EP2584301B1 - High temperature heat exchanger - Google Patents

Description

The invention relates to a high-temperature heat exchanger, in particular for gaseous media. A heat exchanger with the features of the preamble of claim 1 is for example from the FR 2293684 known.

The energy efficiency of high-temperature processes can be significantly increased by means of gas / gas heat exchangers, when the heat exchangers transfer the heat content of one gas stream as completely as possible to another gas stream. The gas streams may be, for example, educts and products of a chemical reaction process, for example in the form of a combustion process. The reaction can take place, for example, in an SOFC fuel cell or a fuel cell system, in micro gas turbines or other heat engines. In many cases, the masses or heat capacity flows of the two gases (for example, fresh air and exhaust gas) are approximately equal.

• hohe Temperaturen und dabei insbesondere für
• eine hohe Temperaturspreizung, d.h. eine große Differenz zwischen den Eintrittstemperaturen der beiden Medien, geeignet sein. Bei SOFC-Systemen kann diese Temperaturspreizung bis zu 800 K betragen. Dabei werden
• hohe Wirkungsgrade der Wärmeübertragung von möglichst über 80% ebenso angestrebt, wie
• eine kompakte Bauart,
• niedrige Druckverluste,
• niedrige Herstellkosten und
• hohe Dauerhaftigkeit. Auch müssen
• Druckdifferenzen zwischen den beiden Gasströmen ausgehalten werden. Weitere Anforderungen, wie bspw.
• hohe Temperaturwechselbeständigkeit, kann bei Systemen eine Rolle spielen, die häufig ein- und ausgeschaltet bzw. hoch- und heruntergefahren werden.

Corresponding heat exchangers must meet various requirements, which are sometimes difficult to agree with each other. The heat exchangers must be for:

• high temperatures and especially for
• a high temperature spread, ie a large difference between the inlet temperatures of the two media, be suitable. For SOFC systems, this temperature spread can be up to 800K. It will be
• high efficiencies of heat transfer of as much as 80% as desired, as well
• a compact design,
• low pressure losses,
• low production costs and
• high durability. Also need
• Pressure differences between the two gas streams are sustained. Other requirements, such as.
• high thermal shock resistance, can play a role in systems that are often switched on and off and / or shut down.

In order to heat exchange media, various heat exchanger arrangements are known. For example, the WO 96/20808 a heat exchanger with a closed approximately cylindrical, closed by rounded end caps vessel and arranged at opposite ends of the vessel tube sheets. The tube plates divide the interior into three separate rooms, namely, for example, two plenums and a tube bundle space between them. The connections of the collecting chambers are, for example, arranged concentrically to the longitudinal axis of the cylindrical housing at the end caps. Inflow and outflow of the tube bundle space are arranged, for example, radially on the cylindrical housing wall. Depending on the embodiment, the tubes of the tube bundle are for example straight and provided with sections of different cross section. It change round cross sections with oval cross sections.

While the aforementioned document discloses a closed heat exchanger, shows EP 1 995 516 B1 an open heat exchanger with only one side taken flat tubes. These are round at their ends and flat in a middle section. In the flat portion, the cross section of the tube is formed by two gap defining portions which are curved with large radius, these being connected at their ends by portions which curve with a small radius are. The flat tubes are arranged on concentric circles of the overall substantially rotationally symmetrical heat exchanger. The same number of tubes is provided on each circle. Corrugated spacers are arranged between the tubes. This flat tube heat exchanger is operated in countercurrent operation. On the side facing the combustion chamber of the flat tubes nozzles are formed, which cause a high gas outlet velocity. This is specifically a Abgaswärmerekuperator, which should cause a flameless oxidation due to the high gas outlet velocity in the connected combustion chamber.

It is an object of the invention to provide a heat exchanger that meets the above conditions. In particular, he should combine a high temperature spread, a high transfer efficiency, a high packing density and a long service life with low pressure losses and low production costs.

