HEAT EXCHANGER FOR A MOTOR VEHICLE
An exhaust gas heat exchanger for a motor vehicle may include an outer tube extending along a longitudinal direction to be flowed-through by a hot gas. The outer tube may define an outer tube interior space and in a cross section perpendicular to the longitudinal direction may include at least two outer tube-tube walls. An inner tube may be arranged in the outer tube interior space and may extend along the longitudinal direction. A longitudinal end of the inner tube may be closed and may define an inner tube interior space and in the cross section perpendicular to the longitudinal direction, may include at least two inner tube-tube walls at least one of which may include a plurality of apertures. A plurality of thermoelectric modules may be arranged on an outside of the at least two outer tube-tube walls and may each include a hot side and a cold side.
This application claims priority to German Application DE 10 2017 210 276.4 filed on Jun. 6. 2017 and German Application DE 20 2016 008 278.8 filed on Nov. 29, 2016, the contents of each of which are hereby incorporated by reference in their entirety.
TECHNICAL FIELDThe invention relates to a heat exchanger, in particular an exhaust gas heat exchanger, for a motor vehicle. The invention, furthermore, relates to a motor vehicle with an internal combustion engine, comprising an exhaust system and such a heat exchanger interacting with the exhaust system.
BACKGROUNDHeat exchangers are employed in combination with exhaust systems of internal combustion engines in order to render utilisable the heat contained in the exhaust gas. For this purpose, thermoelectric modules with thermoelectric elements can be provided in the heat exchanger. Such thermoelectric elements consist of thermoelectric semiconductor materials, which convert a temperature differential into a potential differential, i.e. into an electric voltage and vice versa. In this way, heat energy from the heat exchanger can be converted into electric energy. Physically, the thermoelectric modules are based on the Seebeck effect when they convert heat into electric energy. Within a thermoelectric module, p-doped and n-doped thermoelectric elements are interconnected. Usually, a plurality of such thermoelectric modules is interconnected to form a thermoelectric generator, which can generate electric energy or an electric voltage from a temperature differential in conjunction with a corresponding heat flow. In the heat exchanger, the temperature differential between the hot sides and the cold sides of the thermoelectric modules required for generating electric energy is generated in that the hot gas with the hot sides and a coolant with a temperature that is lower compared to the hot gas is brought into thermal interaction with the cold sides of the thermoelectric modules. This is achieved in that the hot sides and cold sides of the thermoelectric modules are suitably arranged in the heat exchanger flowed-through by the hot gas and by the coolant.
The present invention therefore deals with the problem of stating an improved or at least another embodiment for a heat exchanger of the type described above, which is characterized by an improved efficiency.
This object is solved through the subject of the independent patent claims. Preferred embodiments are subject of the dependent patent claims.
SUMMARYAccordingly, the general basic idea of the invention is to arrange thermoelectric modules with thermoelectric elements in a heat exchanger in such a manner that the hot gas conducted through the heat exchanger strikes the hot sides of the thermoelectric modules in the form of an impact jet. This has the consequence that a particularly high quantity of heat is extracted from the hot gas, which, following the operating principle of a thermoelectric generator, can be converted into electric energy by the thermoelectric modules. This is accompanied by an improved efficiency of the heat exchanger which proves to be particularly advantageous when the same is operated as exhaust gas heat exchanger in order to render utilisable the energy contained in the exhaust gas of an internal combustion engine.
A heat exchanger according to the invention, which can preferentially be employed as exhaust gas heat exchanger, comprises an outer tube extending along a longitudinal direction for being flowed-through by hot gas, which delimits an outer tube interior space and for this purpose comprises two outer tube-tube walls in a cross section perpendicular to the longitudinal direction. In the outer tube interior space, preferentially coaxially to the outer tube, an inner tube for being flowed-through by the hot gas extending along the longitudinal direction is arranged, which delimits an inner tube interior space. At a longitudinal end, the inner tube is designed closed and, in the cross section perpendicularly to the longitudinal direction, comprises at least two inner tube-tube walls. Furthermore, a plurality of apertures is formed in the inner wall tube walls. By means of said apertures, the inner tube interior space fluidically communicates with the outer tube interior space. The heat exchanger according to the invention additionally comprises a plurality of thermoelectric modules arranged on an outside of the outer tube-tube walls. The thermoelectric modules each have a hot side facing the outer tube and a cold side facing away from the outer tube. In addition, the heat exchanger comprises at least one coolant tube for being flowed-through by a coolant, which is arranged on the cold side of at least one thermoelectric module.
