Impact of a Helical Ridge within a Tubular Membrane Channel on Fluid Flow and Particle Behavior: A Model-Based Analysis

Helical inserts or baffles in tubular membranes can provide flux increases without additional energy usage. However, the optimal shape of these turbulence-enhancing structures remains debated, with many experimental studies being performed, though few full-scale applications reported. A model-based approach can assist experimental work in getting detailed insights into the hydrodynamic phenomena near the membrane surface. This creates the opportunity for model-based design of such membranes or an optimization of operating conditions. Both the fluid flow and particle behavior were simulated in a single Pentair X-Flow Compact Helix membrane with helical ridge, and results were compared to those of a plain tubular membrane. Higher mean wall shear stresses were found for the membrane with helical ridge as well as a wider distribution of wall shear stresses, which promote fouling mitigation. Within a shadow zone behind the helical ridge, wall shear stress was, however, slightly lower compared to the plain membrane, highlighting a region of attention for potential fouling issues. The flow's helical motion generates a tangential velocity leading to small centrifugal forces on suspended particles that are significant within the shadow zone, possibly stimulating fouling locally. Based on these model results, further improvements on the design or process can be implemented.