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Title:
Flue gas heat exchanger and fin therefor
Kind Code:
A1
Abstract:
Disclosed is a heat exchanger including a plurality of fins, each having a first aperture and a second aperture. A first aperture of a downstream one of the plurality of fins decreases relative to a first aperture of an upstream one of the plurality of fins. A first fluid from the first aperture of the upstream one of the plurality of fins is received partially in the first aperture of the downstream one of the plurality of fins and the remainder of the first fluid is diverted along the downstream one of the plurality of fins and received in the second aperture of the downstream one of the plurality of fins. An inner jacket contacts each of the plurality of fins. An outer jacket surrounds the inner jacket defining a chamber for containing a second fluid therein. The first aperture and the second aperture each define sectors of a circle extending from a central part to an outer periphery for conducting the first fluid toward the inner jacket. The inner jacket is configured to transfer heat to the second fluid via said plurality of fins. Other embodiments also are disclosed.


Inventors:
Andersen, Jens Otto Ravn (Aarhus C, DK)
Forster, Jesper (Risskov, DK)
Application Number:
10/116122
Publication Date:
11/07/2002
Filing Date:
04/05/2002
Primary Class:
International Classes:
F28D7/02; F28D7/10; F28F1/24; F28F9/22; (IPC1-7): F28D7/02
View Patent Images:
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Attorney, Agent or Firm:
Dykema, Gossett Pllc (FRANKLIN SQUARE, THIRD FLOOR WEST, WASHINGTON, DC, 20005, US)
Claims:

We claim:



1. Heat exchanger comprising: a plurality of fins, each having a first aperture and a second aperture; wherein a first aperture of a downstream one of said plurality of fins decreases relative to a first aperture of an upstream one of said plurality of fins; whereby a first fluid from said first aperture of said upstream one of said plurality of fins is received partially in said first aperture of said downstream one of said plurality of fins and the remainder of the first fluid is diverted along said downstream one of said plurality of fins and received in the second aperture of said downstream one of said plurality of fins; an inner jacket contacting each of said plurality of fins; and an outer jacket surrounding said inner jacket defining a chamber for containing a second fluid therein; wherein said first aperture and said second aperture each define sectors of a circle extending from a central part to an outer periphery for conducting the first fluid toward said inner jacket; wherein said inner jacket is configured to transfer heat to the second fluid via said plurality of fins.

2. Heat exchanger of claim 1, wherein each of said plurality of fins comprises a disk having an outer annular flange for engaging said inner jacket.

3. Heat exchanger of claim 1, wherein said plurality of fins are assembled into blocks, a first one of said blocks comprising an initial fin with an opening forming an inlet, and at least one of said blocks comprising a last fin with an opening forming an outlet.

4. Heat exchanger of claim 3, wherein one to five blocks extend along the inner jacket.

5. Heat exchanger of claim 3, wherein each of said blocks comprises eight fins.

6. Heat exchanger of claim 1, wherein said first aperture and said second aperture define sectors of a circle extending from a central part to an outer periphery so that the first fluid is conducted toward the inner jacket.

7. Heat exchanger of claim 6, wherein a smallest sector ranges between 1° and 22.5°.

8. Heat exchanger of claim 6, wherein the sectors are about 12.5° apart.

9. Heat exchanger of claim 1, wherein said plurality of fins are mounted on a guiding element that extends through openings in a central part of each of said plurality of fins that have a mutual cross section that is non-circular.

10. Heat exchanger of claim 9, wherein the openings have flange portions engaging the guiding element.

11. Heat exchanger of claim 1, further comprising: an inlet fin having an inlet aperture and an outlet fin having an outlet aperture.

12. Heat exchanger of claim 11, wherein said inlet aperture is larger than a first aperture of a downstream one of said plurality of fins.

13. Heat exchanger of claim 11, wherein said inlet aperture defines an area substantially equal to an open area defined by said first aperture and said second aperture.

