Professionally I work at BPT and focus on creating value adding App for Process Simulation. You can find more info on those on the BPT website. Below are posts that should help HYSYS, PetroSIM and UNISIM users alike in their day to day challenges to produce accurate yet fast models efficiently.

Saturday, 28 February 2015

Did you know series: Defer execution of time consuming utilities like a phase envelope to the very end of the solve

A utility like a phase envelope takes a long time to solve, relatively speaking. We are talking here of something like 1 second, some envelopes, especially if they have the hydrate curve as well may take significantly more time. If your model only does a single calculation pass, one second wouldn't register as something that slows down your model. But, if the stream the phase envelope is attached to is located inside one or more loops, the situation is different. The model could easily calculate that stream 25 times and it will recalculate the phase envelope 25 times. So, the model solve will take 25 seconds, just for the phase envelope.

In most models, there is no need for that phase envelope to solve every time the stream solves, you only need that result for the final stream composition. Fortunately you can tell the simulator that is the case. You change the calculation level to a high number.

However, most people don't know about these and for utilities they are fairly hidden. Here is how to change them:
Go to the workbook and use the menu or ribbon bar to access the setup
On the left in the view, click Add and add a page for utility objects (no need to select a specific type). Then move to the right in the. View and Add there to add more variables, the calculation level (Calc level) should show up in the list. Select that, add it and close the view(s). You'll see the default value is 501, increase that to 1e6 or so for each utility you only need at the end.

Now your model should solve a lot faster. Remember that this works for any utility.

Saturday, 21 February 2015

Did You Know Series: Manipulating flows in dynamics

It is common practice when building a dynamic model to only model a single train if two or more identical parallel trains exist in a facility.  The one hurdle to take is to change the flow to a fraction or multiple of the flow at a number of points in the simulation. To my surprise I recently received a HYSYS case that was using an extension called "multipop" that I created 15 years ago for this purpose. You can still get it on the Aspentech support site.

So here is the "Did you know?": There has been a built-in way to do this in HYSYS and most probably UNISIM for quite while. You can use a Mixer operation, just give it one inlet and one outlet, then go to the Dynamics tab and you'll find a "Product Molar Flow Factor" that works just like the extension operation. I am all for extensions, but not if the capability is built-in.


Screenshot in HYSYS V8.3


Note that this multiplier option only works in dynamics!

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