DE102009054988A1 - heat exchangers - Google Patents

Abstract

A heat exchanger (1), which is used in particular as an exhaust gas heat exchanger, comprises coolant channels (8, 9) through which a water-based coolant can be guided, and gas channels (10-12) which are thermally connected to the coolant channels (8, 9) stand and through which a gas to be cooled can be passed. Here, the coolant channels (8, 9) have elevations (19-26) on respective channel tops (16, 18) which are at the top with respect to an installation position.

Description

State of the art

The invention relates to a heat exchanger, in particular an exhaust gas heat exchanger for motor vehicle applications. Specifically, the invention relates to the field of heat exchangers for a steam power process.

Cooling water admixtures which reduce the freezing point of the coolant serving as water can be used in heat exchangers of motor vehicle cooling systems. Freezing of the coolant in the park state at low temperatures is thus prevented. On the other hand, suitable for a steam power process coolant may have a freezing point, which is above the ambient temperature of the motor vehicle. Especially when operating with water, due to the density anomaly, the freezing must be taken into account in the design, as due to the expansion of the freezing water mechanical forces act on the heat exchanger. In addition, while the vehicle is at a standstill, collect all the system's water from the connected components and piping in the heat exchanger, as only here is a heat source available to help liquefy frozen water. For cost reasons and space limitations, heat exchangers for vehicles are usually designed with a large length in relation to the cross section, wherein a horizontal mounting position is also provided.

Advantages of the invention

The heat exchanger according to the invention with the features of claim 1 has the advantage that the working fluid is distributed in an idle state, especially at a standstill of a vehicle in the channel of the heat exchanger and in a possible freezing of the working fluid damage to the heat exchanger is prevented. Specifically, the working fluid may be distributed in the channel so as to uniformly form air cushions in the channel that allow expansion of the freezing working fluid, preventing damage from the outset.

The measures listed in the dependent claims advantageous refinements of the claim 1 heat exchanger are possible.

It is advantageous that the heat exchanger, which is configured in particular as an exhaust gas heat exchanger, at least one coolant channel, through which a water-based coolant can be guided, and at least one gas channel, which is in thermal communication with the coolant channel and through which a gas is feasible, wherein the coolant channel has at least one elevation on at least one upper side of the channel lying above an installation position. As a result, a low-cost and environmentally friendly working fluid, namely a water-based coolant, can be used to cool exhaust gases or other gases.

As a result of the elevations provided on the upper side of the channel, it is advantageously possible to form air cushions in the return flow of water into the heat exchanger, which provide a space between the mirror of the coolant, in particular the water level, and the upper side of the channel. The freezing coolant can spread into the gas space, whereby the mechanical load of the heat exchanger is reduced. As a result, the coolant can be collected at rest in an advantageous manner in the heat exchanger.

It is advantageous that the coolant channel has an elevation at a bottom side of the channel lying below the installation position, which elevation is assigned to the elevation provided on the channel top side. During operation of the heat exchanger, the coolant channel is flowed through by the coolant. In this case, gases provided in the coolant channel are preferably also transported, so that air cushions which have an unfavorable effect on the thermal connection of the coolant with the exhaust gases are avoided during operation. Here, the surveys formed on the channel top side can form a certain flow resistance. A pressure loss along the heat exchanger promotes a uniform distribution of the fluid on the superimposed channels, since the pressure difference due to the geodetic height difference and thus the weight force is less significant. However, a relatively high configuration of the elevation on the upper side of the channel favors the formation of a flow shadow, which inhibits wetting at high flow velocities, especially in a two-phase region. Therefore, it is advantageous that elevations are provided on the lower side of the channel to produce an optionally desired pressure loss instead of a further enlargement of the elevation on the upper side of the channel. Thus, the wetting of the wall of the coolant channel can be supported by the gravitational forces.

Further, it is advantageous that the survey is designed by embossing and / or that the survey is designed as a rib-shaped survey. As a result, the survey can be easily made. In addition, there is an advantageous geometry for the formation of air bubbles at rest.

