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RESEARCH PAPERS: Micro/Nanoscale Heat Transfer

Effects of Various Parameters on Nanofluid Thermal Conductivity

[+] Author and Article Information
Seok Pil Jang

School of Aerospace and Mechanical Engineering, Hankuk Aviation University, Goyang, Gyeonggi-do, 412-791, Korea Energy Systems Division, Argonne National Laboratory, Argonne, IL 60439

Stephen U. S. Choi1

Energy Systems Division, Argonne National Laboratory, Argonne, IL 60439

1

Corresponding author. Current address: High Efficiency Energy Research Department, Korea Institute of Energy Research, Yuseong-gu, Daejeon, 305-343, Korea. email: suschoi@kier.re.kr

J. Heat Transfer 129(5), 617-623 (Aug 02, 2006) (7 pages) doi:10.1115/1.2712475 History: Received April 30, 2005; Revised August 02, 2006

The addition of a small amount of nanoparticles in heat transfer fluids results in the new thermal phenomena of nanofluids (nanoparticle-fluid suspensions) reported in many investigations. However, traditional conductivity theories such as the Maxwell or other macroscale approaches cannot explain the thermal behavior of nanofluids. Recently, Jang and Choi proposed and modeled for the first time the Brownian-motion-induced nanoconvection as a key nanoscale mechanism governing the thermal behavior of nanofluids, but did not clearly explain this and other new concepts used in the model. This paper explains in detail the new concepts and simplifying assumptions and reports the effects of various parameters such as the ratio of the thermal conductivity of nanoparticles to that of a base fluid, volume fraction, nanoparticle size, and temperature on the effective thermal conductivity of nanofluids. Comparison of model predictions with published experimental data shows good agreement for nanofluids containing oxide, metallic, and carbon nanotubes.

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Copyright © 2007 by American Society of Mechanical Engineers
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Figures

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Figure 1

Bright-field transmission electron micrograph of copper nanoparticles produced by a single-step process into ethylene glycol. Nanofluids containing these small (<10nm) nanoparticles with little agglomeration can conduct heat one order-of-magnitude faster than scientists had predicted to be possible.

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Figure 2

Experimental data for nanofluids containing oxide and metallic nanoparticles and predictions from Eq. 26: (a) water-based nanofluids and (b) ethylene glycol-based nanofluids

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Figure 3

Experimental data for nanofluids containing carbon nanotubes and predictions from Eq. 26

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Figure 4

Effect of ratio of thermal conductivity of nanoparticles to that of base fluid on the thermal conductivity of nanofluids

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Figure 5

Effect of diameter of nanoparticle on thermal conductivity of nanofluids

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Figure 6

Effect of diameter of nanoparticle on thermal conductivity of ethylene glycol-based nanofluids containing copper

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Figure 7

Experimental data for temperature-dependent conductivity of and predictions from Eq. 26 and the Maxwell model

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Figure 8

Temperature versus thermal conductivity enhancement predicted by Eq. 26 for water-based nanofluids containing 6nm copper

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