U.S. patent application number 11/639801 was filed with the patent office on 2008-06-19 for high strength fin louver design.
This patent application is currently assigned to Valeo, Inc.. Invention is credited to Omar Dozal, Zaiqian Hu, Brian Kendall.
Application Number | 20080142202 11/639801 |
Document ID | / |
Family ID | 39525746 |
Filed Date | 2008-06-19 |
United States Patent
Application |
20080142202 |
Kind Code |
A1 |
Hu; Zaiqian ; et
al. |
June 19, 2008 |
High strength fin louver design
Abstract
Heat exchanger assemblies of increased strength are provided
having louvered fins that achieve both high thermal efficiency and
high strength simultaneously. By providing for a three-piece
louvered fin, tube-fin heat exchangers having at least one
three-piece single louver block, and, in particular, a streamlined
inclined three-piece single louver block, exhibit fins with
superior characteristics and overall strength for heat exchanger
assembly of louvered fin design, with reduced areas or zones of
boundary layer air.
Inventors: |
Hu; Zaiqian; (Carmel,
IN) ; Dozal; Omar; (Greensburg, IN) ; Kendall;
Brian; (Shelbyville, IN) |
Correspondence
Address: |
JULIA CHURCH DIERKER;DIERKER & ASSOCIATES, P.C.
3331 W. BIG BEAVER RD. SUITE 109
TROY
MI
48084-2813
US
|
Assignee: |
Valeo, Inc.
Auburn Hills
MI
|
Family ID: |
39525746 |
Appl. No.: |
11/639801 |
Filed: |
December 15, 2006 |
Current U.S.
Class: |
165/151 ;
165/152 |
Current CPC
Class: |
F28F 1/128 20130101;
F28D 1/05383 20130101; F28D 1/0391 20130101 |
Class at
Publication: |
165/151 ;
165/152 |
International
Class: |
F28D 1/04 20060101
F28D001/04 |
Claims
1. A tube-fin automotive heat exchanger comprising: a. a plurality
of tubes running basically parallel to one another; b. a plurality
of fins having at least one block of louvers, the plurality of fins
running between the tubes and being basically coplanar relative to
the tubes; c. at least one end tank connected to the tubes; wherein
the block of louvers comprises a set of louvers having at least one
three-piece single louver having two half louver sections and one
flat area louver section.
2. A tube-fin automotive heat exchanger, as in claim 1, having at
least one first end tank and at least one second end tank opposite
the at least one first end tank, wherein one end of the plurality
of tubes is connected to and in fluid communication with the one
first end tank and wherein the other end of the plurality of tubes
is connected to and in fluid communication with the at least one
second end tank.
3. A tube-fin automotive heat exchanger, as in claim 2, having at
least two blocks of louvers.
4. A tube-fin automotive heat exchanger, as in claim 2, wherein the
at least two blocks of louvers are symmetric around an axis
perpendicular to the width of the fin.
5. A tube-fin automotive heat exchanger, as in claim 4, wherein the
one three-piece single louver is a streamlined inclined three-piece
single louver.
6. A tube-fin automotive heat exchanger, as in claim 5, having at
least one non-three piece louver.
7. A tube-fin automotive heat exchanger, as in claim 6, wherein the
streamlined inclined three-piece single louver is an integral
inclined three-piece single louver and the half louvers of the
three-piece single louver have angles of inclination of similar to
or identical with at least one of the non-three piece louvers.
8. A tube-fin automotive heat exchanger, as in claim 7, wherein all
the louvers in at least one block of louvers have an angle (alpha)
with a center plane axis of the length of the fin that is similar
or identical with each other within that block.
9. A tube-fin automotive heat exchanger, as in claim 8, wherein the
louvers in each block have angles (alpha) with the center plane
axis of the length of the fin that are similar or identical with
each other within each respective block.
10. A tube-fin automotive heat exchanger, as in claim 6, wherein at
least one block of louvers has a plurality of three-piece single
louvers and non three-piece louvers along the fin, wherein the flat
area sections of the three-piece single louvers have an average
ratio of width of flat area sections to width of non three-piece
louvers of between about 0.10 and 0.90.
