Heat exchanger and heating apparatus of improved efficiency

Abstract

 A heat exchanger comprising a burner space (2), a flue duct (14) connected to the burner space (2), and a water duct (12), wherein the water duct (12) and the flue duct (14) are at least partly interwoven, such that a part of the water duct (12) is at least partly surrounded on at least three sides by the flue duct (14). A heating apparatus comprising such a heat exchanger, wherein at least the flue duct (14) is at least partly closed off from the surroundings by covering parts which are relatively easily removable for inspection and maintenance of the flue duct portion in question, preferably such that upon removal of the covering parts, the whole flue duct is accessible from the surroundings.

Description

[0001] This invention relates to a heat exchanger, in particular a heat exchanger for use in a heating apparatus, comprising a burner space, a flue duct connected to the burner space, and a water duct. Such a heat exchanger is known from practice.

[0002] This known heat exchanger comprises a plate-shaped part in which a meandering water duct is included which extends between a first end and a second end. Arranged next to the plate-shaped part, and adjacent thereto, is a flue duct, likewise meandering, which extends between the burner space and a flue discharge. The water duct and the flue duct are then located substantially in parallel planes. Such a heat exchanger has as a disadvantage that a relatively small contact surface exists between, on the one hand, the flue duct and, on the other, the water duct, so that during use such a heat exchanger has a relatively low efficiency, in particular relative to the total mass of the heat exchanger in question.

[0003] The object of the invention is to provide a heat exchanger of the type described in the preamble, whereby the disadvantages mentioned are obviated, while maintaining the advantages thereof. To that end, a heat exchanger according to the invention is characterized by the features according to claim 1.

[0004] By interweaving the water duct and the flue duct at least partly, such that always a part of the water duct is surrounded on at least three sides by the flue duct, the advantage is achieved that in a heat exchanger of the same mass a greater contact surface can be obtained between the water duct and the flue duct than in a heat exchanger of the above-mentioned, known kind. As a result, during use, a better heat exchange is obtained between the heated flue gases and the water to be heated, so that efficiency is improved and moreover convenience is increased. Further, the advantage can be achieved that the water duct portions in question are better insulated, so that less of the absorbed heat is released to the surroundings again, which has likewise an efficiency-enhancing effect. A further advantage of a heat exchanger according to the present invention is that the heat exchanger can be made of relatively compact design, which is technically advantageous in terms of space. The flue duct can be made relatively long in proportion to the overall height of the heat exchanger.

[0005] In a particularly advantageous embodiment, a heat exchanger according to the invention is characterized by the features according to claim 4.

[0006] By arranging a portion of the water duct and an adjacent portion of the flue duct in mirrored relation with respect to a main plane, while the relevant portions of the water duct and the flue duct are mutually connected by mutually crossing intermediate parts, the advantage is achieved that a water duct and/or a flue duct of a relatively great length can be provided in a heat exchanger of relatively small outside dimensions, while involving intensive contact between the flue duct and the water duct. This advantage is enhanced still further by a series of first and second portions of the water duct and the flue duct, respectively, arranged in mutually mirrored relation.

[0007] In an advantageous embodiment, the main plane extends in a direction approximately perpendicular to a bottom surface of the burner space, but the main plane can also extend in a different direction and may, for instance, be singly or doubly curved. Optionally, the main plane can also consist of a number of main subplanes mutually including an angle, for instance, extending zigzag or taking an otherwise angular form.

[0008] By having the flue duct intersect the main plane between each first and second position, it is ensured still better that the flue duct surrounds the relevant water duct portions on three sides, yielding a particularly great length of the flue duct relative to the total length of the main plane portion enclosed by the first and second positions in question.

[0009] In further elaboration, a heat exchanger according to the invention is further characterized by the features according to claim 5.

[0010] The mutual connection of the wall portions of the water duct portions, while between the connecting parts flue gas passages are provided, provides the advantage that during use a still better contact is obtained between, on the one hand, the heated flue gases and, on the other, the water to be heated. Moreover, as a result, in a relatively simple manner, a constructionally favorable connection between the different parts is obtained. By designing the connecting elements as partitions or the like, advantageous use can be made of a regular material thickness in the heat exchanger, so that, for instance, heat stresses are limited or prevented.

