how to place a radiator?
 

I need place a radiator in a domain. FLUENT HELP say that the radiator is infinite thin and should be consider as interface. But the radiator is the subdirectory under the ¡°interior¡± not ¡°interface¡± in the Set Boundary panel. What should I do? Is it right to set a face to be ¡°interface¡± in Gambit? Please tell me how to place a radiator in a duct? Thank you in advance!