U.S. patent application number 14/385661 was filed with the patent office on 2015-03-05 for heat exchanger.
This patent application is currently assigned to BEHR GMBH & CO. KG. The applicant listed for this patent is BEHR GMBH & CO. KG. Invention is credited to Peter Geskes, Klaus Irmler.
Application Number | 20150060028 14/385661 |
Document ID | / |
Family ID | 47901977 |
Filed Date | 2015-03-05 |
United States Patent
Application |
20150060028 |
Kind Code |
A1 |
Irmler; Klaus ; et
al. |
March 5, 2015 |
HEAT EXCHANGER
Abstract
The invention relates to a heat exchanger, such as in particular
an exhaust-gas evaporator, having a housing with a fluid inlet, and
with a fluid outlet for a first medium, such as in particular
exhaust gas, and having tubes which are arranged in the housing
transversely with respect to the flow direction of the first fluid
and through which a second medium can flow and which, by way of
their ends at the inlet side and at the outlet side are arranged
and connected in a fluid tight manner in a tube plate, wherein, to
the respective tube plate, there is connected in each case one
structure by means of which groups of tubes are connected to one
another in such a way that an outlet of at east one tube is
fluidically connected to an inlet of at least one other tube.
Inventors: |
Irmler; Klaus; (Tubingen,
DE) ; Geskes; Peter; (Ostfildern, DE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
BEHR GMBH & CO. KG |
Stuttgart |
|
DE |
|
|
Assignee: |
BEHR GMBH & CO. KG
Stuttgart
DE
|
Family ID: |
47901977 |
Appl. No.: |
14/385661 |
Filed: |
March 14, 2013 |
PCT Filed: |
March 14, 2013 |
PCT NO: |
PCT/EP2013/055226 |
371 Date: |
September 16, 2014 |
Current U.S.
Class: |
165/157 |
Current CPC
Class: |
F28D 7/1638 20130101;
F28D 21/0003 20130101; F28D 7/16 20130101; F28D 7/1623 20130101;
F28D 2021/0085 20130101; F28F 21/083 20130101 |
Class at
Publication: |
165/157 |
International
Class: |
F28D 7/16 20060101
F28D007/16 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 16, 2012 |
DE |
10 2012 204 151.6 |
Claims
1. A heat exchanger, such as in particular an exhaust gas
evaporator, having a housing with a fluid inlet and a fluid outlet
for a first medium, such as in particular exhaust gas, and having
tubes which are arranged in the housing transversely with respect
to the flow direction of the first fluid and through which a second
medium can flow and the ends of which are arranged and connected in
a fluidtight manner in a tube sheet at the inlet side and at the
outlet side, wherein the respective tube sheet has connected to it
in each case a structure by means of which groups of tubes are
connected to one another in such a way that an outlet of at least
one tube is fluidically connected to an inlet of at least one other
tube.
2. The heat exchanger as claimed in claim 1, wherein the structure
comprises a deflection plate and a cover plate, wherein the
deflection plate has openings which connect the outlets of one set
of tubes to the inlets of the other set of tubes, and wherein the
cover plate covers the deflection plate in a fluidtight manner.
3. The heat exchanger as claimed in claim 1, wherein the deflection
plate is placed on the respective tube sheet and is connected
thereto, wherein the cover plate is placed on the respective
deflection plate and connected thereto.
4. The heat exchanger as claimed in claim 1, wherein the deflection
plate is of one-piece design with the respective tube sheet,
wherein the cover plate is placed on the respective deflection
plate and connected thereto.
5. The heat exchanger as claimed in claim 1, wherein the deflection
plate is of one-piece design with the respective cover plate,
wherein the deflection plate and the cover plate are placed on the
respective tube sheet and connected thereto.
6. The heat exchanger as claimed in claim 1, wherein the tubes are
arranged in rows, wherein the deflection plate deflects fluid
between tubes in different rows.
7. The heat exchanger as claimed in claim 1, wherein the tubes are
arranged in rows, wherein the deflection plate deflects fluid
between tubes in the same row.
8. The heat exchanger as claimed in claim 1, wherein the rows of
tubes are arranged in segments, wherein the deflection plate
deflects fluid from one segment into another segment.
9. The heat exchanger as claimed in claim 1, wherein a plurality of
tubes is connected in parallel, at least in one segment.
