Can't Solve Liquid Water in PEM.

Looby219 · August 16, 2020, 00:34

I am trying to use the new PEM module with better water transport, but my UDS-2 (cap. pressure) and UDS-4 (liquid water) won't converge. UDS-2 jumps to 1e+10 or so and stays there, while UDS-4 stays stagnant. EVERY OTHER residual falls. The contour results for capillary pressure and liquid water are seemingly random with extreme values. My mesh follows every Ansys recommendation, and I have tried under-relaxation in the model panel. I have set UDS-4 to 0 at inlets. I have the stoichiometry right. What is happening and why won't this work!? Do I need to do something special because I have a non conformal mesh interface at the middle of the electrolyte? My flow field geometry is certainly unique (you can see it in the mesh), could that be causing a failure?

Edit: Also the domain is only 5mm x 5mm, does this cause an issue?

cfd kullanıcısı · December 30, 2020, 12:14

I also have a problem about pemfc. How can I ask questions, can you help?

Looby219 · December 30, 2020, 12:35

In my case the issue was a combination of inlet stoichiometry and not starting from a higher voltage. Start at 0.9V, let it converge, decrease by 0.1V to 0.8V, let it converge, etc. Be aware the UDS for capillary pressure and water won't converge until water is present at lower voltages, and those UDS may be very high or fluctuating, but it is OK.

cfd kullanıcısı · December 31, 2020, 06:51

Hi,

I'm new to the forum, I'm writing from here because I don't know how to open a new topic. I am a senior university student. I'm finishing project on pem fuel cells. For this I am trying to analyze in fluent pemfc module. I want to create I-V curves as a result of the analysis, but I could not find where the generated current density is in the fluent. Or if it is a calculated value, I have no idea how it is calculated. For this, if the current density is a value that can be read in fluent, if it is a value calculated from where it is read, can you help me calculate how?
If so, can you also send a sample study?
Thank you in advance for your help.

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December 30, 2020, 12:14		#2
cfd kullanıcısı New Member isimsiz Join Date: Dec 2020 Posts: 8 Rep Power: 5	I also have a problem about pemfc. How can I ask questions, can you help?

December 30, 2020, 12:35		#3
Looby219 New Member Rob Join Date: Jul 2020 Posts: 4 Rep Power: 5	In my case the issue was a combination of inlet stoichiometry and not starting from a higher voltage. Start at 0.9V, let it converge, decrease by 0.1V to 0.8V, let it converge, etc. Be aware the UDS for capillary pressure and water won't converge until water is present at lower voltages, and those UDS may be very high or fluctuating, but it is OK.

December 31, 2020, 06:51		#4
cfd kullanıcısı New Member isimsiz Join Date: Dec 2020 Posts: 8 Rep Power: 5	Hi, I'm new to the forum, I'm writing from here because I don't know how to open a new topic. I am a senior university student. I'm finishing project on pem fuel cells. For this I am trying to analyze in fluent pemfc module. I want to create I-V curves as a result of the analysis, but I could not find where the generated current density is in the fluent. Or if it is a calculated value, I have no idea how it is calculated. For this, if the current density is a value that can be read in fluent, if it is a value calculated from where it is read, can you help me calculate how? If so, can you also send a sample study? Thank you in advance for your help.