SPACER CHARACTERIZATION AND PRESSURE-DROP MODELING IN SPACER-FILLED CHANNELS FOR ULTRAFILTRATION

A correlation has been developed that allows the characterization and design of net-like feed channel spacers in any combination of geometri c characteristics: angle, mesh size, thickness, strand size and voidag e. Flow visualization was used to determine the flow path in a spacer- filled channel and to assess the effect of spacer characteristics on f luid mixing. Pressure losses in the spacer-filled channel have been mo delled by inclusion of viscous drag on the channel walls and spacer, f orm drag of the spacer and kinetic losses due to directional flow chan ge. This semi-empirical model permits evaluation of spacer performance . Grober's mass transfer laminar flow correlation for developing conce ntration and velocity profiles was modified to account for spacer geom etry. The equation obtained predicts mass transfer in spacer-filled ch annels with a deviation of less than 10% for the majority of spacers t ested. The penalty for improving flux is increased pressure loss along the channel. An illustrative economic analysis which includes operati ng costs (which are pressure drop related) and capital costs (which ar e flux related) is used to identify optimal spacer designs for ultrafi ltration.