U.S. patent application number 16/636165 was filed with the patent office on 2020-11-26 for heat exchanger comprising a multi-channel distribution element.
The applicant listed for this patent is L'Air Liquide, Societe Anonyme pour l'Etude et I'Exploitation des Precedes Georges Claude. Invention is credited to Sebastien CADALEN, Frederic CRAYSSAC, Quentin SANIEZ, Marc WAGNER.
Application Number | 20200370836 16/636165 |
Document ID | / |
Family ID | 1000005022107 |
Filed Date | 2020-11-26 |
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United States Patent
Application |
20200370836 |
Kind Code |
A1 |
CRAYSSAC; Frederic ; et
al. |
November 26, 2020 |
HEAT EXCHANGER COMPRISING A MULTI-CHANNEL DISTRIBUTION ELEMENT
Abstract
A heat exchanger of the brazed plate and fin type, including a
plurality of plates arranged in a mutually parallel manner so as to
define at least one set of passages for a first fluid configured to
exchange heat with at least a second fluid to flow through, the
passages extending in a longitudinal direction and a lateral
direction perpendicular to said longitudinal direction, each
passage being divided, in the longitudinal direction, into at least
one distribution zone and one heat-exchange zone, the at least one
distribution zone of a passage comprising a distribution element,
said distribution element including a plurality of dividing walls
arranged so as to divide said distribution zone into a plurality of
channels for the first fluid to flow through.
Inventors: |
CRAYSSAC; Frederic; (Velizy,
FR) ; CADALEN; Sebastien; (Paris, FR) ;
WAGNER; Marc; (Saint Maur des Fosses, FR) ; SANIEZ;
Quentin; (Paris, FR) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
L'Air Liquide, Societe Anonyme pour l'Etude et I'Exploitation des
Precedes Georges Claude |
Paris |
|
FR |
|
|
Family ID: |
1000005022107 |
Appl. No.: |
16/636165 |
Filed: |
July 16, 2018 |
PCT Filed: |
July 16, 2018 |
PCT NO: |
PCT/FR2018/051804 |
371 Date: |
February 3, 2020 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
F28F 3/025 20130101;
F25J 5/002 20130101; F28F 9/0268 20130101; F28D 9/0062 20130101;
F25J 2290/32 20130101; F28D 2021/0033 20130101 |
International
Class: |
F28D 9/00 20060101
F28D009/00; F25J 5/00 20060101 F25J005/00 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 4, 2017 |
FR |
1757539 |
Claims
1.-17. (canceled)
18. A heat exchanger of the brazed plate and fin type, comprising:
a plurality of plates arranged in a mutually parallel manner so as
to define at least one set of passages for a first fluid configured
to exchange heat with at least a second fluid to flow through, the
passages extending in a longitudinal direction and a lateral
direction perpendicular to said longitudinal direction, each
passage being divided, in the longitudinal direction, into at least
one distribution zone and one heat-exchange zone, the at least one
distribution zone of a passage comprising a distribution element,
said distribution element comprising a plurality of dividing walls
arranged so as to divide said distribution zone into a plurality of
channels for the first fluid to flow through, said channels
defining flow paths of different lengths and having variable
passage sections for fluid along said flow paths, wherein in that
the dividing walls of the distribution element are secured together
via a support, said support being brazed to an adjacent plate.
19. The heat exchanger as claimed in claim 18, wherein the dividing
wall project from the support into the passage.
20. The heat exchanger as claimed in claim 19, wherein the support
comprises a flat bottom, the dividing walls projecting
perpendicularly to the bottom.
21. The heat exchanger as claimed in claim 18, further comprising a
first end forming an inlet or an outlet for the first fluid and a
second end fluidically connected to the heat-exchange zone when the
distribution element is arranged in a distribution zone, each
dividing wall being formed from a single part and extending
continuously from the first end to the second end.
22. The heat exchanger as claimed in claim 21, wherein each channel
is provided with a first opening and a second opening situated at
the first and second ends, respectively, at least one first opening
having a passage section for fluid that is different than the
passage section for fluid of another first opening, and/or at least
one second opening having a passage section for fluid that is
different than the passage section for fluid of another second
opening.
23. The heat exchanger as claimed in claim 22, wherein the first
openings and/or the second openings of one and the same channel
have passage sections for fluid that are larger the longer the flow
path defined by said channel.
24. The heat exchanger as claimed in claim 18, wherein one or more
channels comprise means for modifying the linear flow resistance of
said channels.
25. The heat exchanger as claimed in claim 24, wherein said means
comprise a shape of the interior profiles of said channels.
