Flow studies in stirred tanks by positron emission particle tracking (PEPT)

PEPT is a technique for tracking a small radioactive tracer in Lagrangian coordinates. The technique was used to study the flow patterns of non-Newtonian CMC solutions inside a vessel agitated by an axial now impeller. The agitator behaved predominantly as a radial flow impeller as the fluid viscosity was increased. This remarkable feature seems to be specific to highly viscous fluids. To characterise mixing effectiveness within the vessel, a statistical analysis was performed on trajectories of the Lagrangian tracer tracked over a period of about an hour. The ratio of the average particle flow velocity and the impeller tip velocity was proposed as an index of agitation.