NOVELTY - The reformer (400) has an exterior shell (401) including a diffusion burner (402) and ring shaped angled fins (404), which extend away from an inner surface of the shell and downward toward the burner. The shell forms a cavity in which combustion occurs. An interior reactor is positioned partly within the shell. A portion of the cavity extends between the fins and the reactor. The burner is placed in a bottom portion of the shell. A pipe extends from a top end of the reactor through which a portion of hydrogen generated in the reactor is routed to a fuel cell coupled to the reformer.    USE - Steam reformer for converting mixture of steam and feed gas i.e. methane, to hydrogen and carbon monoxide or dioxide in a fuel cell to generate electricity.    ADVANTAGE - The reformer allows a recuperator to heat or maintain high temperature in an upper part of a reaction chamber using exhaust gas from the burner or exhaust gas from a fuel cell stack to which the reactor supplies fuel. The burner can be positioned below the reactor such that heat from combustion of fuel such as hydrogen generated by the reformer, rises up around the reactor or through a center portion of the reactor due to buoyancy of hydrogen in air, so that hydrogen flames from the burner can ascend rapidly resulting in a low amount of heat transferred to the reactor in a lower region and length of the reactor can be limited by a space in which the reactor is used. The angled fins have a temperature sensor to determine temperature in vicinity of the temperature sensor, so that air and hydrogen can be delivered to the burner in order to increase or decrease temperature based on desired temperature in the vicinity of the angled fin. The angled fins increase an amount of heat transferred to the reactor surrounding without extending the length of the reformer compared to the shell that does not have angled fins. The reformer ensures that the amount of heat transferred to the reactor can be partially controlled by a position, angle and length of each angled fin coupled to an inner surface of the exterior shell by controlling the amount of heat transferred to the reactor via the angled fins, so that the reforming reaction, which occurs within the reactor can be driven toward formation of more products.    DETAILED DESCRIPTION - The angled fins are made of solid or perforated metal or ceramic material.    DESCRIPTION OF DRAWING(S) - The drawing shows a block diagram illustrating flow of gas and energy in a steam reformer.    Methane steam reformer (400)    Exterior shell (401)    Diffusion burner (402)    Ring shaped angled fins (404)    Reaction chamber of interior reactor (405)