Contribution à l'étude des systèmes de refroidissement basés sur le couplage magnétothermique dans les ferrofluides à faible température de Curie : mise en place d'outils de caractérisation et de modélisation

The Electrical Engineering in general and power electronics, in particular, plays an increasingly important role in embedded systems. The reliability of electronic systems strongly depends on the management of their temperature. Cooling systems today are heavy, bulky, and consumers of energy, which is in disagreement with embedded systems. It is therefore necessary to look for new systems, more reliable, lighter and use less energy. The subject of this thesis focuses on the use of ferrofluids, magnetic colloidal suspensions at low Curie temperature, the magnetic properties vary strongly with temperature between ambient and one hundred degrees Celsius, for use as coolant in cooling systems. The magnetic properties strongly dependent on the temperature of such fluid allow the actuation of the latter by the action of a magnetic field coupled at a temperature gradient so that all solid parts are stationary. The cooling system is no longer subject to the wear of the pump for the circulation of the coolant. The system is thus globaly more reliable and less energy consuming. The energy for moving the ferrofluid being extracted directly losses components. The behavior of ferrofluids is too little known today to design and optimize a pump magneto static. A major effort of modeling and characterization should be conducted. This manuscript presents a practical study verifying the principle of hydrostatic pressure created by magnetothermal coupling. A modeling of the distribution of local forces by moving the ferrofluid and the development tool for the characterization of the ferrofluids are also presented. Characterization efforts focused on rheology, under the magnetic field, shear and temperature, as well as on the magnetic behavior of the ferrofluid at different temperatures.