Laminar mixing in an SMX static mixer.

摘要

Laminar mixing in an SMX static mixer was studied using experimental measurement techniques, particle image velocimetry and laser induced fluorescence, along with computational fluid dynamics. The effect of shear-thinning liquids and mixer element designs on pressure drop and mixing, as well as drop breakup mechanism in liquid-liquid dispersion were investigated.; Shear thinning fluids exhibited better mixing quality and lower pressure drop than Newtonian fluids in the mixer. The correlations for pressure drop and friction factor were obtained. A proper apparent strain rate was proposed to calculate pressure drop for non-Newtonian fluids.; The effect of cross-bar number (width of cross-bar) of SMX mixing elements on pressure drop and mixing was studied. The mixing element with 10 cross-bars showed the best mixing quality, followed closely by the standard SMX mixing element with 8 cross-bars. Modified mixing element designs, with a short aspect ratio increase the average and peak strain rate, and provide a more uniform strain rate distribution and faster mixing rate when compared to the standard SMX mixer. In addition, a mixer element with semi-cylindrical cross-bars provided lower pressure drop and better mixing than the standard SMX static mixer.; All three typical flows (shear, elongation and squeezing) appear within the flow field of an SMX static mixer. Fluid elements experience varied strain rate and flow types in the mixer. Drop collision with the cross points of the SMX static mixer elements is most effective for drop breakup. Elongation and folding result in the breakup near the cross-points. Experiments showed that surface wettability of the SMX static mixer has a major influence on drop breakup at low flow rates.