In the present study, the transferred thermal heat by the phenomenon of free convection flow in an annular metal-base porous space inside two vertical concentric cylinders saturated by a (Al₂O₃-water) nanofluid with different shapes of nanoparticles (NPs) has been numerically investigated. The finite difference method is used to solve the governing system of equations. The outer cylinder is kept at constant temperature, and the discrete heat flux and the unheated adiabatic sections are placed on the inner cylinder. The base walls are insulated and impermeable. The obtained results of the numerical simulation are presented to exhibit the consequences of various parameters, such as the Rayleigh number (Ra_Th), Darcy number (Da), porosity (ε), solid NPs volume fraction (φ), and the shape of NPs as well as the conductivity ratio of porous media (λ). It is observed that the transferred thermal flux increases as the conductivity ratio of porous media increases. The results obtained also show an improvement of the rate of heat transfer with the increase in Darcy number, Rayleigh number, and NPs volume fraction. Furthermore, a significant improvement in the overall heat transfer has been found with oblate and prolate alumina (Al₂O₃) spheroid NPs.

中文翻译：

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AL2O3 纳米粒子球形度对通过自由对流进行的热传递的影响，在垂直圆柱体之间的环形金属基多孔空间中，受到离散热通量的影响

在本研究中，在被具有不同形状的纳米粒子 (NPs)的（Al ₂ O _{3 -}水）纳米流体饱和的两个垂直同心圆柱内的环形金属基多孔空间中，自由对流现象传递的热热具有进行了数值研究。有限差分法用于求解控制方程组。外筒保持恒温，离散的热通量和未加热的绝热段放置在内筒上。底墙是绝缘和不透水的。数值模拟的结果展示了各种参数的结果，例如瑞利数 (Ra _Th)、达西数 (Da)、孔隙率 (ε)、固体纳米颗粒的体积分数 (φ)、纳米颗粒的形状以及多孔介质的电导率比 (λ)。可以看出，随着多孔介质的电导率比增加，传递的热通量增加。获得的结果还表明，随着达西数、瑞利数和 NPs 体积分数的增加，传热速率有所提高。此外，已经发现扁长形和扁长形氧化铝 (Al ₂ O ₃ ) 球状体 NP在整体传热方面有显着改善。