Condensing Heat Exchanger

Abstract

The invention relates to a condensation heat exchanger (10) comprising: at least one tube (7) in the form of a helical winding (70) having a planar front face (71) and a planar rear face (72) and housed in a casing (2), means (5) for generating hot gases in said casing, a disc-shaped deflector (8) provided with a peripheral flange (823) and arranged on the helical winding (70) so that said flange is inserted in the gap between two successive turns, a combustion chamber (25) and a condensation chamber (26) being provided in the casing (2). This exchanger is notable in that the front face (8231) of the flange (823) is hermetically attached to the rear face (72) of the last turn (702) of the winding (70) located in the combustion chamber (25), at least one protruding element (8233) is arranged between the rear face (8232) of the flange (823) and the front face (71) of the first turn (703) located in the condensation chamber (26) such that a gap (73') for the circulation of gases is provided therebetween, and the outer diameter (D1) of the disc-shaped deflector is smaller than the inner diameter (D2) of the helical winding (70) and is adapted to provide a passage (27) for the circulation of hot gases.

Description

[Technical Field]

[0001] The invention is in the field of condensing heat exchangers.

[0002] The invention more particularly relates to the structure of a deflector disposed between the condensation chamber and the combustion chamber of the exchanger, and to the manner in which the deflector is secured. Summary of the Invention

[0003] technical level FIG. 1 of the accompanying drawings represents a cross-section of an exemplary embodiment of a condensing heat exchanger according to the state of the art.

[0004] In this figure, it can be seen that the condensing heat exchanger 1 comprises a casing 2, spirally wound tubes 3, a door 4, means for supplying or generating hot gas 5, and a deflector 6.

[0005] This heat exchanger 1 extends along a longitudinal axis X-X'. In Figure 1 it is represented in its normal use position.

[0006] The casing 2 comprises a tubular body 20 of axis X-X', closed at its rear end by a bottom 21 and having at its front end a facade 22. Conventionally, in the remainder of the specification and in the claims, the term "front face" refers to the face directed to the front of the exchanger, i.e. towards the facade 22, and the term "rear face" refers to the face directed to the rear of the exchanger, i.e. towards the bottom 21.

[0007] The casing 2 is provided with a sleeve 23 for discharging the burnt gases, and the lower part of the casing 2 is slightly inclined to allow the discharge of condensed water by gravity through a discharge orifice 24 connected to a duct 240 for discharging these condensates.

[0008] The front part 22 has a rim 220 at its periphery, which is hermetically fixed, preferably welded or crimped, to the front edge of the tubular body 20. The front part 22 has a central opening 221 which can be closed by the door 4.

[0009] The door 4 supports in its central part a burner 50, for example a gas or oil burner, which constitutes an exemplary embodiment of means for producing hot gases 5. This burner 50 can be replaced by means for providing hot gases generated outside the casing 2 and propelled inside it, for example by means of a fan.

[0010] The tube 3 is spirally wound on itself to form a helical winding 30 of a longitudinal axis X-X'. It has two ends, not visible in the figure, which form an inlet and an outlet.

[0011] It is made of a thermally good conducting material, in particular metal, advantageously stainless steel, and is intended to receive a fluid to be heated, such as water.

[0012] The tube 3 has an oval straight section (this case is not shown in the figures) or a rectangular straight section with two longitudinal sides flattened and a long axis perpendicular or nearly perpendicular to the axis X-X' of the helical winding. The tube 3 therefore has a front face 31 and a rear face 32. These faces 31, 32 are planar or substantially planar depending on the cross section.

[0013] Between two adjacent turns of the tube 3 there is a gap 33 of calibrated value. This gap 33 can be obtained, for example, by means of bosses 34 formed on one of the two flat faces of the tube 3, here for example on the front face 31. These bosses are better visible in the attached FIG. 2.

[0014] The deflector 6 is arranged perpendicular to the axis X-X' inside the spiral winding 30 of the tube 3 so as to provide inside the casing 2, on the one hand, a combustion chamber 25 extending between the door 4 and the deflector 6 and including a burner 50, and on the other hand, a condensation chamber 26 extending between the deflector 6 and the bottom 21 of the casing 2.

