MEASUREMENT FOR DIFFUSITIVITY OF HEAT BY INTERMITTENT HEATING

PURPOSE:To enable the determination of thickness-wise heat diffusion rate of a sample plate from a characteristic curve in the logarithm of the amplitude ratio of AC temperature at two points different in the thickness on the back, by intermittently irradiating a wedge-shaped sample plate to be measured with a heat energy of a fixed amplitude. CONSTITUTION:Thermocouples 21 and 22 are mounted at two points on the back of a wedge-shaped sample plate 1 to be measured which is long enough thickness-wise. The surface of the sample plate 1 is irradiated with heat energy of a heat source 3 such as tungsten lamp. Here, the heat energy is interrupted at the frequency set with a chopper 4 to keep the amplitude constant. The energy is amplified with a lockin amplifier 5 through a changeover switch 7 using the output of a sensor 6 as reference signal. With such an arrangement, amplitudes of AC temperatures are determined varying the frequency at two points on the back of the sample plate 1 and then, a characteristics curve in the logarithm of the amplitude ratio of AC temperatures can be plotted at two points with the root of the frequency as variable therefrom to obtain the gradient of the straight line thereof. From the results thereof, the thickness-wise heat diffusion rate of the sample plate 1 is obtained.