U.S. patent application number 12/095892 was filed with the patent office on 2009-02-26 for cooling device for an internal combustion engine.
This patent application is currently assigned to PIERBURG GMBH. Invention is credited to Peter Heuer, Hans-Jurgen Husges, Hans-Ulrich Kuhnel.
Application Number | 20090050302 12/095892 |
Document ID | / |
Family ID | 37686121 |
Filed Date | 2009-02-26 |
United States Patent
Application |
20090050302 |
Kind Code |
A1 |
Husges; Hans-Jurgen ; et
al. |
February 26, 2009 |
COOLING DEVICE FOR AN INTERNAL COMBUSTION ENGINE
Abstract
A cooling device is proposed that can be produced by the
diecasting process, and which has a heat-transfer unit surrounded
by an outer shell, wherein a jacket through which coolant flows is
formed between the heat-transfer unit and the outer shell, said
jacket is subdivided by webs in such a way that a passage through
which coolant flows is formed between the outer shell and the outer
casing of the heat-transfer unit. To this end, the webs are
arranged in such a way that this circulating flow is effected in a
meander shape. Compared with a spiral flow, this results in degrees
of freedom with regard to the arrangement of the coolant inlets and
coolant outlets. Furthermore, such cooling devices can be produced
and assembled in a cost-effective manner and have a high
efficiency.
Inventors: |
Husges; Hans-Jurgen;
(Willich, DE) ; Kuhnel; Hans-Ulrich;
(Monchengladbach, DE) ; Heuer; Peter; (Pulheim,
DE) |
Correspondence
Address: |
GRIFFIN & SZIPL, PC
SUITE PH-1, 2300 NINTH STREET, SOUTH
ARLINGTON
VA
22204
US
|
Assignee: |
PIERBURG GMBH
Neuss
DE
|
Family ID: |
37686121 |
Appl. No.: |
12/095892 |
Filed: |
October 26, 2006 |
PCT Filed: |
October 26, 2006 |
PCT NO: |
PCT/EP2006/067799 |
371 Date: |
October 1, 2008 |
Current U.S.
Class: |
165/143 ;
165/157; 165/164; 60/320 |
Current CPC
Class: |
F28F 3/12 20130101; F28F
9/22 20130101; F28F 3/048 20130101; F28D 9/0031 20130101; F28F
2255/14 20130101; F28F 2250/102 20130101; F28D 7/106 20130101; F28F
9/00 20130101; F28D 21/0003 20130101 |
Class at
Publication: |
165/143 ;
165/157; 165/164; 60/320 |
International
Class: |
F28D 9/00 20060101
F28D009/00; F28D 7/10 20060101 F28D007/10; F28F 3/12 20060101
F28F003/12; F28F 3/04 20060101 F28F003/04; F28F 9/22 20060101
F28F009/22; F01N 3/02 20060101 F01N003/02 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 2, 2005 |
DE |
10 2005 058 204.4 |
Claims
1. A cooling device, comprising: a first outer shell in which at
least one heat transfer unit is arranged that has an outer housing
separating a jacket through which coolant flows and the jacket is
formed between the first outer shell and the heat transfer unit
from a passage formed in the heat transfer unit and through which
fluid to be cooled flows; and webs arranged between the first outer
shell and the outer housing of the heat transfer unit that define a
passage in the jacket, through which coolant flows, wherein the
heat transfer unit is made in a diecasting process and comprises an
upper part and a cover-shaped lower part, wherein the upper part
and the lower part are connected by welding, and said webs are
arranged so that the heat transfer unit is passed by a meandering
positive flow of coolant.
2. The cooling device of claim 1, wherein a first axial web is
arranged between the first outer shell and the heat transfer unit,
and circumferential webs alternately extend from both sides of said
axial web and around the heat transfer unit, and said
circumferential webs end a distance shy of the axial web.
3. The cooling device of claim 1, wherein two opposing axial webs
are arranged between the first outer shell and the outer housing of
the heat transfer unit, a first axial web of the two opposing axial
webs ending shy of a last axial section of the cooling device, and
circumferential webs extend around said heat transfer unit
alternately from the first axial web and from a second axial web of
the two opposing axial webs and each of the circumferential webs
extends from both sides of a respective one of the opposing axial
webs, and said circumferential webs end a distance shy of the
respective other one of the two opposing axial webs, said distance
corresponding to the distance between the circumferential webs.