26. The heat exchanger as claimed in claim 24, wherein said means
comprise partitions arranged within said channels.
27. The heat exchanger as claimed in claim 24, wherein said means
comprise porous structures arranged within said channels.
28. The heat exchanger as claimed in claim 18, wherein the dividing
walls have rectilinear profiles in longitudinal section.
29. The heat exchanger as claimed in claim 18, wherein the dividing
walls have predetermined curvilinear profiles in longitudinal
section.
30. The heat exchanger as claimed in claim 29, wherein said
predetermined curvilinear profiles comprise at least one inflection
point.
31. The heat exchanger as claimed in claim 18, wherein the
distribution element extends along a length in a longitudinal
direction and across a width in a lateral direction, the ratio
between a length and the width being less than 20%.
32. The heat exchanger as claimed in claim 18, wherein the
distribution element extends along a length less than 500 mm.
33. The heat exchanger as claimed in claim 18, wherein the
distribution element has a height, measured in a vertical direction
orthogonal to the plates, of at least 2 mm.
34. The heat exchanger as claimed in claim 18, wherein the
distribution element is a monolithic element manufactured by an
additive manufacturing method or by casting.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application is a 371 of International PCT Application
No. PCT/FR2018/051804, filed Jul. 16, 2018, which claims priority
to French Patent Application No. 1757539, filed Aug. 4, 2017, the
entire contents of which are incorporated herein by reference.
BACKGROUND
[0002] The present invention relates to a distribution element
configured to be arranged in a distribution zone of a heat
exchanger of the plate and fin type, and to a heat exchanger
comprising such a distribution element and at least one set of
passages for a fluid to be put into a heat-exchange relationship
with at least one other fluid. The element according to the
invention allows more homogeneous distribution of the fluid across
the width of said passages.
[0003] The present invention finds application notably in the field
of the cryogenic separation of gases, in particular the cryogenic
separation of air, in what is known as an ASU (air separation unit)
used to produce pressurized gaseous oxygen. In particular, the
present invention may be applied to a heat exchanger that vaporizes
a flow of liquid, for example oxygen, nitrogen and/or argon by
exchange of heat with a gas.
[0004] The present invention may also be applied to a heat
exchanger that vaporizes at least one flow of liquid-gas mixture,
in particular a flow of multi-constituent mixture, for example a
mixture of hydrocarbons, through exchange of heat with at least one
other fluid, for example natural gas.
[0005] The technology commonly used for a heat exchanger is that of
aluminum brazed plate and fin heat exchangers, which make it
possible to obtain devices that are very compact and afford a large
heat-exchange surface area.
[0006] These heat exchangers comprise plates, between which are
inserted heat-exchange corrugations, formed of a succession of fins
or corrugation legs, thereby constituting a stack of passages for
the various fluids to be put into a heat-exchange relationship.
[0007] These passages comprise zones referred to as distribution
zones, which are arranged, in the overall direction of flow of the
fluid in the passage in question, upstream and downstream of the
actual heat-exchange zone. The distribution zones are fluidly
connected to semi-tubular headers configured to distribute the
various fluids selectively to the various passages, and to remove
said fluids from said passages.
[0008] In a known way, these distributors generally comprise
distribution corrugations, arranged in the form of corrugated
sheets between two successive plates. The distribution corrugations
are generally perforated straight corrugations cut into the shape
of triangles or trapeziums. They divert the fluid coming from the
inlet header of the heat exchanger in order to spread it across the
width of the heat-exchange zones, and recover the fluid coming from
said heat-exchange zone. The distribution corrugations also act as
spacers in order to ensure the mechanical integrity upon brazing
and during operation of the distribution zone of the passage. Such
distribution corrugations are known from the documents U.S. Pat.
No. 6,044,902 and EP-A-0507649. Also known, from the document
EP-A-3150952, is a plate heat exchanger in which the distribution
elements are formed by the actual plates, which are pressed.
[0009] One of the problems that arise with the configuration of the
current distribution zones is the poor distribution of fluids
toward toward the heat-exchange zones. Specifically, the
distribution zones are occupied by at least two pads of
corrugations in order to optimize the offcuts from the shaping
process, thus increasing the risk of clearance between the pads.
The assembly of the corrugation pads can also cause incidents along
the flow path of the fluid, and this contributes to increasing the
pressure drops in the distribution zones. Because of these
imperfections in the distribution zones, variations in flow rate
with an amplitude of around 10% may arise, these being detrimental
to the correct operation of the heat exchanger.
[0010] Similarly, distribution defects are found in the
distribution zones dedicated to the recovery of the fluids coming
from the heat-exchange zones.
