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Research Papers

Thermophysical Properties and Pool Boiling Characteristics of Water-in-Polyalphaolefin Nanoemulsion Fluids

[+] Author and Article Information
Bao Yang

Department of Mechanical Engineering,
University of Maryland,
College Park, MD 20742

Boualem Hammouda

Center for Neutron Research,
National Institute of Standards and Technology,
Gaithersburg, MD 20899

1Corresponding author.

Contributed by the Heat Transfer Division of ASME for publication in the JOURNAL OF HEAT TRANSFER. Manuscript received June 29, 2012; final manuscript received January 17, 2013; published online July 26, 2013. Guest Editors: G. P. “Bud” Peterson and Zhuomin Zhang.

J. Heat Transfer 135(9), 091303 (Jul 26, 2013) (6 pages) Paper No: HT-12-1328; doi: 10.1115/1.4024423 History: Received June 29, 2012; Revised January 17, 2013

In this work, thermophysical properties, microstructure, and pool boiling characteristics of water-in-polyalphaolefin (PAO) nanoemulsion fluids have been measured in the water concentration range of 0–10.3 vol. %, in order to gain basic data for nanoemulsion boiling. Water-in-PAO nanoemulsion fluids are formed via self-assembly with surfactant: sodium sullfosuccinate (AOT). Thermal conductivity of these fluids is found to increase monotonically with water concentration, as expected from the Maxwell equation. Unlike thermal conductivity, their dynamic viscosity first increases with water concentration, reaches a maximum at 5.3 vol. %, and then decreases. The observed maximum viscosity could be attributed to the attractive forces among water droplets. The microstructures of the water-in-PAO nanoemulsion fluids are measured via the small-angle neutron scattering (SANS) technique, which shows a transition from sphere to elongated cylinder when the water concentration increases above 5.3 vol. %. The pool boiling heat transfer of these water-in-PAO nanoemulsion fluids is measured on a horizontal Pt wire at room temperature (25 °C, subcooled condition). One interesting phenomenon observed is that the pool boiling follows two different curves randomly when the water concentration is in the range of 5.3 vol. % to 7.8 vol. %.

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Figures

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Fig. 1

Water-in-PAO nanoemulsion fluid (bottle A) and pure PAO (bottle B). The Tyndall effect can be seen in the nanoemulsion fluid (bottle A).

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Fig. 2

Schematic of pool boiling test apparatus

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Fig. 3

Thermal conductivity of water-in-PAO nanoemulsion fluids versus water volume fraction. The prediction from the Maxwell equation is shown for comparison.

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Fig. 4

Dynamic viscosity of water-in-PAO nanoemulsion fluids versus water volume fraction

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Fig. 5

Molecular structure of AOT-Na+ surfactant

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Fig. 6

Small-angle neutron scattering curves for water-in-PAO nanoemulsion fluids: water volume concentration from 1.8% to 10.3%. Three different symbols represent three different scattering curves.

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Fig. 7

Pool boiling curves for water-in-PAO nanoemulsion fluids: water volume fraction from 1.8% to 4.5%. The arrows in the figure represent where the burn out of wire occurs. Tsaturation is 100 °C for water at 1 atm.

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Fig. 8

Pool boiling curves for water-in-PAO nanoemulsion fluids: water volume concentration from 5.3% to 10.3%. The arrows in the figure represent where the burn out of wire occurs. Tsaturation is 100 °C for water at 1 atm.

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