8 replies to this topic

[patrizia86]

hi to everyone,
i'm tring to use hysys for unsteady state processes (batch distillation). i'm following university of florida tutorial http://hysys.che.ufl...tion/batch.html but when i turn from steady state to dynamic icon, the dynamic assistan tells me i've not specified initial conditions. but if you read the tutorial there are no instructions about this. can anyone help me please?

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[Zauberberg]

The Solver button is red (see the green/red "eye" in the window bar), which means that Hysys doesn't have initial values to start with. Press the green Solver button and if there are any other inconsistencies in the Steady State mode, resolve them before you can proceed to Dynamics mode.

[patrizia86]

hi zauerberg, ty for your answer.
my problem is that i don't know where i have to insert initial conditions.
i'm dealing with a batch distillation, so i've put the heat given by reboiler and the initial volume of the mixture in the reboiler and i don't understand which other initial conditions are required
btw i've done as you told me (make changes) but i can't understand which type of changes this causes in my simulation.
pressing "make changes" could compromise the simulation?

[Zauberberg]

You have moved from The Netherlands to Italy in a few hours?

We don't know what is your input data, and what Hysys needs to have resolved before proceeding to Dynamics mode. All I can say from this perspective, is that all your boundary streams have to be fully defined (pressure) and that there should be well defined pressure-flow correlation for the control valves (preliminary sizing). You can let Hysys fix those missing links automatically and see what happens next.

If you are new to the Dynamic simulation field, I would suggest you to get some training first, and definitely read Hysys tutorials on the subject.

[patrizia86]

i'm from italy so as soon as i realised that according to my profile i was from nederlands i wrote the correct country
i'm trying to do some training with this site http://hysys.che.ufl...tion/batch.html 'cause my teacher hasn't given me yet the licence code so i cannot yet download hysys official guide
but i'm very confused about dynamics
can you suggest me any guide?

[Zauberberg]

Try this link from the University of Alberta: http://www.ualberta....micModeling.pdf

[patrizia86]

ty for the link
now i have to size valves; hysys needs initial mass flow to determine the "Cg" of the valve but in batch distillation initial mass flows are 0. how can i solve this problem?

[patrizia86]

i've put a default value for Cv = 60 as the flows are liquid. is it right?

[Zauberberg]

Depends on the flow, and the available pressure drop across the control valve. If you are not familiar with control valve sizing, please refer to some of the manuals/guidelines available online:

http://www.warrencon...g_reference.pdf
http://www.documenta.../book/cvh99.pdf