U.S. patent application number 10/478277 was filed with the patent office on 2004-09-09 for louvered fins for heat exchanger.
Invention is credited to Averous, David, Chatel-Pelage, Fabienne, Fuentes, Francois, Grivel, Michael, Szulman, Claire, Wagner, Marc, Werlen, Etienne.
Application Number | 20040173344 10/478277 |
Document ID | / |
Family ID | 8863441 |
Filed Date | 2004-09-09 |
United States Patent
Application |
20040173344 |
Kind Code |
A1 |
Averous, David ; et
al. |
September 9, 2004 |
Louvered fins for heat exchanger
Abstract
The invention concerns a louvered fin comprising an assembly of
wave stems (123) alternately linked by a wave crest (121) and a
wave base (122), and wherein the wave stems (123) are provided with
flaps (125) cut out in said wave stems (123) and sloping at angle
relative to the main undulating direction (D1). The wave stems
(123), crests (121) and bases (122) form, in cross-section relative
to the main undulating direction (D1), rectilinear segments, the
crests and the bases being mutually parallel.
Inventors: |
Averous, David; (Renauvoid,
FR) ; Grivel, Michael; (Epinal, FR) ; Wagner,
Marc; (Saint Maur Des Fosses, FR) ; Chatel-Pelage,
Fabienne; (Chicago, IL) ; Fuentes, Francois;
(La Vesinet, FR) ; Szulman, Claire; (Meudon,
FR) ; Werlen, Etienne; (Paris, FR) |
Correspondence
Address: |
Air Liquide
Intellectual Property Department
Suite 1800
2700 Post Oak Boulevard
Houston
TX
77056
US
|
Family ID: |
8863441 |
Appl. No.: |
10/478277 |
Filed: |
April 16, 2004 |
PCT Filed: |
May 18, 2001 |
PCT NO: |
PCT/FR02/01674 |
Current U.S.
Class: |
165/173 |
Current CPC
Class: |
B01J 2219/3221 20130101;
B01J 19/249 20130101; F28D 9/0068 20130101; B01J 2219/328 20130101;
B01J 2219/32248 20130101; F25J 2290/10 20130101; B01J 2219/32241
20130101; B21D 53/04 20130101; F28F 2250/108 20130101; B01J
2219/32213 20130101; B01J 19/32 20130101; B01J 2219/32475 20130101;
F28F 3/027 20130101; F25J 5/002 20130101 |
Class at
Publication: |
165/173 |
International
Class: |
F28F 009/02 |
Foreign Application Data
Date |
Code |
Application Number |
May 18, 2001 |
FR |
01/06586 |
Claims
1. A corrugated fin for a plate and fin heat exchanger, of the type
with louvers defining an overall main direction of corrugation
(D1), comprising a set of corrugation legs (123) alternately
connected by a corrugation crest (121) and by a corrugation trough
(122), the corrugation legs (123) being provided with flaps (125)
cut from said corrugation legs (123) and inclined at an angle
(.alpha.) with respect to the main direction of corrugation (D1),
characterized in that the corrugation legs (123), the corrugation
crests (121) and the corrugation troughs (122) form, in cross
section with respect to the main direction of corrugation (D1),
straight segments, the crests (121) and the troughs (122) being
mutually parallel.
2. The corrugated fin as claimed in claim 1, characterized in that
the corrugation legs (123) are all mutually parallel and
perpendicular to the corrugation troughs (122), so that the fin has
a square wave-shaped corrugation.
3. The corrugated fin as claimed in claim 1 or 2, characterized in
that each flap (12) is cut along the direction of the straight
segment defined by the corrugation leg (123) over substantially the
entire length of said segment.
4. The corrugated fin as claimed in any one of claims 1 to 3,
characterized in that the fin has a substantially uniform wall
thickness (e) of between 0.2 and 0.5 mm.
5. The corrugated fin as claimed in any one of claims 1 to 4, in
which the corrugation legs (123) have a thickness (e), a mean
transverse separation (w) with respect to the overall main
direction of corrugation (D1), which defines the width of a passage
channel and a spacing (p), and the flaps (125) have a length
(l.sub.s), characterized in that the length (l.sub.s) is greater
than the spacing (p).
