THE EFFECTIVENESS AND UTILITY OF MODULAR SPRING-SLEEVE STATIC MIXING INSERTS FOR THE INLINE MIXING OF FLUIDS IN STANDARD PIPE AND TUBING

Static mixers are critical for achieving efficient inline blending across industries such as chemical processing, water treatment, and polymer manufacturing. Traditional spiral mixers rely on tight tolerances and wall contact for effective mixing, but these designs can introduce manufacturing challenges and increase costs. This study investigates modular, 3D-printed static mixer inserts that self-secure within loosely toleranced pipes by leveraging elastic properties of the material. These inserts maintain a controlled streamline gap while preserving near-wall attachment, which may influence mixing dynamics and pressure drop characteristics. A combined computational fluid dynamics (CFD) and experimental approach evaluates mixing performance and hydraulic efficiency under controlled laminar flow conditions, with a Reynolds number near 1,000 maintained at the inlet. Tests are performed using a custom static mixing test rig fed by two Masterflex peristaltic pumps. Mixing efficacy is quantified using coefficient of variation (CoV) analysis from specific gravity measurements. ANSYS Fluent simulations of velocity distributions and ΔP are compared to baseline spiral static mixer simulations. Comparative studies with standard spiral mixers provide insight into trade-offs between mechanical functionality and mixing efficacy. Findings suggest the unique flow structures induced by the inserts can compensate for the streamline gap, utilizing radial velocities to achieve near-complete mixing without significant pressure penalties. Pressure drop differences remained within 5%, with no notable deviation in mixture homogeneity using low-viscosity water-soluble fluids (compared to traditional spiral static mixer). The modular design allows rapid reconfiguration for different flow conditions, while structural geometry and material properties can be tailored to optimize holding forces. These results contribute to understanding alternative static mixing designs, and future work will refine geometries and materials to further enhance performance and durability.