3D printing design of turbulence promoters in a cross-flow microfiltration system for fine particles removal

In this study, we designed three turbulence promoters using three-dimensional (3D) printing technology for cross-flow microfiltration. Designing turbulence promoters with optimal geometry for microfiltration systems remains a key challenge. The effects of the operating conditions, such as cross-flow velocity, transmembrane pressure and geometry of the turbulence promoter on the filtration flux and cake properties were investigated. The distribution of the fluid velocity was examined using computational fluid dynamics (CFD). For normal microfiltration tests without promoters, the filtration flux merely increased by 10% when the cross-flow velocity increased from 0.1 to 0.5 m/s under a transmembrane pressure of 20 kPa. Therefore, the turbulence promoters were individually added into the channel of the microfiltration device to induce vortices in the flow stream and increase cross-flow velocity. Three turbulence promoters with different configurations (circular, diamond and elliptic) were made with a 3D printer. The elliptic type of promoter with a hydraulic angle of 90° displays the flux enhancement by approximately 30–64% under a transmembrane pressure of 20 kPa compared to the normal type of microfiltration, whereas the diamond type of promoter with a hydraulic angle of 60° shows a lower flux enhancement by approximately 7–16% under the same transmembrane pressure. Overall, adding the turbulence promoter to the microfiltration module shows a great potential to significantly mitigate membrane fouling and enhance filtration flux in cross-flow microfiltration.