6. The corrugated fin as claimed in claim 5, characterized in that
the length (l.sub.s) of the flaps satisfies the following
relationship: l.sub.s.gtoreq.1.1p.
7. The corrugated fin as claimed in claim 5 or 6, characterized in
that the angle of inclination of the flaps (.alpha.) lies, in terms
of absolute value, strictly between a minimum value
(.alpha..sub.min) and a maximum value (.alpha..sub.max) which are
positive and defined by the following equations: sin
.alpha..sub.min=e/l.sub.s and 5 tan max = p 1 s
8. The corrugated fin as claimed in any one of claims 5 to 7,
characterized in that the angle of inclination (.alpha.) of the
flaps (25) is substantially equal, in terms of absolute value, to
an angle (.alpha..sub.1) defined by the equation: 6 tan 1 = p 21
s
9. The corrugated fin as claimed in any one of claims 5 to 7,
characterized in that the angle of inclination (.alpha.) of the
flaps (125) meets the condition: p.gtoreq.l.sub.s
sin.vertline..alpha..vertline- .+e
cos.vertline..alpha..vertline..
10. A plate and fin heat exchanger of a unit for separating air or
H.sub.2/CO mixtures by cryogenic distillation, particularly an
exchanger of a main heat exchange line or a reboiler/condenser, of
the type comprising a stack of parallel plates (2) which define a
plurality of fluid-circulation passages (3 to 5) of flat overall
shape, closure bars (6) delimiting these passages, and corrugated
fins (8) arranged in the passages, characterized in that at least
some of the corrugated fins (8) are as claimed in any one of claims
1 to 9.
11. A method for the continuous manufacture, from a flat product in
sheet form, of a louvered corrugated fin for a plate heat
exchanger, of the type comprising flaps (25; 125) cut from
corrugation legs (23; 123), in which the product (205) is passed
step by step through a press tool (201, 202) comprising at least a
moving tool part (201) with a reciprocating movement, said tool
part (201) in the one same movement corrugating the fin and cutting
the flaps.
12. The corrugated fin as claimed in claim 11, characterized in
that the flat product (205) is held in position upstream of said
moving tool part (201) by means of a holding device (210) when said
moving tool part (201) is active, and the flat product (205) is
released to continue its journey and to extract the formed
corrugation from the tool when the moving tool part (201) is
inactive.
13. The corrugated fin as claimed in claim 12, characterized in
that the holding device (210) and the moving tool part (201) are
driven and synchronized by command and control means (220).
14. A device for implementing the method as claimed in any one of
claims 11 to 13, comprising a press tool (201, 202), a device for
continuously feeding the tool with flat product in sheet form
(205), said tool comprising at least one punch (202) and one die
(201) that complement each other, said punch (202) being able to be
given a relative translational movement with respect to the die
(202) in a direction substantially orthogonal to the surface of the
flat product in sheet form (205), characterized in that said punch
(202) extends in a longitudinal overall direction (D) and has a
plurality of planar facets of which at least one (251) is directed
in the direction of translation of the punch and said overall
direction (D) and at least another (252), intended to form a flap,
is directed in the direction of translation of the punch and a
direction inclined with respect to the overall direction (D).
15. The device as claimed in claim 14, characterized in that the
punch (202) comprises, between two consecutive facets, a planar
setback (253) in the direction of translation and a direction
substantially orthogonal to the overall direction (D).
16. The device as claimed in claim 15, characterized in that the
punch (202) has grooves (255) running in the direction of
translation, between a facet (251, 252) and a setback (253).
17. The device as claimed in claim 16, characterized in that it
comprises a device (210) for holding the flat product in sheet form
(205) upstream of the tool (201, 202) allowing the flat product
selectively to be fixed with respect to the tool or released to
allow it to progress.
18. The device as claimed in claim 17, characterized in that it
comprises command and control means (220) designed to drive and
synchronize the tool (201, 202) and the holding device (210).
Description
[0001] The present invention relates to a corrugated fin for a
plate and fin heat exchanger.
[0002] There are various types of plate and fin heat exchangers,
each tailored to one field of use. In particular, the invention
applies advantageously to a heat exchanger of a unit for separating
air or H.sub.2/CO (hydrogen/carbon monoxide) mixtures by cryogenic
distillation.
