WO2011072912A2

WO2011072912A2 - Heat exchanger

Info

Publication number: WO2011072912A2
Application number: PCT/EP2010/065755
Authority: WO
Inventors: Ilona Krinn; Juergen Stegmaier; Manfred Schmitt; Bernd Banzhaf; Patrick Glaser
Original assignee: Robert Bosch Gmbh
Priority date: 2009-12-18
Filing date: 2010-10-20
Publication date: 2011-06-23
Also published as: WO2011072912A3; DE102009054988A1

Abstract

The invention relates to a heat exchanger (1), which is used in particular as an exhaust gas heat exchanger, comprising coolant channels (8, 9), through which a water-based coolant can be conducted, and gas channels (10 - 12), which are thermally connected to the coolant channels (8, 9) and through which a gas to be cooled can be conducted. To said end, the coolant channels (8, 9) comprise raised areas (19 - 26) on the respective channel upper face (16, 18) located on top with regard to an installation position.

Description

Description title

Heat exchanger prior 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.

In heat exchangers of motor vehicle cooling systems Kühlwasserbeimischungen can be used, which is the freezing point of the coolant serving as water

decrease. 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 above that

Ambient temperature of the motor vehicle is located. Due to the density anomaly, freezing during construction must be taken into account, especially when operating with water, because due to the expansion of the freezing water, mechanical forces are exerted on the

Heat exchangers act. In addition, while the vehicle is at a standstill, all the system water is from the connected components and piping

Heat exchanger to collect, since only here is a heat source available, with the help of frozen water can be liquefied again. For cost reasons and

Space limitations are heat exchangers for vehicles 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, in particular 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 provide air pockets in the channel Channel are formed, which allow an expansion of the freezing working fluid, whereby damage is prevented from the outset.

The measures listed in the dependent claims are advantageous

Further developments of the heat exchanger specified in claim 1 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 at at least one with respect to a mounting position above

Channel top has at least one survey. 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. In operation of the heat exchanger is the

Coolant channel flows through 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 for generating an optionally desired

Pressure loss instead of further enlargement of the elevation at the top of the channel Elevations are provided on the channel bottom. 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. This allows 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 rates sufficient

Wetting of the wall can be ensured if the height of the elevations on the channel top is optimized, 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 several

Coolant channels and multiple gas channels are provided through the plates are separated from each other, and that the coolant channels are connected to each other via connectors. 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 configured on the plates. As a result, a compact heat exchanger can be produced with an optimized number of components.

It is also advantageous, however, that the plates in the installed position at least

Are arranged approximately vertically and that intermediate floors are provided on which the elevations are designed. Here, it is also advantageous that the shelves are offset from one another, so that through the intermediate floors a serpentine ausgestalteter coolant channel is designed 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 will be described in more detail in the following description with reference to the accompanying drawings, in which corresponding elements are given the same reference numerals. It shows:

1 shows a first embodiment of a heat exchanger of the invention in an excerpt, schematic sectional view.

FIG. 2 shows the detail of the heat exchanger designated II in FIG. 1 in accordance with the first exemplary embodiment in a tilted rest position; FIG. Fig. 3 the in Fig. 1 with I I designated section of the heat exchanger according to a second embodiment of the invention and

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

Embodiments of the invention Fig. 1 shows a first embodiment of a heat exchanger 1 of the invention in a schematic, partial sectional view. The heat exchanger 1 can

especially for motor vehicles. Specifically, the heat exchanger 1 as

Exhaust heat exchanger 1 designed. Here, the heat exchanger 1 in a

Steam power process of a motor vehicle can be used. This can be done by the

Channel geometry a freezer-proof heat exchanger 1 with uniform

Single-channel admission for use in a steam power process to be created. However, the heat exchanger 1 according to the invention is also suitable for others

Use cases.

The heat exchanger 1 has a plurality of plates 2, 3, 4, 5. For the heat exchanger 1, an installation position is predetermined, which is illustrated in FIG. 1 by an axis 6 and a direction 7. Here, the heat exchanger 1 is mounted so that the axis 6 is oriented vertically and the direction 7 points upward.

