A Spectral Emissivity Measurement Facility for Solar Absorbing Coatings

A new facility that uses integrating-sphere reflectometry to measure the spectral emissivity of solar absorbing coatings in the range from 0.4 mu m to 10 mu m and in the temperature range from 300 K to over 900 K has been built at the Harbin Institute of Technology. The technique is based on a system previously developed at the National Institute of Standards and Technology. Measurements have been performed on two different coatings. The results are in good agreement with those obtained by the method of radiant energy comparison using a Fourier transform infrared spectrometer. Emissivity measurements performed with this facility present an uncertainty of 5.3 % (coverage factor = 2).