Extracting model parameters and paradigms from neutron imaging of dead-ended anode operation

In a PEMFC, feeding dry hydrogen into a dead-ended anode (DEA) which is infrequently purged to remove the accumulated water and inert gas, reduces the overall system cost, weight and volume due to reduced need for a hydrogen-grade humidification and recirculation subsystems. Although the DEA method of operation might be undesirable due to its associated high spatial variability it provides a unique perspective on the evolution of the water accumulation in the anode. Sections of the channel nearest the inlets are significantly drier than those nearest the outlet as shown in the neutron imaging of a 53 cm2 PEMFC. Utilizing gravity in the orientation of the fuel cell it is possible to see distinct patterns of water fronts moving through the GDL, causing flooded channels, which consequently cause additional flooding inside the GDL in an upward direction, against gravity and H2 supply, through the GDL/channel boundary conditions. A similar modeling paradigm of moving water fronts was first used by [1], but it is fully justified and elucidated here via neutron imaging data for the first time. This modeling paradigm will be used in the future to develop a 1+1 D model. In this paper we also utilize neutron imaging of the liquid water distributions to (a) identify a range of numerical values for the immobile saturation limit, (b) propose a gravity-driven liquid flow in the channels, and (c) derive the two-phase GDL boundary conditions associated with the presence of liquid water in the channel.