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 heating device has a combustion chamber and a gas flue configured to guide hot exhaust gas generated in the combustion chamber, the flue having an inlet region and an outlet region and is configured connected to the combustion chamber via the inlet region. Heat transfer ribs having a wall thickness are arranged spaced from each other in the gas flue for the heat transfer from hot exhaust gas to the gas flue. The wall thickness of the heat transfer ribs and/or the distances of the heat transfer ribs to one another are optionally configured to be larger on the sides of the inlet region than on the sides of the outlet region.

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 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 boiler includes a chamber designed to receive and conduct hot exhaust gases, the chamber being enclosed by two plate elements which have an angled design and are arranged relative to one another in a sandwich-like manner, and the chamber being connected to a flow guide that is designed between the plate elements and used to cool the hot exhaust gases. The flow guide is designed in the form of a flat gap channel which fully encloses the periphery of the chamber.

A boiler includes a chamber designed to receive and conduct hot exhaust gases, the chamber being enclosed by two plate elements which have an angled design and are arranged relative to one another in a sandwich-like manner, and the chamber being connected to a flow guide that is designed between the plate elements and used to cool the hot exhaust gases. The flow guide is designed in the form of a flat gap channel which fully encloses the periphery of the chamber.

A high efficiency downfired gas water heater is provided which has a tank for storing water to be heated, a combustion chamber extending downwardly through a top end of the tank, and a gas burner operative to create hot combustion products within the combustion chamber. At the bottom end of the tank is a transfer chamber coupled to an external discharge conduit and to a single pass heat exchanger, in the form of multiple flue tubes. extending vertically through the tank and connected to the combustion chamber. In one embodiment of the water heater the burner is a power burner which forces the combustion products sequentially through the combustion chamber, heat exchanger, transfer chamber and discharge conduit. In another embodiment of the water heater a draft inducer fan is used to draw the combustion products through this path from the combustion chamber.

The invention relates to a heat exchanger, comprising a hollow central body which is received in a housing and defines an inner channel for a first medium, wherein a space surrounding the central body in the housing defines at least one outer channel for a second medium, wherein the central body has on either side parts which protrude from a main plane thereof and are connected to mutually opposite parts of the housing and which bound the outer channel such that the outer channel has a meandering form substantially parallel to the main plane of the central body. The invention further relates to a method for forming such a heat exchanger, and to a method for use thereof.

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.