U.S. patent application number 12/103197 was filed with the patent office on 2008-10-30 for heat exchanger for exhaust gas cooling; method for operating a heat exchanger; system with a heat exchanger for exhaust gas cooling.
This patent application is currently assigned to BEHR GMBH & CO. KG. Invention is credited to Tobias Fetzer, Peter Geskes, Klaus Irmler, Rainer Lutz, Eberhard Pantow, Florian Pfister, Jens Ruckwied, Michael Schmidt.
Application Number | 20080264609 12/103197 |
Document ID | / |
Family ID | 39672594 |
Filed Date | 2008-10-30 |
United States Patent
Application |
20080264609 |
Kind Code |
A1 |
Lutz; Rainer ; et
al. |
October 30, 2008 |
HEAT EXCHANGER FOR EXHAUST GAS COOLING; METHOD FOR OPERATING A HEAT
EXCHANGER; SYSTEM WITH A HEAT EXCHANGER FOR EXHAUST GAS COOLING
Abstract
A heat exchanger, in particular for cooling the exhaust of a
motor vehicle internal combustion engine, is disclosed, the heat
exchanger comprising a first partial heat exchanger with at least
one first flow channel through which a medium to be cooled is to
flow and at least one third flow channel through which a first
coolant is to flow, at least one second partial heat exchanger with
at least one second flow channel through which a medium to be
cooled is to flow and at least one fourth flow channel through
which a second coolant is to flow, wherein the at least one first
flow channel and the at least one second flow channel are fluidly
connected, and the at least one first flow channel and the at least
one second flow channel have at least one first specific heat
transfer surface and at least one second heat transfer surface,
wherein second specific heat transfer surface area, divided by
first specific heat transfer surface area, yields a quotient
(.psi.), the at least one first flow channel having a larger
quotient (.psi.) than second flow channel.
Inventors: |
Lutz; Rainer; (Steinheim,
DE) ; Ruckwied; Jens; (Stuttgart, DE) ;
Irmler; Klaus; (Ammerbuch, DE) ; Schmidt;
Michael; (Bietigheim-Bissingen, DE) ; Fetzer;
Tobias; (Ostfildern, DE) ; Pantow; Eberhard;
(Moeglingen, DE) ; Geskes; Peter; (Ostfildern,
DE) ; Pfister; Florian; (Markgroeningen, DE) |
Correspondence
Address: |
LEYDIG VOIT & MAYER, LTD
700 THIRTEENTH ST. NW, SUITE 300
WASHINGTON
DC
20005-3960
US
|
Assignee: |
BEHR GMBH & CO. KG
Stuttgart
DE
|
Family ID: |
39672594 |
Appl. No.: |
12/103197 |
Filed: |
April 15, 2008 |
Current U.S.
Class: |
165/104.19 |
Current CPC
Class: |
F28F 3/025 20130101;
F28F 13/14 20130101; Y02T 10/12 20130101; F28D 21/0003 20130101;
F28D 9/0093 20130101; F02M 26/23 20160201; F02M 26/05 20160201;
F02B 29/0412 20130101; F02M 26/50 20160201; F02M 26/32 20160201;
F02M 26/24 20160201; F28D 7/0091 20130101; Y02T 10/166 20130101;
F28F 3/044 20130101 |
Class at
Publication: |
165/104.19 |
International
Class: |
F28D 15/00 20060101
F28D015/00 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 26, 2007 |
DE |
10 2007 020 103.8 |
Claims
1. A heat exchanger for cooling the exhaust of a motor vehicle
internal combustion engine, comprising a first partial heat
exchanger with at least one first flow channel through which a
medium to be cooled is to flow and at least one third flow channel
through which a first coolant is to flow, at least one second
partial heat exchanger with at least one second flow channel
through which a medium to be cooled is to flow and at least one
fourth flow channel through which a second coolant is to flow,
wherein the at least one first flow channel and the at least one
second flow channel are fluidly connected, and the at least one
first flow channel and the at least one second flow channel have at
least one first specific heat transfer surface having a first
specific heat transfer surface area and at least one second heat
transfer surface having a second specific heat transfer surface
area; wherein the second specific heat transfer surface area,
divided by the first specific heat transfer surface area, yields a
quotient (.psi.), the at least one first flow channel having a
larger quotient (.psi.) than second flow channel.
