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Condensation in a closed thermosyphon??? (heat pipe, evaporation-condensation))

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Old   October 20, 2014, 18:59
Default Condensation in a closed thermosyphon??? (heat pipe, evaporation-condensation))
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Xiaobing Zhang
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Hello,

I'm modeling phase change flow in a closed thermosyphon. Now my status is having evaporation in my evaporator. But little condensation is found in the cold part. The following pics are my results.

I calculated 200s already, but condensation is still very small.

Any guidance or help will be appreciated.

Thanks,
Xiaobing

Limited condensation happens in the condenser.

Limited condensation happens in the condenser.

Evaporation is good.
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Old   April 7, 2015, 15:19
Default Udf
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Muhammed Asmail
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did you use UDF for heat and mass transfer ??
i am not get on condensation ??!!!
i do not know why?
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Old   December 12, 2015, 23:35
Default evaporation condensation in fluent
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Ram Kumar Pal
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Hello friends, I have written UDF for phase change in thermosyphon, boiling is happening inside evaporator but there is no condensation inside condenser, I'm confused why this error is happening. I'm writing UDF below, please notify me what is the error in UDF.

#include "udf.h"
#include "sg_mphase.h"
#include "mem.h"
#include "metric.h"
#include "flow.h"
#include "sg.h"
#define T_SAT 373
#define LAT_HT 2455e3
DEFINE_SOURCE(vap_src,cell,pri_th,dS,eqn)
{
real m_dot_v;
Thread *mix_th, *sec_th;
mix_th = THREAD_SUPER_THREAD(pri_th);
sec_th = THREAD_SUB_THREAD(mix_th,1);
/*m_dot_v=0.0;*/
if (C_T(cell,mix_th)>T_SAT)
{
m_dot_v = 0.1*C_VOF(cell,sec_th)*C_R(cell,sec_th)*(C_T(cell, mix_th)-T_SAT)/T_SAT;
dS[eqn] = 0.0;
}
else if (C_T(cell,mix_th)<T_SAT)
{
m_dot_v = -0.1*C_VOF(cell,pri_th)*C_R(cell, pri_th)*(T_SAT-C_T(cell,mix_th))/T_SAT;
dS[eqn] = -0.1*C_R(cell,pri_th)*(T_SAT-C_T(cell,mix_th))/T_SAT;
}
return m_dot_v;
}
DEFINE_SOURCE(liq_src,cell,sec_th,dS,eqn)
{
real m_dot_l;
Thread *mix_th, *pri_th;
mix_th = THREAD_SUPER_THREAD(sec_th);
pri_th = THREAD_SUB_THREAD(mix_th,0);
/*m_dot_l=0.0;*/
if (C_T(cell,mix_th)>T_SAT)
{
m_dot_l = -0.1*C_VOF(cell,sec_th)*C_R(cell,sec_th)*(C_T(cell, mix_th)-T_SAT)/T_SAT;
dS[eqn] = -0.1*C_R(cell,sec_th)*(C_T(cell,mix_th)-T_SAT)/T_SAT;
}
else if (C_T(cell,mix_th)<T_SAT)
{
m_dot_l = 0.1*C_VOF(cell,pri_th)*C_R(cell,pri_th)*(T_SAT-C_T(cell,mix_th))/T_SAT;
dS[eqn] =0.0;
}
return m_dot_l;
}
DEFINE_SOURCE(enrg_src,cell,mix_th,dS,eqn)
{
real enrg_dot;
Thread *pri_th, *sec_th;
pri_th = THREAD_SUB_THREAD(mix_th,0);
sec_th = THREAD_SUB_THREAD(mix_th,1);
if (C_T(cell,mix_th)>T_SAT)
{
enrg_dot = -0.1*C_VOF(cell,sec_th)*C_R(cell,sec_th)*LAT_HT*(C_ T(cell,mix_th)-T_SAT)/T_SAT;
dS[eqn] = -0.1*C_VOF(cell,sec_th)*C_R(cell,sec_th)*LAT_HT/T_SAT;
}
else if (C_T(cell,mix_th)<T_SAT)
{
enrg_dot = 0.1*C_VOF(cell,pri_th)*C_R(cell,pri_th)*LAT_HT*(T_ SAT-C_T(cell,mix_th))/T_SAT;
dS[eqn] = -0.1*C_VOF(cell,pri_th)*C_R(cell, pri_th)*LAT_HT/T_SAT;
}
return enrg_dot;
}
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Old   December 14, 2015, 10:22
Default Udf
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Muhammed Asmail
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Dear rampal

