Investigation of thermal transport in colloidal silica dispersions (nanofluids) |
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Authors: | David C Venerus Yiran Jiang |
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Institution: | (1) Department of Chemical Engineering and Biological Engineering, Illinois Institute of Technology, Chicago, IL 60616, USA |
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Abstract: | Thermal conductivity enhancement in colloidal silica dispersions (nanofluids) is investigated experimentally using a novel
optical technique. The effects of nanoparticle size, concentration, and state of aggregation are examined. New data on well
dispersed systems are compared to published data obtained using the more conventional transient hot-wire technique and good
agreement was found. Experimental results are also compared with model predictions for relative thermal conductivity based
on effective medium theory. For systems composed of larger diameter nanoparticles (~30 nm), good agreement was found between
the measured thermal conductivity enhancement and that predicted by the classical Maxwell-Garnett model. For systems composed
of smaller nanoparticles (∼10 and 20 nm), thermal conductivity enhancement was reduced by as much as 10%, presumably because
interfacial thermal resistance effects become important. Measurements on two systems that were induced to form gels exhibited
an increase in thermal conductivity of approximately 5% relative to the well-dispersed systems. The observed increase in thermal
conductivity is larger than that predicted by a recently proposed model for aggregated nanofluids. |
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