U.S. patent application number 13/324361 was filed with the patent office on 2012-06-21 for heat exchanger.
This patent application is currently assigned to Benteler Automobiltechnik GmbH. Invention is credited to THORSTEN ANDRES, SVEN PRZYBYLSKI.
Application Number | 20120151938 13/324361 |
Document ID | / |
Family ID | 44719682 |
Filed Date | 2012-06-21 |
United States Patent
Application |
20120151938 |
Kind Code |
A1 |
PRZYBYLSKI; SVEN ; et
al. |
June 21, 2012 |
HEAT EXCHANGER
Abstract
A heat exchanger for installation in a motor vehicle includes a
cooling channel, a heating channel, and heat pipes to thermally
couple the cooling channel with the heating channel. A
thermoelectrical generator is arranged on a cold side of at least
one of the heat pipes and coupled with the heat pipe by a material
joint. The material joint is realized by a liquid metal.
Inventors: |
PRZYBYLSKI; SVEN;
(Paderborn, DE) ; ANDRES; THORSTEN; (Paderborn,
DE) |
Assignee: |
Benteler Automobiltechnik
GmbH
Paderborn
DE
|
Family ID: |
44719682 |
Appl. No.: |
13/324361 |
Filed: |
December 13, 2011 |
Current U.S.
Class: |
62/3.2 ;
165/104.21 |
Current CPC
Class: |
Y02T 10/16 20130101;
F28D 21/0003 20130101; F28D 15/06 20130101; F28D 2021/008 20130101;
F28D 15/0275 20130101; F01N 5/025 20130101; Y02T 10/12
20130101 |
Class at
Publication: |
62/3.2 ;
165/104.21 |
International
Class: |
F25B 21/02 20060101
F25B021/02; F28D 15/02 20060101 F28D015/02 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 15, 2010 |
DE |
10 2010 054 640.2 |
Claims
1. A heat exchanger for installation in a motor vehicle, said heat
exchanger comprising: a cooling channel; a heating channel; heat
pipes thermally coupling the cooling channel with the heating
channel; and a thermoelectrical generator coupled with at least one
of the heat pipe by a material joint.
2. The heat exchanger of claim 1, wherein the material joint is
realized by a liquid metal.
3. The heat exchanger of claim 2, wherein the liquid metal
comprises Galinstan.RTM..
4. The heat exchanger of claim 2, wherein the liquid metal
comprises an alloy having gallium (Ga) and indium (In) as
constituents.
5. The heat exchanger of claim 4, wherein the alloy comprises
tin.
6. The heat exchanger of claim 2, wherein the liquid metal
comprises an alloy of a composition containing, in weight percent,
60 to 80% of gallium, 10 to 30% of indium, and 1 to 20% of tin.
7. The heat exchanger of claim 6, wherein the alloy contains
bismuth or antimony.
8. The heat exchanger of claim 2, wherein the liquid metal
comprises sodium.
9. The heat exchanger of claim 1, wherein the thermoelectrical
generator is arranged on a cold side of the heat pipe.
10. The heat exchanger of claim 1, wherein the heat pipes have a
circular, oval, rectangular and/or polygonal cross section.
11. The heat exchanger of claim 1, further comprising heat
exchanger ribs arranged on a hot side of the heat pipes and
oriented in a flow direction of the heating channel.
12. The heat exchanger of claim 1, wherein the heat pipes are
oriented at least in one of two ways, a first way in which the heat
pipes are oriented transversely to a flow direction of coolant in
the cooling channel, a second way which the heat pipes are oriented
transversely to a flow direction of a heating medium in the heating
channel.
13. The heat exchanger of claim 1, further comprising a plurality
of said thermoelectrical generators arranged substantially about a
circumference of the heat pipe.
14. The heat exchanger of claim 1, wherein the heat pipe operates
in a way that is suited to an operating performance of the
thermoelectrical generator.
15. The heat exchanger of claim 14, wherein the operation of the
heat pipe is constructed for closed-loop control and/or open-loop
control.
16. The heat exchanger of claim 1, wherein the heat pipe has a wall
which is wetted with a metallic carrier substrate.
