Heat transfer in Fluent
 

Hi!
I made model of flow in Fluent. It is a flow through exhaust system, and heat transfer to car's undertray. My problem is with boundary condition, because walls all around undertray are material (solid for example alu). I tried to change from wall to interior, but Fluent shows error. Even if i am trying to make an interior in Gambit, after puuting it into Fluent the programme converts it to wall.
Do You have any idea how to change wall into air?
On print screen You could see the problem.
http://imageshack.us/photo/my-images/190/84238324.jpg/
http://imageshack.us/photo/my-images/37/56208178.jpg/
Thanks

hi
 

i saw your pics but i am not sure what you wanna say . Hopefully you can explain it in a better way.

shk