U.S. patent application number 15/566913 was filed with the patent office on 2018-04-19 for heat exchanger comprising microstructure elements and separation unit comprising such a heat exchanger.
This patent application is currently assigned to L'Air Liquide, Societe Anonyme pour l'Etude et l'Exploitation des Procedes Georges Claude. The applicant listed for this patent is Centre National De La Recherche Scientifique, L'Air Liquide, Societe Anonyme pour l'Etude et l'Exploitation des Procedes Georges Claude. Invention is credited to Erwan LE GULUDEC, Clement LIX, David QUERE, Quentin SANIEZ, Bernard SAULNIER, Evan SPRUIJT, Marc WAGNER.
Application Number | 20180106534 15/566913 |
Document ID | / |
Family ID | 53366158 |
Filed Date | 2018-04-19 |
United States Patent
Application |
20180106534 |
Kind Code |
A1 |
LE GULUDEC; Erwan ; et
al. |
April 19, 2018 |
HEAT EXCHANGER COMPRISING MICROSTRUCTURE ELEMENTS AND SEPARATION
UNIT COMPRISING SUCH A HEAT EXCHANGER
Abstract
The invention relates to a heat exchanger comprising parallel
plates and spacers arranged in parallel and defining i) rough
primary channels and ii) secondary channels arranged so as to
exchange heat. Said heat exchanger comprises a primary liquid inlet
to be fluidically connected to a primary liquid dispenser. Each
rough primary channel has the shape of a prism having a polygonal
cross-section and consisting of a plurality of essentially flat
faces. The primary channels comprise rough primary channels. Each
rough primary channel has microstructure elements which are
distributed along the entire length of the channel and have
dimensions of between 1 .mu.m and 300 .mu.m.
Inventors: |
LE GULUDEC; Erwan;
(Vincennes, FR) ; LIX; Clement; (Moiron, FR)
; QUERE; David; (Paris, FR) ; SANIEZ; Quentin;
(Paris, FR) ; SAULNIER; Bernard; (La Garenne
Colombes, FR) ; SPRUIJT; Evan; (Ws Utrecht, NL)
; WAGNER; Marc; (Saint Maur des Fosses, FR) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
L'Air Liquide, Societe Anonyme pour l'Etude et l'Exploitation des
Procedes Georges Claude
Centre National De La Recherche Scientifique |
Paris
Paris Cedex 16 |
|
FR
FR |
|
|
Assignee: |
L'Air Liquide, Societe Anonyme pour
l'Etude et l'Exploitation des Procedes Georges Claude
Paris
FR
Centre National De La Recherche Scientifique
Paris Cedex 16
FR
|
Family ID: |
53366158 |
Appl. No.: |
15/566913 |
Filed: |
April 13, 2016 |
PCT Filed: |
April 13, 2016 |
PCT NO: |
PCT/FR2016/050851 |
371 Date: |
October 16, 2017 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
F25J 2290/32 20130101;
F25J 2290/44 20130101; F25J 2250/04 20130101; F28D 2021/0033
20130101; F28F 2260/00 20130101; F25J 2290/20 20130101; F25J 5/00
20130101; F28F 13/185 20130101; F28F 3/025 20130101; F28D 9/0062
20130101; F28F 13/187 20130101; F25J 5/005 20130101; F28F 13/12
20130101 |
International
Class: |
F25J 5/00 20060101
F25J005/00; F28F 3/02 20060101 F28F003/02; F28F 13/12 20060101
F28F013/12 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 16, 2015 |
FR |
1553397 |
Claims
1-19. (canceled)
20. A heat exchanger, for producing exchanges of heat between a
primary liquid and a secondary fluid, the heat exchanger
comprising: a plurality of plates disposed parallel to one another;
a plurality of spacers extending between the plates and disposed
parallel to the other spacers so as to define i) primary channels
conformed for the flow of the primary liquid and ii) secondary
channels conformed for the flow of the secondary fluid, each
primary channel being arranged so as to be able to exchange heat
with at least one respective secondary channel; and a primary
liquid inlet, configured to be linked fluidically to a primary
liquid distributor, wherein each primary channel has an overall
prism form with a polygonal section, the prism form being made up
of several overall flat faces, and wherein each primary channel
comprises rough primary channels, each rough primary channel having
microstructure elements having dimensions of between 1 .mu.m and
300 .mu.m, and wherein the microstructure elements are configured
such that, for each rough primary channel:
r>1+1.310.sup.3R.sub.a.epsilon. in which: r is the ratio of the
real surface of a respective rough primary channel, as numerator,
to the geometrical surface of a respective rough primary channel,
as denominator, R.sub.a (in m) is the arithmetic mean deviation
relative to the median line, and .epsilon. is the void fraction of
the real surface of a respective rough primary channel.
21. The heat exchanger as claimed in claim 20, wherein each
polygonal section has dimensions of between 1 mm and 10 mm.
