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Thermal Science 2022 Volume 26, Issue 2 Part B, Pages: 1277-1288
https://doi.org/10.2298/TSCI200620191L
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Measuring surface temperatures of different types of fly ash samples using a CCD camera

Liu Huawei (Key Laboratory of Condition Monitoring and Control for Power Equipment, Ministry of Education of China, School of Energy, Power and Mechanical Engineering, North China Electric Power University, Changping District, Beijing, China )
Zhu Runru (State Key Laboratory of Multiphase Complex Systems, Institute of Process Engineering, Chinese Academy of Sciences, Haidian District Beijing, China ), rrzhu@ipe.ac.cn
Wang Xin (Guodian New Energy Technology Research Institute Co., Ltd, Changping District, Beijing, China )
Li Gengda (Guodian New Energy Technology Research Institute Co., Ltd, Changping District, Beijing, China )
Cui Qingru (Guodian New Energy Technology Research Institute Co., Ltd, Changping District, Beijing, China )
Xu Chao (Key Laboratory of Condition Monitoring and Control for Power Equipment, Ministry of Education of China, School of Energy, Power and Mechanical Engineering, North China Electric Power University, Changping District, Beijing, China )
Huang Yun (State Key Laboratory of Multiphase Complex Systems, Institute of Process Engineering, Chinese Academy of Sciences, Haidian District Beijing, China )

In this work, an optical emission-based two-color method was experimentally investigated for the measurement of surface temperatures of different types of fly ash samples using a CCD camera. A heating system consisting of a Hencken flat-flame burner, a narrow piece of stainless steel wire mesh to separate the flame and the ash samples to be studied, and a thermocouple to record the temperature, was used to heat fly ash samples. A color camera equipped with a tri-band filter was used to capture radiation images. Fly ash samples collected from three kinds of coal-fired boilers were heated and imaged at different temperatures. The chemical compositions, elements, and particle size distributions were analyzed. The emissivity ratios of the wavelengths corresponding to the R and G optical channels and permitted by the tri-band filter were experimentally determined. A two-color method was subsequently used to calculate the average surface temperatures with relative errors within ±2% in the experiments, and an uncertainty analysis was conducted. Surface temperature distributions were also calculated and presented. The results demonstrate that the emission-based two-color method can be used to determine reliable average surface temperatures and surface temperature distributions when the radiation emitted from the ash samples is obviously greater than the ambient light. The results also show that the method has a lower limit of temperature measurement, which will lessen with the use of larger apertures and a higher radiation capacity of the ash samples to be studied.

Keywords: Fly ash, surface temperature, emissivity, two-color method

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