[0011] In a still further elaboration, a heat exchanger according to the invention is further characterized by the features according to claim 7.

[0012] By these features, in a particularly suitable manner, a high degree of interweaving of the water duct and the flue duct is obtained. Moreover, such a heat exchanger is of constructionally simple makeup, with a maximum contact surface between the water duct and the flue duct.

[0013] A heat exchanger according to the present invention is preferably manufactured by casting from a light metal or a light metal alloy. This provides the advantage that a particularly favorable ratio is obtained between the total mass of the heat exchanger, the heat transferring surface between the water duct and the flue duct, and the heat capacity of the heat exchanger. In particular aluminum or an aluminum alloy is then advantageous because of the favorable material properties in connection with flue gases and water, the suitable coefficient of heat conduction, cost price and processability.

[0014] The invention further relates to a heating apparatus comprising a heat exchanger according to the present invention. Such a heating apparatus is characterized according to the invention by the features according to claim 11.

[0015] The use of such covering parts for covering or clearing, as desired, parts of the flue duct, provides the advantage that maintenance of the heat exchanger is easy to carry out. In fact, by removing a covering part, the thus accessed portion of at least the flue duct can be readily inspected and cleaned, whereafter the covering part can be re-placed for sealing the flue duct portion in question. In particular when the heat exchanger is used with fuels of lesser quality, which do not provide for optimum combustion, this is advantageous, since deposits of, for instance, soot in the flue duct can thereby be readily removed, which leads to better performance of the heat exchanger. What is thereby, at least largely, prevented is that the NO_x and the CO₂ contents in the flue gases become unacceptable during use.

[0016] A heating apparatus according to the present invention is preferably designed to be of the condensing type.

[0017] Further advantageous embodiments of a heat exchanger and a heating apparatus according to the invention are given in the further subclaims.

[0018] To clarify the invention, exemplary embodiments of a heat exchanger and a heating apparatus according to the present invention will be described with reference to the drawings. In the drawings:

Fig. 1 is sectional front view of a heat exchanger according to the invention, taken on the line I-I of Fig. 2;

Fig. 2 is a sectional side elevation of a heat exchanger, taken on the line II-II in Fig. 1;

Fig. 3 is a partly sectional top plan view of a heat exchanger according to Figs. 1 and 2;

Fig. 4 is a side elevation of an alternative embodiment of a heat exchanger according to the present invention; and

Fig. 5 schematically shows a heating apparatus comprising a heat exchanger according to the present invention.

[0019] In this description, the same or corresponding parts have the same or corresponding reference numerals.

[0020] A heat exchanger 1 according to the invention comprises a burner space 2 having a substantially cylindrical wall 4, a top face 6 and a bottom face 8. Connected to the bottom face 8 is a body 10 which comprises a water duct 12 and a flue duct 14, as will be further elucidated. Around the wall 4 of the burner space 2 extends an auxiliary water duct 16, which links up via a bend part 18 with a first end 20 of the water duct 12.

[0021] In the side elevation shown in Fig. 2, at least the body 10 comprises a main plane V. The body 10 comprises a first water duct portion 12a, which extends horizontally during use, and a second 12b, third 12c and fourth water duct portion 12d, the four water duct portions extending parallel to each other. Next to each water duct portion 12a-d extends an adjacent flue duct portion 14a-d. A first, upper position 22, which is located against the burner space 2, comprises the first water duct portion 12a and the first flue duct portion 14a; the adjacent, at least subjacent, position 24 comprises the second water duct portion 12b and the second flue duct portion 14b; the third position 26 comprises the third water duct portion 12c and the third flue duct portion 14c; and the lowermost, fourth position 28 comprises the fourth water duct portion 12d and the fourth flue duct portion 14d. In the arrangement shown in Fig. 2, in the first position 22 and the third position 26, the flue duct portions 14a and 14c, respectively, lie on the right side of the main plane V, while the water duct portions 12a and 12c, respectively, lie on the left side of the flue duct portions 14a, 14c in question. In the second position 24 and fourth position 28, the position of the water duct portions 12b, 12d and flue duct portions 14b, 14d is mirrored relative to the main plane, with respect to the first 22 and third position 26. Below the lowermost position 28, the flue duct 14 connects to a flue discharge 30. Viewed from the burner space 2 in the direction of the flue discharge 30, the flue duct portions 14a-d therefore lie alternately on opposite sides of the main plane V. Between the adjacent positions 22 and 24, 24 and 26, and 26 and 28, respective flue passages 32, 34, and 36 have been formed for connecting the flue duct portions 14a-d and the flue discharge 30. The flue duct 14 therefore has a meandering configuration having, during use, alternately a vertical flue duct portion 14a-d and a horizontal flue duct portion which comprises the flue passage 32, 34 and 36, respectively.

