We’re putting the final touches on our new badges platform. Badge issuance remains temporarily paused, but all completions are being recorded and will be fulfilled once the platform is live. Thank you for your patience.
Fluids

Fluids

Topics related to Fluent, CFX, Turbogrid and more.

Converting heat flux to heat source using UDF code

    • Jonathan Park
      Subscriber

      I have a 2D CFD model where rectangle 1 is inserted within rectangle 2. Rectangle 1 represents the cross section of a material with finite length and width, and rectangle 2 represents the cross section of a vacuum chamber where the material is placed. I have to model the heat flux boundary condition onto the surface of rectangle 1 as a heat source boundary condition. Could there be a way to convert heat flux to heat source using UDF code? Heat flux is non-uniform, and I can't really convert heat flux to heat source boundary condition by hand because this is a 2D problem. 

    • Rob
      Forum Moderator

      I'm not sure I quite follow. If you want to add a "volume" source into a thin wall, then the Heat Generation might be appropriate. 

       

    • Jonathan Park
      Subscriber

       

       

      I only have a given non-uniform heat flux distribution as a function of x and y, which is set onto the material. Howeer, in my problem, since the external surface of the material is the internal surface of the vacuum chamber, I must treat treat the incoming heat flux as heat source occuring within the material. 

      I understand that if I had a heat source given in my problem, I would directly use Heat Generation. However, I’m only given a heat flux which must be converted to heat source. 

      For Shell Conduction, if I’m not given a heat source but just a heat flux. In ‘Heat Generation Rate’, can I just divide heat flux by the thickness even if the heat flux q”(x,y) is non-uniform, 2D, dependent on x and y? Does shell conduction consider takes account of both directions normal to the wall and along the wall (or both x and y directions) ? I thought shell conduction only considers heat flux normal to the surface. 

       

       

    • Rob
      Forum Moderator

      You need to figure out what's in the model. If the block is present in both cases, you can use a source into the solid volume. Or you add a flux through a surface, a profile may be suitable for that. 

      Shell conduction means heat can conduct along a thin wall, otherwise it can't. The heat generation doesn't need shell conduction and is a way to get heat into a thin wall: typical use case could be underfloor heating or heating jackets on pipes. 

    • Jonathan Park
      Subscriber

      Yes, the block is present in both cases. Both the reactor (larger rectangle) and substrate (smaller rectangle) are cylindrical cross sections. The substrate has a thickness of 5 mm, so it's thin. Is there a way to apply source into the solid volume (W/m^3) if I only have the non-uniform heat flux profile (W/m^2)? The reason I can't apply the heat flux is because the external surface of the substrate is the internal surface of the CFD model of the reactor. Therefore I must convert my heat flux distribution into a volumetric heat source. 

    • Rob
      Forum Moderator

      If you know the respective volume & area then yes, you can get the correct number of Watts into the system. What you can't do is add a volume source bounded by a heat flux boundary: the source volume will either be 1K or 5000K as Fluent hits the solver (default) limiters. 

Viewing 5 reply threads
  • The topic ‘Converting heat flux to heat source using UDF code’ is closed to new replies.