Hi,

Please post a photo of your geometry for better understanding.

Which software do you use for producing the grid?

Most of the software have an option for thin walls (shell conduction in Fluent). If you want to consider that thin domain, the automated mesh will be very tricky. The smallest element size in your whole domain is influenced by the thin wall. Check this video:

https://www.youtube.com/watch?v=6jJDM62B1o8

However, if you really need to mesh a thin layer, I usually use sweeping strategy for that specific domain, rather than the automatic mesh. In the automated mesh, the smallest mesh size is governed by the smallest feature in your domain (which is the thin wall). This significantly increases the number of meshes in your domain. Of course a conformal mesh (fine around the small feature, coarse elsewhere) is a good strategy for that. However, you have much more control over the mesh if you manually mesh the thin surface and sweep it in the thin direction.

Edward Jenks Make sure the model, thin wall and enclosure are not overlapping, and if not make it a single integrated part to do conformal meshing.

second method is that dont make thin wall in space claim. Mesh it and then,As soon as u launch fluent there is an option call shell conduction. enable it and assign thickness. this for 3D heat transfer. Incase, you want only Normal 1D Heat Transfer use wall thickness instead of shell conduction thanks. hope that answered your question.