EP0061665B1 - Enclosed electric storage heater - Google Patents

Abstract

1. Closed electrical heat storage furnace comprising an outer facing (1), core structure inside said outer facing and made of heat storing material, electrical heating coils (13) mounted inside said core structure, said core structure being enclosed by an insulating layer (3), and storage blocks each having an opening for the passage therethrough of the heating coils and arranged on top of each other in a plurality of rows, characterized by said storage blocks comprising bricks (4) U-shaped in cross section and disposed in pairs in each horizontal row so that their openings face each other to define a continuous duct (9) for receiving heating coils (13), said bricks (4) in each row being placed in a side-by-side relationship so that their small end faces engage each other, with the narrow longitudinal surfaces of the bridge portions of the U-shapes being placed on top of each other in adjacent rows, by a large-area heat exchanger provided between insulating layer (3) and outer facing (1), and by outer facing (1) being assembled from module elements.

Description

The invention relates to an electrical heat storage furnace with an outer clothing, a core structure arranged therein and made of heat storage material and fixed in the core structure electrical heating spirals, wherein the core structure is surrounded by an insulating layer and comprises memory blocks, each having a recess for the passage of the heating spirals and in several rows are arranged one above the other.

Hungarian patent specification 161 254 describes a brick oven which is heated by electrical energy. Electrical heating elements arranged in bricks are provided in the interior of the furnace jacket, air drafts being formed between the bricks. The inside of the brick kiln is lined with firebricks, in which vertical holes are provided. The radiators are guided through these holes. A fan blower is arranged at the lower end of the draft. The radiators in the form of electrical heating spirals are electrically insulated from the surroundings with the chamotte lining. Inside the brick oven, the fan blower creates a forced flow of air that contacts the radiators directly.

Such a brick oven is made to order and has almost no heat storage capacity. Since the forced flow of air directly contacts the radiators, they cool down very quickly. The bricks of the oven store a certain small amount of heat with which the air flow always comes into contact. This heat is only given off by radiation.

The heat capacity of heat storage furnaces is created by means of the heating spirals, which are arranged in a core structure with heat storage capacity.

For example, DE-A-2 803 388 describes a combined convection and heat storage furnace in which a stack of storage blocks in the form of concrete blocks is arranged in a box-shaped metal housing with ventilation and outlet openings and is used to pass heating elements with corresponding bores are provided. A major disadvantage of this known heat storage furnace is its relatively heavy weight and the difficulty in disassembling and reassembling it in the event of repair or maintenance.

In the case of the heat accumulator known from DE-A-2430051, the heating elements and the heat accumulator elements are surrounded by an insulating layer, a water jacket which is connected to a hot water circuit being provided on the outside of the insulating layer.

However, the known ovens present two major difficulties. A sufficient amount of heat cannot be stored in them, so they are cold before starting to heat up outside of the peak load. The other difficulty lies in extracting and transferring the heat to the environment. For this purpose, a fan is provided in a known furnace, which is controlled by a thermostat. The air is heated with this blower by direct contact with the heat-storing core structure and blown into the environment. As a result, the heat capacity of the heat storage furnace is discharged relatively quickly.

Recent experiments with heat-storing materials have shown that the heat capacity of magnesite silicate increases suddenly at a temperature of 500 ° C or higher. This is also a reason for the low heat capacity of the known stoves. The heating device used there cannot be higher than e.g. 700 to 750 ° C are heated; the thinner the resistance wire of the heating coil, the greater its resistance and heat output. This means a limitation in the dimensioning. Heating coils that are short and thinner than 0.5 mm are used in the conventional furnaces. So they cannot be heated to more than 750 ° C, otherwise they would burn. The metal housing of the radiators would also corrode and be destroyed. As a result, however, only a limited mass of the core structure can be used, since this smaller amount of heat is not sufficient to heat larger core structures.

The object on which the invention is based is to create an electrical heat storage furnace which eliminates the disadvantages in known arrangements and which is designed as a closed system, is technically not complex and has a very high heat capacity, can be operated economically and gives a pleasant feeling of warmth.

The invention is based on the knowledge that the object can be achieved simply and satisfactorily by heating the core structure in the temperature ranges of the optimal heat storage capacity and by avoiding direct contact between the air flowing through and the core structure. The heating element of the heat storage furnace should also be designed accordingly.