17. The heat exchanger of claim 16, wherein the metallic carrier
substrate comprises austenitic special steel alloy.
18. A heat exchanger for installation in a motor vehicle, said heat
exchanger comprising: a cooling channel; a heating channel; and a
heat pipe having one part projecting into the heating channel and
another part projecting into the cooling channel.
19. The heat exchanger of claim 18, wherein the heat pipe has in
longitudinal direction a total length, said one part having a
length which is more than half of the total length, and said other
part having a length which is less than half of the total
length.
20. The heat exchanger of claim 18, wherein the heat pipe has in
longitudinal direction a total length, said one part having a
length which is about 2/3 of the total length, and said other part
having a length which is about 1/3 of the total length.
Description
CROSS-REFERENCES TO RELATED APPLICATIONS
[0001] This application claims the priority of German Patent
Application, Serial No. 10 2010 054 640.2, filed Dec. 15, 2010,
pursuant to 35 U.S.C. 119(a)-(d), the content of which is
incorporated herein by reference in its entirety as if fully set
forth herein.
BACKGROUND OF THE INVENTION
[0002] The present invention relates to a heat exchanger for
installation in a motor vehicle.
[0003] The following discussion of related art is provided to
assist the reader in understanding the advantages of the invention,
and is not to be construed as an admission that this related art is
prior art to this invention.
[0004] Exhaust-gas heat recovering systems are known, using
thermoelectrical generator units arranged in an exhaust tract of a
combustion engine to recover energy from heat carried by exhaust
gases. The thermoelectrical generator units have thermoelectric
elements which are arranged in an exhaust passage. The exhaust flow
and the connection of the exhaust pipe to the environment cause a
temperature difference which the thermoelectric elements convert
directly to electric energy by the Seebeck effect.
[0005] In order to provide a temperature difference at the
thermoelectric element, the latter has a hot side and a cold side.
A certain thickness of individual thermoelectric elements is
required to maintain a respective temperature gradient during
operation of the thermoelectric element. The configuration involves
therefore predominantly the application of thin film technology or
sheeting technology. Application of these technologies in an
exhaust tract is however not optimal because of the prevailing high
temperatures.
[0006] In particular as a result of the high exhaust temperatures
of significantly above 600.degree. C. up to more than 1000.degree.
C., assemblies of thermoelectric elements are exposed to extreme
temperature fluctuations. The highly corrosive properties of
exhaust gas also adversely affect the durability of thermoelectric
elements. Proposals have been made to crimp the thermoelectric
elements directly in an exhaust-carrying exhaust pipe so as to be
coupled directly or indirectly with exhaust gas. For example, U.S.
Pat. No. 7,100,369 discloses a direct coupling, with the
thermoelectric generator being exposed directly to the exhaust
gas.
[0007] It would be desirable and advantageous to provide an
improved heat exchanger which obviates prior art shortcomings and
which utilizes the potential of a thermoelectric generator in an
optimum manner while yet being easy to produce and exhibiting a
long service life.
SUMMARY OF THE INVENTION
[0008] According to one aspect of the present invention, a heat
exchanger for installation in a motor vehicle includes a cooling
channel, a heating channel, heat pipes thermally coupling the
cooling channel with the heating channel, and a thermoelectrical
generator coupled with at least one of the heat pipe by a material
joint.
[0009] In accordance with the present invention, a heat pipe
constitutes by itself a heat exchanger, using evaporation heat of a
material to establish a high heat flux density. As a result, large
amounts of heat can be transported across a small cross sectional
area. A fluid in a heat pipe is hereby evaporated in a heating zone
and the created vapor flows to a cooling zone for condensation. The
created vapor ensures a heat transport, with the return flow of the
condensate to the heating zone realized by capillary effect. The
thermoelectric generator is hereby coupled with the heat pipe by a
material joint. In view of the material joint of the heat pipe with
the thermoelectric generator, the heat transfer of heat transported
through the heat pipe to the thermoelectric generator is
effectuated in an optimum manner. As a result, the efficiency is at
an optimum.
