Development of experimental apparatus for precise emissivity determination based on the improved method compensating disturbances by background radiation

To realize precise emissivity determination of solid materials, an experimental apparatus based on the improved measurement method is developed in this paper. This experimental apparatus covers the spectral range between 5 and 20 mu m and temperature region from 373 to 673 K. The improved method effectively enhances the measure precision through the multi-temperature calibration method for robust spectral response function and the compensation disturbances caused by background radiation. Determination of the sample surface temperature is accomplished through iterative computation based on the balance of heat fluxes at the sample surface. The computed temperature data are well coincident with those obtained by the Christiansen wavelength method and the contact method. The spectral emissivity measurements of alumina and aluminum are performed to validate the experimental apparatus with the improved method. The experimental results show good agreements with literature data and theoretical values, demonstrating that our experimental apparatus can provide reliable measurements. The uncertainty sources of emissivity measurements are systematically analyzed and the combined uncertainty for the alumina sample at 373 K is estimated to be less than 2.29%.