U.S. patent application number 11/537103 was filed with the patent office on 2008-04-03 for corrosion resistant bi-metal charge air cooler.
This patent application is currently assigned to INTERNATIONAL TRUCK INTELLECTUAL PROPERTY COMPANY, LLC. Invention is credited to Nirmal M. Tolani.
Application Number | 20080078536 11/537103 |
Document ID | / |
Family ID | 38863080 |
Filed Date | 2008-04-03 |
United States Patent
Application |
20080078536 |
Kind Code |
A1 |
Tolani; Nirmal M. |
April 3, 2008 |
CORROSION RESISTANT BI-METAL CHARGE AIR COOLER
Abstract
A heat exchanger assembly for an automotive vehicle includes at
least one tube having an internal layer and an external layer. The
external layer is an aluminum based material, and the internal
layer is a stainless steel based material. At least one turbulator
is disposed inside the tube and is formed of a stainless steel
based material.
Inventors: |
Tolani; Nirmal M.; (Fort
Wayne, IN) |
Correspondence
Address: |
INTERNATIONAL TRUCK INTELLECTUAL PROPERTY COMPANY,
4201 WINFIELD ROAD, P.O. BOX 1488
WARRENVILLE
IL
60555
US
|
Assignee: |
INTERNATIONAL TRUCK INTELLECTUAL
PROPERTY COMPANY, LLC
Warrenville
IL
|
Family ID: |
38863080 |
Appl. No.: |
11/537103 |
Filed: |
September 29, 2006 |
Current U.S.
Class: |
165/134.1 ;
165/180 |
Current CPC
Class: |
Y02T 10/146 20130101;
F28F 19/06 20130101; F28D 1/0391 20130101; Y02T 10/12 20130101;
F28D 2021/0082 20130101; F28F 21/08 20130101; F28F 13/12 20130101;
F02B 29/0462 20130101 |
Class at
Publication: |
165/134.1 ;
165/180 |
International
Class: |
F28F 19/00 20060101
F28F019/00; F28F 21/00 20060101 F28F021/00 |
Claims
1. A heat exchanger assembly for an automotive vehicle comprising:
at least one tube having an internal layer and an external layer,
said external layer comprising an aluminum based material, and said
internal layer comprising a stainless steel based material.
2. The heat exchanger of claim 1 further comprising: at least one
turbulator disposed inside said tube, said turbulator comprising a
stainless steel based material.
3. The heat exchanger of claim 2 wherein said at least one tube is
made of a stainless steel clad aluminum strip coil.
4. The heat exchanger of claim 2 wherein said stainless steel based
material comprises a steel in the austenitic or ferritic
grades.
5. The heat exchanger of claim 2 wherein said tube and said
turbulator are brazed together at each peak and trough of said
turbulator to said interior surface of said tube.
6. The heat exchanger of claim 2 wherein said tube is roll-formed
into a lock seam.
7. The heat exchanger of claim 2 further comprising a header formed
of aluminum clad with brazing alloy.
8. The heat exchanger of claim 2 further comprising a header formed
of aluminum clad with a stainless steel based material.
9. The heat exchanger of claim 2 further comprising at least one
end cap formed of aluminum.
10. The heat exchanger of claim 2 further comprising at least one
end cap formed of stainless steel.
11. The heat exchanger of claim 2 further comprising at least one
end cap formed of aluminum clad with stainless steel.
12. A method of making a heat exchanger, comprising: providing a
sheet of stainless steel clad aluminum having a first and a second
end; providing a turbulator of stainless steel based material;
forming said stainless steel clad aluminum sheet into a tube so
that an interior surface of said tube is stainless steel; locating
said turbulator inside said tube; and placing said tube in a core
assembly.
13. The method of claim 12 wherein said sheet is formed into said
tube to form a fluid passageway by roll-forming said first and
second ends of said sheet.
14. The method of claim 12 wherein said sheet comprises two
C-channels brazed together to form said tube.
15. The method of claim 12 wherein said turbulator is brazed to
said interior surface of said tube.
16. A tube for a heat exchanger, comprising: a generally
cylindrical housing having an internal layer comprising a stainless
steel based material and an external layer comprising an aluminum
based material.
17. The tube for a heat exchanger of claim 16, further comprising:
at least one turbulator disposed inside said housing, said
turbulator comprising a stainless steel based material.
Description
BACKGROUND OF THE INVENTION
[0001] The present invention relates generally to heat exchangers
in ground vehicles. More specifically, the present invention
relates to a lightweight Charge Air Cooler (CAC) with improved
corrosion resistance needed for new/future exhaust emission
compliant engines.
