The Study On A New PEMFC Humidification Method

Fuel cell is one type of high efficient power generation unit which can turn thechemistry energy of oxidant and fuel into electricity power. Currently, theenvironmental problem is threatening our lives every hour and every minute, thusmore attention is paid on it. Among various types of fuel cells, polymer electrolytemembrane fuel cell (PEMFC) is famous for its advantages like possessing high energydensity, high conversion efficiency, friendly to environment etc.During various factors which can influence the output performance of PEMFC,water management is a major one. Although many researchers have made someimportant achievement in the PEMFC water management, none of the availablesolutions that could solve dry-out and flooding simultaneously has been proposed.Because the solutions for solving dry-out and flooding is contradictory. To avoidflooding, the water in cathode inlet gas is required to be reduced, but this solution willdehydrate PEM at inlet of flow channel, while ensuring the membrane water contentat inlet tends lead flooding at the outlet area. To solve these problems, a newhumidification method was devised, and a simplified math model, which can describethe affect of flooding and dry-out with less calculation, was developed to study theeffect of this new inlet gas humidification method on controlling the occurring offlooding and dry-out.A simplified liquid/gas two-phase flow model was also developed to investigatethe effectiveness of this new method. The simulation results showed that: this newhumidification method can control the dry-out as well as the flooding, improve theoutput performance and better the uniformity of local current density. The addedbypass channel inlet position and main-channel inlet gas fraction has an importantinfluence on dry-out and flooding. When the whole cathode inlet gas was divided intotwo parts, the distance between main channel inlet and added bypass channel inlet issupposed to be20%~40%of channel length, correspondingly the main-channel inletgas fraction should be between50%and60%.