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RESEARCH PAPERS

Performance of Graphite Foam Evaporator for Use in Thermal Management

[+] Author and Article Information
Johnathan S. Coursey

Department of Mechanical Engineering, University of Maryland, College Park, College Park, MD 20742

Jungho Kim

Department of Mechanical Engineering, University of Maryland, College Park, College Park, MD 20742kimjh@eng.umd.edu

Paul J. Boudreaux

 Laboratory for Physical Sciences, College Park, Maryland 20742pjb@lps.umd.edu

J. Electron. Packag 127(2), 127-134 (Jun 01, 2004) (8 pages) doi:10.1115/1.1871193 History: Received November 13, 2003; Revised June 01, 2004

This paper presents the results of an investigation of the thermal performance of a graphite foam thermosyphon evaporator and discusses the foam’s potential for use in the thermal management of electronics. The graphitized carbon foam used in this study is an open-cell porous material that consists of a network of interconnected graphite ligaments whose thermal conductivities are up to five times higher than copper. While the bulk graphite foam has a thermal conductivity similar to aluminum, it has one-fifth the density, making it an excellent thermal management material. Furthermore, using the graphite foam as the evaporator in a thermosyphon enables the transfer of large amounts of energy with relatively low temperature difference and without the need for external pumping. Performance of the system with FC-72 and FC-87 was examined, and the effects of liquid fill level, condenser temperature, and foam height, width, and density were studied. Performance with FC-72 and FC-87 was found to be similar, while the liquid fill level, condenser temperature, geometry, and density of the graphite foam were found to significantly affect the thermal performance. The boiling was found to be surface tension dominated, and a simple model based on heat transfer from the outer surface is proposed. As much as 149W were dissipated from a 1cm2 heated area.

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Copyright © 2005 by American Society of Mechanical Engineers
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Figures

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Figure 3

Boiling curves illustrating the working fluid effect for H=1.2cm, W=2.5×2.5cm, ρ=0.89g∕cm3, liquid level=2cm, Tcond=25°C, and copper plate plus Pb∕Sn solder

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Figure 4

Boiling curves illustrating the condenser temperature effect for H=1.2cm, W=2.5×2.5cm, ρ=0.89g∕cm3, FC-87, liquid level=2cm, and copper plate plus Pb∕Sn solder

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Figure 5

Condenser temperature effect for H=1.2cm, W=2.5×2.5cm, ρ=0.89g∕cm3, FC-87, liquid level=2cm, and copper plate plus Pb∕Sn solder

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Figure 6

Boiling curves illustrating the liquid level effect for H=1.2cm, W=2.5×2.5cm, ρ=0.89g∕cm3, FC-87, Tcond=25°C, and copper plate plus Pb∕Sn solder

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Figure 7

Liquid fill level effect for H=1.2cm, W=2.5×2.5cm, ρ=0.89g∕cm3, FC-87, Tcond=25°C, and copper plate plus Pb∕Sn solder

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Figure 8

Boiling curves illustrating the density effect for H=1.7cm, W=3.75×3.75cm, FC-87, liquid level=2cm, Tcond=25°C, and S-bond™ 220

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Figure 9

Density effect for H=1.7cm, W=3.75×3.75cm, FC-87, liquid level=2cm, Tcond=25°C, and S-bond™ 220

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Figure 10

Boiling curves illustrating the density effect for H=1.2cm, W=2.5×2.5cm, FC-87, liquid level=2cm, Tcond=25°C, and copper plate plus Pb∕Sn solder

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Figure 11

Density effect for H=1.2cm, W=2.5×2.5cm, FC-87, liquid level=2cm, Tcond=25°C, and copper plate plus Pb∕Sn solder

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Figure 12

Boiling curves illustrating the size effects for ρ=0.46g∕cm3, FC-87, liquid level=2cm, Tcond=25°C, and S-bond™ 220

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Figure 2

Experimental setup (TC: thermocouple)

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Figure 1

Scanning electron micrograph of graphite foam [courtesy of James Klett, Oak Ridge National Laboratory]

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