A unified multi-physical-electrochemical and mechanical model for air-cooled proton exchange membrane fuel cells: Analysis of cell performance and stress-strain in membrane

Durability and structural integrity are paramount for scaling up air-cooled proton exchange membrane fuel cells (PEMFCs). Large temperature gradients and membrane dehydration in air-cooled PEMFCs expedite thermal and hygral stress-induced degradation, yet existing models often overlook the complete coupling of mechanical and electrochemical processes. This work presents a unified, three-dimensional, non-isothermal computational fluid dynamics (CFD) model coupling performance, stress, and strain for air-cooled PEMFCs. The model captures mass transport, electrochemical reactions, and membrane stresses in a single framework. The results indicate that localized hot regions and dehydration can elevate stresses near channel outlets, potentially speeding up membrane thinning and catalyst layer deterioration. Additionally, the distribution of hygral stress is notably lower than that of thermal stress. This phenomenon can be attributed to the elevated operating temperature and dry conditions in air-cooled PEMFCs. Analysis of the hygrothermal strain indicates a higher total strain beneath the channel compared to the land area, clearly showing that temperature gradients strongly influence hygrothermal strain distribution in air-cooled PEMFCs. Furthermore, decreasing current loading or raising inlet humidity helps reduce local dryness and heating, thereby reducing stress and improving reliability. Moreover, a key innovation of this work is the incorporation of a scalar-based mean stress formulation directly within the CFD framework, achieving full coupling of thermal, electrochemical, and mechanical interactions in a unified computational domain. This model not only predicts local performance and durability issues but also provides design-oriented insights for improving the structural integrity of air-cooled PEMFC systems.