Empirical correlating equations for predicting the effective thermal conductivity and dynamic viscosity of nanofluids

This article reports on the International Nanofluid Property Benchmark Exercise, or INPBE, in which the thermal conductivity of identical samples of colloidally stable dispersions of nanoparticles or “nanofluids,” was measured by over 30 organizations worldwide, using a variety of experimental approaches, including the transient hot wire method, steady-state methods, and optical methods. The nanofluids tested in the exercise were comprised of aqueous and nonaqueous basefluids, metal and metal oxide particles, near-spherical and elongated particles, at low and high particle concentrations. The data analysis reveals that the data from most organizations lie within a relatively narrow band (±10% or less) about the sample average with only few outliers. The thermal conductivity of the nanofluids was found to increase with particle concentration and aspect ratio, as expected from classical theory. There are (small) systematic differences in the absolute values of the nanofluid thermal conductivity among the various experimental approaches; however, such differences tend to disappear when the data are normalized to the measured thermal conductivity of the basefluid. The effective medium theory developed for dispersed particles by Maxwell in 1881 and recently generalized by Nan et al. [J. Appl. Phys. 81, 6692 (1997)], was found to be in good agreement with the experimental data, suggesting that no anomalous enhancement of thermal conductivity was achieved in the nanofluids tested in this exercise.

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A benchmark study on the thermal conductivity of nanofluids

2.4. Block Copolymer Containing Hybrids 151 3. Block Copolymer Ordering in Thin Films 153 3.1. General Process Steps 153 3.2. Morphology of Thin Films 154 3.3. Thickness-Dependent Nanopatterning 154 3.3.1. Ultrathin Films: Monomolecular Films 155 3.3.2. Sub-L0 Thick Films 155 3.3.3. Thick Films 157 3.4. Placement Control: Directed Self-Assembly (DSA) 162 3.4.1. Topographic Guiding Patterns: Graphoepitaxy 163

Block copolymer based nanostructures: materials, processes, and applications to electronics.

A Benchmark Study on the Thermal Conductivity of Nanofluids

Latest developments on the viscosity of nanofluids

This study investigates the thermal conductivity and viscosity of copper nanoparticles in ethylene glycol. The nanofluid was prepared by synthesizing copper nanoparticles using a chemical reduction method, with water as the solvent, and then dispersing them in ethylene glycol using a sonicator. Volume loadings of up to 2% were prepared. The measured increase in thermal conductivity was twice the value predicted by the Maxwell effective medium theory. The increase in viscosity was about four times of that predicted by the Einstein law of viscosity. Analytical calculations suggest that this nanofluid would not be beneficial as a coolant in heat exchangers without changing the tube diameter. However, increasing the tube diameter to exploit the increased thermal conductivity of the nanofluid can lead to better thermal performance.

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J. B. Gordon

Papers

Enhanced thermal conductivity and viscosity of copper nanoparticles in ethylene glycol nanofluid