U.S. patent application number 11/183687 was filed with the patent office on 2007-01-18 for heat exchangers with corrugated heat exchange elements of improved strength.
Invention is credited to Raymond R. Caron, James S. Cotton, Brian E. Duke, Ihab E. Gerges, Mark S. Kozdras.
Application Number | 20070012430 11/183687 |
Document ID | / |
Family ID | 37660614 |
Filed Date | 2007-01-18 |
United States Patent
Application |
20070012430 |
Kind Code |
A1 |
Duke; Brian E. ; et
al. |
January 18, 2007 |
Heat exchangers with corrugated heat exchange elements of improved
strength
Abstract
A corrugated fin or turbulizer for a heat exchanger comprises a
series of corrugations with parallel side walls. The side walls are
provided with a series of parallel slits between which one-sided or
two-sided louvers are defined. Each of the louvers has first and
second edges extending along an adjacent pair of slits, and at
least one bend located between the edges, thereby causing at least
one of the edges of the louver to project outwardly of the plane of
the side wall, and providing the side wall with improved crush
resistance. The corrugations may preferably be rectangular or
trapezoidal in form, having generally flat top and bottom surfaces
defined by two closely-spaced bends. The top and bottom surfaces
may preferably be provided with protrusions, at least some of which
extend close to the bends. This assists in creating localized areas
of weakness along which the bends can be formed cleanly.
Inventors: |
Duke; Brian E.; (Carlisle,
CA) ; Caron; Raymond R.; (Burlington, CA) ;
Cotton; James S.; (Burlington, CA) ; Gerges; Ihab
E.; (Oakville, CA) ; Kozdras; Mark S.;
(Fergus, CA) |
Correspondence
Address: |
DYKEMA GOSSETT PLLC
39577 WOODWARD AVENUE
SUITE 300
BLOOMFIELD HILLS
MI
48304-5086
US
|
Family ID: |
37660614 |
Appl. No.: |
11/183687 |
Filed: |
July 18, 2005 |
Current U.S.
Class: |
165/109.1 |
Current CPC
Class: |
F28F 1/128 20130101;
F28F 3/027 20130101 |
Class at
Publication: |
165/109.1 |
International
Class: |
F28F 13/12 20060101
F28F013/12 |
Claims
1. A corrugated heat exchange element for a heat exchanger, the
heat exchange element comprising: a plurality of side walls
interconnected by a plurality of top and bottom walls, wherein each
of the side walls defines a plane and extends parallel to a
longitudinal axis, wherein each of the side walls extends between
an adjacent one of the top walls and an adjacent one of the bottom
walls, and wherein longitudinal bends are formed between each side
wall and the adjacent top and bottom walls such that spaces for
flow of a heat exchange fluid are defined between adjacent ones of
said side walls; and at least one group of adjacent louvers
provided in at least some of the side walls, wherein each group of
adjacent louvers is defined by a plurality of parallel slits
extending between the top wall and the bottom wall of the side wall
substantially perpendicular to the axis; wherein each of the
adjacent louvers comprises an area of the side wall between an
adjacent pair of said slits and includes: (i) a first edge
extending along a first slit of the adjacent pair of slits; (ii) a
second edge extending along a second slit of the adjacent pair of
slits; and (iii) at least one bend located between the first and
second edges of the louver which causes at least one of the edges
of the louver to project outwardly of the plane of the side
wall.
2. The corrugated heat exchange element of claim 1, wherein each of
the slits is bounded by the first edge of one of said louvers and
the second edge of an adjacent one of said louvers.
3. The corrugated heat exchange element of claim 1, wherein the
first edge of each of the adjacent louvers projects outwardly of
the plane of the side wall and the second edge of each of the
louvers is located in the plane of the side wall.
4. The corrugated heat exchange element of claim 1, wherein the
first edges of all the adjacent louvers in each said group project
outwardly from the same side of the side wall.
5. The corrugated heat exchange element of claim 1, wherein both
edges of each of the adjacent louvers project outwardly of the
plane of the side wall, and wherein the first edge and the second
edge of each louver project outwardly from opposite sides of the
side wall.
6. The corrugated heat exchange element of claim 1, wherein a
single one of said bends is provided between the first and second
edges of each of the adjacent louvers, wherein the single bend is
angular and extends along a bend line parallel to the first and
second edges of the louver to define an apex of the louver, and
wherein the apex is located in the plane of the side wall.
7. The corrugated heat exchange element of claim 1, wherein a first
louver wall is defined between the apex and the first edge of the
louver and a second louver wall is defined between the apex and the
second edge of the louver.
8. The corrugated heat exchange element of claim 1, wherein the
first and second louver walls are substantially flat.
9. The corrugated heat exchange element of claim 7, wherein the
single bend defines an obtuse angle between the first and second
louver walls.
10. The corrugated heat exchange element of claim 1, wherein a
plurality of said bends is provided between the first and second
edges of each of the adjacent louvers, wherein each of the bends is
angular and extends along a bend line parallel to the first and
second edges of the louver, wherein each of the bends defines an
obtuse angle.
11. The corrugated heat exchange element of claim 1, wherein an
overall obtuse angle is defined between a first edge portion of the
louver proximate the first edge and a second edge portion of the
louver proximate the second edge.
12. The corrugated heat exchange element of claim 10, wherein two
of said bends are provided between the first and second edges of
each said louver so as to define a first edge portion between the
first edge of the louver and a first one of the bends, a second
edge portion between the second edge of the louver and a second one
of the bends, and a central portion between the bends, and wherein
the first edge and the second edge of each louver project outwardly
from opposite sides of the side wall.
13. The corrugated heat exchange element of claim 12, wherein the
central portions of the louvers are substantially coplanar with the
plane of the side wall.
14. The corrugated heat exchange element of claim 1, wherein said
at least one bend comprises an arcuate bend between the first and
second edges of the louver, wherein an obtuse angle is formed
between two lines which meet along a line bisecting the arcuate
bend into two segments and which are tangential to the segments at
their mid-points.
15. The corrugated heat exchange element of claim 1, wherein an
angle between the plane of the side wall and at least one of the
edges of each louver is from about 20 to 30 degrees.
16. The corrugated heat exchange element of claim 15, wherein the
angle between the plane of the side wall and at least one of the
edges of each louver varies among the louvers of each said
group.
17. The corrugated heat exchange element of claim 16, wherein the
angle between the plane of the side wall and at least one of the
edges of the louvers in each said group is progressively increased
so that the louver edges extend outward to a progressively greater
extent from one end of the group to the other.
18. The corrugated heat exchange element of claim 1, wherein a
spacing between adjacent slits is equidistant.
19. The corrugated heat exchange element of claim 1, wherein a
spacing between adjacent slits is variable.
