Field of the invention

The present invention is concerned with an improved boiler heating system, in particular for use in supplying heated water to radiators or the like which form part of a domestic or other hot water system or circuitry, the boiler heating system incorporating a heat recovery module which improves the efficiency of the boiler heating system.

Background of the invention Boiler heating systems are used in many applications, but are primarily utilised in heating water for supply to a domestic heating system comprising a circuit containing one or more radiators and around which circuit hot water from the boiler heating system is pumped, conventionally by one or more electric pumps located at any suitable location along the circuit. Most domestic boiler heating systems rely on fossil fuels, in particular hydrocarbon based fuels such as kerosene, natural gas, or the like as the source of fuel. The fuel is generally fed from a remote fuel reservoir to a burner unit on the boiler heating system, where the fuel is mixed with air and ignited to heat water within a water chamber housed internally of the boiler heating system.

In recent years the global supply of fossil fuels has dwindled to the extent that the cost of such fuels has significantly increased. In addition, the burning of fossil fuels generates exhaust emissions which are harmful to the environment. For both reasons any measures which can increase the efficiency of a boiler heating system, thus using less fuel, are highly desirable.

It is therefore an object of the present invention to provide a boiler heating system having an improved operating efficiency.

Summary of the invention According to the present invention there is provided a boiler heating system comprising a burner; an air intake for supplying air for combustion to the burner; an exhaust for discharging hot flue gas from the burner; and a heat recovery module disposed between the air intake and the exhaust and adapted to effect the transfer of heat from the flue gas to air being supplied to the air intake. Preferably, the heat recovery module comprises a counter flow heat exchanger. Preferably, the heat exchanger comprises a first fluid circulation path and a second fluid circulation path passing between, but in fluid isolation from, one another. Preferably, the second fluid circulation path comprises an enclosure which is elongate in at least one dimension and preferably in two dimensions relative to a third dimension, and through which enclosure at least a part of the first fluid circulation path passes.

Preferably, the first fluid circulation path comprises a plurality of tubes around which a flow path of the second fluid circulation path passes.

Preferably, opposed ends of each of the plurality of tubes is defined by a respective aperture in one of a first plate and a distal second plate, which plates define two walls of the enclosure. Preferably, the first fluid circulation path comprises an array of heat conductive fins in thermal contact with at least some of the tubes.

Preferably, the enclosure comprises one or more baffles arranged to generate a reversing flow path within the second fluid circulation path.

Preferably, the heat recovery module comprises a first manifold and a distal second manifold each defining a manifold into and out of the opposed ends of the plurality of tubes.

Preferably, the heat exchanger is adapted to generate turbulent flow within at least the second fluid circulation path.

Preferably, the first fluid circulation path is supplied by the exhaust while the second fluid circulation path is fed with external air and supplies the air intake. Preferably, the boiler heating system comprises a pressure actuated valve between the air intake and the heat recovery module.

Preferably, the valve is located downstream of an outlet of the second fluid circulation path. Preferably, the valve comprises a port for regulating flow through valve, and a gate displaceable between a position occluding the port a position exposing the port.

Preferably, the valve is adapted to generate a pressure differential between opposed surfaces of the gate during burner combustion, which displaces the flap into the position exposing the port. Preferably, the gate is biased to return to the position occluding the port when combustion ceases.

Preferably, the first fluid circulation path comprises an outlet for exhausting flue gas. Preferably, the second fluid circulation path comprises an inlet for permitting the entry of atmospheric air.

Preferably, the outlet and the inlet are concentrically arranged relative to one another. Preferably, the boiler heating system comprises an air displacement unit arranged to draw air from the second fluid circulation path supply air to the burner from

Preferably, the heat recovery module is retrofittable to a suitable existing boiler heating system.

Brief description of the drawings

The present invention will now be described with reference to the accompanying drawings, in which: Figure 1 illustrates a perspective view of a boiler heating system according to an embodiment of the present invention;

Figure 2 illustrates a perspective view of the boiler heating system of Figure 1 from a reverse viewing angle;

Figure 3 illustrates the view of Figure 1 in which a heat recovery module of the boiler heating system is cut away to expose a sectioned view thereof;

Figure 4 illustrates the sectioned heat recovery module as shown in Figure 3, in isolation from the remainder of the boiler heating system;

Figure 5 illustrates an enlarged view of an upper portion of the heat recovery module as circled in Figure 4; Figure 6 illustrates a perspective view of a pressure actuated valve forming part of the heat recovery module but in isolation therefrom;

Figure 7 illustrates a sectioned view of the valve shown in Figure 6, in an open or exposed position; and Figure 8 illustrates a sectioned view of the valve as depicted in Figure 7 but in a closed or occluded position.

