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Issues with the PEM fuel cell module

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Old   March 8, 2024, 14:00
Default Issues with the PEM fuel cell module
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Hello. I am trying to get running a PEMFC simulation (very simple geometry, essentially several layers of rectangular prisms, with one flow channel on each side) using the PEM cell add-on module. I am trying to follow the tutorial I found (https://www.youtube.com/watch?v=HX9a5uijvF0) using the same operating and boundary conditions:
  • 353 K inlet temperature
  • 3e-7 kg/s mass-inlet BC at the anode (mass fractions 0.6 H2, 0.4 H2O)
  • 2e-7 kg/s mass-inlet BC at the cathode (0.21 O2, 0.15 H2O)
  • No slip boundary conditions for walls
  • 0 V applied at the anode tab and 0.65 V at the cathode tab
I assigned the parts of the geometry accordingly with the exception of the microporous layer (like in the video, I get a warning message about missing microporous layer). I also made two types of mesh, one more refined and another that is coarser, and both are conformal meshes.

I initialize the solution with the hybrid method and I get the following message: "Warning: It is highly likely that the Anode GDL/CAT are not assigned correctly!" (even though it is assigned in the PEM fuel cell model panel). When I start the solution, it diverges within 3 iterations with the error "Divergence detected in AMG solver: temperature. Error: floating point exception". I disabled the energy equation, and restarted initialization and it also diverges: "Divergence detected in AMG solver: uds-3" (uds-3 is water content). I disabled the water content equation. Only then the solution converges, but I end up with essentially 0 current density magnitude in the anode and cathode tabs.

I did not change any of the source defaults in cell zones. But I noticed that in the video there are more sources (udf :: pemfc) being activated for each zone in the version of Ansys that the individual is using. I attached a screenshot from the video of the sources being defined in the anode flow channel to contrast with the ones that are active by default when I enable the model (on the right). I am using the 2023 R2 version. I tried using a finer mesh and the outcome is the same.



I don't understand how this person was able to get the model to converge with everything enabled. I tried following everything exactly, including replicating the geometry. But the geometry won't be identical since I don't have the dimensions of the cell he used, and also Fluent creates several walls and shadow-walls when I import the .msh file. Any help is appreciated.
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Old   March 16, 2024, 01:10
Default Same issue here!!!
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Hello, I also followed the same tutorial and had the same issues. Warning and Floating point exception. I didn't know what to do. I use 2024 R1 Student version. Did you find a solution? If, could you please let me know.
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Old   March 16, 2024, 05:48
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Quote:
Originally Posted by hk0 View Post
Hello, I also followed the same tutorial and had the same issues. Warning and Floating point exception. I didn't know what to do. I use 2024 R1 Student version. Did you find a solution? If, could you please let me know.

My goal was actually to end up simulating a PEM electrolysis cell and I was following the tutorial because the modules are quite similar, but at last I got it to work (the PEM electrolysis cell that is) by adding the porous jump (electrode contact resistance) that the video refers to (I skipped it at first because I thought it was optional). Still getting very odd results though.
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Old   March 16, 2024, 06:31
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Actually i skipped the porous jump layer step too! But I had micro porous layers in my geometry and i set up the case accordingly. Now I'll try including porous layer.
Also, May I know which version of software do you use? cuz I found a comment on youtube stating student version doesn't have few package in PEMFC and that's problem, something like that.

Thanks for the response
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Old   March 16, 2024, 08:43
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Quote:
Originally Posted by hk0 View Post
Actually i skipped the porous jump layer step too! But I had micro porous layers in my geometry and i set up the case accordingly. Now I'll try including porous layer.
Also, May I know which version of software do you use? cuz I found a comment on youtube stating student version doesn't have few package in PEMFC and that's problem, something like that.

Thanks for the response

The version I am using is the Student 2023 R2 version. I haven't found any evidence that the student version doesn't come with the full PEMFC module. However, it is hard to tell because of the black box nature of the software, and comparing the video and the current version there are definitively differences (in the source terms, like I pointed out).
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