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Cp (Specific heat) UDF. When/what version???

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Old   February 19, 2009, 16:10
Default Cp (Specific heat) UDF. When/what version???
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agg
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I've seen release notes saying UDF's can be used for specific heat. I compiled and loaded a DEFINE_PROPERTY UDF in 12.0.7, but when I select "user defined" for specific heat, a dialog pops up saying no UDFs have been loaded. What gives? Is this not fully functional yet or am I doing something wrong? Thanks!
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Old   February 21, 2009, 05:38
Default Re: Cp (Specific heat) UDF. When/what version???
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bohis
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your UDF was not either loaded or you forgot to put return Cp; to your UDF

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Old   February 23, 2009, 17:32
Default Re: Cp (Specific heat) UDF. When/what version???
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agg
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Thanks for responding. Any other possibilities? I've done both.

To check my UDF, I wanted know if a DEFINE_PROPERTY had been loaded. So, I selected user-defined for the density and my UDF is there. However, doing the same with Cp gives a pop-up saying "No user-defined functions have been loaded". So, my thinking is that the Cp UDF functionality has not been completed as of version 12.0.7.
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Old   February 23, 2009, 17:51
Default Use DEFINE_SPECIFIC_HEAT, not DEFINE_PROPERTY
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agg
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The udf.h file contains the define. Here it is:

#define DEFINE_SPECIFIC_HEAT(name, T, Tref, h, yi) real name(real T, real Tref, real *h, real *yi)

So, write a UDF so as the one below...

#include "udf.h"

/* UDF that computes Cp for diatomic oxygen, O_2 */

DEFINE_SPECIFIC_HEAT(cell_cp_o2, T, Tref, h, yi) {

real Cp;

/*

define your version of Cp here...

*/

return Cp; }
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Old   February 25, 2009, 14:02
Default Re: in addition to defining Cp, the code must
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agg
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define the enthalpy for the specie (real *h) as the integral from Tref to T of the defined/returned Cp. The mass fractions, (real *yi) are given in the specie order as defined for the material.

! If the enthalpy is not defined, calculations requiring the energy equation will not work.
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Old   January 10, 2013, 21:25
Default About the equation for h in the UDF for Cp
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Abhijeet Shrawage
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Quote:
Originally Posted by agg
;156886
define the enthalpy for the specie (real *h) as the integral from Tref to T of the defined/returned Cp. The mass fractions, (real *yi) are given in the specie order as defined for the material.

! If the enthalpy is not defined, calculations requiring the energy equation will not work.
Hi
I have been trying to to what you said for a while but I seem to be having a problem with the way FLuent is calculating enthalpy. The integration i have done is correct for the polynomial for Cp (T) but Fluent is pulling a Tref value which causes my h to go negative.
Can you give me any advice regarding this?
Thanks
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Old   May 3, 2013, 09:09
Post udf-cp
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wang hui
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Quote:
Originally Posted by agg
;156886
define the enthalpy for the specie (real *h) as the integral from Tref to T of the defined/returned Cp. The mass fractions, (real *yi) are given in the specie order as defined for the material.

! If the enthalpy is not defined, calculations requiring the energy equation will not work.
can you tell me the detail function of the T, Tref, h, yi?????
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Old   May 3, 2013, 09:17
Thumbs up udf-cp
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wang hui
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Quote:
Originally Posted by ashrawage View Post
Hi
I have been trying to to what you said for a while but I seem to be having a problem with the way FLuent is calculating enthalpy. The integration i have done is correct for the polynomial for Cp (T) but Fluent is pulling a Tref value which causes my h to go negative.
Can you give me any advice regarding this?
Thanks
would you introduce the function of (T, Tref, h, yi) minutely?? especialy the h, yi.
and i also want to know how to get the "T",because there is not any position parameter among (T, Tref, h, yi).....very thanks
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