FIELD OF THE INVENTION

[0001 ] The present invention relates to a fireplace in the form of a convection oven which provides for low emission of carbon monoxide and particulate matter combined with effective heating by convection.

BACKGROUND OF THE INVENTION

[0002] Fireplaces such as small heating systems, also termed as small combustion systems, heating systems for single rooms such as wood-burning stoves, tile stoves, cookers and opened fireplaces which are operated with solid fuel such as wood or wood pellets may often be found in private households. Governmental regulations require reduced emissions. E.g., respective regulations of the Federal Republic of Germany specify for heating systems for single rooms an emission of carbon monoxide below 1250 mg/Nm ³ (13 % 0 ₂ ) and for particulate matter below 40 mg/Nm ³ (13 % 0 ₂ ) (1 . BlmSchV II).

[0003] The heating principle of a fireplace may be based mainly on heat radiation or on convection, and/or a combination of both.

[0004] EP 0 231 424 (filing date: 03.06.1986) discloses a fireplace the heating principle thereof is in essential based on convection. This fireplace has a horizontal cylindrical body enclosing a combustion chamber, wherein the sidewalls thereof consist of curved pipes. Accordingly, the respectively formed inner surface of the combustion chamber is corrugated, thus enlarging the area of said inner surface compared to a respective smooth surface. Said curved pipes have an opening at the lower end, and an opening at the upper end, respectively. During operation, said curved pipes are heated up by the combustible burning in the combustion chamber. Due to the corrugated inner surface resulting in said comparatively enlarged surface, air being in the pipes is heated up outstandingly fast and steadily, and is also fast and steadily discharged via the upper opening, whereas colder air from the environment is aspirated via the opening at the lower end due to convection. This in turn provides for very effective recirculation of the environmental air contained e.g. in a house through said air channels, wherein the recirculating air of the environment is outstandingly fast and steadily heated up.

[0005] It is believed in the art that an essential prerequisite for the efficacy of said fireplace disclosed in this prior art is that the pipes have to be configured to form a corrugated inner surface of the combustion chamber having an enlarged area compared to a smooth surface, and have to be directly heated by the burning combustible, i.e. the pipes have to be in direct contact with fire in order to most effectively provide for said characteristic up-heating.

[0006] The fireplace known from EP 0 231 424 since the end of the 1980s was and is still very successfully in the market. Market participants have presented variations of this fireplace, however, not deviating from the above-addressed principle of up-heating the pipes in terms of the enlarged area and the direct heating by combustible. It is established believe in the art that a deviation from said principle would negatively affect the unique properties of said fireplace in terms of said outstandingly fast and steady heating up of environment.

[0007] EP 2 455 666 discloses a fireplace having a horizontal cylindrical body enclosing a combustion chamber. The outside cladding of this fireplace comprises air channels providing for convection. However, the air channels of the fireplace disclosed in EP 2 455 666 are not part of the combustion chamber, and therefore do not enlarge the heat transmitting steel surface of the combustion chamber. Moreover, the combustion chamber of this fireplace is lined with refractory fireclay. Thus, additionally to the non- enlarged area and hence reduced capacity to direct heat to the environment such as a house, the air channels cannot be directly heated up by the burning combustible. It is believed in the art that these properties are responsible for the observed less effective convection compared to the fireplace disclosed in EP 0 231 424.

[0008] However, the fireplace disclosed in EP 2 455 666 provides for low emission. It is believed in the art that this low emission is due to a probably higher temperature which may be reached in the combustion chamber due to said lining with refractory material, which has a low thermal conductivity, compared to a combustion chamber which is free from a lining with refractory material. Accordingly, the higher temperature may support a more complete burning of combustible. OBJECTS OF THE INVENTION

[0009] In view of the ongoing need for reducing emission of fireplaces such as small heating systems, in particular in view of the ongoing need for efforts to reduce the emission of the fireplace disclosed in EP 0 231 424, it was the object of the invention to provide a fireplace mainly based on convection which provides for low emission without significantly negatively affecting the characteristic of a fast and steady up-heating of the pipes in order to ensure fast and comprehensive occurrence of convection.

SUMMARY OF THE INVENTION

[0010] This object was achieved with a fireplace as defined in claim 1 . Preferred embodiments are defined in the claims depending thereon.

[001 1 ] Contrary to expectation that the reduced thermal conductivity of a refractory material might prevent the air channels from a fast and steady heating up that would ensure outstanding fast and steady occurrence of recirculation of environmental air through said air channels, the inventors unexpectedly observed that the air channels despite being at least partially lined with said refractory material, are heated up nearly as fast as the air channels in the fireplace being free from a refractory material, and reached almost the same steady heat output as the fireplace disclosed in EP 0 231 424. Thus, with the fireplace according to the invention, still outstandingly fast and effective recirculation of the environmental air through the air channels is achieved. Contrary to expectation in view of the established believe in the art that the fireplace would lose its unique characteristic of an outstandingly fast and steady heating up of recirculating air when deviating from the addressed principle, the fireplace according to the invention maintains unique characteristics in terms of a heat output nearly as high as the heat output achieved with the fireplace disclosed in EP 0 231 424 despite an at least partial lining with a refractory material. Moreover, this effective recirculation of environmental air through said air channels is now beneficially connected with a significantly reduced emission compared to the oven disclosed in EP 0 231 424. [001 2] Moreover, the inventors discovered that it is no longer required to necessarily provide the air channels in the form of pipes as disclosed in the prior art in order to achieve a high heat output, but that the air channels may be formed e.g. as extending recesses in the outer surface of the combustion chamber, provided the inner surface is at least partially corrugated. In one embodiment, the outer surface of the combustion chamber may be even a smooth surface, which functions as air channel, provided the inner surface is at least partially corrugated.

[001 3] The construction of the fireplace according to the invention is based on a paradigm change of the hitherto long-lasting believe in the art that air channels in the form of pipeshave to be directly heated up by burning combustible in order to provide for outstandingly fast and steady occurrence of recirculation of environmental air, to the discovery that air channels forming at least partially a corrugated inner surface of a combustion chamber may at least be partially lined with a refractory material, thus reducing the area which can be contacted by burning combustible, however without significantly negatively affecting outstandingly fast and steady occurrence of recirculation of environmental air through said air channels.

[0014] This finding is connected with a beneficial reduced emission. The resulting technical effect of a reduced emission without losing a significant portion of the characteristic heat distribution benefitting from the convection effect could not be foreseen in view of the hitherto understanding as disclosed in the prior art, and the hitherto constructions of convection ovens in which air channels providing for a comparatively enlarged area of the inner surface of a combustion chamber are configured to be directly heated up by the burning combustible.

