WO2007137863A1

WO2007137863A1 - Heat exchanger

Info

Publication number: WO2007137863A1
Application number: PCT/EP2007/004869
Authority: WO
Inventors: Peter Geskes
Original assignee: Behr Gmbh & Co. Kg
Priority date: 2006-06-01
Filing date: 2007-06-01
Publication date: 2007-12-06
Also published as: CN101454559B; EP2029883A1; CN101454559A

Abstract

The invention relates to a heat exchanger, in particular for a motor vehicle, comprising at least one exchanger pipe (4) for conducting a gaseous fluid. Said fluid contains or can contain the exhaust gas of an internal combustion engine as an admixture and a coolant can flow around the exchanger pipe (4) in order to cool the fluid stream. The exchanger pipe (4) is formed as an extruded section from an aluminium-based alloy.

Description

heat exchangers

The invention relates to a heat exchanger, in particular for a motor vehicle, according to the preamble of claim 1.

More recently, heat exchangers have been developed for cooling gas streams for exhaust gas recirculation (EGR), which at least partially, possibly mixed with charge air, exhaust gas of an internal combustion engine. The cooled exhaust gases are usually returned to the internal combustion engine to reduce pollutant emissions on the intake side. These fluids to be cooled are not only of high temperature, but also very acidic. Depending on the operating conditions, condensates with a pH between about 1 and 3 can deposit, so that high demands are placed on the corrosion resistance of the heat exchanger, especially at high temperatures. Regularly such heat exchangers are therefore made of stainless steel or similar materials.

It is the object of the invention to provide a heat exchanger for cooling a gas stream containing at least partly exhaust gas, which can be produced easily and in a cost-effective manner.

This object is achieved according to the invention for a heat exchanger mentioned above with the characterizing features of claim 1. By using extruded profiles from an aluminum alloy tion for the exchanger tubes, a cost-effective and lightweight heat exchanger can be provided, which has a high compressive strength and a good heat exchanger performance for a given size. It has surprisingly been found in experiments that under normal conditions extruded aluminum alloys have a significantly better corrosion resistance to exhaust gas streams, as was previously thought.

In a preferred embodiment, the exchanger tube comprises a plurality of separate channels. This makes it possible to provide a large surface area of the heat exchanger with at the same time good mechanical stability of the exchanger tube, whereby the production of such an exchanger tube, due to the use of extruded profiles, does not represent any significant expense compared to conventional exchanger tubes with only one channel.

Another preferred embodiment of the heat exchanger is characterized in that the channels are separated by webs which are part of the extruded profile. The webs are produced in an advantageous manner during the production of the extruded profile by extrusion.

Another preferred embodiment of the heat exchanger is characterized in that the webs are at least partially interrupted in the extrusion tubes. All or individual webs can be executed continuously. Alternatively, all or individual webs can also be executed interrupted. According to one embodiment of the invention, the webs are executed alternately continuously and interrupted.

A further preferred embodiment of the heat exchanger is characterized in that the outer wall thickness of the exchanger tube is preferably between 0.4 and 2 mm. The outer wall thickness of the exchanger tube is the wall thickness of the outwardly facing wall of the tube. A further preferred embodiment of the heat exchanger is characterized in that the exchanger tube has webs with a web thickness which is smaller than or equal to the outer wall thickness of the exchanger tube. This range has proved to be particularly advantageous in the context of the present invention.

A further preferred embodiment of the heat exchanger is characterized in that separate channels are produced by ribs which are inserted and soldered into the exchanger tubes. Through the inserted ribs all separate channels of an exchanger tube can be created. However, it is possible to create additional separate channels in an exchanger tube which already contains separate channels, for example produced by extrusion.

Generally, the coolant is air. This is particularly advantageous if the heat exchanger as a second cooling stage behind a z. B. liquid-cooled primary exhaust gas heat exchanger is used. In principle, however, a heat exchanger according to the invention can also be a liquid-cooled heat exchanger, the low susceptibility to corrosion of aluminum extruded profiles also being advantageous here. It is essential that the fluid temperatures do not exceed a range suitable for the aluminum extrusion profiles.

