[peterliu]

Hi
I am doing simulation of evaporation of R134a in a channel and I did not observed phase change from R 134a to R134a gas. Does anyone can help me ?

FLUENT
Version: 3d, dp, pbns, vof, lam, transient (3d, double precision, pressure-based, VOF, laminar, transient)
Release: 12.1.4
Models
------

Model Settings
---------------------------------------------------------
Space 3D
Time Unsteady, 1st-Order Implicit
Viscous Laminar
Heat Transfer Enabled


Material Properties
-------------------

Material: r134a-gas (fluid)

Property Units Method Value(s)
----------------------------------------------------------------
Density kg/m3 constant 32.203999
Cp (Specific Heat) j/kg-k constant 1030.98
Thermal Conductivity w/m-k constant 0.01381
Viscosity kg/m-s constant 1.1687e-05
Molecular Weight kg/kgmol constant 102.03
Standard State Enthalpy j/kgmol constant 42063000
Reference Temperature k constant 298.14999

Material: r134a-liquid (fluid)

Property Units Method Value(s)
-----------------------------------------------------------------
Density kg/m3 constant 1207.3
Cp (Specific Heat) j/kg-k constant 1424.41
Thermal Conductivity w/m-k constant 0.081198998
Viscosity kg/m-s constant 0.00019525
Molecular Weight kg/kgmol constant 102.03
Standard State Enthalpy j/kgmol constant 23909000
Reference Temperature k constant 298.14999
Thermal Expansion Coefficient 1/k constant 0
Speed of Sound m/s none #f

Boundary Conditions
-------------------

Zones

name id type
------------------------------------
wall-solid 10009 wall
inlet 6 velocity-inlet
outlet 7 pressure-outlet

wall-solid

Condition Value
-------------------------------------------------------------
Thermal BC Type 1
Temperature (k) 300
Heat Flux (w/m2) 15000
Convective Heat Transfer Coefficient (w/m2-k) 0
Free Stream Temperature (k) 300


inlet

Condition Value
--------------------------------------------
Velocity Magnitude (m/s) 0.2
Coordinate System 0
Temperature (k) 295.15

Solver Settings
---------------
---------------------------------------------
Time Step (s) 0.00050000002
Max. Iterations Per Time Step 100

Relaxation

Variable Relaxation Factor
-----------------------------------
Pressure 0.3
Density 1
Body Forces 1
Momentum 0.7
Volume Fraction 0.5
Energy 1

Pressure-Velocity Coupling

Parameter Value
------------------
Type SIMPLE

Discretization Scheme

Variable Scheme
------------------------------------
Pressure PRESTO!
Momentum First Order Upwind
Volume Fraction First Order Upwind
Energy First Order Upwind

[peterliu]

Forgot to mentioned the UDF, I setted the saturated temperature to 298.15K for R 134a in 5.6bar pressure.

/* UDF to define a simple mass transfer based on Saturation
Temperature. The "from" phase is the gas and the "to" phase is the
liquid phase */

#include "udf.h"

DEFINE_MASS_TRANSFER(liq_gas_source, cell, thread, from_index,
from_species_index, to_index, to_species_index)
{
real m_lg;
real T_SAT = 298.15;
Thread *gas = THREAD_SUB_THREAD(thread, from_index);
Thread *liq = THREAD_SUB_THREAD(thread, to_index);

m_lg = 0.;
if (C_T(cell, liq) >= T_SAT)
{
m_lg = -0.1*C_VOF(cell,liq)*C_R(cell,liq)*
fabs(C_T(cell,liq)-T_SAT)/T_SAT;
}
if ((m_lg == 0. ) && (C_T(cell, gas) <= T_SAT))
{
m_lg = 0.1*C_VOF(cell,gas)*C_R(cell,gas)*
fabs(T_SAT-C_T(cell,gas))/T_SAT;
}

return (m_lg);
}

[vinod500ind]

Hi,
I'm having similar kind of problem. That's unable to observe the phase change.

Did you found any solution on this?

Please do let me know.

Regards,

Vinod

[ma_ta65]

hi
i want the standard state enthalpy of r404a(liquid and gas) for evaporation modeling.

[Muhammed_iraq]

Hi all
after compiling UDF with FLUENT , how can i hook it with FLUENT?
Many Thanks

[Muhammed_iraq]

Hi all
Please, i did not find R134a in list of fluid
how can i find it?

[gjtmawa]

Enable the appropriate NIST real gas model by typing the following text command at the ANSYS Fluent console prompt：
> define/user-defined/real-gas-models/nist-real-gas-model

[gjtmawa]

Enable the appropriate NIST real gas model by typing the following text command at the ANSYS Fluent console prompt：
> define/user-defined/real-gas-models/nist-real-gas-model

[Muhammed_iraq]

Originally Posted by gjtmawa

Enable the appropriate NIST real gas model by typing the following text command at the ANSYS Fluent console prompt：
> define/user-defined/real-gas-models/nist-real-gas-model

Dear gjtmawa
thank you so much
i went to define<<user-define and i did not find the real-gas and<<, why??

[anu02]

hello peterliu,
would u plz tell me how you get standard state enthalpy of r134a?
i want standard state enthalpy of r1234ze and i have searched internet, research papers, softwares but unable to find it.
i would be very thankful to you

[LanLima]

I'm trying to do an equal simulation of an evaporator, but with r507a, the problem is that I can't find a vapor phase and a separate liquid, how could I do this?