Accordingly, the object is achieved in that U-shaped bricks are provided as storage blocks in cross-section, which are arranged in pairs in each horizontal row so that their mutually facing recesses surround a continuous channel for receiving the heating coils, the bricks being arranged in a row next to one another are arranged in such a way that their small end faces lie against each other and are arranged in adjacent rows with the narrow longitudinal faces of their U-webs, that a large-area heat exchanger is provided between the insulating layer and the outer cladding, and that the outer cladding is composed of module elements.

The main advantage of this design of a heat storage furnace is that the draft due to the insulating layer tightly surrounding the core structure, the radiator, i.e. cannot touch the heating coil directly, so that the heat is released and cooled below the critical temperature limit of 500 ° C in a considerably longer time. The heated mass of the core structure is significantly increased and allows a higher end temperature of the heating period. This means that the core structure of the furnace has a higher temperature than the critical temperature of 500 ° C for most or all of the heat emission. As a result of the arrangement of the bricks in the core structure, the boundary area of the furnace is larger than that of conventional furnaces using the same number of bricks.

As a material with good heat storage capacity, magnesite silicate is advantageously used for the core structure.

Because of the higher temperature of the heating coil or the core structure, it is advantageous to make the heating coil from a resistance wire with a diameter of 1 mm or larger.

The insulating layer around the core structure is expediently made of mineral wool provided with aluminum foil, which does not age, does not dust, but has the necessary insulating properties.

According to an advantageous embodiment, the large-area heat exchanger located between the outer cladding and the insulating layer can consist of parallel channels arranged next to one another. These channels can be tubes arranged side by side and parallel to one another or consist of a correspondingly shaped corrugated sheet. The air flow in the channels can be controlled in such a way that the channels are assigned control elements which are provided in the cover of the furnace.

The cover is expediently formed from parallel, fixed and closed profiles which are connected to the channels of the heat exchanger, wing valves being provided in the closed profiles as control elements for the air flow. The air flow control can also be designed such that bores communicating with the channels are provided in the cover, to which a frame that closes the bores is connected.

For aesthetic reasons, but especially for the sake of easy transportability, it is advantageous to design the ceramic outer clothing composed of modular elements so that they can be dismantled.

According to a further feature, the heating coil is arranged in a stationary manner by means of insulating spacers and insulating beads. The heating coil can be installed in electrically insulating, advantageously cordierite tubes.

The heating coil is expediently arranged in four rows in the core structure of the furnace, both ends of the heating coil being fastened to a mounting plate. A switch that controls the heat status of the heating coil can also be provided on this mounting plate, wherein the switch can also be connected to an indicator.

The bricks are advantageously stacked in three rows, so that three channels are created in the core structure of the furnace. Three heating coils which can be operated independently of one another are expediently provided.

Overheating of the furnace can be avoided and an additional setting possibility can be created by providing a thermostat which is connected to the heating coil.

• Fig. 1 perspektivisch einen teilweise geschnittenen Wärmespeicherofen,
• Fig. 2 einen Bereich der Fig. 1 im grösseren Massstab, nämlich einen Ausschnitt des Deckels,
• Fig. 3 perspektivisch zwei Modulelemente der Aussenbekleidung der Ausführungsform nach Fig.1,
• Fig. 4 eine elektrische Schaltung der Vorrichtung nach Fig. 1,
• Fig. 5 eine Seitenansicht einer Isolierperle,
• Fig. 6 eine Isolierplatte,
• Fig. 7 perspektivisch einen Abstandhalter der Ausführungsform nach Fig. 1,
• Fig. 8 schematisch einen Teil der Heizspirale der Ausführungsform nach Fig. 1,
• Fig. 9 ein Heizelement der Ausführungsform nach Fig. 1,
• Fig. 10 eine Teilansicht ähnlich Fig. 2, jedoch einer anderen Ausführungsform,
• Fig. 11 eine elektrische Schaltung des Wärmespeicherofens für eine Ausführungsform mit Glimmlampen als Anzeiger.