[001 5] The fireplace according to the invention allows reducing the emission of carbon monoxide and particulate matter to values below 1250 mg/Nm ³ (13 % 0 ₂ ) carbon monoxide and 40 mg/Nm ³ (13 % 0 ₂ ) particulate matter.

[001 6] The term "Nm ³ " encompasses the term "dry standard cubic meter", which term is synonymously used to the terms "normal cubic meter" or "standard cubic meter". The term "particulate matter" (all terms in quotation marks are used in the meaning of the invention) is synonymously used with the term "dust or "fine dusf. This particulate matter is generated when combustible in a fireplace is not completely combusted to gaseous products.

[001 7] The invention relates to the following items:

1 . Fireplace, at least comprising: a combustion chamber comprising at least two compartments which are arranged one upon the other; wherein the lower and the upper compartment of said at least two compartments are separated by means of a baffle leaving an opening which connects the lower compartment to the upper compartment; or wherein the lower and the upper compartment of said at least two compartments are separated by means of several baffles, which are arranged one upon the other leaving an opening, respectively, which connect the lower compartment to the upper compartment;

wherein said at least two compartments are at least partially formed by air channels, which are opened at their lower and their upper ends, respectively, and wherein the inner surface of the combustion chamber formed by said air channels is corrugated; wherein at least a portion of said lower compartment of said combustion chamber comprises a lining with a refractory material, preferably wherein the portion of the air channels forming said lower compartment of said combustion chamber is at least partially lined with a refractory material.

2. Fireplace of item 1 , comprising: comprising two compartments which are arranged one upon the other, and wherein the lower and the upper compartment are separated by means of one baffle leaving one opening which connects the lower compartment to the upper compartment; or comprising three compartments which are arranged one upon the other, wherein the lower and the middle compartment are separated by means of one baffle leaving one opening which connects the lower compartment to the middle compartment; and wherein the middle and the upper compartment are separated by means of one further baffle leaving one further opening which connects the middle compartment to the upper compartment. Fireplace of item 1 or 2, comprising a further compartment, which is connected to said upper compartment; preferably wherein the further compartment accommodates a damper flap. Fireplace of any one of the preceding items, wherein the corrugated inner surface of the lower compartment of combustion chamber or the air channels forming said lower compartment is not in physical contact with said lining with a refractory material; or wherein at least a portion of the corrugated inner surface of the lower compartment of the combustion chamber or a portion of the air channels forming said lower compartment is in physical contact with said lining with a refractory material. Fireplace of any one of the preceding items, wherein a portion of the lower compartment or a portion of the air channels forming said lower compartment is configured to support combustible, wherein said portion is not lined with a refractory material. Fireplace of item 5, wherein a portion of the lower compartment or a portion of the air channels forming said lower compartment which is configured to support combustible is in the form of a grid; preferably wherein an ash pan is arranged under the grid. Fireplace of any one of items 1 to 6, wherein the lower compartment comprises a rear wall which comprises a lining with a refractory material. Fireplace of any one of the preceding items, wherein at least a portion of the upper compartment comprises a lining with a refractory material. Fireplace of any one of the preceding items, wherein said at least one baffle consists of a refractory material; or is lined with a refractory material. Fireplace of any one of the preceding items, wherein said refractory material of said lining is selected from the group consisting of ceramics, fire proof ceramics, chamotte (fireclay) or refractory concrete; or metal, preferably steel or cast iron; or a combination of two or more thereof; preferably wherein said refractory material is vermiculite. Fireplace of any one of the preceding items, wherein said further compartment is bent upwards or is straight; preferably wherein said further compartment is a pipe. Fireplace of any one of the preceding items, wherein the combustion chamber comprises one aerating means or comprising at least two different aerating means. Fireplace of any one of the preceding items, wherein the combustion chamber is a cylindrical combustion chamber which is positioned horizontally. Fireplace of any one of the preceding items, wherein the air channels extend in a plane, respectively, which is positioned in a vertical direction. Fireplace of any one of the preceding items, at least comprising:

a housing enclosing a combustion chamber, wherein said housing at least comprises: a front wall, which at least partially is construed as door, the door being configured to allow supplying said combustion chamber with combustible, respectively allowing removing ashes from the combustion chamber; one or more side wall/walls;

a rear wall; at least one outlet for gas that is formed when operating the fireplace while burning a combustible in said combustion chamber, preferably wherein said outlet is located in the rear wall or the one or more side walls of the housing; wherein the one or more side wall/walls form a horizontal cylindrical body such that also the combustion chamber has a cylindrical body, wherein the combustion chamber comprises at least a lower and an upper compartment which are arranged one upon the other, and wherein the lower and the upper compartment are separated by means of one baffle leaving one opening which connects the lower compartment to the upper compartment; or

a lower and an upper compartment which are arranged one upon the other, and wherein the lower and the upper compartment are separated by means of more than one baffle, which are arranged one upon the other leaving one opening, respectively, which connect the lower compartment to the upper compartment; wherein the lower compartment is configured to support and burn the combustible, the at least one baffle is configured to direct gases formed in the lower compartment when operating the fireplace via said at least one opening to the upper compartment, and the upper compartment is configured to direct the gas to the outlet, the outlet being configured to discharge said gas from said combustion chamber; preferably wherein said gas is directed via a further compartment which accommodates a damper flap, wherein said further compartment is connected to said outlet; wherein said one or more side walls consists/consist at least partially of air channels in the form of curved pipes, which are opened at their lower ends and their upper ends, respectively, and wherein the inner surface of the combustion chamber formed by said air channels is corrugated; wherein the air channels in the form of curved pipes are configured to be heated up when operating said fireplace, wherein a lower opening of the pipes is configured to aspirate air from the environment of the fireplace, and wherein an upper opening of the pipes is configured to discharge the aspirated and heated air into the environment; and

wherein at least a portion of said lower compartment of combustion chamber comprises a lining with a refractory material being configured to prevent said portion of the air channels in the form of pipes to be contacted by fire of the burning combustible when operating the fireplace, preferably wherein the portion of the air channels forming said lower compartment of said combustion chamber is at least partially lined with a refractory material being configured to prevent said portion of the air channels in the form of curved pipes to be contacted by fire of the burning combustible when operating the fireplace. [001 8] In another aspect, the invention relates to the following item:

16. Fireplace, at least comprising:

a combustion chamber comprising: at least a first and a second compartment, which are arranged one after another; wherein the first and the second compartment are separated by means of one baffle leaving one opening which connects the first compartment to the second compartment; or wherein the first and the second compartment are separated by means of more than one baffle, which are arranged one after another leaving one opening, respectively, which connect the first compartment to the second compartment;

wherein said at least two compartments are at least partially formed by air channels, which are opened at their lower and their upper ends, respectively, and wherein the inner surface of the combustion chamber formed by said air channels is corrugated; wherein at least a portion of said first compartment of the combustion chamber comprises a lining with a refractory material, preferably wherein the portion of the air channels forming said first compartment of said combustion chamber comprises at least partially a lining with a refractory material.

