U.S. patent application number 12/834259 was filed with the patent office on 2011-01-06 for extruded tube for a heat exchanger.
Invention is credited to Peter Geskes, Ulrich Maucher, Jens RUCKWIED.
Application Number | 20110000657 12/834259 |
Document ID | / |
Family ID | 40681768 |
Filed Date | 2011-01-06 |
United States Patent
Application |
20110000657 |
Kind Code |
A1 |
RUCKWIED; Jens ; et
al. |
January 6, 2011 |
EXTRUDED TUBE FOR A HEAT EXCHANGER
Abstract
An extruded tube for a heat exchanger is provided that includes
two at least approximately parallel outer side walls that extend in
a longitudinal direction and a transverse direction of the extruded
tube and that are connected by two outer narrow sides in a vertical
direction of the extruded tube, wherein at least one continuous web
extends between the side walls in the longitudinal direction and in
the vertical direction and separates at least two ducts of the
extruded tube, and wherein at least one of the outer side walls has
embossings that serve to form both bulged portions that project
into the ducts of the side walls and also bulged portions that
extend substantially in the transverse direction of the web,
wherein the bulged portions of the at least one web have a
controlled orientation with respect to the transverse
direction.
Inventors: |
RUCKWIED; Jens; (Stuttgart,
DE) ; Maucher; Ulrich; (Korntal-Muenchingen, DE)
; Geskes; Peter; (Ostfildern, DE) |
Correspondence
Address: |
Muncy, Geissler, Olds & Lowe, PLLC
4000 Legato Road, Suite 310
FAIRFAX
VA
22033
US
|
Family ID: |
40681768 |
Appl. No.: |
12/834259 |
Filed: |
July 12, 2010 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
PCT/EP2008/010829 |
Dec 18, 2008 |
|
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|
12834259 |
|
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Current U.S.
Class: |
165/181 ;
72/253.1 |
Current CPC
Class: |
F28F 2001/027 20130101;
F28F 1/42 20130101; F28F 2255/16 20130101; F28F 1/422 20130101;
F28F 1/022 20130101 |
Class at
Publication: |
165/181 ;
72/253.1 |
International
Class: |
F28F 1/10 20060101
F28F001/10; B21C 23/00 20060101 B21C023/00 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 10, 2008 |
DE |
10 2008 003 737.0 |
Claims
1. An extruded tube for a heat exchanger, the extruded tube
comprising two at least approximately parallel outer side walls,
which extend in a longitudinal direction and a transverse direction
of the extruded tube and are connected by two outer narrow sides in
a vertical direction of the extruded tube; and at least one
continuous web extending between the side walls in the longitudinal
direction and in the vertical direction and separating at least two
channels of the extruded tube, wherein at least one of the outer
side walls has impressions that form bulges of the side walls, the
bulges projecting into the channels and extending substantially in
the transverse direction, and wherein bulges of the at least one
web have a controlled orientation relative to the transverse
direction.
2. The extruded tube according to claim 1, wherein at least one of
the channels of the extruded tube in the longitudinal direction has
a regular, wave-shaped course with respect to the transverse
direction.
3. The extruded tube according to claim 1, wherein a distance in
the transverse direction between two neighboring webs is
substantially constant.
4. The extruded tube according to claim 1, wherein at least one of
the impressions has an elongated form, and wherein a majority of
webs are overlapped and bulged out by the same impression.
5. The extruded tube according to claim 4, wherein the elongated
impression has an orientation angle to the transverse
direction.
6. The extruded tube according to claim 5, wherein the orientation
angle is approximately between 0.degree. and 45.degree., in
particular approximately between 20.degree. and 45.degree., or in
particular approximately between 28.degree. and 42.degree..
7. The extruded tube according to claim 1, wherein at least one of
the impressions coincides substantially only with the at least one
web.
8. The extruded tube according to claim 1, wherein at least one of
the impressions does not coincide with a web.
9. The extruded tube according to claim 8, wherein the impression
has an orientation opposite to the transverse direction.
10. The extruded tube according to claim 9, wherein an orientation
angle of the impression relative to the transverse direction is
approximately between 0.degree. and 45.degree., approximately
between 25.degree. and 45.degree., or approximately between
30.degree. and 40.degree..
11. The extruded tube according to claim 1, wherein at least one of
the impressions is made winglet-shaped, or wherein at least one of
the impressions is made as elongated winglets.
12. The extruded tube according to claim 10, wherein the
winglet-shaped impression has a length-to-width ratio of between
1.2 and 5, preferably between 2 and 5, especially preferably
between 2.5 and 3.2, or preferably between 1.5 and 3, especially
preferably between 1.8 and 2.5.
13. The extruded tube according to claim 1, wherein the
orientations of at least some bulges of neighboring webs, which are
substantially at the same height in the longitudinal direction, are
the same.
14. A heat exchanger for a motor vehicle, comprising an extruded
tube according to claim 1.
15. A method for producing an extruded tube according to claim 1,
the method comprising: producing the extruded tube by an extrusion
process; and subsequently impressing the impressions in the side
walls.
Description
[0001] This nonprovisional application is a continuation of
International Application No. PCT/EP2008/010829, which was filed on
Dec. 18, 2008, and which claims priority to German Patent
Application No. DE 10 2008 003 737, which was filed in Germany on
Jan. 10, 2008, and which are both herein incorporated by
reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The invention relates to an extruded tube for a heat
exchanger and to a heat exchanger with an extruded tube of the
invention, as well as to a method for producing an extruded tube of
the invention.
[0004] 2. Description of the Background Art
[0005] U.S. Pat. No. 3,596,495 A describes tubes that can be
produced by extrusion and drawing for a heat exchanger, in which
according to an exemplary embodiment several chambers are separated
by internal webs. Moreover, the chambers are deformed by externally
introduced depressions both in the area of the side walls and in
the areas of the webs in order to produce turbulences for a fluid
flowing therethrough.
SUMMARY OF THE INVENTION
[0006] It is therefore an object of the present invention to
provide an extruded tube for a heat exchanger in which an
especially high heat transfer is achieved with a proportionally low
pressure drop across the extruded tube.
[0007] In an embodiment, a specific precise shaping of the channel
can be achieved by the controlled orientation of the bulges in the
web not only in the vertical direction but also in the transverse
direction. In contrast, according to the aforementioned state of
the art, only an uncontrolled narrowing of the channels by bulging
of the web, random with respect to the orientation, is possible in
the transverse direction.
[0008] It is provided in an embodiment that at least one of the
channels of the extruded tube in the longitudinal direction has a
regular, wave-shaped course in regard to the transverse direction.
In this way, on the one hand, the turbulences and heat transfer are
increased and, on the other, narrow areas are avoided, which can
cause too great a pressure drop and possibly blockage by
accumulation of fluid or substances precipitated from the fluid.
Especially preferably, in this case, a distance in the transverse
direction between two neighboring webs is substantially
constant.
[0009] In an embodiment, in the interest of simple and reliable
fabrication, at least one of the impressions can have an elongated
form, whereby a majority of webs are overlapped and bulged by the
same impression. The elongated impression can have an orientation
angle to the transverse direction, so that bulges, formed by the
same impression of side walls and webs, are not located at the same
height in the longitudinal direction of the tube. An orientation
angle of this type is advantageously approximately between
0.degree. and 45.degree., preferably approximately between
20.degree. and 45.degree., and especially preferably approximately
between 28.degree. and 42.degree..
[0010] In an embodiment, the elongated impression has an
orientation parallel to the webs and/or is arranged above the webs
or only slightly offset to the webs. Especially advantageously, the
impression has a length that is 1.1- to 3.25-fold, particularly
1.35- to 2.45-fold, particularly 1.62- to 2.16-fold of the channel
width. As a result, possibly a force acting uniformly in sections,
and thus a marked bulging of the web, are assured, because
optionally flowing of the material under the embossing surface that
is only local due to the surface pressure because of an embossing,
made only punctiform or limited in length, and thereby an
undesirable reduction in wall thickness are reduced or avoided.
