U.S. patent application number 12/514476 was filed with the patent office on 2010-09-30 for heat exchanger.
This patent application is currently assigned to BEHR GMBH & CO. KG. Invention is credited to Juergen Barwig, Peter Geskes, Jens Ruckwied.
Application Number | 20100243220 12/514476 |
Document ID | / |
Family ID | 39251989 |
Filed Date | 2010-09-30 |
United States Patent
Application |
20100243220 |
Kind Code |
A1 |
Geskes; Peter ; et
al. |
September 30, 2010 |
HEAT EXCHANGER
Abstract
The invention relates to a heat exchanger, particularly for a
motor vehicle, comprising at least one duct (24-29) through which a
fluid flows and of which at least some section have a curved shape.
Preferably, said heat exchanger comprises several ducts through
which a fluid flows and of which at least some sections have a
curved shape. In order to increase the heat exchanging capacity,
the duct (24-29) of which at least some sections have a curved
shape is provided inside a profiled extruded element.
Inventors: |
Geskes; Peter; (Ostfildern,
DE) ; Barwig; Juergen; (Stuttgart-Vaihingen, DE)
; Ruckwied; Jens; (Stuttgart, DE) |
Correspondence
Address: |
LEYDIG VOIT & MAYER, LTD
700 THIRTEENTH ST. NW, SUITE 300
WASHINGTON
DC
20005-3960
US
|
Assignee: |
BEHR GMBH & CO. KG
Stuttgart
DE
|
Family ID: |
39251989 |
Appl. No.: |
12/514476 |
Filed: |
November 15, 2007 |
PCT Filed: |
November 15, 2007 |
PCT NO: |
PCT/EP07/09878 |
371 Date: |
May 27, 2010 |
Current U.S.
Class: |
165/133 ;
165/148 |
Current CPC
Class: |
F28F 21/08 20130101;
F02M 26/32 20160201; F28F 1/022 20130101; F28F 9/013 20130101; F28F
2275/025 20130101; F28D 2021/0092 20130101; F02M 26/50 20160201;
F28F 2275/06 20130101; F28D 7/1692 20130101; Y02T 10/146 20130101;
F28D 7/08 20130101; F28F 19/02 20130101; F28F 27/02 20130101; F28D
1/0471 20130101; Y02T 10/12 20130101; F28F 21/067 20130101; F28F
2009/029 20130101; F28D 2021/0089 20130101; F28D 21/0003 20130101;
F02B 29/0418 20130101; F28D 7/082 20130101; F28F 9/18 20130101;
F28F 2275/04 20130101; F02M 26/11 20160201; F02B 29/0462 20130101;
F28D 2021/0082 20130101; F02M 26/25 20160201; F02M 26/29 20160201;
F28F 2255/16 20130101 |
Class at
Publication: |
165/133 ;
165/148 |
International
Class: |
F28F 13/18 20060101
F28F013/18; F28D 1/00 20060101 F28D001/00 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 15, 2006 |
DE |
10 2006 054 221.5 |
Claims
1. A heat exchanger for a motor vehicle comprising at least one
flow channel with a fluid throughflow, which at least in sections
has a curved shape, wherein the at least one flow channel is
provided in an extruded profile.
2. The heat exchanger according to claim 1, comprising several flow
channels which at least in sections have a curved shape, wherein
the several flow channels are provided in an extruded profile.
3. The heat exchanger according to claim 2 wherein the extruded
profile has at least one outer wall surrounded by the flow of a
cooling agent, and at least one inner wall along which a combustion
gas, flows.
4. The heat exchanger according to claim 3, wherein the outer wall,
surrounded by the flow of the cooling agent, has an at least
partially rounded shape in the cross section.
5-6. (canceled)
7. The heat exchanger according to claim 1, wherein the at least
one flow channel has a corrosion-inhibiting coating.
8. The heat exchanger according to claim 1, wherein, in addition to
the curved shape at least in sections, the at least one flow
channel has a 180.degree. deflection.
9. (canceled)
10. The heat exchanger according claim 1, wherein the curved shape
varies transversely to and/or in the direction of the extension of
the flow channel.
11. The heat exchanger according to claim 1, wherein the at least
one flow channel has, downstream, an increasing amplitude (A)
and/or a decreasing pitch (T).
12. The heat exchanger according to claim 11, having a ratio
between the amplitude (A) and thickness (d) of the extruded profile
in the range of 0-2.
13. The heat exchanger according to claim 11, having a ratio
between the pitch (T) and thickness (d) of the extruded profile in
the range of 3-10.
14. The heat exchanger according to claim 12, wherein the ratio
between the amplitude (A) and the thickness (d) of the extruded
profile is in the range of 0-0.7.
15. The exchanger according to claim 1, wherein the extruded
profile has a thickness in the range of 3-12 mm.
16-18. (canceled)
19. The heat exchanger according to claim 1, further comprising a
bypass flap upstream or downstream of the heat exchanger.
20-22. (canceled)
23. The heat exchanger according to claim 2, wherein the extruded
profile is fixed at an end on a base element.
24. (canceled)
25. The heat exchanger according to claim 2, wherein the extruded
profile is fixed at an end on two base elements.
26-29. (canceled)
30. The heat exchanger according to claim 1, wherein the extruded
profile is situated in a housing a liquid cooling agent
throughflow, the housing having an inflow and an outflow for the
cooling agent.
31. (canceled)
32. The heat exchanger according to claim 30, wherein at least one
guiding element for guiding the cooling agent is located in the
housing.
