Hi everyone
For calculating the vapour fraction and phase compositions of a hydrocarbon mixture at given Pressure, Temperature and overall compositions, the rachfordrice equation needs to be solved.

Posted 10 July 2019  02:51 AM
Hi everyone
For calculating the vapour fraction and phase compositions of a hydrocarbon mixture at given Pressure, Temperature and overall compositions, the rachfordrice equation needs to be solved.
Posted 10 July 2019  03:19 AM Best Answer
Hi ,
Let you consider the excel sheet attached where you can find several options to support your work .
hope this is helping you and others .
Breizh
Posted 10 July 2019  11:53 AM
Hi ,
Let you consider the excel sheet attached where you can find several options to support your work .
hope this is helping you and others .
Breizh
Dear Breizh
I had a long and detailed look at your spreadsheet and compared it to what DWSIM outputs. Then I compared it to my code. It's a pretty good spreadsheet, only thing is it will not incorporate the new phase compositions to evaluate the new K values.
Anyway, it does what I wanted it to: give me a good way to initialise the rachford rice method and do one iteration with a reasonable output of vapour fraction (ie 0<= V<=1).
Thanks. It helped me validate my code.
Posted 02 February 2021  05:48 AM
I would like to know about convergence pressure Pk ..assume that we have reservoir fluid composition (Pres, Tres, Zi are Known) , and we would like to estimate Pb pressure (unknown), by using Rachford Rice equation(RR eq.) when we want to calculate the K values we need the value of Pk, Is there any equation to calculate it direct with high accuracy ,any example done by spreadsheet !!
Kind regards
Posted 02 February 2021  06:51 AM
Hi,
To get a meaningful answer I encourage you to define the variables included in your post ( Pb , Pk) .
Good luck
Breizh
Posted 04 February 2021  05:34 AM
I would like to know about convergence pressure Pk ..assume that we have reservoir fluid composition (Pres, Tres, Zi are Known) , and we would like to estimate Pb pressure (unknown), by using Rachford Rice equation(RR eq.) when we want to calculate the K values we need the value of Pk, Is there any equation to calculate it direct with high accuracy ,any example done by spreadsheet !!
Kind regards
Typically you use rachford rice to calcuate the amount of vaporisation at a known temperature and pressure, you iterate around until the K values converge. (if your doing it rigorously).
To find the Pressue at a specific level of vaporisation you have another outer convergence loop, whereby you adjust P untl you get the bubble point/dew point or whatever other criteria your trying to meet.
Edited by SilverShaded, 04 February 2021  05:34 AM.
Posted 04 February 2021  06:51 AM
Hi ,
You may consider the excel sheet attached , in particular the methodology used
You may also consider this resource from internet :
https://www.questcon...oftware/canary/
Good luck
Breizh
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