2. The heat exchanger according to claim 1, wherein the quotient
(.psi.) of the at least one first flow channel has a value of
1.0-2.5 and/or the quotient (.psi.) of the at least one second flow
channel has a value of 0-1.5.
3. The heat exchanger according to claim 1, wherein the first flow
channel and second flow channel form a constructive unit.
4. The heat exchanger according to claim 1, wherein the first
coolant has a higher temperature than the second coolant.
5. The heat exchanger according to claim 1, wherein the at least
one first flow channel is tubular and has a first tube interior
surface that forms the first heat transfer surface.
6. The heat exchanger according to claim 1, wherein the at least
one second flow channel is tubular and has a second tube interior
surface that forms the first heat transfer surface.
7. The heat exchanger according to claim 1, wherein the at least
one first flow channel has first turbulence elements and/or the at
least one second flow channel has second turbulence elements.
8. The heat exchanger according to claim 7, wherein the first
turbulence elements have a first turbulence element height and/or
the second turbulence elements have a second turbulence element
height.
9. The heat exchanger according to claim 7, wherein the first
turbulence elements are first dimples or first turbulence plates
with first rib segments and/or the second turbulence elements are
second dimples or second turbulence plates with second rib
segments.
10. The heat exchanger according to claim 7, wherein the first
turbulence plates and/or the second turbulence plates have the
second heat transfer surface.
11. The heat exchanger according to claim 9, wherein the first
turbulence elements have a first turbulence element height and/or
the second turbulence elements have a second turbulence element
height.
12. The heat exchanger according to claim 8 wherein the first
turbulence element height is greater than the second turbulence
element height.
13. The heat exchanger according to claim 7, wherein a first
turbulence element density is defined by the number of first
turbulence elements relative to a first length of first flow
channel and/or a second turbulence element density is defined by
the number of second turbulence elements relative to a second
length of second flow channel.
14. The heat exchanger according to claim 7, wherein a first
turbulence element thickness is greater than a second turbulence
element thickness.
15. The heat exchanger according to claim 7, wherein a first
turbulence element thickness is less than a second turbulence
element thickness.
16. The heat exchanger according to claim 1, wherein the heat
exchanger is a U-flow heat exchanger.
17. The heat exchanger according to claim 1, where in the heat
exchanger is an I-flow heat exchanger.
18. The heat exchanger according to claim 1, wherein the heat
exchanger has a third partial heat exchanger for reducing thermal
stresses.
19. The heat exchanger according to claim 18, wherein the third
partial heat exchanger has 1/8 to 1/4 of a heat exchanger length of
the heat exchanger.
20. The heat exchanger according to claim 18, wherein the first
partial heat exchanger is arranged between the second partial heat
exchanger and the third partial heat exchanger.
21. The heat exchanger according to claim 18, wherein the first
partial heat exchanger and/or second partial heat exchanger and/or
third partial heat exchanger form a constructive unit.
22. The heat exchanger according to claim 18, wherein the medium to
be cooled, and/or the coolant, flow with or against the current in
first partial heat exchanger and/or in second partial heat
exchanger and/or in third partial heat exchanger.
23. A method for operating a heat exchanger comprising a first
partial heat exchanger with at least one first flow channel through
which a medium to be cooled is to flow and at least one third flow
channel through which a first coolant is to flow, at least one
second partial heat exchanger with at least one second flow channel
through which a medium to be cooled is to flow and at least one
fourth flow channel through which a second coolant is to flow,
wherein the at least one first flow channel and the at least one
second flow channel are fluidly connected, and the at least one
first flow channel and the at least one second flow channel have at
least one first specific heat transfer surface having a first
specific heat transfer surface area and at least one second heat
transfer surface having a second specific heat transfer surface
area; wherein the second specific heat transfer surface area,
divided by the first specific heat transfer surface area, yields a
quotient (.psi.), the at least one first flow channel having a
larger quotient (.psi.) than second flow channel, the method
comprising passing exhaust gas to be cooled through the heat
exchanger, condensing out at least water while flowing through
second heat exchanger, and cleaning the second flow channel from
fouling from the exhaust gas.
24. The method according to claim 23, including condensing out at
least water from the exhaust gas substantially at a second coolant
temperature of less than 40.degree. C.