[0015] Conventionally, the first turn of the portion of the helical winding of the tube 3 located in the combustion chamber 25 is the one that lies in contact with the front part 22 and is referenced by 35, while the last turn of this same portion is referenced by 36. Similarly, the last turn of the portion of the helical winding of the tube 3 located in the condensation chamber 26 is the one that lies in contact with the bottom part 21 and is referenced by 38, while the first turn of this same portion is referenced by 37.

[0016] The deflector 6 comprises a disc 61 made of thermally insulating material, which is supported by a thin sheet metal frame 62, the latter being provided with a radial peripheral flange 63.

[0017] The deflector 6 is attached to the inside of the winding 30 of the tube 3 so that its flange 63 is inserted and positioned gas-tightly in the gap 33 that exists between the last turn 36 of the tube 3 located in the combustion chamber 25 and the first turn 37 of the tube 3 located in the condensation chamber 26.

[0018] The operation of this heat exchanger 1 is as follows: the fluid to be heated (water) circulates countercurrently to the hot gas: it is introduced into the last turn 38 and leaves the spiral winding through the first turn 35.

[0019] The hot gases produced inside the combustion chamber 25 by the burner 50 can only leave the latter by passing through the gap 33 from inside to outside (arrow i). In doing so, they heat the walls of the tubes 3 and therefore the water circulating therein. When the hot gases come into contact with the body 20 of the casing 2, they are directed towards the condensation chamber 26 (arrow j), after which they return to the inside of the condensation chamber 26 by passing through the gap 33, this time from outside to inside (arrow k).

[0020] As can be seen in FIG. 1, given the way the deflector 6 is mounted, there is no path for hot gases between the last turn 36 and the flange 63 or between the first turn 37 and the flange 63 .

[0021] Therefore, the heat exchange between the hot gas and the water circulating in the first turn 37 and in the last turn 36 is not good, and therefore the overall efficiency of the exchanger 1 is low.

[0022] Furthermore, this blockage of the passage between the two turns 36 and 37 causes a pressure loss of the hot gas circulating in the casing 2 . Disclosure of the Invention One object of the invention is therefore to overcome the aforementioned drawbacks, in particular to improve the heat exchange between the circulating water and the hot gases in the first turn of the tube on the condensation chamber side and in the last turn on the combustion chamber side, and to increase the number of passages between the turns.

[0023] Another object of the invention is to reduce the pressure loss of the hot gas circulating in the gaps between the turns of the tube.

[0024] To this end, the invention relates to a condensing heat exchanger comprising: - at least one tube wound helically to form a helical winding and inside which a heated fluid, such as water, circulates, the tube being made of a material with good thermal conductivity and having planar or substantially planar front and rear faces facing each other and perpendicular or nearly perpendicular to the axis of the helical winding, the winding being arranged so as to provide gaps between adjacent turns; - an airtight casing inside which said at least one tube is mounted, said casing having a bottom and a front part to which a door is mounted, said casing being provided with a sleeve for discharging the burned gases, the front face of the tube being directed towards the front part of the casing and the rear face of the tube being directed towards the bottom part of the casing; - means for supplying and / or generating hot gases inside the casing, such as a gas or oil burner mounted on the door; - a disc-shaped deflector placed inside the spiral winding of the tube, in order to provide, within the casing, on the one hand, a combustion chamber between the door and said deflector, and on the other hand, a condensation chamber between said deflector and the bottom of the casing, said deflector comprising a disk made of thermally insulating material carried by a sheet metal frame provided with a peripheral flange, said flange being arranged in the gap between two successive turns of said winding, the outer diameter of the disc-shaped deflector being smaller than the inner diameter of the spiral winding caught at the intrados ends of its turns, so as to provide a passage called a "hot gas circulation" passage between the edge of said disc-shaped deflector and the intrados end of the first turn of the winding located in the condensation chamber.

[0025] According to the invention, the flange has a front face directed towards the opposite front part of the casing and a rear face directed towards the bottom of the casing, the front face being arranged in an airtight manner against the rear face of the last turn of the winding located in the combustion chamber, and at least one spacer element is arranged between the rear face of the flange and the front face of the first turn of the winding located in the condensation chamber so as to provide a gap therebetween, called a "gas circulation" gap, so that these hot gases pass radially or almost radially through the gas circulation gap from outside to inside and then axially through the gas circulation passage from front to rear in the direction of the condensation chamber.

