Research Paper

Journal of Nanoparticle Research

, Volume 11, Issue 5, pp 1129-1136

The effect of particle size on the thermal conductivity of alumina nanofluids

  • Michael P. BeckAffiliated withSchool of Chemical & Biomolecular Engineering, Georgia Institute of Technology
  • , Yanhui YuanAffiliated withSchool of Chemical & Biomolecular Engineering, Georgia Institute of Technology
  • , Pramod WarrierAffiliated withSchool of Chemical & Biomolecular Engineering, Georgia Institute of Technology
  • , Amyn S. TejaAffiliated withSchool of Chemical & Biomolecular Engineering, Georgia Institute of Technology Email author 

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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.

Keywords

Nanofluids Thermal conductivity Transient hot wire method Phonon scattering Nanoparticles Colloids