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Research Papers: Energy Systems Analysis

Viscous Dissipation Effect on Streamwise Entropy Generation of Nanofluid Flow in Microchannel Heat Sinks

[+] Author and Article Information
Tiew Wei Ting

School of Engineering,
Monash University Malaysia,
Bandar Sunway 47500, Selangor, Malaysia
e-mail: ting.tiew.wei@monash.edu

Yew Mun Hung

School of Engineering,
Monash University Malaysia,
Bandar Sunway 47500, Selangor, Malaysia
e-mail: hung.yew.mun@monash.edu

Ningqun Guo

School of Engineering,
Monash University Malaysia,
Bandar Sunway 47500, Selangor, Malaysia
e-mail: anthony.guo@monash.edu

Contributed by the Advanced Energy Systems Division of ASME for publication in the JOURNAL OF ENERGY RESOURCES TECHNOLOGY. Manuscript received September 30, 2014; final manuscript received February 3, 2016; published online March 10, 2016. Assoc. Editor: Pirouz Kavehpour.

J. Energy Resour. Technol 138(5), 052002 (Mar 10, 2016) (9 pages) Paper No: JERT-14-1311; doi: 10.1115/1.4032792 History: Received September 30, 2014; Revised February 03, 2016

The effects of viscous dissipation on the entropy generation of water–alumina nanofluid convection in circular microchannels subjected to exponential wall heat flux are investigated. Closed-form solutions of the temperature distributions in the streamwise direction are obtained for the models with and without viscous dissipation term in the energy equation. The two models are compared by analyzing their relative deviations in entropy generation for different Reynolds numbers and nanoparticle volume fractions. The incorporation of viscous dissipation prominently affects the temperature distribution and consequently the entropy generation. When the viscous dissipation effect is neglected, the total entropy generation and the fluid friction irreversibility are nearly twofold overrated while the heat transfer irreversibility is underestimated significantly. By considering the viscous dissipation effect, the exergetic effectiveness for forced convection of nanofluid in microchannels attenuates with the increasing nanoparticle volume fraction and nanoparticle diameter. The increase in the entropy generation of nanofluid is mainly attributed to the intensification of fluid friction irreversibility. From the aspect of the second-law of thermodynamics, the widespread conjecture that nanofluids possess advantage over pure fluid associated with higher overall effectiveness is invalidated.

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References

Figures

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Fig. 1

Variations of Br′ as a function of Reynolds number with ϕ as a parameter

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Fig. 4

Variations of the cross-sectional averaged (a) heat transfer irreversibility and (b) fluid friction irreversibility along the axial direction of the microchannel for both models

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Fig. 3

Variations of the cross-sectional averaged entropy generation along the axial direction of the microchannel for both models

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Fig. 2

Dimensionless temperature distribution along the axial direction with ϕ as a parameter

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Fig. 5

The total entropy generation and the corresponding discrepancy ratio between the two models as a function of Reynolds number

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Fig. 6

(a) The heat transfer irreversibility and (b) the fluid friction irreversibility with the corresponding discrepancy ratio between the two models as a function of Reynolds number

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Fig. 7

The Bejan number and the corresponding discrepancy ratio between the two models as a function of Reynolds number

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Fig. 9

The ratio of deviation due to nanoparticle suspension for (a) heat transfer irreversibility and (b) fluid friction irreversibility as a function of Reynolds number

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Fig. 10

Variations of (a) the total entropy generation and (b) the irreversibility components with respect to the nanoparticle volume fraction with dp as a parameter

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Fig. 11

Variations of (a) the total entropy generation and (b) the irreversibility components with respect to the microchannel aspect ratio with ϕ as a parameter

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Fig. 8

The ratio of deviation due to nanoparticle suspension for total entropy generation as a function of Reynolds number

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