Modeling of Ferrofluid Passive Cooling System

M. Yang[1,2], R. O'Handley[2], and Z. Fang[2,3]
[1]Massachusetts Institute of Technology, Cambridge, MA, USA
[2]Ferro Solutions, Woburn, MA, USA
[3]Pennsylvania State University, University Park, PA, USA

A ferrofluid contains nanoscale ferromagnetic particles suspended in a carrier liquid. It is used in some high-power acoustic speakers to cool the drive coil. The ferromagnetic particles far from the heat source are attracted by the drive coil’s magnetic field. As the fluid approaches the heat source, its temperature rises, causing the nanoparticles to become paramagnetic. Cooler magnetic fluid near the heat sink displaces the hot paramagnetic fluid near the heat source, setting up a simple convective cooling system that fits within the confines of the device. Modeling such systems is challenging because it involves fluid dynamics, thermal boundary conditions, and temperature-dependent magnetic properties. COMSOL Multiphysics is an ideal tool that provides rich insight into the system’s behavior. The approach was to develop a model that supports results from experiments conducted on a cylindrical container of ferrofluid with a heat source and sink. The experiments involved changing the volume of ferrofluid and moving the magnet to different positions outside the ferrofluid container.