[0022] For forming the flue passages 32-36, there are included between the adjacent water duct portions 12 a number of ribs or partitions 38, or like provisions, which extend parallel to each other, perpendicular to the direction of flow of the water duct portions 12 in question. As a result, moreover, the water duct portions 12 and the flue duct portions 14 are physically connected with each other. Between the partitions 38, the flue passages 32 are formed.

[0023] Each water duct portion 2a-d is therefore surrounded on three sides by the flue duct 14. In each flue duct portion 14a-d, on the wall portion of the water duct portion 12 in question proximal to the flue duct portion in question, a number of heat transferring surface enlarging elements, in particular projections 42, are arranged in a pattern of mutually staggered rows and columns. The projections 42 extend preferably perpendicularly to the wall portion in question, perpendicular to the direction of flow through the flue duct portion 14 in question and parallel to the direction of flow through the flue passages 32. As a consequence, for the formation of the projections 42 and partitions 38, a clearing die can be readily manufactured.

[0024] As appears from Fig. 1 in particular, the water duct portions 12a-12d are mutually connected by three U-shaped bend parts 44, which are arranged alternately on the left and right side of the body 10 and extend outside the describing lines of the flue duct 14. As a result, a relatively compact construction is obtained without the flue passage 14 being limited or impeded by the connecting parts 44 in question. The water duct 12, in the elevation shown in Fig. 1, has a meandering configuration between the first end 20 and a water inlet 46, to which a return duct of a heating circuit may be connected, as shown in Fig. 5. The auxiliary water duct 16 is provided, adjacent the upper end, with a second connection opening 48, to which a supply duct of a heating circuit can be connected, as likewise shown in Fig. 5.

[0025] In a heating circuit as shown in Fig. 5, a pump (not shown) may be included in the line 62, for the purpose of pumping water through the heating circuit. Optionally, this pump may also be fitted directly to the heat exchanger, for instance instead of the lowermost connecting bend part 44 represented on the left in Fig. 1, opposite the water inlet 46. Thus a relatively compact construction can be obtained. Figs. 4 and 5 schematically show the fan 56, 156, which extends above the heat exchanger. It is also possible, however, to arrange the fan at a different position, for instance next to the burner chamber 2, while a suitable connecting piece can be arranged between the burner 54, 154 and the fan 56, 156. As a consequence, the overall height can be reduced.

[0026] As appears from Figs. 1 and 2, the water duct 12 and the flue duct 14 are very intimately interwoven in the body 10. The water duct 12 meanders in, at least parallel to, the plane V, while the flue duct 14 meanders in, at least parallel to, a plane K, the planes V and K being mutually perpendicular. In the bottom 8 of the burner space 2, a flue gas inlet opening 50 is provided, of a substantially rectangular cross section. Next to the flue gas inlet opening 50, a closing plate 52 is included in the bottom 8, which is removable for inspection of the burner space 2. As appears clearly from Fig. 3, the body 10 in the embodiment shown has a substantially rectangular cross section. This cross section, viewed in top plan view, lies completely within the circumference of the burner space.

[0027] A heat exchanger according to the present invention is preferably manufactured in one piece by casting. As a result, the advantage is achieved that the heat exchanger can rapidly and simply be manufactured accurately, without different parts needing to be built together, so that the risk of, for instance, leaking gaskets is eliminated.

[0028] A heat exchanger 1 according to the invention can be used as follows.

