[Bin]

Hi all,

I defined a mixture (using species transport model with reaction option disabled) containing liquid A and liquid B with different saturation temperature set in evaporation mass transfer model:

Liquid A: 350K
Liquid B: 370K

The mixture is heated continuously until a point (around 350K), Liquid A evaporated which is good, but I noticed that Liquid A evaporated as well! (Noticed from the residual)

Isn't that Liquid B will evaporate only when the temperature of the mixture reach 370K? Why both liquid evaporate at the same time?

Thanks for your time for reading my question and I hope that anyone can please help me in this problem.

Thank you.

Regards,
Bin

[zombiaska]

Liquids evaporate at any temperature. But their intensity is different. When liquid reaches it's critical temperature it starts to boil and evaporates at big intensity.

[Bin]

Hi zombiaska, thanks for the reply.

I understand that the intensity issue you mentioned. But isn't that in FLUENT the evaporation start only if the saturation temp is reached? Based on the equations, the mass transfer only occurred when the liquid temperature exceed the saturation temperature set. I tried to simulate on water only, it works well as water vaporized (evaporate) when 373.15K is reached. However, when there are two components, it just does not work right.

Is there any other possible mistake that I had made?

Regards,
Bin

[german.gd20]

Hello Bin

I'm trying to simulate water evaporation in Fluent 14.0 but I haven't gotten any result of evaporation after running the simulation.

Can you help me with the simulation?

What are the parameters that you used?

This is what I've been doing


Analysis: 2D, Double Precision
Scale: Specify Scaling Factors: X=Y=0,01
View Length Unit in:m
General Settings: Pressure-Based
Transient
Absolute
Gravity (y=-9,81)
Models: Multiphase->VOF
Energy->ON

Materials: Air
Water-liquid

Phases: Air=Primary Phase
Water-liquid=Second Phase
Interaction-> Mass Tab->Mechanism->Evaporation-condensatio
Interaction-> Surface Tension Tab ->Surface Tension Force Modeling->ON

Boundary Conditions: inlet (Phase=mixture)->Edit->Momentum Tab-> Velocity Magnitude(m/s)=0,5
inlet (Phase=water-liquid)->Edit->Multiphase Tab->Volume Fraction=1
Wall (Phase=wáter-liquid)->Edit->Thermal Tab->Temperature (k)=373

Solution Methods: Pressure-Velocity Coupling->SIMPLE
Spatial Discretization->Gradiet->Least Squares Cell Based
Spatial Discretization->Pressure->PRESTO!
Spatial Discretization->Momentum->QUICK
Spatial Discretization->Volumen Fraction-> QUICK
Spatial Discretization->Energy-> QUICK

Solution Initialization: Standard
Patch:Phase->Mixture
Variable->Temperature
Value(K)->1
Zones to Patch->Fluid_air & Fluid_water

Run:Time Step Size(s)->1e-05
Number of Time Steps->1000

I hope that you can help me.

Regards

[Bin]

Hi,

There are few things that you need to check with:

Firstly, check whether the saturated temperature in your evaporation-condensation model is logic/reasonable.(you might need to consider the reasonable temperature range for your model). There is a tuning parameter in this model that you need alter the value to match your simulation's condition.

Secondly, check the temperature in your domain. If the calculated temperature is lower than the predetermined saturated temperature, no evaporation will occurred.

Lastly, I see that your time step is 1e-5, and no. of time step used is only 1000, means you only run for 0.01sec. I guess you can't expect to see any difference especially evaporation happened in 0.01sec, right?

*correct me if i'm wrong*

These are the things I think you can consider on. I hope these help you on your simulations.

Good Luck!

Regards,
Bin