Simulation of Thermal Conductivity of Nanofluids Using Dissipative Particle Dynamics

2012 ◽  
Author(s):  
Toru Yamada ◽  
Yutaka Asako ◽  
Mohammad Faghri ◽  
Chungpyo Hong
Keyword(s):  
Thermal Conductivity ◽  
Present Model ◽  
Volume Fraction ◽  
Particle Volume Fraction ◽  
Dissipative Particle Dynamics ◽  
Particle Dynamics ◽  
Interfacial Thermal Resistance ◽  
Particle Volume ◽  
Energy Conserving ◽  
Steady Heat

The effective thermal conductivity of Al2O3/water and CuO/water nanofluids were modeled by numerically solving steady heat flow in one-dimensional channels. This was accomplished by using energy conserving dissipative particle dynamics (DPDe). The effects of the interfacial thermal resistance and the Brownian motion of nanoparticles were incorporated in the model by modifying the conductive interaction parameter in the energy equation. The results were presented in the form of the thermal conductivity of nanofluids as functions of particle volume fraction and temperature, and were compared with the available experimental and analytical results. The present model agreed well with the experimental results for Al2O3/water nanofluid while there were discrepancies between the model and the results for CuO/water nanofluid.

Numerical Simulation of Thermal Conductivity of Nanofluids

2010 ◽  
Author(s):  
Jing Fan ◽  
Liqiu Wang
Keyword(s):  
Thermal Conductivity ◽  
Heat Conduction ◽  
Volume Fraction ◽  
Particle Volume Fraction ◽  
Interfacial Thermal Resistance ◽  
Thermal Conductivity Ratio ◽  
Radius Of Gyration ◽  
Particle Volume ◽  
Geometrical Structures ◽  
Conductivity Enhancement

The recent first-principle model shows a dual-phase-lagging heat conduction in nanofluids at the macroscale. The macroscopic heat-conduction behavior and the thermal conductivity of nanofluids are determined by their molecular physics and microscale physics. We examine numerically effects of particle-fluid thermal conductivity ratio, particle volume fraction, shape, aggregation, and size distribution on macroscale thermal properties for nine types of nanofluids, without considering the interfacial thermal resistance and dynamic processes on particle-fluid interfaces and particle-particle contacting surfaces. The particle radius of gyration and non-dimensional particle-fluid interfacial area in the unit cell are two very important parameters in characterizing the effect of particles’ geometrical structures on thermal conductivity of nanofluids. Nanofluids containing cross-particle networks have conductivity which practically reaches the Hashin-Shtrikman bounds. Moreover, particle aggregation influences the effective thermal conductivity only when the distance between particles is less than the particle dimension. Uniformly-sized particles are desirable for the conductivity enhancement, although to a limited extent.

CONSTRUCTAL DESIGN OF NANOFLUIDS FOR ONE-DIMENSIONAL STEADY HEAT CONDUCTION SYSTEMS

NANO ◽  
2010 ◽  
Vol 05 (01) ◽  
pp. 39-51 ◽  
Author(s):  
CHAO BAI ◽  
LI QIU WANG
Keyword(s):  
Thermal Conductivity ◽  
Heat Conduction ◽  
Thermal Resistance ◽  
Volume Fraction ◽  
Particle Volume Fraction ◽  
Particle Volume ◽  
Constructal Design ◽  
Dispersed Particles ◽  
Steady Heat Conduction ◽  
Steady Heat

We perform a constructal design of nanofluid particle volume fraction for four heat-conduction systems and four types of nanofluids to address whether nanofluids with uniformly-dispersed particles always offer the optimal global performance. The constructal volume fraction is obtained to minimize the system overall temperature difference and overall thermal resistance. The constructal thermal resistance is an overall property fixed only by the system global geometry and the average thermal conductivity of nanofluids used in the system. Efforts to enhance the thermal conductivity of nanofluids are important to reduce the constructal overall thermal resistance. The constructal nanofluids that maximize the system performance depend on both the type of nanofluids and the system configuration, and are always having a nonuniform particle volume fraction for all the cases studied in the present work. Nanofluids research and development should thus focus on not only nanofluids but also systems that use them.

