DE202009018892U1 - Heat exchanger for the exhaust system of a motor vehicle with improved temperature compensation in the coolant - Google Patents

Abstract

Heat exchanger (1) for the exhaust gas line of a motor vehicle with a bundle of separately designed, fluidically connected, exhaust gas-carrying exchanger tubes (20), which are arranged in a separately formed closed housing (40), through which a coolant flows, which flows through a coolant inlet into the Housing enters, there flows around the outside of the exchanger tubes (20) and exits the housing (40) via a coolant outlet, a. the exchanger tubes (20) each have an inlet-side and an outlet-side leg, the flow direction in the inlet-side leg being essentially opposite to the flow direction in the outlet-side leg, b. the legs on the inlet side are arranged spatially adjacent to one another and the legs on the outlet side are arranged spatially adjacent to one another as an outlet group, and c. Between the inlet group and the outlet group, a baffle (36) for the flow guidance of the coolant in the housing (40) is arranged, which extends essentially in the direction of extension of the leg on the inlet and / or outlet side between the inlet group and the outlet group and from a first partial flow of the Coolant flows on its way from an inlet area adjacent to the coolant inlet to an outlet area adjacent to the coolant outlet along a first, substantially U-shaped flow path, characterized in that d. At least one overflow opening (70) is provided in the baffle (36), which provides a second flow path for a second partial flow of the coolant, which extends between the inlet area and the outlet area, the thermal interaction length on which heat is exchanged between the exhaust gas and the coolant can, is smaller along the second flow path than along the first flow path.

Description

The present invention is a heat exchanger for the exhaust system of a motor vehicle, in particular for an exhaust gas recirculation system for an internal combustion engine of a motor vehicle, having the features of the preamble of the main claim.

Due to the ever stricter legal regulations with respect to the exhaust emission of motor vehicles, in particular with respect to the immission of nitrogen oxides, is in the field of internal combustion engine recirculation of combustion exhaust gases to the inlet side of the internal combustion engine state of the art. The combustion gases themselves do not take part once again in the combustion process in the combustion chamber of the internal combustion engine and thus constitute an inert gas, which dilutes the mixture of combustion air and fuel in the combustion chamber and provides for a more intimate mixing. In this way it is possible to minimize the occurrence of so-called hot spots during the combustion process, which are characterized by locally extremely high combustion temperatures. Such very high combustion temperatures favor the formation of nitrogen oxides and must therefore be avoided at all costs.

Since the efficiency of an internal combustion engine is typically dependent on the temperature of the combustion air supplied to the combustion chamber of the internal combustion engine, the combustion gases can not be immediately returned to the suction side after they exit the combustion chamber of the internal combustion engine. Rather, a significant reduction of the combustion gas temperature is required. Typical exit temperatures of the combustion gases from the combustion chamber of the internal combustion engine are in the range of 900 ° C and above, the temperature of the input side to the combustion chamber of the internal combustion engine combustion air supplied should not be above 150 °, preferably significantly lower. For cooling the recirculated combustion gases is known from the prior art to use so-called exhaust gas recirculation cooler. A variety of constructions are known from the prior art, in which usually the combustion gases to be cooled are passed through exchanger tubes which are surrounded on the outside by a coolant, wherein the coolant is usually the cooling water of the motor vehicle. In order to increase the efficiency, it is proposed in the prior art to pass the combustion gases to be cooled through a bundle of fluidically connected exchange tubes, which are surrounded by the coolant as a whole.

From the DE 10 2004 019 554 A1 For example, an exhaust gas recirculation system for an internal combustion engine is known, which comprises an exhaust gas heat exchanger, which is designed as a two-part casting. Since the very hot combustion gases are reactive due to the never 100% combustion of the fuel, the problem here is that it is technically difficult or even impossible to design surfaces of a metallic casting as inert surfaces comparable to a stainless steel surface.

