EP1703227B1 - Heat exchanger - Google Patents

Description

The present invention relates to devices for heating liquids, such as boilers and water heaters, and more particularly to the heat exchangers of such devices.

The said devices contain a heat source, usually in the form of a gas burner, the hot exhaust gases are passed to a gas-liquid heat exchanger, which often consists of a helically wound tube through which flows the liquid to be heated.

The hot exhaust gases are, after they have flowed around the pipe and thereby released thermal energy, released into the atmosphere. The thermal efficiency depends on the quality of the energy transfer between exhaust and heat exchanger tube. This transmission is mainly determined by the contact time between the exhaust gas and the pipe and by the turbulence of the flow of the hot exhaust gases. Therefore, it is necessary to extend the area where the hot exhaust gases and the pipe come into contact.

From the US 4,981,171 a heat exchanger is known in which the coils are oval in cross-section and stacked in rows and columns. Warm air is sucked in via a fan and fed to the multi-level lattice-like coils. In the course of its radial flow of the outside air is extracted thermal energy and therefore cooled. The lowered in their temperature air is then fed to a room in which, for example, food, such as meat products, are located, which are cooled Need to become. The heat exchanger therefore has the task of cooling ambient air and making it available to a room. Burner operation is neither intended nor suitable, since the hot exhaust gases originating from the burner would flow radially between the coils without having carried out a sufficient heat exchange.

Furthermore, from the EP 678186 B1 a heat exchanger known, the helical tubes are oval in cross-section and are kept by means of incorporated web-shaped spacers to size. However, the heat exchanger has only one stage or coil for the exchange of thermal energy.

Furthermore, from the DE 4428097 A1 a heat exchanger known in which hot exhaust gases flow through the coils axially. However, there is no direct heat radiation of the coils through the burner. Due to the axial arrangement, each coil is flowed around by different exhaust gas flows. Consequently, no double heat exchange takes place, as in a radial arrangement in which the exhaust gases flow around the heat exchanger tubes, starting from the inner coil to the outer coil, in succession.

DE 299 06 481 U1 discloses a heat exchanger having two coaxial coiled tubing which overlap each other such that heat radiation from a coaxially disposed burner passing through the gap of the inner coil is captured by the outer coil.

The aim of the present invention is to increase the efficiency of heat exchange between hot, from a heat source such as a burner, originating gases and the flowed through by a fluid to be heated coils of a heat exchanger by means of a suitable arrangement.

For this purpose, the invention initially relates to a heat exchanger for thermal coupling of hot, derived from a burner exhaust gases with a tube through which flows a liquid to be heated. The tube is wound helically around the burner. Due to the generous gaps between the windings, the exhaust gases produced during the combustion process can be discharged radially into an exhaust gas duct of a heat exchanger shell, which encloses the pipe. The heat exchanger contains at least two coils, which are arranged mutually coaxial and generally radially overlapping, wherein the two coils have the same coil spacing and the axial offset to each other is almost half a helix distance. Consequently, the two serially or parallelly arranged spirals form two concentric walls which enclose the space in which hot exhaust gases are formed and allow them to escape radially through the gaps of their windings. Due to the offset by half a helix distance, the centers of the circular cross-sectionally or axially flattened turns of both helices are arranged in an axial plane, like the tips of an isosceles triangle. For this reason, the exhaust gases first flow through the gaps of two adjacent turns of the inner coil and then impinge on the turn of the outer coil virtually at the apex of the isosceles triangle. There, the exhaust stream is split into two nearly identical sub-streams, which flow over both sides of the turns of the outer helix, before they exit radially through the gaps of the outer helix. The outer turns are therefore an obstacle, which increases the duration of the exhaust pipe contact and thus the effectiveness. The incorporation of one or more additional coils surrounding the outer coil according to the axial displacement principle described above can further increase the yield.

It should be noted that the invention is independent of the shape of the turns. The cross sections of the turns do not necessarily have to be circular. Thus, the embodiment of the invention with oval, lens or diamond-shaped cross sections is also possible.

