FIELD OF THE INVENTION

This invention relates to a fluid heater, in particular a water heater.

BACKGROUND TO THE INVENTION

Water heaters are used to heat water for various purposes, including hygienic purposes. The latter includes using hot water to bath, shower and wash hands. Warm water is also used to wash dishes and cutlery, and for cleaning various other items such as floors, cars and the like.

A problem with typical water heaters, in the form of so-called geysers, is that these are generally electrically heated and operate on the principle of heating a significant body of water and keeping it above a set temperature. This is extremely inefficient and wastes energy.

An alternative to this is a gas heater, in the form of liquid petroleum ("LP") gas heated geyser. These do not require the heating of the same body of water as an electrically heated geyser since it heats only the water that is used as it is used. However, these require the provisioning of LP gas in high pressure bottles. Logistically this presents a challenge, with the cost of producing and transporting the LP gas also being affected by increasing electricity prices and fluctuating petroleum fuel costs.

Another alternative is the use of solar heating. Although this makes use of a free energy source in the form of sunlight, it has the problem of requiring costly solar energy converter cells, and the energy harvested from such solar cells is still not sufficient to allow a water heater to operate on this energy source alone. Typically these water heaters are thus run in conjunction with conventional electrical or LP gas heating. Solar energy heaters are consequently significantly costlier than conventional electrical or LP gas heaters. If it was not for subsidised programmes which aim to reduce electrical power consumption by providing substantial subsidies on the capital expense cost of installing a solar energy water heater, far fewer of these solar heaters would be sold. Even with such a subsidy (which does not cover the full capital cost of the solar heater installation), the return on investment on installing a solar heater is several years. OBJECT OF THE INVENTION

It is an object of the invention to provide a fluid heater, in particular a water heater, which at least partly overcomes the abovementioned problems. SUMMARY OF THE INVENTION

In accordance with this invention there is provided a fluid heater which includes a flu having first and second ends and including a fluid channel extending at least partly between these ends, the channel including an inlet in fluid communication with a fluid source and a closable outlet, and a burner comprising a base shaped and configured to locate and support a wick in fluid communication with an associated fuel tank to burn fuel and to pass gaseous combustion products through the flu.

There is further provided for the wick to comprise a porous solid and for the fuel to comprise liquid paraffin operatively absorbed into at least some of the pores of the solid.

There is also provided for the burner to be removably securable to the fluid heater, and for the burner to be provided with a handle for this purpose. There is further provided for the burner to be complimentary shaped to the flu, and preferably for the flu to comprise a right circular cylindrical open ended tube.

There is further provided for the fuel tank to be integral with the burner, and for the fuel tank to comprise an annular container located on a base, preferably a circular base, to form a central core closed at one end by the base and being open ended at the opposite end, with the base operatively locating and supporting the wick, with at least one fuel supply conduit extending from the fuel tank to the core, preferably proximate the level of the circular base, and even more preferably on the level of the circular base, and further for the fuel tank to be provided with a handle to facilitate removal of the burner from the flu and a closable inlet to facilitate fuel supply to the fuel tank. There is further provided for the fuel tank to be formed by an outer cylindrical wall extending from the periphery of the circular base and an inner cylindrical wall extending from the base to the same height and coaxial to the outer wall and having a complimentary shaped annular disc secured to the operatively upper rims of the inner and outer walls to define the annular tank.

There is further provided for the burner to include at least three equidistantly spaced apart fuel supply conduits extending between the fuel tank and the core, and preferably for the fuel supply conduits to comprise apertures in the inner cylindrical wall.

There is further provided for the diameter of the burner to exceed its height, preferably by a ratio of about 2:1 .

There is further provided for the core of the burner to have substantially the same diameter as the inner diameter of the flu.

There is further provided for the inlet to the fluid channel to be located proximate, and preferably at, its first end, and for the outlet from the fluid channel to be located proximate, and preferably at, its second end.

There is further provided for the flu to have a double wall construction comprising an inner wall and a coaxial outer wall and for the fluid channel to be integrated in the double wall by means of an inner diving wall that extends from one end of the cavity formed by the double wall to the other end to form a spiral extending end to end in the cavity, alternatively by means of a conduit that is coiled between the inner and outer walls of the flu to extend from one end to the other thereof.