20. The corrugated heat exchange element of claim 1, wherein each
of the side walls is provided with at least two groups of adjacent
louvers, and wherein adjacent groups of louvers are spaced by a
distance which is greater than a spacing between adjacent slits
within said groups.
21. The corrugated heat exchange element of claim 1, wherein at
least some of the slits and the louvers have upper and lower ends
which are in close proximity to the longitudinal bends between each
side wall and the adjacent top and bottom walls, respectively.
22. The corrugated heat exchange element of claim 1, wherein each
of the top walls of the heat exchange element extends between a
pair of longitudinal bends through which it is joined to adjacent
ones of said side walls, and wherein each of the bottom walls of
the heat exchange element extends between a pair of longitudinal
bends through which it is joined to adjacent ones of said side
walls.
23. The corrugated heat exchange element of claim 22, wherein the
side walls are substantially parallel to one another and
substantially perpendicular to the top and bottom walls, such that
the spaces between adjacent side walls are substantially
rectangular in shape.
24. The corrugated heat exchange element of claim 22, wherein the
side walls are angled relative to one another and wherein the top
and bottom walls are substantially parallel to one another, such
that the spaces between adjacent side walls are substantially
trapezoidal in shape.
25. The corrugated heat exchange element of claim 1, wherein the
top walls of the heat exchange element are substantially coplanar
and the bottom walls of the heat exchange element are substantially
coplanar.
26. The corrugated heat exchange element of claim 1, wherein the
top and bottom walls of the heat exchange element are generally
flat and define top and bottom planes of the heat exchange element,
wherein each of the top and bottom walls has a width defined by a
transverse distance between an adjacent pair of said longitudinal
bends, and wherein each of the longitudinal bends is located in
either the top plane or the bottom plane.
27. The corrugated heat exchange element of claim 26, wherein
protrusions are provided in at least some of the top walls and at
least some of the bottom walls of the heat exchange element.
28. The corrugated heat exchange element of claim 27, wherein the
protrusions in each of the top walls causes a portion of said top
wall to deviate away from the top plane of the heat exchange
element in a direction toward the bottom plane of the heat exchange
element, and wherein the protrusions in each of the bottom walls
causes a portion of said bottom wall to deviate away from the
bottom plane of the heat exchange element in a direction toward the
top plane of the heat exchange element.
29. The corrugated heat exchange element of claim 27, wherein the
protrusions extend continuously along the longitudinal axis.
30. The corrugated heat exchange element of claim 27, wherein the
protrusions are discontinuous along the longitudinal axis.
31. The corrugated heat exchange element of claim 30, wherein the
protrusions comprise ribs extending transversely across the width
of the top and bottom walls.
32. The corrugated heat exchange element of claim 30, wherein at
least some of the ribs have opposite ends which are located in
close proximity to the longitudinal bends.
33. The corrugated heat exchange element of claim 1, wherein the
heat exchange element is formed from a material which is relatively
weakened along said longitudinal bends.
34. The corrugated heat exchange element of claim 1, wherein the
material is weakened by coining or by formation of a series of
perforations located along the longitudinal bends.
35. A plate-type heat exchanger, comprising: a pair of plates
secured together at their margins and spaced from one another
between the margins to form a fluid flow passage, the fluid flow
passage having a height and having an inlet opening and an outlet
opening spaced apart along a plate axis; a corrugated heat exchange
element received inside said fluid flow passage and located between
the inlet and outlet openings, the corrugated heat exchange element
comprising: (a) a plurality of side walls interconnected by a
plurality of top and bottom walls which are in contact with the
plates, wherein each of the side walls defines a plane and extends
parallel to a longitudinal axis, wherein each of the side walls
extends between an adjacent one of the top walls and an adjacent
one of the bottom walls, and wherein longitudinal bends are formed
between each side wall and the adjacent top and bottom walls such
that spaces for flow of a heat exchange fluid are defined between
adjacent ones of said side walls; and (b) at least one group of
adjacent louvers provided in at least some of the side walls,
wherein each group of adjacent louvers is defined by a plurality of
parallel slits extending between the top wall and the bottom wall
of the side wall substantially perpendicular to the axis; wherein
each of the adjacent louvers comprises an area of the side wall
between an adjacent pair of said slits and includes: (i) a first
edge extending along a first slit of the adjacent pair of slits;
(ii) a second edge extending along a second slit of the adjacent
pair of slits; and (iii) at least one bend located between the
first and second edges of the louver which causes at least one of
the edges of the louver to project outwardly of the plane of the
side wall.
36. The heat exchanger of claim 35, wherein the heat exchange
element is oriented in the fluid flow passage with the axis
parallel to the plate axis.
37. The heat exchanger of claim 35, wherein the heat exchange
element is oriented in the fluid flow passage with the axis
transverse to the plate axis.
38. The heat exchanger of claim 35, wherein the top and bottom
walls of the heat exchange element are brazed to the plates.
39. The heat exchanger according to claim 35, wherein the side
walls are under vertical compression between the plates, and
wherein the height of the side walls in their uncompressed state is
slightly greater than the height of the fluid flow passage.
40. A corrugated heat exchange element for a heat exchanger, the
heat exchange element comprising: a plurality of side walls
interconnected by a plurality of top and bottom walls, wherein each
of the side walls defines a plane and extends parallel to a
longitudinal axis, wherein each of the side walls extends between
an adjacent one of the top walls and an adjacent one of the bottom
walls, and wherein longitudinal bends are formed between each side
wall and the adjacent top and bottom walls such that spaces for
flow of a heat exchange fluid are defined between adjacent ones of
said side walls; wherein each of the top walls of the heat exchange
element extends between a pair of longitudinal bends through which
it is joined to adjacent ones of said side walls, and wherein each
of the bottom walls of the heat exchange element extends between a
pair of longitudinal bends through which it is joined to adjacent
ones of said side walls; wherein protrusions are provided in at
least some of the top walls and at least some of the bottom walls
of the heat exchange element; and wherein each of the protrusions
in the top walls cause portions of said top walls to deviate away
from the top plane of the heat exchange element in a direction
toward the bottom plane of the heat exchange element, and wherein
the protrusions in the bottom walls cause portions of said bottom
walls to deviate away from the bottom plane of the heat exchange
element in a direction toward the top plane of the heat exchange
element.
Description
FIELD OF THE INVENTION
[0001] The invention relates to heat exchangers and corrugated heat
exchange elements for use therein, and particularly to corrugated
heat exchanger fins and turbulizers of improved strength and
manufacturability, and to heat exchangers incorporating such fins
and turbulizers.
