U.S. patent application number 14/909681 was filed with the patent office on 2016-06-23 for evaporator heat exchanger.
This patent application is currently assigned to Behr GMBH & Co. KG. The applicant listed for this patent is BEHR GMBH & CO., KG. Invention is credited to Peter Geskes, David Mercader Quintana, Gerd Schleier, Michael Schmidt.
Application Number | 20160178260 14/909681 |
Document ID | / |
Family ID | 48917536 |
Filed Date | 2016-06-23 |
United States Patent
Application |
20160178260 |
Kind Code |
A1 |
Geskes; Peter ; et
al. |
June 23, 2016 |
EVAPORATOR HEAT EXCHANGER
Abstract
An evaporator heat exchanger for evaporating a liquid working
medium may include a housing, in which at least one first flow
channel for conducting the working medium and at least one second
flow channel for conducting a gas may be arranged, where heat may
be transferable from the gas to the working medium. The evaporator
heat exchanger may also include a plurality of cover plates and a
profiled fluid plate arranged in between two of the cover plates.
The at least two cover plates and the profiled fluid plate may form
the at least one first flow channel, and at the same time may
delimit at least one of at least one leakage channel and a leakage
space that is separated from the at least one first flow channel
and at least one second flow channel.
Inventors: |
Geskes; Peter; (Ostfildern,
DE) ; Mercader Quintana; David; (Ludwigsburg, DE)
; Schleier; Gerd; (Schwaikheim, DE) ; Schmidt;
Michael; (Bietigheim-Bissingen, DE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
BEHR GMBH & CO., KG |
Stuttgart |
|
DE |
|
|
Assignee: |
Behr GMBH & Co. KG
Stuttgart
DE
|
Family ID: |
48917536 |
Appl. No.: |
14/909681 |
Filed: |
August 2, 2013 |
PCT Filed: |
August 2, 2013 |
PCT NO: |
PCT/EP2013/066248 |
371 Date: |
February 2, 2016 |
Current U.S.
Class: |
62/129 ;
62/228.3; 62/515 |
Current CPC
Class: |
F28F 2265/16 20130101;
F25B 39/024 20130101; F25B 49/00 20130101; F28F 3/005 20130101;
F25B 39/00 20130101 |
International
Class: |
F25B 49/00 20060101
F25B049/00; F25B 39/00 20060101 F25B039/00 |
Claims
1. An evaporator heat exchanger for evaporating a liquid working
medium, comprising: a housing, in which at least one first flow
channel for conducting the working medium and at least one second
flow channel for conducting a gas are arranged, heat being
transferable from the gas to the working medium; and a plurality of
cover plates and a profiled fluid plate arranged in between two of
the cover plates; wherein the at least two cover plates and the
profiled fluid plate form the at least one first flow channel and
at the same time delimit at least one of (i) at least one leakage
channel and (ii) a leakage space that is separated from the at
least one first flow channel and the at least one second flow
channel.
2.-11. (canceled)
12. The evaporator heat exchanger of claim 1, wherein the at least
one of (i) the at least one leakage channel and (ii) the leakage
space is arranged laterally at least one of next to and at a
periphery of the at least one first flow channel.
13. The evaporator heat exchanger of claim 1, wherein at least one
of: a strength of a material of the profiled fluid plate is less
than a strength of a material of at least one of the cover plates
arranged on the profiled fluid plate; and the profiled fluid plate
has a smaller wall or material thickness than at least one of the
cover plates arranged on the profiled fluid plate.
14. The evaporator heat exchanger of claim 1, wherein two cover
plates with a profiled fluid plate arranged in between form at
least one plate pack, said plate pack having at least one leakage
channel encircling at least partially in a peripheral region of the
plate pack.
15. The evaporator heat exchanger of claim 14, further comprising a
plurality of plate packs stacked on top of one another with a
second flow channel arranged between adjacent plate packs, the
profiled fluid plate in each plate pack having a first opening in
at least one of a leakage channel and a leakage space, wherein
cover plates of adjacent plate packs opposite one another each have
a second opening between which a leakage bushing for forming an
outlet duct is arranged.
16. The evaporator heat exchanger of claim 15, wherein the first
opening is connected directly to the leakage bushing.
