Entwicklung neuer Simulationsmethoden zur Untersuchung des Wasserhaushalts in Brennstoffzellen-Gasdiffusionslagen
Auch gedruckt in der BibliothekW: W-H 13.772
FakultätFakultät für Naturwissenschaften
Ressourcen- / MedientypDissertation, Text
Datum der Freischaltung2014-09-15
Due to their high energy conversion efficiency, fuel cells offer a perspective to encounter the challenges regarding sustainable energy supply and mobility of the future. Water management is one of the key topics for further development of polymer electrolyte membrane fuel cells to ensure optimal cell operation and a long life time. For this purpose, not only the operating conditions chosen and the cell design are important, but also the interactions of the components and the respective materials. In the present work, the influence of both different material parameters and operating conditions of the fuel cell on the water distribution resulting within the porous structure of the gas diffusion layer (GDL) are studied using various modelling approaches that are novel for this application. The models developed in the framework of this thesis are Monte Carlo (MC) models working on the µm-scale which allow for the incorporation of interactions between water and the respective materials based on surface energy values. The simulation results show that both the distribution and the size of the GDL pores and their wetting probabilities have a great influence on the amount of water resulting and its distribution inside the GDL. Furthermore, the choice of the external operating parameters of the fuel cell like pressure, temperature and relative humidity also plays an important role. The results of the respective models have been verified by comparing them to other simulation results or experimental visualization data. It could be demonstrated that a so-called threshold value for the ratio of hydrophilic pores inside the GDL exists beyond which almost the complete pore space is blocked by liquid water which may constrain the gas flow through the GDL. Beyond the examination of stationary water distributions, a kinetic modelling approach was developed to examine time-dependent processes using the MC method.
Monte Carlo method
Proton exchange membrane fuel cells