U.S. patent application number 13/882729 was filed with the patent office on 2013-08-22 for multi-channel tube for heat exchangers, made of folded metal sheet.
The applicant listed for this patent is Giandomenico Cappello, Davide Perocchio, Giuseppe Tiziano. Invention is credited to Giandomenico Cappello, Davide Perocchio, Giuseppe Tiziano.
Application Number | 20130213623 13/882729 |
Document ID | / |
Family ID | 43743051 |
Filed Date | 2013-08-22 |
United States Patent
Application |
20130213623 |
Kind Code |
A1 |
Perocchio; Davide ; et
al. |
August 22, 2013 |
MULTI-CHANNEL TUBE FOR HEAT EXCHANGERS, MADE OF FOLDED METAL
SHEET
Abstract
A tube for a heat exchanger comprises a plate provided with a
plurality of parallel flow ports, wherein the plate is formed by a
single folded-up metal sheet and consists of an envelope formed by
a first portion of the metal sheet, and of a partition structure
formed by a second portion of the metal sheet, which extends in an
corrugated manner within the envelope so as to define said flow
ports therewith, and wherein the partition structure has a
substantially polygonal profile having connection segments
interconnecting opposite walls of the envelope and being interposed
between adjacent flow ports. The connection segments are slanted
relative to the opposite walls of the envelope, thereby defining an
angle a>0.degree. relative to the normal to said walls.
Inventors: |
Perocchio; Davide; (Poirino,
IT) ; Cappello; Giandomenico; (Poirino, IT) ;
Tiziano; Giuseppe; (Poirino, IT) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Perocchio; Davide
Cappello; Giandomenico
Tiziano; Giuseppe |
Poirino
Poirino
Poirino |
|
IT
IT
IT |
|
|
Family ID: |
43743051 |
Appl. No.: |
13/882729 |
Filed: |
November 4, 2011 |
PCT Filed: |
November 4, 2011 |
PCT NO: |
PCT/IB11/54920 |
371 Date: |
April 30, 2013 |
Current U.S.
Class: |
165/170 |
Current CPC
Class: |
F28F 1/025 20130101;
F28F 2275/045 20130101; F28F 3/12 20130101; F28D 1/0391 20130101;
F28F 1/022 20130101; F28F 2275/06 20130101 |
Class at
Publication: |
165/170 |
International
Class: |
F28F 3/12 20060101
F28F003/12 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 5, 2010 |
IT |
TO2010A000884 |
Claims
1-12. (canceled)
13. A tube for a heat exchanger, comprising a plate provided with a
plurality of parallel flow ports, wherein said plate is formed by a
single folded-up metal sheet and consists of an envelope formed by
a first portion of the metal sheet, and of a partition structure
formed by a second portion of the metal sheet, which extends in a
corrugated manner within the envelope so as to define said flow
ports along therewith, and wherein said partition structure has a
substantially polygonal profile having connection segments
interconnecting opposite walls of the envelope and being interposed
between adjacent flow ports, and wherein said connection segments
are inclined with respect to the opposite walls of the envelope,
thereby defining an angle .alpha.>0.degree. with respect to the
normal to said walls.
14. The tube according to claim 13, wherein at least the central
ports of said flow ports have an approximately trapezoid section,
and said partition structure further comprises base segments
alternated with said connection segments, approximately parallel to
the opposite walls of said envelope, and in contact to either one
thereof, wherein said base segments have a corrugated transversal
profile, thereby each of said base segments has, at the side ends
thereof, respective ridge portions which join each base segment to
the connection segments adjacent thereto, and a depression portion
interposed between said ridge portions, and defining a recess in
the transversal direction relative thereto.
15. The tube according to claim 13, wherein said partition
structure defines a plurality of corrugations, whose height h
before closing the envelope on said structure, intended as the
difference in height between the maximum and minimum height points
of the corrugations, is greater than the separation distance H
between the opposite walls of said envelope after the latter has
been closed.
