U.S. patent application number 16/045197 was filed with the patent office on 2020-01-30 for heat exchanger.
The applicant listed for this patent is MAHLE International GmbH. Invention is credited to Scott E. Kent, Kurt R. Mittlefehldt.
Application Number | 20200033073 16/045197 |
Document ID | / |
Family ID | 69149121 |
Filed Date | 2020-01-30 |
United States Patent
Application |
20200033073 |
Kind Code |
A1 |
Kent; Scott E. ; et
al. |
January 30, 2020 |
HEAT EXCHANGER
Abstract
A heat exchanger (1) includes a first manifold (2) and a second
manifold (3) fluidically connected by at least one tube (4) with at
least one brazed joint between one manifold (2,3) and the tube (4).
The brazed joint is made of braze material. The first manifold (2)
and the second manifold (3) are formed from non-braze materials
with a higher melting point than the braze material. The non-braze
material does not melt during brazing. At least one of the
manifolds (2,3) has at least two non-braze material layers.
Inventors: |
Kent; Scott E.; (Albion,
NY) ; Mittlefehldt; Kurt R.; (Amherst, NY) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
MAHLE International GmbH |
Stuttgart |
|
DE |
|
|
Family ID: |
69149121 |
Appl. No.: |
16/045197 |
Filed: |
July 25, 2018 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
F28F 2255/06 20130101;
F28F 2275/04 20130101; F28F 9/0224 20130101; F01N 2240/02 20130101;
F28D 1/0391 20130101; F28D 1/05366 20130101; F28F 19/06 20130101;
F28D 2021/008 20130101; F28F 21/089 20130101; F28F 1/126 20130101;
F28F 9/18 20130101; F28F 9/182 20130101 |
International
Class: |
F28F 9/18 20060101
F28F009/18; F28F 9/02 20060101 F28F009/02 |
Claims
1. A heat exchanger (1) comprising: a first manifold (2); a second
manifold (3); at least one tube (4) with a tube profile (5)
fluidically connecting the first manifold and the second manifold,
the tube profile (5) having at least one channel (6) for a flow of
a fluid between the first manifold (2) and the second manifold (3);
and at least one brazed joint between one of the first and second
manifolds (2,3) and the tube (4), the brazed joint being made of
braze material; wherein the first manifold (2) and the second
manifold (3) are formed from non-braze materials with a higher
melting point than the braze material, the non-braze material being
configured not to melt during brazing; and wherein at least one of
the first and second manifolds (2,3) has at least two non-braze
material layers.
2. The heat exchanger according to claim 1, wherein the at least
one of the first and second manifolds (2,3) with the at least two
non-braze material layers has an inner non-braze material layer (7)
and an outer non-braze material layer (8), where the outer
non-braze material layer (8) is more anodic than the inner
non-braze material layer (7).
3. The heat exchanger according to claim 2, wherein the at least
one of the first and second manifolds (2,3) with the at least two
non-braze material layers is formed by roll forming and
welding.
4. The heat exchanger according to claim 2, wherein the at least
one of the first and second manifolds (2,3) with the at least two
non-braze material layers is formed by coextrusion.
5. The heat exchanger according to claim 2, wherein the at least
one of the first and second manifolds (2,3) with the at least two
non-braze material layers is formed by coextrusion followed by
drawing.
6. The heat exchanger according to claim 1, wherein the at least
one of the first and second manifolds (2,3) with the at least two
non-braze material layers has an inner non-braze material layer (7)
and an outer non-braze material layer (8), where the outer
non-braze material layer (8) has an equal or higher strength than
the inner non-braze material layer (7).
7. The heat exchanger according to claim 6, wherein the at least
one of the first and second manifolds (2,3) with the at least two
non-braze material layers is formed by roll forming and
welding.
8. The heat exchanger according to claim 6, wherein the at least
one of the first and second manifolds (2,3) with the at least two
non-braze material layers is formed by coextrusion.
9. The heat exchanger according to claim 6, wherein the at least
one of the first and second manifolds (2,3) with the at least two
non-braze material layers is formed by coextrusion followed by
drawing.