The invention is explained in more detail below using exemplary embodiments with reference to the accompanying drawing. The drawing shows:

• 1 is a perspective view of a partially sectioned heat storage furnace,
• 2 shows an area of FIG. 1 on a larger scale, namely a section of the cover,
• 3 perspective two module elements of the outer clothing of the embodiment according to FIG. 1,
• 4 shows an electrical circuit of the device according to FIG. 1,
• 5 is a side view of an insulating bead,
• 6 is an insulating plate,
• 7 is a perspective view of a spacer of the embodiment according to FIG. 1,
• 8 schematically shows part of the heating coil of the embodiment according to FIG. 1,
• 9 is a heating element of the embodiment of FIG. 1,
• 10 is a partial view similar to FIG. 2, but another embodiment,
• 11 shows an electrical circuit of the heat storage furnace for an embodiment with glow lamps as indicators.

The embodiment of the heat storage furnace shown in FIG. 1 has the shape of a cuboid, which is provided with an outer lining 1. The furnace is supported by stand 8 and covered with a lid 5 at the top. Holding elements 6 are attached to the stands 8 and carry the inner structure of the furnace and the outer lining 1 of the furnace. A heat exchanger in the form of tubes 2 fastened parallel to one another on a strip 10 is provided on the inside of the outer clothing 1.

Furthermore, an insulating layer 3 contacting the heat exchanger is arranged in the interior of the furnace, which in this example is made of mineral wool covered with aluminum foil. This insulating layer 3 encloses the core structure of the heat storage furnace, which are made up of bricks 4. The bricks 4 have good heat storage capacity, in the embodiment shown they are made of magnesite silicate.

As shown in Fig. 1, the core structure exists door of the heat storage furnace made up of three rows of bricks stacked on top of each other. The rows are formed in such a way that two bricks 4, each of which have a U-shaped cross section, face one another with their cutouts and the pairs of bricks 4 are arranged next to one another. In this way, a rectangular closed space in the form of a channel 9 is formed from the spaces between the legs of the bricks 4. This channel is provided in a line, the respectively adjacent bricks 4 with their smallest area being arranged next to one another. The other two similarly designed rows are stacked on top of one another, the bricks 4 standing on their narrow longitudinal surfaces. This creates a narrow, long and not very high shape of the core structure and the entire heat storage furnace. The heating element of the heat storage furnace is provided in the channels 9 formed between the brick pairs.

In the exemplary embodiment according to FIG. 1, the heating element consists of three heating spirals 13 which can be operated independently of one another. The fixed position of the heating spiral 13 in the channel 9 is determined by spacers 12 and a mounting plate 14 arranged at one end of the channel 9. The two ends of the heating coil 13 and a switch 15 are attached to this mounting plate 14. With the switch 15, the heat condition of the heating coil 13 and thus that of the entire heating element can be checked. In the longitudinal direction, the spacers 12 and the mounting plate 14 are fastened with a tube 11.

The bricks 4 are held together by an angle steel frame 37 in the core structure, which is supported at the bottom by core holders 7 which are connected to the holding elements 6. In this way, the construction of the heat storage furnace is stable and safe.

In Fig. 2, part of the cover 5 is shown on a larger scale. A thermostat 16 and an indicator 17 are arranged on this cover 5. The thermostat 16 is a bimetallic switch which is switched on between the heating coils 13 and the electrical network. The indicator 17 shows the operating state of the heat storage furnace and the operational readiness of the heating coil 13.

2 shows an advantageous embodiment for regulating the draft in the channels of the heat exchanger. Bores are provided in the cover 5, which communicate with channels, in this example with the tubes 2, and can be locked with the aid of a frame 18. The frame 18 is provided with bolts 22 which are in engagement with an inclined slideway of a lever 21. The lever 21 can be moved along the vertical and shorter edge of the cover 5. The same device can be provided on the other of the cover 5, which is parallel to the previous edge.

In Fig. 3 two module elements of the outer clothing 1 of the heat storage furnace are shown. In the edge surface of these module elements, a groove 20 is provided, half of which is occupied by a tube 19. The outer clothing 1 can be dismantled in that the free groove 20 of one module element is occupied by the tube 19 of the adjacent module element and a rod can be pushed through the tubes 19. In FIG. 3 the tube 19 and the groove 20 are provided on the one side at the top and the tube 19 and the groove 20 at the bottom on the other side.

4 shows a circuit of the indicator 17 with LED diodes 25. The switches 15 are indicated by their inputs. Resistors 23, diodes 24 and capacitors 26 are interconnected in the circuit in a manner known per se.

In Fig. 5, an insulating bead 27 is shown in side view, in the central bore indicated by the dashed line, a bracing wire 29 is guided. The resistance wire of the heating coil 13 is wound on the jacket of the insulating bead 27.

