EP0576963A1 - Residual heat exchanger for mounting in the boiler casing - Google Patents

Abstract

The invention relates to a residual heat exchanger for mounting in the boiler casing, consisting of a water-conducting and a gas-conducting inner space, which spaces are separated from one another by walls extending parallel to one another and wound spirally round a packing and are closed with respect to one another by edges bent at right angles. To construct such a residual heat exchanger in a special configuration such that the components involved can be dimensioned as thin as possible, taking into account the winding process, the whole nevertheless being sufficiently pressure-resistant in the finished state, that separate spacers not actually belonging to the heat exchanger can be dispensed with, and that, lastly, during the winding process to a spiral the edges to be connected by welding are unable, or virtually unable, to be distorted in undulating fashion and also the wall faces are unable to be deformed, the residual heat exchanger according to the invention is constructed in such a way that the inner wall (1), in relation to the winding axis (WA), has edges (4) which are bent outwards at right angles at the top and bottom and correspond maximally to the width (B) of the water-conducting inner space (3), and the outer wall (2) has edges (6) bent inwards at right angles and of maximally half the width (B), which edges (6) cover over the edges (4) of the inner wall (1) or are aligned therewith and are connected thereto in a fluid-tight manner. Undulating embossed portions (7) of both walls (1, 2), facing into the gas-conducting inner space (3') which is open to the inflow and outflow side, are arranged, in mutually supporting fashion, at a distance (D) from the edges (4, 6) in the walls (1, 2) substantially parallel to the winding axis (WA). The water-conducting inner space (3) at both ends of the spiral is closed, except for the forward and return connection openings. <IMAGE>

Description

The invention relates to a secondary heat exchanger for installation in the boiler housing according to the preamble of claim 1 and it also relates to a method for its production.

Such heat exchangers, which, however, are not intended and suitable as secondary heat exchangers behind the combustion chamber for boilers, are known, for example, from DE-A-925 721 and DE-A-3 014 506. These heat exchangers are not secondary heat exchangers insofar as they contain the combustion chamber itself and the heating gases do not flow axially but also in a spiral. The same also applies to a heat exchanger according to EP-A-0 123 995. For further relevant prior art, reference is made to the following documents:
US-A-2 085 256, DE-A-95 873, DE-A-288 039, DE-A-101 612 and DE-A-1 753 242. Such helically wound heat exchangers are so inexpensive in terms of flow, their compactness and Surprisingly, even the heat exchanger may be found that such heat exchangers, as far as is known, have not been introduced as secondary heat exchangers integrated into the boiler housing behind the combustion chamber, probably not because it is extremely difficult, on the one hand, the resulting, also spiral channels for the media involved in the heat exchanger to be closed on their narrow sides and on the other hand the sheets involved while maintaining their necessary distance from one another, ie without being able to wind spirally at all.

Approaches to feasibility are shown in a proposal for boilers according to DE-A-1 753 242, which, however, has also not proven to be feasible, and a proposal in accordance with DE-PS 925 721, the subject of which, on the one hand, is not suitable as a secondary heat exchanger for boilers is because the heating gases cannot be exposed to an open flow and the heating gas cannot flow axially in a straight line. Also revealed sheet edges exposed on the upstream side of this heat exchanger, which would be subjected to high thermal stresses, and additional spacers must be provided between the channels, which were apparently regarded as a necessary prerequisite in order to be able to wind such a structure spirally at all. Added to this is the fact that the edge bends directed against the winding axis, with which the full width of the individual channels is predetermined, warp in a spiral during winding, since the full width points inwards, which inevitably complicates the welding. The applicability of such spirally wound secondary heat exchangers for boilers thus stands and falls in consideration of the necessary and largely mechanical series production with a design that allows uncomplicated manufacture, i.e. the invention is based on the task, based on the known principle of a spirally wound heat exchanger to design it in a special design in such a way that the components involved, ie essentially the two walls, can be dimensioned as thinly as possible with regard to the winding process, but the whole is still sufficiently pressure-stable in the finished state that that actually does not belong to the heat exchanger, separate spacers can be dispensed with and that, finally, during the winding process to form a spiral, the edges to be connected by welding do not warp, or practically not undulate, and the wall surfaces cannot deform.

