Novel static mixers based on triply periodic minimal surface (TPMS) architectures

Abstract

Static mixers are frequently used in water treatment applications, for example as inline coagulators. A desired geometry of a static mixer is one that results in low mixing energy and high mixing efficiency. Triply periodic minimal surfaces (TPMS) are architectures which are described mathematically such that the mean curvature is zero at any point on their surface. In this work, novel static mixers based on TPMS architectures were modeled as mixers of aqueous feeds, using several computational fluid dynamics (CFD) tools and compared to the state of the art Kenics mixer. The CFD models were verified experimentally. Four TPMS geometries were studied: Gyroid, Diamond, IWP, and Primitive. The dimensionless power number (Kp) was used as a metric to compare the energy requirement of the mixers, while the coefficient of variance (COV) was used to quantify their mixing efficiency. In single element mixers, three TPMS geometries; Gyroid, Diamond and IWP, outperformed the Kenics in terms of mixing energy, with a comparable or better mixing efficiency. In multiple element mixers, however, the Kenics outperformed the TPMS mixers in term of mixing efficiency, while the latter’s energy performance remained superior. Subsequent design modifications of the multi-element TPMS mixers were conducted, including the hybridization of TPMS and Kenics architectures. The changes resulted in mixing efficiencies comparable to the Kenics, but with at least 25 % decrease in energy requirements. The complex, inter-connected and perfectly curved structures of the TPMS shapes are behind their high mixing and energy performance.