Heat Transfer, Pressure Drop, and Entropy Generation in a Solar Collector Using SiO2/Water Nanofluids: Effects of Nanoparticle Size and pH
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Author list: Mahian O., Kianifar A., Sahin A.Z., Wongwises S.
Publisher: American Society of Mechanical Engineers
Publication year: 2015
Journal: Journal of Heat Transfer (0022-1481)
Volume number: 137
Issue number: 6
ISSN: 0022-1481
eISSN: 1528-8943
Languages: English-Great Britain (EN-GB)
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Abstract
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. Copyright ฉ 2015 by ASME.
Keywords
nanofluid pH