DE102017115919B4 - Exhaust gas heat exchanger with two different work areas - Google Patents

Abstract

Exhaust gas heat exchanger (1), having an outer shell (2), with at least two different working areas (6, 7) being arranged parallel next to one another in a lamellar cooler, in plate construction to form an exhaust gas flow channel, in each case at one end a connection for the exhaust gas (A) is arranged on the casing and an inlet (8) and an outlet (16) for a cooling medium (K) are provided in the casing (2), such that the cooling medium (K) is between the plates of the lamellar cooler and the casing (2) flows, the two working areas (6, 7) being formed in a cassette (3), characterized by two lamellar plates (4, 5) arranged next to one another in the cassette (3) and different from one another I net that in a U-shaped flow through exhaust gas heat exchanger (1) at one end a common inlet and outlet diffuser (11) is arranged and at the other end of the shell (2) an end cap (9) is arranged, the one through the lamellar cooler diverts the exhaust gas flow flowing through the lamellar cooler and that a return duct (10) arranged parallel to the lamellar cooler is formed, the end cap (9) fluidically combining the two working areas (6, 7) and the exhaust gas flow into the return duct (10) and back through it the inlet and outlet diffuser (11) leads.

Description

The present invention relates to an exhaust gas heat exchanger according to the features in the preamble of patent claim 1.

In the motor vehicle industry, exhaust gas heat exchangers are used to cool the exhaust gas resulting from the combustion of an internal combustion engine and to feed this exhaust gas back into the combustion as an exhaust gas recirculation system in order to thereby reduce pollutant emissions.

Such exhaust gas recirculation systems are also called EGR systems or EGR coolers.

In the prior art, an EGR cooler or heat exchanger in particular has been established for this purpose, which is designed in a plate construction. This means that tubes through which a medium flows and around which a second medium flows on the outside are not used, but plate-shaped heat exchanger channels are formed. Cassettes are mostly designed for this purpose. The cassettes are made from two half-shells. A lamellar plate is usually used inside the cassette to enlarge the heat exchange surface. Several such cassettes are then stacked one on top of the other, with one medium flowing through the cassettes and a second medium flowing around the cassettes from the outside. Several cassettes are placed one above the other in a case.

From the DE 10 2007 058 947 A1 For example, such a plate-type exhaust gas heat exchanger is described. Lamellar plates are arranged within a first channel in order to enlarge the surface for heat transfer. The exhaust gas flows through the heat exchanger in a U-shape or in a U-stream.

From the DE 10 2008 007 765 A1 Furthermore, an exhaust gas heat exchanger is known, which is also flowed through in a U-shape, whereby different working areas can be flowed through. The flowing exhaust gas is fed into the various work areas through different control flaps.

From the DE 10 2008 014 169 A1 Furthermore, an exhaust gas heat exchanger is known in which the exhaust gas also flows through channels in plate construction, whereby a mutually different heat exchanger performance is provided by the arrangement of different lamellar structures. According to 8th of this document, it is also possible to flow through the exhaust gas heat exchanger in a U-shape, the different working areas being connected linearly one behind the other.

The object of the present invention is to provide an exhaust gas heat exchanger in plate construction, which is more compact than known exhaust gas heat exchangers and at the same time offers the possibility of providing different cooling capacities.

The aforementioned object is achieved with an exhaust gas heat exchanger according to the features in claim 1.

Advantageous configuration variants are the subject of the dependent claims.

The exhaust gas heat exchanger according to the invention has an outer shell. In the outer shell, at least two different work areas are arranged parallel to one another in a plate-type lamellar cooler. The finned cooler or the working areas form the exhaust gas flow channel. In particular, the lamellar cooler is arranged in plate construction by means of cassettes stacked on top of one another. Lamella plates are then used in the cassettes themselves.

According to the invention, the exhaust gas heat exchanger is flowed through in a U-shape, which is explained in more detail in the following description.

A common or combined inlet and outlet diffuser for the exhaust gas is arranged at one end of the shell. This means that here the exhaust gas flows in from the internal combustion engine and flows out of the exhaust gas heat exchanger either directly or after flowing through the exhaust gas flow channel. Furthermore, an inlet and an outlet for a cooling medium are provided in the casing, the cooling medium flowing between the plates of the lamellar cooler and the casing. The cooling medium is in particular a cooling fluid.

An end cap is also arranged at the end of the shell opposite the inlet and outlet diffuser. The end cap deflects an exhaust gas flow flowing through the exhaust gas flow channel, thus through the lamellar cooler. In particular, this deflection takes place by 180 °. The exhaust gas thus flows through the exhaust gas heat exchanger in a U-shape.