This object is achieved with a secondary heat exchanger of the generic type according to the invention by the features stated in the characterizing part of claim 1. Advantageous and special embodiments result from the subclaims.

This training is based on a special manufacturing method in which the welding of the two wall parts takes place during the winding process but immediately after the assembly and the completed differential bending. Here, the two wall parts can still be independent of each other, but already in an assembled form of spiral bending, which is yes for the two parts in radially different spiral planes, follow and are only welded to each other after the bend, whereby it should be noted that "after the bend" does not mean the completion of the entire spiral winding, but only the differential bending processes during the whole spiral winding. In order to take into account series production and continuous production, the method claim 9 is advantageously used, the further method claim constituting a further development which has an advantageous effect on the heat exchanger itself, since the outwardly bent edge of the inner wall is also kept shorter in radial extension can, since the spacing function is taken over by the spacer extending to the welding point. It is essential for the bend width of both edges involved that they remain weldable to each other either in the overlapped position or in the aligned position, the inwardly facing, bent edge being kept as small as possible, since this is more subject to wave deformation during bending than that after outside-facing edge.

The axially oriented wave embossings pointing into the gas-carrying interior have a triple function: on the one hand they contribute to the pressure stability of the walls, on the other hand they increase the heat exchange surface and form the spacers on the gas side for the winding process. "Essentially parallel to the winding axis" is to be understood here that the wave embossments intersect weakly in the assembled state and can thereby be supported selectively. It is important that the crimped edges are not also partially covered with these wave embossings, since this would lead to practically predetermined kinks, which is precisely what is to be avoided. With a greater height of the spiral-wound heat exchanger and possibly also with a view to a special flow on the water side, an advantageous embodiment consists in that the inner wall is provided with at least one wave embossing extending perpendicular to the winding axis. In the case of spiral wrapping, the middle region of the outer wall, which is at risk of being drawn in, is supported and at a precise distance held, and on the other hand, this results in a division of the flow channel on the water side, so that the water can flow through the water in series connection of the two channels in counterflow or, depending on the arrangement of the flow and return connections in parallel flow.

The water-carrying duct simply remains open at both ends and, depending on the boiler design, is connected in a suitable manner in a liquid-tight manner to the boiler's supply and return areas with corresponding openings. Of course, there is no winding directly from the center of the spiral, i.e. the center of the spiral is formed by a correspondingly large filling body, which in the case mentioned above forms the return space to which the spiral or the water-carrying channel is connected with its inner end. Another embodiment in this regard, in which the packing is not hollow and consists of a suitable thermally resilient material, results from claim 3. This embodiment, which will be explained in more detail, however, cannot be produced from strips continuously drawn from coils.

The post-heat exchanger according to the invention is explained in more detail below with reference to the drawing of exemplary embodiments.

Fig. 1

perspektivisch zwei parallele Wickelstränge des Nachschaltwärmetauschers;

Fig. 2, 3

Schnitte durch die abgekröpften Ränder der Wickelstränge;

Fig.2A,3A

Darstellungen verschiedener Arten von Wellenprägungen (in 2A in Seitenansicht und Draufsicht);

Fig. 4

im Schnitt längs Linie IV-IV in Fig. 5 die Anordnung des Wärmetauschers in einem Heizkessel;

Fig. 5

die Ansicht des Heizkessels gemäß Fig. 4 in Pfeilrichtung V;

Fig. 6

im Schnitt längs Linie VI-VI in Fig. 7 die Anordnung des Wärmetauschers in einem Heizkessel in anderer Ausführungsform;

Fig. 7

die Ansicht des Heizkessels gemäß Fig. 6 in Pfeilrichtung VII;

Fig. 8

einen Vertikalschnitt durch das Umkehrende des Wärmetauschers nach Fig. 7;

Fig. 9

eine Ansicht des ausgeflachten Biegebereiches zur Ausbildung des Umkehrendes gemäß Fig. 8;

Fig. 9A

den Biegebereich nach Fig. 8 in Draufsicht und

Fig. 10

stark schematisiert das Verfahrensschema zur kontinuierlichen Herstellung des Nachschaltwärmetauschers.

