It is a small back flow chiller. Through the outer cavity you are able to pump a hot or cold fluid. Through the inner tubing you may pump a fluid which in turn gets heated or chilled by the other fluid. The two fluid are except for the transfer of heat isolated form each other. They will not mix.
If you want to print one, use the BackFlowChillerComplete.stl file. This file is not a version of the chiller with a cutaway to expose the inner structure of the thing.
I don't know how well the makerbot will cope with the overhang of the top covering. If to much sagging occurs you could alway add some more support pillars in the sagging area to keep it level.