33. (canceled)
34. The heat exchanger according to claim 2, further comprising
support elements located between the extruded profiles.
35-38. (canceled)
39. The heat exchanger according to claim 12, having a ratio
between the pitch (T) and the thickness (d) of the extruded profile
in the range of 3-10.
Description
[0001] The invention concerns a heat exchanger, in particular, for
a motor vehicle, in accordance with the preamble of claim 1.
[0002] In the construction of heat exchangers or heat interchangers
for motor vehicles, higher requirements are increasingly demanded
for exchange performance with a simultaneously restricted
installation space. In particular the cooling of combustion gas for
the purpose of recirculating it to a combustion engine means that
increasingly high heat outputs have to be removed. Also with other
heat interchangers, such as oil coolers or charge-air coolers,
increasingly higher requirements are being made for transfer or
exchange performance. In addition to the high performance, the heat
interchangers or heat exchangers must also withstand increasingly
higher pressures. In particular with heat exchangers or heat
interchangers in which a gaseous fluid, for example, combustion gas
or charge air, flows at the site of the heat interchanger to be
cooled, the pressures rise steadily due to higher and higher engine
loads.
[0003] Basically, the performance and the resistance to pressure of
a heat interchanger can be increased in that the flow channel cross
sections are made smaller. The pressure drop thereby rises
considerably both with gas-conducting as well as oil-conducting
channels, so that a high output (pump, engine) is required in order
to pump the fluids through the coolers.
[0004] When using the heat interchanger as a combustion gas cooler
on the high pressure side of the engine, there is also the danger
that considerable quantities of soot lead to a drop in the heat
interchanger performance. Moreover, there is the risk that the
cooler will become clogged due to the soot accumulations. The
problem of soot accumulation is intensified by a reduction of the
channel cross sections.
[0005] The goal of the invention is to create a heat exchanger in
accordance with the preamble of claim 1, which, with a limited
installation space, has a high heat exchanger performance and can
be produced at a low cost.
[0006] With a heat exchanger, in particular for a motor vehicle,
with at least one flow channel with a fluid throughflow, which at
least in sections has a curved shape, preferably with several flow
channels with a fluid throughflow which at least in sections have a
curved shape, the goal is obtained in that the flow channel which
at least in sections has a curved shape is provided in an extruded
profile. The flow channel has a fluid throughflow for the purpose
of a heat exchange. The extruded profile has the advantage that it
can be produced at low cost. In investigations carried out within
the framework of the invention under consideration, it was
determined that the heat exchanger performance of a heat exchanger
can be clearly increased by the extruded profiles curved according
to the invention, without having to select excessively small flow
channel cross sections, which can lead to an enormous rise in
pressure drop, or in the case of combustion gas coolers, to
clogging due to soot particles.
[0007] A preferred embodiment of the heat exchanger is
characterized in that several flow channels, which at least in
sections have a curved shape, are provided in an extruded profile.
At least two flow channels arranged next to one another within an
extruded profile are particularly advantageous thereby. A
separating interior wall which is integrally connected with the
remaining material of the extruded profile is provided between two
adjacent flow channels in the extruded profile. In this way, a
large contact surface between the fluid and the heat-exchanging
material of the extruded profile can be created at low cost and in
an operationally reliable matter. In addition, the extruded profile
has the advantage that the separation wall or the separation walls,
which are also designated as webs, clearly increase the resistance
to internal pressure of the extruded profile, so that with such
profiles higher pressures can also be employed without damage or
deformations appearing in the extruded profile. The interior walls
or separation walls or webs in the extruded profile also lead to an
increase in surface area, and thus to an increase in the rate of
heat release.
[0008] It is generally preferred that several extruded profiles be
provided to enable an effective heat exchange between the cooling
agent and the fluid in the flow channels.
[0009] Another preferred embodiment of the heat exchanger is
characterized in that the extruded profile has at least one outside
wall with a surrounding flow of a medium, in particular, a cooling
agent, and at least one inside wall along which flows a fluid, in
particular, a combustion gas. At least two flow channels are
thereby provided within one extruded profile in a particularly
advantageous manner. In this way, a large surface area of contact
between the fluid and the heat-exchanging material of the extruded
profile can be made available at low cost and in an operationally
reliable manner.
[0010] Another preferred embodiment of the heat exchanger is
characterized in that the outside wall with the surrounding flow of
the medium has a cross-sectional shape which is at least partially
rounded. In this way, the flexibility of the extruded profile is
improved. In accordance with another essential aspect of the
invention, an initially linearly extruded profile is provided, in
an additional processing step, with the curved shape, in
particular, with an undulating profile.
[0011] Another preferred embodiment of the heat exchanger is
characterized in that several extruded profiles are provided in a
particularly integrated manner, which comprises at least one flow
channel that has, at least in sections, a curved shape, preferably
several flow channels that have, at least in sections, a curved
shape. The heat exchanger according to the invention has flow
channels which are separate from one another and are preferably
shaped in an undulating form. This makes it possible to implement
enlarged channel cross sections, and in the case of a combustion
gas cooler a clogging problem due to soot does not develop. The
high output density of the heat exchanger according to the
invention is essentially obtained in that a preferably undulating
deflection of a fluid in an undulating extruded profile leads to a
vortex formation in the flow. The pressure drop rises only slightly
in comparison to a straight extruded profile with the same channel
cross-sectional area. The increased heat output can be attributed
to a prolongation of the flow path and to turbulence or vortex
formation--both on the side of the fluid to be cooled and also on
the cooling fluid side.