[0026] Thanks to the inventive features, the hot gases can circulate between the last turn of the tubes on the combustion chamber side and the first turn of the tubes on the condensation chamber side, thereby improving the heat exchange. Thus, in the exemplary embodiment depicted in Figures 1 and 3, there are four turns in the condensation chamber, and while in the state of the art (see Figure 1) there are only three passages for the hot gases between these four turns, with the inventive solution (see Figure 3) there are four passages, i.e. a 33% increase in the passages for the hot gases.

[0027] Furthermore, the creation of the gas circulation gap and the hot gas circulation passage makes it possible to reduce the pressure loss of the circulation gas, so that the fan (not shown) making it possible to force the air / gas mixture into the burner 50 or the fan of the hot gas supply means 5 does not have to be as powerful as in the state of the art and its electrical consumption is lower.

[0028] According to other advantageous, non-limiting features of the invention, the following may be incorporated, either alone or in combination: - the front face of the first turn of the winding located in the condensing chamber is provided with an annular shoulder extending from the inner end of this turn, and said at least one spacer element extends between said annular shoulder and said rear face of the flange to form said circulation gap; - the rear face of the last turn of the winding located in the combustion chamber is provided with an annular shoulder extending from the inner end of this turn, and the front face of the flange is positioned in an airtight manner against this annular shoulder; - the spacer element is constituted by a protruding element, such as a stamping, formed on the rear face of the flange, which protruding element bears against the front face of the first turn of the winding located in the condensation chamber or against an annular shoulder of this front face, so as to provide the gas circulation gap; - the spacer element is constituted by a protruding element, such as a boss, formed in the wall of the tube, which protrudes from the front face of the first turn of the winding located in the condensation chamber or from an annular shoulder on this front face, and which protruding element rests against the rear face of the flange so as to provide the gas circulation gap.

[0029] - the spacer element is constituted by a comb-like part having teeth interposed between the front face of the first turn of the winding located in the condensation chamber and the rear face of the flange so as to provide the gas circulation gap; - the sheet metal frame of the disc-shaped deflector has a circular bottom bordered by an annular rim perpendicular to the bottom to provide a disc-shaped cavity for receiving a disc made of thermally insulating material, a peripheral flange projecting outwardly from the annular rim; - a disk made of thermally insulating material has a protruding end protruding from a disk-shaped cavity inside the combustion chamber, the diameter of this protruding end being equal to the inner diameter of the spiral winding of the tube caught by the inner end of the turn of the tube, so that the lateral edges of this protruding end come into gas-tight contact with the inner end of the last turn of the tube located in the combustion chamber, thus preventing the passage of hot gases between them; - the exchanger has a single tube forming a helical winding, and the peripheral flange of the sheet metal frame of the deflector is helical; - the exchanger comprises at least two tubes spirally wound to form at least two adjacent spiral windings, one of which is arranged in the combustion chamber and the other in the condensation chamber, the peripheral flange of the sheet metal frame of the deflector arranged between said two adjacent windings being annular and perpendicular to the axes of the two adjacent spiral windings; [Brief explanation of the drawings]

[0030] Other features, objects and advantages of the invention will become apparent from the following description, which is given by way of example only and is not limiting, and which is to be read in connection with the accompanying drawings, in which: [Figure 1] FIG. 1 is a longitudinal section of an exemplary embodiment of a condensing heat exchanger according to the state of the art. [Figure 2] FIG. 2 is a perspective view of a portion of the heat exchanger tube of FIG. [Figure 3] FIG. 3 is a longitudinal sectional view of a first embodiment of a condensing heat exchanger according to the invention. [Figure 4] FIG. 4 is a perspective view of a portion of an exchanger tube located in the condensation chamber of a heat exchanger according to the invention. [Figure 5] FIG. 5 is a perspective view of a first embodiment of a deflector intended to be located in a heat exchanger according to the invention. [Figure 6] FIG. 6 is a perspective view of a second embodiment of a deflector intended to be located in a heat exchanger according to the invention. [Figure 7] FIG. 7 is a detailed view of the lower portion of the condensing heat exchanger of FIG. 3, showing a portion of the deflector, with the last two turns of the tube located in the combustion chamber and the first two turns of the tube located in the condensing chamber. [Figure 8] FIG. 8 is a detailed view similar to FIG. 7, but showing a second embodiment of a condensing heat exchanger according to the invention. [Figure 9] FIG. 9 is a detailed view similar to FIG. 7, but showing a third embodiment of a condensing heat exchanger according to the invention. [Figure 10]FIG. 10 is a detailed view similar to FIG. 7, but showing a fourth embodiment of a condensing heat exchanger according to the invention. [Figure 11] FIG. 11 is a detailed view similar to FIG. 7, but showing a fifth embodiment of a condensing heat exchanger according to the invention. [Figure 12] FIG. 12 is a perspective view of a spacer element. DETAILED DESCRIPTION OF THE INVENTION

