Three-dimensional multi-physical simulation of a reverse electrodialysis stack with profiled membranes

Abstract

To effectively describe the hydrodynamic and electrochemical behaviors of a reverse electrodialysis (RED) stack with profiled membranes, a multi-physical model based on Nernst–Planck framework was developed in three dimensions. Periodic domain of a cell pair of RED stack was simulated by means of finite element method. The spatial distribution of fluid velocity, ion concentration, electrical potential and current density within the cell pair was investigated. The effects of fluid velocity, inlet solution concentration and fixed charge concentration on the performances of RED stack were explored. The simulation results suggested the advantage of wave-profiled membranes with wavy sub-corrugations in improving fluid mixing and ion transport. When the ionic conductivity of feed solutions (usually low concentration solution) is lower than that of membranes, ions tend to be transported through the wavy sub-corrugations, which shortens the ion transport path through flow channels. However, this facilitating effect gradually decreases with the concentrations of feed solutions increasing. Compared with the spacer-type and empty-type stacks, the wave-type stack has the lowest internal resistances. The present model provides an effective prediction tool for the investigation of the effects of stack features and operating parameters.