EP3622235A1

EP3622235A1 - Heat exchanger, in particular u-flow heat exchanger

Info

Publication number: EP3622235A1
Application number: EP17722794.9A
Authority: EP
Inventors: Bernd Krämer; Pramod Barhate; Simon HUND; Christian Faber
Original assignee: Mahle International GmbH
Current assignee: Mahle International GmbH
Priority date: 2017-05-11
Filing date: 2017-05-11
Publication date: 2020-03-18
Also published as: WO2018206108A1

Abstract

The invention relates to a heat exchanger (10), in particular for an exhaust gas cooler, comprising a housing (12) having a first flow path (14) for a first fluid and having a second flow path (16) for a second fluid, which are media-separated and thermally coupled, wherein the housing (12) has a first dividing plane (34) for the first flow path (14) wherein the respective main flow directions (38) of the first flow path (14) on both sides of the first dividing plane (34) are opposite to one another, wherein the housing (12) has a second dividing plane (36) for the second flow path (16) wherein the respective main flow directions (40) of the second flow path (16) on both sides of the second dividing plane (36) are opposite to one another. In order to increase the flexibility of the heat exchanger, it is proposed that the first dividing plane (34) and the second dividing plane (36) have a distance from one another at least in the housing (12).

Description

Heat exchanger, in particular U-flow heat exchanger

The invention relates to a heat exchanger, in particular for an exhaust gas cooler, comprising a housing, comprising a first flow path for a first fluid and comprising a second flow path for a second fluid, which are media-separated and thermally coupled. The invention further relates to an exhaust gas cooler with such a heat exchanger.

Heat exchangers for exhaust gas coolers are known, for example from DE 914 450 B, from DE 14 764 98 A1 and from DE 10 2007 002 459 A1 . These heat exchangers have in common that the exhaust gas to be cooled is guided through a tube bundle which has a coolant flowing around it. In this context, folded flow paths are known for the exhaust gas in order to achieve a particularly compact and efficient structure of the exhaust gas cooler.

It is the object of the present invention to provide an improved or at least different embodiment of a heat exchanger for an exhaust gas cooler which is characterized by the highest possible heat transfer balance with at the same time the lowest possible pressure loss both in the exhaust gas to be cooled in the coolant.

This object is solved according to the invention by the subject matters of the independent claims. Advantageous further developments are the subject matter of the dependent claims.

The invention is based on the general idea of providing three heat transfer regions which differ in respect of the main flow direction of the respective fluids. As a result, an optimization of the heat transfer and a reduction in the pressure losses can be achieved. According to the invention it is therefore provided that the first dividing plane and the second dividing plane have a distance from one another at least in the housing. As a result, the deflection of the fluids in the first flow path and the second flow path takes place at different regions so that overall three heat transfer regions are achieved. These are a region which lies between the two dividing plane and one region each on both sides between the intermediate region between the dividing planes. An extremely compact design of a heat exchanger is thereby achieved which nevertheless can arbitrarily combine different types of flow such as direct flow and counter-current flow of the two paths.

A favourable possibility provides that the first flow path is formed by a plurality of tubes and at least one deflecting chamber, that at least two such tubes are supply tubes which connect an inlet for the first fluid to the deflecting chamber, that at least one such tube is a discharge tube which connects the deflecting chamber to an outlet for the first fluid and that the supply tubes and the at least one discharge tube lie on different sides of the first dividing plane. Thus, ultimately the position of the dividing plane is defined by the position of the supply tubes and the at least one discharge tube. The main flow direction which is defined by the flow of the fluid inside the tubes thus lies on the side on which the supply tubes lie, from the inlet for the first fluid towards the deflecting chamber. On the other side of the dividing plane on which the at least one discharge tube lies, the main flow direction for the second fluid runs from the deflecting chamber back to the outlet. Preferably the inlet for the first fluid and the outlet for the first fluid lie on the same narrow section of the heat exchanger. As a result, a type of U-shaped first flow path is formed.

A further favourable possibility provides that the tubes run substantially parallel to one another. A particularly compact design can thus be achieved. As a result of the parallel arrangement, the distances between the tube can be selected to be very small. In the description and the appended claims, "substantially parallel" is understood to mean that a deviation from "parallel" is allowed within the framework of manufacturing tolerances, in particular by up to 5°, preferably up to 3°, particularly preferably up to 1 °.