Further, it is advantageous that a plurality of adjacent elevations are provided on the upper side of the channel, between which the formation of gas bubbles is made possible in the idle state. In this case, it is further advantageous that a ratio of a distance of the elevations provided on the channel top side to a height of the elevation is approximately equal to ten. In this way, a certain parking gradient of the motor vehicle can be taken into account. For example, a parking gradient of the vehicle can be a maximum of 10% and thus about 5.7 °. At such a pitch angle of 5.7 °, at the ratio of the distance of the projections provided on the channel top to the height of the elevation of about ten, an air cushion may be formed which extends at least substantially over the entire channel top. Here, for example, an air cushion can be created, which occupies at least 8% of the channel volume. As a result, the expansion of the water in the transition from the liquid to the solid state of about 8% can be compensated. However, even a smaller air cushion may suffice, since the ice volume is partially adapted to the geometry of the coolant channel. Pressure increases in the gas cushion are negligible here.

Advantageously, a ratio of a channel height to a height of the survey is not less than 3.5. In this way, a sufficient air cushion can be ensured even with a rest position of the vehicle with a parking slope and at the same time during operation, the formation of air cushions, which prevent wetting of the wall, can be avoided. As a result, in particular strong local heating of the wall of the coolant channel can be prevented, which can lead to local destruction. Specifically, at high flow velocities a sufficient wetting of the wall can be ensured if the height of the elevations is optimized on the channel top, that is not too large. The generation of a pressure loss can be achieved in this case by elevations on the lower side of the channel in an advantageous manner, wherein the wetting of the wall is supported by the gravitational forces.

It is also advantageous that a plurality of plates are provided, that a plurality of coolant channels and a plurality of gas channels are provided, which are separated by the plates, and that the coolant channels are connected to each other via connecting pieces. As a result, a compact construction of the heat exchanger is possible. Specifically, it is advantageous that the plates are arranged in the installed position at least approximately horizontally and that the elevations are designed on the plates. As a result, a compact heat exchanger can be produced with an optimized number of components.

However, it is also advantageous that the plates are arranged in the installed position at least approximately vertically and that intermediate floors are provided, on which the elevations are designed. Here, it is also advantageous that the intermediate floors are arranged offset from one another, so that is designed by the intermediate floors a serpentine ausgestalteter coolant channel between the plates, and that at least a portion of the intermediate floors at their free ends in each case has a survey on the channel top. As a result, air cushions can advantageously be formed in the serpentine coolant channel when the heat exchanger is in an idle state.

Brief description of the drawings

Preferred embodiments of the invention are explained in more detail in the following description with reference to the accompanying drawings, in which corresponding elements are provided with identical reference numerals. It shows:

1 a first embodiment of a heat exchanger of the invention in a partial, schematic sectional view;

2 the in 1 designated II section of the heat exchanger according to the first embodiment in a tilted rest position;

3 the in 1 labeled II section of the heat exchanger according to a second embodiment of the invention and

4 A third embodiment of a heat exchanger of the invention in a schematic sectional view.

Embodiments of the invention

1 shows a first embodiment of a heat exchanger 1 of the invention in a schematic, excerpted sectional view. The heat exchanger 1 can be used in particular for motor vehicles. Special is the heat exchanger 1 as exhaust gas heat exchanger 1 designed. Here, the heat exchanger 1 be used in a steam power process of a motor vehicle. In this case, through the channel geometry a freezer-proof heat exchanger 1 with uniform single channel loading for use in a steam power process. The heat exchanger according to the invention 1 However, it is also suitable for other applications.

The heat exchanger 1 has several plates 2 . 3 . 4 . 5 on. For the heat exchanger 1 is an installation position specified in the 1 through an axis 6 and one direction 7 is illustrated. Here, the heat exchanger 1 mounted so that the axle 6 is oriented vertically and the direction 7 pointing upwards.

In this embodiment, the plates 2 to 5 horizontally lying with respect to the axis 6 and thus also arranged with respect to the predetermined installation position. Here are the plates 2 to 5 along the axis 6 spaced apart. Between the plates 2 . 3 is a channel 8th educated. Further, between the plates 4 . 5 another channel 9 educated. Between the plates 3 . 4 is a gas channel 10 educated. Also, along the axis 6 preferably further plates arranged, so that more channels and further gas channels are provided. In particular, it borders on the plate 2 another gas channel 11 on and to the plate 5 is adjacent to another gas channel 12 at. The conclusion form preferably channels, so that the gas channels 10 . 11 . 12 inside the heat exchanger 1 are provided and from all sides of channels 8th . 9 are surrounded. These are also connectors 13 provided the individual channels 8th . 9 connect with each other. The connectors 13 also serve to limit the gas channels 10 . 11 . 12 , In operation, the channels become 8th . 9 and the connector 13 flows through by a working fluid. This is the entire interior of the channels 8th . 9 and the connector 13 of the heat exchanger 1 filled with the working fluid, causing a heat exchange with the plates 2 to 5 of the heat exchanger 1 and thus with the heat exchanger 1 led exhaust gases is achieved.

