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Research Papers: Evaporation, Boiling, and Condensation

Pool Boiling Heat Transfer Enhancement of Water Using Brazed Copper Microporous Coatings

[+] Author and Article Information
Seongchul Jun

Mechanical Engineering Department,
University of Texas at Dallas,
800 W. Campbell Road,
Richardson, TX 75080
e-mail: seongchul.jun@utdallas.edu

Hyoseong Wi

Mechanical Engineering Department,
University of Texas at Dallas,
800 W. Campbell Road,
Richardson, TX 75080
e-mail: wucwug001@gmail.com

Ajay Gurung

Mechanical and Aerospace Engineering Department,
University of Texas at Arlington,
500 W. First Street,
Arlington, TX 76019
e-mail: ajay.gurung@mavs.uta.edu

Miguel Amaya

Mechanical and Aerospace Engineering Department,
University of Texas at Arlington,
500 W. First Street,
Arlington, TX 76019
e-mail: mamaya@uta.edu

Seung M. You

Mechanical Engineering Department,
University of Texas at Dallas,
800 W. Campbell Road,
Richardson, TX 75080
e-mail: you@utdallas.edu

1Corresponding author.

Contributed by the Heat Transfer Division of ASME for publication in the JOURNAL OF HEAT TRANSFER. Manuscript received September 24, 2015; final manuscript received February 15, 2016; published online April 19, 2016. Assoc. Editor: Amy Fleischer.

J. Heat Transfer 138(7), 071502 (Apr 19, 2016) (9 pages) Paper No: HT-15-1619; doi: 10.1115/1.4032988 History: Received September 24, 2015; Revised February 15, 2016

A novel, high-temperature, thermally conductive, microporous coating (HTCMC) is developed by brazing copper particles onto a copper surface. This coating is more durable than many previous microporous coatings and also effectively creates re-entrant cavities by varying brazing conditions. A parametric study of coating thicknesses of 49–283 μm with an average particle size of ∼25 μm was conducted using the HTCMC coating to understand nucleate boiling heat transfer (NBHT) enhancement on porous surfaces. It was found that there are three porous coating regimes according to their thicknesses. The first regime is “microporous” in which both NBHT and critical heat flux (CHF) enhancements gradually grow as the coating thickness increases. The second regime is “microporous-to-porous transition” where NBHT is further enhanced at lower heat fluxes but decreases at higher heat fluxes for increasing thickness. CHF in this regime continues to increase as the coating thickness increases. The last regime is named “porous,” and both NBHT and CHF decrease as the coating thickness increases beyond that of the other two regimes. The maximum NBHT coefficient observed was ∼350,000 W/m2K at 96 μm thickness (microporous regime) and the maximum CHF observed was ∼2.1 MW/m2 at ∼225 μm thickness (porous regime).

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References

Figures

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Fig. 7

Pool boiling curves of water with different coating thicknesses. The highest heat flux of each curve represents CHF.

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Fig. 4

Particle size distribution. Sizes were measured by image processing program of optical microscope images of copper powders.

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Fig. 1

Pool boiling curves of water with prior microporous coatings [15] and a plain copper surface [16]

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Fig. 6

Cross sections of (a) TCMC [15] and (b) HTCMC

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Fig. 5

SEM of (a) TCMC [15] and (b) HTCMC

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Fig. 3

Schematic of test heater assembly

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Fig. 2

Schematic of the pool boiling chamber

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Fig. 8

Nucleate boiling images of plain copper and HTCMC (225 μm coating thickness) at different heat fluxes: (a) 1 kW/m2, (b) 15 kW/m2, (c) 100 kW/m2, and (d) 1000 kW/m2

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Fig. 9

Pool boiling curves at different coating regimes: (a) microporous, (b) microporous-to-porous transition, and (c) porous regime

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Fig. 10

CHF values with different coating thicknesses

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Fig. 11

Boiling heat transfer coefficient at different coating regimes: (a) microporous, (b) microporous-to-porous transition, and (c) porous regime

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Fig. 12

Variation of boiling heat transfer coefficient with coating thicknesses at different heat fluxes

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Fig. 13

Comparison of boiling heat transfer coefficient of HTCMC with prior microporous coatings [15] in water

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