PEM fuel cell: reversed flow at high current density
I am using Fluent with PEMFC add-on module to investigate the steady-state performance of a single serpentine channel-type flow field.
I had no problem running and obtaining a converged solution for high operating voltage (low current density) down to about 0.70V.
However, when I decreased the voltage down to 0.65V or 0.60V, I could get a converged solution (by this, I mean the point monitors, surface monitors, volume monitors all show unchanging solutions). However, the message REVERSED FLOW AT PRESSURE OUTLET keeps occurring.
When I examine the distribution of the current density, or oxygen, hydrogen on the catalyst surface... this confirms that there was another flow entering the domain from the OUTLET. This makes the results unrealistic according to the physics of PEM fuel cell, where the concentration of reactant gases must decrease along the channel (from inlet to outlet) due to the chemical reaction.
I have tried all possible solution to fix this; extending the outlet, changing VELOCITY INLET to MASS-FLOW-INLET, changing PRESSURE-OUTLET to OUTLET boundary conditions. The reversed flow still persists.
Any comment on this would be much appreciated. Thank you very much
I'm also working on this PEMFCs and almost the same thing has happened. In my case, the "reversed flow" massage is shown after a few iteration and the voltage is around 1-0.9 V
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