A diffuser plate for a thermal transfer device can include a body having a number of first apertures and a second aperture that traverse therethrough, where the first apertures are asymmetrically arranged with respect to the second aperture. The first apertures can have a first shape and a first size, and where the first apertures are configured to receive a plurality of tubes. The second aperture has a second size, where the second size is larger than the first size.

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 (3) having a temperature sensor (16) detecting a temperature of a water passage (300) including heat-transfer pipes (32), (33), a connecting portion (34), an inlet pipe (11), and an outlet pipe (12), and a sensor bracket (6), wherein the sensor bracket (6) is joined and fixed to the connecting portion (34) in a state in which at least a part of a base portion (60) of the sensor bracket (6) forming a mounting surface of the temperature sensor (16) is in surface contact with a planar portion (340) provided in the connecting portion (34), and the temperature sensor (16) is secured to a joint portion (600) of the base portion (60) joined and fixed to the planar portion (340).

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.

A tube for a thermal transfer device can include at least one wall having an inner surface and an outer surface, where the inner surface forms a cavity. The inner surface can be non-cylindrical. The cavity can be configured to receive a fluid that flows continuously along a length of the at least one wall.

A fluid heating system for heating a production fluid using a thermal transfer fluid, the production fluid being contained in a vessel includes an electric blower configured to receive ambient air and electrical input power and to provide output source air, a combustion system configured to receive the source air from the electric blower and to receive fuel and to provide the thermal transfer fluid, a heat exchanger configured to receive the thermal transfer fluid from the combustion system and configured to provide heat exchange from the thermal transfer fluid to the production fluid, and to provide output exhaust gas, and wherein the electric fan provides a predetermined volume flow rate of the output source air at a predetermined blower efficiency such that the fluid heating system has a Bulk Heat Flux of at least about 14.7 kBTU/Hr/ft.sup.2 and a Pressure Drop of at least about 0.7 psi.

A heat transfer tube of a heat exchanger is provided with a first and a second annular convex portions of which outer diameters are partially expanded. The first annular convex portion is positioned on an inner face side of a side plate portion of a case of the heat exchanger and is engaged with a circumferential edge portion of a first hole portion provided for the side plate portion, or the first annular convex portion contacts under pressure with an inner circumferential face of the first hole portion. The second annular convex portion is positioned on an outer face side of a header constituting member and is engaged with a circumferential edge portion of a second hole portion. Thus the side plate portion, the heat transfer tube, and a header are relatively fixed by a simple means.

A turbulence member is made of a flat plate member configured to be inserted into a heat-transfer tube having a substantially elliptical cross-sectional shape. The flat plate member is a generate turbulence in a fluid flowing inside the heat-transfer tube by a plurality of projected pieces projected on both front and back surfaces. A rotation preventing piece configured to prevent rotation of the flat plate member inside the heat-transfer tube is provided in at least one of both side edges along the flow passage direction in the flat plate member. The rotation preventing piece is provided at a predetermined angle to the flat plate member so that a forefront comes into contact with a tube wall inner circumferential surface of the heat-transfer tube. A space through which the fluid can circulate is formed between the rotation preventing piece and the tube wall inner circumferential surface.

A heat exchanger (1) comprising a plurality of heat exchange units (10), wherein each of the plurality of heat exchange units (10) includes: an internal space (14) in which a fluid to be heated flows, a plurality of gas vents (13) penetrating the internal space (14) in a non-communicating state and through which combustion exhaust gas flows, at least one inlet port (20), and at least one outlet port (21), wherein at least the one inlet port (20) and at least the one outlet port (21) in each of the heat exchange units (10) are disposed at both ends in a longitudinal direction of the heat exchange unit (10) and are disposed to be shifted in a lateral direction of the heat exchange unit (10).