According to a further feature of the invention there is provided for the fluid channel to comprise a conduit secured to the flu, preferably to the inner surface of the flu, alternatively to the outer surface of the flu.

According to a further feature of the invention there is provided for the fluid heater to include an optional extended fuel tank, with the extended fuel tank being removably securable to the heater, preferably to the outer wall of the flu, for the extended fuel tank to include a closable inlet and at least one outlet with an integral valve and at least one air vent, and with the outlet in fluid communication with the fuel tank of the burner, preferably through the closable inlet of the fuel tank.

There is further provided for the extended fuel tank to comprise a hollow right part-circular cylindrical tube complimentarily shaped and configured to the outer dimensions of the flu.

There is further provided for the outlet of the extended fuel tank to comprise two tubes which connect the extended fuel tank with the burner fuel tank, the two tubes including a first tube which extends to proximate the base of the burner fuel tank and the second tube which extends to a shallower depth in the burner fuel tank than first tube to define a refill depth of the burner fuel tank, with a vacuum being formed between the closed extended fuel tank and the two tubes in the burner fuel tank as long as the fuel level in the burner fuel tank is above the refill depth, and with the vacuum broken when the fuel level in the burner fuel tank drops to below the refill depth which allows air to be drawn into the extended fuel tank through the second tube and fuel to drain from the extended fuel tank into the burner fuel tank through the first tube until the fuel level rises above the refill depth when the end of the second tube is immersed under fuel in the burner fuel tank and a vacuum is created in the extended fuel tank again, thereby preventing further draining of fuel from the extended fuel tank. According to a further feature of the invention there is provided for the second tube to extend to a greater height into the extended fuel tank than the first tube.

There is further provided for the fluid source to comprise a water supply, preferably a pressurised water supply.

There is further provided for the outlet to be in fluid communication with at least one of a tap, a showerhead or a recirculation conduit in fluid communication with the inlet to the heater or a reservoir in fluid communication with the inlet. There is still further provided for the heater to include a thermally insulated reservoir between the outlet and the tap or showerhead.

There is also provided for the heater to be provided with feet at the first end of the flu to orientate the flu operatively to extend substantially vertically from a support surface, with the first end of the flu being located below the second end. There is further provided for the flu to be provided with a bracket at the first end shaped and configured to receive and support the burner, with the burner being removable locatable within the bracket operatively to locate the core below the first end of the flu. According to a further feature of the invention there is provided a wick comprising a porous solid impregnable with a liquid fuel.

There is further provided for the porous solid to comprise an agglomerate of cement, particulate material and water, preferably for the particulate material to comprise a mixture of sand and crushed rock, further preferably for the sand to comprise silica sand, and still further preferably for the mixture to include the crushed rock-sand-cement-water in a ratio of crushed rock at about 3 parts; silica sand at about 3 parts; cement between about a quarter part and about 2.5 parts; and water between about one eighth part and about 1 .5 parts. There is further provided for the cement to preferably be added at about 1 part, and the water at about one quarter part.

There is further provided for the wick to be formed in a right circular cylindrical shape, with a diameter that exceeds its height, and preferably for its diameter to be about twice its height.

There is further provided for the wick to be shaped and configured to fit within the core of the burner as defined above.

These and other features of the invention are described in more detail below. BRIEF DESCRIPTION OF THE DRAWINGS

A preferred embodiment of the invention is described by way of example only and with reference to the accompanying drawings in which:

Figure 1 is an elevation view of a heater according to the invention;

Figure 2 is a top perspective view of the heater of Figure 1 , including an optional extended fuel tank;

Figure 3 shows detail of the lower end of the heater of Figure 1 , including the optional extended fuel tank;

Figure 4 shows a sectional elevation view of the flu of the heater of Figure 1 on its feet; Figure 5 shows detail of the shower head assembly of the heater of Figure 1 ;

Figure 6 is a perspective view of the burner of the heater of Figure 1 ;

Figure 7 is a perspective view of the optional fuel tank for the heater of Figure 1 ;

Figure 8 is a sectional elevation of the configuration of the burner fuel tank and the extended fuel tank; and

Figure 9 is a plan view of the burner of Figure 6.