A particularly favourable possibility provides that at least one of the supply tubes has a flow cross-section which is smaller than a flow cross-section of the at least one discharge tube. In particular, this means that the discharge tube has a larger cross-section than at least one of the supply tubes. It has been shown that after passing through the supply tubes the exhaust gas is already sufficiently cooled so that no cooling or only slight cooling is required in the discharge tube. As a result, a larger flow cross-section can be selected for the discharge tube which means a lower flow resistance for the fluid so that the pressure losses through the heat exchanger can be reduced.

A further particularly favourable possibility provides that each supply tube has a flow cross-section which is smaller than the flow cross-section of the at least one discharge tube. Thus, as a result of the small flow cross-sections in the supply tubes, a sufficient cooling of the exhaust gas can already be achieved through the supply tubes. The large flow cross-section in the discharge tube can be utilized to achieve the lowest possible pressure loss since only a small amount or no additional cooling is required.

An advantageous solution provides that the heat exchanger has precisely one discharge tube. Thus, the entire fluid, preferably the exhaust gas flows back in the first flow path through the individual discharge tube. Thus, a very large flow cross- section can be used for the discharge tube since only a single one is provided. Consequently the flow resistance in the first flow path can be reduced still further. A further advantageous solution provides that the second flow path is formed by intermediate spaces between the tubes and is delimited by the housing, that the second dividing plane is defined by a partition plate and that an inlet for the second fluid and an outlet for the second fluid lie on different sides of the second dividing plane. Preferably the partition plate extends from the end of the heat exchanger on which the inlet and the outlet for the second fluid are arranged in the direction of the deflecting chamber so that a U-shaped second flow path is formed.

A particularly advantageous solution provides that the second flow path has a deflecting region which is arranged between the deflecting chamber of the first flow path and an end of the partition plate facing the deflecting chamber. The deflecting region of the second flow path thus forms a fluidic gap between the two sides which are separated from one another by the partition plate. Thus, the second fluid can flow into the housing through the inlet for the second fluid, flow on one side of the partition plate as far as the deflecting region, flow from there onto the other side of the partition plate and flow back to the outlet for the second fluid. Since the second fluid path is formed by the intermediate spaces between the tubes, the second fluid is therefore in thermal contact with the first flow path.

A favourable variant provides that the housing has a first heat transfer region which lies outside an intermediate region between the two dividing planes on a first side next to the two dividing planes, that the housing has a second heat transfer region which lies between the first dividing plane and the second dividing plane and that the housing has a third heat transfer region which lies outside the intermediate region between the two dividing planes on a second side opposite the first side next to the two dividing planes. Thus, the main flow directions in the two flow paths are different in the respective heat transfer regions. Starting from the first heat transfer region, one of the flow directions of one of the flow paths is turned in the second heat transfer region. In the third heat transfer region the main flow direction of the other flow path is also turned.

A further favourable variant provides that the main flow directions of the two flow paths provided in the first heat transfer region have the same direction, that the main flow directions of the two flow paths provided in the second heat transfer region are directed opposite to one another and that the main flow directions of the two flow paths provided in the third heat transfer region have the same direction.

For example, when used as an exhaust gas cooler, the exhaust gas can be guided through the first flow path, wherein a first flow flows parallel through the first heat transfer region and the second heat transfer region and then the entire exhaust gas flows through the third heat transfer region. The coolant would then accordingly flow firstly through the first heat transfer region and then parallel through the second heat transfer region and third heat transfer region. In this case, the first fluid which flows through the first heat transfer region is cooled sufficiently strongly since it is cooled by fresh cool coolant in the direct flow. The exhaust gas which flows through the second heat transfer region is also sufficiently cooled since the already heated coolant flows through the second heat transfer region in the counter-flow. In the third heat transfer region as a result, no cooling or only a very small amount of cooling of the exhaust gas needs to be carried out so that an inferior thermal coupling between the two flow paths can be accepted and in return the flow resistance of the two flow paths in the third heat transfer region can be reduced.

