Conjugate Heat Transfer Questions
Hello there
Trying to follow the heat exchanger tutorial and have some inquiries:
Inquiry 1: I am assuming there is no way to get thermo-coupled walls to be fully setup upon import ? It looks to me that eg one of the baffle walls is picked up as Thermo-Coupled but the mating one on the other cellzone is not and one needs to enter the one side picked as Thermo-coupled and manually add the coupled-boundary on the other side .Is that correct or is there a way to automatically get the coupled boundaries fully setup upon import in BaramFlow from BaramMesh without user manual interventions as happens eg with Shadow walls in ANSYS
Inquiry 2:What happens if you have 2 interfaces with not exactly the same geometrical boundary ? For example imagine a heat source solid block sitting atop a bigger non-heat source block - the 2nd bigger block getting heated via conduction .In this case the mating surfaces by default do not have the same heat transfer area .How does one need to prepare such a case ? Just linking the bigger top surface of the big block with the small surface of the heated small block does not sound right as conduction is only going to take place through the small area where the small block touches the bigger block. How should one deal with such case(which is very usual in real life scenarios) in BARAM .Would be helpful to have an example for such case as the Battery Cooling,Heat Exchanger and the basic CHT tutorial do not cover that
Thank you
Dear TFH,
About inquiry 1.
Currently, the coupled boundary for a thermo-coupled wall must be set manually. We agree that this is very inconvenient. So we are developing a feature to automatically set it using the method you mentioned, and it is scheduled to be included in the next version.
About inquiry 2.
When the two surfaces of an interface have different sizes, generating a mesh in baramMesh and exporting it results in the overlapping and non-overlapping parts of the two surfaces being divided into separate boundary surfaces.
Thanks
Thank you for the feedback
About Inquiry 1 : It is good to hear that you are working on it and will have a solution for this soon as it will help with the applicability of BARAM with more real world geometries
About Inquiry 2: Thank you for the feedback - it seems that i will need to create an example and try it and see if it works for me as you mentioned
Some further questions
Inquiry 3: During the initilization value entering process in the heat exchanger example it seems to ask for the Velocity components in X,Y,Z directions ,which is okay if the tube_in is parallel to one of the primary axes but makes things cumbersome when it is not. When one specifies velocity through the velocity boundary , there is the option of *Magnitude, Normal to Boundary* .It seems to me that this same option shall be available through the Initialization panel to make life easier ?
Inquiry 4: I must admit i do not have a lot of runtime with the blockmesh .It would help if you could add an example (or point me to an example) of how one meshes thin elements (like a 2mm plate through which we want to capture thermal gradients accurately . How does one regulate the cells across the gap (cells across the thickness of one particular domain/cellzone - not the whole computational domain) ? Imagine a thin plate sitting within a bigger fluid domain-atop this plate there is a smaller thin heat source (the thin plate and the heat source are apx 2mm in height and we want to accurately capture the thermal gradients in them. In programs like ANSYS one can use body sizing and other parameters for each of the bodies involved in an CHT sim and therefore tune the mesh for the needs of each of those bodies /domains .Is that possible in BARAMmesh as things currently are?
Inquiry 5: Is there a way to import meshes from other programs in BARAM ? Are you planning to add other meshing methods apart from blockmesh (eg CFmesh etc) ?
Inquiry 6: Unfortunately the example of the heat exchanger is not very representative of many of the real world cases when you have 2 or more 3D geometry bodies involved (rather than a solid and 2 surfaces for baffles like in the example) .The Battery cooling tutorial comes closer to a real world geometry scenario where several solids and 3D domains are interacted but there is no tutorial on how to mesh it from scratch (the battery cooling tutorial seems only a BaramFlow tutorial that starts with a pre-existing mesh) .It would be very useful to see in tutorials the whole process starting from CAD 3D bodies until postprocessing with no parts omitted .A proposal also is to have end to end tutorials from CAD 3D to postprocessing as several of the existing tutorials though very useful miss half of the process making it hard to follow end to end
Thank you
Dear TFH,
- for the initialization : As you mentioned, it wouldn't be a bad idea to provide an initial value, but in most cases, there isn't a significant difference in convergence even if the initial value isn't specified precisely, so we didn't make it too complicated.
- for the mesh generation : Baram uses snappyHexMesh, which has a fundamentally different mesh generation method than ANSYS, and it has its own advantages and disadvantages. For thin plates, the number of mesh elements may increase somewhat. I can’t seem to find a suitable example of this type of mesh generation.
- for the mesh conversion : You can convert ANSYS Fluent MSH and CAS files for use. The files just need to be saved in ASCII format.
- for the real world case : We have some difficulties to create tutorials using complex 3D CAD. First of all, we believe tutorials should be as simple as possible for beginners. Also, since the complex simulations we’ve performed all relate to our clients’ specific issues, there are aspects we cannot disclose due to confidentiality concerns. If a suitable problem arises, we’ll try to create a tutorial then.
Thank you for your valuable feedback.
Thank you for the feedback
-Inquiry 3 : I was talking more about the direction of the flow compared to the geom inlet boundary . I guess you are implying that for steady state cases where you might get away with wrong initialization values ? From my experience in transient cases the initialization values need to be right
-Inquiry 4a: Thin wall meshing and capturing thermal gradients in thin walls is pretty popular/common problem in the real world (eg in electronics) .i would be interested to see a tutorial on thin geometry heat transfer (it can be generic in geometry for your case ie a thin flat plate heated by a block sitting on it) .
-Inquiry 4b: I am not sure i can understand from what you mentioned how to import a mesh and case (.cas) from Fluent to Baram . I would be very useful to have a tutorial for that (can be a video tutorial) .I am sure lots of your audience would appreciate that as i guess it will attract lots of people to try BARAM on already setup cases in FLUENT
-Inquiry 6 : The battery cooling tutorial is already in your list of tutorials for BaramFLOW but there is no tutorial on how to mesh it (BaramMESH) . Could you add this in the tutorials ? (can be a video tutorial). As this is the closest heat transfer case of the 3 or so available to real world problems i am sure it would be appreciated by your audience
-Inquiry 7 : personally i would be interested to see tutorials on transient heat transfer with time variable flow conditions (eg velocity) and heat source power magnitudes (typically you insert those as profiles in programs like Fluent .
-Inquiry 8 : How do you setup initial temperatures and flow conditions for heat transfer problems ? In Fluent its done typically via patching in the initialization menu
Thank you & keep up the good work
Dear,
- inquiry 3 : I understand what you mean. It would be necessary when it's a transient. I'll take that into account in our future development plans.
- inquiry 4a, inquiry 6, inquiry 7 : I'll try to create a tutorial when we have some free time.
- inquiry 4b : you can convert fluent file at baramFlow menu, File - load mesh - Fluent (ASCII)
- inquiry 8 : A feature similar to Fluent's “patch” is available in the “Advanced” section of the initialization settings. You can create a section and assign specific values to it.
Thank you for your suggestion.