Note: Descriptions are shown in the official language in which they were submitted.
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HEAT EXCHANGERS WITH TURBULIZERS HAVING CONVOLUTIONS OF
VARIED HEIGHT
Field of the Invention
The invention relates to heat exchangers and conductive inserts for use
therein,
and particularly to plate-type heat exchangers incorporating turbulizers
having
convolutions of varying height.
Background of the Invention
Plate-type heat exchangers comprise at least one pair of spaced-apart plates
sealed together at their margins. Each plate pair defines a fluid flow passage
having an inlet opening and an outlet opening. In a typical heat exchanger,
the
edges of the fluid flow passage have a height which is less than the height at
the center of the fluid flow passage. The reduction in height adjacent the
edges
may be due to the manner in which the plates are joined together and/or the
edges of the plates may be somewhat rounded as in U.S. Patent No. 5,636,685
to Gawve et al.
The fluid flow passage may contain a conductive insert to enhance heat
transfer
and to increase turbulence in the fluid flowing through the flow passage.
These
conductive inserts, which are also known as turbulizers, usually comprise
strips
of metal in which a plurality of convolutions are formed by stamping and/or
rolling. The convolutions are usually of a uniform height and are preferably
in
contact with both plates of the plate pair to maximize heat transfer. Numerous
types of turbulizers are known in the prior art. One type of turbulizer which
may be used in vehicular oil coolers is the louvered fin described in U.S.
Patent
No. 4,945,981 (Joshi) issued on August 7, 1990. Another type of turbulizer for
use in vehicular heat exchangers is the offset strip fin, examples of which
are
described in U.S. Patent No. Re. 35,890 (So) and U.S. Patent No. 6,273,183 (So
et al.).
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As illustrated in Figures 1 to 3 of Gawve et al., a turbulizer of constant
height
cannot fill the entire area of a fluid flow passage which is reduced in height
adjacent its edges, while maintaining effective contact with the plates. This
causes the formation of a fluid bypass B (Figure 3 of Gawve et al.) adjacent
the
edges of the fluid flow passage, which lowers the efficiency of heat transfer.
This problem is partially solved in Gawve et al. by indenting the fin walls to
reduce their height adjacent their ends, thereby reducing the bypass area B'
as
shown in Figure 7.
While the Gawve et al. patent addresses the problem of bypass flow, it is
specific to corrugated fins extending transverse to the direction of fluid
flow and
having fin walls which extend across the entire width of the turbulizer. There
remains a need to address the problem of bypass flow in heat exchangers using
other types of turbulizers, such as the offset strip fins mentioned above.
Summary of the Invention
In one aspect, the invention comprises a heat exchanger comprising: (a) at
least one pair of plates which are joined together to define a hollow fluid
flow
passage between the plates, wherein the flow passage has a height and a width
and extends along a fluid flow axis, wherein the height of the flow passage
varies across its width, wherein the flow passage comprises at least one full-
height area in which the height of the flow passage is at a maximum and at
least one reduced-height area in which the height of the flow passage is less
than the maximum height of the flow passage, and wherein the full-height and
reduced-height areas are located adjacent to one another; (b) a turbulizer
received inside the fluid flow passage, wherein the turbulizer comprises a
plurality of convolutions arranged in at least one row, wherein the
convolutions
of each said row comprise a series of crests and troughs interconnected by
side
walls, and wherein the rows extend transverse to the fluid flow axis and the
side
walls extend along the fluid flow axis; wherein each of the rows includes
convolutions of different heights, including at least one full-height
convolution
positioned in the full-height area of the fluid flow passage and having a
height
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substantially the same as the maximum height of the flow passage, and
including at least one reduced-height convolution positioned in the reduced-
height area of the fluid flow passage and having a height which is less than
the
maximum height of the flow passage.
In another aspect, the invention comprises a heat exchanger comprising: (a) at
least one pair of plates which are joined together to define a hollow fluid
flow
passage between the plates, wherein the flow passage has a height and a width
and extends along a fluid flow axis, wherein the height of the flow passage
varies across its width, wherein the flow passage comprises at least one full-
height area in which the height of the flow passage is at a maximum and at
least one reduced-height area in which the height of the flow passage is less
than the maximum height of the flow passage, and wherein the full-height and
reduced-height areas are located adjacent to one another; (b) a turbulizer
received inside the fluid flow passage, wherein the turbulizer comprises a
plurality of rows of convolutions, wherein adjacent ones of said rows are
connected in side-by-side parallel relation to one another, wherein the
convolutions of each said row comprise a series of crests and troughs
interconnected by side walls, and wherein the rows extend parallel to the
fluid
flow axis and the side walls extend transverse to the fluid flow axis; wherein
at
least two adjacent rows are comprised of convolutions of different heights,
including at least one row of full-height convolutions positioned in the full-
height
area of the fluid flow passage and having a height substantially the same as
the
maximum height of the flow passage, and including at least one row of reduced-
height convolutions positioned in the reduced-height area of the fluid flow
passage and having a height which is less than the maximum height of the flow
passage.
