[nahmed]

Hi,

I am using Fluent to perform heat pipe simulations. I am trying to solve it by VOF multiphase model but i am finding it hard to incorporate the boiling and condensation mechanisms at the liquid and vapor interface, both at condensor and evaporator side.

I was wondering if any one of you have tried to tackle the same sort of problem or could probably suggest me what could be a reasonable way to interact the two phases?

Moreover do i need to use some UDFs for boiling and condensation? What kind of operating conditions are more suitable? steady or unsteady?

Thanks.

[nahmed]

Anyone with good suggestions on my problem?

[nahmed]

gentle bounce!

[hilmi]

i am an undergraduate student, and i was also assigned to develop a CFD analysis of a heat pipe. im really really new with fluent. is FLUENT really can do modeling, meshing, and analysis of a heat pipe?

how to model for the wick structure?

[airleacheri]

I was also assign to build up a CFD examination of a temperature pipe. i am an apprentice undergraduate student , . I am actually new with confident. is FLUENT in truth can do model, mesh, and analysis of a heat pipe?

[barzin]

Hi guys,,,I'm dead new to Fluent and I need to model a heat pipe using Nano fluids as working fluid,please let me know if u find any idea how to it and I'll do the same,,,,cheers

[JohannVV]

Hi all, I'm also working with phase change and use fluent to solve my problems.
I started with the film boiling tutorial from fluent and I have some questions concerning the code and the function of it.(it is not a programming issue)
The question is, where is the information that the evaporation should start at a particular temperature? For example at 100°C with water!
Here the code concerning my problem.


DEFINE_ADJUST(area_density, domain)
{
Thread *t;
Thread **pt;
cell_t c;
Domain *pDomain = DOMAIN_SUB_DOMAIN(domain,P_PHASE);
real voidx, voidy, voidz=0;

...
...
mp_thread_loop_c (t,domain,pt)
if (FLUID_THREAD_P(t))
{
Thread *tp = pt[P_PHASE];

begin_c_loop (c,t)
{

#if RP_3D
C_UDMI(c,t,0) = (C_VOF_G(c,tp)[0]*C_T_G(c,t)[0]+C_VOF_G(c,tp)[1]*C_T_G(c,t)[1]+C_VOF_G(c,tp)[2]*C_T_G(c,t)[2]);
#endif

#if RP_2D
C_UDMI(c,t,0) = (C_VOF_G(c,tp)[0]*C_T_G(c,t)[0]+C_VOF_G(c,tp)[1]*C_T_G(c,t)[1]);
#endif

}
end_c_loop (c,t)
}
...
...
}

DEFINE_SOURCE(gas, cell, thread, dS, eqn)
{

real x[ND_ND];
real source;
Thread *tm = THREAD_SUPER_THREAD(thread);
Thread **pt = THREAD_SUB_THREADS(tm);

real Kl = C_K_L(cell, pt[1])*C_VOF(cell, pt[1]), Kg = C_K_L(cell, pt[0])*C_VOF(cell, pt[0]);
real L = 1e5;

source = (Kl+Kg)*C_UDMI(cell,tm,0) / L;



C_UDMI(cell, tm, 1) = source;


C_UDMI(cell, tm, 2) = -source*L;



dS[eqn] =0;

return source;
}

DEFINE_SOURCE(liquid, cell, thread, dS, eqn)
{
real x[ND_ND];
real source;
Thread *tm = THREAD_SUPER_THREAD(thread);
Thread **pt = THREAD_SUB_THREADS(tm);

source = -C_UDMI(cell, tm, 1);

dS[eqn] = 0;

return source;
}

DEFINE_SOURCE(energy, cell, thread, dS, eqn)
{
real x[ND_ND];
real source;
Thread *tm = thread;



source = C_UDMI(cell, tm, 2);
dS[eqn] = 0;

return source;
}

[nahmed]

@JahanVV
It is not clear if the phase change you want to do is in closed domain like what happens in case of a heat pipe. as for my application I have just started to look into the UDF manual of Fleunt and at this stage, I am trying to write a UDF for heat source in evaporator and heat sink in condensor section of the heat pipe. If any one can guide me in writing the code that would be highly appreciated.

@Others
I am not completely sure but the simulation of heat pipe is possible in Fluent. It depends upto what extent you want to be precise about your simulation. So far I have not come up with a succesful startegy to model phase change inside a heat pipe. I guess we can do without it as well by modelling wick and the vapor region separately.

