WO2009024850A2

WO2009024850A2 - Apparatus for preparing heated water

Info

Publication number: WO2009024850A2
Application number: PCT/IB2008/002157
Authority: WO
Inventors: Hans Zürcher
Original assignee: Zuercher Hans
Priority date: 2007-08-18
Filing date: 2008-08-18
Publication date: 2009-02-26
Also published as: WO2009024850A3; WO2009024850A4; CH700329B1

Abstract

The apparatus is designed for preparing heated water and comprises a hot water source. The hot water source (1) is constituted by a microwave oven (10) which is connected to a pipe network (5) and which can be used for distributing heated water for the heating of rooms. The microwave oven (10) comprises a housing (11) in which a heat exchanger unit (20) is located. This heat exchanger unit (20) is arranged substantially in the center of the housing (11) and comprises the actual heat exchanger (25).

Description

Apparatus for preparing heated water

The present invention relates to an apparatus for preparing heated water.

There are many known apparatus for preparing heated water. Such apparatus may be classified according to different criteria. One of these criteria is the heating location. Normally, an oven/furnace is used in which gas, wood, coal etc. are combusted. During the combustion of these fuels, temperatures in the oven far exceeding 1000⁰C are generated. As a result, the oven has to be de- signed such that it can withstand these very high temperatures as long as possible. For instance, a floor heating requires water having a temperature which is at a maximum of 55°C. Combustion of such materials in a oven/furnace makes such ovens/furnaces not only voluminous, but also expensive. In addition, combustion gases which are a burden to the environment are produced. Also, in a system having pipes distributing such hot water across the rooms to be heated, appropriate safety measures must be taken, again making this installation expensive.

It is an object of the present invention to eliminate the said as well as further drawbacks of the prior art.

According to the invention, this object is achieved by an apparatus for preparing heated water and having a hot water source, wherein the hot water source is a microwave oven and wherein this microwave oven is connected to a pipe network through which heated water for the heating of rooms can be distributed. As a result, operating temperatures far below 1000⁰C can be achieved. In addition, no combustion gases are released by the apparatus according to the invention.

Preferably, the microwave oven comprises a housing in which a heat ex- changer unit is located which is arranged substantially in the center of the inner space of the housing, wherein the heat exchanger unit includes the actual heat exchanger. This type of construction is easily assembled and allows the use of existing microwave oven designs.

In a first preferred embodiment according to the invention, the heat exchanger comprises a core which supports a winding/coil formed by a hose. Using a hose to form the windings simplifies the construction of the apparatus according to the invention and allows different geometries of the apparatus to be built by selecting a hose material having an appropriate hose length, i.e. overall length of the winding/coil, and an appropriate hose diameter as well as hose material.

In a second preferred embodiment according to the invention, the heat ex- changer again comprises a core which supports a duct winding, wherein the core and the duct winding are integral and may be formed by a moulding process, such as injection moulding, using a polymer material. With this embodiment, the heat exchanger can be easily and rapidly formed.

The core may have a central part which is preferably formed as a pipe piece, and an end plate may be attached at each end of the pipe piece. The core may be made of a material which is electrically non-conducting such as a synthetic material. The outer surface of the pipe piece and the inner surfaces of the end plates may delimit a space in which the winding/coil or the duct winding are located through which water and/or another liquid may flow. Preferably, the hose is made of an electrically non-conducting material and may be a silicone hose.

In the first and second embodiment, the winding/coil or duct winding comprises at least two layers of windings, wherein the winding layers lie on top of each other, one of the layers lies on the outside of the pipe piece and the winding layers are connected in series. Advantageously, the ends of the winding layers and, thus, of the winding/coil or the duct winding are adjacent to each other and preferably contacting each other. In addition, openings may be located in one of the walls of the microwave oven housing and a pipe piece may extend from each opening such that the pipe pieces project from the outer surface of the oven wall, and wherein each hose end or duct end passes through one of the pipe pieces. The inner diameter of the pipe pieces may be selected such that each hose end or duct end barely passes through the corresponding pipe piece. Preferably, the portion of the pipe pieces which projects from the outside of the oven wall has a length such that only an admissible amount of microwaves between the hose ends and the inner surface of the pipe pieces can get to the surroundings of the oven from the inside of the oven housing. Preferably, one of the ends of the winding/coil or duct winding outside the pipe ends is connected to the supply line of the pipe network in a liquid-tight manner, and the other end of the winding/coil or duct winding outside the second tube is connected to the return line of the pipe network in a liquid-tight manner.

