Simulation of the flow around spacer filaments between channel walls. 2. Mass-transfer enhancement

A computational fluid dynamics (CFD) code was used to study the effects of Reynolds number, mesh length, and filament diameter on mass-transfer enhancement for three spacer configurations a cavity, a zigzag, and a submerged spacer. For the cavity and zigzag spacers, mass-transfer, enhancement first increases with a decrease in the mesh length, reaches a maximum, and then decreases with a further decrease in the mesh length, while pressure loss showed a continuous increase with a decrease in the mesh length. The submerged spacer shows a continuous increase of the mass-transfer enhancement and pressure loss with a decrease in the mesh length. For all spacer types, mass transfer increases with the filament diameter. However, at a smaller filament diameter, the overall spacer performance increases, as indicated by a high mass-transfer enhancement to pressure loss ratio. Overall, the CFD simulations reveal that the zigzag spacer is the most efficient spacer type for a spiral wound membrane module.