[0011] Another problem relates to the mechanical integrity of the
distribution zones. Specifically, these zones are provided with
corrugations with lower densities, typically between 6 and 10 legs
per inch, than those of the heat-exchange zones. Currently, the
distribution zone of a passage extends typically along a length,
measured in a longitudinal direction corresponding to the direction
of flow of the fluid in the heat-exchange zone of the same passage,
of around 200 to 600 mm, and across a width, measured
perpendicularly to said longitudinal direction, of around 500 to
1500 mm. Since the distribution zones constitute parts with lower
mechanical integrity than the heat-exchange zones, it is desirable
to limit the longitudinal extent thereof as much as possible in
order to ensure better resistance of the heat exchanger during the
circulation of fluids at high pressure within the passages.
SUMMARY
[0012] It is an object of the present invention to fully or
partially solve the abovementioned problems, notably by proposing a
heat exchanger in which the distribution of the fluid(s) in the
heat-exchange zones is as uniform as possible, and which also has
distribution zones that take up less space than in the prior
art.
[0013] The solution according to the invention is therefore a heat
exchanger of the brazed plate and fin type, comprising: [0014] a
plurality of plates arranged in a mutually parallel manner so as to
define at least one set of passages for a fluid intended to
exchange heat with at least one other fluid to flow through, the
passages extending in a longitudinal direction and a lateral
direction perpendicular to said longitudinal direction, [0015] each
passage being divided, in the longitudinal direction, into at least
one distribution zone and one heat-exchange zone, [0016] at least
one distribution zone of a passage comprising a distribution
element, said distribution element comprising a plurality of
dividing walls arranged so as to divide said distribution zone into
a plurality of channels for the fluid to flow through, said
channels defining flow paths of different lengths and having
variable passage sections for fluid along said flow paths.
[0017] As the case may be, the element of the invention may
comprise one or more of the following technical features: [0018]
the dividing walls of the distribution element are secured together
via a support, [0019] the support is brazed to an adjacent plate.
[0020] the dividing walls project from the support into the
passage. [0021] the support comprises a flat bottom, the dividing
walls projecting perpendicularly to the bottom. [0022] the element
comprises a first end forming an inlet or an outlet for the fluid
and a second end fluidically connected to the heat-exchange zone
when the distribution element is arranged in a distribution zone,
each dividing wall being formed from a single part and extending
continuously from the first end to the second end. [0023] each
channel is provided with a first opening and a second opening
situated at the first and second ends, respectively. [0024] at
least one first opening has a passage section for fluid that is
different than the passage section for fluid of another first
opening, and/or at least one second opening has a passage section
for fluid that is different than the passage section for fluid of
another second opening. [0025] the first openings and/or the second
openings of one and the same channel have passage sections for
fluid that are larger the longer the flow path defined by said
channel. [0026] one or more channels comprise means for modifying
the linear flow resistance of said channels. [0027] said means
comprise a shape of the interior profiles of said channels. [0028]
said means comprise partitions arranged within said channels.
[0029] said means comprise porous structures, for example metal
foams, arranged within said channels. [0030] the dividing walls
have rectilinear profiles in longitudinal section. [0031] the
dividing walls have predetermined curvilinear profiles in
longitudinal section. [0032] said predetermined curvilinear
profiles comprise at least one inflection point. [0033] the
distribution element extends along a length in a longitudinal
direction and across a width in a lateral direction, the ratio
between a length and the width being less than 20%, preferably
between 5 and 10%. [0034] the distribution element extends along a
length less than 500 mm, preferably between 50 and 200 mm. [0035]
the distribution element has a height, measured in a vertical
direction orthogonal to the plates, of at least 2 mm, preferably at
least 5 mm, preferably a height of between 2 and 15 mm. [0036] the
distribution element is a monolithic element, preferably
manufactured by an additive manufacturing method or by casting.