[0012] Another preferred embodiment of the heat exchanger is
characterized in that the at least one extruded profile is made of
an alloy based on aluminum. Aluminum has quite good corrosion
resistance and can be extruded in a low-cost manner in largely
arbitrary cross-sectional forms. In particular condensation is
formed during the cooling of combustion gas that has a very low pH
value and is therefore very corrosive. This is the case with all
combustion gas coolers--that is, both with coolers which are used
in high-pressure combustion gas recycling and also with coolers
which are used in low-pressure combustion gas recycling. With
sufficient cooling, aluminum can definitely be used in the
construction of combustion gas heat interchangers. It has thereby
been shown in particular that extruded profiles without a lengthy
heat treatment offer a very good corrosion protection, since the
fine grain of the aluminum is not destroyed. This fine grain
structure, however, is the prerequisite for corrosion not to
produce deep furrows, but rather only a surface material erosion,
which in turn guarantees a long service life of the heat
exchanger.
[0013] Another preferred embodiment of the heat exchanger is
characterized in that the at least one flow channel has a
corrosion-inhibiting coating. In particular in designing the heat
exchanger as a combustion gas heat exchanger, it is possible to
prolong the service life of the heat exchanger by means of such
coatings.
[0014] Another preferred embodiment of the heat exchanger is
characterized in that the at least one flow channel has a
180.degree. deflection, in addition to the shape which is curved at
least in sections. In this way, a heat exchanger with a U-shaped
throughflow is created which is also designated as a U-flow heat
exchanger. In a preferred embodiment, two bases are used with a
heat exchanger with a U-shaped throughflow. The extruded profiles
fit on both sides into these bases. The deflection of the fluid to
be cooled preferably takes place in a separate return cap.
[0015] Another preferred embodiment of the heat exchanger is
characterized in that the curved shape has turbulence-producing
bends or undulations. The extruded profile can have different
sections with different bends and/or undulations.
[0016] Another preferred embodiment of the heat exchanger is
characterized in that the curved shape varies transversely to,
and/or in the extension direction of the flow channel. The
turbulence-producing bends or undulations in the flow channel vary
so as to reduced undesired pressure drops.
[0017] Another preferred embodiment of the heat exchanger is
characterized in that the at least one flow channel has an
increasing undulation downstream, in particular, an increasing
amplitude and/or a decreasing pitch. For the optimal adaptation of
the heat interchanger performance and pressure drop to prespecified
requirements, the amplitude and the pitch of the curved shape, in
particular, the undulations, are changed in the longitudinal
direction of the flow channel. The undulation preferably increases
thereby with increasing flow path of the fluid to be cooled, so as
to keep as low as possible the pressure drop rise. In this context,
increase of the undulation means that either the amplitude
increases toward the rear or the division decreases toward the
rear. It is also possible to combine the change of the amplitude
with the change of pitch.
[0018] The variability has advantages with regard to pressure drop,
since the preferably hot fluid in the front area of the cooler has
the tendency to produce a high pressure drop due to a low fluid
density. An additional, artificially produced high turbulence due
to a strong undulation in the front area of the flow channel would
lead to very high pressure drops there. This strong turbulence is
thereby not absolutely necessary in the front cooler area for a
high heat output, since the large temperature differential between
the fluid to be cooled and the cooling medium is sufficient to
confer a high performance even with a low turbulence.
[0019] In contrast to the front cooler area a strong turbulence is
to be preferred in the rear cooler area since here the increased
pressure drop is due less to an increased fluid density, and the
temperature differential between the two fluids is too small to
transfer the required heat power. Only by means of the high
turbulence that is produced by a strong flow channel undulation can
the performance be increased sufficiently, even with a low
temperature differential between the two fluids. Basically, it is
also possible thereby to increase the waviness continuously from
the front to the rear.
[0020] In addition to the pure sine-like undulation, undulation
forms which do not run uniformly are also conceivable. Thus, flow
channels which have a sawtooth or a trapezoidal shape, with some
straight sections, are conceivable.
[0021] Other preferred embodiments of the heat exchanger are
characterized in that the ratio between the amplitude and the
thickness of the extruded profile is in the range of 0-2, in
particular, in the range of 0-0.7, with particular preference, in
the range of 0-0.3.
[0022] Another preferred embodiment of the heat exchanger is
characterized in that the ratio between the pitch and the thickness
of the extruded profile is in the range of 3-10.
[0023] Another preferred embodiment of the heat exchanger is
characterized in that the extruded profile has a thickness in the
range of 3-12 mm, preferably in the range of 5-9 mm.
[0024] Other preferred embodiments of the heat exchanger are
characterized in that the extruded profile has bent or curved areas
and/or is reshaped to have undulations. Individual sections of the
extruded profile can be reshaped to be undulating. It is, however,
also possible for the extruded profile to be reshaped with
undulations over its entire length or a great part of its
length.
[0025] Another preferred embodiment of the heat exchanger is
characterized in that the extruded profile is reshaped in a
sawtooth or trapezoidal manner. Individual sections of the extruded
profile can be reshaped in a sawtooth or trapezoidal manner.
However, it is also possible for the extruded profile to be
reshaped in a sawtooth or trapezoidal manner over its entire length
or a great part of its length. With the trapezoidal undulation, the
fluid is initially deflected and vortices are produced. In the
following straight stretches, the vortices decay slowly and also
increase the heat output in the straight section. Only when the
turbulence and the vortices have largely subsided is the turbulence
once again stirred up by renewed bends. Basically, moreover, all
other conceivable bend forms are also possible. With the sawtooth
shape, the rising as well as the descending branch can be steeper
than the other branch. The goal of all these variants is to
minimize the pressure drop without the heat exchanger performance
declining too much.
