ABSTRACT
In conductive heat transfer, heat flows from one material to another based on a temperature difference between the materials. Heat can also flow based on internal temperature differences within a material. In steady-state heat conduction problems, there is a choice of two physical boundary conditions that can be used at each material boundary or material interface. In the real world, calculating the gap heat transfer coefficient can be a very messy business. Suppose that an annular fuel rod could increase the surface area available to remove heat from the fuel by approximately 50% compared to a conventional solid fuel rod of the same size. In most power reactors, the fuel rods are cylindrical rather than rectangular in shape. As nuclear fuel is burned, a fresh uranium dioxide fuel pellet will undergo a number of structural changes if the fuel temperature is high enough and if the fuel is irradiated for a long enough period of time.
