c# refprop wrapper and Isentropic Expansion Coefficient

[Jessica Lacetera]

Hi,

I'm trying to use REFPROP and c# wrapper, and it seems that the Isentropic Expansion Coefficient calculation was not included in the c# wrapper.  Also, quality calculation is not included.

Does anyone know if it is there and I just haven't been able to find it because it is named something totally different.

Also, is there a way to access these calculations in REFPROP with the Low-Level interface, if they aren't included in the high-level interface?

Thanks,

Jess

[Jorrit Wronski]

Hi, there is an example for the low-level interface in the docs: http://coolprop.sourceforge.net/coolprop/wrappers/Csharp/index.html#example-code

 

Everything available in the high-level interface is listed here: http://coolprop.sourceforge.net/coolprop/HighLevelAPI.html#table-of-string-inputs-to-propssi-function

 

 

If you are interested in the ratio of the specific heats, I would recommend to calculate that yourself:

gamma = CoolProp.PropsSI('CPMASS','T',300,'P',101325,'R410A')/ CoolProp.PropsSI('CVMASS','T',300,'P',101325,'R410A')

 

Vapour quality can be obtained from the high-level interface.

 

Regards,

Jorrit

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[Jessica Lacetera]

Thank you for the info Jorrit.  I should have realized that 'Quality' was 'Vapor Quality'.  Will try the calculation for Isentropic Coefficient and make sure that the engineers here are ok with the solution.  It should work, but we just have to check that it  matches the Refprop values, since previously we were calculating this with Refprop.

Thanks,

Jess

[Ian Bell]

Also, the isentropic expansion coefficient is not exactly the ratio of specific heats, that is only for an ideal gas.  I forget exactly the thermodynamically precise definition for the isentropic expansion coefficient, but it can certainly be calculated with CoolProp with the first_partial_deriv function in the low-level interface, or with the derivative definition in the high-level interface: http://www.coolprop.org/coolprop/HighLevelAPI.html#partial-derivatives

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[Matthis Thorade]

I looked it up (e.g. Lemmon 2000 Air paper), the isentropic expansion coefficient for real gas is defined as

where the molar mass is only needed if rho is given as molar density,

otherwise the equation is just k=d/p*w^2 where w is the speed of sound.

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Matthis Thorade
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[Ian Bell]

Right, so either you could evaluate the RHS directly, or evaluate the derivative (dp/drho|s).  Both good options! I like the derivative a bit better because it is more clear what the units are (self consistent set)

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Matthis Thorade
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