BRIEF DESCRIPTION OF THE DRAWINGS
[0037] The present invention will now be understood better by
virtue of the following description, which is given solely by way
of nonlimiting example and with reference to the appended drawings,
in which:
[0038] FIG. 1 is a three-dimensional schematic view of a heat
exchanger of the plate and fin type;
[0039] FIG. 2 is a partial schematic view in longitudinal section
of a distribution zone according to one embodiment of the
invention;
[0040] FIG. 3A is a partial schematic view in longitudinal section
of distribution zones according to other embodiments of the
invention;
[0041] FIG. 3B is a partial schematic view in longitudinal section
of distribution zones according to other embodiments of the
invention;
[0042] FIG. 4 is a partial schematic view in longitudinal section
of distribution zones according to other embodiments of the
invention;
[0043] FIG. 5A is a schematic view in longitudinal section of a
distribution zone according to another embodiment of the
invention;
[0044] FIG. 5B is a three-dimensional schematic view of a
distribution zone according to another embodiment of the
invention;
[0045] FIG. 6A presents a result of a simulation carried out with a
distribution element as depicted schematically in FIG. 5B;
[0046] FIG. 6B presents a result of a simulation carried out with a
distribution element as depicted schematically in FIG. 58;
[0047] FIG. 6C presents a result of a simulation carried out with a
distribution element as depicted schematically in FIG. 5B;
[0048] FIG. 7 presents a result of a simulation carried out with a
distribution element as depicted schematically in FIG. 5.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
[0049] As can be seen in FIG. 1, a heat exchanger 1 of the plate
and fin type comprises a stack of plates 2 that extend in two
dimensions, length and width, in the longitudinal direction z and
the lateral direction y, respectively. The plates 2 are disposed
parallel to and above one another with a spacing, and thus form
several sets of passages 3, 4, 5 for fluids F1, F2, F3 to be put
into an indirect heat-exchange relationship via the plates 2. The
lateral direction y is orthogonal to the longitudinal direction z
and parallel to the plates 2. Preferably, the longitudinal axis is
vertical when the heat exchanger 1 is in operation.
[0050] Preferably, each passage has a flat and parallelepipedal
shape. The passages extend lengthwise in the longitudinal direction
z and widthwise in the lateral direction y. The separation between
two successive plates is small in comparison with the length and
the width of each successive plate.
[0051] Each passage 3, 4, 5 is divided, in the longitudinal
direction z, into at least one distribution zone 20 and one
heat-exchange zone 21. The flow of the fluids within the
distribution zones takes place overall parallel to the longitudinal
direction z. The distribution zone 20 and heat-exchange zone 21 are
preferably juxtaposed along the longitudinal axis z.
[0052] According to the depiction in FIG. 1, considering in
particular the passage 3, the internal part of which has been made
visible, two distribution zones 20 are arranged on either side of
the heat-exchange zone 21, one serving to carry the fluid F1 toward
the heat-exchange zone 21 and the other serving to evacuate it from
said zone. Conventional distribution corrugations made in the form
of corrugated products are shown in the distribution zones 20.
[0053] In a manner known per se, the heat exchanger 1 comprises
semi-tubular headers 7, 9 provided with openings 10 for introducing
the fluids into the heat exchanger 1 and evacuating the fluids from
the heat exchange 1. These headers have openings that are less wide
than the passages. The distribution zones 20 serve to distribute
the fluids introduced through the openings in the headers across
the entire width of the passages.
[0054] According to the invention, a distribution element is
arranged in at least one distribution zone 20 of a passage 3 of the
heat exchanger, this element comprising a plurality of dividing
walls 25 that are arranged so as to divide said distribution zone
20 into a plurality of channels 26 for the fluid F1 to flow
through. Said channels 26 define flow paths with different lengths
and have variable passage sections for fluid along said flow paths.
Subdividing the distribution zone into a plurality of separate
channels with variable lengths and sections makes it possible to
divert the fluid while finely controlling the flow conditions for
the fluid within each channel. In particular, it is possible to
balance out the velocities of the fluid flowing through the
different channels, so as to obtain more or less identical fluid
velocities at the outlet of each channel, and hence a uniform or
quasi-uniform distribution of the fluid across the width of the
passages at the outlet of the distribution zone, while minimizing
pressure drops in the distribution zone.
[0055] Moreover, the distribution element confers structural
rigidity on the distribution zone of the heat exchanger since the
spacer function can be ensured by the dividing walls.
[0056] It should be noted that, within the scope of the invention,
the heat exchanger is of the brazed plate and fin type, meaning
that the separate elements that make up the heat exchangers are
secured, directly or indirectly, by brazing. The distribution
element according to the invention is separate from the plates
2.
[0057] "Brazed support" is understood as meaning that the support
is connected or secured by brazing to an adjacent plate of the heat
exchanger via at least a portion of the respective surfaces
thereof.
[0058] It should be noted that the expression "passage section for
fluid" means the area through which the fluid flows within the
channel, this being measured in a plane perpendicular to the
direction of movement of the fluid F1 in said channel, i.e.
perpendicular to the stream lines of the moving fluid F1.
[0059] The length of the flow paths is understood to be the
distance to be covered by the fluid F1 between the inlet and the
outlet of the channel in question.
[0060] According to the invention, the distribution element also
comprises a support 27 configured to keep the walls 25 secured
together. An example of such an element is presented in FIG.