22. The heat exchanger as claimed in claim 21, wherein each
polygonal section has dimensions of between 3 mm and 7 mm, a
rectangular polygonal section having, an approximate length equal
to 5 mm and an approximate width equal to 1.5 mm
23. The heat exchanger as claimed in claim 20, wherein
microstructure elements are distributed substantially over all the
internal periphery of each rough primary channel.
24. The heat exchanger as claimed in claim 20, wherein, for each
respective rough primary channel, the microstructure elements are
distributed over at least 80% of the surface of the rough primary
channel.
25. The heat exchanger as claimed in claim 20, wherein the
microstructure elements have mutually similar dimensions and
mutually similar forms, and in which the microstructure elements
are configured such that, for each rough primary channel:
r>1+1.310.sup.3h.epsilon. in which: h (in m) is the mean height
of the microstructure elements.
26. The heat exchanger as claimed in claim 20, wherein the
microstructure elements are distributed uniformly.
27. The heat exchanger as claimed in claim 26, wherein the
microstructure elements are configured such that, for each rough
primary channel: d < 7.5 10 - 4 P ##EQU00009## in which: d (in
m) is the mean distance between the centers of the adjacent
microstructure elements, the centers being situated on the
geometrical surface of the rough primary channel, P (in m) is the
mean perimeter of the section of the microstructure elements.
28. The heat exchanger as claimed in claim 27, wherein the
microstructure elements are configured such that, for each rough
primary channel: r - 1 - 1.3 10 3 h / h 6.7 10 - 6 / d 2 > 4.2
10 - 8 ##EQU00010## and in which the microstructure elements are
also configured such that, for each rough primary channel: d > S
0.4 ##EQU00011## in which: S (in m.sup.2) is the mean surface of
the section of the microstructures.
29. The heat exchanger as claimed in claim 26, wherein the
microstructure elements are distributed only on the long sides of
the rectangular base.
30. The heat exchanger as claimed in claim 20, wherein the
microstructure elements have irregular forms, the microstructure
elements also being able to be distributed non-uniformly.
31. The heat exchanger as claimed in claim 30, wherein the
microstructure elements are configured such that, for each rough
primary channel: r - 1 - 1.3 10 3 R a / R a + 1.2 10 5 > 4.2 10
- 8 . ##EQU00012##
32. The heat exchanger as claimed in claim 20, wherein each rough
primary channel out of at least a part of the rough primary
channels has an overall prism form with rectangular base.
33. The heat exchanger as claimed in claim 20, wherein the
microstructure elements are distributed so as to define between
them passages for the flow of the primary liquid.
34. The heat exchanger as claimed in claim 20, wherein each rough
primary channel has an arithmetic roughness Ra of between 1 .mu.m
and 60 .mu.m.
35. The heat exchanger as claimed in claim 20, wherein each rough
primary channel has nanostructure elements distributed over at
least 80% of its length, each nanostructure element having
dimensions of between 1 nm and 500 nm.
36. The heat exchanger as claimed in claim 20, wherein the
microstructure elements are formed by a treatment of the surface of
each primary element, wherein the treatment is selected from the
group consisting of anodization; sandblasting; shotblasting;
chemical etching; powder sintering; molten metal projection; laser;
photolithography; mechanical etching of rolling, brushing, or
printing type; and combinations thereof.
37. The heat exchanger as claimed in claim 20, wherein the heat
exchanger is configured to form a vaporizer-condenser, the lengths
of the rough primary channels and the lengths of the secondary
channels being determined such that the exchanges of heat make it
possible to totally or partially vaporize the primary liquid and to
totally or partially condense the secondary fluid introduced in
secondary gas form.
38. The heat exchanger as claimed in claim 20, wherein said primary
liquid inlet is placed at an altitude greater than the rough
primary channels when the heat exchanger is in service such that
the primary liquid distributor introduces the primary liquid in the
form of a film flowing by gravity through said at least one primary
liquid inlet into the rough primary channels.
39. A separation unit, for separating gas by cryogenics, the
separation unit comprising at least one vaporizer-condenser-forming
heat exchanger as claimed in claim 20, the vaporizer-condenser
being configured to allow an exchange of heat between a liquid
containing oxygen and a gas containing nitrogen.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application is a .sctn. 371 of International PCT
Application PCT/FR2016/050851 filed Apr. 13, 2016, which claims the
benefit of FR1553397, filed Apr. 16, 2015, both of which are herein
incorporated by reference in their entireties.
FIELD OF THE INVENTION
[0002] The present invention relates to an exchange of heat between
a primary liquid, for example containing oxygen, and a secondary
fluid, for example containing nitrogen. Furthermore, the present
invention relates to a cryogenic gas separation unit comprising
such an exchange of heat.
[0003] The present invention relates to the field of heat
exchangers configured to produce exchanges of heat between a
primary liquid and a secondary fluid. In particular, the present
invention can be applied to the field of cryogenic gas separation,
in particular the separation of air gases, acid gases and natural
gas.
BACKGROUND
[0004] EP0130122A1 describes a heat exchanger which generally
comprises parallel plates, parallel spacers, which define i)
primary channels and ii) secondary channels, and an inlet linked to
a bath of primary liquid via a distributor. In general, each
primary channel has an overall prism form with rectangular base,
the primary liquid circulating along the prism and at right angles
to the rectangular base.