A further particularly favourable variant provides that the main flow directions of the two flow paths provided in the first heat transfer region are directed opposite to one another, that the main flow directions of the two flow paths provided in the second heat transfer region have the same direction and that the main flow directions of the two flow paths provided in the third heat transfer region are directed opposite to one another. This can be achieved compared with the previously described variant by reversing the flow direction of the second flow path and therefore of the coolant. In this case, a sufficient heat transfer between the two flow paths, in particular a cooling of the first fluid in the first flow path, can also be achieved in the first two heat transfer regions. Here also the third heat transfer region can be configured in such a manner to achieve a reduced pressure loss. In this variant, flow takes place through the third heat transfer region in the counter- flow so that the thermal coupling in the third heat transfer region can possibly be reduced still further.

An advantageous possibility provides that the first flow path runs inside the housing substantially in a U shape and that the second flow path runs inside the housing substantially in a U shape. As a result of the U-shaped configuration of the two flow paths, a particularly compact design of the heat exchanger can be achieved.

The invention is further based on the general ideal of providing an exhaust gas cooler with a heat exchanger according to one of claims 1 to 10, wherein the exhaust gas to be cooled is guided through the first flow path and that a coolant, preferably cooling water, is guided through the second flow path. Thus, the advantages of the heat exchanger are transferred to the exhaust gas cooler, reference being made in this respect to the preceding description thereof. In particular, a particularly favourable cooling of the exhaust gas to be cooled can be achieved in this manner within the first flow path.

Further important features and advantages of the invention are obtained from the subclaims, from the drawings and from the relevant description of the figures with reference to the drawings. It is understood that the features mentioned previously and to be explained further hereinafter can be used not only in the respectively given combination but also in other combinations or alone without departing from the scope of the present invention.

Preferred exemplary embodiments of the invention are presented in the drawings and are explained in detail in the following description, where the same reference numbers relate to the same or similar or functionally the same components.

In the figures, in each case schematically

Fig. 1 shows a perspective view of a heat exchanger,

Fig. 2 shows a sectional view along the plane of intersection A from Fig. 1 ,

Fig. 3 shows a sectional view through the heat exchanger from Fig. 1 along the plane of intersection B

Fig 4 shows a perspective view of the heat exchanger, where a jacket- shaped outer wall of the housing is omitted, where the main flow directions in the first flow path are indicated by arrows,

Fig 5 shows a view corresponding to Fig. 4, wherein the main flow directions in the second flow path are indicated by arrows,

Fig 6 shows a circuit-diagram-like schematic diagram of the interconnection of the three heat transfer regions formed by the two flow paths, Fig. 7 shows a diagram corresponding to Fig. 6, wherein the flow direction in the second flow path is reversed.

A first embodiment of a heat exchanger 10 shown in Figs. 1 -6 can be used for example for an exhaust gas cooler. The heat exchanger 10 has a housing 12 in which a first flow path 14 for a first fluid and a second flow path 16 for a second fluid are formed. The two flow paths 14, 16 are media-separated in the housing 12 and thermally coupled at least in some regions. As a result, heat can be exchanged between the first fluid flowing through the first flow path 14 and the second fluid flowing through the second flow path 16. As a result, for example, exhaust gas flowing through the first flow path 14 can be cooled. A coolant, for example, cooling water which is passed through the second flow path 16 can be used for cooling.

The housing 12 has a jacket-shaped outer wall 18. A deflecting chamber 20 is located at one end of the housing 12. At the other end a connecting region of the housing 12 is provided at which an inlet chamber 22 and an outlet chamber 24 are each provided for the first flow path 14. Accordingly an inlet 26 and an outlet 28 for the first flow path are arranged on the housing 12 in such a manner that the inlet 26 forms a fluid connection to the inlet chamber 22. Furthermore, the outlet 28 is arranged on the housing 12 in such a manner that it forms a fluid connection to the outlet chamber 24.

The housing 12 further has an inlet 30 and an outlet 32 for the second fluid, i.e. for the second flow path 16. The inlet 30 and the outlet 32 for the second flow path 16 are arranged on the jacket-shaped outer wall 18.

