WO1999011101A1

WO1999011101A1 - Induction fluid heater

Info

Publication number: WO1999011101A1
Application number: PCT/GB1998/002284
Authority: WO
Inventors: Paul John Spencer; Walter James Anderson; Philip Anthony Browning
Original assignee: Coreflux Systems International Limited
Priority date: 1997-08-23
Filing date: 1998-07-30
Publication date: 1999-03-04
Also published as: AU8551698A; GB9717880D0

Abstract

An electromagnetic fluid heater comprises a core (1a) of a magnetic material having a coil (2) wound around a part thereof, a fluid jacket (3) surrounding a part of the core and comprising a plurality of magnetic elements, and means for passing an alternating electric current through the coil.

Description

INDUCTION FLU ID HEATER Field of the Invention

This invention relates to an electromagnetic fluid heater, and in particular, but not exclusively, to a water heater for central heating and hot water purposes. Background to the Invention

Conventional electric water heaters usually rely on a resistive heating element within a water-containing vessel. Because of the relatively small surface area of the element, heat transfer to the water is relatively slow and inefficient. It can therefore take a long time to heat up larger volumes of water, for example in the heating circuit of a hot water radiator central heating system. The only way to increase the rate of heating is to use a higher current in the heating element, and this is often impractical or undesirable. Generally, therefore, central heating is achieved by means of fossil-fuel boilers/furnaces, which are of low thermal efficiency, in addition to producing undesirable combustion products. Summary of the Invention

According to the invention, there is provided an electromagnetic fluid heater comprising a core of a magnetic material having a coil wound around a part thereof, a fluid _jacket surrounding a part of the core and comprising a plurality of magnetic elements, and means for passing an alternating electric current through the coil. Preferably, the core is in the form of a ring, with the coil wound around a portion of the ring adjacent to the jacket. More preferably, a pair of coils are provided, one on each side of the jacket.

The magnetic elements in the jacket are preferably located in or define passageways through which the fluid can flow, the elements being heated under the influ- ence of the alternating magnetic field generated by the coils and transferring the heat to the fluid. The jacket may be formed of the same material, which is suitably mild steel, and is preferably encased within thermally insulating material. The jacket is preferably dimensioned so as to surround the core as closely as possible without coming into con The core is preferably formed of a plurality of separate laminations, for example of steel, the laminations being electrically insulated one from another, for example by being individually coated in resin or the like. The laminations extend continuously around the core. The heater of the invention is suitable for use as a water heater for domestic or industrial use. In the latter case, it may be used as a boiler for raising process steam, and may be provided with a two-stage jacket, whereby steam generated in the first stage may be superheated in the second stage.

For industrial use, a single or three-phase electrical supply may be used. In the case of a three phase supply, three separate cores or yokes are used side by side with a single jacket surrounding a portion of all three, each core having its respective coil or coils connected to a respective one of the phases, one of the coils or pairs of coils being connected in the opposite direction from the other coils or pairs of coils so that the alternating magnetic flux is reinforced within the jacket in the manner disclosed in our co- pending application No 9709557.5.

The coil or coils are preferably operated with low frequency alternating current, typically the normal mains supply frequency of 50 or 60Hz, although in some industrial use it may be desirable to use a slightly higher frequency to increase the heating effect without increasing the current required. In domestic use, the heater may be used to generate hot water on demand, avoiding the need for a hot water storage cylinder, and/or as a substitute for a conventional central heating boiler. The heater may also be used for an electric shower, substantially reducing the electric current required as compared with units having conventional resistive heating elements, thereby reducing cost of installation and use, and increasing safety.

In an alternative space heating application to water-circulating central heating systems, the heater of the invention may be used to heat liquids such as oil which can be maintained at a higher temperature than water without boiling, the liquid then being circulated to a central heat exchanger to provide water air for distribution around the building to be heated. Fluid temperature may be controlled very precisely by means of a thermocouple or the like within the fluid in the jacket, the output from the thermocouple being used to control the switching on and off of the electrical power to the coil or coils.

It has been found that the heater of the invention is very efficient in converting electrical energy into thermal energy in the fluid, and can raise the temperature of the fluid very rapidly. For example, a water heater in accordance with the invention is expected to be substantially smaller in size than conventional fossil-fuel boilers, saving space and permitting installation in more convenient locations in a building than are possible for conventional boilers. Brief Description of the Drawings

In the drawings, which illustrate an exemplary embodiment of the invention:

Figure 1 is a side elevation of the heater;

Figure 2 is a vertical section through the jacket of Figure 1 ; and

Figure 3 is a horizontal section through the jacket surrounding a portion of the core in Figure 1.