[001 9] In another aspect, the invention relates to the following item:

17. Use of a corrugated inner surface in a combustion chamber of a fireplace for enhancing convection at the outer surface of said combustion chamber or said fireplace, wherein said corrugated inner surface is at least partially lined with a refractory material; or

Method of enhancing convection at the outer surface of a combustion chamber, which comprises said outer surface and an inner surface, or of a fireplace comprising said combustion chamber, comprising step (X):

(X) providing at least a portion of said inner surface with a corrugated surface, wherein said corrugated inner surface is at least partially lined with a refractory material. FIGURES

[0020] In the figures show

Fig. 1 a longitudinal section of a combustion chamber comprising a lower and an upper compartment of a preferred fireplace according to the invention;

Fig. 2 a longitudinal section of a combustion chamber of Fig. 1 including a further compartment accommodating a damper flap;

Fig. 3 a longitudinal section of a combustion chamber comprising a lower, a middle and an upper compartment of a preferred fireplace according to the invention.

Fig. 4 a longitudinal section of a combustion chamber of Fig. 3 including a further compartment accommodating a damper flap;

Fig. 5 a cross section of a combustion chamber of a fireplace according to the invention;

Fig. 6 a front view of a fireplace according to the invention;

Fig. 7 a side view of a fireplace according to the invention;

Fig. 8 a front view of a cross section of a fireplace according to the invention;

Fig. 9 a perspective view of a part of cross section of a fireplace according to the invention;

Fig. 10 to 19 a top view on a cross section along a horizontal plane of a fireplace according to the invention, respectively the combustion chamber of a fireplace according to the invention.

DETAILED DESCRIPTION OF THE INVENTION

[0021 ] The invention relates to a fireplace at least comprising: a combustion chamber, comprising at least two compartments which are arranged one upon the other, and wherein the lower and the upper compartment of said at least two compartments are separated by means a baffle leaving an opening which connects the lower compartment to the upper compartment; or

wherein the lower and the upper compartment of said at least two compartments are separated by means of several baffles, which are arranged one upon the other leaving an opening, respectively, which connect the lower compartment to the upper compartment; wherein said at least two compartments are at least partially formed by air channels, which are opened at their lower and their upper ends, respectively, and wherein the inner surface of the combustion chamber formed by said air channels is corrugated;

wherein at least a portion of said lower compartment of said combustion chamber comprises a lining with a refractory material, preferably wherein the portion of the air channels forming said lower compartment of said combustion chamber is at least partially lined with a refractory material.

[0022] The term "fireplace" encompasses an architectural structure designed to contain fire. In its broadest meaning, the term encompasses any heating system which may be operated by means of combusting a combustible. Accordingly, the term "fireplace" encompasses terms such as "oven", "furnace" or "stove". In a preferred embodiment, said fireplace encompasses a heating system that is used in a private household, preferably a small heating system. In a preferred embodiment, said heating system provides for a power of from 5 to 15 kW, preferably of from 5 to 10 kW, more preferably 6 to 8 kW. In a further embodiment, said fireplace may provide for a power up to 50 kW.

[0023] The fireplace according to the invention comprises a housing.

[0024] The term "housing" encompasses a hard or stable casing or mantle which encloses a combustion chamber.

[0025] The term "combustion chamber" encompasses the location in which the combustible is supported and combusted. [0026] The term "combustible" encompasses any solid fuel such as wood, wood pellets, or carbon such as coal or brown coal. In a preferred embodiment, the combustible is a solid fuel comprising wood or is wood such as wood billets or wood pellets.

[0027] Said housing of the fireplace according to the invention comprises at least a front wall, which at least partially is construed as door through which said combustion chamber may be supplied with combustible, respectively through which ashes may be removed from the combustion chamber.

[0028] The term "door"' encompasses the term "furnace door"' or "fireplace door".

[0029] The housing of the fireplace according to the invention further comprises a rear wall.

[0030] Said housing further comprises one or more side wall/walls. The term "one or more side wall/walls" encompasses all parts of the housing which are different from the front wall and the rear wall.

[0031 ] According to the invention, said front wall, said one or more side wall/walls and said rear wall form the combustion chamber. Preferably, said walls forming the combustion chamber are made from cast iron or from steel.

[0032] Said door of said front wall may also consist of or may comprise cast iron or steel. In a preferred embodiment, said door of said front wall may be construed in the form of glass such that the combustion of said combustible may be monitored.

[0033] The fireplace according to the invention also comprises an outlet for smoke gas which is generated when combustible is combusted in the combustion chamber.

[0034] The term "outlet' encompasses the portion of the fireplace through which said smoke gas may exit said fireplace. Preferably, said outlet is positioned in the rear wall of said housing. However, said outlet may also be positioned in the one or more side walls (including a top wall). Preferably, said outlet is connected to a chimney.

[0035] The term "smoke gas" is synonymously used with terms such as "flue" or "exhaust' or "exhaust gas".

[0036] The term "compartment' encompasses any space or spatiality. [0037] The term "portion of the air channels forming said lower compartment' means that the portion of the wall of the combustion chamber formed by said air channels consists of said air channels.

[0038] The term "inner surface of the combustion chamber formed by said air channels is corrugated' encompasses any surface which is not smooth, i.e. which comprises recesses and protrusions.

[0039] In one embodiment, the invention relates to a fireplace at least comprising:

a combustion chamber configured to support and burn combustible, wherein the combustion chamber comprises at least two compartments, wherein the lower compartment of said at least two compartments is configured to accommodate and burn said combustible, and the upper compartment of said at least two compartments is configured to direct gas to an outlet when operating the fireplace; wherein the lower and the upper compartment are separated by means of a baffle leaving an opening which connects the lower compartment to the upper compartment; or wherein the lower and the upper compartment are separated by means of several baffles which are arranged one upon the other leaving an opening, respectively, which connect the lower compartment to the upper compartment; wherein said at least one baffle is configured to direct gas from the lower compartment through said at least one opening to the upper compartment;

wherein said at least two compartments are at least partially formed by air channels, which are opened at their lower and their upper ends, respectively; wherein said air channels are configured to be heated up when operating the fireplace, wherein a lower opening of the air channels is configured to aspirate air from the environment of the fireplace, and wherein an upper opening of the air channels is configured to discharge the aspirated and heated air into the environment; wherein the inner surface of the combustion chamber formed by said air channels is corrugated; and

wherein at least a portion of said lower compartment of said combustion chamber comprises a lining with a refractory material being configured to prevent said portion to be contacted by fire of the burning combustible, preferably wherein the portion of the air channels forming said lower compartment of said combustion chamber is at least partially lined with a refractory material which is configured to prevent said portion of the air channels to be contacted by fire of the burning combustible when operating the fireplace.

