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MICRO/NANOSCALE HEAT TRANSFER—PART II

Effect of CuO Nanoparticle Concentration on R134a/Lubricant Pool-Boiling Heat Transfer

[+] Author and Article Information
M. A. Kedzierski

 National Institute of Standards and Technology, Building 226, Room B114, Gaithersburg, MD 20899

Certain commercial equipment, instruments, or materials are identified in this paper in order to specify the experimental procedure adequately. Such identification is not intended to imply recommendation or endorsement by the National Institute of Standards and Technology, nor is it intended ti imply that the materials or equipment identified are necessarily the best available for the purpose.

The equivalent mixture is RL68H/CuO (97.1/2.9) in terms of mass.

The error in the volume fraction in Ref. 5 has been corrected in this manuscript.

At 313.15 K, the measured kinematic viscosities of RL68H1Cu and RL68H2Cu were 71.8μm2/s±0.2μm2/s and 68.1μm2/s±0.1μm2/s, respectively.

J. Heat Transfer 131(4), 043205 (Feb 13, 2009) (7 pages) doi:10.1115/1.3072926 History: Received April 16, 2008; Revised August 08, 2008; Published February 13, 2009

This paper quantifies the influence of copper (II) oxide (CuO) nanoparticle concentration on the boiling performance of R134a/polyolester mixtures on a roughened horizontal flat surface. Nanofluids are liquids that contain dispersed nanosize particles. Two lubricant-based nanofluids (nanolubricants) were made with a synthetic polyolester and 30 nm diameter CuO particles to 1% and 0.5% volume fractions, respectively. As reported in a previous study for the 1% volume fraction nanolubricant, a 0.5% nanolubricant mass fraction with R134a resulted in a heat transfer enhancement relative to the heat transfer of pure R134a/polyolester (99.5/0.5) between 50% and 275%. The same study had shown that increasing the mass fraction of the 1% volume fraction nanolubricant resulted in smaller, but significant, boiling heat transfer enhancements. The present study shows that the use of a nanolubricant with half the concentration of CuO nanoparticles (0.5% by volume) resulted in either no improvement or boiling heat transfer degradations with respect to the R134a/polyolester mixtures without nanoparticles. Consequently, significant refrigerant/lubricant boiling heat transfer enhancements are possible with nanoparticles; however, the nanoparticle concentration is an important determining factor. Further research with nanolubricants and refrigerants is required to establish a fundamental understanding of the mechanisms that control nanofluid heat transfer.

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Copyright © 2009 by American Society of Mechanical Engineers
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Figures

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Figure 1

Schematic of test apparatus

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Figure 2

OFHC copper flat test plate with crosshatched surface and thermocouple coordinate system

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Figure 3

R134a/RL68H with 0.5% volume CuO nanoparticle mixtures boiling curves for plain surface

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Figure 4

R134a/RL68H with 1% volume CuO nanoparticle mixtures boiling curves for plain surface (5)

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Figure 5

R134a/RL68H mixtures boiling curves for plain surface (5)

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Figure 6

Heat flux of R134a/RL68H mixtures with CuO nanoparticles relative to that of R134a/RL68H mixtures without CuO nanoparticles for the 99.5/0.5 composition

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Figure 7

Heat flux of R134a/RL68H mixtures with CuO nanoparticles relative to that of R134a/RL68H mixtures without CuO nanoparticles for the 99/1 composition

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Figure 8

Heat flux of R134a/RL68H mixtures with CuO nanoparticles relative to that of R134a/RL68H mixtures without CuO nanoparticles for the 98/2 composition

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