[0010] By using the heat pipe in accordance with the present
invention, the cooling channel is thermally coupled by the heating
channel. In other words, the heat pipe has at least one part which
projects into the heating channel while another part extends into
the cooling channel.
[0011] In view of the configuration of the heat pipe according to
the present invention, thermoelectric materials can be used as
thermoelectric generator which otherwise would have been conceived
for use only in a low-temperature range. The thermoelectric
generators can now be used via the heat pipes also for
high-temperature function. The linkage of the heat pipe ensures
that the thermoelectric generator for the low-temperature range has
high efficiency also in the high-temperature range.
[0012] In addition, the heat pipe assumes a safety function, as the
heat transport via the heat pipe takes place only up to a maximum
temperature. Thus, the operating performance is restricted,
protecting the thermoelectric generator against overheating.
[0013] The present invention has a further benefit in that a direct
contact of thermoelectric generator and heating channel or exhaust
gas flowing in the heating channel is thermally decoupled. The
thermoelectric generator is thermally coupled solely via the heat
pipe. As a result, stress cracks and/or leakage caused by different
thermal expansions are substantially eliminated so that the service
life of a heat exchanger according to the invention increases.
[0014] According to another advantageous feature of the present
invention, the material joint can be realized by a liquid metal.
Using liquid metal as coupling permits a transfer of heat
substantially free of forces from heat pipe to the thermoelectric
elements and at a same time a high heat transfer factor. The
presence of possibly encountered thermal expansions or stress
within the components caused by different thermal expansion
coefficients is prevented in view of the coupling by liquid metal,
without having to forego the application of a material joint to
achieve an optimal heat transfer rate.
[0015] According to another advantageous feature of the present
invention, Galinstan.RTM. can be used as liquid metal.
Advantageously, the heat conductor may be configured as alloy
having gallium (Ga) and indium (In) as constituents. Other examples
include compositions of gallium and indium with special steel or
ceramics. A heat conductor containing the afore-described alloying
components forms compositions in the boundary zones of the ceramic
carrier material and the heat exchanger wall.
[0016] The connection by material joint is characterized by a high
heat transfer while being less susceptible to stress at the same
time.
[0017] Indium causes slight surface tension and thus tends to wet
many materials, including metal, glass or ceramics, and invades the
lattice of the alloy and thus enhances mechanical properties.
Indium forms a yellow bonding oxide which promotes adherence of
ceramic compounds to metals. The oxidation behavior contributes
hereby substantially to a metal-ceramics composite.
[0018] Gallium lowers the melting temperature of the alloy and
improves in addition the flowability and mold filling capacity of
the alloy.
[0019] According to another advantageous feature of the present
invention, the alloy may include tin (Sn) as alloying element. Tin
reduces carbon absorption and prevents decarburization of the steel
alloys being joined. Moreover, tin promotes bonding oxide formation
of the constituents gallium and indium. This increases strength of
the afore-mentioned alloying elements.
[0020] According to another advantageous feature of the present
invention, the alloy may include 60 to 80% of gallium, 10 to 30% of
indium, and 1 to 20% of tin. Other constituents such as bismuth or
antimony may be added. The alloying constituents are important for
adjusting the melting temperature. The material properties of the
heat conductor as realized by the alloying constituents can be
selected by taking into account processing temperature and
operating temperature range. Currently preferred is the use of
Galinstan.RTM. and sodium as heat conductor.
[0021] According to another advantageous feature of the present
invention, the heat pipe has a wall which may be wetted with a
metallic carrier substrate. Currently preferred is the use of an
austenitic special steel alloy as carrier substrate.
[0022] According to another advantageous feature of the present
invention, the thermoelectrical generator can be arranged on a cold
side of the heat pipe. As a result, the thermoelectric generator is
thermally and physically separated from the heating channel
including exhaust-gas carrying channel. The heat pipe can be
configured through selection of the heat pipe material and fluid
within the heat pipe in such a way as to establish an optimal heat
transfer from exhaust gas to the thermoelectric generator
module.
