The effect of particle size on the thermal conductivity of alumina nanofluids |
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Authors: | Michael P Beck Yanhui Yuan Pramod Warrier Amyn S Teja |
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Institution: | (1) School of Chemical & Biomolecular Engineering, Georgia Institute of Technology, Atlanta, GA 30332-0100, USA |
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Abstract: | We present new data for the thermal conductivity enhancement in seven nanofluids containing 8–282 nm diameter alumina nanoparticles
in water or ethylene glycol. Our results show that the thermal conductivity enhancement in these nanofluids decreases as the
particle size decreases below about 50 nm. This finding is consistent with a decrease in the thermal conductivity of alumina
nanoparticles with decreasing particle size, which can be attributed to phonon scattering at the solid–liquid interface. The
limiting value of the enhancement for nanofluids containing large particles is greater than that predicted by the Maxwell
equation, but is predicted well by the volume fraction weighted geometric mean of the bulk thermal conductivities of the solid
and liquid. This observation was used to develop a simple relationship for the thermal conductivity of alumina nanofluids
in both water and ethylene glycol. |
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Keywords: | Nanofluids Thermal conductivity Transient hot wire method Phonon scattering Nanoparticles Colloids |
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