Thermal property measurement of insulating material used in HTS power device

An experiment to measure the thermal property of insulating material at cryogenic temperature has been performed. The main objective of this study is to develop a precise instrument for measuring the thermal property of insulating materials over a temperature range of 30 K to approximately room temperature by utilizing a cryocooler. In a vacuum chamber, the cold head of the cryocooler is thermally anchored to the copper link and used to bring the apparatus to a desired temperature. An electric heater is placed in the middle of test sample for generating uniform heat flux. The entire apparatus is covered by thermal shields and wrapped in multi-layer insulation to minimize thermal radiation in a vacuum chamber. For a supplied heat flux the temperature distribution in test sample, polypropylene laminated paper (PPLP), is measured in steady state, from which the effective thermal conductivity is calculated and presented with respect to the mean temperature. The correlation near liquid nitrogen temperature is derived from measured data. Moreover, using the measured thermal conductivity, we obtain the specific heat of PPLP by solving one-dimensional heat diffusion equation.

► A new concept of measurement apparatus is developed to estimate thermal property of insulating material.
► For a given heat flux, temperature distribution in PPLP is measured.
► The thermal conductivity of PPLP is 0.047–0.052 W/m K for 50–80 K.
► The specific heat of PPLP is obtained by solving heat diffusion process using the same facility.