A water heater includes an outer casing defining a longitudinal axis, an axial direction being defined as extending along the longitudinal axis. The water heater further includes a combustor for production of hot flue gases, a primary heat exchanger including a tube positioned within the outer casing, and a secondary heat exchanger including a plurality of plates coupled together by brazing to form a brazed plate heat exchanger. The secondary heat exchanger includes a first set of passages defined between the plates, and a second set of passages defined between the plates and alternating with the first set of passages in the axial direction. The primary and secondary heat exchangers are in fluid communication such that the flue gases flow through the second set of passages before being exhausted, and water to be heated flows through the first set of passages to a delivery point for use upon demand.

A heat transfer fin includes a fin body having a plate shape, a plurality of through-holes famed through the fin body and spaced apart from each other in a first direction, in which a heat exchange pipe is inserted into the plurality of through-holes and heating water flows along an empty space in the heat exchange pipe, and two outer body portions protruding outward from at least partial areas of opposite ends of the fin body with respect to the first direction. Each of the outer body portions includes a contact portion that makes contact with a heat-insulating pipe with a heat-insulating side plate therebetween and that has a shape corresponding to at least a partial area of an outer surface of the heat-insulating pipe through which the heating water flows and a separated portion spaced apart from the heat-insulating side plate to form a gap.

A heat exchanger unit according to the present invention comprises: a sensible heat exchanger including a sensible heat exchange pipe disposed in a sensible heat exchange area for heating water used for heating by receiving sensible heat generated by a combustion reaction, wherein the sensible heat exchange pipe receives the water used for heating and flows same through the interior, and a sensible heat fin disposed in the sensible heat exchange area, wherein the sensible heat fin is formed in a plate shape across the sensible heat exchange pipe and penetrated by the sensible heat exchange pipe; and a latent heat exchanger positioned downstream from the sensible heat exchange area on the basis of a reference direction, which is a flow direction of combustion gas generated during the combustion reaction, the latent heat exchanger including a latent heat exchange pipe disposed in a latent heat exchange area.

A heat exchanger unit according to the present invention comprises: a sensible heat exchanger including a sensible heat exchange pipe disposed in a sensible heat exchange area for heating water used for heating by receiving sensible heat generated by a combustion reaction, wherein the sensible heat exchange pipe receives the water used for heating and flows same through the interior, and a sensible heat fin disposed in the sensible heat exchange area, wherein the sensible heat fin is formed in a plate shape across the sensible heat exchange pipe and penetrated by the sensible heat exchange pipe; and a latent heat exchanger positioned downstream from the sensible heat exchange area on the basis of a reference direction, which is a flow direction of combustion gas generated during the combustion reaction, the latent heat exchanger including a latent heat exchange pipe disposed in a latent heat exchange area.

A heat exchanger unit according to the present invention comprises: a sensible heat exchanger including a sensible heat exchange pipe disposed in a sensible heat exchange area for heating water used for heating by receiving sensible heat generated by a combustion reaction, wherein the sensible heat exchange pipe receives the water used for heating and flows same through the interior, and a sensible heat fin disposed in the sensible heat exchange area, wherein the sensible heat fin is formed in a plate shape across the sensible heat exchange pipe and penetrated by the sensible heat exchange pipe; and a latent heat exchanger positioned downstream from the sensible heat exchange area on the basis of a reference direction, which is a flow direction of combustion gas generated during the combustion reaction, the latent heat exchanger including a latent heat exchange pipe disposed in a latent heat exchange area.

A tube sheet for a thermal transfer device can include a body having a plurality of apertures that traverse therethrough, where the plurality of apertures are configured to receive a plurality of tubes of the thermal transfer device. The tube sheet can also include an outer perimeter defining the body, where the outer perimeter has at least one first recess feature disposed therein. The at least one first recess feature can have a first shape and a first size, where the first shape is any shape aside from a semi-circle.

A hybrid heating system is disclosed. The hybrid heating system includes a compressor that is configured to compress refrigerant. The hybrid heating system further includes a first heat exchanger that is configured to adjust a temperature of water by exchanging heat between the water and refrigerant compressed by the compressor. The hybrid heating system further includes a second heat exchanger that is configured to evaporate refrigerant by exchanging heat exchange with exterior air. The hybrid heating system further includes a first boiler heat exchanger that is configured to increase a temperature of water using heat generated by combustion. The hybrid heating system further includes a second boiler heat exchanger that is configured to exchange heat between exhaust gas discharged from the first boiler heat exchanger and refrigerant flowing into the second heat exchanger.

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 (1) includes a heat exchanging body (20) disposed within an outer box (10). A supply pipe (21) and a discharge pipe (22) in fluid communication with the heat exchanging body (20) respectively extend through first and second insertion holes (31, 32) in the outer box (10). Elastic seal members (40; 240) are respectively provided around the supply pipe (21) and the discharge pipe (22) and between a first sidewall (11) of the outer box (10) and the heat exchanging body (20). At least one biasing member (50; 250) exerts a lateral biasing force (F1; F2) on the elastic seal members (40; 240), thereby maintaining the elastic seal members (40; 240) in a state of compressive deformation and contacting the outer box (10) and the heat exchanging body (20) in an air-tight manner to block potential leakage paths (LP1; LP2) via the insertion holes (31, 32).

A plate-type heat exchanger formed by stacking a plurality of heat exchange units on top of each other, wherein adjacent heat exchange units are stacked such that the internal space in one heat exchange unit and the internal space in another heat exchange unit communicate with each other through a first opening in the one heat exchange unit and a second opening in the other heat exchange unit, the one heat exchange unit includes an insertion wall disposed on a peripheral edge of the first opening and inserted in the second opening when the adjacent heat exchange units are stacked, and the insertion wall has a distal end with a circumferentially discontinuous protrusion height.