14. Heat exchanger of claim 1, wherein said first aperture and said second aperture are annularly offset by 90°.

15. Heat exchanger of claim 1, wherein each of said plurality of fins has two said first apertures and two said second apertures.

16. Heat exchanger of claim 1, wherein said plurality of fins defines an inner passage for delivering fluid to one or both of a first aperture and a second aperture of a first of said plurality of fins.

17. Heat exchanger of claim 1, wherein said first aperture and said second aperture define an open area that is substantially constant among said plurality of fins.

18. Heat exchanger of claim 17, wherein said open area is a multiple of 1.1 of a distance between adjacent ones of said plurality of fins.

19. Heat exchanger of claim 17, wherein said open area is a multiple ranging from 1 to 1.5 of a distance between adjacent ones of said plurality of fins.

20. Heat exchanger comprising: a plurality of fins, each having a first aperture and a second aperture that define an open area for receiving a first fluid; wherein said open area is substantially constant among said plurality of fins; an inner jacket contacting each of said plurality of fins; and an outer jacket surrounding said inner jacket defining a chamber for containing a second fluid therein; wherein said first aperture and said second aperture each define sectors of a circle extending from a central part to an outer periphery for conducting the first fluid toward said inner jacket; wherein said inner jacket is configured to transfer heat to the second fluid via said plurality of fins.

21. Heat exchanger of claim 20, wherein a first aperture of a downstream one of said plurality of fins decreases relative to a first aperture of an upstream one of said plurality of fins.

22. Heat exchanger of claim 20, wherein said first aperture and said second aperture are annularly offset by 90°.

23. Heat exchanger of claim 20, wherein each of said plurality of fins has two said first apertures and two said second apertures.

24. Heat exchanger of claim 20, wherein said plurality of fins defines an inner passage for delivering fluid to an open area of a first of said plurality of fins.

25. Heat exchanger of claim 20, wherein each of said plurality of fins comprises a disk having an outer annular flange for engaging said interior jacket.

26. Heat exchanger of claim 20, wherein said open area is a multiple ranging from 1 to 1.5 of a distance between adjacent ones of said plurality of fins.

27. Heat exchanger of claim 20, wherein said open area is a multiple of 1.1 of a distance between adjacent ones of said plurality of fins.

28. Heat exchanger of claim 20, wherein said first aperture and said second aperture define sectors of a circle extending from a central part to an outer periphery so that the first fluid is conducted toward the inner jacket.

29. Heat exchanger of claim 28, wherein a smallest sector ranges between 1° and 22.5°.

30. Heat exchanger of claim 28, wherein the sectors are about 12.5° apart.

31. Heat exchanger of claim 20, further comprising: an inlet fin having an inlet aperture, and an outlet fin having an outlet aperture.

32. Heat exchanger of claim 31, wherein said inlet aperture is larger than a first aperture of a downstream one of said plurality of fins.

33. Heat exchanger of claim 31, wherein said inlet aperture defines an area substantially equal to the open area.

34. Heat exchanger of claim 20, wherein said plurality of fins are assembled into blocks comprising an initial fin with an opening forming an inlet, and of said blocks a last block also comprising a last fin with an opening forming an outlet.

35. Heat exchanger of claim 34, wherein one to five blocks extend along said inner jacket.

36. Heat exchanger of claim 34, wherein each of said blocks comprises eight fins.

37. Heat exchanger of claim 20, wherein said plurality of fins are mounted on a guiding element that extends through openings in a central part of each of said plurality of fins that have a mutual cross section that is non-circular.

38. Heat exchanger of claim 37, wherein the openings have flange portions engaging the guiding element.

39. Heat exchanger comprising: a plurality of fins, each having open area for receiving a first fluid; an inner jacket contacting each of said plurality of fins along a heat transfer area substantially constant for each of said plurality of fins; and an outer jacket surrounding said inner jacket defining a chamber for containing a second fluid therein; wherein said open area defines a sector of a circle extending from a central part to an outer periphery for conducting the first fluid toward said inner jacket; wherein said inner jacket is configured to transfer heat to the second fluid via said plurality of fins.