5B.
[0061] It will thus be understood that the distribution element is
not a corrugated product, in contrast to the distribution
corrugations conventionally disposed in the distribution zones of a
brazed plate and fin heat exchanger. The walls 25 are secured
together via one and the same support 27, thereby conferring
greater rigidity on the distribution element. This also makes it
possible to simplify the brazing operations. Moreover, such a
configuration affords greater design freedom for the distribution
element and geometric freedom for the channels thereof.
[0062] Thus, it is possible to dispose walls 25 with a relatively
great height, typically at least 2 mm, preferably at least 5 mm,
more preferably up to 15 mm, or more, in the passages, this not
being the case with heat exchangers in which the walls result from
pressing of the dividing plates.
[0063] Preferably, said support comprises a bottom 27, preferably a
flat bottom that can be formed from a flat sheet, from which the
dividing walls 25 are erected. The walls 25 are preferably erected
in the vertical direction x. The walls 25 can have heights h of
typically between 2 and 15 mm. Preferably, the heights are chosen
such that the walls 25 extend over virtually all, if not all, of
the height of the passage in the vertical direction x.
[0064] The configuration of the distribution element 22 according
to the invention, in which the distribution element is a separate
part from the plates, also makes it possible to design different
distribution profiles on either side of one and the same plate.
[0065] Preferably, a distribution element according to the
invention is housed in several, if not all, of the distribution
zones of one or more sets of passages of the heat exchanger. Said
element extends over virtually all, if not all, of the height of
the passages, measured in the vertical direction x, such that the
structure is advantageously in contact with each plate 2 forming
the passage 20.
[0066] The channels are preferably fluidically isolated from one
another. The flow parameters of each channel are thus controlled
independently of those of the adjacent channels, thereby making it
possible to precisely adjust the distribution of the fluid across
the width of the passages at the outlet of the distribution zone.
Advantageously, the separating walls 25 are erected perpendicularly
to the plates 2.
[0067] Preferably, the number of channels 26 is at least 6, more
preferably between 5 and 50. Specifically, the number of channels
26 on the one hand has to be high enough to give the element 22 its
mechanical rigidity but on the other hand should not be too high in
order to leave enough free volume for the fluid to flow and to
limit pressure drops.
[0068] Advantageously, the distribution element 22 comprises a
first end 23 forming an inlet or an outlet for the fluid F1, and a
second end 24 fluidically connected to the heat-exchange zone
21.
[0069] More specifically, as can be seen in FIG. 1, the passages 3
to 5 are bordered by closure bars 6, which do not completely shut
off the passages but leave free openings 23, 24 for the inlet or
outlet of the corresponding fluids.
[0070] FIG. 2 schematically partially depicts the "inlet" part of a
passage 3 of a heat exchanger according to one embodiment of the
invention. A fluid header 7 is arranged in the left-hand corner of
the heat exchanger, the first end 23 being fluidically connected to
the header 7 and forming an inlet for the fluid F1, the flow of
which is schematically depicted by dashed arrows.
[0071] The first and second ends 23, 24 extend preferably in a
plane parallel to the lateral direction y and perpendicular to the
longitudinal direction z. The dividing walls 25 extend between the
first and second ends 23, 24 and form channels 26 that lead out at
the second end 24 and are configured to distribute the fluid F1
uniformly in the lateral direction y so as to obtain homogeneous or
quasi-homogeneous distribution towards or from the entire width of
the heat-exchange zone 21 when the other of said first and second
ends 23, 24 is fed with fluid F1.
[0072] Advantageously, each channel is provided with first openings
26a and second openings 26b. Advantageously, as schematically
depicted in FIG. 2, the first and second openings 26a, 26b are
situated at the first and second ends 23, 24, respectively, the
dividing walls 25 extending continuously from the first end 23 to
the second end 24. The flow path of the fluid F1 corresponds to the
path to be followed between the openings 26a and 26b. Each of the
ends 23, 24 can thus be divided into a series of openings 26a and a
series of openings 26b, respectively.
[0073] The openings 26a, 26b of the channels 26 could have passage
sections for fluid that are identical or variable depending on the
channels 26 in question. The passage sections for fluid of the
openings 26a and 26b correspond to the internal areas of the
channels 26 measured at the first and second ends 23, 24 in a plane
parallel to the lateral direction y.
[0074] Preferably, at least one first opening 26a has a passage
section for fluid that is different than the passage section for
fluid of another first opening 26a, and/or at least one second
opening 26b has a passage section for fluid that is different than
the passage section for fluid of another second opening 26b.
