GB2427112A

GB2427112A - Microwave flow heater/boiler

Info

Publication number: GB2427112A
Application number: GB0509445A
Authority: GB
Inventors: Rowland Simpkins
Original assignee: Individual
Current assignee: Individual
Priority date: 2005-05-09
Filing date: 2005-05-09
Publication date: 2006-12-13
Anticipated expiration: 2025-05-09
Also published as: GB0509445D0; GB2427112B

Abstract

An apparatus for heating water or other fluid has a plurality of heating elements comprising microwave susceptible material 17 and microwave generator means 18 arranged to generate microwave radiation and to apply substantially all of said generated radiation to said microwave susceptible material. The microwave generator means may comprise a plurality of individual microwave generators, for example to provide various outputs from the heating apparatus. Waveguide 11 has deflecting surfaces 10 to direct microwaves to respective susceptors 17.

Description

1 2427112 Microwave Boiler The present invention relates to an improved

water heating system in particular using microwaves as the energy source for performing the heating.

It is known to use microwaves as the energy source for heating fluids. For instance, WO 93/0078 1 discloses a system in which a dielectric material which is susceptible to microwave heating is heated by microwave radiation and the fluid is then heated by heat conduction from that material. In the case of heating water, WO 93/00781 shows, in Figure 2, an arrangement in which a pipe is coated with a microwave susceptible coating and irradiated with microwave radiation whereby to heat water flowing through the pipe.

GB 2104258 discloses a heating apparatus comprising a vessel containing a substance which becomes heated under the action of microwave energy, the vessel being surrounded by water which is to be heated, and which flows around the outside of the vessel from an inlet to an outlet.

However, it has been found that the use of a single large block of microwave susceptible material is impractical, as it tends to generate a large amount of waste heat, and not dissipate enough heat into the water. In experiments conducted by the inventor, it has been found that, using a large single element, the apparatus does not in fact significantly raise the temperature of the water moving over it, and that many systems utilising a single element do not work efficiently. In particular, it has been found particularly difficult to raise the temperature to a sufficient level to maintain a constant heat transfer.

Furthermore, although GB 2104258 for example discloses the use of a horn to direct microwave radiation generally towards the substance to be heated, it is noted that conventional microwave heating apparatuses do not efficiently direct the microwave energy, and rely on containing the radiation generally within a reflective casing, with the result that the microwave energy is not efficiently utilised.

It is therefore desirable to provide a microwave heating apparatus in which the above mentioned problems are reduced or eliminated, and which is able to heat water or other fluids more efficiently than known arrangements.

The present invention provides apparatus for heating water or other fluid having a plurality of heating elements comprising microwave susceptible material and microwave generator means arranged to generate microwave radiation and to apply substantially all of said generated radiation to said microwave susceptible material. The microwave generator means may comprise a plurality of individual microwave generators, for example to provide various outputs from the heating apparatus.

This may be achieved by providing the microwave susceptible material as a plurality of blocks of material and providing corresponding waveguides to bring the microwave radiation to the blocks of material. This is advantageous in that the material can he heated by the microwaves and then used as a store of heat once up to temperature, requiring only intermittent activity from the microwave generator to keep LI to temperature. This may improve the efficiency of operation of the microwave generator.

The efficiency of the heating apparatus is increased by the provision of at least two, arid preferably three or more, heating elements. As well as improving the efficiency by increasing the surface area available for heat transfer, it has been found that the heat dissipation created by the process is easier to manage than when using a single clement, in which a large amount of waste heat is generated.

Waveguides are preferably arranged to guide the microwave energy into the respective elements. This is in contrast with known arrangements, which rely on generated microwave energy being guided generally in the direction of a single element or container of microwave susceptible material. The preferred use of a respective waveguide for each of a plurality of elements in the present invention further increases the efficiency of the apparatus.

By contrast with conventional arrangements in which microwaves are reflected around the casing and absorbed in a single large element, in the present invention substantially all of the generated microwave radiation is directed into the heating elements, and a plurality of elements make for smaller individual volumes to be heated. In this way, the microwave energy is effectively focussed into smaller areas, in particular where an individual waveguide is provided for each element.