40. Heat exchanger of claim 39, wherein said plurality of fins defines an inner passage for delivering fluid to an open area of a first of said plurality of fins.

41. Heat exchanger of claim 39, wherein said open area is substantially constant among said plurality of fins.

42. Heat exchanger of claim 39, wherein said open area defines a sector of a circle extending from a central part to an outer periphery so that the first fluid is conducted toward the inner jacket.

43. Heat exchanger of claim 39, wherein each of said plurality of fins comprises a disk having an outer annular flange for engaging said interior jacket.

44. Heat exchanger of claim 39, further comprising: an inlet fin having an inlet aperture; and an outlet fin having an outlet aperture.

45. Heat exchanger of claim 44, wherein said inlet aperture defines an area substantially equal to the open area.

46. Heat exchanger of claim 39, wherein each said open area defines a sector of a circle extending from a central part to an outer periphery.

47. Heat exchanger of claim 46, wherein a smallest sector ranges between 1° and 22.5°.

48. Heat exchanger of claim 46, wherein the sectors are about 12.5° apart.

49. Heat exchanger of claim 39, wherein said plurality of fins are assembled into blocks comprising an initial fin with an opening forming an inlet, and of said blocks a last block also comprising a last fin with an opening forming an outlet.

50. Heat exchanger of claim 49, wherein one to five blocks extend along said inner jacket.

51. Heat exchanger of claim 49, wherein each of said blocks comprises eight fins.

52. Heat exchanger of claim 39, wherein said plurality of fins are mounted on a guiding element that extends through openings in a central part of each of said plurality of fins that have a mutual cross section that is non-circular.

53. Heat exchanger of claim 52, wherein the openings have flange portions engaging the guiding element.

Description:

REFERENCE TO EARLIER APPLICATION

[0001] This Application is a continuation in part of U.S. patent application Ser. No. 09/180,322, filed Oct. 18, 1999, by Jens Otto Ravn Andersen et al., entitled Flue Gas Heat Exchanger and Fin Therefor.

BACKGROUND OF THE INVENTION

[0002] The present invention relates to a flue gas exchanger comprising plane fins that extend from a first end to a second end of a jacket along and inside the jacket and that are assembled into blocks.

[0003] DE 888 255 describes a flue gas exchanger comprising a chamber with a ribbed tube that extends along the chamber. The ribbed tube comprises ribs extending perpendicularly in relation to a longitudinal axis of the chamber. The ribs are provided with inlets and outlets for the flue gas. The inlets and outlets are constituted by segments of a circle having a constantly decreasing or increasing height. A cooling medium extends through a central tubing of the ribbed tube.

[0004] The flue gas exchanger described in the above publication possesses some disadvantages. It involves large costs to produce a ribbed tube and at the same time the production has to be made for a specific dimensioning of the flue gas exchanger. Besides, a flue gas exchanger with a ribbed tube of the above-mentioned type with inlets and outlets constituted by segments of a circle has a limited capacity. The flue gas will be conducted to a centre of the jacket and cooling the ribs must take place by means of the central tubing having a limited surface area. Furthermore, the degree of rib effect is poor in a tube with external ribs. Finally, a ribbed tube having ribs that are provided with segments of a circle has a certain flow resistance towards the flue gas.

[0005] JP,A,59-56089 describes a heat exchanger with annular disk refrigerant flow path members which are inserted into an annular space so that they are connected in a heat conductive manner to the outer wall of the heat transfer tube and are contacted with the inner wall of an outer tube. Each annular disk flow path members are arranged by laminating a multitude of them in vertical direction so that they can form a multitude of annular paths while the annular disk fins, provided with flanges having diameters smaller than the outer diameters of the annular disks and equal to the inner diameters of the same, are provided in the annular path.

