[cscfx]

Hello,everybody,i want to simulate the process of frost formation at the cooling plate.i use the Euler model,adding a mass transfer source in the two phase interaction.In the Euler multiphase flow model ,the primary phase being the gas (humid air) containing dry air and water vapor and the secondary phase being the solid (ice), and one species transport equation was used to consider the masstransfer between vapour and ice. the following is the udf of define_mass_transfer:
#include "udf.h"
#include "sg_mphase.h"
DEFINE_MASS_TRANSFER(liq_gas_source,cell,thread,fr om_phase_index,from_species_index,to_phase_index,t o_species_index)
{
real hr;
real Wvs; //vapour mass fraction in saturated condition//
real Wv; //vapour mass franction in wet air//
real m_lg_m;
real Pvs;
real Pv;
real Td;

Thread *tf = THREAD_SUB_THREAD(thread,from_phase_index);
Thread *ice = THREAD_SUB_THREAD(thread,to_phase_index);

if(C_T(cell,tf)<=273.15 && C_T(cell,tf)>173.15)
{
Pvs=exp(-5674.5359/C_T(cell,tf)
+6.3925247 -9.677843*pow(10,-3)*C_T(cell,tf)+6.22157*pow(10,-7)*C_T(cell,tf)*C_T(cell,tf)
+2.0747825*pow(10,-9)*C_T(cell,tf)*C_T(cell,tf)*C_T(cell,tf)
+9.484024*pow(10,-13)*C_T(cell,tf)*C_T(cell,tf)*C_T(cell,tf)*C_T(cel l,tf)+
4.1635019*log(C_T(cell,tf)));
}
else if

(C_T(cell,tf)<=473.15 && C_T(cell,tf)>273.15)
{
Pvs=exp(-5.8002206*pow(10,3)/C_T(cell,tf)
+1.3914993-4.8640239*pow(10,-2)*C_T(cell,tf)
-4.1764768*pow(10,-5)*C_T(cell,tf)*C_T(cell,tf)
-1.4452093*pow(10,-8)*C_T(cell,tf)*C_T(cell,tf)*C_T(cell,tf)+6.545967 3*log(C_T(cell,tf)));
}

hr=0.622*Pvs/(101325-Pvs);
Wvs=hr/(1+hr);
Wv=C_YI(cell,mix,0);

if
(C_T(cell,tf)<=273.15)
{
m_lg_m=10.0*C_VOF(cell,thread)*C_R(cell,thread)*Wv *(Wv-Wvs)/Wvs;

}
else if (C_T(cell,tf)>273.15)
{
m_lg_m=0;
}
return (m_lg_m);

}
but there always some errors when the fluent computing, after one step,it stopped. So,there is anybody know how to solve this problem when using DEFINE_MASS_TRANSFER? there is no need to define energy source when using DEFINE_MASS_TRANSFER?
Hope someone can give some addvice,thanks !

[vinerm]

There are functions that need phase level thread but you have provided mixture level threads, such as, C_YI and C_VOF. A good way to ensure is to go to Contour Plots and then check whether a field, such as, species mass fraction or volume fraction appear under phase or mixture. If it appears for mixture, then use mixture thread else use phase thread. Species mass fractions and volume fractions, both, belong to their own phase threads, so, use ice or tf instead of mix as their argument.

Mass transfer must always be accompanied with other transfer of momentum, energy, etc. However, that is taken care of by single UDF. So, you don't need to do anything extra.

You may not really need this UDF since you can use Icing simulation in Fluent instead of using your own UDF, provided, icing simulation matches your requirement.

[cscfx]

thanks for your reply. It was really useful. and I want to ask you where I can find the Icing model? or using TUI command to start the model? thanks!

[qntldoql]

Hi, I am currently doing a similar simulation (humid air > ice). I was wondering how you fixed your UDF? Currently I am using very similar UDF to your's with different equation. But encountering a problem with FLUENT where the simulation does not begin as it states that the executable is only for post-processing.

May I ask how you addressed this particular section of your UDF run the simulation?

Wv = C_YI(cell,thread,0);

m_lg = gamma* C_VOF(cell, thread) * C_R(cell, thread) * Wv * (Wv - Wvs) / Wv;

[skathare]

I am modeling a frost formation problem on a cylinder. I am wondering if someone can share their UDF and how to implement it in Fluent?

[aneesham75]

I am also trying to do the same simulation for the study purpose. It would be helpful
for me if any one send the updated udf code to mail (aneesham7589@gmail.com).