U.S. patent application number 09/835409 was filed with the patent office on 2001-12-27 for corrugated fin with partial offset for a plate-type heat exchanger and corresponding plate-type heat exchanger.
Invention is credited to Chatel, Fabienne, Gerard, Claude, Szulman, Claire, Thonnelier, Jean-Yves, Werlen, Etienne.
Application Number | 20010054499 09/835409 |
Document ID | / |
Family ID | 8849342 |
Filed Date | 2001-12-27 |
United States Patent
Application |
20010054499 |
Kind Code |
A1 |
Gerard, Claude ; et
al. |
December 27, 2001 |
Corrugated fin with partial offset for a plate-type heat exchanger
and corresponding plate-type heat exchanger
Abstract
In this corrugated fin, each corrugation leg (10A, 10B) has a
notch (18A, 18B) on at least one edge (11A) and over at least part
of its height. Application to brazed-plate heat exchangers.
Inventors: |
Gerard, Claude; (Chantraine,
FR) ; Szulman, Claire; (Paris, FR) ; Chatel,
Fabienne; (Vanves, FR) ; Thonnelier, Jean-Yves;
(Voisins-Le-Bretonneux, FR) ; Werlen, Etienne;
(Versailles, FR) |
Correspondence
Address: |
YOUNG & THOMPSON
745 SOUTH 23RD STREET 2ND FLOOR
ARLINGTON
VA
22202
|
Family ID: |
8849342 |
Appl. No.: |
09/835409 |
Filed: |
April 17, 2001 |
Current U.S.
Class: |
165/166 ;
165/140 |
Current CPC
Class: |
F25J 2290/42 20130101;
F28F 2250/108 20130101; F28F 3/027 20130101; F25J 2290/44 20130101;
F28D 9/0068 20130101; F25J 5/002 20130101 |
Class at
Publication: |
165/166 ;
165/140 |
International
Class: |
F28D 007/10; F28F
003/00 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 17, 2000 |
FR |
00 04942 |
Claims
1. Corrugated fin with partial offset for a plate-type heat
exchanger, of the type defining a main overall direction of
corrugation (D1) and comprising a number of adjacent rows (9) of
corrugations, each row being more or less transverse with respect
to the said main overall direction and being offset, in its own
longitudinal direction (D2), with respect to the two adjacent rows,
each row of corrugations comprising a set of corrugation legs (10)
connected alternately by a corrugation crest (13) and a corrugation
trough (14), characterized in that at least some corrugation legs
(10) have a notch (18, 21) on at least one edge (11, 12) and over
at least part of their height.
2. Corrugated fin according to claim 1, characterized in that the
depth of the notch (18, 21) is chosen so as to provide a stream of
fluid flowing in a direction close to the said main overall
direction (D1) with a passage cross section (22) that is at least
approximately constant, or increased, in the notched region of each
leg (10).
3. Corrugated fin according to claim 1 or 2, characterized in that
the notch (18) is on the leading edge (11).
4. Corrugated fin according to any one of claims 1 to 3,
characterized in that the notch (21) is on the trailing edge
(12).
5. Corrugated fin according to any one of claims 1 to 4,
characterized in that some notches (18, 21) are offset with respect
to the others at right angles to the overall plane of the fin.
6. Corrugated fin according to claim 5, characterized in that the
notches (18, 21) are offset at right angles to the overall plane of
the fin from one corrugation leg (10) to the next on one and the
same row (9A, 9B).
7. Corrugated fin according to any one of claims 1 to 6,
characterized in that the notch (18, 21) extends over the entire
height of the corrugation leg (10).
8. Corrugated fin according to any one of claims 1 to 7,
characterized in that the notch (18, 21) continues onto the
adjacent corrugation crest (13) and/or onto the adjacent
corrugation trough (14).
9. Corrugated fin according to any one of claims 1 to 8,
characterized in that the offset from one row to the next is less
than half the pitch (p/2) of the corrugations.
10. Plate-type heat exchanger of the type comprising a stack of
parallel plates (2) which define a number of passages (3 to 5) of
flat overall shape for the circulation of fluids, closure bars (6)
which delimit these passages, and corrugated fins (8) arranged in
the passages, characterized in that at least some of the corrugated
fins (8) are according to any one of claims 1 to 9.
Description
[0001] The present invention relates to a corrugated fin with
partial offset for a plate-type heat exchanger, of the type
defining a main overall direction of corrugation and comprising a
number of adjacent rows of corrugations, each row being more or
less transverse with respect to the said main overall direction and
being offset, in its own longitudinal direction, with respect to
the two adjacent rows, each row of corrugations comprising a set of
corrugation legs connected alternately by a corrugation crest and a
corrugation trough.