Substantial for the invention in the case of the thermoelectric heat exchanger introduced here is a surface area-enlarging structure provided on the outer tube inside, i.e. on the hot side of the thermoelectric modules. The term surface area-enlarging structure is to mean any mechanical structures whatsoever such as for example protrusions etc. which enlarge the surface area of the inside of the outer tube or of the outer tube-tube wall of the outer tube. By means of such a surface area-enlarging structure, the effective interactive area, which is available to the impact jet striking the outer tube for transmitting heat to the thermoelectric modules, is increased. This results in an improved heat transfer of heat energy from the impact jet to the thermoelectric modules. As a consequence, correspondingly more electric energy is generated by the thermoelectric modules acting as thermoelectric generators which in turn increases the efficiency of the entire heat exchanger. Independently of this, the flow direction of the impact jet can also be influenced with the help of the surface area-enlarging structure before and after the same strikes the outer tube where it is reflected. Thus it is possible, for example, to direct the reflected impact jet so that subsequent impact jets striking the outer tube are not disturbed by the reflected impact jet or only to a minor extent. Thus it is ensured that the impact area, i.e. that area of the outer tube on which the thermoelectric modules are arranged on the outside, can be impinged with as little interference as possible. In other words, it can be ensured with the help of the surface area-enlarging structure, that the geometric and the aerodynamic stagnation point of the impact jet are identical and thus the angle of the deflection of the impact jet during the reflection assumes a zero value.
According to a preferred embodiment, the surface area-enlarging structure is arranged, with respect to the longitudinal direction, in the region of at least one thermoelectric module. In this way it is ensured that the enlarging heat exchange in the region of the thermoelectric modules is possible so that these can absorb an increased amount of heat from the impact jet or the hot gas.
According to a preferred embodiment, the at least one surface area-enlarging structure is located opposite at least one aperture. In this way it is ensured that the hot gas exiting from the aperture at least partly strikes the surface area-enlarging structure. This measure also ensures that the enlarged heat exchange takes place in the region of the thermoelectric modules so that the thermoelectric modules can absorb an increased heat quantity from the impact jet or the hot gas.
Practically, the surface area-enlarging structure projects away from the at least one outer tube-tube wall to the inside, towards the inner tube. Particularly preferably, the surface area-enlarging structure is integrally moulded on the outer tube. This allows creating the surface area-enlarging structure directly during the course of the outer tube production. This results in cost advantages during the production of the heat exchanger.
In an advantageous further development, the surface area-enlarging structure is formed by a plurality of protrusions which project away from the respective outer tube-tube wall towards the inner tube. By means of this measure, a particularly large surface area enlargement can be achieved in a relatively small area section of the outer tube-tube wall. At the same time, such protrusions can be produced technically in a relatively simple manner which simplifies the production of the structure and thus results in cost advantages. Finally, said protrusions are tied mechanically and thus also thermally to the outer tube-tube wall only in well-defined places, as a result of which the heat transfer of hot gas or impact jet to the outer tube-tube wall and thus also to the thermoelectric modules can be homogenised.
Practically, the protrusions are formed as webs which extend, spaced from one another along an extension direction subject to forming intermediate spaces. By means of such webs, a particularly high surface area enlargement can be achieved in little installation space.
Particularly preferably, the protrusions or webs extend linearly, in a top view of the outer tube-tube wall, along the extension direction at least in sections. Alternatively, a non-linear, in particular a curved extension of the protrusions or webs is also possible. A combination by sections of linearly and non-linearly designed protrusions or webs is also conceivable. Conceivable, in particular, is a wave-shaped or polynomial geometry of a projection or web. In each mentioned case, the webs cannot only be used for enlarging the interactive area but additionally also as flow directing elements, which advantageously influence the flow direction of the hot gas or impact jet, in particular before and/or after the reflection on the outer tube-tube wall.
Particularly preferably, the protrusions or webs can have a wave-like geometry in the top view. In this way, an undesirable pressure loss in the impact jet or in the hot gas when flowing through the intermediate spaces between the adjacent protrusions or webs can be kept low.
According to another preferred embodiment, a plurality of webs forms a web group. The webs of such a web group extend radially away from a virtual centre point defined on the outer tube-tube wall. By means of this version, an even reflection of the hot gases or impact jet on the outer tube wall can be ensured.
Preferably, a plurality of web groups is arranged on the outer tube-tube wall preferentially grid-like with at least two grid columns and/or with at least two grid lines.
Practically, the protrusions or webs can be arranged parallel to one another.
