Numerical Study of the Effective Thermal Conductivity of Nanofluids

2005 ◽  
Author(s):  
Ratnesh K. Shukla ◽  
Vijay K. Dhir
Keyword(s):  
Thermal Conductivity ◽  
Numerical Study ◽  
Free Particle ◽  
Liquid System ◽  
Bulk Liquid ◽  
Dynamics Simulations ◽  
Solid Liquid ◽  
Base Liquid ◽  
Liquid Layering ◽  
Ordered Layers

Nanofluids, that is liquids containing nanometer sized metallic or non-metallic solid nanoparticles show an increase in thermal conductivity compared to that of the base liquid. In this paper we present numerical results obtained from Molecular Dynamics Simulations of a solid-liquid system comprising of Lennard-Jones atoms used to study the liquid layering on solid nanoparticles. It is found that close to the solid surface the liquid atoms form ordered layers which display higher thermal conductivity compared to the bulk liquid. We also present a model for thermal conductivity of nanofluids based on the theory of Brownian motion of a free particle and show that the thermal conductivity of the nanofluid predicted from the model agrees qualitatively with the experimental observations.

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.

Thermal Transport in Self-Assembled Conductive Networks for Thermal Interface Materials

2011 ◽  
Vol 133 (2) ◽  
Author(s):  
Lin Hu ◽  
William Evans ◽  
Pawel Keblinski
Keyword(s):  
Thermal Conductivity ◽  
Effective Thermal Conductivity ◽  
Volume Fraction ◽  
Liquid Solution ◽  
Thermal Interface Materials ◽  
Thermal Interface ◽  
Rapid Formation ◽  
Dynamics Simulations ◽  
Solid Liquid ◽  
Interface Materials

We present a concept for development of high thermal conductivity thermal interface materials (TIMs) via a rapid formation of conductive network. In particular we use molecular dynamics simulations to demonstrate the possibility of a formation of a network of solid nanoparticles in liquid solution and establish wetting and volume fraction conditions required for a rapid formation of such network. Then, we use Monte-Carlo simulations to determine effective thermal conductivity of the solid/liquid composite material. The presence of a percolating network dramatically increases the effective thermal conductivity, as compared to values characterizing dispersed particle structures.

Thermal Conductivity and Thermal Mechanism of Octadecane from Molecular Dynamics Simulations

2012 ◽  
Vol 501 ◽  
pp. 139-144
Author(s):  
Qing Ling Li ◽  
Wen Juan Zheng ◽  
Yan Wang ◽  
Yan Zhou
Keyword(s):  
Heat Transfer ◽  
Phase Transition ◽  
Thermal Conductivity ◽  
Contact Interface ◽  
Transfer Resistance ◽  
Material Studio ◽  
Increasing Trend ◽  
Thermal Mechanism ◽  
Dynamics Simulations ◽  
Solid Liquid

The physical model of the octadecane in the paraffin is established by Material Studio software in this paper, thermal conductivity and micro-thermal mechanism of octadecane are simulated by program LAMMPS. Results show that: the thermal conductivity of octadecane is about , which has an increasing trend with enhancement of temperature; simultaneously it mainly relies on the molecular or atomic thermal vibration to transmit heat. When the octadecane has phase transition, reducing of thermal conductivity is due to the increasing of heat transfer resistance of solid-liquid contact interface.

Vibrational Contribution to Thermal Conductivity of Silicon Near Solid-Liquid Transition

2011 ◽  
Author(s):  
Christopher H. Baker ◽  
Chengping Wu ◽  
Richard N. Salaway ◽  
Leonid V. Zhigilei ◽  
Pamela M. Norris
Keyword(s):  
Thermal Conductivity ◽  
Molecular Dynamics ◽  
Melting Point ◽  
Silicon Substrates ◽  
Liquid Transition ◽  
Electron Contribution ◽  
Non Equilibrium Molecular Dynamics ◽  
Dynamics Simulations ◽  
Solid Liquid ◽  
Vibrational Contribution

Although thermal transport in silicon is dominated by phonons in the solid state, electrons also participate as the system approaches, and exceeds, its melting point. Thus, the contribution from both phonons and electrons must be considered in any model for the thermal conductivity, k, of silicon near the melting point. In this paper, equilibrium molecular dynamics simulations measure the vibration mediated thermal conductivity in Stillinger-Weber silicon at temperatures ranging from 1400 to 2000 K — encompassing the solid-liquid phase transition. Non-equilibrium molecular dynamics is also employed as a confirmatory study. The electron contribution may then be estimated by comparing these results to experimental measurements of k. The resulting relationship may provide a guide for the modeling of heat transport under conditions realized in high temperature applications, such as laser irradiation or rapid thermal processing of silicon substrates.

