MEASUREMENT FOR DIFFUSIVITY OF HEAT BY INTERMITTENT HEATING

PURPOSE:To enable the determination for diffusivity of heat at the right angle (surface way) to the thickness way from AC temperatures at two distance points, by covering a part of a sample plate to be measured to irradiating heat energy intermittently. CONSTITUTION:A sample plate 1 to be measured with a fixed thickness of about 0.1-0.5mm., for instance, is covered partially with a cover plate 2. The exposed section of the plate is irradiated with heat energy converted to AC with a chopper 3. Here, a thermocouple 6 welded at a distance Lf from the end of the cover plate 2 measures AC temperature through a sensor 7 and a lockin amplifier 8. In an equipment thus arranged, amplitudes of AC temperatures are determined varying the frequency with the sample plate 1 set at two points of distances Lf1 and Lf2 to the thermocouple 6 from the end of the cover plate 2. Then, when a characteristic curve of AC temperature is plotted as determined from the logarithm of the amplitude ratio with the root of the frequency as variable, straight line is obtained. Heat diffusion rate can be calculated from the gradient of the straight line.