In an advantageous further development, the protrusions or web comprise multiple interruptions along the extension direction. The interruptions are realised in such a manner that, by these, two adjacent intermediate spaces are fluidically interconnected in each case.
In an advantageous further development, the interruptions of adjacent protrusions or webs can be arranged staggered relative to one another in the extension direction. The staggered arrangement in this case is preferentially arranged in such a manner that because of the interruptions that are arranged in an staggered manner, communication channels are formed which fluidically interconnect a plurality of adjacent intermediate spaces. By means of such a fluid connection it can be achieved that the impact jet or the hot gas is evenly distributed over the regions of the outer tube-tube wall in which the thermoelectric modules are also arranged. Such a homogenisation of the heat exchange leads to a further efficiency increase of the heat exchanger.
In a particularly advantageous further development, a channel direction, along which the communication channels extend, forms an acute angle with the extension direction of the protrusions or webs.
In an advantageous further development, at least one aperture is present in at least one web, which interconnects to adjacent intermediate spaces. In a further development, a plurality of such apertures can also be arranged spaced from one another in the web. By means of this measure it can also be achieved that the hot gas is evenly distributed over the regions of the outer tube-tube wall, on which the thermoelectric modules are arranged. Such a homogenisation of the heat exchange leads to a further efficiency increase of the heat exchanger.
According to another preferred embodiment, the surface area-enlarging structure comprises a plurality of, preferentially dimpled, protrusions and/or of, preferentially dimpled, recesses. The protrusions or recesses in this embodiment are arranged grid-like on the inside of the outer tube-tube wall. Such a grid-like arrangement of protrusions or recesses in the form of dimples allows providing a plurality of surface area-enlarging elements on relative little installation space. In an advantageous further development, the grid-like arrangement therefore comprises at least two grid columns, preferentially a plurality of grid columns, wherein adjacent grid columns are alternately formed by protrusions and recesses. It goes without saying that a plurality of grid lines can also be provided.
In an advantageous further development, the dimpled protrusions and/or recesses have a round, preferentially circular, geometry in the top view of the outer tube-tube wall.
In another advantageous further development, the protrusions taper, preferentially conically, away from the outer tube-tube wall.
According to another preferred embodiment, the surface area-enlarging structures are designed flat. In a version that is alternative to the former, the surface area-enlarging structure comprises at least one first flat section, which merges into a second flat section, which is arranged at an angle, preferentially at an obtuse angle relative to the first section. By means of this embodiment, the reflection behaviour of the impact jet can be adapted to different user-specific requirements.
According to a further preferred embodiment, the outer tube-tube wall with the surface area-enlarging structure is designed flat. In a version that is alternative to the former, the outer tube-tube wall with the surface area-enlarging structure comprises at least one first flat wall section, which merges into a second flat wall section, which is arranged at an angle, preferentially at an obtuse angle, to the first wall section. The reflection behaviour of the impact jet can also be adapted to different user-specific requirements by means of this embodiment.
The invention additionally relates to a heat exchanger arrangement with at least two heat exchangers which are arranged on top of one another and introduced further up, which can be preferentially stacked onto one another. The heat exchangers of the heat exchanger arrangement fluidically communicate with one another via a common gas outlet. The advantages of the heat exchanger explained further up are therefore transferred also to the heat exchanger arrangement according to the invention.
The invention, furthermore, relates to a motor vehicle with an internal combustion engine having an exhaust system and a heat exchanger according to the invention introduced above. The advantages of the heat exchanger explained above are therefore transferred also to the motor vehicle according to the invention.
Further important features and advantages of the invention are obtained from the subclaims, from the drawings and from the associated figure description by way of the drawings.
It is to be understood that the features mentioned above and still to be explained in the following cannot only be used in the respective combination stated but also in other combinations or by themselves without leaving the scope of the present invention.
Preferred exemplary embodiments of the invention are shown in the drawings and are explained in more detail in the following description, wherein same reference characters relate to same or similar or functionally same components.
It shows, in each case schematically:
The outer tube 2 is designed as flat tube 30 with a first outer tube-tube wall 31a and a second outer tube-tube wall 31b located opposite the first outer tube-tube wall 31a. A part of the thermoelectric modules 10—described as first thermoelectric elements 10a in the following—are arranged on the first outer tube-tube wall 31a according to the
In the cross section perpendicularly to the longitudinal direction L, the two inner tube-tube walls 33a, 33b each form a wide side 35a, 35b of the inner tube 4 realised as flat tube 32. Furthermore, the flat tube 32 forming the inner tube 4 comprises two narrow sides 35c, 35d in the cross section perpendicularly to the longitudinal direction L. The side ratio of one of the two wide sides 35a, 35b to one of the two narrow sides 35c, 35d is more than 1, preferentially at least 2, most preferentially at least 6.