[0023] The configuration of the heat pipe may be realized in such a
way that a respective combustion engine for which the heat
exchanger is conceived is operated with a predominant operating
range in a driving cycle. The heat pipe can be configured in an
optimum manner for this operating range. When the operating range
is exceeded, for example at high nominal load range, the heat pipe
assumes a protection function to prevent thermal overload of the
thermoelectric generator. Moreover, the thermoelectric generator is
optimally fed with heat energy by using the heat pipe so as to
achieve high efficiency.
[0024] According to another advantageous feature of the present
invention, the heat pipes extend with more than half of their
length in longitudinal direction into the heating channel and with
less than half of their length into the cooling channel. Currently
preferred is a ratio of about two third of the heat pipe extending
into the heating channel and one third extending into the cooling
channel.
[0025] According to another advantageous feature of the present
invention, the heat pipes can have a circular, oval, rectangular
and/or polygonal cross section. The configuration may also include
round-oval or flat-oval cross sections or also transversely
star-shaped or similar cross sectional shapes. This allows
realization of an optimum flow around the heat pipe to best suit
the flow conditions and field of use at hand. For example, it may
be required to attain a particularly small back pressure, in which
case the cross section should assume a more rounded configuration.
In the event of a desired turbulent flow behavior, the cross
section should be more polygonal.
[0026] According to another advantageous feature of the present
invention, heat exchanger ribs can be arranged on a hot side of the
heat pipes and oriented in a flow direction of the heating channel.
The presence of heat exchanger ribs increases the available surface
area useable for heat transfer. The heat exchanger ribs may be
provided to create a turbulent flow depending on their orientation
and configuration. For example, the heat exchanger ribs may have
break-off edges or other flow-influencing elements to promote heat
transfer.
[0027] According to another advantageous feature of the present
invention, the heat pipes can be oriented transversely to a flow
direction of coolant in the cooling channel and/or the heat pipes
can be oriented transversely to a flow direction of a heating
medium in the heating channel. As a consequence of the
substantially transverse orientation in relation to the flow
direction of the coolant or heating medium, optimum heat transfer
is realized at the heat pipes. The generated back pressure or
pressure loss of the coolant and heating medium flowing through the
heat exchanger can thus be kept to a minimum.
[0028] According to another advantageous feature of the present
invention, the thermoelectrical generators can be arranged
substantially about a circumference of the heat pipe. This means
within the scope of the invention that the thermoelectrical
generators are placed in surrounding relationship to the heat
pipes, at least in surrounding relationship to sections of the heat
pipes. It can be beneficial to arrange the thermoelectrical
generators only on a section of the heat pipes that faces away from
the flow direction or on a section that faces the flow
direction.
[0029] According to another advantageous feature of the present
invention, the heat pipe can be operated in a way that best suits
an operating performance of the thermoelectrical generator. Thus,
the thermoelectrical generator exhibits optimal operating
performance at certain temperature differences. In this operating
performance or in this operating point, the thermoelectrical
generator operates at optimal efficiency. This efficiency
characteristic may for example be established on the side of the
thermoelectrical generator by means of a resistance or preceding
conceptional adjustment. The heat exchanger pipe has advantageously
also a matching operating behavior to thereby realize or ensure an
optimum operating performance of the thermoelectrical
generator.
[0030] According to another advantageous feature of the present
invention, the operation of the heat pipe can be constructed for
closed-loop control and/or open-loop control. The use of valves in
the heat pipes can ensure a closed-loop control and/or open-loop
control. Also conceivable is the use of a throttle to vary the heat
transport within the heat pipe. For example, the presence of a
pressure valve or a throttle allows control of a heat transport
across the heat pipes at high temperature ranges of for example
more than 500.degree. C., preferably above 5600.degree. C.
Currently preferred is a control at a temperature range of more
than 700.degree. C. In this way, the thermoelectrical generator
cannot be overloaded as a result of high heat impacts.