17. The evaporator heat exchanger of claim 15, wherein the cover
plates each has a third opening for conducting the working medium
through the first flow channel, the third openings being connected
together, between mutually opposite cover plates of two plate packs
arranged adjacent to one another, by a fluid bushing, the fluid
bushing having an at least partially encircling fluid bushing
annular channel that is separated from the first flow channel, said
fluid bushing annular channel being connected to the at least one
of a leakage channel and a leakage space in the profiled fluid
plate of the plate packs.
18. The evaporator heat exchanger of claim 15, wherein the housing
has a housing opening which is connected via a housing leakage
bushing to at least one of the first opening and the second opening
in the cover plate of the plate pack arranged adjacent to the
housing.
19. The evaporator heat exchanger of claim 18, wherein the housing
leakage bushing and a plurality of leakage bushings between the
cover plates of adjacent plate packs form the outlet duct for
conducting the fluid, wherein a line into external to the housing
is attachable to the housing leakage bushing, said line having a
sensor configured to measure at least one of a pressure, a flow
rate, and a chemical composition of a fluid in the line.
20. The evaporator heat exchanger of claim 14, wherein at least one
of: a rib structure is arranged in each of the second flow channels
between adjacent plate packs; and for each plate pack, the profiled
fluid plate is at least one of soldered and welded between two
cover plates.
21. The evaporator heat exchanger of claim 19, further comprising a
control device configured to evaluate a signal detected by the
sensor for the control of at least one of a pump delivering the
working medium and an exhaust gas recirculation valve depending
upon the signal detected.
22. The evaporator heat exchanger of claim 2, wherein at least one
of: a strength of a material of the profiled fluid plate is less
than a strength of a material of at least one of the cover plates
arranged on the profiled fluid plate; and the profiled fluid plate
has a smaller wall or material thickness than at least one of the
cover plates arranged on the profiled fluid plate.
23. The evaporator heat exchanger of claim 2, wherein two cover
plates with a profiled fluid plate arranged in between form at
least one plate pack, said plate pack having at least one leakage
channel encircling at least partially in a peripheral region of the
plate pack.
24. An evaporator heat exchanger for evaporating a liquid working
medium, comprising: a housing; and a plurality of plate packs
arranged in the housing one on top of another, each plate pack
having two cover plates with a profiled fluid plate arranged in
between to form a first channel for conducting the working medium,
and at the same time delimiting at least one of at least one
leakage channel and a leakage space separated from the first flow
channel; wherein a second flow channel for conducting a gas is
arranged in between adjacent plate packs.
25. The evaporator heat exchanger of claim 24, wherein each plate
pack has a first opening in at least one of a leakage channel and a
leakage space, and the cover plates of adjacent plate packs
opposite one another each have a second opening between which a
leakage bushing for forming an outlet duct is arranged.
26. The evaporator heat exchanger of claim 25, wherein the cover
plates each has a third opening for conducting the working medium
through the first flow channel, the third openings being connected
together, between mutually opposite cover plates of two plate packs
arranged adjacent to one another, by a fluid bushing, the fluid
bushing having an at least partially encircling fluid bushing
annular channel that is separated from the first flow channel, said
fluid bushing annular channel being connected to the at least one
of a leakage channel and a leakage space in the fluid plate of the
plate packs.
27. The evaporator heat exchanger of claim 25, wherein the housing
has a housing opening which is connected via a housing leakage
bushing to at least one of the first opening and the second opening
in the cover plate of the plate pack arranged adjacent to the
housing.
28. The evaporator heat exchanger of claim 25, wherein the housing
leakage bushing and a plurality of leakage bushings between the
cover plates of adjacent plate packs form the outlet duct for
conducting the fluid, wherein a line into external to the housing
is attachable to the housing leakage bushing, said line having a
sensor configured to measure at least one of a pressure, a flow
rate, and a chemical composition of a fluid in the line.
29. The evaporator heat exchanger of claim 24, wherein at least one
of: a rib structure is arranged in each of the second flow channels
between adjacent plate packs; and for each plate pack, the fluid
plate is at least one of soldered and welded between two cover
plates.