This object is achieved with the flat tube heat exchanger according to claim 1:

The flat tube heat exchanger according to the invention has a closed housing in which two tubesheets and a tube bundle arranged between the tubesheets and carried by the tubesheets are arranged. The tube bundle comprises at least some flat tubes extending in the tube bundle longitudinal direction. The flat tubes are round at their ends and flat in a middle section. The round in cross-section ends of the flat tubes may be circular or have a different round shape. For example, they may have an elliptical cross section, an oval cross section or even a polygonal cross section (triangular, square, rectangular, hexagonal or the like), which has a Round shape approximates. The cross section of the round section lies between preferably 50% to 70% of the cross section of the flat cross section. While the circular cross sections are circular, the flat cross sections have an oval shape, which is preferably composed of arcuate end sections of small radius and straight wall sections without curvature. For example, such flat tubes are produced by initially starting from a tube having a section of circular cross-section and larger diameter between two sections of circular cross section and smaller diameter. The section with a larger diameter can be flattened in a forming process, eg rolling process, eg between cylindrical rollers. The configuration of the flat tubes described so far is preferred for all embodiments of the heat exchanger according to the invention.

Preferably, three zones are formed in the tube bundle space, namely two cross-flow zones formed at the tube-bundle space connections and a longitudinal flow zone formed between these cross-flow zones. The transverse flow zones are preferably defined by the fact that a section is provided in each case on both sides adjacent to the tubesheets, in that the flat tubes have a round cross section (preferably circular cross section) or circular polygonal cross section and are tapered in order to control the inflow or outflow of the gas transversely to the To allow flat tubes. Preferably, corresponding lanes are formed between the individual flat tubes. It is preferred to orient these streets in the inflow and outflow direction. In a rotationally symmetrical structure, these streets are preferably oriented radially. The inflow or outflow can be done radially from the inside or radially from or to the outside. The transverse flow direction defined by the cross-flow zone is preferably vertical to the flat sides of the flat tubes, that is oriented parallel to the surface normal direction of the flat sides. This concept can be applied to all embodiments of the heat exchanger.

The longitudinal flow zone is defined by the fact that there is essentially no crossflow in it. The adjusting between the flat pipe sections flow runs anti-parallel to the flowing in the flat tubes flow. In particular, the flow preferably does not alternate between the various longitudinal flow paths existing between the flat tubes. This is achieved by adjacent flat tubes are arranged touching each other or nearly touching with a small gap.

The flat tube heat exchanger can be constructed as a rectangle or as a round arrangement. In the rectangular arrangement, it has a cuboid tube bundle space. In the round arrangement, it has a cylindrical tube bundle space. Preferably, the heat exchanger is constructed in a round arrangement as a ring heat exchanger. Its housing is then, for example, cylindrical or polygonal limited. Coaxially with the outer wall, the heat exchanger housing may have an inner wall. This may include other aggregates, such as, for example, a reactor in which the supplied process gas undergoes a chemical process, a burner, another heat source, or combinations thereof. In a preferred embodiment, the longitudinal flow space, in which the flat portions of the flat tubes are arranged, annular (ie, hollow cylindrical) is formed. On the other hand, at least one of the two transverse flow spaces is preferably cylindrical and has a free central gas distribution space (gas collection space) from which the gas flow leads radially outwards between the round sections of the flat tubes (or vice versa).

In the transverse flow direction, the tube bundle preferably has an extension that is at most twice as long as the length of the transverse inflow zone measured in the tube bundle longitudinal direction. Thereby, a uniform distribution of the gas can be achieved before it flows through the longitudinal flow zone between the flat tubes along. The said measure also creates a good condition for being able to arrange the flat tubes in the tube bundle relatively dense, so that there is a good use of space and thus a compact design. This can also contribute that certain dimensions are met for the flat tubes. Preferably, the flat tubes have an inner gap width s of 1 mm to 5 mm, preferably 1 mm to 3 mm. The optimal gap width is 2mm. The free width of the flat tube interior is preferably 7 mm to 20 mm. The flat tubes are preferably arranged in a packing density p of 0.9 m ² / dm ³ to 0.2 m ² / dm ³ .

In addition, spacing structures, for example in the form of embossed knobs, ribs or the like, may be present on the flat tubes in order to fix the distance between the tubes. The distance between the flat tubes is preferably at most in the order of the gap width. The gap width is preferably at most a few millimeters. The distance of the rounded portions of the flat tubes from each other is preferably less than the gap width. Thus, the streets formed between the flat tubes are practically separated from each other. The uniform gas distribution in the cross-flow zone is of great importance.

