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Research Papers

Heat Development and Comparison Between the Steady and Pulsating Flows Through Aluminum Foam Heat Sink

[+] Author and Article Information
A. M. Bayomy

Department of Mechanical and
Industrial Engineering,
Ryerson University,
350 Victoria Street,
Toronto, ON M5B 2K3, Canada
e-mail: ayman.bayomy@ryerson.ca

M. Z. Saghir

Department of Mechanical and
Industrial Engineering,
Ryerson University,
350 Victoria Street,
Toronto, ON M5B 2K3, Canada
e-mail: zsaghir@ryerson.ca

1Corresponding author.

Contributed by the Heat Transfer Division of ASME for publication in the JOURNAL OF THERMAL SCIENCE AND ENGINEERING APPLICATIONS. Manuscript received May 26, 2016; final manuscript received September 26, 2016; published online April 4, 2017. Assoc. Editor: Mohamed S. El-Genk.

J. Thermal Sci. Eng. Appl 9(3), 031006 (Apr 04, 2017) (20 pages) Paper No: TSEA-16-1142; doi: 10.1115/1.4035937 History: Received May 26, 2016; Revised September 26, 2016

Continuous improvements in electronic devices for high-performance computers have led to a need for new and more effective methods of chip cooling. The first purpose of this study was to investigate the heat transfer development and characteristics of aluminum foam heat sink subjected to steady water flow for electronics cooling (Intel core i7 processor). The second purpose was to implement a new type of water flow through the aluminum foam, which is pulsating or oscillating flow in order to achieve more uniform temperature distribution over the electronic surfaces. The aluminum foam heat sink was subjected to a water flow covering the non-Darcy laminar flow regime (297–1353 Reynolds numbers). The bottom side of the heat sink was heated with a heat flux between 8.5 and 13.8 W/cm2. The pulsating flow frequency was ranged from 0.04 to 0.1 Hz. In addition, in order to complement the experimental studies, a numerical model was developed using finite element method and compared with the experimental data. The results revealed that the thermal entry length of the fluid flow through metal foam (porous media) is much smaller than that for laminar internal flow through empty channel. The result also showed that the local surface temperature increases along with increasing the axial flow direction for steady water flow case. On the other hand, for pulsating flow, the local temperature distributions act as a convex profile with the maximum surface temperature at the center of the test section. In addition, it was observed that the pulsating water flow through the aluminum foam heat sink achieves enhancement by 14% in the average Nusselt number and by 73% in temperature uniformity over the surface compared with steady water flow case.

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References

Figures

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Fig. 1

Experimental schematic diagram [27]

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Fig. 2

Test section heater [27]

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Fig. 3

Thermocouples positions and arrangements [27]

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Fig. 4

ERG aluminum foam heat sink [27]

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Fig. 5

Boundary conditions [27]

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Fig. 6

Characteristics of pulsating flow through aluminum foam [27]: (a) velocity variation at f = 0.1 Hz and (b) pulsating flow amplitude variation at f = 0.1 Hz

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Fig. 7

Mesh sensitivity and finite element model [27]: (a) mesh independent and (b) finite element model

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Fig. 8

Surface temperature along flow direction axis at different Reynolds numbers: (a) temperature distributions at q″ = 13.8 W/cm2 and (b) temperature distributions at q″ = 8.5 W/cm2

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Fig. 9

Local Nusselt number distributions: (a) Nusselt number distributions for entry and developed regions at q″ = 13.8 W/cm2 and (b) Nusselt number distribution at q″ = 13.8 W/cm2

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Fig. 10

Surface temperature distributions at (a) Re = 1353 and (b) Re = 541

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Fig. 11

Surface temperature distributions at (a) Re = 390 and (b) Re = 297

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Fig. 12

Experimental and numerical results of Nusselt number at Re = 1353 and 902: (a) Nusselt number distributions at Re = 1353 and (b) Nusselt number distributions at Re = 902

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Fig. 13

Comparison between experimental and numerical results of local Nusselt number: (a) Nusselt number distributions at Re = 541 and (b) Nusselt number distribution at Re = 297

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Fig. 14

Average Nusselt number variation with Reynolds number

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Fig. 15

Comparison between the present empirical equation of average Nusselt number and previous experimental data

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Fig. 16

Dimensionless temperature distributions of pulsating and steady water flows: (a) dimensionless surface temperature at Ao = 1353 and (b) dimensionless surface temperature at Ao = 902

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Fig. 17

Comparison between steady and pulsating flows local Nusselt number distributions: (a) local Nusselt number distributions of pulsating and steady flow at Ao = 1353 and (b) local Nusselt number distributions of pulsating and steady flow at Ao = 902

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Fig. 18

Enhancement percentage in local Nusselt number of pulsating flow

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Fig. 19

Cycle average local temperature distributions at (a) Ao = 1353 and (b) Ao = 902

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Fig. 20

Cycle average local temperature distributions at Ao = 1353 and 902: (a) cycle average local Nusselt number distributions at Ao = 1353 and (b) cycle average local Nusselt number distributions at Ao = 902

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Fig. 21

Average Nusselt number of pulsating and steady water flows

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Fig. 22

Uniformity index of pulsating and steady water flow compared with steady air flow [21]

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