[0040] In one embodiment, the fireplace comprises two compartments which are arranged one upon the other, and wherein the lower and the upper compartment are separated by means of one baffle leaving one opening which connects the lower compartment to the upper compartment.

[0041 ] In another embodiment, the fireplace comprises three compartments which are arranged one upon the other, wherein the lower and the middle compartment are separated by means of one baffle leaving an opening which connects the lower compartment to the middle compartment; and wherein the middle and the upper compartment are separated by means of one further baffle leaving one opening which connects the middle compartment to the upper compartment.

[0042] Preferably, said openings are alternatedly arranged. This allows the smoke gas to pass an extended distance before it reaches the outlet. Thus, the probability of combustion of combustible in the combustion chamber being as complete as possible is increased. This further supports a reduced emission.

[0043] In a further embodiment, two further compartments are arranged between the lower and the upper compartments, wherein adjacent compartments are separated by one baffle leaving one opening, respectively.

[0044] If desired, more than two further compartments may be arranged between the lower and the upper compartment, wherein adjacent compartments are separated by one baffle leaving one opening, respectively.

[0045] In a further embodiment, a compartment may be formed of or may comprise at least two sub-compartments, which are arranged one after the other, and which are separated by means of a baffle, respectively. Preferably, these baffles are then arranged in a vertical position. Contrary to this, the one or more baffles separating the at least lower and upper compartment are arranged in a horizontal direction. [0046] The upper compartment is configured to direct said formed gas to an outlet which in turn is configured to discharge said gas from said combustion chamber.

[0047] In one embodiment, the fireplace comprises a further compartment, which is connected to said upper compartment. Preferably, said further compartment accommodates a damper flap.

[0048] Accordingly, said outlet is configured to discharge said gas into said further compartment. Said further compartment is configured to direct said gas to a chimney.

[0049] In one embodiment, said further compartment is bent upwards or is straight.

[0050] In one embodiment, said further compartment is a pipe bent upwards or is a straight pipe.

[0051 ] In a preferred embodiment, said further compartment accommodates a damper flap. Said damper flap is configured to allow further control of the intensity of the combustion. By an appropriate opening or closing of the flap in the further compartment, the gas flow in the fireplace according to the invention may be controlled and adjusted. In an opened position, the intensity of combustion may be increased.

[0052] In turn, by means of said damper flap in the further compartment, a further reduction of emission is supported.

[0053] In one embodiment, a portion of the lower compartment or a portion of the air channels forming said lower compartment is configured to support and burn combustible, wherein said portion is not lined with a refractory material, preferably is not lined with a ceramic or a fire proof ceramic such as vermiculite.

[0054] In one embodiment, the lower compartment is lined with vermiculite, wherein the portion of the lower compartment or a portion of the air channels forming said lower compartment and which is configured to support and burn combustible, is lined with cast iron or steel.

[0055] In one embodiment, said portion of the lower compartment of the air channels forming said lower compartment which is configured to support combustible is in the form of a grid. [0056] Said grid is configured to direct formed ashes downwards when burning combustible.

[0057] Preferably, then an ash pan is arranged under the grid. The ash pan is configured to accommodate ashes.

[0058] In one embodiment, the lower compartment is lined with a refractory material.

[0059] In one embodiment, also the portion of the pipes configured to support and burn combustible is lined with a refractory material.

[0060] In a preferred embodiment, also the rear wall of the lower compartment is lined with a refractory material.

[0061 ] In one embodiment, air channels forming said upper compartment are at least partially lined or completely lined with a refractory material.

[0062] In one embodiment, it is preferred that said air channels of the upper compartment are not completely lined with a refractory material.

[0063] In one embodiment, said at least one baffle consists of a refractory material; or is lined with a refractory material.

[0064] The term "refractory material' encompasses any material which is not destroyed when operating the fireplace, i.e. when combusting combustible. In one embodiment, said refractory material is not destroyed or negatively affected under a temperature of up to at least 700 °C. Refractory materials commonly used in fireplace technology may be used.

[0065] The term "lining with a refractory materia!' is used synonymously with the term "fireplace lining" or "combustion lining" as commonly used in the art.

[0066] Preferably, said refractory material is selected from the group consisting of ceramics, fire proof ceramics, chamotte (fireclay) or refractory concrete; or metal, preferably steel or cast iron; or a combination of two or more thereof; preferably wherein said refractory material is vermiculite. [0067] In one embodiment, the corrugated inner surface of the lower compartment of combustion chamber is not in physical contact with said lining with a refractory material.

[0068] In another embodiment, at least a portion of the corrugated inner surface of the lower compartment of combustion chamber is in physical contact with said lining with a refractory material.

[0069] In one embodiment, when at least a portion of the corrugated inner surface of the lower compartment of combustion chamber is in physical contact with said lining with a refractory material, the corrugated inner surface is in form-fitted contact with said lining with a refractory material.

[0070] In one embodiment, when at least a portion of the corrugated inner surface of the lower compartment of combustion chamber is in physical contact with said lining with a refractory material, the corrugated inner surface is in partial contact with said lining with a refractory material.

[0071 ] In one embodiment, when the air channels forming said lower compartment are at least partially lined with a refractory material or comprise a lining with a refractory material, the corrugated inner surface formed by said air channels is not in physical contact with said lining with a refractory material; or at least a portion of the corrugated inner surface is in physical contact with said lining with a refractory material, wherein the corrugated inner surface is in form-fitted contact with said lining with a refractory material, or the corrugated inner surface is in partial contact with said lining with a refractory material.

[0072] In a preferred embodiment, the combustion chamber is a cylindrical combustion chamber which is positioned horizontally.

[0073] Preferably, the air channels extend in a plane, respectively, which is positioned in a vertical direction or in a substantial vertical position.

[0074] The term "substantial vertical position" allows a deviation from the vertical position, i.e. the air channels may extend in a a plane which may also be arranged in an inclined position.

[0075] Further preferably, the air channels are arranged one after another. [0076] The air channels may have any conceivable form provided they form at least a portion of the inner surface of the combustion chamber such that said inner surface is provided in a corrugated form, or wherein the inner surface is provided in a corrugated form. In one embodiment, the air channels are extending recesses of the outer wall of the combustion chamber.

[0077] Preferably, said channels are in the form of pipes. The cross section of said pipes may be in the form of a triangle, a square, a rectangle or a circle, or any shape.

[0078] In one embodiment, the one or more pipes are construed such to form a double wall in which the inner surface is at least partially corrugated. Accordingly, within said double wall, air from the environment of said fireplace may be heated up by thermal convection and is recirculated.