[0003] This exchanger may be a main heat exchange line or a
reboiler/condenser.
[0004] FIG. 1 of the appended figures depicts, in perspective, with
partial cutaways, one example of such a heat exchanger, of
conventional structure, to which the invention applies.
[0005] The heat exchanger 1 depicted consists of a stack of
parallel rectangular plates 2, all identical, between them defining
a plurality of passages for fluids to be placed in an indirect
heat-exchange relationship. In the example depicted, these passages
are, in succession and cyclically, passages 3 for a first fluid, 4
for a second fluid and 5 for a third fluid.
[0006] Each passage 3 to 5 is bordered by closure bars 6 which
delimit it, leaving inlet/outlet apertures 7 for the corresponding
fluid uncovered. Arranged in each passage are brace corrugations or
corrugated fins 8 which at the same time act as heat-exchange fins,
as braces between the plates, particularly during the brazing and
to prevent any deformation of the plates when fluids under pressure
are used, and also serve to guide the flow of the fluids.
[0007] The stack of plates, closure bars and brace corrugations is
generally made of aluminum or of an aluminum alloy and is assembled
in a single operation by furnace brazing.
[0008] Fluid inlet/outlet boxes 9, of semicylindrical overall
shape, are then welded to the exchanger body thus produced in such
a way as to sit over the rows of corresponding inlet/outlet
apertures, and they are connected to pipes 10 for feeding and
discharging the fluids.
[0009] These exchangers pose specific problems due to the high flow
rates of fluids to be processed and to the magnitude of the heat
exchanges needed in order to produce very high temperature
differences between the inlet and outlet side of the exchanger:
[0010] in order to achieve the desired heat exchange and in order
to process significant flow rates of fluid, the exchangers of
cryogenic type, as described with reference to FIG. 1, have large
sizes (are several meters long) and may be made up of several
individual bodies as described hereinabove. The volumes of such
exchangers are therefore very high;
[0011] the high flow rates and long heat exchange lengths lead to
pressure drops which result in high energy consumption at the main
compressor.
[0012] In order to reduce the volume of the exchanger and/or the
power consumption of the plant, the performance of the heat
exchange corrugation fitted into the exchanger in terms of pressure
drops is of fundamental importance.
[0013] In this industrial field, use is very conventionally made of
brace corrugations 8 of the serrated, straight or perforated
straight type.
[0014] The serrated corrugation, which is the most commonly used,
is thermally very efficient but in terms of pressure drops, its
performance is somewhat penalizing.
[0015] Also known are other heat exchangers used in the automotive
industry to produce air conditioning circuit evaporators. These
exchangers, the corrugations of which are generally made from
aluminum sheet, differ from cryogenic exchangers in that they are
small in size, namely measuring a few centimeters (a maximum of
about ten), in that they are not subjected to much mechanical
stress because they operate at pressures close to atmospheric
pressure, and in that they are not subject to the same requirements
in terms of pressure drop.
[0016] The corrugations of the exchangers of the type used in the
automotive industry are manufactured using wheels, with channels of
triangular or sinusoidal section, and limited densities, from thin
strip (about 0.1 mm thick).
[0017] In the automotive field, use is particularly made of brace
corrugations known as "louvered corrugations", as depicted in FIG.
2.
[0018] A louvered corrugation has an overall main direction of
corrugation D1 defining an overall direction F of flow of the
fluid. In the plane P orthogonal to the overall main direction of
corrugation D1, the corrugation has a cross section of sinusoidal
shape, stretched heightwise. The sinusoid thus defined extends in a
direction D2 perpendicular to the direction D1, these two
directions being assumed, for the convenience of the description,
to be horizontal as has been depicted in FIG. 2.
[0019] The corrugation has corrugation crests 21, defined by the
crests of the sinusoid, and corrugation troughs 22, defined by the
troughs of the sinusoid. The crests 21 and the troughs 22
alternately connect corrugation legs 23 each having a vertical mean
plane perpendicular to the direction D2.
[0020] Two consecutive corrugation legs 23 between them define a
fluid passage with respect to the overall direction F of flow.
