ODE45 is not producing an output

When I run 'gebcat' (which uses 'greact'), matlab stays busy for seemingly ages and never produces a result. It also does not produce an error so I am unsure where the problem is. Would someone be able to help here?

Answer 1

[Maneet Goyal]

It seems that you are working with a stiff system. In chemical engineering context, it means that very fast dynamics are coupled with very slow dynamics. For example, in a reaction, Temperature and Concentration may not change at a comparable rate. Generally, the rate of change of temperature is very low compared to that of composition or concentration.

So consider using 'ode15s' instead of 'ode45'.

I tried and it worked. However, there are a few other errors in your code. They may be minor ones.

Can you please upload the corrected code once you are done? I am somewhat interested in such models.

Best Wishes

[George Warburton]

Hi, Thanks for taking a look for me. I am indeed dealing with a Chemical Engineering problem. I have changed to the ode and am now getting a result. However I am still getting an error in one of the 'plot''s. could you work this out ? (error in Plot in line 71 but it might stem from the (3,3,7) in line 69. I have again attached my programs. Thank you

[George Warburton]

Worked out my problem with the line I described above. I have attached the newest version of the programs. I am somewhat puzzled as to why the reaction seems to happen so quickly. Have you any ideas as to what part of my model is causing this?

[Maneet Goyal]

Hi! I again went through the code but without the problem statement it will be hard for me analyze the system properly. So can you please upload the same?

Secondly, try to figure out why are you getting complex numbers as your outputs. I think this should not happen. Another thing you can do is: check the consistency of the units of all the process parameters and variables. The units should be consistent.

[George Warburton]

http://uk.mathworks.com/matlabcentral/answers/278824-can-someone-model-a-reactor-for-me-all-data-is-provided-i-m-desperate

Maneet Goyal could you take a look at this for me?

Answer 2

[George Warburton]

http://uk.mathworks.com/matlabcentral/answers/278824-can-someone-model-a-reactor-for-me-all-data-is-provided-i-m-desperate

Maneet Goyal could you take a look at this for me?