CFD Prediction of Stirred Tank with Double Helical Ribbon and Helical Screw Ribbon Impellers

The flow field characteristic of high viscosity polystyrene solution in stirred tank with different helical ribbon and helical screw ribbon assemble impellers were calculated by commercial CFD code ANSYS CFX. Different models for flow field calculation were employed in the simulation. Among them, a free liquid surface model for the gasliquid surface in the stirred tank, which is close to reality operation condition, was used. The sliding grids method was employed to deal with the rotating reference frame for impeller area. The liquid phases were the polymer solutions with different viscosities. The flow fields with various combination of impellers were compared. The outstanding performance of double helical ribbon and screw ribbon impellers in high viscosity liquid was confirmed. The shape of liquid surface, the velocity field and the power consumption of stirring were calculated, which are valueable for industrial operation and optimization.