3D fluid flow in a pipe

I am trying to model laminar flows being joined as a number of pipes are joined. I also care about the thermal effects, so I need to model the pipes as well as the flow within them. However, I can't figure out how to create a solidworks model that Comsol understands and being a flow and a pipe; if I model both, it just reads the entire model as a single domain, and if I only model the pipe, I have no way of telling it that there is something inside the pipe.

How can I get comsol to recognize the pipe and the flow domains?