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Heat Transfer Enhancement

Enhanced Thermal Transport in Microchannel Using Oblique Fins

[+] Author and Article Information
Y. J. Lee, S. K. Chou

Energy and Bio-Thermal System Division, Department of Mechanical Engineering,  National University of Singapore, Singapore 119260

P. S. Lee1

Energy and Bio-Thermal System Division, Department of Mechanical Engineering,  National University of Singapore, Singapore 119260mpelps@nus.edu.sg

1

Corresponding author.

J. Heat Transfer 134(10), 101901 (Aug 07, 2012) (10 pages) doi:10.1115/1.4006843 History: Received April 18, 2011; Revised April 23, 2012; Published August 06, 2012; Online August 07, 2012

Sectional oblique fins are employed, in contrast to continuous fins in order to modulate the flow in microchannel heat sinks. The breakage of a continuous fin into oblique sections leads to the reinitialization of the thermal boundary layer at the leading edge of each oblique fin, effectively reducing the boundary layer thickness. This regeneration of entrance effects causes the flow to always be in a developing state, thus resulting in better heat transfer. In addition, the presence of smaller oblique channels diverts a small fraction of the flow into adjacent main channels. The secondary flows created improve fluid mixing, which serves to further enhance heat transfer. Both numerical simulations and experimental investigations of copper-based oblique finned microchannel heat sinks demonstrated that a highly augmented and uniform heat transfer performance, relative to the conventional microchannel, is achievable with such a passive technique. The average Nusselt number, Nuave , for the copper microchannel heat sink which uses water as the working fluid can increase as much as 103%, from 11.3 to 22.9. Besides, the augmented convective heat transfer leads to a reduction in maximum temperature rise by 12.6 °C. The associated pressure drop penalty is much smaller than the achieved heat transfer enhancement, rendering it as an effective heat transfer enhancement scheme for a single-phase microchannel heat sink.

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Copyright © 2012 by American Society of Mechanical Engineers
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Figures

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Figure 1

Plan view of microchannel heat sink with oblique fins

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Figure 2

Plan view of oblique fins with dimensions (500 μm nominal channel width)

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Figure 3

Schematic for experimental flow loop

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Figure 4

Detailed drawings of the test section. (a) Cross-section view of the test section and (b) top view of the test section.

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Figure 5

Comparison of average Nusselt number for microchannel heat sinks (500 μm nominal channel width)

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Figure 6

Velocity vector in the enhanced microchannel

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Figure 7

Comparison of maximum temperature rise above water inlet temperature of copper microchannel heat sinks (500 μm nominal channel width)

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Figure 8

Comparison of pressure drop across microchannel heat sinks (500 μm nominal channel width)

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Figure 9

Comparison of heat transfer enhancement factor and pressure drop penalty (500 μm nominal channel width)

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Figure 10

Comparison of average Nusselt number for microchannel heat sinks (300 μm nominal channel width)

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Figure 11

Comparison of pressure drop across microchannel heat sinks (500 μm nominal channel width)

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Figure 12

Microscopic image of (a) enhanced microchannel heat sink with 500 μm nominal channel width (b) enhanced microchannel heat sink with 300 μm nominal channel width

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