In this embodiment, the plates 2 to 5 are arranged horizontally with respect to the axis 6 and thus also with respect to the predetermined installation position. In this case, the plates 2 to 5 are spaced apart along the axis 6. Between the plates 2, 3, a channel 8 is formed. Furthermore, a further channel 9 is formed between the plates 4, 5. Between the plates 3, 4, a gas channel 10 is formed. In addition, further plates are preferably arranged along the axis 6, so that further channels and further gas channels are provided. In particular, another gas channel 11 adjoins the plate 2, and another gas channel 12 adjoins the plate 5. The conclusion form preferably channels, so that the gas channels 10, 1 1, 12 are provided within the heat exchanger 1 and are surrounded by channels 8, 9 from all sides. Here, also connecting pieces 13 are provided, which connect the individual channels 8, 9 with each other. The connecting pieces 13 also serve to limit the gas channels 10, 1 1, 12. In operation, the channels 8, 9 and the connecting piece 13 are flowed through by a working fluid. Here, the entire interior of the channels 8, 9 and the connecting piece 13 of the heat exchanger 1 is filled with the working fluid, whereby a heat exchange with the plates 2 to 5 of the heat exchanger 1 and thus also achieved with the guided through the heat exchanger 1 exhaust gases.

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 8, 9 then serve as coolant channels 8, 9. The coolant, which is passed through the coolant channels 8, 9, 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.

During operation of the heat exchanger 1, the coolant 14 flows through the coolant channels 8, 9 and the connector 13. Between the coolant channels 8, 9 and the gas channels 10 to 12 there is a thermal connection. In this embodiment, this thermal connection via the plates 2 to 5. The flowing through the gas channels 10 to 12 hot gas thus warms the flowing through the coolant channels 8, 9

Coolant 14. In this way, a heat exchange between the hot exhaust gases and the coolant 14 is possible.

The coolant channel 8 has a channel bottom side 15 and a channel top side 16.

Accordingly, the coolant channel 9 has a channel bottom side 17 and a

Channel top 18 on. In this embodiment, the channel bottom 15 is formed on the plate 3. The channel top 16 is formed on the plate 2. Further, the channel lower side 17 is formed on the plate 5, while the channel top 18 is formed on the plate 4. In the region of the channel upper side 16 of the coolant channel 8 a plurality of elevations 19, 20, 21, 22 are formed. Furthermore, elevations 23, 24, 25, 26 are also formed on the channel upper side 18 of the coolant channel 9. In this

Embodiment, the elevations 19 to 22 formed on the plate 2 in the form of ribs. The elevations 23 to 26 are on the plate 4 in the form of ribs

educated. The elevations 19 to 26 are designed by embossing. In this case, corresponding recesses result from embossing on the plates 2, 4 in the region of the gas channels 1 1, 10. In the installed position, the channel tops 16, 18 with respect to the respective coolant channel 8, 9 above. Thus, the surveys 19 to 26 to elevations 19 to 26 above. By the surveys 19 to 22 at the

Coolant channel 8 are formed during the return flow of the coolant 14 air cushion 27, 28, 29, 30 from. Accordingly, air cushions 31, 32, 33, 34 form on the coolant channel 9. By the air cushion 27 to 34, 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 is formed. When the coolant shown in FIG. 1 freezes and expands, then through the air cushion 27 to 34 a

Expansion allows, so that damage to the plates 2 to 5 is prevented. Thus, the mechanical stress of the heat exchanger 1 can be minimized. The elevations 19 to 26 provide in operation an increased flow resistance, which leads to a reduced influence of the geodetic pressure difference due to the pressure difference between the superimposed coolant channels 8, 9. As a result, a uniform distribution of the coolant to the individual coolant channels 8, 9 is supported during driving. By elevations 52, 53 at the ends of the coolant channels 8, 9, a backflow of the upper channels in the underlying lying additionally be prevented. Thus, a compensation of the volume increase of the water-based coolant 14 during freezing without mechanical stress of the heat exchanger 1 is possible. Furthermore, an increased flow resistance allows a more even distribution of the coolant 14 in the superimposed coolant channels 8, 9 during the driving operation. In addition, bumps 52, 53 at the ends of the coolant channels 8, 9 prevent backflow of the coolant 14 from the upper coolant channels into the underlying.