The spacer 12 shown in FIG. 7 has bores. The heating coil 13 is carried out in its upper and lower bore, and the tube 11 is carried out in the central bore.

The arrangement of the heating coil 13 in the channel 9 of the core structure is shown in FIG. 8, the end of the channel 9 opposite the end provided with the mounting plate 14 being shown. On the side walls of the channel 9, the spacers 12 are supported, in the lower bores the heating coil 13 and the middle bore the tube 11 are performed. The heating coil 13 is wound on the insulating beads 27, the windings of which at dangerous points, e.g. in the curvatures of the heating coil 13, are separated from one another by insulating plates 28 (FIG. 6), so that a possible short circuit is avoided. Since the bracing wire 29 is passed through the bore of the insulating beads 27, the insulating beads 27 are drawn opposite.

Two variants are shown in FIG. 8 for holding the spacers 12 to the tube 11. On the left spacer 12, two nuts 31 a are arranged on both sides of the spacer 12, the tube 11 being provided with a thread at this point. On the right spacer 12 in Fig. 8, the tube 11 is provided with an internal thread, into which a threaded pin 31 b is screwed. On this set screw 31 b, the tube 11 is tightened on both sides of the spacer 12.

The heating coil 13 can additionally be encased by beads 30.

The core structure of the heat storage furnace is heated to a higher temperature than before. Thus, the heating elements are heated to a higher temperature, which would be harmful in known designs. A resistance wire with a minimum diameter of 1 mm is therefore used in the heat storage furnace. In this case, however, a much longer resistance wire must be installed to ensure the resistance required for the heating power.

9 shows three heating coils 13 which can be operated independently of one another before being inserted into the channels 9. The heating coil 13 is moved back and forth four times in a heating element. The four courses of the heating coil 13 are arranged in four cordierite tubes 32 placed side by side. In this way, a four times longer heating coil 13 is provided in each channel 9 compared to its length. The mounting plate 14 and the switch 15 are also shown.

10 shows another embodiment of the cover 5 and the control element of the air flow in the heat exchanger of the heat storage furnace. Here, the cover 5 is formed from closed profiles 36 which are fastened next to one another and communicate with the channels of the heat exchanger, in this example with the tubes 2. At one or both ends of the closed profiles 36, wing valves 35 are provided as control elements which have a common axis and can be opened or closed with a lever arm 34. The thermostat 16 and the indicator, which in this case comprises glow lamps 33, are also shown.

In the circuit according to FIG. 11 for the heat storage furnace, the glow lamps 33 according to FIG. 10 are provided. The switches 15 provided on the mounting plates 14, the thermostat 16 and the heating coil are shown with symbols.

A distinction is made between two periods in the operation of the heat storage furnace according to the invention. In one period, the heat storage furnace is heated, the heating spirals 13 being traversed by electrical current. The other is the cooling period of the heat storage furnace, the heating spirals 13 being disconnected from the electrical network and the heat being released from the core structure.

Due to the design of the core construction, the critical temperature of 500 ° C can be exceeded considerably during the heating period, and temperatures of 1000 to 1050 ° C can also be reached. This is possible on the one hand because the core structure is thermally insulated from the outside by the insulating layer 3, and on the other hand because the heating elements can also endure this elevated temperature. The insulating layer 3 is dimensioned such that the outer surface contacting the heat exchanger also becomes warm. The in the channels, i.e. Air in the tubes 2 of the heat exchanger is heated, after which there is a gravitational flow of the warm air upwards without any means, e.g. Blower or the like to have to use. This air flow can be regulated by the control elements, by the frame 18 or by the wing valves 35. During the cooling period of the heat storage furnace, the insulating layer 3 ensures that the heat-storing core structure, i.e. the bricks 4, even in the last hours before the start of the next heating period, are still warmer than (the critical) 500 ° C.

The greater heat storage capacity means that the bricks 4 made of magnesite silicate can store a larger amount of heat than below 500 ° C with the same energy consumption. With the same energy consumption, the heat storage stove can heat the surrounding room much better than was previously possible. It follows inevitably that less energy is used for this better heatability.

The switches 15 located on the mounting plates 14 control the thermal state of the heating elements. The LED diodes 25 or glow lamps 33 provided in the indicator 17 light up when one or more heating coils 13 have become defective.