[0031] Detailed Description of the Invention The heat exchanger according to the invention, referenced 10, will now be described in more detail with reference to Figure 3. Elements in common with the state-of-the-art exchanger 1, previously described in connection with Figures 1 and 2, are given the same numerical references and will not be described in detail again.

[0032] The heat exchanger 10 differs from the previous one by the structure of the tubes in the vicinity of the deflector and by the structure of this deflector. In this exchanger 10, the tubes have the reference 7 and the deflector has the reference 8.

[0033] As represented in Figure 3, the heat exchanger 10 may comprise a single tube 7 spirally wound about an axis X-X' so as to form a helical winding 70. It has two ends forming an inlet and an outlet section, not visible in the figure. It is made of a material with good thermal conductivity, in particular metal, advantageously stainless steel. The fluid to be heated circulates therein.

[0034] The tube 7 has a straight, preferably oblong, cross-section (for example oval or oval with two flattened longitudinal sides or a straight section of a rectangle), thereby having two opposite lateral faces which are therefore planar or substantially planar front and rear faces 71 and 72, respectively, which are perpendicular or nearly perpendicular to the axis X-X' of the winding 70.

[0035] The different turns of the tube 7 are spaced apart from one another by gaps 73 of calibrated width L.

[0036] The inner end of each turn of the spiral winding 70 (i.e., the end located on the inside of the winding) is referenced 74 and has the shape of a linear arc of a circle. The same is true for the opposite outer end, referenced 75.

[0037] The gap 73 is calibrated using spacer elements.

[0038] Advantageously, the gap 73 can be calibrated in the wall of the tube 7 by means of bosses 76 (or corrugations) formed on one of the flat faces of this tube 7 (for example the front face 71 here). These bosses 76 are arranged substantially radially with respect to the axis X-X'. They are identical to the bosses 34 of the tube 3. Each boss 76 rests against the face of the adjacent turn (which is not provided with a boss). These bosses have a well-defined height, making it possible to precisely calibrate the width of the gap 73.

[0039] The gaps 73 can also be formed with combs 9, such as those depicted in Figures 10 and 11. Such combs have a central bar 90 and a number of vertical tabs 91 (comb teeth). The combs 9 are positioned relative to the winding 70 such that each tooth 91 is inserted between two consecutive turns of the winding 70. Preferably, at least two combs 9 are used, positioned on either side of the winding 70.

[0040] The first and last turns of the portion of the helical winding 70 located in the combustion chamber 25 have numerical references 701 and 702, respectively, and the first and last turns of the portion of the winding 70 located in the condensation chamber 26 have numerical references 703 and 704, respectively (see FIG. 3).

[0041] Deflector 8 comprises a disk 81 made of thermally insulating material supported by a thin sheet metal frame 82. As can be better seen in Figures 5 and 6, frame 82 has a circular bottom 820 bordered by an annular rim 821 perpendicular to the bottom. Bottom 820 and rim 821 together define a disc-shaped cavity 822 that is sized to receive and hold disk 81.

[0042] In the case where the heat exchanger 10 comprises a single spirally wound tube 7, the frame 82 is shaped as shown in Figure 5 and has a flange 823 extending substantially radially outward from the rim annulus 821, the flange 823 being spirally shaped so that it can be inserted between two consecutive spiral turns of the same tube.

[0043] The exchanger 10 can also comprise a number of tubes 7, each wound in a spiral around an axis X-X' and arranged side by side with their axes coaxial. Thus, for example, it is possible to have a first tube winding arranged in the condensation chamber 26, inside which circulates a first fluid to be heated, and a second tube winding in the combustion chamber 25, inside which circulates the same first fluid and possibly a second fluid to be heated.