The invention extends not only to the cooling of a pure exhaust gas but can also be used for the cooling of pure charge air or a mixture of exhaust gas and charge air.

In a generally preferred construction, the heat exchanger comprises a bottom, wherein the exchanger tube terminates in the bottom end and is firmly connected to the bottom. This is in principle the known construction of a tube bundle heat exchanger. Particularly preferably, the exchanger tube can be fixed to the floor by means of one of the group of induction brazing, flame brazing, laser welding or welding. It is important that the connection between the exchanger tube extruded section and the floor is only local and if possible only external and as small as possible. heat experiences. It is believed that the surprising corrosion properties of the extruded-profile exchanger tubes are due to a particularly fine crystal structure, which is produced in particular during the process of extruding the aluminum alloy. Subsequent heating of the extruded-profile exchanger tubes can result in coarseness of the material and deteriorate the corrosion properties.

If slight restrictions in corrosion resistance are accepted, a heat treatment of the entire cooler can be implemented. Although the overall thermal treatment of the cooler block, the grain structure of the aluminum material coarser, but extruded tubes still have a good corrosion behavior due to the low material contamination and the smooth surface. In this entire heat treatment ribs and pipes are soldered and also the connection between pipes and soil takes place by soldering. The soldering can be done in a vacuum or Nocolok process. In the case of such a complete soldering it is also conceivable that not only on the outside a rib is provided, but also on the inside of the tube. This rib (e.g., rib gutter or tubulence generator) is then brazed to the exchanger tube on the inside of the tinter tube. Such ribs can also be additionally protected against corrosion.

In the sense described above, the exchanger tube can alternatively or additionally also be fixed to the floor by means of adhesion. With this possibility of fixing, no local heating of the exchanger tube takes place in the course of assembly. Another alternative or supplemental fixation without heating may be by mechanical means in conjunction with a seal.

Quite generally, it is advantageous in the above-described sense that the exchanger tube does not undergo complete heat treatment in the course of assembly of the heat exchanger, which exceeds a temperature of extruding in the course of production of the exchanger tube. If such temperatures in the case of welding or soldering in the field of fixing the Exchanger tubes are reached on the ground, so this should be locally limited at most.

In a particularly preferred embodiment, at least one rib element is arranged in thermal contact on the exchanger tube. This generally leads to an improvement of the heat exchanger performance, in particular in the case of air-cooled heat exchangers. In this case, the rib element is glued to the exchanger tube in a particularly preferred manner. In this way it is prevented that the extruded exchanger tube undergoes further heating after its production process, which could worsen the corrosion resistance of the exchanger tube in the sense described above. Such bonding is preferably carried out by an adhesive based on epoxy resin, wherein in particular the adhesive is mixed with metal powder. The metal powder may be aluminum powder or other suitable metal powder. Such adhesives are well known and have not only a high strength but also a high temperature resistance. Particularly advantageously, the adhesive of the bond has a temperature resistance which is at least about 180 ^° C., preferably at least about 200 ^° C.

Alternatively or additionally, the rib member may be resiliently pressed against the exchanger tube. Basically, it can be dispensed with a bonding with a resilient pressure. However, a combination of resilient pressure and bonding in terms of a simplified installation of the heat exchanger is advantageous.

As an alternative or in addition, a thermally conductive paste may be provided between the exchanger tube and the rib element. Such a paste may possibly have a higher temperature resistance than known adhesives, so that the combination of a spring-elastic holder with a thermal compound is particularly preferred. Depending on the design of the heat exchanger, it is also possible to provide some exchanger tubes with gluing and another exchanger tube with spring-elastic holder, if necessary with heat-conducting paste. A further preferred embodiment of the heat exchanger is characterized in that the rib elements are soldered on the outside with the exchanger tubes. By soldering a cohesive connection is created with good thermal conductivity properties.