Rheological Study of Micro Particle Laden Polymeric Thermal Interface Materials: Part 1 — Experimental

2002 ◽  
Author(s):  
Ravi S. Prasher ◽  
Jim Shipley ◽  
Suzana Prstic ◽  
Paul Koning ◽  
Jin-Lin Wang
Keyword(s):  
Thermal Conductivity ◽  
Volume Fraction ◽  
Particle Volume Fraction ◽  
Electronics Cooling ◽  
Bond Line ◽  
Rheological Parameters ◽  
Thermal Interface Materials ◽  
Particle Volume ◽  
Thermal Interface ◽  
Interface Materials

Particle laden polymers are one of the most prominent thermal interface materials (TIM) used in electronics cooling. Most of the research groups have primarily dealt with the understanding of the thermal conductivity of these types of TIMs. Thermal resistance is not only dependent on the thermal conductivity but also on the bond line thickness (BLT) of these TIMs. It is not clear that which material property(s) of these particle laden TIMs affects the BLT. This paper discusses the experimental measurement of rheological parameters such as non-Newtonian strain rate dependent viscosity and yield stress for 3 different particle volume fraction and 3 different base polymer viscosity materials. These rheological and BLT measurements vs. pressure will be used to model the BLT of particle-laden systems for factors such as volume fraction.

scholarly journals Improved Heat Transfer in Guar Gel Composites Reinforced with Randomly Distributed Glass Microspheres

2021 ◽  
Author(s):  
Ruifeng CAO ◽  
Taotao WANG ◽  
Yuxuan ZHANG ◽  
Hui WANG
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Particle Size ◽  
Composite Materials ◽  
Effective Thermal Conductivity ◽  
Volume Fraction ◽  
Particle Volume Fraction ◽  
Glass Microspheres ◽  
Particle Volume ◽  
Number Of Particles

Improved heat transfer in composites consisting of guar gel matrix and randomly distributed glass microspheres is extensively studied to predict the effective thermal conductivity of composites using the finite element method. In the study, the proper and probabilistic three-dimensional random distribution of microspheres in the continuous matrix is automatically generated by a simple and efficient random sequential adsorption algorithm which is developed by considering the correlation of three factors including particle size, number of particles, and particle volume fraction controlling the geometric configuration of random packing. Then the dependences of the effective thermal conductivity of composite materials on some important factors are investigated numerically, including the particle volume fraction, the particle spatial distribution, the number of particles, the nonuniformity of particle size, the particle dispersion morphology and the thermal conductivity contrast between particle and matrix. The related numerical results are compared with theoretical predictions and available experimental results to assess the validity of the numerical model. These results can provide good guidance for the design of advanced microsphere reinforced composite materials.

Volume Scattering of Radiation in Packed Beds of Large, Opaque Spheres

2004 ◽  
Vol 126 (6) ◽  
pp. 1048-1050 ◽  
Author(s):  
Quinn Brewster
Keyword(s):  
Monte Carlo ◽  
Present Model ◽  
Volume Fraction ◽  
Particle Volume Fraction ◽  
Radiative Properties ◽  
Particle Volume ◽  
Volume Scattering ◽  
Scattering Wave ◽  
Simple Factor ◽  
The Mean

A simple model is proposed for radiative properties of close-packed large, opaque spheres that accounts for nonvanishing volume of the particles, i.e., volume scattering as opposed to point scattering. It is based on the mean-beam-length concept applied to an assembly of particles, as illustrated by Mills. The resulting particle-scattering properties differ from those of classical pseudocontinuum theory based on point scattering by the simple factor of void fraction, and reduce to the point-scattering expressions in the limit of small particle volume fraction. The volume-scattering model matches detailed Monte Carlo results for extinction obtained by Kaviany and Singh and by Coquard and Baillis, which explicitly accounted for particle volume. The present model also confirms the Monte Carlo finding that the effects of nonvanishing particle volume are felt primarily in the extinction coefficient; albedo and phase function are relatively unaffected. These findings pertain only to the geometric optics regime where dependent scattering (wave coherence effects) are negligible.

