Development of a Generalized Criterion for Selecting the Optimal MRF Rotation Zone for CFD Simulation of Stirred Tank Reactors

Due to increasing industrial concern towards the development of computational models of stirred tank reactors, it is necessary to enhance the accuracy of the model predictions. The rotation of the impeller in a reactor vessel is mainly simulated using the pseudo-steady Multiple Reference Frame (MRF) technique. Earlier studies have highlighted the importance of extending the rotating domain defined for the modelling process, while a definite idea regarding the selection of the same has not been specified so far. The present study aims to develop a generalised criterion for selecting the optimal MRF extents for any configuration of the reactor. The radial and axial extents of MRF boundary were systematically varied in a baffled reactor vessel and the optimal extents of the same were determined from the predictions of underlying flow field characteristics. The balance between the Power number (Npt) computed from the torques of rotating and stationary walls which is based on the principle of conservation of angular momentum is determined as the generalised criterion for selecting the optimal extents of the rotating domain.