An apparatus for noncontact measurement of thermal conductivity by thermal radiation heating

Thermal radiation calorimetry was applied to measure the thermal conductivity of insulating solid specimens. We consider the system in which a disk-shaped specimen and a Ilat heater are mouInted in a vacuum chamber with the specimen heated on one face by irradiation, A temperature difference between two Dces was observed at elevated temperatures under steady-state conditions. An apparatus was developed using a thin graphite sheet as the heater element. Disk-shaped Pyrex glass and Pyroceram specimens, whose surfaces were blackeued with colloidal graphite, were used in the meast.rements. Noncontact temperature measurement was performed using pyrometers and a thermocouple set in the gap between the heater and the specimen. Deviations of the estimated thermal conductivities from the recommended values were about 5% in the temperature range 250 to 800~