From the DE 10 2005 055 482 A1 For example, an exhaust gas heat exchanger for an internal combustion engine is known, which avoids the aforementioned problems by making those surfaces which come into contact with the hot combustion gases as corrosion-resistant steel surfaces. The heat exchanger tubes and the housing, in which the heat exchanger tubes are arranged, formed as separate parts, which are assembled in the context of the manufacturing process.

In the from the DE 10 2006 009 948 A1 known exhaust gas heat exchanger, the channels carrying the hot gas and the housing in which the coolant flowing around the exhaust gas channels, integrally formed in the form of a plate heat exchanger. Both the flow paths for the hot combustion gases and the flow paths for the coolant form only when merging individual, for example, deep-drawn plates to form a plate heat exchanger. A similar concept is also used in the DE 10 2006 049 106 A1 tracked.

General information on the technique of exhaust gas recirculation in internal combustion engines in motor vehicles, for example, the DE 100 119 54 A1 be removed.

From the WO 2007/104580 A2 Various constructions of exhaust gas heat exchangers are known which are based on a plurality of U-shaped exchanger tubes. A disadvantage of the structures disclosed here, their tendency to a highly inhomogeneous temperature distribution in the coolant has been found that under unfavorable circumstances to a local overheating of the coolant above the boiling point, so-called "microboiling" can lead.

An exhaust gas recirculation cooler device consisting of a plurality of cooling plates and a plurality of U-shaped gas passages through the cooling plates is made DE 10 2007 043 231 A1 known. For distributing a coolant flow, if appropriate, the middle coolant plate is used as a lateral dividing wall inside the container.

The DE 10 2005 054 731 A1 discloses a U-shaped exhaust gas heat exchanger with Flat tubes designed for countercurrent operation. A U-shaped flow flow of the coolant is realized by a separating plate between the flat tubes and in addition to be realized by a turbulence of the incoming cooling water flow optimized heat exchange.

Finally, out of the JP 11-241891 A an exhaust gas heat exchanger known in which a plurality of straight, exhaust gas flow and fluidly connected in parallel heat exchanger tubes is arranged in a coolant flowed through housing. By a special arrangement of coolant inlet and outlet and one or more arranged in the housing between the heat exchanger tubes baffles, which also provide a mechanical support for the heat exchanger tubes in the manufacture of the heat exchanger, a U-shaped or Z-shaped coolant flow is generated in the housing.

Object of the present invention is to provide a heat exchanger for the exhaust system of a motor vehicle, which has an improved temperature compensation in the coolant.

This object is achieved by a heat exchanger with the features of the main claim.

An inventive heat exchanger is provided for the exhaust gas line of a motor vehicle. It has a bundle of separately formed flow-related parallel exhaust-carrying exchanger tubes. These are arranged in a separately formed closed housing, which is flowed through by a coolant. The coolant flows around the exchanger tubes on the outside. In this case, it enters the housing via a coolant inlet, flows around the exchanger tubes on the outside there and exits the housing via a coolant outlet. The exchanger tubes each have an inlet-side and an outlet-side leg, the flow direction in the inlet-side leg being essentially opposite to the flow direction in the outlet-side leg.

The inlet-side limbs are arranged spatially adjacent to one another as an "inlet group", as are the outlet-side limbs, which are arranged spatially adjacent to one another as an "outlet group".

According to the invention, a guide plate for the flow guidance of the coolant is now arranged in the housing between the inlet group and the outlet group, which extends essentially in the extension direction of the inlet group and / or the outlet group. The guide plate may for example consist of a corrosion-resistant material such as stainless steel, aluminum, an aluminum alloy, but also of a plastic. Preferably, it is flat.

Due to the arrangement of the baffle in the interior of the housing of the heat exchanger between the groups of legs of the exchanger tubes, the coolant flows around the baffle along a first flow path on its way from an inlet region adjoining the coolant inlet to an outlet region adjoining the coolant outlet.

