# Beginner: 2D heat transfer problem, adding convection boundary to an edge

Hello there.

I’m learning about Calculix and FEM in general. I need a few pointers regarding a very simple problem.

PROBLEM: 2D heat transfer in a rectangular plate with the right edge as a convective boundary with a film coefficient of 5 and sink temperature 273.15K.

I have generated the rectangular surface in gmsh and exported it to calculix *.inp file.

Below is the screenshot of the *.inp file for the plate.

The following is the screenshot of the *.inp file for the problem along with the boundaries assigned.

tat1.nam is just a set of nodes for the bottom edge of the said rectangle which will be an isothermal boundary at t=274K

My question is, in Ansys/Spaceclaim I can set an edge of the said rectangle as a convective boundary. How do I achieve the same effect in Calculix? Accoring to the manual, *FILM command requires a face to be specified. I do not know how to move forward with the same in my case.

I have gone through the manuals (both ccx & cgx), looked into the examples, but I couldn’t find any working example that makes use of *FILM for 2D convective boundaries so far.

I would be grateful if anyone could point me in the right direction.

-v

Hello,

you should remove the ELSET with type=T3D3 element from the .inp file exported from Gmsh and keep just the Surface1 element type S8. Gmsh exports all the elements by default. If you want the boundaries exported from Gmsh, please create the physical line in Gmsh and when exporting select Save Groups of Nodes.

A good alternative to prepare the inp file from Gmsh to CCX is to use the gmsh2ccx:

Best regards,
Carlos

1 Like

It is working as expected. Apologies for not replying earlier.

Also thanks for the script. Now I’m interested in looking up how the various elements are interchanged between gmsh and Calculix.

Also, thank you for helping a beginner such as myself. I am really intrigued by calculix, but it is only recently that I had the chance to actually use it in practice. I’m using Ansys student edition which doesn’t have a linux client; so, while doing the beginner lessons in Ansys I’m also trying to perform the same exercises in Calculix (I have a dual boot setup).

I really like how I have to know what’s going on under the hood when I’m working on calculix, something which I don’t have to do in Ansys (which isn’t necessarily a bad thing but knowing how it works internally is sort of cool)

Anyway, thanks again.

Wish You a Very Happy New Year.

Cheers
-v