[0044] If the heat exchanger 10 comprises at least two spirally wound tubes 7 arranged side by side, the deflector frame is slightly different from the previous one. It has the reference 82' and is shown in FIG. 6. It has a flange 823', which is annular and extends radially outward from an annular rim 821, which has a certain height. The flange 823' is perpendicular to the axis X-X'.

[0045] Next, various embodiments of the invention will be described which make it possible to place a deflector 8 on the tube 7 while leaving space for the passage of gas between this deflector and the first turn of the tube 7 located in the condensation chamber 26.

[0046] For the sake of simplicity, these various embodiments are described only for the case where the heat exchanger 10 comprises a single winding 70 and the deflector 8 comprises a frame 82, as represented in Figure 5. However, all these embodiments can also be implemented with at least two different windings, one attached to the combustion chamber 25 and the other to the condensation chamber 26, on either side of the deflector 8, which then comprises a frame 82' as represented in Figure 6.

[0047] Next, a first embodiment of the flange of the deflector 8 and of the tube 7 will be described in more detail with reference to FIGS. 3 to 5 and 7. FIG.

[0048] The front face 71 of the first turn 703 has an annular shoulder 77. This shoulder is annular in that it extends around the periphery of the first turn 703 (see Figure 4).

[0049] This annular shoulder 77 extends from the inner ring end 74, preferably at a distance between one-third and one-half of the height H of the first turn 703. The width L1 between the front face 71 of the first turn 703 and the rear face 72 of the last turn 702, taken at the level of the shoulder 77, is therefore greater than the width L of the gap 73.

[0050] Due to the presence of this shoulder 77, the bosses on the front face 71 of the first turn 703 are slightly offset towards the outside of the turn without the shoulder 77 and are marked with the reference 76'. Due to the cut plane, these bosses 76' are not visible in Figure 7 but are visible in Figures 3 and 4. The bosses 76' rest against the rear face 72 of the last turn 702.

[0051] The tube 7 is advantageously obtained by hydroforming, which makes it possible to precisely position the shoulder 77 and the bosses 76, 76'.

[0052] The flange 823 of the frame 82 has a front face 8231 facing the front part 22 and an opposite rear face 8232. The rear face 8232 has at least one protruding element 8233, for example in the form of a pin, preferably in the form of several pins. These pins are advantageously obtained by stamping the front face 8231. They are distributed, preferably evenly, over the entire periphery of the flange 823 and act as spacers.

[0053] The deflector 8 is attached to the inside of the winding 70 so that the flange 823 is inserted between the rear face 72 of the last turn 702 and the shoulder 77 of the first turn 703, and one or more protruding elements 8233 rest against this shoulder 77, thus providing a gap 73', referred to as a "gas circulation" gap, between the shoulder 77 and the rear face 72 of the last turn 702. Furthermore, the flange 823 is inserted so that its front face 8231 is gas-tightly positioned (pressed) against the planar rear face 72 of the last turn 702. The flange 823 is thus sandwiched between two successive turns 702 and 703. Hot gas circulates in this gap 73' radially from the outside to the inside of the winding 70 (see arrow m in FIG. 3 ).

[0054] Furthermore, the outer diameter D1 of the deflector 8, more particularly the outer diameter of the disc-shaped cavity 822 of the frame 82 taken here at the level of the outer surface of the rim 821, is smaller than the inner diameter D2 of the helical winding 70 measured at the inner end 74 of the turn so as to provide an axial annular passage called "gas circulation passage" 27 between the rim 821 and the inner end 74 of the first turn 703. Hot gases circulate axially from front to rear in this passage 27 (see arrow n in Figure 3).

[0055] This gas circulation passage 27 connects the gas circulation gap 73' with the condensation chamber 26. Thus, contrary to what is the case in the state of the art, hot gas can circulate between the last turn 702 and the first turn 703, thereby increasing the heat exchange with the heated fluid (e.g. water) circulating in the tube 7.

[0056] Advantageously, the disk 81, made of a thermally insulating material, is thicker than the annular rim 821 and has a protruding end 810 whereby it protrudes in the direction of the combustion chamber 25 (see FIG. 3). Advantageously, this protruding end 810 has a diameter D3 equal to the inner diameter D2 of the helical winding 70, so that a lateral edge 811 of this end 810 comes into contact with the inner ring end 74 of the last turn 702, thereby preventing the passage of hot gases at this location.

