Two-phase slug flow morphology and pressure-drop prediction in PEMFC channels: A validated VOF–Bezier curve modeling approach

Efficient energy conversion in proton exchange membrane fuel cells (PEMFCs) critically depends on effective water management, as slug flow formation within the flow channels can significantly impair performance and uniformity. In this study, a two-phase volume-of-fluid model for a PEMFC flow channel is developed and validated using visualization experiments. The effects of structural and operating parameters-such as channel surface contact angle, air velocity, and temperature-on slug morphology are systematically investigated. Results show that the surface contact angle exerts the most significant impact on slug length; as the contact angle varies from 50° to 130°, the relative change in slug length ranges from −62.6% to +48.8%. A cubic Bezier curve is proposed to characterize the slug detachment morphology profile, achieving a fitting accuracy exceeding 95%. On this basis, a new two-phase pressure-drop prediction model is developed, explicitly incorporating the slug morphology profile. The proposed model demonstrates superior predictive performance compared with the conventional Lockhart–Martinelli method, particularly when the two-phase multiplier exceeds 2.0. When the ratio of slug height to channel height is below 0.85, the prediction error remains within 22.5%. These findings provide critical insights into slug flow behavior and pressure drop in PEMFC channels, offering guidance for more efficient flow-field design and improved energy conversion performance.