Experiment And Simulation Of Water Management In PEM Fuel Cell

PEM (proton exchange membrane) fuel cell is a new, efficient and clean power generation system. Its efficiency of power generation is able to be up to about 60%, while PEM fuel cell causes no pollution to the environment because of no emissions except water. Despite the fact that delightful achievements of basic researches and the application of PEM fuel cell have been made, there are still lots of obstructions in its popularization and application in recent years, and the high cost is one of the major factors. With the cost being unable to be reduced, improvement of its performance is an important way to enhance the performance-price ratio of PEM fuel cell. There are many factors affecting the performance of PEM fuel cell, the key of which is water. Therefore, the experiments and simulation results of water management in PEM fuel cell are of great significance in enhancing its performance which is in favor of the popularization and application of the cell.This paper focuses on PEM fuel cell and intensively studies the performance of PEM fuel cell being assembled with different flow fields. Different pattern of the influences of various conditions on the voltage of the cell and the current output characteristics have been drawn by testing the output characteristics of PEM fuel cell under conditions of different temperature and flow with the purpose to analyze the influence of different flow fields on water transfer and distribution. In this experiment, when the flow fields of anode and cathode interdigitate, the water management inside the cell can balance the water inside it and the output characteristic of it appears to be the best. The conclusion that cathode's impact on output characteristics of PEM fuel cell is bigger than anode's, has also been drawn from the experiment.Through theoretical calculation, the impact of gravity on water management has been analyzed; meanwhile the experiment methods of the impact of gravity on water transit and distribution have been presented. In this experiment, via designing two positioning styles, anode-upward style and cathode-upward style, the testing of the two-phase flow of PEM fuel cell in conditions of different temperature and humidity, by changing the relationship between gravity and water transfer, has been realized. The performance of PEM fuel cell with different positioning styles has been tested, and the regular pattern of the effect of different operating conditions on output characteristics of PEM fuel cell has been obtained. Affected by the gravity, the performance of PEM fuel cell anode-upward is better than that of cathode-upward in this experiment. When the temperature of humidification is higher than that of fuel cell, the water management of the fuel cell with cathode-upward causes water imbalance inside it and the output characteristic of fuel cell appears the worst.A new two-dimensional two-phase flow model has been constructed to simulate mass transfer in PEM fuel cell through combining the three conservation laws of fluid mechanics. It's the first time to consider the impact of gravity on the two-phase flow within fuel cell in the momentum equation source term, and the gravity is set as a vector, whether the gravity appears to be positive or negative depends on the different positioning styles of cathode-upward and anode-upward. Through the staggered grid finite volume and the SIMPLE algorithm, the mass transfer inside the fuel cell is simulated by mathematical simulation, and the simulation results show mass concentration fraction and oxygen concentration fraction of cathode water in fuel cell. Influenced by gravity, the cathode water concentration with anode-up is higher than that with cathode-up, while the oxygen concentration is opposite to water concentration.According to the results of experiment and simulation, a positioning style of optimizing water management in fuel cell and enhancing performance of PEM fuel cell has been presented.