Abstract Summary (Max 250 words)
The Taylor-Couette (TC) reactor represents a distinct type of stirred tank, where mixing is driven by the relative rotation of concentric cylinders. The cylinders generate vortical flows that govern mixing, yet the mechanistic role of gap width (the annular space between concentric cylinders) remains under explored. This study investigates how gap width (radius ratio η = Rᵢ/Rₒ) regulates mixing time and mechanisms via tracer experiments and CFD simulations. Results reveal that gap width critically modulates Taylor vortex structure and mixing efficiency. Narrow gaps (η → 1) delay Taylor vortex onset, requiring higher Taylor numbers for mixing initiation; once formed, vortices are axially compressed, enhancing intra-vortex circulation but limiting radial exchange. Wide gaps (η → 0) promote early vortex formation with larger, axially stretched vortices that enhance axial dispersion but weaken local shear and energy dissipation. Mixing time exhibits a non-monotonic dependence on gap width: optimal efficiency occurs at intermediate η (~0.6-0.8), where intra-vortex circulation and inter-vortex exchange reach a balance. Below this range, excessive axial dispersion prolongs homogenization; above it, confined vortices restrict global mixing. Turbulent kinetic energy dissipation rate profiles confirm that maximum energy efficiency aligns with this optimal window. These findings establish gap width as a key design parameter for TC reactors, providing a mechanistic framework for tailoring mixing performance in applications such as fermentation and nanoparticle synthesis.
