Characterization of macromixing and micromixing performance of unbaffled U-shaped mesoscale oscillatory flow reactor

Background: Unbaffled U-shaped mesoscale oscillatory flow reactors (meso-OFRs) are able to achieve low pressure drop, good plug flow and micromixing performance simultaneously at laminar net flow conditions under a wide "operating windows".Method: We focus on the macromixing and micromixing behaviours of unbaffled meso-OFR, where the net flow and oscillation conditions were in the wide range of Ren=17-51 and Reo=16-1350, respectively.Significant findings: The good plug flow and micromixing performance could be achieved simultaneously at low oscillation intensity with the wide "operating windows" of psi<47. It was believed that oscillatory motion led to periodic destruction and reformation of vortices, as the oscillation intensity increased, the large-scale vortices were decomposed into small-scale vortices, resulting in backmixing or axial dispersion. Meanwhile, the empirical formula of micromixing time and velocity ratio in accordance with the power-law relationship was established: tm/t = 0.00277 psi 0.51658. Finally, the oscillatory mechanism was qualitatively validated by Computational Fluid Dynamics (CFD).