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Research Papers

Macro- to Microscale Boiling Heat Transfer From Metal-Graphite Composite Surfaces

[+] Author and Article Information
Wen-Jei Yang

Department of Mechanical Engineering, University of Michigan, Ann Arbor, MI 48109-2125wjyang@umich.eduf

Nengli Zhang

 Ohio Aerospace Institute at NASA Glen Research Center, Cleveland, OH 44184

Daniel L. Vrable

 Thermal Management and Materials Technology, Del Mar, CA 92014-4217

J. Heat Transfer 131(9), 091001 (Jun 19, 2009) (8 pages) doi:10.1115/1.3153556 History: Received May 04, 2009; Revised May 08, 2009; Published June 19, 2009

This paper introduces a novel heat transfer enhancement surface, referred to as metal-graphite composite surface. It is comprised of high thermal conductivity graphite microfibers interspersed within a metal matrix (copper or aluminum) to enhance the bubble formation at the nucleation sites, and significantly improve the nucleate boiling heat transfer. Experiments revealed that its boiling heat transfer enhancement is comparable or in some respect even superior to the commercially available boiling heat transfer enhancement surfaces such as porous boiling surface and integral roughness surface. In addition, it does not result in any extra pressure loss and it minimizes surface fouling. Macro- to microscale heat transfer phenomena of the composite surfaces is treated. Discussions include characteristics of the surface, enhancement mechanisms, critical heat flux, boiling thermal hysteresis, bubble generation, growth and departure, and applications in electronic cooling, and under reduced gravity conditions.

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Copyright © 2009 by American Society of Mechanical Engineers
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References

Figures

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Figure 1

Scanning electron microscope photograph of the graphite/copper boiling surface showing the 8–12 μm diameter fibers consolidated in a copper matrix

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Figure 2

Experimental test apparatus schematic

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Figure 3

Experimental data comparison between the graphite/copper (50% fiber volume) and the baseline copper boiling surfaces showing boiling heat transfer improvement of three to six times (depending on the amount of superheat) using refrigerant 113 from Yang (4-5)

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Figure 4

Experimental Data comparison between the graphite/copper (ϕ≅0%, 25%, and 50% fiber volume) and the baseline copper boiling surfaces showing boiling heat transfer improvement optimum of between 25–50% using refrigerant 113 from Yang (12)

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Figure 5

Experimental data comparison between the graphite/copper (25% and 50% fiber volume), graphite/aluminum (50% fiber volume), and the baseline copper and aluminum boiling surfaces showing boiling heat transfer improvement of three to six times (depending on the amount of superheat) using n-pentane from Liang (14)

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Figure 6

Summary of boiling hysteresis on the surfaces

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Figure 7

(a) Photomicrograph (3000 times) of the copper/graphite composite surface with 50% fiber volume and (b) growth and coalescence of micro bubbles

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Figure 8

Startup/restart hysteresis on the pure copper surface

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Figure 9

Summary of boiling hysteresis on the graphite/copper composite surfaces

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Figure 10

Bubble formation: (a) formation of micromushrooms and (b) formation of a macro bubble

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Figure 11

Photographs of bubble departure during the incipience of nucleate pool boiling in water

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Figure 12

Departure of a macro bubble: (a) contraction of throat and bottom of the departing bubble and (b) liquid jet in the departed bubble

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Figure 13

Heat transfer coefficients achievable with natural convection, single-phase forced convection, and boiling for typical electronic coolants

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Figure 14

Variation of the surface tension with temperature for aqueous solutions with long-chain alcohols

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