Another preferred embodiment of the heat exchanger is characterized in that the soldering takes place in a soldering oven by means of vacuum or Nocolok soldering. These methods have proven to be particularly advantageous in the context of the present invention for brazing the rib elements with the tandem tubes.

In a preferred embodiment, the rib member is formed as a particular corrugated, arranged between two adjacent exchanger channels sheet metal part. As a result, an improvement in the heat exchanger performance is given in a simple manner, corrugated sheet-metal parts being able to be fixed in a particularly elastic or even glued manner.

Alternatively or additionally, the rib element may be designed as a sheet metal part which is aligned substantially perpendicular to the exchanger tube and in particular penetrated by the exchanger tube. This makes it possible to provide a large surface of the heat exchanger with simple means.

In a generally preferred embodiment, the heat exchanger has at least one box for supplying or discharging the fluid to the at least one exchanger tube. Advantageously, the box consists essentially of an aluminum alloy. In particular, on the temperature-reduced outlet side of the box but also made of a plastic, in particular a polyamide exist. In principle, all known embodiments of heat exchanger boxes are possible insofar as they are compatible with the corrosive and thermal requirements of an exhaust gas heat exchanger.

In a further preferred embodiment, a bypass line can be provided, the fluid flow being selectable by means of an actuator Bypass line or through which at least one exchanger tube is feasible. Such bypass lines for bypassing exhaust gas cooling are often desired to account for various operating conditions of the internal combustion engine.

In a further embodiment, the heat exchanger can have at least one leading and at least one substantially parallel return exchanger tube, which are connected to one another in a deflection region. As a result, the heat exchanger is designed as a "U-flow" heat exchanger, which allows a particularly large cooling of the gas flow at a given size.

More generally, the maximum operating temperature of the fluid supplied to the heat exchanger is less than about 300 ^° C., in particular less than about 250 ^° C. This is advantageous when the heat exchanger has adhesions. Particularly preferably, the heat exchanger according to the invention is then provided as a second stage of exhaust gas cooling and preferably arranged after a liquid-cooled first exhaust gas cooler. In principle, the arrangement of the heat exchanger according to the invention can be carried out in a system of high-pressure exhaust gas recirculation as well as in a system of low-pressure exhaust gas recirculation.

Depending on the exemplary embodiment, pure charge air, pure exhaust gas or a gas mixture of charge air and exhaust gas is passed through the heat exchanger according to the invention.

The invention also includes the use of an aluminum extruded profile as the exchanger tube of a heat exchanger according to one of claims 1 to 21.

Such profiles can be carried out with continuous webs or else have webs which are interrupted in order to avoid blocking by sooting. Also, icing of the cooler is avoided in cold temperatures when the hydraulic diameters are not too high be chosen small. Preferably, the hydraulic diameter is in the range between 1, 5 and 4 mm.

In applications of a gas without soot, the distances between the webs can be less than 1-3 mm, for a gas with soot, distances greater than 1-3 mm are preferable. The tube thickness, i. the shorter length of the tube is ideally in the range 4-10 mm and the tube width in the range 8-100 mm.

An essential feature of extruded pipes is that the outside wall has a thickness that exceeds the thicknesses normally used in coolers. This increased thickness is required to be sufficiently protected against corrosion attack. The thickness is preferably chosen in the range 0.4-2 mm, with a thickness between 0.7 and 1.2 mm being ideal. Thickness is also called wall thickness. Furthermore, it is advantageous if the web thickness is equal to or equal to the wall thickness. This provides a system that is optimal in terms of corrosion, cost, pressure drop, and thermodynamics.

The extruded profile can be particularly thickened in the corner regions by e.g. the radii of the two outer chambers are chosen to be larger. In addition, the extruded tube can also have stiffening ribs in the corners in the shape of a "truss-like" structure These stiffeners have considerable advantages since they bring substantial increases in strength in the case of pressure pulsations and thermal cycling.