16. The tube according to claim 13, said tube being intended to be
coupled to a distributor for a heat exchanger, and having an end
portion suitable to be inserted into a corresponding slot that is
provided on a wall of the distributor, wherein said end portion is
provided with abutment means suitable to define a stop position for
fitting said tube into the slot, said abutment means further
providing slanted surfaces relative to the outer surface of the
tube envelope, which are suitable to engage corresponding coupling
portions provided on the edge of the slot.
17. The tube according to claim 16, wherein said abutment means
comprise one or more projections and/or grooves provided on said
envelope.
18. The tube according to claim 16, wherein said abutment means
comprise an abutment length of said end portion of the tube, at
which the end portion of the tube is widthwise tapered towards the
axial end of the tube.
19. The tube according to claim 16, wherein said end portion of the
tube further comprises a fitting length, at which the end portion
of the tube is widthwise tapered towards the axial end of the tube,
in order to facilitate the fitting of the end portion into the
slot.
20. The tube according to claim 18, wherein said tube end portion
comprises in order, from the axial end towards the center of the
tube, a fitting length, at which the end portion of the tube is
widthwise tapered towards the axial end of the tube, in order to
facilitate the fitting at the end portion into the slot, a sealing
length and said abutment length, said sealing length being suitable
to engage the edge of the slot.
21. The tube according to claim 13, wherein at least the central
ports of said flow ports have an isosceles trapezoid cross section,
said connection segments defining an angle
0<.alpha..ltoreq.arccos(3/5) relative to the normal to the
opposite walls of the envelope.
22. The tube according to claim 13, wherein a first edge strip of
the metal sheet associated with the first portion of said sheet is
welded to the outer side of the envelope, and a second edge strip
of the metal sheet associated with the second portion of said
sheet, adjacent to the separation structure, is welded to the inner
side of the envelope.
23. The tube according to claim 22, wherein said edge strips of the
metal sheet are positioned at opposite side ends of the plate.
24. The tube according to claim 13, wherein said metal sheet has an
overall thickness d such as 0.2 mm.ltoreq.d.ltoreq.0.35 mm, and
has, on each face of the sheet, a clad of brazing filler metal with
a clad to core ratio c%, resulting from the ratio of the clad
thickness to the overall thickness d, 5%.ltoreq.c%.ltoreq.15%.
Description
[0001] The present invention relates to a tube for a
heat-exchanger, comprising a plate provided with a plurality of
parallel flow ports, [0002] wherein said plate is formed by a
single folded-up metal sheet and consists of an envelope formed by
a first portion of the metal sheet, and of a partition structure
formed by a second portion of the metal sheet, which extends in an
corrugated manner within the envelope so as to define said flow
ports along therewith, and [0003] wherein said partition structure
has a substantially polygonal profile with connection segments
interconnecting opposite walls of the envelope and being interposed
between adjacent flow ports.
[0004] Tubes of this type are particularly used in the assembly of
condensers for climatization systems, in the automotive or civil
fields.
[0005] Generally, multiple port tubes for heat exchangers can be
divided into three categories: electro-welded tubes with finned
insert, folded-up tubes with inner fin and folded-up tubes with a
single material.
[0006] The electro-welded tubes with finned insert suffer from the
most serious drawbacks relative to the fabrication process; these
problems are mainly due to: [0007] the quality of the welding
(seam), which is generally difficult to obtain and even more
difficult to control; [0008] the difficulty in forcibly fitting the
fin into the tube body. Different thicknesses are implied, the fin
thickness should be as low as possible and a deformation at the
ends thereof causes an irreparable obstruction to the coolant
flowing therethrough; [0009] the difficulty in providing the
contact between fin and tube to obtain the brazing between both
parts; [0010] the tube-finned insert brazing, which is carried out
in a controlled atmosphere and requires that each part of the heat
exchanger has to be reached by the antioxidant flow, and
consequently the tube interior, too; [0011] the production costs,
as the finished product is the result of several operations (making
of the tube, fin and assembly of both parts).