[0026] Also, undulation modifications can be implemented in a heat
exchanger with a U-shaped throughflow. Thus, a front flow path
before the deflection can have no undulation or a slight one and a
rear flow path behind the deflection can have a strong undulation.
In this way, a high output with a moderate pressure rise is also
obtained for a cooler with a U-shaped throughflow.
[0027] Another preferred embodiment of the heat exchanger is
characterized in that a bypass flap is upstream or downstream from
the heat exchanger. The bypass flap is used to direct the fluid,
uncooled, past the area of the cooled flow channels. With a cooler
with a straight throughflow, a bypass channel must also be
provided, which ideally is thermally insulated via an insulating
tube. Preferably, the insulating tube is constructed from stainless
steel. With a cooler with a U-shaped throughflow, the bypass
function is obtained, for example, in an entry diffuser, in that
the bypass flap allows the fluid to flow past the cooler.
[0028] Another preferred embodiment of the heat exchanger is
characterized in that the fluid is a combustion gas of a combustion
engine of a motor vehicle. In particular, the goal of cooling very
hot combustion gas can in general be obtained particularly well by
a heat exchanger according to the invention, since it has a very
high heat exchange performance for a given installation space.
[0029] Another preferred embodiment of the heat exchanger is
characterized in that the fluid is a charge air of a combustion
engine of a motor vehicle. Here also it is possible to obtain clear
improvements with the heat exchanger according to the
invention.
[0030] Another preferred embodiment of the heat exchanger is
characterized in that the fluid is a lubricating oil from a
lubricating oil circulation of a motor vehicle. Here too it is
possible to obtain clear improvements with the heat exchanger
according to the invention.
[0031] Another preferred embodiment of the heat exchanger is
characterized in that the extruded profile is fixed at the end to a
base element.
[0032] Another preferred embodiment of the heat exchanger is
characterized in that both ends of the extruded profile empty into
the base element.
[0033] Another preferred embodiment of the heat exchanger is
characterized in that the extruded profile is fixed at the end to
two base elements. The extruded profile extends between the two
base elements.
[0034] Another preferred embodiment of the heat exchanger is
characterized in that the ends of the extruded profile empty into
one of the base elements.
[0035] With a heat exchanger with a straight throughflow, the flow
channels preferably empty, on the entry and exit sides, into a base
where they are joined thermally (welded or soldered), joined
mechanically (calked or sealed off), or cemented. The bases are
connected with a housing of the heat exchanger by welding,
soldering, screwing, crimping, or cementing. For a heat exchanger
with a straight throughflow, a diffuser is then added to the
housing on both sides that is screwed on, welded, soldered, or
cemented. For a heat exchanger with a U-shaped throughflow, a
diffuser is added only on the entry side, wherein the diffuser
contains a separation wall. The entry diffuser or the exit diffuser
can each contain a bypass flap so as to direct the fluid, uncooled,
past the area of the cooled flow channels.
[0036] Another preferred embodiment of the heat exchanger is
characterized in that the base element or the base elements are
preferably connected with a diffuser in a material-bonding manner.
The material-bonding connection can be produced, for example, by
welding, soldering, or cementing. The base elements can also be
screwed together with the diffuser.
[0037] Another preferred embodiment of the heat exchanger is
characterized in that the flow channels or extruded profiles are
connected, in a material-bonding manner, with the base element or
the base elements, for example, by cementing, furnace soldering,
flame soldering, induction soldering, or welding.
[0038] Another preferred embodiment of the heat exchanger is
characterized in that the entire heat exchanger is or will be
soldered in a furnace. Basically, in a soldering process the entire
cooler, with all the sealing surfaces such as the tube-bottom
connection or the bottom-housing connection, are soldered in a
soldering furnace (vacuum or Nocolok). In order to maintain the
advantages of the fine grain structure for a good corrosion
behavior, however, only a local, short-term thermal heating, in
particular, in the area of the joint sites, is advantageous. This
can be obtained by a local flame soldering, induction soldering, or
welding, such as laser welding.
[0039] Another preferred embodiment of the heat exchanger is
characterized in that the extruded profile is located in a housing
with, in particular, a liquid cooling agent throughflow. A
particularly effective cooling of the fluid can be obtained in that
the flow channels are situated in the housing. However, it is also
possible for the housing to be absent and for the fluid to be
cooled by means of cooling air.
[0040] Another preferred embodiment of the heat exchanger is
characterized in that the housing has an inflow and an outflow for
the cooling agent.
[0041] Another preferred embodiment of the heat exchanger is
characterized in that at least one conducting element for guiding
the cooling agent is located in the housing. For the further
improvement of the flow around the flow channels, baffle plates can
be preferably placed on the side with the cooling agent; they can
brace the flow channels in vibrations occur and prevent damage to
the cooler. Such baffle elements can direct the flow to certain
areas and/or produce turbulences in the cooling agent.
[0042] Another preferred embodiment of the heat exchanger is
characterized in that support agents in the housing are situated to
hold the flow channels. The support agents are used to limit the
oscillation amplitude of the flow channels and thus to prevent
crack formation even with strong vibrations.
[0043] Another preferred embodiment of the heat exchanger is
characterized in that ribs, baffle plates, or other elements, in
particular, support elements, are located between the extruded
profiles. The support means can be designed as ribs or turbulence
producers and clearly increase the transfer of heat.