[0002] Automotive vehicles with internal combustion engines
commonly have heat exchangers such as radiators, charge air
coolers, condensers, heater cores, and evaporators to provide heat
transfer for the vehicle. Generally, these types of heat exchangers
employ the same thermodynamic principles to transfer heat from a
fluid (liquid or gas) to another fluid, where the two fluids are
physically separated, usually by metal tubing. On a vehicle, the
charge air cooler is a part of the engine air intake system that
uses ambient air to cool the intake air, which improves engine
combustion efficiency.
[0003] A charge air cooler typically has stacks of tubes, two
headers, fins and two end caps. The tubes serve as passages for air
flow. Within each of the tubes are turbulators, which are heat
transfer enhancement devices. The turbulators generally have an
undulating shape to turbulate the flow of fluid through the tube so
that heat can be transferred more effectively. The headers, the
tubes, the turbulators and the fins are typically made of wrought
aluminum alloys. The headers, turbulators and fins are generally
made from aluminum clad with brazing alloy to form brazed joints
between mating components. Conventionally, the turbulators are
placed inside the tubes, and the tubes and fins are stacked
together along with headers to form a core assembly. The core
assembly is processed in the brazing furnace to form bonds between
turbulators and the inside tube walls, fins and tube outer walls,
and tubes and headers. After the core is formed, end caps are
welded to the core to form the charge air cooler assembly.
[0004] The benefits of a CAC include obtaining cooler intake air,
increased horsepower, lower emissions, and increased fuel mileage.
The new federal regulations to reduce the vehicle emissions require
very significant modification to the air intake system of the
engines such as use of Exhaust Gas Recirculation (EGR). These
modifications to the intake air system in many cases give rise to a
highly corrosive condensate inside the charge air cooler. As a
result of highly corrosive condensate, the traditional aluminum CAC
is susceptible to internal, premature failure.
[0005] For increased corrosion resistance, CACs made entirely from
stainless subcomponents are being considered for some commercial
vehicles. The CACs made from stainless steel are much heavier and
more expensive. Additionally, heavier CAC requires heavier and more
expensive structures to support the CAC in the vehicle. This
further increases the weight and the cost of the vehicle, and
reduces the amount of weight that can be transported on the
automotive vehicle. A significant increase in weight as well as
increase in the cost makes the stainless steel CAC less
desirable.
[0006] Thus, there is a need for a charge air cooler that is highly
corrosion resistant and does not significantly increase the weight
and cost.
BRIEF SUMMARY OF THE INVENTION
[0007] The above-listed needs are met or exceeded by the present
heat exchanger assembly for an automotive vehicle, which includes
at least one tube having an internal layer and an external layer.
The external layer is an aluminum based material, and the internal
layer is a stainless steel based material. At least one turbulator
is disposed inside the tube and is formed of a stainless steel
based material.
[0008] A method of making a heat exchanger is provided and includes
the steps of providing a sheet of stainless steel clad aluminum
having a first and second end, and providing a turbulator of
stainless steel based material. The stainless steel clad aluminum
sheet is folded into a tube so that an interior surface of the tube
is stainless steel. The turbulator is located inside the tube and
the tube is sealed.
[0009] Also provided is a tube with a generally cylindrical housing
having an internal layer comprising a stainless steel based
material and an external layer comprising an aluminum based
material. At least one turbulator is disposed inside the housing,
the turbulator comprising a stainless steel based material.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS
[0010] FIG. 1 is an exploded perspective view of a charge air
cooler assembly according to the present invention;
[0011] FIG. 2 is a partial perspective view of a fin and a tube
located in a core of the charge air cooler assembly;
[0012] FIG. 3 is a cross-sectional view of a conventional tube
assembly; and
[0013] FIG. 4 is a cross-sectional view of a tube assembly of the
present invention.
DETAILED DESCRIPTION OF THE INVENTION
[0014] Referring now to FIGS. 1 and 2, an embodiment of a heat
exchanger assembly is shown. In this example, the heat exchanger is
a charge air cooler (CAC) assembly for an automotive vehicle, which
is indicated generally at 10. While the present heat exchanger 10
is a charge air cooler, it is contemplated that the present
invention can be used with other heat exchanger assemblies.
[0015] The charge air cooler assembly 10 includes a core assembly
12 and two end caps 14. The core assembly 12 includes a plurality
of tubes 16 and fins 18. Each tube 16 preferably extends across the
width "w" of the core assembly 12. Additionally, each fin 18
preferably extends along the width of the core assembly 12.
Preferably bounding the periphery of the core assembly 12 are side
members 20 running across the width "w" and thickness "t" of the
core assembly, and header members 22 running in the longitudinal
"l" direction of the core assembly. The two end caps 14 are
preferably welded onto the header members 22.
