The effective thermal diffusivity of unidirectional fiber composites, of which effective thermal conductivity under the steady heat flow condition have been already investigated systematically, under the unsteady transverse and parallel directional heat flow condition were determined by a finite element method. The relation between the effective thermal conductivity and the apparent thermal conductivity of the composites measured by the usual laser flash technique was discussed and the condition that the former agreed with the latter was determined.
A new method for instantaneous measurement of three thermophysical parameters of solids in si-tu is proposed. The measuring principle is based on a transient heat conduction model of a thermal probe point-contacting with a testing body. The measurement of temperature response has been made by using the probe of a sheathed K-type thermocouple in this experiment. Ratios of both thermal conductivity and thermal effusivity between the probe and the testing body are determined from curve- fitting with the theoretical response to the measured one. As a result, it is shown that the measurement is reproducible and the accuracies of measured thermophysical parameters are good enough to apply this method to many kinds of solids.
An instrument for the measuring method reported in the previous paper is so to speak a handy tester for three thermophysical parameters of solids in si-tu. Discussions about measurement errors caused by not strictly satisfying the measuring conditions, such as size and shape of a testing body, and about optimum initial temperature-difference between thermal probe and testing body have been done. As a result of the experiment varing the shape of a probe-end, it is also shown that the radius of contacting surface on a testing body has no influence on measuring thermophysical parameters.
A method of the freezing-point realization, that has a single liquid-solid interface in the metal of the fixed-point cell, was applied for the high-temperature fixed points of the ITS-90. The freezing point of aluminum realized by this method was compared with that realized by the conventional method with two liquid-solid interfaces. The result shows that the difference in the freezing point between the two methods is small and the uncertainty of the realization of the proposed method is as small as the conventional one. lt was found that the calibration of the platinum resistance thermometer could be automatically performed using this method.
The cyclic heat method consists of two kinds of determining ways of thermal diffusivity of thermal insulations. One is the way to measure a time lag of the phase of heat waves conducting in the test specimen, the other is to measure the amplitude decay of a heat wave. We have designed a thermal diffusivity test apparatus by the cyclic heat method, and tested under atmospheric conditions and evacuated conditions. This apparatus is able to test thermal diffusivity at temperature range from 100 to 1000 °C. We have determined thermal conductivity values of thermal insulations by multiplying thermal diffusivity, specific heat, and bulk density. The thermal conductivity values of thermal insulations measured by this apparatus are good agreement with the values by the thermal conductivity test apparatus by the Guarded Hot Plate(GHP) method.