Effect of the attack angle on the roll and trailing vortex structures in an agitated vessel with a paddle impeller

Numerical investigation of the turbulent flow generated with a radial Turbine using a converging hollow blade

The aim of this study is to investigate the effect of the blade shape on the characteristic of the flow patterns in a stirred tank. A new impeller blade design has been proposed. It is characterized by a converging hollow. The investigations of the flow structure generated in the vessel are made by using the computer code ANSYS CFX (version 16.0). The analysis has shown that the converging hollow blade yields highly radial flows which gave an increase in the radial velocity by 35% with less power consumption than the flat blade. Also, the effectiveness of the energy dissipation and the quality of mixing has been obviously noted. A validation test of our predicted results with other literature data was done, and a satisfactory agreement has been found.

Power consumption for an agitated vessel equipped with pitched blade turbine and short baffles

Power characteristics for an agitated vessel equipped with planar short baffles of length L and pitched blade turbine of pitch β are presented in the paper. The studies were carried out in the vessel of inner diameter D = 0.6 m, where the baffles were located in the distance p from the vessel bottom (p + L = H). Torque was measured using strain gauge method within the turbulent regime of the flow of Newtonian liquid in the agitated vessel. The effects of the pitch β and geometrical parameter p/H on the power number Ne were determined mathematically. The results showed that, for the assumed value of the angle β, the function Ne = f (L/H) decreases with the decrease in the baffle length L (i.e. with the increase in the parameter p). Moreover, for the assumed value of the baffle length L, the function Ne = f (β) increases with the increase in the angle β of the inclination of the impeller blade.

Mixing of Shear Thinning Fluids in Cylindrical Tanks: Effect of the Impeller Blade Design and Operating Conditions

The 3D flow fields and power consumption within a cylindrical vessel stirred by a rotating turbine are numerically studied. Simulations are performed to determine the impact of changes in operating parameters on the mixing characteristics. Investigations are focused on effects of the impeller blade curvature, shaft speed and impeller rotational direction. The fluid simulated has a shear thinning behavior. Designing the blade in retreat shape seems very promising in term of power consumption since a reduction of Np is obtained with increasing blade curvature. In the positive rotational direction, the retreat bladed impeller yields highly radial flows with less power consumption than the straight bladed impeller. The 45° retreat blade gave an increase in the radial velocity by 39 %, compared with the straight blade. But, a better axial circulation is obtained with the straight blade. The comparison between the positive rotational direction (+w) and the negative rotational direction (–w) cases revealed that, a reduced mixing time can be obtained with a retreat bladed impeller operating in the negative rotational direction (–w), but with further power consumption.

Microtiter plates versus stirred mini-bioreactors in biocatalysis: a scalable approach

To place the application of miniaturized vessels as microbioreactors on a firm footing, focus has been given to engineering characterization. Studies on this matter have mostly involved carrier-free biological systems, while support-based systems have been overlooked. The present work aims to contribute to fill in such gap. Thus, it intended to establish a robust scaled down approach to identify and optimize relevant operational conditions of naringin hydrolysis by naringinase in PVA lens-shaped particles. The influence of geometric and dynamic (viz. Reynolds number) parameters was evaluated. Naringin hydrolysis in round, flat bottom MTP proved more effective than in square, pyramidal bottom. The bioconversion at MTP and stirred tank reactors scales showed that, given the 12.5-fold scale difference was in agreement between the bioconversion rates. The external mass transfer resistances were negligible as deduced from Damkohler modulus ≤1. The bioconversion was effectively scaled-up 200-fold from shaken microtiter plates to stirred tank reactors.