In yet another aspect, the present invention provides a heat exchanger
comprising: (a) at least one heat exchange tube defining a hollow fluid flow
passage, wherein the flow passage has a height and a width and extends
longitudinally along a fluid flow axis, wherein the height of the flow passage
varies across its width, wherein the flow passage comprises at least one full-
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height area in which the height of the flow passage is at a maximum and at
least one reduced-height area in which the height of the flow passage is less
than the maximum height of the flow passage, and wherein the full-height and
reduced-height areas are located adjacent to one another; (b) a turbulizer
received inside the fluid flow passage; wherein each said heat exchange tube
comprises an elongate upper plate and an elongate lower plate in sealed
engagement with one another; wherein the upper plate comprises a
longitudinally extending central portion and a pair of longitudinally
extending
edge portions provided along either side of the central portion, the central
portion being raised relative to the edge portions; wherein the lower plate
comprises a longitudinally extending central portion located opposite the
upper
plate; a pair of longitudinally extending edge portions extending from the
central portion of the lower plate in a direction toward the upper plate,
wherein
the edge portions of the lower plate each have a proximal edge joined to the
central portion of the lower plate and a distal edge proximate to one of the
edge
portions of the upper plate; and a pair of locking tabs, each of which extends
from the distal edge of one of the lower plate end portions; wherein the
locking
tabs of the lower plate are folded into engagement over the edge portions of
the
upper plate and the plates are sealed together along areas of contact between
the locking tabs and the edge portions of the upper plate.
In yet another aspect, the present invention provides a heat exchanger
comprising: (a) at least one heat exchange tube defining a hollow fluid flow
passage and having a top wall, a bottom wall and a pair of side walls, wherein
the flow passage has a height and a width and extends longitudinally along a
fluid flow axis, wherein the height of the flow passage varies across its
width,
wherein the flow passage comprises at least one full-height area in which the
height of the flow passage is at a maximum and at least one reduced-height
area in which the height of the flow passage is less than the maximum height
of
the flow passage, and wherein the full-height and reduced-height areas are
located adjacent to one another; (b) a turbulizer received inside the fluid
flow
passage; wherein each said heat exchange tube comprises a pair of generally U-
shaped sections, each having a bight portion and a pair of legs extending from
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the bight portion, wherein the bight portions form the side walls of the tube
and
the legs form the top and bottom walls of the tube; wherein the legs of each U-
shaped section have free end portions, each of the end portions of a first one
of
the U-shaped sections being in sealed engagement with one of the end portions
of a second one of the U-shaped sections, such that the top and bottom walls
of
the tube are each formed by one of the legs of the first U-shaped section and
one of the legs of the second U-shaped section.
Brief Description of the Drawings
Preferred embodiments of the invention will now be described, by way of
example only, with reference to the accompanying drawings in which:
Figure 1 is a cross-sectional perspective view of a plate pair provided with a
prior art turbulizer;
Figure 2 is a perspective view of a portion of the turbulizer shown in Figure
1;
Figure 3 is a front view of the turbulizer of Figure 1, showing the relative
orientations of overlapping convolutions in two adjacent rows;
Figure 4 is a cross-sectional perspective view of a plate pair provided with a
turbulizer according to a preferred embodiment of the invention;
Figure 4A is a cross-sectional perspective view of a modified version of the
plate
pair ofFigure4;
Figure 5 is a perspective view of a portion of the turbulizer shown in Figure
4;
Figure 6 is a front view of the turbulizer of Figure 5, showing the relative
orientations of overlapping convolutions in two adjacent rows;
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Figure 7 is a front view of a first variant of the turbulizer of Figures 5 and
6,
showing the relative orientations of overlapping convolutions in two adjacent
rows;
Figure 8 is a front view of a second variant of the turbulizer of Figures 5
and 6,
showing the relative orientations of overlapping convolutions in two adjacent
rows;
Figure 9 is a cross-sectional perspective view of a plate pair provided with a
turbulizer according to another preferred embodiment of the invention;
Figure 10 is a front view of the turbulizer of Figure 9, showing the relative
orientations of overlapping convolutions in two adjacent rows;
Figure 11 is a perspective view of a portion of a turbulizer according to
another
preferred embodiment of the invention;
Figure 12 is a cross sectional side view of one row of the turbulizer of
Figure 11,
taken along line 12-12 of Figure 11;
Figure 13 is a cross sectional side view of one row of the turbulizer of
Figure 11,
taken along line 13-13 of Figure 11;
Figure 14 is a cross sectional end view through a first plate pair including
the
turbulizer strip of Figures 11 to 13;
Figure 15 is a cross sectional end view through a second plate pair including
the
turbulizer strip of Figures 11 to 13;
Figure 16 is a cross sectional end view through a third plate pair including
the
turbulizer strip of Figures 11 to 13; and
Figure 17 is a perspective view of a portion of a turbulizer strip according
to
another preferred embodiment of the invention.
