EP2972011A1

EP2972011A1 - Heat exchanger

Info

Publication number: EP2972011A1
Application number: EP14709663.0A
Authority: EP
Inventors: Klaus Irmler; Frank von Lützau; Peter Geskes; Arthur Strehlau
Original assignee: Mahle International GmbH
Current assignee: Mahle International GmbH
Priority date: 2013-03-12
Filing date: 2014-03-12
Publication date: 2016-01-20
Also published as: CN205227939U; DE102013204295A1; WO2014140131A1

Abstract

The invention relates to a heat exchanger, comprising at least one first flow channel for conducting a first medium, comprising at least one second flow channel for conducting a second medium, in particular in order to evaporate a liquid working medium as the first medium, and comprising a fluid, such as exhaust gas or charge air, as the second medium, for transmitting heat from the second medium to the first medium. The at least one first flow channel has a first circumferential delimiting wall, and the at least one second flow channel has a second circumferential delimiting wall. The first and the second flow channels are arranged adjacently to each other such that a double wall is formed between the flow-conducting channels by mean of the first and the second delimiting wall.

Description

Heat exchanger description

Technical area

The invention relates to a heat exchanger, in particular

Exhaust gas heat exchanger and / or an exhaust gas evaporator.

State of the art

Exhaust gas heat recovery is a topic of increasing interest in increasing the efficiency of internal combustion engines. One possibility is the application of a so-called Rankine process. Exhaust gas evaporators are used for this process. These vaporize a fluid by utilizing the high temperature of the flowing exhaust gas. In exhaust gas heat exchangers and also in exhaust gas evaporators, for example from Rankin cycle applications, a first fluid, such as a coolant, ethanol, etc., is heated by heat transfer from the hot exhaust gas and evaporated, for example. The resulting superheated steam is subsequently expanded in an expander, the resulting mechanical power is thereby returned to the drive motor, This fuel economy reductions of about 5 to 7% can be achieved.

In an exhaust gas recirculation is also at least a portion of the exhaust gas returned to the drive motor again.

In Rankine cycle applications, also Waste Heat Recovery (WHR) applications, different heat sources are used and coupled with each other. These include, for example, exhaust gas recirculation cooler, intercooler and / or main exhaust gas cooler in the exhaust system, etc. In organic working media leaks in the components are particularly unfavorable, which would cause a feeding of the medium to be evaporated in the combustion chamber of the engine. Such components are in particular the exhaust gas evaporator and the indirect intercooler. The exhaust gas evaporator cools the hot exhaust gas, which is diverted in the fluid flow to the engine to supply this cooled exhaust gas back to the engine, thereby lowering nitrogen oxide emissions. The indirect intercooler cools the compressed combustion air, which is then routed to the engine.

When one of the two components leaks, an undesirable amount of the working fluid exits the Rankine cycle and is supplied to the internal combustion engine. In the case of ethanol as a working medium, for example, premature ignition may occur in front of the inlet. What is unfavorable for the combustion engine. In the case of refrigerant as the working medium, an undesired reaction with undesired reaction products can take place.

The emergence of a leak can never be completely ruled out due to the high thermal and mechanical stress of the heat exchanger. In evaporators, the strength is essential because the working medium are usually operated at working pressures above ambient pressure and thus the evaporator with its structure must absorb the pressure forces occurring. Also, thermal stresses due to temperature differences between the two working media must be able to be included.

DE 10 12010 031 561 A1 discloses an exhaust gas evaporator in which adjacent channels for the exhaust gas and for the working medium are separated by a single partition wall and around the duct for the working fluid is guided around a leakage channel which leaks into the surroundings in places. In case of leakage to the edge of the working fluid is guided into the leakage channel and from there into the environment and it does not enter the exhaust duct and thus not in the internal combustion engine collapses, however, the only partition, for example, in a leakage in this partition, so still passes Working medium in the exhaust tract.

Presentation of the invention, object, solution, advantages

It is the object of the invention to provide a heat exchanger which at least largely prevents leakage even in the event that the working medium can enter the internal combustion engine.

The object is achieved with the features of claim 1. One embodiment relates to a heat exchanger with at least one first flow channel for the passage of a first medium and with at least one second flow channel for passing a second medium, in particular for vaporizing a liquid working medium as the first medium and with a fluid, such as exhaust gas or charge air, as the second medium for transmitting heat from the second medium to the first medium, wherein the at least one first flow channel has a circumferential first boundary wall and the at least one second boundary wall Flow channel has a circumferential second boundary wall, wherein the first and the second flow channels are arranged adjacent to each other such that a double wall between the flow-guiding channels is formed by the first and the second boundary wall. Due to the double-walled design of the partition between two flow channels or between the flow paths, a discharge of a fluid can take place, if this should leak through a leak. It is particularly expedient if the two boundary walls forming a double wall lie flat against one another. As a result, a better heat transfer between the two adjacent flow channels is achieved. It is also expedient if the two boundary walls forming a double wall are connected to one another only selectively or in regions but not over the entire surface, as are preferably soldered. As a result, a mechanically strong connection is formed _» whereby nevertheless a channel remains in order to be able to discharge an exiting fluid,

It is also advantageous if between the two boundary walls forming a double wall a profiled element, such as sheet metal, is provided, which is in thermal contact with the two boundary walls. Thus, a good thermal Koniakt can be achieved with the simultaneous formation of a leakage channel.

