CFD Model to Evaluate Performance of a Kenics Static Mixer

A three-dimensional (3-D) computational fluid dynamics (CFD) model of a Kenics static mixer, consisting of 10 helical units, is presented in the paper. The model was used to simulate flow and mixing at high Reynolds numbers (R_E) that are typical (10₃ to 10₆) in water treatment plants (WTPs). A high resolution computational grid, consisting of 1.25 million polyhedral cells, was used to resolve the geometric features of the mixer. An analysis of radial and circumferential velocities shows that the flow field is characterized by regions of reverse flow and the growth and interaction of strong longitudinal vortices. A conservative tracer injected just upstream of the first unit was used to determine coefficient of variation (CV), a ratio of standard deviation of concentration to its mean, of each unit. For flow conditions found in WTPs, the study suggests that four helical units can achieve the desired level of mixing (CV ≤ 0.001).