11. A tube-fin automotive heat exchanger, as in claim 10, wherein
the flat area sections of the three-piece single louvers have an
average ratio of width of flat area sections to width of non
three-piece louvers of between about 0.30 and 0.70.
12. A tube-fin automotive heat exchanger, as in claim 6, wherein
the relative difference between the width of two half louver
sections of the three-piece single louver and the width of half of
the a non-three piece louver is less than 1/3.
13. A tube-fin automotive heat exchanger, as in claim 6, wherein
the gauge of the fin is 0.10 mm or less.
14. A tube-fin automotive heat exchanger, as in claim 7, wherein
the gauge of the fin is 0.10 mm or less and wherein the inclination
of the two half louver sections is within a range of about
.alpha..+-.1/3.alpha., where a is the average inclination of non
three-piece louvers.
15. A tube-fin automotive heat exchanger, as in claim 6, wherein at
least two of the plurality of tubes are folded tubes in a row that
have a joint at the fold area and at least one three-piece single
louver is located adjacent to or immediately across from, the area
of the joint location of the folded tube.
16. A tube-fin automotive heat exchanger, as in claim 7, wherein at
least two of the plurality of tubes are folded tubes in a row that
have a joint at the fold area and at least one three-piece single
louver is located adjacent to or immediately across from, the area
of the joint location of the folded tube.
17. A tube-fin automotive heat exchanger as in claim 6, wherein at
least two of the plurality of tubes are folded tubes in a row that
have a joint at the fold area and the at least one block of louvers
is located adjacent to or immediately across from, the area of the
joint location of the folded tube.
18. A tube-fin automotive heat exchanger as in claim 17, wherein
the fin height changes across the length of the block of louvers
and wherein the fin height is at its highest at the location of the
three-piece single louver.
19. A fin system for a heat exchanger having louvers to enhance
transfer of heat from a first medium to a second medium, comprising
at least two blocks of louvers, each block having at least one set
of louvers per block, and each block having at least one set of
louvers having at least one three piece single louver and at least
one non three-piece louver.
20. A fin system, as in claim 19, wherein at least one block of
louvers comprises a plurality of non three-piece louvers and a
plurality of three-piece single louvers, and wherein the average
length of the non-three piece louvers is approximately equal to the
average length of the three-piece single louvers.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to heat exchangers having
tubes and fins, and, particularly, automotive heat exchangers with
fins having louvers.
BACKGROUND OF THE INVENTION
[0002] Automotive heat exchangers used is applications such as
engine cooling, air conditioning and the like, are of various
types. Examples of such heat exchangers are the so called plate-fin
types and tube-fin types, depending on the conduits and principle
heat exchanger areas of the exchangers.
[0003] Tube-fin type heat exchangers are the most common. This is
due mainly because of their relatively high thermal efficiency, and
mass manufacturing friendly design. A tube-fin type heat exchanger,
for example, uses a heat carrying liquid (water for radiator, and
R134a for condenser, CO.sub.2 for gas cooler for example), which
can transmit or transfer heat to the tubes, and the tubes,
subsequently, can transmit or transfer such heat either by directly
(rejecting or otherwise dispersing or dissipating) heat to air, or
transferring heat to fins, and having the heat then dissipated into
the air.
[0004] Heat exchanger fins, and, particularly those used in
automotive heat exchange applications, often have features, such as
louvers, to increase thermal performance. Air has a low thermal
conductivity, meaning that when fins are exposed to air, the air
side of the fin has a thermal resistance which is a major
contributor to the total thermal resistance of the heat
exchanger.
[0005] Air is presented to the heat exchanger, typically at a
certain air speed, due to movement of the vehicle and/or fans that
cause air to pass by or through the heat exchanger elements. A
typical air speed range (1 m/s to 5 m/s) is often found at the
areas of contact of air and heat exchanger in automotive engine
cooling or air conditioning applications, especially when measured
near the fin surface. At the fin surface a so called the air speed
and/or air temperature "boundary layer, is formed close to the area
of the fin louvers. This layer is a temperature and/or air speed
area, due to "air temperature" and/or "air speed", that results in
a boundary layer of lower heat transfer at the area of the surface
of the fin. Such a boundary layer of air, therefore, results in a
low thermal efficiency overall for the heat exchanger due to this
boundary layer effect.