[0021] Cut from each corrugation leg 23 is a series of flaps 25,
which are mutually parallel and inclined with respect to the
vertical mean plane and to the overall main direction of
corrugation D1. The flaps 25 define openings constituting secondary
passages for the fluid, in a mainly transverse direction, from one
channel to an adjacent channel. These flaps extend over just part
of the height of the corrugation leg.
[0022] Louvered, triangular or sinusoidal corrugations of the type
described hereinabove have hitherto not been used in
industrial-scale plate heat exchangers for the following
reasons.
[0023] Firstly, the corrugation crests and troughs, whether the
corrugation be triangular or sinusoidal, offer brazing lines only
on the dividing plates, and therefore offer only very small surface
area for mechanical connection to the plates. Such fin geometries
are therefore not suited to the high pressures used in industrial
exchangers, which are conventionally between 6 and 10 bar, and
sometimes reach as high as 80 bar.
[0024] Secondly, the shape of the louvered corrugations used in the
automotive industry is closely connected to the method of
manufacture using the wheel, which is particularly suited to high
manufacturing throughputs. Other corrugation shapes can be obtained
only with great difficulty using such a method of manufacture
involving the wheel. With such a method of manufacture, the cutting
of the flaps can be done correctly only over part of the height of
the corrugation legs. This cutting-out is not enough to achieve the
level of heat exchange performance required in industrial
exchangers.
[0025] Thirdly, the conventional method of manufacture of louvered
corrugations, that is to say using the wheel, may prove difficult
to adapt to significant strip thicknesses, of the order of 0.2 to
0.5 mm, as used in industrial exchangers in order to withstand the
mechanical stresses on the fins.
[0026] The object of the invention is therefore to propose a fin of
the louvered type, whose performance in terms of pressure drop is
better in particular than the serrated corrugation, and which can
be used in industrial exchangers, particularly plate and fin heat
exchangers of a unit for separating air or H.sub.2/CO mixtures by
cryogenic distillation, whether this be in the main heat exchange
line or in a reboiler/condenser.
[0027] To this end, the subject of the invention is a corrugated
fin for a plate and fin heat exchanger, of the type with louvers
defining an overall main direction of corrugation, comprising a set
of corrugation legs alternately connected by a corrugation crest
and by a corrugation trough, the legs being provided with flaps cut
from said corrugation legs and inclined at an angle with respect to
the main direction of corrugation, characterized in that the
corrugation legs, the corrugation crests and the corrugation
troughs form, in cross section with respect to the main direction
of corrugation, straight segments, the crests and the troughs being
mutually parallel.
[0028] Thus, the fin offers a brazing area that allows it to be
used in exchangers of the aforementioned type.
[0029] According to other features of the invention, taken alone or
in any technically conceivable combination:
[0030] the corrugation legs are all mutually parallel and
perpendicular to the corrugation troughs, so that the fin has a
square wave-shaped corrugation;
[0031] each flap is cut along the direction of the straight segment
defined by the corrugation leg over substantially the entire length
of said segment; and
[0032] the fin has a substantially uniform wall thickness of
between 0.2 and 0.5 mm.
[0033] One significant difficulty in the design of the corrugated
fins lies in obtaining an optimum compromise between performance in
terms of pressure drop and performance in terms of the thermal
efficiency of the corrugation. The problem is that, when producing
such fins, one is looking for effects of turbulence and remixing of
the fluid within the passage channels, so as to increase the local
temperature difference between the fluid and the wall, and thus
encourage heat exchange. However, it is essential to keep control
over these effects of turbulence and of remixing of the fluid, so
as to limit the pressure drops generated by the fin. It is
essential, particularly in industrial plants, for example plants
for separating air or H.sub.2/CO mixtures by cryogenic
distillation, to limit the power consumption needed to set the
fluid in motion in the heat exchangers.
[0034] Another object of the invention is to propose a louvered fin
geometry of the type described hereinabove making it possible to
limit the pressure drops induced in the fin and to obtain good heat
exchange quality, to an extent that will allow this type of fin to
be used in industrial cryogenic exchangers.
[0035] To this end, a fin according to the invention, in which the
corrugation legs have a thickness e, a mean transverse separation w
with respect to the overall main direction of corrugation, which
defines the width of a passage channel and a spacing P, and the
flaps have a length l.sub.s, is characterized in that the length of
the flaps is greater than the spacing.
