Through past research, it is known that carbon nanotubes have the potential of enhancing
the thermal performance of heat transfer fluids. The research is of importance in
electronics cooling, defense, space, transportation applications and any other area where
small and highly efficient heat transfer systems are needed. However, most of the past
work discusses the experimental results by focusing on the effect of varying
concentration of carbon nanotubes (CNTs) on the thermal performance of CNT
nanofluids. Not much work has been done on studying the effect of processing variables.
In the current experimental work, accurate measurements were carried out in an effort to
understand the impact of several key variables on laminar flow convective heat transfer.
The impact of ultrasonication energy on CNT nanofluids processing, and the
corresponding effects on flow and thermal properties were studied in detail. The
properties measured were viscosity, thermal conductivity and the convective heat
transfer under laminar conditions. Four samples of 1 wt % multi walled carbon
nanotubes (MWCNT) aqueous suspensions with different ultrasonication times were
prepared for the study. Direct imaging was done using a newly developed wet-TEM technique to assess the dispersion characteristics of CNT nanofluid samples. The results
obtained were discussed in the context of the CNT nanofluid preparation by
ultrasonication and its indirect effect on each of the properties.
It was found that the changes in viscosity and enhancements in thermal conductivity and
convective heat transfer are affected by ultrasonication time. The maximum
enhancements in thermal conductivity and convective heat transfer were found to be 20
% and 32 %, respectively, in the sample processed for 40 minutes. The thermal
conductivity enhancement increased considerably at temperatures greater than 24 °C.
The percentage enhancement in convective heat transfer was found to increase with the
axial distance in the heat transfer section. Additionally, the suspensions were found to
exhibit a shear thinning behavior, which followed the Power Law viscosity model.
| Identifer | oai:union.ndltd.org:tamu.edu/oai:repository.tamu.edu:1969.1/ETD-TAMU-3281 |
| Date | 15 May 2009 |
| Creators | Garg, Paritosh |
| Contributors | Alvarado, Jorge, Annamalai, Kalyan |
| Source Sets | Texas A and M University |
| Language | en_US |
| Detected Language | English |
| Type | Book, Thesis, Electronic Thesis, text |
| Format | electronic, application/pdf, born digital |
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