Heat Transfer in a Furnace

Hello. If I want to model heat transfer in an object inside a furnace that is heating up according to a time-dependent temperature function, what is the best way to simulate the heating conditions? Do I simply create a boundary around the object being heated and assign the temperature of that boundary to the function that describes the temperature, or is there another way? It seems that the way mentioned above will not accurately model the circumstances because now there is a layer of air separating the heated boundary and the object, and I would like to have the environment right next to the surface of the object follow the temperature curve instead. I am working in a 2D model, FYI.

Thanks!