Thermal conduction of the magnetic fluids mixing micrometer size particles

Abstract

In this study, thermophysical properties of magnetic fluids mixing micrometer size spherical copper particles were investigated experimentally. To examine the behavior of dispersed micrometer size copper particles in the magnetized magnetic fluid, visualization experiments were performed by using a dark field microscope. From the visualization experiments, cluster formations of the copper particles in the magnetic field direction in the magnetic fluid under applied uniform magnetic field were observed. The thermal conductivity of the test fluid was measured by using the transient hot wire method. Thermal conductivity of the magnetic fluid with randomly dispersing copper particles is larger than the thermal conductivity of the base magnetic fluid. In case of the magnetic fluid mixed 12 vol% of spherical copper particles, it was estimated that the thermal conductivity in the field direction increases by 1.7 times or more of the thermal conductivity of the fluid in the absence of magnetic field. The Landau-Lifshitz equation for estimating the relationship between the thermal conductivity and the internal structure was expanded to consider spherical shape of the dispersed particles in the fluid and the particle distribution state was estimated by using the expanded Landau-Lifshitz equation.