[0044] Another preferred embodiment of the heat exchanger is
characterized in that the elements are soldered in, cemented in, or
clamped in between the extruded profiles. To the extent that the
support means in a housing are located in the liquid cooling agent,
they can also be made of a thermally nondemanding material (such as
plastic), so as to lower costs.
[0045] Another preferred embodiment of the heat exchanger is
characterized in that the housing is essentially made of aluminum.
Production costs are reduced in this way.
[0046] Another preferred embodiment of the heat exchanger is
characterized in that the housing is essentially made of plastic.
The production is simplified in this way.
[0047] If the cooling medium is not a cooling medium but rather
cooling air, then the housing can also be dispensed with. Such a
cooler can then be incorporated in the cooling module or another
suitable site in the engine compartment, where it is sufficiently
supplied with cooling air.
[0048] The invention moreover concerns a method for the production
of a heat exchanger which will be described first, in which an
extruded tube is reshaped in such a way that it has, at least in
sections, a curved shape.
[0049] Other advantages, features, and details of the invention can
be deduced from the following description, in which various
embodiments are described in detail with reference to the drawings.
The figures show the following:
[0050] FIG. 1, a schematic sectional view of a heat exchanger in
accordance with a first embodiment, without a bypass channel;
[0051] FIG. 2, a schematic sectional view of a heat exchanger
similar to that in FIG. 1, with a bypass channel;
[0052] FIG. 3A, a schematic sectional view of a heat exchanger in
accordance with another embodiment, with a U-shaped throughflow and
with a bypass flap;
[0053] FIG. 3B, a heat exchanger similar to that in FIG. 3A,
without a bypass flap;
[0054] FIG. 3C, an extruded profile according to the invention, in
cross section;
[0055] FIG. 4, a schematic sectional view of a heat exchanger
similar to that in FIG. 3B, according to another embodiment;
[0056] FIG. 5, a schematic sectional view of a heat exchanger
similar to that in FIG. 3B, in accordance with another
embodiment;
[0057] FIG. 6, a schematic sectional view of a heat exchanger in
accordance with another embodiment;
[0058] FIGS. 7A and B, two embodiments of undulating flow
channels;
[0059] FIG. 8, another embodiment of a flow channel with
trapezoidal undulations;
[0060] FIG. 9, a schematic sectional view of a heat exchanger
similar to that in FIG. 1, without a housing;
[0061] FIG. 15.2, a representation of the preferred selection of a
hydraulic diameter based on measurements and calculations, with a
view to an improved heat transfer;
[0062] FIG. 17.2, a demonstration of a hydraulic diameter, based on
measurements and calculations, in which a stabilization of a
pressure drop can be expected at a defined level even with
increasing operating time of the flow channel;
[0063] FIG. 18.2, a representation of a preferred selection of a
hydraulic diameter based on measurements and calculations, with
reference to the ratio of the circumference that can be wetted with
the first fluid and an outer circumference of the flow channel;
[0064] FIG. 19A.2, a modification of a preferred embodiment of a
cross section of a flow channel with extruded channel jacket and
with the webs extruded with the channel jacket;
[0065] FIG. 100A.2, a modification of another embodiment as in FIG.
19A.2, with partial webs;
[0066] FIGS. 111A.2 and 111B.2, two modifications of another
embodiment as in FIG. 19A.2, with partial webs.
[0067] In FIG. 1, a heat exchanger 1 is represented schematically
in section. The heat exchanger 1 comprises a housing 2, which
emerges from a collecting box 4. The collecting box 4 represents a
diffuser and is equipped with an inlet connection 5. Gas is
supplied to the collecting box 4 through the inlet connection 5, as
is indicated by an arrow 6. A collecting box 8 is located on the
opposite side of the housing 2; it also represents a diffuser. The
collecting box 8 has a gas outlet connection 9. The exiting gas is
indicated by an arrow 10.
[0068] Moreover, an inlet connection 14 for a cooling agent is
provided on the housing 2. The entering cooling agent is indicated
by an arrow 15. Furthermore, the housing 2 is equipped with an
outlet connection 16 for the cooling agent. The exiting cooling
agent is indicated by an arrow 17. The interfaces between the
housing 2 and the collecting box 4, 8 are each defined by a base
element 21, 22. Flow channels 24-29 extend between the base
elements 21, 22. The flow channels 24-29 are formed in tubes, which
are constructed as the extruded profile. In accordance with an
essential aspect of the invention, the extruded profiles with the
flow channels 24-29 do not have a straight-line, but rather an
undulating shape.
[0069] FIG. 2 schematically represents in section a heat exchanger
31 similar to the heat exchanger 1 from FIG. 1. To designate the
same parts, the same reference symbols are used. In order to avoid
repetitions, reference is made to the preceding description of FIG.
1. The differences between the embodiments of FIGS. 1 and 2 are
mainly discussed below.
[0070] The heat exchanger 31 represented in FIG. 2 comprises a
housing 32 with an integrated bypass channel 33. The bypass channel
33 creates a direct connection between the collecting boxes 4 and
8, circumventing the cooled flow channels 24-29. To control the
flow, a bypass flap 34 is provided in the collecting box 4. In the
position of the bypass flap 34, represented with a solid line, the
flow runs through the flow channels 24-29 and not through the
bypass channel 33. If the bypass flap 34 is moved into a position
35, indicated with a broken line, then the flow runs only through
the bypass channel 33 and not through the flow channels 24-29.
