Magnetic field induced augmented thermal conduction phenomenon in magneto nanocolloids

TL;DR

This study investigates how magnetic fields significantly enhance the thermal conductivity of magneto nanocolloids containing magnetic nanoparticles, with experimental and analytical insights into the underlying mechanisms.

Contribution

It introduces an analytical model that predicts thermal conductivity enhancement in magneto nanocolloids based on physical parameters and magnetic field conditions.

Findings

Maximum 114% thermal conductivity enhancement at 0.1 T for Fe3O4/EG.

Kerosene-based MNCs show higher sensitivity to magnetic fields.

Co3O4 nanoparticles have negligible effect due to minimal magnetic moment.

Abstract

Magnetic field induced drastically augmented thermal conductivity of magneto nanocolloids involving magnetic oxide nanoparticles, viz. Fe2O3, Fe3O4, Nickel oxide (NiO), Cobalt oxide (Co3O4), dispersed in different base fluids (heat transfer oil, kerosene, and ethylene glycol) have been reported. Experiments reveal the augmented thermal transport under the external applied magnetic field, with kerosene based MNCs showing at relatively low magnetic field intensities as compared to the heat transfer oil and EG based MNCs. A maximum thermal conductivity enhancement of 114 % is attained at 7.0 vol. % concentration and 0.1 T field intensity for Fe3O4/EG magneto nanocolloid. However, a maximum of 82% thermal conductivity enhancement is observed for Fe3O4/Kerosene magneto nanocolloid for the same concentration but relatively at low magnetic field (600 G). Thereby, a strong effect of fluid as well as particle physical properties on the chain formation propensity, leading to enhanced conduction, in such systems is observed. Co3O4 nanoparticles show insignificant effect on the thermal conductivity enhancement of MNCs due to their minimal magnetic moment. An analytical approach has been proposed to understand the mechanism and physics behind the thermal conductivity enhancement under external applied magnetic field, in tune with near field magnetostatic interactions as well as Neel relaxivity of the magnetic nanoparticles. Furthermore, the analytical model is able to predict the phenomenon of enhanced thermal conductivity as a function of physical parameters such as chain length, size and types of nanoparticles, fluid characteristics, magnetic field intensity, saturation magnetic moment, nanoparticle concentration etc. and good agreement with the experimental results has been observed.