The outer coil is colder than the inner coil in operation which, in addition to the hot exhaust gases, is also exposed to the direct thermal radiation of the burner, while the outer coil provides a large surface area for the condensation of the liquid, usually water, which is mainly in the the inner spiral confined space was previously evaporated.

The outer diameter of the inner coil is larger than the inner diameter of the outer coil. Consequently, the inner coil can not be inserted by a simple translational movement in the outer coil. The turns of the built-in inner coil radially project into the interstices of the turns of the outer coil and thus define axially oblique gaps between the turns of both coils, which can be calibrated on the basis of the purely axial gaps between the turns of a coil. It therefore gives the impression as if the turns of both coils are firmly intermeshed.

The exhaust gases initially flow through the gaps of the inner coil and pass through an oblique, located between the two coils, gap in the gaps of the outer coil. If the gaps between the turns and between the helices are the same size, the exhaust gases experience an almost constant pressure loss during the flow through the helices.

A plate axially divides the interior of the inner coil into a first region in which the burner is placed and a second, axially remote region in which the exhaust port is located. In this way, the exhaust gases exit radially from the burner region, then follow an axial path into a layer-like region lying between the outside of the outer coil and the inside of the heat exchanger shell, and finally flow along a radial path into the second region before they pass flow out through the exhaust port. It is advantageous in this embodiment of the baffle obtained deflection, which ensures a double heat exchange.

In a further advantageous embodiment, an axially aligned comb has brackets for supporting the inner coil. The comb is disposed between the inner and outer coils and keeps the gaps between the turns of the inner coil at the desired distance. The comb therefore forms a template which limits a thermally induced axial deformation of the inner coil.

The comb may also have brackets for the outer coil, whereby it can be arranged with respect to the inner coil with an axial offset of half a helix distance and a desired radial distance. The comb can also be mounted on the radially outer side of the outer coil to define these supports and their distances.

• der Wärmetauscher, wie besagt, zwei separate schraubenlinienförmig aufgewickelte innere und äußere Wendeln enthält,
• die beiden Wendeln gegenseitig unter Einhaltung des besagten Versatzes von P / 2 positioniert sind und dies durch die Einführung der inneren Wendel in einen von der äußeren Wendel begrenzten Raum gewährleistet wird, während die Einführung anhand einer translatorischen Bewegung in eine Richtung erfolgt, die axial zu den Windungen ist, und
• die beiden Wendeln miteinander verbunden sind.

In addition to a device, the invention also relates to a method of manufacturing a heat exchanger according to claim 1, wherein:

• the heat exchanger, as stated, contains two separate spirally wound inner and outer coils,
• the two helices are mutually positioned in compliance with said offset of P / 2 and this is ensured by the introduction of the inner helix in a space bounded by the outer helix, while the introduction takes place by means of a translational movement in a direction axially to the Turns, and
• the two coils are connected.

Since the above-described inner and outer coil diameters do not permit installation of the inner coil by axial translation, in order to allow said axial translation, torque must be applied to the inner coil to reduce its outer diameter. In this loaded state clips or brackets can be attached, which maintain the torque during assembly. As a result, this production step in the manufacture of the heat exchanger is substantially simplified. After insertion, the inner coil is relieved by removing the clips.

As a further alternative for enabling said axial translation, a torque is applied to the outer coil to increase its inner diameter. The outer coil is relieved after said translation of the inner coil again.

Alternatively, but not according to the invention, the translational can be accompanied by a screwing or rotating movement. The process is similar to tightening a screw whose external thread mates with the internal thread of a bore.

Object of the present invention is to increase the efficiency of heat exchange in heaters, especially gas-fired condensing appliances by a suitable heat exchanger, which is inexpensive and is characterized by a simple manufacturing process.

According to the above object is achieved by the features of claim 1 and claim 11.

