Simulation of the Flow around Spacer Filaments between Channel Walls. 2. Mass-Transfer Enhancement

Abstract

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, masstransfer 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.

Numerical study of mass transfer in three-dimensional spacer-filled narrow channels with steady flow

“…This paper presents a description of the spatially-periodic mass transport boundary condition, and its application to the analysis of the flow features and performance of a simple 3D non-woven spacer filament mesh. In principle, it extends the work of Schwinge et al [9] to 3D geometries, focusing on the effects of form and viscous drag on mass transfer. Moreover, it explores the connection between mass-transfer enhancement and flow features exclusive to 3D flow under steady flow conditions.…”

“…Due to the high memory requirements for 3D simulation, a different approach to that used for 2D simulations in our previous work [7,9] was employed, bypassing the entrance region effects and focusing on the spatially periodic region of the spacer-filled channel. This approach reduces the computational requirements and enables us to perform accurate and reliable 3D simulations of the flow inside a SWM module, with applicability to real-world operations.…”

“…Due to its simplicity and smaller computational demands, many researchers have opted for modeling spacer-filled channels in two dimensions, as is evidenced by the amount of work undertaken in this area [1,3,[9][10][11][12][13][14][15]. As a result, CFD is now accepted as a reliable tool, and gradually threedimensional (3D) studies are beginning to emerge [4,[16][17][18][19], most of them finding good agreement between predicted and experimental results.…”

Entrance length effects on Graetz number scaling in laminar duct flows with periodic obstructions: Transport number correlations for spacer-filled membrane channel flows

“…Note that the redistribution of the velocity profile depends on the size, separation distance, and position of the obstacles. Thus, a redistribution in favor of a higher center velocity decreases the Nusselt number -as, for instance, seen in filaments adjacent to the wall in the study by Schwinge et al [39].…”

“…The numerical results presented in Schwinge et al [39] are based on a short channel with a maximum length of L s /H = 8, high Schmidt numbers 100 < Sc < 50, 000 and a Reynolds number of 200. For the lowest Schmidt number examined, the thermal entrance length is L s /H = 200, for which all the results fall in the range of the entrance length.…”