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Detailed Description of Preferred Embodiments
The following is a description of a number of preferred heat exchangers, plate
pairs and turbulizer strips according to the invention. Each heat exchanger
described below comprises a pair of plates defining a fluid flow passage. The
heat exchangers according to the invention may comprise a single pair of
plates, for example as in the oil coolers described by Joshi and Gawve et al.
Alternatively, the heat exchangers according to the invention may comprise a
plurality of plate pairs extending between a pair of manifolds, such as the
type
described in the So et al. patent. In the heat exchangers according to the
invention, a turbulizer is provided in the fluid flow passage. Unless
otherwise
stated below, the turbulizers used in the heat exchangers according to the
invention may be simple corrugated fins as in the Joshi and Gawve et al.
patents or may comprise offset strip fins as described in the So and So et al.
patents mentioned above. Preferably, the turbulizers comprise offset strip
fins.
Throughout the following description and claims, terms such as "top",
"bottom",
"upper" and "lower" are used to refer to the specific orientation of the plate
pairs and turbulizers. It will be appreciated that these terms are used for
convenience only. The tops and bottoms of the turbulizers are preferably
indistinguishable from each other and the plate pairs do not necessarily have
the orientation shown in the drawings when in use.
Problems associated with the prior art are now discussed below with reference
to Figure 1, showing a portion of a plate pair 61 of a heat exchanger provided
with a prior art turbulizer 33 having convolutions of constant height, and
with
reference to Figures 2 and 3 which show the prior art turbulizer 33 in
isolation.
The plate pair 61 is comprised of an upper plate 62 and a lower plate 63, with
a
turbulizer 33 located therebetween. Plates 62, 63 are arranged back-to-back
and have joined peripheral flanges 64, 65. Plates 62, 63 also have raised
central portions 66, 67 which define a flow passage 68 therebetween in which
the turbulizer 33 is located.
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It will be seen that the plates 62, 63 making up plate pair 61 are rounded
adjacent to the peripheral flanges 64, 65 and therefore the flow passage 68 is
reduced in height along its edges 69, 71.
The turbulizer 33 shown in Figures 1 to 3 is an offset strip fin similar to
that
shown in above-mentioned patent'890 to So. Turbulizer 33 is a planar member
comprising a plurality of rectangular shaped convolutions 35 disposed in
transverse rows shown at 47, 49, 51, 53 and 55. The rows are joined to one
another through connecting portions 43. A complete turbulizer 33 would include
a number of additional rows of convolutions. The convolutions 35 comprise a
top surface portion 36, a bottom surface portion 37 (portions 36 and 37 are
also
referred to herein as "crests"), and side portions 38 which interconnect the
top
and bottom surface portions 36, 37. Convolutions 35 define apertures or flow
passageways 39 opening in a direction transverse to the direction of rows 47,
49, 51, 53, 55. When a fluid such as oil flows through the flow passage 68
defined by plate pair 61, it will periodically encounter leading edges 41
associated with convolutions 35.
All the convolutions 35 of turbulizer 33 are of the same height H and the same
width W (Fig. 3), the width being defined as the width of the top and bottom
portions 36, 37 of corrugations 35. In order to maximize heat transfer, the
top
and bottom portions 36, 37 of corrugations 35 are preferably in contact with
the
central portions 66, 67 of the upper and lower plates 62, 63. The turbulizer
33
is arranged in the "low pressure drop" or "LPD" orientation, meaning that
fluid
flows through the openings defined by the convolutions, in a direction
transverse to the rows. In this orientation, the fluid passing through the
flow
passage 68 encounters relatively little resistance to flow and therefore the
pressure drop is relatively low.