Both flow paths 14 and 16 are configured to be substantially U-shaped. As a result, a compact design can be achieved. In particular, the inlets 26, 30 and outlets 28, 32 of both flow paths 14, 16 can thus be arranged at the same end of the heat exchanger 10.

Furthermore, a first dividing plane 34 is defined in the heat exchanger 10, which separates the two legs of the U of the first flow path 14. Furthermore a second dividing plane 36 is formed which separates the two legs of the U of the second flow path 16.

Accordingly, a provided main flow direction 38 of the first flow path 14 on both sides of the first dividing plane 34 is directed in opposite directions. The same applies for a provided main flow direction 40 of the second flow path 16 relative to the second dividing plane 36.

The first flow path 14 is formed by the deflecting chamber 20, the inlet chamber 22, the outlet chamber 24 and by a plurality of tubes 42. The tubes 42 can be divided into supply tubes 44 and discharge tubes 46.

The supply tubes 44 connect the inlet chamber 22 to the deflecting chamber 20. The discharge tubes 46 connect the deflecting chamber 20 to the outlet chamber 24. Thus, the first fluid which flows through the first flow path 14 initially flows through the inlet 26 into the inlet chamber 22. The first fluid flows through the supply tubes 44 as far as the deflecting chamber 20. In the deflecting chamber 20 the fluid is deflected by substantially 180° whereupon it is then returned through the discharge tubes 46 and finally enters into the outlet chamber 24. From the outlet chamber 24 the first fluid can flow through the outlet 28 from the housing 12.

The first dividing plane 34 is therefore defined by the position of the supply tubes 44 and the position of the discharge tubes. In particular the supply tubes 44 lie on one side of the first dividing plane 34 and the at least one discharge tube 46 lies on the other side of the first dividing plane 34.

The fluidic connection between the in the inlet chamber 22 and the deflecting chamber 20 can be made by passing the supply tubes 44 through an inner wall 48 of the inlet chamber 22 and an inner wall 50 of the deflecting chamber 20. The at least one discharge tube 46 can also pass through the inner wall 50 of the deflecting chamber 20 and at the other end of the discharge tube 46, the discharge tube 46 can pass through an inner wall 52 of the outlet chamber 24. Alternatively the discharge tube 46 can go over flush into the outlet chamber 24.

The inner wall 48 of the inlet chamber 22, the inner wall 50 of the deflecting chamber 20 and the inner wall 52 of the outlet chamber 24 thus separate the first flow path 14 from an intermediate space 54 between the tubes 42 in which the second flow path 16 is formed.

Preferably the supply tubes 44 have a smaller flow cross-section than the discharge tube 46. As a result, the supply tubes 44 have a stronger thermal coupling to the second flow path 16 so that when the exhaust gas has entered into the deflecting chamber 20, it is already sufficiently cooled. As a result, the discharge tube 46 can be provided with a large flow cross-section so that only low pressure losses occur in the discharge tube 46.

As already mentioned, the second flow path 16 is formed by the intermediate space 54 formed between the tubes 42 or between the tubes 42 and the jacket- shaped outer wall 18 of the housing 12. Furthermore, the second flow path 16 is in particular delimited or defined by the jacket-shaped outer wall 18 of the housing 12. On the front side the second flow path 16 is delimited by the inner wall 48 of the inlet chamber 22, by the inner wall 50 of the deflecting chamber 20 and by the inner wall 52 of the outlet chamber 24. A partition plate 56 which defines the second dividing plane 36 is arranged between the tubes 42, in particular between the supply tubes 44. The inlet 30 of the second flow path 16 and the outlet 32 of the second flow path 16 are arranged on different sides of the partition plate 56. The partition plate 56 thus brings about the U-shaped profile of the second flow path 16.

As shown for example in Figure 3, the partition plate 56 runs from the inner wall 48 of the inlet chamber 22 in the direction of the deflecting chamber 20. Formed between the deflecting chamber 20 and an end 58 of the partition plate 56 facing the deflecting chamber is a deflecting region 60 at which the second fluid in the second flow path 16 can flow from one side of the partition plate 56 onto the other side of the partition plate 56. As a result, the second fluid can flow from the inlet 30 to the outlet 32 of the second flow path 16.

