Aspen Plus simulation

[GERLASA]

Hallo!

I'm using Aspen Plus for a continuous simulation. I want to generate a mass balance, but when i try to calculate streams or components i always get the error message: Number of variables and equations are different.
Can anyone give me a hint, how to deal with this problem?

Thanks in advance.

 

[sshep]

Gerlasa,

This is probably something you could send to the hotline to see if they can reproduce your problem. One of the few things I think Aspentech does well is their hotline- even if they can't solve your problem, there are a few guys there who will at least try and find some workarounds.

I see that in Aspentechs knowledge base (

http://www.support.aspentech.com)

there are a few similar problems errors that were hotfixed previously (at least 13 hotfixes have been issued for AES12.1), for example:

"RadFrac reports that the number of equations is not equal to the number of variables when using a thermosyphon reboiler with a duty spec."

This also leads to another suggestion which is to start removing suspected offending blocks of the simulation in hopes of isolating the problem to a particular block, component, etc, especially if you can prove that another simulation report results properly. For example if you have a thermosyphon reboiler change it to a kettle. A thermosyphon reboiler is often better modeled to the side as a detail anyway.

Best wishes to solving your problem, sshep

 

[MortenA]

My guess (based on limited knowlede from HYSYS dynamics) is that your boundary vaules are incorrectly defined.

From HYSYS the problem usually was that when setting up your model in SS you could get away with defining the boundary values in ways that could not be solved in dynamic. Usually the problems would concern the definition of flow and pressure.

Best regards

Morten