Calorimetric determination of emissivity for metallic foils: An innovative approach for thermal analysis.

In vacuum environments, thermal radiation significantly influences heat transfer, making accurate emissivity predictions crucial for improving the efficiency of refrigeration systems. However, emissivity is a highly sensitive parameter that is challenging to measure with precision due to the limited availability of reliable measurement methods. This paper introduces an innovative method for measuring the total hemispherical emissivity of metallic foils, specifically targeting highly reflective metals. In this study, the emissivity of the 99.9 % pure aluminum with a thickness of 25.4 μm was measured across a temperature range of 170.1 K to 283.8 K, varying from 0.0185 to 0.0205, with a comparative analysis revealing a 38.3 % difference between the shiny and matte sides of the foil. Additionally, the influence of absorber temperature was examined using an insulation layer. The experimental results were validated against published data within the same temperature range and further corroborated through simulations. This approach offers a reliable and precise method for measuring emissivity in highly reflective metals under low-temperature conditions.