BACKGROUND OF THE INVENTION
[0002] Heat exchangers are commonly provided with heat exchange
elements such as corrugated fins and/or turbulizers in order to
enhance heat transfer between two or more fluids. Corrugated fins
and turbulizers are structurally similar, and typically comprise a
thin metal sheet in which parallel bends define a series of
corrugations of a generally rectangular or triangular form. A
turbulizer is generally inserted inside a fluid flow passage
defined by the interior of a tube or a plate pair, whereas a fin is
generally mounted on an exterior surface of a tube or plate pair.
The fluids which come into contact with these heat exchange
elements may be on the hot or cold heat transfer side and may
consist of gaseous, liquid or two-phase fluids.
[0003] Corrugated heat exchange elements can take the form of
corrugated turbulizers such as those described in U.S. Pat. No.
4,945,981 (Joshi) issued on Aug. 7, 1990. Joshi describes an
automotive oil cooler comprising a pair of plates defining an oil
passage with a turbulizer inserted therein. The Joshi turbulizer
comprises a metal foil having a plurality of parallel V-shaped
corrugations and is orientated in the oil passage with the
longitudinal direction of the corrugations extending either
parallel or transverse to the direction of oil flow. The top and
bottom surfaces of the corrugations are in heat exchange contact
with the plates of the oil cooler and are preferably brazed to the
plates. The side surface of each corrugation is provided with a
series of louvers which create turbulence in the oil and enhance
heat transfer. Where the corrugations are transverse to the flow
direction, the oil must flow through the louver openings in order
to pass from the inlet to the outlet.
[0004] One disadvantage of the Joshi turbulizer is that the
triangular or V-shaped corrugations make contact with the plates
only along the relatively narrow top and bottom surfaces of the
turbulizer, thereby limiting heat transfer. Furthermore, the
sloping side walls of the Joshi turbulizer result in the formation
of relatively large spaces between adjacent side walls. Where the
corrugations are aligned parallel to the direction of fluid flow,
there is significant duct flow between the side walls, which
results in poor heat transfer.
[0005] Heat exchange elements having rectangular corrugations, with
substantially vertical side walls and flat top and bottom walls,
are preferred over those of Joshi because the relatively constant
spacing between adjacent side walls provides reduced duct flow as
compared to inserts with V-shaped corrugations.
[0006] However, the formation of rectangular corrugations involves
additional bending operations, with the top and bottom wall of each
corrugation being defined by a pair of closely-spaced substantially
90-degree bends. The metal foil used in these inserts is very thin
and therefore it is difficult to form clean bends along the edges
of the top and bottom walls.
[0007] In order to ensure that the top and bottom walls of the
corrugations are in contact with the plates or tubes of the heat
exchanger, these corrugated heat exchange elements are usually
compressed between the plates or tubes during assembly. Due to the
thinness of the foil, the heat exchange elements can be easily
crushed by this compression, resulting in irreparable damage to the
heat exchanger. While the strength of the corrugated heat exchange
element may be improved by the provision of louvers, this
improvement is sometimes insufficient to resist crushing during
assembly. Furthermore, in conventional louvered fins or turbulizers
as taught by Joshi, there is an unsupported area between the ends
of the louvers and the top and bottom walls. This unsupported area
is particularly vulnerable to crushing during assembly of the heat
exchanger.
[0008] There is a need for corrugated heat exchange elements having
improved strength, manufacturability, thermal performance and/or
reduced gauge, and which preferably comprise corrugations with
generally flat top and bottom walls.
SUMMARY OF THE INVENTION
[0009] In one aspect, the present invention provides a corrugated
heat exchange element for a heat exchanger, the heat exchange
element comprising a plurality of side walls interconnected by a
plurality of top and bottom walls, wherein each of the side walls
defines a plane and extends parallel to a longitudinal axis,
wherein each of the side walls extends between an adjacent one of
the top walls and an adjacent one of the bottom walls, and wherein
longitudinal bends are formed between each side wall and the
adjacent top and bottom walls such that spaces for flow of a heat
exchange fluid are defined between adjacent ones of said side
walls; and at least one group of adjacent louvers provided in at
least some of the side walls, wherein each group of adjacent
louvers is defined by a plurality of parallel slits extending
between the top wall and the bottom wall of the side wall
substantially perpendicular to the axis; wherein each of the
adjacent louvers comprises an area of the side wall between an
adjacent pair of said slits and includes: (i) a first edge
extending along a first slit of the adjacent pair of slits; (ii) a
second edge extending along a second slit of the adjacent pair of
slits; and (iii) at least one bend located between the first and
second edges of the louver which causes at least one of the edges
of the louver to project outwardly of the plane of the side
wall.
[0010] In another aspect, the present invention provides a
corrugated heat exchange element for a heat exchanger, the heat
exchange element comprising a plurality of side walls
interconnected by a plurality of top and bottom walls, wherein each
of the side walls defines a plane and extends parallel to a
longitudinal axis, wherein each of the side walls extends between
an adjacent one of the top walls and an adjacent one of the bottom
walls, and wherein longitudinal bends are formed between each side
wall and the adjacent top and bottom walls such that spaces for
flow of a heat exchange fluid are defined between adjacent ones of
said side walls; wherein each of the top walls of the heat exchange
element extends between a pair of longitudinal bends through which
it is joined to adjacent ones of said side walls, and wherein each
of the bottom walls of the heat exchange element extends between a
pair of longitudinal bends through which it is joined to adjacent
ones of said side walls; wherein embossments are provided in at
least some of the top walls and at least some of the bottom walls
of the heat exchange element; and wherein each of the embossments
in the top walls cause portions of said top walls to deviate away
from the top plane of the heat exchange element in a direction
toward the bottom plane of the heat exchange element, and wherein
the embossments in the bottom walls cause portions of said bottom
walls to deviate away from the bottom plane of the heat exchange
element in a direction toward the top plane of the heat exchange
element.
