GB2076955A

GB2076955A - Heating device

Info

Publication number: GB2076955A
Application number: GB8114810A
Authority: GB
Original assignee: MERLANG HOLDING SA
Current assignee: MERLANG HOLDING SA
Priority date: 1980-05-16
Filing date: 1981-05-14
Publication date: 1981-12-09
Also published as: DE3118598A1; BE888810A; LU83354A1; FR2482707A1; NL8102412A; NL8002866A; JPS5719544A

Abstract

A heating device comprising a combustion chamber 4 and a stack 3 spaced from said combustion chamber, with a plurality of relatively long ducts 17 for flue gases between said combustion chamber and said stack. The ducts 17 and optionally the combustion chamber are surrounded by a heat storage material 20, and means are provided for the discharge of heat from the heat storage material. According to the present invention, the flue gas ducts are substantially straight ducts, and the means for the discharge of heat stored in the heat storage material consist of a plurality of pipes or conduits 19 extending through or along the heat storage material between a first compartment 12 to which a heat transporting medium can be supplied, and a second compartment 13, from which the heat transporting medium can be discharged after passing through the pipes or conduits 19. <IMAGE>

Description

SPECIFICATION Heating device This invention relates to a heating device comprising a fire compartment in which a fire can be maintained, and a stack spaced from said fire compartment, with a plurality of relatively long ducts for flue gases between said fire compartment and said stack, the ducts and optionally the fire compartment being surrounded by a heat storage material, and means being provided for the discharge of heat from the heat storage material.

Such an arrangement is disclosed in European patent application 79.100657.0, Publication Number 0.004.058. In the prior arrangement, the ducts for flue gases are substantially curved and extend through a compartment filled with sand or other suitable heat storage material before terminating in a central duct. In the central duct, a fan is arranged to ensure proper discharge of the flue gases. Such a fan, which is exposed to the flue gases, which may contain corrosive components, is a vulnerable part in the system. Provided above the device is a chamberforthe discharge ofthe heat stored in the storage compartment, through which chamber air can be passed by means of a second fan. Such a discharge of stored heat is not optimal.

It is an object of the present invention to improve the device according to the state of the art, and to avoid at least some of the apparent shortcomings of the prior device. This object is achieved, according to the present invention, with a device in which the flue gas ducts are substantially straight ducts, and the means for the discharge of heat stored in the heat storage material consist of a plurality of pipes or conduits extending through or along the heat storage material between a first compartment to which a heat transporting medium can be supplied, and a second compartment, from which the heat transporting medium can be discharged after passing the pipes or conduits.

By virtue of the use of substantially straight flue gas ducts, which in the most favourable embodiment extend vertically upwardly above the fire compartment, the flue gases are discharged without the intermediary of a fan by natural "draft". Furthermore, the discharge of heat through pipes or conduits extending through or along the heat storage material makes it possible for the heat stored to be discharged in an optimal manner.

In a preferred embodiment of the device according to the invention, the flue gas ducts are each built up from a plurality of ceramic tubes fitting one in the other, and insulated relatively to each other to prevent the transfer of heat between adjacent tubes.

The tubes of heat-resistant ceramic material are preferably provided on the inside with a coating of glaze. As a result of the fact that the tubes making up a flue gas duct are insulated relatively to each other, and heat cannot be transferred direct from one tube to another, but exclusively via the flue gases to the tubes, a very large portion of the heat is stored in the heat storage material close to the fire compartment.

It is accordingly possible to produce a gradient in the storage section, which can be used for the discharge of heat from the storage section to suit requirements.

In a suitable embodiment of the device according to the present invention, there is provided a compartment filled with heat storage material under and/or next to the fire compartment, and a plurality of heat conducting rods are provided, which on one end extend into the heat storage material under and/or next to the fire compartment, and at the other end extend into the heat storage material surrounding the ducts for the flue gases.

The heat transporting medium can be any suitable medium. In many cases, air can be used. It is also possible to use liquid salts for the discharge of heat from the storage section.

In a suitable embodiment, the first and the second compartment are disposed between two spaced pipe plates, the first pipe plate forming the separation between the heat storage section and the compartments, and the second pipe plate forming the separation between the compartments and the stack, the compartments being separated from each other by a wall extending from the first pipe plate to the second pipe plate, the pipes for the discharge of the stored heat having a U-shape, and being secured with both ends in orto said first pipe plate with one end being connected to the first compartment and the other end being connected to the second compartment, the flue gas ducts extending through said first pipe plate and through one of the two compartments, and being secured in orto the second pipe plate, thereby communicating with the stack.