According to
In the example of the
The first coolant tube 13a is arranged on the cold sides 12 of the first thermoelectric modules 10a. The second coolant tube 13b is arranged on the cold sides 12 of the second thermoelectric modules 10b. The outer tube 2 in this case is arranged along a stacking direction S, which runs transversely to the longitudinal direction L of the outer tube 2, between the first and the second coolant tube 13a, 13b. In this way, the installation space required in stacking direction S for the heat exchanger 1 can be kept small. Each of the coolant tubes 13a, 13b can also be designed as flat tube 36, the wide sides 37a of which face the first or second thermoelectric modules 10a, 10b in the cross section perpendicularly to the longitudinal direction L.
The inner tube 4 is designed closed at a first longitudinal end 26a. To this end, the inner tube has a front wall 16. At a second longitudinal end 26b of the inner tube 4 located opposite the first longitudinal end 26a, a gas inlet 27, by contrast, follows the inner tube 4 for introducing the hot gas H into the inner tube 4. In other words, the inner tube 4 is designed open at the second longitudinal end 26b. In the first inner wall tube wall 33a and in the second inner wall tube wall 33b of the inner tube 4, a plurality of apertures 7 is formed in each case, by means of which the inner tube interior space 5 fluidically communicates with the outer tube interior space 3. In this way, the hot gas H flowing through the outer tube 2 can be thermally coupled to the hot sides 11 of the thermoelectric modules 10.
By way of the
The heat exchanger 1 according to
The
In the perspective representation of
Compared with this, the
In the example of
Attention is now directed at the further version according to
In a further development of the example of
The
In the example of the
In
In two further versions shown in the
In
In conclusion, attention is directed at the representation of
Claims
1. An exhaust gas heat exchanger for a motor vehicle comprising:
- an outer tube extending along a longitudinal direction configured to be flowed-through by a hot gas, the outer tube defining an outer tube interior space and in a cross section perpendicular to the longitudinal direction, comprises at least two outer tube-tube walls,
- an inner tube arranged in the outer tube interior space extending along the longitudinal direction, wherein a longitudinal end of the inner tube is closed and defines an inner tube interior space and in the cross section perpendicular to the longitudinal direction, comprises at least two inner tube-tube walls,
- wherein at least one of the at least two inner tube-tube walls includes a plurality of apertures, wherein the inner tube interior space fluidically communicates with the outer tube interior space via the plurality of apertures,
- wherein a plurality of thermoelectric modules are arranged on an outside of the at least two outer tube-tube walls and each include a hot side facing the outer tube and a cold side facing away from the outer tube,
- wherein at least one coolant tube configured to be flowed-through by a coolant is arranged on the cold side of at least one of the plurality of thermoelectric modules,
- wherein an inside of at least one of the at least two outer tube-tube walls includes at least one surface area-enlarging structure.
2. The heat exchanger according to claim 1, wherein the at least one surface area-enlarging structure, with respect to the longitudinal direction, is disposed in a region of at least one of the plurality of thermoelectric modules.
3. The heat exchanger according to claim 1, wherein the at least one surface area-enlarging structure is disposed opposite at least one aperture of the plurality of apertures, so that the hot gas exiting the at least one aperture at least partly strikes the at least one surface area-enlarging structure.
4. The heat exchanger according to claim 1, wherein the at least one surface area-enlarging structure projects from at least one of the at least two outer tube-tube walls away towards the inner tube and is integrally moulded on the outer tube.
5. The heat exchanger according to claim 1, wherein the at least one surface area-enlarging structure comprises a plurality of protrusions projecting away from the at least one outer tube-tube wall towards the inner tube.
6. The heat exchanger according to claim 5, wherein the plurality of protrusions comprise a plurality of webs extending along an extension direction spaced from one another to define a plurality of intermediate spaces.
7. The heat exchanger according to claim 5, wherein one of the plurality of protrusions or the plurality of webs, in a top view of the at least two outer tube-tube walls, extend along an extension direction at least one of linearly and non-linearly at least in sections.
8. The heat exchanger according to claim 5, wherein one of the plurality of protrusions or the plurality of webs comprise a wave-like geometry in a top view.
