Measurenent of Emissivities of Metals, Alloys and Materials for Space Station in Space Conditions

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In Thermal design of "Space Station", many data of the total hemispherical emissivities of materials at low temperatures are needed, but we can find a few data in literatures.We studied a measuring technique for the total hemisperical emissivities of materials. Using a transient calorimetric method, a new technique which measure a total hemispherical emissivity within a short period is developed. To measure the emissivity accurately, guard heater is incorporated in the emissivity aparatus and is regurated to reduce a heat loss through fine thermocouple leads suspending a specimen.Emissivity measurements were performed for copper wire as a specimen. The heat losses through the leads were analyzed in considering combined radiation and conduction heat transfer from the leads. Temperature distribution in the specimen were also analyzed. Measurement were also performed with annealed specimen.It was found that the emissivity of copper for mechanical polished surface is about 0.012 to 0.018 in the temperature range 170 K to 350 K, and the emissivity with annealing is about 0.006 to 0.012 in 137 K to 320 K.