25. A system comprising at least one heat exchanger comprising a
first partial heat exchanger with at least one first flow channel
through which a medium to be cooled is to flow and at least one
third flow channel through which a first coolant is to flow, at
least one second partial heat exchanger with at least one second
flow channel through which a medium to be cooled is to flow and at
least one fourth flow channel through which a second coolant is to
flow, wherein the at least one first flow channel and the at least
one second flow channel are fluidly connected, and the at least one
first flow channel and the at least one second flow channel have at
least one first specific heat transfer surface hang a first
specific heat transfer surface area and at least one second heat
transfer surface having a second specific heat transfer surface
area; wherein the second specific heat transfer surface area,
divided by the first specific heat transfer surface area, yields a
quotient (.psi.), the at least one first flow channel having a
larger quotient (.psi.) than second flow channel; at least one
second heat exchanger for cooling an internal combustion engine of
a motor vehicle and at least one third heat exchanger for cooling
the second coolant.
26. The system according to claim 25, further comprising at least
one fourth heat exchanger for cooling the first coolant.
27. The system according to claim 25, wherein the third heat
exchanger is arranged first, as viewed in the direction of the air
flow, followed by the second heat exchanger.
28. The system according to claim 26, wherein the fourth heat
exchanger is arranged downstream of second heat exchanger, as
viewed in the direction of air flow.
29. The system according to claim 26, wherein the fourth heat
exchanger is arranged adjacent to second heat exchanger as viewed
in the direction of air flow (LR) and/or essentially at the same
height as second heat exchanger.
30. The system according to claim 26, wherein the second heat
exchanger and the fourth heat exchanger are identical.
31. The system according to claim 25, further comprising a first
control member for regulating the mass flow of the medium to be
cooled and/or for bypassing the medium to be cooled around at least
one partial heat exchanger, arranged on the inflow side of the
first heat exchanger.
32. The system according to claim 31, further comprising a second
control member for regulating the mass flow of the medium to be
cooled and/or for bypassing medium to be cooled around at least one
partial heat exchanger arranged on the outflow side of first
partial heat exchanger and on the inflow side of second partial
heat exchanger.
Description
[0001] The present invention relates to heat exchangers, more
particularly, for cooling the exhaust gas of an internal combustion
engine of a motor vehicle, with at least one flow channel through
which a medium to be cooled is to flow, and at least one third flow
channel through which a first coolant is to flow, at least one
second partial heat exchanger with at least one second flow channel
through which the medium to be cooled is to flow and with at least
one fourth flow channel through which a second coolant is to flow,
wherein the at least one first and the at least one second channel
are fluidically connected, and the at least one first flow channel
and the at least one second flow channel have at least one first
specific heat transfer surface and at least one second specific
heat transfer surface.
[0002] The invention further relates to methods for operating the
heat exchanger according to one of Claims 1-22.
[0003] The present invention further relates to a system with at
least one heat exchanger according to one of Claims 1-22.
[0004] Due to increasingly strict emission regulations, a part of
the exhaust gas produced in an internal combustion engine is
supplied back to the engine after cooling.
[0005] A multistage heat exchanger is known from DE 103 28 746 A1.
The heat exchanger has turbulence-generating shape elements in the
form of ribs, ridges, bumps or embossings.
[0006] A system with two-stage exhaust gas cooling is disclosed in
DE 10 2005 029 322 A1. The exhaust gas cooler is arranged on the
low-pressure side of a turbo charger. In this case in particular,
acidic condensate appears, which leads to corrosion of the exhaust
gas cooler.
[0007] A two-stage exhaust gas cooler, wherein one stage of the
exhaust gas cooler is air-cooled and the other stage of the exhaust
gas cooler is cooled by means of a liquid coolant, is known from DE
10 2005 042 396 A1.
[0008] A two-stage exhaust gas cooler with a high-temperature
circuit and a low-temperature circuit is known from DE 10 2007 005
723.9, as yet unpublished. The high-temperature circuit and the
low-temperature circuit are separated in this case by a separating
wall.
BRIEF SUMMARY OF THE INVENTION
[0009] The problem of the present invention is to optimize a heat
exchanger of the type mentioned above with regard to overall
installation space and costs. In particular, the problem is to
prevent the fouling of the heat exchanger by exhaust gas and the
associated performance decrease of the heat exchanger in continuous
operation.
