Hydronic heating system

Abstract

A hydronic heating system includes a heat exchanger, a container, and a micro-wave heating means associated with the container for heating water therein. The container and heat exchanges are connected by a closed circulation loop which includes a storage tank between the container and heat exchanger and a by-pass means to allow flow of water from the heat exchanger to flow directly to the storage tank without passing through the container. A valve is provided in the circulation loop downstream of the by-pass means. A temperature sensor in the storage tank controls operation of a switch in circuit with the valve and micro-wave heating means. When the temperature of the water in the storage tank is below a predetermined temperature, the switch is closed to simultaneously activate the micro-wave heating means and to open the valve to allow water to flow from the heat exchanger into the container. When the water temperature in the storage tank is above the predetermined temperature, the switch is opened to simultaneously de-activate the microwave heating means and to close the valve to divert water from the heat exchanger through the by-pass means into the storage tank. The by-pass means is provided with a check valve and a pump circulates the water through the closed circulation loop.

Description

This invention relates generally to a heating system for indirect space and area heating and more particularly to an improved and practical central heating system employing hot water circulated through a heat exchanger.

Central heating systems employing hot water circulated through a heat exchanger such as a radiator or the like have been used for many years for room space heating in homes, offices and the like. Such systems have become known as hydronic heating systems. The hydronic system is preferred to hot-air systems because the heated air of hot-air systems discharged into the room space often carries dirt or picks-up dirt in the room and circulates it where it is inhaled by the occupants of the room. Hydronic heating has the disadvantage, however, of being slower to respond to sudden changes in temperature particularly if an electric heater is used to heat the water. Electric heating is preferable to gas, oil or other heating means for some purposes, however, particularly in rural areas where the other fuels are not readily available.

It is therefore an object of this invention to provide an improved hydronic heating system. Another object of the invention is to provide a central water heating system which includes a practical means for heating the water with an electric heater. Still another object of the invention is to provide a hydronic water system for space or area heating which is quickly responsive to decrease in temperature and is adapted to conserve electric power.

The foregoing objects are accomplished in accordance with the invention, generally speaking by providing a hydronic heating system having means for heating water with a magnetron oscillator for generation of micro-wave energy, a heat exchanger for indirect heating of an area or space and means for circulating the heated water between the heat exchanger and the heating means. More specifically, in a preferred embodiment of the invention, a closed central heating system is provided having one or more heat exchangers disposed in a space or spaces to be heated, a container for water associated with a magnetron oscillator for heating the water, a guide or horn for guiding micro-waves from the oscillator to the container, a wall transparent to micro-waves between the container and the horn, and a means for circulating heated water from the container to the heat exchanger. The means for circulating water between the heat exchanger and the container includes a water storage means adapted to permit escape of air from the system and expansion of the water in the system, and means for recirculating the water from the storage means to the heat exchanger without heating with micro-wave energy.

Other objects will become apparent from the following description with reference to the accompanying drawing wherein the only FIGURE is a schematic representation of one embodiment of the invention.

Referring now to the drawing, a heat exchanger 10 which may be a conventional radiator or a heat exchanger disposed in a base board or other suitable heat radiating means is connected by pipe 11 through pump 12 to a water storage tank 13 which is only partially filled with water so an air space is present above the water level. A magnetron oscillator 14, illustrated schematically, is disposed above horn 15 and water container 16 to heat water in container 16. Container 16 has plastic or other suitable end and bottom walls and fittings for connecting it to pipes 18, 19 and 36 to insulate it from metal. Container 16 is filled with water. Pipe 18 connects container 16 to storage tank 13 and pipe 19 connects heat exchanger 10 with container 16. Temperature sensor 20 is disposed in tank 13 for determining the temperature of the water in tank 13 and switch 21, connected to a suitable source of electricity, is opened and closed in response to the water temperature to activate or deactivate magnetron oscillator 14. Wall 17 between the space enclosed by horn 15 must be transparent to micro-waves and may be a vitrous material. Container 16 is electrically insulated from all metal pipes and the wall of horn 15.

In the embodiment shown in the drawing, a by-pass pipe 22 connects pipes 18 and 19. A valve 23 is in circuit with switch 21 and is closed when switch 21 is opened by temperature sensor 20 to direct water from pipe 19 through bypass 22 and check valve 24 to storage tank 13 and is opened when switch 21 is opened when switch 21 is closed by temperature sensor 20 to permit water to flow into container 16. Pressure responsive check valve 24 permits the flow of water from pipe 19 to pipe 18 when valve 23 is closed. A pressure-sensitive valve 25 permits the escape of air from above the water in tank 13.

