CN101454559B - Heat exchanger - Google Patents

Abstract

The invention relates to a heat exchanger, in particular for a motor vehicle, comprising at least one heat exchanger tube (4) for conducting a gaseous fluid. The fluid contains at least an internal combustion engine exhaust gas mixture, wherein the heat exchange tubes (4) cool the gas stream by means of a coolant loop. The heat exchanger tube (4) is formed from an aluminium based alloy extrusion.

Description

heat exchanger

technical field

The invention relates to a heat exchanger, especially suitable for automobiles.

Background technique

At present, heat exchangers are developed for cooling the gas flow in the exhaust gas recirculation, which gas flow contains at least part of the exhaust gas of the internal combustion engine (possibly also mixed with charge air). To reduce harmful emissions, the cooled exhaust gas is returned to the combustion engine from the intake side. The fluid to be cooled is not only hot, but also highly acidic. Depending on the operating conditions, deposits of condensate with a pH value of 1 to 3 can occur, which places high demands on the high-temperature corrosion resistance of the heat exchanger. Such heat exchangers are therefore generally manufactured from stainless steel or similar materials.

Contents of the invention

The object of the present invention is to provide a heat exchanger for cooling a gas which at least partially contains exhaust gas, which has a lightweight construction and is inexpensive to produce.

This object is achieved by a heat exchanger mentioned above, which is used in a motor vehicle and comprises at least one heat exchange tube for conducting a gaseous fluid, wherein the fluid contains at least an exhaust gas mixture of an internal combustion engine, wherein the heat exchange tube passes a condensing agent The circulating cooling airflow is characterized in that the heat exchange tube is an extruded aluminum alloy, and the heat exchange tube is not subjected to complete heat treatment that exceeds the extrusion processing temperature during the process of manufacturing the heat exchange tube. By manufacturing heat exchange tubes from aluminum alloy extrusions, it is possible to produce low-cost lightweight structural heat exchangers with high compressive strength and good heat transfer performance for a given size. Experiments have unexpectedly shown that the corrosion resistance of aluminum alloy extrusions to exhaust gases under normal conditions is significantly better than previously thought.

In a preferred embodiment, the heat exchange tubes have multiple independent tubes. This allows the heat exchanger to have a large surface area while the heat exchange tube has good mechanical stability, and due to the use of extruded profiles, the manufacturing cost of this heat exchange tube is lower than that of traditional heat exchange tubes with only one channel. Didn't improve much.

A further preferred embodiment of the heat exchanger is characterized in that the channels are separated by webs, which are part of the extrusion. The spacers are preferably extruded during the manufacture of the extruded part.

A further preferred embodiment of the heat exchanger is characterized in that the webs in the extruded tube are at least partially interrupted. All or several spacers may be continuous. As an option, all or several spacers can also be interrupted. According to one embodiment of the invention, the spacers are alternately interrupted and continuous.

Another preferred embodiment of the heat exchanger is characterized in that the thickness of the outer wall of the heat exchange tube is preferably 0.4-2 mm. The wall thickness of the outward tube is referred to as the outer wall thickness of the heat exchange tube.

Another preferred embodiment of the heat exchanger is characterized in that the heat exchange tubes have spacers with a thickness which is less than or equal to the thickness of the outer wall of the heat exchange tubes. According to the invention, this area proves to be very advantageous.

A further preferred embodiment of the heat exchanger is characterized in that the individual channels are formed by ribs inserted into the heat exchange tubes and brazed. All channels of the heat exchange tubes are formed by the inserted ribs. However, it is also possible to form additional individual channels in heat exchange tubes which already have individual channels formed by eg extrusion.

The cooling medium is generally preferably air. It is particularly advantageous if the heat exchanger is used as a second cooling stage after the liquid-cooled first-stage exhaust gas heat exchanger. In principle, the heat exchanger according to the invention can also be a liquid-cooled heat exchanger, wherein the high corrosion resistance of the aluminum extrusions is advantageous. It is important that the fluid temperature does not exceed the range for which aluminum extrusions are suitable.

The invention is not only suitable for cooling pure exhaust gas, but also can be used for cooling pure charge air or the mixed gas of exhaust gas and charge air.