The waveguides may be formed as channels defining a path between the microwave generator or generators and each heating element, and may be curved in cross-section. Fhe end of the waveguidc nearest a given heating element may also he curved in such a way as to guide or deflect the microwaves into the heating element.

In another aspect, the present invention provides apparatus for heating water or other fluid comprising a vessel having an inlet and an outlet arranged to permit a flow of water through the vessel, a plurality of heating elements comprising a microwave susceptible material provided within the vessel, and microwave generator means arranged to generate microwave radiation and to apply said radiation to said microwave susceptible material. Again, the microwave generator means may comprise a plurality of individual microwave generators.

Preferably the vessel is generally formed of microwave reflective material with the exception of a microwave transparent portion to which the heating element is attached to permit the application of the microwave radiation to the element from a source external to the vessel.

The vessel may be closed by a lid to which the heating elements are attached.

In a particularly preferred arrangement the above mentioned aspects of the invention arc combined such that efficient heating of the element by the microwaves is achieved, while also enabling efficient conduction of the heat to the fluid to he heated by virtue of the positioning of the element within the fluid.

The present invention is accordingly of simple construction providing efficient heating, and produces a reduced amount of waste heat.

The present invention will be better understood from the following description of a preferred embodiment given by way of example with reference to the accompanying drawings, of which: Figure 1 shows a schematic view of the preferred embodiment; Figure 2 shows an alternative configuration of the waveguide means; and Figure 3 shows in a perspective view from above, a schematic diagram of the relative arrangement of the key components of a further configuration.

The preferred embodiment of the invention, as shown in Figure 1, is a unit 10 which may he utilised in place of a conventional boiler in a domestic or other heating system. As is well known, such a boiler is generally simply arranged to heat a flow of water passing through it. Other elements of a system into which the boiler is incorporated may he configured to utilise the heated water flow for indirect heating of domestic water and/or a central heating system. Alternatively the flow of water through the boiler may be supplied directly to hot water taps.

The present system may be used in any of these contexts.

As can be seen from Figure 1, boiler 10 comprises a vessel 12 having a lid 13, inlet 14 and outlet 1 5. Associated with the water flow path thus defined is a pump 16 shown in this embodiment in the pipe work leading the inlet 14.

S Vessel 12 is provided with a lid 13, attached to the inside of which are a plurality of heating elements 17. In this embodiment, three heating elements are provided, and the elements preferably comprise elongate members, such as cylinders or tubes, which may be of any of a variety of cross-sections. Each heating element 1 7 comprises a microwave susceptible material, and in the present embodiment, the elements are made of copper pipe. Depending on the material used, the element may be macIc entirely of the microwave susceptible material or may be a container of heat conductive and microwave transparent material containing the microwave susceptible material. One suitable material for use in an arrangement of the latter type is a microwave susceptible gel of the type used in commercially available handwarmers at the present time.

The plan view in Figure I shows the arrangement of the heating elements 17, which are spaced within the vessel 12, and run parallel to the axis of the cylindrical vessel in this embodiment.

The microwave radiation is generated by microwave unit 1 8 and guided by waveguide means 11 to pass through lid 13 and into the heating elements 17.

The elements are heated thereby and thus caused to heat the water surrounding them within vessel 12.

The waveguide means 11 comprise individual microwave guides which correspond respectively to the heating elements, such that the microwave energy is directed by the waveguides into each heating element, and is effectively guided away from being directed into parts of the vessel which are distant from a heating element. This guiding of the microwave energy directly into the individual waveguides increases the efficiency of the boiler.

Although in Figure 1 the microwave unit and waveguides are shown at the top of the vessel, the apparatus may alternatively be arranged such that the microwave energy is guided into the vessel via its lower end, with the waveguides being accordingly located underneath the vessel. Alternatively, a combination of these arrangements may be employed, in particular where more than one microwave generator is provided.

An alternative configuration of the waveguides is shown in plan view in Figure 2, and may be used either above or below the vessel, as described above. It can be seen that the waveguides arc arranged so as to taper from the microwave unit towards the respective heating elements, in order to collect the generated microwaves and guide them into the heating elements.

