As one of the basic parameters characterizing the radiation heat transfer of material surface, the emissivity is of important significance to perform non-contact thermometry research. Comparing with the traditional measurement method, measurement method of spectral emissivity based on the Fourier spectrometer has many advantages such as high accuracy and fast measurement. However, the measurement accuracy is subject to the influence of the radiant energy and the spectrometer electromagnetic radiation noise resulted from the environment. In this study, the geometric factor of the sample was defined and the reflectance of the background radiation in the surface of the sample was applied to accurately determine the energy of the radiation received on the detector. An emissivity measurement model was established and a mathematical formula was derived in this study to eliminate the influence of the background radiation noise. To improve the measurement accuracy of the surface temperature of samples, a heat conduction model is established so that the radiation heat transfer of the sample surface can be calculated and the surface temperature of the sample was obtained by equilibrium calculation. Moreover, we conducted emissivity measurement of black paint samples with high emissivity using the Fourier spectrometer and the proposed model is proven valid. Comparing the experimental results modified by the eliminating calculation formula with the experimental data obtained by the monochromator, it was found that there was good qualitative agreement between two sets of results.
Fourier transform spectrometer for spectral emissivity measurement in the temperature range between 60 and 1500°C