NUMERICAL STUDY OF NATURAL CONVECTION DOMINATED MELTING OF A PCM WITH CONJUGATE FORCED CONVECTION

1995 ◽  
Vol 19 (4) ◽  
pp. 455-469
Author(s):  
M. Lacroix
Keyword(s):  
Thermal Conductivity ◽  
Natural Convection ◽  
Forced Convection ◽  
Numerical Study ◽  
Convection Heat Transfer ◽  
Melting Process ◽  
Reynolds Numbers ◽  
Solid Liquid Interface ◽  
Solid Liquid ◽  
Convection Dominated

This paper presents a numerical analysis of natural convection dominated melting inside a rectangular enclosure coupled with forced convection heat transfer in a transport fluid via a finite conductance heat exchanging surface. A computational methodology based on a stream function-vorticity-temperature formulation is adopted and the irregular shape of the moving solid-liquid interface is treated with body-fitted coordinates. The model is then employed to investigate the interaction between natural convection in the PCM filled cavity and forced convection in the HTF. Numerical experiments were carried out for Rayleigh numbers, Ra, between 2.08‧108 and 4.60‧109, modified Reynolds numbers, Re between 4.23 and 423.0, wall-PCM thermal diffusivity ratios, α, between 5.0 and 10.0 and dimensionless wall thickness, w, between 0.005 and 0.05. Results show that the melting process is increasingly delayed by heat conduction across a wall of decreasing thermal conductivity and/or increasing thickness. This effect is accentuated for low HTF flow rates (Re ~ 4.23). On the other hand, for a wail of given thickness and thermal conductivity, the effect of increasing the HTF flow rate on the melting process becomes imperceptible for Re ≥ 4.23.

scholarly journals Interfacial Thermal Conductivity and Its Anisotropy

Processes ◽  
2019 ◽  
Vol 8 (1) ◽  
pp. 27
Author(s):  
Xiaoyu Wang ◽  
Cynthia J. Jameson ◽  
Sohail Murad
Keyword(s):  
Thermal Conductivity ◽  
Heat Dissipation ◽  
Safety Concern ◽  
Kapitza Resistance ◽  
Density Profiles ◽  
Efficient Operation ◽  
Dynamics Simulations ◽  
Solid Liquid ◽  
Interfacial Films ◽  
Significant Effort

There is a significant effort in miniaturizing nanodevices, such as semi-conductors, currently underway. However, a major challenge that is a significant bottleneck is dissipating heat generated in these energy-intensive nanodevices. In addition to being a serious operational concern (high temperatures can interfere with their efficient operation), it is a serious safety concern, as has been documented in recent reports of explosions resulting from many such overheated devices. A significant barrier to heat dissipation is the interfacial films present in these nanodevices. These interfacial films generally are not an issue in macro-devices. The research presented in this paper was an attempt to understand these interfacial resistances at the molecular level, and present possibilities for enhancing the heat dissipation rates in interfaces. We demonstrated that the thermal resistances of these interfaces were strongly anisotropic; i.e., the resistance parallel to the interface was significantly smaller than the resistance perpendicular to the interface. While the latter is well-known—usually referred to as Kapitza resistance—the anisotropy and the parallel component have previously been investigated only for solid-solid interfaces. We used molecular dynamics simulations to investigate the density profiles at the interface as a function of temperature and temperature gradient, to reveal the underlying physics of the anisotropy of thermal conductivity at solid-liquid, liquid-liquid, and solid-solid interfaces.

Effects of anisotropy and solid/liquid thermal conductivity ratio during inverted Bridgman growth

2002 ◽  
Author(s):  
Julaporn Kaenton ◽  
Victoria Timchenko ◽  
Mohammed El Ganaoui ◽  
Graham de Vahl Davis ◽  
Eddie Leonardi ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Thermal Conductivity Ratio ◽  
Conductivity Ratio ◽  
Bridgman Growth ◽  
Liquid Thermal Conductivity ◽  
Solid Liquid

Numerical Performances Study of Curved Photovoltaic Panel Integrated with Phase Change Material

2020 ◽  
Vol 22 (4) ◽  
pp. 1439-1452
Author(s):  
Mohamed L. Benlekkam ◽  
Driss Nehari ◽  
Habib Y. Madani
Keyword(s):  
Phase Change ◽  
Phase Change Material ◽  
Numerical Study ◽  
Numerical Data ◽  
Navier Stokes ◽  
Photovoltaic Panel ◽  
Pv Panel ◽  
Energy Equations ◽  
Solid Liquid ◽  
Change Material

AbstractThe temperature rise of photovoltaic’s cells deteriorates its conversion efficiency. The use of a phase change material (PCM) layer linked to a curved photovoltaic PV panel so-called PV-mirror to control its temperature elevation has been numerically studied. This numerical study was carried out to explore the effect of inner fins length on the thermal and electrical improvement of curved PV panel. So a numerical model of heat transfer with solid-liquid phase change has been developed to solve the Navier–Stokes and energy equations. The predicted results are validated with an available experimental and numerical data. Results shows that the use of fins improve the thermal load distribution presented on the upper front of PV/PCM system and maintained it under 42°C compared with another without fins and enhance the PV cells efficiency by more than 2%.

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