Detailed description of the drawings

Referring now to the accompanying drawings there is illustrates an improved boiler heating system, generally indicated as 10, for use in heating water for supply to a domestic hot water system including radiators (not shown) or the like, the boiler system 10 having improved efficiency relative to conventional boiler systems not incorporating the modifications hereinafter described.

The boiler system 10 comprises a boiler body 12 within which is located a water chamber (not shown) to which unheated water can be supplied, for example from a mains water supply (not shown), and within which chamber said water can be heated/boiled as hereinafter described, before being pumped from the chamber around a convention domestic hot water system or the like. It should be understood that reference to boiling water, or a boiler, should be understood to encompass heating of water to an elevated temperature without requiring that the water is actually boiled. The boiler heating system 10 further comprises a burner 14 which is arranged, in use, to receive a supply of fuel, for example kerosene, natural gas, or any other suitable alternative, which fuel is mixed with air within the burner 14 and ignited in order to provide a source of heat to boil the water within the water chamber internally of the boiler body 12. The burner 14 incorporates a fan or functional equivalent internally thereof, which is preferably electrically powered, and during operation of the boiler heating system 10 is driven in order to draw air into the burner 14 for mixing with the fuel prior to combustion. The burner 14 comprises an air intake 16 through which such air is drawn for combustion purposes. At the other end of the combustion process the boiler heating system 10 comprises a flue gas exhaust 18 via which the hot flue gases are exhausted from the boiler body 12, again in conventional fashion.

Unlike a conventional boiler however, the boiler heating system 10 additionally comprises a heat recovery module 20 which, in the embodiment illustrated, is mounted to one side of the boiler body 12, but may be positioned as required, and which is adapted to capture at least some of the heat energy of the hot flue gas exiting the flue gas exhaust 18, and to transfer this captured heat to the supply of air being drawn through the air intake 16 for supply to the burner 14. In this way the air is preheated, using heat which would otherwise be exhausted to the atmosphere in the hot flue gases, thereby improving the efficiency of the combustion process within the burner 14. The detailed configuration and operation of the heat recovery module 20 is described in greater detail hereinafter.

Thus referring in particular to Figures 3 to 5 the interior of the heat recovery module 20 is visible. The heat recovery module 20 defines a first fluid circulation path 22 along which, in use, the hot flue gas flows from the fluid gas exhaust 18, before finally being exhausted to the atmosphere as hereinafter described. The heat recovery module 20 further comprises a second fluid circulation path 24 along which, in use, atmospheric air flows before being drawn into the burner 14 via the air intake 16. The heat recovery module 20 is arranged such that the first fluid circulation path 22 and the second fluid circulation path 24 pass between or are interwoven with one another, while remaining in fluid isolation from one another such that the hot flue gas flowing through the first fluid circulation path 22 do not mix with the atmospheric air flowing through the second fluid circulation path 24.

Turning to the first fluid circulation path 22, an inlet 26 is provided in a first manifold 28 provided as part of the heat recovery module 20, which first manifold 28 defines an entry to a plurality of tubes 30, in the embodiment illustrated running essentially parallel to one another, and running substantially vertically upwardly through the heat recovery module 20. The plurality of tubes 30 exit into a second manifold 32 again provided as part of the heat recovery module 20, which forms an exhaust for the hot fluid gases passing through the tubes 30. An inner face of both the first manifold 28 and the second manifold 32 is defined by an aperture plate 34, each of which apertures therein define a respective end of one of the tubes 30. The aperture plates 34 additionally serve to provide a fluid tight barrier between the respective manifold 28, 32 and the remaining interior space of the heat recovery module 20. From the second manifold 32 the hot flue gases then pass upwardly through a fluid stack 36 to be exhausted to the atmosphere.