[0011] Alternatively or in addition, it can be provided that at
least one of the impressions coincides substantially only with the
at least one web. In this case, another impression cannot coincide
with a web. In this way, impressions for bulging out the side walls
and impressions for bulging out the webs can be placed as desired
spatially separated from one another, so that there are especially
broad design options for the shaping of the channels. This type of
isolated impression of a side wall can have in particular an
orientation opposite to the transverse direction. An orientation
angle of these impressions relative to the transverse direction can
be advantageously approximately between 0.degree. and 45.degree.,
preferably approximately between 25.degree. and 45.degree., and
especially preferably approximately between 30.degree. and
40.degree..
[0012] For an especially effective generation of turbulence, at
least one of the impressions can be made winglet-shaped. In
optimized form, the winglet-shaped impression in this regard has a
length-to-width ratio of between 2 and 5, preferably between 2.3
and 4, and especially preferably between 2.5 and 3.2. According to
an advantageous variant, the winglet-shaped impression has a
length-to-width ratio of between 1.2 and 5, preferably between 1.5
and 3, and especially preferably between 1.8 and 2.5.
[0013] It became evident that too long impressions can also lead to
a flat deformation of the side walls or can cause the short side
walls to bulge. This disadvantageously changes the outer dimension
of the extruded tube and worsens the coolant flow; similarly,
buckling of the side wall and blockage or reduction of the channel
cross section and thereby an increased pressure loss can occur
during deformation processes of the extruded tube in the area of
the impression.
[0014] It is advantageously provided in general that the
orientations of at least a few bulges of neighboring webs, which
are substantially at the same height in the longitudinal direction,
are the same. As a result, a largely constant cross section of the
channel at least in regard to the transverse direction is made
possible, so that the risk of blockage by deposits, for example,
during use for exhaust gas cooling, is low. Alternatively,
depending on the requirements; it can also be provided that the
orientations of at least a few bulges of neighboring webs, which
are substantially at the same height in the longitudinal direction,
are opposite. As a result, narrow areas of the tubes can be formed
in a controlled manner, which can produce an especially great
turbulence. This can be advantageous when the risk of blockage by
deposits is low, for example, in the case of charge air coolers,
coolant coolers, and exhaust gas coolers for low-pressure EGR
[exhaust gas recirculation] or high-pressure EGR coolers in the
case of moderate soot and/or HC emissions.
[0015] In an embodiment, in the longitudinal direction of a
channel, bulging of one of the side walls and bulging of the web
are provided alternately one behind the other to produce a uniform
turbulence in all spatial directions. Bulging of the web in a first
orientation in the transverse direction occurs in the longitudinal
direction of a channel in an especially advantageous manner, then
bulging of one of the two side walls, followed by bulging of the
web in the other orientation, and then bulging of the other side
wall. In this way, a screw-like course of the channel is created
which advantageously gives the fluid stream a twist. Several such
sections with particularly different twist directions can be
provided over the length of the extruded tube.
[0016] Another embodiment provides that the bulging of the webs
and/or the channel walls is designed alternately in the opposite
direction, so that an alternating acceleration and deceleration of
the flow result.
[0017] In another embodiment, in the longitudinal direction of a
channel, bulges of two webs bounding the channel have bulges
directed toward one another and lying at the same height, so that
the channel width is reduced by the bulges. As a result,
acceleration of the flow at this narrow area can be achieved.
Alternatively or in addition, it is provided that in the
longitudinal direction of a channel, bulges of two webs bounding
the channel have bulges directed away from one another and lying at
the same height, so that the channel width is increased by the
bulges. As a result, deceleration of the flow at this area can be
achieved. As previously noted, in a preferred embodiment, an
alternate widening and narrowing of the channels can also be
provided.
[0018] In an embodiment, it is provided that the bulging of the web
is formed both by an impression of the first side and also an at
least partially coinciding impression of the second side. As a
result, an especially marked bulging of the web with only a small
bulging of the side walls can be achieved. In a first variant, the
orientation of the bulging thereby is opposite to the coinciding
impressions. In an alternative or additional second variant the
orientation of the bulging is aligned relative to the coinciding
impressions.
[0019] In a simple realization of an extruded tube of the
invention, the controlled oriented bulging of the web occurs by
means of an embossing tool inclined relative to the side walls. In
this way, during embossing a force oriented in the transverse
direction is exerted on the web, so that the direction of its
bulging or buckling is predefined. In an alternative or additional
solution, the controlled oriented bulging of the web occurs by
means of an embossing tool acting eccentrically relative to the
web. In particular, the embossing tool in the transverse direction
in this case can only be as broad as the web, and the deviation of
the embossing center from the web middle relatively small, so that,
on the one hand, a controlled directed bulging of the web occurs
and, on the other, the side wall, adjacent to the web, is bulged
out as little as possible in the vertical direction.
[0020] In order to be able to mount the extruded tube of the
invention simply and sealingly in a bottom of a heat exchanger, an
end area of the extruded tube is preferably not provided with
bulges. A distance of a tube end to a first embossing in this case
is advantageously approximately between 2 mm and 15 mm, especially
preferably approximately between 4 mm and 8 mm. In an alternative
exemplary embodiment, a distance of a tube end to a first embossing
is advantageously approximately between 4 mm and 20 mm, especially
preferably approximately between 6 mm and 12 mm.
[0021] In an embodiment of the invention, an extruded tube has a
curved area, so that the heat exchanger can be, for example, a
U-flow heat exchanger or in general adapted by the bending of the
tube to a predefined space. To avoid an excessive channel narrowing
within the curved region, the bulges there expediently have an at
least reduced depth. Especially preferably, in this case, no bulges
are arranged in the curved region at least in sections.
[0022] In an embodiment, the tube material can be a material that
is mad of, for example, aluminum alloys, AlMn alloy, AlMg alloy,
and AlMgSi alloy. Such light metal alloys can be extruded
especially well and shaped with the impressions of the invention.
It became evident that extruded tubes made of such alloys when used
as exhaust gas coolers have a good corrosion resistance to
aggressive condensate.
[0023] In the case of an optimized geometry of the extruded tube, a
depth of the impressions is less than about 75%, preferably less
than about 45%, and especially preferably less than about 30% of an
inside tube diameter in the vertical direction.
[0024] Furthermore, tests have shown that in the longitudinal
direction a distance between an impression of the tube bottom side
to a next impression of the tube top side is advantageously no more
than 10-fold, preferably no more than 6-fold, and especially
preferably no more than 3.5-fold of an inside tube diameter in the
vertical direction. In addition, an optimized realization has the
property that in the longitudinal direction a distance between an
impression for bulging of a side wall to a next impression for
bulging of a web is no more than 8-fold, preferably no more than
6-fold, and especially preferably no more than 3-fold of an inside
tube diameter in the vertical direction.
[0025] In case of impressions overlapping several webs in the
transverse direction, a length of the impression in the transverse
direction optimally is approximately between 25% and 100%,
preferably between 35% and 90%, and especially preferably between
45% and 80% of a width of the extruded tube in the transverse
direction.
[0026] In case of an impression bounded only between two webs,
their length in the transverse direction is approximately between
25% and 130%, preferably between 35% and 95%, and especially
preferably between 45% and 75% of a width of the channel, bounded
by the webs, in the transverse direction.
[0027] To improve the heat transfer, it is advantageous in general
for a fin element to be arranged from the outside on at least one
of the side walls, particularly by means of a material connection.
This can be in particular planar soldering. To assure as uniform a
heat transfer as possible between fins and extruded tubes, it is
advantageous that a repeat unit of the impressions in the
longitudinal direction and a repeat unit of the fins of the fin
element are not integer multiples of one another. As a result,
unfavorable regular overlappings of contact areas of the fins with
impressed areas of the tube surface can be avoided.
[0028] For further improvement of heat transfer, in an extruded
tube of the invention at least one half-web can project from one of
the side walls into one of the channels.
[0029] In an optimized embodiment, a hydraulic diameter, defined as
four times the ratio of the area of the flow-through cross section
to a perimeter wettable by the first fluid, is provided within a
range between 1.2 mm and 6 mm.
[0030] Preferred ranges for the hydraulic diameter are particularly
between about 2 mm and about 5 mm, especially preferably between
3.0 mm and 3.4 mm, particularly preferably between 3.1 mm and 3.3
mm, and particularly about 3.2 mm.
[0031] In general and particularly for structural designs of
high-pressure heat exchangers, it was found that the hydraulic
diameter (dh) is advantageously between about 2.5 mm and 4 mm,
particularly preferably between about 2.8 mm and 3.8 mm.
