Heat transfer from air to solid
 

I need some tips on how to solve the problem of heat transfer from air to solid. My case is about some copper tubes, whit water running through them at a constant flow.The bars cross a room heated at 320 K. How do I simulate the heat transfer from the air to the solid bars, then eventually to the water inside them.
I figure it must be something I'm missing while setting the boundary conditions of the copper "wall", but I don't know what.
Appreciate any help, thanks !!!