Abstract.

Compared to nanofluids with spherical particles, nanofluids with anisotropic particles possess higher thermal conductivity and present a better enhancement option in heat transfer applications. The viscosity variation of such nanofluids becomes of great importance in evaluating their pumping power in thermal systems. This paper presents a comprehensive review of the experimental and theoretical studies on the viscosity of nanofluids with anisotropic particles. The internal mechanisms of viscosity evolution are investigated considering three aspects: particle clustering, particle interactions, and Brownian motion. In experimental studies, important factors including classification and synthetic methods for particle preparation, base fluid, particle loading, particle shape and size, temperature, p H, shear stress and electric field are investigated in detail. Classical theoretical models and empirical relations of the effective viscosity of suspensions are discussed. Some crucial factors such as maximum particle packing fraction, fractal index and intrinsic viscosity models, are examined. A comparison of predictions and experimental results shows that the classical models underestimate suspension viscosity. A comprehensive combination of the modified Krieger-Dougherty (K-D) model with intrinsic viscosity relations for different aspect ratios is suggested for low particle loadings, and the modified Maron-Pierce model (M-D) is recommended for high particle loadings. Possible directions for future works are discussed.

Graphical abstract

中文翻译：

---

包含各向异性粒子的纳米流体的粘度：关键评论和全面的模型

摘要。

与具有球形颗粒的纳米流体相比，具有各向异性颗粒的纳米流体具有更高的导热率，并且在热传递应用中呈现出更好的增强选项。此类纳米流体的粘度变化对于评估其在热系统中的泵浦功率至关重要。本文对具有各向异性颗粒的纳米流体的粘度的实验和理论研究进行了全面综述。研究了粘度演化的内部机制，其中考虑了三个方面：粒子聚类，粒子相互作用和布朗运动。在实验研究中，重要因素包括颗粒制备的分类和合成方法，基础流体，颗粒负载，颗粒形状和大小，温度，p对H，剪切应力和电场进行了详细研究。讨论了悬浮液有效粘度的经典理论模型和经验关系。研究了一些关键因素，例如最大颗粒堆积分数，分形指数和特性粘度模型。预测结果与实验结果的比较表明，经典模型低估了悬浮液的粘度。对于低颗粒负载，建议将改良的Krieger-Dougherty（KD）模型与特性粘度关系针对不同的长宽比进行全面组合，对于高颗粒负载，建议使用改良的Maron-Pierce模型（MD）。讨论了未来工作的可能方向。

图形概要