[0011] In yet another aspect, the present invention provides a
plate-type heat exchanger comprising a pair of plates secured
together at their margins and spaced from one another between the
margins to form a fluid flow passage, the fluid flow passage having
a height and having an inlet opening and an outlet opening spaced
apart along a plate axis. A corrugated heat exchange element
according to the invention is received inside said fluid flow
passage and is located between the inlet and outlet openings with
its top and bottom walls in contact with the plates.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] The invention will now be described, by way of example only,
with reference to the accompanying drawings in which:
[0013] FIG. 1 is a perspective view of a preferred corrugated heat
exchange element according to the invention;
[0014] FIG. 2 is a cross section along line 2-2 of FIG. 1;
[0015] FIG. 3 is a cross section along line 3-3 of FIG. 1;
[0016] FIG. 4 is a cross section along line 4-4 of FIG. 1;
[0017] FIG. 5 is a cross section of a corrugated heat exchange
element according to a another preferred embodiment of the
invention;
[0018] FIG. 6 is cross sectional end view of the corrugated heat
exchange element shown in FIG. 5;
[0019] FIG. 7 is a cross section of a portion of a corrugated heat
exchange element according to another preferred embodiment of the
invention;
[0020] FIG. 8 is a cross section of a portion of a corrugated heat
exchange element according to another preferred embodiment of the
invention;
[0021] FIG. 9 is a cross section of a portion of a corrugated heat
exchange element according to another preferred embodiment of the
invention;
[0022] FIGS. 10 to 14 illustrate corrugated heat exchange elements
according to the invention having various types of protrusions in
their top and bottom walls;
[0023] FIG. 15 is a plan view of a flattened section of corrugated
heat exchange element of FIGS. 1 to 4;
[0024] FIG. 16 is a plan view of a flattened section of corrugated
heat exchange element according to another preferred embodiment of
the invention;
[0025] FIG. 17 is a cut-away perspective view of a plate-type heat
exchanger incorporating the corrugated heat exchange element of
FIGS. 1 to 4;
[0026] FIG. 18 is a cross section along line 18-18 of FIG. 17;
[0027] FIG. 19 is cross section through a preferred heat exchange
element according to the invention having trapezoidal
corrugations;
[0028] FIG. 20 is a cross sectional end view through a heat
exchange element with triangular corrugations according to the
invention;
[0029] FIG. 21 is a cross section through the side wall of a heat
exchange element according to another preferred embodiment of the
invention;
[0030] FIG. 22 is a cross section through the side wall of a heat
exchange element according to another preferred embodiment of the
invention; and
[0031] FIG. 23 is a perspective view of a corrugated heat exchange
element according to the invention having protrusions formed in its
top and bottom walls.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
[0032] The following is a detailed description of preferred
corrugated heat exchange elements according to the invention, as
well as preferred heat exchangers in which they are used. As used
herein, the term "corrugated heat exchange element" is intended to
include both corrugated fins and turbulizers which, as mentioned
above, are structurally similar and differ primarily in the way
they are incorporated into heat exchangers.
[0033] A first preferred corrugated heat exchange element 10
according to the invention is now described with reference to FIGS.
1 to 4. Heat exchange element 10 comprises a plurality of
corrugations 11 extending along a longitudinal axis A, the
corrugations 11 being defined by a plurality of spaced-apart side
walls 12 interconnected by a plurality of top and bottom walls 14,
16. Each side wall 12 defines a plane S (FIG. 2) and extends
parallel to axis A. Each of the side walls 12 has a height H and
extends between an adjacent top wall 14 and an adjacent bottom wall
16 of the heat exchange element 10 and is joined to the adjacent
top and bottom walls 14, 16 by longitudinal bends 18 such that
spaces 19 for flow of a heat exchange fluid are defined between
adjacent pairs of side walls 12. Height H is defined as the
distance measured along the side walls 12 between the top and
bottom walls 14, 16. Although terms such as "top", "bottom",
"upper" and "lower" are used herein, it is to be appreciated that
these terms are used for convenience only. The top and bottom of
heat exchange element 10 are preferably indistinguishable from each
other. Furthermore, it is to be appreciated that the drawings
illustrating the preferred embodiments are not necessarily to
scale, and certain features are exaggerated in order to better
explain the invention.
[0034] In the first preferred embodiment described herein, the
corrugations 11 and the spaces 19 between adjacent side walls 12
are substantially rectangular, having substantially flat top and
bottom walls 14, 16 and side walls 12 which are substantially
parallel to one another along their entire height H and with
longitudinal bends 18 having an angle of about 90 degrees.
[0035] The top and bottom walls 14, 16 of heat exchange element 10
are generally flat and parallel to one another and have a width W,
which is defined as a transverse distance between an adjacent pair
of longitudinal bends 18 through which they are joined to adjacent
side walls 12. The top and bottom walls 14,16 define respective top
and bottom planes T and B of the heat exchange element 10, wherein
each of the longitudinal bends 18 is located in either the top
plane T or the bottom plane B. In the first preferred heat exchange
element 10, all the top walls 14 are preferably located in top
plane T and all the bottom walls 16 are preferably located in
bottom plane B. It will, however, be appreciated that this is not
necessarily the case and that the objects of the invention can be
achieved where the height H of the side walls 12 is varied, for
example to conform to an irregularly-shaped fluid flow passage.
[0036] At least some of the side walls 12 of the corrugated heat
exchange element 10 are provided with one or more groups 20 of
closely-spaced louvers 24. In the first preferred embodiment, each
side wall 12 is provided with two groups 20 of louvers 24. Each
group 20 of louvers 24 is defined by a plurality of parallel slits
22 formed in the side wall 12 and extending substantially between
the top and bottom walls 14, 16. In the first preferred embodiment,
the slits 22 are substantially perpendicular to the axis A and are
spaced equidistantly from one another.
[0037] Adjacent groups 20 of louvers 24 may preferably be spaced
apart by a distance which is greater than the spacing between
adjacent slits 22. In the first preferred embodiment, the groups 20
of louvers 24 are separated by a dividing web 46 which is located
in the plane S of the side wall 12. It will, however, be
appreciated that the provision of dividing web 46 between the
groups 20 of louvers 24 is not necessary.
[0038] Each of the adjacent louvers 24 within each group 20
comprises an area of the side wall 12 between an adjacent pair of
slits 22 and includes a first edge 28 extending along one slit 22
and a second edge 30 extending along an adjacent slit 22. Each of
the louvers 24 further comprises at least one bend located between
the first and second edges 28, 30. In the first preferred
embodiment, there is a single, angular bend 26 provided between the
first and second edges 28, 30 of each louver 24. Preferably, the
bend 26 is located approximately midway between the edges 28, 30,
although this is not necessarily the case. The bend 26 extends
along a line which is substantially parallel to the edges 28, 30 of
the louver 24 and extends throughout substantially the entire
height of louver 24. The bend 26 also defines an apex 34 of the
louver 24, the apex 34 being located in the plane S of the side
wall 12. The apex 34 divides the louver 24 into a substantially
flat first louver wall 32 and a substantially flat second louver
wall 38 which meet at the apex 34 and extend from the apex 34 to
the respective first and second edges 28, 30 of louver 24.
[0039] The bend 26 defines an angle .alpha..sup.1 between the first
and second louver walls 32, 38. The provision of bend 26 between
the edges 28, 30 of louvers 24 causes at least one of the edges of
the louver 24 to project outwardly of the plane S of the side wall
12, thereby providing gaps 40 through which the heat exchange fluid
can flow through the side walls 12.