In a third preferred embodiment, the hot water source is a microwave oven hav- ing at least one water-cooled magnetron. Using water-cooling instead of air- cooling for cooling the magnetrons prevents uncontrolled excessive heating of the room air surrounding the apparatus according to the invention.

Preferably, the magnetron water cooling is connected to the pipe network. Thus, not only the microwaves generated by the magnetron, but also the heat generated in the magnetron contributes to the heating of the water in the pipe network. As a result, the overall electrical energy to thermal energy conversion efficiency is greatly improved.

The heat exchanger should have a wall thickness of each winding/coil or duct winding made of polymer material in the range of 2 mm to 10 mm, preferably in the range of 3 mm to 6 mm. This allows most of the microwave energy to pass through the polymer windings/ducts ("wound hose embodiment") or polymer duct windings ("integral moulded embodiment") into the water within the wind- ings/ducts or duct windings without being absorbed by the polymer material.

Further aspects of the present invention disclosure are best understood from the following detailed description together with the accompanying figures. In the following description, referring to the enclosed figures, embodiments of the pre- sent invention will be explained in more detail, wherein:

Fig. 1 shows a schematic of the present invention comprising a hot water source;

Fig. 2 schematically shows the hot water source of Fig. 1 ;

Fig. 3 schematically shows a further embodiment of the hot water source; and

Fig. 4 shows a vertical section across the heat exchanger of the hot water source of Fig. 2.

Fig. 1 is an illustration of the present apparatus for preparing hot water. This apparatus comprises a hot water source 1 which is connected via connections to a pipe network 5, known per se, by means of which the hot water can be dis- tributed for heating several rooms which are heated by a floor heating 2. The hot water source 1 is connected via a water switch 3 and via a supply line 38 and a return line 39 to a heating system including the pipe network 5 and a basic hot water source 4 constituted by a boiler/furnace which may be of any type, also known per se. The floor heating 2 is connected to the water switch 3 via a supply line 38' and a return line 39'. The heating system is connected to the water switch 3 via a supply line 38" and a return line 39". The additional hot water source 1 complements the basic hot water source 4 of the overall heating system shown in Fig. 1. The pumps, valves, vents, etc. of the pipe network 5 shown in Fig. 1 will not be described in more detail.

The hot water source is schematically shown in Fig. 2. It comprises a microwave oven 10 of the usual type. However, the power rating of this oven 10 should be adapted to the energy required in the heating device 5. The oven 10 comprises a housing 11 having lateral walls 12 and 13.

The front part of the housing 11 is predominantly open having an opening which can be closed in a known manner by a preferably glazed door 14. Next to this door, there is a portion of a front wall 15 of the housing 11 with the electronic part of the oven 1 usually located behind this front wall portion. In the illustrated embodiment, an activation element 16 is arranged in front of this front wall portion 15.

Inside the microwave housing 11 , there is a heat exchanger unit 20 of which Fig. 2 primarily shows a housing 21 in which the actual heat exchanger 25 is arranged. This heat exchanger unit 20 is appropriately located in the center of the inner space of the housing 21.

The actual heat exchanger 25 (Fig. 4) comprises a core 26 which is configured as a classical core of a coil. This coil core 26 has a central part 27 which is shaped as a piece of a pipe. At either end of this pipe piece 27 there is an end- plate 28 and 29, respectively. This coil core 26 is made of a non-conducting material. Since the inside of the oven housing 11 may have temperatures in the range of 60 ⁰C, as will be explained below, this coil core 26 may be made from a synthetic/plastic material. The outer surface 30 of the pipe piece 27 and the inner surfaces 31 and 32 of the end plates 28 and 29 delimit a space in which a winding/coil 40 is located. This winding/coil 40 is formed by a hose 41 through which water or some other liquid can flow. This hose 41 too consists of an electrically non-conducting ma- terial. For instance, it may be a silicone hose.

