Performance analysis of a membrane humidifier containing porous metal foam as flow distributor in a PEM fuel cell system

Abstract

Using metal foam as flow distributor in membrane humidifier for proton exchange membrane (PEM) fuel cell system has some unique characteristics like more water transfer, low manufacturing complexity and low cost compared to the conventional flow channel plate. Metal foam can be applied at wet side or dry side or both sides of a humidifier. The three-dimensional CFD models are developed to investigate the performance of the above mentioned meanwhile compare them with the conventional humidifier. This model consists of a set of coupled equations including conservations of mass, momentum, species and energy for all regions of the humidifier. The results indicate that with the metal foam installed at wet side and both sides, water recovery ratio and dew point at dry side outlet are more than that of the conventional humidifier, indicating a better humidifier performance; while using metal foam at dry side has no positive effect on humidifier performance. At dry side mass flow rates higher than 10mgr/s pressure drop in humidifier containing metal foam at wet side is lower than that of the conventional humidifier. As the mass flow rate increases from 9 to 15mgr/s humidifier containing metal foam at wet side has better performance, while at mass flow rates lower than 9mgr/s, the humidifier containing metal foam at both sides has better performance. At dry side inlet temperatures lower than 303K, humidifier containing metal foam at wet side has better performance and at temperatures higher than 303K, humidifier containing metal foam at both sides has better performance.