1 5 The waveguides may be made of copper, for ease of manufacture, or of any other suitable material which enables them to perform the function of guiding the microwaves into the heating elements, such as stainless steel.

Figure 3 shows the relative arrangement of the microwave generator 18, heating elements 17 and waveguide 11 in a further alternative configuration of the invention. In this arrangement, three heating elements are again provided; a central element nearest the microwave generator, and two further elements spaced at a greater distance from the generator, with the three elements being approximately equally spaced from one another to provide even heating within the vessel.

The waveguide lorms an enclosure surrounding the path between the microwave generator and the heating elements, with an individual portion defining the path to each element. In particular, the waveguide defines a channel tapering outwards from the generator towards the elements and, after reaching the closest element, continues in the form of two separate channels towards the two further ci ements.

Other arrangements of elements and waveguides may he employed. However, it will be appreciated that in each case the waveguide preferably defines channels specifically towards each of the elements.

In the illustrated arrangement, the tapering channel and individual smaller channels defined by the waveguide are of generally rectangular cross-section, although a curved cross-section may he provided. Deflecting surfaces 20 are provided to guide the microwaves into each of the elements 1 7. These are shown as flat angled surfaces, although they may also be curved, or otherwise shaped in such a way as to efficiently deflect or guide the microwaves into the elements.

Finally the boiler comprises a CPU control unit 19 which controls the operation of the microwave unit 1 8 and pirnp 16. For this purpose the temperatures of the heating elements and the water are sensed, together with the water flow rate from outlet 15, and provided as inputs to the CPU 19. The Cpu can therefore cause the microwave generator to heat the water to a specific temperature as well as turning the generator off and running the pumps to prevent overheating. A cooling fan is also provided to cool the microwave unit 18.

Accordingly this embodiment provides a simple and efficient water heating boiler.

It will be appreciated that any appropriate power source may he used to supply power to the heating apparatus. In one particular embodiment, the invention may be used to provide a portable boiler suitable for use in caravans, boats, etc. En such an embodiment, it is prefi.rab1e to use a low voltage microwave generator, which may be powered by a suitable source typically used in such environments, and may he Sofar powered.

Claims

I

CLAIMS: 1. Apparatus for heating watcr or other fluid comprising a vessel having an inlet and an outlet arranged to permit a flow of water through the vessel, a plurality of heating elements comprising a microwavc susceptible material provided within the vessel, and microwave generator means arranged to generatc microwave radiation and to apply said radiation to said microwave susceptible material.
2. Apparatus for heating water or other fluid having a plurality of heating elements comprising microwave susceptible material and microwave generator means arranged to generate microwave radiation and to apply substantially all of said generated radiation to said microwave susceptible material.
3. Apparatus according to claim 2, comprising a vessel having an inlet and an outlet arranged to permit a flow of water through the vessel, the heating elements being provided within the vessel.
4. Apparatus according to claim 1 or 3 in which said vessel is generally formed of microwave reflective material.
5. Apparatus according to claim 4 in which said vessel comprises a microwave transparent portion to which the heating element is attached to permit the application of the microwave radiation to the element from a source external to the vessel.
6. Apparatus according to claim 5 in which said microwave transparent portion forms a lid for the vessel.
7. Apparatus according to any preceding claim, in which the microwave susceptible material of each heating element is provided as one or more blocks of material.
8. Apparatus according to any preceding claim, comprising at least three heating elements.
9. Apparatus according to claim 7 or 8, further comprising waveguide means arranged to bring the microwave radiation to the block or blocks of material.
10. Apparatus according to claim 9, wherein the waveguide means comprise a plurality of waveguidcs each arranged to direct the microwave radiation to a respective one of the plurality of heating elements. is
11. Apparatus according to any preceding claim, wherein the microwave generator means comprises a plurality of individual microwave generators.
12. Apparatus according to claim 11, wherein an individual microwave generator is provided for each heating element.
13. Apparatus substantially as hereinbefore described, with reference to the accompanying drawings.