[0010] The problem is solved by the characteristics of Claim 1.
[0011] A heat exchanger is proposed, particularly for cooling the
exhaust of an internal combustion engine. The heat exchanger has a
first partial heat exchanger with at least one first flow channel
through which a medium to be cooled, more particularly, exhaust
gas, is to flow, and with at least one third flow channel through
which a first coolant, more particularly, an aqueous coolant or
air, is to flow.
[0012] The heat exchanger further comprises at least one second
partial heat exchanger with at least one second flow channel
through which a medium to be cooled, more particularly, an exhaust
gas, is to flow, and with at least one fourth flow channel through
which a second coolant is to flow.
[0013] The at least one first and the at least one second channel
are fluidically connected, and the at least one first flow channel
and the at least one second flow channel have at least one first
specific heat transfer surface and at least one second specific
heat transfer surface.
[0014] The second specific heat transfer surface area divided by
the first specific heat transfer surface area yields a quotient
.psi., the at least one first flow channel having a larger quotient
.psi. than the second flow channel.
[0015] In this manner one can particularly advantageously achieve a
heat transfer surface coming into contact with the exhaust gas in
the first partial heat exchanger that is large enough that the
fouling from the exhaust gas can settle on this surface without the
performance substantially decreasing during continuous operation,
and at the same time, the heat transferring surface in the second
partial heat exchanger is constructed such that the fouling from
the exhaust gas is especially advantageously removed from the
exhaust gas heat exchanger by condensed water without the
occurrence of corrosion in the second partial heat exchanger, which
could lead to nonfunctionality of the heat exchanger.
[0016] In an advantageous refinement of the invention, the quotient
.psi. of the at least one first flow channel takes on values of
1.0-2.5 and/or the quotient of the at least one second flow channel
takes on values of 0-1.5.
[0017] In an advantageous refinement of the invention, the first
flow channel and the second flow channel form one constructive
unit. In this manner, the heat exchanger particularly
advantageously comprises a continuous flow channel for the first
and second partial heat exchangers. The heat exchanger is thereby
particularly compact and economical, as well as being more easily
installable.
[0018] In an advantageous refinement of the invention, the first
coolant has a higher temperature than the second coolant. In this
manner, a high-temperature circuit and a low-temperature circuit
are especially advantageously formed.
[0019] In an advantageous refinement of the invention, the at least
one first flow channel is constructed like a tube and has a first
interior tube wall surface that forms the first heat transfer
surface.
[0020] In an advantageous refinement of the invention, the at least
one second flow channel is constructed like a tube and has a second
interior tube wall surface that forms the second heat transfer
surface.
[0021] In an advantageous refinement of the invention, the at least
one first flow channel has first turbulence elements. The at least
one second flow channel has second turbulence elements. In this
manner, the heat transfer performance between the exhaust gas to be
cooled and the coolant can be particularly advantageously
increased.
[0022] In an advantageous refinement of the invention, the first
turbulence elements have a first turbulence element height and/or
the second turbulence elements have a second turbulence element
height.
[0023] In an advantageous refinement of the invention, the first
turbulence elements are formed as first dimples or first turbulence
plates with first rib segments. The second turbulence elements are
formed as second dimples or second turbulence plates with second
rib segments. In this manner, the turbulence element can be
manufactured particularly easily by stamping or pressing and can be
matched to the requirements in the first and second partial heat
exchanger--in particular, a large surface area for holding the
fouling of the exhaust, and a surface shape in the second partial
heat exchanger that brings about a condensation of water and
rinsing of the fouling.
[0024] In an advantageous refinement of the invention, the first
turbulence plates and/or the second turbulence plates comprise the
second heat transfer surface. In particular, the areas of the
second heat transfer surface are particularly advantageously
exposed to exhaust gas from both sides. The first heat exchanger
surfaces are acted upon by exhaust gas on one side of the wall and
by coolant from the opposite side.
[0025] In an advantageous refinement of the invention, the first
turbulence elements have a first turbulence element height and/or
the second turbulence elements have a second turbulence element
height.
[0026] In an advantageous refinement of the invention, the first
turbulence element height is greater than that of the second
turbulence element.
