Effects of nanoparticle clustering and alignment on thermal conductivities of Fe3O4 aqueous nanofluids

Zhu, Haitao; Zhang, Canying; Liu, Shiquan; Ya-ming, Tang; Yin, Yansheng

doi:10.1063/1.2221905

Cited by 316 publications

(135 citation statements)

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“…13 It was also shown that at the same volume fractions, Fe 3 O 4 nanofluids have higher thermal conductivity than other metal oxide nanofluids such as CuO, TiO 2 , and Al 2 O 3 as a result of nanoparticle alignment. 26 Although the thermal conductivity of aqueous nanofluids increases, while that of non-aqueous nanofluids decreases with temperature, the ratio of the nanofluid thermal conductivity to base fluid thermal conductivity remains constant, 25,27 implying that the temperature dependency of thermal conductivity does not change upon addition of nanoparticles. This enhancement in thermal conductivity was found to be higher 19,26 than predictions by the effective medium theory (EMT) proposed by Maxwell 28 and other theoretical models.…”

Section: Introductionmentioning

confidence: 99%

“…26 Although the thermal conductivity of aqueous nanofluids increases, while that of non-aqueous nanofluids decreases with temperature, the ratio of the nanofluid thermal conductivity to base fluid thermal conductivity remains constant, 25,27 implying that the temperature dependency of thermal conductivity does not change upon addition of nanoparticles. This enhancement in thermal conductivity was found to be higher 19,26 than predictions by the effective medium theory (EMT) proposed by Maxwell 28 and other theoretical models. 29 On the other hand, Timofeeva et al 10,30 Based on specific experimental data, some empirical models were also presented.…”

Section: Introductionmentioning

confidence: 99%

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Deterioration in effective thermal conductivity of aqueous magnetic nanofluids

Altan

Gurten²,

Sommerdijk

et al. 2014

Journal of Applied Physics

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Common heat transfer fluids have low thermal conductivities, which decrease their efficiency in many applications. On the other hand, solids have much higher thermal conductivity values. Previously, it was shown that the addition of different nanoparticles to various base fluids increases the thermal conductivity of the carrier fluid remarkably. However, there are limited studies that focus on the thermal conductivity of magnetic fluids. In this study, thermal conductivity of magnetic nanofluids composed of magnetite nanoparticles synthesized via co-precipitation and thermal decomposition methods is investigated. Results showed that the addition of magnetite nanoparticles decreased the thermal conductivity of water and ethylene glycol. This decrease was found to increase with increasing particle concentration and to be independent of the synthesis method, the type of surfactant, and the interfacial thermal resistance. V C 2014 AIP Publishing LLC.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Deterioration in effective thermal conductivity of aqueous magnetic nanofluids

Altan

Gurten²,

Sommerdijk

et al. 2014

Journal of Applied Physics

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“…Among these additives, oxide nanoparticles [5][6][7][8] consitute one of the important classes. In order to investigate the thermal transport properties of nanofluids containing oxide nanoparticles, five kinds of nanofluids were prepared and the measurement techniques and conditions were the same in order to ensure consistency of the experimental data.…”

Section: Introductionmentioning

confidence: 99%

MgO nanofluids: higher thermal conductivity and lower viscosity among ethylene glycol-based nanofluids containing oxide nanoparticles

Xie

Chen

2010

Journal of Experimental Nanoscience

153

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Five kinds of oxides, including MgO, TiO 2 , ZnO, Al 2 O 3 and SiO 2 nanoparticles were selected as additives and ethylene glycol (EG) was used as base fluid to prepare stable nanofluids. Thermal transport property investigation demonstrated substantial increments in the thermal conductivity and viscosity of all these nanofluids with oxide nanoparticle addition in EG. Among all the studied nanofluids, MgO-EG nanofluid was found to have superior features, with the highest thermal conductivity and lowest viscosity. The thermal conductivity enhancement ratio of MgO-EG nanofluid increases nonlinearly with the volume fraction of nanoparticles. In the experimental temperature range of 10-60 C, thermal conductivity enhancement ratio of MgO-EG nanofluids appears to have a weak dependence on the temperature. Viscosity measurements showed that MgO-EG nanofluids demonstrated Newtonian rheological behaviour, and the viscosity significantly decreases with the temperature. The thermal conductivity and viscosity increments of the nanofluids are much higher than the corresponding values predicted by the existing classical models for the solid-liquid mixture.

