real-gas properties calculation references - cp_mole()

[Kang, SiYoon]

Hi, everyone.

Now I'm studying real-gas eos.

but i have a question about Peng-robinson and Redlich-Kwong EOS.

i've seen a different way of calculating Cp at constant pressure.

but the Cantera calculated the Cp at constant volume.

so I wonder where it came from.

Thank you !

[Steven DeCaluwe]

Hi Simon,

It is not all that clear what you are referring to.  Do you feel that the algorithm in the code should look different?  

We have the derivations in a document somewhere (getting these onto the website is currently on the to-do list), but in the mean time I’ll just point out that the algorithms are tested against a finite-difference approximation for dh/dT at constant P, here.

Best regards,

Steven

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[Kang, SiYoon]

Oh sorry. DeCaluwe.

i think i misrepresented it.

What i was saying was that i was curious about the reference equations of how to calculate Cp from real-gas EOS (RK or PR) in the source file (c++).

as far as i know, Cp should be dHdT_P because it represents specific heat under constant pressure.

but in the source file, dHdT_V appears to represent Cp under constant volume conditions.

i woud appreciate it if you could check it again.

Thank you

2023년 4월 19일 수요일 오후 3시 50분 12초 UTC+9에 S. DeCaluwe님이 작성:

[Steven DeCaluwe]

Ah, thanks for the clarification.

The key there is that the returned value is not dHdT_v, but rather dHdT_v - (vbar + T*dPdT/dPdV)*dPdT.

The second term comes from thermodynamic identities and transforms dHdT_v to dHdT_p.

Best wishes,

Steven 

On Apr 19, 2023, at 1:21 AM, Kang, SiYoon <rkd52...@gmail.com> wrote:

Oh sorry. DeCaluwe.

i think i misrepresented it.

What i was saying was that i was curious about the reference equations of how to calculate Cp from real-gas EOS (RK or PR) in the source file (c++).

as far as i know, Cp should be dHdT_P because it represents specific heat under constant pressure.

but in the source file, dHdT_V appears to represent Cp under constant volume conditions.

<dHdT_V.png>

i woud appreciate it if you could check it again.

Thank you

2023년 4월 19일 수요일 오후 3시 50분 12초 UTC+9에 S. DeCaluwe님이 작성:

Hi Simon,

It is not all that clear what you are referring to.  Do you feel that the algorithm in the code should look different?  

We have the derivations in a document somewhere (getting these onto the website is currently on the to-do list), but in the mean time I’ll just point out that the algorithms are tested against a finite-difference approximation for dh/dT at constant P, here.

Best regards,

Steven

On Apr 19, 2023, at 12:03 AM, Kang, SiYoon <rkd52...@gmail.com> wrote:

Hi, everyone.

Now I'm studying real-gas eos.

but i have a question about Peng-robinson and Redlich-Kwong EOS.

i've seen a different way of calculating Cp at constant pressure.

but the Cantera calculated the Cp at constant volume.

so I wonder where it came from.

Thank you !

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You received this message because you are subscribed to the Google Groups "Cantera Users' Group" group.
To unsubscribe from this group and stop receiving emails from it, send an email to cantera-user...@googlegroups.com.
To view this discussion on the web visit https://groups.google.com/d/msgid/cantera-users/8a1dc8c9-6f77-4863-b947-a0cb4a4ce079n%40googlegroups.com.

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<dHdT_V.png>

[Kang, SiYoon]

Oh, Really thanks for DeCaluwe.

Thank you and Have a nice day!

2023년 4월 19일 수요일 오후 5시 49분 1초 UTC+9에 S. DeCaluwe님이 작성: