An existing single-pass sectional boiler is retrofitted with one or two replacement sections to become a multi-pass boiler. One intermediate section of the original boiler is replaced by a new section having a downwardly extending water-filled target wall portion that divides the original combustion chamber into a smaller combustion chamber on the front side and a heat exchange chamber on the rear side of the target wall portion. The target wall portion also forces at least most of the combustion gas to flow from the combustion chamber upwardly through a first flue passage of the boiler's heat exchanger, into the upper flue collector chamber. Another intermediate section of the original boiler may be replaced by a new section having an upwardly extending draft diverter portion, or a draft diverter is installed in the upper flue collector chamber, to divert the flue gas back downwardly through a second flue passage of the heat exchanger to the heat exchange chamber. From there, the flue gas flows again upwardly through a third flue passage of the heat exchanger to the breech.

A dielectrically insulated secondary tubular flue for mounting inside a water holding tank of a gas-fired water heater is provided to increase the efficiency of the water heater. The secondary tubular flue has opposed tubular end sections and an helical tubular section integrally formed therewith. The tubular end sections each have connecting end sections adapted to form a part of a dielectric connector for securing the secondary tubular flue inside of the water holding tank by the dielectric connectors.

The present invention relates to a smoke tube boiler including: a mix chamber which includes a mixing space in which combustion gas and air are mixed, a mix chamber body having a flat shape, and a flat plate-shaped burner disposed in a horizontal direction above a combustion chamber; and a heat exchanger which includes an outer shell forming an outer wall of a water tank into and from which a heat medium is introduced and discharged and which accommodates the heat medium, a plurality of tubes formed in a flat shape that are configured to allow combustion gas generated in the combustion chamber to flow therein and cause a heat exchange to occur between the combustion gas and the heat medium flowing outside the tubes, turbulators coupled to an inner side of the tube and configured to induce occurrence of a turbulent flow in the flow of the combustion gas, and multi-stage barriers disposed between the outer shell and the tube and configured to induce a heat medium flow direction to be alternately changed between a radially inward direction and a radially outward direction.

A tank assembly for a heating device and the heating device are provided. The tank assembly includes: a tank body including a first side plate assembly and a second side plate assembly, a main heat exchange pipe assembly including first heat exchange pipes, a condensation pipe assembly including second heat exchange pipes, and a heat exchange fin assembly. First water boxes are defined by the first side plate assembly, and second water boxes are defined by the second side plate assembly. Every two of the first heat exchange pipes are formed as a reciprocating heat exchange group. Each reciprocating heat exchange group is in communication with one of the first water boxes and two of the second water boxes to form a series water passageway.

A condensing combustion apparatus comprising: an upward combustion burner (20); a sensible-heat exchanger (40) which absorbs sensible combustion heat generated by the burner (20); and a latent-heat exchanger (50) which absorbs latent heat of steam included in a combustion gas which has passed the sensible-heat exchanger (40), wherein the sensible-heat exchanger (40) and the latent-heat exchanger (50) have the same lateral widths and are configured as fin-tube heat exchangers having common structures, and wherein a flow path through which the combustion gas, which has passed the sensible-heat exchanger (40), flows upward is formed on one side portion of the latent-heat exchanger (50), a flow path through which the combustion gas, which has passed the one side portion of the latent-heat exchanger (50), flows downward corresponding to a direction in which condensed water falls is formed on a middle portion of the latent-heat exchanger (50), and a flow path through which the combustion gas, which has passed the middle portion of the latent-heat exchanger (50), flows upward and discharges is formed on another side portion of the latent-heat exchanger (50).

A water heater has a tank, a burner, and a heat exchanger within the tank interior volume that has three tubes. The burner exhausts gas into the first tube. The second tube is non-linear, and the third tube connects the first tube with the second tube. The cross-sectional area of the first tube is greater than the cross-sectional area of the third tube. The cross-sectional area of the third tube is greater than the cross-sectional area of the second tube.

The present invention provides an outdoor water heater (10) having a lower chamber (12) located in a cabinet (14) which substantially sealingly encloses a naturally aspirated or natural draught burner 16, a combustion chamber, a heat exchanger (18), a flue (20) for conveying combustion gases from the burner (16), the flue (20) extending away from the heat exchanger (18) and passing through a middle chamber (22) located above the lower chamber (12), the flue (20) not opening into the middle chamber (22) and opening into an upper chamber (24) which has two opposed openings (24.2, 24.3), the upper chamber (24) and middle chamber (22) being substantially sealed with respect to each other to prevent combustion gas flow between the middle chamber (22) and the upper chamber (24), and wherein the middle chamber (22) has divider formations (22.1, 22.2) separating one side of the middle chamber (22) from an opposed side of the middle chamber (22), whereby the divider formations (22.1, 22.2) direct air flowing from one side of the middle chamber (22) to pass downwardly into the lower chamber (12) on one side then upwardly out of the lower chamber (12) to exit the middle chamber (22) on the other or opposite side.

Aspects of the invention relate to water heaters including a water storage tank having a top wall, a bottom wall, and a side wall extending between the top wall and the bottom wall; a combustion chamber extending below the bottom wall of the water storage tank and a heat exchanger configured to receive combustion gases and to transfer heat to water in the water storage tank. The heat exchanger includes a first pass flue extending through the water storage tank and a plurality of second pass flues coupled to receive combustion gases from the first pass flue. The second pass flues extending through the water storage tank and having a straight top portion, a curved bottom portion, and a longitudinal axis residing in a plane. The curved bottom portion of the second pass flues exits the water storage tank through at least one aperture defined in the side wall of the water storage tank.

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 be in thermal communication with the production fluid to provide convective 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 fin-and-tube type heat exchanger includes: a plurality of plate fins arranged in a case side by side in a fore-and-aft direction of the case; and a heat transfer tube including a plurality of straight-type tubular bodies each passing through these plurality of plate fins. First and second plate fins arranged side by side in the right-and-left width direction of the case are provided as a plurality of plate fins. The heat transfer tube has a connection tubular body connecting the straight-type tubular bodies passing through the first and second plate fins. The heat transfer tube passes through areas in which the first and second plate fins are arranged.