7 replies to this topic

[sacarove]

Dear all,

 

I am getting an on z-factor calculation on hysys because I have found two diffent formulas for the same method.

 

On Hysys manual the EoS for Lee-Kleser is decribed  shown on attachement. The second formula from a jounal give give better results than the first formula.

 

Which Lee-Kleser expression is the correct one?

 

Thanks

Attached Files

•  journal.JPG   22.64KB   7 downloads
•  Hysys.JPG   19.61KB   3 downloads

[PingPong]

Journal is correct. Hysys formula contains 2 mistakes (typing errors).

[sacarove]

Hi PingPong,

If the journal is correct and the values they calculated by that formula is very different from hysys, do you think that that is a bug in hysys?

Bceuase the values from the journal and hysys are different which means that is may not just be a typing error.

[PingPong]

I have no experience with Hysys so I don't know, but I find it hard to imagine that those mistakes are also in the source code of Hysys.

 

For what substance are you trying to calculate Z ?

[aqassam]

Hysys implements the journal formula. I'm not sure why your calculation is resulting in a different value from Hysys, but remember that Hysys uses numerical methods to estimate properties to within a tolerance. I will submit this to Hysys so that the formula in the documentation is updated. 

Regards

[sacarove]

I have some experimental data used for z factor by Lee-Kesler which is different from the one obtained by hysys. I tried to use V7.3 but it did not improve.

 

Please find attached the composition and the conditions.

 

 

Attached Files

•  Comp.JPG   23.11KB   6 downloads
•  LK.JPG   50.69KB   4 downloads

Edited by sacarove, 21 October 2013 - 03:34 AM.

[aqassam]

Just a few more clarifications so I can check on this:

 

Are the fractions on a molar basis? Also, what temperature are you considering here? Are the hydrocarbons pure component or modeled as hypotheticals? 

[sacarove]

Hi Again,

sorry for the missing information.

Yes they are all in molar bases and pure components ,no hypothetical.

T=63.5C

 

thanks