Research On Emissivity Online Measurement System For Medium Temperature Target Between 100? And 500?

Emissivity is a parameter used to characterize the thermal radiation law of an object.According to investigations,there were few domestic studies on emissivity online measurement,especially long-term on-line testing for medium and high temperature targets.Unlike laboratory measurements,on-line emissivity testing requires that the system be characterized by low delay and strong resistance to vibration,high temperature and electromagnetic interference.This article proposed a research method for the medium temperature emissivity on-line test system which measured the band emissivity.The temperature range was 100~500°C,the waveband range was 2~16um,and the maximum measurement uncertainty was 3.4%.One of the problems faced by such a system was the drift of the sensor due to high temperature interference.The second was that the measurement system was highly nonlinear and sensitive to changes in the ambient temperature.In this paper,through detailed theoretical calculations and analysis of the system,a dual temperature control method using external liquid forced cooling and internal heating had been proposed to solve the first problem,so that the measuring element could maintained a lower temperature in any environment.Special mechanical structural were also designed to protect against the target radiation.For the second problem,this paper used a linearization circuit that made the system have a good linear relationship within the sensor operating temperature range(20±3°C),and reduced the influence of the ambient temperature to 0.027V/°C,which could be ignored.In the past,few quantitative research were made on radiation propagation models.In this paper,a detailed analysis and calculation of the radiation propagation models inside and outside the system were made using geometric optics theory,which ultimately led to a more accurate emissivity calculation formula.And the system was calibrated and exponentially fitted using the reference blackbody furnace,with small fitting error(±0.02).The system was also verified using the black body equivalent method and the standard template,and the verification error was within ±0.06.Finally 4 metal samples were tested and the results showed that the metal emissivity increased with the degree of its oxidation.Through measurement and calculation,it was found that the uncertainty of the system mainly came from the inconsistency of the aperture and the non-uniformity of the sample temperature.These were one of the directions for subsequent improvement.