[0006] This heat exchanger has the disadvantage that the flow of flue gas through the heat exchanger is very restricted thereby reducing the capacity. Consequently, the area of inlets or outlets in the flow path members amounts to a very low multiple of the size of a cross section area of channels between adjacent flow path members. Furthermore the heat exchanger both has actual flow path members but also has annular disk fins without inlets or outlets. This further restricts the flow of flue gas through the heat exchanger and thereby the capacity of the heat exchanger and gives a different flow of flue gas compered to as example DE 888 255.

[0007] Thus, it is the object of the present invention to provide a flue gas exchanger that does not possess the disadvantages discussed above and which consequently increases the possibility of cooling the flue gas and reduces the flow resistance in order to increase the capacity.

[0008] This object is obtained by a flue gas exchanger where said fins being arranged at a mutual distance and forming channels between adjacent fins, each of said blocks comprising an initial fin with an opening forming an inlet and subsequent fins each being provided with a first opening forming an inlet, alternatively an outlet, and a second opening forming an outlet, alternatively an inlet, and of said blocks a last block also comprising a last fin with an opening forming an outlet, and said inlets, respectively outlets, being intended for admitting a flow of a flue gas from the first end of the jacket through the inlets and outlets of the fins to the second end of the jacket, and said inlets, respectively outlets, forming inlet chambers, respectively outlet chambers, which are interconnected by the channels, and a total open area of inlets and outlets in the fits which is identical for each fin amounting to a multiple of between 1.0 and 1.5, preferably 1.1, of the size of a cross section area of the channels between adjacent fins, and the open area of the inlets, alternativly the outlets, decreasing, and simultaneously the open area of the outlets, alternatively the inlets, increasing through each block in the intended direction of flow of the flue gas.

[0009] In an exemplary embodiment the inlets and outlets in the fins are constituted by sectors of a circle extending from a central part to an outer periphery so that the flue gas is conducted towards the jacket.

[0010] By constructing a flue gas exchanger with these characteristics, one obtains a flue gas exchanger having a very low flow resistance. This means that the capacity is exclusively determined by the physical dimensions of the flue gas exchanger and the cooling taking place in the flue gas exchanger and is not limited by unfavourable flow conditions in the flue gas exchanger. Also, the flue gas being conducted towards the inner jacket increases the heat exchange substantially.

[0011] The fins may be produced as individual fins, which are positioned on a central guiding element. The number and dimensions of the fins may vary in order to provide the flue gas exchanger with different capacities and with different other physical and thermal characteristics. This means that the diameter and length of the flue gas exchanger may be altered by using fins of a different diameter or by using a different number of fins.

[0012] EP 0 571 881 describes a heat exchanger formed by fins, which are assembled into a block. The fins comprises openings that constitute sectors of a circle. The fins are assembled in such a manner that two helical channels are formed in the block. The heat exchanger described may be used for both fluent and gaseous media. U.S. Pat. No. 3,731,733 describes a similar heat exchanger formed with fins, which are assembled in blocks each with two fins. These fins also are assembled in such a manner that two, alternatively three, helical channels are formed in tire block.

[0013] The fins of these heat exchangers have the disadvantages that they are not to a sufficient extent able to create a forced flow, e.g. of a flue gas. The object of the heat exchanger described is to reduce tire flow resistance. However, a helical channel established with this known technique will not to a sufficient extent ensure proper cooling of the flue gas since the latter will be conducted through a short channel with a large flow cross-section resulting in a high ratio between the cross section area of the channels between the fins and the area of tire inlets and outlets of the fins. Furthermore the fins of EP 0 571 881 are not provided with an actual inlet and outlet but merely help to form the helical channels. Thus, two openings forth two channel systems. Besides, the material consumption is very large compared to the heat transmission area, and the surface in the channels is angular, which increases the flow resistance.

