As a core component of membrane separation technology, the spiral wound membrane's structural design directly determines its separation efficiency, operational stability, and application adaptability. Through the precise combination of multiple functional materials and the winding process, spiral wound membranes maximize the effective membrane area per unit volume while constructing ordered fluid channels, making it the preferred configuration for industrial-scale separation.
Structurally, a spiral wound membrane mainly consists of four parts: the separation membrane, the support layer, the flow guiding mesh, and the central water collection pipe. The separation membrane is the core functional layer. Depending on the separation requirements, different materials and pore sizes can be selected, such as reverse osmosis, nanofiltration, and ultrafiltration, to selectively retain target substances. The support layer, usually made of porous polymer materials, adheres closely to the membrane surface, enhancing mechanical strength, preventing membrane compression deformation, and ensuring uniform stress on the membrane surface. A flow-guiding mesh, located between adjacent membrane layers, guides the feed liquid flow with a grid structure, reducing concentration polarization by increasing turbulence and preventing localized contaminant accumulation. The central water collection pipe runs through the core of the assembly, collecting and discharging the permeate through the membrane. Its porosity and distribution must match the membrane area to ensure uniform hydraulic distribution.
During assembly, the above materials are alternately stacked in a "membrane-membrane-membrane" sequence, ultimately spirally wound into a cylindrical assembly along the central pipe. This winding logic allows the feed liquid to penetrate radially through multiple membrane layers under pressure, while the permeate seeps through the membrane surface into the mesh gaps and finally flows into the central pipe. The concentrate is discharged axially along the mesh channels, forming a continuous cross-flow filtration mode. In structural design, the thickness, porosity, and winding tension of the separator require precise control-too dense a mesh increases flow resistance, while too sparse a mesh weakens the disturbance effect; the winding tightness directly affects the membrane surface flatness and sealing performance, and deviations in any aspect can lead to performance degradation.
It is this precise structure of "functional stratification-fluid guidance-integrated collection" that enables spiral wound membranes to achieve high-fluidity, low-energy separation efficiency within a limited space, and also provides the structural foundation for their long-term stable operation under complex conditions.