[0036] According to yet other features of the fin according to the
invention:
[0037] the length of the flaps satisfies the following
relationship:
[0038] l.sub.s.gtoreq.1.1p;
[0039] the angle of inclination of the flaps lies, in terms of
absolute value, strictly between a minimum value and a maximum
value which are positive and defined by the following
equations:
[0040] sin .alpha..sub.min=e/l.sub.s
[0041] and 1 tan max = p 1 s ;
[0042] the angle of inclination of the flaps is substantially
equal, in terms of absolute value, to an angle defined by the
equation: 2 tan 1 = p 21 s
[0043] and
[0044] the angle of inclination of the flaps meets the
condition:
[0045] p.gtoreq.l.sub.s sin.vertline..alpha..vertline.+e
cos.vertline..alpha..vertline..
[0046] The invention also relates to a method for the continuous
manufacture, from a flat product in sheet form, of a louvered
corrugated fin for a plate heat exchanger, of the type comprising
flaps cut from corrugation legs, particularly a fin as described
hereinabove.
[0047] According to the method of the invention, the product is
passed step by step through a press tool comprising at least a
moving tool part with a reciprocating movement, said tool part in
the one same movement corrugating the fin and cutting the
flaps.
[0048] According to other features of the method:
[0049] the flat product is held in position upstream of said moving
tool part by means of a holding device when said moving tool part
is active, and the flat product is released to continue its journey
and to extract the formed corrugation from the tool when the moving
tool part is inactive,
[0050] the holding device and the moving tool part are driven and
synchronized by command and control means.
[0051] The invention also relates to a device for implementing the
method described hereinabove.
[0052] This device comprises a press tool, a device for
continuously feeding the tool with flat product in sheet form, said
tool comprising at least one punch and one die that complement each
other, said punch being able to be given a relative translational
movement with respect to the die in a direction substantially
orthogonal to the surface of the flat product in sheet form.
[0053] It is characterized in that said punch extends in a
longitudinal overall direction and has a plurality of planar facets
of which at least one is directed in the direction of translation
of the punch and said overall direction and at least another,
intended to form a flap, is directed in the direction of
translation of the punch and a direction inclined with respect to
the overall direction.
[0054] According to other features of the device according to the
invention:
[0055] the punch comprises, between two consecutive facets, a
planar setback in the direction of translation and a direction
substantially orthogonal to the overall direction;
[0056] the punch has grooves running in the direction of
translation, between a facet and a setback;
[0057] the device comprises a device for holding the flat product
in sheet form upstream of the tool allowing the flat product
selectively to be fixed with respect to the tool or released to
allow it to progress; and
[0058] the device comprises command and control means designed to
drive and synchronize the tool and the holding device.
[0059] An exemplary embodiment of the invention will now be
described with reference to FIGS. 3 to 8 of the attached drawings,
in which:
[0060] FIG. 3 is a perspective view of part of a corrugated fin
according to the invention;
[0061] FIG. 4 is an enlarged sectional view on the vertical plane V
depicted in FIG. 3;
[0062] FIG. 5 is an enlarged schematic view in section, on the
horizontal plane H, of the corrugation depicted in FIG. 3, just
three corrugation legs being depicted;
[0063] FIG. 6 is a similar partial depiction, on a larger
scale;
[0064] FIG. 7 is a schematic depiction of a device for
manufacturing a louvered corrugated fin according to the invention;
and
[0065] FIG. 8 combines views from above of a punch, a guide, and
outlet, central and inlet braces, respectively, used in the device
of FIG. 7.
[0066] FIG. 3 depicts a louvered corrugation according to the
invention, which has a main overall direction of corrugation D1,
and a cross section (FIG. 4) in the form of a square wave, square
waves thus defined running in a direction D2 perpendicular to the
direction D1. Here again, for the convenience of the description,
these two directions are assumed to be horizontal.
[0067] The term "square wave" here means a succession, in
alternation, of horizontal and vertical segments, the horizontal
segments being aligned.