In an alternative construction, two headers are provided on opposite sides of the heat storage section, said headers being interconnected by means of conduits extending across the heat storage section.

Furthermore, it is possible to use a construction in which a vertical space adjoins the wall of the storage section, and entrances to said space are provided at the top and bottom thereof from, for example, a room in which the device is installed. Air will then be passed through convection along the wall of the storage section, and in this way heat will be passed from the device to the room.

In the embodiment employing U-shaped pipes, these may extend fully within the heat storage section and be surrounded by the heat storage material.

Advantageously, however, the U-shaped pipes may be passed through the pipe plate which separates the fire compartment from the heat storage section, in such a way that the base of the U extends through the fire compartment. In that case it will be possible for a heat transporting medium passed through the U-shaped pipes to absorb heat direct from the fire in the fire compartment in the base portion of the U.

The flue gas pipes in the device according to the invention preferably have an inside diameter in the order of 20-35 mm, the number of pipes is in the order of 40-60 per square metre of a plane crosssection through the heat storage section perpendicularto the axis ofthe pipes.

It will be clear that, instead of substantially straight pipes or U-shaped pipes for the discharge of the heat, pipes of other configuration may be used, for example, pipes extending through the heat storage section in a coil. Such pipes, however, are not prefer red, because they have a greater resistance to a transporting medium to be passed through them.

The device according to the invention may be built-in in a house or other building, but may also be installed in it as a loose unit. The device is extremely suitable for heating larger objects, such as green houses in market-gardens and the like. The term "fire compartment" as used herein should be given a broad interpretation. In particular, it is meant to include a compartment in which no fire is maintained, but to which hot flue gases are supplied, for example, from a combustion engine.

Some embodiments of the invention will now be described, by way of example, with reference to the accompanying drawings, in which Fig. 1 is a cross-sectional view, showing a first embodiment of the device according to the present invention; Fig. 2 is a cross-sectional view, showing a portion of a different embodiment of the device according to the invention; and Fig. 3 is a cross-sectional view, showing still another embodiment of the device according to the invention.

The embodiment of the device according to the invention shown in Fig. 1 comprises a furnace section 1, a heat storage section 2 disposed above the furnace section 1, and a stack section 3 disposed above the heat storage section 2. The entire apparatus may be disposed in, or built-in, in a house or other building to be heated. Naturally, it is also possible for the apparatus to be installed in a separate building, whence the heat from the apparatus is transported through conduits to a building to be heated or installation in which the heat is utilized.

The furnace section 1 comprises a fire compartment 4 in which a fire can be laid. The laying of the fire can be done in any suitable manner. Thus, for example, a solid fuel, such as wood, peat or coal can be used for the fire. It is also possible to install gas or oil burners in the fire compartment 4 for maintaining a fire therein. Fire compartment 4 is surrounded, in a manner conventional for furnaces, by walls 5 of, for example, brick or concrete, and provided with a floor 6 of similar material. The walls and floor may be lined on the inside with so-called firebrick. At the top, fire compartment 4 is bounded by a pipe plate 7, which separates furnace section 1 from heat storage section 2. Pipe plate 7 consists, for example, of steel and is, for example, 20 mm thick.The furnace section may be provided in a suitable manner with means to prevent that, if no fire is burning, there is a natural draft from the outside through the fire compartment to and through the heat storage section, such a natural draft being undesirable in connection with the resulting cooling of the heat storage section. Such means may take the form, for example, of a dosing valve in the furnace door, which valve may be automatic or hand-operated. If a fire burns in the furnace section, the supply of air is controlled through the dosing valve, so that optimal combustion with the greatest possible heat production is achieved. If the fire is extinguished, the valve should be closed to prevent any draft.

The heat storage section 2 has walls 8, for exam ple, of steel. Spaced some distance around walls 8 is an envelope 9 of a heat-insulating material, arranged to provide an air gap 10 between walls 8 and envelope 9. The heat storage section 2 is closed at the top by a pipe plate 11, which forms the bottom boundary of a pair of spaces 12 and 13. Spaces 12 and 13 are bounded at the top by a pipe plate 14, there being provided a wall 15 between pipe plates 1 7 and 14to separate space 12 from space 13. Pipe plates 11 and 14 and wall 15 consist, for example, of steel having a thickness of approximately 4-5 mm.