[0079] In one embodiment, the air channels are simply the outer surface of the combustion chamber, which even may be a smooth surface, provided the inner surface is at least partially corrugated. Preferably, said corrugation is achieved by fins which protrude into the combustion chamber.

[0080] In one embodiment, the invention relates to a fireplace, at least comprising:

a housing enclosing a combustion chamber, wherein said housing at least comprises: a front wall, which at least partially is construed as door, the door being configured to allow supplying said combustion chamber with combustible, respectively allowing removing ashes from the combustion chamber; one or more side wall/walls;

a rear wall; at least one outlet for gas that is formed when operating the fireplace while burning a combustible in said combustion chamber, preferably wherein said outlet is located in the rear wall or the one or more side wall/walls of the housing; wherein the one or more side wall/walls form a horizontal cylindrical body such that also the combustion chamber has a cylindrical body, wherein the combustion chamber comprises at least a lower and an upper compartment which are arranged one upon the other, and wherein the lower and the upper compartment are separated by means of one baffle leaving one opening which connects the lower compartment to the upper compartment; or a lower and an upper compartment which are arranged one upon the other, and wherein the lower and the upper compartment are separated by means of more than one baffle, which are arranged one upon the other leaving one opening, respectively, which connect the lower compartment to the upper compartment; wherein the lower compartment is configured to support and burn the combustible, the at least one baffle is configured to direct gases formed in the lower compartment when operating the fireplace via said at least one opening to the upper compartment, and the upper compartment is configured to direct the gas to the outlet, the outlet being configured to discharge said gas from said combustion chamber; preferably wherein said gas is directed via a further compartment which preferably accommodates a damper flap, wherein said further compartment is connected to said outlet; wherein said one or more side walls consists/consist at least partially of air channels in the form of curved pipes, which are opened at their lower ends and their upper ends, respectively, and wherein the inner surface of the combustion chamber formed by said air channels is corrugated;

wherein the air channels in the form of curved pipes are configured to be heated up when operating said fireplace, wherein a lower opening of the pipes is configured to aspirate air from the environment of the fireplace, and wherein an upper opening of the pipes is configured to discharge the aspirated and heated air into the environment; and

wherein at least a portion of said lower compartment of the combustion chamber comprises a lining with a refractory material configured to prevent said portion of the pipes to be contacted by fire of the burning combustible when operating the fireplace, preferably wherein the portion of the air channels in the form of curved pipes forming said lower compartment of said combustion chamber is at least partially lined with a refractory material configured to prevent said portion of the pipes to be contacted by fire of the burning combustible when operating the fireplace. [0081 ] Further embodiments

[0082] In a further preferred embodiment the combustion chamber comprises at least one or at least two different aerating means.

[0083] The term "means for aerating" encompasses any conceivable means or device or equipment by means of which the combustion chamber may be aerated in order to support the combusting of the combustible. By means of said aerating, air is fed into or flows into the combustion chamber. Said air may also be termed "combustion air".

[0084] In one embodiment, one aerating means or one of said at least two different means for aerating is construed such that it extends from an opening in the front wall, the one or more side wall/walls and/or the rear wall of the housing into the interior of said combustion chamber, wherein the means are configured to allow combustion air flowing through said opening into said means for aerating. Preferably, said means for aerating comprise(s) one or a multitude of openings through which said combustion air may further flow into said combustion chamber. The fireplace according to the invention may be provided with one or more of said means for aerating.

[0085] The other one of said at least two different means for aerating is construed as at least one opening in the front wall, the one or more side wall/walls and/or the rear wall of the housing, wherein combustion air may flow through said at least one opening into the combustion chamber. The fireplace according to the invention may be provided with one or more of said means for aerating.

[0086] The term "opening" used in connection with means for aerating encompasses a hole such as a borehole. In one embodiment, if one of said means for aerating is construed as an opening in the front wall, the one or more side wall/walls and/or the rear wall of the housing, said opening may also be provided in the form of a pipe through which combustion air may be aspirated from the environment of the fireplace. If one of said walls is lined with a refractory material, preferably, vermiculite, then the openings or pipes extend also through said refractory material.

[0087] In a further preferred embodiment, the fireplace according to the invention comprises at least one first means for aerating which is construed such that it extends from an opening in the rear wall of the housing into the interior of the combustion chamber. This means is configured to allow combustion air flowing through said opening into said first means for aerating, wherein said first means for aerating comprises one or a multitude of openings through which said combustion air may further flow into said combustion chamber.

[0088] Preferably, the openings of the first means for aerating are circular. However, other forms are conceivable, too, such as elliptic or rectangular forms. The openings may also be provided in the form of one slit or more slits.

[0089] In one embodiment, when operating the fireplace, said at least one first means for aerating is at least partially covered by embers which are formed when burning the combustible.

[0090] The term "embers" encompasses the terms "burning ash" or "blaze" or "gloW.

[0091 ] Thus, before operating the fireplace according to one embodiment of the invention, said first means for aerating is preferably totally covered with combustible. During the combustion of said combustible, said first means for aerating preferably remains at least partially covered by embers. Accordingly, the first means for aerating preferably is positioned at the lowest portion or at a low portion of the combustion chamber such as the bottom of the combustion chamber.

[0092] In one embodiment, the fireplace according to the invention comprises one first means for aerating.

[0093] In another embodiment, the fireplace according to the invention comprises more than one first means for aerating such as two or three or more first means for aerating.

[0094] In one embodiment, the fireplace according to the invention comprises at least one second means for aerating which is construed such that it extends from an opening in the rear wall of the housing into the interior of the combustion chamber, wherein the means is configured to allow combustion air flowing through said opening into said second means for aerating, wherein said second means for aerating comprises a multitude of openings being configured to allow said combustion air further flowing into said combustion chamber. [0095] Preferably, when operating the fireplace according to the invention, said second means for aerating is not covered or at least is only partially covered by embers which are formed when burning the combustible. Preferably, said second means is not covered by embers. Accordingly, the second means for aerating preferably is positioned in the combustion chamber above the first means for aerating. Preferably, said second means is positioned close to the at least one side wall or is positioned at one side wall.

[0096] Preferably, the openings of the first means for aerating are circular. However, other forms are conceivable, too, such as elliptic or rectangular forms. The openings may also be provided in the form of one slit or more slits.

[0097] Further preferably, the fireplace according to the invention comprises more than one second means for aerating, e.g. two or three or more second means for aerating.

[0098] The at least one first means for aerating or the at least one second means for aerating or the at least one first means for aerating and the at least one second means for aerating comprise one or a multitude of openings, respectively.

[0099] The term "multitude" encompasses at least two or three or four or five or six or seven or eight or nine or ten or more openings. In case of at least three openings, the openings may be arranged randomly or may be arranged in a regular manner on or in said at least one first means for aerating or said at least one second means for aerating.

