Research On Method Of Measurement Of Emissivity Of Material At Medium And Low Temperatures

Temperature is the physical quantity which characterized the hotand cold degree of objects. And it is one of the seven basic physicalquantities in the international system of units (SI).As one of the wid ely usedtemperature measuring methods, Radiation temperature measurement is notinterfere with the temperature field distribution, quick, safety andnon-pollution. In the past, Radiation temperature measurement mainly used inhigh-temperature measurement(higher than800℃), the wavelengths of thecorresponding radiation thermometer is mostly short, most between0.66~3.9μm. An important problem is that the influence of environmentradiation can not be ignored with the radiation temperature measurementexpand to medium-and-low temperature(less than420℃) and long wavedirection, it could become a major source of error in the actual measurement.This article present the theory of effective radiance temperature, basedon classical radiance temperature, environment radiation is considered in thisnew theory. From two aspects of theoretical calculation and experimentalmeasurement has carried on the comparative analysis on two kinds oftemperature theory. The results of theoretical calculation and experimentalmeasurement show that together, Compared with the classical theory ofclassical radiance temperature, the theory of effective radiance temperaturehas better applicability in medium-and-low temperature and long wavedirection, Can greatly improve the measurement accuracy.The emissivity is an important parameter which describes the thermalradiation property of material, and it has a wide application in the aeronautics,astronautics, national defence, science research, industry, agriculture andother research fields. In the radiation temperature measurement, the radiationis a necessary prior parameter before the true temperature is known, so theproblem of the measurement of radiation is a bottle-neck in the radiationtemperature research.This article present the concept of effective spectral emissivity, that takethe environment radiation into consideration. Design experimental scheme that measure the spectral emissivity of material based on standard threecavity blackbody radiation source and high precision radiation thermometer.Standard three cavity blackbody radiation source is unified temperaturecontrol with the reference blackbody temperature and measured samples,error caused by inconsistent temperature control on measured samples andreference blackbody is effectively reduces. Several kinds of metal,non-metallic materials are measured by using this scheme. And put forward ascheme to test the performance of high emissivity coating that based on thisscheme. The performance of sample coating in changing the spectralemissivity of materials is evaluation by experiment with this scheme.