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International Heat Transfer Conference 16

ISSN: 2377-424X (online)
ISSN: 2377-4371 (flashdrive)

PORE-SCALE NUMERICAL STUDY ON THE HEAT TRANSFER PROCESS IN POROUS MEDIA UNDER DIFFERENT THERMAL CONDITIONS

Shen DU
Xian Jiaotong University, 28 Xian Ning West Rd. Xi'an, Shaanxi 710049, China

Ming-Jia Li
Department of Earth and Environmental Engineering, Columbia University, New York, NY 10027, USA; Key Laboratory of Thermo-Fluid Science and Engineering of Ministry of Education, School of Energy and Power Engineering, Xi'an Jiaotong University, Xi'an, Shaanxi 710049, China

Zhan-Bin Liu
Xian Jiaotong University, 28 Xian Ning West Rd. Xi'an, Shaanxi 710049, China

Ya-Ling He
Key Laboratory of Thermo-fluid Science and Engineering, Ministry of Education, School of Energy and Power Engineering, Xi'an Jiaotong University, Xi'an, Shaanxi 710049, China

Wen-Quan Tao
State Key Laboratory of Pollution Control and Resources Reuse, College of Environmental Science & Engineering, Tongji University, Shanghai 200092, China; Key Laboratory of Thermo-Fluid Science and Engineering of MOE, School of Energy and Power Engineering, Xian Jiaotong University, Xian 710049, China

DOI: 10.1615/IHTC16.cov.022234
pages 3247-3254


KEY WORDS: Porous media, Solar energy, Porous volumetric solar receiver, X-ray computed tomography, Thermal boundary condition, Volumetric convective heat transfer coefficient

Abstract

The convective heat transfer coefficient is a key parameter when investigating the heat transfer process in the porous volumetric solar receiver. Previous researches pay little attention to the influence of thermal conditions on the determination of this value. In this paper, a fully coupled pore-scale heat transfer model is proposed and three different thermal conditions such as constant surface temperature, constant heat flux, and incident solar radiation are investigated. The computational domain is reconstructed by the X-ray computed tomography technique and the governing equations are solved directly with finite volume method in FLUENT. The energy source due to solar radiation is modeled by Beer's law while the radiation transfer inside the porous media is solved with discrete ordinates method. The results show that the convective heat transfer coefficient increases and the Nusselt number decreases as the intensity of thermal conditions increases in all cases. When the average temperature or average heat flux of the porous volumetric solar receiver is imposed, the Nusselt number under constant temperature thermal boundary condition is a good approximation to that of the porous volumetric solar receiver but the constant heat flux thermal boundary condition leads to a smaller value. The detailed temperature fields also demonstrate that the heating processes are similar in cases under constant temperature and incident solar radiation. As a result, the heat transfer characteristics under different thermal conditions in porous media are revealed and the correlation of Nusselt number versus Reynolds number for the porous volumetric solar receiver is proposed.

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