4. The cooling device of claim 1, wherein two heat transfer units
are arranged in a second outer shell, and third axial webs and
fourth circumferential webs are formed therebetween so that, in
cross section, each of the heat transfer units are passed on all
sides by a positive circulating flow of coolant.
5. The cooling device of claim 4, wherein, in cross section, the
circulating flow of coolant around the two heat transfer units is
substantially in the shape of an eight.
6. The cooling device of claim 4, wherein between the second outer
shell and each of the two heat transfer units is arranged a
respective third axial web, and these respective two third axial
webs are provided at opposite circumferential sides of said
passage, and fourth circumferential webs comprising fifth
circumferential webs and sixth circumferential webs alternately
extend around the heat transfer units from both sides of the third
axial webs, wherein each fifth circumferential web ends a distance
shy of one of the third axial webs and each sixth circumferential
web ends a distance shy of the other one of the third axial
webs.
7. The cooling device of claim 1, wherein the webs are at least
partly formed on the outer housing of the heat transfer unit.
8. The cooling device of claim 1, wherein the first outer shell is
at least bipartite and made by diecasting, and seventh webs are
formed at least partly on an inner wall of the first outer
shell.
9. The cooling device of claim 1, wherein two opposing axial webs
and two circumferential webs are formed substantially at the outer
housing of the heat transfer unit and have discontinuities in a
junction area between the upper part and the lower part, and which,
in the assembled state, the discontinuities are filled by
corresponding seventh webs of the first outer shell.
10. The cooling device of claim 7, wherein, in cross section, two
circumferential webs are continuous in a junction area between the
upper part and the lower part of the heat transfer unit.
11. The cooling device of claim 1, wherein the cooling device is an
exhaust gas cooling device for an internal combustion engine.
12. The cooling device of claim 1, wherein the upper part and the
lower part are connected by friction stir welding.
13. The cooling device of claim 2, wherein the axial web
corresponds to the distance between said circumferential webs.
14. The cooling device of claim 5, wherein between the second outer
shell and each of the two heat transfer units is arranged a
respective third axial web, and these respective two third axial
webs are provided at opposite circumferential sides of said
passage, and fourth circumferential webs comprising fifth
circumferential webs and sixth circumferential webs alternately
extend around the heat transfer units from both sides of the third
axial webs, wherein each fifth circumferential web ends a distance
shy of one of the third axial webs and each sixth circumferential
web ends a distance shy of the other one of the third axial webs.
Description
[0001] The invention refers to a cooling device, in particular an
exhaust gas cooling device, for an internal combustion engine, with
an outer shell in which at least one heat transfer unit is arranged
that has an outer casing separating a jacket, formed between the
outer shell and the heat transfer unit and through which coolant
flows, from a passage formed in the heat transfer unit and through
which the fluid to be cooled flows, with webs being provided
between the outer shell and the outer casing of the heat transfer
unit that define channels in the shell through which coolant
flows.
[0002] Such cooling devices are used, for example, in internal
combustion engines as exhaust gas cooling devices to reduce
pollutant emission by cooling the exhaust gas, mixing it with the
air freshly taken in and supplying it to the cylinders. By this
decrease of the temperature of the cylinder filling, the emission
of pollutants is reduced. To achieve this, very different
embodiments of cooling devices have been applied for.
[0003] A problem with many of these cooling devices are dead spaces
or turbulences in the jacket through which coolant flows, where no
coolant exchange occurs, whereby the efficiency of the cooling
device is significantly reduced. Further, damage could be done to
the cooling device should the coolant seethe.
[0004] To avoid such dead water spaces and to increase the
efficiency of the heat exchanger, cooling devices have been
developed that include a positive flow of the coolant.
[0005] DE 20 48 474, for example, discloses a partition wall for a
cooling device that is located in the coolant casing and defines a
flow-through channel. This cooling device is cylindrical, the webs
for the positive flow of the coolant flow being formed by a
separating blade provided subsequently on the inner heat transfer
unit, said blade surrounding the inner heat transfer unit helically
so that a spiral positive flow about the heat transfer unit is
achieved.
[0006] A similar embodiment is also known from DE 20 2004 008 737
which also discloses a cylindrical heat transfer unit, whose
partition walls are spirally, i.e. helically, arranged around the
inner passage. These partition walls are formed by a wire that is
almost square in shape. This wire is subsequently materially
fastened to the inner pipe, i.e. the heat transfer unit.