[0075] Advantageously, the first openings 26a and/or the second
openings 26b of one and the same channel 26 have passage sections
for fluid that are larger the longer the flow path defined by said
channel 26, i.e. the greater the distance to be covered by the
fluid F1 between the first opening 26a and the second opening
26b.
[0076] Thus, in the example in FIG. 3A, 3B or 5B, where the first
end 23 is arranged at an extreme edge of the element 22 along the
direction y, the first end 23 is subdivided into a first series of
first openings 26a that have passage sections for fluid that
increase in the lateral direction y. This encourages the supply of
the channels that are configured to distribute the fluid F1 from
the header 7 toward the part of the second end 23 that is
diagonally opposite said extreme edge.
[0077] According to another example (FIG. 5A), in which the element
22 has a median plane M and the first end 23 is centered with
respect to the plane M, the first openings 26a, which are arranged,
preferably symmetrically, on either side of the plane M, have
passage sections for fluid that increase with increasing distance
from said median plane M.
[0078] This compensates for the natural tendency of the fluid to
pass into the region of the distribution zone that is situated next
to the header rather than through the zones that are further away
from the header, and thus to homogenize the distribution of the
fluid across the width of the passage 3 of the heat exchanger.
[0079] Advantageously, when the distribution element 22 is disposed
in the distribution zone 20 of a heat exchanger, the first end 23
is situated by the inlet header 7 of the heat exchanger and forms
an inlet for the fluid F1. The first openings 26a in the first end
23 have passage sections for fluid that are variable depending on
their position along the lateral direction y.
[0080] By virtue of the use of openings 26a with different passage
sections, it is notably possible to overfeed the channels that are
less favorable to the passage of the fluid, specifically from the
inlet of the fluid F1 into the distribution zone 20, this causing
fewer pressure drops and thus leading to a more efficient fluid
distribution system.
[0081] According to an advantageous embodiment of the invention,
all or some of the channels 26 comprise means 28 for modifying the
linear flow resistance of said channels 26. The linear flow
resistance of each channel can thus be adjusted depending on the
flow characteristics desired in each channel 26, in particular
fluid flow rate and velocity. Thus, the linear flow resistance of
the channels can be adjusted such that each channel 26 has a
similar overall flow resistance. The characteristics of the fluid
at the outlet of the channels 26 are thus homogenized in the
lateral direction y, thereby allowing uniform distribution toward
or from the heat-exchange zone 21.
[0082] The expression "flow resistance" is understood to mean the
capability of the channel not only to generate viscous friction but
also to divert the flow (pressure force normal to the wall). This
resistance is expressed in the form of a reaction force of the
solid structure to the flow in newtons, this resulting in the fluid
in a pressure drop in pascals. This force depends firstly on the
kinetic energy of the fluid (rho*u.sup.2) and secondly on the
Reynolds number (rho*u*D/mu). The linear flow resistance
corresponds to the flow resistance of the channel expressed per
unit of length.
[0083] Advantageously, a channel 26 will comprise modification
means 28 that are configured to produce an increase in the linear
flow resistance that is all the greater the closer the opening 26a
of said channel is, in terms of distance to be covered by the fluid
F1, to the other opening 26b. For example, in the configuration
illustrated in FIG. 3B, the channels 26 comprise modification means
28 that are configured to produce an increase in linear flow
resistance that is increasingly small in the lateral direction y.
Specifically, this makes it possible to compensate for the natural
preferred passage of the fluid along the axis rather than along the
side of the heat exchanger, and thus to obtain good distribution of
the fluid. In the case in which the header 7 is centered with
respect to the median plane M of the heat exchanger, as shown in
FIG. 5A, the fluid resistance of a channel will be all the greater
the closer it is to the median plane M.
[0084] The channels 26 could have internal profiles that are shaped
to produce different variations in flow resistance.
[0085] Obstacles 28 that produce different flow resistances could
also be arranged within one or more channels 26. The insertion of a
porous structure 28, for example a metal foam, into a channel will
make it possible to increase the flow resistance thereof. The
linear flow resistance of the channels 26 could thus be adjusted by
varying the characteristics of the inserted structures 28, such as
volume, density, etc. in accordance with the channels. In the
example illustrated in FIG. 3B, the volume taken up by the porous
structures 28 decreases in the lateral direction y, so as to
produce variations in linear flow resistance that are smaller along
y.
[0086] According to the example schematically indicated in FIG. 4,
partitions 28 can be arranged in one or more channels 26 so as to
create an additional stage for dividing the distribution zone 22.
