Heating boiler

The invention relates to a heating boiler according to the preamble in claim 1.

In state-of-the-art heating boilers, warm air generated by the burner and flue gases are led directly upwards to the duct and through it out of the building to be heated. The efficiency of the heating boiler depends on the size of the burner and on the inner surface area of the heating boiler, which is heated by the flue gases. For example, the inner surface area of oil vessels used in the heating of detached houses is in the range of 1.5 - 2 m ² . The flue gas temperature of these kinds of heating boilers in the chimney is typically in the range of approximately 1000 ⁰ C. As a consequence, a very considerable part of thermal energy, which is generated by the burner and which could be used for heating the building, exits through the chimney.

In the publication DE 361329 there is known a solution, in which flue gases are circulated from the combustion chamber with an open upper section to below the combustion chamber. In this solution, the transfer of flue gases occurs all the way to the duct along a channel, the cross-section of which is essentially of the same size.

The purpose of the invention is to increase the efficiency of the heating boiler so that a bigger part of the thermal energy generated by the burner can be used for heating a building.

According to the invention, this purpose can be achieved by circulating hot flue gases inside the heating boiler so that thermal energy has more time to better transfer to the structures of the heating boiler and can thus be used for heating the building. At the same time, it is possible to burn the burner with a hotter flame, in order to make the combustion transaction more efficient.

In addition, when the burner is used with hotter capacity, it is possible to take service water from the boiler's water circulation near the combustion chamber, the temperature of the water being then considerably high.

More specifically, the heating boiler of the invention is characterised in what is disclosed in the characterising part of claim 1.

The invention is next described in more detail referring to the enclosed drawing, illustrating a cross-section of the heating boiler of the invention.

The combustion chamber 2 of the heating boiler 1 comprises the burner 3. This burner 3 can be an oil or gas burner. From the combustion chamber 2, flue gases are led out advantageously through the opening 4 on the lower section of the combustion chamber to the channel 5 and upwards to the expanded space 7 above the com- bustion chamber, as is illustrated with the arrow 6. The opening 4 from the combustion chamber 2 to the channel 5 can also be placed to an upper position in the combustion chamber, even to the upper edge or roof of the combustion chamber, but the circulation of flue gases is best/most efficiently achieved through an opening in the lower section. The space 7 above the combustion chamber has one or several struc- tures 8 essentially transverse to the direction of flow of the flue gases, the purpose of the structures being to intensify the turbulent flow of the flue gases and, on the other hand, to partly absorb part of the thermal energy of the flue gases for heating purposes. The structure(s) 8 mixing the flow of the flue gases can be solid, but water circulation is preferably arranged inside them so that it is possible to efficiently transfer thermal energy away from the said structures 8. The cross-section of the space 7 above the combustion chamber 2 is preferably slightly enlarged in the direction of flow of the flue gases so that the mixing of the flue gases would be more efficient. The space 7 acts as a so-called expansion chamber for hot flue gases. The essentially transverse structures 8 in the space 7 above the combustion chamber 2 are preferably located so that flue gases can circle the structures both from above and below (if the structures are installed vertically, the circulation occurs respectively from right and left). On the other hand, their arrangement can be relatively free and, for example, the first structure 8 can be placed to the upper edge of the space 7 and the second structure to the lower section of the space 7 slightly later in the direction of flow (or respectively, to the right and left edge). Also other similar variations are possible. Further, it has not been restricted that the structures 8 would only be located in the space 7 of the channel 5, but they can be freely placed also elsewhere in the flue gas exhaust channel 5.

From the space 7 above the combustion chamber 2, flue gases are led downwards to the space 9 below the combustion chamber 2. From the space 9, flue gases are further led up to the duct from the side of the combustion chamber (not shown in the figure).

The combustion chamber 2 of the heating boiler 1 according to the invention can have relatively different dimensions. At its smallest, the size of the combustion chamber 2 is approximately 30 cm * 30 cm, and at its largest, in the heating of big buildings, the size of the combustion chamber can be even as much as 120 cm * 120

cm. Naturally, the size of the burner 3 to be used has to be selected correspondingly. In state-of-the-art boilers, the temperature of the burner flame is approximately 800 ⁰ C, while in the solution of the invention the burner can be adjusted (by increasing the amount of air) so that the burner flame is over 1200 ⁰ C. This is possible, because the structure of the heating boiler 1 generates sufficient counter pressure to the burner 3 and makes possible the use of the burner with a higher output. The use of the burner 3 with a higher output produces sufficient pressure in the combustion chamber 2 so that flue gases exit even through the opening 4 in the lower section of the combustion chamber. In state-of-the-art solutions, the pressure provided by the burner is not sufficient for this purpose. Because of the higher output, it is not necessary to drive the burner 3 for as long as in the state-of-the-art heating boilers, which saves fuel. A hotter flame also produces a cleaner combustion transaction so that the need to clean/service the heating boiler 1 is reduced.

By circulating flue gases inside the heating boiler 1 spirally as is described above, the temperature of flue gases in the duct can be considerably reduced from the state- of-the-art temperature, which can be even 1000 ⁰ C.

Transferring heat from the structures of the heating boiler 1 further to be used for heating buildings can be advantageously intensified by water circulation arranged inside the structure, which efficiently cools the spiral structure of the boiler and transfers heat to efficient use (not shown in the figure). In this case, a duct temperature of even less than 50 ⁰ C can be achieved in favourable circumstances. Another alternative is to provide air circulation inside the structure, with which it is also possible to efficiently transfer heat to efficient use.

Warm water can be advantageously withdrawn from the water circulation of the heating boiler 1 to efficient use by arranging the water take-off at the wall of the combustion chamber 2 in the heating boiler (not shown in the figure). In this case, water can be even in the form of vapour (approximately 140 ⁰ C) when it comes out. By choosing the water take-off point in an advantageous way, hot water of approximately 90 - 95 ⁰ C can be taken from the water circulation.

It is further preferable to arrange a flap to the upper end of the duct (to the chimney outlet), which is opened by means of pressure generated by the burner 3 and closed again by means of gravity as the burner stops. Compared with a state-of-the-art heating boiler, which uses as small a burner as possible and transfers flue gases directly to the duct, possibly a slightly more efficient burner 3 has to be used in the solution according to the invention. This is a consequence of that the pressure drag

caused by the spiral structure is slightly bigger than in the state-of-the-art solution, so that in order to ensure the operation of the heating boiler 1, the burner 3 possibly has to have a slightly higher output, providing sufficient blow/pressure to remove the flue gases.

With the above-described spiral structure of the heating boiler 1 the area of the heating boiler can be increased, by means of which thermal energy generated by the burner can be recovered. The increase is from 1.5 - 2 m ² of the state-of-the art heating boilers to approximately 5 m ² . In this example, the size of the combustion chamber is in the range of 40 cm * 40 cm. In addition to this, the water circulation arranged inside the boiler structure increases the recovery of thermal energy.

It has been managed to reduce the consumption of fuel (oil) used, for example, for heating a detached house of approximately 360 m ² (~ 800 m ³ ) from 8 - 10 m ³ to less than 2 m ³ . This means a rather significant saving of 70 - 80 % in the annual heating costs. At the same time, the heating boiler of the invention runs so cleanly that it is actually not necessary to service or clean it. Only the nozzle of the burner as a wearing part has to be replaced from time to time.