In addition, at least one overflow opening is provided in the guide plate, which provides a second flow path for the coolant, which extends between the inlet region and the outlet region. In this way, a direct overflow of cold coolant in the area in which the coolant has been heated up due to a strong heat transfer from the exhaust gas flow, allows.

Preference is given to the thermal interaction length, d. H. the length at which heat can be exchanged between the exhaust gas and the coolant may be realized in the concrete design of the heat exchanger so that it is smaller along the second flow path than along the first flow path. The flowing through the overflow second, i. A. smaller partial flow of cold coolant is thus significantly less heated than the first along the first flow path flowing around the baffle first, i. A. larger partial flow. Both partial flows preferably mix in a housing region which adjoins the coolant outlet, which results in a local temperature reduction in the coolant.

By suitable dimensioning and spatial arrangement of the second partial flow relative to the first partial flow, the temperature distribution in the coolant can be influenced in a targeted manner. This can be done in particular by adjusting the number and dimensioning of the overflow openings and their exact arrangement on the guide plate, in particular for the arrangement of coolant inlet and outlet on the housing of the heat exchanger.

Thus, a preferred embodiment of the heat exchanger according to the invention comprises a plurality of overflow openings. In particular, their density can vary spatially on the baffle. Thus, the density of the overflow openings on the baffle in the areas of the baffle may be the highest, which adjoin those areas of the housing interior, in which the highest temperatures occur in the coolant during normal operation of the heat exchanger. Alternatively or additionally, the density of the overflow openings on the baffle in the areas of the baffle can be selected to be the lowest, which adjoin those areas of the housing interior, in which occur during normal operation of the heat exchanger, the lowest temperatures in the coolant.

In the practical testing of the heat exchangers according to the invention, it has proved to be advantageous if the density of the overflow openings on the baffle in the areas of the baffle selected to be highest, which adjoin those areas of the housing interior adjacent to the coolant outlet. In addition, it has proven to be advantageous if the density of the overflow openings on the baffle in the areas of the baffle is lowest, which adjoin those areas of the housing interior, which adjoin the coolant inlet.

Instead of varying the density of the overflow openings, their size and / or shape can also be locally varied in accordance with the desired local strength of the second substream. A simultaneous variation of all three parameters density, size and shape of the overflow is possible and possibly useful.

For reasons of efficient use of space, it has proved to be advantageous if the exchanger tubes are substantially U-shaped or semicircular. The inventive concept is not limited to such embodiments, but it can always be used when the flow path of the coolant flow is extended in the housing by arranging a somehow shaped baffle in the interior of the heat exchanger housing. By targeted introduction of overflow openings in the baffle can then generate a second partial flow with reduced thermal exchange length. If this second partial stream is mixed with the hotter first partial stream, a local temperature reduction in the coolant can be realized there in a targeted manner.

In a preferred embodiment of a heat exchanger according to the invention, the density of the overflow openings is lowest on the baffle, for example in the region of the baffle adjacent to the deflection of the exchanger tubes, wherein the exchanger tubes include a deflection angle between 45 ° and 135 °, preferably U-shaped or semicircular.

Advantages with regard to the NVH behavior (NVH = noise, vibration, harshness) of a heat exchanger according to the invention, in particular of such a heat exchanger, in which the exchanger tubes have a deflection region, at which the exchanger tubes include a deflection angle between 45 ° and 135 °, particularly preferred U-shaped or semicircular, resulting when a plurality of exchanger tubes is mechanically connected to the baffle. As a result, natural oscillations of the exchanger tubes in the heat exchanger housing can be significantly reduced.

In a particularly preferred construction, the housing of the heat exchanger comprises a jacket part, which is closed by a separately formed housing cover. In this case, the inlet-side legs and / or the outlet-side legs of the exchanger tubes are guided through the housing cover and mechanically connected thereto, in particular sealed, passed through it. In addition, the guide plate may be mechanically fixedly connected to the housing cover. The baffle may be formed both separately from the housing cover, z. B. in the form of a stamped sheet metal part, which is suitably connected to the housing cover, z. B. by soldering or welding. But it can also be integrally formed with the housing cover.