[0027] In an advantageous refinement of the invention, a first
turbulence element density is defined by the number of first
turbulence elements relative to a first length of the first flow
channel and/or a second turbulence element density is defined by
the number of second turbulence elements relative to a second
length of the second flow channel.
[0028] In an advantageous refinement of the invention, a first
turbulence element thickness is greater than a second turbulence
element thickness. A particularly good heat transfer through the
material concentration is guaranteed in this manner.
[0029] In an advantageous refinement of the invention, a first
turbulence element thickness is less than a second turbulence
element thickness. A particularly good corrosion resistance is
guaranteed in this manner.
[0030] In an advantageous refinement of the invention, the heat
exchanger is a U-flow heat exchanger. In this case, the exhaust gas
flows particularly advantageously into the heat exchanger at one
side, flows through it, is deflected by 180.degree. and flows back
in the opposite direction.
[0031] In an advantageous refinement of the invention, the heat
exchanger is an I-flow heat exchanger. The exhaust gas flows into
the heat exchanger at one side, flows through it and flows back out
of the heat exchanger at the opposite end.
[0032] In an advantageous refinement of the invention, the heat
exchanger has a third partial heat exchanger for reducing thermal
stresses. Because of the relatively short heat exchanger, large
bending strains due to the high exhaust gas temperature do not
arise.
[0033] In an advantageous refinement of the invention, the third
partial heat exchanger has 1/8 to 1/4 of a heat exchanger length of
the heat exchanger.
[0034] In an advantageous refinement of the invention, the first
partial heat exchanger is arranged between the second partial heat
exchanger and the third partial heat exchanger.
[0035] In an advantageous refinement of the invention, the first
partial heat exchanger and/or the second partial heat exchanger
and/or the third partial heat exchanger form a constructive unit.
In this manner, the first partial heat exchanger and/or the second
partial heat exchanger and/or the third partial heat exchanger can
be connected particularly advantageously by means of flanges or can
be connected into a constructive unit by means of a single housing.
In this manner, final installation in a vehicle can be accomplished
particularly quickly and simply.
[0036] In an advantageous refinement of the invention, the medium
to be cooled, and/or the coolant, flow against or with the current
in the first partial heat exchanger and/or in the second partial
heat exchanger and/or in the third partial heat exchanger.
[0037] Additionally, a method for operating the heat exchanger
according to one of Claims 1-22 is proposed. The medium to be
cooled, in particular, exhaust gas, condenses out at least water
while flowing through the second heat exchanger in order to cleanse
the second flow channel of fouling from the medium to be cooled. In
this manner, fouling is particularly advantageously removed from
the second partial heat exchanger, and performance is kept stable
over the long term.
[0038] In an advantageous refinement of the invention, the medium
to be cooled condenses out at least water substantially at a second
coolant temperature of less than 40.degree. C.
[0039] Additionally, a system with at least one heat exchanger
according to one of Claims 1-22 is proposed. Therein at least one
second heat exchanger for cooling an internal combustion engine of
a motor vehicle and at least one third heat exchanger for cooling
the second coolant are provided.
[0040] In an advantageous refinement of the invention, at least one
fourth heat exchanger for cooling the first coolant is
provided.
[0041] In an advantageous refinement of the invention, the third
heat exchanger is arranged first, followed by the second heat
exchanger, as viewed in the direction of the air flow.
[0042] In an advantageous refinement of the invention, the fourth
heat exchanger is arranged downstream of the second heat exchanger,
as viewed in the direction of air flow.
[0043] In an advantageous refinement of the invention, the fourth
heat exchanger is arranged adjacent to the second heat exchanger as
viewed in the direction of air flow and/or essentially at the same
height as the second heat exchanger.
[0044] In an advantageous refinement of the invention, the second
heat exchanger and the fourth heat exchanger are identical.
[0045] In an advantageous refinement of the invention, a first
control member for regulating the mass flow of the medium to be
cooled and/or for bypassing medium to be cooled around at least one
partial heat exchanger is arranged on the inflow side of the first
heat exchanger.
[0046] In an advantageous refinement of the invention, a second
control member for regulating the mass flow of the medium to be
cooled and/or for bypassing medium to be cooled around at least one
partial heat exchanger is arranged on the outflow side of the first
partial heat exchanger and the inflow side of the second partial
heat exchanger.
