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 includes a plurality of heat transfer tubes housed in a predetermined case, a connecting tube body for connecting the plurality of heat transfer tubes, a predetermined tube expansion portion provided on each heat transfer tube, a first peripheral wall portion provided on the tube expansion portion, and a second peripheral wall portion that is positioned on an end portion of the connecting tube body and fitted to the tube expansion portion, wherein the first and second peripheral wall portions have different sectional shapes and are fitted together in a partial contact state including predetermined contact and non-contact portions. According to this configuration, the heat transfer tubes can be fixed to a side wall portion of the case and the connecting tube body can be connected to the heat transfer tubes easily and appropriately.

A heat exchanger including a gas inlet through which a combustion gas flows in and a gas outlet through which the combustion gas flows out is provided. The heat exchanger includes a housing in which the gas outlet is formed, a partition member, and a plurality of heat transfer tubes accommodated in the housing. The partition member is mounted in the housing so that there is a portion in which a flow area of the combustion gas is smaller than that of the gas inlet between the gas inlet and the gas outlet.

Provided are a heat exchanger capable of cooling a shell plate and having good assemblability and a hot water apparatus having the same. A primary heat exchanger includes a heat exchanging portion, a shell plate, and a shell pipe portion. The shell plate surrounds the heat exchanging portion. The shell pipe portion is for cooling the shell plate. The shell plate includes a front surface portion and a main body portion. The main body portion is installed on the front surface portion and is formed by bending one sheet of plate into a U shape. The shell pipe portion is bent in a U shape along an inner surface of the main body portion and installed on the inner surface.

Provided are a heat exchanger capable of cooling a shell plate and having good assemblability and a hot water apparatus having the same. A primary heat exchanger includes a heat exchanging portion, a shell plate, and a shell pipe portion. The shell plate surrounds the heat exchanging portion. The shell pipe portion is for cooling the shell plate. The shell plate includes a front surface portion and a main body portion. The main body portion is installed on the front surface portion and is formed by bending one sheet of plate into a U shape. The shell pipe portion is bent in a U shape along an inner surface of the main body portion and installed on the inner surface.

A heat exchanger includes a plurality of heat transfer tubes extending in a first direction and aligned in a second direction intersecting with the first direction, and a plurality of fins disposed in the first direction. The fins each include a plurality of fin main bodies aligned in the second direction, and a bridging portion connecting two adjacent ones of the fin main bodies. At least one of the fin main bodies is provided with a through hole next to the bridging portion in the second direction.

Provided is a heat exchanger which includes a plurality of meandering heat transfer pipes that includes first and second heat transfer pipes, as the plurality of heat transfer pipes, which are adjacent to each other in a predetermined y direction and are misaligned with each other in a z direction such that a plurality of straight pipe parts are in a non-overlapping state in the y direction, in which a first recessed part recessed in the y direction is provided in each curved pipe part of the first heat transfer pipe, and a part of each curved pipe part of the second heat transfer pipe is fitted into the first recessed part.

A heat source device comprising: a combustion chamber (2) provided between a burner (31) and a heat exchanger (1); an inlet pipe (20) for allowing a fluid to be heated to flow in the heat exchanger (1); an outlet pipe (21) for allowing the fluid to be heated to flow out from the heat exchanger (1); and a winding pipe (27) wound around an outer surface of a peripheral wall of the combustion chamber (2), wherein either the inlet pipe (20) or the outlet pipe (21) has an orifice (91) for throttling a fluid flow path of the fluid to be heated flowing in the inlet pipe (20) or the outlet pipe (21).

A heat exchanger including a gas inlet through which a combustion gas flows in and a gas outlet through which the combustion gas flows out is provided. The heat exchanger includes a housing in which the gas outlet is formed, a partition member, and a plurality of heat transfer tubes accommodated in the housing. The partition member is mounted in the housing so that there is a portion in which a flow area of the combustion gas is smaller than that of the gas inlet between the gas inlet and the gas outlet.

A heat exchanger includes: a casing into which heating gas is supplied; and a plurality of heat transfer tubes which are arranged in the casing, wherein the plurality of heat transfer tubes are set in a posture in which a plurality of straight tube portions are arranged in a direction intersecting a heating gas flow direction, are stacked a plurality of stages in the heating gas flow direction, and are distinguished into first and second heat transfer tubes respectively located on an upstream side and a downstream side in the heating gas flow direction, and wherein the second heat transfer tube is formed so that an outer diameter of the tube and an arrangement pitch of the plurality of straight tube portions are smaller than those of the first heat transfer tube.