It shows

Fig. 1

in perspective two parallel winding strands of the secondary heat exchanger;

2, 3

Cuts through the cranked edges of the winding strands;

Fig. 2A, 3A

Representations of different types of wave embossing (in side view and top view in FIG. 2A);

Fig. 4

in section along line IV-IV in Figure 5, the arrangement of the heat exchanger in a boiler.

Fig. 5

the view of the boiler of Figure 4 in the direction of arrow V;

Fig. 6

in section along line VI-VI in Figure 7, the arrangement of the heat exchanger in a boiler in another embodiment.

Fig. 7

the view of the boiler of Figure 6 in the direction of arrow VII.

Fig. 8

a vertical section through the reverse end of the heat exchanger according to Fig. 7;

Fig. 9

a view of the flattened bending area to form the reversing end of FIG. 8;

Figure 9A

8 in plan view and

Fig. 10

the process scheme for the continuous production of the secondary heat exchanger is highly schematic.

The secondary heat exchanger consists in a known manner of a water-carrying and a gas-carrying interior 3, 3 ', which spaces are separated from one another by walls 1, 2, which extend parallel to one another and are spirally wound around a packing 5, and are sealed off from one another by cranked edges.

For such a secondary heat exchanger, hereinafter referred to briefly as NWT, it is now essential that the inner wall 1, which is bent at the top and bottom with respect to the winding axis WA, has edges 4 corresponding to the maximum width B of the water-carrying interior 3. The outer wall 2 has inwardly bent edges 6 with a maximum half width B, which edges 6 overlap the edges 4 of the inner wall 1 or are flush with them and are connected to them in a liquid-tight manner. In the gas-carrying interior that is open on the inflow and outflow sides 3 'pointing wave embossments 7 of both walls 1, 2 are at a distance D from the edges 4, 6 in the walls 1, 2 substantially parallel to the winding axis WA, mutually supporting and arranged, and the water-carrying interior 3 is at both ends of the The spiral is closed except for the attached supply and return connection openings.

Such a NWT is shown in plan view according to FIG. 5, from which it can also be seen that the inner winding end of the spiral naturally does not begin in the center of the spiral, but on a filler 5, which in the embodiment according to FIGS. 4, 5 is a hollow body is formed and forms the return port. A winding from the center is not allowed since the bending radii would be too small. 4, 5, it is a NWT with a relatively large height H, and in consideration of this, the inner wall 1 is provided with a central wave embossing 10 extending perpendicular to the winding axis WA, the depth of which is width B. corresponds to the water-bearing interior 3. This wave embossing 10 (see also FIG. 1) supports the wall 2 in the middle and divides the water-carrying interior 3, so that the filler 5 (return connection) flows through it in two corresponding spiral parallel flows and from the two openings 11, 11 '' gets into the water-bearing interior IK of the boiler. The heating gases entering the NWT from the combustion chamber BK of the boiler flow through the gas-carrying interior 3 'open on both sides parallel to the winding axis WA.

The two walls 1, 2, which in the case of the exemplary embodiment according to FIGS. 4, 5 can be pulled off as strips of coils, are milled with the corrugations 7, if necessary also the corrugations 10, before they are joined together in the sense of FIG. 1 (in the longitudinal direction) and the cranked edges 4, 6, which can be done by rolling or embossing the strips.

The welding of the edges 4, 6, which overlap in the sense of FIG. 2 with a basic dimensioning, as shown, or aligned with each other according to FIG. 3, takes place during the winding process, specifically differentially immediately behind the bending point, that is, after the bending has been carried out, since a previous welding would amount to this, bend a tube with a flat cross section, largely rigid in itself wanting, which would lead to tension, kinks and sweat cracks. An overlap of the edges 4, 6 in the sense of FIG. 2 is preferred, since this ensures a more problem-free welding.