As will be described hereinafter, the tubes 30 function to facilitate the transfer of thermal energy or heat from the hot flue gas to the atmospheric air being drawn into and flowing along the second fluid circulation path 24. Thus in order to improve the thermal efficiency of said heat transfer, an array of thermally conductive fins 38 are located in thermal contact with at least some, and preferably all of, the tubes 30 in order to effectively increase the surface area from which heat energy may be transferred from the hot flue gas via the tubes 30. It will therefore be appreciated that the tubes 30 are formed from a heat conductive material, in particular a metal or the like. It will also be understood that the exact number, length, and orientation of the tubes 30 may be varied as required once performing the intended heat transfer function.

Turning then to the second fluid circulation path 24, there is provided an inlet 40 through which atmospheric air may be drawn into the second fluid circulation path 24. In the preferred embodiment illustrated the inlet 40 is disposed concentrically outwardly of the fluid stack 36, in order to immediately begin capturing or constraining heat from the hot flue gas as soon as the atmospheric air is drawn through the inlet 40. From the inlet 40 the second fluid circulation path 24 extends into a housing 42 defined internally of the heat recovery module 20 and between the pair of aperture plates 34. Disposed internally of the housing 42 are a plurality of staggered baffles 44 which each extend from one side of the housing 42 across a substantial length thereof while leaving a small gap at the opposed wall of the housing 42. The staggered array of baffles 44 serves to define a reversing fluid flow path within the housing 42 which forms part of the second fluid circulation path 24. The reversing flow path terminates at a valve 46 forming at or in fluid communication with an exit to the housing 42, which valve 46 is pressure actuated as described in detail hereinafter.

The valve 46 is defined by a casing 48 mounted to or adjacent the recovery module 20 and defining a port 50 which permits access into the valve 46 from the housing 42. The valve 46 additionally comprises a gate 52 displaceable between a position occluding the port 50 and a position exposing the port 50, such as to allow air to pass through the port 50 and through an opening 54 in the casing 48 to which is connected the air intake 16 feeding the burner 14. In this way the fan or other air displacement unit within the burner 14, once actuated, draws air from the inlet 40, all the way along the second fluid circulation path 24 through the housing 42, to exit the valve 46 and pass to the burner 14. As this air passes along the path 24, in particular the circuitous and reversing path defined within the housing 42, it flows passed and across the tubes 30 which pass from a lower end to an upper end of the housing 42, in addition to the thermally connected fins 38 which are dimensioned to fill a substantial volume of the housing 42 in order to maximise contact with the air flowing through the housing 42 along the second fluid circulation path 24. The length of flow path defined within the housing 42 is chosen to provide sufficient gas retention time of the atmospheric air within the housing 42, such as to ensure that suitable heat transfer occurs from the tubes 30 and thermally conductive fins 38. When the fan within the burner 14 is operating, namely during combustion within the boiler heating system 10, the action of the fan creates a negative pressure on the downstream side of the gate 52, which forces the gate 52 into the open position or position exposing the port 50, thereby allowing air to be drawn through the second fluid circulation path 24 in order to capture heat from the hot flue gas flowing through the first fluid circulation path 22. When combustion temporarily ceases the fan within the burner 14 is also temporarily switched off, thereby relieving the suction or negative pressure on the downstream face of the gate 52, allowing the gate 52 to return to the closed position occluding the port 50. The gate 52 may be spring biased into the closed position, or may use gravity as the return biasing means. By closing the gate 52 and thus occluding the port 50 when combustion has ceased, cold atmospheric air is prevented from entering the burner 14, thus further increasing the efficiency of the boiler heating system 10.

In an exemplarily embodiment of the invention the addition of the heat recovery module 20 to an otherwise conventional boiler heating system raised the fuel load from 97.8% to 102%, and the part load from 103.1 % to 108.0%. In addition the temperature of the flue gas emissions of the conventional boiler heating system, in the absence of the heat recovery module 20, was between 61 °C and 65°C, and with the heat recovery module 20 connected to the boiler heating system and operating as described above, the flue gas temperature fell to approximately 48°C.

It will therefore be appreciated that the improved boiler heating system 10 of the present invention, incorporating the heat recovery module 20, provides an effective means of significantly improving the efficiency of a boiler heating system 10. It will be appreciated that the heat recovery module 20 may also be retrofitted to an existing boiler heating system.