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Stability of nanofluids in quiescent and shear flow fields.

Witharana S, Chen H, Ding Y - Nanoscale Res Lett (2011)

Bottom Line: An experimental study was conducted to investigate the structural stability of ethylene glycol-based titanium dioxide nanoparticle suspensions (nanofluids) prepared by two-step method.Particle size and thermal conductivity measurements in quiescent state indicated the existence of aggregates and that they were stable in temperatures up to 60°C.These findings show directions to resolve controversies surrounding the underlying mechanisms of thermal conduction and convective heat transfer of nanofluids.

View Article: PubMed Central - HTML - PubMed

Affiliation: Institute of Particle Science and Engineering, University of Leeds, Leeds LS2 9JT, UK. pmsw@leeds.ac.uk.

ABSTRACT
An experimental study was conducted to investigate the structural stability of ethylene glycol-based titanium dioxide nanoparticle suspensions (nanofluids) prepared by two-step method. The effects of particle concentration, fluid temperature, shear rate and shear duration were examined. Particle size and thermal conductivity measurements in quiescent state indicated the existence of aggregates and that they were stable in temperatures up to 60°C. Shear stability tests suggested that the structure of nanoparticle aggregates was stable in a shear interval of 500-3000 s-1 measured over a temperature range of 20-60°C. These findings show directions to resolve controversies surrounding the underlying mechanisms of thermal conduction and convective heat transfer of nanofluids.

No MeSH data available.


Related in: MedlinePlus

Titania particles as received.
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Figure 1: Titania particles as received.

Mentions: Nanofluids were formulated using TiO2 nanopowder and EG. The dry TiO2 nanopowder purchased from Degussa Corporation in Germany was claimed to be consisting of spherical particles of 25-nm diameter. Electron microscopy (EM) imaging such as in Figure 1 suggests that the particles were in the form of agglomerates. In order to manufacture a stable nanoparticle suspension, a sequence of processes were followed. Further details of formulation can be found elsewhere [7,21]. The EM images of the nanofluid confirmed that the nanoparticles were well dispersed. Moreover, the light-scattering data collected using the Malvern Zetasizer-nano device showed that the suspended particles were in the order of around 130 nm in size. This is an indication of the formulation technique substantially reducing the aggregate size but failing to break them down to primary particles. This observation agrees with the recently concluded International Nanofluids Property Benchmarking Exercise (INPBE) [22]. These nanofluids were stable for 2 months without a visible separation, indicating the stability of aggregates in the long run.


Stability of nanofluids in quiescent and shear flow fields.

Witharana S, Chen H, Ding Y - Nanoscale Res Lett (2011)

Titania particles as received.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3211290&req=5

Figure 1: Titania particles as received.
Mentions: Nanofluids were formulated using TiO2 nanopowder and EG. The dry TiO2 nanopowder purchased from Degussa Corporation in Germany was claimed to be consisting of spherical particles of 25-nm diameter. Electron microscopy (EM) imaging such as in Figure 1 suggests that the particles were in the form of agglomerates. In order to manufacture a stable nanoparticle suspension, a sequence of processes were followed. Further details of formulation can be found elsewhere [7,21]. The EM images of the nanofluid confirmed that the nanoparticles were well dispersed. Moreover, the light-scattering data collected using the Malvern Zetasizer-nano device showed that the suspended particles were in the order of around 130 nm in size. This is an indication of the formulation technique substantially reducing the aggregate size but failing to break them down to primary particles. This observation agrees with the recently concluded International Nanofluids Property Benchmarking Exercise (INPBE) [22]. These nanofluids were stable for 2 months without a visible separation, indicating the stability of aggregates in the long run.

Bottom Line: An experimental study was conducted to investigate the structural stability of ethylene glycol-based titanium dioxide nanoparticle suspensions (nanofluids) prepared by two-step method.Particle size and thermal conductivity measurements in quiescent state indicated the existence of aggregates and that they were stable in temperatures up to 60°C.These findings show directions to resolve controversies surrounding the underlying mechanisms of thermal conduction and convective heat transfer of nanofluids.

View Article: PubMed Central - HTML - PubMed

Affiliation: Institute of Particle Science and Engineering, University of Leeds, Leeds LS2 9JT, UK. pmsw@leeds.ac.uk.

ABSTRACT
An experimental study was conducted to investigate the structural stability of ethylene glycol-based titanium dioxide nanoparticle suspensions (nanofluids) prepared by two-step method. The effects of particle concentration, fluid temperature, shear rate and shear duration were examined. Particle size and thermal conductivity measurements in quiescent state indicated the existence of aggregates and that they were stable in temperatures up to 60°C. Shear stability tests suggested that the structure of nanoparticle aggregates was stable in a shear interval of 500-3000 s-1 measured over a temperature range of 20-60°C. These findings show directions to resolve controversies surrounding the underlying mechanisms of thermal conduction and convective heat transfer of nanofluids.

No MeSH data available.


Related in: MedlinePlus