The width B₁ of the gas-carrying interior 3 'is determined by the height H₁ of two point-touching wave embossments 7 in the walls 1, 2, which thus simultaneously form spacers during winding. The wave embossments 7 can be formed as shown in FIG. 2A or also in FIG. 3A. It is essential in both cases that these end at a distance D in front of the edges 4, 6 or also in front of the central wave embossing 10, if there is one.

The NWT according to FIGS. 6, 7 differs from the above-described exemplary embodiment in that the two walls 1, 2 are formed from a band blank that is twice the length of the spiral course, which in the region of its center M has bent edges 44, 6 and at least deep wave embossments 7 are kept free and are bent in this area by 180 ° and on the overflow channel 8 formed in this way and parallel to the winding axis WA, the areas free of edges 4, 6 are closed with cover surfaces 9.

For this purpose, reference is also made to FIGS. 8, 9, in which the bending area is designated by 12. In a top view, this is illustrated again in FIG. 9A with reference to FIG. 7. This structure is then introduced with the overflow channel 8 first into a spiral winding device and wound into a spiral, as can be seen in FIG. 7.

If there is no central division by a wave embossing 10 (for example at a low height H of the NWT), the return connection RA would, as indicated by dashed lines in FIGS Overflow channel 8 are connected. In the presence of wave embossing 10, the return is initiated on the outside of the spiral, goes inwards to the overflow channel 8, arrives there in the other part of the water-carrying interior 3 and flows there from the inside to the outside in a suitable manner into the water-carrying interior IK of the boiler housing to arrive, ie in this case the NWT would be a parallel counterflow.

Apart from this, a separating web 13 could also be used in the overflow channel 8, as is indicated by dash-dotted lines in FIG. 8, in alignment with the wave embossing 10. If both parts of the water-carrying interior are then connected in a suitable manner to separate flow and return connections, there are separate interiors, the part on the fume cupboard being connected, for example, to underfloor heating, the temperature level of which is known to be lower. Otherwise, this configuration can also be realized in the NWT according to FIGS. 4, 5, if, as shown, it has a wave embossing 10, it does not require a separating web 13, but a corresponding breakdown of the hollow body forming the filler 5, such as, for example 4 indicated by dashed lines.

4, 5 could in principle also be carried out in such a way that the walls 1, 2 provided with corrugated embossments 7 and offset elbows were initially loosely assembled, wound and then welded to a welding device following the spiral path of the edges 4, 6 to be welded will. In any case, this would ensure that the edges 4, 6 or the two walls 1, 2 can shift relative to each other to a certain extent during winding. However, it is much more advantageous and time-saving to proceed (which also applies to the embodiment according to FIGS. 6, 7) in that the two walls 1, 2 at their edges 4, 6 during the spiral winding are differential in bending immediately after bending with continuous radial guidance of a winding device 17 are welded to one another in a liquid-tight manner and in and in a further embodiment, since the winding process to form a spiral is more or less continuous, anyway (here, however, only for the embodiment according to FIG. 4, 5) to introduce the two walls 1, 2 as sheet metal strips of coils 15 of a wave embossing and edge crimping device 16 and then the embossed sheet metal strips into the joining and a spiral winding device 17 arranged directly behind them, as is shown very schematically in FIG. 10. If the edges 4, 6 to be welded are designed and arranged in the sense of FIG. 3, the two walls 1, 2 are guided when they are joined together along a spacer AH held stationary between the walls 1, 2 and extending to the welding point S.

The welding of the edges 4, 6, which extend in the planes E₁, E₂, between which the "plane spiral" forms during winding, is of course carried out simultaneously in both planes E₁, E₂ above and below or behind and in front, the welding device 14 is stationary behind the bending point BS and the spiral winding device 17 must be mounted so that it can take into account the increasing diameter of the spiral.

