Fluids

Fluids

How to prescribe the energy source term the right way?

    • shitizsehgal
      Subscriber

      Hi,

      I am sorry if this post is shown twice on your feed. My question is about correctly accounting the energy source term in a VOF simulation. My query is as follows:

       

      1. When using a UDF (DEFINE_SOURCE) for prescribing energy source, is it mandatory to select /solve/set/multiphase-numerics/heat-mass-transfer/alternative-energy-source-treatment? to yes ( or can it stay to the default value of [no]). Please help me understand the purpose of this command line or the alternative treatment.
      2. I have latent heat value with me, which is 2706.2 kj/kg. Now should I prescribe it in the material properties of the vapor phase by converting it to kmol units there? I am guessing not, because I am using DEFINE_SOURCE to precribe the energy source. So, in that case
        1. what would be the appropriate units for latent heat in the UDF (kj/kg) or something else? I am currently using J/kg because that coupled with other terms (mass source term) gives me W/m^3 as the units for the energy source. I just want to be sure about what I am doing.
        2. Also, what should i prescribe in the material properties for standard state enthalpy of vapor? (0?)

      Thank you,

       

      Shitiz Sehgal 

    • Rob
      Ansys Employee

      Source terms are assigned to the CELL ZONE, and are mass/heat/momentum etc per unit volume, so some care is needed to make sure you add the correct amount of material. 

      No need to alter the alternative treatment, as to what it does, check the manual  https://ansyshelp.ansys.com/account/Secured?returnurl=/Views/Secured/corp/v221/en/flu_ug/flu_ug_sec_mphase_massxfr.html%23flu_ug_sec_mphase_massxfr_altern_e

    • shitizsehgal
      Subscriber

      Hi Rob, 

      Thanks for your response, but the link that you shared requires me to register as a customer. I am not able to access the information beyond the registration. 

       

      Also, I am still not sure about the units of latent heat in DEFINE_SOURCE. Is it going to be in kj/kg or j/kg or something else? Can you please clarify? 

       

      Thanks, 

      Shitiz Sehgal

    • Rob
      Ansys Employee

      Click on Help in the solver, when the browser opens copy the link into another tab. 

      The source term is for energy, it's for you to work out how much to add. If you're modelling phase change you may want to look at the Fluent multiphase models. 

    • DrAmine
      Ansys Employee

      Energy source term to be provided in W/m³.

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