Numerical simulation study on the impact of baffle geometric characteristics on mixing performance in microchannel mixers

Abstract Microchannel mixers are extensively used in fine-chemical synthesis and reaction processes. Incorporating passive baffles into microchannels dramatically enhances mixing by inducing flow perturbations. Performance depends critically on baffle geometry, number, spacing and length. Based on chaotic-advection principles, this study compares rectangular, trapezoidal and triangular baffles via numerical simulation and experimental validation. Qualitative flow visualizations match simulated streamlines, and quantitative measurements agree within 2%. We assess mixing using the intensity of segregation, pressure drop and mixing intensity. Results show that inter-stream collisions and shear dominate mixing, and that baffle shape governs disturbance generation: rectangular and trapezoidal baffles sustain stronger, longer-lasting perturbations than triangular ones, which cannot maintain stable recirculation zones. Under optimal conditions (baffle length 0.6 mm, spacing 0.4 mm), the rectangular design achieves a mixing intensity of 97.61% at a 6702.6 Pa pressure drop; the trapezoidal reaches 97.07% at 7529.21 Pa; and the triangular (0.5 mm length, 0.5 mm spacing) attains 96.08% at 8170.47 Pa. These configurations strike the best balance between high mixing intensity and moderate energy loss.