Simulation of Scale-up Criteria for Side-entry Stirred Tank in Laboratory Scale

Abstract

The hydrodynamics in side-entry stirred tanks with similar geometry ratio were studied using Computational Fluid Dynamics (CFD) simulation methods. Scale up is done using a flat bottomed cylindrical side-entry stirred tank with diameter D=0.4 m (T40) and D=0.6 m (T60) in a laboratory scale. The type of stirrer is a commercial three-blade marine propeller with a ratio propeller to tank diameter d/D = 0.1. The effect of the constant propeller rotational speed (N) and constant tip speed (utip ) is evaluated on the pumping capacity and fluid velocity profile in the discharge stream area as well as the flow pattern in the whole tank. Flow patterns are a form of fluid behavior that is easily changed when there are operating conditions in the tank varying, for example when the propeller speed is changed. Considered from the effectiveness of mixing performance, the scale-up criteria similar geometry to the constant N is more beneficial. Visually shows that in the same time span the flow pattern on the T60 is more able to reach the entire tank area. The stagnant area is not visible, whereas in T40 there is still a stagnant flow area in the upper left corner of the tank. However, constant N cannot be used as a reference for scale-up of side-entry stirred tank into a larger scale. Because the phenomenon changes quite dramatically which is caused by a change in propeller diameter. Meanwhile constant utip gives results that are closer to T40 and T60 in the flow pattern and the distribution of velocity in the discharge stream. So for side-entry stirred tank that has a similar geometry, scale-up criteria with constant utip is more appropriate to be applied.