WO2017220999A1

WO2017220999A1 - Boiler

Info

Publication number: WO2017220999A1
Application number: PCT/GB2017/051805
Authority: WO
Inventors: Peter Evans; Arben Sallaku
Original assignee: Peter Evans; Arben Sallaku
Priority date: 2016-06-20
Filing date: 2017-06-20
Publication date: 2017-12-28
Also published as: GB2551600B; EP3472530A1; GB201610729D0; GB2551600A; GB201701334D0

Abstract

A boiler comprising: a heating element; and a pipe configured to carry a fluid to be heated; wherein the pipe is arranged around the perimeter of the heating element and the heating element comprises an exit region that is aligned with the pipe, wherein the exit region comprises one or more exit ports that are configured to facilitate heating of the fluid by the heating element.

Description

BOILER

This invention relates to an improved design of boiler.

Conventional boilers comprise some form of heating element and a heat exchanger for transferring heat from the heating element to the liquid to be heated. The heating element is commonly powered by natural gas, but other heating means such as oil or electricity can also be used. The heating element is often configured to heat some type of chamber within the boiler. The liquid (often water) is then carried in a pipe through this chamber and the transfer of heat from the chamber and through the wall of the pipe causes the water to exit the boiler at a higher temperature than when it flowed in.

The fundamental design of most boilers has not changed much for decades. They are often complex, with many moving parts that are susceptible to breakage or failure. They are also inefficient in how they use fuel, which is at least in part due to the rudimentary design of burner in many boilers. This conflicts with energy price rises and environmental concerns, both of which dictate that energy should be used as efficiently as possible. Therefore, there is a need for an improved boiler design.

According to a first aspect, there is provided a boiler comprising a heating element and a pipe configured to carry a fluid to be heated, wherein the pipe is arranged around the perimeter of the heating element and the heating element comprises an exit region that is aligned with the pipe, wherein the exit region comprises one or more exit ports that are configured to facilitate heating of the fluid by the heating element.

Other aspects may include one or more of the following:

The heating element may be configured to burn fuel and thereby cause flames to exit from the series of exit ports and impinge on the pipe. The exit ports may be spaced such that flames that exit neighbouring exit ports will overlap each other. The exit ports may be spaced such that the overlap occurs only in a relatively cool, outer region of the flames. The exit ports may be spaced such that no overlap occurs in a relatively hot, inner region of the flames. The exit ports may be equally spaced. The heating element may be configured such that the flames exit from the one or more exit ports to extend beyond the outer edge of the pipe.

The pipe may be coiled around the heating element. The heating element may comprise a chamber and a fan operable to distribute fuel throughout the chamber. The heating element may comprise a cylindrical chamber and the one or more exit ports may be formed in that chamber.

The exit region comprising one or more exit ports, may comprise a series of discrete or semi-continuous exit ports, or one continuous exit port.

According to a second aspect, there is provided a boiler comprising a first pipe and a second pipe that are both configured to carry a fluid to be heated and a heating element configured to heat at least one of the pipes, wherein the first and second pipes are axially aligned with each other and coiled around the heating element and wherein the heating element comprises an exit region that is aligned with the first pipe and/or the second pipe, wherein the exit region comprises one or more exit ports, that are configured to facilitate heating of a pipe with which they are aligned by the heating element.

Other aspects may include one or more of the following:

The heating element may be configured to directly heat only one of the first and second pipes at a time. The first and second pipes may be configured such that the heating element directly heating one of the first and second pipes has the effect of indirectly heating the other of the first and second pipes. The second pipe may be coaxially arranged within the first pipe. The second pipe may be configured such that it can be heated by fluid carried in the first pipe. The first and second pipes may be separate pipes that are coiled in parallel around the heating element. The exit region, comprising the one or more exit ports, may be configured to be aligned with only one of the first and second pipes at a time. The heating element may be moveable between a first position in which it is configured to directly heat the first pipe and a second position in which it is configured to directly heat the second pipe. The heating element may be configured such that moving it from the first position to the second position moves the exit region comprising one or more exit ports from being aligned with the first pipe to being aligned with the second pipe. The heating element may be configured to move along one of its axes, said axis being the axis around which the first and pipes are coiled. The boiler may comprise a screw that is rotatable to move the heating element along said axis. The boiler may comprise a servo configured to rotate said screw. The heating element may form the chamber of a burner and the burner may be configured such that its other components remain stationary when the chamber moves.

The first and second pipes may be configured to carry fluids intended for different purposes. One of the first and second pipes may be configured to carry potable water and the other of the first and second pipes is configured to carry non-potable water.

There is also provided a connector having an inner pipe comprised within an outer pipe, wherein a curved wall of the outer pipe incorporates an opening through the wall through which the inner pipe protrudes.