Rheological Study of Micro Particle Laden Polymeric Thermal Interface Materials: Part 2 — Modeling

2002 ◽  
Author(s):  
Ravi S. Prasher ◽  
Jim Shipley ◽  
Suzana Prstic ◽  
Paul Koning ◽  
Jin-Lin Wang
Keyword(s):  
Thermal Conductivity ◽  
Thermal Resistance ◽  
Yield Stress ◽  
Volume Fraction ◽  
Particle Volume Fraction ◽  
Thermal Interface Materials ◽  
Particle Volume ◽  
Thermal Interface ◽  
Complete Set ◽  
Interface Materials

Currently there are no models to predict the thickness or the bondline thickness (BLT) of particle laden polymeric thermal interface materials (TIM) for parameters such as particle volume fraction and pressure. TIMs are used to reduce the thermal resistance. Typically this is achieved by increasing the thermal conductivity of these TIMs by increasing the particle volume fraction, however increasing the particle volume fraction also increases the BLT. Therefore, increasing the particle volume fraction may lead to an increase in the thermal resistance after certain volume fraction. This paper introduces a model for the prediction of the BLT of these particle laden TIMs. Currently thermal conductivity is the only metric for differentiating one TIM formulation from another. The model developed in this paper introduces another metric: the yield stress of these TIMs. Thermal conductivity and the yield stress together constitute the complete set of material parameters needed to define the thermal performance of particle laden TIMs.

Experimental Study of Preparation, Characterisation and Thermal Behaviour of Water-Based Nanofluids Containing Titanium Oxide Nanoparticles

2015 ◽  
Vol 766-767 ◽  
pp. 348-354 ◽  
Author(s):  
M. Arulprakasajothi ◽  
K. Elangovan ◽  
K. Hemachandra Reddy ◽  
S. Suresh
Keyword(s):  
Thermal Conductivity ◽  
Volume Fraction ◽  
Particle Volume Fraction ◽  
Particle Volume ◽  
Titanium Oxide Nanoparticles ◽  
Potential Measurement ◽  
Stable Suspension ◽  
Heat Transfer Fluids ◽  
Uniform Dispersion ◽  
Insight Into

This paper presents the preparation, characterisation and thermal behavior of TiO2/water Nanofluids with different concentration. The presence of Nanosized particles in the conventional heat transfer fluids enhances its thermo physical character. In the present work, TiO2/water Nanofluids with various volume concentrations were prepared by dispersing a specified amount of spherical sized TiO2 Nanoparticles in distilled water without any surfactant. To get a uniform dispersion and stable suspension, the Nanofluids were kept under ultrasonic vibration continuously for 3 hours. Zeta potential measurement brought detailed insight into the causes of dispersion, aggregation of Nanofluids. The KD2 Pro, fully portable thermal properties analyser, was used to measure thermal conductivity of nanofluids. The viscosity of the nanofluid was measured using a Brookfield Viscometer. The experimental results show that the thermal conductivity increases with an increase of particle volume fraction and the enhancement was observed to be 9.22% over the base fluid for volume concentration of 0.75%. From the experimental observations, enhancement in thermal conductivity is larger than the enhancement in viscosity.

Dependence of Thermal Conductivity and Mechanical Rigidity of Particle-Laden Polymeric Thermal Interface Material on Particle Volume Fraction

2003 ◽  
Vol 125 (3) ◽  
pp. 386-391 ◽  
Author(s):  
Ravi S. Prasher ◽  
Paul Koning ◽  
James Shipley ◽  
Amit Devpura
Keyword(s):  
Experimental Data ◽  
Thermal Conductivity ◽  
Mechanical Response ◽  
Volume Fraction ◽  
Effective Medium Theory ◽  
Particle Volume Fraction ◽  
Thermal Interface Material ◽  
Particle Volume ◽  
Thermal Interface ◽  
Medium Theory

This paper reports the measurement of the thermal conductivity of particle-laden polymeric thermal interface materials for three different particle volume fractions. The experimental data are further compared with the percolation model and effective medium theory. We then introduce a method of obtaining the contact resistance between the particles and the polymeric matrix by a combination of percolation modeling and experimental data. We also discuss the dependence of the mechanical response of these particle-laden polymers for different filler or particle loading. A novel mechanical length scale is defined to understand the mechanical response of these materials, and is correlated to the viscosity of these materials.

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