0
RESEARCH PAPERS

Metal Foam and Finned Metal Foam Heat Sinks for Electronics Cooling in Buoyancy-Induced Convection

[+] Author and Article Information
A. Bhattacharya1

Mechanical Engineering Department,  Indian Institute of Technology, Bombay, Powai, Mumbai 400076, India

R. L. Mahajan

Mechanical Engineering Department,  University of Colorado, Campus Box 427, Boulder, CO 80309-0427

1

Current address: Intel Technology India Pvt. Ltd., Outer Ring Road, Bangalore – 560037, India.

J. Electron. Packag 128(3), 259-266 (Sep 23, 2005) (8 pages) doi:10.1115/1.2229225 History: Received May 25, 2005; Revised September 23, 2005

In this paper, we present our recent experimental results on buoyancy-induced convection in aluminum metal foams of different pore densities [corresponding to 5, 10, 20, and 40 pores per in. (PPI)] and porosities (0.89–0.96). The results show that compared to a heated surface, the heat transfer coefficients in these heat sinks are five to six times higher. However, when compared to commercially available heat sinks of similar dimensions, the enhancement is found to be marginal. The experimental results also show that for a given pore size, the heat transfer rate increases with porosity, suggesting the dominant role played by conduction in enhancing heat transfer. On the other hand, if the porosity is held constant, the heat transfer rate is found to be lower at higher pore densities. This can be attributed to the higher permeability with the larger pores, which allows higher entrainment of air through the porous medium. New empirical correlations are proposed for the estimation of Nusselt number in terms of Rayleigh and Darcy numbers. We also report our results on novel finned metal foam heat sinks in natural convection. Experiments were conducted on aluminum foams of 90% porosity with 5 and 20 PPI with one, two, and four aluminum fins inserted in the foam. All of these heat sinks were fabricated in-house. The results show that the finned metal foam heat sinks are superior in thermal performance compared to the normal metal foam and conventional finned heat sinks. The heat transfer increases with an increase in the number of fins. However, the relative enhancement is found to decrease with each additional fin. The indication is that there exists an optimum number of fins beyond which the enhancement in heat transfer, due to increased surface area, is offset by the retarding effect of overlapping thermal boundary layers. Similar to normal metal foams, the 5 PPI samples are found to give higher values of h compared to the 20 PPI samples due to higher permeability of the porous medium. Future work is planned to arrive at the optimal heat sink configuration for even larger enhancement in heat transfer.

FIGURES IN THIS ARTICLE
<>
Copyright © 2006 by American Society of Mechanical Engineers
Your Session has timed out. Please sign back in to continue.

References

Figures

Grahic Jump Location
Figure 1

Schematic of the experimental setup—foam is shown in horizontal orientation

Grahic Jump Location
Figure 2

Picture of a metal foam sample

Grahic Jump Location
Figure 3

Experimental data for natural convection in metal foams in vertical orientation

Grahic Jump Location
Figure 4

Experimental Nusselt number and empirical correlation (Eq. 9)

Grahic Jump Location
Figure 5

Experimental data for natural convection in metal foams in horizontal orientation

Grahic Jump Location
Figure 6

Picture of a finned metal foam sample (20 PPI, four fins)

Grahic Jump Location
Figure 7

Thermal performance of the finned metal foam heat sinks in horizontal orientation

Grahic Jump Location
Figure 8

Thermal performance of the finned metal foam heat sinks in vertical orientation

Tables

Errata

Discussions

Some tools below are only available to our subscribers or users with an online account.

Related Content

Customize your page view by dragging and repositioning the boxes below.

Related Journal Articles
Related eBook Content
Topic Collections

Sorry! You do not have access to this content. For assistance or to subscribe, please contact us:

  • TELEPHONE: 1-800-843-2763 (Toll-free in the USA)
  • EMAIL: asmedigitalcollection@asme.org
Sign In