Effect of magnetic fields on thermal conductivity in a ferromagnetic packed bed

Parameters like solid particle conductivity, shape, size, contraction/expansion and porosity along with saturating fluid conductivity and pressure are important parameters when studying effective thermal conductivity of a porous bed. This paper introduces a novel heat transfer enhancement method for ferromagnetic material particle beds by exposing them to an external magnetic field. Two materials were experimentally studied: magnetite (Fe3O4) and iron filings (random composition of iron oxides). A series of twelve trials were performed using different magnetic field configurations and intensities. The magnetic fields which were used include non-uniform, semi-homogeneous and non-homogeneous fields which formed by four different magnet configurations with magnetic intensities from 819 Gauss to 4667 Gauss. In all the cases it is shown that applying magnetic fields increases the heat transfer rate in particle beds. The improvement rate is 7-15% for most cases studied. However, the configuration and intensity of the field determined the extent of improvement while non-homogeneous fields produced the greater effect. (C) 2017 Elsevier Inc. All rights reserved.