Submerged-helical module design for pressure retarded osmosis:A conceptual study using computational fluid dynamics

Recent research efforts in taking pressure retarded osmosis closer to commercialization have concentrated on the development of pressure retarded osmosis-specific membranes. The module design, on the other hand, has not attracted much attention, although the need for pressure retarded osmosis-specific module designs was identified, when traditional desalination module designs were proven unfeasible for pressure retarded osmosis applications. This work introduces a novel, pressure retarded osmosis-specific module design. The submerged-helical module is a low packing density, spacer-free design, which implicates a significantly lower pressure drop along the draw stream with a power density, similar to more densely packed module types. In this article a theoretical model for the performance of the submerged-helical module design is developed. The model shows that the submerged-helical module may yield a significant net energy generation, under specific geometry configurations and operation conditions. Its results indicate that the design is advantageous to spiral-wound modules and plate-and-frame modules for pressure retarded osmosis, in terms of operation costs.