[0032] In general and particularly for structural designs of
low-pressure heat exchangers, it was found that the hydraulic
diameter (dh) is advantageously within a range between 2 mm and 3.5
mm, particularly preferably between 2.5 mm and 3.5 mm.
[0033] To optimize the weight and quantity of material, a ratio of
the hydraulic diameter (dh) and a channel cover thickness (s) is
advantageously within a range between 0.8 and 8, preferably within
a range between 1.2 and 6, and especially preferably within a range
between 1.4 and 6. For the same reason, a ratio of a web thickness
(d) and a channel cover thickness (s) is preferably less than
1.0.
[0034] A ratio of a perimeter of the extruded tube and the
perimeter wettable by the first fluid is within a range between 0.1
and 0.9, particularly between 0.1 and 0.5, whereby the last range
named is especially suitable for exhaust gas coolers.
[0035] In the optimized structural design of an exemplary
embodiment, a ratio of a distance (e) between two, particularly
opposite partial webs and/or partial webs offset with respect to
one another to a height (b) of the tube cross section is within a
range below 0.8, particularly within a range between 0.3 and 0.7. A
ratio of a distance (a3) of a first partial web to a full web to a
distance (a4) of a second partial web to the full web with a
suitable structural design is preferably within a range between 0.5
and 1.0, particularly preferably within a range between 0.6 and
0.8.
[0036] In general, to increase the lifetime and particularly during
involvement of a fluid with corrosive properties, such as, for
example, exhaust gas, it can be provided that at least one web
and/or the channel cover, preferably the inner surface of the
channel cover, have corrosion protection, preferably in the form a
zinc coating and/or paint.
[0037] Depending on requirements, a cross section of the extruded
tube can advantageously be formed, for example, rectangular, oval,
or semi-oval.
[0038] In an especially suitable structural design of an extruded
tube for use in a heat exchanger, a number of 2 to 20, preferably 5
to 15, especially preferably 7 to 12, especially preferably 8 to
11, and particularly preferably 9 webs are arranged next to one
another across a tube cross section.
[0039] The object of the invention is achieved, by a heat exchanger
with an extruded tube of the invention. In this regard, a first
fluid, which exchanges heat with a fluid flowing outside around the
tube, is conveyed in the extruded tube. Such heat exchangers are
widely used particularly in motor vehicles, whereby here, because
of the high weight and space requirements, optimization of the
exchanger performance by the impressions of the invention is
particularly advantageous.
[0040] In an embodiment, in this case, air flows around the
extruded tube. In an alternative embodiment, a cooling fluid can
also flow around the extruded tube, for example, in the case of an
indirect exhaust gas cooler of a motor vehicle.
[0041] The heat exchanger of the invention can be an exhaust gas
cooler for cooling a recirculated exhaust gas stream, but also a
charge air cooler of a combustion engine, an oil cooler, or also a
coolant cooler. These heat exchangers are used especially
preferably in a motor vehicle.
[0042] The object of the invention is also achieved for a
manufacturing method for the extruded tube. Expediently, the
extruded profiles are first shaped by a known extrusion process
depending on the type of a generally prismatic base body and then
the impressions are introduced. This can occur in a step, directly
following the extrusion, particularly also in the case of a still
warm profile, or also in a completely separate step on a cooled
and/or temporarily stored profile strip.
[0043] In an advantageous detail design, the impression occurs by
means of an embossing roller. Alternatively or in addition,
however, it can also occur by means of a press die.
[0044] In an embodiment, to optimize the manufacturing cost, a
step, following the impression, of separating the extruded tube
from an endless or quasi-endless profile strip is provided. This
can occur, for example, by a sawing process. In an especially
advantageous detail design, the separation occurs by a tear-off
process, however, particularly after a preceding scoring. In this
way, the occurrence of chips during the separation can be largely
avoided.
[0045] According to an embodiment, the orientations of at least a
few bulges of neighboring webs, which are substantially at the same
height in the longitudinal direction, are opposite, whereby
preferably in the longitudinal direction of a channel, bulging of
one of the side walls and bulging of the web are provided
alternately one behind the other, whereby preferably a first
bulging of the web in a first orientation in the transverse
direction occurs in the longitudinal direction of a channel, then
bulging of one of the two side walls, followed by bulging of the
web in the other orientation in each case, and then bulging of the
other side wall in each case, whereby preferably in the
longitudinal direction of a channel, bulges of two webs, bounding
the channel, have bulges directed toward one another and lying at
the same height, so that the channel width is reduced by the
bulges, whereby preferably in the longitudinal direction of a
channel bulges of two webs, bounding the channel, have bulges
directed away from one another and lying at the same height, so
that the channel width is increased by the bulges, whereby
preferably the bulging of the web is formed both by an impression
of the first side and also an at least partially coinciding
impression of the second side, whereby especially preferably the
orientation of the bulging in regard to the coinciding impressions
is in the opposite or same direction.
[0046] According to an embodiment, the controlled oriented bulging
of the web occurs by means of an embossing tool inclined relative
to the side walls, whereby preferably the controlled oriented
bulging of the web occurs by means of an embossing tool acting
eccentrically relative to the web, whereby preferably an end region
of the extruded tube is not provided with bulges, whereby
preferably a distance of a tube end to a first embossing is
approximately between 2 mm and 15 mm, particularly approximately
between 4 mm and 8 mm.
[0047] According to an embodiment, the extruded tube has a curved
region, whereby preferably in the curved region there is an at
least reduced depth of the bulges, whereby preferably no bulges are
arranged in the curved region at least in sections, whereby the
tube material is made of a material, such as, aluminum alloys, AlMn
alloy, AlMg alloy, and AlMgSi alloy, whereby preferably a depth of
the impressions is less than about 75%, particularly less than
about 45%, and particularly less than about 30% of an inside tube
diameter in the vertical direction, whereby preferably in the
longitudinal direction a distance between an impression of the one
side wall to a next impression of the other side wall is no more
than 10-fold, particularly no more than 6-fold, and particularly no
more than 3.5-fold of an inside tube diameter in the vertical
direction, whereby preferably in the longitudinal direction a
distance between an impression for bulging of a side wall to a next
impression for bulging of a web is no more than 8-fold,
particularly no more than 6-fold, and particularly no more than
3-fold of an inside tube diameter in the vertical direction,
whereby preferably a length of the impression, overlapping several
webs, in the transverse direction is approximately between 25% and
100%, particularly between 35% and 90%, and particularly between
45% and 80% of a width of the extruded tube in the transverse
direction, whereby preferably a length of an impression arranged
between two webs in the transverse direction is approximately
between 25% and 130%, particularly between 35% and 95%, and
particularly between 45% and 75% of a width of the channel, bounded
by the webs, in the transverse direction.
[0048] According to an embodiment, a fin element is arranged from
the outside on at least one of the side walls, particularly by
means of a material connection, whereby preferably a repeat unit of
the impressions in the longitudinal direction and a repeat unit of
fins of the fin element are not integer multiples of each other,
whereby preferably at least one half-web projects from one of the
side walls into one of the channels.
[0049] According to an embodiment, a hydraulic diameter, defined as
four times the ratio of the area of the flow-through cross section
to a perimeter wettable by the first fluid, is within a range
between 1.2 mm and 6 mm, whereby preferably the hydraulic diameter
is between about 2 mm and about 5 mm, particularly between 3.0 mm
and 3.4 mm, particularly between 3.1 mm and 3.3 mm, and
particularly about 3.2 mm, whereby preferably the hydraulic
diameter is between about 2.5 mm and 4 mm, particularly between
about 2.8 mm and 3.8 mm, particularly for a high-pressure heat
exchanger, whereby preferably the hydraulic diameter is within a
range between 2 mm and 3.5 mm, particularly between 2.5 mm and 3.5
mm, particularly for a low-pressure heat exchanger, whereby
preferably a ratio of the hydraulic diameter and a channel cover
thickness is within a range between 0.8 and 9, particularly within
a range between 1.2 and 6, particularly within a range between 1.4
and 6, whereby preferably a ratio of a web thickness and a channel
cover thickness is less than 1.0, whereby preferably a ratio of an
outer perimeter of the extruded tube and the perimeter wettable by
the first fluid is within a range between 0.1 and 0.9, particularly
between 0.1 and 0.5, whereby preferably a ratio of a distance
between two, particularly opposite partial webs and/or partial webs
offset with respect to one another to a height of the tube cross
section is within a range below 0.8, particularly within a range
between 0.3 and 0.7, whereby preferably a ratio of a distance of a
first partial web to a full web to a distance of a second partial
web to the full web is within a range between 0.5 and 1.0,
particularly within a range between 0.6 and 0.8.
