U.S. patent application number 09/901695 was filed with the patent office on 2002-01-31 for heat-exchange fin for a brazed-plate heat exchanger, and corresponding heat exchanger.
This patent application is currently assigned to L'AIR LIQUIDE, SOCIETE ANONYME POUR L'ETUDE ET L'EXPLOITATION DES PROCEDES GEORGES CLAUDE. Invention is credited to Lehman, Jean-Yves, Werlen, Etienne.
Application Number | 20020011331 09/901695 |
Document ID | / |
Family ID | 8852341 |
Filed Date | 2002-01-31 |
United States Patent
Application |
20020011331 |
Kind Code |
A1 |
Lehman, Jean-Yves ; et
al. |
January 31, 2002 |
Heat-exchange fin for a brazed-plate heat exchanger, and
corresponding heat exchanger
Abstract
A fin (9) includes a perforated and/or recessed corrugated
product which has a main direction of corrugation (F1) and which is
bounded by two lateral edges (13). The main direction of
corrugation (F1) is oblique with respect to the two lateral edges
(13). The fin is useful in the main heat-exchange lines of air
distillation plants.
Inventors: |
Lehman, Jean-Yves; (Maisons
Alfort, FR) ; Werlen, Etienne; (Paris, FR) |
Correspondence
Address: |
YOUNG & THOMPSON
745 SOUTH 23RD STREET 2ND FLOOR
ARLINGTON
VA
22202
|
Assignee: |
L'AIR LIQUIDE, SOCIETE ANONYME POUR
L'ETUDE ET L'EXPLOITATION DES PROCEDES GEORGES CLAUDE
|
Family ID: |
8852341 |
Appl. No.: |
09/901695 |
Filed: |
July 11, 2001 |
Current U.S.
Class: |
165/166 ;
62/903 |
Current CPC
Class: |
F25J 2290/42 20130101;
F28D 9/0068 20130101; F28D 9/0093 20130101; F28F 2250/108 20130101;
F28D 2021/0033 20130101; F25J 2290/32 20130101; F28F 3/027
20130101; F25J 5/002 20130101 |
Class at
Publication: |
165/166 ;
62/903 |
International
Class: |
F28F 003/00; F25J
005/00 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 11, 2000 |
FR |
00 09033 |
Claims
1. Heat-exchange fin for a brazed-plate heat exchanger, of the type
comprising a perforated and/or recessed corrugated product which
has a main direction of corrugation (F1) and which is bounded by
two lateral edges (13), characterized in that the main direction of
corrugation (F1) is oblique with respect to the two lateral edges
(13).
2. Fin according to claim 1, characterized in that it has an
overall direction (F2) of least resistance to the flow of a fluid
which makes a substantial angle with the main direction of
corrugation (F1).
3. Fin according to claim 2, characterized in that the overall
direction (F2) of least resistance to the flow of a fluid is
approximately parallel to the two lateral edges (13).
4. Fin according to either of claims 2 and 3, characterized in that
it includes, on its wave legs (17), features (18; 20; 21) which
favour movement of the fluid transversely to the overall direction
(F2) of least resistance to the flow.
5. Fin according to one of claims 1 to 4, characterized in that it
includes, on its wave legs (17), features (18; 20; 21) for creating
turbulence in the fluid.
6. Fin according to claim 4 or 5, characterized in that the
features (18) consist of openings provided on that side of the wave
legs (17) which receives the fluid flow, these openings being open
towards the upstream of this flow.
7. Fin according to claim 4 or 5, of the serrated type,
characterized in that the features consist of tabs (20) projecting
on that side of the wave legs (17) which receives the fluid
flow.
8. Fin according to claim 7, characterized in that the tabs (20)
are provided on the leading edge of the wave legs (17).
9. Fin according to claim 4 or 5, of the serrated type,
characterized in that the features consist of indentations (21) on
the leading edges and/or trailing edges of the wave legs (17),
these indentations being provided on the offset lines (19) of the
fin (9) so as to increase the flow area for the fluid in a
direction which, compared with the main direction of corrugation
(F1), approaches the direction (F2) of the said lateral edges
(13).
10. Brazed-plate heat exchanger of the type comprising a plurality
of parallel rectangular plates (2) which between them define
passages (3, 4, 5) of flat overall shape and, in each passage, a
heat-exchange fin (9), each fin forming a spacer between two
plates, together with lateral closure bars (6), characterized in
that at least one heat-exchange fin (9) is in accordance with any
one of claims 1 to 9.
11. Heat exchanger according to claim 10, characterized in that it
constitutes a main heat-exchange line of an air distillation plant.
Description
[0001] The present invention relates to a heat-exchange fin for a
brazed-plate heat exchanger, of the type comprising a perforated
and/or recessed corrugated product which has a main direction of
corrugation and which is bounded by two lateral edges.