10. The heat exchanger as claimed in claim 1, wherein a plurality
of tubes connected in parallel is connected in series with one
another, at least in one segment.
Description
TECHNICAL FIELD
[0001] The invention relates to a heat exchanger, such as in
particular an exhaust gas evaporator, having a housing with a fluid
inlet and a fluid outlet for a first medium, such as in particular
exhaust gas, and having tubes which are arranged in the housing
transversely with respect to the flow direction of the first fluid
and through which a second medium can flow and the ends of which
are arranged and connected in a fluidtight manner in a tube sheet
at the inlet side and at the outlet side.
PRIOR ART
[0002] In the case of motor vehicles, there is a general trend
towards reducing fuel consumption. A not inconsiderable proportion
of the energy content of the fuel is transferred during combustion
in the internal combustion engine to the hot exhaust gas, which
often leaves the vehicle unused, and therefore a not inconsiderable
proportion of the energy content is not used.
[0003] To further reduce the fuel consumption of vehicles, such as
commercial vehicles or passenger vehicles, it is therefore
expedient to recover some of the energy content of the hot exhaust
gas in order to drive the motor vehicle.
[0004] There are various methods for this energy recovery currently
being tested. Thus, there are attempts to recover the energy
content electrically by means of thermoelectric elements. However,
this is currently restricted to low powers, and therefore only
about 1 kW is achieved by this means in the case of passenger
vehicles.
[0005] This recovery can be accomplished thermally, i.e. the energy
of the exhaust gas is used to heat the passenger compartment or to
heat the engine and/or transmission.
[0006] In a variant that has been under discussion for some time,
thermal energy is indeed taken from the exhaust gas, but the energy
is returned to the engine in mechanical form. The method is based
on a steam power process, in which a certain suitable medium is
evaporated and superheated in an evaporator and expanded in an
expander or in a turbine, thus producing mechanical energy.
[0007] Evaporation of the medium is accomplished by means of
heating using the hot exhaust gas. To achieve as high as possible
efficiency, it is expedient here if the medium can be raised to a
relatively high pressure. In the case of water as a medium, it is
possible here to achieve about 40-50 bar. When using organic
refrigerants, pressures of up to about 30 bar are advantageous.
[0008] In what is referred to as an evaporator, the medium to be
evaporated is heated to boiling temperature in a first step, then
evaporated and finally superheated. This can take place at two
different locations in a vehicle. Firstly, heat can be removed from
the exhaust gas to evaporate the fluid which is to be evaporated in
an evaporator, which is used instead of the exhaust gas cooler or
in addition thereto. Secondly, the main exhaust gas flow can also
be used as a heat source in order likewise to evaporate a fluid in
what is referred to as a main exhaust gas evaporator.
[0009] In the vehicle air-conditioning sector, "tray evaporators"
have been disclosed by WO 2011/051163 A2, wherein ribs are soldered
in between pairs of trays and a row of such pairs of trays is
connected in parallel with one another. In this case, a fluid flows
through the pairs of trays and another fluid flows around these in
a conventional manner. The fluid flowing through then evaporates in
the trays when the exhaust gas flows around the trays.
[0010] Evaporators which consist of trays and ribs have a high
power density which makes it possible to provide very compact
high-performance evaporators, even for vehicles. However, the
disadvantage is that such evaporators are relatively expensive to
produce.
DESCRIPTION OF THE INVENTION, OBJECT, SOLUTION AND ADVANTAGES
[0011] It is the object of the invention to provide a heat
exchanger which is simple and yet inexpensive to produce in
comparison with the prior art and which has a good power
density.
[0012] This object is achieved by means of the features of claim
1.
[0013] A preferred illustrative embodiment discloses a heat
exchanger, such as in particular an exhaust gas evaporator, having
a housing with a fluid inlet and a fluid outlet for a first medium,
such as in particular exhaust gas, and having tubes which are
arranged in the housing transversely with respect to the flow
direction of the first fluid and through which a second medium can
flow and the ends of which are arranged and connected in a
fluidtight manner in a tube sheet at the inlet side and at the
outlet side, wherein the respective tube sheet has connected to it
in each case a structure by means of which groups of tubes are
connected to one another in such a way that an outlet of at least
one tube is fluidically connected to an inlet of at least one other
tube. It is particularly advantageous here if the respective outlet
of one group of tubes is connected to the respective inlet of one
group of tubes.