Fire compartment 4 is in communication with the header 16 of stack section 3 above pipe plate 14 by means of large number of pipes 17. Pipes 17 are secured at their bottom ends in orto pipe plate 7.

Being secured to may means, for example, being secured to pipe stubs secured to pipe plate 7 or forming part thereof. Pipes 17 are passed atthetop through pipe plate 11 and terminate in pipe plate 14 or are secured thereto. Through this construction flue gases may be discharged from fire compartment 4 through pipes 17 to header 16 of the stack section 3 and thence through stack 18 to the outside.

Pipes 17 are selected depending on the material with which furnace section 1 is fired. With most fuels, brass pipes will be satisfactory. When gas is used as the fuel, stainless steel pipes will be more suitable. The pipes have, for example, an inside diameter of 28 mm and a wall thickness of 2 mm.

The number of pipes used is relatively large. Thus, for example, with a heat storage section 2 having a horizontal cross-section of 0.7 x 1.5 metre, there may be 50 pipes.

In addition to pipes 17, a plurality of U-shaped pipes 19 are disposed within heat storage section 2.

U-shaped pipes 19 are secured with their ends in or to pipe plate 11 in such a manner that, of each U-shaped pipe 19, one end communicates with space 12 and the other end with space 13. In this manner spaces 12 and 13 are interconnected through U-shaped pipes 19. Just as pipes 17, pipes 19 may be made of brass or of stainless steel. The number of U-shaped pipes is preferably less than the number of pipes 17. With the above dimensions of the heat storage section 2, the number of U-shaped pipes 19 is, for example, 14.

Heat storage section 2 is filled virtually completely with sand 20 or another medium having good heat storage properties, for example, a suitable salt.

In operation, a fire is maintained in the fire compartment 4 of furnace section 1. The flue gases generated are discharged through pipes 17 to header 16 and thence through stack 18 to the outside. This is indicated in Fig. 1 by means of arrows. The initially hot flue gases give up their heat to the walls of pipes 17 and this heat is transferred through these walls to heat storage medium 20. When a relatively tall heat storage section 2 is used, with a height for example of approximately 5 metres, virtually all the heat from the flue gases is stored in heat storage medium 20.

In an embodiment of the device according to the invention having the dimensions given above by way of example and having the number of pipes indicated it was found, after very intensive stoking for more than four hours that the wall 16' of header 16 was just lukewarm. The heat storage medium 20, in this case sand, however, turned out to have a temperature of some hundreds of degrees Centigrade.

The heat stored in the heat storage section 2 is utilized as follows. A heat transporting medium is passed from space 12 through U-shaped pipes 19 to spaced 13 and thence discharged for further utilization. Suitably, air is used as the transporting medium. The air may be blown, for example, through pipes 19 by a fan or pump disposed in a supply line or supply aperture to space 12. Suitable conduits may be connected to space 13 forthe discharge of the air heated in pipes 19. The heated air may be used direct for heating purposes, for example, in a hot-air heating system. It is also possible to use the hot air for heating a different medium, for example, water in a heat exchanger, and to utilize such other medium for heating purposes or otherwise.Naturally, when a heat exchanger is used for the transfer of the absorbed heat, the heat transporting medium may be circulated in a closed circuit: from space 12 through pipes 19 to space 13 and thence through suitable conduits and the heat exchanger incorporated in them back to space 12. In such a case, the fan will be mounted in such a circuit.

Fig. 2 is a cross-sectional view, showing a portion of a different embodiment of the device according to the present invention. The parts corresponding to parts shown in Fig. 1 are designated by the same reference numerais. In the embodiment shown in Fig. 2, U-shaped pipes 19 are also passed through pipe 7, so that the base of the U If the pipes 19 is in fire compartment 4. In operation, in this embodiment, the transporting medium passed through pipes 19 is heated direct by the fire in fire compartment 4.

Fig. 3 shows still another embodiment of the device according to the invention in cross-section. In this embodiment the fire compartment 21 is bounded at the top by a heat storage section filled with heat storage material, e.g. sand. At the bottom and at the rear of fire compartment 21, too, there is a space filled with heat storage material. Extending through the heat storage section located above fire compartment 21 are the flue gas ducts, which are each built up from a plurality of tubes 22 of ceramic material. The tubes 22 of ceramic material are provided on one end with a broadened portion, which engages over the other end of an adjacent tube.

