefficient on the thermocouple surface is not large enough to neglect the thermal radiation effect from the sheath tube. Therefore, the measured temperature is determined from the energy balance between the convective heat transfer and the radiation heat transfer on the sheath tube. Korea Atomic Energy Research Institute has tested the methodology to correct the thermal radiation effect for the gas temperature measurement. The methodology is the usage of a couple of thermocouples with unequal diameters called the Reduced Radiation Error (RRE) method. The RRE value is defined as the ratio of the temperature difference between the true gas temperature and the measured temperature from large diameter thermocouple over the measured temperature difference between the thermocouples with the small and large diameters. The RRE value is calculated from the convective heat transfer coefficients and the radiation heat transfer coefficient between two thermocouples. The experimental results with two thermocouples of unequal diameters of 1/8 inch and 1/16 inch showed that the RRE method would have good applicability to the gas temperature measurement in the high temperature and mass flux condition under negligible conditions with the conductive dissipation through the sheath tubes. © 2012 WIT Press.