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Research Papers: Micro/Nanoscale Heat Transfer

Hydrodynamic and Thermal Performance of Microchannels With Different Staggered Arrangements of Cylindrical Micro Pin Fins

[+] Author and Article Information
Ali Mohammadi

Faculty of Engineering and Natural
Sciences (FENS),
Sabanci University,
Orhanli,
Tuzla 34956, Istanbul, Turkey
e-mail: alimohammadi@sabanciuniv.edu

Ali Koşar

Professor
Faculty of Engineering and Natural
Sciences (FENS),
Sabanci University,
Orhanli,
Tuzla 34956, Istanbul, Turkey
e-mail: kosara@sabanciuniv.edu

1Corresponding author.

Contributed by the Heat Transfer Division of ASME for publication in the JOURNAL OF HEAT TRANSFER. Manuscript received August 18, 2016; final manuscript received December 16, 2016; published online February 28, 2017. Assoc. Editor: Amy Fleischer.

J. Heat Transfer 139(6), 062402 (Feb 28, 2017) (14 pages) Paper No: HT-16-1522; doi: 10.1115/1.4035655 History: Received August 18, 2016; Revised December 16, 2016

This study focuses on microheat sinks with different staggered arrangements of micro pin fins (MPFs). A rectangular microchannel with the dimensions of 5000 × 1500 × 100 μm3 (l′ × w′ × h′) was considered for all the configurations while different MPF diameters, height over diameter ratio (H/D), and longitudinal and transversal pitch ratios (SL/D and ST/D) were considered in different arrangements. Using the ansys fluent 14.5 commercial software, the simulations were done for different Reynolds numbers between 20 and 160. A constant heat flux of 30 W/cm2 was applied through the bottom heating section. The performances of the microheat sinks were evaluated using design parameters, namely pressure drop, friction factor, Nusselt number, and thermal-hydraulic performance index (TPI). The effect of each geometrical parameter as well as wake-pin fin interaction patterns were carefully studied using the streamline patterns and temperature profiles of each configuration. The results reveal a great dependency of trends in pressure drops and Nusselt numbers on the wake region lengths as well as the local velocity and pressure gradients. Moreover, the wake region lengths mostly contribute to the increase in obtained pressure drop and Nusselt number with Reynolds number. Although an increase in the H/D and SL/D ratios results in an increase and a decrease in pressure drop, respectively, the effect on the Nusselt number depends on other geometrical parameters and Reynolds number. A larger ST/D ratio generally results in a decrease in the pressure drop and Nusselt number. Finally, while the friction factor decreases with Reynolds number, two different trends are seen for the TPI values of configurations with the H/D ratio of 1 and 2 (D = 100 and 50 μm). While the trend in the TPIs is increasing for Reynolds numbers between 20 and 40, it reverses for higher Reynolds numbers with a steeper slope in the configurations with the ST/D ratio of 1.5.

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References

Figures

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Fig. 1

Details on the 3D model of the LVdHd configuration

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Fig. 2

Validation of the numerical model with the results of Koşar and Peles [18]—ΔP versus Reynolds number and ΔT(Tout − Tin) versus Reynolds number

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Fig. 3

Pressure drop in different configurations ((a) with SL/D = 1.5 and (b) with SL/D = 3)

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Fig. 4

Streamlines at the midheight sections of the LVdHd, MVdHd, and SVdHd configurations (Re = 80)

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Fig. 5

Streamlines at the 10% and 90% height of the cross sections of the LVdHd and MVdHd configurations (Re = 80)

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Fig. 6

Streamlines at the midheight sections of the LVdHd and LVdHs configurations (Re = 80)

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Fig. 7

Streamlines at the midheight sections of the MVdHd and MVsHd configurations (Re = 80)

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Fig. 8

Pressure drop as a function of Reynolds number

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Fig. 9

Friction factor in different configurations at different Reynolds numbers

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Fig. 10

Nusselt number in different configurations ((a) with SL/D = 1.5 and (b) with SL/D = 3)

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Fig. 11

Temperature profiles at the 10%, 50%, and 90% height of the cross sections of the LVdHd configuration (Re = 80)

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Fig. 12

Thermal-hydraulic performance index (TPI) as a function of Reynolds number

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