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Thermal conductivity enhancement in micro- and nano-particle suspensions
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Thermal conductivity enhancement in micro- and nano-particle suspensions
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ETD_2206
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http://hdl.rutgers.edu/1782.2/rucore10001600001.ETD.000051795
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eng
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theses
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Mechanical and Aerospace Engineering
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(authority = ETD-LCSH)
Topic
Liquids--Thermal properties
Subject
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(authority = ETD-LCSH)
Topic
Nanoparticles
Subject
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(authority = ETD-LCSH)
Topic
Thermal conductivity
Abstract
It has been recognized that the addition of highly conductive particles can significantly increase the thermal conductivity of heat-transfer fluids. Particles in the micro- and nano-size range have attracted the most interest because of their enhanced stability against sedimentation and, as a result, reduction in potential for clogging a flow system. Additional interest has been drawn by recent reports of anomalous enhancements in thermal conductivity above predictions of classical theory for suspensions containing nano-particles. In this research we report on an experimental study of the effective thermal conductivity of suspensions containing micro- and nano-particles.
First, we investigated the effect of the particle aspect ratio on heat transfer in fluids. Spherical and cylindrical silicon-carbide particles were dispersed in ethylene glycol, and multi-walled nanotubes were suspended in water with surfactant. To carry out a detailed analysis, size and geometry of the particles were determined from optical and transmission-electron-microscopy imaging. Provided the volume-averaged aspect ratio was used in theoretical calculations, the conductivity of the silicon carbide suspensions was found to be in excellent agreement with effective-medium theory. Experimental data on the thermal conductivity of multi-walled nanotubes dispersions could also be interpreted in terms of the aspect-ratio dependence predicted by effective medium theory if the additional nanoscale effect of interfacial resistance was considered. The aspect ratio of dispersed particles was changed through further processing of both micro- and nano-fluids. As the result, the obtained thermal conductivities doubtlessly revealed that aspect ratio is a key factor affecting conductive heat transport in suspensions. For nanofluids, despite the promise of enhanced stability due to the nanoscale size of particles, particle agglomeration state can have a profound effect on the resulting thermal conductivity of the suspension. This was investigated by coupling thermal conductivity experiments with optical-absorbance and zeta-potential measurements of the stability of carbon nanotube-based nanofluids.
An optimal surfactant-to-carbon nanotube mass ratio was found that resulted in both maximum thermal conductivity enhancement and suspension stability. Comparison of thermal conductivities for well-dispersed and agglomerated suspensions was carried out with the aid of ethanol de-stabilization. The experimental data indicated that only individualized nanotubes contribute appreciably to the thermal conductivity enhancement and, as a result, suspension stability is another essential parameter affecting the thermal conductivity of nanoparticle suspensions.
First, we investigated the effect of the particle aspect ratio on heat transfer in fluids. Spherical and cylindrical silicon-carbide particles were dispersed in ethylene glycol, and multi-walled nanotubes were suspended in water with surfactant. To carry out a detailed analysis, size and geometry of the particles were determined from optical and transmission-electron-microscopy imaging. Provided the volume-averaged aspect ratio was used in theoretical calculations, the conductivity of the silicon carbide suspensions was found to be in excellent agreement with effective-medium theory. Experimental data on the thermal conductivity of multi-walled nanotubes dispersions could also be interpreted in terms of the aspect-ratio dependence predicted by effective medium theory if the additional nanoscale effect of interfacial resistance was considered. The aspect ratio of dispersed particles was changed through further processing of both micro- and nano-fluids. As the result, the obtained thermal conductivities doubtlessly revealed that aspect ratio is a key factor affecting conductive heat transport in suspensions. For nanofluids, despite the promise of enhanced stability due to the nanoscale size of particles, particle agglomeration state can have a profound effect on the resulting thermal conductivity of the suspension. This was investigated by coupling thermal conductivity experiments with optical-absorbance and zeta-potential measurements of the stability of carbon nanotube-based nanofluids.
An optimal surfactant-to-carbon nanotube mass ratio was found that resulted in both maximum thermal conductivity enhancement and suspension stability. Comparison of thermal conductivities for well-dispersed and agglomerated suspensions was carried out with the aid of ethanol de-stabilization. The experimental data indicated that only individualized nanotubes contribute appreciably to the thermal conductivity enhancement and, as a result, suspension stability is another essential parameter affecting the thermal conductivity of nanoparticle suspensions.
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electronic resource
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xii, 90 p. : ill.
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Ph.D.
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Includes bibliographical references (p. 83-89)
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by Anna S. Cherkasova
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Cherkasova
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Anna S.
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1979-
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Anna Cherkasova
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Shan
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Jerry
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chair
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Jerry W Shan
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Jaluria
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Yogesh
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internal member
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Yogesh Jaluria
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Guo
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Zhixiong
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Zhixiong Guo
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Riman
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Richard
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Richard E Riman
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Rutgers University
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Graduate School - New Brunswick
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2009
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2009-10
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xx
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Rutgers University Electronic Theses and Dissertations
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Graduate School - New Brunswick Electronic Theses and Dissertations
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doi:10.7282/T37P8ZKD
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ETD doctoral
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Rights
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The author owns the copyright to this work
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Copyright protected
Notice
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Open
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Cherkasova
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Anna
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Anna Cherkasova
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Rutgers University. Graduate School - New Brunswick
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I hereby grant to the Rutgers University Libraries and to my school the non-exclusive right to archive, reproduce and distribute my thesis or dissertation, in whole or in part, and/or my abstract, in whole or in part, in and from an electronic format, subject to the release date subsequently stipulated in this submittal form and approved by my school. I represent and stipulate that the thesis or dissertation and its abstract are my original work, that they do not infringe or violate any rights of others, and that I make these grants as the sole owner of the rights to my thesis or dissertation and its abstract. I represent that I have obtained written permissions, when necessary, from the owner(s) of each third party copyrighted matter to be included in my thesis or dissertation and will supply copies of such upon request by my school. I acknowledge that RU ETD and my school will not distribute my thesis or dissertation or its abstract if, in their reasonable judgment, they believe all such rights have not been secured. I acknowledge that I retain ownership rights to the copyright of my work. I also retain the right to use all or part of this thesis or dissertation in future works, such as articles or books.
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