The inner and outer pipes may be not aligned along at least part of their longitudinal axes. The inner pipe may incorporate a bend that alters the direction of the inner pipe's longitudinal axis such that the inner pipe protrudes from the opening. The inner and outer pipes may be aligned along their longitudinal axes on the other side of the bend from the opening. An outer surface of the inner pipe may be sealably connected to an edge of the opening. The outer surface of the inner pipe may be welded to the edge of the opening. At least one end of the inner pipe and/or the outer pipe may be connected to another pipe. The at least one end may be connected to the other pipe via a push-fit connection.

According to a third aspect, there is provided a boiler comprising a heating element and a pipe configured to carry a fluid to be heated, wherein the pipe is arranged around the perimeter of the heating element and the heating element a series of exit ports aligned with the pipe that facilitate heating of the fluid by the heating element.

According to a fourth aspect, there is provided a boiler comprising a heating element and a pipe configured to carry a fluid to be heated, wherein the pipe is arranged around the perimeter of the heating element and the heating element comprises an exit region, comprising one or more exit ports, that is aligned with the pipe, wherein the one or more exit ports facilitate heating of the fluid by the heating element.

According to a fifth aspect, there is provided a boiler comprising a first pipe and a second pipe that are both configured to carry a fluid to be heated and a heating element configured to heat at least one of the pipes, wherein the first and second pipes are axially aligned with each other and coiled around the heating element and wherein the heating element comprises an exit region, comprising one or more exit ports, that is aligned with the first pipe and/or the second pipe, wherein the one or more exit ports are configured to facilitate heating of a pipe with which they are aligned by the heating element.

According to a sixth aspect, there is provided a pipe comprising a channel for carrying a fluid to be heated by a heating element, wherein the channel has a cross-section that is shaped so as to concentrate the flow of fluid towards a part of the pipe that is configured to experience the greatest heating effect from the heating element. The present invention will now be described by way of example with reference to the accompanying drawings. In the drawings:

Figures 1 a to c show an example of a twin pipe, twin function boiler; Figures 2a to c show an example of a single pipe, twin function boiler; Figure 3 shows a cross-section through a burner; Figure 4 shows flames exiting a burner; Figure 5 shows a connector; and Figure 6 shows a connector.

Figures 7a to d show examples of heating elements having exit regions comprising one or more exit ports.

Figure 8 a to d show examples of irregular pipe cross-sections.

A boiler may comprise a pipe that is coiled around a heating element. The pipe is configured to carry a fluid to be heated. In many examples that fluid will be a liquid such as water, but it could equally be a gas. The centrally-located heating element could use any suitable heat source, including natural gas, oil, electricity etc. The heating element could also use any suitable heating means, including a burner, filament etc. In one example, the central heating means incorporates a closed chamber or vessel that serves to separate the high temperature within the chamber from the surrounding environment. The pipe could be coiled within the chamber or outside of it.

Two examples of boilers in which the pipe is coiled around a heating element are shown in Figures 1 a to c and in Figures 2a to c. In both of these examples there are two pipes, which are both coiled around the perimeter of the heating element. The two pipes are axially aligned with each other. In the example of Figures 1 a to c, this axial alignment takes the form of the pipes being coiled separately but in parallel around the heating element. In Figures 2a to c, the axial alignment takes the form of a "pipe- within-a-pipe" arrangement in which one pipe is coaxially arranged within the other. In both arrangements, the heating element is configured to heat at least one of the pipes.

The boiler shown in Figures 1 a to c is an example of a twin pipe, twin function boiler. The boiler is shown in side elevation in Figure 1 a and in cross-section in Figures 1 b and c (which show the heating element with and without its surrounding pipes respectively). The boiler comprises two pipes 101 , 102. The two pipes suitably carry fluid for different purposes. For example, one pipe may carry potable water intended for a hot water system while the other pipe may carry non-potable water intended for a central heating system. Each pipe may be provided with connectors 103, 104 enabling it to be connected to a wider fluid distribution system - such as a tap water system or central heating system. The connectors may be quick release connectors.

As mentioned above, the two pipes are coiled in parallel around heating element 105 in a grouped arrangement such that the pipes, viewed from the side of the boiler, alternate between the first pipe and the second pipe along the longitudinal axis of the heating element. This is indicated by pipes 101 , 102 in the cross-section shown in Figure 1 b.

