Limits...
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

Experimental measured thermal conductivity. Alumina nanofluids in EG versus volume fraction concentration at different temperatures: 283.15 K (filled circle); 303.15 K (empty circle), and 323.15 K (downturned triangle).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC3211279&req=5

Figure 3: Experimental measured thermal conductivity. Alumina nanofluids in EG versus volume fraction concentration at different temperatures: 283.15 K (filled circle); 303.15 K (empty circle), and 323.15 K (downturned triangle).

Mentions: The thermal conductivity enhancement of five different ethylene glycol-based Al2O3 nanofluids corresponding to the denoted S1 samples has been measured at 283.15 K, 303.15 K, and 323.15 K. The volume fraction, ϕ, varied between 1.5% and 8.6% estimated from the densities of the pure liquid, determined in our laboratory with an Anton Paar DMA 4500 vibrating tube densimeter (Anton Paar, Graz, Österreich), and the bulk solid oxide [41]. The experimental thermal conductivities of alumina nanofluids, knf, at several temperatures are presented in Table 2 as a function of volume fraction. At the tested concentrations, thermal conductivity increases with nanoparticle volume fraction, ϕ, as shown in Figure 3. This behavior is in agreement with Timofeeva et al. [24,29] for different particle shapes, including spheres, and with those reported by Beck et al. [25] and Wang et al. [43] for nanofluids consisting of ethylene glycol with 20- and 28-nm alumina nanoparticles, respectively. Concerning temperature dependence, the thermal conductivity of all nanofluids also increases with temperature. As observed, the addition of nanopowder systematically increases the thermal conductivity of the nanofluid as compared with the pure fluid. If Table 2 is analyzed, we can conclude that this enhancement for a given nanofluid is nearly temperature-independent, as Peñas et al. [38] have also stated. Average enhancements values from 3% at the lowest volume fraction up to 19% for the highest concentration are found, showing good agreement (average 1% deviation) with the data from Timofeeva et al. [24] at 296.15 K for suspensions prepared from 40-nm alumina nanoparticles. However, the S1 sample data reported here and those from [24] with 11-, 20-, and 40-nm nominal sizes do not show the same trend as reported by Beck et al. [28] in their study on the effect of particle size on alumina nanofluids in ethylene glycol. This may be due to the different pH of the samples studied [29], an effect that has been cited to have an influence on this property.


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

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

Experimental measured thermal conductivity. Alumina nanofluids in EG versus volume fraction concentration at different temperatures: 283.15 K (filled circle); 303.15 K (empty circle), and 323.15 K (downturned triangle).
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Figure 3: Experimental measured thermal conductivity. Alumina nanofluids in EG versus volume fraction concentration at different temperatures: 283.15 K (filled circle); 303.15 K (empty circle), and 323.15 K (downturned triangle).
Mentions: The thermal conductivity enhancement of five different ethylene glycol-based Al2O3 nanofluids corresponding to the denoted S1 samples has been measured at 283.15 K, 303.15 K, and 323.15 K. The volume fraction, ϕ, varied between 1.5% and 8.6% estimated from the densities of the pure liquid, determined in our laboratory with an Anton Paar DMA 4500 vibrating tube densimeter (Anton Paar, Graz, Österreich), and the bulk solid oxide [41]. The experimental thermal conductivities of alumina nanofluids, knf, at several temperatures are presented in Table 2 as a function of volume fraction. At the tested concentrations, thermal conductivity increases with nanoparticle volume fraction, ϕ, as shown in Figure 3. This behavior is in agreement with Timofeeva et al. [24,29] for different particle shapes, including spheres, and with those reported by Beck et al. [25] and Wang et al. [43] for nanofluids consisting of ethylene glycol with 20- and 28-nm alumina nanoparticles, respectively. Concerning temperature dependence, the thermal conductivity of all nanofluids also increases with temperature. As observed, the addition of nanopowder systematically increases the thermal conductivity of the nanofluid as compared with the pure fluid. If Table 2 is analyzed, we can conclude that this enhancement for a given nanofluid is nearly temperature-independent, as Peñas et al. [38] have also stated. Average enhancements values from 3% at the lowest volume fraction up to 19% for the highest concentration are found, showing good agreement (average 1% deviation) with the data from Timofeeva et al. [24] at 296.15 K for suspensions prepared from 40-nm alumina nanoparticles. However, the S1 sample data reported here and those from [24] with 11-, 20-, and 40-nm nominal sizes do not show the same trend as reported by Beck et al. [28] in their study on the effect of particle size on alumina nanofluids in ethylene glycol. This may be due to the different pH of the samples studied [29], an effect that has been cited to have an influence on this property.

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