Effects of U-type and Z-type configurations on proton exchange membrane fuel cell stack performances considering non-uniform flow distribution phenomena

To investigate the proton exchange membrane fuel cell stack performance heterogeneity, a pseudo two-dimensional stack model integrating non-uniform flow distributions is developed. The frictional and local pressure drop losses in stack manifolds as well as detailed transport processes inside every fuel cell are considered. After being validated against experimental data under different tested conditions, effects of U-type and Z-type configurations, manifold cross-sectional area, and fuel cell number on stack performances are investigated. It is observed that the cell voltage consistency of U-type stack is significantly better than that of Z-type stack. Besides, smaller manifold cross-sectional area is required for the U-type stack, which contributes to the decrease of overall stack geometric dimensions. As the manifold cross-sectional area increases, the uniformity of cell voltage and reactant distribution improve obviously in both configurations. Meanwhile, temperature differences between U-type and Z-type configurations are significantly reduced, which mainly results from improved reactant flow distributions and enhanced performance homogeneity. For large-scale commercial stacks, it is inferred that the voltage distribution follows a decrease-increase trend in the Z-type stack while it is likely to follow a decreasing trend in the U-type stack.