• Fig.1: eine Prinzipskizze eines Heizkreislaufs mit einem Wärmetauscher
• Fig. 2: eine perspektivische Darstellung des Wärmetauschers ohne Seitenwand
• Fig. 3: einen Querschnitt durch den Wärmetauscher ohne Seitenwand
• Fig. 4: einen kammartigen Abstandshalter zwischen zwei Wendeln im Querschnitt
• Fig. 5: einen kammartigen Abstandshalter in der Draufsicht
• Fig. 6: die Rückseite eines kammartigen Abstandshalters
• Fig. 7: einen stegförmigen Abstandshalter

Further advantageous embodiments will become apparent from the subclaims and the following description of an embodiment of an apparatus and a method for manufacturing a heat exchanger according to the present invention. In the drawing show:

• Fig.1 : a schematic diagram of a heating circuit with a heat exchanger
• Fig. 2 : a perspective view of the heat exchanger without side wall
• Fig. 3 : a cross section through the heat exchanger without side wall
• Fig. 4 a comb-like spacer between two coils in cross-section
• Fig. 5 : a comb-like spacer in plan view
• Fig. 6 : the back of a comb-like spacer
• Fig. 7 : a bar-shaped spacer

The embodiments according to the FIGS. 1 and 4 to 6 are not covered by the scope of the claims.

FIG. 1 is a schematic diagram of the heat exchanger in cross-section. The heat exchanger is bounded by a housing 1, the lateral wall 1 C is cylindrical, has a predetermined axial length and is preferably radially symmetrical to a vertical center axis 9, wherein axially opposite water supply lines 5 and 6 Wasserauslassleitungen two up and down also opposite sealing walls 1A, 1B, in the present embodiment, they are plates, are connected.

In the housing 1, a burner 3 is arranged, which heats the water flowing in the heat exchanger tubes. The tubes are preferably made of stainless steel and processed into spirals with spiral turns. The heat exchanger includes at least two such coils 20, 30 coaxially disposed and radially overlap. The helix diameters have the values D1 and D2, whereby D2 is greater than D1.

The axial length of the coils 20, 30 is almost equal and corresponds to the length of the housing 1. The turns of an outer coil 30, whose average radius of curvature R2 = D2 / 2, limit an internal volume, which receives the turns of an inner coil 20, whose winding or radius of curvature R1 = D1 / 2 and is therefore less than R2. The helix spacing has the same value P for both helices 20, 30. Due to an axial offset of the helices 20 and 30 by P / 2, a radial plane X - X contacts both the center of an inner helical turn and the center of the opposite outer helical turn.

The inner coil 20 includes an approximately cylindrical volume, which is divided by a deflecting plate 19 axially into two sub-volumes. This deflecting plate 19 is arranged in a radial plane, preferably axially in the center of the housing 1, and defines a first inner upper volume 10, in which the burner 3 is located, and a second inner lower volume 15, which is connected to an exhaust pipe 4, from each other.

The turns of the inner coil 20 are held by U-shaped brackets 23 and the turns of the outer coil 30 via a comb-like holder 33 at a defined distance.

The heat exchanger is integrated in a heating circuit in which a pump 50 is connected via the water supply lines 5 to the water inlets 21 and 31 of the two coils 20, 30. In the upper part of the water outlets 22 and 32 are connected to the water outlet 6, which in turn to a consumer device, such as a radiator 7, are connected. The hydraulic heating circuit to Pump 50 is closed via a feedback with a return line 8.

The disclosure of the invention, which relates to the structure and operation of the device, is made for an operating position in which the axis of the device is arranged vertically. However, the present disclosure also applies to a different axis alignment with the corresponding conversions of the respective components.

The burner 3 is supplied via a gas line 2 from an external gas source 40. In the lower part of the housing 1 there is an exhaust pipe 4, via which the cooled off at the heat exchanger tubes exhaust gases are removed. The gas stream is preferably assisted by a fan, which is not shown.

