ETD

• circulation time
• fluid viscosity
• impeller speed
• Lagrangian sensor particles (LSPs)
• mass concentration (wt. %)
• mixing
• stirred tank reactor
• viscous non-Newtonian fluids

This thesis investigates the hydrodynamic behavior and circulation dynamics of a non-Newtonian fluid with the Lagrangian sensor particles (LSPs) in a mechanically agitated reactor under different operating conditions. The study focuses on the influence of impeller speed and weight concentration (wt. %) on particle transport, mixing efficiency, and flow uniformity along the reactor height. Experimental measurements of circulation times were analyzed at multiple axial positions to characterize spatial variations in the flow structure.
The results show a strong dependence of the circulation dynamics on the impeller speed, with higher agitation leading to shorter circulation times, increased mixing intensity, and enhanced particle mobility, particularly in the central region of the reactor. Conversely, lower stirring speeds are associated with slower circulation and more heterogeneous flow behavior. The effect of increasing mass concentration was also found to be significant: higher mass concentration values and the resulting increase in fluid viscosity, directly impact the presence and motion of LSPs, in some cases limiting their ability to reach specific regions of the reactor. The dispersion of circulation time distributions was quantified using the coefficient of variation (CV), revealing pronounced spatial variability and intermittent dynamics under certain operating conditions.
Overall, the study highlights the combined role of impeller speed and viscous fluid rheology in governing particle circulation and mixing performance, providing valuable insights for the design and optimization of stirred tank reactors handling non-Newtonian fluids.