HEAT CONSTANT MEASURING APPARATUS

PURPOSE:To enhance the reproducibility and accuracy of a measured value, by bringing one of incident radiant light and detected heat rays to an annular shape and forming the other into a circular shape having a diameter sufficiently smaller than the inner diameter of said annular shape. CONSTITUTION:A specimen holding cylinder 3 and a specimen stand 4 are engaged with the inside of the cylindrical base stand 2 provided in a cylindrical heating furnace 1 and a window plate 5 permitting heat rays to transmit is arranged to the lower end of the stand 2 and a shield cylinder is provided thereon. Further, a specimen 7 is arranged in the specimen stand 4 at a right angle with respect to the axis of said stand 4 and a radiant light shielding plate 9 having a circular small hole window 8 is provided to the upper part of the specimen and a window 10 composed of a circular slit having an inner diameter sufficiently larger than the diameter of the window 8 is provided to the lower part thereof and a heat ray shielding plate 11 is arranged. The specimen 7 is irradiated with fine circular beam from the radiant light source 12 provided to the upper part of the base stand 2 and discharged heat rays are throttled into annular shape to be detected by a heat ray detector 13 to measure the heat diffusivity, heat capacity and specific heat of the specimen 7.