Heat transfer through boiler walls

- May 2, 2019 at 3:17 pm
  
  Tamoor
  Subscriber
  
  Hi
  
  I am simulating combustion inside boiler using Fluent. I have a question regarding heat transfer through walls. I want to remove certain amount of heat from the walls (13MW) but I have problem using boundary conditions. I tried to use negative heat flux but then wall temperature becomes negative or too low and temperature profile has a strong gradient near walls. I want to remove fixed amount of heat and heat flux is not working. If anyone has an idea how to handle this problem please let me know
- May 3, 2019 at 5:08 am
  
  veera
  Subscriber
  
  did u assigned material property clearly?
- May 3, 2019 at 6:50 am
  
  Tamoor
  Subscriber
  
  The entire domain is fluid domain, however, I have assigned walls as aluminium in boundary conditions with small thickness
- May 6, 2019 at 9:58 am
  
  DrAmine
  Ansys Employee
  
  Are the walls internal walls? Can you insert the screenshot of the geometry, the cell zones and the wall boundary condition?
- May 6, 2019 at 10:05 am
  
  DrAmine
  Ansys Employee
  
  Have you tried giving the wall a finite thickness and using a negative heat generation rate?
- May 6, 2019 at 10:15 am
  
  Tamoor
  Subscriber
  
  Thank you for your reply Amine, I modelled only the fluid domain with no separate walls, I have attached snapshots of geometry (inlet is at bottom, outlet at top, one side is symmetry and three walls from which heat is to be removed). Also attached you will find cell zone and boundary conditions. Your help is highly appreciated.
  
  Kind regards,
  
  Tamoor
- May 6, 2019 at 10:18 am
  
  Tamoor
  Subscriber
  
  Yes, I tried using negative heat generation but it's not working. Sorry I couldn't attach pictures due to some error. But you can find geometry picture attached to original post. I have only one zone (which is fluid with methane-air 2 step mixture) and at walls I have tried heat flux and negative heat generation rate as well but they don't work
- May 6, 2019 at 11:21 am
  
  DrAmine
  Ansys Employee
  
  I do not download attachments. Please try insert intsead of attaching.
- May 6, 2019 at 11:28 am
  
  Tamoor
  Subscriber
  
  I cannot insert picture, I am getting an error
- May 6, 2019 at 11:36 am
  
  DrAmine
  Ansys Employee
  
  If this is an external wall it is just safe to provide a negative heat flux. Have you tried that?
- May 6, 2019 at 11:39 am
  
  Tamoor
  Subscriber
  
  I haven't tried that. Actually, I only modeled fluid domain with internal walls, but I think I can try modelling external wall and then specify the negative heat flux. Thanks for helping I'll try that and will let you know.
  
  Kind regards,
  
  Tamoor
- May 7, 2019 at 8:56 am
  
  DrAmine
  Ansys Employee
  
  With internal walls what you are removing from one side will be added to the other side and so back to fluid. Use external walls