[0014] Fins in which inlets and outlets consist of sectors of a circle have the advantage that the flue gas is conducted towards outer areas of the ribs. Thus, cooling of the ribs may take place at the jacket, which has a considerably larger surface area than any central tubing. The jacket and the ribs correspond to a tube with internal ribs as opposed to a tube with external ribs, in which cooling takes place at the internal tube having a small surface area. This increases the capacity of the flue gas exchanger and, also, the flue gas exchanger according to the invention with a given capacity has considerably smaller dimensions than known flue gas exchangers with the same capacity.

[0015] The sectors of a circle help to obtain the low flow resistance. The sectors of a circle vary in size in such a manner that in a block of fins there is a constant reduction of the open area of the inlets while at the same time there is a constant widening of the open area of the outlets through the block. The total area of inlet and outlet is identical for each fin.

[0016] A simple way of producing the sectors of a circle in each fin is using a punching tool having the shape of a sector of a circle and with an angle corresponding to the smallest sector to be made in a fin. Other sectors of a circle are produced as a multiple of the smallest sector by using the same punching tool and simply perform a number of adjacent punchings corresponding to the required multiple of the smallest sector. The fins of an exemplary embodiment are produced from aluminum.

[0017] The flue gas exchanger according to the invention may be used in many contexts, e.g. as a heat exchanger from a fuel device in a central heating installation. It is also possible to use the flue gas exchanger according to the invention for different kinds of vessels.

[0018] What are needed, and not taught or suggested in the art, are a method and an apparatus for Flue Gas Heat Exchanger And Fin Therefor.

SUMMARY OF THE INVENTION

[0019] An embodiment of the invention is a heat exchanger including a plurality of fins, each having a first aperture and a second aperture. A first aperture of a downstream one of the plurality of fins decreases relative to a first aperture of an upstream one of the plurality of fins. A first fluid from the first aperture of the upstream one of the plurality of fins is received partially in the first aperture of the downstream one of the plurality of fins and the remainder of the first fluid is diverted along the downstream one of the plurality of fins and received in the second aperture of the downstream one of the plurality of fins. An inner jacket contacts each of the plurality of fins. An outer jacket surrounds the inner jacket defining a chamber for containing a second fluid therein. The first aperture and the second aperture each define sectors of a circle extending from a central part to an outer periphery for conducting the first fluid toward the inner jacket. The inner jacket is configured to transfer heat to the second fluid via said plurality of fins.

[0020] Another embodiment of the invention is a heat exchanger including a plurality of fins, each having a first aperture and a second aperture that define an open area for receiving a first fluid. The open area is substantially constant among the plurality of fins. An inner jacket contacts each of the plurality of fins. An outer jacket surrounds the inner jacket defining a chamber for containing a second fluid therein. The first aperture and the second aperture each define sectors of a circle extending from a central part to an outer periphery for conducting the first fluid toward the inner jacket. The inner jacket is configured to transfer heat to the second fluid via said plurality of fins.

[0021] A further embodiment of the invention is a heat exchanger including a plurality of fins, each having open area for receiving a first fluid. An inner jacket contacts each of the plurality of fins along a heat transfer area substantially constant for each of the plurality of fins. An outer jacket surrounds the inner jacket defining a chamber for containing a second fluid therein. The open area defines a sector of a circle extending from a central part to an outer periphery for conducting the first fluid toward the inner jacket. The inner jacket is configured to transfer heat to the second fluid via the plurality of fins.

