[gaza]

Hi everyone,
I implemented Lee model in the following UDF:

#include "udf.h"
#include "sg_mphase.h"
#include "mem.h"
#include "metric.h"
#include "flow.h"
#include "sg.h"

DEFINE_SOURCE(vap_src, cell, vap_th, dS, eqn)
{
    real m_dot_v;
    const real T_SAT = 373.0;
    Thread *mix_th, *liq_th;
    mix_th = THREAD_SUPER_THREAD(vap_th);
    vap_th = THREAD_SUB_THREAD(mix_th, 0);
    liq_th = THREAD_SUB_THREAD(mix_th, 1);
    m_dot_v = 0.0;
    if (C_T(cell, mix_th) > T_SAT)
    {
        //Message("Jestem w if vap\n");
        m_dot_v = 0.1*C_R(cell, liq_th)*C_VOF(cell, liq_th)*(C_T(cell, mix_th) - T_SAT)/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;
        //dS[eqn] = 0.1*C_R(cell, liq_th)*C_VOF(cell, liq_th)/T_SAT;
        //Message("VOF = %f", C_VOF(cell, liq_th), " \n");
        //Message("T = %f", C_T(cell, mix_th), " \n");
        //Message(" m_dot_v = %f%s", m_dot_v, "\n");
    }
    else 
    {
        //Message("Jestem w else vap\n");
        m_dot_v = -0.1*C_R(cell, vap_th)*C_VOF(cell, vap_th)*(T_SAT - 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;
        dS[eqn] = 0.0;
        //dS[eqn] = 0.1*C_R(cell, vap_th)*C_VOF(cell, vap_th)/T_SAT;
        //Message("VOF = %f", C_VOF(cell, vap_th), " \n");
        //Message("T = %f", C_T(cell, mix_th), " \n");
        //Message(" m_dot_v = %f%s", m_dot_v, "\n");
    }
    //Message(" M_DOT_v = %f%s", m_dot_v, "\n");
    return m_dot_v;
}
DEFINE_SOURCE(liq_src, cell, liq_th, dS, eqn)
{
    real m_dot_l;
    const real T_SAT = 373.0;
    Thread *mix_th, *vap_th;
    mix_th = THREAD_SUPER_THREAD(liq_th);
    vap_th = THREAD_SUB_THREAD(mix_th, 0);
    liq_th = THREAD_SUB_THREAD(mix_th, 1);
    m_dot_l = 0.0;
    if (C_T(cell, mix_th) > T_SAT)
    {
        //Message("Jestem w if liq\n");
        m_dot_l = -0.1*C_R(cell, liq_th)*C_VOF(cell, liq_th)*(C_T(cell, mix_th) - T_SAT)/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] = 0.0; //-0.1*C_R(cell, sec_th)*(C_T(cell, mix_th) - T_SAT) / T_SAT;
        //dS[eqn] = -0.1*C_R(cell, liq_th)*C_VOF(cell, liq_th)/T_SAT;
        //Message("VOF = %f", C_VOF(cell, liq_th), " \n");
        //Message("T = %f", C_T(cell, mix_th), " \n");
        //Message(" m_dot_l = %f%s", m_dot_l, "\n");
    }
    else 
    {
        //Message("Jestem w else liq\n");
        m_dot_l = 0.1*C_R(cell, vap_th)*C_VOF(cell, vap_th)*(T_SAT - 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;
        //dS[eqn] = -0.1*C_R(cell, vap_th)*C_VOF(cell, vap_th)/T_SAT;
        //("VOF = %f", C_VOF(cell, vap_th), " \n");
        //Message("T = %f", C_T(cell, mix_th), " \n");
        //Message(" m_dot_l = %f%s", m_dot_l, "\n");
    }
    //Message(" M_DOT_l = %f%s", m_dot_l, "\n");
    return m_dot_l;
}
DEFINE_SOURCE(enrg_src, cell, mix_th, dS, eqn)
{
    real enrg_dot = 0.0;
    const real T_SAT = 373.0;
    const real LAT_HT = 2200e3;
    Thread *vap_th, *liq_th;
    vap_th = THREAD_SUB_THREAD(mix_th, 0);
    liq_th = THREAD_SUB_THREAD(mix_th, 1);
    if (C_T(cell, mix_th) > T_SAT)
    {
        enrg_dot = -0.1*C_VOF(cell, liq_th)*C_R(cell, liq_th)*LAT_HT*(C_T(cell, mix_th) - T_SAT)/T_SAT;
        dS[eqn] = 0.0;//-0.1*C_VOF(cell, sec_th)*C_R(cell, sec_th)*LAT_HT / T_SAT;
        //dS[eqn] = -0.1*C_VOF(cell, liq_th)*C_R(cell, liq_th)*LAT_HT/T_SAT;
    }
    else 
    {
        enrg_dot = 0.1*C_VOF(cell, vap_th)*C_R(cell, vap_th)*LAT_HT*(T_SAT - C_T(cell, mix_th))/T_SAT;
        dS[eqn] = 0.0;//-0.1*C_VOF(cell, pri_th)*C_R(cell, pri_th)*LAT_HT / T_SAT;
        //dS[eqn] = -0.1*C_VOF(cell, vap_th)*C_R(cell, vap_th)*LAT_HT/T_SAT;
    }
    return enrg_dot;
}