[0029] The heat exchanger 1, as schematically shown in Fig. 5, is received within a housing 3, represented by a chain-dotted line, while in the burner space 2 a burner 54 is received, for instance with a cylindrical burner surface. To the burner 54, in a conventional manner, a fan 56 is connected for premixing air and gas. To that end, in the top wall 6 of the burner space 2 a suitable opening 58 is provided. To the flue discharge 30, a chimney 60 is connected. In addition, the inlet opening 46 and the outlet opening 48 of the water passage made up of the water duct 12, the bend pieces 44, the bend part 18 and the auxiliary water duct 16 are connected, respectively, to the return duct 62 and the supply duct 64 of a space heating circuit 66 with heating elements 68 included therein, schematically represented in Fig. 5. During use, flue gases heated with the burner 54 are produced, which, partly under the influence of the fan 56, are forced from the burner space 2 through the flue gas inlet opening 50 into the flue duct 14 and, meandering therein, led to the flue discharge 30 and the chimney 60. This gives rise, in particular via the heat transferring surface enlarging elements 42 and the water duct wall portions proximal to the flue duct 14, to heat exchange with water flowing through the water duct, which is further heated in the auxiliary water duct 16 before being led to the heating circuit 66. As a result of the relatively great length of the meandering water duct and the meandering flue duct and the relatively great heat transferring surface, a particularly high efficiency is obtained, so that an energy saving can be obtained compared with equivalent aluminum heat exchangers, for instance a saving of about 30%. Moreover, a heating apparatus as shown in Fig. 5 is of compact construction and hence simple to install.

[0030] On opposite sides of the body 10, covering parts 70 are arranged, which close off the flue duct 14 from the surroundings, which covering parts 70 are easily removable for clearing a flue duct portion 14a-14d located behind them. As a consequence, maintenance can be readily carried out on the heat exchanger 1. In particular, the flue duct 14 can be easily cleaned and inspected, for instance for removing deposits such as soot, in order to ensure optimum functioning of the heat exchanger. Certainly when inferior fuel, or fuel of varying quality, is used in the burner 54, this is of particular importance.

[0031] In Fig. 4, an alternative embodiment of a heat exchanger 101 is shown, with covering plates 170 mounted thereon. In this embodiment, the heat exchanger comprises two juxtaposed bodies 110, which are identical. It will be clear that it is also possible, as desired, to use one such body 110 or several of them in one heat exchanger, depending on the desired capacity. The bodies 110 are connected to each other in a manner known per se, for instance by clamped joints, bolt connections or the like, preferably such that the bodies 110 can be separated from each other for maintenance. Each body 110 again comprises four water duct portions 112a-112d, which are located above each other in mutually staggered relation, mirrored relative to a main plane V, each with an adjacent flue duct portion 114a-114d. The walls of the adjacent water duct portions 112 are again mutually connected by partitions 138 extending parallel to each other.

[0032] In the embodiment shown in Fig. 2, each water duct portion 12 has a substantially rectangular cross section with four flat wall portions 13. The water duct portions 12a-12d are at a mutual distance H, viewed parallel to the plane V, which distance corresponds with the height H1 of the partitions 38 and the wall thickness of the facing wall portions 13a, 13b of the relevant water duct portions 12. In the alternative embodiment shown in Fig. 4, the water duct portions 112a-112d have a hexagonal cross section, in that two corners 115 thereof, located adjacent the main plane V, are beveled. Further, the water duct portions are so positioned relative to each other that the facing beveled corners 115 are located approximately straight above each other and are connected with each other by the partitions 138. The proximal wall portions 113a, 113b of the water duct portions, extending perpendicularly to the main plane V, are located approximately in line with each other, so that the water duct portions can be stacked somewhat more closely on top of each other than in the embodiment described earlier, while the flue duct 114 has a great length and, as a consequence of the relatively gentle bends, has a low flow resistance. In the embodiment shown in Fig. 4, the flue duct portions on the facing sides of the two bodies 110 are closed off by oppositely located vertical wall portions 113c of corresponding water duct portions, so that closed flue ducts 114 are obtained. Upon separation of the two bodies 110, the flue duct portions in question are rendered accessible for inspection and maintenance. In this way, a particularly compact heat exchanger is obtained, having a very large heat exchanging surface and a simple construction. In such an embodiment too, a heat exchanger has a particularly high efficiency during use. For each body, for the flue duct included therein, a flue gas inlet opening 150 is provided, while the two flue ducts 114 are mutually connected adjacent their lower end and link up with the flue discharge 130.