In the illustrated case, the winding/coil 40 consists of two layers 42 and 43 of windings which are formed by the hose 41. The first one 42 of these layers is located at the external side 30 of the pipe piece 27. The second one 43 of these layers is located at the external side of the windings of the first one 42 of these layers. In addition, these two winding layers 42 and 43 are connected in series. In the illustrated case, these winding layers 42 and 43 are connected in the region of the upper end plate 28. The free ends 44 and 45 of the two winding layers 42 and 43 and, therefore, of the winding/coil 40 as well are thus lo- cated in the region of the upper end plate 29. Starting from here, these free ends 44 and 45 of the winding/coil 40 are fed through the lateral wall of the heat exchanger housing 21.

As shown on the left-hand side in Fig. 2, the lateral wall 12 of the oven housing 11 has through-passages 34 and 35 through which small tubes 36 and 37 are fitted in such a manner that these tubes 36 and 37 project at least from the outer surface of this lateral wall 12 of the oven housing 11. The inner diameter of these tubes 36 and 37 is selected such that an end 45 and 46, respectively, of the winding/coil 40 barely passes through the corresponding tube 36 and 37, respectively.

The portion of the tubes 36 and 37 projecting from the outer surface of the oven lateral wall 12 must have a minimal length in order to prevent microwaves between the tube ends 44 and 45, respectively, from getting to the surroundings of the oven 10 from the inside of the oven housing 11. Outside the first tube 36, the first end 44 of the winding/coil 40 is connected to the supply line 38 of the pipe network 5 in a liquid-tight fashion. Outside the second tube 37, the second end 45 of the winding/coil 40 is connected to the return line 39 of the pipe network 5 in a liquid-tight manner. If appropriate, the tube/hose ends 44 and 45 may be connected to the pipe network 5 vice versa. This means that the first end 44 of the winding/coil 40 is connected to the return line 39 of the pipe network 5 and the second end 45 of the winding/coil 40 is connected to the supply line 38 of the pipe network 5 in a liquid-tight fashion (not shown).

Alternatively, the described heat exchanger 25 (Fig. 4) with its core 26, central part 27 as well as end plates 28 and 29 may be integrally formed. Preferably, an electrically non-conducting polymer material such as polypropylene is used for an integral heat exchanger of that type. It may be manufactured using a moulding process, preferably injection moulding. In this integral version as well, the duct winding corresponding to the winding/coil 40 comprises two layers 42 and 43 of windings which are formed by a duct instead of the hose 41. The first one 42 of these layers is located on the outside or on the outer surface 30 of the pipe piece 27 in this case as well. The second one 43 of these layers is located on the outside or on the outer surface of the windings of the first one 42 of these layers. In this case as well, these winding layers 42 and 43 are connected in series and, in the region of the upper end plate 28, are connected to each other. The free ends 44 and 45 of both winding layers 42 and 43 and therefore the ones of the duct winding 40 corresponding to the winding/coil 40 are located in the region of the lower end plate 29 in this case as well. Starting from here, these free ends 44 and 45 of the duct winding 40 are passed through the lateral wall of the heat exchanger housing 21.

In the described heat exchanger 25, both in its wound hose type version or in its integral version, the wall thickness of each winding or duct winding 40 of polymer material (e.g. silicone or polypropylene) is within a range of 2 mm to 10 mm, preferably in the range of 3 mm to 6 mm. This guarantees that the windings or duct windings have sufficient mechanical strength on the one hand and sufficient transmissibility for microwaves on the other. As a result, a major portion of the microwave energy makes it into the heat carrying fluid such as water and is nor or at least hardly absorbed in the polymer material.

The microwave oven 10 is able to provide such a large amount of power that the water in the heat exchanger 25 could start to boil. In the present case, however, this is not desired. Rather, the temperature of the water in the supply line 38 should be around 60 ⁰C only. In order to guarantee such a low water temperature in the oven 10, the winding layers 42 and 43 are connected in series as described above.

In the illustrated example, the exit end 44 of the winding/coil 40 is located in the region of the lower end plate 29 of the coil core 26. The water located in the exit end 44 of the winding/coil 40 has flown through the entire winding/coil 40 and thus, has the highest temperature in the winding/coil 40. In contrast, the water passing from the return line 39 into the entrance end 45 of the winding/coil 40 is cold. Also, this entrance end 45 of the winding/coil is located in the lower region of the end plate 29 of the coil core 26. Since the windings of the winding layers 42 and 43 are resting on each other in close relationship in the region of the lower end plate 29, the cold water in the winding supply 45 cools down the water in the winding exit 44. It may be appreciated that such heat exchange also takes place in the other region of the winding 40 where the por- tions of the winding layers 42 and 43 are located, which portions rest on each other and run in mutually opposite directions. This allows to guarantee such low water temperatures in the winding/coil 40.

