Quasistatic thermal conduction measurement by thermal radiation calorimetry

Instrumentation based on thermal radiation calorimetry (TRAC), in which a specimen is heated by thermal radiation from a heater, is described. The thermal conductivity of a disk-shaped solid specimen is derived by measurement of the temperature gradient in the specimen with the same temperature change rate on both heating and cooling. The present measurement method enables the value of the conductivity to be obtained continuously with temperature unlike the case of a conventional method performed under a thermal equilibrium state. A noncontact technique has been developed for measurement of surface temperature by means of a pyrometer and two thermocouples which are set in the gap between the heater and the specimen and set behind the heater, giving a deviation of 2 degrees C at most between the two processes at elevated temperatures. The thermal conductivities of Pyroceram 9606 and Pyrex 7740 glass have been obtained in the temperature ranges 250-400 degrees C and 400-600 degrees C, respectively The errors involved in the measurement are in the order of 10% to 20%.