[0014] It is particularly advantageous if the structure comprises a
deflection plate and a cover plate, wherein the deflection plate
has openings which connect the outlets of one set of tubes to the
inlets of the other set of tubes, and wherein the cover plate
covers the deflection plate in a fluidtight manner. Thus, the
deflection plate is connected to the tube sheet and has openings
within which inlets and outlets of a predeterminable number of
tubes are in fluid connection.
[0015] It is particularly advantageous if the deflection plate is
placed on the respective tube sheet and is connected thereto,
wherein the cover plate is placed on the respective deflection
plate and connected thereto.
[0016] It is also expedient if the deflection plate is formed
integrally with the respective tube sheet, wherein the cover plate
is placed on the respective deflection plate and connected
thereto.
[0017] In another illustrative embodiment, it is also advantageous
if the deflection plate is formed integrally with the respective
cover plate, wherein the deflection plate and the cover plate are
placed on the respective tube sheet and connected thereto.
[0018] It is particularly advantageous if the tubes are arranged in
rows, wherein the deflection plate deflects fluid between tubes in
different rows. This means that the deflection plate deflects fluid
from a first tube or from a group of first tubes into a second tube
or into a group of second tubes, wherein the first tubes and the
second tubes are preferably arranged in a different row of
tubes.
[0019] It is particularly advantageous if the tubes are arranged in
rows, wherein the deflection plate deflects fluid between tubes in
one row. This means that the deflection plate deflects fluid from a
first tube or from a group of first tubes into a second tube or
into a group of second tubes, wherein the first tubes and the
second tubes are preferably arranged in the same row of tubes.
[0020] It is also advantageous if the rows of tubes are arranged in
segments, wherein the deflection plate deflects fluid from one
segment into another segment.
[0021] It is furthermore expedient if a plurality of tubes is
connected in parallel, at least in one segment.
[0022] It is also advantageous if a plurality of tubes connected in
parallel is connected in series with one another, at least in one
segment.
[0023] Further advantageous embodiments are described by the
following description of the figures and by the dependent
claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0024] The invention is explained in greater detail below on the
basis of at least one illustrative embodiment with reference to the
drawings, in which:
[0025] FIG. 1 shows a first illustrative embodiment of a heat
exchanger according to the invention in a three dimensional
view,
[0026] FIG. 2 shows a view of the heat exchanger from the side,
[0027] FIG. 3 shows a partial view of a header zone,
[0028] FIG. 4 shows a partial view of a header zone,
[0029] FIG. 5 shows a partial view of a header zone,
[0030] FIG. 6 shows a view of the heat exchanger core,
[0031] FIG. 7 shows a view of a front deflection zone of the heat
exchanger,
[0032] FIG. 8 shows a view of a rear deflection zone of the heat
exchanger,
[0033] FIG. 9 shows another illustrative embodiment in a view of a
front deflection zone,
[0034] FIG. 10 shows another illustrative embodiment in a view of a
front deflection zone,
[0035] FIG. 11 shows another illustrative embodiment in a view of a
front deflection zone, and
[0036] FIG. 12 shows another illustrative embodiment in a view of a
front deflection zone.
PREFERRED EMBODIMENT OF THE INVENTION
[0037] FIGS. 1 and 2 show a heat exchanger 1, which is embodied as
an exhaust gas evaporator in the illustrative embodiment in FIG. 1.
In this case, there is a flow of a first fluid, in this case
preferably exhaust gas, and of a second fluid, in this case a fluid
to be evaporated, through the exhaust gas evaporator. The exhaust
gas transfers heat to the fluid to be evaporated and evaporates
said fluid. In this case, the heat exchanger 1 has a housing 2
having a fluid inlet 3 and a fluid outlet 4 for a first fluid. The
exhaust gas flows through the housing from the inlet 3 to the
outlet 4, and a row of tubes 5 is arranged between the inlet 3 and
the outlet 4, preferably transversely to the flow direction 7 of
the first fluid, and a second fluid can flow through said row. To
improve heat transfer between the first fluid and the second fluid,
ribs 6 which promote heat transfer are provided around the outside
of the tubes 5 and between the tubes 5. These ribs can be provided
as corrugated ribs or as flat ribs or as turbulence generators. The
tubes 5 for the through flow of the second fluid are preferably
round tubes or flat tubes. The ends of said tubes are preferably
also mounted in a fluidtight manner in tube sheets on both sides.
