Performance evaluation of commercial-size proton exchange membrane fuel cell stacks considering air flow distribution in the manifold

This study offers an efficient method for commercial-size proton exchange membrane fuel cell (PEMFC) stack performance evaluation to improve designing of fuel cell and maximize power density in PEMFC stack. The flow distribution in the manifold of the stack is critical to the energy conversion of the assembled unit cells in series due to the typical short-board effect. Most existing works studying on the flow distribution focus on small fuel cell stack and does not establish a clear relationship to performance, which are not able to thoroughly guide commercial-size PEMFC stack design and development. In the present study, an effective method combining computational fluid dynamics (CFD) model and empirical model is proposed to evaluate the performance of commercial-size stack considering air flow distribution in the manifold. Firstly, the air flow distribution in the manifold is predicted by a CFD model. A performance evaluation empirical model is developed by a series of experiments to evaluate the effects of flow maldistribution on the performance of PEMFC stack. Then, the predicted flow distribution and performance are respectively validated by a novel experimental setup. Finally, the effects of stack configuration, cell number, and current density on flow distribution and performance of PEMFC stacks are discussed. The results show that U-type configuration promotes more uniform voltage among unit cells than Z-type. The voltage unevenness of unit cells caused by flow maldistribution climbs dramatically as the cell number and current density increase. The methodology developed is beneficial to the energy management and the efficiency improvement of commercial-size PEMFC stack.