Fluids

Fluids

Condensation Issue

    • Hassan_Kashif
      Subscriber
      I am commenting on this thread as I am having a similar problem. I am attempted to model condensation of water vapor into water vapor. I am quite new to this type of modelling and so far I have come across the use of VoF model and Mixture modelling. I am now using Eurlerian model to model Water as a Primary phase and Air and Water Vapor as 2 secondary phases. From tutorials modelling condnesation, all focus on condensation on a 2D surface. Most use VoF and the evaporation-condensation model but confusingly set mass transfer as water-liquid to water vapor, which is the opposite of what they are modelling. I ran this set up and it worked for 2D geometry. The set up initialisation conditions are shown in the file name (model, phases, condenser material, vapor temperature, condenser wall temp, RH).
      The results are adequate however I am still unsure why this works when this is the mass transfer set up:
      The real problem arises when I transfer this method set up to 3D geometry, if I keep the mass transfer the same I do not get any condensation in my results:
      This is after 1500 iteration with a time step of 0.05s.
      From this I assumed the problem was the fact that the mass transfer was set up the wrong way since I had water vapor at 273.15 degrees that would not condense at all. So I changed the mass transfer from 'water liquid to water vapor' to 'water vapor to water liquid'. When I initialise this I get the warning:
      Compute Node ID: 0
      From-phase Domain ID: 2
      To-phase Domain ID: 0
      Cell Number: 0
      Latent Heat: -2.26922e+06

      ERROR: Latent heat cannot be less than zero!
      From researching for the past few weeks I assume my main problem lies in the material properties as stated in this very thread however the material properties for Standard State Enthalpy are correct and Latent heat for water liquid is defined correctly as 2263073 J/kg. The Latent heat for air and water vapor are left as 0. I tried setting the latent heat of water vapor as -2263073 and initialised but the same error was present. I hope you have some guidance on the issue and let me know whether I have missed something glaringly obvious, this is my first time modelling something like this.
      Hassan
    • System
      Subscriber
      This discussion was created from comments split from: Latent Heat cannot be less than zero.
    • DrAmine
      Ansys Employee
      Do you have thin film condensation?
    • DrAmine
      Ansys Employee
      If the condensation will occur at the free surface level: you require UDF to implement an appropriate mass transfer model or rely in VOF in 2022R1 Beta feature Model.
    • Hassan_Kashif
      Subscriber
      Hello DrAmine Apologies, I did not know how to access this thread and have just found it now after asking the question again with more details in a new thread. The problem is shown in there.

      Hassan
    • DrAmine
      Ansys Employee
      I do not follow: what is shown there? What is here?
    • Rob
      Ansys Employee
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