Calculation of Thermal Conductivity in Nanofluids From Atomic-Scale Simulations
Calculation of Thermal Conductivity in Nanofluids From Atomic-Scale Simulations
复制标题
通过原子尺度模拟计算纳米流体的热导率
DOI：
10.1115/imece2005-80849
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发表时间：
2005
影响因子：
7
通讯作者：
P. Sachdeva
中科院分区：
文献类型：
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作者：
Xuan Wu;Ranganathan Kumar;P. Sachdeva
纳米流体是由纳米颗粒和纤维分散在基础液体中组成的，具有增强传热性能的潜力。尽管纳米流体的三个特征（包括在非常低的纳米颗粒浓度下的非常高的热导率、强烈的温度依赖性热导率和临界热通量的显著增加）已经被广泛研究，并且液体分子在颗粒-液体界面处的分层、纳米颗粒中的热传输的弹道性质，和纳米颗粒聚集被认为是负责这种传热增强的可能原因，但很少有原子尺度的研究工作来验证或解释纳米流体的这些迷人特征。本文建立了一个结合BKS势的SiO_2原子相互作用和SPC/E模型的水分子动力学模型。为了保证模型的真实性，我们采用晶体学方法计算了纳米颗粒中每个原子的位置。纳米粒子与水之间的界面相互作用被简化为许多离子之间的相互作用的总和。由于静电相互作用，纳米颗粒表面的离子可以吸引一定数量的水分子，因此研究了纳米颗粒与水之间的相互作用对纳米流体强化传热的影响。利用Green-Kubo方程在导热系数和热流时间自相关函数之间架起了一座桥梁，建立了一个由二氧化硅纳米颗粒和纯水组成的稀纳米流体导热系数的计算模型。模拟结果揭示了纳米流体强化传热的可能机理。Copyright © 2005 by ASME
Nanofluids that consist of nanometer sized particles and fibers dispersed in base liquids have shown the potential to enhance the heat transfer performance. Although three features of nanofluids including anomalously high thermal conductivities at very low nanoparticle concentrations, strongly temperature dependent thermal conductivity and significant increases in critical heat flux have been studied widely, and layering of liquid molecules at the particle-liquid interface, ballistic nature of heat transport in nanoparticles, and nanoparticle clustering are considered as the possible causations responsible for such kind of heat transfer enhancement, few research work from atomic-scale has been done to verify or explain those fascinating features of nanofluids. In this paper, a molecular dynamic model, which incorporates the atomic interactions for silica by BKS potential with a SPC/E model for water, has been established. To ensure the authenticity of our model, the position of each atom in the nanoparticle is derived by the crystallographic method. The interfacial interactions between the nanoparticle and water are simplified as the sum of interaction between many ions. Due to the electrostatic interaction, the ions on the nanoparticle’s surface can attract a certain number of water molecules, therefore, the effect of interaction between the nanoparticle and water on heat transfer enhancement in nanofluids is studied. By using Green-Kubo equations which set a bridge between thermal conductivity and time autocorrelation function of the heat current, a model which may derive thermal conductivity of dilute nanofluids that consist of silica nanoparticles and pure water is built. Several simulation results have been provided which can reveal the possible mechanism of heat enhancement in nanofluids.Copyright © 2005 by ASME