[0050] According to an embodiment, at least one web and/or the
channel cover, preferably the inner surface of the channel cover,
have corrosion protection, preferably in the form of a zinc coating
and/or paint, whereby preferably a cross section of the extruded
tube is formed rectangular, oval, or semi-oval, whereby preferably
a number of 2 to 20, particularly 5 to 15, particularly 7 to 12,
particularly 8 to 11, particularly 9 webs are arranged next to one
another across a tube cross section.
[0051] According to an embodiment, air flows around the extruded
tube of the heat exchanger, whereby preferably cooling fluid flows
around the extruded tube, whereby preferably the heat exchanger is
an exhaust gas cooler for cooling a recirculated exhaust gas
stream, a charge air cooler, an oil cooler, or a coolant
cooler.
[0052] According to an embodiment of the method, the impression
occurs by means of an embossing roller, whereby preferably the
impression occurs by means of an press die, whereby preferably the
impression is followed by a step of separating the extruded tube
from an endless or quasi-endless profile string, whereby preferably
the separation occurs by means of a sawing process or by a tear-off
process, particularly after a preceding scoring.
[0053] Further scope of applicability of the present invention will
become apparent from the detailed description given hereinafter.
However, it should be understood that the detailed description and
specific examples, while indicating preferred embodiments of the
invention, are given by way of illustration only, since various
changes and modifications within the spirit and scope of the
invention will become apparent to those skilled in the art from
this detailed description.
BRIEF DESCRIPTION OF THE DRAWINGS
[0054] The present invention will become more fully understood from
the detailed description given hereinbelow and the accompanying
drawings which are given by way of illustration only, and thus, are
not limitive of the present invention, and wherein:
[0055] FIG. 1 shows a schematic illustration of an extruded tube
for the definition of the individual spatial axes.
[0056] FIG. 2 shows a first exemplary embodiment of an extruded
tube of the invention with overall nine variations 2.1 to 2.9.
[0057] FIG. 3 shows an illustration of embossing processes for
manufacturing an extruded tube according to FIG. 2.
[0058] FIG. 4 shows a spatial illustration of an extruded tube
according to the first exemplary embodiment.
[0059] FIG. 5 shows a detail from the extruded tube of FIG. 4.
[0060] FIG. 6 shows a second exemplary embodiment of an extruded
tube of the invention with 10 variations 6.1 to 6.10.
[0061] FIG. 6a shows additional variations 6.11 to 6.17 of the
second exemplary embodiment.
[0062] FIG. 7 shows stereoscopic views of two embossing rollers for
the production of an extruded tube according to the invention.
[0063] FIG. 8 shows an illustration, based on measurements and
calculations, of a preferred selection of a hydraulic diameter in
regard to the ratio of the perimeter wettable by the first fluid
and an outer perimeter of the extruded tube.
[0064] FIG. 9A and FIG. 9B show two variations of a preferred
embodiment of a cross section of an extruded tube having an
extruded channel cover and webs extruded with the channel
cover.
[0065] FIG. 10A and FIG. 10B show two variations of another
embodiment, as in FIG. 9A and FIG. 9B, with partial webs.
[0066] FIG. 11A and FIG. 11B show two variations of another
embodiment, as in FIG. 9A and FIG. 9B, with partial webs.
[0067] FIG. 12 shows another embodiment of a cross section of an
extruded tube with partial webs.
[0068] FIG. 13 shows another embodiment of a cross section of an
extruded tube with partial webs.
DETAILED DESCRIPTION
[0069] According to the illustration according to FIG. 1, the
invention relates to extruded tubes, which extend at least in
sections in a longitudinal direction designated by z. The extruded
tubes have a longitudinal extension transverse to the longitudinal
direction, whereby they are formed particularly as flat tubes. A
transverse direction within the meaning of claim 1 is designated as
the y direction in FIG. 1, whereby the (long) side walls 1, 2 of
the extruded tube extend substantially in this direction. A
vertical direction is designated by x in FIG. 1 and extends
perpendicular to the longitudinal direction and to the transverse
direction. The side walls 1, 2 need not necessarily extend straight
in cross section but can also be curved and in this sense are
oriented only "substantially" in the transverse direction or "at
least nearly parallel."
[0070] The side walls 1, 2 are connected together to form a closed
flat tube via shorter, curved, narrow sides 3, 4 running
substantially in the vertical direction.
[0071] Within the flat tube, the side walls are connected via at
least one web, in the shown exemplary embodiments in each case via
several continuous webs 5, 79, 89 with separation of separate
channels 6 from one another. Apart from these continuous webs or
full webs 5, 79, 89, partial webs 5', 79', 89' can optionally also
be provided (see, for instance, FIG. 4 or also FIG. 10A to FIG.
11B), which project into channels 6 like fins to increase the
contact area between the channel wall and the fluid.
[0072] To optimize the turbulences of the flowing fluid, the
extruded tubes are provided with impressions 7, which form local
bulges relative to the longitudinal direction, which project into
channels 6 and influence the fluid flow. In this case, this can
refer to bulges in side walls 1, 2, which protrude accordingly in
the vertical direction, or also bulges or bucklings of the
continuous webs 5, 79, 89, which project accordingly in the
transverse direction. Such bulges of the webs are achieved in that
an impression is carried out at least partially coinciding with the
attachment area of the web to the side wall.
[0073] It is achieved by suitable measures in this case that the
orientation of the bulging of the web is predefined in a controlled
manner in the transverse direction and does not occur arbitrarily
or randomly. To achieve this, two different approaches can be taken
during the production of the impressions:
[0074] On the one hand, a press die 8 (see FIG. 3) or an embossing
roller 9' as well (see FIG. 7) has an inclined embossing edge 8a,
10'. FIG. 3 under A shows a simple embossing of an extruded tube by
means of a smooth and not inclined embossing edge, overlapping most
of the extruded tube in the transverse direction, by means of which
webs 5 are bulged out in an uncontrolled manner toward the left or
right. Under B, the embossing edge, in contrast, is provided with
an angle alpha of a few degrees, typically no more than 10 degrees,
relative to the side surface 1. As a result, all of webs 5 in
example B are bulged out toward the right in a controlled manner,
because the forces during embossing act asymmetrically in the
region of the web attachments.
[0075] On the other hand, control of the bulging direction can also
be achieved for punctiform impressions. To this end, in Example C
of FIG. 3, a toothed embossing edge 8b is shown, which acts on the
extruded tube only with small local projections or in a point-like
manner. The points of action are thereby localized substantially
over webs 5, but slightly off-center. As a result, a buckling of
webs 5 is also achieved in a predefined orientation relative to the
transverse direction. The direction of the bulging of webs 5 in
Example C would also be to the right, because the embossing points
act somewhat to the left of the center of webs 5.
[0076] An option that is an alternative or an addition to press
dies 8 of a substantially punctiform embossing with local
projections is given by embossing roller 9, shown in FIG. 7, with
punctiform local projections 10. Embossing roller 9', also shown in
FIG. 7, in contrast, has elongated projections 10', which extend
over at least one entire channel width or also over the
substantially entire width of the extrusion profile. Embodiments
such as those in FIG. 4, for example, can be produced with this
type of roller 9', whereby embodiments such as those shown in FIG.
6 and FIG. 6a can be produced with the local projections of
embossing roller 9. In principle, both types of projections 10, 10'
can also be provided together on the same embossing roller.