Heat-insulating rings 23 are provided between tubes 22 at the connecting point. As a result the tube do not transfer heat to each other, and the heat supplied by the flue gases from the fire compartment 21 is stored in the heat storage section rather layer-wise.

Tubes 22 consist for example of porcelain or other heat-resistant ceramic material with a wall thickness of 8-25 mm and an internal diameter of 2-15cm.

The flue gas ducts terminate above the heat storage section in a header 24, to which a stack 25 is connected.

The device is surrounded on all sides by a heatinsulating wall 26. Provided at the back is a space 28 between wall 26 and a heat-conducting or heatpermeable inner walk 27. Two gaps 29 and 30 give access to space 28 at the top and botton. In operation, owing to a convection effect, air will be drawn through gap 29 into space 28. In space 28, this air is heated. Through gap 30 the air escapes again. In this way a room adjoining the device can be heated. If desired, gaps 29 and 30 may be provided with closure means.

Arranged in the storage section are a plurality of brass or steel heat conductors in the form of rods 31.

Each of rods 31 extends in the storage section above fire compartment 21, continues through the storage section behind fire compartment 21 and extends into the storage section below fire compartment 21. In operation, thanks to the presence of rods 31 heat is rapidly transported to the storage section above fire compartment 21. If subsequently the fire in fire compartment 21 is extinguished, heat can be dissipated from the storage section behind and below the fire compartment through the fire compartment. As a consequence, these portions would give up the heat stored fasterthan the storage section above the fire compartment. Owing to the presence of rods 31, however, heat is transported from above downwardly.

The fire compartment 21 may be closed at the front by a glass door 32, in which case air supply apertures will be provided for maintaining the fire in fire compartment 21. The fire compartment 21 may also, however, be constructed as the fire compartment of the o pen-fu mace type.

Claims

1. In a heating device comprising a fire compartment in which a fire can be maintained, and a stack spaced from said fire compartment, with a plurality of relatively long ducts for flue gases between said fire compartment and said stack, the ducts and optionally the fire compartment being surrounded by a heat storage material, and means being provided for the discharge of heat from the heat storage material, the improvement which comprises that the flue gas ducts are substantially straight ducts, and the means for the discharge of heat stored in the heat storage material consist of a plurality of pipes or conduits extending through or along the heat storage material between a first compartment to which a heattransporting medium can be supplied, and a second compartment, from which the heat transporting medium can be discharged after passing the pipes or conduits.

2. A device as claimed in claim 1, characterized in that the flue gas ducts are each built up from a plurality of ceramic tubes fitting one in the other, and insulated relatively to each other to prevent the transfer of heat between adjacent tubes.

3. A device as claimed in claim 2, characterized in that the ceramic tubes are provided on the inside with a coating of glaze.

4. A device as claimed in claims 1-3, characterized by the provision of a compartment filled with heat storage material under and/or next to the fire compartment, and a plurality of heat conducting rods which on one end extend into the heat storage material under and/or next to the fire compartment, and at the other end extend into the heat storage material surrounding the ducts for the flue gases.

5. A heating device as claimed in claims 1-4, characterized in that the first and the second compartment are disposed between two spaced pipe plates, the first pipe plate forming the separation between the heat storage section and the compartments, and the second pipe plate forming the separation between the compartments and the stack, the compartments being separated from each other by a wall extending from the first pipe plate to the second pipe plate, the pipes for the discharge of the stored heat having a U-shape, and being secured with both ends in or to said first pipe plate with one end being connected to the first compartment and the other end being connected to the second compartment, the flue gas ducts extending through said first pipe plate and through one of the two compartments, and being secured in orto the second pipe plate, thereby communicating with the stack.

6. A heating device as claimed in claim 5, characterized in that the U-shaped pipes extend fully within the heat storage section and are surrounded by the heat storage material.

7. A heating device as claimed in claim 5, characterized in that the U-shaped pipes are passed through the pipe plate which separates the fire compartment from the heat storage section, in such a way that the base of the U extends through the fire compartment.

8. A heating device as claimed in claims 1-7, characterized in that the flue gas pipes have an inside diameter in the order of 20-35 mm, and the number of pipes is in the order of 40-60 per square metre of a plane cross-section through the heat storage section perpendicular to the axis ofthe pipes.

9. A heating device substantially as described herein with reference to any one of Figs. 1-3 of the accompanying drawings.

10. The features as herein described, or their equivalents, in any novel selection.