Instead of the flax tubes and so-called structured tubes can be used in which the heat transfer is improved by turbulence. For the production of Turbulence vortices may be formed on the inner and / or outer surfaces of the flat tubes turbulence generating elements, for example. Ribs, projections, dents or the like.

Preferably, all flat tubes have the same shape, so they are uniform, which keeps the production costs low.

The tubes may be formed in one piece or in several parts. This can be expedient in particular with a very high temperature spread. It can pipes made of different materials butt joined to each other in particular welded. Thus, other materials can be used in the cold zone than in the warm zone. On the housing, an expansion element can be arranged, which compensates for expansion differences between the housing and the tube bundle. The expansion compensation element is preferably arranged on the cold side of the heat exchanger.

If the heat exchanger tubes are arranged in an annular zone which encloses a central region, a burner with a combustion chamber can be arranged there, for example in order to heat a reactor present there. Between the combustion chamber and the heat exchanger, an insulating layer is preferably arranged. This combination of heat exchanger and combustion chamber is suitable, for example, for heating the cathode air for an SOFC fuel cell.

In the interior, in particular in the tube bundle space of the heat exchanger and a catalytic reactor may be mounted. This can be arranged, for example, as a reformer in the anode gas cycle of an SOFC fuel cell system.

With the flat tube heat exchanger according to the invention, efficiencies of more than 80% can be achieved in countercurrent operation. Preferably, the gas to be heated in the tubes and the heat-emitting gas is passed between the tubes. It can gases with very high inlet temperatures, such as. 1000 ° C are processed. The heat transfer rates are based on the volume of construction in the same range as that of plate heat exchangers and regenerators at comparable gap widths. However, welded plate heat exchangers are not suitable for such high temperatures. The proposed flat tube heat exchanger is thus particularly suitable for decentralized power generation, e.g. in SOFC fuel cells or micro gas turbines. It does not require the changeover valves and controls required for regenerators.

• Figur 1 einen erfindungsgemäßen Flachrohrwärmetauscher im schematisierten Längsschnitt,
• Figur 2 den Flachrohrwärmetauscher nach Figur 1, geschnitten entlang der Linie A-A in Figur 1,
• Figur 3 den Flachrohrwärmetauscher nach Figur 1, geschnitten entlang der Line B-B in Figur 1,
• Figur 4 ein Flachrohr des Flachrohrwärmetauschers, in Draufsicht, in schematisierter Darstellung,
• Figur 5 das Flachrohr nach Figur 4, in einer abschnittsweisen Seitenansicht,
• Figur 6 das Flachrohr nach Figur 4 und 5, in einer Perspektivansicht,
• Figur 7 den Flachrohrwärmetauscher mit eingebautem Brenner, in einer längs geschnittenen Prinzipansicht,
• Figur 8 eine abgewandelte Ausführungsform des erfindungsgemäßen Flachrohrwärmetauschers, im Vertikalschnitt,
• Figur 9 eine weitere abgewandelte Ausführungsform des erfindungsgemäßen Flachrohrwärmetauschers, in vertikal geschnittener Seitenansicht,
• Figur 10 den Flachrohrwärmetauscher nach Figur 9, geschnitten an der Linie X-X in Fig. 9 und mit einer Schnittlinie IX-IX zur Veranschaulichung der Schnittführung in Fig. 9, und
• Figur 11 den Flachrohrwärmetauscher nach Figur 9, geschnitten entlang der Linie XI-XI in Figur 9.

Further details of advantageous embodiments of the invention are the subject of subclaims of the drawings and the description. In the description, a few embodiments of the invention are illustrated. It is understood that the invention is not limited to the specific embodiments and examples. Show it:

• FIG. 1 a flat tube heat exchanger according to the invention in a schematic longitudinal section,
• FIG. 2 the flat tube heat exchanger after FIG. 1 , cut along the line AA in FIG. 1 .
• FIG. 3 the flat tube heat exchanger after FIG. 1 , cut along the line BB in FIG. 1 .
• FIG. 4 a flat tube of the flat tube heat exchanger, in plan view, in a schematic representation,
• FIG. 5 the flat tube after FIG. 4 in a sectionwise side view,
• FIG. 6 the flat tube after FIGS. 4 and 5 in a perspective view,
• FIG. 7 the flat tube heat exchanger with built-in burner, in a longitudinal sectional view,
• FIG. 8 a modified embodiment of the flat tube heat exchanger according to the invention, in vertical section,
• FIG. 9 a further modified embodiment of the flat tube heat exchanger according to the invention, in a vertically sectioned side view,
• FIG. 10 the flat tube heat exchanger after FIG. 9 , cut along the line XX in Fig. 9 and with a section line IX-IX illustrating the incision in Fig. 9 , and
• FIG. 11 the flat tube heat exchanger after FIG. 9 , cut along the line XI-XI in FIG. 9 ,

In FIG. 1 a flat tube heat exchanger 10 is illustrated, which is housed here in a cylindrical housing 11. At both ends of the housing 11 preferably curved closure cap 12, 13 are attached, which belong to the housing 11 and may be part of the same, for example. The housing 11 encloses, together with the covers 12, 13, an interior which, through two tube sheets 14, 15 in a total of three spaces, namely an input-side collecting space 16 (FIG. FIG. 1 below), a tube bundle space 17 and an output-side collecting space 18 are divided. The collecting chambers 16, 18 are each provided with a connection 19, 20. The connection 19 is, for example, subjected to cold air. For example, hot air is to be delivered to the connection 20.

Between the tube sheets 14, 15, a tube bundle 21 is arranged. This consists of numerous mutually preferably equal flat tubes 22. The cross sections of the flat tubes 22 have straight flanks which define the inner gap cross-section between each other. The flat flanks are interconnected by small radius bent sections. Each flat tube 22 is preferably formed straight and arranged parallel to an imaginary central axis 23 of the housing 11. The flat tubes 22 are anchored with their ends 24, 25 to the tube sheets 14, 15. For example, they are welded to the respective tubesheet 14, 15, brazed, pressed, crimped or connected in any other suitable manner. Preferably, the compound is fluid-tight and temperature-resistant.

Each flat tube 22 has a comparatively long central section A with a flat cross section and at its two ends 24, 25 a shorter section B with a circular cross section. FIG. 2 illustrates the tube bundle 21 in the region of its section A in a sectional view. As can be seen, each flat tube 22 has an inner gap cross-section whose width is 1 mm to 4 mm, preferably 2 mm to 3 mm. The circumference of this cross section is preferably between 20 mm and 40 mm. As can be seen, the flat tubes 22 are each arranged in an annularly closed row, each row being circular (strictly speaking polygonal) and concentric with the central axis 23.

Within the row, the flat tubes 22 are at least preferably arranged such that the individual flat tubes 22 just do not touch with their strongly curved sections. However, the remaining gaps between the flat tubes 22 within a row are small. The flat tubes can alternatively also touch each other at any temperature or only at certain temperatures. The flat sides of the flat tubes are oriented in the circumferential direction, that is tangent to the respective circle on which they are arranged.

The annular spaces formed between the rows or boundaries of different flat tubes 22 are relatively narrow. It is largely free of other internals held annular flow channels. The individual annular flow channels are largely separated from one another by the flat tube rings in terms of flow.

It should be noted that other flat tube configurations are applicable. For example, the flat tubes may be arranged in a single spiral wound row. Also, they can be slightly inclined against the circumferential direction, so be rotated slightly about their respective longitudinal axis. With the tangential direction they then enclose an acute angle. However, the above statements regarding cross-sectional shape and tube spacing apply accordingly.

Preferably, in each of FIG. 2 illustrated annular array of tubes arranged in number so as to give a closed as possible row. Preferably, the number of flat tubes 22 in the rows do not match each other. The number of tubes preferably increases radially from the inside to the outside. Preferably, the numbers of tubes of adjacent annular rows differ by 1 to 3, preferably 2.