The boiler shown in Figures 2a to c is an example of a single pipe, twin function boiler. The boiler is shown in side elevation in Figure 2a and in cross-section in Figure 2b. The boiler comprises two pipes 201 , 202. One of the pipes is located within the other, as shown in Figure 2b. The two pipes are preferably aligned along their longitudinal axes. In most embodiments, the inner pipe will not touch the outer pipe, so that it is surrounded by fluid on all sides. The inner pipe will also typically be centred within the outer pipe, so that it is surrounded by largely equal volumes of fluid on all sides. The inner pipe could also be positioned off-centre of the outer pipe. The two pipes are then coiled together along the longitudinal axis of the heating element 203. As with the boiler shown in Figures 1 a to c, the pipes in Figures 2a to c suitably carry fluid intended for different purposes, such as potable and non-potable water supplies. Either pipe could carry either supply. In a preferred embodiment the inner pipe is configured to carry the potable water supply, meaning that the potable water is heated indirectly via the temperature of the non-potable water in the outer pipe. This may be preferable from a water-quality perspective to heating the pipe carrying the potable water supply directly, e.g. via a burner. The pipes may be provided with connectors 204, 205 that enable them to be connected to a wider fluid distribution system, as before. Those connectors may be quick release connectors.

Coiling the pipes around the burners in this way greatly increases the efficiency of the boiler. The boiler uses around 60% of the natural gas of a conventional boiler to achieve the same level of water heating. The design is also compact, which saves material resources and also space in domestic environments. The boiler may also be fixed in a vertical or horizontal configuration, which increases flexibility. The boiler is also of relatively simple construction with few moving parts, which increases reliability and reduces maintenance costs.

A boiler may also comprise one or two pipes and a heating element that comprises an exit region. The exit region is an area on the surface of the heating element that comprises one or more exit ports. The exit region is aligned with the pipe, which is suitably arranged around the perimeter of the heating element. This has the advantage that heat exiting the heating element via the exit region is focussed exactly where it is required. In most implementations, the heating element will be configured to output a stream of heated fluid through exit ports in the exit region. Having the exit region aligned with the pipe arranged around the outside of the heating element means that this stream of heated fluid impinges directly on the pipe carrying the fluid to be heated. This exit port arrangement can be advantageously implemented together with a twin pipe arrangement (such as those described above). It can also be implemented separately, e.g. as part of a conventional boiler. The exit region is elongate with a longitudinal axis. The exit region also extends laterally, at least to the edge of the exit ports that it comprises. In many implementations, there will be multiple exit ports contained in the exit region. The longitudinal axis of the exit region will follow the line that joins the series of exit ports. The longitudinal axis of the exit region may 'follow the line that joins the series of exit ports' by coinciding with that line or being in parallel with it. The multiple exit ports in the exit region are thus also aligned with the pipe. In some implementations, there might be only one exit port. For example, the exit region might contain a single slit that spirals around the heating element. In this example, the longitudinal axis of the exit region will follow the longitudinal axis of the slit. Thus, the slit will be aligned with the pipe in the same way as the exit region. The end result is that all of the exit ports in the exit region - whether those are a series of individual ports or a continuous slit - are aligned with the pipe.

Figure 7a shows an example of a heating element that comprises an exit region (702). The exit region is depicted by pairs of dotted lines. The exit region (702) coils around the heating element. In Figure 7a the exit region (702) comprises a series of exit ports (703). The series of exit ports (703) are shown as being equally spaced and arranged along a line. The series of exit ports (703) may be considered a series of discrete exit ports. The longitudinal axis of the exit region is depicted in figure 7a as the line (706) that joins each of the exit ports in the series of discrete exit ports (703). The longitudinal axis of the exit region coincides with the longitudinal axis of a pipe (701 ) coiled around the heating element. Hence, the series of discrete exit ports comprised within the elongate exit region are aligned with the pipe.

Figure 7b shows another example of a heating element that comprises an exit region (702). The exit region is depicted by pairs of dotted lines. The exit region (702) coils around the heating element. In Figure 7b, the exit region comprises one exit port (705). The exit port (705) is implemented as a continuous slit/opening (705) that follows the longitudinal axis (not shown) of the exit region. The exit port (705) may be considered a continuous exit port. The longitudinal axis of the exit region coincides with the longitudinal axis of a pipe (701 ) coiled around the heating element. Hence, the continuous exit port comprised within the elongate exit region is aligned with the pipe.

Figure 7c shows yet another example of a heating element that comprises an exit region (702). The exit region is depicted by pairs of dotted lines. The exit region (702) coils around the heating element. In Figure 7c, the exit region comprises a series of exit ports (704). Each of the exit ports in the series of exit ports (704) are arranged on, and are partially extended along, the longitudinal axis (not shown) of the exit region (702). The series of exit ports (704) may be considered a series of semi-continuous exit ports. A semi-continuous exit port may be any exit port that is longer than it is wide. A series of semi-continuous exit ports may be any series of exit ports where the length of each exit port is greater than the length of the gaps between the exit ports. The longitudinal axis of the exit region coincides with the longitudinal axis of a pipe (701 ) coiled around the heating element. Hence, the series of semi continuous exit ports comprised within the elongate exit region are aligned with the pipe.