[0002] The invention applies, for example, to the main
heat-exchange lines of air distillation plants, which bring the
incoming air and the cold products resulting from the air
distillation column into heat-exchange relationship.
[0003] Brazed-plate heat exchangers are widely used as they offer a
large heat-exchange area in a particularly compact volume and, in
addition, they are relatively easy to manufacture.
[0004] These exchangers, often made of aluminium or aluminium
alloy, consist of a plurality of parallel, generally rectangular,
plates between which are placed, on the one hand, spacer waves or
fins of varied geometry and, on the other hand, bars for closing
off the flat-shaped fluid flow passages bounded by the plates. The
flows may be counter-current, co-current or crossed-current
flows.
[0005] The function of the fins is to increase the heat-exchange
area and therefore the overall heat transfer performance.
Specifically, they transfer heat fluxes by conduction to the
adjacent plates to which they are fastened by brazing.
[0006] The fins are produced very inexpensively from a folded,
perforated, recessed and/or stamped flat product. The basic wave
may have an approximately square, rectangular or triangular cross
section. Basically, the known fins are called "straight waves",
which are a simple corrugated sheet, "perforated waves",
"herringbone waves", having corrugated generatrices, "louvered
waves", the wave legs of which have recesses, and "serrated waves"
or "partially offset waves" in which a transverse offset of the
wave is produced at regular intervals along the generatrices, this
offset generally being a wave half-period.
[0007] In all these known fins, the main direction of corrugation,
which is the mean direction of corrugation in the case of
herringbone waves, defines the direction of least resistance to the
flow of the fluid.
[0008] In each passage of the exchanger, a main part of the length
of the passage constitutes the actual heat-exchange part, which is
fitted with a fin called a heat-exchange fin. In certain cases,
this part is bordered by fluid inlet and outlet distribution parts
fitted with distribution fins.
[0009] The heat-exchange part is bounded by two lateral closure
bars parallel to two opposed sides of the plates, and the main
direction of corrugation of the heat-exchange fin is parallel to
these closure bars, with the exception sometimes of limited regions
in which this main direction is perpendicular to the lateral
closure bars (so-called "hard-way" arrangement) in order to create
a local pressure drop. In the description which follows, hard-way
fins will be ignored.
[0010] In the distribution parts, the fins have a general direction
of corrugation which is highly inclined to that of the
heat-exchange fins.
[0011] It is an object of the invention to increase the compactness
of brazed-plate exchangers by improving their thermal
performance.
[0012] For this purpose, the subject of the invention is a
heat-exchange fin of the aforementioned type, characterized in that
the main direction of corrugation is oblique with respect to the
two lateral edges, and in that the fin has an overall direction of
least resistance to the flow of a fluid which is approximately
parallel to the two lateral edges.
[0013] The subject of the invention is also a brazed-plate heat
exchanger of the type comprising a plurality of parallel
rectangular plates which between them define passages of flat
overall shape and, in each passage, a heat-exchange fin, each fin
forming a spacer between two plates, together with lateral closure
bars, and in which exchanger a heat-exchange fin is as defined
above.
[0014] Illustrative examples of the invention will now be described
with reference to the appended drawings in which:
[0015] FIG. 1 shows, in perspective, with partial cutaways, a
brazed-plate heat exchanger according to the invention;
[0016] FIG. 2 shows a passage in this heat exchanger;
[0017] FIG. 3 shows, in perspective, part of a fin according to the
invention;
[0018] FIG. 4 shows the same fin, taken in cross section on the
mid-plane IV of FIG. 3;
[0019] FIGS. 5 and 7 show, in perspective, two other embodiments of
the fin of the invention; and
[0020] FIGS. 6 and 8 show the fins of 5 and 7 in cross section in
the mid-planes VI of FIG. 5 and VIII of FIG. 7, respectively.
[0021] The heat exchanger 1 shown in FIG. 1 is, for example, a
cryogenic heat exchanger. It consists of a stack of parallel
rectangular plates 2 which are all identical and between them
define a plurality of passages for fluids to be brought into
indirect heat-exchange relationship. In the example shown, these
passages are, in succession and cyclically, passages 3 for a first
fluid, passages 4 for a second fluid and passages 5 for a third
fluid.
[0022] Each passage 3 to 5 is bordered by lateral closure bars 6
and end closure bars 7 which define the passage, leaving
inlet/outlet windows 8 of the corresponding fluid free. Placed in
each passage are spacer waves or corrugated fins which serve as
thermal fins, as spacers between the plates, especially during
brazing and in order to avoid any deformation of the plates when
pressurized fluids are used, and as a means of guiding the fluid
flows. These fins are, over essentially the entire length of the
passage, heat-exchange fins 9. In their regions adjacent to the
windows, these fins 9 are extended by distribution fins 10. The
latter distribute the incoming fluid from an inlet window over the
entire width of the fin 9, or collect the fluid coming off this
entire width into an outlet window.