The helices 20 and 30 are connected in parallel. In a parallel operation, the two coils 20, 30 are flowed through in the same direction by the liquid to be heated. Consequently, the inner 20 and outer 30 coils are fed via their respective water inlet 21, 31 through the corresponding water supply line 5. In a parallel operation, the liquid passes in the inner 20 and the outer coil 30 first a colder 15, then a warmer 10 area and thus undergoes gradual heating, the inner coil 20 in the lower region 15 initially colder, in the upper region 10th but warmer water leads than the outer coil 30. The exhaust gases give off part of their thermal energy during heat exchange in the upper region 10, before they reach the lower region 15. Since in the latter area 15 cold liquid is fed and a temperature gradient from the exhaust gas to the liquid exists, takes place in this area 15, a heat exchange. Advantageously, the resulting higher energy yield and greater efficiency than in an operation in which the liquid is passed from a warmer 10 in a colder area. A disadvantage is the parallel flow through the Both coils 20, 30, that possible dirt deposits, especially in the tubes of the outer coil 30, which are responsible for an additional energy yield, lead to a reduction in the efficiency.

Alternatively, the coils 20, 30 may be connected in series. In a serial operation, the two coils 20, 30 are flowed through in opposite directions by the liquid to be heated. In this case, the coupling of the helices 20, 30 can be done in two ways.

In the first case, the return can take place via the water inlet 21 of the inner coil 20. The cold liquid hits in the lower area 15 on the coldest exhaust gases. Due to the heat exchange that takes place, thermal energy is withdrawn from the cold exhaust gases, which leads to an increased formation of condensate in this section. Preheated, the liquid enters the warmest area 10, in which, in addition to the hottest exhaust gases and the direct heat radiation of the burner 3 heats the water. Subsequently, the water is passed through the two upper connected water outlets 22, 32 in the outer coil 30, where it is further heated and finally exits as a flow from the water inlet 31. A disadvantage of this constellation is the relatively low energy yield due to the rather short preheating of the inner coil 20 in the lower region 15th

The return can take place in the second case via the lower end 31 of the outer coil 30. The cold liquid hits the already cooled exhaust gases in the lower region 15 and is preheated. Finally, a further preheating in the upper region 10 takes place based on the hotter exhaust gases located there. The water passes through the upper interconnected water outlets 22, 32 in the inner coil 20 and is in the warmest region 10, in which, in addition to the hottest exhaust gases and the direct heat radiation of the burner 3 strikes the turns of the inner coil 20, heated. in the Finally, in the lower region 15, no or hardly any heat energy is withdrawn from the coldest exhaust gases, since the water present in the inner coil 20 is substantially warmer than the exhaust gases present in this section, which leads to a reduction of the yield in this region 15. Condensation is relatively small in this arrangement. About the water inlet 21 of the inner coil 20, the water finally exits as a flow. Due to the extended preheat range, which extends over virtually the entire length of the outer coil 30, the thermal energy yield can be increased.

Regardless of whether the coils 20, 30 are operated in parallel or in series, the heat exchanger always finds a heat exchange at the inner 20 and the outer coil 30 due to a radial exhaust gas flow through the coils 20, 30, their advantageous arrangement and a radially arranged baffle plate 19 both in the upper region 10, and in the lower region 15 instead. This has over known single-stage or multi-stage heat exchangers, which have no mutual axial offset, the advantage of higher energy yield and greater efficiency.

The radial arrow F0 represents the path of a flow of hot exhaust gases leaving the burner 3, said flow F0 being directed from the central axis 9 to the outer coil 30. The flux F0 passes through a first gap or a first gap E1 of calibrated height between the turns of the inner coil 20. The axial height coincides with the difference resulting from the helix pitch P and a diameter value d1, which is obtained from the cross section of FIG Tube receives the inner coil 20 results. The first gap E1 in the present embodiment is 0.9 mm at a pipe diameter d1 of the inner coil 20 of 14 mm and therefore at a coil pitch P of 14.9 mm, wherein the coil diameter D1 of the inner coil 20 is approximately 20 cm.

