Investigation and Visualization of Flow Fields in Stirred Tank Reactors Using a Fluorescence Tracer Method

Abstract

In this study, flow fields in stirred tank reactors are investigated by a fluorescence tracer method. For these measurements, a fluorescent dye is inserted into a stirred tank reactor and distributed by the impeller flow, following the characteristic main circulation pathways. By this means, the main flow fields can be detected and visualized. Originally developed and used for the investigation of viscoelastic fluids, the method was adapted for Newtonian fluids with low viscosity in this study, with impeller installation height and impeller Reynolds numbers selected as influencing parameters. The resulting flow fields in both single-and double-impeller setups match the known structures from literature excellently. Therefore, the developed fluorescence tracer method has proven to be a promising supplement to the established repertoire of fluid investigation methods, with little effort in both experiment itself as well as the following data analysis steps.

Flow Field Investigations of Two‐Stage Stirrer Configurations Combining Axially and Radially Conveying Turbines

“…1 were chosen for the Rushton, flat blade and pitched blade turbine. The diameters were selected close to the previously used standard diameter of D /3 9, 14, 35 to ensure comparability with investigations from this workgroup as well as literature.…”

“…The investigated height setups were selected based on previous projects 14, 19, with an even distribution of the impellers across the liquid filling height defined as the standard configuration 4, 13. An overview of the examined setups can be found in Tab.…”

“…In the other two systems (Fig. 9b and 9c), the merging flow regime forms, with the main discharge stream located midway between the two impellers 14, 35, 42.…”

“…Similar to the combination of two Rushton turbines 14, 35, 37, 38, the RT+PBT combination induces two separate circulations when installed with maximum height difference and a combined flow field in the two other setups. However, the resulting specific flow structures differ significantly from these presented in the previous sections, as they are distinctly influenced by both present impeller types and their characteristics.…”

“…For the first set of experiments, i.e., the torque measurements, the investigated impeller types include a propeller (PR) and a pitched blade turbine (PBT) as primarily axially conveying impellers and a Rushton turbine (RT) and a flat blade turbine (FBT) as primarily radially conveying impellers; the same impeller types have been used in a previous study [14]. The impellers were constructed according to established geometric recommendations given in DIN 28131 [15] as well as by Liepe et al [16], as far as reasonably possible.…”