In operation, pump 12 withdraws water from storage tank 13 and pumps it through pipe 11, heat exchanger 10 and pipe 19 towards container 16. In the embodiment provided with valve 23, the water passes to container 16 if the water in tank 13 is below normal temperature and is heated by micro-wave energy generated by magnetron oscillator 14. The heated water is drawn from container 16 into tank 13. Check valve 24 prevents water leaving container 16 from passing to pipe 22. If the temperature of the water in tank 13 is up to normal, valve 23 closes and water in pipe 19 is forced through pipe 22 and check valve 24 into tank 13 without passing through container 16. Magnetron oscillator 14 operates only when switch 21 is closed in response to temperature sensor 20 when the water temperature in tank 13 is below the preselected temperature to permit electric current to pass to oscillator 14. It is to be understood that both by-pass 22 and thermostatically responsive switch 21 may not be required in some embodiments and that only one or the other may be furnished to avoid unnecessary use of electricity by activation of the magnetron oscillator 14 when the water temperature in tank 13 is up to normal.

Storage tank 13 permits expansion of the water with temperature increase in the closed system. Tank 13 should be insulated with fiber glass, polyurethane foam or other suitable insulating material to reduce heat loss. Air dissolved in the water entering from a city water supply through pipe 36 into container 16 will escape from the heated water into the space above the water level in tank 13. Pressure responsive valve 25 permits air in the space in tank 13 to escape and prevents the development of dangerous pressures in the system.

Magnetron oscillator 14 may be of any conventional type having a tube with a strong magnet surrounding it. A klystron or other source of micro-wave energy may be substituted for the magnetron tube. The one illustrated schematically in the drawing has a cathode 30 surrounded by a conducting envelope 31 and a plurality of radially extending vanes 32 which are connected together to form an anode. Means is provided to supply a high voltage of say 3000 volts to 7000 volts to the magnetron. Such an oscillator is adapted to produce an output of high-frequency energy in the micro-wave range. A coaxial transmission line 33 is coupled to the magnetron oscillator by means of a suitable loop 34 disposed between a pair of vanes 32 and extends downwardly into horn 15 from the loop 34 through housing 35. The walls of horn 15 are metal so micro-wave energy cannot pass therethrough. The micro-wave energy is reflected downwardly to plate 17 forming a common wall for horn 15 and container 16. Plate 17 is made from a material which permits micro-wave energy to pass therethrough such as a vitrous material. Plate 17 may be any material which is transparent to high frequency energy but will not permit water or steam to pass therethrough into the horn 15. For example, quartz may be used for plate 17.

It should be apparent from the foregoing description that the invention accomplishes its objects by providing a practical hydronic heating system adapted to use micro-wave energy for heating space in controlled amounts on an economical basis. Because the temperature of the water can be increased rapidly, the actual operation of the magnetron oscillator is held at a minimum and unnecessary waste of energy is avoided. The use of micro-wave energy permits the use of a small volume container, small volume storage tank and small volume heat exchanger with accompanying rapid increase in room temperature when space heating is required. The heating system of the invention not only provides for uniform temperature with less time lag when raising the temperature of a room but also provides electric heating at a practical cost.

The embodiment illustrated in the drawing has the storage tank 13 and water heating unit separated from each other. One of the advantages of the apparatus is that it can occupy a very small space. In fact, if desired the tank 13, container 16 with magnetron tube 14 can be disposed one over the other in a compact housing and sold as a unit. Container 16 may be provided with a plastic tube coil instead of the single reservoir or tank illustrated in the drawing.

Although the invention has been described in detail for the purpose of illustration, it is to be understood that such detail is solely for that purpose and that variations can be made therein by those skilled in the art without departing from the spirit and scope of the invention except as it may be limited by the claims.

Claims

I claim:

1. A hydronic heating system comprising a heat exchanger, a container for water, means for heating water in the container comprising a source of micro-wave energy, a guide means having walls which reflect micro-wave energy generated by the said source and direct the micro-waves towards the container, a wall common to said guide means and said container which is transparent to microwaves, means forming a closed circulation loop between the heat exchanger and the container, means for circulating the water in said closed loop between the heat exchanger and the container, a water storage means between the outlet of the container and the inlet of the heat exchanger and having means for accommodating expansion of water in the system and for the escape of air from the system, by-pass means in the circulation loop between the heat exchanger and the container for by-passing the container to allow water flowing from the heat exchanger to flow directly to the storage means, a check valve in said by-pass means which prevents flow of water from the container through the by-pass means, and means responsive to the temperature of the water in the system externally of the container for directing flow of water from the heat exchanger to the storage means while by-passing the container, said temperature responsive means comprising a valve in the circulation loop downstream of the by-pass means for diverting flow of water flowing from the heat exchanger towards the container into the by-pass, and thermostatic means for simultaneously activating the source of micro-wave energy and opening the last said valve for flow of water from the heat exchanger into the container when the temperature of the water in the system externally of the container is below a predetermined temperature and for simultaneously deactivating the source of micro-wave energy and closing said valve to divert the water from the heat exchanger through said by-pass means into the storage means when the temperature of the water in the system externally of the container is at least equal to said predetermined temperature.