[001 00] The openings may have different diameters.

[001 01 ] In one embodiment, said openings are arranged in a regular manner, preferably in a row or in several rows.

[001 02] In one embodiment, the fireplace according to the invention comprises at least one third means for aerating which is construed as at least one opening in the rear wall of the housing. Preferably, said at least one third means comprises one, two or more than two openings in the rear wall, preferably three or four of five or six or seven or ten or more openings. Since in a preferred embodiment, at least the rear wall of the lower compartment is lined with a refractory material, preferably vermiculite, also the openings extend through said refractory material. [001 03] In one embodiment, the rear wall of the fireplace according to the invention bears another wall that insulates the fireplace towards the environment. Preferably, said rear wall and said another wall are spaced apart from one another.

[001 04] In a one embodiment, the fireplace according to the invention comprises at least one fourth means for aerating which is construed as at least one opening in the front wall of the housing. In one embodiment, said at least one opening may be positioned in the door of the front wall. In another embodiment, said opening may be positioned in a part of the front wall not forming the door of the fireplace. In one embodiment, said at least one fourth means comprises more than one opening in the front wall, preferably two or three or four of five or six or seven or ten or more openings.

[001 05] In one embodiment, the fireplace according to the invention comprises at least one fifth means for aerating which is construed as at least one opening in the one or more side wall/walls. In one embodiment, said at least one fifth means for aerating comprises more than two openings in the front wall, preferably three or four of five or six or seven or ten or more openings.

[001 06] In one embodiment, the fireplace according to the invention comprises at least one of said first means for aerating and at least one of said at least one third means for aerating, one of said at least one fourth means for aerating and/or one of said at least one fifth means for aerating.

[001 07] In another embodiment, the fireplace according to the invention comprises at least one of said second means for aerating and at least one of said third means for aerating, one of said at least one fourth means for aerating and/or one of said at least one fifth means for aerating.

[001 08] Preferably, the fireplace according to the invention comprises at least one of said first means for aerating and at least one of said second means for aerating in combination with at least one of said third means for aerating, one of said at least one fourth means for aerating and/or one of said at least one fifth means for aerating.

[001 09] In a one embodiment, the fireplace according to the invention comprises at least one of said first means for aerating and at least one of said second means for aerating in combination with at least one of said third means for aerating and at least one of said fourth means for aerating.

[001 1 0] Accordingly, in one embodiment, combustible in the combustion chamber is aerated from at least two sides, further preferred from at least three sides, further preferred from at least four sides, further preferred from at least five sides or even from six sides.

[001 1 1 ] In one embodiment, the at least one first means for aerating or the at least one second means for aerating or the at least one first means for aerating and the at least one second means for aerating are construed as a pipe, respectively.

[001 1 2] The term "pipe" encompasses a pipe having a circular cross section, an oval cross section, a triangular cross section or a rectangular cross section. In one embodiment, the cross section may have any conceivable shape.

[001 1 3] In a further preferred embodiment, the first means for aerating is arranged in said combustion chamber such that combustion air may exit the openings of said first means substantially vertically upwards when flowing into the combustion chamber.

[001 14] The term "substantially vertically upwards" means that said combustion air may exit said openings in an angle of from 0 to 60° measured against the vertical.

[001 1 5] In one embodiment, the second means for aerating is arranged in said combustion chamber such that combustion air may exit said openings of said second means substantially horizontally when flowing into the combustion chamber.

[001 1 6] The term "substantially horizontally" means that said combustion air may exit said openings in an angle of from 0 to 45 ° measured against the horizontal.

[001 1 7] In another embodiment, wherein the at least one second means for aerating is attached at the top of the combustion chamber, the openings of said second means for aerating are arranged such that combustion air may exit said openings substantially downwards when flowing into the combustion chamber.

[001 1 8] The term "substantially downwards" means that said combustion air may exit the openings in an angle of from 0 to 45 ° measured against the vertical. [001 1 9] In one embodiment, the openings of the second means for aerating are arranged in a row when the second means for aerating is construed as a pipe.

[001 20] In one embodiment, the fireplace according to the invention comprises at least two second means for aerating. Preferably, said at least two second means for aerating are arranged such in the combustion chamber that the openings of one of said at least two second means face the openings of the other second means for aerating, i.e. said at least two second means for aerating are positioned in the combustion chamber such that they face each other.

[001 21 ] In one embodiment, the fireplace according to the invention comprises at least three second means for aerating. Preferably, at least two second means for aerating are arranged such in the combustion chamber that the openings of the said at least two second means face each other, wherein combustion air may exit said openings substantially horizontally. Thus, said at least two second means for aerating are positioned in the combustion chamber such that they face each other, wherein each of said second means for aerating is positioned close to the at least one side wall or is positioned at one side wall. The third second means for aerating preferably is positioned at the top of the combustion chamber, wherein the openings of said third second means for aerating are arranged such that combustion air may exit said openings substantially downwards into the combustion chamber.

[001 22] Suitable aerating means are disclosed in WO 2015/05191 1 .

[001 23] In a further preferred embodiment of the invention, the combustion chamber of the fireplace according to the invention comprises at least one cleaning device for smoke gas.

[001 24] The term "cleaning device" encompasses any conceivable device which is suitable for at least partially lowering the amount of carbon monoxide or particulate matter in the smoke gas formed when combusting combustible in the combustion chamber.

[001 25] In case of solid emissions, said cleaning device may be construed such to act as a filter, and/or to catalytically convert same. In case of gaseous emissions, said cleaning device may be construed such to absorb or adsorb said gaseous emissions, and/or to catalytically convert same.

[001 26] Preferably, said cleaning device is arranged in the combustion chamber such that formed smoke gas at least partially flows through said cleaning device before said smoke gas at least partially exits the combustion chamber through said outlet.

[001 27] Preferably, said combustion chamber comprises a plate that is positioned such that it is suitable for guiding smoke gas at least partially to said cleaning device. Said plate may also be termed as a baffle plate.

[001 28] Preferably, said cleaning device comprises a plate or baffle plate that is fixed to said cleaning device such that it is suitable for guiding smoke gas at least partially to said cleaning device.

[001 29] Preferably, said cleaning device is selected from the group consisting of: a filter device or a catalytic device. Preferably, the catalytic device at least partially may oxidize generated carbon monoxide to carbon dioxide when operating said fireplace according to the invention.

[001 30] A suitable catalytic device is e.g. described in EP 2 418 425 B1 .

[001 31 ] The combination of means for aerating and cleaning device, preferably means for aerating in combination with a catalytic device, is particularly effective for further reducing emission of carbon monoxide and particulate matter formed in the combustion chamber of the fireplace according to the invention.

