[WaCky]

Hi, everyone,

I'm going to simulate the transient heat transfer problem in a scroll compressor with CFX, where the orbiting scroll moves without rotating.

The orbiting scroll is created with solid domain in CFX. However, its motion or mesh Deformation can Not be set as translation. I also tried to use MRF method, but the rotating Coord Frame can Not be referred by Solid domain either.

I have found a paper where they use expression to describe the motion of orbiting scroll of a vacuum pump .( CFD simulation of a dry scroll vacuum pump with clearances, solid heating and thermal deformation by Spille-Kohoff etc. :"the motion of the orbiting solid and of the axial gap between the orbiting scroll and the stationary disc is described with expressions"). Would anybody help with this?

Or may I deal this issue with system coupling ? It seems would be much more time consuming without the 'timescale control' in CFX.


It's a pity that the heat transfer option is not given in Rigid Body or Immersed Body models!




A sample for the fluid domain calculation only is given in the following webpage with software CONVERGE:
http://www.idaj.cn/product/show/id/235/subid/241

[ghorrocks]

You have a few options:
* Moving mesh - you need to define the motion of the mesh throughout the entire motion. For your case this will probably be difficult
* Moving Mesh with remeshing - You will probably need this if you use moving mesh as you will stretch and squish the mesh too much without it.
* Immersed solid - probably the easiest way to do it, but can have difficulties with the thin passages. But many people live with these difficulties because it is so much easier to implement.

Note when you use moving mesh you have more options than simply translation. You can define translation to whereever you like, and if you translate nodes to different locations you get rotation, stretching, bending and so on.

Also have a think about rigid body. That might simplify the mesh specification.
You

[WaCky]

Thanks a lot for your information Glenn,

As the Orbiting scroll is defined as solid domain, the moving mesh option (or the Mesh Deformation ?) seems disable.

The Immersed solid or rigid body is great for the simulation of FSI problem without heat transfer while the heat transfer is also disable in these cases.

The moving mesh for fluid domain is well generated and prepared in advance. The issue is how to translate the solid domain to follow the moving interface boundary.


A sample for the fluid domain calculation only is given in the description in main text for your further evaluation.

[ghorrocks]

Do you want to model heat flow inside the scroll, so you get the temperature variation over scroll? Or do you just want to temperature profile of the fluid and can assume the scroll to be constant temperature?

[WaCky]

I focus on the heat transfer between the scroll and compression chamber in order to obtain the temperature distribution on scroll wall (Solid Domain).
The temperature profile of fluid can be obtained without solid domain. However, I'm worried about the influence of heat transfer between compression chamber through scroll wall. That's why I try to use solid domain.

[ghorrocks]

If the scroll wall can be modelled using a convective boundary condition (heat transfer coefficient) then you don't need to model the solid domain and things become much easier. It will give you a variable surface temperature depending on local heat transfer, but it won't include any effects of heat transferred through the scroll.

Will a convective boundary condition on the scroll achieve what you need?