Problem in simulating Heterogeneous Reactor

[antoinetonee]

Hi all,

I'm currently facing a problem in simulating heterogeneous reactor with user-defined reaction kinetic expression. The reactor converts NO, CO, and H2O into NH3 and N2, hence it has two reactions (namely NTA_NH3 and NTA_N2, respectively). My intention is to parametrize the dimension and inlet flow rate of the reactor. Disclaimer: the pressure was expressed in kPa, hence it was divided by 1000.

As seen in the attached .fsd file, the simulation for the particular base case worked just fine. However, the parametrization didn't work at all. The main error is "NTA_N2: negative base in power", so I suppose there is something wrong with the rate expression of N2 formation, which I cannot find. What does this error message mean? And does anybody have an idea to solve this problem?

Thanks in advance.

[jasper]

[jasper]

Re-checking your expression, it does go to zero in case X[nitric oxide] goes to zero - it is the only term in the numerator.

The negative rate of nitric oxide however is within integration tolerance. Perhaps try the solution with max(0, ... ) to avoid the negative value.

[antoinetonee]

[jasper]

Works for me if I just change X("Nitric oxide") into max(0,X("Nitric oxide")) in both reaction terms (2x each).

[jasper]

that in fact makes all runs work:

Screenshot 2021-11-17 091411.png (166.89 KiB) Viewed 23911 times

[antoinetonee]

[jasper]

Glad to hear it.