[0077] A first exemplary embodiment according to FIG. 2 and a
second exemplary embodiment according to FIG. 6 with several
variations in each case are substantially shown in the present
case. The first exemplary embodiment according to FIG. 6 deals with
impressions of the first type with smooth, inclined embossing
edges, which in each case at the same time overlap more than one
web 5 of the extruded tube and thereby also at the same time bulge
the side walls between the webs inwardly. Expediently, the
embossing edges or impressions are arranged in this case at an
orientation angle relative to the transverse direction. As a
result, the bulges, caused by the same impression, of neighboring
webs are offset in the longitudinal direction to one another, so
that in a simple manner a wave-shaped modulation of channels 6 is
achieved with a channel wall distance, largely constant in the
transverse direction. This type of orientation angle in a typical
embodiment is about 35.degree. and is present in Examples 2.3 to
2.9. Such impressions with an angled course to the transverse
direction are especially highly suitable for combining with a
cooling fin (not shown) soldered in a planar manner to the extruded
tube, because a disadvantageous overlapping of impressions and fins
with the result of areas of poor heat removal is avoided.
[0078] In general, in Examples 2.1 to 2.9 impressions of the top
side are shown as solid lines and impressions of the bottom side,
which are not visible in the top view, as dashed lines. The
controlled bulging direction of the webs is depicted in each case
as a direction arrow within the impressions.
[0079] The impressions are expediently made in both side surfaces
1, 2. These opposite impressions can be arranged coinciding (e.g.,
FIG. 2, Examples 2.2 and 2.4) or offset in an alternating manner
(e.g., 2.1, 2.3). The orientation angle of the impressions can vary
and in particular alternate as in Examples 2.5, 2.8, and 2.9.
Several impressions, shorter in the transverse direction, with
varying orientation angles can also be provided over the width of
the extruded tube; see, for instance, Examples 2.6 to 2.9.
[0080] In some of the described examples, for example, in case 2.1,
2.3, or 2.7, the bulging directions of the webs by impressions from
above are opposed by those of the impressions from below
alternating in the longitudinal direction, to achieve turbulence
generation as great as possible with a moderate increase in
pressure loss.
[0081] In the second exemplary embodiment according to FIG. 6,
these are largely local impressions of the second type. In contrast
to the first case according to FIG. 2, hereby an embossing is not
made over the entire tube width but only locally limited. This has
the advantage that the buckling of the tube webs and the
constriction of the channel height in the vertical direction can
occur separately one after the other. Thus, there is additional
design flexibility, which is very helpful particularly in view of
the generation of spin flow in the channels. In this way, even more
complex 3-dimensional swirling and flow conditions can be generated
than in the first case.
[0082] Advantageously, the impressions are made in the longitudinal
direction alternately in the form that in the longitudinal flow
direction after embossing of the tube webs, an embossing of the
tube wall occurs and then again a shaping of the tube webs, etc.
The embossments can be made in addition alternately in both side
walls 1, 2, specifically particularly in the form that in the
longitudinal direction after the buckling of a web 5 in the one
direction by an impression 7 on the upper side wall 1 an impressing
of the lower side wall 2 occurs, in the longitudinal direction then
the buckling of a web 5 in the other orientation direction by an
impression 7 on the lower side wall 2, and in the longitudinal
direction then an impression 7 of the upper side wall 1.
Afterwards, the embossing of the webs by means of bulging of a web
5 in the first direction by impression on the top side wall 1,
etc., repeats cyclically. Any other combinations and sequences of
the impressions in the flow direction are also conceivable,
however; see the exemplary illustrations 6.1 to 6.17 in FIGS. 6 and
6a. In the illustrations, the impressions that bulge out because of
the spatial overlapping of a web 5 have a direction arrow. A
deviation from the central position is not shown in the drawings
for the sake of clarity. Basically, only a small control deviation
of the press die from the central position over a web 5 is
necessary to predefine the bulging direction of the web.
[0083] To be able to achieve the greatest and most uniform bulging
of the webs possible, these can also be bulged out on both sides
from the top and bottom side, as shown in FIG. 6a, Examples 6.11 to
6.13. In this case, the impressions of the side walls acting on the
webs in each case overlap at least partially, so that the web is
largely bulged out at the same location from both side walls. The
direction of the bulging relative to the overlapping impressions in
this case can be in the same direction (see, for instance, 6.11 and
6.13) or in the opposite direction as well (see 6.12).
[0084] The embossing of the tube webs and the tube walls, on the
one hand, causes a reduction in the hydraulic diameter and thereby
an increase in tube performance in regard to heat transfer, but, on
the other, also a directed flow deflection both in the y-z plane
and also in the x-z plane.
[0085] FIG. 6 shows advantageous impressions by way of example in a
tube with three intermediate webs 5. The impression of the top side
wall 1 in each case is shown using a solid line and the impression
of the bottom side wall 2 using a dashed line. The direction of the
web buckling is indicated in each case with an arrow. Depending on
the requirements, the impressions in the x-, y-, and z-direction
can be made round, oval, elongated oval, rectangular, or also in
another form. The impressions are carried out alternately as
previously described. The deformation of the channel tube wall at a
location can be carried out by one or two embossings per channel
(see, for instance, Examples 6.4, 6.5, 6.9, and 6.10). However, in
special cases, particularly in very broad channels, this can be
also done by more than two impressions at one location.
[0086] In FIG. 6.3, impressions of the side walls 1, 2 are shown
between webs 5, which are oriented in a defined orientation angle
to the transverse direction. The orientation angle of the
impression relative to one of the axes z or y in the present case
is approximately between 30.degree. and 40.degree.. Any other
combinations between the deflection direction and impression
sequence also beyond the depicted variants are conceivable.
[0087] Examples 6.4, 6.5, 6.9, and 6.10 show variants with
winglet-like impressions, i.e., elongated and preferably angled to
one another, between webs 5. Depending on the requirements, any
combinations of winglets beyond the depicted embodiments both
relative to position and orientation to one another, as well as to
the direction of the webs, are conceivable. For the impressions in
the form of winglets, it became evident that an orientation angle
of the impression relative to one of the axes z or y is especially
preferable between about 28.degree. and 42.degree..
[0088] To be able to increase the turbulence still further, it can
also be provided apart from the shown variants, particularly for
very broad channels, to impress more than one winglet per channel
in the transverse direction.
[0089] The shape of the winglet is selected so that the ratio of
its length to its width is a multiple, particularly about 1.8-fold
to 2.5-fold or about 2.5-fold to 3.2-fold.
[0090] Impressions between webs 5 in winglet form have the
advantage over more simply shaped impressions that with this type
of flow guidance an even greater heat transfer performance can be
achieved, because the flow experiences a still greater directed
deflection with considerably greater swirling.
[0091] It applies to both exemplary embodiments according to FIG. 2
and FIG. 6 that during use of highly contaminated fluids, such as,
e.g., exhaust gas from a combustion engine, with the narrowing of
channels 6 the risk of blockage due to accumulation of components
from the gas phase, particularly soot and/or unburned hydrocarbons,
increases. Therefore, in this case, the bulges of webs 5 are
designed so that they bulge out in the transverse direction always
in the same orientation, so that the free channel distance between
neighboring webs 5 does not change or changes only slightly. In the
longitudinal direction, the webs therefore have a parallel wave
shape to one another in regard to the transverse direction.
[0092] Depending on the use, however, it can also be advantageous
to lay out webs 5 so that the orientations of the bulges of
neighboring webs 5 are precisely in the opposite direction to one
another, to alternately narrow channel 6 as much as possible and
then again to widen it as greatly as possible. An example of such
an arrangement is shown in FIG. 6a, Example 6.13. This alternate
narrowing and widening of the channel cross section makes possible
an additional increase in performance for applications, in which
deposits are not critical, such as charge air coolers, coolant
coolers, oil coolers, or exhaust gas coolers for low-pressure EGR
applications or high-pressure EGR applications with moderate soot
and/or HC emissions. Depending on the requirements, in this case,
the appropriate compromise with a drop in pressure resulting from
the swirling and narrowing must always be considered.
[0093] In FIG. 6a, Examples 6.14 and 6.15, another option is shown
to allow the side wall and also the web/neighboring webs to buckle
with only one impression in that the die in addition to the channel
width also covers another part or more than this part of the
neighboring web(s). Apart from the variants shown in FIGS. 6.14 and
6.15, all already mentioned combinations of web bucklings for a
channel impression direction are also conceivable here.
