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Research Papers: Micro/Nanoscale Heat Transfer

# Experimental Study of Heat Conduction in Aqueous Suspensions of Aluminum Oxide Nanoparticles

[+] Author and Article Information
Y. Sungtaek Ju1

Mechanical and Aerospace Engineering Department, University of California, Los Angeles, CA 90095just@seas.ucla.edu

Jichul Kim, Ming-Tsung Hung

Mechanical and Aerospace Engineering Department, University of California, Los Angeles, CA 90095

1

Corresponding author.

J. Heat Transfer 130(9), 092403 (Jul 10, 2008) (6 pages) doi:10.1115/1.2945886 History: Received June 06, 2007; Revised January 03, 2008; Published July 10, 2008

## Abstract

We report measurements of the thermal conductivity of aqueous suspensions of aluminum oxide nanoparticles with nominal diameters of $20nm$, $30nm$, and $45nm$ and at volume concentrations up to 10%. Potential complications in the pulsed transient hot-wire technique for characterizing nanofluids are examined, which motivate the development of a microhot strip setup with a small thermal time constant. The average particle size is monitored for samples subjected to different durations of sonication and the thermal conductivity is determined at two different temperatures for each of the samples. The present data do not reveal any anomalous enhancement in the thermal conductivity previously reported for comparable nanofluids. The concentration dependence of the thermal conductivity can be explained using the conventional effective medium model with a physically reasonable set of parameters.

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## Figures

Figure 7

Sonication time dependence of the particle size in the nanofluids prepared using Nanopowder II

Figure 1

The time evolution of the thermal conductivity of a sonicated water sample and the wire temperature obtained from our macroscale hot-wire setup. The literature value of the thermal conductivity at each wire temperature is shown as the dashed line.

Figure 2

The thermal conductivity of water measured using the macroscale hot-wire setup as a function of time interval between successive heating pulses

Figure 3

Schematic of the microhot-wire device

Figure 4

The ratio between the thermal conductivity of the nanofluids and that of pure water at 23°C. The lines are the predictions of the effective medium model.

Figure 5

Callaway’s model prediction for the thermal conductivity of sapphire wires and alumina nanostructures

Figure 6

Sonication time and temperature dependence of the thermal conductivity of the nanofluids prepared with Nanopowder II

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