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## Undefined value found

Posted Sep 18, 2023, 7:05 a.m. EDT Chemical Reaction Engineering, Results & Visualization, Studies & Solvers Version 6.1 0 Replies

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I am trying to model a reaction in a triangular duct reactor. The only reaction is CO2 methanation and phase is gas. The reaction rate part I selected user defined and the rate equation is a function of temperature and partial pressure.

I first used space dimension (0D) and Physics (reaction engineering), and study was time dependent or stationary plug flow. I could get the results of the changes of molar flow rate and temperature along the time or reactor volume.

But when I tried to generate space-dependent model, I set all parameters and values and I used stationary study to run the model, but I had the error:

Concentrations Undefined value found. - Detail: Undefined value found in the stiffness matrix. There are 3759 equations giving NaN/Inf in the matrix rows for the variable comp2.cCH4. at coordinates: (0.04,0,0.348899), (0.0388536,0.00198571,0.347577), (0.0377071,0,0.347577), (0.0377071,0,0.35022), (0.04,0,0.351542), ...

There are 3759 equations giving NaN/Inf in the matrix rows for the variable comp2.cCO2. at coordinates: (0.04,0,0.348899), (0.0388536,0.00198571,0.347577), (0.0377071,0,0.347577), (0.0377071,0,0.35022), (0.04,0,0.351542), ...

There are 3759 equations giving NaN/Inf in the matrix rows for the variable comp2.cH2. at coordinates: (0.04,0,0.348899), (0.0388536,0.00198571,0.347577), (0.0377071,0,0.347577), (0.0377071,0,0.35022), (0.04,0,0.351542), ...

There are 3759 equations giving NaN/Inf in the matrix rows for the variable comp2.cH2O. at coordinates: (0.04,0,0.348899), (0.0388536,0.00198571,0.347577), (0.0377071,0,0.347577), (0.0377071,0,0.35022), (0.04,0,0.351542), ...

There are 3759 degrees of freedom giving NaN/Inf in the matrix columns for the variable comp2.cCH4. at coordinates: (0.04,0,0.348899), (0.0388536,0.00198571,0.347577), (0.0377071,0,0.347577), (0.0377071,0,0.35022), (0.04,0,0.351542), ...

There are 3759 degrees of freedom giving NaN/Inf in the matrix columns for the variable comp2.cCO2. at coordinates: (0.04,0,0.348899), (0.0388536,0.00198571,0.347577), (0.0377071,0,0.347577), (0.0377071,0,0.35022), (0.04,0,0.351542), ...

There are 3759 degrees of freedom giving NaN/Inf in the matrix columns for the variable comp2.cH2. at coordinates: (0.04,0,0.348899), (0.0388536,0.00198571,0.347577), (0.0377071,0,0.347577), (0.0377071,0,0.35022), (0.04,0,0.351542), ...

There are 3759 degrees of freedom giving NaN/Inf in the matrix columns for the variable comp2.cH2O. at coordinates: (0.04,0,0.348899), (0.0388536,0.00198571,0.347577), (0.0377071,0,0.347577), (0.0377071,0,0.35022), (0.04,0,0.351542), ...

Please could I ask, what was wrong with my simulation? I tried to use some simple rate equations for reaction rate before and I could get the results where I could clearly find the temperature and concentration distribution in my reactor model. So is there anything wrong with the reaction rate equation?

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Hello Yuang Zhang

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