Study On The Measurement Of Material Spectral Emissivity At High Temperature

Emissivity is a basic parameter of thermal properties and plays an extremely important part in industry. With the development of the contactless temperature measurement technology, the demand of the material emissivity at high temperature is higher than before. The paper describes a method based on energy and measures the material emissivity under the high temperature condition and normal spectral emissivity at different temperatures are calculated based on emissivity definition and measured by Fourier Transform Infrared Spectroscopy (FTIR).At first, focus on the transfer process of the radiation energy, analyzing the sample’s radiation transfer characteristic in the heating device and the FTIR and its energy balance relationship in the detector. Establishing the theory of relational between the sample’s radiation, black body and the signal of FTIR, utilizing two-temperature method to calibrate FTIR to get the response function and offset function, finally, the method of emissivity measurement is established.Secondly, the experimental device of the spectral emissivity is designed. The kind of sample devices is designed and optimized; the method based on Christiansen effect of measurement on sample surface temperature and been proved. Optical transmission device between blackbody and samples is designed to calibrate the black body.Thirdly, based on establishing system for spectral emissivity measurement, tests on spectral emissivity at high temperature are arranged to investigate the offset function, the response function of detector, as well as its stability and nonlinear error for measuring system. Taking advantage of typical high temperature resistance material such as SiC、MgO, tests for spectral emissivity measurement at800～1500℃are planned to analyze the spectral emissivity characteristics of experimental samples at different temperatures.At last, relative uncertainty of SiC normal Spectral emissivity at different temperature is analyzed by uncertainty synthetic formula. The uncertainty of response function and offset function are also analyzed. The relative uncertainty influence of emissivity with wavelength is calculated by response function, offset function, signal, the temperature of sample surface and ambient temperature. At last, the total uncertainties of SiC at different temperature are calculated.