Numerical characterization of low Reynolds number flow in the Kenics static mixer

Low Reynolds number how in a six element Kenics static mixer was modeled using finite element computations. The numerical approach takes into account aspects of the fluid flow within the Kenics mixer which have been neglected in previous studies, including transitions between mixer elements and finite-thickness mixer plates. The pressure drop information obtained from the simulations was compared to Several experimental correlations available in the literature for Kenics mixer pressure drop. Analysis of the low Reynolds number velocity field indicates a spatially periodic flow which matches the periodicity of the mixer geometry. Flow transitions at the entrance and exit of each element strongly affect the velocity held for up to similar to 25% of the element's length under creeping flow conditions. Comparison of the velocity held over a range of Reynolds numbers from 0.15 to 100 indicated that Re-independent velocity profiles are obtained up to Re = 10, with significant deviations in the velocity held at Reynolds numbers above this limit. The magnitude of the rate-of-strain tensor, which represents an upper bound for mixing efficiency, was computed and profiled within the mixer. The profile for the magnitude of the rate-of-strain tensor was roughly uniform over the central 75% of a single mixer element, but shifted toward higher values in the end regions, indicating that the greatest potential mixing effects take place at the element-to-element transitions. (C) 1998 Elsevier Science Ltd. All rights reserved.