As shown in Figure 1, the turbulizer 33 is of a constant height which is
substantially the same as the height of the flow passage 68 between the
central
portions 66, 67 of plates 62, 63. It is not possible to extend the turbulizer
33 to
the edges 69, 71 of the flow passage 68 because the edges 69, 71 are reduced
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in height. Therefore the turbulizer 33 will not fit within these areas, at
least not
without being crushed. This causes the formation of bypass areas 40, 42 which
are coincident with the edges 69, 71 of the flow passage 32. The resistance to
fluid flow is at a minimum in these bypass areas 40, 42. Therefore, fluid
preferentially flows through these areas and the efficiency of heat transfer
is
reduced.
Figure 4 illustrates a portion of a plate pair 44 for use in a heat exchanger
according to a first preferred embodiment of the invention, and Figures 5 to 8
illustrate preferred turbulizers according to the invention. Plate pair 44
comprises an elongate upper plate 12 and an elongate lower plate 14. The
upper plate 12 has a central portion 16 extending along longitudinal axis L
and
edge portions 18 and 20 extending longitudinally along either side of the
central
portion 16. The central portion 16 is raised relative to the edge portions 18
and
20, for reasons which will be discussed below.
The lower plate 14 comprises a longitudinal central portion 22 and comprises
longitudinal edge portions 24 and 26 projecting at an approximately right
angle
from central portion 22, thereby forming side walls of the plate pair 44. The
edge portions 24 and 26 are provided with locking tabs 28 and 30 which are
bent down into locking engagement over the edge portions 18 and 20 of the
upper plate 12. The tabs 28 and 30 mechanically lock the plates 12 and 14
together (as better shown in Figure 4A) and provide surfaces along which a
sealed connection can be made with the edge portions 18 and 20 of the upper
plate. A sealed connection may preferably be provided by brazing the upper
and lower plates 12 and 14 together so that a fillet of braze filler metal
(not
shown) is formed between the locking tabs 28 and 30 of lower plate 14 and the
edge portions 18 and 20 of upper plate 12.
As shown in Figure 4, the central portion 16 of upper plate 12 is raised
relative
to the edge portions 18 and 20 so that the locking tabs 28 and 30 of lower
plate
14 are approximately coplanar with the central portion 16 of upper plate 12.
This provides the plate pair 44 with a substantially flat upper surface which
is
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free of projections. This is advantageous, for example where the ends of the
plate pair 44 must fit into a rectangular slot of a header plate (not shown).
Since the edge portions 18 and 20 are recessed relative to the central portion
16, the fluid flow passage 32 formed by the plate pair 44 is relatively higher
in
the middle than at its edges.
Figure 4A illustrates a plate pair 44' which is a modified version of plate
pair 44
described above. Plate pair 44' includes an upper plate 12' having a central
portion 16' extending along longitudinal axis L and edge portions 18' and 20'
extending longitudinally along either side of the central portion 16'. The
central
portion 16' is raised relative to the edge portions 18' and 20'. The edge
portions 18' and 20' are provided with downward extensions 17, 19 extending
at an approximately right angle from the edge portions 18', 20' and preferably
extending longitudinally along the entire length of upper plate 12'.
Plate pair 44' also includes a lower plate 14 which is identical to that of
plate
pair 44, having a central portion 22 and edge portions 24, 26 projecting at an
approximately right angle from central portion 22, thereby forming side walls
of
the plate pair 44'. The edge portions 24, 26 are provided with locking tabs
28,
30 which, as shown in dotted lines in Figure 4A, are initially upstanding and
coplanar with the edge portions 24, 26, but which are bent downwardly in the
direction of the curved arrows into engagement with the edge portions 18', 20'
of the upper plate 12'. As shown in Figure 4A, the downward extensions 17, 19
are of sufficient height such that their lower free ends (distal to the edge
portions 18', 20') make contact with the central portion 22 of the lower plate
14
and are nested in parallel relation with the edge portions 24, 26 of the lower
plate 14. The downward extensions 17, 19 provide the plate pair 44' with a
double edge wall thickness for increased strength; provide increased surface
area for braze joints; facilitate assembly by permitting the turbulizer to be
inserted into one of the plates prior to assembly of the plate pair; and
provide
support for the edge portions 24, 26 of the lower plate 14 during the
forming/locking operation.
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The plate pairs 44 and 44' of Figures 4 and 4A each define a fluid flow
passage
46, 46A in which a turbulizer 48 is provided. The turbulizer 48 is described
below in relation to Figure 4 only. The turbulizer 48 comprises an offset
strip fin
similar to the strip fin 33 described above, having a plurality of rectangular
shaped convolutions 50 disposed in a plurality of transverse rows shown at 75,
77, 79, 81, 83, 85, 87 and 89 (Figure 5). The rows are joined together through
connecting portions 91. It will be appreciated that a complete turbulizer 48
would also include a number of additional rows of convolutions 50.