10. A heat exchanger (1) comprising: a first manifold (2); a second
manifold (3); at least one tube (4) with a tube profile (5)
fluidically connecting the first manifold and the second manifold,
the tube profile (5) having at least one channel (6) for a flow of
a fluid between the first manifold (2) and the second manifold (3);
and at least one brazed joint between one of the first and second
manifolds (2,3) and the tube (4), the brazed joint being made of
braze material; wherein the first manifold (2) and the second
manifold (3) are formed from non-braze materials with a higher
melting point than the braze material, the non-braze material being
configured not to melt during brazing; and wherein at least one of
the first and second manifolds (2,3) is formed from a single strip
of a non-braze material by roll forming and welding.
Description
TECHNICAL FIELD
[0001] The present invention relates to a heat exchanger applying
to residential, commercial, transport and the automotive
market.
BACKGROUND
[0002] Heat exchangers such as radiators and heater cores have used
folded tubes for many years, welded tubes were also common. A
folded tube is defined as a tube formed partially or completely
from strip stock and typically roll formed to a shape which, after
brazing, is able to contain a working fluid used for the particular
type of heat exchanger for which the tube was intended for. The
tube can be formed, typically roll formed, from one or more
individual strips of material of heat conductive material. The heat
conductive material is shaped in such a way that the tube body has
at least one internal channel or formed port for a flow of a fluid.
Due to the folding of the heat conductive material, at least one
external seam extending in a longitudinal direction of the tube
body is created. This seam may have a triangular-shaped or
delta-shaped cross-section due to the radius which occurs as the
result of forming the material strip. Folded tube use for other
heat exchangers including oil coolers, condensers and evaporators
is more recent. Prior to folded tube use in condensers primarily
extruded tubes were used. For evaporators, flat plate or extruded
tubes were the most common tube technologies.
[0003] Regardless of heat exchanger type a heat exchanger, using
either extruded tubes or welded tubes or folded tubes, typically
comprise a first manifold and a second manifold being spaced apart
and fluidically connected by at least one tube. A first fluid
flowing from the first manifold to the second manifold through the
tube is in thermal contact with interior surfaces of the tube while
a second fluid like ambient air is in thermal contact with exterior
surfaces of the tube. Typically, such heat exchangers are assembled
with a plurality of tubes (folded and/or extruded and/or welded),
where two adjacent tubes are spanned by an extended surface such as
corrugated fins to increase the available surface area for heat
transfer. As long as the two fluids have different temperatures, a
heat transfer from the warmer to the colder fluid can be achieved
through the tube.
[0004] Such heat exchangers are typically manufactured in two
steps. In the first step, the components of the heat exchanger,
i.e. at least the manifolds, tubes, and fins are assembled to
create a unitary structure. In the second step, the components are
joined together by furnace brazing. The brazing process requires a
filler or braze material with a lower melting point than the
adjoining components of the heat exchanger.
[0005] The type of tube construction influences which parts are
designed with braze material and which parts are not. In order to
ensure that the heat exchanger can be produced consistently and
cost-effectively, the braze material is typically rolled integrally
with the base material to the raw material and most frequently on
those parts which are rolled sheet products; although coextruded
manifolds do exist where the outer material is braze material. When
the braze material is applied on the roll formed sheet, it is often
referred to as "braze clad". A suitable braze material must have a
melt temperature specifically designed to melt at a temperature
lower than the primary or parent material such that the structure
of the part can be maintained while the braze material melts and
flows to form metallurgical bonds once the braze process is
complete.
[0006] For extruded tubes, the braze clad is rolled integrally with
the base material of the header or of the manifold in the case of a
manifold where the manifold cylinder is made from a single part.
During the brazing process, the braze cladding of the manifolds
melts and creates brazed joints between the manifolds and the
extruded tubes.
[0007] For folded tubes, the braze material is typically rolled
integrally with the base material as one of the layers of the
folded tube roll formed strip stock sheet. Braze material can as
well be present on the manifold or header but doing so comes with
the risk of causing folded tube erosion.
[0008] Although there is a substantially uniform temperature
distribution within the furnace, the folded tubes reach the final
temperature more quickly than the heavier manifolds. This results
in a temperature gradient along the heat exchanger at least
temporarily. During this time, the maximum temperature is reached
in the middle of the respective folded tube. Due to this
temperature gradient and the capillary effect of the gap of the
respective tube body, the liquid braze material flows along the gap
of the respective tube body from the manifolds toward the middle of
the respective folded tube. While the liquid braze material flows
over the surface of the seam of the folded tube, it partially
dissolves this surface resulting in an erosion along the folded
tube in longitudinal (guttering) as well as transverse
(undercutting) direction. Due to this, the structural strength of
the folded tube is reduced in the vicinity of such an erosion. This
may result in lower pressure resistance to of the fluid flowing
along the internal channels or ports of the folded tube.
