GB2048629A

GB2048629A - Water heating method

Info

Publication number: GB2048629A
Application number: GB8001219A
Authority: GB
Original assignee: WILLCOCK W
Current assignee: WILLCOCK W
Priority date: 1979-04-30
Filing date: 1980-01-14
Publication date: 1980-12-10

Abstract

Water heating apparatus comprises a cast iron tank 1 having a window 3 of ceramic or armoured plate heat resistant glass through which a magnetron 6 is arranged to emit microwaves of frequency from 2400 to 2500 KHz (preferably 2450 KHz) into the tank 1. The internal surface of the walls of the tank is left rough and unmachined to diffuse incident radiation throughout the tank, or faceted to promote reflection of the waves. The tank is described in a simple central heating circuit but may be used for heating any domestic or industrial water supply, including for laundry and catering purposes. <IMAGE>

Description

SPECIFICATION Water heating method This invention relates to a water heating apparatus and method of applying microwaves aquathermally.

An object of the invention is to present an econom ical method and apparatus for heating water for use in domestic and industrial processes, and for heating of domestic, industrial, and commercial premises.

Heating of water for such purposes is usually carried out by combustion of oil, gas or solid fuel, or by thermal contact with an electrical resistance element. in the case of combustion boilers, a substantial proportion ofthe energy released in burning is dissipated without heating the water by convection from exhaust outlets, and radiation in directions away from the water. In the case of an electrical resistance element, a considerable amount of energy is consumed in raising the temperature of the element, and maintaining its temperature during the heating process.

According to this invention, a water heating apparatus comprises a vessel for containing water to be heated, and a transducer adapted to convert electrical signals into microwave radiation arranged to direct the radiation into the vessel.

The vessel preferably has a 'window' of ceramic tiles or armour-plate heat resistant glass, which admits the microwave radiation, and the remainder of its walls are preferably of rough finished cast iron which provides an effective shield to escape of radiation.

Micro-wave radiation is usually defined as radio waves having a wave length less than 20 cm, or a frequency above 1500 MHz. A broad band in this region in the electromagnetic spectrum is subject to absorbtion by molecules of water, and this absorbtion causes the water to be heated, the mechanism possibly being that the water molecules, being polar, are caused to oscillate by the alternating field induced by the electromagnetic waves, and this oscillation causes heating the energy from which comes from the waves. This phenomenon is made use of in microwave cookers, where the water in animal and veg etabletissues is heated rapidly to cook the food. It also has to be guarded against for personnel working on or near micro-wave communications transmitting receiving or relay stations.

It is preferred that a magnetron tuned to produce a micro-wave frequency of 2400 - 2500 KHz (e.g. 2450 KHz) is used, as this is near the middle of the micro-wave water absorbtion band, and cast iron is an adequate shield against such frequencies.

Awaterheating apparatus and method will now be described with reference to the accompanying drawing which is a sectional view of a water heater according to the invention, shown with diagramatic connections, by way of example to a domestic central heating installation.

In the embodiment shown and described by way of example, a heating tank 1 has top, bottom and four side walls of rough internal finished cast iron.

One side wall 2 of the tank has a window into which a panel or armour plate glass 3 is fitted with a water tight seal. The tank also has an inlet 4 for unheated water and an outlet 5 for heated water.

A micro-wave emitter, in the form of a magnatron 6 tuned to a frequency of 2450 MHz is disposed so as to direct its radiation into the tank 1. Water in the tank absorbs the energy of the radiation, and thereby becomes heated. The rough finish of the inner surface of the tank provides for enhanced reflection and scattering of the micro-waves emitted, thereby spreading their effect beyond the primary beam of the magntron 6. As an alternative to a rough unmachined internal finish, the interior of the tank walls may be faceted; this would however greatly increase the cost of their production.

As shown, the heating tank 1 is connected into an exemplified simple space heating installation. Outlet 5 for heated water is connected by a pipe 7 to a plurality of radiators 8, and leads to a cold water pipe 9 from a cold water reservoir or header tank 10 to the cold water inlet 4. In practice, the heating tank may be used for heating more complex heating installations, including hot water supply for bathing, laundry etc, and alternatively may be used for industrial purposes for space heating or for heating thermal fluid for process purposes. Usually liquids having a measurable dipole moment may be employed, nevertheless not all such are necessarily operative and the heating effect varies generally'speaking as a function of the dielectric constant; it is recommended to use town water and to be watchful of additives that inhibit temperature elevation.Such dielectric active fluids are called 'thermal fluid' in the data sheet, specification and claims.

The tank 1 contains thermostats 11 which operates to switch off the magnatron when a desired temperature is reached, and to restart it when water temperature falls below a desired minimum. Using micro-waves to heatwateras herein proposed, heating can be carried out quickly and efficiently, since virtually all the energy of the electric supply is converted into molecular agitations of the water, the only substantial losses being occasioned by absorbtion in the glass window, and in conversion from electrical to micro-wave energy in the magnatron.

This is especially advantageous relative to flue-pipe losses that otherwise occur in combustion heated installations, and also compares favourably with electrical resistance heating. A volume of water may, once heated economically be maintained within predetermined temperature limits.

The water itself and the cast iron walls of the tank 1 provide very effective shielding against leakage of microwaves, but for complete safety, additional shielding may be added, using an adaptation of the known shielding constructions devised for microwave ovens.

Alternatively or additionally the heating tank may be located in an area away from living spaces, such as in an attic, cellar or under stair store cupboard. The tank may alternatively or additionally be adapted for heating water for catering purposes e.g.

for preparation of beverages; or for laundry purposes.

Claims

1. Water heating apparatus comprising a vessel for containing waterto be heated, and a transducer adapted to convert electrical signals into microwave radiation arranged to direct the radiation into the vessel.

2. Apparatus according to claim 1 wherein said vessel comprises a tank of rough internal finished cast iron having a window of ceramic tiles or armour-plate heat resistant glass which admits the microwaves.

3. Apparatus according to claim 1 or 2 wherein said transducer is a magnetron tuned to emit microwaves of a frequency within the water absorbtion band.

4. Apparatus according to claim 3 wherein the magnetron is tuned to emit microwaves with a frequency between 2400 and 2500 KHz.

5. Apparatus according to claim 4 wherein the magnetron is tuned to emit microwaves with a frequency of 2450 KHz.

6. Apparatus according to claim 1 wherein the interior surface of the vessel is faceted to promote reflection of the radiation.

7. Apparatus according to any preceding claim provided with additional shielding against microwave leakage.

8. Apparatus according to any preceding claim connected into a central heating circuit.

9. Apparatus according to any preceding claim including thermostat means for switching off the transducer when a preset temperature is exceeded, and for reactivating it when the water in the tank falls below a second preset temperature.

10. Water heating apparatus substantially as hereinbefore described, with reference to and as illustrated in the accompanying drawing.

11. An aquathermal microwave method employing apparatus as claimed in any preceding claim.

12. Amethod of elevating the temperature of a mass fluid substantially as and for the purpose hereinbefore disclosed reference being had to the annexed drawings.