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Research Papers

The Effect of Thermal Contact Resistance at Porous-Solid Interfaces in Finned Metal Foam Heat Sinks

[+] Author and Article Information
Christopher T. DeGroot1

Department of Mechanical and Materials Engineering, University of Western Ontario, London, ON, N6A 5B9, Canadacdegroo@uwo.ca

Derek Gateman

Department of Mechanical and Materials Engineering, University of Western Ontario, London, ON, N6A 5B9, Canadadgatema@uwo.ca

Anthony G. Straatman

Department of Mechanical and Materials Engineering, University of Western Ontario, London, ON, N6A 5B9, Canadaastraatman@eng.uwo.ca

1

Corresponding author.

J. Electron. Packag 132(4), 041007 (Nov 24, 2010) (7 pages) doi:10.1115/1.4002724 History: Received February 05, 2010; Revised August 08, 2010; Published November 24, 2010; Online November 24, 2010

A numerical study on the effect of thermal contact resistance and its impact on the performance of finned aluminum foam heat sinks has been conducted. Calculations are based on the solution of the volume-averaged mass, momentum, and energy equations under conditions of local thermal nonequilibrium using a finite-volume-based computational fluid dynamics code for conjugate fluid/porous/solid domains. Numerical results have been obtained for a wide range of contact resistances at the porous-solid interfaces, up to the limit of an effectively infinite resistance. As the contact resistance is increased to such high levels, the heat transfer is found to asymptote as conduction into the solid constituent of the foam is completely blocked. Even without conduction into the solid, a convective enhancement is obtained due to the presence of the foam material. It is reasoned that this is due to the thinning of the momentum boundary layers as a result of the presence of the porous material, which acts as a momentum sink. As a result of the thinner boundary layers, the flow speed near the finned surfaces and base is increased, which serves to increase the rate of convection from these surfaces. It is also found that for most reasonable interface materials, such as thermal epoxies, the impact of thermal contact resistance on the heat transfer performance in comparison to that for an ideal bond is small.

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Copyright © 2010 by American Society of Mechanical Engineers
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Figures

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Figure 2

Schematic diagram of the domain under consideration

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Figure 3

Thermal resistance network for parallel interface conduction with thermal contact resistance

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Figure 4

A comparison of the present results including contact resistance with the experimental results of Bhattacharya and Mahajan (4) and the numerical results of DeGroot (5), which did not include contact resistance

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Figure 5

Plot of the bulk Nusselt number as a function of the nondimensional thermal contact resistance for various number of fins with and without foam at Red=19.8

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Figure 6

Contour plots of the dimensionless velocity field in the yz-plane at the outlet of a six-finned heat sink (a) without foam and (b) with foam

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Figure 7

Contour plots of the dimensionless fluid temperature in the yz-plane at the outlet of a six-finned heat sink with nondimensional contact resistances of (a) Rt,c∗=7.51×10−4, (b) Rt,c∗=7.51, and (c) Rt,c∗=7.51×104 in comparison to (d) finned channels without foam

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Figure 1

A photograph of an aluminum foam with 20 PPI

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