In this case, the tubes 5 are preferably arranged by way of their
ends 9 in a tube sheet 8 on the inlet side and the outlet side and
are connected in a fluidtight manner.
[0038] The heat exchanger is connected to an inlet branch 10 to
allow the second fluid to enter and to an outlet branch for
discharge. Starting from the inlet, the fluid is distributed
between a first number of tubes. The second fluid preferably flows
in parallel through these tubes. The fluid is then deflected at the
opposite ends of said tubes into a further number of different
tubes. The second fluid flows through these, in turn.
[0039] To redirect the fluid, the respective tube sheet 8 has
connected to it in each case a structure 12 by means of which
groups of tubes 5 are connected to one another in such a way that
an outlet 15 of at least one tube 5 is fluidically connected to an
inlet 16 of at least one other tube 5.
[0040] In this case, the structure 12 consists of at least one
deflection plate 13 and one cover plate 14, which are formed and
arranged one on top of the other. Here, the cover plate 14 covers
the deflection plate 13 in a fluidtight manner. The cover plate 14
is preferably welded or soldered or adhesively bonded to the cover
plate 13 or even formed integrally therewith.
[0041] In this case, the deflection plate 13 has openings which
connect the outlets 15 of one set of tubes 5 to the inlets 16 of
the other set of tubes 5.
[0042] In this case, the tubes 5 are inserted on at least one side
in the tube sheet 8, in openings 17, where the tubes are soldered
or welded to the plate.
[0043] It is possible to use aluminum, but particularly preferably
stainless steel, as a material for the tubes and tube sheets. It is
also possible for the entire heat exchanger to consist of aluminum
or stainless steel.
[0044] The deflection plate 13 has openings or channel structures,
which are suitable for connecting outlets of tubes to inlets of
other tubes.
[0045] As an alternative to the separate formation of tube sheet 8,
deflection plate 13 and cover plate 14, it may also be advantageous
if the deflection plate is designed to give a single part with the
tube sheet or if the deflection plate is designed as one part with
the cover plate. FIG. 4 shows that the deflection plate is designed
to give a single part 18 with the tube sheet. FIG. 5 shows that the
deflection plate is designed to give a single part 19 with the
cover plate.
[0046] In this case, the common part 18 or 19 is in each case
placed on the other part 14 or 8 and connected in a fluidtight
manner thereto.
[0047] In this case, the tube sheet can also be designed in such a
way, being milled for example, that the tube sheet modified in this
way so as to be multifunctional also additionally assumes the task
of fluid distribution and acts as a combination of a tube sheet and
a deflection plate. In that case, only one cover plate is mounted
on and connected to the tube sheet. In a corresponding manner, part
19 can likewise act as a milled component which integrates the
deflection plate and the cover plate.
[0048] It is furthermore also possible for the tube sheet and/or
the deflection plate and/or the cover plate to be designed as a
casting which has a corresponding structure with recessed
integrated openings for distributing the medium.
[0049] The connection between the two or three elements, the tube
sheet, the deflection plate and the cover plate, is advantageously
accomplished by means of welding, soldering or screwing, and it is
also possible to employ a combination of these connection options.
For this purpose, it is also possible for the upper plate to have
holes in order to connect the plates to one another by a welding
method at particular points distributed over the surface.
[0050] Particularly to achieve a good soldered joint, the 3 plates
can be fixed relative to one another and pressed against one
another by means of riveting or tack welds, alternative means being
spot welds, stamped features or screwed joints.
[0051] The deflection plate contains openings as structures in
order to collect the medium from at least one tube and redistribute
it to at least one other tube. The fluid to be evaporated is
preferably collected in the openings from up to 4 or more tubes and
is then redistributed to 4 or more tubes. During each collection
and distribution of the fluid, thermal instabilities leading to
nonuniform mass flow distribution in the tubes and hence to
different temperatures and/or vapor contents are very largely
compensated. It is thereby possible to compensate for instability
effects that lead to considerable losses of performance.
[0052] This is also a significant advantage of the 2 sandwich
sheets over the solution with tube bends and just one sandwich
sheet. As a result, the mixing processes take place in both
sheets.
