CFD Modeling of Rotating Spiral Wound Membrane with Corrugated Spacer: Shear Rate Effect

Abstract

Shear rate is proven in many studies to be playing an important role in reducing the concentration polarization and membrane fouling. This paper investigates the effect of rotation speed of corrugated spacer on the shear rate using computational fluid dynamics (CFD). Two small channels with the inner membrane (IM) 39 mm from the axis of rotation and outer membrane (OM) with 41.5 mm were used for the studies. The inlet pressure is set as 100 kPa and water is used to study the shear stress on the rotating membrane. The average surface shear rate between the two membranes is found out to be increasing with the rotation. The average shear rate on stationary membrane is 25,645 s -1 and increased to 46,961 s -1 at rotation speed of 250 rad/s. The shear rate of OM is larger than IM when the rotation speed is lower than 75 rad/s but the shear rate on IM is larger when rotation speed is higher than 75 rad/s. The rotation of corrugated spacer can be applied to the spiral wound membrane module to increase the shear rate and thus increase the permeate flux and reduce the concentration polarization.