NUMERICAL CHARACTERIZATION OF LOW-REYNOLDS-NUMBER FLOW IN THE KENICS STATIC MIXER

Low Reynolds number how in a six element Kenics static mixer was model ed using finite element computations. The numerical approach takes int o account aspects of the fluid flow within the Kenics mixer which have been neglected in previous studies, including transitions between mix er elements and finite-thickness mixer plates. The pressure drop infor mation obtained from the simulations was compared to Several experimen tal 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 geo metry. Flow transitions at the entrance and exit of each element stron gly affect the velocity held for up to similar to 25% of the element's length under creeping flow conditions. Comparison of the velocity hel d over a range of Reynolds numbers from 0.15 to 100 indicated that Re- independent velocity profiles are obtained up to Re = 10, with signifi cant deviations in the velocity held at Reynolds numbers above this li mit. The magnitude of the rate-of-strain tensor, which represents an u pper 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 s hifted toward higher values in the end regions, indicating that the gr eatest potential mixing effects take place at the element-to-element t ransitions. (C) 1998 Elsevier Science Ltd. All rights reserved.