[0053] FIG. 6 shows schematically a core 20 of the heat exchanger
1, in which a multiplicity of tubes 5 is arranged. These tubes 5
are arranged between the distributor plates 21, 22, which are
designed as deflection zones, and are received there in tube sheets
and deflection and cover plates.
[0054] As viewed in the exhaust gas flow direction 23, the
distributor plates 21, 22 are divided into individual segments 24,
25, 26, 27, 28 and 29. A number of tube rows 30, 31 are in turn
provided within a segment 24 to 29. In the example in FIG. 6, two
tube rows are provided for each segment. Ideally, a segment
consists of just a few tube rows, e.g. of two tube rows in the
exhaust gas flow direction, with the result that the temperature
gradient across a segment is as small as possible and hence all the
tubes are subjected to virtually the same exhaust gas temperature.
However, it is also possible, depending on the working medium, for
up to 6 tube rows to form a segment or for a plurality of segments
to be connected to one another in parallel.
[0055] In the illustrative embodiment of FIG. 6, up to 4 tubes per
tube row 30, 31 are furthermore connected in parallel
perpendicularly to the exhaust gas flow direction.
[0056] As can be seen in FIG. 6, the second fluid flows in in the
region of the tube ends 32 and is distributed between four tubes 5.
The fluid flows through these tubes to the ends of these tubes on
the opposite side and there flows into zone 33. The deflection zone
35 guides the fluid into the inlets of zone 34, from where the
fluid flows back to zone 36 through the tubes concerned. The fluid
is then deflected by deflection zone 37 to zone 38 at the tube ends
and distributed, with the result that the fluid then flows back
through the tubes which lie below the first passage.
[0057] Thus, the fluid flows through the first segment in
alternating passes and finally emerges from the segment in zone 39
and is diverted into the second segment 28 at crossover 40 from the
first segment 29.
[0058] The corresponding pass through the second segment 28 then
takes place, until the fluid flows into the third segment 27 at
crossover 41. The corresponding pass through the third segment 27
then takes place, until the fluid flows into the fourth segment 26
at crossover 42. The corresponding pass through the fourth segment
26 then takes place, until the fluid flows into the fifth segment
25 at crossover 43. The corresponding pass through the fifth
segment 25 then takes place, until the fluid flows into the sixth
segment 24 at crossover 44. The corresponding pass through the
sixth segment 24 then takes place, until the fluid flows out of the
sixth segment 24 at the outlet 4.
[0059] FIGS. 7 and 8 again show the configuration of connections
for the tubes at the front and rear deflection zone. It can be seen
that four tubes in each case are connected in parallel and that
fluid is deflected out of four tubes into four other tubes. In this
case, the fluid enters tubes 5 on the front side according to FIG.
7 and emerges from said tubes on the rear side. The tubes 5 are
therefore also marked with complementary inlets and outlets in the
front deflection zone according to FIG. 7, as in FIG. 8.
[0060] FIG. 9 shows a corresponding view of six segments 50 to 55,
which each have two tube rows. In this case, three tubes in each
case are combined and connected in parallel to form a passage 56.
In the case of passage 56, the fluid flows in and flows through the
tubes to the rear deflection zone. There, the fluid is deflected
from one tube row to the adjacent tube row. The fluid then flows
through the next three tubes and is deflected in the front
deflection zone into three further tubes in the same row of tubes.
The fluid then flows through the tubes to the rear deflection zone.
There, the fluid is again deflected from one tube row to the
adjacent tube row. The fluid then flows through the next three
tubes and is deflected in the front deflection zone into three
further tubes in the same row of tubes. This continues until the
fluid flows out of the tubes in zone 57 and is transferred into the
next segment through crossover 58. The crossover can preferably be
integrated into the deflection plate or can be implemented by means
of an external crossover for each tube.
[0061] The flow through the heat exchanger in FIG. 9 reveals a
difference with respect to the previous illustrative embodiment. In
FIG. 9, the fluid is deflected in the front deflection plate from
tubes in one row into tubes in the same row in accordance with
opening 60, while, in the rear deflection plate, the fluid is
deflected from tubes in one row into tubes in a different row in
accordance with opening or openings 59.