How out FIG. 3 it can be seen, form the flat tubes 22 with their sections B, an arrangement which is radially flow-permeable, at least permeable than the arrangement of the sections A according to FIG. 2 , It forms flow paths 26 to 28, which allow a radial flow. Thus, in the round sections B of the flat tubes 22, a cross-flow zone 29 is formed. This applies both to the ends 24 of the flat tubes adjacent to the upper tube bottom 14 and to the ends 25 of the flat tubes 22 which adjoin the lower base 15. The tube bundle 21 has a thickness C in the transverse inflow direction, which is preferably at most twice as great the length of section B, ie the transverse inflow zone. The flat portions A of the flat tubes 22 may extend into the lateral inflow zone 29. This is especially true if the transverse inflow, as it is also possible, is parallel or at an acute angle to the flat sides of the flat sections. This applies to all embodiments.

The lying between the two transverse flow zones 29 sections A of the flat tubes 22 form a longitudinal flow zone 30, which serves the actual heat exchange.

For introducing and discharging fluid into the tube bundle space 17 are tube bundle space connections 31, 32, which may be arranged coaxially to the central axis 23, for example may be arranged coaxially to the central axis 23 and in this case, the closure cover 12, 13 and the tube sheets 14, 15 prevail. It should be noted that the tube bundle connections 32, 33 can also be arranged elsewhere. For example, they may be formed by the housing 11 passing through in the areas B radially or tangentially to the housing 11 attaching. Further, concentric with the central axis 23, an inner housing wall 33 may be arranged. This can be formed by a solid body or a hollow body. It can surround other parts of the plant, a heat storage or the like, or it can be empty.

The housing 11 may be provided at a suitable location with a strain compensation element 34. Preferably, this is in the cylindrical portion of the housing 11 between the tubesheets 14, 15, preferably in the vicinity of the colder tube bottom, i. attached to the input-side terminal 19. The expansion compensation element may allow, within certain limits, an axial expansion and compression of the housing 11, so that the distance between the tube sheets 14, 15 is determined by the temperature and thus the length of the tube bundle 21. The housing 11 adapts accordingly.

The flat tube heat exchanger 10 described so far operates as follows:

In operation, the flat tube heat exchanger 10 via the tube bundle space 31 hot, preferably gaseous fluid, eg. Exhaust gas of a micro gas turbine or the like supplied. Above the approximately cylindrical central body enclosed by the inner housing wall 33, this flow is deflected essentially in the radial direction. She reaches the in FIG. 3 apparent lanes 26 to 28 and distributes radially and circumferentially in the tube bundle 21. Starting from the cross clean-flow zone 29, the hot gas stream then runs in the longitudinal direction substantially parallel to the central axis 23 through the annular zones between the flat tubes 22, which are in FIG. 2 can be seen. The heat contained in the hot gas flow is transferred to the wall of the flat tubes 22.

At the same time, cold gas, for example air at ambient temperature, is conducted into the collecting space 16 via the inlet-side connection 19. It enters from there into the round lower ends of the flat tubes 22 and flows through the inner gap volumes of the flat tubes 22 in the opposite plenum 18 from. It flows in countercurrent to the hot gas, whose inlet temperature, for example, by 1000 ° C may be. The supplied cool air absorbs a large part of the heat and can reach in the collecting space, for example. 800 ° or 900 °. It then flows via the output-side terminal 20.

Due to the illustrated flow structure, the flat tube heat exchanger 10 has only a small differential pressure requirement both for the hot gas stream and for the cold gas stream. The resulting pressure loss is low. Due to the narrow gap width of the flat tubes 22 and the dense arrangement thereof, a high heat utilization is achieved. The exhaust gas leaving the tube bundle space 17 via the tube bundle connection 32 is, for example, cooled to low temperatures of a few 100.degree. C., for example 200.degree. C. or 300.degree.

FIGS. 4 to 6 illustrate optional details of the flat tube 22. Preferably, it has different circumferences in the sections A and B, as already explained above with reference to the cross sections.

Further optionally, in particular the flat sides of the portion A of each flat tube 22 with projections 35, for example. Be provided in the form of knobs or ribs, fins or the like. These projections 35 may serve as spacers to prevent flat tubes 22 of different rows from approaching too much and obstructing the flow channel therebetween. It is also possible to use these projections 35 as turbulence-generating elements in order to improve the heat transfer from the hot gases flowing between the flat tubes 22 to the flat tubes 22.