A generally preferred design of the heat exchanger comprises a tube sheet, wherein the ends of the heat exchange tubes are inserted into the tube sheet and are fixedly connected to the tube sheet. In principle, this is the design of the well-known tube-bundle heat exchanger. Moreover, the heat exchange tube can be fixedly connected with the tube sheet by induction brazing, heat welding, laser welding or welding. It is important here that the heat exchange tube extruded part is connected to the tube sheet only locally and if possible only externally and with as little heating as possible. It has been speculated that the excellent corrosion resistance of heat exchange tube extrusions is due to their particularly fine crystal structure, which is formed especially during the extrusion of aluminum alloys. After the heat exchange tube extruded parts are heated, the material grains may be coarsened, thereby reducing the corrosion resistance.

If a slight reduction in corrosion resistance can be tolerated, the entire cooler can be heat treated. Although the overall heat treatment of the cooler core will cause the grain structure of the aluminum material to coarsen, the extruded tube still has good corrosion resistance due to the low material impurities and flat surface. During the bulk heat treatment, the ribs and tubes are brazed together, and the tubes and tube sheets are also brazed together. Brazing can be done by vacuum brazing or Nocolok-Verfahren. In the case of such integral brazing, it is also conceivable to provide ribs not only on the outside of the tube, but also on the inside of the tube. These ribs (for example spacer ribs or vortex generators) are then brazed to the heat exchange tubes inside the heat exchange tubes. These ribs can also be provided with additional corrosion protection.

According to the purpose mentioned above, as an alternative or supplementary solution, the heat exchange tubes can also be fixedly connected to the tube sheet by an adhesive. This fixing method does not require local heating of the heat exchange tubes during assembly. An alternative or supplementary fixation that does not require heating is by mechanical means associated with sealing.

In view of the above-mentioned intentions, it is generally advantageous not to carry out a complete heat treatment of the heat exchange tubes during the assembly of the heat exchanger, which exceeds the extrusion processing temperature during the production of the heat exchange tubes. If this temperature is to be reached when the heat exchange tubes are fixed to the tube sheet by welding or brazing, this temperature must be limited locally.

In a preferred embodiment, at least one rib element is in thermal contact with the heat exchange tubes. This improves heat transfer efficiency, especially for air-cooled heat exchangers. Here, the connection of the rib elements and the heat exchange tubes is preferably carried out by means of adhesive bonding. In this way, reheating after extrusion processing of the heat exchange tube is avoided, which may reduce the corrosion resistance of the heat exchange tube. The bonding preferably uses an epoxy-based adhesive, wherein in particular metal powder is incorporated into the adhesive. The metal powder can be aluminum powder or other suitable metal powder. This adhesive is well known and has high heat resistance in addition to high strength. It is particularly advantageous if the bonding adhesive has a heat resistance of at least 180°C, preferably at least 200°C.

As an alternative or in addition, the rib elements can be elastically pressed against the heat exchange tubes. In principle, elastic compression can be done without adhesive. However, elastic compression plus adhesive is a simple heat exchanger assembly method.

Furthermore, as an alternative or in addition, a thermally conductive paste can be used between the heat exchange tubes and the rib elements. Such a paste may have a higher heat resistance than known adhesives, making it suitable for use with elastic compression. Depending on the structure of the heat exchanger, some heat exchange tubes can be bonded, others can be compressed elastically, and thermal paste can also be used if necessary.

A further preferred embodiment of the heat exchanger is characterized in that the rib elements are brazed to the heat exchange tubes on the outside. A material-fit connection with good thermal conductivity is achieved by soldering.

A further preferred embodiment of the heat exchanger is characterized in that the brazing in the brazing furnace is carried out by vacuum brazing or Norko Rock brazing. In the present invention, this method is particularly suitable for brazing the rib plate element and the heat exchange tube.

In a preferred embodiment, the rib elements are formed by corrugated parts which are arranged between two adjacent heat exchange tubes. This is a simple way of increasing heat exchange efficiency, wherein the corrugated plate is particularly easy to elastically fix or glue.

As an alternative or in addition, the rib element can be formed by a plate which is substantially perpendicular to the heat exchange tubes and which is passed through by the heat exchange tubes. In this way, the surface area of the heat exchanger can be increased in a simple manner.

In a generally preferred embodiment, the heat exchanger has at least one housing for feeding or discharging fluid to at least one heat exchange tube. Particularly preferably, the box body is basically made of aluminum alloy. However, at the outlet with a lower temperature, the box body can also be made of plastic materials, such as polyamide. In principle, all known embodiments of the heat exchanger housing can be used as long as they meet the corrosion resistance and heat resistance requirements of the exhaust gas heat exchanger.

