A conceptual design of spacers with hairy structures for membrane processes

Abstract

The development of membrane technology requires spacers that can significantly enhance the mass-transfer rate while avoiding a severe pressure drop across the membrane module. A potential solution to this challenge is to introduce some flexible and dynamic structures into the spacer mesh. The current work was motivated to explore a conceptual design of spacers with hairy structures. The hairy structures were simulated using highly flexible nylon fibers that were fixed on a well-designed framework. The effects of fiber asymmetry and spacing on the vibrations were discussed in terms of the observations via a high speed camera. A variety of spacer prototypes were employed in a forward osmosis process to examine the performance of the hairy structures. The experimental results indicate that fiber vibrations could have a great impact on the mass transfer in the vicinity of the membrane surface and enhance the filtration flux (up to ~20%). This fundamental study not only provides insight into the mechanisms underlying the complex fiber-flow interactions but also charts the direction for future hairy spacer design.