Further advantages and features will become apparent from the embodiments described below and from the dependent claims.

Hereinafter, six preferred embodiments of a heat exchanger according to the invention will be described and explained in more detail with reference to the accompanying drawings. Show it:

Fig. 1 is a schematic plan view of a first embodiment of the invention; Fig. 2 is a sectional view of a second embodiment of the invention;

Fig. 3 is a sectional view of a third embodiment of the invention; Fig. 4 is a sectional view and a side elevational view of a fourth embodiment of the invention;

Fig. 5 is a side elevational view of a fifth embodiment of the invention;

6 is a schematic plan view of a sixth embodiment of the invention and

FIG. 1 shows a heat exchanger tube in cross-section with separate casings. FIG.

7-10 channels according to further embodiments.

1 is an air-cooled heat exchanger for cooling recirculated exhaust gas of a diesel engine. The heat exchanger is arranged as a second stage after a not shown, known liquid-cooled heat exchanger in the exhaust stream.

The heat exchanger comprises an input-side connection 1, which opens into a distribution box 2, which comprises a bottom 3.

Several exchanger tubes 4 open into the bottom 3 and are set close to this. The exchanger tubes 4, the base 3 and the box 2 each consist of an aluminum alloy.

In the schematic exemplary embodiments shown, only four exchanger tubes are usually shown for reasons of clarity. In practice, significantly more exchanger tubes will be provided on a regular basis.

The exchanger tubes 4 are manufactured as extruded profiles. In terms of temperature, pressure and speed, the extrusion process is a standard process known per se for the production of aluminum profiles. In the present embodiment, an alloy according to the European standard EN-AW 3103 is used as the aluminum alloy. In the case of This alloy contains relatively little silicon and relatively little copper (in each case 0.05% by weight). It is suspected that these properties further improve the corrosion resistance.

The exchanger tubes or extruded profiles 4 are generally not subjected to any special corrosion protection after extrusion.

In principle, however, an applied corrosion protection is also conceivable for extruded profiles.

In the direction of the exhaust gas flow, the parallel exchanger tubes 4 open into an outlet-side collection box 5, which comprises a bottom 6 and the inlet-side box 2 is substantially equal.

Between the extruded profiles 4 each rib elements 7 are arranged. At the end, the row of exchanger tubes 4 terminates in each case with a side part 8, which on the one hand has covering and protective functions and on the other hand terminates an end-side rib 7 on a respective outer exchanger tube 4.

The rib elements 7 are glued to contact points with the exchanger tubes 4, respectively. The adhesive used here is an epoxy resin-based adhesive provided with a high proportion of aluminum powder. This has a temperature resistance of about 200 ⁰ C.

On the inlet side, the pre-cooled exhaust gas flow temperatures of less than 250 ⁰ C. Due to the flow around the exchanger tubes 4 and rib elements 7 with cooling air, it is ensured that the bonds 9 of the rib elements 7 on the exchanger tubes 4 are not destroyed by thermal action.

At the transition of the exchanger tubes 4 in the bottom elements 3, the exchanger tubes 4 by means of a local soldering, z. As flame brazing, induction brazing or the like. It is important that the exchanger tubes 4 after their extrusion no complete heating to temperatures experienced, which are comparable to the temperatures of the extrusion process or are higher. This ensures that the microcrystalline structure of the exchanger tubes 4 caused by the extrusion is maintained. This in turn, according to previous findings, is essential for a good corrosion resistance of the exchanger tubes 4. The local soldering of the exchanger tubes 4 to the bottoms 3, 6 is preferably carried out such that at least the surfaces of the exchanger tubes facing the exhaust gas do not experience a thermally induced change in their crystal structure and thus their corrosion resistance.