[0002] Corrugated fins of this type, generally known as "serrated
corrugations", are widely used in brazed-plate heat exchangers,
which have the advantage of offering a large heat-exchange area in
a relatively small volume, and of being easy to manufacture. In
these exchangers, fluid flows may be cocurrent, countercurrent or
cross-flow.
[0003] FIG. 1 of the appended drawings depicts, in perspective and
with partial cutaways, one example of such a heat exchanger, of a
conventional structure, to which the invention applies. This may,
in particular, be a cryogenic heat exchanger.
[0004] The heat exchanger 1 depicted consists of a stack of
parallel rectangular plates 2, all identical, which between them
define a number of passages for fluids to be placed in an indirect
heat-exchange relationship. In the example depicted, these passages
are, successively and cyclically, passages 3 for a first fluid, 4
for a second fluid and 5 for a third fluid.
[0005] Each passage 3 to 5 is bordered by closure bars 6 which
delimit it, leaving inlet/outlet openings 7 free for the
corresponding fluid. Placed in each passage are corrugated spacer
pieces or corrugated fins 8 which act simultaneously as
heat-exchange fins and as spacer pieces between the plates,
particularly during the brazing operation, and to avoid any
deformation of the plates when pressurized fluids are used, and
serve to guide the flow of fluids.
[0006] The stack of plates, closure bars and corrugated spacer
pieces is generally made of aluminum or aluminum alloy and is
assembled in a single operation by furnace brazing.
[0007] Fluid inlet/outlet boxes 9, of semicylindrical overall
shape, are then welded onto the exchanger body thus produced, to
cap the corresponding rows of inlet/outlet openings, and are
connected to pipes 109 for conveying and removing the fluids.
[0008] There are various types of corrugated spacer pieces 8 in
existence. The conventional corrugated spacer piece known as the
"serrated corrugation" is depicted in FIG. 2.
[0009] This serrated corrugation has a main overall direction of
corrugation D1 and comprises a great many rows of adjacent
corrugations 9, all identical 9A, 9B, 9C etc., oriented in a
direction D2 perpendicular to the direction D1.
[0010] For the convenience of the description, it will be assumed
that, as depicted in FIG. 2, the directions D1 and D2 are
horizontal.
[0011] Each row of corrugations 3 has a crinkled shape and
comprises a great many rectangular corrugation legs 10, each
contained in a vertical plane at right angles to the direction D2.
With respect to an overall direction F of flow of the fluid in the
direction D1 in the passage in question, each leg has a leading
edge 11 and a trailing edge 12. The legs are connected alternately
along their upper edge by flat and horizontal rectangular
corrugation crests 13 and along their lower edge by corrugation
troughs 14 which are also rectangular, flat and horizontal.
[0012] The rows 9 are offset from one another in the direction D2,
in one direction and the other alternately. By terming distance p
separating two successive legs 10 as the "pitch" (neglecting the
thickness e of the thin-sheet material of which the corrugation is
made), the offset is p/2.
[0013] Thus, each row 9 is connected to the next row 9 by the
crests 13, in sections of straight line 15 measuring p/2, and by
the troughs 14, in sections of straight line 16 with the same
length p/2. The planes of offsetting are the vertical planes
P.sub.AB, P.sub.BC, etc., and the planes of offsetting when viewed
from above are denoted by 17.
[0014] Incidentally, the length of each row 9 in the direction D1
is denoted 1, this length being termed the "serration length", and
the height of the corrugation is denoted h.
[0015] In practice, the shapes of the various parts of the
corrugations may differ somewhat from the theoretical shapes
described hereinabove, particularly as regards the flatness of the
facets 10, 13 and 14, the verticality and the rectangular shape of
these facets.
[0016] FIGS. 3 to 5 of the appended drawings are schematic cross
sections taken, respectively, on the vertical plane III-III of FIG.
2, approximately on an offsetting plane P and on the horizontal
mid-plane Q of the corrugation. These views illustrate the
disadvantage of conventional serrated corrugations.
[0017] What happens is that a given stream of fluid flowing in the
overall direction D1 has available to it, within a row 9, for
example 9A, a wide passage cross section (FIG. 3), but this cross
section is reduced in each plane P because of the presence of the
legs 10 from the next row 9, in this instance the legs 10B of the
row 9B.
[0018] Thus, the characteristic offsetting of the serrated
corrugations introduces a substantial pressure drop. In order to
limit this effect, relatively long serration lengths 1 need to be
adopted, although these are not optimum from the thermal efficiency
standpoint.
[0019] The object of the present invention is to reduce or even to
eliminate the pressure drops induced in the serrated corrugations
by the offset from one row to the next.
[0020] To this end, a subject of the invention is a corrugated fin
with partial offset of the aforementioned type, characterized in
that at least some corrugation legs have a notch on at least one
edge and over at least part of their height.
