Defining Cp as a function of temperature and pressure

suysal · May 23, 2017, 06:27

Hi all,

I do analysis of c-d nozzle with R245fa organic fluid and the fluid is in super-critical region at inlet. Then, the fluid is in vapor region.

I can define specific heat constant (Cp) as a function of temperature, but it depends on pressure also.

For example, At 432 K (which is my inlet total temperature), Cp is 1.095 kJ/kg-K at 1 bar, it increase up to 3.365 kJ/kg-K at 37 bar which is in supercritical region.

I don't know how to define Cp as a function of T and P. I searched but I couldn't find that I want.

If it is not possible, which pressure value should I use as a constant to define Cp only as a function of temperature, ?

KaLium · June 2, 2017, 08:04

UDF is possible

UDF for specific heat

http://www.afs.enea.it/project/neptu...udf/node51.htm

This option is not available with the premixed, non-premixed and partially premixed models, and should be used as a compiled UDF only.

estevaotolentino · June 13, 2017, 12:59

Hi,

I'm having a similar problem and I would like to know if this issue has been solved. If so, how was it solved? Thank you.

suysal · June 14, 2017, 04:09

Thank you KaLium. I have just seen this message, sorry for late reply.

I couldn't define Cp as a function of both T and P. I selected an average pressure value and I define Cp only depends on temperature for my graduation project. @estevaotolentino

estevaotolentino · June 14, 2017, 14:01

Ok, I got it. Thank you for the reply.

May 23, 2017, 06:27	Defining Cp as a function of temperature and pressure	#1
suysal New Member Sergen Uysal Join Date: Feb 2017 Posts: 5 Rep Power: 9	Hi all, I do analysis of c-d nozzle with R245fa organic fluid and the fluid is in super-critical region at inlet. Then, the fluid is in vapor region. I can define specific heat constant (Cp) as a function of temperature, but it depends on pressure also. For example, At 432 K (which is my inlet total temperature), Cp is 1.095 kJ/kg-K at 1 bar, it increase up to 3.365 kJ/kg-K at 37 bar which is in supercritical region. I don't know how to define Cp as a function of T and P. I searched but I couldn't find that I want. If it is not possible, which pressure value should I use as a constant to define Cp only as a function of temperature, ?

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June 2, 2017, 08:04		#2
KaLium Senior Member Kal-El Join Date: Apr 2017 Location: Finland Posts: 150 Rep Power: 9	UDF is possible UDF for specific heat http://www.afs.enea.it/project/neptu...udf/node51.htm This option is not available with the premixed, non-premixed and partially premixed models, and should be used as a compiled UDF only.

June 13, 2017, 12:59		#3
estevaotolentino New Member Estêvão Lannes Tolentino Join Date: Oct 2016 Posts: 9 Rep Power: 10	Hi, I'm having a similar problem and I would like to know if this issue has been solved. If so, how was it solved? Thank you.

June 14, 2017, 04:09		#4
suysal New Member Sergen Uysal Join Date: Feb 2017 Posts: 5 Rep Power: 9	Thank you KaLium. I have just seen this message, sorry for late reply. I couldn't define Cp as a function of both T and P. I selected an average pressure value and I define Cp only depends on temperature for my graduation project. @estevaotolentino

June 14, 2017, 14:01		#5
estevaotolentino New Member Estêvão Lannes Tolentino Join Date: Oct 2016 Posts: 9 Rep Power: 10	Ok, I got it. Thank you for the reply.