[0006] In order to attempt to overcome the boundary layer effect, a
louvered fin design is widely used, as shown in the FIG. 1. Each
louver tries to break-up the air boundary layer, and, thereby allow
better heat exchanger with the moving air, and, thus, increase
thermal efficiency.
[0007] But louvered fins, (as opposed to "plain" or "unlouvered"
fins), do present drawbacks. For example, the louver in the fin has
led to lower strength in the fin column direction of the fin,
particular in the louvered area. The column strength of the fin is
the strength of the fin against compression in the fin height
direction (FIG. 3). This can be important because the column
strength of the fin. A strong fin is important during the tube/fin
assembly process.
[0008] This drawback becomes even more important when the fin gauge
is reduced. For example, in prior art fins the fin gauge was often
greater than or equal to 0.16 mm. Fin gauge for present
applications are often found in much lower ranges under 0.16 m,
even under 0.12 mm.
[0009] One solution to these problems has been to use special
high-strength material in louvered fin design.
SUMMARY OF THE INVENTION
[0010] A tube-fin automotive heat exchanger, in aspects of the
present invention, have at least one first end tank and at least
one second end tank opposite the at least one first end tank,
wherein one end of the plurality of tubes is attached to and in
fluid communication with the one first end tank and wherein the
other end of the plurality of tubes is attached to and in fluid
communication with the at least one second end tank.
[0011] Various aspects of the present invention propose solutions
for prior art problems which improve the strength of the heat
exchanger assembly by providing for louvered fins that achieve both
high thermal efficiency and high strength simultaneously. By
providing for a louvered fin, tube-fin heat exchanger having at
least one three-piece single louver, various aspects of the present
invention provide for fins with superior characteristics of
louvered fin, with reduced areas or zones of boundary layer air,
than that of prior art fin designs.
[0012] Various aspects of the present invention, therefore, provide
advantages such as increased column strength of louvered fins under
compression and design flexibility to put fin strength where it is
needed, in spite of the use of louvers with little or no negative
impact to the air flow that flows over and around the fin louvers.
In addition, these advantages can be obtained at no additional cost
of that of louvered fins without the three-piece single louver
feature.
[0013] As described herein, the at least one three-piece single
louver has a flat area that increases column strength of fins under
compression. Looking at the fin height from the fin top to fin
bottom, it appears to have a continuous structure in the flat area.
In aspects of the present invention, three-piece single louvers
with flat areas reduce the total space available for non
three-piece louvers. It is therefore clear that location of the
three-piece single louver or louvers in the appropriate plane leads
to a level of optimization of both fin strength and effectiveness,
especially when the flat area of the three-piece single louver is 2
mm or less in width.
[0014] As used herein, `half louver section` and `half louver`, as
they relate to the three-piece single louver, are used
interchangeably. Likewise, as it relates to the three-piece single
louver, `flat area` or `flat area section` or `flat area louver`
may be used interchangeably.
[0015] In various aspects of the present invention, the at least
one three-piece single louver is present on a fin, along with at
least one non three-piece louver. The three-piece single piece and
non three-piece louver or louvers form part of a block of louvers.
At least two blocks of louvers form a part of the set of louvers
that are present as a fin system in the heat exchanger. Preferably,
the two blocks of louvers are symmetric, as shown in FIG. 3 (A - -
- A is center line of symmetry).
[0016] The ratio of the average flat area length of the three-piece
single louver(s) to the average width of the non three-piece
louvers is between about 0.10 and 0.90. Particularly increased
strength has been found when the ratio is between about 0.30 and
0.70; and highly increased strength when the ratio is between 0.40
and 0.60. In various aspects of the present invention, at least one
block of louvers has a plurality of three-piece single louvers and
non three-piece louvers along the fin, wherein the flat area
sections of the three-piece single louvers have an average ratio of
width of flat area sections to width of non three-piece louvers of
between about 0.10 and 0.90.