The spacer AH, which protrudes between the two incoming sheet metal strips, and outer guides AF ensure precise spacing between the two walls 1, 2, which is particularly suitable for the embodiment according to FIG. 3. The rollers 18 of the winding device 17 are, as indicated, arranged radially adjustable therein, in accordance with the increase in the circumferential plane of the spiral during winding. Since the spiral is already welded and can be removed after the winding is finished, this procedure is preferred. However, it is also possible to carry out the winding first, and only then carry out the welding with the planar spiral remaining held in the winding device 17, the welding device 14 being guided in a correspondingly controlled manner. Furthermore, it should be pointed out that, in particular in the embodiment according to FIGS. 4, 5, the two inner ends of the walls 1, 2 are first welded to the filler 5 designed as a hollow body and this, also located in the winding device 17, forms the winding core.

Apart from the described installation examples according to FIGS. 4-7, such a "plane spiral" can of course also be used for the passage and heating of process water with a corresponding connection design.

Claims (10)

Post-heat exchanger for installation in the boiler housing, consisting of a water-bearing and a gas-bearing interior, which rooms are separated from each other by walls that extend parallel to one another, spirally wound around a packing element, and are sealed off from one another by cranked edges.
characterized,
that with respect to the winding axis (WA) inner wall (1) bent up and down to the outside, maximally corresponding to the width (B) of the water-carrying interior (3) has edges (4) and the outer wall (2) bent inwards Edges (6) with a maximum of half the width (B), which edges (6) overlap or align with the edges (4) of the inner wall (1) and are connected to them in a liquid-tight manner, the gas-carrying, parallel to the winding axis (WA ) flow-through interior (3 ') which is open on the inflow and outflow sides and has wave embossments (7) oriented in the throughflow direction of both walls (1, 2) with a distance (D) to the edges (4, 6) in the walls (1, 2) are arranged and designed to support each other and the water-carrying interior (3) is closed at both ends of the spiral except for the supply and return connection openings. Heat exchanger according to claim 1,
characterized,
that the inner wall (1) is provided with at least one wave embossing (10) extending perpendicular to the winding axis (WA), the depth of which corresponds to the width (B) of the water-carrying interior (3). Heat exchanger according to claim 1 and 2,
characterized,
that the two walls (1, 2) are formed from a band blank corresponding to twice the length of the spiral, which in the region of its center (M) is kept free from bent edges (4, 6) and at least deep corrugations (7) and in this area Is bent 180 ° and on the overflow channel (8) formed in the process and parallel to the winding axis (WA), the areas free of edges (4, 6) are closed off with cover surfaces (9). Heat exchanger according to claim 3 with a longitudinal wave embossing (10),
characterized,
that a separating web (13) is arranged in the overflow channel (8) in alignment with the wave embossing (10). Heat exchanger according to claim 3 with a longitudinal wave embossing (10),
characterized,
that one of the cover surfaces (9) is designed as a return connection (RA). Heat exchanger according to claim 1 or 2,
characterized,
that the filling body (5) is designed as a hollow body forming the return connection. Heat exchanger according to claim 2 and 6,
characterized,
that the interior of the filler (5) designed as a hollow body is divided into at least two return spaces (I, II) and to which the parts of the water-carrying interior (3) of the secondary heat exchanger are connected. Method for producing a secondary heat exchanger according to claim 1,
characterized,
that the two walls (1, 2) are welded at their edges (4, 6) during the spiral winding with differential bending immediately after bending with continuous radial guidance of a welding device to the outside in a liquid-tight manner. A method according to claim 8,
characterized,
that the two walls (1, 2) as sheet metal strips of coils a wave embossing and edge cranking device and afterwards the embossed sheet metal strips are introduced into a joining device and a spiral winding device arranged immediately behind it. Method according to claim 8 or 9,
characterized,
that the two walls (1, 2) are guided along a spacer (AH) which is held stationary between the walls (1, 2) and extends to the welding point (S).

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