Characterizing the flow of stirred vessels with anchor type impellers

Despite its importance in chemical industries, there are few works which st udies anchor type impellers and only a fraction of the works investigate th ese systems under a computational approach. The great majority refers to tu rbine impellers, specially Rushton turbines, under turbulent now. Anchor im pellers are used specially for highly viscous flow, typical of polymer reac tions. The viscosity is normally in the range 1000-10000 cp. Since this ran ge of viscosity describe highly viscous flows, the reactions for anchor agi tated systems are normally carried out under laminar flow. This work presen ts a detailed computational fluid dynamics (CFD) approach to study the beha viour of stirred vessels using anchor impellers. The axial plane of the tan k, which is being modelled, is divided into small control volumes, which co llectively is referred to as the mesh, ol grid. In each of these cells the momentum balance, energy and mass conservation, which describes the model, are rewritten algebraically using the finite volumes method to relate such variables as velocity, pressure and temperature to values in neighbouring c ells. The equations are then solved numerically, and the results yield the now corresponding to the model. Since the geometry of a vessel with anchor impellers strictly calls for a three dimensional method, an approximation i s made to account for the effect of the blades (Kuncewics, 1992). The main objective of this work is to give a detailed description of the flow genera ted by this axial impeller with a view to indicate ways in which the design and operation of these systems can be improved.