Simulation Of Heat Transfer Enhancement In Nanoparticle Suspensions


Effective thermal conductivity; Green-Kubo equation; Heat transfer enhancement; Molecular dynamics; Nanofluid; Silica nanoparticle suspension


Nanofluids, also known as complex or smart fluids, are liquids with suspended nanoparticles at low concentration. They are effective in enhancing heat transfer characteristics and hence the energy transport. The novel heat transfer fluids not only exhibit anomalously enhanced thermal properties, but also overcome the vulnerability of quick settling down that usually hinders practical applications. All these characteristics make nanofluids promising for nanotechnology-based heat transfer applications including electronic chip cooling, lubricants and heat exchangers. Since the characteristic length scales are of the order of mean free path, continuum hypothesis does not hold, so intermolecular attraction and repulsion, collisions and other surface interactions need to be considered using the Molecular Dynamics (MD) simulation in order to understand the mechanisms responsible for the enhancement of heat transfer. In this paper, two types of models have been discussed. First, a nonequilibrium molecular dynamic model for calculating thermal conductivity of nanofluids has been presented, in which all interactions in nanofluids, including fluid atom-fluid atom, nanoparticle-nanoparticle, and nanoparticle-fluid atoms have been considered. Lennard-Jones-like potential expressions are used to derive the interactions between nanoparticles and base liquid atoms, while an exponential expression is used to obtain the interactions between nanoparticles. By this model, a general method to explore the mechanisms of heat transfer enhancement in nanofluids has been established. Simultaneous to this effort, an equilibrium molecular dynamic model which incorporates the atomic interactions for silica by van Beest-Kramer-van Santen (BKS) potential with an SPC/E model for water has been established. To ensure the authenticity of this 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 interactions 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 the Green-Kubo equation which bridges the thermal conductivity with the 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.

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Materials Science and Technology



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Article; Proceedings Paper

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33845539882 (Scopus)

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