Although the efficiency of the microwave oven (ratio between the thermal power generation in the target volume to be heated by the device and the elec- trical power input into the device) is not particularly high, such a device is still worthwhile and pays off, since the purchase price of a microwave oven is significantly lower than the purchase price of a boiler/furnace.

Fig. 3 shows a microwave oven 10' having a water-cooled magnetron or water- cooled magnetrons (not visible in Fig.3). In this device, the water-cooling 51 , 52 of the magnetron or of each magnetron of the microwave oven 10' is brought into a heat exchange relationship with the heating circuit. This can be done by connecting the water-cooling of an individual magnetron to the heating circuit via the inlet 51 and outlet 52 of the magnetron water-cooling in addition to the heat exchanger described above. Compared to microwave ovens with air- cooled magnetrons, this has the advantage that no magnetron waste heat enters the air, thus preventing any uncontrolled warming or even over-heating of a room or building section. Rather, according to the invention, the use of a mi- crowave oven with a water-cooled magnetron or water-cooled magnetrons guarantees that a very high percentage of the electrical energy fed into the microwave oven is transmitted into the heating circuit by the microwaves from the magnetrons irradiated into and absorbed by the heat carrying fluid on the one hand and by the magnetron waste heat passing into the heat carrying fluid by heat conduction on the other. The efficiency of a microwave oven with water- cooled magnetrons in a heating installation, i.e. the ratio bet-ween the heat input into the heating installation by the integrated microwave oven and the electrical energy fed into the microwave oven, is clearly above 90%. In fact, up to 94% efficiency could be achieved.

In the apparatus according to the invention, the heat exchanging, i.e. heating regions of the heat exchanger unit 20 (as shown in Fig. 2) and of the magnetron water cooling 51 , 52 (as shown in Fig. 3) can be connected in series or in parallel, the apparatus preferably having a main inlet and a main outlet by which it may be integrated into the supply line and/or the return line and/or into the boiler/furnace of an existing heating installation. Several apparatus according to the invention may be readily integrated into an existing heating installation.

As this apparatus operates at temperatures around or below 100⁰C, i.e. significantly below 1000⁰C, the maintenance of such an apparatus is significantly more cost-efficient than the maintenance of a conventional apparatus. Due to the low operating temperatures, the temperature gradient with respect to the surroundings of the apparatus is lower, thus reducing energy losses during the operation of the apparatus according to the invention. Since there is no combustion of materials, no CO₂ is produced. The microwave oven does not require any chimney connection and it can be switched on and off without any problems. After switching-on, warm water is provided rapidly, since the microwave oven itself has only limited mass which has to be warmed up together with the water. The apparatus can be used for simultaneously heating several rooms. When renovating an existing conventional installation, the boiler/furnace can be replaced by the microwave oven. The present invention is space- saving, since no space for storing fuel materials, which may constitute a source of danger, is required.

The apparatus according to the invention may be provided as a retrofit kit which can be readily integrated into the supply line, the return line or in the boiler/furnace of a conventional heating installation or into a solar heating installation with hot water solar collectors. The electrical energy to be fed into the mi- crowave oven may be generated using photovoltaic equipment with solar cells.

The invention is particularly suitable with low temperature panel heatings (wall heatings and/or floor heatings) and with self-contained heatings for only one apartment or one floor of a building where the transport of the heat carrier fluid is aided by circulating pumps. In such cases, both the microwave oven and the circulating pump may be operated using directly generated solar electricity, battery-stored solar electricity or low-cost off-peak electricity such as night-time generated electricity.

The apparatus according to the invention enables a commercial microwave oven to be used as a source of electrical energy in a heating installation. When using a microwave oven having a water-cooled magnetron, the cooling of the magnetron can be effected for instance by passing the return line of the heating installation through the magnetron cooling zone.