[0040] In the first preferred embodiment, the louvers 24 are of the
"one-sided" type, meaning that only the first edge 28 (and the
first wall 32) of each louver 24 projects outwardly of the plane S
of the side wall 12, while the second edge 30 (and the second wall
38) of the louver 24 is located in plane S. Furthermore, the first
edges 28 of all the louvers 24 within each group 20 project
outwardly from the same side of the side wall 12. In preferred
embodiments where the heat exchange element 10 is orientated such
that the flow of heat exchange fluid is parallel to axis A, i.e.,
the "low pressure drop" orientation, the first louver wall 32 is
preferably at an angle .beta..sup.1 of about 20 to 30 degrees
relative to plane S, with angle .alpha..sup.1 being
180-.beta..sup.1. In the first preferred embodiment, the angles
.alpha..sup.1 and .beta..sup.1 are the same for all the louvers 24,
although this is not necessarily the case. Furthermore, each louver
24 projects outwardly of the side wall 12 by the same amount,
although this is not necessary either.
[0041] As shown in the drawings, the louvers 24 within each group
20 face in the same direction, i.e., each of the slits 22 is
bounded by the first edge 28 of one of the louvers 24 and the
second edge 30 of an adjacent one of the louvers 24. Moreover, the
louvers 24 of the two groups 20 preferably face the same direction,
and preferably project from opposite sides of the side wall 12.
[0042] FIGS. 5 to 8 illustrate corrugated heat exchange elements
according to other preferred embodiments of the invention in which
the louvers are two-sided, i.e., each louver projects outwardly
from both sides of the side wall. Two-sided louvers provide
improved heat transfer because they disrupt fluid flow along both
sides of the side wall and provide better transition of fluid flow
from one side wall to another than one-sided louvers.
[0043] FIGS. 5 and 6 illustrate a second preferred corrugated heat
exchange element 72 according to the invention which incorporates
two-sided louvers 74. Heat exchange element 72 comprises a
plurality of corrugations 76 extending along longitudinal axis A,
the corrugations 76 having generally the same rectangular shape as
the corrugations 11 of heat exchange element 10 described above.
Corrugations 76 are defined by a plurality of spaced-apart side
walls 78 interconnected by a plurality of top and bottom walls 80,
82. Each side wall 78 defines a plane S and is parallel to the axis
A. The side walls 78 and walls 80, 82 are joined by longitudinal
bends 84, each bend 84 defining an angle of about 90 degrees and
being located in a top plane T or a bottom plane B of the heat
exchange element 72.
[0044] FIG. 5 is a cross section through one of the side walls 78,
taken in a plane corresponding to that of FIG. 2, showing that the
louvers 74 are arranged in much the same way as louvers 24 of heat
exchange element 10, i.e., the louvers 74 are arranged as two
groups 86 separated by a dividing web 88. Each group 86 of louvers
74 is defined by a plurality of parallel, equidistantly spaced
slits 90 formed in the side wall 78 and extending between the top
and bottom walls 80, 82.
[0045] Each of the adjacent louvers 74 within each group 86
comprises an area of the side wall 78 between an adjacent pair of
slits 90 and includes a first edge 92 extending along one of the
slits 90 and a second edge 94 extending along an adjacent slit 90.
Each of the louvers 74 further comprises a single, angular bend 96
provided approximately midway between the edges 92, 94, similar to
louvers 24 described above, and extending along a bend line which
is substantially parallel to edges 92, 94. The bend 96 defines an
apex 98 which divides the louver 74 into a substantially flat first
louver wall 100 and a substantially flat second louver wall 102
which meet at the apex 98 and extend to the respective edges 92, 94
of the louver 74. The apex 98 is preferably located in the plane S
of the side wall.
[0046] The bend 96 defines an angle .alpha..sup.2 between the
louver walls 100, 102 and the bend 96 is orientated so that both
edges 92, 94 of louver 74, as well as the respective louver walls
100, 102, are caused to project outwardly from opposite sides of
the side wall 78, with the angles between the louver walls 100, 102
and the side wall 78 or plane S being .beta..sup.2 and
.beta..sup.3. Where angle .alpha..sup.2 is an obtuse angle as shown
in FIG. 5, it is preferably within the range from about 150 degrees
to less than 180 degrees. Angle .alpha..sup.2 may, however, be
greater than 180 degrees and may be as great as about 240 degrees.
Angles .beta..sup.2 and .beta..sup.3 may preferably be the same or
different and are greater than zero, preferably being in the range
from about 20 to 30 degrees as in the embodiment of FIGS. 1 to
4.
[0047] FIGS. 7 to 9 illustrate cross-sectional views through the
side walls of heat exchange elements, corresponding to the
cross-sections of FIGS. 2 and 5, illustrating two-sided louvers
according to other preferred embodiments of the invention. The heat
exchange elements shown in FIGS. 7 to 9 embody substantially the
same principles described above in connection with FIGS. 1 to 6.
Therefore, these embodiments are only briefly described below,
focusing on the differences from the first two embodiments
described above.
[0048] FIG. 7 illustrates a side wall 104 of a corrugated heat
exchange element 106 having a plurality of rectangular corrugations
of generally the same shape as in heat exchange elements 10 and 72
described above. The side wall 104 is provided with two groups 108
of two-sided louvers 110 arranged on either side of a dividing web
112. In this preferred embodiment, each group 108 of louvers 110 is
defined by a plurality of equidistantly spaced slits 114 formed in
the side wall and extending between the top and bottom walls (not
shown) of the heat exchange element 106.
[0049] Each of the adjacent louvers 110 within each group 108
comprises an area of side wall 104 between an adjacent pair of
slits 114 and includes a first edge 116 extending along one of the
slits 114 and a second edge 118 extending along an adjacent slit
114. Each of the adjacent louvers 110 further comprises a plurality
of angular bends, specifically two angular bends 120, 122, provided
between the edges 116, 118 and extending along bend lines which are
substantially parallel to edges 116, 118. The individual bends 120,
122 define obtuse angles .gamma..sup.1 and .gamma..sup.2 and divide
each of the louvers 110 into three segments: a first edge portion
124 between the first edge 116 and bend 120; a second edge portion
126 between the second edge 118 and bend 122; and a central portion
128 between the bends 120, 122. An overall angle .alpha..sup.3 of
louver 110 is defined as the angle between the first and second
edge portions 124, 126 of the louver, and may preferably be the
same as angle .alpha..sup.2 described above. In FIG. 7, the angle
.alpha..sup.3 is an obtuse angle.
