Quantitative Evaluation of Spatial Fluctuations in PEMFCs for Optimal Operating Conditions Using Coefficient of Variation Analysis

Spatial non‐uniformity in current density, temperature, and reactant distribution can promote hotspot formation, membrane dehydration, excess water accumulation, and performance degradation in proton exchange membrane fuel cells (PEMFCs). This study quantitatively evaluates spatial fluctuation in a PEMFC and identifies a practical operating condition that maintains high output while reducing internal instability. A 3D numerical model of a single cell with a commercial serpentine‐parallel flow field was developed. Five hydrogen flow rates (3.2–16 LPM), five oxygen flow rates (10.6–53 LPM), and cell voltages from 1.0 to 0.4 V were examined. Electrochemical reactions were modeled using the Butler–Volmer equation and Nernst potential, and spatial uniformity was quantified using the coefficient of variation (CV) over seven planes along the flow direction. Increasing the inlet flow rate improved reactant supply and mitigated concentration loss, but the performance gain saturated at high flow rates; the maximum power density difference between Cases 4 and 5 was only 2.08%. At 0.7 V, Cases 4 and 5 yielded mean current densities of 0.855 and 0.850 A/cm ² with CV values of 0.060 and 0.042, respectively. Considering the additional reactant supply required for Case 5, Case 4 at 0.7 V was identified as the more practical stable operating condition.