Study of laminar mixing in kenics static mixer by using Positron Emission Particle Tracking (PEPT)

Abstract

Positron Emission Particle Tracking is a unique Lagrangian flow visualization technique, which allows measuring experimentally the flow patterns by recording the movements of a radioactive particle. We used PEPT to characterize the mixing performance of a high viscosity Newtonian fluid in a Kenics static mixer (KM), in order to develop methods for quantifying flow and mixing in laminar system. A single radioactive tracer is pass through the mixer several times in order to record several trajectories. By using the data from PEPT, particle trajectories of the various passes have been plotted and superimposed, to obtain an understanding of flow behavior and residence time distribution. We were being able to observe the local RTD along the mixer, and the effect of different entrance position of the tracer on the residence time distribution. The particle tends to move at constant axial velocity through the elements but can undergo a significant step change in velocity in the transition between elements. For the first time the degree of segregation inside the KM has been experimentally quantified using PEPT data. The introduction of a new method to study the segregation along the mixer has opened the way to comparison of these finding to previous numerical works that have been done on KM, to see whether using PEPT gives us more information about the mixing performance in comparison with other experimental techniques