【摘要】 导出了奠定前置反射器辐射温度计理论基础的被围表面有效发射率新公式。此式也是红外辐射测温技术的基本公式之一。被测表面在反射器作用下会引起表面温升现象,由此根据所拟定的边界条件和初始条件解一维热传导方程,求得被测表面温升的理论公式。上述两式都与实验结果相吻合。为深入了解该类型仪表的测温原理,对该类型辐射测温仪表的系统误差进行了分析,各项有效发射率增量的累计与理论有效发射率之和(实际有效发射率)同实际测量误差相比,吻合较好。此种辐射温度计在1000℃时,误差在±10℃以内。更多还原

【Abstract】 Jn general, the radiation pyrometer widely used for temperature measurement can only determine the brilliancy or radiation temperature of the object to be measured. In order to eliminate the influence of emissivity on thermal measurement by use of radiation pyrometer hence to determine the actual temperature, to find out the surface emissivity of the object to be measured is indispensable. But the surface emissivity is difficult to be determined because it is related to so much factors especially the complicate surface conditions of various objects. For this reason, some earlier works have been done in different ways and the authors have also developed a kind of pyrometer with which a reflector is preceded. This paper offers a theoretical equation to calculate the effective emissivity of a surrounded surface for determining the actual temperature using the thermal measurement device we developed.Summary, Effective emissivity is defined as aratio of effective surface emission to the effective emission of a surface at the same temperature as its emissivity is equal to 1. The equation expressing effective emissivity of a surrounded surface has been derived aswhere p is the reflectivity of the inner surface of a hemispherical reflector which covers over the surrounded surface and forms an enclosed chamber together with the surrounded surface, e the emissivity of surrounded surface and F1 and F2 the surface areas respectively. This fundamental equation is provided not only for this kind of pyrometer but also for the infrared thermal measurement. Four cases of application approaching to different limits are discussed. If the effective emissivity of the inner surface of hemispherical reflector appraches to 1, the energy emitted through an aperture located at the top of hemisphere is nearly enough the heat emission of a black body at a temperature as the same as that of surrounded surface. Thus, the actual temperature of surrounded surface can be measured by setting up a thermoplie or the other detector on the top aperture of reflector. This is just the basic principle of the radiation pyrometer preceded with a reflector we developed (see Fig.3). An apparatus indication equation in terms of voltage output and its sensitivity expresion are derived, the latter is given as a first derivative of volt output with respect to temperature and shows that the sensitivity greatly increases with the temperature raising. Calculation of the raising of surface temperature measured due to the preceded reflector has been discussed and the plate specimens made of cast iron and stainless steel are measured for instance, it is shown that calculated values are basically in agreement with those measured. Finally, the systematic error of this kind of pyrometer has been analyzed taking account of different influencing factors on the effective emissivity, the result also shows a good con-formability of εeff between the values using the equation as above and those measured. Fig.1 Enclosed hemispherical chamber formed by the surface measured with the preceded reflectorFig.2 The e -εeff curves as ρ = 0.97 and different F1/F2 ratios Fig.3 Schematic of radiation pyrometer preceded with a reflector1-thermopile; 2-zero adjustment; 3-aperture; 4-metal plate to be measured;5-lens; 6-hemisphere with inner surface goldplated. Fig.4 Calculation representation of temperature raising Fig.5 Temperature raising values calculated and compared with thosemeasuredFig.6 The gap 6 between reflector and surface measured Tab.1 Systematic errors calculated under various measuring conditions based on formula(21)Tab.2 Comparison of mv values of oxidized cast iron, copper and aluminium plates indicated by blackbody furnace with those measured, at 400, 500, 600 and 700℃.Fig. 3更多还原