[001 32] In a further preferred embodiment said combustion chamber is provided with a plate that is suitable for guiding smoke gas at least partially to the outlet, wherein the plate is construed such to enclose a cavity. Said plate enclosing a cavity is connected to the outlet and extends into the upper compartment of the combustion chamber.

[001 33] Said plate enclosing a cavity comprises one or a multitude of openings configured to allow smoke gas flow through to reach the exhaust nozzle when operating the fireplace. Subsequently, said smoke gas is guided to the outlet where it exits the fireplace. Thus, said plate enclosing a cavity serves for guiding smoke gas to the outlet. Smoke gas exiting the outlet may be further guided to a chimney. [001 34] It has been discovered that the provision of such baffle enclosing a cavity in the combustion chamber may further support the reduction of emission of carbon monoxide and particulate matter.

[001 35] The form of the cavity may be any conceivable form as long as said form is suitable for guiding smoke gas to the outlet. Thus, said plate is hollow in order to allow smoke gas to flow through said plate to the outlet when operating the fireplace.

[001 36] Accordingly, the term "plate enclosing a cavity' is synonymously used with the term " hollow plate" .

[001 37] In one embodiment, the plate enclosing a cavity is in the form of a tubular plate.

[001 38] The term "tubular plate" encompasses a plate in the form of a pipe having a circular cross section, an oval cross section, a triangular cross section or a rectangular cross section. In one embodiment, the cross section may have any conceivable shape.

[001 39] Preferably, said plate enclosing a cavity, preferably a tubular plate, extends in a direction that runs in parallel to the one or more side wall/walls.

[00140] The length of said plate enclosing a cavity, preferably a tubular plate, may correspond to the shortest distance of the front wall from the rear wall. In one embodiment, the length of the baffle corresponds to 100 % or less than 100 % or less than 99 % or less than 98 % or less than 97 % or less than 96 % or less than 95 % of the distance of the front wall from the rear wall, and from more than 1 % or more than 10 % or more than 20 % or more than 30 % or more than 40 % or more than 50 % of the distance of the front wall from the rear wall.

[00141 ] Preferably, said opening/s of said plate are arranged at least on a portion of said baffle such that smoke gas may enter said openings in a direction which is oriented substantially downwards. The term "substantially downwards" means that said smoke gas may enter the baffle through said openings in an angle of from 0 to 45 ° measured against the vertical.

[00142] In another embodiment, said opening/s of said plate are arranged at least on a portion of said plate such that smoke gas may enter said openings in a direction which is oriented substantially upwards. The term "substantially upwards" means that said smoke gas may enter the plate through said openings in an angle of from 0 to 45 ° measured against the vertical.

[00143] In one embodiment, the openings of the said plate are arranged in a row.

[00144] In one embodiment, said openings are construed such to form one or more slits.

[00145] Preferably, said plate enclosing a cavity, preferably a tubular plate, has or comprises a lid by means of which said plate may be opened such that e.g. a cleaning device for cleaning smoke gas may be inserted into said tubular plate.

[00146] In a preferred embodiment, said plate enclosing a cavity, preferably a tubular plate, has or comprises in the interior of said plate at least one cleaning device for cleaning said smoke gas which is formed when burning combustible, and when said smoke gas enters said tubular plate.

[00147] In another preferred embodiment, said plate enclosing a cavity such as a tubular plate comprises in the interior of said plate at least one plate which is arranged such in said plate that it is suitable for guiding formed smoke gas to the outlet.

[00148] In one embodiment, said plate enclosing a cavity such as a tubular plate comprises a cleaning device for cleaning smoke gas and a plate for guiding smoke gas to said cleaning device or to the outlet.

[00149] In a further embodiment, said plate enclosing a cavity such as a tubular plate comprises a cleaning device for cleaning smoke gas or a plate for guiding smoke gas to said cleaning device or to the outlet.

[00150] In a further embodiment, the plate enclosing a cavity such as a tubular plate neither comprises a cleaning device for cleaning smoke gas nor a plate for guiding smoke gas to said cleaning device or to the outlet.

[00151 ] Fig. 1 shows a side view of a longitudinal section through a combustion chamber 30 of a fireplace 10 according to the invention. Combustion chamber 30 comprises a lower compartment 50 and an upper compartment 60. The compartments are separated by baffle 80 which leaves an opening 81 between the upper compartment 60 and the lower compartment 50, and which connects the two compartments. The dashed arrow shows the direction of smoke gas flowing through the combustion chamber 30 to outlet 40. The air channels are not shown.

[001 52] Fig. 2 shows the combustion chamber 30 of Fig. 1 , wherein the upper compartment 60 is connected to a further compartment 65 via outlet 40. The further compartment accommodates damper flap 66 which may be switched to a closed position as shown or to an opened position. The air channels are not shown.

[001 53] Fig. 3 shows a side view of a longitudinal section through a combustion chamber 30 of a fireplace 100 according to the invention. Combustion chamber 30 comprises a lower compartment 50, a middle compartment 55 and an upper compartment 60. The compartments are separated by baffles 80 which leave one opening 81 between the upper compartment 60 and the middle compartment 55, and one opening between the middle compartment 55 and the lower compartment 50. The dashed arrow shows the direction of smoke gas flowing through the combustion chamber 30 to outlet 40. The air channels are not shown.

[001 54] Fig. 4 shows the combustion chamber 30 of Fig. 3, wherein the upper compartment 60 is connected to a further compartment 65 via outlet 40. The further compartment accommodates damper flap 66. The air channels are not shown.

[001 55] Fig. 5 shows a front view of a cross section through a combustion chamber 30 of a fireplace according to the invention. Baffle 80 consists of a refractory material. The side walls of the lower compartment 50 are lined with refractory material 90 such that the portion of the air channels, respectively the portion of the lower compartment which is configured to support combustible, is not lined with a refractory material 90. The air channels are not shown.

[001 56] Fig. 6 shows a front view of a preferred fireplace 10 according to the invention. Fireplace 10 comprises air channels in the form of curved pipes 20 made from cast iron or steel which form the one or more side wall/walls 16 of fireplace 10. Thus, at least a portion of said side wall/walls 16 consists of said curved pipes 20. Side wall 16, front wall 1 1 and rear wall 15 (not shown) form a cylindrical combustion chamber 30 wherein at least a portion of the inner surface of the combustion chamber is corrugated. The combustion chamber 30 is construed as in Fig. 5. During operation of fireplace 10, air from the environment being contained in curved pipes 20 is heated up very fastly and steadily. Heated air ascends and exits pipes 20 at the upper opening thereof. Cold air is aspirated at the lower opening of pipes 20 and is thus heated up. Consequently, the environmental air is recirculated through said pipes. Thus, heat transfer from the fireplace to the environment is effected by thermal convection.

