Precise measurement of thermophysical properties of solids by a direct electrical heating method. 5th report. Measurement of thermal expansion and specific heat by using a rectangular rod sample.

Abstract

The principle of the newly developed methods for measuring thermal expansion and specific heat using a rectangular rod sample is described. From the data of potential drop, current, and sample temperature under the condition of a uniform temperature in the longitudinal direction, electrical resistivity, total hemispherical emittance, and thermal expansion are simultaneously obtained. Specific heat is calculated from the cooling rate, which is determined immediately after current cut-off. Theoretical estimation of error in the measurement of specific heat is conducted, and thereby the optimum sample size is determined. Techniques of correction for the measured cooling rate with the error caused by thermal contact resistance between sample and thermocouple probe are presented. Experimental results on the rod sample of austenitic stainless steel SUS 304, of 1-mm thickness, 8-mm width, and 200-mm length, are shown in order to verify the applicability of this method in the temperature range of 300 to 900 K.