Rotating membrane disk filters: Design evaluation using computational fluid dynamics

Computational fluid dynamics is used to investigate designs for rotating membrane disk filters. Simulations have been run for the case of water permeating through a membrane disk rotating in a pressurized housing. The water was assumed to be Newtonian, incompressible, non-fouling and isothermal. A κ-ε model was used to describe turbulent flow in the vessel surrounding the rotating disk. Similar to a non-porous disk, the rotation of the membrane disk induces a recirculating flow pattern of the fluid within the vessel. However, the centrifugal force acting on the permeate may locally increase the permeate side pressure above the feed side pressure resulting in a negative local transmembrane pressure. Hence, a portion of the membrane is subject to a reversed flow of permeate which reduces effectiveness of membrane area and may damage the membrane. This 'back pressure' phenomenon can be avoided by a careful choice of the operating conditions and design parameters. The propensity for 'back pressure' is higher when the membrane is more permeable but can be reduced by increasing the feed flow rate or decreasing the disk diameter (i.e. the membrane area).

Duke Scholars

Author Mark Wiesner Civil and Environmental Engineering