Thermal conductivity and particle agglomeration in alumina nanofluids: experiment and theory.

By E. Timofeeva, A. N. Gavrilov, J. M. McCloskey, Y. Tolmachev, S. Sprunt, L. Lopatina, Jonathan V Selinger. Physical review. E, Statistical, nonlinear, and soft matter physics, 2007

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In recent years many experimentalists have reported an anomalously enhanced thermal conductivity in liquid suspensions of nanoparticles. Despite the importance of this effect for heat transfer applications, no agreement has emerged about the mechanism of this phenomenon, or even about the experimentally observed magnitude of the enhancement. To address these issues, this paper presents a combined experimental and theoretical study of heat conduction and particle agglomeration in nanofluids. On the experimental side, nanofluids of alumina particles in water and ethylene glycol are characterized using thermal conductivity measurements, viscosity measurements, dynamic light scattering, and other techniques. The results show that the particles are agglomerated, with an agglomeration state that evolves in time. The data also show that the thermal conductivity enhancement is within the range predicted by effective medium theory. On the theoretical side, a model is developed for heat conduction through a fluid containing nanoparticles and agglomerates of various geometries. The calculations show that elongated and dendritic structures are more efficient in enhancing the thermal conductivity than compact spherical structures of the same volume fraction, and that surface (Kapitza) resistance is the major factor resulting in the lower than effective medium conductivities measured in our experiments. Together, these results imply that the geometry, agglomeration state, and surface resistance of nanoparticles are the main variables controlling thermal conductivity enhancement in nanofluids.

Subfields: Biomedical Engineering, Mechanical Engineering

View Paper: https://www.semanticscholar.org/paper/4de5c295ff6a95339666139aa8f2a7b95e99478f

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Citations in the corpus

Latest developments on the viscosity of nanofluids (2012, neutral): “having different contents including heat transfer enhancement [5–7], thermal conductivity measurement [8–10], thermal conductivity enhancement [11–21], effective thermal conductivity [22– 28], thermal conductivity of suspensions [29–31], thermal properties enhancement [32], thermal transport [33], t”
Stability and electrical conductivity of water-base Al2O3 nanofluids for different applications (2016, background): “Many researchers have reported the necessity of proper dispersion of nanofluids and various dispersion techniques [13].”
A comprehensive review of thermo-physical properties and convective heat transfer to nanofluids (2015, background): “[184] argued that thermal conductivity enhancement of nanofluids relative to base fluids at elevated temperatures is independent of temperature by investigating both water- and EG-based nanofluids.”
Thermal conductivity and viscosity of stabilized ethylene glycol and water mixture Al2O3 nanofluids for heat transfer applications: An experimental study☆ (2014, background): “[17] have studied both thermal conductivity and viscosity of Al2O3/water and Al2O3/ethylene glycol nanofluids with influence of particle diameters (11 nm, 20 nm and 40 nm).”
Thermal conductivity and viscosity of Al2O3 nanofluid based on car engine coolant (2010, background): “Similar observations have been reported by Timofeeva et al [3] for water and glycol based Al2O3 nanofluids.”
Thermal conductivity and specific heat capacity measurements of Al2O3 nanofluids (2012, background): “[43] (open triangles, 40 nm, 5 %), Patel et al.”