[0057] Furthermore, it is noted that the shoulder 77 arranged facing the flange 823 makes it possible to obtain a constant rolling space in the last turn 702 without it being reduced by the thickness of the sheet metal of the flange 823.

[0058] A second embodiment of the flange of the deflector 8 and the tube 7 will now be described in more detail with reference to FIG.

[0059] This embodiment differs from the first in that the flange 823 does not have any protruding elements, and the first turn 703 has at least one protruding element 770 (spacer), preferably a plurality of protruding elements, formed on the other annular shoulder 77. These protruding elements 770 are preferably evenly distributed radially on the shoulder 77. As described above, the front surface 8231 of the flange 823 is positioned (pressed) gas-tightly against the planar rear surface 72 of the last turn 702. Furthermore, the protruding element 770 (preferably a boss) abuts against the rear surface 8232 of the flange 823, which makes it possible to provide a gas circulation gap 73'.

[0060] A third embodiment of the flange 823 and tube 7 of the deflector 8 will now be described with reference to Figure 9. It differs from the first embodiment described in connection with Figure 7 simply in that the rear face 72 of the last turn 702 on the combustion chamber side has an annular shoulder 78. Preferably, this annular shoulder 78 extends from the inner ring end 74 to one-third to one-half of the height H of the last turn 702. The front face 8231 of the flange 823 is arranged gas-tight against this annular shoulder 78, and the height of the protruding element 8233 is accordingly adapted to contact the shoulder 78.

[0061] Next, a fourth embodiment of the flange of the deflector 8 and the tube 7 will be described with reference to FIG.

[0062] It differs from the third embodiment of FIG. 9 in that the flange 823 does not include a protruding element 8233 and the first turn 703 does not include a shoulder 77 but does include a protruding element 770 on the other hand.

[0063] It is easy to understand that different embodiments can be combined by providing shoulders 77 and / or 78 and various spacer elements 8233 and / or 770, as long as circulation space 73' is provided.

[0064] Finally, a fifth embodiment will be described with reference to Figures 11 and 12. The aforementioned comb 9 is also used to form the gas circulation gap 73'. In this case, one of its teeth 91 is interposed (clamped) on the condensation chamber side 26 between the rear face 8232 of the flange 823 and the front face 71 of the first turn 703, while the flange 823 is placed gas-tightly against the rear face 72 of the last turn 702.

Claims

1. A condensation heat exchanger (10), comprising: at least one tube (7) wound helically to form a helical winding (70) and inside which a heated fluid, such as water, circulates, said tube (7) being made of a material with good thermal conductivity and having, facing each other, a planar or substantially planar front face (71) and a planar or substantially planar rear face (72) perpendicular or nearly perpendicular to the axis (X-X') of said helical winding (70), said winding being arranged so as to provide gaps (73) between adjacent turns; a gas-tight casing (2) inside which said at least one tube (7) is mounted, said casing (2) having a bottom part (21) and a front part (22) to which a door (4) is mounted, said casing (2) being provided with a sleeve (23) for discharging the burnt gases, said front face (71) of said tube (7) being directed towards said front part (22) of said casing (2) and said rear face (72) of said tube (7) being directed towards said bottom part (21) of said casing (2); - means (5) for supplying and / or generating hot gas inside the casing, such as a gas or oil burner (50), attached to the door (4); a disk-shaped deflector (8) arranged inside the helical winding (70) of the tube, so as to provide, inside the casing (2), a combustion chamber (25) between the door (4) and the deflector (8) on the one hand, and a condensation chamber (26) between the deflector (8) and the bottom (21) of the casing on the other hand, said deflector (8) being made of a thermally insulating material carried by a sheet metal frame (82', 82) provided with peripheral flanges (823, 823'); a disk-shaped deflector (8) comprising a flange (81) which is interposed in the gap between two successive turns of the winding (70), the outer diameter (D1) of the disk-shaped deflector (8) being smaller than the inner diameter (D2) of the helical winding (70) captured at the inner end (74) of its turn, so as to provide a passage called the "hot gas circulation" passage (27) between the edge of the disk-shaped deflector (8) and the inner end (74) of the first turn (703) of the winding located in the condensation chamber (26); Equipped with The flanges (823, 823') have a front face (8231) facing the front part (22) of the casing (2) opposite each other and a rear face (8232) facing the bottom part (21) of the casing (2), the front face (8231) being positioned gas-tight against the rear face (72) of the last turn (702) of the winding (70) located in the combustion chamber (25), and at least one spacer element (8233, 770, 91) is provided between the flanges (823, 823' ) and the front face (71) of the first turn (703) of the winding (70) located in the condensation chamber (26), so as to provide a gap therebetween called a "gas circulation" gap (73'), whereby these hot gases pass radially or approximately radially through the gas circulation gap (73') from outside to inside, and then pass axially through the gas circulation passage (27) from front to rear in the direction of the condensation chamber (26), Condensing heat exchanger (10).

