Membrane spacers for ultrafiltration: Modelling of mass transfer and pressure

Membrane spacers are an essential part of spiral wound modules and can significantly influence the mass transfer performance and pressure drop in the modules. To develop further understanding of the importance of spacer selection, the performance of two configurations of parallel spacers for ultrafiltration using Dextan T40 was analysed in this study using lab-scale experiments and CFD simulations supported by a large-scale Plexiglas model. In configuration I, the filaments transverse to the flow direct are touching the membrane, while in configuration II, the filaments parallel to the flow direction touching the membrane. From the lab-scale experiments it appears that the spacer design is an important parameter for low pressure applications, while with increasing pressure the differences between the two configurations tested diminished. Using further the CFD simulation, it was possible to reproduce the trends of the two configurations but the CFD simulation overestimates fluxes. It was therefore concluded that the present model used for the CFD simulation does not cover all phenomena involved in the mass transfer. However, the authors believe this work presents the foundation to develop a closed chain between lab-scale experiments and CFD-simulations, which can be used in future spacer selection and development.