The convolutions 50 comprise flat top surface portions 52, flat bottom surface
portions 54 and vertical side portions 56 which interconnect the top and
bottom
surface portions 52, 54. Convolutions 50 define apertures or flow passageways
93 opening in a direction transverse to the direction of the rows. When a
fluid
such as oil flows through the flow passage 46 defined by plate pair 44, it
will
periodically encounter leading edges 95 associated with convolutions 50.
The turbulizer 48 includes convolutions 50 of varying height. More
specifically,
each row includes a first plurality of convolutions 50 of width W and height
H,
wherein height H is substantially the same as the height of the flow passage
46
between the central portion 16 of upper plate 12 and the central portion 22 of
lower plate 14. The convolutions of height H are located inward of the ends of
the rows, such that the top and bottom surface portions 52, 54 of convolutions
50 make contact with the central portions 16 and 22 of the upper and lower
plates 12 and 14.
Located at either end of each row is at least one convolution 50, labelled as
50A, having width WA and height HA, wherein width WA is the same as width W
and height HA is less than height H. Furthermore, height HA is substantially
the
same as the height of the flow passage 46 between the edge portions 18 and 20
of the upper plate 12 and the central portion 22 of lower plate 14. These
convolutions 50A are comprised of top surface portions 52A, bottom surface
portions 54A and side portions 56A. In the preferred embodiment shown in
Figures 4 to 6, the side portions 56A are shorter than side portions 56 of
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convolutions 50, while the top and bottom surface portions 52A, 54A are the
same width as top and bottom surface portions 52, 54 of convolutions 50. In
addition, the bottom surface portions 54 and 54A are coplanar while the top
surface portions 52A are reduced in height relative to top surface portions 52
in
order to conform to the shape of the flow passage 46. Therefore, as shown in
Figure 4, the convolutions 50A occupy the areas referred to as bypass areas 40
and 42 of Figure 1, with the top surface portions 52A of convolutions 50A in
contact with the edge portions 18, 20 of upper plate 12, and with the bottom
surface portions in contact with the lower plate 14.
The turbulizer 48 shown in Figures 4 to 6 shows only one reduced-height
convolution 50A at the end of each row. However, it will be appreciated that
more than one reduced-height convolution 50A may be provided at one or both
ends of each row, depending on the configuration of the flow passage and the
width of the convolutions 50. It will also be appreciated the reduced-height
convolutions 50A may preferably be provided only at one end of turbulizer 48,
depending on the configuration of the flow passage 46. It will also be
appreciated that the reduced height convolutions at one end of the rows may
differ in height and/or width relative to the reduced height convolutions at
the
other end of the rows.
Figures 7 and 8 illustrate two variants of the turbulizer shown in Figures 4
to 6,
designed to fit flow passages of varying configuration, and like elements of
these turbulizers are identified by like reference numerals. Figure 7
illustrates
two rows 75, 77 of a turbulizer 58. Each row comprises a plurality of
centrally-
located convolutions 50 having height H and width W. Located at either end of
each row 75, 77 is at least one convolution 50B having width WB which is the
same as width W and height HB which is less than height H. The convolutions
50B have side portions 56B which are shorter than side portions 56 of
convolutions 50, and top and bottom surface portions 52B, 54B having the
same width as top and bottom surface portions 52, 54 of convolutions 50. In
addition, the top surface portions 52 and 52B are coplanar while the bottom
surface portions 54B are elevated relative to top surface portions 54.
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Figure 8 illustrates two rows 75, 77 of a turbulizer 60. Each row comprises a
plurality of centrally-located convolutions 50 having height H and width W.
Located at either end of each row 75, 77 is at least one convolution 50C
having
width We which is less than width W and height Hc which is less than height H.
The convolutions 50C have side portions 56C which are shorter than side
portions 56 of convolutions 50, and top and bottom surface portions 52C, 54C
which are narrower than top and bottom surface portions 52, 54 of convolutions
50. In addition, the top surface portions 52C are reduced in height relative
to
top surface portions 52 while the bottom surface portions 54C are elevated
relative to bottom surface portions 54.
It will be appreciated that turbulizers 48 and 58 of Figures 6 and 7 could be
modified by increasing or decreasing the widths of the top surface portions
52A,
52B and/or the widths of the bottom surface portions 54A, 54B thereof, thereby
varying the pitch as well as the height of the convolutions 50A, 50B along the
longitudinally extending edges of turbulizers 48, 58. It will also be
appreciated
that turbulizer 60 of Figure 8 could be modified by either making the width of
top surface portions 52C and/or bottom surface portions 54C the same as or
greater than the width of top and bottom surface portions 52, 54.