UDF compiles and works well. I did two simulations: first with domain filled with water at saturation temperature 373 K and left boundary at T = 398 K. I ran simulation and evaporation appeared (volume phase of water and vapor changed). When I set initial conditions to only vapor in the domain, at sat. tempr. 373 K and boundary condition at right wall at 300 K I haven't noticed any condensation. I do not know why because I checked m_dot_l and m_dot_v in both cases and they are not zero (by uncomment lines in UDF). Is it bug in Fluent?? Can anybody help? I append the case file.

[Nitin Minocha]

Hi
I am using mixture model and using evaporation-condensation model for mass transfer. I am not able to model condensation.
Any help will be greatly appreciated.


Thank You
Nitin Minocha

[gaza]

I see that you have the same problem as me
Few other guys on this forum also reported on that
I don't know why it is so

[gaza]

Hi All,
I found the solution. Fluent 16.2 has a bug. Everything works well in 17.1 version.

[Abdelhamid Kassem]

Originally Posted by gaza

Hi All,
I found the solution. Fluent 16.2 has a bug. Everything works well in 17.1 version.

Could you upload the working files after fixing the problem because, i still stuck with errors while doing the analysis,and i need it in my bachelor project, and i'm a beginner user of fluent.
My email: Abdelhamidkassem93@gmail.com

Thanks in advance.

[ImVKMahato]

Hello sir, I m new to heat pipe (wick or wickless ) simulation using UDF.I have done a lot of research but has not been very much fruitful. Could you plz guide me How to do it using UDF. I request you. It is very essential for my project. Thank u

[gaza]

Originally Posted by ImVKMahato

Hello sir, I m new to heat pipe (wick or wickless ) simulation using UDF.I have done a lot of research but has not been very much fruitful. Could you plz guide me How to do it using UDF. I request you. It is very essential for my project. Thank u

Hi All
The code in the post #1 is correct. It did not work in Fluent 16 but it works in 17. The is to compile this on linux because windows compiler sometimes does not see the errors.

[ImVKMahato]

I have watch few videos on youtube regarding using UDFs n compiling them. However I m not very clear about it. Do you have any suggestion where I can make my concept clear about compiling , running these codes and getting desired results. Thanks for the previous reply.... Regards

[gaza]

Originally Posted by ImVKMahato

I have watch few videos on youtube regarding using UDFs n compiling them. However I m not very clear about it. Do you have any suggestion where I can make my concept clear about compiling , running these codes and getting desired results. Thanks for the previous reply.... Regards

read the udf manual ...

[ImVKMahato]

I have been reading UDF manual for quiet a few days now...Could you advice or suggest something which can help me move ahead in my work in simulation. I donot have much knowledge about the various models eg. Lee model etc..

[gaza]

The udf is in post #1
You have to compile it and hook the udf into your simulation.
The tutorial on that is film boiling

https://www.google.pl/url?sa=t&rct=j...ci9r3Q&cad=rja

[ImVKMahato]

Thankful for the tutorial you provided .. Leme try it and i will let you know if i have some problem.. Thank you again.. Regards

[ImVKMahato]

Could you email me the files mentioned in the tutorial test-2d.msh and boiling.c? i could not find them ..thanks

[ImVKMahato]

VOF multiphase model too..if u have..

[Rezaa]

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

[manan13]

Increase condensation frequency

[gaza]

Originally Posted by gaza

Hi All
The code in the post #1 is correct. It did not work in Fluent 16 but it works in 17. The is to compile this on linux because windows compiler sometimes does not see the errors.

Hi
sorry I was wrong. It also does not work in fluent 17. I got evaporation and condensation but also artificial condensation at the liquid-vapor interface. I do not know how to solve it.

[phong6495]

Hi gazza, you uses VOF models or mixture model????

[gaza]

I used VOF model

[phong6495]

Thanks gazza. I'm also simulating evaporation, condensation with thermosyphon. With condensation, your boundary conditions like? Are the heat transfer coefficients used?
Thanks!!!!