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Thermal conductivity and viscosity measurements of ethylene glycol-based Al2O3 nanofluids.

Pastoriza-Gallego MJ, Lugo L, Legido JL, Piñeiro MM - Nanoscale Res Lett (2011)

Bottom Line: The dispersion and stability of nanofluids obtained by dispersing Al2O3 nanoparticles in ethylene glycol have been analyzed at several concentrations up to 25% in mass fraction.Measured enhancements on thermal conductivity (up to 19%) compare well with literature values when available.These experimental results were compared with some theoretical models, as those of Maxwell-Hamilton and Crosser for thermal conductivity and Krieger and Dougherty for viscosity.

View Article: PubMed Central - HTML - PubMed

Affiliation: Departamento de Física Aplicada, Facultade de Ciencias, Universidade de Vigo, Campus Universitario s/n, E-36310, Vigo, Spain. mmpineiro@uvigo.es.

ABSTRACT
The dispersion and stability of nanofluids obtained by dispersing Al2O3 nanoparticles in ethylene glycol have been analyzed at several concentrations up to 25% in mass fraction. The thermal conductivity and viscosity were experimentally determined at temperatures ranging from 283.15 K to 323.15 K using an apparatus based on the hot-wire method and a rotational viscometer, respectively. It has been found that both thermal conductivity and viscosity increase with the concentration of nanoparticles, whereas when the temperature increases the viscosity diminishes and the thermal conductivity rises. Measured enhancements on thermal conductivity (up to 19%) compare well with literature values when available. New viscosity experimental data yield values more than twice larger than the base fluid. The influence of particle size on viscosity has been also studied, finding large differences that must be taken into account for any practical application. These experimental results were compared with some theoretical models, as those of Maxwell-Hamilton and Crosser for thermal conductivity and Krieger and Dougherty for viscosity.

No MeSH data available.


Related in: MedlinePlus

Enhancement of viscosity increase for alumina nanofluids as a function of volume fraction of nanoparticles. S1 (diamond) and S2 (triangle) samples. Prediction of Einstein equation (broken solid line), Equation 3 with N = 1 (dashed line), Equation 5, considering variable aa/a ratio (dashed-dot line), and Equation 5 considering constant aa/a ratio (solid line).
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Figure 6: Enhancement of viscosity increase for alumina nanofluids as a function of volume fraction of nanoparticles. S1 (diamond) and S2 (triangle) samples. Prediction of Einstein equation (broken solid line), Equation 3 with N = 1 (dashed line), Equation 5, considering variable aa/a ratio (dashed-dot line), and Equation 5 considering constant aa/a ratio (solid line).

Mentions: Viscosity increases with volume fraction, as expected, and this enhancement, defined as (ηnf - η0)/η0, η0 being the viscosity of the base fluid, can be considered temperature-independent by analyzing Table 3. This approximation was also considered by Chen et al. [45] and Prasher et al. [47]. Thus, average viscosity increase values for each studied nanofluid were assumed over the temperature range because it allows a convenient representation of results (Figure 6). S1 and S2 samples, although sharing the same nature and nanoparticle concentration, exhibit remarkably different viscosity enhancements, and the difference between both trends is increased with concentration, as can be observed in Table 3 or in Figure 6. S2 samples, whose average nanoparticle size is smaller, show a significantly larger viscosity than S1 samples. These variations must be carefully considered because they indicate that the differences in size or aggregation of the nanoparticles used to produce a nanofluid have a determining influence on its viscosity. This effect should be analyzed when any practical application of the nanofluid is envisaged. As an example, at 10% weight fraction, viscosity enhancements of 46% and 96% are obtained for S1 and S2 samples, respectively, while for S1 samples, enhancements from 5% up to more than twice the base fluid value for the lower and higher volume fractions are found. The influence of particle size in a colloid viscosity is well known [48] due to effects, as for instance, of the electric double-layer repulsion.