[0071] In FIGS. 3A, 3B, and 4, various embodiments of a heat
exchanger 41 with a housing 42 are depicted. The housing 42 is
equipped with an inlet connection 43 for the cooling agent. The
entering cooling agent is indicated by an arrow 43A. The housing 42
is in addition equipped with an outlet connection 44 for the
cooling agent. The exiting cooling agent is indicated by an arrow
44A. The housing 42 passes at one side into a collecting box 45
that is equipped with a bypass flap 46 or a mixing valve 46. An
arrow 48 indicates that a gas flow is supplied to the collecting
box 45. The entering gas flow 48 is cooled by the cooling agent
43A, 44A in the housing 42. The cooled exiting gas flow is
indicated by an arrow 49.
[0072] A base element 51 is located at the interface between the
housing 42 and the collecting box 45. Flow channels 53-55 open into
the base element 51; they also proceed from the base element 51.
The flow channels 53-55 do not run straight but rather undulate in
one section 58 and are deflected by 180.degree. in another section
59.
[0073] The mixing valve or bypass flap (46 in FIG. 3A) was omitted
in the embodiment depicted in FIG. 3B. Otherwise, the embodiment
shown in FIG. 3B is identical with the embodiment depicted in FIG.
3A.
[0074] FIG. 3C indicates that the flow channel 53 from FIGS. 3A and
3B is constructed as an extruded profile. The extruded profile 53
comprises four channels 61-64, which are respectively separated
from one another by a web 65, 66, 67. The webs 65-67 are also
designated as interior walls or separation walls. Gas for the
cooling is conducted through the channels 61-64. Channels 61-64 are
delimited on the outside by an outer wall 68. The outer wall 68
essentially has a rectangular cross section with rounded-off
corners.
[0075] The embodiment shown in FIG. 4 indicates that flow channels
71-73 can also be located in the housing 42; they run curved only
in one section 75. After a section 76 in which the flow channels
71-73 are deflected by 180.degree., the flow channels 71-73 run in
a straight line in another section 77.
[0076] In FIG. 5, a heat exchanger 81 is depicted schematically in
section that comprises a housing 82. On one side of the housing 82,
a collecting box 84 is provided which is itself subdivided. The
entering gas is indicted by an arrow 85. The exiting gas is
indicated by an arrow 86. The housing 82 is in addition equipped
with an inlet connection 91 for the cooling agent. The entering
cooling agent is indicated by an arrow 92. The housing 82 is in
addition equipped with an outlet connection 94 for the cooling
agent. The exiting cooling agent is indicated by an arrow 95.
[0077] A base element 98 is provided at the interface between the
collecting box 84 and the housing 82. Another base element 99 is
provided on the adjacent end of the housing 82.
[0078] At the base element 99, the housing 82 has a deflection
section 100. Flow channels 101A, 102A, 103A, 104A, 105A, and 106A
extend between the two base elements 98 and 99. The flow channels
101A have an undulating shape. The entering gas 85 from the
collecting box 84 arrives at the base element 99 via the flow
channels 104A-106A. The gas exiting from the flow channels
104A-106A is deflected jointly in the deflection section 100 of the
housing 82 and arrives at the collecting box 84 once again via the
flow channels 101A-103A.
[0079] FIG. 6 represents in section a heat exchanger 101 that
comprises a housing 102. The housing 102 proceeds from a collecting
box 104. Gas is supplied to the collecting box 104, as is indicated
by an arrow 105. On the opposite side, the housing 102 is delimited
by a collecting box 106. The exiting gas is indicated by an arrow
107. The housing 102 is in addition equipped with an inlet
connection 109 for the cooling agent. The entering cooling agent is
indicated by an arrow 110. The housing 102 is in addition equipped
with an outlet connection 111 for the cooling agent. The exiting
cooling agent is indicated by an arrow 112.
[0080] A base element 114, 115 is in each case provided at the
interfaces between the housing 102 and the collecting boxes 104,
106. Flow channels 121 or 126 extend between the two base elements
114 and 115. The flow channels 121-126 are provided in a section
131 with a flatter undulation than in another section 132.
[0081] In FIG. 7A, a section of a tube 140 is depicted in a top
view. The tube 140 is constructed as an extruded profile and is
equipped with a flow channel 141. As is depicted in FIG. 3C, the
tube 140 can also be equipped, however, with several flow channels.
The tube 140 has an essentially sinusoidal undulating form. The
amplitude of the undulating shape is designated by A. The pitch is
designated by T. The thickness of tube 140 is designated by d.
[0082] FIG. 7B indicates that a tube 145, constructed as an
extruded profile with a flow channel 146, can also be undulating in
sawtooth form. The amplitude of the sawtooth-like undulation is
designated with A. The pitch is designated by T. The thickness of
the tube 145 is designated by d.
[0083] FIG. 8 depicts a tube 148 with a flow channel 149, which has
a trapezoidal undulation. The amplitude of the trapezoidal
undulation is designated with A. The pitch of the trapezoid
undulation is designated by T. The thickness of the tube 148,
constructed as an extruded profile, is designated by d.
[0084] FIG. 9 shows a heat exchanger 151 schematically in section.
The heat exchanger 151 comprises an inlet element 152 for a fluid.
The entering fluid is indicated by an arrow 153. The heat exchanger
151 comprises, moreover, an outlet element 154 for the fluid. The
exiting fluid is indicated by an arrow 155. Flow channels 161-166
run between the inlet element 152 and the outlet element 154; they
are provided in extruded profiles. Conducting elements 157 for
cooling air are situated between the individual extruded profiles.