[0017] The flat area section is in the same plane as fin central
plan. The inclination of the two half louver sections is usually
identical on opposite sides of the ends of the flat area.
[0018] In various aspects of the present invention, the angle off
from the plane of the flat area of the three-piece single louver of
the half louver (the inclination) is of a specific orientation. For
example, inclination of the two half louver sections within the
three-piece single louver is or can be at the same or at a similar
angle as non three-piece louvers to a plane. In various aspects,
the inclination of the two half louver sections are such that they
are at angles similar to at least one, and preferably, to a
plurality of non three-piece single louvers within the same louver
set. By same louver set it is meant several louvers having almost
the same louver angle/inclination. Also, by symmetrical louver
block it is meant a group of two or more louvers sets having
inclinations in opposing direction to one another (for example, the
reverse louvers as in FIG. 1, louvers angles in the left block of
the fin (see left area left of A - - - A) are almost opposite to
those in the right block on the fin (area right of A - - - A)). In
various aspects of the present invention, the at least two blocks
of louvers are symmetrics, the blocks are symmetric around an axis
(perpendicular) to the width of the fin.
[0019] The average width of the two half louver sections of the
three-piece single louver is 1/2 of the average width of the non
three-piece louvers.
[0020] This fin louver design can be applicable for wide range of
fin width (or core depth), for example, ranging from 8 mm to 70 mm
as shown by w in FIG. 1.
[0021] The inclination of the two half louver sections within the
three-piece single louver can be slightly different from the
inclination of other non three-piece louvers. In this case, the
relative difference should be less than 1/3. More specifically, the
inclination of the two half louver sections should be within the
range of a .alpha..+-.1/3.alpha., where .alpha. (alpha) is the
average inclination of non-three piece louvers (see FIG. 4).
[0022] The width of the two half louver could be slightly different
from 1/2 of width of a non three-piece louver. However, their
relative difference is normally less than about 1/3.
[0023] In various aspects of the present invention, a plurality of
the louvers in at least one block of louvers have an angle (alpha)
with a center plane axis of the length of the fin that is similar
or identical with each other within that block.
[0024] In various aspects, all or essentially all of the louvers in
each block have angles (alpha) with the center plane axis of the
length of the fin that are similar or identical with each other
within each respective block.
[0025] The gauge of material used as fin stock, and, eventually
provided for in the fins, various. Various aspects of the present
invention provide for use of fins and/or use of fin stock in gauges
of less than 0.10 mm (thin gauge fin). Other aspects of the present
invention provide for fin stock and fins in ranges from about 0.05
mm-0.10 mm, other aspects in ranges of from about 0.07 mm-0.10
mm.
[0026] In various aspects of the present invention, a three-piece
single louver is provided as part of a thin gauge fin. The
three-piece single louver comprises two half louver sections,
connected by a central flat area section. Various aspects of the
present invention have two half louver sections with orientations
relative to the plane of the flat area that are in opposite, that
is to say, pointing upward or downward at approximately the same
.alpha., in the orientation of the plane B - - - B streamlined
inclined three-piece single louver SITSL (see FIG. 4). In
particular, various aspects of the present invention provide for a
"streamlined inclined three-piece single louver", wherein the
louver comprises two half louver section that are at approximately
or at the same angle, but on opposite sides, of the plane of the
flat area of the louver, i.e. allows air flow to continue in the
same general direction (streamlined with air stream) in that
block.
[0027] As described herein in various aspects of the present
invention, folded tubes and fins are present. In various aspects
having a plurality of tubes, at least two of the plurality of tubes
are folded tubes in a row that have a joint at the fold area and
the at least one block of louvers is located adjacent to or
immediately across from, the area of the joint location of the
folded tube. Also, in various aspects of the present invention
having a plurality of tubes, at least two of the plurality of tubes
are folded tubes in a row that have a joint at the fold area and
the at least one block of louvers is located adjacent to or
immediately across from, the area of the joint location of the
folded tube.
