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| Effect of wall local emissivity variation on cavity emissivity of isothermal cavity blackbody |
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Abstract Cavity blackbody is a commonly used radiation source in the field of thermal metrology, and the emissivity of its inner wall material is an important factor affecting the emissivity of the blackbody cavity. At present, the existing research mainly considers the impact of the overall change of the emissivity of the inner wall material on the cavity emissivity, and the relevant research on the impact of the local wall material emissivity change is rarely reported in the literature. Therefore, the integral emissivity of the blackbody cavity is simulated by the finite volume method, and the results are compared with those obtained by the Monte-Carlo method. The influence of the material emissivity variation of the cavity wall and the inner wall of the cavity bottom on the emissivity of the blackbody cavity under different aspect ratios is simulated and calculated, and then the influence of the local material emissivity variation on the emissivity of the blackbody cavity is discussed. The results show that the deviation between the finite volume method and Monte-Carlo method is less than 0.1%. When the emissivity of the bottom wall is above 0.3 and the aspect ratio L/R>5, the change of the integral emissivity of the cavity is less than 0.002. The change of the wall material emissivity has a more significant effect on the cavity integral emissivity. When the wall emissivity is changed from 0.8 to 0.5, the change of the cavity integral emissivity is more than 0.09. When the local wall material emissivity changes, the change of the integral emissivity of the cavity gradually increases as the axial relative position is closer to the cavity opening.
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Received: 28 October 2024
Published: 03 April 2025
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2025, Vol. 46 
