On the influence of a DC magnetic field upon a bubble
Résumé
Molten Salt Fast Reactor (MSFR) is a new fast nuclear reactor, which is at present under memoranda and understanding (MOU) from Generation IV International Forum (GIF). In the MSFR concept, fissile material dissolved in molten fluoride salts serves as a liquid fuel in a primary loop. One of the issues that need to be addressed is the development of an extraction technique of fission products from the fuel [1]. The technique addressed here is based on the injection of helium bubbles in the molten salt in order to absorb fission products by liquid/gas mass transfer. Solid particles are expected to adsorb at bubble surfaces as well. Taking into account that molten salts, as a continuous phase, are electrically conductive, an externally applied magnetic field offers opportunities for a contactless flow control. In addition, the jump in electrical conductivities between molten salts and contaminated bubbles is expected to enhance electromagnetic separation of gaseous phase after ad/absorption processes. To address this online extraction, it is important to simulate the dynamics of bubbles flowing in a molten salt, taking into account magnetohydrodynamics of the liquid phase. Numerical simulations of the process are performed with a CFD code based on finite volume method (ANSYS FLUENT). Bubble surfaces are captured by Volume of Fluid (VOF) strategy while the electric current densities are calculated in the carrier phase by making use of the Magnetic Induction Method. In this way, we are able to describe bubble deformation due to the hydrodynamic forces and the Lorentz force, which makes the fluid to circulate mainly in planes perpendicular to the magnetic field. We investigate the transient regime required to get the terminal bubble velocity. The way the magnetic field is able to change the streamlines around a bubble is particularly investigated while varying the Hartmann number.
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