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 N400 December 23, 2012 21:46

UDF for phase change

I want to simulate the phase tranfer in the heat pipe, and a udf was compiled in FLUENT,which is as follow:

#include "udf.h"
#include "sg_mphase.h"
#define T_SAT 323
#define LAT_HT 2356e3
DEFINE_SOURCE(vap_src, cell, pri_th, dS, eqn)
{
real m_dot_v;
/*m_dot_v=0.;*/
if(C_T(cell, mix_th)>=T_SAT)
{
m_dot_v = 0.1*C_VOF(cell, sec_th)*C_R(cell, sec_th)*fabs(C_T(cell, sec_th) - T_SAT)/T_SAT;

dS[eqn] = 0.;
}

if(C_T(cell, mix_th)<=T_SAT)
{
m_dot_v = -0.1*C_VOF(cell, pri_th)*C_R(cell, pri_th)*fabs(T_SAT-C_T(cell,pri_th))/T_SAT;
dS[eqn] = -0.1*C_R(cell, pri_th)*fabs(C_T(cell, pri_th) - T_SAT)/T_SAT;
}
return m_dot_v ;
}

DEFINE_SOURCE(liq_src, cell, sec_th, dS, eqn)
{
real m_dot_l;
/*m_dot_l=0.;*/
if(C_T(cell, mix_th)>=T_SAT)
{
m_dot_l = -0.1*C_VOF(cell, sec_th)*C_R(cell, sec_th)*fabs(C_T(cell, sec_th) - T_SAT)/T_SAT;
dS[eqn] = -0.1*C_R(cell, sec_th)*fabs(C_T(cell, sec_th) - T_SAT)/T_SAT;
}
if(C_T(cell, mix_th)<=T_SAT)
{
m_dot_l = 0.1*C_VOF(cell, pri_th)*C_R(cell, pri_th)*fabs(T_SAT-C_T(cell,pri_th))/T_SAT;
dS[eqn] =0.;
}

return m_dot_l;
}

DEFINE_SOURCE(enrg_src, cell, mix_th, dS, eqn)
{
real m_dot;
if(C_T(cell, mix_th)>=T_SAT)
{
m_dot = -0.1*C_VOF(cell, sec_th)*C_R(cell, sec_th)*fabs(C_T(cell, sec_th) - T_SAT)/T_SAT;
dS[eqn] = -0.1*C_VOF(cell, sec_th)*C_R(cell, sec_th)*LAT_HT/T_SAT;
}

if(C_T(cell, mix_th)<=T_SAT)
{
m_dot = 0.1*C_VOF(cell, pri_th)*C_R(cell, pri_th)*fabs(T_SAT-C_T(cell,pri_th))/T_SAT;
dS[eqn] = 0.1*C_VOF(cell, pri_th)*C_R(cell, pri_th)*LAT_HT/T_SAT;
}
return LAT_HT*m_dot; }

Using the code above, I can simulate the evaporation, but the condensation did not appear, even the temperature of vapor was much lower than the saturation temperature.
Now I am so confused. Anyone can help me?

You may have not defined boundary conditions correctly. Please share files to check.

 N400 December 24, 2012 01:09

Quote:
 Originally Posted by msaeedsadeghi (Post 398844) You may have not defined boundary conditions correctly. Please share files to check.
My case and data files are bigger than the attachment allowing, may I send them to you via email?
Thank you !

PS:
Anyone else who is intersting in my problem or have the relevant experiences please contact me, we can communicate directly and quickly via emails! ^_^

 N400 December 24, 2012 05:40

Thanks!:)
I just sent you the files via email, and l am looking forward your reply!

 Shengchao Hu April 19, 2013 04:51

Hi,N400
I am writing the udf for the phase change of LNG，i have some questions to share with you.Could you send me your files ?
Thanks very much! My email adress:shengchaohu2012@163.com

 yangbinsunshine November 18, 2013 02:33

Hi,I am working on this udf recently.and I am confused about this sentence"m_dot_v = 0.1*C_VOF(cell, sec_th)*C_R(cell, sec_th)*fabs(C_T(cell, sec_th) - T_SAT)/T_SAT".
First,in this sentence,the coefficent is 0.1,but i do not know why.
Second,what is the unit of "m_dot_v"?
Thank you very much,and any advice will be highly appreciated.

 rampal December 30, 2015 00:28

Dear friends,
I am doing the simulation of heat pipe in Fluent. I'm using udf for mass and energy source, but results are not coming specially condensation in condenser zone . All of you done this problem some times ago. I think you are more familiar with this problem. Please help me regarding this so can I complete my project work.

I will be very very thankful for your valuable help

 CFD Engineer December 30, 2015 03:16

Hello,
Did you got the new UDF with condensation. Please i need it can you send it to cfdengineer44@gmail.com.

Thank You

Quote:

 rampal December 31, 2015 01:15

Dear friend, till now not successful to get results, as soon as result will came, I'll inform you.

 CFD Engineer December 31, 2015 01:48

Reg Hooking the UDF

Dear Friends,
i am using the UDF which you showed on cfdonline.com in the comment given by Mr nowbelle, it is good but i am confuse where to hook the UDF. I mean i had compiled it but which option should i selecte in Cell Zone condition and for which domain i have to define which part of the UDF. i tried giving udf_vap:: for vapour domain and udf_liq:: for liquid domain but it is showing error.

 MDSHUJAN June 15, 2016 21:35

Hi N400. Did you complete your udf, and got condensation? I am working on a similar udf for simulating a heat pipe. Please can you send me your final udf at mdshujan@nevada.unr.edu

If condensation doesn't work, you can change the coefficient from 0.1 to other values, you can also try other condensation models instead of LEE Model.

Thanks and good luck

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