10 replies to this topic

[djack77494]

Has anyone heard of the Conison Equation in connection with compressible fluid hydraulics? I may have the spelling wrong since I don't get any relevant hits on google. I've got an Excel book that was developed for compressible flow calcs and claims to use the Conison Equation. I'd like to check the assumptions and validate the implementation. Thanks.

[Qalander (Chem)]

Dear Doug Hello/Good Evening

I just googled 'Conison equation for compressible fluids'
hits 83
few links and one attachment pdf
http://www.grc.nasa....e/isentrop.html

http://www.dtic.mil/...oc=GetTRDoc.pdf

Kindly check if this helps
Best regards
Qalander

[JoeWong]

http://books.google....A...;lr=&pgis=1
Looks like the isothermal equation.

Checked API Std 521, there are couple of paper written by Joseph.E. Conison... may help.

Still browsing my collection... Hope can find some references...

[djack77494]

Dear Qalander & JoeWong,
Many thanks for your help. Very strange thing happened. I again did a google search for:
'Conison equation for compressible fluids'
hits = 0??
I must not be living right. Anyway, I remain interested in anything anyone might want to add to the topic, especially if it provides practical insights to compressible fluid flow hydraulics in Excel.

[Qalander (Chem)]

Dear Qalander & JoeWong,
Many thanks for your help. Very strange thing happened. I again did a google search for:
'Conison equation for compressible fluids'
hits = 0??
I must not be living right. Anyway, I remain interested in anything anyone might want to add to the topic, especially if it provides practical insights to compressible fluid flow hydraulics in Excel.

Dear Doug we are there to mutually get light from each other;
I believe.
Not sure but 'very rare' possibility that while googling you did not check web pages in general
But your country/location was somehow checked;thus this filtered search aspect.
Best Regards
qalander

[djack77494]

Since last posting, I have found an article by Joseph Conison on compressible gas flow. It is based on isothermal flow (no problem) but seems to require ideal gas behavior (big problem). I am dealing with supercritical CO2 which is far from an ideal gas. Anyone have any suggestions other than a return to first principles?

[Qalander (Chem)]

Since last posting, I have found an article by Joseph Conison on compressible gas flow. It is based on isothermal flow (no problem) but seems to require ideal gas behavior (big problem). I am dealing with supercritical CO2 which is far from an ideal gas. Anyone have any suggestions other than a return to first principles?

Dear Doug,
I've just googled again 'Supercritical Co2 Compressible flow' and got 3710 plus hits.
May be useful for you;by the way if this is not confidential then tell the application.
This may help supporting you!
Some results referred Use in polymerization reaction and some in drilling in special circumstance and quite a few other application were also seen described.
Best Regards
Qalander

[katmar]

djack,

I do not know the Conison article but if it is anything like the isothermal flow treatment by Crane or by Coulson & Richardson then it may still be usable, even though it assumes ideal gas behaviour. Looking at Crane Eq 3-7 it seems to me that what they have assumed by "ideal gas behaviour" is actually "constant compressibility".

The equations assume that as the pressure decreases along the pipe the change in density will be proportional to the ratio of absolute pressures. If your supercritical CO2 is not undergoing large swings in pressure or temperature, and your know the actual density (i.e. compressibility) at the start of the line then your compressibility may not be changing much and it may still be reasonable to use this type of equation.

If you are undergoing large pressure drops then maybe you have choked flow and the pressure drop is actually irrelevant.

Please could you post a reference to the Conison article - it sounds interesting. Thanks.

Regards
Katmar

[djack77494]

Looking at Crane Eq 3-7 it seems to me that what they have assumed by "ideal gas behaviour" is actually "constant compressibility".

Thank you all for your responses. Harvey, I was suspicious about this possibility even before you brought it up. The assumption of constant compressibility is much less severe than that of ideal gas behaviour. I really wish the author's would clearly state such limitations. The article you ask about is entitled, "How to Design a Pressure Relief System" by Joseph Conison. It appeared in the July 25, 1960 issue of Chemical Engineering. Unfortunately, only a small portion of the article deals with pipe compressible flow, and my copy is very hard to read. The application was for doing compressible fluid hydraulic calcs within Excel. I know the ending pressure and needed to work upstream to calculate starting pressures in a network. Ultimately, I have turned to a simulator to do the calcs.
Thanks all.

[JoeWong]

I understood that you are dealing with supercritical CO2. What simulator you are using for supercritical fluid pressure drop calc ?

[djack77494]

I understood that you are dealing with supercritical CO2. What simulator you are using for supercritical fluid pressure drop calc ?

Yes, I am working with supercritical CO2 using the P-R EOS in Hysys.