[0050] The bends 120, 122 are orientated so that both edges 116,
118 of louver 110 project outwardly from opposite sides of the side
wall 104, with an angles .beta..sup.4 and .beta..sup.5 between
respective edge portions 124, 126 and the side wall 104 preferably
being the same as angles .beta..sup.2 and .beta..sup.3 described
above. Although FIG. 7 illustrates louvers 110 having two angular
bends 120, 122, it will be appreciated that corrugated heat
exchange elements according to the invention may be constructed
with louvers having more than two angular bends.
[0051] FIG. 8 illustrates a side wall 130 of a corrugated heat
exchange element 132 having a plurality of rectangular corrugations
of generally the same shape as in heat exchange elements 10 and 72
described above. The side wall 130 is provided with two groups 134
of two-sided louvers 136 arranged on either side of a dividing web
138. Each group 134 of louvers 136 is defined by a plurality of
equidistantly spaced slits 140 formed in the side wall 130 and
extending between the top and bottom walls (not shown) of the heat
exchange element 132.
[0052] Each of the adjacent louvers 136 within each group 134
comprises an area of side wall 130 between an adjacent pair of
slits 140 and includes a first edge 142 extending along one of the
slits 140 and a second edge 144 extending along an adjacent slit
140. Each of the adjacent louvers 136 further comprises an arcuate
bend 146 located between the first and second edges 142, 144 of the
louver 136. In the specific arrangement shown in FIG. 8, the
louvers 136 are arcuately shaped across their entire width,
although this is not necessarily the case. In the embodiment of
FIG. 8, an angle .alpha..sup.4 is formed between two lines 148, 150
which intersect at a line 152 bisecting the arcuate bend into two
segments 154, 156 and which are tangential to the segments 154, 156
at their midpoints. Angle .alpha..sup.4 may preferably be the same
as angles .alpha..sup.2 and .alpha..sup.3 described above and is
shown in FIG. 8 as being an obtuse angle.
[0053] As shown in FIG. 8, the edges 142, 144 of each louver 136
extend outwardly from opposite sides of the side wall 130, with the
an angle .beta..sup.6 being formed between line 148 and side wall
130 and an angle .beta..sup.7 being formed between line 150 and
side wall 130. The angles .beta..sup.6 and .beta..sup.7 may
preferably be the same as angles .beta..sup.2 to .beta..sup.5
described above.
[0054] FIG. 9 is a cross section through a side wall 196 of a
corrugated heat exchange element 194 having a plurality of
rectangular corrugations of generally the same shape as in heat
exchange elements 10, 72 and 132 described above. The side wall 196
is provided with two groups 198 of two-sided louvers 200 arranged
on either side of a dividing web 202. Each group 198 of louvers 200
is defined by a plurality of equidistantly spaced slits 204 formed
in the side wall 196 and extending between the top and bottom
surfaces (not shown) of heat exchange element 194.
[0055] Each of the adjacent louvers 200 within each group 198
comprises an area of the side wall 196 between an adjacent pair of
slits 204 and includes a first edge 206 extending along one of the
slits and a second edge 208 extending along an adjacent slit 204.
Each of the adjacent louvers 200 further comprises a pair of
angular bends 210, 212 provided between the edges 206, 208 and
extending along bend lines which are substantially parallel to
edges 206, 208. The individual bends 210, 212 define obtuse angles
.gamma..sup.3 and .gamma..sup.4 and divide each of the louvers 200
into three segments; a first edge portion 214 between the first
edge 206 and bend 210; a second edge portion 216 between the second
edge 208 and bend 212; and a central portion 218 between the bends
210, 212. The central portions 218 of louvers 200 are preferably
located in the plane S of side wall 196 and the bends 210, 212 are
oppositely directed so that the first and second edge portions 214,
216 project outwardly from opposite sides of the side wall 196. In
the preferred heat exchange element 194, the obtuse angles
.gamma..sup.3 and .gamma..sup.4 are the same, and may preferably be
the same as obtuse angle .alpha..sup.1 of heat exchange element 10
described above, which results in the first and second edge
portions 214, 216 of louvers 200 being parallel to each other. It
will, however, be appreciated that angles .gamma..sup.3 and
.gamma..sup.4 are not necessarily the same.
[0056] In the heat exchange element 194 of FIG. 9, the edges 206,
208 of each louver project outwardly from opposite sides of the
side wall 196. The first edge portion 214 forms an angle
.beta..sup.8 with side wall 196 and the second edge portion 216
forms an angle .beta..sup.9 with side wall 196. As in the
embodiments described above, the angles .beta..sup.8 and
.beta..sup.9 are preferably in the range from about 20 to 30
degrees. Where the central portions 218 of the louvers 200 are
located in the plane S of side wall 196, the angle
.gamma..sup.3=180-.beta..sup.8 and .gamma..sup.4=180-.beta..sup.9.
It will, however, be appreciated that the central portions 218 of
louvers 200 may preferably be angled relative to the side wall
196.
[0057] Although specific one-sided and two-sided louvers have been
described above in connection with heat exchange elements having
rectangular corrugations, it will be appreciated that louvers
according to the invention could be used in any type of corrugated
heat exchange element regardless of the specific shape of the
corrugations. Some of these alternate shapes are described in
greater detail below. It will also be appreciated that the louvers
according to the invention could be incorporated into a heat
exchange element with generally triangular or V-shaped corrugations
(not shown) as described in the above-mentioned Joshi patent.
[0058] In another preferred aspect of the invention, the top and
bottom walls 14, 16 of at least some of the corrugations 11 are
provided with protrusions, which serve the following two purposes.
Firstly, the protrusions increase the rigidity of the top and
bottom walls 14, 16, thereby reducing the radius of curvature of
the longitudinal bends 18 and enabling the formation of rectangular
convolutions 11. Secondly, the protrusions augment heat transfer in
areas proximate to the top and bottom walls 14, 16.
[0059] In the corrugated heat exchange element 10 shown in FIGS. 1
to 4, the protrusions comprise embossments formed as elongate ribs
54 extending transversely across the width of the top and bottom
walls 14, 16. The ribs 54 are spaced apart along the axis A. The
ribs 54 are all of the same length, although this is not necessary.
It is however preferred that the ends of at least some of the ribs
54 are in close proximity to the longitudinal bends 18, for reasons
which will be discussed below. The ribs 54 in the top wall 14 are
depressed, i.e., they deviate away from the top plane T of the heat
exchange element 10 in a direction toward the bottom plane B of the
heat exchange element 10. On the other hand, the ribs 54 in the
bottom wall 16 are raised, i.e., they deviate away from the bottom
plane B in a direction toward the top plane T. This ensures that
the top and bottom walls 14, 16 will remain substantially flat,
ensuring maximum contact with the plates of the heat exchanger.
