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Research Papers: Heat Transfer Enhancement

Numerical Study of Fluid Flow and Heat Transfer in the Enhanced Microchannel With Oblique Fins

[+] Author and Article Information
P. S. Lee

e-mail: mpelps@nus.edu.sg

S. K. Chou

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

1Corresponding author.

Contributed by the Heat Transfer Division of ASME for publication in the Journal of Heat Transfer. Manuscript received March 30, 2011; final manuscript received November 5, 2012; published online March 20, 2013. Assoc. Editor: Srinivas Garimella.

J. Heat Transfer 135(4), 041901 (Mar 20, 2013) (10 pages) Paper No: HT-11-1177; doi: 10.1115/1.4023029 History: Received March 30, 2011; Revised November 05, 2012

Sectional oblique fins are employed in contrast to continuous fins in order to modulate flow in microchannel heat sink. The breakage of continuous fin into oblique sections leads to the reinitialization of both hydrodynamic and thermal boundary layers at the leading edge of each oblique fin, effectively reducing the thickness of boundary layer. This regeneration of entrance effect causes the flow to be always in a developing state thus resulting in better heat transfer. In addition, the presence of smaller oblique channels diverts a small fraction of flow into the adjacent main channels. The secondary flows thus created improve fluid mixing which serves to further enhance the heat transfer. Detailed numerical study on the fluid flow and heat transfer of this passive heat transfer enhancement technique provides insight to the local hydrodynamics and thermal development along the oblique fin. The uniquely skewed hydrodynamic and thermal profiles are identified as the key to the highly augmented and uniform heat transfer performance across the heat sink. The associated pressure drop penalty is much smaller than the achieved heat transfer enhancement, rendering it as an effective heat transfer enhancement scheme for single phase microchannel heat sink.

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Figures

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Fig. 1

Plan view of microchannel heat sink with oblique fins

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Fig. 2

Plan view of oblique fins with dimensions

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Fig. 3

Enlarged view of the computation domain for microchannel with oblique fins

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Fig. 4

Velocity contour (in m/s) of flow inside (a) conventional microchannel; (b) enhanced microchannel heat sinks at X′ = 0.5 and Y′ = 0.5

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Fig. 5

Axial velocity profiles (in m/s) at the mid-depth plane of microchannel heat sinks at X′ = 0.5 and Y′ = 0.5

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Fig. 6

Variation of velocity profiles (in m/s) with channel depth at X′ = 0.5

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Fig. 7

Development of velocity profiles (in m/s) along the oblique fin

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Fig. 8

Temperature contour (in  °C) of flow inside (a) conventional microchannel; (b) enhanced microchannel heat sinks at X′ = 0.5 and Y′ = 0.5

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Fig. 9

Water temperature profile (in  °C) at the mid-depth plane of microchannel heat sinks at X′ = 0.5 and Y′ = 0.5

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Fig. 10

Development of water temperature profile (in  °C) along the oblique fin

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Fig. 11

Variation of water temperature profiles (in  °C) with channel height at X′ = 0.5

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Fig. 12

Heater temperature profile for microchannel heat sinks

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Fig. 13

Heat transfer coefficient profile for (a) comparison between microchannel heat sinks; (b) enhanced microchannel with percentage of secondary flows

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Fig. 14

Effective heat flux along microchannel heat sinks

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Fig. 15

(a) Percentage of heat dissipated from each surface; (b) effective heat flux dissipated from each surface

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Fig. 16

Pressure drop profile for microchannel heat sinks

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Fig. 17

Local pressure profile along the oblique fin

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