Viscosity and thermal conductivity of nanofluids containing multi-walled carbon nanotubes stabilized by chitosan
- National Energy Technology Lab. (NETL), Pittsburgh, PA, (United States)
- Univ. of Central Florida, Orlando, FL (United States). Dept. of Mechanical, Materials and Aerospace Engineering
Thermal conductivity, viscosity, and stability of nanofluids containing multi-walled carbon nanotubes (MWCNTs) stabilized by cationic chitosan were studied. Chitosan with weight fraction of 0.1%, 0.2 wt%, and 0.5 wt% was used to disperse stably MWCNTs in water. The measured thermal conductivity showed an enhancement from 2.3% to 13% for nanofluids that contained from 0.5 wt% to 3 wt% MWCNTs (0.24 to 1.43 vol %). These values are significantly higher than those predicted using the Maxwell's theory. We also observed that the enhancements were independent of the base fluid viscosity. Thus, use of microconvection effect to explain the anomalous thermal conductivity enhancement should be reconsidered. MWCNTs can be used either to enhance or reduce the fluid base viscosity depending on the weight fractions. In the viscosity-reduction case, a reduction up to 20% was measured by this work. In the viscosity-enhancement case, the fluid behaved as a non-Newtonian shear-thinning fluid. By assuming that MWCNT nanofluids behave as a generalized second grade fluid where the viscosity coefficient depends upon the rate of deformation, a theoretical model has been developed. The model was found to describe the fluid behavior very well.
- Research Organization:
- National Energy Technology Laboratory (NETL), Pittsburgh, PA, Morgantown, WV, and Albany, OR (United States)
- Sponsoring Organization:
- USDOE Assistant Secretary for Fossil Energy (FE)
- OSTI ID:
- 1014877
- Report Number(s):
- NETL-TPR-3243
- Journal Information:
- International Journal of Thermal Sciences, Vol. 50, Issue 1; ISSN 1290-0729
- Publisher:
- Elsevier
- Country of Publication:
- United States
- Language:
- English
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