Abstract Recent developments in nanofluids have led to a renewed interest in the geometrical effects of nanoparticles on the effective thermal conductivity (ETC) of nanofluids. Although the experimental data for the effect of nanoparticles shapes (the aspect ratio) on ETC are quite consistent, there are still controversial results regarding the effect of the nanoparticles size. Theoretical approaches have been proposed to shed light on the experimental observations in both macroscopic and microscopic scales. However, these approaches cannot be generalized due to the collective interrelated behaviours of nanoparticles. In this paper, a mesoscale numerical simulation, Lattice Boltzmann method (LBM), is implemented to study the effect of nanoparticle geometry on the nanofluids thermal conductivity. The results demonstrate that the nanofluids thermal conductivity and the nanoparticles volume fraction can be linearly correlated. In essence, increasing the nanoparticles aspect ratio can improve ETC of nanofluids. However, the nanoparticle size is not statistically significant (P-value>0.05) to be considered as an influencing parameter (as observed in the controversial results of the experiments) when the interfacial phenomena are not taken into account. The surface to volume ratio of the particle is the parameter that should be studied as all the solid/liquid interfacial interactions depends on this ratio.

中文翻译：

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纳米粒子尺寸/纵横比对纳米流体热导率影响的数值模拟使用格子 Boltzmann 方法

摘要 纳米流体的最新发展使人们重新关注纳米粒子对纳米流体有效热导率 (ETC) 的几何影响。尽管纳米颗粒形状（纵横比）对 ETC 的影响的实验数据非常一致，但关于纳米颗粒尺寸的影响仍然存在争议。已经提出了理论方法来阐明宏观和微观尺度的实验观察。然而，由于纳米粒子的集体相关行为，这些方法不能推广。在本文中，实施了中尺度数值模拟，即格子玻尔兹曼方法 (LBM)，以研究纳米颗粒几何形状对纳米流体热导率的影响。结果表明纳米流体的热导率和纳米颗粒的体积分数可以线性相关。从本质上讲，增加纳米颗粒的纵横比可以提高纳米流体的 ETC。然而，当不考虑界面现象时，纳米颗粒尺寸在统计上不显着（P值>0.05）被视为影响参数（如在有争议的实验结果中观察到的）。颗粒的表面积与体积比是应该研究的参数，因为所有的固/液界面相互作用都取决于这个比例。0.05）被认为是当不考虑界面现象时的影响参数（如在有争议的实验结果中观察到的）。颗粒的表面积与体积比是应该研究的参数，因为所有的固/液界面相互作用都取决于这个比例。0.05）被认为是当不考虑界面现象时的影响参数（如在有争议的实验结果中观察到的）。颗粒的表面积与体积比是应该研究的参数，因为所有的固/液界面相互作用都取决于这个比例。