Effect of chain-like magnetite nanoparticle aggregates on thermal conductivity of magnetic nanofluid in magnetic field

This paper investigated the effect of chain-like magnetic nanoparticles aggregates on the thermal conductivity of magnetic nanofluids (MNFs) in magnetic field via a proposed model of thermal conductivity of MNFs. The anisotropic feature of thermal conductivity ratio was predicted based on the field induced chain-like magnetic nanoparticles aggregates in MNFs. It was indicated that for a magnetic field parallel to temperature gradient, the thermal conductivity component along the magnetic field was significantly enhanced due to the magnetic field induced chain-like magnetic nanoparticles aggregates. The experimental data of thermal conductivity enhancement along the magnetic field direction were similar to those predicted by the proposed model.

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► Simulated thermal conductivity enhancement ratio of magnetic nanofluids increased with increasing magnetic field for an engine oil based magnetite nanofluid.
► The observed thermal conductivity enhancement was related to the particle volume fraction.
► Simulated results were similar to measured data for the magnetic nanofluid in magnetic field.
► The thermal conductivity enhancement was due to the chainlike aggregates formation in magnetic nanofluids.