A heat exchanger includes a plurality of serpentine or U-shaped first heat transfer tubes disposed in a case and formed by connecting a plurality of straight tube body portions, which are arranged at intervals in an up-down height direction so as to extend in a horizontal direction, in series via a first connecting tube body portion, upper side and lower side header portions connected to respective end portions of the plurality of first heat transfer tubes, and a second heat transfer tube disposed in the case so that upper side and lower side end portions thereof are connected respectively to the upper side and lower side header portions and configured such that an intermediate region, which excludes at least the respective end portions and a region of an uppermost portion that is adjacent to the upper side end portion, is constituted by tube body portions that are tilted over the entire length thereof so as to gradually decrease in height from one end side toward another end side of the intermediate region. As a result, a malfunction in which a hot water supply operation becomes difficult due to freezing of the heat transfer tubes can be prevented appropriately.

A heat exchanger according to the present invention comprises a heat exchange portion in which heating water flow paths where heating water flows through a space between a plurality of plates, hot water flow paths through which hot water flows, and combustion gas flow paths are adjacently and alternatingly formed, wherein the heat exchange portion comprises: a heating sensible heat portion, which surrounds the outside of a combustion chamber and comprises an area on one side of the plates, for heating the heating water using the sensible heat of the combustion gas generated by combustion of the burner; a heating latent heat portion, which comprises a partial area on the other side of the plates, for heating the heating water using the latent heat of water vapors in the combustion gas which has completed heat exchanging in the heating sensible heat portion; and a hot water latent heat portion, which comprises the remaining area on the other side of the plates, for heating direct water using the latent heat of water vapors in the combustion gas which has passed through the heating latent heat portion.

A water heater includes a combustion device, a primary heat exchanger, and a secondary heat exchanger. The combustion device burns gas to generate high-temperature air. The primary and the secondary heat exchangers are provided sequentially above the combustion device. When the high-temperature air passes through the primary heat exchanger, part of thermal energy is absorbed by exchange plates and a water pipe therein. When the high-temperature air continues to pass through the secondary heat exchanger, part of the rest thermal energy is absorbed by a heat tube set therein to preheat water flowing through the heat tube set. The preheated water then flows into the water pipe of the primary heat exchanger. The secondary heat exchanger includes a case and a cover board which detachably seals a bore on the case. Whereby, it is convenient for a user to clean pipes inside the secondary heat exchanger.

The invention discloses a condensing gas water heater, a condensing heat exchanger as well as heat exchanger plates. The condensing heat exchanger comprises: a housing and at least one heat exchanger plate disposed in the housing; the heat exchanger plate comprises a first metal board and a second metal board butting each other, wherein a surface of the first metal board and a surface of the second metal board which butt each other are butting surfaces, and two outer surfaces opposite to the butting surfaces are a first surface and a second surface, respectively; at least one of the first metal board and the second metal board is formed with a convex flow guide portion along a direction away from the butting surface; the first metal board and the second metal board form a fluid passage via the flow guide portion.

An extreme condensing boiler includes cold and hot water headers, burner, and multi-tubing heat exchanger, so that cold water absorbs heat from exhaust gas of the burner being heated to medium-hot, which absorbs heat generated by the burner being heated to hot water through absorbing heat from both sides of tube portion of the multi-tubing heat exchanger, and so that the hot water is delivered to the hot water header, and a combustion air heat exchanger is provided around the multi-tubing heat exchanger. The condensing boiler uses dual/triple tubes for fire and water tubes, increasing efficiency by absorbing heat from both sides. The fire tube is surrounded by the cold water tube so as to minimize exhaust gas temperature and maximize condensing by absorbing waste heat. The condensing boiler realizes a direct fire boiler through the fire and water tubes, and an energy-saving tankless boiler including headers and tubes only.

A latent heat recovery heat exchanger includes a case, a heat exchange portion, and a straightening vane. The heat exchange portion includes a plurality of heat transfer plates surrounded by a peripheral wall portion of the case and layered on one another, each of the plurality of heat transfer plates extending in a direction from an inlet toward an outlet. The straightening vane includes a top plate portion covering the plurality of heat transfer plates so as to close a space between the plurality of heat transfer plates in end portions of the plurality of heat transfer plates in a direction intersecting with a direction of layering of the plurality of heat transfer plates when the heat exchange portion is viewed from the inlet toward the outlet.

A latent heat recovery heat exchanger includes a heat exchange portion and a case. The heat exchange portion includes a plurality of heat transfer plates layered on one another. The case accommodates the plurality of heat transfer plates of the heat exchange portion. The heat exchange portion includes a front plate portion provided as an outermost layer of the heat exchange portion. The front plate portion of the heat exchange portion forms a part of the case.

The heat exchange device includes a primary heat exchanger and a secondary heat exchanger. The secondary heat exchanger is disposed to overlap the primary heat exchanger in a vertical direction in a state in which the heat exchange device is installed. The secondary heat exchanger includes a plurality of first pipes and a plurality of second pipes. Each of the plurality of first pipes and the plurality of second pipes extends in a zigzag manner in the vertical direction by a plurality of linear portions being connected to a plurality of curved portions in series. Each of the plurality of linear portions of each of the plurality of second pipes is disposed to be displaced from each of the plurality of linear portions of each of the plurality of first pipes in the vertical direction.

A hot water apparatus includes a burner, a latent heat recovery heat exchanger, a housing, a fixing member, an attachment member, and a straightening vane. The fixing member is configured to fix the latent heat recovery heat exchanger to the housing. The attachment member is configured to attach the fixing member to a case. The straightening vane is arranged in the case. The attachment member protrudes into the case. The straightening vane includes a top plate portion arranged upstream from the attachment member in a direction of flow of the heating gas in the case.

A forced convection fin tube condensing heat exchanger for supplying heat includes a shell, burner and fin tubes bundle. The burner is at the top of the shell, circular fin tubes bundle installed around the burner tightly, circularly and coaxially. The flue channel which is formed by the shell and a row of fin tubes bundle is below the burner. The flue flows along the flue channel to flue outlet. There are front and rear water manifolds at the two ends of the fin tubes. Water baffles inside the rear water manifold divide the rear water manifold into water inlet and outlet areas. The water enters the small portion of circular fin tubes bundle from water inlet area, through the front water manifold, back to the water outlet area via the main portion of the circular fin tubes bundle. The use of bent fin tube to improves efficiency.