DETAILED DESCRIPTION OF THE INVENTION A preferred embodiment of a fluid heater according to the invention is shown in the drawings and comprises a water heater (1 ) which includes a flu (2) with a first end (3) and a second end (4), and a water channel (5) that extends from the first end (3) to the second end (4) of the flu (2). The channel (5) includes, at the first end (3) of the flu (2), an inlet (6) that is in fluid communication with a fluid source (not shown). The channel (5) includes at the second end (4) of the flu (2) an outlet (7).

The heater (1 ) further includes a burner (8) that is configured to burn fuel and to pass gaseous combustion products thereof through the flu (2), operatively to heat fluid in the channel (5). The first end (3) of the flu (2) operatively forms the lower end and the second end (4) of the flu (2) operatively forms the upper end of the flu (2). The heater (1 ) is provided with feet (27) to allow it stand upright with the first end (3) below the second end (4). The flu (2) has a double wall (9) construction and the channel (5) is integrated into the double wall (9) by means of an inner diving wall (10) that spirals around the core (1 1 ) of the flu (2) between its two ends (3, 4).

The burner (8) includes an annular fuel tank (29) formed on a circular base (17) to define a core (37). The annular fuel tank (29) is formed by an outer cylindrical wall (15) that extends from the periphery of the circular base (17) and an inner cylindrical wall (16) that extends from the base (17) to the same height and coaxial to the outer wall (15) and having a complimentary annular shaped disc (14) secured to the operatively upper rims of the inner (16) and outer (15) walls to define the tank (29). The burner (8) includes a handle (13). The core (37) of the burner (8) is complimentary shaped and configured to the core (1 1 ) of the flu (2), with both having a circular shape of the same size. As shown in Fig 1 , the heater (1 ) includes a bracket (18) that forms a receptacle that is complimentary shaped to the burner (8) and this bracket (18) is located underneath the lower end (3) of the flu (2), operatively spaced above a supporting surface for the feet (27) of the heater (1 ).

The heater (1 ) of this preferred embodiment also includes an optional fuel tank (19) as shown in Fig 7. The optional fuel tank (19) includes a closable inlet (36) and has two outlets (30, 31 ).

In use, the annular fuel tank (29) provides on its circular base (17) a support for a porous wick block (12) that acts as a wick for the heater. The wick block (12) is placed on the tray where it absorbs fuel from the fuel tank (29). Fuel from the fuel tank (29) is fed under force of gravity through two opposing apertures (40) in the inner cylindrical wall (16) onto the base (17). The fuel is absorbed by the wick block (12). The fuel is lit on the wick block (12) to burn underneath the core (1 1 ) of the flu (2). The gaseous combustion products from the burning fuel passes through the flu (2) towards its upper end (4).

The gas from the burning fuel is hot and as it passes through the flu (2) it transfers some, if not most, of its heat to the inner wall of the flu (2) which forms the core (1 1 ). The channel (5) is located between the inner wall and the outer wall of double wall (9) the flu (2), and is filled with water from the water source (not shown). The heat from the gas transfers to the water and heats it. The water, which is under pressure from the water source, can be utilized by opening a shower (24) or a tap (25) connected to the outlet (7) of the heater (1 ). The tap (25) may also be connected to the shower (24) by means of a removable flexible heat resistant hose (28).

To prevent the heater from creating dangerously high pressures due to the heating water, the channel (5) is provided with a pressure relief valve (26). This valve (26) safely bleeds of water when it exceeds a predetermined pressure level, which is still within the safe pressure limit of the heater (1 ) itself and for a water heater in general.

When the user is finished he simply smothers the flame which ceases the generation of heat. The wick block (12) remains on the base (17) ready for the next time the heater (1 ) is required. The double wall (9) construction of the flu (2) which forms the water channel (5) is thin enough to have only a relatively small amount in water in the channel (5) at any given time. This ensures that heat transfer to the water is very fast, and that not a lot of heat remains in the water to be lost when the burner is extinguished.