30. The evaporator heat exchanger of claim 28, further comprising a
control device configured to evaluate a signal detected by the
sensor for the control of at least one of a pump delivering the
working medium and an exhaust gas recirculation valve depending
upon the signal detected.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application is a US National Phase application of
International Patent Application PCT/EP2013/066248, filed on Aug.
2, 2013, which is hereby incorporated by reference in its
entirety.
TECHNICAL FIELD
[0002] The present invention relates to an evaporator heat
exchanger for evaporating liquid working medium.
BACKGROUND
[0003] In order to further lower the fuel consumption in commercial
vehicles and passenger cars, attempts are made to recover a part of
the energy of the exhaust gas. This can take place thermally, i.e.
the energy of the exhaust gas is used for example to heat a
passenger compartment or to heat the internal combustion engine or
the transmission. In a variant that has been discussed for some
time, although thermal energy is removed from the exhaust gas, said
thermal energy is returned to the internal combustion engine in a
mechanical form. This method is based on a steam power process, in
which a particular working medium is evaporated and superheated in
an evaporator and is expanded in an adjoining expander, for example
a turbine, with the result that mechanical energy is generated. The
evaporation takes place here by means of heating via the exhaust
gas. The working medium to be evaporated is in this case usually
first heated up to boiling point in an evaporator, then evaporated
and subsequently superheated. This can take place in principle at
two different locations in a motor vehicle. Firstly, heat can be
withdrawn from the exhaust gas in an evaporator, which is used
instead of an exhaust gas cooler, in order to evaporate the working
medium. In this case, the exhaust gas is cooled by the evaporation
of the fluid to be evaporated and is then fed back to the motor
together with the fresh air. Secondly, the main exhaust gas flow is
also intended to be used as a heat source, in order likewise to
evaporate working medium here in what is known as a main exhaust
gas evaporator. Such a main exhaust gas evaporator is usually
arranged by the vehicle manufacturers after the silencer or after
the entire exhaust gas aftertreatment device in the exhaust gas
system. Alternatively, the charge air in supercharged engines is
used as a heat source.
[0004] WO 2012/010349 A1 discloses a generic evaporator heat
exchanger for evaporating liquid working medium and for using waste
heat from an internal combustion engine. In the known system,
introduction of the working medium into the combustion air fed to
the internal combustion engine on account of a sealing problem or
leakage in the evaporator heat exchanger is intended to be
substantially ruled out. To this end, at least one first flow
channel is formed by at least one first delimiting component and at
least one second flow channel is formed by at least one second
delimiting component, wherein there is a fluid-conducting
connection into the surroundings or into a receiving chamber from
at least one of these delimiting components, such that in the event
of a leakage at the delimiting components, the working medium is
introducible into the surroundings or into the receiving
chamber.
[0005] Concepts of a gas-operated evaporator heat exchanger that
are described in the prior art provide for the risk of gas and
working medium mixing to be reduced. If for example a fluorinated
refrigerant flows into the exhaust gas and is fed together
therewith into the internal combustion engine and combusted
therein, hydrofluoric acid is produced, and this can pass out of
the exhaust pipe and cause damage there. If, rather than this
refrigerant, use is made for example of an alcohol, in the event of
a leakage, the alcohol would be co-combusted in the internal
combustion engine, and this would become noticeable on account of a
sudden increase in power of the internal combustion engine. Under
certain circumstances, this may be manageable only with difficulty,
in particular for inexperienced drivers.
SUMMARY
[0006] Therefore, the present invention deals with the problem of
specifying an improved embodiment for an evaporator heat exchanger
of the generic type, in which undesired mixing of working medium
and gas, in particular exhaust gas or charge air, can be ruled
out.
[0007] This problem is achieved according to the invention by way
of the subject matter of the independent claim. Advantageous
embodiments are the subject matter of the dependent claims.
