Research Papers

Investigation of Multiple Miniature Axial Fan Cooling Solutions and Thermal Modeling Approaches

[+] Author and Article Information
Jason Stafford

Bell Labs,
Thermal Management Research Group,
Dublin D15, Ireland
e-mail: jason.stafford@alcatel-lucent.com

Florian Fortune

Institut Catholique des Arts et Métiers,
Toulouse, France

1Corresponding author.

Contributed by the Electronic and Photonic Packaging Division of ASME for publication in the JOURNAL OF ELECTRONIC PACKAGING. Manuscript received April 10, 2013; final manuscript received December 5, 2013; published online January 24, 2014. Assoc. Editor: Amy Fleischer.

J. Electron. Packag 136(1), 011008 (Jan 24, 2014) (12 pages) Paper No: EP-13-1025; doi: 10.1115/1.4026351 History: Received April 10, 2013; Revised December 05, 2013

This paper investigates the thermal and fluid dynamic characteristics due to multiple miniature axial fans with blade chord and span length scales less than 10 mm, impinging air onto finned surfaces. A coupled approach, utilizing both experimental and numerical techniques, has been devised to examine in detail the exit air flow interaction between cooling fans within an array. The findings demonstrate that fans positioned adjacently in an array can influence heat transfer performance both positively and negatively by up to 35% compared to an equivalent single fan—heat sink unit operating standalone. Numerical simulations have provided an insight into the flow fields generated by adjacent fans and also the air flow interaction with fixed fan motor support structures downstream. A novel experimental approach utilizing infrared thermography has been developed to locally assess the validity of the numerical models. In particular, an assessment on implementing compact lumped parameter fans and fans modeled with full geometric detail is shown for two configurations that are impinging air onto finned and flat surfaces. Overall, the study provides an insight into fan cooled heat sinks incorporating multiple miniature axial fans and general recommendations for improving current numerical modeling approaches.

Copyright © 2014 by ASME
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Fig. 1

(a) Nondimensional fan performance curve and (b) a schematic of the characterization facility used to measure fan performance

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Fig. 2

Single axial fan mounted to (a) 4-exit and (b) 2-exit heat sink designs

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Fig. 3

One of the integrated cooling solutions investigated comprising of three axial fans

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Fig. 4.

Experimental apparatus for local heat transfer measurements of (a) fan and heat sink and (b) fan and flat surface arrangements

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Fig. 5

Numerical model of a three fan arrangement using (a) fan geometric details and (b) compact fans

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Fig. 6

Numerical model of a three fan arrangement using (a) fan geometric details and (b) compact fans with inclusion of fan motor supports

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Fig. 7

Temperature distribution on the base of a three fan cooling solution using (a) experimental measurement, (b) numerical simulation and fan geometric details, and (c) numerical simulation and compact fans (ω = 9,000 rpm,T∞ = 27°C, contour level: 0.7 °C)

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Fig. 8

Numerical model of a miniature axial fan impinging air onto a flat surface. Compact fan shown with detailed fan inset.

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Fig. 9

Local heat transfer pattern due to flow impingement on a flat surface. (a) Experimental measurement and numerical simulations using (b) fan geometric details, and (c) a compact fan approach. (ω = 9,000 rpm, H/D = 0.203).

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Fig. 10

Simulated flow field around one of the fan motor supports at the blade mid span including (a) velocity magnitude and (b)–(d) three components of velocity (ω = 9,000 rpm, H/D = 0.203).

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Fig. 11

Thermal resistance of the 4-exit multiple fan arrays compared to a single fan—heat sink solution

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Fig. 12

Thermal resistance of the 2-exit multiple fan arrays compared to a single fan—heat sink solution

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Fig. 13

Simulated velocity fields for three fan array with (a) 2-exit and (b) 4-exit heat sinks

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Fig. 14

The influence of fan failure on thermal performance within a 4-exit three fan array




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