As a result of the lateral mounting of the inlet 30 and the outlet 32, transverse flows are also present in the second flow path but the provided main flow directions 40 in the second flow path 16 are only defined in the longitudinal direction of the tubes 42.

The first dividing plane 34 of the first flow path 14 and the second dividing plane 36 of the second flow path 16 have a distance from one another. As a result, the deflection of the main flow direction 38 of the first flow path 14 and the main flow direction 40 of the second flow path 16 are not located on the same plane in the housing 12. Thus, three heat transfer regions are formed in the housing 12.

A first heat transfer region 62 lies on an inlet side of the first dividing plane 34 and the second dividing plane 36. As a result, the first heat transfer region 62 is located outside an intermediate region 64 which lies between the two dividing planes 34 and 36. The inlet 26 of the first flow path 14 and the inlet 30 of the second flow path 16 both lie on the same side outside the intermediate region 64 so that in the first heat transfer region 62 the main flow direction 38 of the first flow path 40 and the main flow direction 40 of the second flow path 16 have the same direction.

A second heat transfer region 66 is formed between the two dividing planes 34, 36. In the variant shown in Figures 2 to 5, the partition plate 56 which defines the second dividing plane 36 is offset towards the inlet side between the supply tubes 44, i.e., with respect to the first dividing plane 34 of the first flow path 14. Thus, in the second heat transfer region 66 the main flow direction 40 of the second flow path 16 is reversed compared with the first heat transfer region 62. Consequently, the main flow direction 38 of the first flow path 14 and the main flow direction 40 of the second flow path 16 in the second heat transfer region 66 are opposite to one another. The third heat transfer region 68 now lies on the outlet side outside the intermediate region 64. Thus, both the main flow direction 38 of the first flow path 14 and the main flow direction 40 of the second flow path 16 are reversed compared with the first heat transfer region 62. Thus, the two main flow directions 38 and 40 of the two flow paths 14 and 16 in the third heat transfer region 68 have the same direction.

When the heat exchanger 10 is used in an exhaust gas cooler and the exhaust gas to be cooled is passed through the first flow path 14 and a coolant is passed through the second flow path 16, a sufficient cooling of the first fluid, i.e. the exhaust gas, can already be achieved in the first heat transfer region 62 and in the second heat transfer region 66.

In the first heat transfer region 62 the exhaust gas is cooled by fresh, i.e. cool coolant in the direct flow. In the second heat transfer region 66 the exhaust gas is cooled by already-heated coolant but the two fluids flow in the second heat trans- fer region 66 in counter-flow so that a particularly good heat transfer is achieved. Thus, a sufficient cooling of the exhaust gas is already possible in the second heat transfer region 66.

This has the result that in the third heat transfer region 68 no cooling or only a small amount of cooling of the exhaust gas is required. It is thus possible to provide the discharge tube 46 with a very large flow cross-section which certainly brings about a reduced heat transfer between the two flow paths 14 and 16 but at the same time reduce the flow resistance caused. Thus, a sufficient cooling of the exhaust gas with a simultaneous reduction of the flow resistance can be achieved by this design.

Figure 6 shows as an example the interconnection of the two heat transfer regions 62, 66 and 68. It can be clearly seen from the diagram that flow takes place through the first heat transfer region 62 in direct flow, through the second heat transfer region 66 in counter-flow and through the third heat transfer region 68 again in direct flow.

The variant shown in Figure 7 shows an example in which inlet 30 and outlet 32 of the second flow path 16 are transposed. That is the main flow direction 40 of the second flow path 16 is just reversed. This has the result that the flow takes place through the first heat transfer region 62 in counter-flow, through the second heat transfer region 66 in direct flow and through the third heat transfer region 68 again in counter-flow. In such a configuration it can also be achieved that a tube having a larger cross-section can be used in the third heat transfer region 68 in order to reduce the flow resistance.

In general, the idea of separating the first dividing planes 34 for the first flow path 14 and the second dividing plane 36 for the second flow path 16 enables a sub- stantially more flexible and more adaptable structure of a heat exchanger. For example, the second dividing plane 36 can be displaced towards the outlet side instead of towards the inlet side compared with the first dividing plane. This results in further scope for adaptation for the heat exchanger so that the additional requirements of the automobile manufacturer can be met.