It will be appreciated that the turbulizers 48 and 58 shown in Figures 6 and 7
are particularly useful where only one of the top or bottom wall of the plate
pair
converges toward the opposing top or bottom wall of the plate pair adjacent to
the edges of the plate pair, as in Figure 4. On the other hand, the turbulizer
60
shown in Figure 8 is particularly useful where both the top and bottom walls
of
the plate pair converge toward one another adjacent to the edges of the plate
pair, as in Figure 1.
Figure 9 illustrates a portion of another preferred plate pair 70 according to
the
invention, incorporating a turbulizer 94, and Figure 10 illustrates a portion
of
turbulizer 94 in isolation. Plate pair 70 is constructed from first and second
U-
shaped plates 72 and 74. The first U-shaped plate 72 has a pair of straight
parallel side portions 76 and 78 (also referred to herein as "legs") joined by
a
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curved portion 80 (also referred to herein as a "bight portion"). The second U-
shaped plate 74 similarly has substantially straight, parallel side portions
82 and
84 joined by a curved portion 86. The side portions 82 and 84 of the second U-
shaped plate 74 are provided with shoulders 88 and 90 which engage the inner
surfaces of side portions 76 and 78 of the first U-shaped plate 72. The
engagement of shoulders 88 and 90 with the side portions 76 and 78 provides a
mechanical connection between the plates 72 and 74 and also provides surfaces
along which the plates 72 and 74 can be joined, for example by brazing.
It will be appreciated that both shoulders 88 and 90 are not necessarily
provided on same U-shaped plate section, but rather each U-shaped plate
section may be provided with one shoulder on one of its side portions.
The plate pair 70 defines a fluid flow passage 92 in which a turbulizer 94 is
provided. The turbulizer 94 comprises an offset strip fin similar to strip
fins 33,
48, 58 and 60 described above. Turbulizer 94 comprises a plurality of
convolutions 96 disposed in a plurality of transverse rows, of which only two
rows 97, 99 are shown in Figures 9 and 10. The convolutions 96 comprise top
surface portions 98 and bottom surface portions 100 which are more rounded
than the top and bottom surface portions of the turbulizers described above,
but
which have flat portions for engaging the side portions 76, 78, 82, 84 of the
plates 72, 74. The convolutions 96 further comprise side portions 102 which
interconnect the top and bottom surface portions 98, 100. In turbulizer 94 the
side portions 102 are sloped rather than vertical as in the turbulizers
described
above. It will be appreciated that the convolutions 96 of turbulizer 94 do not
necessarily have the shape shown in Figures 9 and 10, but may have an
alternate shape. For example, they may be rectangular as in the turbulizers
described above.
Convolutions 96 define apertures or flow passageways 101 opening in a
direction transverse to the direction of the rows 97, 99. When a fluid such as
oil
flows through the flow passage 46 defined by plate pair 44, it will
periodically
encounter leading edges 103 associated with convolutions 96.
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The turbulizer 94 includes convolutions 96 of varying height. More
specifically,
each row includes a first plurality of convolutions 96 of width W and height
H,
wherein height H is substantially the same as the maximum height of the fluid
flow passage 92 between the side walls of the plates 72 and 74.
The first plurality of convolutions 96 comprises two groups which are
separated
by at least one convolution 96A having a width WA the same as height W and a
height HA which is less than height H. Height HA is substantially the same as
the height of the flow passage 94 at the point where the first and second U-
shaped plates 72 and 74 are joined, i.e. between shoulders 88 and 90. The
convolutions 96A comprise top surface portions 98A, bottom surface portions
100A and side portions 102A. In the preferred embodiment shown in the
drawings, the side portions 102A are shorter than side portions 102 of
convolutions 96, while the top and bottom surface portions 98A, 100A are same
width as the top and bottom surface portions 98 of convolutions 96. In
addition, the top surface portions 98A are reduced in height relative to the
top
surface portions 98 while the bottom surface portions 100A are elevated
relative
to bottom surface portions 100.
Located at either end of each row 97, 99 is at least one convolution 96B
having
a width WB which is the same as width W and height HB which is less than
heights H and HA. The convolutions 96B have side portions 102B which are
shorter than side portions 102 and 102A and have top and bottom surface
portions 98B, 100B which are the same with as top and bottom surface portions
98, 100. In addition, the bottom surface portions 1008 and 100A are coplanar
while the top surface portions 98B are reduced in height relative to the top
surface portions 98 and 98A of convolutions 96 and 96A. It will be appreciated
that convolutions 96B extend into the areas of reduced height adjacent to the
edges of flow passage 92.
