GB2248681A

GB2248681A - Microwave space and water heating system

Info

Publication number: GB2248681A
Application number: GB9121131A
Authority: GB
Inventors: Alan Keith Baker; Paul David Neale Cain; David Alan Combes
Original assignee: Individual
Current assignee: Individual
Priority date: 1990-10-05
Filing date: 1991-10-04
Publication date: 1992-04-15
Anticipated expiration: 2011-10-04
Also published as: GB2248681B; GB9121131D0; GB9021656D0

Abstract

A microwave heating system includes a heat generator and means for circulating fluid through said generator in order to abstract heat therefrom for transfer to the space to be heated, said heat generator comprising a microwave source 9 and a microwave absorber and transfer device 10, said device comprising a tortuous passageway through which said heat transfer fluid is passed, the passageway including a plurality of surfaces which absorb the microwave energy and reflect the energy into the heat transfer fluid. The heat transfer fluid may be water, and may contain sodium chloride to increase its absorbency of microwave energy. The heat transfer fluid may be piped to a pumped radiator system and to a hot water cylinder. <IMAGE>

Description

MICROWAVE SPACE HEATING SYSTEM This invention relates to microwave heating systems for space heating.

Space heating of buildings, including portable buildings and mobile homes, is frequently carried out by circulating a heated fluid, especially air or water, from a primary heat source in which fossil fuel is burnt and heat is transferred to a heat exchanger. There are, however, some situations where conventional boilers are not satisfactory or impractical for a variety of reasons.

For example, many small apartments, chalets or mobile homes do not have suitable wall space for accommodating a flue or are manufactured from unsuitable building materials for installation of a conventional boiler.

There are also problems in areas where a gas supply is unavailable or there is insufficient space for storage of fluid or solid fuels. It is also a consideration of growing significance to reduce the burning of fossil fuels in certain areas, or at least to reduce the burning of fossil fuels in small boilers which produce heat less efficiently than centrally generated electric power.

The present invention overcomes many of the above problems by providing a space heating system which obviates the burning of fuels and instead involves the use of a heat source which can be safely fitted to any kind of dwelling to provide a compact heat source which can be fitted to a standard heat distribution system such as a pumped radiator system.

According to the present invention there is provided a microwave space heating system which comprises a heat generator and means for circulating fluid through said generator in order to extract heat therefrom for transfer to the space to be heated, said heat generator comprising a microwave source and a microwave absorber and transfer device, said device comprising a tortuous passageway through which said heat transfer fluid is passed, the passageway including a plurality of surfaces which absorb the microwave energy and reflect the energy into the transfer fluid.

Typically, the heat transfer fluid is water and the heat generator is piped to a pumped radiator system to distribute the heated water to the spaced to be heated.

The system can be incorporated in a conventional hot water and space heating package using a conventional hot water cylinder. Alternatively, the system may be employed solely for space heating.

The microwave source may take the form of a magnetron tube which will generate electromagnetic wave energy in the microwave region of the spectrum. The microwave band is between the radiowave band and the radar band and ranges from about 2 to 100 cm in wavelength. Microwave oscillation rate is between about 20,000 MHz to 400 MHz.

However, in order to avoid interfering with radar and other means of communication, the most commonly used microwave frequencies are about 2,000 MHz and about 900 MHz.

The microwave generator is mounted within a compartment which is screened to prevent microwave leakage, the compartment including the microwave absorber and transfer device.

A material which is substantially transparent to microwaves is used for construction of the microwave absorber and the tortuous passageway through the microwave absorber is formed by fins which extend partially across a chamber through which the transfer fluid is passed. The fins and wall surfaces of the chamber are coated with a microwave absorbent material. This material absorbs the energy of the microwaves and reflects it into the water flowing through the chamber either in the form of microwave energy or partly in the form of heat and microwave energy.

Further features and advantages of the present invention will be apparent from the following description and accompanying drawings, in which: Figure 1 is a schematic sectional view of part of the system including the microwave generator and absorber and transfer device, and Figure 2 is an enlarged view of the microwave absorber and heat transfer device.

