Potential/Electrochemistry model – continuity equation diverges

- March 6, 2024 at 3:31 pm
  
  void crow
  Subscriber
  
  I am attempting to simulate a simple PEMEC cell using the Potential/Electrochemistry model which comes built-in in Ansys Fluent 2023 versions (not sure about the older versions). I set up the regions as required by the model and maintained the default values and materials. I am unable to achieve convergence when the Butler-Volmer reaction rate is used (this is the checkbox option 'Butler-Volmer rate'), the solution quickly diverges (within 10 iterations) because of the increasing residuals of the continuity equation, and also there seems to be some regions of extreme temperatures (prior to diverging altogether there are some messages about limiting the temperature to 1.0 K or 5000 K in some of the cells). I can only get to lower residuals when the option is disabled (which uses the Tafel approximation).
  Has anyone ever been able to successfully use this module? I found some research papers on modeling electrolyzers in Fluent but researchers end up using UDFs instead of the built-in module (possibly because it did not exist at the time, not sure).
- March 20, 2024 at 5:30 am
  
  John Ibrahim
  Ansys Employee
  
  Hello,
  Try to reduce the under relaxation for the potential to 0.1 or 0.05. This may help. Also use peudo transient solver with time scale factor of 0.1 Also make sure you have a good mesh quality and there is no jump at the interfaces. Make sure you use option 9 when activating the PEMFC as compared to option 3 (for old releases).
  Best,
  John