The conducting elements 157 are used simultaneously or
alternatively as support elements, and can be cemented, soldered,
or wedged with the extruded profiles.
[0085] In the embodiment shown in FIG. 9, the extruded profiles
with the flow channels 161-166 preferably have a surrounding flow
of cooling air. Therefore, in the heat exchanger 151 shown in FIG.
9, it is possible to dispense with a housing. The heat exchanger
151 can be incorporated in a cooling module or on another suitable
site in the engine compartment where it is provided with sufficient
cooling air.
[0086] FIG. 15.2 shows a heat transfer behavior or degree of
exchange, and thus the exemplary behavior of a heat transfer
performance of a heat interchanger with reference to a calculation
based on measurement data, for an example of a heat interchanger
designed as a combustion gas cooler. The data are indicated for
typical inlet conditions, wherein a combustion gas pressure in the
range of 1 bar was selected for simplification. The results,
however, are exemplary also for other combustion gas pressures. A
curve A shows the behavior of a heat interchanger when not dirtied;
a curve B, the behavior of a heat interchanger in the dirtied
state. FIG. 15.2 represents the degree of exchange as a function of
the hydraulic diameter.
[0087] As can be seen with the aid of curve A in FIG. 15.2, the
degree of exchange/heat transfer, which is decisive for the heat
interchanger performance, increases further with a declining
hydraulic diameter for the case that the heat interchanger is not
dirtied. The degree of exchange is found in an acceptable range
below a hydraulic diameter of 6 mm. As can be seen with the aid of
curve B in FIG. 15.2, the degree of exchange declines further below
a certain hydraulic diameter in an unacceptable manner, for the
case that the heat interchanger is dirtied. Such a lower limit of a
hydraulic diameter lies at 1.5 mm. The concept of the invention
thus provides for the flow channel to be characterized by a
hydraulic diameter which is formed as four times the ratio of the
area of the throughflow cross section to a circumference which is
wettable by the combustion gas, and which lies in a range between
1.5 mm and 6 mm. Moreover, one can see from the differently shaded
areas of FIG. 15.2 that in a preferred manner, the hydraulic
diameter should be in a range between 2 mm and 5 mm. As the area of
dark shading shows, the comparatively flat upper level of a degree
of exchange in a dirtied heat interchanger is in the preferred
range of a hydraulic diameter between 2.5 and 3.5 mm or 2.8 mm and
3.8 mm, wherein the latter range is relevant above all for a
high-pressure heat interchanger. It has been shown that as a result
of an upstream combustion gas purifier before the heat interchanger
in the form of the combustion gas cooler, the degree to which a
low-temperature heat interchanger is dirtied is less relevant than
for a high-pressure heat interchanger in the form of a combustion
gas cooler, which is usually exposed to higher particle and fouling
loads than a low-temperature heat interchanger. Nevertheless, a
pressure drop is relevant for a low-temperature heat interchanger
just as it is for a high-pressure temperature heat
interchanger.
[0088] From the upper curve in FIG. 17.2, one can see that the
pressure drop increases further--in this case depicted on the basis
of a pressure drop for a flow channel with a limit-value hydraulic
diameter of 1.5 mm--with increasing fouling--indicated as operating
time in hours. On the other hand, it has been shown that with a
selection of a hydraulic diameter of 3.2 mm--also with a selection
of a hydraulic diameter in the range between 3.0 mm and 3.4 mm,
preferably between 3.1 mm and 3.3 mm--the degree of fouling is
obviously stabilized even with increasing operating time, so that
the pressure drop is stabilized at an acceptable level.
[0089] FIG. 18.2 represents the ratio of the circumference that is
wettable by a combustion gas and an outer circumference of the flow
channel, as a function of the hydraulic diameter. A preferred ratio
is produced from the previously explained, shaded areas of a
preferred hydraulic diameter of 2 mm to 5 mm, in particular, 2.8 mm
to 3.8 mm. The aforementioned ratio lies in the range between 0.1
and 0.5 in order to obtain improved degrees of exchange and degrees
of pressure drop. A comparable tendency can also be determined with
the additional constructive designs, described in more detail
below, of a cross section in a flow channel with a throughflow.
Thus, FIG. 18.2 shows the explained ratio for various web spacings
a, (in this case, for two examples a=2 mm and a=5 mm) and for
various values of a ratio of a distance between two opposite
partial webs to a height of the tube cross section, which, in this
case, is designated by k. The ratio k should be in a range below
0.8 mm, preferably in a range between 0.3 mm and 0.7 mm. In this
case, the ratio k of a distance e between two opposite partial webs
to a height b of the tube cross section increases from 0.25-0.75 in
the direction of the arrow. This analysis is valid both for a
combustion gas cooler within the framework of a high-pressure
design in a combustion gas recycling system, and a combustion gas
cooler within the framework of a low-pressure design in a
combustion gas recycling system.
[0090] Below, FIG. 19A.2 to FIG. 111B.2 describe, by way of
example, constructive designs of a cross section of different
preferred flow channels. It should be equally clear thereby that
modifications of the same and an arbitrary combination of features
of the embodiments specifically described in the figures are
possible, and a hydraulic diameter in the range between 1.5 mm and
6 mm, preferably between 2 mm and 5 mm, preferably between 2.8 mm
and 3.8 mm, can nevertheless be obtained. In particular, with the
embodiments shown in the following figures, a modification is shown
in which a channel jacket thickness and a web thickness d are the
same or similar, and another modification is shown in which a ratio
of a web thickness d and a channel jacket thickness s is less than
1.0 mm. Accordingly, it is also possible to vary and adapt the wall
thicknesses of partial webs or similar dimensions, depending on the
objective to be attained.