Referring to the drawings, the system comprises a boiler 1 having connections 2 and 3 to flow and return pipes which are connected to a pump for circulation through a radiator system. The boiler has an outer casing 4, which houses a heat generator 5 to which the flow and return pipes 2 and 3 are connected via unions 6 and 7. The core of the system comprising a microwave screened inner casing 8 in which a microwave emitter 9 is positioned to focus microwave energy on a microwave absorber device 10. The construction of the microwave absorber device 10 will be described in greater detail in connection with Figure 2. As can be seen from Figure 1, water is caused to be passed through microwave absorber 10, which comprises a chamber 11 which is formed with tortuous passageways for water flow through the chamber by fins 12, which extend partly across the chamber.A thermostat probe 13 is positioned to sense the temperature of water leaving chamber 12 and is connected to a control unit and programmer 14, which also controls the microwave source 9. Additionally, a flow sensor 15 is located in the flow pipework 2 and is similarly connected to the control panel. A screen of microwave leakage sensors 16 is located on the side of the heat absorber remote from the microwave emitter, to detect any leakage of microwave energy from the inner casing 8 and the sensors are similarly linked to the control unit so as to cause the magnetron to be switched off should leakage be detected.

Referring to Figure 2, this shows an enlarged view of the microwave absorber 10 in a view at right-angles to that shown in Figure 1. As can be seen, chamber 11 is filled with a series of fins or baffles 12, which cause the water to follow a tortuous path through the chamber and thereby to maximise its exposure to the energy emitted from the microwave source 9. The surfaces of the fins or baffles 12 and preferably also that of the base 17 of the chamber 11 are coated with a microwave absorbent material so as to reflect energy back into the liquid circulating through chamber 11. The unit including the microwave emitter 9 may also include microwave reflecting surfaces which throw back into the chamber 11 any microwave energy which is reflected back in the direction of the microwave emitter.

In order to further increase the efficiency of the transfer of heat to the heat transfer liquid, the liquid circulated through the boiler may contain salts such as sodium chloride to increase the absorbency of the liquid itself to microwave energy.

Claims

1. A microwave space heating system which comprises a heat generator and means for circulating fluid through said generator in order to abstract heat therefrom for transfer to the space to be heated, said heat generator comprising a microwave source and a microwave absorber and transfer device, said device comprising a tortuous passageway through which said heat transfer fluid is passed, the passageway including a plurality of surfaces which absorb the microwave energy and reflect the energy into the heat transfer fluid.

2. A system according to claim 1 in which the tortuous passageway is formed by fins extending partially across a chamber through which said heat transfer fluid is passed.

3. A system according to claim 2 in which the fins and/or walls of the chamber are coated with a microwave absorbing compound.

4. A system according to claim 2 or 3 in which the chamber has a generally flat shape which is disposed at right angles to the microwave source.

5. A system according to claim 4 in which the chamber is divided into a tortuous passageway by partitions which extend between the panels, some of said partitions extending in a direction at right angles to the plane of said panels so as to prevent fluid flowing from an inlet into said chamber directly to the outlet.

6. A system according to any one of the preceding claims in which the microwave source includes a housing having microwave reflecting surfaces for reflecting microwave energy in the direction of the microwave absorber.

7. A system according to any one of the preceding claims which includes a thermostat arranged to raise the temperature of the output fluid from the microwave absorber and transfer device, a flow sensor for sensing the rate of flow of fluid in the system and control means for regulating the power supplied to the microwave generator and/or a valve for controlling said rate of flow so as to maintain the temperature of said output fluid at a predetermined level.

8. A system according to claim 2 and any claim appendent thereto wherein the chamber is constructed at least partially from a material which is permeable to microwaves.

9. A system according to claim 8 in which said material is a plastics material.

10. A system according to claim 9 in which the plastics material is polyethylene, polypropylene, ABS or a polyester.