A review of devices and methods for measuring thermal emissivity at cryogenic temperatures

Abstract

Abstract Thermal emissivity is an important parameter in characterizing the thermal radiative properties of materials and a critical factor in radiative heat transfer. The radiation of an actual object is different from that of the blackbody: its radiation energy varies irregularly with wavelength and temperature. To investigate the thermal radiative properties, thermal emissivity could be measured at cryogenic temperatures. In this paper, measuring methods and factors affecting the thermal emissivity of metals and infrared coatings at low temperatures were comprehensively reviewed. Two existing methods for measuring thermal emissivity at low temperatures, the calorimetry and radiometry methods, were described. Moreover, this work also discussed several factors such as material properties, surface temperature, and surface conditions. Testing devices for measurement of emissivity at low temperatures based on calorimetry and radiometry were reviewed and analyzed emphatically.