[0028] Various aspects of the present invention provide for a fin
system for a heat exchanger having louvers to enhance transfer of
heat from a first medium to a second medium, comprising at least
two blocks of louvers, each block having at least one set of
louvers per block, and each block having at least one set of
louvers having at least one three piece single louver and at least
one non three-piece louver. In other aspects, at least one block of
louvers comprises a plurality of non three-piece louvers and a
plurality of three-piece single louvers, and wherein the average
length of the non-three piece louvers is approximately equal to the
average length of the three-piece single louvers.
BRIEF DESCRIPTION OF THE DRAWINGS
[0029] FIG. 1 is a schematic representation of a prior art louvered
fin design used in automotive heat exchangers.
[0030] FIG. 2 is a schematic representation of an automotive
louvered fin design wherein boundary layer air formation is broken
up in four directions by louver using a non-streamlined inclined
louver.
[0031] FIG. 3 is a schematic representation as seen from above
showing a prior art louvered fin design under compression during
tube fin assembly, and used in automotive heat exchanger
applications.
[0032] FIGS. 4a and 4b are schematic representations of a fin
having streamlined inclined three-piece single louver design,
showing louver angle a, in accordance with an aspect of the present
invention.
[0033] FIG. 5 is a schematic cross sectional representation from
above of a fin and tube arrangement having an automotive louvered
fin and two rows of folded tube, with three-piece louver block
facing a joint of the folded tube, in accordance with an aspect of
the present invention.
[0034] FIG. 6 shows an automotive tube-fin heat exchanger, having
fins with louvers, in accordance with an aspect of the present
invention.
DETAILED DESCRIPTION OF THE INVENTION
[0035] FIG. 1 illustrates a prior art fin (11) having louvers (12,
14) in a pattern symmetrical around line A - - - A and oriented in
a column Axis (A - - - A) represents fin length direction. M
represents air flow through one block of non three-piece louver. N
represents air flow through another block of non three-piece
louver. Q represents air flow at reversal louver. Breaking louver
(14), non three-piece louver (12) and reversal louver wings (13)
are shown.
[0036] FIG. 2 shows a fin design in which a non-streamlined
inclined three-piece single louver (25) is a reversal louver and
has two half louvers (24) and connected by a flat area. In this
design, the two downward facing half louvers are along/with similar
angles (.alpha.), having two opposite directions, therefore forcing
air (F) to change flow directions, resulting in additional air side
pressure drop.
[0037] FIG. 3 illustrates a second louvered fin (31) having louver
blocks (32a) (32b) arranged around a central axis (A - - - A), B -
- - B being the line of fin length direction. Arrows (X and Y)
illustrates force of compression from tubes on fin end radius area,
with louvers breaking structure integrity causing reduced fin
column strength in the X-Y orientation. Blocks of louvers (32a)
(32b) of fin (31) could be weakened by compression.
[0038] In various aspects of the present invention, a tube-fin
automotive heat exchanger comprising: a plurality of tubes running
basically parallel to one another; a plurality of fins having at
least one block of louvers, the plurality of fins running between
the tubes and being basically coplanar relative to the tubes; at
least one end tank connected to the tubes is provided.
[0039] In various aspects of the present invention, the block of
louvers comprises a set of louvers having at least one three-piece
single louver having two half louver sections and one flat area
louver section.
[0040] FIG. 4 illustrates a fin (40) having a louvers (46-49),
oriented in a pattern. The streamlined inclined three-piece single
louver (44) is found in a zig-zag shape oriented such that two half
louvers (48a, 48b) have almost the same inclination as other
louvers (46, 49). Fin (40) has two symmetric blocks of louvers,
only one is shown on the left of A - - - A in this figure. Each
block has breaking louvers (46), streamlined inclined three-piece
single louvers (44), regular louvers (49) and reversal louvers may
be present. The "streamlined inclined" three-piece louver (44) has
at least one flat area (47). FIG. 4b illustrates angle a of one of
the louvers of FIG. 4a.
