Shell elements
Shell elements
(OP)
Hello,
I have a problem were a stainless tube (.011 thick) is plated on the inside with copper (.002). I have a heat source generated inside the plated tube and I am trying to see how hot the internal parts are getting? Just a note the stainless pipe has heat sink disks brazed to the outside at a specified pitch which are held at a constant temp and the internal parts consist of another assembly that will be omitted for now to simplify the problem. So to resume I basically have a stainless pipe with copper plating on the inside. I have placed a heat flux on the copper and held the outside surface of the stainless steel at constant temp. I have modeled the assembly as two tubes with the outer tube representing the stainless pipe and a thinner tube representing the copper plating. I then used a bonded contact and meshed the outer tube with bricks and the inner tube (due to its thin thickness) with shell elements meshed using midplane. When I run the analysis no heat is transferred through the copper into the stainless tube. I am not sure why? Did I not fill in a parameter some were for the shell elements? If I use brick elements for the inner tube the mesh is very poor even at fine settings but heat does transfer through (do not trust the results with this mesh). Any help would be great.
Thanks
Steve
I have a problem were a stainless tube (.011 thick) is plated on the inside with copper (.002). I have a heat source generated inside the plated tube and I am trying to see how hot the internal parts are getting? Just a note the stainless pipe has heat sink disks brazed to the outside at a specified pitch which are held at a constant temp and the internal parts consist of another assembly that will be omitted for now to simplify the problem. So to resume I basically have a stainless pipe with copper plating on the inside. I have placed a heat flux on the copper and held the outside surface of the stainless steel at constant temp. I have modeled the assembly as two tubes with the outer tube representing the stainless pipe and a thinner tube representing the copper plating. I then used a bonded contact and meshed the outer tube with bricks and the inner tube (due to its thin thickness) with shell elements meshed using midplane. When I run the analysis no heat is transferred through the copper into the stainless tube. I am not sure why? Did I not fill in a parameter some were for the shell elements? If I use brick elements for the inner tube the mesh is very poor even at fine settings but heat does transfer through (do not trust the results with this mesh). Any help would be great.
Thanks
Steve





RE: Shell elements
Heat will not "jump" across the distance from the mid-plane of the copper over to the inner surface of the stainless steel...that is your biggest problem.
Thought #1
Model the 2-D cross-section of a segment of the piping system as a 2-D axisymmetric model. Basically, cut the pipe longitudinally and take the upper cross-section. Place the heat flux along the inner surface. Doing this, you can make the mesh very fine, get the same or better answer and keep the surface representing the copper in intimate contact with the steel. You should probably model from the center between two heat sinks to the next (1 pitch starting at the mid-point between two heat sinks).
Thought #2
Instead of holding the outer surface of the steel at a constant temperature, provide a convective boundary with ambient temp. If you sent the nodal temperature at the surface of the steel, you want get the cooling from your heat sink and you will actually register higher temperatures than you would measure.
RE: Shell elements
Thanks for your thoughts
RE: Shell elements
When meshing thin parts in an assembly I usually have better luck by avoiding using the mid-plane mesher at all costs.
Instead of MP meshing, deactivate surfaces on thin parts and use the plate/shell surface mesher (right click + CAD Mesh Options + Selected for Meshing).
This prevents ALGOR from having make decisions about collapsing surfaces and mainatining connectivity which results in a much more pleasurable meshing experience.
RE: Shell elements
I turned off the surfaces for my thin part but I am not doing something correct because the mesher would just crash when. Are you using plate or brick elements? Are you turning off all surfaces or just the ends of the thin part?
Thanks
RE: Shell elements
Can you upload an image of either your model or your geometry. If you are doing what I am picturing in my head, you really should use 2-D axi-symmetry. It would be much faster, better refined mesh, and produce at least as accurate results.
RE: Shell elements
Thanks GBor and rybose for your time and comments. I have found that there are not too many forums to go to with respect to algor. It is nice to get feedback from other users.
I would like to upload an image of my model but unfortunately I have been told not to. Sorry about that.
Thanks
RE: Shell elements
Like GBor said, turn off all of the surfaces *except* the ones you'd like to mesh with plates/shells.
If you try an mesh a part with no surfaces "selected for meshing", the mesher will give you an error just like you said.
RE: Shell elements
Like GBor said, turn off all of the surfaces *except* the ones you'd like to mesh with plates/shells.
If you try to mesh a part with no surfaces "selected for meshing", the mesher will give you an error just like you said.
RE: Shell elements
Like GBor said, turn off all of the surfaces except the ones you'd like to mesh with plates/shells.
If you try to mesh a part with no surfaces "selected for meshing", the mesher will give you an error just like you said.