The gas holdup and flow dynamics in a laboratory scale Rushton-turbine flotation tank were simulated using the dispersed k- turbulence model and Eulerian-Eulerian multiphase modelling approach. The inherent uncertainties in the CFD predictions were quantified by examining the model and numerical (i.e., discretization) uncertainties. The contribution of model uncertainty was explored by conside...

Abstract A computational fluid dynamics simulation is done for comparative study from the pumping effect on four surfaces of stirred tank. The flow field generated by one-stage and bi-stage six-bladed Rushton turbine in unbaffled square tank was studied. Reynolds-averaged Navier-Stokes equation with steady-state multi-reference frame approach (MRF) used to simulate hydrodynamic turbulent viscos...

In the present work, the effects of dual impeller configurations comprising of Rushton turbine (RT) and Concave-bladed disk turbine (CD-6) on the oxygen transfer profile and fermentation performance of kojic acid production by Aspergillus flavus Link 44-1 was investigated. Batch cultivations of A. flavus Link 44-1 were performed in 2 L stirred tank bioreactor. The fermentations were conducted u...

This paper presents the preliminary steps required for conducting experiments to obtain the optimal operating conditions of a hybrid impeller mixer and to determine the residence time distribution (RTD) using computational fluid dynamics (CFD). In this paper, impeller speed and clearance parameters are examined. The hybrid impeller mixer consists of a single Rushton turbine mounted above a sing...

Problem Statement: Mixing filamentous fungi entails delicate balance between promoting high volumetric oxygen transfer coefficient (kLa) while keeping low hydrodynamic stresses in the microenvironment of cultures. This study examined the oxygen transfer capability of a prototype low shear helical impeller as a potential replacement for the standard Rushton turbine. Approach: The dependence of k...

Chaotic features of the macro-instability (MI) of flow patterns in stirred tanks are studied in this paper. Datasets obtained by measuring the axial component of the fluid velocity and the tangential force affecting the baffles are used. Two geometrically identical, flat-bottomed cylindrical mixing tanks (diameter of 0.3m) stirred with either pitched blade turbine impellers or Rushton turbine i...

A quantitative description of flow and mixing in bioreactors is necessary to assess the exposure microorganisms suboptimal conditions, which may negatively impact key performance parameters a process, such as yield productivity. The traditional approach quantifying mixing, by means terminal time, inadequate because it rests on assumption that homogeneous state reached, provides little informati...