Liquid Layering and the Enhanced Thermal Conductivity of Ar-Cu Nanofluids: A Molecular Dynamics Study

2016 ◽  
Author(s):  
Jithu Paul ◽  
A. K. Madhu ◽  
U. B. Jayadeep ◽  
C. B. Sobhan
Keyword(s):  
Thermal Conductivity ◽  
Molecular Dynamics ◽  
Particle Size ◽  
Molecular Dynamics Simulations ◽  
Volume Fraction ◽  
Strong Dependence ◽  
Particle Sizes ◽  
Dynamics Simulations ◽  
Enhanced Thermal Conductivity ◽  
Liquid Layering

Nanofluids — colloidal suspensions of nanoparticles in base fluids — are known to possess superior thermal properties compared to the base fluids. Various theoretical models have been suggested to explain the often anomalous enhancement of these properties. Liquid layering around the nanoparticle is one of such reasons. The effect of the particle size on the extent of liquid layering around the nanoparticle has been investigated in the present study. Classical molecular dynamics simulations have been performed in the investigation, considering the case of a copper nanoparticle suspended in liquid argon. The results show a strong dependence of thickness of the liquid layer on the particle size, below a particle diameter of 4nm. To establish the role of liquid layering in the enhancement of thermal conductivity, simulations have been performed at constant volume fraction for different particle sizes using Green Kubo formalism. The thermal conductivity results show 100% enhancement at 3.34% volume fraction for particle size of 2nm. The results establish the dominant role played by liquid layering in the enhanced thermal conductivity of nanofluids at the low particle sizes used. Contrary to the previous findings, the molecular dynamics simulations also predict a strong dependence of the liquid layer thickness on the particle size in the case of small particles.

Enhanced Thermal Conductivity of Nanofluids Diagnosis by Molecular Dynamics Simulations

2008 ◽  
Vol 8 (7) ◽  
pp. 3710-3718 ◽  
Author(s):  
Kuo-Liang Teng ◽  
Pai-Yi Hsiao ◽  
Shih-Wei Hung ◽  
Ching-Chang Chieng ◽  
Ming-Shen Liu ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Molecular Dynamics ◽  
Brownian Motion ◽  
Molecular Dynamics Simulations ◽  
Intermolecular Interactions ◽  
Layer Structure ◽  
Particle Interactions ◽  
Fundamental Physics ◽  
Dynamics Simulations ◽  
Enhanced Thermal Conductivity

Molecular Dynamics simulations are performed to calculate the thermal conductivity of nanofluids, and to understand the fundamental physics of the enhancement of thermal conductivity observed in experiments. Based on the analysis, intermolecular interactions between copper–copper atoms, layer structure surrounding nanoparticles, convection effect induced by the Brownian motion of copper atoms, as well as particle–particle interactions are identified and confirmed on the enhancement using Green-Kubo method in thermal conductivity.

Enhanced Thermal Conductivity of Nanofluids Diagnosis by Molecular Dynamics Simulations

2008 ◽  
Vol 8 (7) ◽  
pp. 3710-3718 ◽  
Author(s):  
Kuo-Liang Teng ◽  
Pai-Yi Hsiao ◽  
Shih-Wei Hung ◽  
Ching-Chang Chieng ◽  
Ming-Shen Liu ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Molecular Dynamics ◽  
Molecular Dynamics Simulations ◽  
Dynamics Simulations ◽  
Enhanced Thermal Conductivity

Pore-size effects on thermal conductivity of SiO2 quartz using non-equilibrium molecular dynamics simulations

2018 ◽  
Vol 17 (01) ◽  
pp. 1850010
Author(s):  
Jin Hyeok Cha ◽  
Woongpyo Hong ◽  
Sujung Noh ◽  
Shinhu Cho
Keyword(s):  
Thermal Conductivity ◽  
Molecular Dynamics ◽  
Molecular Dynamics Simulations ◽  
Porous Materials ◽  
Thermal Conduction ◽  
Volume Fraction ◽  
Nonequilibrium Molecular Dynamics ◽  
Volume Fractions ◽  
Low Volume ◽  
Dynamics Simulations

Porous materials are commonly used to decrease or regulate thermal transport in insulating materials due to the very low thermal conductivity of the pores. More pores can achieve a better insulating effect; however, this can also be a shortcoming when the materials are directly involved in physical movement with friction, such as an interior wall of a cylinder in an automobile engine intended to prevent heat loss. Thus, it is important to clarify the mechanisms of the pore-dependent thermal properties of porous materials. In this study, the effects of the number and size of pores in silica quartz on thermal conductivity were investigated using nonequilibrium molecular dynamics simulations. The results revealed that the thermal conductivity of porous silica quartz decreased in all cases with an increase in the volume fraction of pores. A lower number of pores in the system showed higher thermal conductivity in the range of low volume fractions. We also showed that the interstitial distance between pores mostly governs thermal conduction at low volume fractions [Formula: see text] vol.%. Additionally, the mechanism of thermal conduction was assessed with respect to several theoretical models.