Preferably, the exchanger tubes are integrally formed between their inlets and outlets, but this is not mandatory. In particular, it may be advantageous to provide a separately formed deflection region between the inlet-side and the outlet-side limb of a U-shaped exchanger tube, in which the flow paths of the different exchanger tubes may in particular contact or unite. The exchanger tubes are in all embodiments preferably made of a corrosion-resistant and heat-resistant material such as stainless steel, aluminum or an aluminum alloy. In this case, they can be designed, in particular, as one-piece tubes formed separately, as a plurality of plates, or as one or more extruded profiles.

Further advantages and features of the heat exchanger according to the invention will become apparent from the dependent claims and the embodiments discussed below, which are explained in more detail with reference to the drawings. In this show:

1 FIG. 4 is an exploded view of a first embodiment of an exhaust gas heat exchanger according to the invention, FIG.

2 FIG. 2 is a plan view of the mounting interface F of an exhaust gas heat exchanger according to a second exemplary embodiment, FIG.

3 FIG. 4 is a plan view of a bundle of exchanger tubes of an exhaust gas heat exchanger according to a third embodiment, FIG.

4 FIG. 2: a perspective view of the basic flow paths of coolant and exhaust gas in the exhaust gas heat exchanger according to a fourth exemplary embodiment similar to the first exemplary embodiment, FIG.

5 FIG. 2: a plan view of the housing cover of the exhaust gas heat exchanger according to the fourth exemplary embodiment, in which the risk areas for a local overheating of the coolant are schematically indicated, FIG.

6 : a section through the heat exchanger after 4 along the plane AA, and

7 : A perspective view of the first and second flow paths in the open housing of the heat exchanger according to the fourth embodiment.

1 shows an exploded view of an exhaust gas heat exchanger according to the invention 1 according to a first embodiment. The heat exchanger 1 includes a housing 40 , which consists of a jacket part 50 which consists of a housing cover 60 is closed. The jacket part 50 is designed as a casting and may in particular be made of die-cast aluminum. Alternatively, a production of the shell part 50 in the illustrated embodiment of any material possible, which can be processed on the one hand in the casting process and on the other hand has sufficient thermal stability. But since the jacket part 50 the heat exchanger according to the invention 1 only comes with the coolant in contact, which usually comes from the coolant circuit of the motor vehicle, a temperature resistance up to temperatures up to 150 ° C for most applications is sufficient. As further materials for the shell part magnesium or magnesium alloys, gray cast iron or heat-resistant and injection-moldable plastics have been found.

The front part of the shell part forms a flange 59 for a connection with a housing cover 60 out. The housing cover 60 consists in the illustrated embodiment of a stamped stainless steel plate with a thickness of a few millimeters, preferably about 2 mm. The jacket part 50 is with the housing part 60 liquid and gas tight connected with the interposition of a seal 52 which is formed in the embodiment shown as a metal-thickness seal. The housing cover 60 is doing with the flange 59 of the jacket part 50 by means of screws 54 screwed, this forms the shell part 50 a plurality of large threaded holes 55 out. The housing cover 60 has through holes at the corresponding positions 65 with large diameter, through the appropriately sized screws 54 passed and into the threaded holes 55 be inserted so that the housing cover 60 with the jacket part 50 can be screwed.

The jacket part 50 forms an interior 42 made, which is intended to a bundle of U-shaped bent exchanger tubes 20 to absorb. Here are the exchanger tubes 20 identical to their tube dimensions such as inner and outer diameter, but varies the opening width W of the U-shaped profile. The shape of the interior 42 and thus also of the jacket part 50 but is a total of the shape of the bundle of exchanger tubes 20 adapted, so that the most effective use of space in the interior 42 through the bundle of exchanger tubes 20 results.

