How can I create a geometry in PDE toolbox to include entrance/exit plumbing with a packed column between?

I am attempting to model flow through a packed bed using the PDE toolbox. I am having a hard time with the geometry. I would like to include both the entrance and exit plumbing as well as the entrance/exit zones of the column with the packed bed in the area between those. I think that I'd like to create the empty column with the tubing as 1 geometry and then add the packed bed zone as another. How would I go about doing that? Any thoughts or recommendations?