[0012] Folded-up tubes with inner fin suffer from the most serious
problems in the fabrication process, which are mainly due to:
[0013] the junction of two (inner and outer) bodies, the first
being made from a thinner material than the second, during the tube
folding and forming operations; [0014] the fact that a static phase
is reached, in which the two parts are in close contact to each
other; [0015] the cutting of the tube on line with a fin previously
fitted thereto (leading edge-trailing edge). This operation can
cause a deformation of the fin at the ends thereof, which is then
difficult to recover.
[0016] The best solution from the point of view of the process,
quality and fabrication costs results to be that of using folded-up
tubes with a single material.
[0017] Within this category, tubes with generally rectangular ports
are known.
[0018] An object of the present invention is to provide a multiple
port tube, of the folded-up type with a single material; which
allows to achieve better thermal exchange performances as compared
with conventional tubes. Another object of the present invention is
to provide a multiple-port tube which further allows reducing the
consumption of raw material for making the same.
[0019] This object is achieved according to the invention by means
of a tube of the type as defined in the preamble herein, wherein
said connection segments are inclined with respect to the opposite
walls of the envelope, thereby defining an angle
.alpha.>0.degree. with respect to the normal to said walls.
[0020] With a tube according to this solution idea, significant
improvements can be achieved as compared with conventional
folded-up tubes, given that: [0021] with the hydraulic diameter,
and consequently the thermal exchange performance of the tube being
the same, a lower number of ports can be made available as compared
with a rectangular port tube; [0022] a lower number of ports
corresponds to a lower amount of raw material used to obtain a
finished tube.
[0023] Furthermore, in case the flow ports have a trapezoid
section, within a determined range of values of the angle a, a
material saving can be obtained as compared with a tube with
rectangular ports, with the number of ports being the same.
[0024] Preferred embodiments of the invention are as defined in the
dependent claims, which should be intended as an integral part of
the present description.
[0025] Further characteristics and advantages of the tube according
to the invention will be more apparent with the following detailed
description of an embodiment of the invention, given with reference
to the annexed drawings, which are provided by way of a
non-limiting illustration thereof, in which:
[0026] FIG. 1 is a cross-sectional view of a multiple port tube,
with rectangular section ports;
[0027] FIG. 2 is a cross-sectional view of a multiple port tube,
with trapezoid section ports according to the invention;
[0028] FIG. 3 is a cross-sectional view of a multiple port tube,
with triangular section ports according to the invention;
[0029] FIGS. 4 and 5 are illustrative drawings showing the
advantageous features of the tube according to the invention as
compared with conventional tubes;
[0030] FIG. 6 shows the graph of a function f(.alpha.) related to
the consumption of material for a tube with trapezoid ports, based
on the angle .alpha.;
[0031] FIG. 7 shows the graph of a function h'(.alpha.) related to
the saving of material for a tube with trapezoid ports, based on
the angle .alpha.;
[0032] FIG. 8 is a perspective view of an end portion of a
multiple-port tube according to the invention;
[0033] FIG. 9 is a cross-sectional view of a cylindrical
distributor, to which a tube according to the invention has been
assembled;
[0034] FIG. 10 is a sectional view in an enlarged scale of a detail
in FIG. 9, taken on a plane parallel to that in FIG. 9, and
intersecting the multiple-port tube;
[0035] FIGS. 11 to 13 are perspective views of different
embodiments of multiple-port tubes according to the invention;
[0036] FIG. 14 is a cross-sectional view of a variant embodiment of
a tube with approximately trapezoid section ports; and
[0037] FIG. 15 is a cross-sectional view of a tube with trapezoid
section ports, which highlights several geometric characteristics
of the tube.
[0038] With reference to FIG. 1, a cross section of a multiple-port
tube 1 for a heat exchanger has been illustrated comprising a plate
provided with a plurality of parallel flow ports 2, 3 suitable for
one or more fluids to flow therein, depending on the use that will
be made of the tube 1. The central ports 2 of the tube 1 in FIG. 1
have a rectangular section, whereas the peripheral ports 3 have a
section depending on the configuration of the side ends of the
plate of tube 1.
