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-   -   temperature and pressure dependent specific heat? (http://www.cfd-online.com/Forums/fluent/99522-temperature-pressure-dependent-specific-heat.html)

xechvol April 5, 2012 05:51

temperature and pressure dependent specific heat?
 
How to add pressure dependence in DEFINE_SPECIFIC_HEAT?
I'm doing with plasma, Cp varies with T and P drastically.....:confused:
Thank you for any suggestion.

misagh April 5, 2012 06:08

hi.im not sure.if it was dependent to only T it was easy.but now with T and P dependence i think UDF will work.

OscarD April 18, 2012 12:16

specific heat func. of temperature
 
I'm working with plasma modeling and require thermodynamic properties of argon as a function of temperature (at least, but it should also be pressure dependant).
I did a simple UDF for the specific heat, but it keeps giving me the same error once I try to initializate the calculation: "Warning: Incorrect Specific Heat value"

the UDF is:

DEFINE_SPECIFIC_HEAT(SpecHeat_Ar,T,Tref,h,yi)
{
real SpecHeat,a1,b1,c1,a2,b2,c2;
real x = T/1000.; /*input temp in kK*/
a1 =8.064;b1 =13.92;c1 =2.721;a2 =2.907;b2 =28.19;c2 =19.67;

SpecHeat = a1*exp(-pow(((x-b1)/c1),2.)) + a2*exp(-pow(((x-b2)/c2),2.));
SpecHeat=SpecHeat/1000.; /* the specific heat material property value is in [J/kg-K]*/

return SpecHeat;
}

I used similar eqs for thermal conductivity and viscosity. Does anybody what could be wrong?.

Thanks

msaeedsadeghi December 16, 2012 03:10

I have the same problem when injected particles get vaporized, the warning "incorrect specific heat value" occures.
Any solution?

beer December 18, 2012 10:46

Hi
I made a Service Request and Fluent answered that it is NOT possible to write an UDF with pressure-dependend Specific Heat right now. I hope they will change this in the future. I tried it on my own, DEFINE_PRPERTY works fine but DEFINE_SPECIFIC_HEAT is crap.
Use the USER FORTRAN in CFX :D


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