This makes it possible to vary the linear flow resistance and to
control the flow parameters of the fluid distributed toward or
recovered from the heat-exchange zone 21 even more finely. The use
of additional partitions 28 is notably advantageous when the first
end 23 of the distribution element has a width that is too small to
be able to be divided into a sufficient number of channels 26.
[0087] As the case may be, the dividing walls 25 and/or the
partitions 28 may have, in longitudinal section, rectilinear
profiles, as illustrated in FIGS. 2 and 4, or curvilinear profiles,
as illustrated in FIGS. 3A, 3B and 5A, 5B.
[0088] According to a particularly advantageous embodiment, the
dividing walls 25 have predetermined curvilinear profiles
comprising at least one inflection point P.
[0089] Such a geometry makes it possible to divert the fluid more
quickly, that is to say over a shorter distance L1, specifically
across a great width of the passage of the heat exchanger. It is
thus possible to reduce the longitudinal extent of the distribution
zone 20 and consequently to increase the mechanical integrity of
the heat exchanger since the compactness of what is known as the
"weak" zone of the heat exchanger is increased.
[0090] This also affords the possibility of reducing the width of
the first end 23 of the distribution element 22 and thus the width
of the header 7, which is a relatively expensive part. Preferably,
the first end 23 forming the inlet or outlet of the distribution
element 22 has, in the lateral direction y, a width L3 of between
50 and 1000 mm, more preferably between 100 and 500 mm.
[0091] Such profiles also make it possible to reduce the pressure
drops within the channels 26, sudden changes in channel profiles
being known to bring about fluid recirculations that cause pressure
drops.
[0092] Preferably, the distribution element 22 has, parallel to the
longitudinal direction z, a length L1 less than 500 mm, preferably
between 50 and 200 mm, more preferably between 80 and 100 mm.
Preferably, the length L1 of the distribution element 22 represents
less than 20% of the length of the heat-exchange zone 21. Parallel
to the lateral direction y, the distribution element 22 has a width
L2, the ratio between a length L1 and the width L2 being less than
20%, preferably between 5 and 10%. The width L2 is preferably
between 500 and 1500 mm.
[0093] The distribution element 22 is advantageously formed from a
metal material, preferably aluminum or an aluminum alloy. The
element may be formed in particular from a porous material,
preferably with closed pores, for example a metal foam.
[0094] Preferably, the distribution element 22 is monolithic,
thereby making it possible to minimize incidents along the flow
paths of the fluid.
[0095] The element 22 may be manufactured using an additive
manufacturing method, preferably by thermal spraying, making it
possible to produce parts with complex geometries in one piece. In
particular, a cold spray method could be used.
[0096] It should be noted that the additive manufacturing method
can also be referred to as "3D printing". Additive manufacturing
makes it possible to produce a real object using a specific
printer, which deposits and/or solidifies material, layer by layer,
to obtain the final part. The stack of these layers makes it
possible to create a volume.
[0097] The element 22 may also be manufactured using the following
additive manufacturing methods: [0098] the FDM (Fused Deposition
Modeling) method, which consists in modeling by deposition of
molten material, [0099] stereolithography (SLA), a method in which
ultraviolet radiation solidifies a layer of liquid plastic, or
[0100] selective laser sintering, in which a laser is used to
agglomerate a layer of powder.
[0101] Alternatively, the distribution element 22 may be
manufactured by casting. This manufacturing method makes it
possible to produce parts with complex geometries at a relatively
low cost compared with additive manufacturing. Preferably, the
element 22 is formed from an aluminum alloy by casting, that is to
say an alloy of which the main constituent is aluminum, with a
density lower than intended to be converted by casting
techniques.
[0102] As regards the heat-exchange zones 21 of the heat exchanger,
these advantageously comprise heat-exchange structures 8 disposed
between the plates 2, as shown in FIG. 1. These structures have the
function of increasing the heat-exchange area of the heat exchanger
and act as spacers between the plates 2, notably during the
assembly of the exchanger by brazing, in order to avoid any
deformation of the plates during the use of pressurized fluids.
[0103] Preferably, these structures comprise heat-exchange
corrugations 8 which advantageously extend across the width and
along the length of the passages of the heat exchanger, parallel to
the plates 2. These corrugations 8 may be formed in the form of
corrugated sheets. In this case, the corrugation legs that connect
the successive tops and bottoms of the corrugation are referred to
as "fins". The heat-exchange structures 8 can also cover other
particular shapes defined depending on the desired fluid flow
characteristics. More generally, the term "fins" covers blades or
other secondary heat-exchange surfaces, which extend from the
primary heat-exchange surfaces, that is to say the plates of the
heat exchanger, into the passages of the heat exchanger.
