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Research Papers: Electronic Cooling

Self-Contained, Oscillating Flow Liquid Cooling System for Thin Form Factor High Performance Electronics

[+] Author and Article Information
R. Wälchli

 IBM Research GmbH, Zurich Research Laboratory, 8803 Rüschlikon, Switzerland; Department of Mechanical and Process Engineering, Laboratory of Thermodynamics in Emerging Technologies, ETH Zürich, 8092 Zürich, Switzerlandeto@zurich.ibm.com

T. Brunschwiler, B. Michel

 IBM Research GmbH, Zurich Research Laboratory, 8803 Rüschlikon, Switzerland

D. Poulikakos

Department of Mechanical and Process Engineering, Laboratory of Thermodynamics in Emerging Technologies, ETH Zürich, 8092 Zürich, Switzerland

J. Heat Transfer 132(5), 051401 (Mar 08, 2010) (9 pages) doi:10.1115/1.4000456 History: Received April 02, 2009; Revised August 26, 2009; Published March 08, 2010; Online March 08, 2010

A self-contained, small-volume liquid cooling system for thin form-factor electronic equipment (e.g., blade server modules) is demonstrated experimentally in this paper. A reciprocating water flow loop absorbs heat using mesh-type microchannel cold plates and spreads it periodically to a larger area. From there, the thermal energy is interchanged via large area, low pressure drop cold plates with a secondary heat transfer loop (air or liquid). Four phase-shifted piston pumps create either a linearly or radially oscillating fluid flow in the frequency range of 0.5–3 Hz. The tidal displacement of the pumps covers 42–120% of the fluid volume, and, therefore, an average flow rate range of 100–800 ml/min is tested. Three different absorber mesh designs are tested. Thermal and fluidic characteristics are presented in a time-resolved and a time-averaged manner. For a fluid pump power of 1 W, a waste heat flux of 180W/cm2(ΔT=67K) could be dissipated from a 3.5cm2 chip. A linear oscillation flow pattern is advantageous over a radial one because of the more efficient heat removal from the chip and lower hydraulic losses. The optimum microchannel mesh density is determined as a combination of low pump losses and high heat transfer rates.

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Copyright © 2010 by American Society of Mechanical Engineers
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Figures

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Figure 1

Illustration of the oscillating liquid cooling principle. (a) Heat spreading system with a chip waste heat absorber (HA) in the center and the four heat dissipator (HD) cold plates in the periphery. The fluid oscillations are created by means of phase-shifted piston pumps (PP). (b) Heat exchange from the chip via the oscillating fluid to the collector plane (CP) of the secondary heat transfer loop.

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Figure 2

Microchannel cold plate design of (a) the heat absorber (HA) and (c) the heat dissipator (HD). The axially symmetric unit cell heat transfer mesh is displayed in (b).

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Figure 3

Averaged (RMS) pressure drop (a) for V3, various flow patterns (lin and rad), pump displacements DPP, and frequencies f, and (b) for various absorber designs Vi, pump displacements DPP, and frequencies f

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Figure 4

Temporal temperature oscillations over two cycles at for HA V1, Pchip=235 W, and f=1.5 Hz: Panels (a–d) show the chip temperature at two different locations (RTD1: corner region, RTD4: center region) and flow patterns. Panels (e–f) give the fluid temperature in the interconnecting tube between the absorber and the dissipator cold plates.

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Figure 5

Dependence of the averaged thermal resistance of the different flow patterns (lin, rad) and heat absorber mesh designs (V1,V2,V3) on the fluid pumping power at (a) 0.5 W and at (b) 1.0 W)

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Figure 6

Division of the overall thermal resistance into a simplified linear resistor network including RSi+TIM, RHA, RHD, and RCP

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