A burner unit includes first and second burner assemblies supplied with a gas mixture via first and second valves, respectively. A first valve control assembly controls the first and second valves between open and closed positions. Third and fourth burner assemblies of the burner unit are supplied with a gas mixture via third and fourth valves, respectively. A second valve control assembly controls the third and fourth valves between open and closed positions. The first and second valve control assemblies are separate assemblies that are configured to cooperate to simultaneously provide a gas mixture to the first, second, third and fourth burner assemblies in respective high power settings of the first and second valve control assemblies.

A gas burner assembly includes an elongated burner and a round burner positioned at a middle portion of the elongated burner. The elongated burner defines a plurality of flame ports adjacent a first end portion of the elongated burner. Flame ports of the plurality of flame ports that are positioned on a pair of parallel linear segments of the elongated burner have a first total port area, and flame ports of the plurality of flame ports that are positioned on an arcuate segment of the elongated burner have a second total port area. The second total port area is greater than the first total port area.

Systems and methods are disclosed that include providing a cooking system that comprises a burner assembly and a heat exchanger submerged in a vessel. The burner assembly includes a high velocity burner and a low velocity burner, the high velocity burner configured to provide the necessary high velocity, volumetric flowrate through a fluid duct of the heat exchanger that includes a plurality of compactly-arranged, alternatingly-disposed vertical and horizontal tubes passing through the fluid duct, and the low velocity burner configured to significantly reduce and/or substantially eliminate lift off that could result from operation of only the high velocity burner. The heat exchanger is submerged in the vessel with the tubes of the heat exchanger open to the vessel to allow ingress and egress of a fluid contained within the vessel.

Burner assemblies and methods for operating burner assemblies are provided. A method includes outputting a maximum gaseous fuel supply to a first burner and no gaseous fuel supply to a second burner when a burner assembly knob is in a first position, outputting a minimum gaseous fuel supply to the first burner and no gaseous fuel supply to the second burner when the knob is in a second position, outputting a minimum gaseous fuel supply to the first burner and a maximum gaseous fuel supply to the second burner when the knob is in a third position, and outputting a minimum gaseous fuel supply to the first burner and a minimum gaseous fuel supply to the second burner when the knob is in a fourth position.

A radiant tube burner, wherein an opening cross section of the tube is virtually divided into four areas with two straight lines as boundaries, the two straight lines being obtained by tilting a minor axis of the oval, which is a shape of the opening cross section, by 45 with a center of the oval as a center, and a flow rate of primary combustion air injected from primary combustion air nozzles located in the areas containing the minor axis of the oval of the virtually divided four areas is lower than a flow rate of the primary combustion air injected from the primary combustion air nozzles located in the areas not containing the minor axis of the oval the four areas.