[0039] With reference to FIG. 2, a cross section of a multiple-port
tube 10 for a heat exchanger has been illustrated, which comprises
a plate 11 provided with a plurality of parallel flow ports 20, 30
suitable for one or more fluids to flow therein, depending on the
use that will be made of the tube 10. The central ports 20 of the
tube 10 in FIG. 2 have a trapezoid section, whereas the peripheral
ports 30 have a section depending on the configuration of the side
ends of the plate 11 of tube 10.
[0040] With reference to FIG. 3, another embodiment of the
invention is illustrated, in which the central ports have a
triangular section. In this embodiment, the same numerals have been
used for those elements that correspond to those of the previous
embodiments.
[0041] With reference to FIGS. 2 and 3, the plate 11 of the tube 10
is made from a single folded-up metal sheet, for example aluminum
sheet. Preferably, this metal sheet has an overall thickness d such
as 0.2 mm.ltoreq.d.ltoreq.0.35 mm, and has, on each face of the
sheet, a clad of brazing filler metal (e.g., low-melting aluminum
alloy) with a clad to core ratio c%, resulting from the ratio of
the clad thickness to the overall thickness d, such as
5%.ltoreq.c%.ltoreq.15%.
[0042] The plate 11 consists of an envelope 12 formed by a first
portion of the metal sheet, and of a partition structure 14 formed
by a second portion of the metal sheet, which extends in an
corrugated manner within the envelope 12 in order to define the
flow ports 20, 30 therewith.
[0043] The corrugations of the partition structure 14 have a
polygonal profile, whereby the whole separation structure 14 has
also a polygonal profile. Particularly, in the embodiment in FIG. 2
the partition structure 14 comprises base segments 14a, parallel to
the opposite main walls 12a, 12b of the envelope 12 of the plate
and in contact with either one of the latter, which base segments
14a are alternated with slanted connection segments 14b. The
connection segments 14b thus interconnect the opposite walls 12a,
12b of the envelope and are interposed between adjacent flow ports.
In the embodiment in FIG. 3, the partition structure 14 only
comprises oblique connection segments 14b, as the base segments are
reduced to the edges at which the connection segments are joined to
each other, and which are in contact with either one of the
opposite main walls 12a,12b of the plate envelope 12. The joints
between base segments 14a and connection segments 14b (example in
FIG. 2), or the joints between connection segments 14b (example in
FIG. 3) can have a certain bending.
[0044] In the examples illustrated herein, in order to seal the
folded-up metal sheet, a first edge strip 17 of the metal sheet
associated with the first portion of this sheet is welded to the
outer side of the envelope 12, and a second edge strip 18 of the
metal sheet, associated with the second portion of this sheet and
adjacent to the partition structure, is welded to the inner side of
the envelope 12. Particularly, the edge strips 17, 18 of the metal
sheet are located at opposite ends of the plate.
[0045] It is now demonstrated that the tubes 10 according to the
invention, which have either triangular or trapezoid ports, allow
to obtain a desired hydraulic diameter O.sub.i (O.sub.i=4S/P, where
S=gas flow inner area and P=wet inner perimeter) with a lower
number of port than they would require if they had a rectangular
geometry.
[0046] With reference to FIGS. 4 and 5, it is assumed to compare
tubes having rectangular, trapezoid, and triangular ports, and to
switch from one shape to another by rotating the vertical side of
the rectangle about a point A, A' positioned half-way along that
side.
[0047] With reference to the figures, from the construction method
there results that 2L=a+c=B, where L is the length of the rectangle
base, a is the length of the trapezoid large base, c is the length
of the trapezoid small base, and B is the length of the triangle
base.
