Optimization of Stirred Tank
Manufacturers and operators in the food and pharmaceutical industries face several challenges regarding fluid mixing like inhomogeneous flow patterns, solid deposition, or prolonged mixing time. To overcome these challenges, Creaform Engineering uses Computational Fluid Dynamics (CFD) simulations to design or troubleshoot processing tanks, mixers, and all sorts of vessels. Our CFD team has analyzed numerous mixers for miscible and immiscible liquids, viscous emulsions and solid-liquid suspensions.
In this case, an important customer in the pharmaceutical industry was forced to extend the mixing time of the product in order to achieve the proper homogeneity. This situation was causing significant production delays. Creaform Engineering’s mandate was to optimize the top-filled stirred tank for mixing time. Over 20 configurations of shafts, blades, impellers and baffles were simulated. The different solutions were compared based on two competing objectives, namely the mixing time to achieve 95% uniformity (t95), and the brake horsepower. Other metrics were also extracted from the simulations to provide relevant insights for the optimization such as torque, axial load, power number and mixing intensity. All the simulations were performed based on proven methods specified in the Handbook of Industrial Mixing.
Finally, our customer included the design modifications recommended by our CFD analysis team and this allowed them to reduce the product mixing time by 20%. The main challenge was to limit the increase of power associated with the modifications. The power increase was limited to 10%, which was largely available with the motor already installed. The reduction of mixing time in this primary part of the processing chain provided significant and perpetual time savings.
- Geometry parametrization for optimization runs
- Volumetric meshing using polyhedral cells and prism layers for finite volume method
- Configuration of physical models and numerical parameters
- Setup of turbulence models
- Multiple reference frame setup for rotating shafts
- Species blending method implemented for evaluating mixing time
- Test case for parameters validation and mesh independency
- Simulations monitoring
- Post-processing of CFD solutions: mixing performance and visualisations
- Comparison of configurations
- Results and recommendations presentation to the end customer and production of all methodology and substantiation reports
Tools and Methods Used
- Species blending