Measurement of total hemispherical emittance of a nonconducting and semitransparent material by a transient calorimetric technique
Seizi Sasaki, Hidetoshi Masuda, Heung Kou
An improved transient calorimetric technique was previously proposed for the measurement of the total hemispherical emittance, eh, of nonconducting materials and the results measured for Pyrex-glass sheets by the technique were reported. In this study, the eh values of a fused-silica glass sheet are measured by the same technique. A simple analytical way to evaluate the local total directional emittance, e*, of a glass sheet semitransparent to radiation is presented, and the e* values are computed on the surfaces of the specimen used. Further, values of the local total hemispherical emittance, eh*, on the specimen surfaces are obtained from e*. From the results for eh*, the edge effect of the specimen caused by the eh* distributions on the measured eh is clarified. The temperature distributions in the specimen are obtained by three-dimensional analysis, and then the edge effect caused by the distributions on eh is presented. It is found that the improved transient calorimetric technique is very suitable for measuring eh of nonconducting materials.