[0033] The invention is not in any way limited to the exemplary embodiments disclosed in the description and the figures. Many variations thereof are possible within the scope of the invention as outlined by the appended claims.

[0034] Thus, a heat exchanger according to the present invention can include several flue ducts and/or water ducts in mutually interwoven configuration. In addition, the main plane, or each main plane, can be, for instance, singly or doubly curved. Thus, the main plane can extend like the circumferential surface of a cylinder, parallel to the outer wall of the burner chamber, at least with a centerline extending parallel to a longitudinal direction of the burner space. The flue passages between each first and second position are then oriented substantially radially, the direction of flow of each water duct is approximately axial, and the direction of flow of each flue duct portion is substantially parallel to the circumferential surface. Thus, a heat exchanger of a relatively small overall height is obtained. Also, the body can be positioned differently with respect to the burner space, for instance rotated through an angle in the main plane V. Further, the heat transferring surface enlarging elements can be differently designed, for instance as ribs, fins or the like. A heating apparatus according to the present invention can be of condensing design, while at the lower end of the heating apparatus, in a manner known per se, a siphon or the like may be connected for discharging condensate. Further, more or fewer water duct portions can be provided, which, moreover, can have cross sections of a different nature, for instance oval, circular, or polygonal, while the covering parts may also be included between the water duct portions.

[0035] These and many comparable variations are understood to fall within the scope of the invention as set forth in the claims.

Claims

1. A heat exchanger comprising a burner space, a flue duct connected to the burner space, and a water duct, wherein the water duct and the flue duct are at least partly interwoven, such that a part of the water duct is at least partly surrounded on at least three sides by the flue duct.

2. A heat exchanger according to claim 1, wherein at least the interwoven part of the water duct and the flue duct comprise a main plane, while, viewed in the direction of flow of the flue duct,

- a first part of the flue duct and an adjacent first part of the water duct take a first position relative to the main plane, and

- a second part of the flue duct and an adjacent second part of the water duct have a second position, mirrored relative to the first position, in particular mirrored relative to the main plane.

3. A heat exchanger according to claim 2, wherein the flue duct and the water duct take a series of first and a series of second positions.

4. A heat exchanger according to claim 2 or 3, wherein the flue duct intersects the main plane between each first and a second position.

5. A heat exchanger according to claim 4, wherein the facing wall portions of the water duct in a first position and the adjacent second position are mutually connected by connecting elements, in particular partitions, while between the connecting elements flue passages are provided.

6. A heat exchanger according to any one of claims 2-5, wherein the water duct, at least between the or each first and second position, comprises a bend part which extends substantially out of contact with the wall of the flue duct.

7. A heat exchanger according to any one of the preceding claims, wherein the flue duct, viewed in a first view, extends substantially in meandering configuration between the burner space and a flue discharge, while the water duct, viewed in a second view, extends substantially in meandering configuration between a first end and a second end, and the second view includes an angle with the first view, preferably approximately a right angle.

8. A heat exchanger according to any one of the preceding claims, wherein the flue duct is at least partly provided with heat transferring surface enlarging elements, in particular projections or fins, which are in communication with at least one wall of the water duct.

9. A heat exchanger according to any one of the preceding claims, wherein the burner space is at least partly surrounded by an auxiliary water duct which links up with the water duct.

10. A heat exchanger according to any one of the preceding claims, which has been manufactured substantially in one piece by casting from a light metal or a light metal alloy, in particular aluminum or an aluminum alloy.

11. A heating apparatus comprising a heat exchanger according to any one of the preceding claims, wherein at least the flue duct is at least partly closed off from the surroundings by covering parts which are relatively easily removable for inspection and maintenance of the flue duct portion in question, preferably such that upon removal of the covering parts, the whole flue duct is accessible from the surroundings.

Drawing