Experimental and computational investigation of coaxial contra‐rotating impellers design in baffled‐free stirred reactors

Abstract

AbstractFluid mixing is a common topic in contemporary industry. The search for more efficient processes and reliable equipment is a constant challenge. In this work, numerical and experimental tests analyzed a 45° pitched blade turbine in a contra‐rotating coaxial impeller system (CRCIS) configuration mounted on baffles‐free reactors and compared it with conventional systems with one (CS1I) and two (CS2I) impellers mounted on tanks with baffles. Experimental tests were carried out using a pilot reactor with reduced scales of 1.0 m in diameter and 1.0 m in height (square batch). The behaviour of the physical variables was analyzed for mixing operations, solid particle suspension, and formation of vortices, and the power consumption was recorded through a torque transducer for different rotations. The acquired results helped in the validation of models and numerical simulations. The numerical simulation was carried out using the OpenFOAM® open‐source field operation and manipulation software. In addition, the velocity profile along with the height of the reactor, flow lines, pumping number, power consumption variations, and mixing time were compared. The conclusion of this study showed that CRCIS can be used in tanks without baffles. It also showed promising results for applications involving the suspension of solids, developing axial velocities at the bottom of the reactor higher than those of the CS1I and CS2I arrangements for the same rotation, with less energy consumption, proving to be a technically promising option for application on an industrial scale.