[0047] In an advantageous refinement of the invention, the heat
transfer surface on the coolant side is adapted to the flow
conditions prevailing there. The flow there should be turbulent.
The turbulent flow is generated particularly advantageously by
adapting the flow cross section and/or by means of turbulence
generating elements in this area. Coolant-side ribs and/or winglets
are particularly advantageous turbulence generating elements.
[0048] In an advantageous refinement of the invention, the
turbulence generating means are realized particularly in the second
stage, in the low temperature cooler stage. In this manner, the
mass coolant flow of the low temperature cooler is markedly smaller
than that of the high-temperature cooler.
[0049] Additional advantageous configurations of the invention
follow from the subordinate claims and the drawing. The subject
matter of the subordinate relates both to the heat exchanger of the
invention, as well as to the system of the invention and the method
for operating the heat exchanger of the invention.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING(S)
[0050] Embodiments of the invention are represented in the drawing
and will be described below in detail, wherein there is no
limitation of the invention. What is shown are
[0051] FIG. 1, a two-stage exhaust gas cooler;
[0052] FIG. 2a, a cutout of the first or second flow channel with a
first heat transfer surface;
[0053] FIG. 2b, a cutout of the first or second flow channel with a
second heat transfer surface;
[0054] FIG. 3a, a diagram of the factor .gamma. versus the factor
.psi. for the first partial heat exchanger;
[0055] FIG. 3b, a diagram of the factor .gamma. versus the factor
.psi. for the second partial heat exchanger;
[0056] FIG. 3c, a diagram of the factor .gamma. versus the
temperature of the second coolant for the second partial heat
exchanger.
[0057] FIG. 4a, a sectional representation of a two-stage exhaust
cooler in a plate construction with continuous plates;
[0058] FIG. 4b, a plan view of another embodiment of a two-stage
exhaust gas cooler in a plate construction with continuous
plates;
[0059] FIG. 5, continuous flow channels with two corrugated
turbulence plates;
[0060] FIG. 6, a sectional representation of a continuous flow
channel with an inserted turbulence plate in the first partial heat
exchanger and with dimples in the form of winglets in the second
partial heat exchanger;
[0061] FIG. 7a, b, c, d, additional embodiments of
turbulence-generating plates;
[0062] FIG. 8, a two-stage exhaust gas cooler in U-flow;
[0063] FIG. 9, a system with a two-stage exhaust gas cooler;
[0064] FIG. 10, a graph with the advantages of two-stage
cooling;
[0065] FIG. 11, an additional system with a first control member on
the inflow side of the first partial heat exchanger and a second
control member on the outflow side of the first partial heat
exchanger and the inflow side of the second partial heat
exchanger;
[0066] FIG. 12, a three-stage exhaust gas cooler;
[0067] FIG. 13, a first system with a three-stage exhaust gas
cooler;
[0068] FIG. 14, a second system with a three-stage exhaust gas
cooler;
[0069] FIG. 15, a third system with a three-stage exhaust gas
cooler;
[0070] FIG. 16, a fourth system with a three-stage exhaust gas
cooler.
DETAILED DESCRIPTION OF THE INVENTION
[0071] FIG. 1 shows a two-stage exhaust gas cooler 1. The exhaust
gas cooler has a first partial heat exchanger 11 and a second
partial heat exchanger 12.
[0072] Partial heat exchanger 11 has a housing of special steel of
aluminum or of plastic. First coolant medium flows into partial
heat exchanger 11 via a coolant inlet KE1 and, in a first stage,
cools the exhaust gas AE flowing in via the inlet diffuser. The
coolant exits via outlet KA1. The already cooled exhaust gas flows
farther into second partial heat exchanger 12, where it is farther
cooled, and subsequently exits in direction AA via outlet diffuser
3. The second coolant, air or water, for example, flows via
additional inlet EA2 into partial heat exchanger 12 and out via
outlet EA. Second partial heat exchanger 12 has a housing of
special steel of aluminum, or of plastic.
[0073] FIG. 2a shows a cutout of first or second flow channel 21,
22 with a first heat transfer surface 23.
[0074] FIG. 2b shows a cutout of first or second flow channel 21,
22 with a second heat transfer surface 24.
