WO1992006572A1

WO1992006572A1 - Electromagnetic heating apparatus

Info

Publication number: WO1992006572A1
Application number: PCT/GB1991/001719
Authority: WO
Inventors: Steven Thomas Gribby
Original assignee: Steven Thomas Gribby
Priority date: 1990-10-05
Filing date: 1991-10-04
Publication date: 1992-04-16
Also published as: GB9021707D0; AU8636091A

Abstract

The device includes a housing (1) having water inlet and outlet connections (4 and 5) coupled to a heating bed (6) mounted within the housing. The bed (6) is formed of a pair of identical plastics mouldings which are heat-welded together to define a flat sheet-like flow path. Magnetrons (10-12) are arranged to heat water flowing through the bed (6) by microwave energy.

Description

ELECTROMAGNETIC HEATING APPARATUS

TECHNICAL FIELD OF THE INVENTION

This invention relates to apparatus for heating a liquid (which will almost invariably comprise water) by means of electromagnetic energy, usually (but not exclusively) by means of microwave energy.

BACKGROUND

Known water heating devices generate heat by combustion of a fuel such as gas or oil, or from electrical energy. Electrical heating has the advantage that it is clean and can be made readily available in most locations.

US 3 816 689 discloses liquid heating apparatus which utilises microwave energy. The liquid to be heated passes through a large coil embedded in a matrix which absorbs the microwave energy. In GB 1 585 356 it is proposed to pass the liquid to be heated through tubing arranged in the form of a parabola, and microwave energy is emitted at the focus of the parabola. However, both of these proposals are considered to be relatively inefficient, they would take up a considerable amount of space, and they would also be costly to manufacture.

An object of the present invention may be viewed as being to provide inexpensive microwave heating apparatus which is capable of operating at improved efficiency.

SUMMARY OF THE INVENTION

The present invention proposes electromagnetic heating apparatus which is distinguished by the fact that the liquid is heated in bed which contains the liquid in a sheet-like layer.

The bed may be curved but is preferably substantially flat to reduce the volume of the apparatus and for ease of manufacture.

For improved efficiency the bed may include internal dividing walls which increase the length of the flow path through the bed.

The means of generating the electromagnetic energy will usually comprise a microwave energy generating device such as a magnetron.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is exemplified in the accompanying drawings, in which:

Figure 1 is a diagrammatic sectional view of microwave water heating apparatus of the invention, Figure 2 is a side view of the heating bed which is at the heart of the apparatus, the lower half of the bed being sectioned on line II-II of Fig. 4,

Figure 3 is an end view of the heating bed, and

Figure 4 is a plan view of one of the two mouldings which form the bed.

DETAILED DESCRIPTION OF THE DRAWINGS

The device includes a housing 1 which is internally divided to form a compartment 2 and a separate heating chamber 3. The heating chamber 3 has steel-lined walls to internally reflect microwave energy and is provided with water inlet and outlet connections 4 and 5 respectively. The heating chamber also contains a flat heating bed 6 which is coupled to the inlet 4 and outlet 5 and is supported in a substantially horizontal position by brackets or other suitable means (not shown) .

The compartment 2 contains three magnetrons 10, 11 and 12 which generate microwave energy. The microwave region of the electromagnetic spectrum extends from about 400 to 20,000 MHz, but frequencies around 2,450 MHz are preferred since energy in this region is well absorbed by water and is also reflected by steel. The microwave energy emitted by the magnetrons 10 - 12 is conducted to the heating chamber 3 via respective waveguides 14, 15 and 16 which terminate above the heating bed 6 .

The heating bed is shown in more detail in Fig.s 2 to 4 and comprises a pair of substantially identical polypropylene top and bottom mouldings 18 and 19 measuring about 450mm by 250mm. Each moulding comprises a substantially flat and rectangular top/bottom wall 20 surrounded by a short peripheral side wall 21, and includes an integral tubular connector 22, 23 which form inlet and outlet connections to the bed. As best shown in Fig. 3, each connector 22, 23 is offset in two directions from the central axis A of the bed. The two mouldings are heat welded together around the free edges of the side walls 21 to form a thin flat enclosed space of about 5mm in thickness.