The elevations 19 to 26 extend over the entire width of the plates 2, 4 of the heat exchanger. 1 As a result, between each adjacent elevations, for example, the elevations 19, 20, in the vehicle standstill an air cushion,

for example, the air cushion 28, included. This air cushion 28 can be partially displaced in the volume increase of the coolant 14. A height 40 of the elevations 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 illustrated with reference to FIG. 2.

Fig. 2 shows the designated in Fig. 1 with II section of the heat exchanger 1 in a schematic sectional view. In this embodiment, the heat exchanger is installed according to the initial position shown in FIG. 1 in a motor vehicle. Thus, the axis 6 is 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 is tilted with respect to a vertical axis 41 by an angle 42 of 5.7 °. This corresponds to a parking slope of the vehicle of 10%. Such an angle 42 can serve as a maximum parking gradient for determining the configuration of the heat exchanger 1. However, it is also possible a different default. Due to the oblique parking position, the coolant 14 is at rest in several stages in the coolant channel 9. In this case, this level division by the elevations 24, 25 at the Plate 4 is achieved, which prevent a flow of the coolant 14, since it comes to the inclusion of the air bubbles 32, 33, 34. Thus, even with an oblique shutdown of

Vehicle through a space formed by the air cushion 32 to 34 space available to allow the expansion of an optionally freezing coolant 14 without damaging the plates 4, 5. The pressure increase in the air bubbles 32 to 34 is

negligible in this regard.

A distance 43 of the elevations 24, 25 on the plate 4 is in this case predetermined so that with respect to the height 40 of the elevation 24, a sufficient air cushion 33 results, which preferably extends from the elevation 24 to the elevation 25. This is a

Ratio of the distance 43 provided on the channel top 18 surveys 24, 25 to the height 40 of the survey 24 is approximately equal to ten. By this definition, a sufficient air cushion 33 is formed even at a relatively large angle 42. This determination can for all surveys 19 to 26 at the channel tops 16, 18 of the

Be given coolant channels 8, 9. In addition, a ratio of a channel height 44 to the height 40 of the elevations 24, 25 is not less than 3.5 predetermined. This prevents air bubbles from remaining behind the elevations 24, 25 during operation.

The height 40 may be predetermined by the configuration of the embossments. About the height 40, the throttle effect is determined in this case, whereby the flow pressure loss of the coolant channels 8, 9 influenced and thus a uniform distribution of the coolant 14 to the coolant channels 8, 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 may then elevations are also designed by longitudinal embossing, which extend along the coolant channels 8, 9. Thus, even with an inclination in the transverse direction, the design of air cushions 27 to 34 is made possible with a correspondingly large gas space. The

Elevations 19 to 22 on the channel upper side 16 of the coolant channel 8 may in this case form a grid-like or honeycomb-like structure. Accordingly, the elevations 23 to 26 may be configured on the coolant channel 9.

FIG. 3 shows the section of the heat exchanger 1 designated II in FIG. 1

according to a second embodiment. In this embodiment, the heat exchanger 1 is in an orientation in which the axis 6 is oriented vertically and the direction 7 points upward. 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 not so severely limited, 17 further surveys 50, 51 are provided in this embodiment, the channel bottom side. The elevations 50, 51 are in this case designed according to the elevations 24, 25 by embossing. In this way, the height 40 of the elevations 24, 25 in the region of the channel top 18 can be optimized. An additional throttling effect can be achieved by the elevations 50, 51.

Thus, advantageous embodiments of the coolant channels 8, 9 are possible. In this case, moreover, sections 52, 53 of the plates 4, 5 can be guided upwards in the region of the connecting piece 13, in order to prevent the coolant 14 from the upper channels, when the vehicle is stationary, from flowing into the underlying channels via the connecting piece 13 designed as a supply or return channel arrives.