[0016] As seen in FIG. 2, within each of the tubes 16 is a
turbulator 26. The turbulator 26 is preferably a metal sheet having
a series of waves or undulations that is configured to break up or
turbulate the flow of fluid through the tube 16 to more effectively
transfer heat. In the present invention, the turbulator 26 is made
of a stainless steel based material.
[0017] Referring now to FIG. 3, the prior art tube 16P is made from
extruded aluminum and the prior art turbulator 26P is made from
sheet aluminum clad with a brazing alloy. Additionally, the end
caps (not shown) are formed of cast aluminum, the fins and the
header (not shown) are formed of sheet aluminum clad with brazing
alloy, and the sides (not shown) are formed of sheet aluminum, as
is known in the art. The prior art core assembly (not shown) is
generally vacuum brazed, and the cast aluminum end caps (not shown)
are welded to the core headers.
[0018] Referring to FIG. 4, a tube assembly 48 is made of a tube 16
having a housing 16A and a turbulator 26. The housing 16A has two
layers, an external layer 28 and an internal layer 30. The external
layer 28 of the tube 16 is preferably formed of a conventional
aluminum based material, and the internal layer 30 is preferably
formed of a stainless steel based material. The external layer 28
has an outer surface 32, which defines the outer surface of the
tube, and an inner surface 34, contacting the internal layer 30.
The internal layer 30 contacts the external layer 28 with an outer
surface 36. The internal layer 30 also includes an inner surface
38.
[0019] There are over seventy standard types of stainless steel and
many special alloys. Generally, all stainless steel is iron-based
with 12 to 30 percent chromium (Cr), 0 to 22 percent nickel (Ni),
and minor amounts of carbon, niobium, copper, molybdenum, selenium,
tantalum, and titanium. Generally, the stainless steel alloys are
heat and corrosion resistant, non-contaminating and easily
fabricated.
[0020] Further, stainless steel alloys are generally grouped in
three groups: (1) Martensitic, (2) Ferritic, and (3)
Austenitic.
[0021] Preferably, the tube 16 is formed of an aluminum sheet clad
with austenitic or ferritic stainless steel. The turbulators 26 are
disposed inside the tube 16 and are preferably attached to the
inner surface 38 of the internal layer 30. The turbulators 26 are
preferably made of stainless steel, and more preferably, are made
of an austenitic or a ferritic a sheet stainless steel.
[0022] In this embodiment, the tube 16 is preferably made from a
stainless steel clad aluminum sheet. Stainless steel clad aluminum
strip coils are commercially available and generally produced by
mechanically welding the aluminum sheet and the stainless steel
sheet using a rolling mill, as known in the art. The stainless
steel clad strip is roll formed in a traditional tube mill to form
a tube 16, with the stainless steel layer forming the internal
layer 30, and the aluminum forming the external layer 28. The tube
16 is formed from the strip and has a seam 44 that is either roll
formed into a lock seam 46 or a braze-joined seam. Alternate
methods of tube-making may be employed to make the tube 16, such as
by brazing two C-channels with a lap joint. The turbulator 26 is
placed inside the tube 16 and is brazed at each peak 40 and trough
42 to join the turbulator to the tube 16 using traditional
stainless steel brazing processes.
[0023] Referring back to FIG. 1, the tubes 16 containing
turbulators 26 can be used to make CAC core assemblies 12 using
conventional methods of manufacturing. Specifically, the tube
assemblies 48, along with the fins 18, can then be placed into a
core assembly 12, as is conventionally known. The core assembly 12
will have highly corrosion resistant stainless steel surfaces for
the air passages.
[0024] Since the header members 22 and the end caps 14 are
relatively thick members compared to the tubes 16 and turbulators
26, a certain amount of corrosion of the these components can be
tolerated without affecting the integrity or performance of the
charge air cooler 10. For this reason, conventional materials
(aluminum alloys, wrought aluminum) and processes can be used to
produce the charge air cooler with the present tube assembly.
[0025] However, to further enhance the corrosion resistance of the
charge air cooler 10, the header members 22 and the end caps 14 can
be formed of stainless steel clad material, or with a stainless
steel layer on the inside surface of the aluminum surfaces.
[0026] The advantage of using a stainless steel clad aluminum tube
16, as opposed to a tube formed completely of stainless steel, is
that the interior corrosion resistance is addressed by the internal
layer 30 of stainless steel, but the weight is significantly
reduced since the external layer 28 is formed of aluminum. Aluminum
is lighter than stainless steel and offers more efficient heat
transfer due to its higher thermal conductivity. Further, since the
external layer 28 is formed of aluminum, the fins 18 can also be
formed of aluminum, which further reduces weight and cost.
[0027] While particular embodiments of the present CAC have been
shown and described, it will be appreciated by those skilled in the
art that changes and modifications may be made thereto without
departing from the invention in its broader aspects and as set
forth in the following claims.
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