[0091] In particular, the following true-to-scale figures show
embodiments of flow channels for a combustion gas recycling system
or a heat interchanger, for example, instead of the flow channels
in the combustion gas heat interchanger. In particular, the flow
channels explained below all fulfill the prerequisites of a
hydraulic diameter in accordance with the concept of the
invention.
[0092] FIG. 19A.2 shows two modifications of a flow channel 1061,
wherein the jacket thickness s and the web thickness d are
essentially the same. Moreover, the same reference symbols are used
for the same features.
[0093] The flow channel 1061 is formed as a profile which is, as a
whole, extruded--that is, as an extruded channel jacket together
with the extruded webs. Accordingly, the flow channel 1061 has a
channel jacket 1063 with an interior space 1067 that is surrounded
by a channel jacket inner side 1065, which in this case is designed
for the heat-exchanging conduction of the first fluid in the form
of a combustion gas. Furthermore, the flow channel 1061, in this
case, has five webs 1069, situated in the interior space 1067 on
the channel jacket inner side 1065, which are formed together with
the channel jacket 1063 as an integral extruded profile. A web 1069
runs entirely parallel to a flow channel axis, standing
perpendicular to the drawing plane, uninterrupted along the flow
path formed in the housing of a heat interchanger. The throughflow
cross section shown, transverse to the flow channel axis, is
designed to conduct the combustion gas in the interior space 1067.
Dimensioning is effected based on the hydraulic diameter d.sub.h
for the flow channel profile 1061 under consideration, with
reference to the distances a, b. The hydraulic diameter turns out
to be four times the ratio of the of the throughflow
cross-sectional area to a circumference which can be wetted by the
combustion gas. The area of the throughflow cross section is in
this case a multiple of the product of a and b. The wettable
circumference is in this case also the multiple of double the sum
of a and b. In this case a gives the width of the free cross
section of a flow path 1074 that is subdivided by the webs 1069 in
the flow channel, and b in this case gives the free height of the
flow path 1074.
[0094] Explained in more detail, in this flow channel 1063 and in
the following flow channels, a wall thickness s is in the range
between 0.2 mm and 2 mm, preferably in the range between 0.8 mm and
1.4 mm. A height b of a line of flow 1074 or a height of the
interior space 1067 is, in this case, in the range between 2.5 mm
and 10 mm, preferably in the range between 4.5 mm and 7.5 mm. A
width a of a line of flow 1074 is in the range between 3 mm and 10
mm, preferably in the range between 4 mm and 6 mm.
[0095] FIG. 100A.2 shows a modification of a particularly preferred
embodiment of a flow channel 1071, which--as explained
previously--differs merely in the wall thickness of the channel
jacket 1073 relative to the wall thickness of a web 1079. The flow
channel 1071 also has the webs 1079 in the form of whole webs and
in addition, partial webs 1079', situated alternately relative to
the whole webs 1079. The flow channel 1071 is in turn formed
entirely as an extruded profile, wherein a line of flow 1074 is
formed in turn by the distance between two whole webs 1079. In this
case, two partial webs 1079' are situated with front ends 1076
opposite one another.
[0096] In FIG. 111A.2 and FIG. 111B.2, two other modifications
1081, 1081' of a particularly preferred embodiment of a flow
channel 1081, 1081' are shown in which two partial webs 1089' are
located with front ends 1086 that are staggered laterally with
respect to one another.
[0097] A ratio of a distance a.sub.3, from a first partial web
1089' to a whole web 1089, to a distance a.sub.4, from a second
partial web 1089' to the whole web 1089, lies in a range between
0.5 mm and 0.9 mm, preferably in a range between 0.6 mm and 0.8 mm.
Basically, the distance e between two opposite partial webs 1079'
and/or between two partial webs 1089', staggered with respect to
one another, to a height b of the tube cross section is in a range
below 0.8 mm, in particular, in a range between 0.3 mm and 0.7
mm.
[0098] The extruded parts described in FIGS. 1, 2, 3A, 3B, 3C, 4,
5, 6, 7A, 7B, 8, 9, 15.2, 17.2, 18.2, 19A.2, 100A.2, 111A.2, and
111B.2 are in particular made from aluminum. In particular, the
extrusion materials have the following percentages by mass,
especially for corrosion protection.
[0099] Silicon: Si<1%, in particular Si<0.6%, in particular
Si<0.15%
[0100] Iron: Fe<1.2%, in particular Fe<0.7%, in particular
Fe<0.35%
[0101] Copper: Cu<0.5%, in particular Fe<0.2%, in particular
Cu<0.1%
[0102] Chromium: Cr<0.5%, in particular 0.05%<Cr<0.25%, in
particular 0.1%<Cr<0.25%
[0103] Magnesium: 0.02%<Mg<0.5%, in particular
0.05%<Mg<0.3%
[0104] Zinc: Zn<0.5%, in particular 0.05%<Zn<0.3%
[0105] Titanium: Ti<0.5%, in particular 0.05%<Ti<0.25%
[0106] To obtain a high corrosion resistance of the aluminum
alloys, the grain sizes, measured in the section of the component
in the extrusion direction, <250 micrometers, in particular,
<100 micrometers, in particular, <50 micrometers.
* * * * *