The exchanger tubes 20 each form an inlet at their respective ends 22 and an outlet 24 out. The ends of the exchanger tubes 20 are in corresponding holes in the housing cover 60 passed through, the implementation points 66 . 68 for the inlets or the outlets of the exchanger tubes 20 form. The inlets and outlets 22 . 24 the exchanger tubes 20 are thereby by the in the housing cover 60 trained holes passed, the exchanger tubes 20 are at the execution points 66 . 68 gas and liquid-tight with the housing cover 60 connected, for example by means of soldering or welding. This results in a mechanical support of the exchanger tubes 20 on the housing cover 60 ,

In a preferred embodiment, the exchanger tubes exist 20 from thin-walled stainless steel tubes, here are the exchanger tubes 20 provided with an embossed structure, so that from the inner surface of the exchanger tubes 20 a spiral structure 26 rises. The bundle of exchanger tubes 20 is arranged so that all inlets 22 and all outlets 24 are each arranged in a coherent group, so that a connection of the heat exchanger according to the invention 1 to the exhaust system of the motor vehicle is possible in a simple manner. For this purpose, the front side of the housing cover forms 60 a mounting interface S from, due to the flat design of the housing cover 60 is designed substantially flange. For mounting the heat exchanger 1 on the motor vehicle are in the shell part 50 further threaded holes 53 formed, the one opposite the threaded holes 55 having reduced inner diameter. In the metal bead seal 52 as well as in the housing cover 60 are corresponding through holes 63 educated. This can be the heat exchanger 1 over a plurality of in 1 not shown screws are connected to the exhaust and coolant system of the motor vehicle.

The jacket part 50 forms next to the interior 42 in which the bundle of exchanger tubes 20 is not arranged, an inlet channel 56 and exhaust duct 58 for a coolant, which may be, for example, cooling fluid of the motor vehicle. The inlet channel 56 and exhaust duct 58 are arranged so that in the normal operation of the heat exchanger 1 one from top to bottom (in 1 ) extending flow path through the interior 42 of the jacket part 50 results, so that the bundle of exchanger tubes is thoroughly washed by the coolant. To the highest possible interaction of the coolant with the surface of the exhaust-carrying exchanger tubes 20 is to realize within the legs of the U-shaped exchanger tubes 20 continue a baffle 36 arranged, which in the embodiment shown again preferably made of stainless steel and butt with the housing cover also made of stainless steel 60 welded or soldered. The baffle 36 extends the flow path of the coolant in the interior 42 of the housing 40 and thus provides for a more intense thermal exchange between that in the exchanger tubes 20 flowing exhaust gas and the interior 42 flowing exhaust gas.

According to the invention is in baffle 36 a plurality of overflow openings provided in 1 are not shown for reasons of clarity.

For details, reference is made to the following description of the fourth embodiment, in the first embodiment in the baffle 36 provided overflow openings are formed and arranged in an equivalent manner.

The in the shell part 50 trained inlet channel 56 as well as the outlet channel 58 also end in the jacket part 50 trained flange 59 , being at the ends of the channels 56 and 58 Stege 57 are formed, which provide a mechanical support for the on the flange 59 Overlying metal bead seal 52 form. This also forms passages for the heat exchanger 1 flowing through coolant, which with the housing cover 60 trained coolant inlet 62 and coolant outlet 64 correspond. In the assembled heat exchanger 1 can therefore over the front of the housing cover 60 both coolant through the coolant inlet 62 supplied as well as via the coolant outlet 64 be discharged as well as the combustion exhaust gas to be cooled through the inlets 22 the exchanger tubes 20 fed and over the outlets 24 be dissipated. In the illustrated construction, this is possible via a single common mounting interface S.

