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Solution not converging!! Please help!!

Posted Jul 17, 2017, 4:42 p.m. EDT Chemical Reaction Engineering, Modeling Tools & Definitions, Parameters, Variables, & Functions, Studies & Solvers 2 Replies

Saurabh Sharma
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Hi all,

I am trying to build a model for gas absorption in liquid falling film. I have tried to solve it many times but the solution doesn't converge and COMSOL says " maximum number of iteration reached". I tried increasing the number of iterations as well but it didn't help. I will be thankful if someone can help me out with this.

Best,
Saurabh

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2 Replies Last Post Jul 17, 2017, 8:55 p.m. EDT
Kyle Minor
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Posted: 7 years ago Jul 17, 2017, 6:35 p.m. EDT
You need to go back through your model. There are a number of mistakes, it's not set up properly. Your mass transfer flux equations have inconsistent units, you have both a reaction (which is really your flux) through one domain, and then you have the flux boundaries. You should get rid of the reaction term and go back and fix your mass transfer flux equations.

Also, you have all your parameters in defined as variables.
You need to go back through your model. There are a number of mistakes, it's not set up properly. Your mass transfer flux equations have inconsistent units, you have both a reaction (which is really your flux) through one domain, and then you have the flux boundaries. You should get rid of the reaction term and go back and fix your mass transfer flux equations. Also, you have all your parameters in defined as variables.
Saurabh Sharma
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Posted: 7 years ago Jul 17, 2017, 8:55 p.m. EDT
Hi Kyle,

First of all, I would like to thank you for replying. I appreciate your efforts. I have tried solving the model and it works when I write c1 as some constant in the reaction rate term for c13. This means that issue is not with defining parameters or inconsistent units. Also, there is reaction involved in the system. The gas will first dissolve in the liquid and then react. The concentration in the liquid will be given by Henry's law.

I would appreciate if you could point out some mistake in solving. Also, I tried solving time dependent study and it works!!

Best
Saurabh






You need to go back through your model. There are a number of mistakes, it's not set up properly. Your mass transfer flux equations have inconsistent units, you have both a reaction (which is really your flux) through one domain, and then you have the flux boundaries. You should get rid of the reaction term and go back and fix your mass transfer flux equations.

Also, you have all your parameters in defined as variables.


Hi Kyle, First of all, I would like to thank you for replying. I appreciate your efforts. I have tried solving the model and it works when I write c1 as some constant in the reaction rate term for c13. This means that issue is not with defining parameters or inconsistent units. Also, there is reaction involved in the system. The gas will first dissolve in the liquid and then react. The concentration in the liquid will be given by Henry's law. I would appreciate if you could point out some mistake in solving. Also, I tried solving time dependent study and it works!! Best Saurabh [QUOTE] You need to go back through your model. There are a number of mistakes, it's not set up properly. Your mass transfer flux equations have inconsistent units, you have both a reaction (which is really your flux) through one domain, and then you have the flux boundaries. You should get rid of the reaction term and go back and fix your mass transfer flux equations. Also, you have all your parameters in defined as variables. [/QUOTE]

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