A comprehensive proton exchange membrane fuel cell system model integrating various auxiliary subsystems

© 2019 Elsevier Ltd A comprehensive proton exchange membrane fuel cell (PEMFC) system model is developed, including a pseudo two-dimensional transient multiphase stack model, a one-dimensional transient multiphase membrane humidifier model, a one-dimensional electrochemical hydrogen pump model, an air compressor model with proportion-integral-derivative control and a ribbon-tubular fin radiator model. All sub-models have been rigorously validated against experimental data to guarantee the system model accuracy. The effects of stack operating temperature, gas flow pattern and humidifier structural design are investigated to cast insights into the interaction among stack and auxiliary subsystems. The results indicate that the stack is successfully maintained at required operating temperatures (60 °C, 70 °C, 80 °C) with help of the radiator when the whole system starts from ambient temperature (25 °C). However, the stack is likely to suffer from membrane dehydration when operated at 70 °C, and the problem becomes more severe at 80 °C, causing significant performance deterioration. The water and temperature distribution inside the system are further demonstrated. The co-current flow pattern contributes to better water utilization of the whole system which may lead to higher output performances. But the counter-current flow pattern has positive effects on parameter distribution uniformity inside fuel cell, which is beneficial for the stack durability. As regards the membrane dehydration, it is found that optimizing membrane humidifier area does not fundamentally solve the problem. Increasing humidifier area contributes to higher water vapor transfer rate, however, it results in much slower humidification responses

Two-dimensional simulation of cold start processes for proton exchange membrane fuel cell with different hydrogen flow arrangements

© 2020 Hydrogen Energy Publications LLC Proton exchange membrane (PEM) fuel cells with an off-gas recirculation anode (ORA) or dead-ended anode (DEA) are widely adopted in engineering. However, those two hydrogen flow arrangements may cause anodic water and nitrogen accumulation in comparison with the flow-through anode (FTA) mode, which causes significant performance degradation. In this paper, a two-dimensional cold-start model is developed with detailed consideration of water phase changes and the nitrogen crossover phenomenon. A simplified electrochemical module is built to calculate the current density distribution in the model. The simulation results are consistent with the experimental data at both subzero temperatures and normal operating temperatures. The effects of hydrogen flow arrangements, flow configurations, and startup strategies are investigated during startup process from subzero to normal operating temperatures. Much less ice is generated in counter-flow cases than in co-flow cases during constant current operation. A relatively lower startup voltage can effectively shorten the cold-start process and enhance the cold-start capacity for the PEM fuel cell. The ORA mode has the best hydrogen flow arrangement due to its general abilities, including higher hydrogen utilization efficiency, higher anodic nitrogen tolerance, better output performance and better startup capability