SIMPLE-MODELS AND MEASUREMENTS OF MAGNETICALLY INDUCED HEATING EFFECTS IN FERROMAGNETIC FLUIDS

This paper discusses several approximate analytic techniques for calcu lating power dissipation and forces in ferromagnetic fluids subjected to a spatially uniform but time varying magnetic field. This power dis sipation results in a rising temperature in a ferrofluid sample. Sever al possible heating mechanisms in magnetic fluids have been investigat ed, including electromagnetic and hydrodynamic processes, and a simple method for prediction of power dissipation in a sample has been devel oped. Experimental results are given for an induction heating problem where it is shown that the power dissipation in a sample of ferrofluid cannot be explained by induction heating of the individual suspended particles. A simple viscous drag model is introduced which shows bette r agreement with measured power dissipation in the sample than an eddy current model for excitation frequencies under 1 MHz.