Research Papers

Enhanced Miniature Loop Heat Pipe Cooling System for High Power Density Electronics

[+] Author and Article Information
J. H. Choi

Zalman Tech Co., Ltd.,Seoul, 153-803, South Korea; School of Mechanical Engineering,  Sungkyunkwan University, Suwon, 440-746, South Korea

B. H. Sung, C. J. Kim

School of Mechanical Engineering,  Sungkyunkwan University, Suwon, 440-746, South Korea

J. H. Yoo

Zalman Tech Co., Ltd., Seoul 153-803, South Korea

D.-A. Borca-Tasciuc

Mechanical, Aerospace, and Nuclear Engineering Department,  Rensselaer Polytechnic Institute, Troy NY, 12180-3590

J. Thermal Sci. Eng. Appl 4(2), 021008 (Apr 20, 2012) (7 pages) doi:10.1115/1.4005734 History: Received July 06, 2011; Revised November 23, 2011; Published April 19, 2012; Online April 20, 2012

The implementation of high power density, multicore central and graphic processing units (CPUs and GPUs) coupled with higher clock rates of the high-end computing hardware requires enhanced cooling technologies able to attend high heat fluxes while meeting strict design constrains associated with system volume and weight. Miniature loop heat pipes (mLHP) emerge as one of the technologies best suited to meet all these demands. Nonetheless, operational problems, such as instable behavior during startup on evaporator side, have stunted the advent of commercialization. This paper investigates experimentally two types of mLHP systems designed for workstation CPUs employing disk shaped and rectangular evaporators, respectively. Since there is a strong demand for miniaturization in commercial applications, emphasis was also placed on physical size during the design stage of the new systems. One of the mLHP system investigated here is demonstrated to have an increased thermal performance at a reduced system weight. Specifically, it is shown that the system can reach a maximum heat transfer rate of 170 W with an overall thermal resistance of 0.12 K/W. The corresponding heat flux is 18.9 W/cm2 , approximately 30% higher than that of larger size commercial systems. The studies carried out here also suggest that decreasing the thermal resistance between the heat source and the working fluid and maximizing the area for heat transfer are keys for obtaining an enhanced thermal performance.

Copyright © 2012 by American Society of Mechanical Engineers
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Figure 2

Full loop configuration of mLHP systems. Details on thermocouple positioning are also provided in Fig. 4.

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Figure 8

Operational characteristics of the mLHP system with increasing heat loads: (a) model #1—water; (b) model #1—n-pentane; and (c) model #2

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Figure 9

The thermal resistance associated with heat transfer from the base plate to the vapor inlet temperature, Rb-f , as function of applied heat load

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Figure 1

Schematic of the commercial cooling system CNPS-9900

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Figure 3

(a) Model #1 evaporator, (b) model #2 evaporator

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Figure 4

Schematic of working fluid flow and heat transfer paths inside the evaporator of the mLHP system: (a) model #1; (b) model #2

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Figure 5

(a) Schematic of the experimental setup. (b) Detailed schematic of the dummy heater.

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Figure 6

Junction temperature as function of the heat load

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Figure 7

Total thermal resistance, Rt , as function of applied heat load



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