The working fluid may be liquid, two-phase or gaseous. This results in the requirement of adequate wetting especially of the plates 2 to 5 for the heat exchange. However, the working fluid may also be present in a single phase in the relevant work area.

Specifically, the working fluid can serve as a coolant. The channels 8th . 9 then serve as coolant channels 8th . 9 , The coolant flowing through the coolant channels 8th . 9 guided, based in this embodiment on water. This can serve as a coolant water. Additives, in particular an anticorrosion agent, can also be added to this water.

In operation of the heat exchanger 1 the coolant flows 14 through the coolant channels 8th . 9 and the connector 13 , Between the coolant channels 8th . 9 and the gas channels 10 to 12 there is a thermal connection. In this embodiment, this thermal connection is via the plates 2 to 5 , That through the gas channels 10 to 12 flowing hot gas thus warms that through the coolant channels 8th . 9 flowing coolant 14 , In this way there is a heat exchange between the hot exhaust gases and the coolant 14 allows.

The coolant channel 8th has a channel bottom 15 and a channel top 16 on. Accordingly, the coolant channel also has 9 a channel bottom 17 and a channel top 18 on. In this embodiment, the channel bottom is 15 at the plate 3 educated. The channel top 16 is at the plate 2 educated. Further, the channel bottom is 17 at the plate 5 formed while the channel top 18 at the plate 4 is trained. In the area of the channel top 16 of the coolant channel 8th are several surveys 19 . 20 . 21 . 22 educated. Furthermore, also on the channel top 18 of the coolant channel 9 surveys 23 . 24 . 25 . 26 educated. In this embodiment, the surveys 19 to 22 at the plate 2 formed in the form of ribs. The surveys 23 to 26 are at the plate 4 formed in the form of ribs. The surveys 19 to 26 are embossed. This results in corresponding depressions by embossing on the plates 2 . 4 in the field of gas channels 11 . 10 , In the installation position are the channel tops 16 . 18 with respect to the respective coolant channel 8th . 9 above. So these are the surveys 19 to 26 around elevated elevations 19 to 26 , Through the surveys 19 to 22 on the coolant channel 8th Form at the return flow of the coolant 14 bubble 27 . 28 . 29 . 30 out. Accordingly, they form on the coolant channel 9 bubble 31 . 32 . 33 . 34 out. Through the air cushion 27 to 34 is a space between a water level 35 of the coolant 14 and the channel top 15 or between a water level 36 and the channel top 18 educated. If that is in the 1 shown coolant freezes and expands, then by the air cushion 27 to 34 allows for expansion, causing damage to the plates 2 to 5 is prevented. Thus, the mechanical stress of the heat exchanger 1 be minimized.

The surveys 19 to 26 offer in operation an increased flow resistance, which leads to a reduced influence of the geodetic pressure difference due to the pressure difference between the superposed coolant channels 8th . 9 leads. This results in a uniform distribution of the coolant to the individual coolant channels 8th . 9 while driving supported. By surveys 52 . 53 at the ends of the coolant channels 8th . 9 In addition, a backflow of the upper channels into the underlying can be additionally prevented.

Thus, a compensation of the volume increase of the water-based coolant 14 when freezing without mechanical Load on the heat exchanger 1 possible. Furthermore, an increased flow resistance allows a more even distribution of the coolant 14 in the superimposed coolant channels 8th . 9 while driving. In addition, surveys prevent 52 . 53 at the ends of the coolant channels 8th . 9 a reflux of the coolant 14 from the upper coolant channels to the lower ones.