[0094] For dimensional stability of the outer dimensions of the
extruded tube, it is advantageous not to bulge out the closing
narrow sides 3, 4 with use of impressions. In this case, in both
lateral outer channels, however, only a wave-shaped bulging of the
web, arranged closer to the tube middle, occurs whereas the outer
wall remains undeformed. Depending on the application, it is
therefore advantageous to provide outer channels with a larger or
smaller flow cross section, in order to minimize in the first case
the risk of blocking of the gas channel by the greater narrowing of
the distance between web 5 and the outer narrow side 3, 4 in the
area of the bulge, or in the second case to achieve a similarly
high turbulence in outer channel 6 as well as in the inner
channels. If no special requirements are made for the outside
dimension of the extruded tube, it can naturally be expedient to
provide the narrow sides 3, 4 as well with impressions and to bulge
them out in the transverse direction.
[0095] Joining the extruded tube in a bottom and for configuring
the tube ends:
[0096] To join the extruded tube in a tube bottom, it is
advantageous not to emboss the embossments in the end regions, so
that a defined insertion of the extruded tube with a
circumferentially constant gap in the bottom is possible and
thereby good joining of the extruded tube-bottom connection is
assured. Another reason is that a defined widening of the extruded
tube for fixing the extruded tube and bottom via a common contact
surface remains possible.
[0097] The required distance of the profile end to the first
embossing depends in particular on the depth of the impressions.
The distance is to be selected so that no or only a very minor
deformation of the original tube geometry occurs in the area of the
joint. In typical cases of heat exchangers dimensioned for use in
motor vehicles, this means a distance between 2-15 mm, particularly
4-8 mm. In special cases, this dimension can also exceed these
distances.
[0098] Bending of the embossed extruded tubes:
[0099] A great advantage of the extruded tube heat exchanger
compared with other exchanger tubes, e.g., stainless steel tubes,
is the very great design flexibility, particularly because of the
option of bending the extruded tube.
[0100] For bending the extruded tube, it is particularly
advantageous when impressions are not used in the area of the
bending, to prevent too great a deformation and perhaps even
closing of individual channels. Alternatively, in the bending area,
the impression depth only can be reduced or, for example, only
embossing of the webs or only narrowing of the channel walls can be
provided. In the manufacturing process, the embossing of the tubes
occurs first and then the bending into the desired form.
[0101] Manufacturing method:
[0102] The manufacturing of the impressions can occur
advantageously in two alternative or also cumulative ways: the
extruded tube is embossed by means of at least one tool roller
[roller-shaped tool]. Such a roller 9 is pictured by way of example
in FIG. 7. Advantageously, at least two counterrotating tool
rollers are used, by which in one work step both the top side wall
1 and the bottom side wall 2 are embossed; and/or the extruded tube
is embossed by a die set or various single press dies.
[0103] For both types of fabrication, the impression can be created
both in a single stage and multistage manner via several embossing
rollers or die sets provided one after another in the fabrication
direction.
[0104] To prevent bending of the extruded tube during the
fabrication process, the extruded tube is held in position by means
of at least one holding function before and/or after the embossing
step. It is assured by a lateral roller guidance that the extruded
tube does not shift in the transverse direction during the
embossing process. If this holding function can prevent the warping
of the extruded tube only partially, this can be corrected by a
subsequent work step via stretching or resizing of the extruded
tube via another set of rollers or a press.
[0105] The embossing by means of rollers has the advantage that the
method can be carried out with a continuous feed motion of the
extruded tube, whereas timing of the feed motion is generally
necessary for fabrication by means of die sets.
[0106] In order to be able to join the extruded tube optimally in
the bottom later, it is important that there are no embossments
and/or a change in cross section of the extruded tube in the area
of the profile separation. This can be achieved in several ways:
the distance of the impressions is so great that separation of the
extruded tube is possible; and/or embossments are omitted at the
separation point.
[0107] The latter can be provided for the embossment by means of
rollers, for example, by a suitable geometry of the embossing
rollers. In this case, the roller circumference is always an
integer multiple of the later profile length. Another possibility
for providing a sufficiently broad sawing or joining area is to
make the provision of the roller variable, so that depending on the
provision of the rollers embossments are or are not shaped.
[0108] Another advantage of the fabrication by means of rollers is
that different profile variants can be produced by an exchange of
rollers in a very simple way with the same production line.
[0109] Besides an exchange of embossing rollers, alternatively,
also only one embossing roller can be used in which the raised
areas for embossing are placed such that they are exchangeable. In
this case, the work is done with a basic roller in which variable
embossing sets can be used. Alternatively, it is also conceivable
for this purpose to pull onto a basic roller without or with a few
embossments an additional sheathing body, which provides the
desired embossing arrangement. In both cases, work is done with
only one basic roller body.
[0110] For embossing the extruded profile by means of die sets,
optionally to achieve a large sawing region the dies must be
totally or partially discontinued in the sawing and joining region,
so that no or only very faint embossments are produced.
[0111] The production sequence for the embossed extruded tube is
therefore described as follows:
[0112] (1) The extruded tubes are provided either in a
prefabricated length minus the fabrication-related stretching
during the embossing process, or as bar material with a multiple of
the later tube length, or as continuous material in a coil shape
for the embossing process.
[0113] (2) Embossing of the extruded tubes by means of rollers or
die set
[0114] (3) Correction of possible bending by means of extension
and/or standardizing rollers/press
[0115] (4) Possibly separation of the extruded tubes
[0116] (5) Possibly bending of the extruded tubes
[0117] (6) Cleaning of the extruded tubes.
[0118] The sequence of these steps is selected so that they can be
linked very simply to one another to create a production line that
is very simple and cost-effective to realize.
[0119] Separation of the extruded tubes:
[0120] The separation occurs preferably by means of a saw running
concurrently during the embossing process, but can also occur in a
separate sawing process following the embossing process.
Alternatively, the separation of the extruded tubes can also occur
by means of scoring and subsequent tearing off of the tubes. This
has the advantage that no chips arise and no additional saw
lubricant is required. As a result, depending on the application, a
subsequent cleaning step may be totally or partially omitted.
[0121] Material:
[0122] In principle, the embossed extruded tubes can be produced
with any extrudable material. All extrudable aluminum alloys,
particularly Al alloys, especially AlMn alloys, AlMg alloys, and
AlMgSi alloys, are advantageous for the application pursued here of
heat exchangers, such as exhaust gas coolers, oil coolers, coolant
coolers, and charge air coolers.
[0123] If the extruded tube is used in a corrosion-critical
application, e.g., as a gas-conducting extruded tube of an exhaust
gas cooler or a low-pressure charge air cooler, corrosion studies
have shown that an especially high corrosion resistance can be
achieved in that reducing contaminations in the extruded tube
material are present in the following percentages by weight:
[0124] Silicon: Si<1%, particularly Si<0.6%, especially
Si<0.15%
[0125] Iron: Fe<1.2%, particularly Fe<0.7%, especially
Fe<0.35%
[0126] Copper: Cu<0.5%, particularly Cu<0.2%, especially
Cu<0.1%
[0127] Chromium: Cr<0.5%, particularly 0.05%<Cr<0.25%,
especially 0.1%<Cr<0.25%
[0128] Magnesium: 0.02%<Mg<0.5%, particularly
0.05%<Mg<0.3%
[0129] Zinc: Zn<0.5%, particularly 0.05%<Zn<0.3%
[0130] Titanium: Ti<0.5%, particularly 0.05%<Ti<0.25%
[0131] An especially high corrosion resistance of these extruded
tubes can be achieved in general when the grain sizes measured in
the extrusion direction are <250 .mu.m, particularly <100
.mu.m, especially <50 .mu.m.
[0132] Impression depth:
[0133] The specific depth of the impression depends greatly on the
application. It became evident, however, that especially from the
standpoint of thinning of the material and the pressure loss
generated by the impression, an impression depth less than 75% of
the clear tube height b, particularly less than 45%, especially
less than 30%, has proven advantageous.
[0134] Distance of the impressions:
[0135] The distance of the impressions to one another also greatly
depends on the application. An especially advantageous range could
also be found for this, however:
[0136] (1) In the longitudinal direction based on embossments of
the one side wall 1 to those of the other side wall 2 between
0-fold and 10-fold of the clear tube height b, particularly between
0-fold and 6-fold of the clear tube height b, especially between
0-fold and 3.5-fold of the clear tube height b.
