Numerical Simulation of Membrane Processes

Funding Agency: USEPA, National Science Foundation

Principal Researchers: Sandeep Sethi

Numerical representations of membrane performance will ultimately allow us improve membrfane facility design, operator training, and process control. This work considers dominant mechanisms of particle transport in crossflow membrane filtration which are unified to obtain a generalized model for time-dependent permeate flux.

The unified model extends an earlier model based on shear-induced diffusion and a concentrated flowing layer to include Brownian diffusion and inertial lift. It is applicable over a broad range of contaminant sizes encompassing macromolecules, colloidal and fine particles, and large particles. The combined theory predicts an unfavorable particle size where the net back transport away from the membrane attains a minimum, leading to maximum cake growth. For the system simulated in this work, this implies lowest permeate flux in the size range of 0.01 - 0.1 µm, depending on the operating time.

Theoretical comparisons have been made between the flat slit and the inside-out cylindrical membrane geometries by applying the model to a range of particle sizes and analyzing the cake growth and permeate flux behavior. Effects of transmembrane pressure and shear-rate on the permeate flux decline have been evaluated for a typical inside-out cylindrical geometry.