Uninterrupted swirling motion facilitating ion transport in electrodialysis

Performance analysis (ion transport per unit power consumption) of three different classes of flow promoters e.g. (i) twisted tape, (ii) twisted tape with cuts, and (iii) rod was tested in an electrodialysis setup with rectangular flow channel of fixed aspect ratio. Pressure drop inside flow channel with each flow promoter geometry was estimated at four different flow rates (5, 10, 15, 20 LPH). Comparison of Sherwood number, Sh, power number, Pn, Reynolds' number, Re and friction factor, f, indicated relative performance of any geometry with reference to the empty channel. 40% rise in Sh was recorded with monolayer layer twisted tape with spacing per unit membrane gap, d/h = 5.3 relative to empty channel. It is also reported that reduced spacing i.e. lower d/h did not show consistent improvement in ion transport. Twisted tapes causing uninterrupted swirling motion showed 80% better performance compared to twisted tape with cuts which caused an interrupted swirling flow at Re ~ 276.