Ansys Chemkin: Issue of using sample “Multiphase psr urea decomposition”

[fumi.tbf]

I am writing to inquire about the calculation results of the sample project "multiphase_psr__urea_decomposition.ckprj" in Ansys Chemkin 2025 R1.

I recently ran this sample project to verify the results with no changes.
However, when I output the weight history for each chemical species by culculated mole fractions,
the trends did not match the reference graph (Figure 3.15, Section 3.4. Three-phase Processes: Urea Decomposition, website manual).
Especially, the mole fractions of Urea(s) and Urea(l) (at time =0.0) were different from initial conditions. I believe the mole fraction of Urea(s) needs to be around 1.0 at time = 0.0.
Below is the result of my calculation test.

 

Interestingly, the history of the total weight (the sum of the liquid and solid phases) perfectly matched the reference graph (Figure 3.14).
Could you please advise on what might be causing this discrepancy where the total mass aligns, but the individual species weight histories differ from the reference?

[cooperj]

Hi:

I’m seeing the same thing. 

The plot in the reference graph is showing Mass vs.Temperature and not mole fraction or mass fraction, however. Converting each specie to mass will completely change the shapes of the curves.

When I plot the total bulk moles of urea(l) and urea (g), which should follow the same trend as mass, I get curve shapes that match the plot a lot better:

…

… but the numerical values are obviously different.

Regards,

Judy

 

 

 

 

 

 

[fumi.tbf]

Hi Judy. Thank you for your reply.
The graph which you gave might be a clue to solve this problem.
I guess "total_bulk_moles_ureaLiquid" and "total_bulk_moles_urea_s" refer to molar amout of liquid phase and solid phase, respectively. (Liquid phase: the sum of urea(l), HCNO(l), and biu(l))
Then, I checked the .out file and found A_urea(l), A_urea(s).... they are the mole fractions in each phase.
I culculated the mass of each species, and I got this graph.

But there's one point of concern... The initial Mass was set at 100 mg, the manual seys 50 mg, though.
We have to change this parameter, probably.

Fumi

[cooperj]

Hi Fumi:

Yes you are right; I suspect the instructions are out-of-date, since they mention release 2022.  I will submit this as a documentation defect.  Thank you for sharing these results!

Regards,

Judy

[fumi.tbf]

Hi Judy,Thank you for reporting it!
I really appreciate your help until now.

Regards, 
Fumi