2 replies to this topic

[catia]

Hello everyone!

 

I'm simulating a heat exchanger in rigorous mode using real process conditions. I have values for inlet temperature for both process and utility, mass flow for both as well and inlet pressures for both. What I don't have is the process side mass fractions. 

 

Can I use the data fits function from aspen hysys to adjust the mass fractions of the process stream to match the conditions I have. If so, can you detail the "how to"? 

 

I have tried to do it but aspen always returns "possible false convergence" along with mass fractions that don't meet the other conditions I have.

 

Thanks in advance.

[Pilesar]

I've not used the data fits function so cannot help you there, but I offer this advice: first adjust the parameters so that the software provides a converged answer. This may mean making the heat exchanger twice its real size to begin or doubling the flow for the utility stream. Once you have a converged answer, move the parameters toward where you really want them by steps -- not all at once -- and get new convergences as you go. Maybe at some point in between you will see where the constraints are and can make adjustments. Note also that there is a difference between 'real process conditions' and 'measured process conditions'. If you are using 'measured process conditions' then there may be opportunity for legitimate data reconciliation to make the data set consistent with thermodynamic laws. Also, the AspenTech support team may be a useful resource. You can find how to contact them. What is the worst they would do if you asked them? Hearing a 'no, I won't help you' does you no harm. You asked for help here and we don't get paid to give you answers. If the support team knows the answer, they may give it to you if you ask them.

[shvet1]

Aspen's products family has definite problems with model convergence algorithms. My personal experience with those is not to rely on built-in features when deals with a non-converged sheet. Only careful manual iteration with saving file at each positive substep.

Edited by shvet1, 17 June 2024 - 11:53 PM.