This is in particular also the representation according to 2 clearly what a top view on a mounting interface of the heat exchanger 1 in a slightly modified embodiment shows. Clearly visible in the housing cover 60 trained coolant inlet 62 and the coolant outlet 64 , The majority of inlets 22 as well as outlets 24 the exchanger tubes 20 is, however, according to the illustration 2 through lattice structures 23 covered, the arrangement of the inlets 22 as well as outlets 24 in the housing cover 60 but essentially corresponds to the in 1 illustrated configuration. Otherwise, the heat exchanger differs according to the illustration of 2 essentially by the changed arrangement of attachment points 51 on the jacket part 50 , these attachment points 51 a fastening of the heat exchanger 1 serve on mounting structures of the motor vehicle.

Out 1 is still visible, as by means of technical measures unwanted vibrations of the bundle of exchanger tubes 20 in the interior 42 of the housing 40 be prevented. So on the one hand is the baffle 36 which is mechanically rigid with the housing cover 60 is connected and which within the bundle of exchanger tubes 20 is arranged, at its bent tip mechanically fixed to the adjacent arranged exchanger tubes 20 connected, for example by means of soldering or welding. The baffle 36 thus provides a mechanical stiffening for the internal exchanger tubes 20 the exchanger tube bundle and thus dampens their vibrations.

As a further vibration-reducing measure is a bandage 30 provided, which consists of a stamped stainless steel sheet of low wall thickness. This bandage surrounds the bundle of exchanger tubes 20 complete and is at the points of contact with the adjacent exchanger tubes 20 mechanically firmly connected, for example by means of soldering or welding. By the Tauscherrohrbündel encompassing arrangement prevents the bandage 30 Relative vibrations of the outer exchanger tubes 20 to each other. In addition, the bandage forms 30 integrally formed supports 32 from, which consist of angled projections. These supports 32 provide a resilient support of the entire exchanger tube bundle with respect to the inner wall of the housing 40 represents.

Finally, inside the bundle of exchanger tubes 20 stiffeners 34 arranged, which also consist of stamped stainless steel strips. These stiffening elements 34 provide a mechanically rigid support of the exchanger tubes 20 of the exchanger tube bundle, they are mechanically fixed to the exchanger tubes for this purpose 20 connected, for example by welding or soldering.

It should be noted that on the mechanically strong connection of the bandage 30 or the stiffening elements 34 with the individual exchanger tubes 20 can be dispensed with in individual cases, if necessary, the mere positive connection between Tauscherrohrbündel and bandage 30 or stiffening element 34 already for a sufficient support of the Tauscherrohrbündels and for a sufficiently tight fit of the bandage 30 or the stiffening elements 34 on the exchanger tube bundle.

3 shows a perspective view of a bundle of exchanger tubes 20 a heat exchanger 1 in a third embodiment. Opposite the heat exchanger 1 according to 1 differs the bundle shown here of exchanger tubes 20 essentially by the fact that it is the exchanger tubes 20 smooth, preferably, but not necessarily seamless drawn thin-walled stainless steel tubes, which is not a spiral structure 26 exhibit as they are in 1 is shown. In addition, the exchanger tubes 20 arranged so that they cross each other in pairs, which at the reversal points of the U-shaped exchanger tubes 20 in 3 becomes visible. A ready to use heat exchanger 1 also between the inlet side and outlet side legs of the exchanger tubes 20 provided baffle is in 3 not shown for reasons of clarity.

4 shows a perspective view of the basic flow path of the coolant in the housing of an exhaust gas heat exchanger according to a fourth embodiment, the construction of which substantially coincides with that of the first embodiment. The relevant statements are hereby incorporated by reference. Differences lie in the concrete form of the housing 40 , the precise arrangement and shaping of coolant inlet 62 and coolant outlet 64 as well as the number and arrangement of exchanger tubes 20 ,

• • die Temperatur des zu kühlenden Abgasstrom besonders hoch ist, d. h. angrenzend an die Eintrittsöffnungen der Tauscherrohre 20, oder
• • die Temperatur im kühlenden Kühlmittelstrom bereits besonders hoch ist, d. h. angrenzend an den Kühlmittelauslass 64.