The surveys 19 to 26 extend over the entire width of the plates 2 . 4 of the heat exchanger 1 , As a result, between each adjacent surveys, such as the surveys 19 . 20 , in the vehicle standstill an air cushion, such as the air cushion 28 , locked in. This air cushion 28 can increase the volume of the coolant 14 partially displaced. A height 40 the surveys 19 to 26 is designed so that even with maximum inclination of the vehicle, a sufficiently large gas space is available to compensate for the increase in volume of the freezing fluid, as well as based on the 2 is illustrated.

2 shows the in 1 with II designated section of the heat exchanger 1 in a schematic sectional view. In this embodiment, the heat exchanger according to the in the 1 illustrated starting position installed in a motor vehicle. Thus, the axis is located 6 usually in a vertical orientation. However, the motor vehicle can be turned off at an angle. This results in a certain parking slope. For example, the axis 6 with respect to a vertical axis 41 at an angle 42 tilted by 5,7 °. This corresponds to a parking slope of the vehicle of 10%. Such an angle 42 can be used as the maximum parking gradient to determine the design of the heat exchanger 1 serve. However, it is also possible a different default. Due to the sloping parking position is the coolant 14 at rest in several stages in the coolant channel 9 , Here is this graduated by the surveys 24 . 25 at the plate 4 achieved, which is a drainage of the coolant 14 prevent it from trapping the air bubbles 32 . 33 . 34 comes. Thus, even with an oblique shutdown of the vehicle through the air cushion 32 to 34 formed space to the extent of an optionally freezing coolant 14 without damaging the plates 4 . 5 to enable. The pressure increase in the air bubbles 32 to 34 is negligible in this regard.

A distance 43 the surveys 24 . 25 at the plate 4 is set so that in relation to the height 40 the survey 24 a sufficient air cushion 33 that results preferably from the survey 24 until the survey 25 extends. This is a ratio of the distance 43 the at the top of the canal 18 provided surveys 24 . 25 to the height 40 the survey 24 about ten. By this definition is also at a relatively large angle 42 a sufficient air cushion 33 educated. This determination can be for all surveys 19 to 26 at the channel tops 16 . 18 the coolant channels 8th . 9 be predetermined. In addition, a ratio of a channel height 44 to the height 40 the surveys 24 . 25 not less than 3.5 predetermined. This prevents air bubbles behind the elevations during operation 24 . 25 remain.

The height 40 can be predetermined by the design of the imprints. About the height 40 In this case, the throttle effect is determined, whereby the flow pressure loss of the coolant channels 8th . 9 influences and thus a uniform distribution of the coolant 14 on the coolant channels 8th . 9 can be supported.

It should be noted that an inclination of the vehicle is also possible laterally. For example, a vehicle may be standing sideways on a curb. This also leads to an inclination of the heat exchanger 1 , It can then surveys are also designed by longitudinal embossing along the coolant channels 8th . 9 run. Thus, even with an inclination in the transverse direction, the design of air cushions 27 to 34 enabled with a correspondingly large gas space. The surveys 19 to 22 at the channel top 16 of the coolant channel 8th can here form a grid-like or honeycomb-like structure. Accordingly, the surveys 23 to 26 on the coolant channel 9 be designed.

3 shows the in 1 with II designated section of the heat exchanger 1 according to a second embodiment. In this embodiment, the heat exchanger is located 1 in an orientation in which the axis 6 is oriented vertically and the direction 7 pointing upwards. At high required pressure losses and correspondingly large Kanalversperrung the wetting of the plate 4 at the channel top 18 especially at high flow velocities are not so severely limited, in this embodiment, at the bottom of the channel 17 further surveys 50 . 51 intended. The surveys 50 . 51 are here according to the surveys 24 . 25 embossed. This allows the height 40 the surveys 24 . 25 in the area of the channel top 18 be optimized. An additional throttle effect may be due to the elevations 50 . 51 be achieved.

Thus, advantageous embodiments of the coolant channels 8th . 9 possible. This can also include sections 52 . 53 the plates 4 . 5 in the area of the connector 13 be guided upward to prevent the coolant in vehicle standstill 14 from the upper channels via the designed as a supply or return passage connector 13 into underlying channels.