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“…[2][3][4][5][6][7][8] Heat conduction in nanofluids has been extensively studied, [9][10][11][12][13][14][15][16] and the variation in results has led to much debate as to the mechanisms of thermal conduction in nanofluids. By freezing nanofluids consisting of alumina nanoparticles in different base fluids, Gao et al 16 demonstrated that clustering is a key factor for enhancing the thermal conductivity.…”

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confidence: 99%

Viscosity and Thermal Conductivity of Stable Graphite Suspensions Near Percolation

Wang

Marconnet

et al. 2014

Nano Lett.

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Abstract:Nanofluids have received much attention due, in part, to the range of properties possible with different combinations of nanoparticles and base fluids. In this work, we measure the viscosity of suspensions of graphite particles in ethylene glycol as a function of the volume fraction, shear rate, and temperature below and above the percolation threshold. We also measure and contrast the trends observed in the viscosity with increasing volume fraction to the thermal conductivity behavior of the same suspensions: above the percolation threshold, the slope that describes the rate of thermal conductivity enhancement with concentration reduces compared to below the percolation threshold, whereas that of the viscosity enhancement * These authors contributed equally to this work. † Corresponding author: gchen2@mit.edu 2 increases. While the thermal conductivity enhancement is independent of temperature, the viscosity changes show a strong dependence on temperature and exhibit different trends with respect to the temperature at different shear rates above the percolation threshold. Interpretation of the experimental observations is provided within the framework of Stokesian dynamics simulations of the suspension microstructure, and suggest that although diffusive contributions are not important for the observed thermal conductivity enhancement, they are important for understanding the variations in the viscosity with changes of temperature and shear rate above the percolation threshold. The experimental results can be collapsed to a single master curve through calculation of a single dimensionless parameter (a Péclet number based on the rotary diffusivity of the graphite particles). The viscosity of the graphite dispersion at room temperature is measured using a controlled stress rheometer (TA Instruments AR-G2) with a coneand-plate geometry. The viscosity results show good repeatability; during repeated measurements with the same suspension the viscosity curves coincide with each other with standard deviation less than 2%. Two key trends of viscosity with shear rate are evident in Fig. 2. First, the viscosity of the graphite suspension increases as the volume fraction increases. Second, the graphite suspension exhibits non-Newtonian behavior. Specifically, the 6 viscosity decreases with increasing shear rate (i.e. the dispersion is shear thinning), and the level of shear thinning increases for higher volume fractions. This is likely due to the graphite clusters and flakes preferentially realigning themselves along the flow direction under the application of an imposed shear stress. This structural reorganization reduces particle-particle interactions and, thus, reduces the viscosity.In a previous paper, 17 some of the present authors observed that the thermal conductivity of graphite suspensions increases more rapidly with concentration below the percolation threshold than above percolation. To further study this effect, we measured the thermal conductivity of the samples (following a similar preparation proto...

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Effects of nanoparticle clustering and alignment on thermal conductivities of Fe3O4 aqueous nanofluids

Cited by 316 publications

References 16 publications

Deterioration in effective thermal conductivity of aqueous magnetic nanofluids

Deterioration in effective thermal conductivity of aqueous magnetic nanofluids

MgO nanofluids: higher thermal conductivity and lower viscosity among ethylene glycol-based nanofluids containing oxide nanoparticles

Viscosity and Thermal Conductivity of Stable Graphite Suspensions Near Percolation

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