The flow F0, which leaves the inner upper volume 10 bounded by the inner coil 20 radially outward, after having been initially axially constricted, reaches a position which is at the same height as the centers C1 of the tube cross-sections of the inner coil 20 Following its radial path beyond the first gap E1, the flux F0 axially extends into an inner cylindrical space 11 defined by the coils 20 and 30. The flow F0 then encounters a turn of the outer coil 30. Because of the offset by half a helix distance (P / 2) between the helices 20 and 30, the flow F0 splits into practically two equal sub-flows F1, F2 and flows over both sides of the impacted turn of the outer helix 30. The sub-flows F1, F2 each pass through a further gap E2, which are bounded axially by two turns of the outer coil 30. The partial flows F1 and F2 then impinge radially on the cylindrical wall of the housing 1.

The flows F1 and F2 then flow axially in an outer cylindrical space 12 to the ground. In the intermediate space 12, which is bounded by the inner surface of the cylindrical housing wall 1 and the outer coil 30, run all, corresponding to the rivers F1 and F2, Teilflüsse together until they reach the height of the deflecting plate 19 axially.

Axially below the baffle plate 19, the outer cylindrical gap 12 merges into a volume 13 from which flows, as shown by arrow F10, flow radially in the direction of the central axis 9. The flows pass through the gaps E2 and split in the intermediate space 14, which is analogous to the intermediate space 11, into two practically identical partial flows F11 and F12, which flow through the corresponding columns E1, the flow direction being opposite to the direction of the flows F1, F2 is. A detailed description will be omitted here.

The baffle 19, which delimits the volume 10 from the volume 15, directs the Exhaust flow radially in the direction of the cylindrical outer volumes 12, 13 and thus forms two cascade-like heat exchanger stages. In general, the incorporation of an odd or even number of such separator plates 19 may be considered. In this case, a direct connection between the cylindrical outer volume 13 and the exhaust pipe 4 can be made by the lower turns of the coils 20, 30 are omitted at the level of the water inlets 21 and 31.

For a given pipe diameter d1 of the inner coil 20 and an axial gap E1 between its turns, the coil pitch P can be determined. The tube diameter d2 of the outer coil 30 may be smaller than, equal to or larger than the diameter value d1 of the inner coil 20. In other words, the second gap E2 may or may not have a value identical to that of the first gap E1. In addition, a difference value for the average curvature radii R1 and R2 may be selected from a predefined range. The choice of the dimensions determines a composite gap E3, that is, a gap that reflects the oblique spacing between the two coils 20, 30.

An interesting embodiment is obtained in the choice of approximately equal values for the first gap E1 and the composite gap E3 of, for example, 0.9 mm, as well as approximately equal values for the tube diameters d1 and d2. For the second gap E2, a distance value of 0.9 mm can likewise be selected.

An inner spacer has the shape of a U-shaped bracket 23, which is fastened to the tubes of the inner coil 20 like a clip. In cross-section, the U-shaped bracket 23 preferably extends to the tube centers C1 to ensure better adhesion to the tube sections. The diameter of the wire from which the clip 23 was made defines the gap E1. The U-shaped bracket 23 is advantageously mounted between the outer 30 and the inner 20 coil, so that in addition to the columns E1 additionally the oblique columns E3 are defined via the wire diameter. By attaching the U-shaped brackets 23 to the tubes of the outer coil 30, and its coil pitch P can be kept to size.

