Learning Forum

[fth987]

Hi,

What is the role of under-relaxation parameters in fuel cell modeling and what are the optimum values of these parameters in fuel cell modeling?

[vinaraya]

Hi,

There are two set of URF's (one within the PEMFC module for Source terms) and one under Controls panel (for transport equations). May i know on which set of URF's is your question addressed to.

The objective of URF's is to steer the solution to stable results when convergence is challenging. In Fuel cell modelling, the default URF's can be used to start with and should work well for low power operations (ie. low current density), it could become challenging when we migrate to higher current density conditions. In such cases, we can reduce the source term URF's by half from default.

It is highly recommended to keep the UDS, Species and Energy transport equation URF to 1 (though could be under relaxed in the beginning of simulation, but should be eventually pushed to 1 URF).

Thanks,

 

[fth987]

Thank you very much for the answer. Why should the URF be increased back to 1?

[vinaraya]

It is the best practice to be followed.