scholarly journals Ballistic Heat Transport in Nanocomposite: The Role of the Shape and Interconnection of Nanoinclusions

Nanomaterials ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 1982
Author(s):  
Paul Desmarchelier ◽  
Alice Carré ◽  
Konstantinos Termentzidis ◽  
Anne Tanguy
Keyword(s):  
Thermal Conductivity ◽  
Molecular Dynamics ◽  
Molecular Dynamics Simulations ◽  
Free Path ◽  
Mean Free Path ◽  
Strong Increase ◽  
Moderate Increase ◽  
Energy Propagation ◽  
The Mean ◽  
Dynamics Simulations

In this article, the effect on the vibrational and thermal properties of gradually interconnected nanoinclusions embedded in an amorphous silicon matrix is studied using molecular dynamics simulations. The nanoinclusion arrangement ranges from an aligned sphere array to an interconnected mesh of nanowires. Wave-packet simulations scanning different polarizations and frequencies reveal that the interconnection of the nanoinclusions at constant volume fraction induces a strong increase of the mean free path of high frequency phonons, but does not affect the energy diffusivity. The mean free path and energy diffusivity are then used to estimate the thermal conductivity, showing an enhancement of the effective thermal conductivity due to the existence of crystalline structural interconnections. This enhancement is dominated by the ballistic transport of phonons. Equilibrium molecular dynamics simulations confirm the tendency, although less markedly. This leads to the observation that coherent energy propagation with a moderate increase of the thermal conductivity is possible. These findings could be useful for energy harvesting applications, thermal management or for mechanical information processing.

A Molecular Dynamics Study of Thermal Conductivity in Nanocomposites via the Phonon Wave Packet Method

2009 ◽  
Author(s):  
Zhiting Tian ◽  
Sang Kim ◽  
Ying Sun ◽  
Bruce White
Keyword(s):  
Thermal Conductivity ◽  
Molecular Dynamics ◽  
Wave Packet ◽  
Molecular Dynamics Simulations ◽  
Phonon Scattering ◽  
Flow Direction ◽  
Normal Incidence ◽  
Material Interfaces ◽  
Non Equilibrium Molecular Dynamics ◽  
Dynamics Simulations

The phonon wave packet technique is used in conjunction with the molecular dynamics simulations to directly observe phonon scattering at material interfaces. The phonon transmission coefficient of nanocomposites is examined as a function of the defect size, thin film thickness, orientation of interface to the heat flow direction. To generalize the results based on phonons in a narrow frequency range and at normal incidence, the effective thermal conductivity of the same nanocomposite structure is calculated using non-equilibrium molecular dynamics simulations for model nanocomposites formed by two mass-mismatched Ar-like solids and heterogeneous Si-SiCO2 systems. The results are compared with the modified effective medium formulation for nanocomposites.

Thermal Conductivity in Thin Silicon Nanowires with Rough Surfaces by Molecular Dynamics Simulations

2010 ◽  
Author(s):  
Xueming Yang ◽  
Albert C. To ◽  
Jane W. Z. Lu ◽  
Andrew Y. T. Leung ◽  
Vai Pan Iu ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Molecular Dynamics ◽  
Molecular Dynamics Simulations ◽  
Silicon Nanowires ◽  
Rough Surfaces ◽  
Thin Silicon ◽  
Dynamics Simulations

Multiscale Simulations of Thermoelectric Properties of PBTE

2008 ◽  
Author(s):  
Bo Qiu ◽  
Hua Bao ◽  
Xiulin Ruan
Keyword(s):  
Thermal Conductivity ◽  
Molecular Dynamics ◽  
Molecular Dynamics Simulations ◽  
Thermoelectric Properties ◽  
Transport Coefficients ◽  
Multiscale Simulation ◽  
Full Potential ◽  
Boltzmann Transport ◽  
Pair Potentials ◽  
Dynamics Simulations

In this paper, thermoelectric properties of bulk PbTe are calculated using first principles calculations and molecular dynamics simulations. The Full Potential Linearized Augmented Plane Wave (FP-LAPW) method is first employed to calculate the PbTe band structure. The transport coefficients (Seebeck coefficient, electrical conductivity, and electron thermal conductivity) are then computed using Boltzmann transport equation (BTE) under the constant relaxation time approximation. Interatomic pair potentials in the Buckingham form are also derived using ab initio effective charges and total energy data. The effective interatomic pair potentials give excellent results on equilibrium lattice parameters and elastic constants for PbTe. The lattice thermal conductivity of PbTe is then calculated using molecular dynamics simulations with the Green-Kubo method. In the end, the figure of merit of PbTe is computed revealing the thermoelectric capability of this material, and the multiscale simulation approach is shown to have the potential to identify novel thermoelectric materials.

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