[0068] The fin has corrugation crests 121 defined by the crests of
the square waves, which are flat and horizontal. It has corrugation
troughs 122, defined by the troughs of the square waves, which are
also flat and horizontal. The crests 121 and the troughs 122
alternately connect corrugation legs 123 which are planar and
vertical, the mean plane of which runs perpendicular to the
direction D2.
[0069] Cut from the corrugation legs 123 is a series of flaps 125
which are mutually parallel and inclined with respect to the
vertical plane and to the overall direction of corrugation D1. The
flaps 125 define openings constituting secondary passages for the
fluid, in a mainly transverse direction, from one channel to an
adjacent channel.
[0070] As can be seen in FIGS. 3 and 4, the flaps 125 of a
corrugation leg are cut over the entire height (or practically over
the entire height) of the straight segment defined by the mean
plane of the corrugation leg considered in cross section.
[0071] This arrangement makes it possible, by comparison with
louvered corrugations in which the flaps are cut over just part of
the height, to increase the effect of remixing of the fluid flowing
through the fin.
[0072] With reference to FIG. 5, we shall now describe the
parameters that characterize the louvered corrugation of the type
described hereinabove, and influence its performance in terms of
pressure drop and in terms of thermal efficiency.
[0073] FIG. 5 is a schematic view in section, on the horizontal
plane (H) of symmetry, of the corrugation depicted in FIG. 3, just
three corrugation legs being depicted here.
[0074] The lines denoted by the reference 130 represent the
vertical plane of a corrugation leg 123, with respect to which
plane the angle of inclination .alpha. of the flaps 125 is
defined.
[0075] The spacing of the corrugation, corresponding to the
separation of two consecutive planes 130, corresponding to two
consecutive corrugation legs 23, is denoted by the reference p.
[0076] The thickness e of the walls of the corrugation is assumed
to be constant. As a result, the width of the channel defined by
two consecutive corrugation legs 123 is equal to w=p-e.
[0077] In the type of application at which the invention is aimed,
the thickness e is between 0.2 and 0.5 mm, essentially so as to
reach a compromise between the mechanical integrity and the density
of the fin.
[0078] Along the corrugation, in the direction of corrugation D1,
the flaps 125 are configured in a pattern which repeats with a
geometric periodicity characterized by a period .PI.. This pattern
here comprises two groups of six flaps inclined respectively at a
positive angle .alpha. and at a negative angle .alpha., with,
between these two groups, a planar region 132, 134 directed in the
direction D1. Two transversely consecutive corrugation legs 123 are
identical, and therefore are made up of the same sequence of
patterns repeating periodically without a relative offset or
shift.
[0079] In the planar regions 132, 134, the corresponding
corrugation legs 123 have no openings.
[0080] Reference is now made more specifically to FIG. 6.
[0081] One aspect of the invention relies on the observation that
some of the geometric parameters of a louvered corrugation, which
are described above, have a significant influence on the thermal
performance and pressure drop performance of the fin.
[0082] It has been found that this performance is improved when the
length l.sub.s of the flaps 25 is greater than the spacing p or
even than the mean transverse separation w increased by the
thickness e, that is to say when the length l.sub.s satisfies the
following relationship:
[0083] l.sub.s.gtoreq.p or alternatively l.sub.s.gtoreq.w+e.
[0084] As a preference, a flap length l.sub.s will be chosen such
that:
[0085] l.sub.s.gtoreq.1.1p,
[0086] and more preferably still:
[0087] l.sub.s.gtoreq.1.2p.
[0088] It is thus possible to produce cryogenic exchangers equipped
with exchange corrugations of varying densities corresponding to
the various modes of operation of the passages in one and the same
heat exchanger, particularly having different pressures according
to the passages, these pressures being able to be as high as
several tens of bar. For example, it is possible to produce
high-density fins for short flap lengths or, alternatively,
lower-density fins with longer flap lengths.
[0089] According to another aspect of the invention, optimum fin
performance is obtained when the angle of inclination of the flaps
.alpha. lies strictly between a minimum value .alpha..sub.min and a
maximum value .alpha..sub.max which are positive, defined by the
following equations:
[0090] sin .alpha..sub.max=e/l.sub.s
[0091] and 3 tan max = p 1 s
[0092] The first of these conditions
.vertline..alpha..vertline.>.alpha- ..sub.min gives a strictly
positive opening v between two consecutive flaps 125A, 125C on the
same corrugation leg, namely it defines an orientation of the flaps
excluding contact between the trailing edge of the first flap 125A
and the leading edge of the second flap 125C.