[0048] The following assumptions are also made during the
comparison: [0049] the tubes involved in the comparison have equal
overall height and width; [0050] the tubes involved in the
comparison have the same number of ports; [0051] the tubes involved
in the comparison are obtained from an equally thick coil; [0052]
finally, referring to the angle .alpha. as indicated in the
figures, with reference to the normal to the main walls 12a, 12b of
the plate, it is also assumed to work in the interval
0<.alpha.<90.degree..
[0053] As to the central ports 20, it is now demonstrated that the
wet perimeter is increased when switching from the rectangular to
the triangular shape, while the passage area is unchanged. As to
the side ports 30, it is assumed that the differences between
perimeter and area are neglectable.
[0054] With reference to FIG. 4, wherein, according to the above,
B=2L, it is demonstrated that the wet perimeter of the triangular
section is greater than the rectangular section
0<.alpha.<90.degree., i.e. the following relations holds
true:
(2T+B)/(2L+H)>1 (1) [0055] where T is the length of the triangle
hypotenuse, and H is the height that is assumed equal both for
triangle and rectangle.
[0056] In fact, given B=2L (hypothesis),
and also given H/T=cos.alpha., from which: T=H/cos.alpha., there
results T>H being: cos.alpha.<1 within the interval
0<.alpha.<90.degree..
[0057] According to the above, therefore: 2T>2H, per
0<.alpha.<90.degree., which demonstrates the expression
(1).
[0058] With reference to FIG. 5, wherein, for constructional
reasons, c+.alpha.=2L, it is demonstrated that the wet perimeter of
the trapezoid section is greater than that of the rectangular
section 0<.alpha.<90.degree., i.e. the following relation
holds true:
(2T+c+a)/(2L+2H)>1 (2)
where H is the height that is assumed equal for both trapezoid and
rectangle.
[0059] In fact, given c+a=2L (hypothesis),
and further given H/T=cos.alpha., from which: T=H/cos.alpha., there
results T>H, being: cos.alpha.<1 within the interval
0<.alpha.<90.degree..
[0060] According to the above, therefore: 2T>2H, for
0<.alpha.<90.degree., which demonstrates the expression
(2).
[0061] It will be now demonstrated that the port passage area
remains unchanged. Assuming that the differences in the side port
30 areas are neglectable, it is clear that the rectangular port 2
areas coincide with the triangular port 20 areas. In fact, given
B=2L;
Triangle area=(B*H)/2=(2L*H)/232 H*L=rectangle area (QED)
[0062] This assumption holds true also for the trapezoid ports 20;
in fact, given the sum of the small base and large base of the
trapezoid is 2L, then:
Trapezoid area=((a+c)*H)/2=(2*L*H)/2=H*L=rectangle area (QED)
[0063] It will be now demonstrated that, for multiple-port
folded-up tubes with trapezoid section ports the consumption of
material (coil) for slanting .alpha. the connection segments 14b of
the partition wall 14 ranging between 0 and arccos(3/5), i.e. about
53.13.degree. can be reduced.
[0064] With reference to FIG. 5, by rotating the vertical sides of
the rectangle about the points A and A' and given that:
H/T=cos.alpha., it is clear that the length increase .DELTA.1 in
the trapezoid side relative to the rectangle side can be expressed
as follows:
.DELTA.1=T-H=T-Tcos.alpha.=T*(1-cos.alpha.)
[0065] The increase in the material of the trapezoid port, as
compared with the rectangular port, can be thus expressed as
follows:
Material increase=2T*(1-cos.alpha.) (3)
[0066] With further reference to FIG. 5, the reduction in the
length .DELTA.b of the small base of the trapezoid relative to the
rectangle base, which reduction can be intended as a reduction in
the material of the trapezoid port as compared with the rectangular
couterpart thereof, can be expressed as follows:
Material reduction=.DELTA.b=Tsen.alpha. (4)
[0067] In order that the switching beween rectangular sections to
trapezoid sections results in a reduction in the coil consumption,
the following inequality shall be proved:
reduction in material increase in material > 1 ##EQU00001##
[0068] Using the expressions (3) and (4), the inequality
becomes:
.DELTA. b 2 * .DELTA. l = T * sen .alpha. 2 * T * ( 1 - cos .alpha.