[JohannVV]

Hi nahmed,
with the phase change Ii want to model an evaporator an a condenser in a heat pump. For my understanding is my problem with the heat pump similar to yours with the heat pipe.

I do not see a problem to set up a case in fluent, including the programming stuff. I have a problem with the mechanism of evaporation and condensation. I'm desperately searching for some equitation’s to establish the model from the mathematical/physical side.

So if you could help me with the theory (equitation’s, treatments), I could help you with the case setup including writing of the udf!

[haghshenasfard]

Originally Posted by barzin

Hi guys,,,I'm dead new to Fluent and I need to model a heat pipe using Nano fluids as working fluid,please let me know if u find any idea how to it and I'll do the same,,,,cheers

hello
could you please send me any information about CFD simulation of heat pipes? I need a udf for simulations, I you need I can send you a new paper in this field,
masoud734@yahoo.com

[sharonbashyam]

please any one kindly mail me the udf regarding the evaporation and condensation process in heat pipe ..if u would do kindly i would be obliged....my email id is sharon340mech@yahoo.com

[mecman]

Hi all
i want simulate heat pipe in fluent,but i dont Know haw simulate boilnig with Vof model in heat pipe...please any one kindly mail me the udf regarding the evaporation and condensation process in heat pipe ..if u would do kindly i would be obliged....my email id is m.bahreini1990@gmail.com

[shahid nadeem]

Originally Posted by barzin

Hi guys,,,I'm dead new to Fluent and I need to model a heat pipe using Nano fluids as working fluid,please let me know if u find any idea how to it and I'll do the same,,,,cheers

Dear Go through this paper http://www.ansys.com/staticassets/AN...-heat-pipe.pdf.

[Ajai]

Hi
have you tried the UDF manual .. there you will find some useful udf's which you can alter and hook it to your simulation.

[Muhammed_iraq]

Hi all
Please i need UDF

[shahid nadeem]

so much so whether this code worked for Heat Pipe bro

Originally Posted by JohannVV

Hi all, I'm also working with phase change and use fluent to solve my problems.
I started with the film boiling tutorial from fluent and I have some questions concerning the code and the function of it.(it is not a programming issue)
The question is, where is the information that the evaporation should start at a particular temperature? For example at 100°C with water!
Here the code concerning my problem.


DEFINE_ADJUST(area_density, domain)
{
Thread *t;
Thread **pt;
cell_t c;
Domain *pDomain = DOMAIN_SUB_DOMAIN(domain,P_PHASE);
real voidx, voidy, voidz=0;

...
...
mp_thread_loop_c (t,domain,pt)
if (FLUID_THREAD_P(t))
{
Thread *tp = pt[P_PHASE];

begin_c_loop (c,t)
{

#if RP_3D
C_UDMI(c,t,0) = (C_VOF_G(c,tp)[0]*C_T_G(c,t)[0]+C_VOF_G(c,tp)[1]*C_T_G(c,t)[1]+C_VOF_G(c,tp)[2]*C_T_G(c,t)[2]);
#endif

#if RP_2D
C_UDMI(c,t,0) = (C_VOF_G(c,tp)[0]*C_T_G(c,t)[0]+C_VOF_G(c,tp)[1]*C_T_G(c,t)[1]);
#endif

}
end_c_loop (c,t)
}
...
...
}

DEFINE_SOURCE(gas, cell, thread, dS, eqn)
{

real x[ND_ND];
real source;
Thread *tm = THREAD_SUPER_THREAD(thread);
Thread **pt = THREAD_SUB_THREADS(tm);

real Kl = C_K_L(cell, pt[1])*C_VOF(cell, pt[1]), Kg = C_K_L(cell, pt[0])*C_VOF(cell, pt[0]);
real L = 1e5;

source = (Kl+Kg)*C_UDMI(cell,tm,0) / L;



C_UDMI(cell, tm, 1) = source;


C_UDMI(cell, tm, 2) = -source*L;



dS[eqn] =0;

return source;
}

DEFINE_SOURCE(liquid, cell, thread, dS, eqn)
{
real x[ND_ND];
real source;
Thread *tm = THREAD_SUPER_THREAD(thread);
Thread **pt = THREAD_SUB_THREADS(tm);

source = -C_UDMI(cell, tm, 1);

dS[eqn] = 0;

return source;
}

DEFINE_SOURCE(energy, cell, thread, dS, eqn)
{
real x[ND_ND];
real source;
Thread *tm = thread;



source = C_UDMI(cell, tm, 2);
dS[eqn] = 0;

return source;
}