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Stability and rheology of dilute TiO2-water nanofluids.

Penkavova V, Tihon J, Wein O - Nanoscale Res Lett (2011)

Bottom Line: In this study, a series of dilute TiO2 aqueous dispersions were prepared and tested for the possible presence of the AWS effect by means of a novel viscometric technique.The resulting stable nanofluid samples were dilute, below 0.7 vol.%.No case of important slip contribution was detected: the Navier slip coefficient of approximately 2 mm Pa-1 s-1 would affect the apparent fluidity data in a 100-μm gap by less than 1%.

View Article: PubMed Central - HTML - PubMed

Affiliation: Institute of Chemical Process Fundamentals, Academy of Sciences of the Czech Republic, Rozvojova 135, 165 02 Prague 6, Czech Republic. wein@icpf.cas.cz.

ABSTRACT
The apparent wall slip (AWS) effect, accompanying the flow of colloidal dispersions in confined geometries, can be an important factor for the applications of nanofluids in heat transfer and microfluidics. In this study, a series of dilute TiO2 aqueous dispersions were prepared and tested for the possible presence of the AWS effect by means of a novel viscometric technique. The nanofluids, prepared from TiO2 rutile or anatase nanopowders by ultrasonic dispersing in water, were stabilized by adjusting the pH to the maximum zeta potential. The resulting stable nanofluid samples were dilute, below 0.7 vol.%. All the samples manifest Newtonian behavior with the fluidities almost unaffected by the presence of the dispersed phase. No case of important slip contribution was detected: the Navier slip coefficient of approximately 2 mm Pa-1 s-1 would affect the apparent fluidity data in a 100-μm gap by less than 1%.

No MeSH data available.


Related in: MedlinePlus

KK sensor for AWS viscometry operating under HAAKE RS 600 rotational viscometer. Common geometry parameters for all the KK sensors: H = 60 mm, R = 17.5 mm, cot(θ) = 10. The actual gap thickness h is adjustable through axial shift Δz, see Equation 2. When applying Equation 1 for description of the AWS effect, take ΩR = U.
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Figure 5: KK sensor for AWS viscometry operating under HAAKE RS 600 rotational viscometer. Common geometry parameters for all the KK sensors: H = 60 mm, R = 17.5 mm, cot(θ) = 10. The actual gap thickness h is adjustable through axial shift Δz, see Equation 2. When applying Equation 1 for description of the AWS effect, take ΩR = U.

Mentions: The experimental realization of AWS viscometry needs a series of sensors of different and well-calibrated hydraulic radii (tube radius in the capillary viscometry, gap thickness between cup and bob in the rotational viscometry, etc.). The novel KK-type sensor for the rotational AWS viscometry [19], shown in Figure 5 complies with this need by means of an axial shift facility for adjusting Δz and, subsequently, the gap thickness h is given by(2)


Stability and rheology of dilute TiO2-water nanofluids.

Penkavova V, Tihon J, Wein O - Nanoscale Res Lett (2011)

KK sensor for AWS viscometry operating under HAAKE RS 600 rotational viscometer. Common geometry parameters for all the KK sensors: H = 60 mm, R = 17.5 mm, cot(θ) = 10. The actual gap thickness h is adjustable through axial shift Δz, see Equation 2. When applying Equation 1 for description of the AWS effect, take ΩR = U.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3211337&req=5

Figure 5: KK sensor for AWS viscometry operating under HAAKE RS 600 rotational viscometer. Common geometry parameters for all the KK sensors: H = 60 mm, R = 17.5 mm, cot(θ) = 10. The actual gap thickness h is adjustable through axial shift Δz, see Equation 2. When applying Equation 1 for description of the AWS effect, take ΩR = U.
Mentions: The experimental realization of AWS viscometry needs a series of sensors of different and well-calibrated hydraulic radii (tube radius in the capillary viscometry, gap thickness between cup and bob in the rotational viscometry, etc.). The novel KK-type sensor for the rotational AWS viscometry [19], shown in Figure 5 complies with this need by means of an axial shift facility for adjusting Δz and, subsequently, the gap thickness h is given by(2)

Bottom Line: In this study, a series of dilute TiO2 aqueous dispersions were prepared and tested for the possible presence of the AWS effect by means of a novel viscometric technique.The resulting stable nanofluid samples were dilute, below 0.7 vol.%.No case of important slip contribution was detected: the Navier slip coefficient of approximately 2 mm Pa-1 s-1 would affect the apparent fluidity data in a 100-μm gap by less than 1%.

View Article: PubMed Central - HTML - PubMed

Affiliation: Institute of Chemical Process Fundamentals, Academy of Sciences of the Czech Republic, Rozvojova 135, 165 02 Prague 6, Czech Republic. wein@icpf.cas.cz.

ABSTRACT
The apparent wall slip (AWS) effect, accompanying the flow of colloidal dispersions in confined geometries, can be an important factor for the applications of nanofluids in heat transfer and microfluidics. In this study, a series of dilute TiO2 aqueous dispersions were prepared and tested for the possible presence of the AWS effect by means of a novel viscometric technique. The nanofluids, prepared from TiO2 rutile or anatase nanopowders by ultrasonic dispersing in water, were stabilized by adjusting the pH to the maximum zeta potential. The resulting stable nanofluid samples were dilute, below 0.7 vol.%. All the samples manifest Newtonian behavior with the fluidities almost unaffected by the presence of the dispersed phase. No case of important slip contribution was detected: the Navier slip coefficient of approximately 2 mm Pa-1 s-1 would affect the apparent fluidity data in a 100-μm gap by less than 1%.

No MeSH data available.


Related in: MedlinePlus