Near-field radiative heat transfer in mesoporous alumina

• Published in: Chinese physics B Vol. 24; no. 1; pp. 338 - 344
• Main Author: 李静 冯妍卉 张欣欣 黄丛亮 王戈
• Format: Journal Article
• Language: English
• Published: 2015
• Subjects: Aluminum oxide; Equivalence; Heat transfer; Insulation; Porosity; Radiative heat transfer; Theorems; Thermal conductivity; 中孔材料; 介孔二氧化硅; 介孔氧化铝; 当量热导率; 温度升高; 热传导率; 辐射热传递; 近场
• ISSN: 1674-1056; 2058-3834; 1741-4199
• DOI: 10.1088/1674-1056/24/1/014401

The thermal conductivity of mesoporous material has aroused the great interest of scholars due to its wide applications such as insulation, catalyst, etc. Mesoporous alumina substrate consists of uniformly distributed, unconnected cylindrical pores. Near-field radiative heat transfer cannot be ignored, when the diameters of the pores are less than the characteristic wavelength of thermal radiation. In this paper, near-field radiation across a cylindrical pore is simulated by employing the fluctuation dissipation theorem and Green function. Such factors as the diameter of the pore, and the temperature of the material are further analyzed. The research results show that the radiative heat transfer on a mesoscale is 2～4 orders higher than on a macroscale. The heat flux and equivalent thermal conductivity of radiation across a cylindrical pore decrease exponentially with pore diameter increasing, while increase with temperature increasing. The calculated equivalent thermal conductivity of radiation is further developed to modify the thermal conductivity of the mesoporous alumina. The combined thermal conductivity of the mesoporous alumina is obtained by using porosity weighted dilute medium and compared with the measurement. The combined thermal conductivity of mesoporous silica decreases gradually with pore diameter increasing, while increases smoothly with temperature increasing, which is in good agreement with the experimental data.The larger the porosity, the more significant the near-field effect is, which cannot be ignored.