[0008] The present invention is based on the general idea of
providing a leakage channel and/or leakage space between a first
flow channel that conducts working medium and a second flow channel
that conveys gas, in particular exhaust gas or charge air, and in
the process of configuring both the first flow channel and the
leakage channel and/or the leakage space with a particularly simple
structure by way of two cover plates and a profiled fluid plate
arranged in between. The evaporator heat exchanger according to the
invention for evaporating liquid working medium in this case has a
housing in which said first flow channel for conducting the working
medium and the second flow channel for conducting the gas are
arranged. By way of heat transfer from the gas, for example charge
air or exhaust gas, to the working medium, the latter is
evaporated, with the result that it can subsequently be expanded in
an expansion machine, for example in a turbine, and as a result
exerts mechanical work. As mentioned, according to the invention,
the first flow channel and at least one leakage channel and/or
leakage space are formed by two comparatively thick cover plates
and a profiled fluid plate arranged in between, wherein a plate
pack formed from two cover plates and a fluid plate located in
between thus accommodates the first flow channel and the at least
one leakage channel and/or leakage space fluidically separated
therefrom. The connection between the two cover plates and the
fluid plate arranged in between is produced in a cohesive manner,
for example via a soldered connection. Arranged in this case
between two adjacent plate packs is in each case a second flow
channel through which the heat transfer gas, for example exhaust
gas or charge air, flows. If the fluid plate breaks and/or if the
soldered seam between the fluid plate and the cover plate fails,
the working medium passes from the first flow channel into the
leakage channel and/or into the leakage space and can be discharged
from there without being directly mixed with the gas, for example
exhaust gas, flowing through the second flow channel. In the same
way, the leakage channel and/or the leakage space can also be used
to discharge gas passing undesirably out of the second flow
channel, if for example detaching of a soldered connection between
the fluid plate and the cover plate or breaking of a wall of the
fluid plate would result in a fluidic connection between the
leakage channel and the second flow channel. As a result of this,
too, gas now flowing into the leakage channel and/or into the
leakage space can be discharged and as a result direct mixing with
the working medium in the first flow channel can be avoided. The
leakage channel and/or leakage space thus forms a natural safety
barrier located between the two flow channels. The leakage channel
and/or the leakage space is usually filled with air.
[0009] Expediently, the strength of a material of the fluid plate
is less than the strength of a cover plate arranged on the fluid
plate. This brings about a kind of predetermined breaking point of
the fluid plate, such that if the evaporator heat exchanger is
overloaded in the region of the first flow channel, the working
medium conducted through the first flow channel passes into the
leakage channel. If, for example, the fluid plate breaks, the cover
plate delimiting the first flow channel expands under certain
circumstances and compresses the rib structure arranged for example
in the second flow channel. During the expansion of the cover
plate, a soldered seam connecting the fluid plate to said cover
plate can be detached, with the result that a fluidic connection
between the first flow channel and the leakage channel is created.
From the latter, the working medium can be discharged without
mixing with the gas flowing through the second flow channel. In the
same way, such a predetermined breaking point can also be formed by
a smaller wall thickness or material thickness of the fluid plate
compared with the cover plates connected thereto. What is important
here is always that, in the event of an overload, first of all the
fluid plate breaks or ruptures and not the cover plates. In this
way, regardless of the type of failure, it is always possible to
ensure that the leakage channel and/or leakage space located
between the first and the second flow channel can be used to
discharge the working medium or the gas. The leakage channel and
leakage space are preferably impressed in an encircling manner in
the fluid plate, wherein larger areas are denoted leakage space and
smaller areas are denoted leakage channel.
[0010] In a further advantageous embodiment of the solution
according to the invention, the evaporator heat exchanger has a
plurality of plate packs stacked on top of one another with in each
case a second flow channel arranged in between, wherein the leakage
channel and/or the leakage space in a fluid plate has a first
opening and a plurality of cover plates, arranged opposite one
another, of two adjacent plate packs each have a second opening,
wherein a leakage bushing for forming a (leakage) outlet duct, is
arranged between the second openings. In this way, the leakage
fluid or gas can be reliably drained from the second flow channel
or the working medium can be reliably drained from the first flow
channel.