[0137] (2) In the longitudinal direction based on embossments which
are used to reduce the channel height to embossments which are used
to bulge out the webs on the one side wall between 0-fold and
8-fold of the clear tube height b, particularly between 0-fold and
6-fold of the clear tube height b, especially between 0-fold and
3-fold of the clear tube height b.
[0138] Length of the impressions:
[0139] The length of the impressions also depends greatly on the
application. For this purpose, however, an especially advantageous
range, associated with the tube width or channel width, could also
be found:
[0140] The length of the impression in case of the exemplary
embodiment according to FIG. 2 should be between 100% and 25% of
the tube width, particularly between 90% and 35%, especially within
the range between 80% and 45% of the tube width.
[0141] The length of the impression in case of the exemplary
embodiment according to FIG. 6 should be between 130% and 25% of
the channel width, particularly between 90% and 35%, especially
within the range of 75% and 45% of the channel width.
[0142] The length of the impression in the case of an exemplary
embodiment that is not shown is between 325% and 25% of the channel
width, particularly between 250% and 35%, especially within the
range of 215% and 45% of the channel width.
[0143] Soldering of an outer fin, e.g., for coolant coolers, charge
air coolers:
[0144] If an additional outer fin is attached to the embossed
extruded tube, for instance, in a cross-flow cooler, care must be
taken that the impressions in the transverse direction are not
arranged aligned but rather slightly offset, to assure the best
possible soldering of the outer fin. The arrangements of
impressions, shown in FIGS. 2.3-2.9 and FIGS. 6.6-6.10, are
especially suitable for this. For the arrangements of impressions
shown in FIGS. 6.6-6.10, the distances of similar impressions in
channels neighboring each other in the longitudinal direction are
realized advantageously so that these are not an integer multiple
of the fin density but rather either smaller or greater,
particularly advantageously within the range of k/3 to n/3 of the
fin depth, for k=1, 4, 7, 10, . . . and n=2, 5, 8, 11, . . . , so
that the best possible soldering of the outer fin results.
[0145] Exemplary embodiments of extruded tube cross sections that
are not impressed:
[0146] A hydraulic diameter within a range between 2 mm and 5 mm
has proven especially preferable for realizing the concept of the
invention. The size of said range realizes particularly
advantageously--as explained in detail with use of FIG. 8--a
balance between the tendency to realize as good a heat transfer as
possible in an extruded tube, on the one hand, and the tendency, on
the other, to reduce a pressure loss, or to realize an acceptable
pressure loss while nevertheless realizing good heat transfer. In
this connection, a hydraulic diameter within the range between 3 mm
and 3.4 mm, in particular between 3.1 mm and 3.3 mm, has proven to
be further particularly preferable. In particular in regard to the
latter range of a hydraulic diameter between 3.1 mm and 3.3 mm, it
became evident that a hydraulic diameter of approximately 3.2 mm is
especially expedient. Although it is fundamentally not possible to
prevent fouling of the extruded tube or the heat exchanger tube
within the stated range either, tests have shown, however, that in
said range, fouling stabilizes in such a way that a decline in
performance is also kept at a relatively low level. Whereas it is
to be expected in ranges of the hydraulic diameter outside the
aforementioned ranges that an extruded tube will become
increasingly fouled with an increase in pressure loss the longer it
is operated, in the case of the aforementioned preferred ranges of
a hydraulic diameter of demonstrated dimensions, it is to be
assumed that a pressure loss stabilizes at a relatively low level.
A possible suboptimal heat-transfer performance of a heat exchanger
is not reduced further with continued heat exchanger operation. In
the case of a hydraulic diameter outside the aforementioned ranges,
in contrast, a disproportionate increase in pressure loss and
ultimately in the worst case blockage of the channels occur during
further operation of the flow channel.
[0147] An extruded tube according to the concept of the invention
can be used advantageously both within the context of high-pressure
exhaust gas recirculation and within the context of low-pressure
exhaust gas recirculation. Furthermore, an application for charge
air cooling or coolant cooling is also possible. In all fields of
application, in particular those stated above or the like, an
increase in the number of webs to improve heat transfer is avoided
according to the concept of the invention by selecting the
hydraulic diameter within a range between 1.2 mm and 6 mm. However,
tests have shown that a selection, optimized for low-pressure
exhaust gas recirculation, high-pressure exhaust gas recirculation,
or charge air cooling, of a range for the hydraulic diameter can be
different. In the case of high-pressure exhaust gas recirculation,
as has been found, both the increase in pressure loss and the
increased risk of blockage or significant fouling of a channel by
soot particles or the like are relatively critical. For a
high-pressure heat exchanger, a range of a hydraulic diameter
between 2.5 mm and 4 mm, particularly between 2.8 mm and 3.8 mm,
has proven particularly advantageous.
[0148] In a low-pressure exhaust gas recirculation concept, there
is no or only a very low soot entry, so that in this case smaller
hydraulic diameters than in high-pressure EGR coolers can also be
used advantageously. For a low-pressure heat exchanger, a range of
a hydraulic diameter between 2 mm and 3.5 mm, in particular between
2.5 mm and 3.5 mm, has proven especially advantageous.
[0149] It has proven particularly advantageous, especially to
increase corrosion resistance, to select a ratio of a web thickness
and a channel cover thickness below the value of 1.0. In other
words, to increase the corrosion resistance, it is advantageous to
provide the channel cover with a greater wall thickness than a web.
This is advantageous in particular in regard to the design of an
extruded tube in which at least the channel cover is produced based
on an aluminum material.
[0150] Furthermore, it has proven to be fundamentally relevant to
optimize a channel cover thickness in such a way that, on the one
hand, a corrosion resistance, in particular in the case of an
extruded tube based on an aluminum material, is sufficiently
assured and, on the other, a sufficient number of extruded tubes
are provided in the available installation space of a heat
exchanger. Installation space for a heat exchanger in an engine is
usually rather limited, so that it is basically within the scope of
an improvement to provide as many extruded tubes as possible in a
heat exchanger, and therefore to design a channel cover thickness
not to be too thick. According to a particularly preferred
refinement of the invention, a ratio of the hydraulic diameter and
a channel cover thickness within a range between 0.8 and 9 has
proven to be particularly advantageous. Said range has proven to be
particularly expedient in particular in an extruded tube based on
an aluminum material, in particular in an extruded tube in which at
least the channel cover is based on an aluminum material. Also
advantageous is a range between 1.2 and 6.0, in particular a range
between 1.4 and 6, with regard to the design of the channel cover
thickness (installation space requirement, corrosion resistance)
and the hydraulic diameter (heat transfer, pressure loss).
[0151] The concept of the invention and/or one or more of the
aforementioned refinements individually or in combination have
proven particularly advantageous for dimensions of an extruded tube
that realize a ratio of an outer perimeter of the extruded tube and
the perimeter wettable by the first fluid within a range between
0.1 and 0.9, particularly between 0.1 and 0.5 for an exhaust gas
cooler. The tests carried out in this regard have shown that within
the range of the specified dimensions, the behavior of an extruded
tube is particularly advantageous in regard to the above-explained
problem.
[0152] In regard to production aspects and the aforementioned
problem, an extruded tube is especially expedient in which a web as
a full web is arranged in the tube cross section at one end and on
the channel cover inner surface at the other end. In particular, a
tube cross section may have only full webs. A full web is
advantageously made continuous, without openings, between a first
channel cover inner surface and a second channel cover inner
surface. As is explained by way of example using FIGS. 9A and 9B,
this makes it possible to realize an extruded tube with a hydraulic
diameter according to the concept of the invention.
[0153] Furthermore, an extruded tube has proven advantageous in
which a web as a partial web is arranged in the tube cross section
only at one end on the channel inner surface and projects freely
into the interior space at the other end. As explained by way of
example using FIG. 10A and FIG. 10B, as well as FIG. 11A and FIG.
11B, a hydraulic diameter may be realized in an especially
advantageous manner by means of an extruded flow channel according
to the concept of the invention.
[0154] It became evident that advantageously two partial webs can
be arranged with opposing end sides at the other end. Alternatively
or in combination with the aforementioned arrangement of partial
webs, two partial webs can be arranged with end sides offset
laterally with respect to one another at the other end. Preferably,
a partial web and a full web are arranged alternately next to one
another.