) = sen .alpha. 2 * ( 1 - cos .alpha. ) > 1 ( 5 )
##EQU00002##
[0069] By diagramming the function
f(.alpha.)=sen.alpha./(2*(1-cos.alpha.)) in the interval
0<.alpha.<90.degree., it is obtained that this function is
greater than 1 for .alpha. between 0 and arccos(3/5), as
highlighted in the diagram in FIG. 6.
[0070] N being the number of ports, the material saving obtained in
the central ports when a trapezoid section is used instead of a
rectangular section can be thus expressed as follows:
h ( .alpha. ) = ( N - 2 ) ( .DELTA. b - 2 .DELTA. l ) = = ( N - 2 )
[ Tsen .alpha. - 2 T ( 1 - cos .alpha. ) ] = = ( N - 2 ) T [ sen
.alpha. - 2 ( 1 - cos .alpha. ) ] = = ( N - 2 ) ( H / cos .alpha. )
( sen .alpha. - 2 + 2 cos .alpha. ) = = ( N - 2 ) H [ tg .alpha. -
2 / cos .alpha. + 2 ] ##EQU00003##
[0071] The function h(.alpha.) shows that the reduction in the
material consumption (resulting from the use of trapezoid ports
instead of rectangular ports) is directly proportional to the
number of ports and tube height. This reduction further depends on
the function h'(.alpha.) as defined below:
h'(.alpha.)=tg.alpha.-2/cos.alpha.+2
[0072] This function becomes zero at the angle .alpha.=0 (i.e. when
the trapezoid is collapsed into the rectangle) and
.alpha.=arccos(3/5) (which is the angle at which the function
f(.alpha.) is 1, i.e. the angle beyond which the trapezoid geometry
is no longer convenient in terms of material saving as compared
with the rectangular geometry) and has a peak about the angle
.alpha.=30.degree. approximately, as shown in FIG. 7.
[0073] The above-described tube is intended to be assembled, at
each end thereof, to a heat exchanger distributor or collector.
This assembly is carried out by fitting the end of the tube into a
corresponding slot provided on the distributor outer wall.
[0074] To the purpose, a preferred embodiment of the invention is
illustrated in FIGS. 8 to 10, which show an end portion 40 of the
tube 10 according to the invention, and a distributor 50 to which
the tube 10 is assembled. In order to allow for the coupling of the
tube 10 to the distributor 50, a slot 51 is provided on the outer
wall of the latter for fitting the end portion 20 of the tube
10.
[0075] Particularly, the end portion 40 of the tube 10 comprises in
order, from the axial end to the center of the tube, a fitting
length 42, a sealing length 44 and an abutment length 46. At the
fitting length 42, the end portion 40 of the tube 10 has bevelled
side edges or is, more generally, widthwise tapered towards the
axial end of the tube, in order to facilitate fitting the portion
40 into the slot 51. The sealing length 44 of the end portion 40 of
the tube 10 is, on the contrary, suitable to engage the edge of the
slot 51. At the abutment length 46, the end portion 40 of the tube
10 has bevelled side edges or is, more generally, widthwise tapered
towards the axial end of the tube. This length 46 defines an
abutment position for fitting the end portion 40 into the slot 51,
and simultaneously provides slanting surfaces in order to
compensate for any clearance between the tube 10 and the slot 51
and to prevent (by friction) any relative rotation between the
distributor and the tube which can occur during the brazing
process. To the purpose, the slot 51 edge is provided with a
matching coupling portion 53 (seen in FIG. 10) which is suitable to
be engaged by the abutment length 46 of the end portion 40 of the
tube 10, at which the slot 51 has bevelled edge side faces or, more
generally, it has a section widthwise tapered inwardly of the
distributor. This coupling portion can be obtained, for example, by
means of cutting.