your Ansys-Fluent is original version??
I mean original from the company no commercial that it is bought from the market
case of heat pipe is very complex and it needs original license and the condensation will not appear to you if the Ansys not original version as it happened with me through 8 months and i did not get result
Ansys can solve simple cases if it is not original version but heat pipe is complex case and it needs original version
i hope that you understand me
many thanks
Mohammed













Quote:
Originally Posted by rampal View Post
Hello friends, I have written UDF for phase change in thermosyphon, boiling is happening inside evaporator but there is no condensation inside condenser, I'm confused why this error is happening. I'm writing UDF below, please notify me what is the error in UDF.

#include "udf.h"
#include "sg_mphase.h"
#include "mem.h"
#include "metric.h"
#include "flow.h"
#include "sg.h"
#define T_SAT 373
#define LAT_HT 2455e3
DEFINE_SOURCE(vap_src,cell,pri_th,dS,eqn)
{
real m_dot_v;
Thread *mix_th, *sec_th;
mix_th = THREAD_SUPER_THREAD(pri_th);
sec_th = THREAD_SUB_THREAD(mix_th,1);
/*m_dot_v=0.0;*/
if (C_T(cell,mix_th)>T_SAT)
{
m_dot_v = 0.1*C_VOF(cell,sec_th)*C_R(cell,sec_th)*(C_T(cell, mix_th)-T_SAT)/T_SAT;
dS[eqn] = 0.0;
}
else if (C_T(cell,mix_th)<T_SAT)
{
m_dot_v = -0.1*C_VOF(cell,pri_th)*C_R(cell, pri_th)*(T_SAT-C_T(cell,mix_th))/T_SAT;
dS[eqn] = -0.1*C_R(cell,pri_th)*(T_SAT-C_T(cell,mix_th))/T_SAT;
}
return m_dot_v;
}
DEFINE_SOURCE(liq_src,cell,sec_th,dS,eqn)
{
real m_dot_l;
Thread *mix_th, *pri_th;
mix_th = THREAD_SUPER_THREAD(sec_th);
pri_th = THREAD_SUB_THREAD(mix_th,0);
/*m_dot_l=0.0;*/
if (C_T(cell,mix_th)>T_SAT)
{
m_dot_l = -0.1*C_VOF(cell,sec_th)*C_R(cell,sec_th)*(C_T(cell, mix_th)-T_SAT)/T_SAT;
dS[eqn] = -0.1*C_R(cell,sec_th)*(C_T(cell,mix_th)-T_SAT)/T_SAT;
}
else if (C_T(cell,mix_th)<T_SAT)
{
m_dot_l = 0.1*C_VOF(cell,pri_th)*C_R(cell,pri_th)*(T_SAT-C_T(cell,mix_th))/T_SAT;
dS[eqn] =0.0;
}
return m_dot_l;
}
DEFINE_SOURCE(enrg_src,cell,mix_th,dS,eqn)
{
real enrg_dot;
Thread *pri_th, *sec_th;
pri_th = THREAD_SUB_THREAD(mix_th,0);
sec_th = THREAD_SUB_THREAD(mix_th,1);
if (C_T(cell,mix_th)>T_SAT)
{
enrg_dot = -0.1*C_VOF(cell,sec_th)*C_R(cell,sec_th)*LAT_HT*(C_ T(cell,mix_th)-T_SAT)/T_SAT;
dS[eqn] = -0.1*C_VOF(cell,sec_th)*C_R(cell,sec_th)*LAT_HT/T_SAT;
}
else if (C_T(cell,mix_th)<T_SAT)
{
enrg_dot = 0.1*C_VOF(cell,pri_th)*C_R(cell,pri_th)*LAT_HT*(T_ SAT-C_T(cell,mix_th))/T_SAT;
dS[eqn] = -0.1*C_VOF(cell,pri_th)*C_R(cell, pri_th)*LAT_HT/T_SAT;
}
return enrg_dot;
}
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