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Old   October 20, 2014, 18:59
Default Condensation in a closed thermosyphon??? (heat pipe, evaporation-condensation))
  #1
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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, 22:35
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, 09:22
Default Udf
  #4
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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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Old   June 17, 2016, 09:43
Default
  #5
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SHUJAN
Join Date: Jun 2016
Posts: 17
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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;
}
Hi. Did you get condensation. I am working on similar project, and can't get condensation. Let me know if you get condensation.
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Old   July 5, 2016, 12:47
Default
  #6
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Przemek
Join Date: Jun 2011
Posts: 249
Rep Power: 15
gaza is on a distinguished road
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;
}
Hi Rampal,
Can you send errors you got?
__________________
best regards
pblasiak
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Old   July 14, 2016, 12:02
Default
  #7
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Przemek
Join Date: Jun 2011
Posts: 249
Rep Power: 15
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Quote:
Originally Posted by xiaobingwill View Post
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.
Hi Xiaobing,
Did you model this with UDF or built-in Fluent model?
__________________
best regards
pblasiak
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Old   July 27, 2016, 11:37
Default
  #8
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Przemek
Join Date: Jun 2011
Posts: 249
Rep Power: 15
gaza is on a distinguished road
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;
}
Hi Rampal
Have you solved your problem with no condensation? I have the same problem. Please see here:
http://www.cfd-online.com/Forums/flu...on-doesnt.html
__________________
best regards
pblasiak
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Old   October 18, 2016, 13:18
Default
  #9
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Anyone succeed to simulate the heat pipe evaporator and condenser?
I'm doing my bachelor project on it and i will appreciate any help in this case because, i'm beginner with fluent however, i know the equations of energy and momentum which need to be written in the udf but i failed to simulate it.
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Old   December 21, 2016, 11:25
Default Heat Pipe
  #10
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Reza
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Hi everyone. I am new in the two-phase flow and heat pipe field and I should simulate a wicked heat pipe by OpenFoam. It is appreciated if anyone can help me ... Thanks
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