[0021] Another subject of the invention is a plate-type heat
exchanger comprising corrugated fins as defined above. This
exchanger, of the type comprising a stack of parallel plates which
define a number of passages of flat overall shape for the
circulation of fluids, closure bars which delimit these passages,
and corrugated fins arranged in the passages, is characterized in
that at least some of the corrugated fins are according to the
definition provided above.
[0022] Some exemplary embodiments of the invention will now be
described with reference to FIGS. 6 to 17 of the appended drawings,
in which:
[0023] FIG. 6 depicts, in perspective, a corrugated fin according
to the invention;
[0024] FIGS. 7 to 13 are views similar to FIG. 6 but corresponding
to various other embodiments of the corrugated fin according to the
invention;
[0025] FIG. 14 is a view similar to FIG. 5 but relating to a
corrugated fin like those of FIGS. 6, 7 and 8;
[0026] FIG. 15 is a view similar to FIG. 14 but relating to a
corrugated fin like those of FIGS. 9, 10 and 11; and
[0027] FIGS. 16 and 17 are details of FIGS. 5 and 14 respectively,
illustrating one property of the corrugated fins according to the
invention.
[0028] In the embodiment of FIG. 6, each leg 10 comprises a notch
18 on its single leading edge 11. This notch 18 extends from the
trough 14 to mid-height, that is to say to the level h/2.
[0029] In each of FIGS. 6 to 13, two rows of corrugations 9A and 9B
have been depicted in perspective. The corrugation elements have
been given suffixes A and B according to the row to which they
belong.
[0030] The embodiment of FIG. 7 differs from that of FIG. 6 only in
that the notches 18, which again have the length h/2, are mid-way
along the leading edges 11 of the legs 10.
[0031] The embodiment of FIG. 8 differs from the preceding
embodiments only in that the notches 18 have the length h and
extend over the entire height of the leading edges 11, without,
however, affecting the crests 13 and the troughs 14.
[0032] The embodiment of FIG. 9 differs from the previous one only
in that the legs 10 also have a notch 21 over the entire height of
the height of their trailing edge 12, these notches 21 not
affecting the crests 13 and the troughs 14 either.
[0033] The corrugated fin of FIG. 10 differs from that of FIG. 7
only in the addition of a notch 21 of length h/2 mid-way along the
trailing edge 12 of each leg. As an alternative, the notches 18 and
21 may have a length other than h/2, and less than h.
[0034] In the embodiment of the corrugated fin of FIG. 11, each leg
10 has a notch 18 on its leading edge and a notch 21 on its
trailing edge; these two notches have the same height which is
between h/2 and h, and the same vertical position, but the notches
are offset vertically from one leg to the other. Thus, on one row
9A or 9B, from one leg to the next, the notches 18 and 21 are
alternately adjacent to the crest of the corrugation 13 and to the
trough 14.
[0035] The embodiment of FIG. 12 differs from that of FIG. 9 only
in that the notches 18 and 21 continue alternately into the crests
13 and into the troughs 14, weakening these. This weakening may be
disadvantageous in the case of fluids conveyed under pressure,
because it reduces the area of fin brazed to the adjacent plates of
the exchanger.
[0036] This is why it may be preferable, in certain applications,
as depicted in FIG. 13, in this variant to adopt an offset less
than p/2 from one row 9 to the next. This thus yields an advantage
of greater mechanical strength but, on the other hand, gives rise
to a loss of thermal efficiency.
[0037] As illustrated in FIGS. 14 and 15, in all the variant
embodiments of the fin 8 described above, the notches 18 or 18 and
21 (or 21) encourage two-dimensional flow of the fluid in the
region of the offsetting lines 17. Accordingly, the streams of
fluid coming from the various channels in the fin are partially
remixed. The efficiency of the heat exchange is thus improved.
[0038] When there is also a vertical offset between the notches 18
and 21, as in the case of FIG. 11, a three-dimensional effect is
introduced into the flow of the fluid, and this encourages heat
exchange even more.
[0039] A comparison between FIGS. 16 and 17, which respectively
illustrate the flow of a stream of fluid through a conventional
serrated corrugation (FIG. 16) and through a serrated corrugation
according to the invention (FIG. 17) shows that the pressure drop
by restriction at the passage of an offsetting line 17 is greatly
reduced if the passage cross section 22 defined by the notch 18 (or
by the notch 21 if only the trailing edge is notched, or by the
notches 18 and 21 facing each other) is at least equal to half the
passage cross section 23 of each channel defined between two legs
10. In effect, the throttling upon crossing the line 17 is then
eliminated.
[0040] The fins described hereinabove can be made of various
materials commonly used in plate-type heat exchangers: aluminum and
aluminum alloys, copper and copper alloys, stainless steels and
titanium.
* * * * *