The second Ausfϋhrungsbeispiel according to FIG. 2 shows a sectional view through exchanger tubes 4, which correspond in cross section to those in the first embodiment. As can be seen, each extruded exchanger tube 4 has four separate channels 4a, wherein inner dividing walls 10 separate the individual channels 4a from each other. In addition to improved heat dissipation, the partitions 10 also ensure a high mechanical stability and pressure resistance of the exchanger tubes 4, even with relatively soft aluminum alloy and relatively small wall thicknesses.

The difference to the embodiment of FIG. 1 consists essentially in the formation of the rib elements 7 '. In the present case, the rib elements T are sheet metal parts which are aligned perpendicular to the exchanger tubes 4 and have gills 1 1 to increase their surface area. The ribs 7 'can be kept purely mechanically between the exchanger tubes 4, z. B. by resilient forces. Alternatively or additionally, the rib elements 7 may be glued to the exchanger tubes 4. It is also possible to provide a thermally conductive paste between fin elements T and exchanger tubes 4.

In the third embodiment according to FIG. 3, there is a modification with respect to the exemplary embodiment according to FIG. 2, in which the exchanger tubes 4 are provided with lateral webs 12 at their respective corner regions, so that the rib elements 7 'are held in a form-fitting manner between the exchanger tubes 4. In particular, in the embodiment according to FIG. 3, a spring-elastically clamping holder of the rib elements T is particularly special safe way allows. Not shown means ensure a defined spacing of superimposed in the direction of the diver tubes rib elements.

In the fourth embodiment according to Figure 4, the rib elements 7 "each consist of sheets extending over the entire width of the heat exchanger, which have gills 11 to increase their surface area. As shown in the lateral plan view, the rib elements 7" form a stack of by suitable means Each of the rib elements 7 "in this case comprises a number of exchanger tubes 4 corresponding number of mutually aligned punched-out. In the course of assembly, the exchanger tubes 4 are inserted through the stack of rib elements 7 "or the aligned punched-out portions In the present exemplary embodiment, the exchanger tubes 4 and the associated stampings are of substantially elliptical cross-section.

The mechanical fixation and the thermal contact between fin elements 7 "and exchanger tubes 4 can in this embodiment be carried out in a simple manner by expanding the exchanger tubes 4 after preassembly of the heat exchanger 10. The expansion can be effected by means of suitable expansion punches, by filling with water and water Freezing, by high pressurization or similar suitable means Alternatively or additionally, thermally conductive paste and / or adhesive can be used at the contact points between rib elements 7 "and exchanger tubes 4.

The embodiment of FIG. 5 is similar to the first embodiment of FIG. 1, wherein a frame of transverse struts 13 is provided, so that a mechanical tension of the exchanger tubes 4 and rib elements 7 is given between the end-side side parts 8. In particular, with the help of such a bracing can be dispensed with bonding of the rib elements 7 to the exchanger tubes 4. But even with the bonding of rib elements 7 and exchanger tubes 4, the bracing tion according to FIG. 5 an overall improved mechanical stability of the heat exchanger.

The embodiment of FIG. 6 shows a heat exchanger corresponding to the first embodiment with respect to the exchanger tubes 4 and fin elements 7. In contrast to the first embodiment, the boxes of the heat exchanger were modified. A first box 14 has both an inlet-side connecting piece 15 and an outlet-side connecting piece 16. The relative to the exchanger tubes 4 opposite box 17 is closed and causes only a connection of the exchanger tubes 4 with each other. An actuator 18 within the first box 14 connects depending on its position, the inlet nozzle 15 directly to the outlet 16 (dashed line) or separates the nozzle 15, 16 from each other. In the first case, the box 14 forms a bypass channel, bypassing the exchanger tubes 4. In the second case (solid line of the actuator 18), the heat exchanger works on the principle of a U-flow heat exchanger. The exhaust gas enters through the first port, flows through the two according to FIG. 6, the two exchanger tubes 4, is deflected in the second box 17 and flows in the opposite direction, the upper two exchanger tubes 4, after which it exits the outlet 16.