FIG. 7 illustrates a modified embodiment of the flat tube heat exchanger 10. This is here combined with a burner 36 for generating hot gas and structurally unified. For this purpose, the tube bundle space connection 31 is designed or used as a supply air duct for combustion air. In this channel, for example, a fuel channel 37 is arranged concentrically. For example, anode residual gas or another fuel can be conducted into the combustion chamber 38 via this. The combustion chamber 38 may be arranged in the interior of the container enclosed by the inner housing wall 33. Eie ignition electrode 39, which can extend through the fuel channel 37, for example, completes the burner. The inner housing wall 33 may be internally provided with a thermally insulating lining 40. It forms with a combustion chamber 38 delimiting tube an annular channel 41, which is open to the cross flow space 29 out. From there, the hot gas discharged from the burner 36 flows through the longitudinal flow zone 30 (pipe sections A) to release the heat there. The cooled exhaust gas exits the flat tube heat exchanger 10 again through the cross flow zone 29 (in FIG FIG. 7 left) and the tube bundle space connection 32. The fed via the terminal 19 Air is passed in countercurrent through the flat tubes 22 and thereby strongly heated to be discharged through the plenum 18 and the port 20 at high temperature, for example. Significantly higher than 700 ° or 800 °. In this arrangement, the flat tube heat exchanger 10 forms a heat exchanger with an internal heat source. The heat source is a burner. However, other heat sources can also be integrated into the heat exchanger 10 with an otherwise identical design.

The principles described above can also be realized on non-annular or non-cylindrical heat exchangers. FIG. 8 illustrates such a flat tube heat exchanger 10. The tube bundle 21 formed by the flat tubes 22 is enclosed by a rectangular in cross-section or square housing 11. The flat tubes 22 are arranged in mutually parallel rows and formed as described above. Their round sections B form cross-flow zones. For example, the tube bundle space 17 can be supplied with hot gas via one or more connections 31. Cooled hot gas can be discharged via one or more ports 32 from the tube bundle space 17. The collecting chambers 16, 18 may be box-shaped. In this as in the embodiments described above, the tube bundle formed by the flat tubes 22 in the transverse inflow direction has a thickness which is preferably at most twice as long as the length of the section B, ie the transverse inflow zone. This serves to achieve a uniform gas distribution between the flat tubes 22. While the direction of the transverse inflow in the embodiment of the flat tube heat exchanger 10 after FIG. 8 is determined by the longitudinal direction of the terminals 31, 32 (in FIG. 8 perpendicular to the plane of the drawing) in the above embodiments, this direction is the radial direction. Thus, the thickness C of the tube bundle 21 in the exemplary embodiment Figure 1 to 3 determined by the distance of the outer wall of the housing 11 with the inner housing wall 33. This distance C is preferably at most 1.5 to 2 times as long as the length B.

To illustrate a further modified heat exchanger 10 FIG. 9 to FIG. 11 , As far as structural and / or functional agreement with the heat exchanger 10 after FIG. 8 and in the broader sense with the heat exchanger 10 after Figure 1-7 is made, reference is made to the previous description based on the already introduced reference numerals. In addition, attention is paid to the projections 35, which are formed here as thickenings of the flat sections A of the flat tubes 22. The thickenings serve as spacers. The eg between 0.5 and 1 m flat tubes 22 may have such thickening 35 at a distance of several dm, for example 2 dm. They stabilize the distances between the flat tubes 22 and make the heat exchanger 10 insensitive gege thermal Versug, eg due to temperature differences.

To improve the energy efficiency of high temperature processes, a flat tube heat exchanger 10 is proposed, which is suitable for high temperatures, tolerates a high temperature spread and reaches countercurrent operation transmission efficiencies of over 80%. In addition, it has a high packing density, low pressure drops and eg less than 50 mbar, a high durability and robustness and low production costs. The flat tube heat exchanger has flat tubes, which have flat heat exchanger sections and round ends. The rounded ends define transverse inflow zones which provide a uniform gas distribution of hot gas between the flat sections of the flat tubes 22 at low pressure drops. The efficiency of such a flat tube heat exchanger is comparable to that of a plate heat exchanger, but a much higher robustness is given.