[0155] It has proven especially advantageous to make dimensions and
arrangements of the partial webs as follows. According to an
especially preferred refinement, a ratio of a distance between two
partial webs, especially two opposite partial webs and/or two
partial webs offset with respect to one another, to a height of the
tube cross section is within a range below 0.8, particularly within
a range between 0.3 and 0.7. Preferably, a ratio of a distance of a
first partial web to a full web to a distance of a second partial
web to the full web is within a range between 0.5 and 1.0,
preferably within a range between 0.6 and 0.8.
[0156] FIG. 8 illustrates the ratio of the perimeter wettable by a
fluid, such as, e.g., an exhaust gas, and an outer perimeter of the
extruded tube as a function of the hydraulic diameter. A preferred
ratio results from the above-explained shaded areas of a preferred
hydraulic diameter of 2 mm to 5 mm, particularly 2.8 mm to 3.8 mm.
It is evident from FIG. 8 that said ratio should lie within the
range between 0.1 and 0.5 in order to achieve the improved degrees
of exchange and degrees of pressure loss. FIG. 8 in the present
case is provided by way of example for an extruded tube profile
shown in greater detail in FIG. 10B. A comparable tendency can also
be observed in the additional structural designs, described in
greater detail hereinafter, of a flow-through cross section in an
extruded tube. Thus, FIG. 8 shows the explained ratio for different
web distances a, inter alia of FIG. 10B (in the present case for
two examples a=2 mm and a=5 mm), and for different values of a
ratio, designated here by k, of a distance between two opposite
partial webs to a height of a tube cross section. The ratio k, as
illustrated in FIG. 8 by arrows, should be within a range below
0.8, preferably within a range between 0.3 and 0.7. In the present
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 to 0.75
in the direction of the arrow. This analysis applies both to an
exhaust gas cooler within the scope of a high-pressure design in an
exhaust gas recirculation system and to an exhaust gas cooler
within the scope of a low-pressure design in an exhaust gas
recirculation system.
[0157] Exemplary structural designs of a cross section of different
preferred extruded tubes are described hereinafter in FIG. 9A to
FIG. 11B. In this case, it should nevertheless be clear that
modifications of the same and any desired combination of features
of the embodiments specifically described in the figures are
possible, and a hydraulic diameter within 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 still be achieved. In particular, the
embodiments shown in the following figures each show a modification
in which a channel cover thickness and a web thickness d are
identical or similar, and show another modification in which a
ratio of a web thickness d and a channel cover thickness s is less
than 1.0 mm. Accordingly, the wall thicknesses of partial webs or
similar dimensions can also be varied and adapted according to the
aim to be achieved.
[0158] FIG. 9A and FIG. 9B show two modifications of an extruded
tube 61, 61'; in this case, the modifications differ in that the
cover thickness s in extruded tube 61', illustrated in FIG. 9B, is
thicker than a web thickness d, whereas said thicknesses are
substantially identical in extruded tube 61 illustrated in FIG. 9A.
Furthermore, the same reference characters are used for identical
features.
[0159] Flow channel 61, 61' is formed as an overall extruded
profile, therefore, as an extruded channel cover together with the
extruded webs. Flow channel 61, 61' accordingly has a channel cover
63 having an interior space 67 which is surrounded by a channel
cover inner surface 65 and in the present case is designed for the
heat-exchanging guiding of the first fluid in the form of an
exhaust gas. Furthermore, flow channel 61, 61', in the present
case, has a number of five webs 69, which are arranged in inner
space 67 on channel cover inner surface 65 and are formed together
with channel cover 63, 63' as an integral extruded profile. A web
69 runs entirely parallel to a flow channel axis, which is
perpendicular to the plane of the drawing, continuously along the
flow path formed in housing of a heat exchanger. The shown
flow-through cross section, transverse to the flow channel axis, is
designed for guiding the exhaust gas in interior space 67. The
design is carried out on the basis of the hydraulic diameter dh,
which is given for the present extruded tube 61, 61' with reference
to the distances a, b at the bottom right in FIG. 9B. The hydraulic
diameter arises as four times the ratio of the area of the
flow-through cross section to a perimeter wettable by the exhaust
gas. The area of the flow-through cross section in the present case
is a multiple of the product of a and b. The wettable perimeter in
the present case is likewise a multiple of twice the sum of a and
b. In this case, a denotes the width of the free cross section of a
flow line 74, divided in the flow channel by webs 69, and b denotes
the free height of flow line 74.
[0160] In said flow channel 63, 63', and also in the flow channels
explained in greater detail hereinafter, a wall thickness s is
within the range between 0.2 mm and 2 mm, for corrosion-critical
applications preferably within the range between 0.5 mm and 1.4 mm,
for corrosion-non-critical applications preferably within the range
between 0.3 mm and 0.8 mm. A height b of a flow path 74 or a height
of the inner space 67 in the present case is within the range
between 2.5 mm and 10 mm, preferably within the range between 4.5
mm and 7.5 mm. A width a of a channel 74 in the transverse
direction is within the range between 3 mm and 10 mm, preferably
within the range between 4 mm and 6 mm.
[0161] FIG. 10A and FIG. 10B show two additional modifications of
an especially preferred embodiment of an extruded tube 71, 71',
which--as explained heretofore--differ only in the wall thickness
of channel cover 73, 73' relative to the wall thickness of a web
79. Flow channel 71, 71' has in addition webs 79 in the form of
full webs and partial webs 79', arranged alternately next to full
webs 79. Extruded tube 71, 71' is in turn formed entirely as an
extruded profile, a channel 74 in turn being formed by the distance
between two full webs 79. The hydraulic diameter of the
flow-through cross section in extruded tubes 71, 71', shown in FIG.
10A and FIG. 10B, is specified below FIG. 10B. In the present case,
two partial webs 79' are each arranged with opposing end sides
76.
[0162] FIG. 11A and FIG. 11B show two further modifications 81, 81'
of an especially preferred embodiment of an extruded tube 81, 81'
in which two partial webs 89' are arranged with end sides 86
laterally offset with respect to one another. A hydraulic diameter
dh for the shown profile is again obtained from the formula shown
below FIG. 10B, where a1 is to be replaced by a4.
[0163] A ratio of a distance a3 of a first partial web 89' to a
full web 89 to a distance a4 of a second partial web 89' to the
full web 89 is preferably within a range between 0.5 mm and 1.0 mm,
preferably within a range between 0.6 mm and 0.8 mm. The distance e
between two opposite partial webs 79' and/or between two partial
webs 89', offset with respect to one another, to a height b of the
tube cross section is basically within a range below 0.8 mm, in
particular within a range between 0.3 mm and 0.7 mm.
[0164] Each extruded tube shown in FIG. 9A to FIG. 11B is provided
according to the invention with impressions and bulges according to
the explained exemplary embodiments, to optimize the turbulences
and heat transfer, as well as the pressure drop, in the specific
application.
[0165] Particularly for the extruded profiles shown in FIGS. 10A,
10B, 11A, and 11B, apart from the described procedure for
impressing the tube wall and the tube web, an embodiment with
exclusive buckling of the full and half-webs is also advantageous.
Due to the large number of webs and/or the length of the half-webs,
an impression of the tube wall can cause the blocking of the flow
channel by contacting or almost contacting half-webs. Therefore,
depending on the distance e, particularly for the profiles shown in
FIGS. 10A, 10B and 11A, 11B, it is often more advantageous to allow
only the webs or half-webs to buckle by selective impressions in
the vicinity of the web attachments and to impress the tube walls
only as little as possible. This applies particularly for
e<1/3b.
[0166] FIG. 12 and FIG. 13 in each case show additional embodiments
91, 101 of cross sections of extruded tubes as yet without bulges.
In each case, partial webs 92, 102 are present, which extend
proceeding from webs 5 in the transverse direction into channels 6.
In the example of FIG. 12, the partial webs are each arranged at
the same height and in the example of FIG. 13 at a different
height.
[0167] The illustrations according to FIG. 12 and FIG. 13 are
according to scale, so that specific dimensional ratios of the
drawn dimensions can be derived from them.
[0168] The invention being thus described, it will be obvious that
the same may be varied in many ways. Such variations are not to be
regarded as a departure from the spirit and scope of the invention,
and all such modifications as would be obvious to one skilled in
the art are to be included within the scope of the following
claims.
* * * * *