Additionally, the chemical composition and grain structure of the
folded tube near such an erosion is changed, potentially making the
heat exchanger more susceptible to corrosion.
SUMMARY OF THE INVENTION
[0009] The present application is based on the objective of
specifying a heat exchanger with improved corrosion resistance as
well as improved structural strength.
[0010] This objective is achieved by using manifolds with at least
two non-braze material layers.
[0011] According to one aspect of the present invention, the heat
exchanger comprises a first manifold and a second manifold which
are fluidically connected by at least one tube. The tube may be a
folded tube, welded tube or extruded tube. A folded tube may be
created using multi-layer rolled sheet with at least the outer
layer being braze clad material. The multi-layer sheet may comprise
at least one layer of primary or "core" material. The tube profile
may be formed from using at least one strip of the multi-layered
composite material by roll forming, where the core material has a
higher melting point than the braze clad layer(s). The core
material may be aluminium or an aluminium alloy. The braze cladding
may be an aluminium-silicon alloy which has lower melting point
compared to the core aluminium. With the selection of the amount of
silicon in the aluminium-silicon alloy, the melting point and
liquidus line of the braze cladding can be adjusted according to
the requirements of the manufacturing process
[0012] According to a further aspect, the tube profile may have at
least one channel or port for flow of a fluid between the first
manifold and the second manifold. The tube profile may be shaped in
such a way that the tube profile comprises several internal folds
creating webs or ribs which extend substantially along the length
of the folded tube. The internal webs or ribs may define a
plurality of channels through which the fluid can flow. These
internal webs or ribs increase the surface area between the tube
and the fluid flowing through the tube improving the heat transfer.
In addition, the internal webs or ribs increase the structural
strength of the tube.
[0013] According to a further aspect of the present invention, the
first manifold and the second manifold are formed from non-braze
materials with a higher melting point than the braze material,
therefore the non-braze material does not melt during brazing. The
term "non-braze materials" includes that the manifolds may be
formed from a single non-braze material, a composition of several
non-braze materials, a non-braze alloy or a composition of several
non-braze alloys. Since at least one manifold has at least two
non-braze material layers, where one layer may form a sacrificial
layer, the corrosion resistance as well as structural strength of
the manifold and thus of the whole heat exchanger is improved.
[0014] During the brazing process, at least one brazed joint
between one manifold and the tube is created, with the brazed joint
being made of braze material. If a folded tube is used, the braze
cladding of the respective folded tube melts and creates a
longitudinal braze joint seam closing the seam gap of the
respective folded tube. Chemically, the tube clad layer and the
outer surface of the tube core material interact to form a
sacrificial corrosion layer.
[0015] In an advantageous development of the solution according to
the invention, the manifold with at least two non-braze material
layers may have an inner non-braze material layer and an outer
non-braze material layer, where the outer non-braze material layer
is more anodic compared to the inner non-braze material layer and
is more corrosion-prone than the inner non-braze material. Since
the outer non-braze material layer is more susceptible to
corrosion, this layer is sacrificial to the inner non-braze
material layer. The outer non-braze material layer protects the
inner non-braze material layer (core material) by encouraging the
corrosion to move laterally over the sacrificial outer layer as
opposed to penetrating the core material. For a certain period of
time, corrosion will only affect the outer non-braze layer. Thus,
the corrosion resistance of the manifold is improved.
[0016] In a further advantageous aspect of the invention, the
manifold with at least two non-braze material layers has an inner
non-braze material layer and an outer non-braze material layer,
where the outer non-braze material layer has an equal or higher
strength than the inner non-braze material layer. Thus, the
strength as well as the pressure resistance of the manifold is
improved. It is also possible that the outer non-braze material
layer is not sufficiently different electro chemically to be
sacrificial but still offers a strength improvement over the inner
non-braze material layer.
[0017] In an advantageous development of the solution according to
the invention, the manifold with at least two non-braze material
layers is formed by roll forming and welding. The manifold with at
least two non-braze material layers may be formed from a
multi-layer composite sheet by roll forming. The manifold may be
formed in one piece from multi-layer composite sheet. After
performing the roll forming process, a welding procedure may be
used to obtain a fluid-impermeable construction of the manifold.