The operation of the heating installation can be regulated using a control, in particular for two-stage operation, and a sensor. Such sensor may be installed in the supply line of the heating installation. This allows the heating installation to be operated in float operation which prevents condensations and damage to the heat exchanger.

The apparatus can be used in heating installations of family homes or in self- contained heatings for only one floor or one apartment. Also, it can be used as a supplementary heating for minergy buildings and with solar heating instaila- tions. It can be operated at night using low-cost off-peak electricity in order to store electrically generated thermal energy in a hot water reservoir or in a phase change reservoir. This stored energy can then be retrieved upon demand during the day-time.

Claims

1. Apparatus for preparing heated water and having a hot water source, char- acterized in that the hot water source (1 ) is a microwave oven (10) and that this microwave oven is connected to a pipe network (5) through which heated water for heating rooms can be distributed.

2. Apparatus according to claim 1 , characterized in that the microwave oven (10) comprises a housing (11) in which a heat exchanger unit (20) is located, that the heat exchanger unit (20) is arranged substantially in the center of the inner space of the housing (11), and that the heat exchanger unit (20) includes the actual heat exchanger (25).

3. Apparatus according to claim 2, characterized in that the heat exchanger (25) comprises a core (26), and that the core (26) supports a winding/coil (40) formed by a hose (41).

4. Apparatus according to claim 2, characterized in that the heat exchanger (25) comprises a core (26), and that the core (26) supports a duct winding (40), wherein the core (26) and the duct winding (40) are integrally formed.

5. Apparatus according to claims 3 or 4, characterized in that the core (26) has a central part (27) which is preferably formed as a pipe piece, that an end plate (28, 29) is attached at each end of the pipe piece (27), and that the core (26) is made of a material which is electrically non-conducting such as a synthetic material.

6. Apparatus according to claims 3 or 4, characterized in that the outer surface (30) of the pipe piece (27) and the inner surfaces (31 , 32) of the end plates (28, 29) delimit a space in which the winding/coil or the duct winding (40) are located through which water and/or another liquid may flow.

7. Apparatus according to claim 6, characterized in that the hose (41) is made of an electrically non-conducting material and that it may be a silicone hose.

8. Apparatus according to claims 3 or 4, characterized in that the winding/coil or duct winding (40) comprises at least two layers (42, 43) of windings, wherein the winding layers (42, 43) lie on top of each other, that one (42) of the layers lies on the outside (30) of the pipe piece (27), and that the winding layers (42, 43) are connected in series.

9. Apparatus according to claim 8, characterized in that the ends (44, 45) of the winding layers (42, 43) and, thus, of the winding/coil or the duct winding (40) are adjacent to each other and preferably contacting each other.

10. Apparatus according to claim 9, characterized in that openings (34, 35) are located in one of the walls (12) of the oven housing (11), that a pipe piece (36, 37) extends from each opening (34, 35), that the pipe pieces (36, 37) project from the outer surface of the oven wall (12), that each hose end or duct end (45, 46) passes through one of the pipe pieces (36, 37), and that the inner diameter of the pipe pieces (36, 37) is selected such that each hose end or duct end (45, 46) barely passes through the corresponding pipe piece (36, 37).

11. Apparatus according to claim 10, characterized in that the portion of the pipe pieces (36, 37) which projects from the outside of the oven wall (12) has a length such that only an admissible amount of microwaves between the hose ends (44, 45) and the inner surface of the pipe pieces (36, 37) can get to the surroundings of the oven (10) from the inside of the oven housing (11).

12. Apparatus according to claim 9, characterized in that one of the ends (44) of the winding/coil or duct winding (40) outside the pipe ends (36, 37) is connected to the supply line (38) of the pipe network (5) in a liquid-tight manner, and that the other end (45) of the winding/coil or duct winding (40) outside the second tube (36) is connected to the return line (39) of the pipe network (5) in a liquid-tight manner.

13. Apparatus according to any one of claims 1 to 12, characterized in that the hot water source (1) is a microwave oven (10') having at least one water-cooled magnetron (51 , 52).

14. Apparatus according to claim 13, characterized in that the magnetron water cooling is connected to the pipe network (5).

15. Apparatus according to claims 3 or 4, characterized in that the heat exchanger (25) has a wall thickness of each winding/coil or duct winding (40) made of polymer material in the range of 2 mm to 10 mm, preferably in the range of 3 mm to 6 mm.