Greetings!
I have successfully created a few flow models, but I have now been tasked with showing how heat from equipment within a building.
I have read through the documentation and watched some of the videos, but none have helped. I have tried to create the model with Total Heat Generation (in W) and with surfaces set to a Temperature (F), but I am not getting what I expected.
This building houses several generators and engines. I created a pretty simplified model in Revit, I setup two options in this file, one using Total Heat and the other with surface Temperature.
Ambient is 97F
Engines operate at 214f (large polygonal)
Exhaust and Turbo operates a732f (60"d Duct and boxes)
Generators (Boxes opposite end from Exhaust) operate at 241f
all openings in walls are outside air for cooling (18m3/s)
vents in roof
Hi,
Please can you share a CFZ file with us? We cannot open a CFDST without the associated files, which are all created when you double click a CFZ.
There will be one (_support) in the folder above or you can save one from the interface 'S' -> Save Share File.
Thanks,
Jon
Here is my base model with only materials and (air) boundary conditions assigned. This model was working earlier but now refuses to solve.
Hi Kevin,
This should be a pretty easy and quick fix, there are 2 rules to note and making these changes should see this running well:
Otherwise, this looks great, nice work.
Kind regards,
Jon
Thank Jon.
What I am really trying to show is how the heat for the engines, exhaust, and generators build up within the envelope of the building so we can see where we can and can not run cable tray (derating due to excessive heat). Once we have a base line done, I will change the location(s) and size(s) of the inlets to see how the changes things. Lastly, we may design some kind of additional HVAC to cool the areas where the cable trays are.
I have taken everything except inlet volume and outlet press out of the model. it looks to be running.
Would you recommend using total heat generation or temperature to represent the heat gain (from the equipment) into the space?
No problem.
Volumetric heat load is probably best. You could use a fixed temp if you suppressed the engines from the mesh, I would have thought this would be less realistic?
Kind regards,
Jon
Hello Jon,
(Atleast) one more question....
the generator actually have an internal fan that blows the heated air up into the ceiling space. if I can't have a BC within the model space, how should I show that air/heat flow?
Hi Kevin,
There are 2 approaches here.
There is a decent reference in the Wiki on Axial Fans here. The inlet to that model is less than ideal though, very short.
Kind regards,
Jon
Jon,
Does it need to be a cylinder? Could I recess a rectangular void in Revit?
Yup 🙂
Can I still apply a total heat factor to the supress volume? We want to show the heat convection off the equipment and the exhaust (temp/cfm) too. I'm thinking that I can not.
Does the supressed volume still affect air flow?
Jon,
Can you please tell me what I have done wrong. I am getting flow, but no convection from the equipment.
I keep getting this error when I try to upload the cfz file "The contents of the attachment doesn't match its file type"
Hi Kevin,
You should be able to apply a Volumetric Heat Load to each solid, provided it is not suppressed from the mesh.
Be sure to suppress the volume where the temp and flow outlet is though, so we avoid an internal Boundary Condition - you may need to split the volume into different parts in CAD to enable you to do this.
If you can share your CFZ also it would help. The max file size is 2MB on here I think, Dropbox or Autodesk360 ?
Jon,
I'm completely stumped. I'm sure it's an obvious answer like BC internal to the model.
I couldn't upload it to dropbox (blocked by IT), see if you can get it from my google drive folder
https://drive.google.com/file/d/0B-YDZPVOWv4Remh2ZG1tT1lxRjg/edit?usp=sharing
Hi Kevin,
It will likely be something really simple as you say, helps for me to look at it though.
I'll pm you, I have an idea how we can share the model.
Hi Kevin,
Thank you for sharing this file.
Your setup looks really good to me, I cannot fault it.
The questions you raise regarding applying a temperature vs a heat load are ones that you alone can answer. I suggest you assign what is most realistic. If the part surface temperatures are constant, known and uniform then we can use this (you will need to suppress the solid parts). If not then I would suggest a heat load. You can always double check the surface temps of the converged model.
I suggest 3 things:
Kind regards,
Jon
By way of demonstrating how we can view results, check this out. It shows velocities on a cut-plane, flow from each of the exhausts and where it travels to and also the temperatures of each of the generators. This is your model with no changes applied, we should still do the above.
I have attached a view settings file for you to import to show it like this (View -> Apply View).
Thanks again Jon.
I had made several section, and views to go over with the design team and the owner. I'm still working with the building and the equipment to get it more accurate.