Study on the heat and mass transfer mechanisms of liquid-cooled PEMFC stacks based on non-isothermal model.

• A 5-cell stack model coupling electrochemistry and manifold configuration has been constructed. • Effects of manifold configuration and cooling intensity on PEMFC stack internal heat and mass transfer mechanisms is revealed. • The U-type configuration and increasing coolant velocity can effectively enhance stack performance and consistency. • Adequate cooling effectively improves temperature consistency but exacerbates concentration polarization. The heat transfer and mass transfer mechanisms in proton exchange membrane fuel cell (PEMFC) stacks are crucial for ensuring performance, consistency, and safety. A three-dimensional PEMFC 5-cell stack simulation model with cooling flow fields is developed to observation of the internal heat and mass transfer characteristics of the stack. This contributes to understanding the impact of the cooling flow field on performance. Results highlight the significant impact of coolant velocity on heat and mass transfer performance, adequate cooling effectively improves temperature consistency but exacerbates concentration polarization. Additionally, manifold configurations exhibit distinct effects. The U-type configuration not only exhibits superior single-cell consistency but also improves temperature uniformity under adequate cooling. At a current density of 3.6 A cm−2 and with adequate cooling, the Z-type configuration exhibits a maximum voltage difference of 117.52 mV, while the U-type configuration only exhibits 38.12 mV, indicating a difference exceeding 300 %. At high current densities, significant dead zones are present near the outlet side of each cell's flow field, where the oxygen molar fraction is nearly zero, which is a primary cause of concentration polarization. Under the Z-type configuration, the maximum difference in oxygen molar concentration among single cells reached 72 %. For stacks operating at high current densities, employing the U-type configuration and increasing coolant velocity can effectively enhance stack performance and consistency. [ABSTRACT FROM AUTHOR]