The temperature on the cover 5 is felt by the thermostat 16. This prevents the heat storage furnace from possibly overheating, e.g. when the stove is switched on in warm weather. On the other hand, the furnace can be disconnected from the electrical power supply by means of the thermostat 16.

Due to the composition of the heat storage furnace from module elements and from the bricks 4, the production can be simplified considerably and the expansion options can be expanded with various services. The complete heat storage stove can be delivered in a single package and assembled at the place of installation.

The measurements carried out in a test with the heat storage furnace have shown that under the same conditions and characteristics it has a 1.25 times greater heat storage capacity than the conventional heat storage furnaces. Because of the large difference in heat between the two sides of the channels of the heat exchanger, there is an intensive heat exchange with the air in the channels. There is therefore no need for a circulation medium for the air, which makes the feeling of warmth in the room heated with this heat storage stove much more pleasant and similar to that of a radiator operated with hot water.

Claims (19)

1. Closed electrical heat storage furnace comprising an outer facing (1), core structure inside said outer facing and made of heat storing material, electrical heating coils (13) mounted inside said core structure, said core structure being enclosed by an insulating layer (3), and storage blocks each having an opening for the passage therethrough of the heating coils and arranged on top of each other in a plurality of rows, characterized by said storage blocks comprising bricks (4) U-shaped in cross section and disposed in pairs in each horizontal row so that their openings face each other to define a continuous duct (9) for receiving heating coils (13), said bricks (4) in each row being placed in a side-by-side relationship so that their small end faces engage each other, with the narrow longitudinal surfaces of the bridge portions of the U-shapes being placed on top of each other in adjacent rows, by a large-area heat exchanger provided between insulating layer (3) and outer facing (1), and by outer facing (1) being assembled from module elements.

2. Heat storage furnace as in claim 1, characterized by the heat storing core structure being formed of magnesite silicate.

3. Heat storage furnace as in claim 1 or 2, characterized by heating coil (13) being made of resistance wire having a minimum diameter of one millimeter.

4. Heat storage furnace as in any one of the preceding claims, characterized by said insulating layer (3) being made of mineral wool provided with aluminum foil.

5. Heat storage furnace as in any one of the preceding claims, characterized by said large-area heat exchanger provided between outer facing (1) and insulating layer (3) being formed of ducts arranged in a side-by-side parallel relationship.

6. Heat storage furnace as in claim 5, characterized by said ducts being formed of tubing (2) arranged in parallel side-by-side relationship, or of correspondingly shaped corrugated sheet material.

7. Heat storage furnace as in any one of the preceding claims, characterized by said heat exchanger ducts having associated therewith elements (18, 35) for air flow control.

8. Heat storage furnace as in claim 7, characterized by air flow control elements (18, 35) being formed in a cover (5) of the heat storage furnace.

9. Heat storage furnace as in claim 8, characterized by cover (5) being formed of closed section elements (26) fixed in a parallel relationship and communicating with said heat exchanger ducts, and by said air flow control elements being damper valves (35) provided inside said closed section elements (36).

10. Heat storage furnace as in claim 8, characterized by cover (5) having therethrough bores communicating with heat exchanger ducts (9), said air flow control element comprising a frame for sealing the aforesaid bores.

11. Heat storage furnace as in any one of the preceding claims, characterized by outer facing (1) being assembled from module elements, the facing consisting of ceramic material and being adapted to be disassembled.

12. Heat storage furnace as in any one of the preceding claims, characterized by heating coil (13) being held stationary by insulating spacers (12) and by insulating beads (27).

13. Heat storage furnace as in any one of the preceding claims, characterized by heating coil (13) being mounted inside insulating cordierite tubes (32).

14. Heat storage furnace as in any one of the preceding claims, characterized by heating coil (13) being arranged in four rows inside said core structure, with both ends of heating coil (13) being secured to a mounting panel (14).

15. Heat storage furnace as in claim 14, characterized by switch (15) being provided on mounting panel (14) to control the thermal condition of heating coil (13).

16. Heat storage furnace as in claim 15, characterized by switch (15) being coupled to display means (17).

17. Heat storage furnace as in any one of the preceding claims, characterized by bricks (4) being arranged in three superimposed rows.

18. Heat storage furnace as in claim 17, characterized by three heating coils (13) being provided, with each said coils being independently operable.

19. Heat storage furnace as in any one of the preceding claims, characterized by a thermostat coupled to heating coil (13).

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