Predicting the directional spectral emissivity for rough surfaces polished by sandpaper

A new method was proposed to accurately predict the emissivity of rough surface polished by sandpaper. The complex rough surface was numerically reestablished based on the surface characteristic parameters extracted from the statistical data of 3D optical profiler measurement. Directional spectral emissivity of the established surface was simulated by the finite element method in the wavelength range of 2–20 µm and in the emission angle range of 0–80°. The influence of roughness on spectral emissivity was carefully studied. The calculated emissivity was compared to the data measured by a self-made emissivity measurement apparatus. The predicted results are in good agreement with the experimental data, which well proves the reliability of the proposed method.