[0041] As also illustrated on FIGS. 4 and 5, the streamlined
inclined three-piece single louver (44, 57), therefore, consists of
three parts: two half louvers (48a, 48b) (58a, 58b) connected by a
flat area (47) (57). The two half louvers (48a, 489b) (58a, 58b)
incline in the same direction. That is to say that the two half
louver sections (sometime referred to as `half louvers`) exist
relative to plane B - - - B, such that half louver (48a) (58a) is
on one side of the plane B and half louver (48b) (58b) is on the
other side of plane B - - - B. The two half louvers are connected
to or touching or integral to each other via a flat connecting
area, and particularly, the two half louvers are found, one on each
flat area end section.
[0042] Preferably, the three parts of the "streamlined inclined"
single louvers (two half louvers or louvers pieces and flat area
louver or louver piece) are structurally integral or form one
unity. In various aspects of the present invention, the .alpha. of
the half louver at the end of the flat areas is between about
5.degree. to 48 degrees, as measured from the plane of the flat
area louver section. The width of the flat area louver section is
greater than zero. The ratio of flat louver piece width to width of
the half louver in various aspects of the present invention is
approximately between 0.2 to 1.8.
[0043] The streamlined inclined three-piece single louver
comprises, therefore, two non-flat or half louvers and at least one
flat area section The flat area (louver) section lies in a plane
that follows B - - - B. By having a flat area between two half
louvers, the column strength of fin is significantly increased,
particularly under compression, and in particular if the
compression is mainly concentrated near the flat area louver
section.
[0044] FIG. 5 illustrates a portion of a tube fin heat exchanger
(55) comprising two rows of folded tube (56a) (56b), and tube joint
areas (J) and (J'). Tube joint areas are typically highly
compressed in order to obtain good braze of folded tube joint.
Streamlined inclined integral three-piece single louver in block
(54) is formed or placed such that flat area (57) of the
streamlined inclined three-piece single louver faces folded tube
joint (J, J'), enhancing the resistance of the tube joint to
compression.
[0045] Fins comprising at least one "streamlined inclined"
three-piece single louver, in various aspects of the present
invention, are designed such that the fin height at location of the
streamlined inclined three-piece single louver or louvers is higher
than other parts of the fin in order to ensure the streamlined
inclined three-piece single louver portion bears the compression
force during the tube/fin assembly.
[0046] The streamlined inclined three-piece single louver found in
various aspects of the present invention, comprises two half
louvers having the same or almost identical inclination, relative
to the plane of the flat area louver (see B - - - B of figures).
Due to this orientation, air can flow through the three-piece
single louver with little or no disturbance on its air flow.
Therefore, the boundary layer, normally present at the area of the
louvers, is reduced and, in general, at start of each louver, the
thickness of boundary layer restarts from zero.
[0047] FIG. 6a shows a heat exchanger (60) comprising tubes (66)
and louvered fins (61). FIG. 6s shows tubes (66) and the louvered
fins (61) comprising a group of non three-piece (not shown) and
integral "streamlined inclined" three-piece louver fins (62). The
"streamlined inclined" three-piece louver (62) faces the folded
tube joint (J), leading to increased column compression strength of
fins. First and second tanks (69, 70) and connected to and in fluid
communication with a plurality of tubes (66).
[0048] Unless stated otherwise, dimensions and geometries of the
various structures depicted herein are not intended to be
restrictive of the invention, and other dimensions or geometries
are possible. Plural structural components can be provided by a
single integrated structure. Alternatively, a single integrated
structure might be divided into separate plural components. In
addition, while a feature of the present invention may have been
described in the context of only one of the illustrated
embodiments, such feature may be combined with one or more other
features of other embodiments, for any given application. It will
also be appreciated from the above that the fabrication of the
unique structures herein and the operation thereof also constitute
methods in accordance with the present invention.
[0049] The preferred embodiment of the present invention has been
disclosed. A person of ordinary skills in the art would realize,
however, that certain modifications will come within the teachings
of this invention. Therefore, the following claims should be
studied to determine the true scope and content of the
invention
* * * * *