[0007] A cylindrical oil cooler with webs for the positive flow of
the coolant is known from U.S. Pat. No. 1,983,466, which webs do
not extend fully around the circumference, respectively, wherein
discontinuities in the webs are provided in alternate order on
opposite sides so that the coolant can flow to the opposite side in
both circumferential directions.
[0008] Further, a heat exchanger is known from U.S. Pat. No.
2,796,239 through which coolant flows on one side, with webs being
formed on the partition wall between the two media or at the cover
part of the cooling channel, which cause a meandering positive
flow.
[0009] It is a drawback of such embodiments that, with such helical
positive flows, the heat exchanger is fixed with respect to the
positioning of the coolant inlet and outlet. With a helical flow
circulating around the inner heat transfer unit, the inlets and
outlets for the coolant have to be situated at the axial ends of
the heat exchanger.
[0010] Furthermore, it is disadvantageous that it is only very
difficult and complex under aspects of manufacturing to make the
inner heat transfer unit not cylindrical, but parallelepiped or of
several parts, for example, or to arrange a plurality of heat
transfer units in a outer shell, with a positive circulating flow
possibly flowing around each heat transfer unit completely. In such
a case, it would be necessary to be able to exactly associate the
respective helical extensions of the webs defining the passages in
both parts so that no clefts or gaps exist between the individual
parts.
[0011] It is thus the object of the invention to provide a cooling
device with a positive coolant flow, which has high degrees of
freedom with respect to the arrangement of coolant inlets and
outlets, while simultaneously allowing the inner heat transfer unit
to be readily made from multiple parts. Moreover, it is also
intended to be possible, for example, to arrange a plurality of
heat transfer units in a housing around which a positive
circulating flow still flows as completely as possible.
[0012] This object is solved by making the heat transfer device in
a diecasting process and by forming it from an upper part and a
lid-shaped lower part, which parts are connected by welding,
especially by friction stir welding, the webs defining the passage
through which the coolant flows being arranged such that a positive
circulating flow passes through the heat transfer unit in a
meandering shape. This meander-shaped flow allows for a free choice
of the positions of the inlets and outlets, as well as of the shape
of the cooling device and the heat transfer unit. Even with a
multipart design of the heat transfer unit, the webs can be made
with the heat transfer unit in a simple manner and without offset.
Using aluminum or magnesium diecasting, the heat transfer unit can
be made lightweight, yet at low cost. At the same time it is also
suited for high temperatures. Friction stir welding is particularly
well suited for used with magnesium or aluminum diecast coolers.
Additional protrusions or eyelets for screw connections, as they
are known from other cooling devices for the connection of two
parts, are not needed here, so that a very compact and still tight
assembly without additional seals is guaranteed.
[0013] In a preferred embodiment, a first axial web is provided
between the outer shell and the outer casing of the heat transfer
unit, from which web circumferential webs alternately extend from
both sides of the axial web and around the heat transfer unit, the
circumferential webs ending a distance shy of the axial web that
preferably corresponds to the distance between the circumferential
webs. In such an arrangement, there are only webs that are
perpendicular to each other, which webs can be arranged in a simple
and precise manner with respect to each other even in a multipart
heat transfer unit, so that dead spaces are completely avoided. In
such a cooling device, the coolant inlet is arranged at the first
axial end of the cooling device, while the coolant outlet is
located at the opposite axial end. Along the circumference, a full
positive circulating flow exists around the heat transfer unit and
thus a high efficiency.
[0014] In an embodiment alternative thereto, two opposing axial
webs are formed between the outer shell and the outer casing of the
heat transfer unit, a first web thereof ending shy of a last axial
section of the cooling device, and from which webs circumferential
webs extend alternately from the first axial web and the second
axial web to both sides of the respective axial web and around the
heat transfer unit, the circumferential webs ending a distance shy
of the respective other axial web that corresponds to the distance
between the circumferential webs. With such an embodiment, the
coolant inlet and the coolant outlet can be located at the same
axial end of the cooling device so that the cooling device is flown
around in meander-like manner first in its first half and then in
its second half. In such an embodiment, the flow through the heat
transfer unit can be chosen to be correspondingly unshaped, so that
the cooling device can be operated both in counter flow and in
parallel flow. The relative arrangement of the webs remains simple
to realize and dead spaces are still avoided.
[0015] In a further alternative embodiment, two transfer units are
arranged in an outer shell, with webs formed between them such
that, in cross section, each of the transfer units is passed on all
sides by a positive circulating flow. Such a case pertains to a
two-stage cooler having the advantage of a more compact axial
length so that also in this case clearly higher degrees of freedom
exist when compared with coolers with a helical positive
circulating flow therethrough.
