Product water in NT-PEM fuel cells is formed in the cathode catalyst layer between the membrane and the gas diffusion layer (GDL); depending on operating conditions, most of it condenses within the GDL—preferably at the coolest point beneath the ribs—and must be directed through the GDL into the gas channels and transported out of the cell from there.

If excessive accumulations of liquid water occur in the cell, gas transport is restricted and cell losses increase, which also leads to a reduction in service life. In this collaborative project between the Chair of Fluid Mechanics (LSM) and the Center for Fuel Cell Technology (ZBT), the transport of liquid water in GDLs and flow channels (and specifically their interaction) in NTPEM fuel cells using flow measurements and high-resolution two-phase simulations (LSM), and to use this data to develop a simplified simulation method as well as flowfield designs for improved water transport (ZBT).

Compared to the current state of the art, this study specifically examines the influence of parallel channels and their fluid-dynamic interaction caused by the GDL, for example, in the case of local pressure differences. Since the liquid water balance is one of the most physically complex phenomena and cannot yet be easily captured using measurement or simulation methods, various measurement techniques (ex-situ flow measurements, in-situ EIS and polarization measurements) as well as simulation methods (high-resolution VoF-CFD flow simulation, macrohomogeneous multiphysics 3D-CFD, pore network model with analytical channel modeling) will be employed and further developed, and their partial results will be synthesized into a consistent overall picture. In addition to the fundamental insights gained regarding two-phase transport in the coupled domains (channels + GDL), the computationally efficient simulation model and the design studies and concepts for flow fields with improved liquid water transport are of particular relevance to SMEs. 

The project (01IF23927N) of the IUTA e.V. research association is funded by the Federal Ministry for Economic Affairs and Energy as part of the Program for the Promotion of Joint Industrial Research (IGF), based on a resolution of the German Bundestag.