The fuel provides instant and cheap heat to the water. By making use of this heater (1 ) the need to have a conventional geyser is dispensed with in many instances. This is especially true for remote areas where electricity supply or a steady supply of bottled or piped LP gas is expensive or not available. With a heater (1 ) according to the invention a person simply heats up water when he needs it, and when done extinguishes the flame.

The heater (1 ) also includes integrated safety mechanism in the form of the tubes that connects the extended fuel tank (19) to the burner fuel tank (29). As shown in Figure 8 two tubes (30, 31 ) connect the extended fuel tank (19) with the burner fuel tank (29). A first tube (30) extends from the extended fuel tank (19), located above the burner fuel tank (29), to a depth in the burner fuel tank (29) proximate its base (32). This first tube (30) extends from just inside the bottom wall (33) of the extended fuel tank (19), i.e. proximate its base (33). The second tube (31 ) extends from a closer to the top (34) of the extended fuel tank (19), i.e. higher in the extended fuel tank (19), than the first tube (30). The second tube (31 ) extends to a depth into the burner fuel tank (29) shallower than the first tube (30), i.e. closer to the top (35) of the burner fuel tank (29).

The depth to which the second tube (31 ) extends into the burner fuel tank (29) determines its refill depth of the burner fuel tank (29) from the extended fuel tank (19). When the burner fuel tank (29) is filled and the ends of both tubes (30, 31 ) covered by fuel and the cap (36) of the extended fuel tank (19) is sealed, a vacuum is formed in the extended fuel tank (19) which prevents fuel from draining from the extended fuel tank (19) into the burner fuel tank (29).

When the fuel (38) in the burner fuel tank (29) is consumed to a point where the fuel level drops to below the end of the second tube (31 ), the vacuum is broken which allows air to be drawn into the extended fuel tank through the second tube (31 ) and fuel (39) to drain from the extended fuel tank (19) into the burner fuel tank (29) through the first tube (30) until the fuel level in the burner fuel tank (29) rises above the refill depth. At this point the end of the second tube (31 ) in the burner fuel tank (29) is again immersed under fuel (38) and a vacuum is established again in the extended fuel tank (19), thereby preventing further draining of fuel (39) from the extended fuel tank (19). This process repeats itself to continuously replenish the burner fuel tank (29) in a controlled manner. The supply of fuel (39) from the extended fuel tank (19) to the burner fuel tank (29) is thus in this manner self- regulatory. Another safety feature is the fuel supply conduits (40) which connects the burner fuel tank (29) with the core (37) of the burner (8). Two of these conduits (40) are located on the base (17) of the burner (8) in the inner wall (16) of the burner fuel tank (29). These conduits feed fuel (38) onto the base (17) of the core where it is absorbed by the wick (12) located in the core (37). Due to the small size of the conduits (40) and the presence of a fuel filled wick (12) the flow of fuel (38) from the burner fuel tank (29) into the core (37) is limited. This is further aided by the close fit of the wick in the core (37), with the wick (12) having a sliding fit within the core (37).

The porous solid which forms the wick (12) is any cylindrically shaped porous solid, such as porous stone or a so-called fire stone. An agglomerate is preferably used which is comprised of cement, particulate material and water. In a preferred embodiment the particulate material comprises a mixture of sand and crushed rock, with the sand comprising silica sand and the crushed rock comprising crushed rock commercially available as "Rasa crusher". This agglomerate is formed by mixing crushed rock-sand-cement-water in a ratio of crushed rock at about 3 parts; silica sand at about 3 parts; cement between about a quarter part about 2.5 parts; and water between about one eighth part and about 1 .5 parts, and allowing it to set. The cement is most preferably added at about 1 part, and the water at about one quarter part.

The agglomerate is formed into a right circular cylindrical shape complimentary to the core (37).

The heater (1 ) is also useful in heating non-pressurised water. When the water in the channel (5) is heated it expands and since it has nowhere to go at the inlet (6) to the channel (5) the expanding water pushes to the outlet (7), and flows from it. This creates flow through the channel (5) which draws in cooler water from the inlet (6) below, in the form of a thermo syphon effect. It will be appreciated that modifications to the heater (1 ) are possible without departing from the essence of the invention.

It is for example possible for the fluid channel to comprise a conduit secured to the flu instead of being formed by the double wall structure of the wall.