Investigation of thermal conductivity, viscosity, and electrical conductivity of graphene based nanofluids

Kole, Madhusree; Dey, T.K.

doi:10.1063/1.4793581

Cited by 228 publications

(111 citation statements)

References 35 publications

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“…[26][27][28][29][30][31] Past work has shown that the steady shear viscosity ( , ) of nanofluids typically decreases with increasing temperature at a fixed shear rate. [32][33][34][35][36][37] Although the viscosity of suspensions has been extensively studied in the literature, 21,[37][38][39][40][41][42] there have been few studies that focus on thermal effects on the macroscopic suspension viscosity when the volume loadings pass from the dilute regime into the percolated regime. In this work, we measure the thermal conductivity and viscosity of graphite suspensions as a function of temperature and volume fraction, focusing on the percolation behavior.…”

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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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confidence: 99%

Viscosity and Thermal Conductivity of Stable Graphite Suspensions Near Percolation

Wang

Marconnet

et al. 2014

Nano Lett.

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“…As indicated by many experiments, the effective electrical conductivity of nanofluids may increase by orders of magnitude by adding a little amount of nanoparticles [61,62]. Previous studies have suggested various models [63][64][65][66] for the effective electrical conductivity of nanofluid, but none of them always provides good predictions.…”

Section: Lorentz Forcementioning

confidence: 99%

“…Previous studies have suggested various models [63][64][65][66] for the effective electrical conductivity of nanofluid, but none of them always provides good predictions. Therefore, in this paper, based on the literature review [59][60][61][62][67][68][69], we consider σ n f = 4.0 S/m (a constant).…”

Section: Lorentz Forcementioning

confidence: 99%

Effects of Anisotropic Thermal Conductivity and Lorentz Force on the Flow and Heat Transfer of a Ferro-Nanofluid in a Magnetic Field

Yan

Massoudi

et al. 2017

Energies

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Abstract:In this paper, we study the effects of the Lorentz force and the induced anisotropic thermal conductivity due to a magnetic field on the flow and the heat transfer of a ferro-nanofluid. The ferro-nanofluid is modeled as a single-phase fluid, where the viscosity depends on the concentration of nanoparticles; the thermal conductivity shows anisotropy due to the presence of the nanoparticles and the external magnetic field. The anisotropic thermal conductivity tensor, which depends on the angle of the applied magnetic field, is suggested considering the principle of material frame indifference according to Continuum Mechanics. We study two benchmark problems: the heat conduction between two concentric cylinders as well as the unsteady flow and heat transfer in a rectangular channel with three heated inner cylinders. The governing equations are made dimensionless, and the flow and the heat transfer characteristics of the ferro-nanofluid with different angles of the magnetic field, Hartmann number, Reynolds number and nanoparticles concentration are investigated systematically. The results indicate that the temperature field is strongly influenced by the anisotropic behavior of the nanofluids. In addition, the magnetic field may enhance or deteriorate the heat transfer performance (i.e., the time-spatially averaged Nusselt number) in the rectangular channel depending on the situations.

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“…The electrical conductivity requirement, which is as low as 1.5 to 2 S/cm [39] and 5 S/cm at 20 C [37], needs to be maintained over time. A few researchers have investigated the effect of electrical conductivity on various types of nanofluids [40][41][42][43][44][45][46][47][48][49][50][51]. Wong and Kurma [40] studied the effect of volume concentration on the electrical conductivity of Al 2 O 3 nanofluid.…”

Section: Challenges Of Nanofluids In Pemfc Electrical Conductivitymentioning

confidence: 99%

A Review of Nanofluid Adoption in Polymer Electrolyte Membrane (Pem) Fuel Cells as an Alternative Coolant

et al. 2015

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Continuous need for the optimum conversion efficiency of polymer electrolyte membrane fuel cell (PEMFC) operation has triggered varieties of advancements, namely in the thermal management engineering scope. Excellent heat dissipation is correlated with higher performance of a fuel cell, thus increasing its conversion efficiency. This study reveals the potential advancement in thermal engineering of a fuel cell cooling system with respect to nanofluid technology. Nanofluids are seen as a potential evolution of nanotechnology hybridization with the fuel cell serving as a cooling medium. The available literature on the thermophysical properties of potential nanofluids, especially on the electrical conductivity property, has been discussed. The lack of electrical conductivity data for various nanofluids in open literature was another challenge in the application of nanofluids in fuel cells. Unlike in any other thermal management system, a nanofluid in a fuel cell is dealt with using a thermoelectrically active environment. The main challenge in nanofluid adoption in fuel cells was the formulation of a suitable nanofluid coolant with heat transfer enhancement, as compared to its base fluid, but still complying with the strict limits of electrical conductivity as low as 2 S/cm and several other restrictions discussed by the researchers. It is concluded that a nanofluid in PEMFC is advantageous in terms of both heat transfer and simplification of the cooling system through radiator size reduction and potential elimination of the deionizer as compared to the current PEMFC cooling system. However, there are challenges that need to be well addressed, especially in the electrical conductivity requirement.

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Investigation of thermal conductivity, viscosity, and electrical conductivity of graphene based nanofluids

Cited by 228 publications

References 35 publications

Viscosity and Thermal Conductivity of Stable Graphite Suspensions Near Percolation

Viscosity and Thermal Conductivity of Stable Graphite Suspensions Near Percolation

Effects of Anisotropic Thermal Conductivity and Lorentz Force on the Flow and Heat Transfer of a Ferro-Nanofluid in a Magnetic Field

A Review of Nanofluid Adoption in Polymer Electrolyte Membrane (Pem) Fuel Cells as an Alternative Coolant

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