# UDF for phase change

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 December 23, 2012, 21:46 UDF for phase change #1 New Member   nowbelle Join Date: Dec 2012 Posts: 3 Rep Power: 7 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_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) { 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_SAT-C_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_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? SACHIN1639 likes this.

 December 24, 2012, 00:35 #2 Senior Member   SSL Join Date: Oct 2012 Posts: 226 Rep Power: 8 You may have not defined boundary conditions correctly. Please share files to check.

December 24, 2012, 01:09
#3
New Member

nowbelle
Join Date: Dec 2012
Posts: 3
Rep Power: 7
Quote:
 Originally Posted by msaeedsadeghi 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?
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 Posts: 226 Rep Power: 8 Yes. Please email me.

 December 24, 2012, 05:40 #5 New Member   nowbelle Join Date: Dec 2012 Posts: 3 Rep Power: 7 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 Rep Power: 0 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 New Member   yangbin Join Date: Nov 2013 Location: haerbin Posts: 4 Rep Power: 6 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: 29 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: 8
Rep Power: 4
Hello,
Did you got the new UDF with condensation. Please i need it can you send it to cfdengineer44@gmail.com.

Thank You

Quote:
 Originally Posted by N400 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_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) { 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_SAT-C_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_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?

 December 31, 2015, 01:15 #10 New Member   Ram Kumar Pal Join Date: Apr 2015 Posts: 29 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: 8 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 Chiara_riccio likes this.

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