## Fluids

#### vapor condensation

• Astro45
Subscriber

I am trying to simulate condensation of steam for an application of Moisture separator device.first i would like to explain my problem in a brief for understanding,

• steam has a moisture content of 5% of its volumetric flow rate  with a pressure of 1 bar absolute.

• i used Three phases air-Primary Phase, Vapor- secondary phase ,Water- secondary phase

• for multiphase i used VOF formulations ,Implicit scheme

• For mass Transfer in between Liquid and Vapor i used Lee model with the evaporation condensation frequencies of  0.1 and  10000 respectively.

•  standard K-epsilon is what i used to solve my turbulence in this modelling.

• velocity inlet is defined for the mixture with the value of 2.25 m/s.

Though i am not observing any condensation in my model, i run this model in a steady state condition.

when i change my primary phase as water i am observing some condensation of vapor to liquid but at the same time after initialization when i check for the volume fraction for mixture it shows 2 in the inlet (taking the volume fraction as 1 for water).

Is there any problem with my Primary and secondary phases modelling or  else with the source term modelling for the mass transfer?

Astro

• DrAmine
Ansys Employee

You mean: you have wet air and you expect condensation of the condensable component in the bulk (far away from any walls)?

• Astro45
Subscriber

Thanks for the reply sir,

Ya the walls are in the temperature of 300K .I expect the vapor content to get condensates in this process.

• DrAmine
Ansys Employee

If Bulk Condensation: You better write an UDF for mass transfer . There is another option to use Raoul'ts law and species mass transfer.

If the condensation happens at wall you can just model in single phase and use Eulerian Wall FIlm or Lagrangian Wall Film to capture the wall condensation.

• Astro45
Subscriber

Is there any other ways rather than Writing UDF sir.Because i am new to FLUENT.

• DrAmine
Ansys Employee
Try with species mass transfer under mixture model.
• Astro45
Subscriber

Sir,

as far as i know species are different and has transport equations on its own. Please clarify the difference in between species and normal gases in fluent sir.

Thanks