[0022] The invention provides improved elements and arrangements thereof, for the purposes described, which are inexpensive, dependable and effective in accomplishing intended purposes of the invention. Other features and advantages of the present invention will become apparent from the following description of the exemplary embodiments which refers to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The invention is described in detail below with reference to the following figures, throughout which similar reference characters denote corresponding features consistently, wherein:

[0024] FIG. 1 is a section view through an embodiment of a heat gas exchanger according to the invention;

[0025] FIGS. 2A-2F are plan views of fins according to the invention;

[0026] FIG. 3 is a side view of a fin according to the invention;

[0027] FIG. 4 is a plan view of a block with several fins according to the invention; and

[0028] FIG. 5 is a cross-sectional detail view of another embodiment configured according to the invention; and

[0029] FIG. 6A-L are plan views of fins of the embodiment of FIG. 5.

DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS

[0030] FIG. 1 shows a section view through an embodiment of a flue gas exchanger according to the invention. The flue gas exchanger comprises a front cover 1 and a rear cover 2. An inner jacket 3 and an outer jacket 4 extend between the covers 1, 2. A chamber 5 between the inner jacket 3 and the outer jacket 4 is sealed by packings 6, 7 contacting the covers 1, 2. An inlet 8 for flue gas extends through the inner jacket 3 and the outer jacket 4. The inlet 8 may alternatively be provided in the front cover 1. A corresponding outlet 9 for the flue gas extends through the rear cover 2.

[0031] Fins 10 are assembled into blocks 11, which extend through the inner jacket 3. In the embodiment shown the flue gas exchanger comprises eight blocks 11 with eight adjacent fins 10 in each. Openings 20-34 (see FIGS. 2A-2H) form an inlet chamber 35 and an outlet chamber 36 for each block 11. The inlet chamber and the outlet chamber are indicated by hatching. The fins 10 are mounted on a guiding element 13 extending through openings in a central part of the fins 10 (see FIG. 2). The guiding element 13 may have a rectangular cross section, and the openings in the fins 10 a corresponding rectangular cross-section (see FIG. 2). Hereby the fins 10 are prevented from rotating around the guiding element 13. The guiding element 13 is fastened to the rear cover 2 by means appropriate for the purpose (not shown).

[0032] A flow gas, illustrated by means of flow lines 14, extends through the flue gas exchanger from the inlet 8 to the outlet 9. The flue gas passes the fins 10, all of which, except from a frontmost fin and a rearmost fin, are provided with both an inlet and an outlet (see FIGS. 2A-2H). Inlet and outlet are formed in the fins in such a manner that the flue gas is conducted towards the inner jacket 3. The frontmost fin is only provided with an inlet and the rearmost fin is only provided with an outlet.

[0033] The chamber 5 between the inner jacket 3 and the outer jacket 4 is designed to contain a cooling agent for cooling the flue gas that extends through the flue gas exchanger. An inlet (not shown) and an outlet (not shown) conduct the cooling medium into the chamber. The cooling medium may be a liquid, such as water. The flue gas is cooled, and the cooling medium is heated and may subsequently be used as a heating medium, e.g. in a heat exchanger in a central heating installation.

[0034] FIGS. 2A-2H show the fins 10 seen in a plan view. Shown in the figure are eight different fins 10 corresponding to the eight fins of which each block 11 (see FIG. 1) consists. The fins 10 comprise a plane part 15 and are all, except from a first fin, provided with openings, which constitute inlets and outlets. The inlets and outlets are substantially constituted by a sector of a circle extending from a central part 16 of each fin 10 to the vicinity of an outer periphery of the fin. The central part 16 of each fin is provided with an opening 18 having a rectangular cross-section. The guiding element 13 (see FIG. 1) is designed to extend through the openings 18 in each fin 10. Along the outer periphery 17 each fin is provided with a flange 19 (see FIG. 3).

[0035] A first fin shown in FIG. 2A is provided with a first opening 20 constituting an inlet, alternatively an outlet. Whether the opening 20 constitutes an inlet or an outlet (see FIG. 1), depends on the block 11 in which the fin 10 is positioned. If the fin 10 is positioned in a first block, a third block, a fifth block, etc., seen from the left in FIG. 1, the opening constitutes an inlet. If the fin 10 is positioned in a second block, a fourth block, a sixth block, etc., seen from the left in FIG. 1, the opening constitutes an outlet.