The use of at least two non-braze material layers provides a way to
produced manifolds with customized properties. Due to the roll
forming process, the manifold provides an adequate strength at a
given wall thickness. Additionally, high strength alloys may be
used having a hardness which is too high to extrude the material.
Thus, high strength roll formed alloys provide a hardness which
would be impossible to extrude.
[0018] According to further aspects of the invention, the manifold
with at least two non-braze material layers may be formed by
coextrusion and may be followed by drawing. The manifold may be
formed in one piece. The outer non-braze material layer has may be
extruded over the inner non-braze material layer. This solution is
advantageous if the tools for roll forming are not available, so
that initial investment is avoided since there is no need to
purchase such tools. The manifold may be single drawn or double
drawn providing a higher strength.
[0019] According to yet another aspect of the invention, an
innovative heat exchanger comprises a first manifold and a second
manifold which are fluidically connected by at least one tube. The
tube may be a folded tube, welded tube or extruded tube. A folded
tube may be created using multi-layer rolled sheet with at least
the outer layer being braze clad material. The multi-layer sheet
may comprise at least one layer of primary or "core" material. The
tube profile may be formed from using at least one strip of the
multi-layered composite material by roll forming, where the core
material has a higher melting point than the braze clad layer(s).
The core material may be aluminium or an aluminium alloy. The braze
cladding may be an aluminium-silicon alloy which has lower melting
point compared to the core aluminium. With the selection of the
amount of silicon in the aluminium-silicon alloy, the melting point
and liquidus line of the braze cladding can be adjusted according
to the requirements of the manufacturing process
[0020] The tube profile may have at least one channel or port for
flow of a fluid between the first manifold and the second manifold.
The tube profile may be shaped in such a way that the tube profile
comprises several internal folds creating webs or ribs which extend
substantially along the length of the folded tube. The internal
webs or ribs may define a plurality of channels through which the
fluid can flow. These internal webs or ribs increase the surface
area between the tube and the fluid flowing through the tube
improving the heat transfer. In addition, the internal webs or ribs
increase the structural strength of the tube.
[0021] The first manifold and the second manifold are formed from
non-braze materials with a higher melting point than the braze
material, therefore the non-braze material does not melt during
brazing. The wording non-braze materials means that the manifolds
may be formed from a single non-braze material, a composition of
several non-braze materials, a non-braze alloy or a composition of
several non-braze alloys.
[0022] At least one manifold is formed from a single strip of a
non-braze material by roll forming and welding. This manifold may
be formed in one piece from single-layer roll formed sheet. After
performing the roll forming process, a welding procedure may be
used to obtain a fluid-impermeable construction of the manifold.
The use of a single strip of a non-braze material provides a simple
and cost-effective method of manufacturing the heat exchanger.
[0023] While a single layer sheet will not have the advantage of an
additional layer of sacrificial material, the alloy selection for
roll formed strip has fewer limitations than that of single
extruded material. The control of grain shape of roll formed strip
and the ability to vary the chemistry of roll formed strip beyond
what would be practically possible to extrude make a one piece
rolled strip non-clad manifold an inexpensive solution with high
strength and good corrosion resistance. This may not be the highest
strength option or the option with the ultimate corrosion
resistance, but it is a solution which is still far better than any
existing solution.
[0024] Further important features and advantages of the invention
emerge from the de-pendent claims, from the drawings and from the
associated description of the figures with reference to the
drawings.
[0025] Any features mentioned above and described below can be used
not only in the respectively stated combination, but also in
different combinations or individually without departing from the
scope of the present invention.
[0026] Preferred exemplary embodiments of the invention are
illustrated in the drawings and are explained in more detail in the
description below, wherein the same reference characters refer to
identical or similar or functionally identical components.
BRIEF DESCRIPTION OF THE DRAWINGS
[0027] In the drawings,
[0028] FIG. 1 shows a heat exchanger according to the
invention,
[0029] FIG. 2 shows a cross-section of a manifold with two
non-braze material layers according to the invention,
[0030] FIG. 3 shows a cross-section of a folded tube before brazing
according to the invention.
