Thermal conductivity and particle agglomeration in alumina nanofluids: Experiment and theory
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- 28 December 2007
- journal article
- research article
- Published by American Physical Society (APS) in Physical Review E
- Vol. 76 (6), 061203
- https://doi.org/10.1103/physreve.76.061203
Abstract
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.Keywords
This publication has 51 references indexed in Scilit:
- Critical review of heat transfer characteristics of nanofluidsRenewable and Sustainable Energy Reviews, 2007
- Heat transfer characteristics of nanofluids: a reviewInternational Journal of Thermal Sciences, 2007
- Heat Transfer in Nanofluids—A ReviewHeat Transfer Engineering, 2006
- Thermal Conductivity of Nanofluids – Experimental and TheoreticalInternational Journal of Thermophysics, 2006
- Nanofluids for thermal transportMaterials Today, 2005
- THERMAL TRANSPORT IN NANOFLUIDSAnnual Review of Materials Research, 2004
- Mechanisms of heat flow in suspensions of nano-sized particles (nanofluids)International Journal of Heat and Mass Transfer, 2001
- Anomalously increased effective thermal conductivities of ethylene glycol-based nanofluids containing copper nanoparticlesApplied Physics Letters, 2001
- Alteration of Thermal Conductivity and Viscosity of Liquid by Dispersing Ultra-Fine Particles. Dispersion of Al2O3, SiO2 and TiO2 Ultra-Fine Particles.Netsu Bussei, 1993
- Thermal Conductivity of Heterogeneous Two-Component SystemsIndustrial & Engineering Chemistry Fundamentals, 1962