According to the invention, the exhaust gas heat exchanger is characterized in that a return duct is arranged parallel to the lamellar cooler. The flowing exhaust gas is deflected by the end cap after the lamellar cooler and directed into the return duct. The flowing exhaust gas from both work areas is fluidically combined or combined and transferred into the return duct. The return duct then directs the exhaust gas in turn into the inlet and outlet diffuser, the exhaust gas then flowing through an outlet channel.

According to the invention, the exhaust gas heat exchanger is further characterized in that the two working areas are formed parallel to one another in a cassette, by means of two mutually different lamella plates arranged next to one another in the same cassette.

As is known from the prior art, the two working areas lying next to one another do not have to flow through different working areas in series one after the other, but can instead be flowed through by a partial flow at the same time in parallel next to one another. Accordingly, alternatively, it is possible to purposefully guide a partial flow of the exhaust gas only through one work area, which is not possible with work areas connected in series, since the entire work area must be flowed through.

In the context of the invention, however, it is also possible for the exhaust gas heat exchanger to be designed with only one of the features described above. This means that either only one return channel is formed or that the two working areas arranged next to one another are formed in a cassette.

The mutually different lamellar plates can be designed, for example, in that they have different materials and / or have a different shape. Alternatively or in addition, the two lamellar plates can have a surface area that is different from one another.

According to the invention, the working areas can be switched on in particular in certain areas, so that the exhaust gas flowing through the exhaust gas flow channel can transfer heat as required. This offers advantages in particular during production, since to form a cassette from two half-shells, two mutually different lamellar plates are simultaneously inserted next to one another in the half-shells. For this purpose, the lamellar plates in particular can be clamped to one another at the end face in the adjoining areas. Furthermore, the lamellar plates are preferably cohesively coupled to the cassette, in particular an inner circumferential surface of the cassette, in particular soldered.

So that the flowing exhaust gas can be introduced into the exhaust gas flow channel in some areas or, alternatively, the exhaust gas heat exchanger can also flow around in the bypass, two adjustable flaps are arranged next to one another on an axis in the inlet and outlet diffuser, with the adjustable flaps being adjustable separately from one another. It is thus possible for a first adjustable flap to be assigned to a first working area and the second adjustable flap to be assigned to the second working area. This means that the exhaust gas heat exchanger can be completely flowed around when the regulating flaps are closed. This means that no exhaust gas is passed through the exhaust gas flow channel of the exhaust gas heat exchanger. Alternatively, the individual work areas can be flown through independently of one another or together, depending on the heat exchanger capacity required for the operating situation.

A particular structural advantage of the invention results from the fact that the two adjusting flaps are each pivotably mounted via a separate axle shaft, but both axle shafts are on one axle. It is therefore possible, in particular, to control the adjustable flaps separately on the one hand. On the other hand, an internal common bearing point can be formed. This means that each axle shaft does not have to be sealed separately from the environment in at least two places. Each axle shaft only needs to be sealed off from the environment on one side. In particular, adjusting actuators of the axle shafts can thus be arranged outside the exhaust gas heat exchanger and are therefore not exposed to the exhaust gas flow and the thermal load. In particular, in the case of the inner bearing point, no additional sealing function has to be implemented, since it is arranged within the exhaust gas flow channel.

The exhaust gas heat exchanger, in particular the lamellar cooler located therein, is formed from several cassettes arranged one above the other, each with lamellar plates arranged therein. The cassettes themselves are produced in particular by half-shells which are soldered to one another, with a lamellar plate being inserted into the half-shells accordingly.

Due to the different working areas, the heat exchanger output can be controlled in a targeted manner and is also increased compared to heat exchangers known from the prior art. At the same time, this also offers the possibility of a compact construction. At the same time, the overall dimensions can be further reduced by the return channel. In particular, no internal components are arranged in the return duct, so there are no lamellar plates or anything else. The return duct can thus be designed to be smaller in cross section than the cross section of the lamellar cooler with both working areas. The cross section of the return duct is particularly preferably smaller than half, and therefore 50% smaller than the cross section of the lamellar cooler. Farther the cross-sectional area of the return duct is particularly preferably smaller than 40%, in particular smaller than 30%, particularly preferably smaller than 20% of the cross-sectional area of the lamellar cooler. However, the cross-sectional area of the return duct is preferably at least 5% of the cross-sectional area of the lamellar cooler.

The features mentioned above and described below can be combined with one another as required within the scope of the invention.

• 1 einen erfindungsgemäßen U-förmig durchströmten Abgaswärmetauscher in perspektivischer Ansicht ohne Endkappe,
• 2 eine Kassette des Abgaswärmetauschers,
• 3a und b eine Längsschnittansicht durch einen erfindungsgemäßen Abgaswärmetauscher,
• 4 eine perspektivische Teilschnittansicht durch den Abgaswärmetauscher.