Figure 7d shows yet another example of a heating element that comprises an exit region (702). The exit region is depicted by pairs of dotted lines. The exit region (702) coils around the heating element. In Figure 7d, the exit region comprises a series of exit ports (707). The series of exit ports (707) comprises a repeating pattern of two exit ports, one exit port intentionally offset either side of the longitudinal axis (706) of the exit region (702). The series of exit ports (707) may be considered a series of offset discrete exit ports. The longitudinal axis of the exit region coincides with the longitudinal axis of a pipe (701 ) coiled around the heating element. Hence, the exit region is aligned with the pipe. The series of offset discrete exit ports comprised within the elongate exit region are also substantially aligned with the pipe because by being alternately located either above or below that pipe's longitudinal axis, the average effect is to focus the heating effort on the pipe.

The heating elements shown in Figure 1 b and Figure 2b are both examples of heating elements that comprise an exit region with a series of exit ports (106, 206) that is aligned with a pipe arranged around the perimeter of the central heating element. The exit ports (106, 206) are preferably equally spaced around the perimeter of the heating element so that pipes are heated evenly. The exit ports are preferably formed such that heated jets of fluid leaving the central heating portion expand on exiting the ports. The spacing between neighbouring exit ports is preferably selected so that, in use, heated jets of fluid leaving the exit ports at least partially overlap by the time they hit the pipe. This may help to heat the pipes evenly. The spacing is preferably selected so that any overlap is minimal. This may help to save energy.

The exit ports could simply be holes formed in a perimeter wall of the heating element. The exit holes could also incorporate some form of insert. The exit ports could have a constant diameter throughout or could have walls that incorporate some form of sloping or shaping. The exact form of the exit ports may be determined based on factors such as type of fuel, size of pipes, desired shape of exiting jets etc. The cross- section of the exit ports could be of any suitable shape, for example the exit ports could be circular, square, rectangular, triangular or otherwise. The cross-section of the exit ports may be of regular or irregular shape. The cross-section of the exit ports may be of a symmetrical or non-symmetrical shape. The exit ports may be a plurality of discrete ports, or could be formed from one or more extended exit ports such as a continuous slit or opening around the perimeter of the heating element.

The example boilers shown in Figures 1 a, 1 b, 2a and 2b will now be described in more detail.

The heating elements in the boilers shown in Figures 1 a to c and 2a to c are both based on a burner. In these examples, the burner comprises a cylindrical combustion chamber. This cylindrical chamber comprises a series of ridges that protrude from the main body of the cylinder. This is shown in Figure 3, with circle 301 representing the outer edge of the cylinder and circle 302 representing the outer edge of the ridge. These ridges are suitably aligned with the coils of pipe. This may require them to be tilted at an angle to the cylinder bases. The ridges may spiral around the cylindrical chamber or be arranged in a series of concentric rings. Each ridge is of a comparable thickness to the walls of the cylindrical burner.

The cylindrical chamber of the burner is preferably made of a highly heat resistant material such as heat resistant stainless steel. The circumferential ridge comprising the one or more exit ports could be formed within the chamber via upset forging or any suitable manufacturing technique. The exit ports may be around 3mm in diameter for a domestic application.

The heating element also comprises a fan (not shown) for distributing fuel throughout the chamber. The fuel/oxygen mixture is often termed a premix. The effect of the fan is to push the premix through the chamber at a slight pressure, which causes the ignited flame to sit slightly above the exit port. This is represented by semi-circle 403 in the figures, which indicates the point of transition from the premix to an ignited flame. Because the fan blows the combusting mixture throughout the chamber, this also results in high, even temperatures around the surrounding pipes. The burner may also comprise an ignition electrode (again not shown) that sits between the chamber and the pipes. Typically, once the premix exiting one exit port has been ignited by the ignition electrode, the others follow rapidly.

Figure 4 shows a cross-section through a burner cylinder. The burner may be configured to burn any suitable fuel. In one example it may be configured to burn a methane/oxygen mix. Figure 4 shows the inner and outer walls of the cylinder (401 , 402). These walls encapsulate the intense heat that is generated by the combusting fuel. This heat radiates out to heat the pipes coiled around the burner. Figure 4 also shows ridges 404 through which the exit ports are formed. The exit ports output hot jets of fluid to heat the pipes directly. In this example, where the heating element incorporates a burner, those hot jets take the form of intense, mushroom-shaped flames. The outer edges of the flames are represented by the heavily dashed lines (406). The hotter inner cores of the flames are represented by the lighter dashed lines (405). The inner core will typically be around 50 to 75% hotter than the cooler outer regions of the flames. The exact temperatures of the inner and outer portions of the flames will depend on the fuel and factors such as the amount of oxygen available for combustion. For methane, a typical range would be from around 900°C for the coolest part of the flame to around 1500°C in the hottest part of the flame. There is preferably no overlap between the hotter cores of flames output by neighbouring exit ports and minimal overlap between the cooler regions of the flames (as shown at 407).