[0075] FIGS. 3a, 3b and 3c present three diagrams
[0076] The factor .gamma. is a quotient that is formed by dividing
the thermal power of the cooler without fouling by the thermal
power of the fouled cooler, which has fouling deposits.
[0077] The factor .psi. is a quotient that is formed by dividing
the secondary heat transfer surface area 24 by the primary heat
transfer surface area 23.
[0078] FIG. 3a shows a diagram of the factor .gamma. plotted versus
the factor .psi. for first partial heat exchanger 11. In area 33
with .psi.<1, too little secondary surface area 24 is available,
and the heat transfer power of the cooler is too low. In area 35
with .psi.>2.5, there is obstruction and clogging of the exhaust
gas cooler. The optimal range 34 (1.ltoreq..psi..ltoreq.2.5)
assures high power with low clogging of the exhaust gas cooler.
[0079] FIG. 3b shows a diagram of the factor .gamma. plotted versus
the factor .psi. for second partial heat exchanger 12. In range 36
(0.ltoreq..psi..ltoreq.1.5) the performance is optimal and the
fouling is washed out well. For .psi.>1.5, area 37, there is
clogging of second flow channels 22.
[0080] FIG. 3c shows a diagram of the factor .gamma. plotted versus
the temperature of the second coolant for the second partial heat
exchanger Experiments have shown that at temperatures
.ltoreq.40.degree. C., fouling is particularly advantageously
washed out by condensing water.
[0081] FIG. 4a shows a sectional view of a two-stage exhaust gas
cooler 1 in a plate construction with continuous plates 41, 42, 43,
44. Identical features are furnished with the same reference
numbers as in the preceding figures.
[0082] First flow channels 21, second flow channels 22, third flow
channels 41 and fourth flow channels 42 are formed by stacked upper
plates with sections 43 and 45 and lower plates with sections 44
and 46. In the illustrated embodiment, the plates can be
constructed to be continuous, but can also be connected by a
form-fit or a material joint. First turbulence elements 47 in the
form of turbulence plates or dimples are arranged in first flow
channels 21, Second turbulence elements 48 in the form of
turbulence plates or dimples are arranged in second flow channels
22.
[0083] The plates are formed of a metal such as special steel or
aluminum, or of a different metal. The plates are surrounded by a
housing 40.
[0084] FIG. 4b shows a plan view of another embodiment of a
two-stage exhaust gas cooler 1 in plate construction with
continuous plates. Identical features are furnished with the same
reference numbers as in preceding figures.
[0085] In contrast to FIG. 4a, coolant inlets and outlets KE1 and 2
as well as KA1 and 2 are on the same side in FIG. 4b. Area 11 has
flat plates that are soldered or to the rib elements of the first
turbulence plates. Area 12 shows a corrugated structure. The height
of the corrugation corresponds to half the channel height. The
gas-side rib has a reduced height. The height of the corrugation
structure is correspondingly reduced. The plate can also form a
stamped structure, wherein two plates form a tube bundle.
[0086] FIG. 5 shows continuous flow channels 50 with two corrugated
turbulence plates 47, 48. Identical features are furnished with the
same reference numbers as in the preceding figures.
[0087] The rib density of second turbulence plates 48 is greater
than that of first turbulence plates 47. Therefore there is no
clogging in section 11, and water that washes away fouling is
condensed out in section 12. A separating wall 49 separates the two
coolant circuits from one another.
[0088] FIG. 6 shows a sectional representation of continuous flow
channel 60 with an inserted turbulence plate 61 in first partial
heat exchanger 11, and with dimples 62 in the form of winglets in
second partial heat exchanger 12. Identical features are furnished
with the same reference numbers as in the preceding figures.
[0089] FIGS. 7a, b, c, d show other embodiments of
turbulence-generating plates. Identical features are furnished with
the same reference numbers as in the preceding figures.
[0090] FIG. 7a shows a flat plate 71 with a turbulence plate 70.
FIG. 7b shows two soldered corrugated plates 72, 73. The
corrugation structure can also be rounded. FIG. 7c shows corrugated
plates with ribs soldered between them. The corrugation structure
can also be rounded. FIG. 7d shows tube bundles from two stamped
plates 74.