Further advantages, features and aspects of the invention are the subject of the following description. Preferred design variants are shown in schematic figures. These serve to make the invention easier to understand. Show it:

• 1 a U-shaped exhaust gas heat exchanger according to the invention in a perspective view without end cap,
• 2 a cassette of the exhaust gas heat exchanger,
• 3a and b a longitudinal sectional view through an exhaust gas heat exchanger according to the invention,
• 4th a perspective partial sectional view through the exhaust gas heat exchanger.

In the figures, the same reference numerals are used for the same or similar components, even if a repeated description is omitted for reasons of simplicity.

1 shows a perspective view of an exhaust gas heat exchanger according to the invention 1 . In an outer shell 2 are several stacked cassettes to form a lamellar cooler in plate construction 3 placed in each of the cassettes 3 Lamellar plates 4th , 5 are arranged.

The lamellar sheets 4th , 5 differ from each other, making two different work areas 6th , 7th parallel to each other in the envelope 2 are arranged. It is also on the side of the case 2 an entrance 8th intended. A cooling medium (not shown in more detail) can be introduced here and then between the casing 2 and cassettes 3 stream. The exhaust A. itself flows through the cassettes 3 .

At the other end of the shell 2 is an end cap 9 intended. The end cap 9 directs that through the cassettes 3 flowing exhaust gas A. at the end by 180 ° and leads this through the return channel 10 back. The cross-sectional area A10 of the return channel 10 is smaller than the cross-sectional areas A6 , A7 both work areas 6th , 7th together. Thus, the exhaust gas flows A. through the return channel 10 back to the common inlet and outlet diffuser 11 , which is particularly in the 3a and 3b is shown.

In case of 3a the exhaust gas flows A. via an inflow channel 12th in the inlet and outlet diffuser 11 and flows directly through an outlet channel 13 again from this bypassing the exhaust gas heat exchanger 1 out. According to 3b is at least one of those in the entry and exit diffusers 11 arranged two butterfly valves 14th , 15th opened so that according to 3b the exhaust A. through the cassettes 3 flows and in the end cap 9 is deflected by 180 ° to go through the return channel 10 then the outflow channel 13 in the inlet and outlet diffuser 11 to be fed.

Between the cassettes 3 are flow channels 28 for the cooling medium K formed so that this between the cassettes 3 and the shell 2 can flow. The exhaust A. flows through the cassettes 3 . Furthermore is on the case 2 still an exit 16 formed so that the cooling medium K can be discharged.

In 2 shown in an exploded view is a cassette according to the invention 3 . This is made up of two half-shells 29 , being between the half-shells 29 each lamellar plates 4th , 5 are arranged. The lamellar sheet is on the right-hand side in relation to the image plane 4th formed in the longitudinal direction as a corrugated sheet. On the one hand, because of this geometric design, and on the other hand, because of a larger area, a greater heat exchanger performance is provided here than in the case of the lamellar plates referred to the plane of the drawing 5 on the left. This runs in a straight line in the longitudinal direction and thus has a smaller area, so that there is a lower heat exchanger performance here. The lamellar plates are in place during assembly 4th , 5 at least directly in the separation area 18th to each other.

There is also a bracket as a guide element 17th provided with which the lamellar plates 4th , 5 are bracketed to each other. The guiding element 17th however, its primary function is to separate the exhaust gas flow, especially in the entrance area. This is therefore arranged at the end in the flow direction on the lamellar plates or upstream of the lamellar plates. The lamellar plates are in the installed state 4th , 5 directly parallel to each other. Above and below the separation area 18th the lamellar sheets 4th , 5 are spacer bosses in the cassettes 29 designed in the form of outwardly directed features 19th . The case 2 has inwardly directed impressions in this area 20th . This results in a higher contact pressure from the cassette during a manufacturing process 3 on the lamellar plate 4th , 5 exercised. The lamellar sheets 4th , 5 are thus in the separation area 18th form-fitting to each other and to the inner circumferential surfaces of the cassettes 3 pressed and, as a result of the melting solder, cohesively with the cassettes 3 joined so that in the separation area 18th the lamellar sheets 4th , 5 close to the cassettes 3 are welded and thus the two work areas 6th , 7th are separated from each other gas-tight.

4th shows a perspective partial sectional view. Left and right of the exhaust gas heat exchanger 1 are actuators 21st outside the exhaust gas heat exchanger 1 arranged. Every actor 21st can be a respective valve 14th , 15th not shown in detail over the pin 32 head for. The flaps 14th , 15th are both on one axis 22nd , however, are on separate axle shafts 23 , 24 stored. At a middle bearing point not shown in detail 25th they are therefore within the inlet and outlet diffuser 11 arranged. It only needs the outer bearing points 26th , 27 also towards the environment U be sealed.