The burner flames can be fairly short - typically there is approximately 75 to 90mm between the output of the exit port and the outer reaches of the flame. The outer edge of the flame preferably extends to the outer edge of the pipe coiled around the burner (as shown in Figure 4). The burner may therefore be configured to output a length of flame that is dependent on the thickness of the pipes coiled around it. The burner in the single-coil implementation, for example, may be configured to output a longer flame than the burner in the twin-coil implementation because of the greater width of the outer pipe used in the single-coil implementation (see e.g. table 1 below).

The burner is preferably configured so that the flames are projected substantially perpendicularly to the surface of the cylinder. The flames also preferably impact the pipes substantially perpendicularly to their longitudinal axes. The pipes are suitably spaced far enough from the edge of the cylinder that waste gases can escape in the gap between the two. The pipe coils are also suitably spaced from each other for the same reason. The circulation of waste gases around the pipes provides a beneficial secondary heat exchange effect so that the pipes are heated via indirect means in addition to the direct application of heat from the burner flames. The pipes might, for example, be spaced between 50 and 60mm from the cylindrical walls of the burner. The pipe coils might be spaced between 2 and 10mm from each other, and one implementation they may be spaced 5mm apart.

In a twin-pipe, twin-function boiler, the heating element may be configured to directly heat only one of the pipes at a time. The boiler shown in Figures 1 a to c is an example of a boiler configured in this way. The burner cylinder 105 comprises exit ports 106 that are aligned with only one of the pipes 101 , 102 at a time. The pipe with which the exit ports are aligned is therefore directly heated by the heating element, e.g. via the flames shown in Figure 4. The other pipe may be indirectly heated via the high temperature environment created by the heating element, including any waste gas emissions.

The heating element is moveable relative to the pipes so that the exit ports can be aligned with either pipe. The heating element can thus selectively heat either the potable or the non-potable water supply. The water supply to be heated may be selected in dependence on time of day, user requirements etc. The boiler may be controlled by a user-operated timing system, such as those conventionally used in domestic central heating and hot water systems, so that a user can select which coil should be the focus of direct heating at different times of day. The user is preferably also able to override any pre-programmed arrangement to take account of circumstances, such as wanting a shower or bath in the middle of the day. If the user wants to use both systems simultaneously, the boiler may be configured to alternate between making the hot water system and the central heating system its focus, e.g. by spending 5 or 10 minutes alternately heating each.

Any suitable mechanism could be employed to move the heating element. The boiler shown in Figures 1 a to c comprises a servo-powered screw 107 to move the central chamber of the burner relative to the coiled pipes. The other components of the burner - such as the fuel pipes, fan and fuel injection system - preferably remain stationary.

Focussing the output of the heating element on only one of the pipes results in very fast and efficient heating of the water within that pipe. This has advantages for users, since hot water for showers, baths and taps can be provided very quickly. Combining the two pipes within one housing also offers benefits because there is some transfer of heat between the two pipes and also their surroundings. For users, this means that there will still be some central heating/hot water available even if the other water supply has been receiving the focussed direct heating, e.g. during a long shower. The boiler therefore offers significant fuel efficiency benefits compared with conventional boilers. It is estimated that this improved design will use around 40% less energy than a conventional boiler for the same heating performance. In a single-pipe, twin-function boiler, the heating element may also be configured to directly heat only one of the pipes at a time. In this implementation, this is achieved by having one of the pipes comprised within the other. The boiler shown in Figures 1 a to c is an example of a boiler configured in this way. The burner cylinder 203 comprises exit ports 206 that are aligned with the outer pipe 201 coiled around the burner. That outer pipe is suitably wider than its equivalent in the twin-pipe implementation since it has to be wide enough to incorporate inner pipe 202 within it. Heat from the burner flame impinges directly on the outer pipe. The inner pipe is then heated indirectly via the heat-exchanger effect provided by the water in the outer pipe.

Having a pipe-within-a-pipe arrangement is energy efficient because the two pipes are heated together rather than having to be heated separately. In most implementations it is expected that the outer pipe will carry the non-potable water supply while the inner pipe will carry the potable water supply. For users, the single-pipe implementation offers instant hot water for most of the year in cooler countries, where the central heating will usually be on. Even if the central heating is off, the heat rapidly transfers from the central heating water to the hot water pipe when the burner is activated.

