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Effect of contact pressure on the apparent thermal conductivity of thermal insulating material
M. Kim and Y. Choi
The multi-layer insulation (MLI) has been known as one of the most apparent cryogenic insulating materials. The MLI is consisted of reflecting layer and netting spacer between reflecting layers. Therefore, conduction heat transfer phenomenon can be occurred between layers of MLI because they are physically contacted each other. The accurate measurement and analysis of heat transfer of MLI is necessary to predict heat invasion through MLI and design of temperature control apparatus. We have developed the thermal conductivity measurement apparatus using a refrigerator as a heat sink and MLI is used as a specimen. The apparent thermal conductivity of specimen is measured over a temperature range of 40-240 K using a steady state method. The specimen is thermally connected to the refrigerator and electrical heater is installed between the specimens to generate heat and axial flow into the specimen symmetrically. The temperature gradient is measured between specimens, from which the apparent thermal conductivity value is calculated. The effect of temperature and contact pressure on the apparent thermal conductivity of MLI is quantitatively discussed.
Keyword: Apparent thermal conductivity, axial heat flow, contact pressure, insulating material, multi-layer insulation, steady state method