In a preferred more detailed embodiment, a bypass is provided, wherein the fluid can be selectively directed to the bypass or to the at least one heat exchange tube via an adjusting element. Such a bypass to the cooling of the exhaust gas is often required in order to adapt to different operating conditions of the internal combustion engine.

In a modified embodiment, the heat exchanger can have at least one heat exchange tube for the feed and one heat exchange tube for the return essentially parallel thereto, which are connected to one another in the deflection zone. Thus, the heat exchanger is a U-flow heat exchanger capable of rapidly cooling the exhaust gas for a given size.

It is generally preferred that the maximum operating temperature of the fluid delivered to the heat exchanger is below 300°C, preferably below 250°C. The heat exchanger is preferably bonded using an adhesive. It is particularly advantageous if the heat exchanger according to the invention is used as a second stage of exhaust gas cooling and is preferably arranged downstream of the liquid-cooled first exhaust gas cooler. In principle, the heat exchanger according to the invention can be arranged in a high-pressure exhaust gas recirculation system as well as in a low-pressure exhaust gas recirculation system.

Depending on the embodiment, the heat exchanger according to the invention can introduce pure charge air, pure exhaust gas or a mixture of charge air and exhaust gas.

The invention also includes the application of the aluminum extrusions as heat exchange tubes in heat exchangers.

In order to avoid clogging due to dirt, these profiles can have continuous webs or can have interrupted webs. Under the condition that the hydraulic diameter is not too small, freezing of the cooler at low temperatures can be avoided. The hydraulic diameter is preferably between 1.5 and 4 mm.

In the case that the gas does not contain carbon black, the distance between the spacers can be less than 1-3 mm, and in the case of the gas containing carbon black, the distance between the spacers is preferably greater than 1-3 mm. The tube thickness, ie the shorter length of the tube, is ideally 4-10 mm, while the tube width is 8-100 mm.

An important feature of extruded tubes is that the outer wall thickness is greater than that used for normal undercoolers. In order to ensure sufficient corrosion resistance, the thickness must be increased. The thickness is preferably 0.4 to 2 mm, ideally 0.7 to 1.2 mm. Thickness is also called wall thickness. In addition, the spacer thickness is preferably less than or equal to the wall thickness. This allows the system to be optimized for corrosion, cost, pressure loss and thermodynamics.

The thickness of the extruded part in the corner regions can be increased, for example by making the radii of the two outermost chambers larger. In addition, the extruded tube can also be provided with reinforcement ribs at the corners in a "skeleton form". This reinforcement has clear advantages, since it increases strength in the event of pressure fluctuations and temperature fluctuations.

Further advantages and characteristics are given by the embodiments described below and the associated requirements.

Description of drawings

Six preferred embodiments of the heat exchanger according to the present invention will be described below, and detailed according to the drawings shown. in:

Figure 1 shows a top view of a first embodiment of the invention;

Figure 2 shows a cross-sectional view of a second embodiment of the invention;

Figure 3 shows a cross-sectional view of a third embodiment of the invention;

Figure 4 shows a cross-sectional view and a side view of a fourth embodiment of the invention;

Figure 5 shows a side view of a fifth embodiment of the invention;

Figure 6 shows a top view of a sixth embodiment of the invention;

7 to 10 show cross-sectional views of heat exchangers with separate channels according to other embodiments.

Detailed ways

The heat exchanger according to the invention shown in FIG. 1 is an air-cooled heat exchanger for cooling recirculated exhaust gas from a diesel engine. This heat exchanger is arranged as a second stage in the exhaust gas flow downstream of a known first-stage liquid-cooled heat exchanger (not shown).

The heat exchanger includes an inlet-side connection 1 , which leads into a distribution box 2 with a tube sheet 3 .

Several heat exchange tubes 4 are inserted into the tube sheet 3 and fixedly connected thereto in a sealed manner. The heat exchange tube 4, the tube plate 3 and the box body 2 are all made of aluminum alloy.

In the illustrated embodiment, only 4 heat exchange tubes are shown for sake of illustration. In practical applications, more heat exchange tubes are usually provided.

The heat exchange tubes 4 are formed by extrusion. The extrusion process is a well-known standard process for aluminum profiles in terms of temperature, pressure and speed. In the exemplary embodiment shown, an alloy according to European standard EN-AW 3103 is used as the aluminum alloy. This aluminum alloy contains relatively small amounts of silicon and copper (0.05 weight percent each). Presumably, this improves corrosion resistance.

