CAPE-OPEN

Hi all,

I'm encountering a persistent problem in the simulation of heterogeneous reaction in PFR. The simulation file is attached. Similar to that in a , I put max(0,X("component name")) to avoid the value in question from getting below zero. Instead, the simulation gives error message as follows:

Unit "PFR_NTA": calculate failed for unit PFR_NTA: Failed to obtain reactionRate for reaction NTA_N2: Failed to calculate reactionRate: CalcReactionProps failed using property package NTA_NH3: Failed to obtain fraction for phase Vapor: no values set for fraction, phase Vapor

What's wrong with my simulation? Why does all the sudden it failed to calculate the fraction (the reactions are entirely in vapor phase, so I suppose this error shouldn't be there in the first place)? Thanks in advance.

You can see the reason if you calculate the unit (which fails) and go to the Profiles report:

Screenshot 2022-11-01 103957.jpg (156.55 KiB) Viewed 11878 times

Your integration fails and pushes values to NaN, which is CAPE-OPEN-ese for numbers are not available. At first glance, I suspect your problem is 0^-0.5 for X["Carbon monoxide"] dropping to zero. Zero to the power of a positive number is defined, but zero to the power of a negative number is not.

Apologies for the very late response. Thanks for the answer, I've also found and fixed the faulty rate equation.