Detailed Description of the Illustrated Embodiment

The heater comprises a laminated mild steel core 1 shown in the drawings as an open rectangle, although it will be appreciated that a toroidal or other shape might also be suitable in certain circumstances. On one arm 1 a of the core 1 are wound two elec- trical coils 2 spaced apart to accommodate between them a jacket 3, shown without surrounding thermal insulation for convenience, although it will be understood that an insulating cover will be essential in practice, to maintain efficiency as well as to protect the coils from the generated heat.

The jacket has a water inlet 4 at a lower part thereof and a water outlet 5 at an upper part thereof. Internally, the jacket is arranged so that the water flowing from the inlet 4 to the outlet 5 passes over the maximum amount of steel within the jacket to maximise heat transfer. To this end, the jacket is formed with a plurality of vertical steel plates 6 spaced apart therearound, forming channels 7 through which the water flows. The plates 6 may be arranged so that the water repeatedly reverses direction to flow through all, or a significant number of, the channels 7 in passing from the inlet 4 to the outlet 5, thereby maximising heat exchange. It is important to maximise the mass of steel within the jacket in order to maximise the heating effect of the alternating magnetic field induced therein by the core.

As may be seen from Figure 3, the core 1 is formed of a plurality of insulated laminae extending vertically through the coils and the jacket.

Although the water inlet and outlet are shown for convenience of illustration as being located on the same side of the jacket, in practice it may be desirable to locate them on opposed sides and to cause the water flow to split around the jacket, rejoining at the outlet.

Claims

1. An electromagnetic fluid heater comprising a core of a magnetic material having a coil wound around a part thereof, a fluid jacket surrounding a part of the core and comprising a plurality of magnetic elements, and means for passing an alternating electric current through the coil.

2. An electromagnetic fluid heater according to Claim 1 , wherein the core is in the form of a ring, with the coil wound around a portion of the ring adjacent to the jacket.

3. An electromagnetic fluid heater according to Claim 1 or 2, comprising a pair of coils, one on each side of the jacket.

4. An electromagnetic fluid heater according to Claim 1 , 2 or 3, wherein the magnetic elements in the jacket are located in passageways through which the fluid can flow.

5. An electromagnetic fluid heater according to Claim 1 , 2 or 3, wherein the magnetic elements in the jacket define passageways through which the fluid can flow.

6. An electromagnetic fluid heater according to Claim 5, wherein the jacket is formed of the same material as the core.

7. An electromagnetic fluid heater according to Claim 6, wherein said ma- te╧Çal is mild steel.

8. An electromagnetic fluid heater according to any preceding claim, wherein the jacket is encased within thermally insulating material.

9. An electromagnetic fluid heater according to any preceding claim, wherein the jacket is dimensioned so as to surround the core as closely as possible without coming into contact with it.

10. An electromagnetic fluid heater according to any preceding claim, wherein the core is formed of a plurality of separate laminations, the laminations being electrically insulated one from another.

1 1. An electromagnetic fluid heater according to Claim 10, wherein the laminations are individually coated in resin or the like.

12. An electromagnetic fluid heater according to any preceding claim, for use in generating steam, the heater comprising a two-stage jacket, whereby steam generated in the first stage may be superheated in the second stage.

1 3. An electromagnetic fluid heater according to any preceding claim, wherein the means for passing an electric current through the coil comprises a single or three-phase electrical supply.

14. An electromagnetic fluid heater according to Claim 1 3, comprising a three phase supply, and wherein three separate cores or yokes are used side by side with a single jacket surrounding a portion of all three, each core having its respective coil or coils connected to a respective one of the phases, one of the coils or pairs of coils being connected in the opposite direction from the other coils or pairs of coils.

1 5. An electromagnetic fluid heater according to any preceding claim, wherein the or each coil is operated with low frequency alternating current.

16 An electromagnetic fluid heater according to Claim 14, wherein the sup- ply frequency of the alternating current is 50 or 60Hz.

17. An electromagnetic fluid heater according to any preceding claim, comprising a thermocouple or the like within the fluid in the jacket, the output from the thermocouple being used to control the switching on and off of the electrical power to the coil or coils.