In the embodiments of the invention described above, the turbulizers are
positioned in the fluid flow passages in the low pressure drop orientation,
i.e.
with the rows of convolutions disposed transverse to the flow direction and
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transverse to the longitudinal axis of the plate pair. The present invention
also
includes embodiments in which the turbulizers are arranged in the high
pressure
drop orientation, in which the rows of convolutions are disposed parallel to
the
flow direction and parallel to the longitudinal axis of the plate pair. These
embodiments are now described below.
Figures 11 to 14 illustrate another preferred embodiment of the invention
utilizing a turbulizer 120 comprising a plurality of convolutions 124, 134
disposed in rows 122 extending along longitudinal axis L, which is parallel to
the
direction of fluid flow.
A first plurality of rows 122, spaced from the longitudinal edges of
turbulizer
120, is comprised of generally sinusoidal-shaped convolutions 124 having a
first
height H. Convolutions 124 comprise smoothly curved top and bottom surface
portions 126, 127 connected by sloping side portions 128. The sloping side
portions 128 are interrupted at about their midpoints by shoulders 130 through
which adjacent rows 122 are connected together. These shoulders 130 are
interconnected to form continuous lines 132 extending transversely across the
turbulizer 120.
The turbulizer 120 also includes a plurality of rows 122, labelled 122A,
comprised of convolutions 134 which are of a somewhat reduced height HA
relative to the convolutions 124. These rows 122A extend along the
longitudinal edges of the turbulizer 120. A cross sectional view through a
portion of a row 122A of reduced height convolutions 134 is shown in Figure
13.
As shown, the convolutions 134 are comprised of flat top and bottom surface
portions 136, 137 which are connected by sloping side portions 138. The side
portions 138 are interrupted by shoulders 140 which are relatively wider than
shoulders 130 of convolutions 124 and through which the convolutions 134 at
the edges of the turbulizer strip 120 are connected to convolutions 124 in
neighbouring rows.
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The convolutions 124, 134 define apertures or flow passageways 125 open in a
direction transverse to the direction of rows 122 and transverse to the flow
direction. When a fluid such as oil flows through the turbulizer 120 by
following
a tortuous path through the transverse openings between convolutions of
adjacent rows 122, it will periodically encounter the side portions 128, 138
of
the convolutions 124, 134. This orientation is referred to as the high
pressure
drop orientation.
Figure 14 illustrates a turbulizer strip 120 located in the fluid flow passage
142
of a plate pair 144 which is comprised of upper and lower plates 146, 148 and
is
generally of the same shape as prior art plate pair 61 shown in Figure 1. The
cross section of Figure 14 is taken in a transverse plane through the
continuous
line 132 formed by the shoulders of the convolutions 124, 134. The plates 146,
148 are arranged back-to-back and have joined peripheral flanges 152, 158.
Plates 146, 148 also have raised central portions 150, 156 which are connected
to flanges 152, 158 through sloping, rounded side walls 154, 160. Due to the
presence of sloping, rounded side walls 154, 160, the fluid flow passage 142
of
plate pair 144 has a central portion having a height which is equal to the
distance between the central raised portions 150, 156 of the plates 146 and
148. The area approaching the flanges 152, 158 is gradually reduced in height.
As mentioned above, the turbulizer 120 is positioned in the fluid flow passage
142 in the high pressure drop orientation. The rows 122 having convolutions
124 of height H are located between and in contact with the central raised
portions 150, 156 of the plates 146, 148. The rows 122A along the edges of
turbulizer strip 120 having convolutions 134 of height HA are located adjacent
the edges of the fluid flow passage 142, i.e. adjacent to flanges 152, 158. In
order to minimize the bypass area adjacent the edges of the flow passage 142,
it is preferred that the reduced height convolutions 134 make at least some
contact with the upper and lower plates 146 and 148, as shown in Figure 14.
However, due to the curved shape of the edges of flow passage 142 and the
square shape of the convolutions, it will be appreciated that complete contact
with the plates 146 and 148 is not possible.
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Figures 15 and 16 show that the turbulizer 120 can be used in heat exchangers
formed from flat, extruded tubes of varying shapes, rather than the plate
pairs
described above. The cross sections of Figures 15 and 16 are taken in a
transverse plane through the top and bottom surface portions of convolutions
124, 134.
In Figure 15, the turbulizer 120 is disposed in the high pressure drop
orientation
in a flat heat exchange tube 180 having flat, parallel top and bottom walls
182,
184 and substantially vertical side walls 186, 188. Together, the walls 182,
184, 186, 188 define a fluid flow passage 190. The top, bottom and side walls
are connected together by angled transitions 192, 194, 196 and 198 which
reduce the height of the flow passage 190 adjacent to its outer edges. It will
be
seen that the reduced height convolutions 134 of turbulizer 120 fill a large
portion of the area located between angled transitions 192 and 194 and the
area located between angled transitions 196 and 198, thereby substantially
reducing bypass flow through the tube 180.