5 shows a plan view of the plane of the housing cover of the exhaust gas heat exchanger according to the fourth embodiment, wherein the housing cover 50 itself is not shown for reasons of clarity. The illustration thus shows a view into the interior of the housing 40 with the U-shaped exchanger tubes arranged therein 20 , In the illustration are the risk areas 100 are schematically indicated for a local overheating of the coolant, which lie adjacent to the housing cover in the areas where either:

• • the temperature of the exhaust gas flow to be cooled is particularly high, ie adjacent to the inlet openings of the exchanger tubes 20 , or
• • The temperature in the cooling coolant flow is already particularly high, ie adjacent to the coolant outlet 64 ,

In both cases, moreover fluidic details have to be taken into account. B. different high local coolant flows along the through the baffle 36 forced first flow path due to "shading effects"

6 finally shows a section through the heat exchanger 4 along the in 4 indicated level AA, in which also the flat baffle 36 extends. Clearly visible is a plurality of overflow openings 70 in the baffle 36 are formed. The density of the overflow openings varies 70 on the baffle 36 local. In the embodiment shown, the density of the overflow openings on the guide plate 36 in the areas of the baffle highest, which adjoin those areas of the housing interior, in which the highest temperatures occur in the coolant during normal operation of the heat exchanger.

In addition, the density of the overflow openings 70 on the baffle 36 in the areas of the baffle 36 lowest, adjacent to those areas of the housing interior, in which occur during normal operation of the heat exchanger, the lowest temperatures in the coolant. As determined by simulations as well as practical trials, this means that the density of overflow openings on the baffle 36 in those areas of the baffle 36 is highest, which are adjacent to those areas of the housing interior, which at the coolant outlet 64 adjoin. In addition, the density of the overflow on the baffle 36 in the areas of the baffle 36 lowest, which are adjacent to those areas of the housing interior, which at the coolant inlet 62 adjoin.

7 shows a perspective view of the first and the second flow path according to the invention in the open housing 40 of the heat exchanger 1 according to the fourth embodiment. The large arrows indicate the first flow path, which is essentially along the exchanger tubes 20 around the baffle 36 extends around, but the coolant is guided in countercurrent to the exhaust gas flow. The second flow path on which the coolant flow varies locally in strength and overall under realistic operating conditions of the exhaust gas heat exchanger 1 is much smaller than the coolant flow along of the first flow path, in particular less than 30%, preferably less than 20% or less, of the coolant flow along the first flow path is symbolized by the small arrows extending through the overflow openings 70 in the baffle 36 extend through.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 102004019554 A1 [0004]
• DE 102005055482 A1 [0005]
• DE 102006009948 A1 [0006]
• DE 102006049106 A1 [0006]
• DE 10011954 A1 [0007]
• WO 2007/104580 A2 [0008]
• DE 102007043231 A1 [0009]
• DE 102005054731 A1 [0010]
• JP 11-241891 A [0011]

Claims (17)