The single-pipe implementation is a particularly compact design. It also offers similar fuel savings to the twin-pipe implementation, being expected to use around 40% less energy than a conventional boiler for the same heating performance.

The dimensions of the boiler will tend to vary depending on the application and how much power the boiler is required to output. For example, the boiler may be sized differently for domestic applications from commercial ones. A domestic boiler would typically output between 15kW and 60kW whereas a commercial boiler would typically output between 60kW and 1000kW. The table below includes approximate, indicative dimensions for a domestic boiler Examples of dimensions that might be expected for a domestic boiler configured to output around 20kW and a commercial boiler configured to output around 2000kW. Dimension Domestic application Commercial application

Cylindrical chamber 200mm 200cm

length

Cylindrical chamber outer 75mm 75cm

diameter

Cylindrical chamber wall 1 .5mm 4mm

thickness

Ridge thickness 2mm 2cm

Number of exit ports per 13 13

circumference

Distance from exit port to 31 mm 31 cm

inner edge of non-potable

water pipe

Non-potable water pipe 22mm 22cm

outer diameter (single

pipe)

Non-potable water pipe 15mm 15cm

outer diameter (twin pipe)

Potable water pipe outer 15mm 15cm

diameter (single pipe)

Potable water pipe outer 15mm 15cm

diameter (twin pipe)

Non-potable water pipe 1 mm 3mm

thickness

Potable water pipe 1 mm 3mm

thickness

Table 1 : Example dimensions for different applications

The aim of the domestic specification detailed above is to be able to consistently deliver central heating water at 50°C and 10 litres per minute, rising to 70°C after 10 to 15 minutes of heating. Another aim is to be able to consistently deliver hot water at 60°C and 10 litres per minute. The pipes carrying the fluid to be heated by the boiler are formed of a material that is capable of withstanding high temperatures. In the twin-pipe implementation both pipes may be formed of stainless steel. In the single-pipe implementation the outer pipe may be formed of stainless steel while the inner pipe may be formed of copper. In the single-pipe example the inner pipe can be made of a different material from the outer pipe, since it does not need to withstand direct application of heat from the heating element, e.g. a burner's flames. The inner pipe may be capable of withstanding temperatures of around 200°C, for example, whereas the outer pipe may be capable of withstanding a flame temperature of around 1500°C (at least while the pipe is filled with water, which helps to maintain a cooler temperature of the pipe than that of the flame) The piping should also be formed of material that is resistant to corrosion by the fluid it is intended to carry.

The single-pipe implementation requires a suitable connector so that two separate pipes can be brought together to form a pipe-within-a-pipe configuration. An example of a suitable connector is shown in Figure 5. The connector comprises an inner pipe 501 comprised within an outer pipe 502. The wall of the outer pipe incorporates an opening or hole 503 through which the inner pipe protrudes. The opening is formed in the curved outer wall of the pipe and is surrounded by that wall. The inner and outer pipes are aligned along part of their longitudinal axes and not aligned along at least another part. Suitably this non-alignment provides the means by which the inner pipe is able to exit the outer pipe through the opening. In Figure 5, for example, the inner pipe incorporates a bend 505 that alters the direction of the inner pipe's longitudinal axis such that the inner pipe connects with the curved outer wall of the outer pipe and is able to protrude from the hole. The edge of the opening and the outer wall of the inner pipe are preferably sealed together to prevent leakage. Any suitable form of seal could be used but a preferred option is to weld the inner pipe within the opening to provide a robust construction. The inner and outer pipes may be connected to other, longer pipes at either end. Any suitable form of connection could be used, including the push-fit connectors 504 shown in Figure 5. Figure 6 shows another representation of the connector. It should be understood that this connector could be used for any application where it is desired to integrate two separate pipes into a pipe-within-a-pipe configuration and its use is not limited to the boilers described herein.

The pipe(s) may be configured to increase the efficiency of a boiler. The time and energy required to heat the portion of fluid flowing in the centre of a hollow cylindrical pipe can be undesirably high, particularly when compared to the time and energy required to heat the portion of fluid flowing nearest the circumferential edge of the pipe. The time and energy required to heat the portion of fluid flowing on the opposite side of a pipe to an applied heat source (e.g. a flame) can also be undesirably high. To address this, the pipe may be configured to concentrate fluid flow towards the portion of the pipe that is configured to experience the greatest heating effect from the heating element. In most implementations, this is likely to be the part of the pipe upon which a heat source (such as a flame) generated by the heating element impinges directly. In most implementations, this is likely to be the part of the pipe that is closest to the heating element. Other parts of the pipe may be heated only indirectly, e.g. due to heat transfer around the circumference of the pipe.