After extrusion, the heat exchange tubes and/or the extruded part 4 generally do not receive any special corrosion protection.

In principle, however, corrosion protection of the extruded profile is also conceivable.

The parallel heat exchange tubes 4 are connected to the header box 5 on the outlet side along the exhaust gas direction, which includes a tube plate 6 and is basically the same as the box body 2 on the inlet side.

Rib elements 7 are respectively arranged between the extruded profile parts 4 . The ends of the row of heat exchange tubes 4 are respectively connected with side parts 8 having covering and protecting functions. On the other hand, the ribs 7 at the ends are connected to an outer heat exchange tube 4 .

The rib elements 7 are bonded to the heat exchange tubes 4 at the contact points. The adhesive material here is an epoxy resin-based adhesive mixed with a large amount of aluminum powder. It has heat resistance around 200°C.

On the inlet side, the temperature of the pre-cooled exhaust gas is below 250°C. The circulation of the cooling air around the heat exchange tubes 4 and the rib elements 7 ensures that the bond 9 of the rib elements 7 to the heat exchange tubes 4 is not damaged by high temperatures.

At the transition point where the heat exchange tube 4 enters the tube sheet element 3 , the heat exchange tube 4 is fixed by partial brazing, such as heat welding, induction welding and the like. What is important is that the heat exchange tube 4 is no longer subjected to complete heating after the extrusion process, so that the temperature during the extrusion process will not be reached or exceeded. This will ensure that the microcrystalline structure of the heat exchange tube 4 formed by the extrusion process is maintained. According to current knowledge, this is important for a good corrosion resistance of the heat exchange tubes 4 . When the heat exchange tubes 4 are preferably locally brazed on the tube sheets 3 , 6 , at least the crystal structure and the corrosion resistance of the surfaces of the heat exchange tubes facing the exhaust gas should not be altered by the high temperature.

The second embodiment described according to FIG. 2 shows a cross-sectional view of the heat exchange tube 4 , which is the same as the cross-section of the first embodiment. It can be seen from the figure that each extruded heat exchange tube 4 has four independent channels 4a, wherein the inner partition wall 10 separates the independent channels 4a from each other. In addition to improving the thermal conductivity of the heat exchange tubes 4, the partition walls 10 also increase the mechanical stability and compressive strength, even when softer aluminum alloys are used and the wall thickness is relatively thin.

The difference from the embodiment of Fig. 1 lies in the configuration of the rib elements 7'. The rib element 7' is here a plate, which is perpendicular to the heat exchange tubes 4 and has scales 11 which increase the surface area. The rib elements 7' can be fixed between the heat exchange tubes 4 purely mechanically, for example by elastic force. As an alternative or in addition, the rib elements 7 can be glued to the heat exchange tubes 4 . It is also possible to use thermal paste between the rib plate element 7' and the heat exchange tube 4.

The third embodiment shown in FIG. 3 has been changed with respect to the embodiment shown in FIG. 'Fixed between the heat exchange tubes 4 in a form-locking manner. In particular according to the embodiment shown in FIG. 3, the rib element 7' can be fastened in a particularly reliable manner by means of elastic compression. Elements not shown in the figure ensure that a certain distance is maintained between the rib elements stacked on top of each other in the direction of the heat exchange tubes.

In a fourth embodiment shown in FIG. 4, the rib elements 7" are each composed of plates extending over the entire width of the heat exchanger, which have scales 11 which increase the surface area. As shown in this side view , The rib elements 7" are spaced from each other in an appropriate manner to form a stack of rib elements 7". Each rib element 7" includes the same number of punching holes as the number of heat exchange tubes 4, which are aligned with each other. During installation, the heat exchange tubes 4 pass through the stack of rib elements 7" or the punched holes aligned with each other. In the above embodiment, the cross section of the heat exchange tubes 4 and the associated punched holes is substantially elliptical Shape. Each heat exchange tube has 8 independent channels 4a.

In this embodiment, the mechanical fixation and thermal contact between the rib elements 7" and the heat exchange tubes 4 can be achieved in a simple manner by expanding the diameter of the heat exchange tubes 4 after the pre-assembly of the heat exchanger. The diameter can be realized by a suitable expansion head, by filling with water and then freezing it, by pressurizing or other similar means. As an alternative or in addition, the Use thermal paste and/or adhesive on the contacts.