Heat exchanger ( 1 ) for the exhaust gas line of a motor vehicle with a bundle of separately formed, fluidically connected in parallel exhaust-carrying exchanger tubes ( 20 ) housed in a separately formed closed housing ( 40 ), which is flowed through by a coolant which enters the housing via a coolant inlet, there the exchanger tubes ( 20 ) flows around the outside and via a coolant outlet from the housing ( 40 ), where a. the exchanger tubes ( 20 ) each having an inlet-side and an outlet-side legs, wherein the flow direction in the inlet-side leg of the flow direction in the outlet side leg is substantially opposite, b. the inlet-side legs are arranged as an inlet group spatially adjacent to each other and the outlet-side legs are arranged as an outlet group spatially adjacent to each other, and c. between the inlet group and the outlet group a baffle ( 36 ) for the flow guidance of the coolant in the housing ( 40 ) extending substantially in the direction of extent of the inlet side and / or outlet side legs between the inlet group and the outlet group and from a first partial flow of the refrigerant on its way from an inlet region adjacent to the coolant inlet to an outlet region adjacent to the coolant outlet along a flows around the first, substantially U-shaped flow path, characterized in that d. in baffle ( 36 ) at least one overflow opening ( 70 ) providing a second flow path for a second partial flow of the coolant extending between the inlet region and the outlet region, wherein the thermal interaction length at which heat can be exchanged between the exhaust gas and the coolant is smaller along the second flow path than along of the first flow path. Heat exchanger ( 1 ) according to claim 1, characterized in that a plurality of overflow openings ( 70 ) is provided. Heat exchanger ( 1 ) according to claim 2, characterized in that the density of the overflow openings ( 70 ) on the baffle ( 36 ) varies spatially. Heat exchanger ( 1 ) according to claim 3, characterized in that the density of the overflow openings ( 70 ) on the baffle ( 36 ) is highest in the areas of the baffle, which adjoin those areas of the housing interior, in which the highest temperatures occur in the coolant during normal operation of the heat exchanger. Heat exchanger ( 1 ) according to claim 3, characterized in that the density of the overflow openings ( 70 ) on the baffle ( 36 ) is lowest in the areas of the baffle, which adjoin those areas of the housing interior, in which occur during normal operation of the heat exchanger, the lowest temperatures in the coolant. Heat exchanger ( 1 ) according to claim 3, characterized in that the density of the overflow openings ( 70 ) on the baffle ( 36 ) in the areas of the baffle ( 36 ) are the highest, which adjoin those areas of the housing interior, which at the coolant outlet ( 64 ). Heat exchanger ( 1 ) according to claim 3, characterized in that the density of the overflow openings ( 70 ) on the baffle ( 36 ) in the areas of the baffle ( 36 ) are the lowest, which adjoin those areas of the housing interior, which at the coolant inlet ( 62 ). Heat exchanger ( 1 ) according to claim 1, characterized in that the exchanger tubes ( 20 ) are formed substantially U-shaped or semicircular. Heat exchanger ( 1 ) according to claim 3 and 8, characterized in that the density of the overflow openings ( 70 ) on the baffle ( 36 ) in the area of the baffle ( 36 ) is the lowest, which at the deflection of the exchanger tubes ( 20 ) adjoins. Heat exchanger according to claim 1, characterized in that a plurality of exchanger tubes ( 20 ) mechanically with the guide plate ( 36 ) connected is. Heat exchanger ( 1 ) according to claim 1, characterized in that the housing is a shell part ( 50 ), which by a separately formed housing cover ( 60 ), wherein the inlet-side legs and / or the outlet-side legs of the exchanger tubes ( 20 ) through the housing cover ( 60 ) are passed. Heat exchanger according to claim 11, characterized in that the baffle ( 36 ) mechanically fixed to the housing cover ( 60 ) connected is. Heat exchanger according to claim 11, characterized in that the baffle ( 36 ) separately from the housing cover ( 60 ) is trained. Heat exchanger according to claim 11, characterized in that the baffle ( 36 ) in one piece with the housing cover ( 60 ) is trained. Heat exchanger ( 1 ) according to claim 1, characterized in that the exchanger tubes ( 20 ) between their inlets ( 22 ) and outlets ( 24 ) are integrally formed. Heat exchanger ( 1 ) according to claim 1, characterized in that the exchanger tubes ( 20 ) consist of a corrosion-resistant and heat-resistant material such as stainless steel, aluminum or an aluminum alloy. Heat exchanger ( 1 ) according to claim 1, characterized in that the exchanger tubes ( 20 ) consist of separately formed one-piece tubes, a plurality of plates or one or more extruded profiles.

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