Some examples of pipes that are configured in this way are shown in Figures 8 a to d. In each of these examples the channel that carries the fluid has an irregularly-shaped cross-section. The channels are configured to concentrate fluid flow towards a part of the pipe that is closest to the heating element and configured to be directly heated by an impinging heat source generated by the heating element. The arrangement of the channel shown in each of the figures may enable the fluid flowing therethrough to be heated more efficiently by concentrating fluid flow towards the sections of the pipe that are likely to be hottest.

Figure 8a depicts a pipe 801 having an irregular cross-section, in which the fluid 810 is constrained to flow in a C-shaped channel. The C-shaped channel is positioned on the same side of the pipe as the impinging heat source 806. The heat source 806 may be a flame. Figure 8b shows an example in which the fluid 810 is constrained to flow in a crescent-shaped channel 81 1 . The crescent shaped channel 81 1 provides for a non-uniform depth of flow, with the greatest flow width being concentrated at what is expected to be the hottest part of the pipe because it corresponds to where the impinging heat source is at its hottest. For example, if impinging heat source 806 is a flame, that flame is generally hottest at its centre. Figure 8c depicts a pipe having a semi-circular cross-section (812). This arrangement also offers a non-uniform flow depth. Other irregular channel cross-sections are also possible.

A pipe comprising a channel with an irregularly-shaped cross-section may be manufactured by securing an insert within a pre-existing pipe that has a differently shaped cross-section from the channel. For example, the pipe may have a regularly- shaped cross-section (such as a circle) and the insert may have the effect of creating a C-shaped channel (Figure 8a) or a crescent-shaped channel (Figure 8b). A pipe with an irregular cross-section may alternatively be specifically manufactured with an irregular cross-section. The irregular cross-section pipes depicted in Figures 8c and d may be manufactured in this way.

Typically, the heating process is incremental from the point of entry for the fluid to the point of exit of the fluid. For a typical domestic boiler heating water, the point of entry temperature is approximately 5 degrees centigrade and the desired point of exit temperature is approximately 50 degrees centigrade. The efficiency of such a boiler may be measured by the amount of gas consumption required to perform the incremental heating of the water from the typical entry temperature to the desired exit temperature. The applicants believe that using pipe(s) configured to concentrate fluid flow towards the directly heated portions of the pipe may enable a reduction of up to 50% in gas consumption for incremental heating when compared to current pipe arrangements.

The pipes described above may advantageously be combined with any of the boiler arrangements described above to further improve the efficiency of those boilers. The pipes described above may also be implemented completely independently of the boiler arrangements described above, and particularly may be incorporated within existing boilers or in any other arrangement for heating a fluid.

The applicant hereby discloses in isolation each individual feature described herein and any combination of two or more such features, to the extent that such features or combinations are capable of being carried out based on the present specification as a whole in the light of the common general knowledge of a person skilled in the art, irrespective of whether such features or combinations of features solve any problems disclosed herein, and without limitation to the scope of the claims. The applicant indicates that aspects of the present invention may consist of any such individual feature or combination of features. In view of the foregoing description it will be evident to a person skilled in the art that various modifications may be made within the scope of the invention.

Claims

1 . A boiler comprising:

a heating element; and

a pipe configured to carry a fluid to be heated;

wherein the pipe is arranged around the perimeter of the heating element and the heating element comprises an exit region that is aligned with the pipe, wherein the exit region comprises one or more exit ports that are configured to facilitate heating of the fluid by the heating element.

2. A boiler as claimed in claim 1 , wherein the heating element is configured to burn fuel and thereby cause flames to exit from the one or more exit ports and impinge on the pipe.

3. A boiler as claimed in claim 2, wherein the exit port(s) are spaced such that flames that exit neighbouring exit port(s) will overlap each other.

4. A boiler as claimed in claim 3, wherein the exit port(s) are spaced such that the overlap occurs only in a relatively cool, outer region of the flames.

5. A boiler as claimed in claim 3 or 4, wherein the exit port(s) are spaced such that no overlap occurs in a relatively hot, inner region of the flames.

6. A boiler as claimed in any preceding claim, wherein the exit port(s) are equally spaced.

7. A boiler as claimed in any preceding claim, wherein the heating element is configured such that the flames exit from the one or more exit port(s) to extend beyond the outer edge of the pipe.

8. A boiler as claimed in any preceding claim, wherein the pipe is coiled around the heating element.

9. A boiler as claimed in any preceding claim, wherein the heating element comprises a chamber and a fan operable to distribute fuel throughout the chamber.