The embodiment according to FIG. 5 is similar to the first embodiment shown in FIG. 1 , wherein a beam 13 is provided so that the heat exchange tubes 4 and the rib elements 7 between the side parts 8 at the ends are subjected to mechanical stress. Clamp. With this clamping method, it is possible to dispense with bonding the rib element 7 to the heat exchange tube 4 . However, the clamping according to FIG. 5 can increase the mechanical stability of the heat exchanger as a whole in the case of adhesive bonding of the rib elements 7 and the heat exchange tubes 4 .

In the embodiment shown in FIG. 6, the heat exchange tubes 4 and the rib elements 7 of the heat exchanger are the same as in the first embodiment. The difference from the first embodiment lies in the casing of the heat exchanger. The first tank 14 not only has an inlet-side connection 15 but also an outlet-side connection 16 . The box body 17 opposite to the heat exchange tubes 4 is closed, and its function is only to connect the heat exchange tubes 4 to each other. Depending on its position, the adjusting element 18 in the first housing 14 directly connects the inlet connection 15 to the outlet connection 16 (broken line) or separates the connections 15 , 16 from each other. In the first case, the tank 14 forms a bypass channel bypassing the heat exchange tubes 4 . In the second case (regulating element 18 in solid line), the heat exchanger works according to the principle of a U-flow heat exchanger. The exhaust gas enters the first connecting pipe, flows through the lower two heat exchange tubes 4 shown in Figure 6, and then deflects in the second box 17, flows through the upper two heat exchange tubes 4 in the opposite direction, and then flows from the The outlet connection 16 flows out.

7 to 10 show sections of heat exchanger tubes according to other embodiments. The shown heat exchange tube 4 is formed from an extruded part with a closed rectangular cross-section 40 . Inside the rectangular section 40, a generally substantially rectangular cavity 41 is divided into several channels 4a or chambers. Several channels 4a are separated from each other by partitions 43,44.

In the embodiment shown in Figure 7, the cavity 41 in the rectangular section 40 is divided into 8 channels or chambers 4a by a total of 7 consecutive partitions 43,44. The spacers 43, 44 are parallel to the short sides of the rectangular section 40 and perpendicular to the long sides. The extension of the rectangular section in the direction along the short sides is denoted rd in FIG. 7 . The extension rd is also called thickness. The extension of the rectangular section 40 in the direction along the long sides is denoted rb in FIG. 7 . The extension rb may also be referred to as the tube width. The outer wall thickness of the rectangular section 40 is marked as d in FIG. 7 and may also be referred to as wall thickness. The thickness of the spacers 43 , 44 is marked as s in FIG. 7 , and may also be referred to as spacer thickness s.

In order to avoid undesired freezing of the cooler at low temperatures, the hydraulic diameter, ie the inner diameter, of the channel 4a should not be too small. The hydraulic diameter of the channel 4a is preferably between 1.5mm and 4mm.

As shown in FIG. 8 , the rectangular section 40 may also have interrupted webs 48 . The spacer 48 includes two spacer pieces 49 , 50 which extend perpendicularly inwardly from the long sides of the rectangular section 40 , but do not touch. The interrupted webs 48 serve to avoid undesired clogging by carbon black. The embodiment shown in FIG. 8 uses interrupted spacers 48 and continuous spacers 43 , 44 alternately.

In the embodiment shown in FIG. 9, the extrusion is particularly thickened at the corners. This is achieved by making the channels 54 , 55 arranged at the corners elliptical. This results in the outer channels 54 , 55 or chambers having a larger radius than the channels in the embodiment shown in FIGS. 7 and 8 .

In the embodiment shown in FIG. 10 , the outer channels or chambers 64 , 65 have two reinforcing ribs 66 , 67 , 68 , 69 respectively, which extend into the corners of the associated chambers 64 , 65 in the form of skeletons. . The ribs 66 to 68 increase the strength, especially in the event of pressure fluctuations and temperature fluctuations.