[0093] The maximum value .alpha..sub.max of the angle .alpha.
corresponds, for its part, to the angle of alignment of two
consecutive flaps 125B, 125C of two consecutive corrugation legs,
and the second condition
.vertline..alpha..vertline.<.alpha..sub.max ensures an opening
such that the passages in the consecutive corrugation legs are not
aligned, and thus generate turbulence.
[0094] As a preference, some fins are centered in the middle of the
passage defined by two corresponding fins belonging to a
consecutive corrugation leg, by choosing an angle of inclination of
the flaps .alpha. substantially equal, in terms of absolute value,
to an angle .alpha..sub.1 defined by the equation 4 tan 1 = 1 21 s
.
[0095] To ensure optimum circulation of the fluid in the secondary
channels formed by the flaps 125, an angle of inclination .alpha.
is chosen that satisfies the condition
[0096] p.gtoreq.l.sub.s sin.vertline..alpha..vertline.+e
cos.vertline..alpha..vertline..
[0097] In addition, this condition makes it possible to ensure ease
of manufacture of the corrugation and a separation e.sub.c between
two rows of flaps 125 that is strictly positive.
[0098] The invention is also aimed at a cryogenic plate heat
exchanger of the type comprising a stack of parallel plates 2 which
define a plurality of fluid-circulation passages 3 to 5 of flat
overall shape, closure bars 6 delimiting these passages, and
corrugated fins 8 arranged in the passages, characterized in that
at least some of the corrugated fins 8 are of the type described
hereinabove.
[0099] A device or machine allowing the manufacture of a louvered
corrugated fin, particularly a fin of the type described with
reference to FIGS. 3 to 6, and particularly a thick-walled fin will
now be described with reference to FIG. 7.
[0100] This device comprises a press tool essentially comprising a
die 201 and a punch 202 which can be given a relative translational
movement.
[0101] For the convenience of the description, it will be assumed
that the die 201 is fixed and the punch 202 can move. The punch 202
may be given a reciprocating translational movement assumed to be
vertical. The punch 202 and the die 201 have complementary
shapes.
[0102] The tool has an inlet 203 and an outlet 204 via which a
metal product in sheet form that is to be processed continuously
passes.
[0103] The device possesses means, not depicted, for moving along
and guiding the metal sheet 205, which allow the metal sheet to be
moved regularly step by step through the tool, in a plane assumed
to be horizontal.
[0104] The punch 202, by collaborating with the die 201, in regular
intervals shapes the metal sheet fed continuously into the
tool.
[0105] The device also comprises means 210 for holding the sheet
upstream of the inlet 203, allowing the sheet to be selectively
fixed with respect to the tool or released to allow it to
progress.
[0106] The holding means 210 may for example essentially consist of
two clamping jaws situated one on each side of the surface of the
sheet 205.
[0107] The device further comprises command and control means 220
able to command the operation of the tool, in this case the
movements of the punch 202 and of the holding means 210, in
response to measured and/or prerecorded parameters.
[0108] The command and control means for this purpose comprise a
sensor 221 sensing the position of the punch 202, and a sensor 222
sensing the position or status of the holding means 210.
[0109] The command and control means 220 also comprise a computer
225 connected to the position sensors 221, 222 so as to receive
their respective detection signals S.sub.1, S.sub.2.
[0110] The computer 225 is also designed to receive other
prerecorded parameters P.sub.i and the preprogrammed command laws
L.sub.i. The computer 225 sends the punch 202 (that is to say its
drive member), and the holding means 210, respective command
signals C.sub.1, C.sub.2 formulated on the basis of the detection
signals S.sub.1, S.sub.2, of the prerecorded external parameters
P.sub.i and of the command laws L.sub.i.
[0111] For simplification purposes, the die 201 has been assumed to
be fixed, but it may in reality be moveable, in alternation with
the punch 202. In this case, the die 201 is driven by a drive
member also receiving a command signal from the computer 225.