[0016] Such a flow on all sides is achieved by the two heat
transfer units being passed substantially in the shape of an eight,
seen in cross section. Additional forward and backward flows are
thus avoided, and coolant inlet and outlet channels can be arranged
on the axially opposite sides heat transfer unit.
[0017] In such a preferred embodiment, a respective axial web is
provided between the outer shell and each of the two heat transfer
units, the two axial webs being arranged on opposite
circumferential sides of the shell and circumferentially extending
webs alternately running from both sides of the axial webs and
around the heat transfer units, each circumferential web ending a
distance shy of the first axial web and each second circumferential
web ending a distance shy of the second axial web. In a
particularly simple manner, such an embodiment guarantees a
circulating flow around the two-stage heat exchanger in the shape
of an eight.
[0018] Preferably, the webs are at least partly arranged at the
outer casing of the heat transfer unit, so that no additional
inserts are needed to allow a functioning positive circulating
flow. In the diecasting process, these webs can then be produced in
only a single step together with the heat transfer unit.
[0019] In an advanced or alternative embodiment, the outer shell is
made of at least two parts and is manufactured by diecasting, the
webs being formed at least in part on an inner wall of the outer
shell. Of course, also in such an embodiment, the webs may be
formed entirely on the outer shell and extend to the outer wall of
the heat transfer unit. Intermediate solutions are also
conceivable, where the webs are formed in part on the outer casing
of the heat transfer unit and in part on the inner wall of a
bipartite outer shell. In both instances, additional inserts and
thus manufacturing steps are avoided.
[0020] In an embodiment continuative to the above, the webs are
substantially formed on the outer casing of the heat transfer unit
and are provided with discontinuities in the junction between the
upper part and the lower part, which, in the assembled state, are
filled by corresponding webs of the outer shell.
[0021] Such an embodiment is particularly useful with multipart
heat transfer units that are afterwards welded. Typically, this
requires a cutout in the region between the components of the heat
transfer unit in order to allow the application of the
corresponding welding tool. In order to still prevent an overflow
of coolant at these locations in the assembled state, they may
intentionally be recessed in the heat transfer unit and be filled
again in the assembled state by corresponding webs on the inner
wall of the outer shell, so that no regions with stagnant coolant
exist.
[0022] In an embodiment alternative thereto, the webs in the
junction between the upper part and the lower part of the heat
transfer unit are formed so as to extend continuously, seen in
cross section. This may result in minor pressure losses in the
coolant casing since the cross section is no longer equal over the
entire extension, however, such an embodiment allows to pass a
welding tool across the webs formed continuously in this region,
without destroying the reliable separation of the channels by the
webs.
[0023] The cooling devices claimed have a high efficiency, while
their structural size and the arrangement of the coolant inlets and
outlets can be chosen almost freely. Such cooling devices are
simple and economical to manufacture and assemble, without having
to use additional components.
[0024] Three embodiments are illustrated in the drawings and will
be detailed hereinafter.
[0025] FIG. 1 is a top plan view of a heat transfer unit of a
cooling device according to the present invention.
[0026] FIG. 2 is a side elevational view of the heat transfer unit
of FIG. 1.
[0027] FIG. 3 is a bottom view of the heat transfer unit of FIGS. 1
and 2.
[0028] FIG. 4 is a bottom view of an alternative cooling device
with a two-stage outer casing, a part of the outer shell being cut
away.
[0029] FIG. 5 is a sectional view of a front view of the cooling
device of FIG. 4.
[0030] FIG. 6 illustrates a third embodiment of a cooling device
according to the present invention in a partly sectional top plan
view.
[0031] FIGS. 1 to 3 illustrate a heat transfer unit 1 of a cooling
device typically enclosed by a one-piece outer shell, not
illustrated. The heat transfer unit 1 has an outer casing 2 at
which webs 3, 4, 5, 6 are formed. These webs 3, 4, 5, 6 serve to
provide a positive circulating flow around the heat transfer unit
1. Their height corresponds to the distance between an inner wall
of the outer shell and the outer casing 2 of the heat transfer unit
1, so that a jacket formed between the outer shell, not
illustrated, and the heat transfer unit 1 is divided into a
continuously extending passage 7 by the webs 3, 4, 5, 6.