4 shows a heat exchanger 1 in a schematic sectional view according to a third embodiment. In this embodiment, vertically standing plates 2 provided, of which the plate 2 is shown. Here are intermediate floors between the plates 60 to 65 arranged, which are offset from one another that a serpentine ausgestalteter coolant channel 8th is formed. Here is also a bottom plate 66 and a ceiling tile 67 intended. Furthermore, side plates 68 . 69 intended. The individual shelves 60 to 65 have free ends 70 to 75 on. At the free ends 70 to 75 are surveys 76 to 81 educated. Through these surveys 76 to 81 The formation of air cushions is possible, of which in the 4 the air cushion 82 is marked. Here are more surveys 83 to 87 at the intermediate floor 65 be provided to the air cushion 82 in parts 88 to 92 to divide. By dividing the air cushion 82 in the parts 88 to 92 is at a tilt of the heat exchanger 1 allows the formation of multiple air bubbles, creating a larger total volume of the air cushion 82 achieved. This corresponds to the basis of the 2 described principle.

Through the air cushion 82 becomes freezing of the coolant 14 created a certain equalization space, causing damage to the heat exchanger 1 is prevented. The surveys 76 to 81 on the shelves 60 to 65 are designed in the form of beads. This can also also on the ceiling plate 67 at least one survey 93 be designed. The heat exchanger 1 of the third embodiment thus enables a standing installation. Here, a serpentine or meandering structure of the coolant channel 8th and other coolant channels can be achieved.

The invention is not limited to the described embodiments.

Claims (10)

Heat exchanger ( 1 ), in particular exhaust gas heat exchanger, with at least one channel ( 8th . 9 ), through which a working fluid can be guided, and at least one gas channel ( 10 - 12 ) connected to the channel ( 8th . 9 ) is in thermal communication and through which a gas is feasible, wherein the channel ( 8th . 9 ) on at least one with respect to a mounting position overhead channel top ( 16 . 18 ) at least one survey ( 19 - 26 ) having. Heat exchanger according to claim 1, characterized in that the channel ( 8th . 9 ) as a coolant channel ( 8th . 9 ) serves that the working fluid is a coolant and that through the gas channel, a gas to be cooled is feasible and / or that the coolant is a water-based coolant. Heat exchanger according to claim 1 or 2, characterized in that the channel ( 8th . 9 ) on at least one lower side of the channel relative to the installation position ( 15 . 17 ) a survey ( 50 . 51 ), which at the top of the channel ( 16 . 18 ) ( 19 - 26 ), and / or that the survey ( 19 - 26 ) is formed by an embossing and / or that the survey as a rib-shaped elevation ( 19 - 26 ) is configured. Heat exchanger according to one of claims 1 to 3, characterized in that on the channel top side ( 16 . 18 ) several adjacent surveys ( 19 - 26 ) between which in a quiescent state the formation of gas bubbles ( 27 - 34 ) is possible. Heat exchanger according to claim 4, characterized in that a ratio of one distance ( 43 ) at the top of the canal ( 16 . 18 ) ( 19 - 26 ) to a height ( 40 ) of the surveys ( 19 - 26 ) is about equal to ten. Heat exchanger according to one of claims 1 to 5, characterized in that a ratio of a channel height to a height ( 40 ) of the survey ( 19 - 26 ) is not less than 3.5. Heat exchanger according to one of claims 1 to 6, characterized in that a plurality of plates ( 2 - 5 ) are provided that several coolant channels ( 8th . 9 ) and several gas channels ( 10 - 12 ) provided by the plates ( 2 - 5 ) are separated from each other, and that the channels ( 8th . 9 ) via at least one connecting piece ( 13 ) are interconnected. Heat exchanger according to claim 7, characterized in that the plates ( 2 - 5 ) are arranged in the installed position at least approximately horizontally and that the surveys ( 19 - 26 ) on the plates ( 2 - 5 ) are configured. Heat exchanger according to claim 7, characterized in that the plates ( 2 - 5 ) are arranged in the installed position at least approximately perpendicular and that intermediate floors ( 60 - 65 ), on which the surveys ( 76 - 81 . 83 - 87 ) are configured. Heat exchanger according to claim 9, characterized in that the intermediate floors ( 60 - 65 ) are arranged offset to one another, so that through the intermediate floors ( 60 - 65 ) a snake-shaped channel ( 8th ) between the plates ( 2 ), and that at least a part of the intermediate floors ( 60 - 65 ) at their free ends ( 70 - 75 ) one survey each ( 72 - 81 ) on the channel top ( 16 ) having.

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