[0062] FIG. 10 shows another illustrative embodiment in another
view, wherein six segments 70 to 75 each have two rows 76, 77 of
tubes. As can be seen, segments 71 and 72 are combined to form a
common segment connected in parallel. The same applies to segments
73 and 74.
[0063] Moreover, three tubes in each case are combined and
connected in parallel to form a passage 78. In the case of passage
78, the fluid flows in and flows through the tubes to the rear
deflection zone. There, the fluid is deflected from one tube row to
the adjacent tube row through openings 79 in the deflection plate.
The fluid then flows through the next three tubes and is deflected
in the front deflection zone into three further tubes in the same
row of tubes through the opening 80 in the front deflection plate.
After this, the fluid flows through the tubes to the rear
deflection zone. There, the fluid is again deflected from one tube
row to the adjacent tube row. The fluid then flows through the next
three tubes and is deflected in the front deflection zone into
three further tubes in the same row of tubes. This continues until
the fluid flows out of the tubes in zone 81 and is transferred into
the next segment 71, 72 through crossover 82. Crossover 82 can
preferably be integrated into the deflection plate or can be
implemented by means of an external crossover for each tube.
[0064] The flow through segments 71, 72 takes place in the same way
as in segment 70, although these segments are connected in parallel
and the entry of fluid into zones 83 and 84 takes place in
parallel. The fluid then flows through the tubes of segments 71 and
72 in the same way as through the tubes of segment 70, before the
fluid is discharged from the segment again in zones 85 and 86 and
is transferred by means of crossover 87 into segments 73 and 74,
which are connected in parallel. In segments 73 and 74, the fluid
flows through as in segments 71 and 72. The fluid is then collected
from segments 73 and 74 and directed into the final segment 75,
where it flows through segment 75 as in the inlet-side segment 70
before it is discharged from the heat exchanger.
[0065] FIG. 11 shows another illustrative embodiment in another
view, wherein six segments 90 to 95 each have two rows 96, 97 of
tubes. As can be seen, segments 90 and 91 are combined to form a
common segment connected in parallel. The same applies to segments
92, 93 and 94, which are combined to form a common segment.
[0066] In segments 90 and 91 and in segments 92 to 94, the fluid in
each case flows through just one tube 98 parallel to one tube 99 of
the other segment. Within the segment, the flow through the tubes
98 is exclusively serial. This continues as far as the center of
the segment. There, the fluid flows out of the tubes 101, 102 of
both segments. There, there is a mixing zone 100, allowing the
fluid from the first segment 90 to mix with the fluid from the
second segment 91 before it is again distributed between tubes 103,
104 of the segments.
[0067] In the case of passage 98, the fluid flows in and flows
through a tube to the rear deflection zone. There, the fluid is
deflected from one tube row to the adjacent tube row through an
opening 105 in the deflection plate.
[0068] The fluid then flows through the next tube and is deflected
in the front deflection zone into another tube in the same row of
tubes through the opening 106 in the front deflection plate. After
this, the fluid flows through the tubes to the rear deflection
zone. There, the fluid is again deflected from one tube row to the
adjacent tube row. The fluid then flows through the next tube and
is deflected in the front deflection zone into another tube in the
same row of tubes. This continues until the fluid flows out in the
mixing zone 100. In the second zone after the mixing zone there is
a corresponding flow through the tubes. The fluid is then
transferred to the next segment 92, 93, 94 through crossover 107.
Crossover 107 can preferably be integrated into the deflection
plate or can be implemented by means of an external crossover for
each tube.
[0069] The flow through segments 92, 93, 94 takes place in the same
way as in segment 90, 91, although all three of these segments are
connected in parallel. The fluid then flows through the tubes of
segments 92 to 94, before the fluid is discharged from the segment
again and is transferred to segment 95 by means of crossover 108.
In segment 95, the fluid flows through as in segment 70 in FIG. 10,
in which three tubes are in each case connected in parallel. The
fluid is then discharged from the heat exchanger.
[0070] FIG. 12 shows another illustrative embodiment in another
view, wherein six segments 110 to 115 each have two rows 116, 117
of tubes. As can be seen, segments 110 to 112 and 113 to 115 are
combined to form a common segment connected in parallel.
