Development of Thermal-Conductivity Measurement System Using Cryocooler

Key Words: Heat Transfer(열전달), Thermal Conductivity(열전도도), Cryogenic(극저온), Cryocooler(극저온냉동기)초록: 액체질소온도부근에서작동하는고온초전도케이블시스템을개발하기위해서는고온초전도케이블시스템에사용되는극저온절연재료의정확한열물성자료가필요하다. 금속재료와달리, 비금속계열의재료는열저항이크기때문에정확한열유입량을측정하기위해서는특별한주의가요구된다.본연구에서는극저온냉동기를이용하여30K 부터상온사이에서절연재료의열전도도를정확하게측정할수있는시스템을개발하였다. 설계와제작과정을포함한열전도도측정시스템을자세하게기술하였다. 또한상온으로부터침입하는불가피한열유입량을최소화하기위한열전도도측정시스템의최적화과정을소개한다.Abstract: The thermal property of insulation material is essential in developing a high-temperaturesuperconductor (HTS) power cable to be operated at around liquid-nitrogen temperature. Unlike metallicmaterials, nonmetallic materials have a high thermal resistance; therefore, accurate estimate of the heat flow isdifficult in the case of nonmetallic materials. The aim of this study is to develop an instrument for preciselymeasuring the thermal conductivity of insulating materials over a temperature range of 30 K to approximatelythe room temperature by using a cryocooler. The details of the thermal-conductivity measurement system,including the design and fabrication processes, are described in this paper. In addition, the design optimizationto minimize unavoidable heat leakage from room temperature is discussed.