[0011] In an advantageous development of the solution according to
the invention, the housing has a housing opening which is
connected, via a housing leakage bushing, to the first or second
opening in the cover plate of a plate pack arranged adjacent to the
housing. In this case, the housing leakage bushing and all further
leakage bushings form an outlet duct, also known as a leakage
outlet duct, for conducting the leakage fluid, wherein a line into
the surroundings or periphery is attachable to the housing leakage
bushing, a sensor which is configured to measure the pressure
and/or the flow rate and/or a chemical composition of the fluid in
the line being arranged in the region of said line. Ambient air
pressure usually prevails in the outlet duct. At the same time air
with the usual quality is present. If, on account of an overload,
the fluid plate breaks or ruptures and thus working medium passes
out of the first flow channel or gas passes out of the second flow
channel into the leakage channel, then the pressure, the
temperature and/or the chemical composition changes therein, since
the leakage fluid, regardless of whether it is exhaust gas or
working medium, has different physical and/or chemical properties
than air. If a corresponding change indicating a leakage is
detected by the sensor, then the latter can for example control a
pump delivering the working medium or an exhaust gas recirculation
valve depending on the signal detected by the sensor. It is
likewise conceivable for a warning signal, which visually and/or
acoustically notifies a user of the motor vehicle of a malfunction
in the evaporator heat exchanger, to be output. Ambient air
pressure of about 1 bar is usually present--as described above--at
the sensor. If the evaporator heat exchanger is put into operation,
the pressure in the leakage channel and/or in the leakage space
rises to about 1-1.5 bar on account of the temperature-related
expansion, this being normal. However, if the pressure does not
rise, then either the sensor is defective or the leakage channel
and/or leakage space has a sealing problem via which a drop in
pressure can occur. If the pressure rises considerably during
operation of the evaporator heat exchanger, this usually indicates
a leakage of the first flow channel or of the second flow channel.
The operation of the leakage channel is thus tested each time the
motor vehicle is restarted, in particular upon each cold start.
[0012] Further important features and advantages of the invention
can be gathered from the dependent claims, from the drawings, and
from the associated description of the figures with reference to
the drawings.
[0013] It goes without saying that the abovementioned features and
those yet to be explained in the following text are usable not only
in the combination given in each case but also in other
combinations or on their own, without departing from the scope of
the present invention.
[0014] Preferred exemplary embodiments of the invention are
illustrated in the drawings and are described in more detail in the
following description, wherein identical reference signs refer to
identical or similar or functionally identical components.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] In the figures, in each case schematically,
[0016] FIG. 1 shows a view of an evaporator heat exchanger
according to the invention,
[0017] FIG. 2 shows a sectional illustration through the evaporator
heat exchanger in the region of first and second flow channels in
the intact state,
[0018] FIG. 3 shows an illustration as in FIG. 2 but with the fluid
plate broken and working medium passing into a leakage channel,
[0019] FIG. 4 shows an illustration as in FIG. 3, but with gas
passing from the second flow channel into the leakage channel,
[0020] FIG. 5 shows a possible embodiment of the fluid plate
according to the invention,
[0021] FIG. 6 shows an exploded illustration of the evaporator heat
exchanger,
[0022] FIG. 7 shows a sectional illustration through the evaporator
heat exchanger in the region of the fluid inlet or outlet,
[0023] FIG. 8 shows an illustration as in FIG. 7, but in the region
of an outlet duct for leakage fluid,
[0024] FIG. 9 shows a pressure/time diagram with different curves
which indicate different operating states or leakages of the
evaporator heat exchanger according to the invention.
DETAILED DESCRIPTION
[0025] According to FIG. 1, an evaporator heat exchanger 1
according to the invention for evaporating liquid working medium 2
(cf. also FIGS. 2 to 4) has a housing 3 in which a first flow
channel 4 for conducting the working medium 2 and a second flow
channel 5 for conducting a gas 6 are arranged. The working medium 2
is heated in this case by heat transfer from the gas 6, for example
from exhaust gas or charge air. According to the invention, the
first flow duct 4 is now formed by two cover plates 7 and 8 and a
profiled fluid plate 9 arranged in between, wherein the fluid plate
9, together with the two cover plates 7 and 8, at the same time
delimits at least one leakage channel 10 and/or leakage space 11
that is separated from the two flow channels 4, 5. The two cover
plates 7, 8 form, together with a fluid plate 9 arranged in
between, a plate pack 12, as is illustrated for example in FIGS. 2
to 4. The respective leakage channel 10 and the leakage space 11
are in this case arranged laterally next to or at the periphery of
the first flow channel 5, as can be gathered in particular also
from FIG. 5.