[0060] Although the protrusions are shown in FIGS. 1 to 4 as being
in the form of substantially identical ribs 54, it will be
appreciated that the protrusions could be any one of a number of
continuous, discontinuous, regular or irregular shapes without
deviating from the present invention. FIGS. 10 to 14 and 23
illustrate corrugated heat exchange elements according to the
invention having variously shaped protrusions in their top and
bottom walls. In FIGS. 10 to 14, all details of louvers in the side
walls are omitted for convenience and similar reference numerals
are used to refer to similar elements.
[0061] FIG. 10 illustrates a heat exchange element 158 having
rectangular corrugations comprising side walls 160, top walls 162
and bottom walls 164 connected by longitudinal bends 165 forming
angles of about 90 degrees. The top and bottom walls 162, 164 of
heat exchange element 158 are each embossed with an elongate
V-shaped rib 166 extending parallel to the axis and preferably
extending continuously along the entire length of the top and
bottom walls 162, 164.
[0062] FIG. 11 illustrates a heat exchange element 168 embossed
with an irregularly-shaped, longitudinal continuous rib 170 having
portions which extend relatively close to the longitudinal bends
165 at the edges of the top and bottom walls 162, 164.
[0063] FIG. 12 illustrates a heat exchange element 172 in which the
top and bottom walls 162, 164 are embossed with generally circular
dimples 174 of substantially constant diameter which are spaced
apart along the longitudinal axis of the heat exchange element 172.
The dimples 174 are relatively large, extending proximate to the
longitudinal bends 165 at the edges of the top and bottom walls
162, 164.
[0064] FIG. 13 illustrates a heat exchange element 176 in which the
top and bottom walls 162, 164 are embossed with relatively large
circular dimples 174 separated by smaller generally circular
dimples 178.
[0065] FIG. 14 illustrates a heat exchange element 182 in which the
protrusions in the top and bottom walls 162, 164 are in the form of
pierced holes 184 in which the material 186 displaced from the
holes 184 protrudes from the top and bottom walls 162, 164.
[0066] FIG. 23 illustrates a heat exchange element 250 comprised of
a series of generally V-shaped corrugations 252 comprised of angled
side walls 254 joined by curved top and bottom surfaces 256, 258.
Each of the side walls 254 is provided with a plurality of louvers
260 arranged in two groups 262 separated by a dividing web 264. The
top and bottom surfaces 256, 258 are provided with protrusions
which are in the form of hemispheric depressions 266 having a width
substantially the same as the width of the top and bottom surfaces
256, 258. In the preferred embodiment shown in the drawings, the
depressions 266 of adjacent corrugations 252 are aligned with each
other and with the dividing webs 264. The depressions 266 function
to re-direct fluid flow away from the top and bottom surfaces 256,
258 and into contact with the louvers 260, thereby minimizing duct
flow and improving heat transfer. It will be appreciated that the
depressions 266 can be of any desired shape, and are not
necessarily hemispherical.
[0067] FIG. 15 is a plan view of heat exchange element 10 of FIGS.
1 to 4, which has been flattened to better illustrate some
preferred features of the invention. As shown, the ribs 54 are
formed in the top and bottom walls 14, 16 of heat exchange element
10 and the louvers 24 are formed in the side walls 12. The
longitudinal bends 18 of heat exchange element 10 are formed
between the side walls 12 and the adjacent top and bottom walls 14,
16 along dotted lines 52.
[0068] As mentioned above, it is preferred that the bends 18 have a
small radius so that the corrugations of heat exchange element 10
will be as close as possible to an ideal rectangular shape. In
order to minimize the radius of bends 18, it is preferred that the
ends of at least some of the louvers 24 and the ends of at least
some of the ribs 54 extend as close as possible to the dotted lines
52 along which the bends 18 are formed, thereby causing the
formation of narrow areas of relatively low rigidity (low moment of
inertia) along dotted lines 52.
[0069] In heat exchange element 10, the ends of all the louvers 24
and the ends of all the ribs 54 extend close to the dotted lines
52. However, as shown in FIG. 16, this is not necessary. FIG. 16 is
a plan view of a flattened heat exchange element 188 which is
similar to heat exchange element 10 in that it comprises side walls
12, top and bottom walls 14, 16 and longitudinal bends 18 formed
along dotted lines. The heat exchange element 188 also includes a
plurality of louvers 24 and ribs 54 having ends which extend close
to the longitudinal bends 18, thereby creating narrow areas of low
rigidity along dotted lines 52. Heat exchange element 188 also
includes a plurality of ribs 190 which are shorter than ribs 54 and
a plurality of louvers 192 which are shorter than louvers 24. The
relative numbers and spacing of the louvers 24, 192 and ribs 54,
190 can be varied from that shown in FIG. 16, so long as the number
of full length louvers 24 and full length ribs 54 is sufficient to
form the areas of low rigidity along dotted lines 52.
[0070] The relative difference in rigidity between the bends 18 and
the surrounding areas containing ribs 54 and louvers 24 may be
further enhanced by weakening the foil 48 along lines 52. This can
be accomplished for example by providing a series of small
perforations (not shown) along line 52. It will be appreciated that
this feature of the present invention is not restricted to use in
louvered heat exchange elements such as heat exchange element 10,
but can be used in any heat exchange element having rectangular
corrugations.
[0071] FIGS. 17 and 18 describe a plate-type heat exchanger 56 in
which heat exchange element 10 functions as a turbulizer. Heat
exchanger 56 may, for example, comprise an engine oil cooler for
automotive applications. It will, however, be appreciated that
preferred heat exchange elements according to the invention may be
incorporated into any type of heat exchanger which incorporates a
fin or turbulizer, including concentric tube heat exchangers,
without departing from the scope of the present invention.
[0072] Heat exchanger 56 comprises a pair of plates 58, 60 secured
together at their margins 62, 64 and spaced from one another to
form a fluid flow passage 66. The fluid flow passage has a height
which is defined by the vertical spacing between the plates 58, 60
and also has fluid inlet and outlet openings 68, 70 which are
spaced apart along a plate axis P. Although heat exchanger 56 is
shown as comprising only two plates 58, 60, it will be appreciated
that heat exchanger 56 may also include one or more additional
plate pairs and may have alternating fluid flow passages for heat
transfer between two or more fluids.
[0073] As shown in FIGS. 17 and 18, the corrugated heat exchange
element 10 is received inside the fluid flow passage 66 and is
located between the inlet and outlet openings 68, 70 so that fluid
flowing between openings 68, 70 will be forced to pass through the
heat exchange element 10. Preferably, as shown in FIG. 15, the
edges of heat exchange element 10 are in contact with or in close
proximity to the margins 62, 64 of plates 58, 60 to prevent
substantial amounts of fluid from bypassing heat exchange element
10.