LIST OF REFERENCE NUMBERS

10

Flat tube heat exchanger

11

casing

12, 13

cap

14, 15

tube sheets

16

input-side collecting space

17

Tube bundle space

18

output collecting space

19

input side connection

20

output side connection

21

tube bundle

22

flat tube

23

central axis

A

flat portion of the flat tube 22nd

B

Round portion of the flat tube 22nd

C

Rohbündeldicke

24, 25

End of the flat tube 22

26 - 28

streets

29

Cross-flow zone

30

Longitudinal flow zone

31, 32

Tube bundle Utilities

33

inner housing wall

34

Expansion compensating element

35

projections

36

burner

37

fuel channel

38

combustion chamber

39

ignition electrode

40

lining

41

annular channel

Q

Cross-flow direction

Claims (15)

1. Tubular heat exchanger (10), in particular for gaseous media,
   with a closed housing (11, 12, 13), which on two opposing sides has two tube bottoms (14, 15), which in the housing (11, 12, 13) divide off a collecting chamber (16) on the inlet side, a tube bank chamber (17) and a collecting chamber (IS) on the outlet side, with a tube bank (21), which defines a tube bank longitudinal direction (23) and consists of tubes, which are arranged parallel to the tube bank longitudinal direction (23) and are fastened to the tube bottoms (14, 15) at corresponding openings, so that the tubes (22) communicate with the collecting chambers (16, 18),
   wherein each collecting chamber (16, 18) is provided with at least one collecting chamber connection (19, 20) and the tube bank chamber (17) is provided with at least two tube bank chamber connections (31, 32) spaced from one another in tube bank longitudinal direction (23),
   wherein the tube bank chamber (17) has three zones, namely two cross flow zones (29) configured at the tube bank chamber connections (31, 32) and a longitudinal flow zone (30) configured between these cross flow zones (29),
   characterised in that the tube bank at least predominantly consists of straight flat tubes (22) with round or polygonal ends (B).
2. Tubular heat exchanger according to claim 1, characterised in that the cross flow zones (29) directly adjoin the two tube bottoms (14, 15).
3. Tubular heat exchanger according to claim 1 or 2, characterised in that the flat tubes (22) respectively have a round, circular or polygonal cross-section in the cross flow zones (29) and a flat cross-section in the longitudinal flow zone (30).
4. Tubular heat exchanger according to claim 3, characterised in that in the longitudinal flow zone (30) the flat tubes (22) have a flat cross-section with plane flanks.
5. Tubular heat exchanger according to one or more of the preceding claims, characterised in that when the tube bank (21) has a cross dimension (C) in cross flow direction (Q) in the cross flow zone (29) and when the cross flow zone (29) has a length (B) in tube bank longitudinal direction (23), the length (B) amounts to at least 0.5-times the cross dimension (C).
6. Tubular heat exchanger according to one or more of the preceding claims, characterised in that the housing (11, 12, 13) has an inside wall (33) closed in a ring shape in cross-section and an outside wall (11) likewise closed in a ring shape on cross-section.
7. Tubular heat exchanger according to claim 6, characterised in that the inside wall (33) encloses a heat source (36).
8. Tubular heat exchanger according to claim 6, characterised in that the flat tubes (22) are arranged in concentric circles.
9. Tubular heat exchanger according to claim 8, characterised in that distances to be measured in circumferential direction are smaller than the gap width of the flat tube sections (A).
10. Tubular heat exchanger according to one or more of the preceding claims, characterised in that cross flow channels (26, 27, 28) are configured between the round ends of the flat tubes.
11. Tubular heat exchanger according to claim 6, characterised in that the tube bank chamber connections (31, 32) are arranged to pass through the tube bottom (1.4, 15).
12. Tubular heat exchanger according to one or more of the preceding claims, characterised in that the flat tubes (22) are provided with spacer structures (35).
13. Tubular heat exchanger according to one or more of the preceding claims, characterised in that at least some of the flat tubes (22) are provided with turbulence-generating structures (35).
14. Tubular heat exchanger according to one or more of the preceding claims, characterised in that the housing (11, 12, 13) is provided with at least one extension compensating element (34).
15. Tubular heat exchanger according to one or more of the preceding claims, characterised in that a catalyst is arranged in the tube bank chamber (17).

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