A directional spectral emissivity measurement device with built-in calibration radiation source

Abstract

Infrared emissivity is a fundamental parameter that characterizes the thermal radiation of materials, and has a large number of measured needs in the fields of aerospace, nuclear power generation, solar energy utilization, and building energy conservation. Based on the principle of Fourier transform spectrometer, a high-temperature directional spectral emissivity measurement device was constructed using an interferometer module, liquid nitrogen cooled HgCdTe (MCT-LN) detector, and infrared focal plane array (IRFPA) detector. The device was designed with a built-in calibration radiation source, which can timely correct the stored calibrated black body data at multiple temperature points based on the changes in detector spectral responsiveness, breaking away from the dependence of traditional measurement devices based on energy comparison method on the bulky and cumbersome black body, and providing technical exploration and application possibility for the field application of high-temperature emissivity measurement devices. In addition, the focal plane detection that can achieve synchronous thermal imaging function is applied in the device, which is beneficial for the optical path alignment and heating state discrimination of the target to be measured. In the experiment, the emissivity values of GH5188 superalloy from 473 K to 1473 K after heat treatment were proportional to the temperature change, and the total hemispherical emissivity values increased by 0.204. The total directional emissivity of 0–60° changed slightly, but decreased sharply at 60°. The measured data were compared with data from published literatures, at the same temperature, the maximum deviation in spectral emissivity values for SiC material 316 L stainless steel material is 0.044 and 0.022 and the comparison results showed satisfactory consistency. Through uncertainty analysis, the results indicate that the combined uncertainty of the measuring device was less than 2.6 %.