[0074] Each of the side walls 12 has a vertical height which is
substantially equal to the height of the fluid flow passage so as
to produce intimate contact between the top and bottom walls 14, 16
of heat exchange element 10 and the plates 58, 60. Where the heat
exchange element and the plates 58 and 60 are formed from a
brazeable metal such as aluminum, this contact permits the
formation of a good braze joint between the heat exchange element
10 and plates 58, 60, thereby providing good heat transfer. In
order to provide good contact, the side walls 12 of heat exchange
element 10 are preferably provided with a height slightly greater
than that of the fluid flow passage 66. Thus, when plates 58 and 60
are brought together during assembly of heat exchanger 56, the side
walls 12 are vertically compressed and the top and bottom walls 14,
16 of heat exchange element 10 are pressed against the plates 58,
60. As mentioned above, the vertical reinforcement provided by
louvers 24 permits the heat exchange element 10 to resist
deformation during compression, thereby ensuring intimate heat
exchange contact between the rib 10 and the plates 58, 60. It will
be appreciated that the improved resistance to deformation provided
by the present invention would permit a reduction in the thickness
(gauge) of the foil from which heat exchange element 10 is formed,
thereby resulting in material savings.
[0075] As mentioned above, the plates 58, 60 and heat exchange
element 10 may preferably be formed of a brazeable metal such as
aluminum. More preferably, the plates 58, 60 and/or the heat
exchange element 10 may be clad with an aluminum brazing alloy
which forms a filler metal when heated to a sufficiently high
temperature. The filler metal flows into the gaps between the top
and bottom walls 14, 16 of heat exchange element 10 and the plates
58, 60, thereby joining the heat exchange element 10 to the plates
58, 60.
[0076] In the preferred embodiment shown in the drawings, the heat
exchange element 10 is orientated in the "low pressure drop"
orientation in the flow passage 66, i.e., with the axis A parallel
to the plate axis P. In this orientation, the fluid flowing through
the flow passage 66 flows between and along the side walls 12, with
the louvers 24 and the embossments (ribs 54) causing flow mixing of
the louver-aligned flow and the duct flow.
[0077] In other preferred embodiments, the heat exchange element 10
may be oriented in the "high pressure drop" orientation, i.e., with
the axis A being transverse to the plate axis P, as shown in FIGS.
3 and 4 of Joshi. In this orientation, the fluid flowing through
the flow passage 66 must flow through the louver openings in order
to pass from the inlet opening 68 to the outlet opening 70. In this
orientation, the angle between the louver wall 32 and the axis A
may be increased so as not to unduly restrict flow through the
passage 66. With the heat exchange element 10 in the high pressure
drop orientation and the overall direction of fluid flow being
transverse to the axis A, it will be appreciated that the
protrusions in the top and bottom walls 14, 16 do not significantly
improve heat transfer.
[0078] Another preferred aspect of the present invention is now
described below with reference to FIGS. 3 and 19. As shown in the
view of FIG. 3, the rectangular corrugations 11 of heat exchange
element 10 provide mixing of louver-aligned and duct flow along and
between the side walls 12, due to the presence of louvers 24, and
also along the top and bottom walls 14, 16, due to the presence of
the protrusions (i.e., ribs 54). There is, however, an area 180
indicated by hatching in FIG. 3 in which there is significant duct
flow. The presence of duct flow 180 has the effect or reducing heat
transfer.
[0079] FIG. 19 illustrates a heat exchange element 10' which is
comprised of identical elements as heat exchange element 10, and
therefore corresponding numbering is used to identify corresponding
elements. The only difference between heat exchange elements 10 and
10' is that the corrugations 11' of heat exchange element 10' are
trapezoidal rather than rectangular. In other words, the heat
exchange element 10' has been compressed in a direction transverse
to axis A so as to reduce the width of the spacing between adjacent
top walls 14 and between adjacent bottom walls 16. This has the
effect of improving flow mixing, thereby reducing the amount of
duct flow and improving heat transfer.
[0080] Although the preferred embodiments of the invention have
been described with reference to heat exchange elements having
rectangular corrugations, it will be appreciated that at least some
of the features of the present invention can be applied to heat
exchange elements having corrugations of other shapes, such as
generally triangular or V-shaped corrugations. FIG. 20 illustrates
such a heat exchange element 220 having V-shaped corrugations 222
comprised of angled side walls 224 joined by bends 226. The heat
exchange element 220 is provided with two-sided louvers 228 which
are preferably similar or identical in form to the louvers
described above with reference to FIGS. 5 to 9. The ends of louvers
228 extend in close proximity to the bends 226, thereby creating
narrow areas of weakness at the bends 226. By extending close to
the bends 226, the louvers 228 provide support for the side walls
224 throughout substantially their entire height, thereby
preventing crushing of the heat exchange element 220 during
assembly of the heat exchanger, as discussed above.
[0081] Further preferred aspects of the invention are shown in
FIGS. 21 and 22. FIG. 21 illustrates the side wall 230 of a heat
exchange element 232, the side wall 230 having two-sided louvers
234 of generally the same shape as the louvers in FIG. 9. Obtuse
angles .gamma..sup.5.sub., .gamma..sup.6 and .gamma..sup.7 are
formed between the edge portions and the central portions of
louvers 234. As seen, these obtuse angles increase in magnitude
from left to right, causing the edge portions of louvers 234 to
project outwardly from side wall 230 by a greater amount from left
to right. The edges of louvers 234 define inclined lines 236, 238
which diverge away from the side wall 230 from left to right. Thus,
the embodiment shown in FIG. 21 illustrates how varying the angles
of the louver walls can alter the amount by which the louvers
project from the side wall.
[0082] FIG. 22 illustrates how the same effect can be achieved by
varying the spacing of the slits, thereby varying the widths of the
edge portions of the louvers. FIG. 22 illustrates the side wall 240
of a heat exchange element 242, the side wall 240 having two-sided
louvers 244 of generally the same shape as the louvers in FIGS. 9
and 21. Obtuse angles .gamma..sup.8 are formed between the edge
portions and the central portions of louvers 234, and these angles
are kept constant in this embodiment. As seen, the width of the
edge portions of the louvers 244 increases from left to right,
causing the edge portions of louvers 244 to project outwardly from
side wall 240 by a greater amount from left to right. The edges of
louvers 244 define inclined lines 246, 248 which diverge away from
the side wall 240 from left to right. It will be appreciated that
gradually increasing the amount by which the louvers project from
the side wall, as in FIGS. 21 and 22, can improve flow mixing with
reduced pressure drop.
[0083] Although the invention has been described with reference to
certain preferred embodiments, it is not intended to be restricted
thereto. Rather, the invention includes within its scope all
embodiments which may fall within the scope of the following
claims.
* * * * *