9. The heat exchanger according to claim 5, wherein
- a plurality of webs form a web group, and
- the plurality of webs of the web group radially extend away from a virtual centre point defined on at least one of the at least two outer tube-tube walls.
10. The heat exchanger according to claim 9, wherein on at least one of the at least two outer tube-tube walls a plurality of web groups are arranged grid-like with at least two grid columns and with at least two grid lines.
11. The heat exchanger according to claim 5, wherein at least one of the plurality of protrusions or the plurality of webs are arranged parallel to one another.
12. The heat exchanger according to claim 6, wherein at least one of the plurality of protrusions or the plurality of webs along the extension direction each have a plurality of interruptions, the plurality of interruptions each fluidically interconnecting two adjacent intermediate spaces.
13. The heat exchanger according to claim 12, wherein the plurality of interruptions of one of the adjacent plurality of protrusions or the plurality of webs along the extension direction are staggered relative to one another so that through the plurality of interruptions arranged staggered, a plurality of communication channels are defined and fluidically interconnect a plurality of adjacent intermediate spaces between one of the plurality of protrusions or the plurality of webs.
14. The heat exchanger according to claim 13, wherein the plurality of communication channels extend along a channel direction, the channel direction forming an acute angle with the extension direction of one of the plurality of protrusions or the plurality of webs.
15. The heat exchanger according to claim 5, wherein at least one web of the plurality of webs includes an aperture fluidically interconnecting two adjacent intermediate spaces of the plurality of intermediate spaces.
16. The heat exchanger according to claim 1, wherein the at least one surface area-enlarging structure comprises at least one of a plurality of dimpled protrusions and a plurality of dimpled recesses arranged grid-like on an inside of at least one of the at least two outer tube-tube walls.
17. The heat exchanger according to claim 16, wherein the grid-like arrangement comprises at least two grid columns, wherein adjacent grid columns are alternately formed by one of the plurality of protrusions or the plurality of recesses.
18. The heat exchanger according to claim 16, wherein at least one of the plurality of protrusions and the plurality of recesses comprise a round, circular geometry in a top view of one of the at least two outer tube-tube walls.
19. The heat exchanger according to claim 16, wherein at least one projection of the plurality of projections and at least one recess of the plurality of recesses tapers, conically, away from at least one of the at least two outer tube-tube walls.
20. The heat exchanger according to claim 16, wherein one of:
- at least one of the at least two outer tube-tube walls with the at least one surface area-enlarging structure is; or
- at least one of the at least two outer tube-tube walls with the at least one surface area-enlarging structure comprises at least one first flat wall section that merges into a second flat wall section, arranged at an obtuse angle to the first wall section).
21. A heat exchanger arrangement, comprising:
- at least two heat exchangers arranged on top of one another, and stacked onto one another, wherein the at least two heat exchangers fluidically communicate with one another via at least one common gas outlet configured to discharging a hot gas from the heat exchange arrangement.
22. A motor vehicle comprising: a heat exchanger interacting with the exhaust system, the heat exchanger comprising one of: an outer tube extending along a longitudinal direction configured to be flowed-through by a hot gas, the outer tube defining an outer tube interior space and in a cross section perpendicular to the longitudinal direction, comprises at least two outer tube-tube walls, an inner tube arranged in the outer tube interior space extending along the longitudinal direction, wherein a longitudinal end of the inner tube is closed and defines an inner tube interior space and in the cross section perpendicular to the longitudinal direction, comprises at least two inner tube-tube walls, wherein at least one of the at least two inner tube-tube walls includes a plurality of apertures, wherein the inner tube interior space fluidically communicates with the outer tube interior space via the plurality of apertures, wherein a plurality of thermoelectric modules are arranged on an outside of the at least two outer tube-tube walls and each include a hot side facing the outer tube and a cold side facing away from the outer tube, wherein at least one coolant tube configured to be flowed-through by a coolant is arranged on the cold side of at least one of the plurality of thermoelectric modules, wherein an inside of at least one of the at least two outer tube-tube walls includes at least one surface area-enlarging structure; or at least two heat exchangers arranged on top of one another and stacked onto one another, wherein the at least two heat exchangers fluidically communicate with one another via at least one common gas outlet configured to discharging a hot gas from the heat exchange arrangement.
- an internal combustion engine including an exhaust system;
Type: Application
Filed: Nov 29, 2017
Publication Date: May 31, 2018
Inventors: Matthias Ganz (Stuttgart), Fahmi Ben Ahmed (Stuttgart), Holger Schroth (Maulbronn), Klaus Luz (Herrenberg)
Application Number: 15/826,303