[001 57] Front wall 1 1 is partially construed as door 12. Combustion chamber 30 of fireplace 10 may be monitored through a glass plate 13. Front wall 1 1 may have a handle for closing combustion chamber 30. The handle or the front wall 1 1 may bear one or more openings (means for aerating 4) through which combustion air may enter combustion chamber 30 in order to support the combustion of combustible, preferably wood.

[001 58] Fig. 7 shows a side view of the preferred fireplace 10 according to the invention. Curved pipes 20 form said cylindrical combustion chamber 30 (not shown). Smoke gas being formed when combusting combustible may exit outlet 40 which is located in the rear wall 15 of fireplace 10. The portion of rear wall 15 forming a part of the lower compartment 50 is lined with a refractory material.

[001 59] Fig. 8 shows a front view of a cross section along rear wall 15 of the preferred fireplace 10 according to the invention. Rear wall 15 has openings which represent third means for aerating 3. From further openings in rear wall 15, second means for aerating 2 extend into the interior of combustion chamber 30. Said second means 2 extend through the refractory material 90 of the lining. Optionally, first means for aerating 1 extend from a further opening in rear wall 15 into the interior of combustion chamber 30, i.e. into the lower compartment. The air channels are not shown.

[001 60] Fig. 9 shows a perspective view of a part of a cross section of a preferred fireplace 10 according to the invention as presented in Fig. 8. The view represents a part of combustion chamber 30 which is formed by side wall 16 and rear wall 15. First means for aerating 1 and second means for aerating 2 are positioned in combustion chamber 30 in the form of pipes extending from openings in rear wall 15, respectively. First means for aerating 1 bears two rows of parallel openings through which combustion air enters combustion chamber 30 substantially vertically upwards. The first means 1 are optional means. Both second means for aerating 2 bear one row of openings through which combustion air may enter combustion chamber 30 substantially horizontally. Both second means for aerating 2 face each other. Rear wall 15 bears third means for aerating 3. Front wall 1 1 bears at least one fourth means for aerating 4 (front wall 1 1 and fourth means for aerating 4 not shown). The air channels, the upper and lower compartment including the baffle separating said lower from said upper compartment and the lining with a refractory material are not shown.

[001 61 ] The openings of the first means for aerating 1 and second means for aerating 2 preferably have a diameter of from 1 to 10 mm, more preferred 2 to 7 mm, respectively.

[001 62] Means for aerating 3 and means for aerating 4 preferably have a diameter of from 1 to 15 mm, more preferred of from 5 to 10 mm, respectively.

[001 63] Preferably, the length of first means for aerating 1 and second means for aerating 2 approximately equals the distance between rear wall 15 and front wall 1 1 , respectively.

[001 64] Fig. 10 shows a top view on a cross section along a horizontal plane of a fireplace 10 according to the invention. Combustion chamber 30 is formed by curved pipes 20 having a circular diameter. The pipes form a corrugated inner surface of the combustion chamber 30. The lining with a refractory material is not shown.

[001 65] Fig. 11 shows a top view on a cross section along a horizontal plane of a fireplace 10 according to the invention. Combustion chamber 30 is formed by curved pipes 20 having a circular diameter. The pipes are alternatedly arranged. The pipes form a corrugated inner surface of the combustion chamber 30. The pipes (of the lower compartment) are lined with a refractory material such that the refractory material partially is in physical contact with the lining (90).

[001 66] Fig. 12 shows a top view on a cross section along a horizontal plane of a fireplace 10 according to the invention. Combustion chamber 30 is formed by air channels 20 having a cross section in the form of semicircles which are formed as recesses in the side wall/walls of combustion chamber 30. The air channels form a corrugated inner surface of the combustion chamber 30. The lining with a refractory material is not shown.

[001 67] Fig. 13, 14 and 15 show a top view on a cross section of a fireplace 10 according to the invention along a horizontal plane, respectively. Combustion chamber 30 is formed by air channels 20 having a cross section in the form of semicircles (Fig. 13), rectangles (Fig. 14), and triangles (Fig. 15). The air channels form a corrugated inner surface of the combustion chamber 30. The lining with a refractory material is not shown.

[001 68] Fig. 16 shows a top view on a cross section along a horizontal plane of a fireplace 10 according to the invention. Combustion chamber 30 is formed by air channels 20 having a cross section in the form of triangles which are formed as recesses in the side wall/walls of combustion chamber 30. The air channels form a corrugated inner surface of the combustion chamber 30. The lining with a refractory material is not shown.

[001 69] Fig. 17 shows a top view on a cross section along a horizontal plane of a fireplace 10 according to the invention. Combustion chamber 30 is formed by double walls which form two air channels. Fins protrude into the combustion chamber 30 in order to provide a corrugated inner surface of the combustion chamber 30. The lining with a refractory material is not shown.

[001 70] Fig. 18 shows a top view on a cross section along a horizontal plane of a fireplace 10 according to the invention. Fins protrude into the combustion chamber 30 in order to provide a corrugated inner surface of the combustion chamber 30. The air channels 20 are merely formed by the side walls of the combustion chamber. The lining with a refractory material is not shown.

[001 71 ] Fig. 19 shows a top view on a cross section along a horizontal plane of a fireplace 10 according to the invention. Combustion chamber 30 is formed by wavy air channels 20. The pipes form a corrugated inner surface of the combustion chamber 30. The lining with a refractory material is performed such that said lining is not in physical contact with the air channels.

EXAMPLES

[001 72] Emissions of fireplaces having pipes allowing for recirculation of environmental air based on convection were determined according to EN13240. The fireplaces had the same construction principle except that one series contained a lining with a refractory material in the lower compartment (fireplaces according to the invention), whereas the series for comparison was free from a lining with a refractory material (fireplaces fror comparison). The fireplaces were further equipped with the further compartment in the form of a pipe bent upwards containing a damper flap, and with second, third and fourth means for aerating.

[001 73] The results are summarized in the following Tables 1 to 3. The results evidence a considerable reduction of emission in terms of carbon monoxide (CO) and particulate matter (PM) for the fireplaces according to the invention.

[001 74] Table 1

[001 75] Table 2

[001 76] Table 3

Without lining With lining Reduction

[%] Capacity [kW] 13.5 14.2

CO(130 ₂ ) 2,875 1,250 57 [mg/Nm ³ ]

PM (1302) 32 22 31 [mg/Nm ³ ]

1 77] Reference numerals , 100 fireplace

air channels, e.g. in the form of curved pipes combustion chamber

outlet

lower compartment

middle compartment

upper compartment

further compartment

damper flap baffle for separating compartments from one another opening refractory material front wall

door

glass plate

rear wall

side wall first means for aerating

second means for aerating

third means for aerating

fourth means for aerating

fifth means for aerating