Electric heating – Microwave heating – Fluid heater
Patent
1998-01-23
1999-12-07
Leung, Philip H.
Electric heating
Microwave heating
Fluid heater
219761, H05B 680
Patent
active
059987731
DESCRIPTION:
BRIEF SUMMARY
FIELD AND BACKGROUND OF THE INVENTION
The present invention relates to microwave devices in general. In particular, it concerns compact, efficient microwave devices for heating liquids.
It is known to use electromagnetic radiation of microwave frequencies to heat various materials, including water and other liquids.
Conventional microwave heating devices have three elements: a microwave generator, a waveguide, and an applicator. The microwave generator, which may be any of a number of types, produces microwaves of a frequency or range of frequencies suited to the material to be heated. The waveguide is coupled at one end to the microwave generator and at the other to the applicator so that radiation passes to the applicator which contains the material to be heated. Depending on the type of material to be heated, the applicator may be a cavity, as in a domestic microwave oven, or an extended waveguide through which the material to be heated is passed.
Conventional microwave heating devices have two major disadvantages. Firstly, the need for a separate waveguide and applicator in addition to the microwave generator limits the minimum size and cost of the device. And secondly, coupling losses both between the microwave generator and the waveguide, and between the waveguide and the applicator, reduce the efficiency of the device. Furthermore, most conventional microwave generators require a high-voltage power supply which leads to a high cost of manufacture.
There is therefore a need for compact, efficient microwave devices for heating liquids which overcomes the aforementioned shortcomings of the prior art.
SUMMARY OF THE INVENTION
The present invention is of compact efficient microwave devices for heating liquids.
Hence, there is provided according to the teachings of the present invention, a microwave heater which uses electromagnetic radiation for heating liquid flowing from a liquid source to a liquid receiver, the microwave heater comprising a microwave generator having: (a) at least one interaction region within which the electromagnetic radiation is generated; and (b) at least one conduit having an inlet connected to the liquid source and an outlet connected to the liquid receiver, a portion of the at least one conduit deployed within at least one of the at least one interaction region, the liquid flowing through the portion acting as a dielectric load of the microwave generator so as to be heated by the electromagnetic radiation.
According to a further feature of the present invention, the inlet is positioned lower than the outlet such that, when the microwave heater is in use, convective effects tend to generate a flow of the liquid from the liquid source to the liquid receiver.
According to a further feature of the present invention, the at least one interaction region is substantially cylindrical and has an axis, and wherein a beam of electrons passes through the interaction region substantially parallel to the axis, the at least one conduit forming a substantially peripheral flow path within the interaction region.
According to a further feature of the present invention, the substantially peripheral flow path is tapered along the axis so as to synchronize the phase velocity of the electromagnetic radiation with the velocity of the beam of electrons along the interaction region.
According to a further feature of the present invention, the interaction region includes an axially periodic structure.
According to a further feature of the present invention, the axially periodic structure is metallic.
According to a further feature of the present invention, the axially periodic structure is helical.
According to a further feature of the present invention, there is also provided means for applying an axial magnetic field through at least part of the interaction region parallel to the axis.
According to a further feature of the present invention, the axial magnetic field is fixed so as to define the frequency of the electromagnetic radiation generated.
According to a further feature of the present inve
REFERENCES:
patent: 2978562 (1961-04-01), Fox
patent: 3812315 (1974-05-01), Martin
patent: 3980855 (1976-09-01), Boudouris et al.
patent: 5300743 (1994-04-01), Park
Friedman Mark M.
Leung Philip H.
Ramot University Authority for Applied Research & Industrial Dev
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