[0112] Some of the constituent elements of the die (or fixed part
of the tool) 201 and of the punch (or moving part of the tool) 202
will now be described with reference to FIG. 8.
[0113] The die 201 comprises an inlet brace 231, a central brace
232, and an outlet brace 233, while the punch 202 comprises a first
punch part 241 (or "first punch") and a second punch part 242 (or
"second punch").
[0114] Each of these elements 231, 232, 233, 241, 242 is elongate
in a horizontal overall direction D.
[0115] The inlet brace 231 and the central brace 232 are arranged
parallel to each other so as to define between them a space 245 of
a shape that complements the first punch 241. Likewise, the central
brace 232 and the outlet brace 233 are arranged parallel to one
another and spaced in such a way as to define between them a
passage 246 that complements the second punch 242.
[0116] The movements of the punch 202 with respect to the die 201
as defined with reference to FIG. 7, which are reciprocating
vertical movements orthogonal to the surface of the sheet 205,
correspond to reciprocating integral movements of the punch parts
241, 242 orthogonal to the plane of FIG. 8.
[0117] The first pressing of the metal sheet by the first punch 241
between the braces 231, 232 makes it possible to carry out a first
corrugation and flap-cutting step, while the second pressing step
performed on the tool part thus formed by means of the second punch
241 and the central 232 and outlet 233 braces allows the
corrugation to be given its definitive shape.
[0118] The first punch 241 and the second punch 242 are of
substantially identical shapes, while the braces 231, 232, 233 are
of complementary shapes, which means that it will be beneficial to
describe the shape of just one punch, for example the first punch
241.
[0119] In the example depicted, this first punch 241 is of a shape
designed to shape a square wave louvered corrugation. It has a
succession of vertical planar facets, of which facets 251 run in
the overall longitudinal direction D of the punch. The "straight"
facets 251 correspond to the shapes of the corrugation leg sections
devoid of flaps. The punch 241 has other planar lateral facets 252
which are facets that are inclined with respect to this main
direction D, and are intended to cut out the flaps. Between two
consecutive facets, whether these be two inclined facets 252, or an
inclined facet 252 and a "straight" facet 251, the punch has a
setback 253 in the form of a planar vertical face orthogonal to the
overall direction D.
[0120] Between a setback 253 and a facet 251 or 252 there is formed
a vertical groove 255 allowing flaps to be cut from the corrugation
legs.
[0121] The operation of the device will now be described in greater
detail, it being understood that this operation is repeated a great
many times at high speed throughout the time that the metal sheet
progresses through the tool.
[0122] In the method of manufacture of a corrugated fin by means of
the device which has just been described, the following steps are
performed, starting from the initial state in which the punch 202
is in a raised position with respect to the die 201, that is to say
is in an inactive position or top-dead-center position (any other
position of the punch will be termed "active"):
[0123] the progress of the metal sheet 205 is halted by the holding
means 210;
[0124] the punch 202 is actuated in vertical translation toward the
die 201, carrying the first punch 241 and the second punch 242
along in the same movement so as, in one and the same movement of
the punch 202, to corrugate the fin and cut out the flaps;
[0125] the sheet 205 is released from the holding means 210 so as
to allow it to progress through the tool and so as to allow the
corrugations already formed to be extracted from the tool; and
[0126] the metal sheet 205 is advanced by one step before the
aforementioned operations are repeated, in the same order.
[0127] It should be noted that the prerecorded parameters P.sub.i
and the command laws L.sub.i correspond to the datum geometry of
the corrugated fin. These laws and parameters vary according to the
type of corrugation to be produced and according to the desired
thermal performance of the corrugated fin or according to the
desired flow characteristics of the fluid.
[0128] At each moment, the movement of the punch 202 and of the
holding means 210 are synchronized by the computer 225 using the
signals S.sub.1 and S.sub.2 supplied by the sensors 221, 222.
[0129] The method and the device which have just been described
allow the continuous production of louvered corrugated fins,
particularly square wave corrugations, from metal sheet of
significant thickness.
[0130] Thus, this method and this device make it possible to
produce louvered corrugations that can be used in industrial
exchangers, with high manufacturing throughputs comparable with the
throughputs in the manufacture of louvered fins used in the
automotive industry.
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