Thermal conductivity and viscosity measurements of ethylene glycol-based Al2O3 nanofluids.

Pastoriza-Gallego MJ, Lugo L, Legido JL, Piñeiro MM - Nanoscale Res Lett (2011)

Enhancement of viscosity increase for alumina nanofluids as a function of volume fraction of nanoparticles. S1 (diamond) and S2 (triangle) samples. Prediction of Einstein equation (broken solid line), Equation 3 with N = 1 (dashed line), Equation 5, considering variable aa/a ratio (dashed-dot line), and Equation 5 considering constant aa/a ratio (solid line).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3211279&req=5

Figure 6: Enhancement of viscosity increase for alumina nanofluids as a function of volume fraction of nanoparticles. S1 (diamond) and S2 (triangle) samples. Prediction of Einstein equation (broken solid line), Equation 3 with N = 1 (dashed line), Equation 5, considering variable aa/a ratio (dashed-dot line), and Equation 5 considering constant aa/a ratio (solid line).
Mentions: Viscosity increases with volume fraction, as expected, and this enhancement, defined as (ηnf - η0)/η0, η0 being the viscosity of the base fluid, can be considered temperature-independent by analyzing Table 3. This approximation was also considered by Chen et al. [45] and Prasher et al. [47]. Thus, average viscosity increase values for each studied nanofluid were assumed over the temperature range because it allows a convenient representation of results (Figure 6). S1 and S2 samples, although sharing the same nature and nanoparticle concentration, exhibit remarkably different viscosity enhancements, and the difference between both trends is increased with concentration, as can be observed in Table 3 or in Figure 6. S2 samples, whose average nanoparticle size is smaller, show a significantly larger viscosity than S1 samples. These variations must be carefully considered because they indicate that the differences in size or aggregation of the nanoparticles used to produce a nanofluid have a determining influence on its viscosity. This effect should be analyzed when any practical application of the nanofluid is envisaged. As an example, at 10% weight fraction, viscosity enhancements of 46% and 96% are obtained for S1 and S2 samples, respectively, while for S1 samples, enhancements from 5% up to more than twice the base fluid value for the lower and higher volume fractions are found. The influence of particle size in a colloid viscosity is well known [48] due to effects, as for instance, of the electric double-layer repulsion.

Bottom Line: The dispersion and stability of nanofluids obtained by dispersing Al2O3 nanoparticles in ethylene glycol have been analyzed at several concentrations up to 25% in mass fraction.Measured enhancements on thermal conductivity (up to 19%) compare well with literature values when available.These experimental results were compared with some theoretical models, as those of Maxwell-Hamilton and Crosser for thermal conductivity and Krieger and Dougherty for viscosity.

View Article: PubMed Central - HTML - PubMed

Affiliation: Departamento de Física Aplicada, Facultade de Ciencias, Universidade de Vigo, Campus Universitario s/n, E-36310, Vigo, Spain. mmpineiro@uvigo.es.

ABSTRACT
The dispersion and stability of nanofluids obtained by dispersing Al2O3 nanoparticles in ethylene glycol have been analyzed at several concentrations up to 25% in mass fraction. The thermal conductivity and viscosity were experimentally determined at temperatures ranging from 283.15 K to 323.15 K using an apparatus based on the hot-wire method and a rotational viscometer, respectively. It has been found that both thermal conductivity and viscosity increase with the concentration of nanoparticles, whereas when the temperature increases the viscosity diminishes and the thermal conductivity rises. Measured enhancements on thermal conductivity (up to 19%) compare well with literature values when available. New viscosity experimental data yield values more than twice larger than the base fluid. The influence of particle size on viscosity has been also studied, finding large differences that must be taken into account for any practical application. These experimental results were compared with some theoretical models, as those of Maxwell-Hamilton and Crosser for thermal conductivity and Krieger and Dougherty for viscosity.

No MeSH data available.


Related in: MedlinePlus