[0026] The leakage channel 10 according to the invention creates a
barrier between the two flow channels 4, 5, such that it is not
possible for the working medium 2 to mix directly with the gas 6
and as a result to damage an internal combustion engine. In the
case of evaporator heat exchangers that are known from the prior
art, the working medium to be evaporated flows into the exhaust gas
in the event of a leakage and can, if for example a fluorinated
refrigerant, for example R245fa, is used, be combusted in the
internal combustion engine, thereby producing poisonous
hydrofluoric acid. This would pass out of the exhaust pipe and
cause damage there. If, rather than such a refrigerant, use is made
of alcohol, for example ethanol or methanol, in the event of a
leakage, the latter would be co-combusted in the internal
combustion engine, and this would be reflected in a sudden increase
in power of the internal combustion engine. In particular
inexperienced drivers would be exposed to an increased risk of an
accident as a result. However, as a result of the barrier according
to the invention of the leakage channel 10 and leakage space 11
type, in the event of virtually any kind of failure of the fluid
plate 9, mixing of the gas 6 with the working medium 2 can be
reliably prevented.
[0027] In addition to the provision of the leakage channel 10
and/or of the leakage space 11 (cf. also FIG. 5) the strength of
the material for the fluid plate 9 is less than the strength of the
cover plates 7, 8 connected to the fluid plate 9, such that the
fluid plate 9 generally represents a kind of predetermined breaking
point in the system of the plate pack 12. In a similar manner, such
a predetermined breaking point can also be realized by a smaller
wall thickness or material thickness of the fluid plate 9 compared
with the wall thickness or material thickness of the cover plates
7, 8.
[0028] In FIG. 2, the evaporator heat exchanger 1 is in this case
shown in a normal operating state in which gas, in particular
exhaust gas, flows through the second flow channel 5 and transfers
heat to the working medium 2 in the first flow channel 4. For
better heat transfer, a rib structure 13 can be arranged in this
case in the second flow channel 5, i.e. between two plate packs 12.
A connection of the fluid plate 9 to the two cover plates 7, 8, or
a connection of the rib structure 13 to the respective cover plates
7, 8, is produced in this case preferably in a cohesive manner, for
example via a soldered connection 14.
[0029] FIG. 3 now shows a case of failure of the fluid plate 9, in
which the central fluid plate 9 has broken and as a result has
resulted in deformation or upward bending of the more strongly
dimensioned cover plate 7. The deformation of the cover plate 7 in
turn results in detaching of the soldered connection 14, with the
result that the working medium 2 present in the first flow channel
4 can flow into the leakage channel 10. A fluidic connection with
the second flow channel 5 and thus with the gas 6 does not
occur.
[0030] FIG. 4 shows a case in which the fluid plate 9 has likewise
broken on account of an overload and in the process has created a
fluidic connection between the second flow channel 5 and the
leakage channel 10. The gas 6 passing out of the second flow
channel 5 can in this case be discharged via the leakage channel 10
without mixing with the working medium 2 in the first flow channel
4. In both of the cases of failure that are shown in FIGS. 3 and 4,
undesired mixing of the working medium 2 with the gas 6 and the
resulting difficulties is thus reliably avoided.
[0031] Considering the fluid plate 9 according to FIG. 5, the first
flow channel 4 and the leakage channel 10 extending at the
periphery and leakage spaces 11 located in between can be seen very
clearly. A fluid infeed 15 and a fluid drain 16, via which working
medium 2 can be fed to the fluid plate 9 and discharged therefrom
again can likewise be seen. Likewise, the fluid plate 9 has a first
opening 17 via which the leakage channel 10 and the leakage space
11 are connected to a (leakage) outlet duct 18 (cf. FIG. 1). A
plurality of cover plates 7, 8, arranged opposite one another, of
two adjacent plate packs 12 additionally each have a second opening
19, wherein a leakage bushing 20 for forming the outlet duct 18, in
particular the leakage outlet duct 18, is arranged between two
second openings 19. In the case of an assembled plate pack 12, the
first openings 12 are thus aligned with the second openings 19 and
the leakage bushings 20 and as a result form the outlet duct
18.