[0032] Inside the heat transfer unit 1 a passage is formed through
which exhaust gas flows and in which ribs may be provided, for
example, for better heat transfer. In the present embodiment, the
heat transfer unit 1 is U-shaped, i.e. at least one axial web is
formed within the heat transfer unit 1, which is interrupted in the
rear portion, thereby allowing a deflection of the exhaust gas
flow. Correspondingly, an exhaust gas inlet 8 and an exhaust gas
outlet 9 are formed at the same axial end of the heat transfer unit
1.
[0033] To be able to pass the coolant flow along the heat transfer
unit 1, substantially either against the exhaust flow or with the
exhaust flow, the webs 3, 4, 5, 6 are configured such that the heat
transfer unit 1 is traversed by a positive circulating flow in a
meandering manner first in its first half 10 and then, in the
reverse direction, in its second half 11, so that a coolant inlet
12 and a coolant outlet are located at the same axial end of the
heat transfer unit 1.
[0034] For this purpose, the outer casing 2 of the heat transfer
unit 1 is provided with two axial webs 3, 4, a first axial web 3
being located on the upper side illustrated in FIG. 1 and a second
axial web 4 being located on the lower side of the heat transfer
unit 1 illustrated in FIG. 2. From these axial webs 3, 4, webs 5, 6
extend alternately in the circumferential direction on either side
of the webs 3, 4, seen in the axial direction, which each end shy
of the axial web 4, 3 located on the opposite side. The distance
between the end of a circumferential web 5, 6 and the respective
concerned axial web 3, 4 substantially corresponds to the distance
between two successive circumferential webs 5, 6, so that only
little pressure loss exists.
[0035] From FIGS. 1 to 3, the coolant path is now evident. Through
the coolant inlet 12, the coolant flows in the direction of the
axial web 3 visible in FIG. 1 and, between the end of the
circumferential web 8 and the axial web 3, it flows between the two
circumferential webs 5, 6. From there, the coolant flows along the
side wall illustrated in FIG. 2 to the lower side of the heat
transfer unit 1, illustrated in FIG. 3. here, the flow is again
deflected into the axial direction, so that the coolant is again
deflected by 90.degree. between the end of the circumferential web
5 and the axial web 4 and can flow back to the upper side between
the webs 5, 6. This meandering movement is carried on with repeated
deflection up to the other axial end of the heat transfer unit 1,
where the coolant can flow on the upper side of the heat transfer
unit 1, shown in FIG. 1, to the opposite side wall of the heat
transfer unit 1, since the axial web 3 is interrupted in this
region. From there, the meandering movement goes on respectively
about half the cross section of the heat transfer unit 1 to the
outlet 13.
[0036] FIGS. 4 and 5 illustrate a similar cooling device, with an
outer shell 14 being shown as well, which is open in FIG. 4. The
inner walls of the outer shell 14 are formed with double webs 15
that embrace the webs 3, 4, 5, 6, so that a reliable sealing is
achieved. To be able to achieve this, the outer shell is formed by
an upper part 16 and a lower part 17, as is evident from FIG.
5.
[0037] As already obvious from FIGS. 1 to 3, the heat transfer unit
1 is also of bipartite structure with an upper part 18 and a
cover-shaped lower part 19. The flow through the cooling device
illustrated in FIGS. 4 and 5 is effected in the same manner as
described with reference to FIGS. 1 and 3, with the present
illustration also showing the jacket 20 and, in FIG. 5, the inner
passage 21 through which exhaust gas flows, with ribs 22 extending
into the passage 21 from both parts 18, 19. Further, a central rib
23 is illustrated that separates the first half 10, through which
the flow passes first, from the second half 11 that is flown
through in the opposite direction.
[0038] It is obvious from FIG. 4 that in the area of the outer
edges of the cover-shaped lower part 19 of the heat transfer unit 1
the circumferential webs 5, 6 have discontinuities 24. These
discontinuities 24 exist because the fastening of the lower part 19
to the upper part 18 includes a welding operation in which
sufficient free space is required for the welding tool. A
discontinuous course of the webs 5, 6 at this location has the
effect that no exact and tight welding would be possible without
destroying the webs 5, 6. For this reason, these existing
discontinuities 24 are filled, upon assembly of the cooling device,
with short webs 25 provided at the outer shell 14. Such a web 25 is
visible in FIG. 5, in particular.