[0071] In segments 110 to 112 and in segments 113 to 115, the fluid
in each case flows through just one tube 116 parallel to one tube
117, 118 of the other segment. Within the segment, the flow through
the tubes 116, 117 or 118 is exclusively serial. This continues as
far as the center of the segment. There, the fluid flows out of the
tubes 119, 120, 121 of the three segments. There, there is a mixing
zone 122, allowing the fluid from the first segment 110 to mix with
the fluid from the second and third segment 111, 112 before it is
again distributed between tubes 123, 124 and 125 of segments 110,
111, 112.
[0072] In the case of passage 116, the fluid flows in and flows
through a tube to the rear deflection zone. There, the fluid is
deflected from one tube row to the adjacent tube row through an
opening in the deflection plate. The fluid then flows through the
next tube and is deflected in the front deflection zone into
another tube in the same row of tubes through the opening in the
front deflection plate. After this, the fluid flows through the
tubes to the rear deflection zone. There, the fluid is again
deflected from one tube row to the adjacent tube row. The fluid
then flows through the next tube and is deflected in the front
deflection zone into another tube in the same row of tubes. This
continues until the fluid flows out in mixing zone 122. In the
second zone after the mixing zone there is a corresponding flow
through the tubes. The fluid is then transferred to the next
segment 113, 114, 115 through crossover 126. Crossover 126 can
preferably be integrated into the deflection plate or can be
implemented by means of an external crossover for each tube.
[0073] In segments 113, 114 and 115, the fluid flows through as in
segments 110, 111 and 112. The fluid is then discharged from the
heat exchanger.
[0074] In the figures, the configuration envisaged for the
deflection plate is rectangular. It can also be round, allowing it
to be installed in a round cylindrical aperture in a housing or in
a muffler.
[0075] To improve performance, gas-side ribs can be mounted on the
tubes, see ribs 6 in FIG. 2. The gas-side ribs form the "secondary
surface" for heat transfer and the tubes form the primary surface
for heat transfer. The ribs 6 can be soldered to the tubes 3, or a
thermally conductive joint is achieved without the addition of
solder during the process of soldering the overall evaporator. This
can be achieved by means of a very tightly toleranced rim hole for
the tube, which leads to a very narrow gap between the rib and the
tube. A thermally conductive joint between the ribs and the tubes
is thereby produced by means of diffusion processes during the
high-temperature soldering process, even if there is no solder
present.
[0076] A better bond between the ribs and the tubes, with or
without solder, can be achieved through a combination of austenitic
tubes and ferritic ribs. Ferrites expand less at high temperatures
than austenites, with the result that the tubes are pressed against
the ribs at the soldering temperature. In order to avoid the ribs
coming away from the tubes during cooling, the rib can have small
slots around the tubes.
[0077] The ribs have rim holes for the tubes, said holes having
what are referred to as collars, which ensure the spacing between
the ribs. As an alternative, it is also possible for the rib
spacing to be ensured by raising spacers in the rib. The rib
density here can be between 30 Ri/dm and 80 Ri/dm. The ribs can be
punched and have cut and raised fins or can also have merely
stamped-in structures, such as winglets, dimples or bosses, to
improve performance. In particular, it is expedient to stamp
structures into the ribs which guide the flow to the tubes in a
controlled manner and thus enable greater heat transfer to be
achieved at the
[0078] In this case, the rib thickness is 0.1 mm to 0.5 mm or
preferably between 0.25 and 0.4 mm, this being advantageous for
stainless steel as the rib material.
[0079] It is furthermore possible to make slots at the top and/or
bottom in the plate assembly, allowing differential thermal
expansion on the basis of different temperatures from the gas inlet
to the gas outlet and ensuring that this does not lead to any
damage.
[0080] The tube diameter of the tubes is preferably in a range of
3-20 mm, ideally in a range of 5-15 mm and preferably in a range of
6-10 mm.
[0081] Turbulence-generating structures can be introduced into the
tubes, e.g. swirl generators, in order to promote heat transfer,
particularly in the region where the fluid is superheated.
[0082] The tube can also be embodied as a rifled tube but in that
case preferably has no external ribs. In particular, it is also
possible to use tubes with very deep grooves which are of similar
design to a bellows with relatively large tubing diameters in order
to increase heat transfer on the gas side and, at the same time, to
enable the differential thermal expansion between the tubes to be
accommodated. In principle, different performance classes can be
achieved if an evaporator consists of individual modules in the
exhaust gas flow direction.
* * * * *