2. 2. The heat exchanger (10) of claim 1, characterized in that the front face (71) of the first turn (703) of the winding (70) located in the condensation chamber (26) is provided with an annular shoulder (77) extending from the inner ring end (74) of this turn, and the at least one spacer element (8233, 770) extends between the annular shoulder (77) and the rear face (8232) of the flange (823, 823') to form the gas circulation gap (73').

3. 2. The heat exchanger (10) of claim 1, characterized in that the rear face (72) of the last turn (702) of the winding located in the combustion chamber (25) is provided with an annular shoulder (78) extending from the inner ring end (74) of that turn, and that the front face (8231) of the flange (823, 823') is arranged in an air-tight manner against that annular shoulder (78).

4. 2. The heat exchanger (10) according to claim 1, characterized in that the spacer element comprises a protruding element (8233), such as a stamping, formed on the rear face (8232) of the flange (823, 823'), which protruding element (8233) bears against the front face (71) of the first turn (703) of the winding located in the condensation chamber (26) or against the annular shoulder (77) of this front face (71) so as to provide the gas circulation gap (73').

5. 2. The heat exchanger (10) according to claim 1, characterized in that the spacer element comprises a protruding element (770), such as a boss formed in the wall of the tube (7), which protrudes from the front face (71) of the first turn (703) of the winding (70) located in the condensation chamber (26) or from the annular shoulder (77) of this front face (71), and which protrudes against the rear face (8232) of the flange (823, 823') so as to provide the gas circulation gap (73').

6. 2. The heat exchanger (10) according to claim 1, characterized in that the spacer element comprises a comb (9) having teeth (91) interposed between the front face (71) of the first turn (703) of the winding (70) located in the condensation chamber (26) and the rear face (8232) of the flange (823, 823') so as to provide the gas circulation gap (73').

7. 2. A heat exchanger (10) according to claim 1, characterized in that the sheet metal frame (82) of the disc-shaped deflector (8) has a circular bottom (820) bordered by an annular rim (821) perpendicular to said bottom so as to provide a disc-shaped cavity (822) for receiving said disk (81) made of thermally insulating material, and in that said peripheral flanges (823, 823') project outwardly from said annular rim (821).

8. 8. The heat exchanger (10) according to claim 7, characterized in that the disk (81), made of thermally insulating material, has a protruding end (810) protruding from the disk-shaped cavity (822) inside the combustion chamber (25), and that the diameter (D3) of this protruding end (810) is equal to the inner diameter (D2) of the spiral winding (70) of the tube captured at the inner end (74) of the turn of the tube, so that the lateral edge (811) of this protruding end (810) is in gas-tight contact with the inner end (74) of the last turn (702) of the tube located in the combustion chamber (25), thereby preventing the passage of hot gas between the two.

9. 2. A heat exchanger (10) according to claim 1, characterized in that it comprises a single tube (7) forming the helical winding (70) and that the peripheral flange (823) of the sheet metal frame (82) of the deflector (8) is helical.

10. A heat exchanger (10) according to claim 1, characterized in that it comprises at least two tubes (7) wound in a spiral to form at least two adjacent spiral windings (70), one arranged in the combustion chamber (25) and the other arranged in the condensation chamber (26), and that the peripheral flange (823') of the sheet metal frame (82) of the deflector, arranged between the two adjacent windings (70), is annular and perpendicular to the axis (X-X') of the two adjacent spiral windings (70).

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