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

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! ^_^ 
Yes. Please email me.

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