10. A boiler as claimed in any preceding claim, wherein the heating element comprises a cylindrical chamber and the one or more exit ports are formed in that chamber.

1 1 . A boiler as claimed in any preceding claim, wherein the exit region comprising one or more exit ports, comprises a series of discrete or semi-continuous exit ports, or one continuous exit port.

12. A boiler as claimed in any preceding claim, wherein the pipe comprises a channel for carrying the fluid, the channel having a cross-section that is shaped so as to concentrate the flow of fluid towards a part of the pipe that is configured to experience the greatest heating effect from the heating element.

13. A boiler comprising:

a first pipe and a second pipe that are both configured to carry a fluid to be heated;

a heating element configured to heat at least one of the pipes;

wherein the first and second pipes are axially aligned with each other and coiled around the heating element; and

wherein the heating element comprises an exit region that is aligned with the first pipe and/or the second pipe, wherein the exit region comprises one or more exit ports that are configured to facilitate heating of the pipe with which they are aligned by the heating element.

14. A boiler as claimed in claim 13, wherein the heating element is configured to directly heat only one of the first and second pipes at a time.

15. A boiler as claimed in claim 13 or 14, wherein the first and second pipes are configured such that the heating element directly heating one of the first and second pipes has the effect of indirectly heating the other of the first and second pipes.

16. A boiler as claimed in any of claims 13 to 15, wherein the second pipe is coaxially arranged within the first pipe.

17. A boiler as claimed in any of claims 13 to 16, wherein the second pipe is configured such that it can be heated by fluid carried in the first pipe.

18. A boiler as claimed in any of claims 13 to 15, wherein the first and second pipes are separate pipes that are coiled in parallel around the heating element.

19. A boiler as claimed in any of claims 13 to 15 or claims 17 to 18, wherein the exit region, comprising one or more exit ports, is configured to be aligned with only one of the first and second pipes at a time.

20. A boiler as claimed in any of claims 18 to 19, wherein the heating element is moveable between a first position in which it is configured to directly heat the first pipe and a second position in which it is configured to directly heat the second pipe.

21 . A boiler as claimed in claim 20, wherein the heating element is configured such that moving the heating element from the first position to the second position moves the exit region comprising one or more exit ports from being aligned with the first pipe to being aligned with the second pipe.

22. A boiler as claimed in claim 20 or 21 , wherein the heating element is configured to move along an axis around which the first and second pipes are coiled.

23. A boiler as claimed in claim 22, wherein the boiler comprises a screw that is rotatable to move the heating element along said axis.

24. A boiler as claimed in claim 23, wherein the boiler comprises a servo configured to rotate said screw.

25. A boiler as claimed in any of claims 20 to 24, wherein the heating element forms a chamber of a burner and the burner is configured such that the burner's other components remain stationary when the chamber moves.

26. A boiler as claimed in any of claimsl 3 to 25, wherein the first and second pipes are configured to carry fluids intended for different purposes.

27. A boiler as claimed in any of claims 13 to 26, wherein one of the first and second pipes is configured to carry potable water and the other of the first and second pipes is configured to carry non-potable water.

28. A boiler as claimed in any of claims 13 to 27, wherein the one or more exit ports comprise a series of discrete exit ports, a series of semi-continuous exit ports, or one continuous exit port.

29. A boiler as claimed in any of claims 13 to 28, wherein the pipe comprises a channel for carrying the fluid, the channel having a cross-section that is shaped so as to concentrate the flow of fluid towards a part of the pipe that is configured to experience the greatest heating effect from the heating element.

30. A pipe comprising a channel for carrying a fluid to be heated by a heating element, wherein the channel has a cross-section that is shaped so as to concentrate the flow of fluid towards a part of the pipe that is configured to experience the greatest heating effect from the heating element.

31 . A pipe as claimed in claim 30, wherein the channel has a cross-section that is irregularly shaped.

32. A pipe as claimed in claim 30 or 31 , wherein the channel has a cross-section that provides for non-uniform depth of fluid flow relative to an outer surface of the pipe.

33. A pipe as claimed in claim 32, wherein the channel has a cross-section that provides for the greatest depth of fluid flow in a part of the pipe that is configured to experience the greatest heating effect from the heating element.

34. A pipe as claimed in any of claims 30 to 33, wherein the cross-section of the channel is C-shaped, crescent-shaped or semi-circular.

35. A pipe as claimed in any of claims 30 to 34, wherein the pipe has a cross- section that is a different shape from the channel cross-section.

36. A pipe as claimed in any of claims 30 to 35, wherein the pipe has a cross- section that is regularly-shaped.

37. A pipe as claimed in any of claims 30 to 36, wherein the pipe comprises an insert that forms the channel within the pipe.