An experimental study on the effect of ultrasonication on viscosity and heat transfer performance of multi-wall carbon nanotube-based aqueous nanofluids |
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| Authors: | Paritosh Garg Jorge L Alvarado Charles Marsh Thomas A Carlson David A Kessler Kalyan Annamalai |
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| Affiliation: | 1. Engineering Faculty, Shahrekord University, PO Box 115, Shahrekord, Iran;2. Department of Mechanical Engineering, Najafabad Branch, Islamic Azad University, Najafabad, Iran;1. Department of Energy Technology, Aalborg University, Pontoppidanstraede 111, DK-9220 Aalborg, Denmark;2. Department of Mechanical Engineering, University of Kashan, Kashan, Iran;1. Heat and Fluid Flow Research Laboratory, Department of Mechanical Engineering, University of Tabriz, Tabriz, Iran;2. Department of Mechanical Engineering, University of Sistan and Baluchestan, Zahedan, Iran |
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| Abstract: | Four samples of 1 wt% multi-walled carbon nanotube-based (MWCNT) aqueous nanofluids prepared via ultrasonication were thermally characterized. Direct imaging was done using a newly developed wet-TEM technique to assess the dispersion state of carbon nanotubes (CNT) in suspension. The effect of dispersing energy (ultrasonication) on viscosity, thermal conductivity, and the laminar convective heat transfer was studied. Results indicate that thermal conductivity and heat transfer enhancement increased until an optimum ultrasonication time was reached, and decreased on further ultrasonication. The suspensions exhibited a shear thinning behavior, which followed the Power Law viscosity model. The maximum enhancements in thermal conductivity and convective heat transfer were found to be 20% and 32%, respectively. The thermal conductivity enhancement increased considerably at temperatures greater than 24 °C. The enhancement in convective heat transfer was found to increase with axial distance. A number of mechanisms related to boundary layer thickness, micro-convective effect, particle rearrangement, possible induced convective effects due to temperature and viscosity variations in the radial direction, and the non-Newtonian nature of the samples are discussed. |
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| Keywords: | Convective heat transfer Nanofluids Multi-walled Carbon nanotubes Thermal conductivity Viscosity Heat transfer enhancement Non-Newtonian fluid TEM |
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