Abstract: An apparatus for heating water having three vertically aligned water heating process sections. The upper section includes an annular water storage tank disposed around a combustion chamber having a downward firing burner. The intermediate section, disposed vertically below the upper section receives flue gas from the combustion chamber, which flue gas is cooled and dehumidified, producing a hot condensate which collects in a passive condensate flow control device disposed proximate the bottom of the intermediate section. The lower section, disposed vertically below the intermediate and separated therefrom by the passive condensate flow control device receives hot condensate from the flow control device, which is used to preheat and humidify air, such as room air, which is then recycled to the combustion process of the upper section for use as combustion air.

Abstract: An annular tube heat exchanger immersed in a medium, such as a fluid. The heat exchanger comprises a fluid-tight combustion tube including a gas-fired radiant burner for providing a source of heat, at least one heat exchange tube including an inner tube disposed within an outer tube, the outer tube in thermal contact with the combustion tube, the inner tube being open-ended to allow the fluid to pass therethrough, and a fluid-tight combustion tube in thermal contact with the outer tube of the at least one heat exchange tube. The combustion gas from the radiant burner passes through the outer tube of the at least one heat exchange tube to cause an increase in the temperature of the fluid. By providing the maximum amount of heat transfer surface area, the annular tube heat exchanger provides a highly efficient means of increasing the temperature of the fluid.

Abstract: A cyclonic type combustion apparatus that may be constituted so as to jet out a premixed gas made up of a mixture of a gaseous fuel and air into a cylindrical combustion chamber, from nozzle ports provided on an inside cylinder wall, the combustion apparatus being especially adapted for heating the liquid medium in hot water heaters, smoke tube boilers, and the like. For instance, a premixed gas obtained by mixing a gaseous fuel with air is jetted out into a cylindrical combustion chamber from a nozzle port opened on its inner peripheral surface along the inner peripheral surface in its tangential direction. The combustion chamber is disposed in a storage region containing heating medium water. The peripheral wall of the combustion chamber is constituted to be a heat conductive wall which is in contact with the heating medium water. The flame formed by the premixed gas jetted out from the nozzle port is cooled by the heating medium water.