[0076] The end portion 40 of the tube 10 as shown in FIG. 8 can be
obtained by means of stock removal processing, wherein a tool, for
example a laser beam or finger bit, processes the side edges of the
multiple-port tube 10 such that the desired profile is
obtained.
[0077] According to other embodiments, as shown in FIGS. 11 to 13,
formations provided on the envelope 12 of the tube 10 act as
abutment and rotation-restraining elements. In FIG. 11, these
formations consist of point bosses 46' provided on both main faces
of the envelope 12 and projecting outwards from the surface of this
envelope, which provide slanted surfaces suitable to engage
corresponding coupling portions provided on the edge of the slot
51. In FIG. 12, the abutment and anti-rotation formations consist
of linear bosses 46'' provided on the two main faces of the
envelope 12, which are transversally extended relative to the tube
10 and outwardly project from this tube envelope surface. Similarly
to the point bosses 46', the linear bosses 46'' provide slanted
surfaces which are suitable to engage corresponding coupling
portions which are provided on the slot 51 edge. According to a
further embodiment, not illustrated herein, the abutment and
anti-rotation function can be provided by a collar surrounding the
entire tube section. In FIG. 13, the abutment and anti-rotation
formations consist of linear grooves 46''' provided on the two main
faces of the envelope 12, which are transversally extended relative
to the tube 10 and inwardly recessed within the tube. The linear
grooves 46''' provide slanted surfaces which are suitable to engage
corresponding coupling portions which are provided on the slot 51
edge. In this case, it is provided that, during the assembly step
the slot 51 edge is elastically deformated to allow for the tube
being fitted into the slot 51 to the position of the linear grooves
46'''.
[0078] With reference to FIG. 14, a preferred variant embodiment of
the multiple port tube with trapezoid section ports will be now
described, wherein the base segments 14a of the separation
structure 14 have an corrugated transversal profile, instead of
being substantially flat. Particularly, each of these base segments
14a having an corrugated profile has, at the side ends thereof,
respective ridge portions 14c which join each base segment 14a to
the connection segments 14b adjacent thereto, and a depression
portion 14d interposed between the ridge portions 14c, and defining
a recess in the transversal direction relative to the ridge
portions. For each base segment 14a the ridge portions 14c thus
provide two points of contact with the wall of the envelope 12,
thereby improving the brazability of this envelope segment. In the
meanwhile, the depression portion 14d cooperates with the envelope
12 wall to form a cavity suitable to collect the plating material
melted during the brazing process. Preferably, the pitch Po of the
corrugations is such that 1 mm.ltoreq.Po.ltoreq.5 mm, the distance
Pc between the ridge portions 14c of a base segment 14a is such
that 0.241 mm .ltoreq.Pc.ltoreq.1.205 mm (Pc being approximately
0.241 Po), and the depth g of the depression portion 14d is such
that 0.05 mm.ltoreq.g.ltoreq.0.20 mm.
[0079] With reference to FIG. 15, a solution will be now described
to provide a greater contact area between the corrugation ridges of
the partition structure 14 and the envelope 12 wall of the tube 10,
and thereby improve the efficacy of the brazing process. This
solution consists in providing that the height h of the
corrugations of the partition structure 14, intended as the
difference in height between the corrugation maximum and minimum
points, before the envelope 12 is closed on said structure, is
greater than the separation distance H between the main walls 12a
and 12b of the envelope 12 after it has been closed. The
compressive elastic strain of the partition structure corrugations
creates a "spring effect" which provides for a greater contact area
between the ridges of the partition structure 14 corrugations and
the wall of the envelope 12 of the tube 10. The dotted line S in
FIG. 15 represents the virtual profile that the tube would have due
to the height h of the partition structure 14 corrugations if the
compression of the tube were not operated in the direction
perpendicular to the walls 12a and 12b of the envelope, and
accordingly it gives a qualitative measure of the spring effect
that is obtained when the tube 10 is closed. The solution for
obtaining the above-described elastic effect can be applied to any
profile of the corrugations of the tube separation structure
according to the invention.
* * * * *