Effect of external magnetic field on thermal conductivity and viscosity of magnetic nanofluids: a review

Magnetic nanofluids are colloidal mixtures of ferromagnetic nanoparticles dispersed in a base fluid. They can be actuated and manipulated under the influence of the external magnetic field. This makes them especially attractive to be employed in microfluidics and nanofluidics. In the presence of the external magnetic field, thermal conductivity and viscosity of the magnetic nanofluids can be tuned, hence magnetic field dependent thermal conductivity and viscosity measurements have become a hot topic for the researchers. In this paper, studies in the available literature on the thermal conductivity and the viscosity of the magnetic nanofluids in the presence of the magnetic field have been collected, compared and discussed. The observations reveal that there is a contradiction between the results which were presented in the literature. The differences between the available experimental results which may be caused by the application of the external magnetic field have been discussed by categorizing and comparing the studies which investigated the influence of the similar parameters by using most similar samples. Additionally, magnetic field dependent thermal conductivity and viscosity models available in the literature have been reviewed.