[0031] The drawings are schematic representations that are not
necessarily drawn to scale, unless expressly mentioned. The
drawings are included for illustrative purposes only and are not
intended to limit the scope of the present invention.
DETAILED DESCRIPTION OF THE DRAWINGS
[0032] According to FIG. 1, a heat exchanger 1 according to the
invention has a first manifold 2 and a second manifold 3 being
spaced apart and fluidically connected by at least one tube 4. The
heat exchanger 1 comprises a plurality of tubes 4 which are spaced
apart. Adjacent tubes 4 are respectively interconnected by a fin
arrangement 9 with a corrugated fin in order to increase the
available surface area for heat transfer.
[0033] The heat exchanger 1 may be fluidically connected to fluid
circuit of a vehicle which is not shown in the figures. This fluid
circuit may have least one electrically driven conveying unit for
driving a first fluid within the fluid circuit. The fluid circuit
may be a part of an HVAC (Heating, Ventilation and Air
Conditioning) system of a vehicle.
[0034] The first manifold 2 has an inlet 10 and the second manifold
3 has an outlet 11. The first fluid may flow through the inlet 10
into the heat exchanger 1 and may leave the heat exchanger 1
through the outlet 11.
[0035] The first fluid flowing from the first manifold 2 to the
second manifold 3 through the tubes 4 is in thermal contact with
interior surfaces of the tubes 4, while a second fluid, such as
ambient air, is in thermal contact with exterior surfaces of the
tubes 4. Additionally, the second fluid is in contact with the fin
arrangements 9. As long as the two fluids have different
temperatures, a heat transfer from the warmer to the colder fluid
can be achieved through the tubes 4 and fin arrangements 9.
[0036] The first manifold 2, the second manifold 3 and the tube 4
are assembled such that the first manifold 2 and the second
manifold 3 are fluidically connected by the tube 4. This assembly
is brazed or furnace brazed in order to create brazed joints
between the manifolds 2,3 and the tube 4. This provides a
cost-efficient and modular production of the heat exchanger.
[0037] FIG. 2 shows a cross-section of a manifold 2 with two
non-braze material layers according to the invention. The manifold
2 has a tube-like cross-section with an inner non-braze material
layer 7 and an outer non-braze material layer 8. The outer
non-braze material layer 8 may have a higher strength than the
inner non-braze material layer 7. Additionally, the outer non-braze
material layer 8 may be more anodic than the inner non-braze
material layer 7. For a certain period of time, corrosion will only
affect the outer non-braze layer 8. Thus, the corrosion resistance
and the structural strength of the manifold 2 may be improved. The
manifold 2 may comprise several non-braze material layers with
different material properties in order to meet technical
requirements. The manifold 2 shown in FIG. 2 may be manufactured by
roll forming or coextrusion.
[0038] FIG. 3 shows a cross-section of a tube 4 before brazing
according to the invention. In this case, the tube 4 is a folded
tube 4a. The folded tube 4a comprises a tube profile 5 and braze
material 12. The first manifold 2, the second manifold 3 and the
tube profile 5 are formed from non-braze materials with a higher
melting point than the braze material 12.
[0039] The tube profile 5 is formed from a strip of heat conductive
material by roll forming. The heat conductive material is shaped in
such a way that the tube profile 5 provides two channels 6 for a
flow of the first fluid between the first manifold 2 and the second
manifold 3. Due to the folding of the heat conductive material, at
least one gap 13 extending in a longitudinal direction of the tube
profile 5 is created. This gap 13 may have a triangular-shaped or
delta-shaped cross-section. The braze material 12 may extend
substantially along the length of the folded tube 4a and may
enclose the tube profile 5. During a brazing process, the braze
material 12 of the respective folded tube 4a melts and creates a
longitudinal seam closing the gap 13 of the respective folded tube
4a. Additionally, the braze material 12 creates brazed joints
between the first manifold 2 and the second manifold 3 and the
respective folded tube 4. Since the liquid braze material fills the
gap 13 evenly, a flow of the liquid braze material along the gap 13
in longitudinal direction of the tube profile 5 is avoided. Due to
this, an erosion of the respective folded tube 4a is supressed.
[0040] While the above description constitutes the preferred
embodiments of the present invention, it will be appreciated that
the invention is susceptible to modification, variation and change
without departing from the proper scope and fair meaning of the
accompanying claims.
* * * * *