In Figure 16, the turbulizer 120 is disposed in the high pressure drop
orientation
in a flat heat exchange tube 200 having flat, parallel top and bottom walls
202,
204 connected by rounded side portions 206, 208. Together, the walls 202,
204 and side portions 206, 208 define a fluid flow passage 210. The height of
the flow passage 210 is reduced within the rounded side portions 206, 208. It
will be seen that the reduced height convolutions 134 of turbulizer 120 fill a
large portion of the area located within the rounded side portions 206, 208,
thereby substantially reducing bypass flow through the tube 200.
In the turbulizer 120 shown in Figures 11 to 13, the flat top portions 136 of
the
reduced height convolutions 134 are reduced in height relative to the top
portions 126 of the full-height convolutions 124 and the flat bottom portions
137 of the reduced-height convolutions 134 are elevated relative to the bottom
portions 127 of the full-height convolutions 124. Thus, the turbulizer 120 is
particularly useful in heat exchange tubes or plate pairs such as those shown
in
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Figures 14 to 16 in which the top and bottom walls of the tube or plate pair
converge toward a central plane.
It will however be appreciated that the turbulizer 120 could be modified for
use
in a tube or plate pair similar or identical to those shown in Figures 4 and
4A
where the bottom wall of the tube or plate pair is flat and the top wall of
the
tube or plate pair converges toward the bottom wall adjacent its edges.
Specifically, the turbulizer 120 could be modified so that the bottom portions
137 of the reduced-height convolutions 134 are coplanar with the bottom
portions 127 of the full-height convolutions 124. For example, the lower
portions of the reduced height convolutions 134 (below shoulders 140) could
have the same or similar sinusoidal shape and height as the full height
convolutions 124. This possibility is illustrated by dotted line portion 123
in the
cross section of Figure 13.
Figure 17 illustrates another preferred turbulizer 170 for use in heat
exchangers
according to the invention. Turbulizer 170 is similar in a number of respects
to
turbulizer 120 shown in Figures 11 to 13, and like reference numerals are used
to identify like components in the turbulizer of Figure 17. Turbulizer 170
comprises a plurality of rows 122 of convolutions. Some of these rows 122 are
comprised of full height convolutions 124 which are spaced inwardly from the
edges of the turbulizer strip 170. The turbulizer strip 170 also includes a
number of rows 122, labelled 122A, comprised of reduced height convolutions
134. Rows 122A are located along the longitudinally extending edges of
turbulizer strip 170. In the embodiment of Figure 17, there is one row 122 of
reduced height convolutions 134 along each edge of the turbulizer strip 170.
The convolutions 124 and 134 of turbulizer strip 170 are exactly the same as
in
turbulizer 120 and therefore further discussion of these convolutions is not
necessary. Turbulizer 170 is preferably disposed in a plate pair or extruded
heat exchanger tube in a high pressure drop orientation as shown in Figures 14
to 16, that is with rows 122 extending transverse to the direction of fluid
flow.
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In addition, the turbulizer 170 of Figure 17 is provided with spaced apart
rows
172 which are comprised of reduced height convolutions 174. Rows 172 are
located between the rows of full height convolutions 122. Convolutions 174
may preferably have the same shape and dimensions as convolutions 134
shown in Figure 13, although this is not necessary. The rows 172 comprised of
reduced height convolutions 174 provide pressure recovery zones to avoid
excessive pressure drop as the fluid flows through the turbulizer 170 in the
high
pressure drop orientation.
Although the preferred plate pairs 44, 44 and 70 shown in Figures 4, 4A and 9
are shown in the drawings as being provided with turbulizers arranged in the
low pressure drop orientation, it will be appreciated that these and similar
plate
configurations can be used in combination with turbulizers arranged in the
high
pressure drop orientation, such as the turbulizers shown in Figures 11 to 13
and
17. For example, the turbulizer 170 shown in Figure 17 could be used in a
plate
pair 70 as shown in Figure 9. To fit within the flow passage of plate pair 70,
the
turbulizer 170 would be provided with at least one row 122 of reduced height
convolutions 134 along each of its edges and would be provided with at least
one row 172 of reduced height convolutions 174 to fit between the shoulders 88
and 90 formed in the overlapping end portions of the U-shaped plates.
Although the invention has been described in connection with certain preferred
embodiments, it is not restricted thereto. Rather, the invention includes all
embodiments which may fall within the scope of the following claims.
