I need to model a round cylindrical heating element (volume) with thin fins attached perpendicular to the cylinder axis. The fins obviously need to be "connected" to the heating element, but I do not want to model them as volumes for meshing reasons. Basically, this involves two questions: 1) Is it possible (if so, how) to connect/join/merge perpendicular faces such as my heater cylinder face and the thin fin? 2)Is there a way to connect a face/wall to a volume and have the face/wall be in thermal contact with the volume? Thanks for any response.

Just create the walls in GAMBIT and assign them a name in the boundaries panel. In FLUENT, you will be able to specify a thickness for use in computations and a material. You will need to enable shell conduction for these walls.