In FIGS. 7 to 10, a heat exchanger tube is shown in cross section according to further embodiments. The illustrated heat exchanger tubes 4 are each designed as extruded profiles with a closed rectangular cross section 40. Inside the rectangular cross-section 40, an overall substantially rectangular cavity 41 is divided into individual channels 4a or chambers. The individual channels 4a are separated from one another by webs 43, 44.

In the embodiment shown in Fig. 7, the cavity 41 in the interior of the rectangular cross section 40 is divided by a total of seven continuous webs 43, 44 in eight channels or chambers 4a. The webs 43, 44 extend parallel to the short sides and perpendicular to the long sides of the rectangular cross section 40. The extent of the rectangular cross section in the direction of the short sides is shown in FIG. records. The extent rd is also referred to as thickness. The extension of the rectangular cross-section 40 in the direction of the long sides is designated rb in FIG. The expansion rb is also referred to as tube width. The thickness of the outer wall of the rectangular cross-section 40 is designated by d in FIG. 7 and is also referred to as wall thickness or wall thickness. The thickness of the webs 43, 44 is designated s in FIG. 7 and is also referred to as web thickness s.

The hydraulic diameters, that is, the inner diameters, of the channels 4a should not be too small to avoid undesirable freezing of the cooler at cold temperatures. Preferably, the hydraulic diameter of the channels 4a is in the range between 1, 5 and 4 mm.

In Fig. 8 it is shown that the rectangular cross-section 40 can also be equipped with interrupted webs 48. The web 48 comprises two web portions 49, 50, each extending from the long sides of the rectangular cross section 40 vertically inward, but not touching. The interrupted design of the webs 48 serves to avoid undesirable fouling by sooting. In the embodiment shown in FIG. 8, in each case an interrupted web 48 alternates with a continuous web 43, 44.

In the exemplary embodiment illustrated in FIG. 9, it is indicated that the extruded profile is made particularly thickened in the corner regions. This is achieved in that the channels 54, 55 arranged in the corner regions are designed substantially elliptically. As a result, the radii of the outer channels 54, 55 or chambers are larger than in the embodiments shown in FIGS. 7 and 8.

In the embodiment shown in Figure 10, the outer channels or chambers 64, 65 are each provided with two stiffening ribs 66, 67; Equipped 68, 69, which extend like a truss in the corners of the associated chamber 64, 65. The stiffening ribs 66 to 68 increase the strength, especially at pressure pulsations and thermal cycling.

Claims

Patent claims

1. A heat exchanger, in particular for a motor vehicle, comprising at least one exchanger tube (4) for passing a gaseous fluid, wherein the fluid contains at least as admixture exhaust gas of an internal combustion engine or can contain, wherein the exchanger tube (4) by a coolant for cooling the FIu - idstroms is flowed around, characterized in that the exchanger tube (4) is formed as an extruded profile of an alloy based on aluminum.

2. Heat exchanger according to claim 1, characterized in that the exchanger tube (4) comprises a plurality of separate channels (4a).

3. Heat exchanger according to claim 2, characterized in that the channels (4a) by webs (43,44,49) are separated from each other, which are part of the extruded profile.

4. Heat exchanger according to claim 3, characterized in that the webs (49) in the extruded tubes are at least partially interrupted.

5. Heat exchanger according to one of the preceding claims, characterized in that the outer wall thickness (d) of the exchanger tube (4) is preferably between 0.4 and 2 mm.

6. Heat exchanger according to claim 5, characterized in that the exchanger tube (4) webs (43,44,49) having a web thickness (s) which is smaller than or equal to the outer wall thickness (d) of the exchanger tube ( 4).

7. Heat exchanger according to one of the preceding claims, characterized in that separate channels (4a) are produced by ribs which are inserted and soldered into the exchanger tubes (4).

