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Research Papers

Finless Heat Sinks, High Performance and Low Cost for Low Profile Cooling Applications

[+] Author and Article Information
Ed Walsh

Stokes Institute,
University of Limerick,
Castletroy, Limerick, Ireland;
Osney Thermo-Fluids Laboratory,
Department of Engineering Science,
University of Oxford,
Southwell Building,
Osney Mead, Oxford, OX2 0ES, UK
e-mail: edmond.walsh@bnc.ox.ac.uk

Jason Stafford

Stokes Institute,
University of Limerick,
Castletroy, Limerick, Ireland

1Present address: Engineering Science Department, University of Oxford, Oxford, UK.

2Corresponding author.

Manuscript received December 23, 2011; final manuscript received October 24, 2012; published online June 24, 2013. Assoc. Editor: Ravi Prasher.

J. Thermal Sci. Eng. Appl 5(3), 031001 (Jun 24, 2013) (7 pages) Paper No: TSEA-11-1181; doi: 10.1115/1.4023267 History: Received December 23, 2011; Revised October 24, 2012

The need for low profile, sustainable thermal management solutions is becoming critical in information and communications technology applications ranging from consumer products to server cabinets. This work presents a finless thermal management solution that utilizes fluidic structures generated within an empty cavity to enhance the heat transfer coefficient. The finless thermal management solution can be manufactured to have a height of less than 5 mm when using low profile motors. Particle image velocimetry (PIV) combined with infrared (IR) imaging techniques are used to explain the underlying flow physics that results in increased heat transfer rates compared to typical laminar flows. It is found that the local heat transfer coefficients in the finless design are up to 500% greater than those achieved at the same Reynolds number using conventional boundary layer theory. The design is compared to an existing commercial solution and is found to provide benefits in terms of cost, reliability, weight, acoustics, and fan power consumption. These advancements over current state of the art lead to a more sustainable solution for low cost, low profile cooling applications.

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References

Figures

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Fig. 3

Experimental setup for the temperature measurements with the IR camera. The dimensions of the thin foil were ∼80 mm × 200 mm and the spacing between the top and bottom surfaces was 4 mm.

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Fig. 2

PIV setup for measurements on finless heat sink; measurement setup for the radial–axial plane. The fan draws air in the top orifice axially and expends the air radial through the open (finless) passage. The distance between the top and bottom surfaces was 4 mm.

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Fig. 1

Photograph of the experimental configuration employing the straightening diffusers with finned and finless heat sinks (adapted from Ref. [3])

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Fig. 7

(Right) Measured IR temperature field on lower surface of finless heat sink. (Left) Calculated local heat transfer coefficients from measured surface temperature field.

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Fig. 6

(Top) PIV velocity measurements between the upper and lower plates using the radial-circumferential PIV plane. (Bottom) Streamline images that represent the 3D toroidal vortex rings (drawing inferred from PIV measurements).

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Fig. 5

PIV velocity measurements between the upper and lower plates using the radial-height PIV plane as shown in Fig. 2. (Top) Velocity vectors in flow field; (bottom) streamlines interpreted from the velocity field in the radial-height plane.

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Fig. 4

(Left) Experimental setup with 12 mm2 chip surface. (Right) Experimental setup with finless heat sink in situ, the confining plates have a spacing of 14.7 mm to represent the distance between adjacent slots in a PCB motherboard.

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Fig. 8

(Right) Measured IR temperature field on half of lower and upper surfaces of finless heat sink. (Left) Calculated local heat transfer coefficients from the measured surface temperature field.

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Fig. 9

Local Nusselt number in the developing flow region of a radial finless heat sink

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Fig. 10

(Left) Manufactured finless heat sink solution made from 2 mm thick aluminum and (right) commercially implemented cooler for low end graphic cards. The total height of both solutions was ∼12 mm with the fan in place. The total height of the solutions without fans was 8 mm and 12 mm for the finless and commercial solution, respectively.

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Fig. 11

Thermal resistance measurements versus fan rotational speed for the finless heat sink solution and existing current state of the art solution, maximum uncertainty in the thermal resistance was estimated to be less than 5%, and more typically 2–3% using the method of Kline and McClintock [23]

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