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December 23, 2012, 21:46 
UDF for phase change

#1 
New Member
nowbelle
Join Date: Dec 2012
Posts: 3
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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) { Thread *mix_th, *sec_th; real m_dot_v; mix_th = THREAD_SUPER_THREAD(pri_th); sec_th = THREAD_SUB_THREAD(mix_th, 1); /*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_SATC_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) { Thread * mix_th, *pri_th; real m_dot_l; mix_th = THREAD_SUPER_THREAD(sec_th); pri_th = THREAD_SUB_THREAD(mix_th, 0); /*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_SATC_T(cell,pri_th))/T_SAT; dS[eqn] =0.; } return m_dot_l; } DEFINE_SOURCE(enrg_src, cell, mix_th, dS, eqn) { Thread *pri_th, *sec_th; real m_dot; pri_th = THREAD_SUB_THREAD(mix_th, 0); sec_th = THREAD_SUB_THREAD(mix_th, 1); 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_SATC_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? 

December 24, 2012, 00:35 

#2 
Senior Member
SSL
Join Date: Oct 2012
Posts: 226
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You may have not defined boundary conditions correctly. Please share files to check.


December 24, 2012, 01:09 

#3  
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nowbelle
Join Date: Dec 2012
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Quote:
My email address is nowbelle@yeah.net 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! ^_^ Last edited by N400; December 24, 2012 at 03:14. 

December 24, 2012, 05:09 

#4 
Senior Member
SSL
Join Date: Oct 2012
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Rep Power: 7 
Yes. Please email me.


December 24, 2012, 05:40 

#5 
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nowbelle
Join Date: Dec 2012
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Thanks!
I just sent you the files via email, and l am looking forward your reply! 

April 19, 2013, 04:51 

#6 
New Member
Join Date: Apr 2013
Posts: 1
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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 

November 18, 2013, 02:33 

#7 
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yangbin
Join Date: Nov 2013
Location: haerbin
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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. 

December 30, 2015, 00:28 

#8 
New Member
Ram Kumar Pal
Join Date: Apr 2015
Posts: 22
Rep Power: 4 
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 

December 30, 2015, 03:16 

#9  
New Member
Join Date: Mar 2015
Posts: 6
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Hello,
Did you got the new UDF with condensation. Please i need it can you send it to cfdengineer44@gmail.com. Thank You Quote:


December 31, 2015, 01:15 

#10 
New Member
Ram Kumar Pal
Join Date: Apr 2015
Posts: 22
Rep Power: 4 
Dear friend, till now not successful to get results, as soon as result will came, I'll inform you.


December 31, 2015, 01:48 
Reg Hooking the UDF

#11 
New Member
Join Date: Mar 2015
Posts: 6
Rep Power: 4 
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. 

June 15, 2016, 21:35 

#12 
New Member
SHUJAN
Join Date: Jun 2016
Posts: 11
Rep Power: 3 
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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