LAUSR

Abstract In this paper, a two-dimensional steady-state theoretical model was established, to model the internal transport phenomena in a polymeric electrolyte membrane-based (PEM-based) air dehumidification element. The influences of electrochemical reactions, activation and concentration over-potentials, and Ohmic and electro-osmotic effects were considered. The model was solved by the finite difference method with conjugate boundary conditions. So, with this model, the heat, mass and current transfer through the five layers of the element (diffusion layers, catalyst layers and a PEM) could be described theoretically, as well as the convective heat and mass exchange with adjacent airflows. Compared with the results from previous models, this model showed a much closer trend to the experimental data. The overall error was less than 15%, with an acceptable average error of 8.6%. However, greater deviations were observed under larger airflow conditions, probably due to the assumption of laminar airflow and steady-state heat conduction. Furthermore, by the performance analysis, the maximum moisture gradient was found inside the PEM, so the PEM’s parameters could largely affect the system performance. With the increase in PEM water content, the dehumidification was significantly enhanced, especially when the air humidity was high. If the PEM water content was doubled, the dehumidification rate was increased by 42%. Then, decreasing the PEM thickness also improved the performance. However, the effect became minor if the thickness was less than 100 μm. It was also helpful by increasing the PEM conductivity, although the effect of this variable was relatively small. This study provided theoretical guidance for further system improvement and material preparation for PEM-based dehumidification systems.