Hydrodynamics and mixing in continuous oscillatory flow reactors—Part II: Characterisation methods

• Novel quantitative measures of oscillatory flow reactor performance are presented.
• Measures include fluid stretching and shear strain rate history.
• The performance of five baffle designs is compared.
• Disc-and-donut baffles provide high shear rates but also high axial dispersion.
• Helical baffles can decrease axial dispersion and maintain shear strain levels.

This work presents and exploits quantitative measures to better quantify the performance of oscillatory baffled reactors, being complementary to simple vector plots and shear strain rate fields. Novel performance criteria, including radial and axial fluid stretching and mixing, as well as the shear strain rate history of fluid elements have been developed and used to compare the performance of five different baffle designs, namely single orifice baffles, disc-and-donut baffles and three novel variations of helical blades. Analysis of residence time distributions has also been used to evaluate the geometries. The performance measures highlight that the disc-and-donut baffles can provide significant shear strain rates, which could be useful for multiphase applications, but also significant axial dispersion that is comparable with that for the single orifice baffles. The results also suggest that helical blade designs could be promising for decreasing axial dispersion, whilst maintaining significant levels of shear strain rate.