In FIG. 4 another comb-like support 36 located between the coils 20, 30 is shown. The comb-like holder 36 has arms 34 which support the tubes of the inner coil 20. The height of the arms 34 defines the axial gap E1 between two turns of the inner coil 20. Thus, on the radially outer side, the rear side, the comb-like support 36 preferably has a V-shape, wherein the axial distance from the V-tips to the adjacent arms 34 is a half helix pitch P / 2. The holder 36 can be considered as a chain of Vs with an opening angle of 120 degrees that propagates in the axial direction to the coils 20, 30. In cross section, each three adjacent turns form an equilateral triangle. Due to the dimensions and the wedge effect of the V-shape, in addition to the gaps E1, the mutual axial offset of both coils 20, 30 and thus the gaps E2 are calibrated. In addition, the holder 36 defines over its profile and its width the oblique gap E3 between the helices 20, 30th

The arms 34 of the comb-like support 36 preferably extend at least to the centers C1, C2 of the helical tubes. Furthermore, by notches on the open sides of the arms 34 springs 35 can be created, which clamp the tubes between two arms 34.

The comb-like holder 36 is made of a rectangular piece of sheet metal. This sheet is initially provided with notches, which represent the later springs 35. Subsequently, the arms 34 are punched out, which have an angle of about 90 ° to the original sheet. In a subsequent step, the main piece is pressed into the said V-shape ( Fig. 4-6 ).

The comb-like holder 36 is looped through into the spaces 11, 14 located between the coils 20, 30, wherein an optional elastic deformation of the holder 36 and / or the coils 20, 30 facilitates insertion. Also, the use of the holder 36 in the region of the outer coil 30, as in Fig. 1 shown, possible. A combination of the previously described U-shaped bracket 23 and the comb-like holder 36 is also conceivable. Thus, for example, the comb-like holder 36 can be introduced between the two coils 20, 30, while on the radially outer side of the outer coil 30 placed U-shaped brackets 23, the columns E2 additionally hold to measure.

The Figures 2 and 3 show the housing 1 with the opposite walls 1A and 1B without the side wall 1C. In between, the helices 20, 30 are clamped and fixed by web-shaped spacers 41 such that there is a constant gap between the helical turns. The spacers 41 have a pin-shaped structure with notches 42 in the upper and lower edge region ( Fig. 7 ). The helices 20, 30 are axially clamped over at least two walls 1A, 1B. This tension is maintained by attaching at least two web-shaped spacers 41 to the walls so that their notches engage the walls 1A, 1B thereby avoiding their discharge. The length of the spacers 41 determines the distance of the axially opposite walls 1A and 1 B. Subtracting now of this total distance, the height of the walls 1A and 1B, we obtain the length of the coils 20, 30. To the columns E1 and E2 To calculate the difference between the helix length and the number of turns multiplied by the pipe diameter d1 or d2, first of all has to be determined. The resulting amount is finally divided by the number of columns. The result is the size of the gap E1 or E2. The aforementioned devices 23 and 36 may find application in combination with the web-shaped spacers 41.

• Zum einen kann ein Drehmoment, vorzugsweise im Bereich des Wasserein- (21) sowie Wasserauslasses (22), auf die innere Wendel 20 ausgeübt werden, die eine Verkleinerung seines Außendurchmessers zur Folge hat. Clips oder Klammern, die im Bereich des Wasserein- (21) und Wasserauslasses (22) angebracht werden, halten die bestehende Spannung während des Montageprozesses aufrecht. Natürlich kann die Einführung durch eine entgegengesetzt gerichtete axiale Translation beider Wendeln 20, 30, oder einer axialen Translation der inneren 20/äußeren 30 Wendel bei ruhender äußerer 30/innerer 20 Wendel erfolgen. Nach erfolgter Montage werden die Clips entfernt und die innere Wendel 20 entlastet, die schließlich ihre ursprüngliche Form einnimmt.
• Zum anderen kann ein Drehmoment, vorzugsweise im Bereich des Wasserein- (31) sowie Wasserauslasses (32), auf die äußere Wendel 30 ausgeübt werden, die eine Vergrößerung seines Innendurchmessers zur Folge hat. Clips oder Klammern, die im Bereich des Wasserein- (31) und Wasserauslasses (32) angebracht werden, halten die bestehende Spannung während des Montageprozesses aufrecht. Natürlich kann die Einführung durch eine entgegengesetzt gerichtete axiale Translation beider Wendeln 20, 30, oder einer axialen Translation der inneren 20/äußeren 30 Wendel bei ruhender äußerer 30/innerer 20 Wendel erfolgen. Nach erfolgter Montage werden die Clips entfernt und die äußere Wendel 30 entlastet, die schließlich ihre ursprüngliche Form einnimmt.
• Ferner kann die Montage der Wendeln (20, 30) durch eine entgegengesetzt gerichtete Schraubbewegung beider Wendeln (20, 30) oder aber eine schraubende Drehbewegung der inneren 20/äußeren 30 Wendel bei ruhender äußerer 30/innerer 20 Wendel erfolgen. Die Wendelgänge verhalten sich wie paarende Gewindegänge eines Innengewindes einer Bohrung und eines Außengewindes einer Schraube. Dieses dritte Montageverfahren ist jedoch aus dem Stand der Technik bekannt.