[0036] The openings in the fins 10 are produced by punching with a punching tool having the shape of the smallest opening. The larger openings all form a multiple of the smallest opening. Thus, one and the same tool may be used for all openings by performing several adjacent punchings corresponding to the multiple of the smallest punching constituted by the opening in question. It is only necessary to produce five different fins in order to provide eight fins such as shown in the figure since the fins in FIGS. 2B, 2C, respectively 2D, are identical with the fins in FIGS. 2F, 2G, respectively 2H, only rotated 180° in relation to one another.

[0037] As mentioned, the first fin is provided with a first opening 20. The opening is constituted by a sector of a circle having an angle of 100°. A second fin is provided with a first opening 21 constituted by a sector of a circle having an angle of 87.5° and a second opening 22 constituted by a sector of a circle of 12.5°. A third fin is provided with a first opening 23 constituted by a sector of a circle having an angle of 75° and a second opening 24 constituted by a sector of a circle of 25°. A fourth fin is provided with a first opening 25 constituted by a sector of a circle having an angle of 62.5° and a second opening 26 constituted by a sector of a circle of 37.5°. A fifth fin is provided with a first opening 27 constituted by a sector of a circle having an angle of 50° and a second opening 28 constituted by a sector of a circle of 50°. A sixth fin is provided with a first opening 29 constituted by a sector of a circle having an angle of 37.5° and a second opening 30 constituted by a sector of a circle of 62.5°. A sixth fin is provided with a first opening 31 constituted by a sector of a circle having an angle of 25° and a second opening 32 constituted by a sector of a circle of 75°. A sixth fin is provided with a first opening 33 constituted by a sector of a circle having an angle of 12.5° and a second opening 34 constituted by a sector of a circle of 87.5°. The total open area of the openings forming inlet and outlet is identical for each fin.

[0038] FIG. 3 shows a fin 10 seen in a side view. As mentioned, the fin has a plane part 15 with the central part 16 in which the opening 18 is provided. Along the outer periphery 17 the fin is provided with the flange 19. The opening 18 in the central part 16 is also provided by a flange. The flange 19 along the outer periphery 17 gives the fin rigidity while at the same time creating a distance a between adjacent fins in a block 11 (see FIG. 1). The flange 19 is intended to contact the inner jacket 3 in a situation of use.

[0039] FIG. 4 shows a block 11 consisting of eight fins 10 as illustrated in FIG. 2. The fins 10 are put together in the block II in such a manner that the plane part 15 of the first fin contacts the flange 19 of an adjacent second fin. The inlets, alternatively the outlets, are illustrated. It appears that the open area of the inlets, alternatively the outlets, decreases as the flue gas passes through the block 11. Simultaneously, the open area of the outlets, alternatively the inlets, increases. These are not illustrated. The channels 12 have a cross section area A seen parallel with the plane of the figure seen in an upward or downward direction. The cross section area A is determined as the distance a between the fins (see FIG. 3) multiplied by an extension b of the fins. The extension b of the embodiment shown is equal to the diametrical distance of the planes subtracted by an extension c of the guiding element. The total open area of each fin is equal to the cross section area A of each chamber 12 (see FIG. 1) multiplied by a factor of between 1.0 and 1.5, an exemplary factor being 1.1.

[0040] Referring to FIG. 5, another embodiment of a flue gas exchanger according to the invention includes a front cover 101 and rear covers 102a and 102b. Cover 102b is fixed to an outer jacket 104, while cover 102a is releasably attached to cover 102b with threaded fasteners 125. An inner jacket 103 and outer jacket 104 extend between the covers 101, 102b and define a chamber 105. A second inner jacket 123 defines chamber 105 with respect to cover 101. A guide 120 extending from cover 102a defines an inner passage 121 and an outer passage 122. An inlet 108 in cover 102a admits flue gas into inner passage 121. Inner passage 121 conveys the flue gas to outer passage 122. An outlet 109 vents the flue gas from outer passage 122.

