Effect of channel structure on the performance of a planar membrane humidifier for proton exchange membrane fuel cell

In the present study, the performance of a planar membrane humidifier for proton exchange membrane fuel cell is evaluated experimentally for different channel structures. For this purpose, three performance indices including water flux, water recovery ratio (WRR), and pressure loss are employed. The measured results disclose that the humidifier using counter flow approach and the channel with width of 1 mm and depth of 1.5 mm has the best overall humidification performance in this work. Increasing the channel depth increases the water flux and therefore increases the WRR of the humidifier. Moreover, the pressure loss decreases with increasing the channel depth because the friction factor at an identical flow rate decreases with increasing the hydraulic diameter of the flow channel. Increasing the channel width expands the contact area with the membrane, leading to an improvement of heat and water vapor transfer. Thus, a higher WRR and pressure loss can be obtained at elevated channel widths. Both depth and width of the channel must be taken into precise consideration in order to minimizing the pressure loss and maximizing the heat and mass transfer.