By operating one of the two adjustable flaps 14th , 15th can then the respective work area 6th , 7th with the lamellar plates arranged therein 4th , 5 flowed through or can exhaust gas A. in the respective work area 6th , 7th be directed.

List of reference symbols

1 -

Exhaust gas heat exchanger

2 -

Shell

3 -

cassette

4 -

Lamellar sheet

5 -

Lamellar sheet

6 -

first work area

7 -

second work area

8th -

entrance

9 -

End cap

10 -

Return channel

11 -

Entry and exit diffuser

12 -

Inflow duct

13 -

Outlet duct

14 -

Control flap

15 -

Control flap

16 -

exit

17 -

Bracket

18 -

Separation area

19 -

Expression

20 -

Imprint

21 -

Actuator

22 -

axis

23 -

Axle shaft closed 15th

24 -

Axle shaft closed 14th

25 -

Depository

26 -

outer bearing point

27 -

outer bearing point

28 -

Flow channel

29 -

Half-shells

30 -

Inlet diffuser

31 -

Exit diffuser

32 -

Cones

A -

Exhaust gas

U -

Surroundings

A6 -

Cross section too 6th

A7 -

Cross section too 7th

A10 -

Cross section too 10

K -

Cooling medium

Claims (9)

Exhaust gas heat exchanger (1), having an outer shell (2), with at least two different working areas (6, 7) being arranged parallel next to one another in a lamellar cooler, in plate construction to form an exhaust gas flow channel, in each case at one end a connection for the exhaust gas (A) is arranged on the casing and an inlet (8) and an outlet (16) for a cooling medium (K) are provided in the casing (2), such that the cooling medium (K) is between the plates of the lamellar cooler and the casing (2) flows, the two working areas (6, 7) being formed in a cassette (3), characterized by two lamellar plates (4, 5) arranged next to one another in the cassette (3) and different from one another I net that in a U-shaped flow through exhaust gas heat exchanger (1) at one end a common inlet and outlet diffuser (11) is arranged and at the other end of the shell (2) an end cap (9) is arranged, the one through the lamellar cooler diverts the exhaust gas flow flowing through the lamellar cooler and that a return duct (10) arranged parallel to the lamellar cooler is formed, the end cap (9) fluidically combining the two working areas (6, 7) and the exhaust gas flow into the return duct (10) and back through it the inlet and outlet diffuser (11) leads. Exhaust heat exchanger after Claim 1 , characterized in that the exhaust gas (A) flows through it in a U-shape and / or that in the Case (2) several cassettes (3) are arranged in parallel. Exhaust gas heat exchanger after one of the Claims 1 or 2 , characterized in that the two lamellar plates (4, 5) are made of different materials and / or that the two lamellar plates (4, 5) have a different shape and / or that the two lamellar plates (4, 5) are different from one another have a large surface. Exhaust gas heat exchanger after one of the Claims 1 to 3 , I denote that in the inlet and outlet diffuser (11) two adjustable flaps (14, 15) are pivotably arranged on an axis (22) next to each other, the adjustable flaps (14, 15) being adjustable separately from each other. Exhaust heat exchanger after Claim 4 , characterized in that the adjustable flaps (14, 15) are each pivotably mounted via a separate axle shaft (23, 24), with both axle shafts (23, 24) lying on an axle (22). Exhaust heat exchanger after Claim 5 , characterized in that both axle shafts (23, 24) have a common internal bearing (25) located in the exhaust gas flow channel (13). Exhaust gas heat exchanger after one of the Claims 1 to 6th , characterized in that the lamellar cooler is formed from several cassettes (3) arranged one above the other with integrated lamellar plates (4, 5) and the two working areas (6, 7) have different heat exchanger capacities. Exhaust gas heat exchanger after one of the Claims 1 to 7th , characterized in that the lamellar plates (4, 5) each have a guide element and / or are soldered at their contact points at least in the flow direction, in particular the lamellar plates (4, 5) are at least partially soldered to the inner surface of the cassette (3) . Exhaust gas heat exchanger after one of the Claims 1 to 8th , characterized by the fact that the inlet and outlet diffuser (11) has an inflow channel (12) for supplying the exhaust gas (A) and an outflow channel (13) for discharging the exhaust gas (A), with the regulating flaps (14, 15 ) the exhaust gas flow is optionally routed into one or both lamellar coolers and / or is at least partially routed from the inflow channel (12) directly into the outflow channel (13).

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