[Problems to be Solved] An exhaust duct (4) for assembly into a combustion apparatus has: a burner (1) to eject air-fuel mixture downward; and a combustion box (3) disposed on a lower side of the burner (1). The exhaust duct includes: a riser duct section (42) elongated in a vertical direction and having, at a lower portion thereof, an inlet port (41) connected to an exhaust port (35) for combustion gas which is opened in a lower portion of the combustion box (3); and a flat horizontal duct section (43) bent at an upper end of the riser duct section (42) so as to be elongated forward. By restraining the resonance of an upper wall part (431) and a lower wall part (432) of the horizontal duct section (43), noises due to resonance sounds are reduced.

[Solving Means] The natural frequencies in an upper wall part (431) and the lower wall part (432) of the horizontal duct section (43) are varied from each other. For example, the lower wall part (432) is fixed to a burner body (11) in order to vary the natural frequencies of the upper wall part (431) and of the lower wall part (432) from each other.

In a combustion apparatus that includes a heat exchanger which is disposed in a combustion box, on a premise that a direction from a burner to the heat exchanger is defined as a Z-axis plus direction, a direction opposite to the Z-axis plus direction is defined as a Z-axis minus direction, and an orthogonal direction to a Z-axis direction, which is along fins of the heat exchanger is defined as a X-axis direction, a thermal insulation material is arranged on an inner surface of a swelling part that is formed at a side plate part of a combustion box and outwardly swells in the X-axis direction so as to be sandwiched from both sides in the Z-axis direction by a step that is outwardly bent in the X-axis direction, which is positioned an end, in the Z-axis plus direction, of the swelling part and a structural member of a burner, which inwardly protrudes in the X-axis direction from an end, in the Z-axis minus direction, of the side plate part. A vicinity portion of an end, in the Z-axis plus direction, of the thermal insulation material is held from an inside in the X-axis direction by a side edge portion, on each side in the X-axis direction, of the fins.

A water heater includes a primary heat exchanger, a secondary heat exchanger disposed above the primary heat exchanger, a flow path member, and a flow restriction member. The secondary heat exchanger includes a case and heat transfer pipes arranged in the case. The case includes a wall having a gas inlet through which combustion exhaust gas discharged from the primary heat exchanger is introduced into the case. The flow path member connects the primary heat exchanger and the secondary heat exchanger and is disposed adjacent to the gas inlet and is configured to introduce the combustion exhaust gas discharged from the primary heat exchanger into the secondary heat exchanger through the gas inlet. The flow restriction member is disposed on the wall of the case to suppress upward flowing of the combustion exhaust gas that is introduced into the case through the gas inlet.

Transition castings are disclosed which comprise a steam tube, a water tube, and a pass-through tube, which are joined together by membranes. The ends of the tubes on one vertical end are aligned in a plane, while the ends of the tubes on the other vertical end are aligned in alternating planes, or put another way are angled instead of being in a straight line. The transition castings are used in a transition section of a boiler in which the furnace is divided into a lower furnace and an upper furnace. The lower furnace uses water-cooled membrane walls, while the upper furnace uses steam-cooled membrane walls that act as superheating surfaces. The transition section joins the lower furnace and the upper furnace together.

A tankless water heater includes a scale control module (SCM). The SCM is mounted inside or outside of a cabinet which encloses a heat exchanger and source of heat of the water heater. The SCM may include a connector and a cartridge removably attaching to the connector or may only include a cartridge permanently affixed to the tankless water heater. The tankless water heater includes a continuous water pathway inside the cabinet to supply water to all components of the tankless water heater, including the SCM. The tankless water heater receives supply water at its inlet, treats the supply water in the SCM to generate treated water having reduced scale-forming characteristics compared to the supply water, and heats the treated water in the heat exchanger to generate heated treated water.

A tankless water heater includes a scale control module (SCM). The SCM is mounted inside or outside of a cabinet which encloses a heat exchanger and source of heat of the water heater. The SCM may include a connector and a cartridge removably attaching to the connector or may only include a cartridge permanently affixed to the tankless water heater. The tankless water heater includes a continuous water pathway inside the cabinet to supply water to all components of the tankless water heater, including the SCM. The tankless water heater receives supply water at its inlet, treats the supply water in the SCM to generate treated water having reduced scale-forming characteristics compared to the supply water, and heats the treated water in the heat exchanger to generate heated treated water.

The present invention discloses a round plate heat exchanger having a heat exchange part in which a plurality of heat medium flow paths and a plurality of combustion gas flow paths are formed alternately adjacent to each other between a plurality of plates. The plurality of plates are formed by stacking a plurality of unit plates comprising a first plate and a second plate stacked each therein. The plurality of heat medium flow paths are formed to be spaced from each other between the first plate and the second plate, a plurality of heat medium connection flow paths are formed in some areas of the plurality of heat medium flow paths, and each of the plurality of combustion gas flow paths is formed between the second plate of one unit plate and the first plate of another unit plate stacked adjacent to the unit plate.

The present invention discloses a round plate heat exchanger having a heat exchange part in which a plurality of heat medium flow paths and a plurality of combustion gas flow paths are formed alternately adjacent to each other between a plurality of plates. The plurality of plates are formed by stacking a plurality of unit plates comprising a first plate and a second plate stacked each therein. The plurality of heat medium flow paths are formed to be spaced from each other between the first plate and the second plate, a plurality of heat medium connection flow paths are formed in some areas of the plurality of heat medium flow paths, and each of the plurality of combustion gas flow paths is formed between the second plate of one unit plate and the first plate of another unit plate stacked adjacent to the unit plate.

A heat exchanger includes a tube expansion portion formed by expanding a heat transfer tube so that an outer peripheral surface of the heat transfer tube is pressed against an inner peripheral surface of a hole provided in a side wall portion of a case. The tube expansion portion includes first and second bulge portions positioned respectively on the inside and the outside of the side wall portion so as to sandwich the side wall portion in an axial length direction of the heat transfer tube and configured such that respective outer peripheral surfaces thereof partially bulge outward in a radial direction of the heat transfer tube, an end portion tip end of the heat transfer tube is positioned apart from the second bulge portion, and the end portion tip end and a part in the vicinity thereof are expanded so as to be included in a part of the tube expansion portion. Thus, effects such as improving the precision with which the side wall portion of the case, the heat transfer tube, and a connecting tube are fitted to each other can be achieved, and as a result, the respective parts can be brazed easily and appropriately.

A heat exchanger and a water heater are provided. The heat exchanger is provided with an auxiliary member including a trunk pipe joint portion joined to a trunk pipe and an extension portion extending from the trunk pipe joint portion toward a plurality of fins. The plurality of fins is provided apart from a sidewall portion so as not to directly contact the sidewall portion of a case, the extension portion of the auxiliary member includes an entry portion that enters between the plurality of fins and the sidewall portion, and a first abutment portion which is provided in the entry portion and abuts outer end portions of the plurality of fins, the first abutment portion is separated from the sidewall portion, and a space portion in which inflow of the heating gas is suppressed is formed between the first abutment portion and the sidewall portion.