[0091] FIG. 8 shows a two-stage exhaust air heat exchanger 80 in a
U-flow design. Identical features are furnished with the same
reference numbers as in the preceding figures.
[0092] The exhaust gas cooler has a housing 81 and a deflection
element 82.
[0093] FIG. 9 shows a system 90 with a two-stage exhaust gas
cooler. Identical features are furnished with the same reference
numbers as in the preceding figures.
[0094] System 90 has a turbocharger 103. Via charge air inlet 96,
charge air from the environment is compressed in turbocharger 103,
cooled in first charge air cooler 100, further condensed in second
turbocharger 104 and again cooled in the second charge air cooler,
a high-pressure cooler, and subsequently supplied to engine 95.
[0095] The exhaust gas arising in engine 95 flows through line 97.
A line 99 conducts a part of the exhaust gas via turbochargers 104,
103 to the exhaust pipe; another part of the exhaust gas is fed
back in line 98 and, before that, cooled in heat exchanger 1 in
first stage 11 and then in second stage 12, and mixed in with the
cooled charge air. Second charge air cooler 94 and second partial
heat exchanger 12 are supplied by low-temperature circuit 102 with
coolant, which is cooled in low-temperature cooler 93 by air drawn
in by fan 91. Between fan 91 and low-temperature cooler 93, coolant
cooler 92 is arranged. The latter supplies coolant to engine 95 as
well as first partial heat exchanger 11. Air flows in the LR
direction through second and third heat exchangers 92, 93.
[0096] FIG. 10 shows a graph with the advantages of two-stage
exhaust gas cooling. The low-temperature cooler LT-EGR (second
partial heat exchanger 12) achieves clearly lower temperatures and
scarcely any fouling.
[0097] FIG. 11 shows an additional system 110, with a first control
member 111 on the inflow side of first partial heat exchanger 1 and
second control member 112 on the outflow side of first partial heat
exchanger 11 and the inflow side of second partial heat exchanger
12. Identical features are furnished with the same reference
numbers as in the preceding figures.
[0098] FIG. 12 shows a three-stage exhaust gas cooler with an
additional third partial heat exchanger 123. The latter reduces the
alternating thermal stresses of sections 11 and 12, and has 1/4 to
1/8 the overall length of the heat exchanger. Part 123 can be
operated with co-current or countercurrent gas flow and cools the
gas down to 300-400.degree. C. There is a high gas flow rate and a
low pressure drop on the gas side because of the low number of ribs
and the few turbulence-generating structures, Smooth ribs or only a
few winglets are formed, so that there is a low rib density. A
third circuit 133, with a temperature level above that of the
engine coolant such as propylene glycol at 160.degree. C. to
200.degree. C. This yields a performance increase with an
appropriate arrangement of the recooler.
[0099] The most heat is removed from the exhaust gas in section 11,
but there must be no clogging due to fouling.
[0100] The desired temperature is ultimately reached in section 12.
The water contained in the exhaust gas condenses and thus
facilitates the cleaning of section 12.
[0101] FIG. 13 shows a first system 130 with a three-stage exhaust
gas cooler. Identical features are furnished with the same
reference numbers as in the preceding figures. In contrast to FIG.
9, a fourth heat exchanger 134 is provided.
[0102] FIG. 14 shows a second system 140 with a three-stage exhaust
gas cooler. Identical features are furnished with the same
reference numbers as in the preceding figures. Second heat
exchanger 142 and fourth heat exchanger 144 are arranged at
essentially the same height with respect to the LR direction.
[0103] FIG. 15 shows a third system 150 with a three-stage exhaust
gas cooler. Identical features are furnished with the same
reference numbers as in the preceding figures. In this case, a
separate second fan 152 is provided for the fourth heat
exchanger.
[0104] FIG. 16 shows a fourth system 160 with a three-stage exhaust
gas cooler. Identical features are furnished with the same
reference numbers as in the preceding figures. In this case, the
second heat exchanger and the fourth heat exchanger are realized in
a single heat exchanger 162.
[0105] The heat exchangers of FIGS. 1-16 can be charge air coolers
and/or oil coolers and/or coolant radiators in addition to exhaust
gas coolers.
[0106] The characteristics of the various embodiments can be
combined with one another in any desired manner. The invention can
also be used for fields other than those shown.
* * * * *