Theoretical analysis on cold start process of proton exchange membrane fuel cell with different flow fields based on the coupling of redox reaction and dynamic response of porous materials. (1st February 2022) - Pan, Chengjie
Highlights: Developed three kinds of fuel cell models for simulating cold start process. The relationship between ice content and stress expansion is investigated. Proposed the homomorphic volume comparison method to analyze the cold start. Explained the macroscopic phenomena of cold start by micro response. Abstract: The species transport, electrochemical reaction, and the mechanical stress caused by water phase-change within the proton exchange membrane fuel cell have combined effect on the cold start performance. It is necessary to investigate the cold start process of the fuel cells with different flow fields, aiming to provide theoretical basis for improving cold start performance. Based on the cathode side models of fuel cells with single-channeled straight flow field, single-channeled serpentine flow field, and triple-channeled serpentine flow field at −20 °C, the electrochemical reaction and dynamic response in these fuel cells are considered to study the failed cold-start process in this paper. Then the homomorphic volume comparison method is used to analyze the cold start process of the fuel cells with different flow fields. It is found that when the average volume fraction of ice within the porous layer reaches 0.13, the maximal ice content of the porous layer is 0.493 under the inlet of the fuel cell with the single-serpentine channel, which causes the minimal stress acting on the porous layer among the three flow fields. However, the structure of the single-channeled serpentine flow field increases the pressure loss during the species transport, and the pressure drop in the flow field exceeds 347 Pa. Thus, although the single-channeled serpentine flow field has the best start-up performance among the three flow fields, the distance between the inlet and outlet of the channel can be reduced by increasing the number of channels to decrease the additional power during the cold start.