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Research Papers: Micro/Nanoscale Heat Transfer

Flow and Heat Transfer in Micro Pin Fin Heat Sinks With Nano-Encapsulated Phase Change Materials

[+] Author and Article Information
Bahram Rajabifar, Hamid Reza Seyf

Department of Mechanical and
Aerospace Engineering,
University of Missouri,
Columbia, MO 65211

Yuwen Zhang

Fellow ASME
Department of Mechanical and
Aerospace Engineering,
University of Missouri,
Columbia, MO 65211
e-mail: zhangyu@missouri.edu

Sanjeev K. Khanna

Fellow ASME
Department of Mechanical and
Aerospace Engineering,
University of Missouri,
Columbia, MO 65211

1Corresponding author.

Contributed by the Heat Transfer Division of ASME for publication in the JOURNAL OF HEAT TRANSFER. Manuscript received January 23, 2014; final manuscript received February 11, 2016; published online March 22, 2016. Editor: Portonovo S. Ayyaswamy.

J. Heat Transfer 138(6), 062401 (Mar 22, 2016) (8 pages) Paper No: HT-14-1037; doi: 10.1115/1.4032834 History: Received January 23, 2014; Revised February 11, 2016

In this paper, a 3D-conjugated heat transfer model for nano-encapsulated phase change materials (NEPCMs) cooled micro pin fin heat sink (MPFHS) is presented. The governing equations of flow and heat transfer are solved using a finite volume method based on collocated grid and the results are validated with the available data reported in the literature. The effect of nanoparticles volume fraction (C = 0.1, 0.2, and 0.3), inlet velocity (Vin = 0.015, 0.030, and 0.045 m/s), and bottom wall temperature (Twall = 299.15, 303.15, 315.15, and 350.15 K) is studied on Nusselt and Euler numbers as well as temperature contours in the system. The results indicate that significant heat transfer enhancement is achieved when using the NEPCM slurry as an advanced coolant. The maximum Nusselt number when NEPCM slurry (C = 0.3) with Vin = 0.015, 0.030, and 0.045 (m/s) is employed is 2.27, 1.81, and 1.56 times higher than the ones with base fluid, respectively. However, with increasing bottom wall temperature, the Nusselt number first increases then decreases. The former is due to higher heat transfer capability of coolant at temperatures over the melting range of phase change material (PCM) particles due to partial melting of nanoparticles in this range. However, the latter phenomenon is due to the lower capability of the NEPCM particles and consequently coolant in absorbing heat at coolant temperatures is higher than the temperature correspond to fully melted NEPCM. It was observed that the NEPCM slurry has a drastic effect on the Euler number, and with increasing volume fraction and decreasing inlet velocity, the Euler number increases accordingly.

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References

Figures

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Fig. 1

Schematic of the computational domain

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Fig. 2

The specific heat of NEPCM particles is a function of temperature and is represented by a sine profile

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Fig. 3

Comparison of result using current model, numerical model in Ref. [12] and experimental data in Ref. [28]

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Fig. 4

The temperature distribution in the system at three different inlet velocities for C = 0.3 and Tw = 315.15 K (unit: K)

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Fig. 5

The temperature distribution in the system at three volume fraction for Vin = 0.045 m/s and Tw = 315.15 K (unit: K)

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Fig. 6

Nusselt number of the system (cooling performance) as a function of volume fraction of NEPCM particles and various inlet velocities

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Fig. 7

The distribution of specific heat of slurry in the system at constant inlet velocity of 0.015 m/s and volume fraction of 0.3 (unit: J/kg K)

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Fig. 8.

The distribution of specific heat of slurry in the system at bottom wall temperature of 315.15 K and volume fraction of 0.3 (unit: J/kg K)

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Fig. 9

Effect of volume fraction on Euler number at various bottom wall temperatures

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Fig. 10

The distribution of viscosity of slurry in a plane cutting the fins at the middle of height computational domain for last seven fins, for a bottom wall temperature of 315.15 K and inlet velocity of 0.045 m/s at various volume fractions (unit: kg/m s)

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