Fig. 4 shows a heat exchanger 1 in a schematic sectional view

according to a third embodiment. In this embodiment, vertically standing plates 2 are provided, of which the plate 2 is shown. Here, intermediate plates 60 to 65 are arranged between the plates, which are arranged offset from one another so that a serpentine ausgestalteter coolant channel 8 is formed. Here, a bottom plate 66 and a ceiling plate 67 is also provided. Further, side plates 68, 69 are provided. The individual shelves 60 to 65 have free ends 70 to 75. At the free ends 70 to 75 are elevations 76 to 81

educated. Through these elevations 76 to 81, the formation of air cushions is possible, of which in Fig. 4, the air cushion 82 is marked. In this case, further elevations 83 to 87 may be provided on the intermediate bottom 65 in order to divide the air cushion 82 into parts 88 to 92. By dividing the air cushion 82 into the parts 88 to 92, the formation of a plurality of air bubbles is made possible with an inclined position of the heat exchanger 1, whereby a larger total volume of the air cushion 82 is achieved. This corresponds to the principle described with reference to FIG. 2. By the air cushion 82 is at a freezing of the coolant 14 a certain

Compensation space created so that damage to the heat exchanger 1 is prevented. The elevations 76 to 81 on the shelves 60 to 65 are configured in the form of beads. In this case, at least one elevation 93 can also be configured on the ceiling plate 67. The heat exchanger 1 of the third embodiment thus enables a vertical installation. In this case, a serpentine or meandering structure of the coolant channel 8 and further coolant channels can be achieved.

The invention is not limited to the described embodiments.

Claims

claims

1 . Heat exchanger (1), in particular exhaust gas heat exchanger, with at least one channel (8, 9), through which a working fluid can be guided, and at least one gas channel (10 - 12) which is in thermal communication with the channel (8, 9) and through a gas is feasible, wherein the channel (8, 9) at least one with respect to a mounting position overhead

Channel top (16, 18) has at least one elevation (19 - 26).

2. Heat exchanger according to claim 1,

characterized,

in that the channel (8, 9) serves as a coolant channel (8, 9), that the working fluid is a coolant and that a gas to be cooled can be guided through the gas channel

and or

the coolant is a water-based coolant.

3. Heat exchanger according to claim 1 or 2,

characterized,

the channel (8, 9) has an elevation (50, 51) on at least one lower channel side (15, 17) with respect to the installation position, which elevation is associated with the elevation (19-26) provided on the upper channel side (16, 18) .

and or

that the elevation (19 - 26) is embossed and / or that the

Survey as a rib-shaped elevation (19 - 26) is configured.

4. Heat exchanger according to one of claims 1 to 3,

characterized,

in that a plurality of adjacent elevations (19-26) are provided on the upper side of the channel (16, 18), between which the formation of gas bubbles (27-34) is possible in an idle state.

5. Heat exchanger according to claim 4,

characterized, in that a ratio of a distance (43) to that on the channel upper side (16, 18)

provided elevation (19 - 26) to a height (40) of the surveys (19 - 26) is approximately equal to ten.

6. Heat exchanger according to one of claims 1 to 5,

characterized,

a ratio of a channel height to a height (40) of the elevation (19-26) is not less than 3.5.

7. Heat exchanger according to one of claims 1 to 6,

characterized,

in that a plurality of plates (2 - 5) are provided, that a plurality of coolant channels (8, 9) and a plurality of gas channels (10 - 12) are provided, which are separated from one another by the plates (2-5), and in that the channels (8, 9) via at least one connecting piece (13) are interconnected.

8. Heat exchanger according to claim 7,

characterized,

that the plates (2-5) are arranged horizontally in the installed position at least approximately and that the elevations (19-26) on the plates (2-5) are configured.

9. Heat exchanger according to claim 7,

characterized,

that the plates (2-5) are arranged in the installed position at least approximately vertically and that intermediate floors (60-65) are provided, on which the

Surveys (76 - 81, 83 - 87) are designed.

10. Heat exchanger according to claim 9,

characterized,

the intermediate floors (60-65) are arranged offset relative to one another so that a serpentine-shaped channel (8) is formed between the plates (2) through the intermediate floors (60-65), and that at least part of the intermediate floors (60-65 ) at their free ends (70 - 75) each have a survey (72 - 81) on the channel top (16).