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RESEARCH PAPERS: Micro/Nanoscale Heat Transfer

Brownian-Motion-Based Convective-Conductive Model for the Effective Thermal Conductivity of Nanofluids

[+] Author and Article Information
Ravi Prasher1

 Intel Corporation, CH5-157, 5000 W. Chandler Blvd., Chandler, AZ 85226-3699ravi.s.prasher@intel.com

Prajesh Bhattacharya, Patrick E. Phelan

 Arizona State University, Department of Mechanical & Aerospace Engineering, Tempe, AZ 85287-6106

1

Corresponding author. Adjunct Professor, Dept. of Mechanical & Aerospace Engineering, Arizona State University.

J. Heat Transfer 128(6), 588-595 (Nov 07, 2005) (8 pages) doi:10.1115/1.2188509 History: Received August 10, 2005; Revised November 07, 2005

Here we show through an order-of-magnitude analysis that the enhancement in the effective thermal conductivity of nanofluids is due mainly to the localized convection caused by the Brownian movement of the nanoparticles. We also introduce a convective-conductive model which accurately captures the effects of particle size, choice of base liquid, thermal interfacial resistance between the particles and liquid, temperature, etc. This model is a combination of the Maxwell-Garnett (MG) conduction model and the convection caused by the Brownian movement of the nanoparticles, and reduces to the MG model for large particle sizes. The model is in good agreement with data on water, ethylene glycol, and oil-based nanofluids, and shows that the lighter the nanoparticles, the greater the convection effect in the liquid, regardless of the thermal conductivity of the nanoparticles.

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Copyright © 2006 by American Society of Mechanical Engineers
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Figures

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Figure 1

Effect of particle diameter and interfacial thermal resistance (Rb) on the effective thermal conductivity predicted by the Maxwell-Garnett model, for water as the fluid

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Figure 2

Comparison of the Maxwell-Garnett predicted k and experimental data for water-based nanofluids. The number in the legend indicates the diameter of the particles, in nanometers (Rb=0.77×10−8Km2W−1).

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Figure 3

Comparison of the Maxwell-Garnett predicted k and experimental data for EG-based nanofluids. The number in the legend indicates the diameter of the particles, in nanometers (Rb=1.2×10−8Km2W−1).

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Figure 4

Comparison of the Maxwell-Garnett predicted k and experimental data for oil-based nanofluids. The number in the legend indicates the diameter of the particles, in nanometers (Rb=1.925×10−8Km2W−1).

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Figure 5

Comparison of single sphere Brownian model (SGBM) with data on various water-based nanofluid

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Figure 6

Comparison of the multisphere Brownian model with experimental data on EG-based nanofluids for Rb=1.2×10−8Km2W−1, A=4×104, and the corresponding values of m are given in Table 1. The number in the legend indicates the mean diameter of the particles, in nanometers.

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Figure 7

Comparison of the multisphere Brownian model with experimental data on oil-based nanofluids for Rb=1.925×10−8Km2W−1, A=4×104, and the corresponding values of m are given in Table 2. The number in the legend indicates the mean diameter of the particles, in nanometers.

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Figure 8

Comparison of the semiempirical Brownian model with experimental data for 28.6-nm CuO nanoparticles in water (5), for varying temperatures assuming constant Rb=0.77×10−8Km2W−1

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Figure 9

Comparison of the multisphere Brownian model with data for different nanoparticle diameters

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Figure 10

Effect of nanoparticle density on the thermal conductivity of nanofluids

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