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Dense Phase Area Identification With Prode

state gas liquid dense area prode properties

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#1 pdender

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Posted 13 February 2014 - 02:36 AM

To identify the state of a fluid in dense area with PRODE PROPERTIES one can select the Isothermal Compressibility or Minimum Liquid Density option which allows you to define a minimum acceptable value for liquid density.

 

How can I edit and modify this value ?



#2 PaoloPemi

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Posted 13 February 2014 - 04:20 AM

To identify the state (vapor, liquid) in the dense phase, Prode Properties has a procedure which analyzes the sign of derivatives of isothermal compressibility.  In addition, the user can specify a minimum acceptable values for liquid density.  This allows a better identification of state.

 

You can define the minimum accepted value for liquid density in the settings section:

 

Prode Properties Editor->Config->Settings

 

It's the last row in this section (see attached file).

 

By the way, set the value to 0.0 if you do not wish to check for density, too (not recommended).

Attached Files



#3 pdender

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Posted 04 March 2014 - 11:05 AM

thanks Paolo,

useful information (the operating manual doesn't seem to discuss this topic)



#4 marchem

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Posted 19 March 2014 - 06:16 AM

I think Prode has updated those settings in version 1.19.  Previously the identification of state (vapor or liquid) was based only on derivatives of isothermal compressibility.

 

The possibility to define a minimum value for liquid density (or set to 0 if you do not wish this option, as suggested by Paolo) adds much flexibility.



#5 pdender

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Posted 16 April 2014 - 06:07 AM

thanks marchem



#6 bponcet

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Posted 15 May 2014 - 01:54 AM

Gentlemen,

 

Which are the best options for phase equilibria settings when simulating a oil+gas pipeline with PRODE?

 

Thanks.



#7 marchem

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Posted 15 May 2014 - 03:39 AM

You should select models and setting suitable for the fluid composition and conditions.

 

In general, PRODE PROPERTIES has a very reliable convergence, even near the critical point, once converged errors are within 1.0E-10  (you can change the tolerance in settings).  But final accuracy will depend form model and you can obtain very different values setting Soave or Peng Robinson or the different variants of Soave and Peng Robinson available in PRODE.  I have read that std. Soave should work better for light fluids but Extended Versions should work fine for many components (when the three specific parameters are available).

 

To identify the correct state in the dense area (outside VLE area) I think that isothermal compressibility criteria plus

the default minimum value of 200 Kg/m3 for liquid density gives reliable results for natural gas mixtures.  You can easily change these settings if required.



#8 bponcet

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Posted 18 May 2014 - 12:54 AM

thanks,

I work mainly with natural gas (Mw in the range 18-24),

is the default value for liquid density (200 Kg/m3) suitable for these mixtures ?



#9 frpe

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Posted 24 June 2014 - 01:45 AM

bponcet,

don't forget that in dense phase the values of density for vapor and liquid phases are the same,

while for other properties Prode adopts the methods for liquid or vapor phase,

in my experience the limiting value of 200 Kg/m3 is good for natural gas.



#10 bponcet

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Posted 06 July 2014 - 11:35 AM

frpe,

it's not for density, it's for viscosity of vapor or liquid phase,

simulating a oil+gas pipeline in Excel,


Edited by bponcet, 06 July 2014 - 11:42 AM.


#11 serra

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Posted 31 July 2014 - 12:53 AM

bponcet,

estimating the values of transport properties in dense phase could be a problem,

if that may help I have compared methods given in The Properties of Gases and Liquids

(Reid, Prausnitz,Poling) with the values for viscosity calculated by Prode at high pressures,

different methods can predict values 10-30% different (or more).

However if your estimating pressure drop in piping probably you don't need

very accurate values (apart density which is calculated with a EOS)



#12 bponcet

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Posted 06 October 2014 - 07:08 AM

thanks Serra,

I agree about the difficult to estimate the transport properties in dense phase,

it seems that most procedures discussed in books as the Properties of... have very large errors.



#13 mrbabu

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Posted 23 December 2014 - 11:19 AM

in some cases I get two vapor phases (for some reason the method doesn't work as expected),

however, changing the settings as suggested by marchem, can solve the problem.






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