It will also be noted in Fig. 4 that each moulding includes an arrangement of internal dividing walls 26 which project from the top/bottom wall 20. The dividing walls 26 are symmetrical about the central axis A so that when the two mouldings are joined together the dividing walls meet to divide the internal space of the bed into an elongate flow path extending between the two connectors 22 and 23.

The inlet and outlet couplings 4 and 5 conduct water to and from the heating bed 6 via the respective connectors 22 and 23. A temperature sensor 28 (Fig. 1) is mounted on the outlet coupling 5, and this sensor is arranged to switch off one or more of the magnetrons 10 - 12 when the temperature of water flowing through the outlet coupling exceeds a predetermined operating temperature. Thus, once a working temperature has been attained the power consumption of the apparatus is automatically reduced.

The mouldings 18 and 19 do not appreciably absorb, and are not heated by, microwave energy. In use, the microwave energy emitted by the magnetrons 10 - 12 and fed to the chamber 3 via the waveguides 14 - 16 causes water flowing through the bed 6 to be heated. Tests have shown that the use of a flat bed of the kind described produces more efficient heating of water than other configurations of bed. The bed described is also lightweight, inexpensive to manufacture, and can also result in a relatively compact form of water heater.

It will be appreciated that only one magnetron may be necessary in some applications. In other applications a greater number of magnetrons may be required.

The bed 6 could be of various shapes other than those shown, e.g. circular, whilst still maintaining a thin bed. The bed may also be formed entirely of glass or a combination of glass and plastics, in one or more pieces.

The device may be used as an in-line water heater for supplying hot water to a shower head or a tap for example. The device may also be suitable for use as a "boiler" for a central heating system of the kind in which water is recirculated through a number of radiator devices by a pumped or gravity feed arrangement.

Claims

1» Electromagnetic heating apparatus comprising a heating chamber (3) having a wall which is substantially non-permeable to electromagnetic energy, generating means (10 - 12) for producing electromagnetic energy, the chamber being arranged to receive said electromagnetic energy and including an inlet (4), an outlet (5), and conduit means formed of a material which is permeable to said electromagnetic energy and which extends between the inlet and the outlet to define a flow path for a liquid which, in use, is heated by exposure to said electromagnetic energy, the distinguishing feature being that the conduit means comprises a heating bed (6) which contains the liquid in a sheet-like layer during passage therethrough.

2. Electromagnetic heating apparatus according to Claim 1, in which the heating bed (6) is substantially flat.

3. Electromagnetic heating apparatus according to Claim 1 or 2, in which the heating bed (6) comprises a moulded plastics component (18, 19).

4. Electromagnetic heating apparatus according to Claim 3, in which the heating bed comprises a pair of moulded plastics components (18, 19) which are secured together.

5. Electromagnetic heating apparatus according to Claim 4, in which the moulded plastics components (18, 19) are substantially identical.

6. Electromagnetic heating apparatus according to Claim 4, in which the moulded plastics components (18, 19) are secured together by heat welding.

7. Electromagnetic heating apparatus according to Claim 1, in which the heating bed (6) includes internal dividing walls (26) which define an elongate flow path through the bed.

8. Electromagnetic heating apparatus according to Claim 1, in which the electromagnetic generating means comprises a plurality of electromagnetic generating devices (10 - 12).

9. Electromagnetic heating apparatus according to Claim 8, including sensor means (28) for sensing the temperature of the liquid in the flow path, and in which a proportion of the electromagnetic heating devices (10 - 12) are arranged to be shut down when the liquid attains a predetermined temperature.

10. A space heating system comprising a circulatory path for water, a plurality of heat radiating devices arranged in the circulatory path, and electromagnetic heating apparatus according to Claim 1, the flow path of the apparatus being connected in the circulatory path such that the device heats the water on passage therethrough.