[0041] Referring also to FIGS. 6A-6L, fins 110a-l are ordered and extend between guide 120 and inner jacket 103. Fins 10a and 110g respectively have only openings 112a and 114g. Fins 110b-f and 110h-l respectively have openings 112b-f and 112h-l, and 114b-f and 114h-l. Openings 112a-f decrement from a maximum area, defined by opening 112a, to a minimum area, defined by 112f, while openings 112h-l increment from a minimum area, defined by opening 112h, to a maximum area, defined by 112l. Conversely, openings 114b-g increment from a minimum area, defined by opening 114b, to a maximum area, defined by 114g, while openings 114g-l decrement from the maximum area, defined by opening 114g, to a minimum area, defined by 114l. In an exemplary embodiment, openings 112a-g and openings 114g-a, and openings 112h-l and openings 114l-h respectively describe substantially identical areas. For example, opening 112b and opening 114f describe substantially identical areas.

[0042] Consequently, in operation, flue gas received from passage 121 into passage 122 encounters fin 110a where the flue gas forms a stream through opening 112a. Thereafter, because opening 112b in fin 110b defines a smaller area than opening 112a in fin 110a, a major portion of the stream continues through opening 112b, while the remaining minor portion of the stream is diverted by fin 110b then through 114b. Downstream fins 110c-f pass and divert streams of flue gas in a similar fashion until the flue gas reaches fin 110g. At fin 110g, the major and minor stream portions recombine and form a unified stream through opening 114g, similar to the stream received through opening 112a. Thereafter, because opening 114h in fin 10h defines a smaller area than opening 114g in fin 1 10g, a major portion of the stream continues through opening 114h, while the remaining minor portion of the stream is diverted by fin 110h then through 112h. Downstream fins 110i-l pass and divert streams of flue gas in a similar fashion. The foregoing series of fins 110a-l then may repeat to recombine the major and minor stream portions, then re-divide same as needed.

[0043] Openings 112 and 114 in one fin 110 increase or decrease annularly with respect to an adjacent fin. For example, relative to opening 112a of fin 110a, opening 112b of fin 110b has substantially the same radial width, but describes a smaller arc. This feature aids in diverting streams of flue gas, as described above.

[0044] The diverting of streams of flue gas across fins 110 promotes heat transfer of the heat of the flue gas to the fin 110. Heat transfers from fins 110 to inner jacket 103, then to chamber 105. Some heat may transfer from flue gas to inner jacket 103, however in a relatively small amount as compared to the amount of heat transferred via a fin 110 to inner jacket 103.

[0045] In an exemplary embodiment, chamber 105 contains a cooling agent for cooling the flue gas. An inlet 130 and an outlet 135 provide for conducting the cooling medium through chamber 105. The cooling medium may be a liquid, such as water. As the flue gas decreases in temperature, the cooling medium increases in temperature, which subsequently may be used as a heating medium, e.g. in a heat exchanger in a central heating installation.

[0046] The openings 112 and 114 in the fins 110 may be produced by punching with a punching tool having the shape of the smallest opening. The larger openings all form a multiple of the smallest opening. Thus, one and the same tool may be used for all openings by performing several adjacent punches corresponding to the multiple of the smallest punching constituted by the opening in question. It is only necessary to produce six different fins 110 to obtain the configurations of all fins 110a-l.

[0047] The invention has been described above with reference to a specific embodiment of a flue gas exchanger according to the invention and for specific embodiments of fins. It will be possible to use alternative embodiments of both flue gas exchanger and fins. Thus, the flue gas exchanger may contain a number of blocks of fins other than eight, and the number of fins in each block may be different.

[0048] The invention is not limited to the particular embodiments described herein, rather only to the appended claims.