Since the inner diameter of the outer coil 30 is smaller than the outer diameter of the inner coil 20, the introduction of the inner 20 into the outer coil 30 by an axially directed translational movement can not be performed. There are consequently the following three possibilities, which allow a mounting of the coils 20, 30:

• On the one hand, a torque, preferably in the region of the water inlet (21) and water outlet (22), can be exerted on the inner coil 20, which results in a reduction of its outer diameter. Clips or clips placed in the area of the water inlet (21) and water outlet (22) maintain the existing tension during the assembly process. Of course, the introduction may be by oppositely directed axial translation of both coils 20, 30, or axial translation of the inner 20 / outer 30 helix with the outer 30 / inner helix resting. After installation, the clips are removed and relieves the inner coil 20, which finally assumes its original shape.
• On the other hand, a torque, preferably in the region of the water inlet (31) and water outlet (32), can be exerted on the outer coil 30, which results in an increase in its inner diameter. Clips or clips placed in the area of the water inlet (31) and water outlet (32) maintain the existing tension during the assembly process. Of course, the introduction may be by oppositely directed axial translation of both coils 20, 30, or axial translation of the inner 20 / outer 30 helix with the outer 30 / inner helix resting. After installation, the clips are removed and the outer coil 30 relieved, which finally assumes its original shape.
• Furthermore, the assembly of the helices (20, 30) by an oppositely directed screwing movement of both helices (20, 30) or a screwing rotational movement of the inner 20 / outer 30 helix with resting outer 30 / inner 20 helix done. The helical turns behave like mating threads of an internal thread of a bore and an external thread of a screw. However, this third assembly method is known from the prior art.

LIST OF REFERENCE NUMBERS

1

casing

1A

ceiling wall

1 B

bottom wall

1C

lateral wall

2

gas pipe

3

burner

4

exhaust pipe

5

Water supply line

6

water outlet

7

radiator

8th

Return line

9

central axis

10

inner upper volume

11

Space between inner and outer helix in the upper volume

12

cylindrical space in the upper outer volume

13

cylindrical space in the lower outer volume

14

Space between inner and outer helix in the lower volume

15

inner lower volume

19

baffle

20

inner helix

21

Water inlet of the inner coil

22

Water outlet of the inner coil

23

U-shaped bracket

30

outer helix

31

Water inlet of the outer coil

32

Water outlet of the outer coil

33

comb-like holder

34

poor

35

feather

36

comb-like holder

40

external gas source

41

bar-shaped spacer

42

notch

50

pump

C1

Center of the inner spiral tubes

C2

Center of the outer helical tubes

d1

Diameter of the inner helical tubes

d2

Diameter of the outer helical tubes

D1

Diameter of the inner coil

D2

Diameter of the outer coil

E1

axial gap between the turns of the inner coil

E2

axial gap between the turns of the outer coil

E3

oblique gap between inner and outer helix

F0

from the central axis radially away pointing gas flow in the region of the inner coil

