Abstract: A gas burner (1) according to one aspect of the present invention includes a fuel supply pipe (10) extending in a predetermined combustion air jet direction and supplied with fuel gas, an air jet port (40) arranged around the fuel supply pipe (10) and jetting combustion air in the combustion air jet direction, and multiple outflow nozzles (70) extending so as not to protrude outward from the fuel supply pipe (10) beyond the air jet port (40) and so as to form an acute inclination angle with respect to the combustion air jet direction and having tip ends forming fuel outlet ports (71) through which the fuel gas flows out.

Abstract: A boiler according to the present invention includes: a plurality of heat transfer tubes arranged to form a cylindrical shape between an upper header and a lower header to constitute a heat transfer tube row; a boiler body cover of a cylindrical shape provided between the upper header and the lower header so as to surround the heat transfer tube row; and a heat insulating material provided to a predetermined region of a space between the heat transfer tube row and the boiler body cover.

Abstract: A boiler has an upper header, a lower header and a heat-transfer tube. The heat-transfer tube connects the upper header with the lower header. The hear-transfer tube is provided with projections such that a heat-transfer area per unit length of the heat-transfer tube is smaller in an upstream region than that in a downstream region of combustion gas.

Abstract: A boiler has a plurality of inner heat-transfer tubes which makes up an inner heat-transfer tube row, and a plurality of outer heat-transfer tubes which makes up an outer heat-transfer tube row. Inner fins project from each of the inner heat-transfer tubes on an outer circumferential side of the inner heat-transfer tube row. Outer fins project from each of the outer heat-transfer tubes on an inner circumferential side of the outer heat-transfer tube row. An inner row communicating portion is provided in a lower end portion of the inner heat-transfer tube row. An outer row communicating portion is provided in an upper end portion of the outer heat-transfer tube row. An inner-fin absent region is provided in a lower end portion of each of the inner heat-transfer tubes. An outer-fin absent region is provided in a longitudinally middle portion of each of the outer heat-transfer tubes.

Abstract: A boiler has a plurality of inner heat-transfer tubes which makes up an inner heat-transfer tube row, and a plurality of outer heat-transfer tubes which makes up an outer heat-transfer tube row. Inner fins project from each of the inner heat-transfer tubes on an outer circumferential side of the inner heat-transfer tube row. Outer fins project from each of the outer heat-transfer tubes on an inner circumferential side of the outer heat-transfer tube row. An inner row communicating portion is provided in a lower end portion of the inner heat-transfer tube row. An outer row communicating portion is provided in an upper end portion of the outer heat-transfer tube row. An inner-fin absent region is provided in a lower end portion of each of the inner heat-transfer tubes. An outer-fin absent region is provided in a longitudinally middle portion of each of the outer heat-transfer tubes.

Abstract: The present invention relates to a various kinds of boilers including a steam boiler, a hot water boiler, a waste-heat boiler and an exhaust gas boiler. Projections are provided on a heat-transfer tube which connects an upper header and a lower header with each other such that a heat-transfer area pet unit length of the heat-transfer tube becomes smaller in an upstream region than that in a downstream region of combustion gas. It is preferable that installation pitches between adjacent upper and lower projections and/or projecting lengths of the projections from the heat-transfer tube are changed such that the heat-transfer area per unit length of the heat-transfer tube becomes smaller in the upstream region than those in the downstream region of the combustion gas.

Abstract: To provide a boiler equipped with a water tube group performing heat recovery effectively and having expansion heating surfaces (fins or the like) of high durability, the present invention provides a boiler (1) including: a boiler body (10) having an inner water tube group (20) and an outer water tube group (30) that are arranged in an annular fashion; and a burner (40) arranged at a central portion of the inner water tube group (20), in which: intervals between adjacent inner water tubes constituting the inner water tube group (20) are closed except for portions where a gas flow passage is provided; and stud fins (22 and 32) are provided on a portion of at least one of the inner water tube group (20) and the outer water tube group (30) in a vicinity of the gas flow passage.

Abstract: Provided is a boiler including: a plurality of heat transfer tubes arranged to form a cylindrical shape between an upper header and a lower header to constitute a heat transfer tube row; and a plurality of longitudinal fins provided to close gaps between the heat transfer tubes without connecting the adjacent heat transfer tubes, the plurality of longitudinal fins being provided to a portion other than one of one end in a vertical direction of the heat transfer tube row and a part in a peripheral direction thereof.

Abstract: A boiler according to the present invention includes: a plurality of heat transfer tubes arranged to form a cylindrical shape between an upper header and a lower header to constitute a heat transfer tube row; a boiler body cover of a cylindrical shape provided between the upper header and the lower header so as to surround the heat transfer tube row; and a heat insulating material provided to a predetermined region of a space between the heat transfer tube row and the boiler body cover.

Abstract: To provide a boiler equipped with a water tube group performing heat recovery effectively and having expansion heating surfaces (fins or the like) of high durability, the present invention provides a boiler (1) including: a boiler body (10) having an inner water tube group (20) and an outer water tube group (30) that are arranged in an annular fashion; and a burner (40) arranged at a central portion of the inner water tube group (20), in which: intervals between adjacent inner water tubes constituting the inner water tube group (20) are closed except for portions where a gas flow passage is provided; and stud fins (22 and 32) are provided on a portion of at least one of the inner water tube group (20) and the outer water tube group (30) in a vicinity of the gas flow passage.