8. Heat exchanger according to one of the preceding claims, characterized in that the coolant is air.

9. Heat exchanger according to one of the preceding claims, comprising a bottom (3,6), wherein the exchanger tube (4) ends in the bottom (3,6) opens and is firmly connected to the bottom (3,6).

10. Heat exchanger according to claim 9, characterized in that the exchanger tube (4) is fixed by means of one of the group of induction brazing, flame brazing, laser welding or welding to the bottom (3,6).

11. Heat exchanger according to claim 9, characterized in that the exchanger tube (4) is fixed by gluing to the floor.

12. Heat exchanger according to one of the preceding claims, characterized in that on the exchanger tube (4) at least one rib element (7,7 ', 7 ") is arranged in thermal contact.

13. Heat exchanger according to claim 12, characterized in that the rib element (7,7 ', 7 ") is glued to the exchanger tube.

14. Heat exchanger according to claim 13, characterized in that the bonding is carried out by an adhesive based on epoxy resin, wherein in particular the adhesive is mixed with metal powder.

15. Heat exchanger according to claim 13 or 14, characterized in that an adhesive of the bond has a temperature resistance of at least about 180 ⁰ C, in particular of at least about 200 ⁰ C.

16. Heat exchanger according to one of claims 12 to 15, characterized in that the rib element (7,7 ', 7 ") is resiliently pressed against the exchanger tube.

17. Heat exchanger according to one of claims 12 to 16, characterized in that a thermally conductive paste between the exchanger tube (4) and rib member (7 7 ', 7 ") is arranged.

18. Heat exchanger according to claim 12, characterized in that the rib elements (7,7 ', 7 ") on the outside with the exchanger tubes

(4) are soldered.

19. Heat exchanger according to the preceding claim, characterized in that the soldering takes place in a soldering oven by means of vacuum or No-colok soldering.

20. Heat exchanger according to one of claims 12 to 19, characterized in that the rib element (7) is designed as a particular corrugated, arranged between two adjacent exchanger channels sheet metal part.

21. Heat exchanger according to one of claims 12 to 20, characterized in that the rib element is designed as (7 ', 7 ") substantially perpendicular to the exchanger tube (4) aligned and in particular of the exchanger tube (4) through-penetrated sheet metal part.

22. Device according to one of the preceding claims, characterized in that the heat exchanger has a box (2,5) for supplying or discharging the fluid to the at least one exchanger tube (4).

23. Heat exchanger according to claim 22, characterized in that the box (2,5) consists essentially of an aluminum alloy.

24. Heat exchanger according to claim 22, characterized in that the box (2,5) consists essentially of a plastic, in particular a polyamide.

25. Heat exchanger according to one of the preceding claims, characterized in that a bypass line (14) is provided, wherein the fluid flow by means of an actuator (18) selectable through the bypass line (14) or through the at least one exchanger tube (4) can be guided.

26. Heat exchanger according to one of the preceding claims, characterized in that the heat exchanger at least one hinführendes

Exchanger tube (4) and at least one substantially parallel return exchanger tube (4), which are connected to each other in a deflection region (17).

27. Heat exchanger according to one of the preceding claims, characterized in that the exchanger tube (4) in the course of assembly of the heat exchanger does not undergo complete heat treatment, which exceeds a temperature of extrusion in the course of the production of the exchanger tube.

28. Heat exchanger according to one of the preceding claims, characterized in that a maximum operating temperature of the heat exchanger supplied fluid is less than about 300 ° C, in particular less than about 250 ° C.

29. Heat exchanger according to one of the preceding claims, characterized in that pure charge air is passed through the heat exchanger.

30. Heat exchanger according to one of the preceding claims, characterized in that pure exhaust gas is passed through the heat exchanger.

31. Heat exchanger according to one of the preceding claims, characterized in that a gas mixture of charge air and exhaust gas is passed through the heat exchanger.

32. Use of an aluminum extruded profile as the exchanger tube of a heat exchanger according to one of claims 1 to 31.