Numerical investigation of L-shaped obstacle geometrical parameters effects on the planar membrane humidifier performance in the PEM fuel cell application

Humidification of polymer membrane fuel cell (PEMFC) reactant gases is necessary for keeping the membrane humidified. Planar membrane humidifiers are widely used for reactant gas humidification due to their proper performance, simple structure, and long life span. In this study performance of a planar membrane humidifier with symmetrical L-shaped obstacles in both channels is investigated numerically by ANSYS fluent and its performance is compared with a simple planar humidifier. The Effects of geometrical parameters are studied by 3D numerical modeling. Accordingly, two parameters of water recovery ratio (WRR) and dew point temperature at the dry channel outlet are considered the main performance criteria. Results show performance decreases with the increase of the gasses mass flow rates. Dry gas outlet temperature noticeably increases by the L-shaped obstacles insertion which indicates better heat transfer. The effect of four geometrical parameters of the obstacle consisting of obstacle length, height, the distance between the obstacles and the top and bottom of the channels, and their relative distance are investigated. Three values are considered for each geometrical variable, and the distance between the obstacles and the membrane exhibits more influence on the performance of the humidifier. The geometrical study improves the performance of the obstacles and raises the WRR and the dew point temperature by about 3% and 3.5 degrees, respectively.