F1

Partial flow pointing radially away from the central axis in the region of the outer coil

F2

further from the central axis radially away pointing partial flow in the outer coil

F10

radially to the central axis pointing gas flow in the outer coil

F11

Partial flow pointing radially to the central axis in the region of the inner coil

F12

further partial flow pointing radially to the central axis in the region of the inner coil

P

Wendel distance

R1

Radius of the inner coil

R2

Radius of the outer coil

Claims (11)

1. Heat exchanger to transfer the thermal energy of a gas to at least two coils (20, 30) that are flown through by liquid, made from heat-conducting material, which have the same coil distance (P), wherein the coils (20, 30) are arranged to be able to be flown through radially as well as to overlap coaxially and radially, and the intermediate space between two windings of a coil (20, 30) is covered in the radial direction by at least one other coil (20, 30) characterised in that , the coils (20, 30) are clamped axially by means of at least two walls (1A, 1 B) and at least two bar-shaped spacers (41) keep the axial distance between the walls (1A, 1 B) and the gap (E1, E2) between the coil paths of the coils (20, 30) constant.
2. Heat exchanger according to claim 1, characterised in that, two adjacent coils (20, 30) are arranged to be offset axially around a half coil distance (P/2).
3. Heat exchanger according to claim 1 or 2, characterised in that, the coils (20, 30) are formed as spiral coils having a coil diameter which constantly increases or decreases in the axial direction.
4. Heat exchanger according to claim 1 or 2, characterised in that, the coils (20, 30) are formed as spiral coils having coil diameters which alternate in axial direction.
5. Heat exchanger according to one of claims 1 to 4, characterised in that, the gap between two coil paths of the innermost coil (20) is larger than the gap between the two coil paths of the at least one outer coil (30).
6. Heat exchanger according to one of claims 1 to 5, characterised in that, the at least two coils (20, 30) are connected in parallel.
7. Heat exchanger according to one of claims 1 to 5, characterised in that, the at least two coils (20, 30) are connected in series behind one another.
8. Heat exchanger according to one of claims 1 to 7, characterised in that, a baffle plate (19) is arranged in a radial plane and the interior of the innermost coil (20) axially divides into a first volume (10), in which a heat source (3) is located and a second, axially-offset volume (15), which is connected to an exhaust outlet (4).
9. Heat exchanger according to one of claims 1 to 8, characterised in that, at least one, preferably several comb-shaped brackets (33, 36) distributed over the periphery keep the gap (E1, E2) between two coil paths of at least one coil (20, 30) constant.
10. Heat exchanger according to one of claims 1 to 9, characterised in that, at least one, preferably several U-shaped brackets (23) distributed over the periphery keep the gap (E1, E2) between two coil paths of at least one coil (20, 30) constant.
11. Method for the production of a heat exchanger to transfer the thermal energy of a gas to at least two coils (20, 30) that are flown through by liquid, made from heat-conducting material, which have the same coil distance (P), wherein the coils (20, 30) are arranged to be able to be flown through radially as well as to overlap coaxially and radially, and the intermediate space between two windings of a coil (20, 30) is covered in the radial direction by at least one other coil (20, 30), wherein the coils (20, 30) are clamped axially by means of at least two walls (1A, 1 B) and at least two bar-shaped spacers (41) keep the axial distance between the walls (1A, 1B) and the gap (E1, E2) between the coil paths of the coils (20, 30) constant, characterised in that, by exerting torque on at least one of the coils (20, 30), the external diameter of the inner coil (20) is reduced and/or the internal diameter of the outer coil (30) is increased and subsequently the coils (20, 30) are inserted into one another by a translational movement of at least one coil (20, 30) that is directed axially, in the case of axial translation of at least one other coil (20, 30) that is inactive or is in the opposite direction, the coils (20, 30) are clamped via the walls (1A, 1 B) and
    at least two bar-shaped spacers (41) are attached to the walls (1 A, 1B).

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