A system-level multicell cluster model with manifold-induced flow distribution for performance evaluation of PEMFC stacks

Air maldistribution in proton exchange membrane fuel cell (PEMFC) stacks degrades both steady-state performance and transient stability. However, existing models either resolve internal flow distribution without system-level integration or capture balance-of-plant (BOP) operation without spatial resolution. In this study, a one-dimensional PEMFC system model is extended with a multicell cluster stack model and a quasi-steady manifold representation capturing branch-flow maldistribution induced by pressure recovery and pressure drop. Component submodels are experimentally validated, while stack predictions are benchmarked against an experimentally validated high-fidelity model. The framework compares U-type and Z-type stack configurations under BOP-integrated transient operation. Under identical air supply conditions, the reinforcing pressure gradients in the Z-type configuration produce a maximum absolute airflow deviation from the mean of 95.02%, compared with 45.80% in the U-type configuration. At 1.5 A/cm 2 , the steady-state voltage distribution becomes nonmonotonic in both configurations: membrane dehydration in high-flow clusters increases ohmic resistance beyond the benefit of excess oxygen supply, while oxygen starvation degrades low-flow clusters. During load transients, compressor delays interact with flow maldistribution to amplify transient voltage drops, with the maximum absolute deviation of the minimum transient voltage from the mean reaching 9.9% in the Z-type configuration but only 2.0% in the U-type configuration. Nonuniform heat generation, combined with coolant maldistribution arising from the same manifold geometry, causes Z-type cluster temperatures to exceed the coolant outlet setpoint by 3.5 K, whereas the U-type remains within 1.5 K. These results highlight the coupled effects of BOP operation and flow maldistribution on PEMFC performance.