A baffle for a fluid collection portion of a thermal transfer device can include a body having an inner perimeter, an outer perimeter, and an asymmetric feature, where the asymmetric feature is configured to create a pressure drop within the fluid collection portion of the thermal transfer device. The inner perimeter can be configured to be at least as large as an inner surface of a first wall that forms the fluid collection portion of the thermal transfer device. The outer perimeter can be configured to be no larger than an outer surface of a second wall that forms the fluid collection portion of the thermal transfer device.

A boiler includes a tank, a gas circuit that includes a main combustion chamber in the tank and branch tubes in the tank that extend off of the main combustion chamber, and a water circuit fluidly isolated from the gas circuit. The water circuit includes a first manifold and water tubes that extend off of the first manifold. Each water tube extends through a respective one of the branch tubes, which may serve to preheat the water prior to discharge of the water into the tank.

A fluid heating system including: a pressure vessel; an assembly comprising: a heat exchanger core including a second inlet and a second outlet; a first conduit having a first end connected to the second inlet of the heat exchanger core and a second end disposed outside of the pressure vessel; a second conduit having a first end connected to the second outlet of the heat exchanger core and a second end disposed outside of the pressure vessel; and a blower in fluid connection with the first end of the first conduit, wherein the fluid heating system satisfies the condition that a Bulk Heat Flux between the first end of the first conduit and the first end of the second conduit is between 45 kW/m.sup.2 and 300 kW/m.sup.2, and wherein the Pressure Drop between the first conduit and the second conduit is between 3 kiloPascals and 30 kiloPascals.

A boiler system comprises a housing with a generally cylindrical shape extends between first and second walls to provide a generally cylindrical space. A fire tube is positioned near a bottom of the generally cylindrical housing and extends longitudinally from a first wall of the cylindrical housing to a fire tube end wall. The boiler system also includes a burner with a generally cylindrical housing which defines a generally cylindrical chamber and an end plate. The burner extends into the fire tube, and the fire tube provides a combustion chamber where combustion of an air-fuel mixture is accomplished using the burner. The end plate of the burner is adjustable so as to adjust the flame that extends from within the burner housing into the fire tube.

A boiler system comprises a housing with a generally cylindrical shape extends between first and second walls to provide a generally cylindrical space. A fire tube is positioned near a bottom of the generally cylindrical housing and extends longitudinally from a first wall of the cylindrical housing to a fire tube end wall. The boiler system also includes a burner with a generally cylindrical housing which defines a generally cylindrical chamber and an end plate. The burner extends into the fire tube, and the fire tube provides a combustion chamber where combustion of an air-fuel mixture is accomplished using the burner. The end plate of the burner is adjustable so as to adjust the flame that extends from within the burner housing into the fire tube.

A heat exchanger having a drainage member (1) mounted on an open end (322) of a heat-transfer tube (32), wherein the drainage member (1) contains a flow guide portion (11) including an insertion portion (11a) configured to be inserted into the heat-transfer tube (32) from the open end (322), and a projecting portion (11b) projecting toward an outside of the heat-transfer tube (32) from the open end (322) and extending downward.

A boiler system comprises a housing with a generally cylindrical shape extends between first and second walls to provide a generally cylindrical space. A fire tube is positioned near a bottom of the generally cylindrical housing and extends longitudinally from a first wall of the cylindrical housing to a fire tube end wall. The boiler system also includes a burner with a generally cylindrical housing which defines a generally cylindrical chamber and an end plate. The burner extends into the fire tube, and the fire tube provides a combustion chamber where combustion of an air-fuel mixture is accomplished using the burner. The end plate of the burner is adjustable so as to adjust the flame that extends from within the burner housing into the fire tube.

A boiler system comprises a housing with a generally cylindrical shape extends between first and second walls to provide a generally cylindrical space. A fire tube is positioned near a bottom of the generally cylindrical housing and extends longitudinally from a first wall of the cylindrical housing to a fire tube end wall. The boiler system also includes a burner with a generally cylindrical housing which defines a generally cylindrical chamber and an end plate. The burner extends into the fire tube, and the fire tube provides a combustion chamber where combustion of an air-fuel mixture is accomplished using the burner. The end plate of the burner is adjustable so as to adjust the flame that extends from within the burner housing into the fire tube.

A dual energy gas water heater is described and wherein a square flange, curved resistor style resistive heating element, is secured in a bottom portion of the tank of the water heater spaced above a top wall of the combustion chamber. A gas burner is secured in the combustion chamber and connected to a gas supply line through a gas valve. The curved resistive heating element is a low density, long life, element having a density in the range of about 20 to 80 watts/sq. inches. A switch is secured between the thermostat of the resistive heating element and the voltage supply line. A controller selectively operates the switch and the gas valve to disconnect the voltage supply line from the thermostat and/or shut-off the gas valve secured to the gas supply line depending on the desired source of energy. The controller is adapted to be optionally controlled by a utility/provider through a communication link. Renewable energy source may also be secured to an additional resistive heating element to improve the efficiency thereof.

A fire tube boiler includes a perforated flame holder configured to hold a combustion reaction that produces very low oxides of nitrogen (NOx).