The efficient suspension and controlled transport of microparticles in heterogeneous photocatalytic systems significantly influence reaction rates and product quality, particularly in coiled flow inverter (CFI) reactors, which promise enhanced mixing due to their complex geometry and secondary flow effects. Despite their increasing industrial relevance, a comprehensive understanding of particle dynamics within CFIs across a broad range of operational conditions remains incomplete. To address this critical knowledge gap, we present a multi-physics numerical investigation to analyze particle trajectories within a CFI reactor. In this work, we systematically explore particle tracing under laminar flow conditions at various operational velocities matching a preliminary experimental setup, with simulations expanded to a wide range of flow velocities to encompass diverse dimensionless flow regimes. Particle sizes ranging from 100 nm to 100 µm, covering nanoparticle and microparticle regimes relevant for various heterogeneous photocatalytic processes, have been investigated to elucidate size-dependent flow and sedimentation behaviors. The computational approach integrates fluid dynamics and discrete particle tracking physics, explicitly considering drag, gravity, and additional relevant forces to accurately capture particle-fluid interactions and sedimentation probabilities. Preliminary simulation results demonstrate clear dependencies of particle distribution uniformity and sedimentation rate on flow velocity, particle diameter, and associated dimensionless parameters. Smaller particles exhibited near-ideal suspension behavior with minimal sedimentation across a broad range of flow rates, while larger particles showed significantly higher susceptibility to sedimentation, particularly at reduced velocities. We anticipate identifying optimal velocity ranges that minimize sedimentation and enhance particle suspension, directly informing reactor operational strategies. This computational study not only advances the fundamental understanding of particle-fluid interaction in complex flow geometries but also provides practical insights into the scale-up and design optimization of CFI photo-reactors. Ultimately, our findings will support enhanced reactor performance, greater efficiency in catalytic reactions, and improved process scalability.