BRIEF DESCRIPTION OF THE DRAWING
[0031] Other features and advantages of the present invention will
be more readily apparent upon reading the following description of
currently preferred exemplified embodiments of the invention with
reference to the accompanying drawing, in which:
[0032] FIG. 1 is a schematic cross sectional view of one embodiment
of a heat exchanger with heat pipes in accordance with the present
invention;
[0033] FIG. 2 is a cross sectional view taken along the line II-II
in FIG. 1; and
[0034] FIG. 3 is a sectional view of another embodiment of a heat
exchanger according to the present invention.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
[0035] Throughout all the figures, same or corresponding elements
may generally be indicated by same reference numerals. These
depicted embodiments are to be understood as illustrative of the
invention and not as limiting in any way. It should also be
understood that the figures are not necessarily to scale and that
the embodiments are sometimes illustrated by graphic symbols,
phantom lines, diagrammatic representations and fragmentary views.
In certain instances, details which are not necessary for an
understanding of the present invention or which render other
details difficult to perceive may have been omitted.
[0036] Turning now to the drawing, and in particular to FIG. 1,
there is shown a schematic cross sectional view of one embodiment
of a heat exchanger in accordance with the present invention,
generally designated by reference numeral 1 and including a cooling
channel 2 and a heating channel 3. A separation layer 4 is arranged
between the cooling channel 2 and the heating channel 3. The
cooling channel 2 and the heating channel 3 are coupled with one
another by heat pipes 5. A flow direction S.sub.K of the cooling
channel 2 is established in parallel relation to a flow direction
S.sub.H of the heating channel 3. A heat transfer takes place at
the partition layer 4 on one hand, and across the heat pipes 5 on
the other hand. The heat pipes 5 have a cooling section 6 which
extends in the cooling channel 2 and a heating section 7 which
extends in the heating channel 3. In other words, coolant 8 in the
cooling channel 2 sweeps about the heat pipes 5 in the area of the
cooling section 6, and a heating medium 9 in the heating channel 3
sweeps about the heat pipes 5 in the area of the heating section 7.
The surface area in the heating section 7 is increased by the
provision of heat exchanger ribs 10 which are arranged on the
heating section 7 of the heat pipes 5 and oriented in the flow
direction S.sub.H of the heating channel 3. Arranged on the cooling
section 6 are thermoelectric generators 11 which have connections,
not shown here, for discharge of electric energy generated by the
thermoelectric generators 11.
[0037] FIG. 2 shows a cross sectional view taken along the line
II-II in FIG. 1 and depicts by way of example three different types
of arrangements of the thermoelectric generators 11 in the area of
the cooling sections 6 of the heat pipes 5. Reference numeral 2a
relates to an illustration of an internal heat pipe 5 which, in
relation to the flow direction S.sub.K of the coolant 8, has on the
outside thermoelectric generators 11, some of which face the flow
direction S.sub.K and some of which face away from the flow
direction S.sub.K. Reference numeral 2b relates to an illustration
of an internal heat pipe 5 which has a thermoelectric generator 11
only on the side of the heat pipe 5 in facing relation to the flow
direction S.sub.K. Reference numeral 2c relates to an illustration
of an internal heat pipe 5 which is completely embraced by a
thermoelectric generators 11.
[0038] Referring now to FIG. 3, there is shown a sectional view of
another embodiment of a heat exchanger according to the present
invention, generally designated by reference numeral 1a. Parts
corresponding with those in FIG. 1 are denoted by identical
reference numerals and not explained again. The description below
will center on the differences between the embodiments. In this
embodiment, the heat pipes 5 project into the heating channel 3
from opposite sides and thus are intertwined. This type of
configuration saves space and can be arranged, for example when a
heating channel 3 is involved in the form of an exhaust pipe, on
top or on the bottom or also in star formation or at an angular
offset to one another.
[0039] While the invention has been illustrated and described in
connection with currently preferred embodiments shown and described
in detail, it is not intended to be limited to the details shown
since various modifications and structural changes may be made
without departing in any way from the spirit and scope of the
present invention. The embodiments were chosen and described in
order to explain the principles of the invention and practical
application to thereby enable a person skilled in the art to best
utilize the invention and various embodiments with various
modifications as are suited to the particular use contemplated.
[0040] What is claimed as new and desired to be protected by
Letters Patent is set forth in the appended claims and includes
equivalents of the elements recited therein:
* * * * *