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首页> 外文期刊>International Journal of Heat and Mass Transfer >Heat conduction in nanofluids: Structure-property correlation
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Heat conduction in nanofluids: Structure-property correlation

机译：纳米流体中的热传导：结构-性质相关

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摘要

We examine numerically the effects of particle-fluid thermal conductivity ratio, particle volume fraction, and particle morphology on nanofluids effective thermal conductivity and phase lags of heat flux and temperature gradient, for six types of nanofluids containing sphere, cube, hollow sphere, hollow cube, slab-cross and column-cross nanoparticles, respectively. The particle's radius of gyration and the non-dimensional particle-fluid interfacial area are found to be two characteristic parameters for the effect of particles' geometrical structure on the effective thermal conductivity. The nanoparticles with larger values of these two parameters can change fluid conductivity more significantly. Due to the enhanced particle-fluid interfacial heat transfer, the nanofluid effective thermal conductivity can practically reach the Hashin-Shtrikman bounds when the particle-phase connects to form a network and separates the base fluid into a dispersed phase. The particle aggregation can effectively affect the effective thermal conductivity when the separation distance among particles is smaller than about one fifth of the particles' dimension. For the nanofluids considered in the present work, the phase lags of heat flux and temperature gradient scale with the square of particle dimension and range from 10~n s to 10~7 s; the effect of cross-coupling between the heat conduction in the fluid and particle phases is weak; the phase lag of temperature gradient is larger than that of heat flux such that the heat conduction in them is diffusion-dominant and their effective thermal conductivity can be well predicted by the predictive models developed in the present work based on the classical diffusion theory for two-phase systems.
机译：我们用数值方法研究了六种类型的包含球体，立方体，空心球，空心立方体的纳米流体的颗粒-流体导热率，颗粒体积分数和颗粒形态对纳米流体有效导热率以及热流和温度梯度的相位滞后的影响。 ，平板状和圆柱状纳米颗粒。发现颗粒的回转半径和无量纲的颗粒-流体界面面积是影响颗粒的几何结构对有效导热率影响的两个特征参数。具有这两个参数的较大值的纳米颗粒可以更显着地改变流体电导率。由于颗粒-流体界面传热的增强，当颗粒相连接形成网络并将基础流体分离成分散相时，纳米流体的有效导热率实际上可以达到Hashin-Shtrikman界。当颗粒之间的分离距离小于颗粒尺寸的大约五分之一时，颗粒聚集可以有效地影响有效的热导率。对于目前研究中的纳米流体，热通量和温度梯度的相位滞后与颗粒尺寸的平方成正比，范围为10〜n s至10〜7 s。流体相和颗粒相之间的热传导之间的交叉耦合作用很弱。温度梯度的相位滞后大于热通量的相位滞后，使得它们中的热传导以扩散为主，并且可以通过本工作基于经典扩散理论针对两个模型建立的预测模型很好地预测它们的有效导热率。相系统。

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