[0023] The stack of plates, closure bars and spacer waves is
generally made of aluminium or aluminium alloy and is assembled in
a single operation by oven brazing.
[0024] Fluid inlet/outlet boxes 11, of semicylindrical overall
shape, are then welded to the exchanger body thus produced so as to
sit over the rows of corresponding inlet/outlet windows 8, these
boxes 11 being connected to fluid feed and discharge pipes 12.
[0025] FIG. 2 shows schematically one of the passages in the same
exchanger, namely a passage 3. The heat-exchange fin 9 has a main
direction of corrugation F1 which makes a positive acute angle
.alpha., typically between 1.degree. and 30.degree. and preferably
between 2.degree. and 10.degree., with the longitudinal direction
F2 of the passage, which is that of the lateral closure bars 6.
[0026] However, the arrangement of the fin 9 is such that the
overall direction of least resistance to the flow in the passage
remains approximately the direction F2.
[0027] Moreover, FIG. 2 shows the two distribution fins 10 adjacent
to the inlet/outlet windows 8 of the passage. The angle .beta. that
the corrugations of these distribution fins make with the direction
F2 is very much greater than the angle .alpha. and typically close
to 75.degree., and their overall direction of least resistance to
the flow is their main direction of corrugation, so that they can
fulfil their distributing function.
[0028] The fin 9 is made from a folded sheet material, the
longitudinal direction of which is perpendicular to F1. This
material is, after folding, cut to length along two lines 13
parallel to the direction F2, thereby resulting in several wave
sheets 14, numbering three in FIG. 2, in the form of a
parallelogram (in the case of the intermediate sheet or sheets) or
in the form of a rectangular trapezium or a right-angled triangle
(in the case of the two end sheets).
[0029] FIGS. 3 to 8 show three different embodiments of the fin
9.
[0030] In the embodiment in FIGS. 3 and 4, the fin comprises a
corrugation of rectangular cross section, with wave troughs 15 and
wave crests 16 joined together by wave legs 17.
[0031] Each leg 17 is provided, at regular intervals, with openings
18 pushed back on that side of the leg which receives the fluid
flux (the left-hand side in FIGS. 3 and 4), which openings are open
towards the upstream of this flux. Thus, as shown by arrows in FIG.
4, a stream of fluid guided in the direction F1 between two legs 17
is partially deflected transversely to this direction by the
opening 18.
[0032] Thus, overall, the direction of least resistance to the flow
of the fin 9 is approximately the direction F2 when the shape and
the dimensions of the openings 18 are chosen appropriately. In
addition, the inclination F1 and the openings 18 give the flow a
two-dimensional and turbulent configuration which is conducive to
efficient heat exchange.
[0033] In the embodiment in FIGS. 5 and 6, the fin is of the
"serrated" type. It thus comprises, at regular intervals along the
direction F1 called the "serration length" 1, a lateral offset d,
alternately on one side and the other, which is generally equal to
one half of the distance which separates two legs 17, called the
"separation period" p. In this way, the fin has parallel offset
planes P which, seen from above (FIG. 4), are parallel offset lines
19.
[0034] Each individual leg 17 has its leading edge bent through a
right angle over its entire height, thereby defining a deflection
tab 20. All the tabs 20 are oriented on the same side, namely on
that side of the legs 17 which receives the fluid flow.
[0035] The tabs 20 have the effect of reducing the flow area for
the fluid on that side where they are provided and of increasing
this flow area on the opposite side. Thus, as FIG. 6 shows, each
stream of fluid guided between two legs 17 sees its flow favoured
in a direction close to F2, or even an oblique direction in the
opposite sense to F1 with respect to F2.
[0036] On account of the turbulence generated in the fluid, the fin
9 has overall, as previously, a direction of least resistance to
the flow close to F2, by means of a suitable choice of the
parameters of the fin and of the dimensions of the tabs 20.
[0037] The embodiment in FIGS. 7 and 8 differs from the previous
one by the omission of the tabs 20 and by the presence of
indentations 21 over the entire height of certain leading edges and
of certain trailing edges of the legs 17. More specifically:
[0038] in every other row of legs 17, the latter have, alternately,
an indentation on both their leading edge and their trailing edge,
and no indentation;
[0039] in the intermediate rows, the legs 17 have, alternately, an
indentation 21 on their leading edge and an indentation on their
trailing edge.
[0040] The resulting effect is substantially the same as that
described above with regard to FIGS. 5 and 6.
* * * * *