6 replies to this topic

[J_Leo]

Hello,

 

I found that Unisim Stream Reporter cannot extract true critical temperature and pressure directly from simulation. I have to attach the utility to each stream and use Design Browser to extract them. It is very tedious because there are many streams and many cases for the H&MB.

 

Anybody have used a better way to extract Ture Tc nd Pc from the simulation?

 

Thank you very much.

 

Regards,

Leo

[Bobby Strain]

Use the utility provided as you have suggested. It's the only thing that gives critical temperature and pressure (I think). I don't know if versions later than HYSYS 2.4 do things differently. And, why can you possibly need Tc and Pc for every stream? You really only need true Pc for boiling heat transfer coefficients . And it is only needed at pressures near the critical pressure. Otherwise the pseudo values are sufficient to use with correlations. But, if you want them all, you can do this through automation with Excel VBA. Maybe there are already modules at the Honeywell support site to do this. I always fetched the true critical values for the situation where they are needed. This is usually a very small number.

 

Bobby

Edited by Bobby Strain, 14 July 2015 - 10:25 PM.

[J_Leo]

Bobby,

 

Thank you. Our ealier HMB were issued with True Tc and Pc by Others. I cannot delete these items for the new revisions. I have to go with them. I am using Unisim Design Brower which can extract True Tc and Pc. To do this I have to add the utility to each stream and use GetUnisimDesign function in excel to connect each cell with the stream utility. It is very tedious.

 

Thank you,

Leo

Edited by J_Leo, 15 July 2015 - 12:45 PM.

[Bobby Strain]

So, you must do that, or follow my response about using VBA in Excel. It shouldn't take you long. You just have to create one utility, give it a stream, fetch the values, then remove the utility. Repeat for all the streams. Or create one for each stream, fetch the values, then delete them all (or not).  You can probably find what you need, or something similar, on Honeywell's support site. Or find someone who will do it for you. All process engineers should learn to use process simulator automation through some programming language that can read and write to Excel.

 

Bobby

Edited by Bobby Strain, 15 July 2015 - 06:48 PM.

[serra]

which is the reason to use true Tc, Pc ?

If you need to do something in Excel (or Matlab or Mathcad etc.) then in my opinion much better to use a library

and simply put a macro as StrTc() , StrPc() in a cell to get rigorous (True) Tc, Pc etc. see

"http://www.prode.com...seenvelope.htm"

 

Note that in many cases you will need the so called pseudocritical values (not the rigorous values).

Edited by serra, 16 July 2015 - 06:17 AM.

[J_Leo]

Serra,

 

I don't understand why they got True Tc and Pc in HMB either. I always used Pseudo properties before. The method you mentioned looked more complicated to me.

 

Regards,

Leo

[serra]

then, if rigorous Tc, Pc are not required, continue to use pseudo crtical properties,

the method is not more complicate it is the only way to calculate rigorous critical properties,

different procedures are available, Prode Properties adopts direct minimization of Gibbs while

Hysys has Heidemann and Khalil,

both procedures are slow compared to the simple (or weighted) average of pseudo crtical properties

and in some cases do not converge (there are mixtures without a vapor-liquid critical point)

so my suggestion is to use these procedures with care and only when required...