Claims

1 . Heat exchanger (10), in particular for an exhaust gas cooler, comprising a housing (12) having a first flow path (14) for a first fluid and having a second flow path (16) for a second fluid, which are media-separated and thermally coupled,

- wherein the housing (12) has a first dividing plane (34) for the first flow path (14) wherein the respective main flow directions (38) of the first flow path (14) on both sides of the first dividing plane (34) are opposite to one another,

- wherein the housing (12) has a second dividing plane (36) for the second flow path (16) wherein the respective main flow directions (40) of the second flow path (16) on both sides of the second dividing plane (36) are opposite to one another,

characterized in

that the first dividing plane (34) and the second dividing plane (36) have a distance from one another at least in the housing (12).

2. The heat exchanger according to claim 1 ,

characterized in,

- that the first flow path (14) is formed by a plurality of tubes (42) and at least one deflecting chamber (20),

- that at least two such tubes (42) are supply tubes (44) which connect an inlet (26) for the first fluid to the deflecting chamber (20),

- that at least one such tube (42) is a discharge tube (46) which connects the deflecting chamber (20) to an outlet (28) for the first fluid and - that the supply tubes (44) and the at least one discharge tube (46) lie on different sides of the first dividing plane (34).

3. The heat exchanger according to claim 2,

characterized in

that at least one of the supply tubes (44) has a flow cross-section which is smaller than a flow cross-section of the at least one discharge tube (46), preferably that each supply tube (44) has a flow cross-section which is smaller than the flow cross-section of the at least one discharge tube (46).

4. The heat exchanger according to claim 2 or 3,

characterized in

that the heat exchanger (10) has precisely one discharge tube (46).

5. The heat exchanger according to any one of claims 1 to 4,

characterized in

- that the second flow path (16) is formed by an intermediate space (54) between the tubes (42) and is delimited by the housing (12),

- that the second dividing plane (36) is defined by a partition plate (56) and

- that an inlet (30) for the second fluid and an outlet (32) for the second fluid lie on different sides of the second dividing plane (36).

6. The heat exchanger according to claim 5,

characterized in

that the second flow path (16) has a deflecting region (60) which is arranged between the deflecting chamber (20) of the first flow path (14) and an end (58) of the partition plate (56) facing the deflecting chamber (20).

7. The heat exchanger according to any one of claims 1 to 6, characterized in,

- that the housing (12) has a first heat transfer region (62) which lies outside an intermediate region (64) between the two dividing planes (34, 36) on a first side next to the two dividing planes (34, 36),

- that the housing (12) has a second heat transfer region (66) which lies between the first dividing plane (34) and the second dividing plane (36) and

- that the housing (12) has a third heat transfer region (68) which lies outside the intermediate region (64) between the two dividing planes (34, 36) on a second side opposite the first side next to the two dividing planes (34, 36).

8. The heat exchanger according to claim 7,

characterized in

- that the main flow directions (38, 40) of the two flow paths (14, 16) provided in the first heat transfer region (62) have the same direction,

- that the main flow directions (38, 40) of the two flow paths (14, 16) provided in the second heat transfer region (66) are directed opposite to one another and

- that the main flow directions (38, 40) of the two flow paths (14, 16) provided in the third heat transfer region (68) have the same direction

9. The heat exchanger according to claim 7,

characterized in

- that the main flow directions (38, 40) of the two flow paths (14, 16) provided in the first heat transfer region (62) are directed opposite to one another,

- that the main flow directions (38, 40) of the two flow paths (14, 16) provided in the second heat transfer region (66) have the same direction and

- that the main flow directions (38, 40) of the two flow paths (14, 16) provided in the third heat transfer region (68) are directed opposite to one another.

10. The heat exchanger according to any one of claims 1 to 9, characterized in

- that the first flow path (14) runs inside the housing (12) substantially in a U shape and

- that the second flow path (16) runs inside the housing (12) substantially in a U shape.

1 1 . The exhaust gas cooler having a heat exchanger according to one of claims 1 to 10,

characterized in

that exhaust gas to be cooled is guided through the first flow path (14) and that a coolant, preferably cooling water is guided through the second flow path (16).