[0039] In the heat transfer unit of FIGS. 1 to 3, this problem has
been solved differently by forming the regions needed as free space
for the tool during welding between the upper part 18 and the lower
part 19 of the heat transfer unit 1 in a continuous manner around
the webs 5, 6 provided at the outer casing 2. This results in the
undulated profile on the lower side, obvious from FIG. 2. This is
advantageous in that friction stir welding can take place, for
example, without interrupting the webs 5, 6, yet it is
disadvantageous in that the through-flow cross section of the
coolant passage 20 has to be maintained the same to avoid flow
losses, so that an exact calculation of the existing surfaces has
to be performed and has to be realized in the casting.
[0040] Further, it is obvious from FIGS. 4 and 5 that the cooling
device is mounted to the actual cooling device by means of a top
element 26 at which the exhaust gas inlet 8 and the exhaust gas
outlet 9 are formed.
[0041] It is clear that both embodiments achieve a reliable
meander-like positive circulating flow through the heat transfer
unit 1, the coolant inlet and outlet 12, 13 being situated at the
same axial end of the heat transfer unit 1. It should be obvious
that an arrangement of the coolant inlet 12, as well as the exhaust
gas inlet 8 and the coolant outlet 13 and the exhaust gas outlet 9
at axially opposite ends of the cooling device, with a meandering
flow, is also possible, where merely one axial web would be
required, from which axial web circumferential webs would have to
extend alternately to either side and would each have to end before
meeting the axial web again.
[0042] Another embodiment of a cooling device according to the
invention is represented in FIG. 6. The coolant path is indicated
by arrows. Elements or flows on the rear are indicated in broken
lines.
[0043] Within this cooling device are two heat transfer units 27,
28 which are each completely passed by a positive circulating flow
around their circumference. This flow is in the shape of an eight.
For this purpose, each of the heat transfer units 27, 28 has an
axial web 29, 30 extending from one axial end to the other. After
assembly into the outer shell 31, both axial webs 29, 30 are
located on opposite circumferential sides of the cooling device, so
that the axial web 29 is indicated in broken lines.
[0044] A coolant inlet 32 is located on the side opposite with
respect to the present view, from where the coolant flows in the
circumferential direction about the first heat transfer unit 27.
From here, the coolant flows on between the first heat transfer
unit 27 and the second heat transfer unit 28, since the further
path is interrupted by the web 30. The coolant flows on to the side
of the cooling device averted from the present view and
circumferentially around the second heat transfer unit 28. A
lateral limitation of the passage 33 through which the coolant
flows is formed by a circumferential web 34 extending around the
entire heat transfer unit 27, and a circumferential web 35 that
extends around the entire heat transfer unit 28, but ends before
meeting the axial web 30. The flow in the circumferential direction
thus ends at the axial web 30, where the coolant is deflected and
flows on in the axial direction between the axial web 30 and the
circumferential web 35. Then, the coolant is deflected again, since
an axial flow is blocked by a web 36 extending circumferentially
around the heat transfer unit 28. It flows around the second heat
transfer unit 28, limited by the webs 35 and 36, and, due to the
resistance formed by the second axial web 29, flows from there
between the two heat transfer units 27, 28 to the side that
corresponds to the present view.
[0045] In this manner, the further progress of the coolant proceeds
past a web 37 at the first heat transfer unit 27, which ends shay
of the web 30 on the rear side, to a coolant outlet 38. The
necessary webs 42 between the two heat transfer units 27, 28 may
optionally be formed at one or both het transfer units 27, 28. In
the embodiment illustrated in FIGS. 6 and 7, the heat transfer
units 27, 28 have a common casing 39ahich is closed on the opposite
circumferential sides with a respective cover element 40, 41, so
that the webs 42 between the heat transfer units 27, 28 are formed
integrally with the casing 39.
[0046] When connecting the exhaust gas outlet of the first heat
transfer unit 27 with the exhaust gas inlet of the second heat
transfer unit 28, the exhaust gas cooling distance can thus be
doubled without having to extend the axial structural length of a
cooling device.
[0047] It should be evident that such a meandering positive
circulating flow through a cooling device provides the advantages
of an entirely freely selectable positioning of the coolant inlets
and outlets 12, 13, 32, 38. Using this positive flow, a high
efficiency of cooling devices thus structured is achieved. Assembly
and manufacturing costs are significantly reduced as compared to
known designs. In how far the existing webs are formed on the outer
shell or on the outer casing of the heat transfer unit or are
possibly configured as individual elements, remains free to choose.
The outer shape of the hat transfer unit is also largely optional
due to such a configuration of the coolant through-flow passages by
the webs.
* * * * *