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Research Papers

Heat Transfer, Pressure Drop, and Entropy Generation in a Solar Collector Using SiO2/Water Nanofluids: Effects of Nanoparticle Size and pH

[+] Author and Article Information
Omid Mahian

Department of Mechanical Engineering,
Faculty of Engineering,
Ferdowsi University of Mashhad,
Mashhad 91777-1111, Iran
e-mail: omid.mahian@gmail.com

Ali Kianifar

Department of Mechanical Engineering,
Faculty of Engineering,
Ferdowsi University of Mashhad,
Mashhad 91777-1111, Iran

Ahmet Z. Sahin

Mechanical Engineering Department,
King Fahd University of Petroleum and Minerals,
Dhahran 31261, Saudi Arabia

Somchai Wongwises

Fluid Mechanics,
Thermal Engineering
and Multiphase Flow Research Lab. (FUTURE),
Department of Mechanical Engineering,
Faculty of Engineering,
King Mongkut's University
of Technology Thonburi,
Bangmod, Bangkok 10140, Thailand

1Corresponding author.

Manuscript received May 16, 2014; final manuscript received August 1, 2014; published online March 17, 2015. Assoc. Editor: Giulio Lorenzini.

J. Heat Transfer 137(6), 061011 (Jun 01, 2015) (9 pages) Paper No: HT-14-1316; doi: 10.1115/1.4029870 History: Received May 16, 2014; Revised August 01, 2014; Online March 17, 2015

In this paper, an analytical study is carried out on the heat transfer, pressure drop, and entropy generation in a flat-plate solar collector using SiO2/water nanofluid with volume concentration of 1%. In the study, the effects of two different values of pH, i.e., 5.8 and 6.5, and two different sizes of nanoparticles, i.e., 12 nm and 16 nm, on the entropy generation rate in turbulent flow are investigated. The results are compared with the results obtained for the case of water. The findings show that by using the Brinkman model to calculate the viscosity instead of experimental data one obtains a higher heat transfer coefficient and thermal efficiency than that in the case of water, while, when the experimental data are used, the heat transfer coefficient and thermal efficiency of water are found to be higher than that of nanofluids. The results reveal that using nanofluids increases the outlet temperature and reduces the entropy generation rate. It is also found that for nanofluids containing the particles with a size of 16 nm, the increase in pH value would increase the entropy generation rate, while for nanoparticles with a size of 12 nm the increase in pH would decrease the entropy generation.

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Figures

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Fig. 1

A schematic view of the solar collector structure

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Fig. 2

Values of solar irradiance on solar collector, ambient temperature, and wind velocity in a typical day in Bangkok weather conditions

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Fig. 3

Simplified thermal network for the solar collector

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Fig. 9

Values of entropy generation rate for different cases and water (a) during day and (b) at 11:00 am

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Fig. 4

Values of (a) Nusselt number and (b) heat transfer coefficient for different cases and water

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Fig. 5

Values of outlet temperature (a) for different cases and water during the day (b) for different cases at 11:00 am

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Fig. 6

Values of thermal efficiency of solar collector (a) for different cases and water at 11:00 am (b) for cases 3–6 during the day

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Fig. 7

Values of (a) total head loss and (b) pressure drop for different cases and water

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Fig. 8

Bejan number for different cases and water at 11:00 am

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Fig. 10

Variations of entropy generation rate for different cases and water at various mass flow rates

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