Furthermore is. it is expedient if a flow channel is formed by two discs, each having at least one upstanding edge and touch at the edges and are sealed together and form a channel hiss form. As a result, a simplified production can be carried out It is also expedient if a flow channel is formed by means of a frame and two covering disks arranged thereon and sealed. So also a simple design can be achieved. It is also advantageous if at least the flow medium leading to the working medium, a leakage channel is assigned as a fluid-conducting connection, which is open to the environment. As a result, in addition to the removal of leaks between the walls of the double-walled partition wall, a leakage flow to the environment can also be dissipated at the end regions or around the fluid channel.

It is particularly advantageous if the leakage channel is formed on an edge region and / or end region of the flow channel. Thus, at an end region where the flow channel is completed, a leakage channel can be provided cheaply. This is advantageously provided where the flow channel is completed. Thus, in case of leakage, the escaping fluid can be removed.

It is also expedient if the leakage channel is arranged on a collecting region of a plurality of flow channels. Thus, in the event of a leak in the region of a collector or of a fluid supply or a fluid discharge, a fluid can be removed from a leak before it enters the flow channel for the second fluid, such as exhaust gas or charge air. It is also expedient if the flow channel is limited by an insert or frame and the leakage channel is formed by a recess in the insert or the frame. As a result, the leakage channel is simultaneously formed by the completion of the flow channel. It is particularly advantageous if the recess is a groove, which occupies the height of the insert or of the frame or assumes a height _"which is less than the height of the insert or of the frame. This can be incorporated in the manufacture of the frame or a closure element or an insert of the leakage channel with, such as by embossing or punching. It is also advantageous if the recess is formed by two adjacently arranged inserts or frame elements.

Further advantageous embodiments are described by the following description of the figures and by the subclaims.

Brief description of the drawings

The invention will be explained in more detail on the basis of at least one embodiment with reference to the drawings. These show:

1 is a schematic representation of flow channels »

2 is a schematic representation of flow channels,

Fig. 3 is a view of a package of flow channels of a

Heat exchanger, and

4 is a view of a package of flow channels of a

Heat exchanger.

Preferred embodiment of the invention

1 shows a schematic representation of three flow channels 2, 3, 4 of a heat exchanger according to the invention 1. Each flow channel is shown in section and has a circumferential wall 5, 6, 7, such as boundary wall, which defines the flow path for the fluid. The channels are advantageously designed as a flat tube. As can be seen in Figure 1, the flow channels 2, 3, 4 stacked on each other and the respective partition wall 8, 9 between two flow channels 2, 3 or 3, 4 is double-walled, because two adjacent walls 5, 6 and 6, 7 are arranged adjacent to each other.

In this case, the fluid channels 2, 4 are provided for exhaust gas or charge air and the fluid channel 3 for the working fluid, this fluid channel 3 further has a leakage channel 10, which is defined by a double wall provided 1 1, 12.

Thus, a double-walled design of the partition wall 8, 9 is achieved, so that the working fluid as the first fluid and the exhaust gas or charge air as the second fluid separately in a respective Strömungskana! 2, 3, 4 is performed. In the design of the fluid channel for the working medium, the design is preferably realized by a double disc, between which the first fluid is passed in introduced channels. These channels can be embossed in the discs. The two discs are soldered together.

Alternatively, the flow channel can also be formed from two cover disks, a peripheral frame and optionally a turbulence insert.

At the fluid channel for the first fluid, an inlet opening and an outlet opening for the first fluid is provided as the working medium. The second fluid, such as exhaust gas or the charge air, is preferably routed in tubes, which may also contain imprints as winglets or ribs. Alternatively, a flow channel can also be formed here, which is formed from two cover disks, a frame and optionally a turbulence insert. The flow channels, for example as double discs and / or tubes and / or frames with cover plates are alternately stacked and soldered together. The gas-carrying channels of the second flow channels are sealed at their end faces in each case via an insert or a frame, such as tube sheet, to which a diffuser can be conceived.

The supply and discharge of the first fluid, the working medium, via a distribution and collection channel, which is not visible in Figure 1. This channel is advantageously located on a side region of the stack of the heat exchanger, which lies outside the flow channels, such as the tubes formed. In one embodiment, these distribution and collection channels are arranged centrally of the longitudinal extension of the heat exchanger. In other embodiments, the distribution and collection channels can also be arranged at a different location of the heat exchanger.

The double wall as a partition is not completely soldered together or otherwise connected, so that a channel remains as a leakage channel between the two walls.

Now, if a connection between the double discs or the double wall or a double disc leaking, the fluid exits to the outside and not to the gas.