[0104] Within a passage, the distribution element 22 according to
the invention and the heat-exchange structure 8 are preferably
juxtaposed along the longitudinal axis z, that is to say positioned
end to end. Note that a small clearance can exist between these
elements in order not to block the channels of the heat-exchange
zone 21 which face the walls 25 of the channels of the distribution
zone 22. Preferably, the first end 23 of the element 22 is arranged
end to end with at least one part of the header 7, while the second
end 24 is arranged end to end with at least one part of the
structure 8. Preferably, the structure 8, the header 7 and/or the
element 22 are connected by brazing to the plate 2 and are
connected indirectly together via their respective connections to
the plates 2. Advantageously, the element 22 is assembled on the
plates 2 by brazing the support 27 to the plates 2, the support or
bottom 27 comprising at least one face coated with a brazing agent.
This face is positioned next to a plate 2 so as to form a
connecting surface with said plate 2. Alternatively or in addition,
the plate 2 entirely or partially have at least one face coated at
least partially with a brazing agent layer.
[0105] In order to demonstrate the effectiveness of a distribution
element 22 according to the invention for uniformly distributing
the fluid, fluid flow simulations were carried out with a
distribution element according to FIG. 5B.
[0106] The dimensional characteristics of the distribution element
22 were as follows: [0107] length L1 of the element 22: 85 mm,
[0108] half-width L2/2 of the element 22: 485 mm, [0109] width L3
of the first end 23 forming an inlet: 370 mm [0110] mechanical
clearance between the distribution element 22 and the heat-exchange
structure 8: 2 mm, [0111] height of the element 22: 9.5 mm (the
walls 25 having a height, in the vertical direction x, of 7.5 mm,
and the bottom 27 having a thickness of 2 mm), [0112] thickness of
the walls 25: 2.3 mm.
[0113] As regards the fluid, the simulation parameters were as
follows: [0114] nature of the fluid: nitrogen, [0115] pressure of
the fluid at the outlet of the distribution element 22: 1.2 bar,
[0116] temperature of the fluid at the inlet of the header 7:
-80.degree. C., [0117] temperature of the fluid at the outlet of
the header 9: 17.degree. C., [0118] mass flow rate of fluid flowing
through the passage of the heat exchanger: 100 kg/h.
[0119] The results of these simulations are presented in FIGS. 6A,
6B, 6C and 7. FIGS. 6A, 6B and 6C show plots of the velocities,
pressures and temperatures of the fluid flowing within the channels
26 of the distribution element 22. A quasi-homogeneous distribution
of the fluid at the outlet of the channels 26 can be seen. FIG. 7
indicates the change in the values of what is known as the axial
velocity, that is to say the velocity in the longitudinal direction
z, that are obtained at the outlet of the element 22, depending on
the position in the lateral direction y. The change thus starts
from the center of the distribution element 22 (position at 0 mm)
as far as the edge of the second end 23 (position at 485 mm). The
distribution of the velocity values along the lateral direction y
is characterized by a standard deviation of 0.9% and a maximum
deviation of 2.8% with respect to the mean value of the velocity in
the heat-exchange zone, this being much less than the variations
found with the conventional distribution elements, for which the
standard deviations are around 3%. By virtue of the invention, the
velocity variations are thus reduced in the lateral direction at
the outlet of the distribution zone, making it possible to
distribute the fluid as homogeneously as possible across the entire
width of the heat-exchange zone.
[0120] Of course, the invention is not limited to the particular
examples described and illustrated in the present application.
Other variants or embodiments within the competence of a person
skilled in the art may also be considered without departing from
the scope of the invention. For example, other directions and
senses for the flow of the fluids in the heat exchanger are of
course conceivable, without departing from the scope of the present
invention. A distribution element according to the invention may
thus be arranged in any distribution zone of the heat exchanger, in
one or more series of passages 3, 4, 5 of the heat exchanger,
upstream and/or downstream of one or more of the headers of the
heat exchanger. For example, FIG. 5B illustrates the case in which
a heat-exchanger passage comprises two distribution elements
according to the invention arranged on either side of the
heat-exchange zone 21 (schematically depicted with a deliberately
shortened length). It should also be noted that passages 3, 4, 5 of
the heat exchanger can be formed equally well between two
successive plates 2 and between a closure bar 6 of the heat
exchanger and an immediately adjacent plate 2.
[0121] It will be understood that many additional changes in the
details, materials, steps and arrangement of parts, which have been
herein described in order to explain the nature of the invention,
may be made by those skilled in the art within the principle and
scope of the invention as expressed in the appended claims. Thus,
the present invention is not intended to be limited to the specific
embodiments in the examples given above.
* * * * *