3-D HYDRODYNAMICS IN A TANK STIRRED BY A DOUBLE-PROPELLER SYSTEM AND FILLED WITH A LIQUID HAVING EVOLVING RHEOLOGICAL PROPERTIES

Some chemical reactions in the liquid phase can generate drastic chang es of the rheological behavior of the liquid. This often happens in ag itated tanks entirely baffled equipped with impellers which generate c irculations which depend on the hydrodynamic regime - laminar or turbu lent. Results issued from Computational Fluid Dynamics (CFD) are prese nted here concerning fields of velocity components and local energy di ssipation, corresponding to a liquid initially with a low viscosity be coming highly viscous Newtonian and then pseudo-plastic. It clearly ap pears that the flow patterns generated by the two propellers settled i n the vessel are quite different, especially with large recirculations and dead zones in the laminar flow range. Depending on the rheologica l properties of the fluid, energy dissipation occurs in the vicinity o f the propellers and/or near the walls.