Claims (33)

1. A heat exchanger for a motor vehicle, comprising at least one heat exchange tube (4) for conducting a gaseous fluid, wherein the fluid contains at least an exhaust gas mixture of an internal combustion engine, wherein the heat exchange tube (4) cools the gas flow by circulating a condensate, which It is characterized in that the heat exchange tube (4) is an extruded aluminum alloy, and the heat exchange tube (4) is not subjected to complete heat treatment exceeding the extrusion processing temperature during the process of manufacturing the heat exchange tube. 2. The heat exchanger according to claim 1, characterized in that the heat exchange tube (4) has a plurality of independent channels (4a). 3. Heat exchanger according to claim 2, characterized in that the individual channels (4a) are separated from each other by partitions (43, 44, 49) which are part of the extrusion. 4. Heat exchanger according to claim 3, characterized in that the partitions (49) in the extruded tube are at least partially discontinuous. 5. The heat exchanger according to claim 3 or 4, characterized in that the thickness of the outer wall of the heat exchange tube (4) is 0.4-2 mm. 6. The heat exchanger according to claim 5, characterized in that the thickness of the spacer (43, 44, 49) of the heat exchange tube (4) is less than or equal to the thickness of the outer wall of the heat exchange tube (4). 7. The heat exchanger according to claim 2, characterized in that the independent channels (4a) are constructed by inserting and welding ribs in the heat exchange tubes (4). 8. The heat exchanger of claim 1, wherein the condensing agent is air. 9. The heat exchanger according to claim 1, characterized in that the heat exchanger has a tube sheet (3, 6), wherein the terminal of the heat exchange tube (4) passes through the tube sheet (3, 6) and connects with the tube sheet (3,6) fixed connection. 10. The heat exchanger according to claim 9, characterized in that the heat exchange tubes (4) are fixedly connected to the tube sheets (3, 6) by heat welding. 11. The heat exchanger according to claim 10, characterized in that the heat exchange tubes (4) are fixedly connected to the tube sheets (3, 6) by induction brazing, laser welding or fusion welding. 12. The heat exchanger according to claim 9, characterized in that the heat exchange tubes (4) are fixedly connected to the tube sheet by bonding. 13. The heat exchanger according to claim 1, characterized in that at least one rib element (7, 7', 7") is in thermal contact with the heat exchange tubes (4). 14. The heat exchanger according to claim 13, characterized in that the rib elements (7, 7', 7") are bonded to the heat exchange tubes (4). 15. Heat exchanger according to claim 14, characterized in that the bonding is effected by an epoxy-based adhesive incorporating metal powder. 16. A heat exchanger according to claim 14 or 15, characterized in that the bonding adhesive has a heat resistance of at least 180°C. 17. The heat exchanger according to claim 16, wherein the bonding adhesive has a heat resistance of at least 200°C. 18. The heat exchanger according to claim 13, characterized in that the rib elements (7, 7', 7") are elastically connected to the heat exchange tubes. 19. The heat exchanger according to claim 13, characterized in that a thermally conductive paste is arranged between the heat exchange tubes (4) and the rib elements (7, 7', 7"). 20. The heat exchanger according to claim 13, characterized in that the outside of the rib elements (7, 7', 7") is welded to the heat exchange tubes (4). 21. The heat exchanger according to claim 13, characterized in that the rib elements (7) are formed by corrugated plates between adjacent exchange channels. 22. The heat exchanger according to claim 13, characterized in that the rib elements (7', 7") consist of plates perpendicular to the heat exchange tubes (4) and passed through by the heat exchange tubes (4) constitute. 23. The heat exchanger according to claim 1, characterized in that the heat exchanger has a tank (2, 5) for the flow of fluid into or out of at least one heat exchange tube (4). 24. The heat exchanger according to claim 23, characterized in that the box body (2, 5) is made of aluminum alloy. 25. The heat exchanger according to claim 23, characterized in that the tank (2, 5) is made of plastic material. 26. The heat exchanger according to claim 23, characterized in that the tank (2, 5) is made of polyamide. 27. The heat exchanger according to claim 1, characterized in that the heat exchanger has a bypass (14), wherein the fluid can selectively flow through the bypass (14) or at least one of the exchangers via the regulating element (18). heat pipes (4). 28. The heat exchanger according to claim 1, characterized in that the heat exchanger has at least one heat exchange tube (4) for input and at least one heat exchange tube (4) for return flow substantially parallel thereto. ), they are connected to each other in the baffle area (17). 29. The heat exchanger of claim 1, wherein the maximum operating temperature of the fluid in the heat exchanger is less than 300°C. 30. The heat exchanger of claim 1, wherein the maximum operating temperature of the fluid in the heat exchanger is less than 250°C. 31. The heat exchanger of claim 1, wherein pure charge air is passed through the heat exchanger. 32. The heat exchanger of claim 1, wherein pure exhaust gas is passed through the heat exchanger. 33. The heat exchanger of claim 1, wherein a mixture of charge air and exhaust gas passes through the heat exchanger.

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