In the event of a leakage in the inlet and outlet regions 13, 14 of the second fluid, such as the exhaust gas or the charge air, a leakage channel 10 is provided on the side of the first fluid.

To avoid the mixing of an exiting first fluid with the second fluid of the frame 1 1. 12 at the front edge, so on Entry area 13 and also at the gas outlet side 14 designed so that a leakage channel 10 is formed.

Optionally, the leakage channel can be connected via a spacer with other leakage channels. As a result, a common discharge can be formed, as is advantageous centrally on the upper side of the heat exchanger.

The leakage channel can be formed by a double web 1 1, 12 or frame, so that between the webs 11, 12, the first or the second fluid can be removed.

Alternatively, in the case of a failure of the base materials of the cover disks, a leakage from the working medium side to the charge air or exhaust side, ie from the first fluid to the second fluid, can be avoided. It is advantageous if a fluid channel 2, 3, 4 of separate cover plates 5, 6, 7 is constructed with interposed frame. These channels 2, 3, 4 of both adjacent cover plates 5, 6, 7 are not soldered surface to each other but soldered only at a few points for fixing and in the inlet and outlet areas of the charge air / exhaust gas. This ensures that in the event of failure of the cover disks 5, 6, 7 itself, the fluid is first discharged to the environment in each case and leakage can be detected before there is leakage into the respective other flow channel.

This also ensures that adjacent pairs of disks are in good thermal contact in order to achieve sufficient power or heat transfer can.

Alternatively, instead of purely thermal contact due to the contact of the walls without soldering of the two adjacent Cover discs of the respective fluid, the thermal contact can be achieved by inserting a profiled sheet 20, see Figure 2.

This profiled sheet 20 may be formed similarly to a turbulence or corrugated fin having a very small height. For example, a height of 0.5 mm can be achieved with a material thickness of 0.1 mm.

The profiled sheet 20 may be on the top partially or selectively connected to a cover plate of the first fluid channel and / or the second flow channel, as soldered.

Conveniently, the partial or punctual connection of the profiled sheet 20 with both the one and with the other cover, between which the profiled sheet is arranged.

This ensures a good thermal contact in order to achieve sufficient power and at the same time this results in a leakage channel to the environment.

3 shows schematically a stack 30 of flow channels, wherein an upper cover plate is not shown. It can be seen in the end region 32 of the first flow channel 33, a leakage channel 31, which extends over the width of the flow channels along. In the middle of a constriction 34 of the leakage channel 31 is provided, which divides the channel.

In order to ensure that leakage does not occur in the working medium-side collection or distribution channels 41 in the charge air or exhaust gas channel, the connection elements 42 between the flow channels 40 also have leakage channels 43 which lead into the environment.

Claims

Patent claims

1 . Heat exchanger with at least one first flow channel for passing through a first medium and with at least one second flow channel for passing through a second medium, in particular for evaporating a liquid working medium as the first medium and with a fluid, such as exhaust gas or charge air, as the second medium, for the transmission of Heat from the second medium to the first medium, wherein the at least one first flow channel has a circumferential first boundary wall and the at least one second flow channel has a circumferential second boundary wall, the first and the second

Flow channels are arranged adjacent to one another in such a way that a double wall is formed between the flow-carrying channels by the first and second boundary walls.

2. Heat exchanger according to claim 1, characterized in that the two boundary walls forming a double wall lie flat against one another.

3. Heat exchanger according to claim 1 or 2, characterized in that the two boundary walls forming a double wall are only connected to one another at points or in areas but not over the entire surface, as is preferably soldered.

4 Heat exchanger according to claim 1 or 2, characterized in that a flow channel is formed by two disks, each of which has at least one raised edge and is located on the edges touch and are sealed together and form a channel,

5. Heat exchanger according to one of the preceding claims, characterized in that a profiled element, such as sheet metal, is provided between the two boundary walls forming a double wall, which is in thermal contact with the two boundary walls,

6. Heat exchanger according to claim 1 or 2, characterized in that a flow channel is formed by means of a frame and two cover disks arranged thereon and connected in a sealed manner,

7. Heat exchanger according to at least one of the preceding claims, characterized in that at least the fluid channel carrying the working medium is assigned a leakage channel as a fluid-conducting connection, which is open to the environment.

8. Heat exchanger according to at least one of the preceding claims, characterized in that the leakage channel is formed on an edge region and / or end region of the flow channel.

9, heat exchanger according to at least one of the preceding claims, characterized in that the leakage channel is arranged at a collecting area of a plurality of flow channels.

10. Heat exchanger according to at least one of the preceding claims, characterized in that the flow channel through is limited to an insert or frame and the leakage channel is formed by a recess in the insert or frame.

1 1 . Heat exchanger according to claim 10, characterized in that the recess is a groove which occupies the height of the insert or the frame or occupies a height that is less than the height of the insert or the frame,

12. Heat exchanger according to claim 10 or 1 1, characterized in that the recess is formed by two adjacently arranged inserts or frame elements.