[0032] Considering FIG. 6 further, it can be seen that the cover
plates 7, 8 each have a third opening 21 for conducting the working
medium 2 through the first flow channel 4, wherein the third
openings 21 are connected together, between mutually opposite cover
plates 7, 8 of two adjacently arranged plate packs 12, in each case
by a fluid bushing 22, and the fluid bushing 22 has an at least
partially encircling fluid bushing annular channel 23 that is
separated from the first flow channel 4, said fluid bushing annular
channel 23 being connected to the leakage channel 10 and/or the
leakage space 11 in the fluid plate 9 of the plate pack 12. As a
result, it is likewise possible to create a safeguard against
working medium 2 passing undesirably out of the fluid bushings 22.
The third openings 21 in this case form a corresponding fluid feed
duct 24 and fluid drain duct 25 together with the fluid bushings 22
arranged in between and the fluid infeed 15 and fluid drain 16,
arranged in a manner aligned therewith, in the fluid plates 9.
[0033] FIG. 7 shows a sectional illustration through the
evaporation heat exchanger 1 according to the invention in the
region of the fluid feed duct 24 and of the fluid drain duct 25.
The uppermost fluid bushing 22 is in this case welded to the
housing 3 in a fluid-tight manner via a welded connection 26.
Between in each case two adjacent fluid bushings 22, a plate pack
12 having two cover plates 7, 8 and a fluid plate 9 arranged or
soldered in between can be seen.
[0034] FIG. 8 shows a sectional illustration through the
evaporation heat exchanger 1 according to the invention in the
region of the outlet duct 18, wherein the uppermost leakage bushing
20 is again welded to the housing 3 in a fluid-tight manner via a
welded connection 26. The individual plate packs 12 again
consisting of the two cover plates 7, 8 and the fluid plate 9
arranged in between are in this case soldered both together and to
the individual leakage bushings 20 in a fluid-tight manner via a
respective soldered connection 14. The uppermost leakage bushing 20
is in this case also referred to as the housing leakage bushing 27.
The housing leakage bushing 27 is adjoined by a line 28 (cf. FIG.
1) into the surroundings or the periphery, said line 28 continuing
outside the evaporator heat exchanger 1. In the line 28 or the
outlet duct 18, provision can be made of a sensor 29 which is
configured to measure the pressure and or the flow rate and/or a
chemical composition of the fluid in the line 28, i.e. in
particular also in the leakage channel 10 or in the outlet duct
18.
[0035] Provision can likewise be made of an open-loop and/or
closed-loop control device 30 which is configured to evaluate a
signal detected by the sensor 29, in particular the pressure, the
flow rate and/or the chemical composition of the fluid, in
particular of the leakage fluid, in the line 28, and for the
open-loop/closed-loop control of a pump (not shown) delivering the
working medium and/or of an exhaust gas recirculation valve
(likewise not shown) depending on the signal detected.
[0036] The ambient air pressure of about 1 bar is usually present
at the sensor 29, as long as the evaporator heat exchanger 1 is
switched off and is at ambient temperature. This is shown in FIG. 9
by way of the curve A. If the evaporator heat exchanger 1 is put
into operation, the pressure within the line 28 and within the
leakage channels 10 rises to about 1 to 1.5 bar on account of the
temperature-related expansion of the air, this being illustrated in
FIG. 9 by way of the curve B. If the evaporator heat exchanger 1 is
put into operation and the pressure does not rise, this likewise
being shown in FIG. 9 by way of the curve A, either the sensor 29
is defective or the line 28 and the leakage channel 10 have a leak.
In the event of a leakage in the fluid plate 9, the pressure rises
considerably when the working medium 2 passes into the leakage
channel 10, this being illustrated in FIG. 9 by way of the curve C,
and somewhat less when the fluid plate 9 ruptures in the direction
of the second flow channel 5 and thus gas 6 passes into the leakage
channel 10, this being illustrated in FIG. 9 by way of the curve D.
Generally, the operation of the leakage channel 10 can be tested
each time the internal combustion engine or the system is
restarted, with the result that high operational reliability can
likewise be ensured. In addition, it is immediately possible to
draw conclusions about the type of failure from the curve
profile.
[0037] In general, the evaporation heat exchanger 1 according to
the invention has the following advantages:
[0038] avoidance of undesired mixing of the working medium 2 with
the gas 6, for example exhaust gas or charge air,
[0039] no health risk when refrigerant is used,
[0040] no safety risk when alcoholic working medium 2 is used,
[0041] ongoing testability of the function of the leakage
concept.
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