[0005] When the heat exchanger of EP0130122A1 is in service, the
primary liquid which circulates in the primary channels exchanges
heat with the secondary fluid which flows in the secondary
channels. In the case of a cryogenic air separation unit, the
primary liquid contains a large proportion of oxygen and the
secondary fluid contains a large proportion of gaseous nitrogen.
The primary liquid flow rate is relatively low in a primary
channel.
[0006] However as FIG. 1 shows in the present application, the
primary channels of EP0130122A1 have small transverse dimensions,
in this case millimetric, such that primary liquid is not
distributed uniformly over all the rectangular perimeter 51 of each
smooth primary channel 50. Therefore, the primary liquid forms
menisci 52 and is concentrated in the corners 53 of the rectangular
perimeter 51 of each smooth primary channel 50, which induces the
occurrence of dry zones on the long sides 54 of the rectangular
perimeter 51 of each smooth primary channel 50.
[0007] The number and the surface area of the dry zones increase as
the primary liquid flowing toward the outlets of the smooth primary
channels vaporizes. These dry zones are therefore not used in
exchanges of heat, which reduces the efficiency of the heat
exchanger. Furthermore, these dry zones risk causing deposits of
impurities, which can ultimately cause a failing in the safety of
personnel and of the equipment.
SUMMARY OF THE INVENTION
[0008] The aim of the present invention is in particular to wholly
or partly resolve the abovementioned problems, by providing a heat
exchanger that makes it possible to conserve primary and secondary
channels with a conventional geometry, without generating
additional head losses, while increasing the thermal transfer and
the safety of the heat exchanger.
[0009] To this end, the subject of the invention is a heat
exchanger, for producing exchanges of heat between a primary liquid
and a secondary fluid, the heat exchanger comprising at least:
[0010] several plates disposed parallel to one another, [0011]
spacers extending between the plates and disposed parallel to one
another so as to define i) primary channels conformed for the flow
of the primary liquid and ii) secondary channels conformed for the
flow of the secondary fluid, each primary channel being arranged so
as to be able to exchange heat with at least one respective
secondary channel, [0012] a primary liquid inlet, intended to be
linked fluidically to a primary liquid distributor,
[0013] the heat exchanger being characterized in that each primary
channel has an overall prism form with polygonal section, the prism
being made up of several overall flat faces, and
[0014] in that the primary channels comprise rough primary
channels, each rough primary channel having microstructure elements
having dimensions of between 1 .mu.m and 300 .mu.m, preferably
between 1 .mu.m and 100 .mu.m, and
[0015] in that the microstructure elements are configured such
that, for each rough primary channel:
r>1+1.310.sup.3R.sub.a.epsilon.
[0016] in which: [0017] r is the ratio of the real surface of a
respective rough primary channel, as numerator, to the geometrical
surface of a respective rough primary channel, as denominator,
[0018] R.sub.a (in m) is the arithmetic mean deviation relative to
the median line, and [0019] .epsilon. is the void fraction of the
real surface of a respective rough primary channel.
[0020] The ratio r is sometimes called "roughness coefficient" or
"roughness". The arithmetic mean deviation R.sub.a (in m)
represents the roughness of the rough primary channel. In the
present application, the term "median line" designates a line
situated at the mean altitude of the real surface. In practice, the
median line can be calculated from the topographic recording of the
cross-sectional profile of the surface by applying the least
squares method.
[0021] In the present application, the term "void fraction of a
surface" corresponds to a fraction calculated as follows: a slice
is considered whose thickness is equal to the height of the highest
peak (relative to the lowest point) of this surface. On this slice,
the void fraction c corresponds to the ratio of the volume not
occupied by microstructure elements to the total volume of the
slice. This ratio is expressed as follows:
= V tot - V surf V tot ##EQU00001##
[0022] in which:
[0023] V.sub.tot (in m.sup.3) is the volume contained between the
highest point and the lowest point of the real surface, and
[0024] V.sub.surf (in m.sup.3) is the volume contained between the
real surface and the lowest point of the real surface.
[0025] Consequently:
.epsilon.=1-z/R.sub.z
[0026] in which: R.sub.z is the height of the highest peak relative
to the lowest point of the surface,
[0027] z (in m) is the height of a respective point relative to the
lowest point of the real surface, the height z being measured
point-by-point, z (in m) is the arithmetic mean of the height z
measured point-by-point.
[0028] Thus, such a heat exchanger makes it possible to conserve
primary and secondary channels with a conventional geometry,
therefore simple to manufacture and implement, without generating
additional head losses, while increasing the thermal transfer and
safety when the heat exchanger is in service. In effect, the
microstructure elements make it possible to increase the thermal
transfer, because the exchange surface area and the wetted surface
are greater. Also, the safety of the heat exchanger is enhanced,
because of the great wettability of the primary channels, which
makes it possible to avoid any dry vaporization of oxygen.
Moreover, measurements have shown that the prismatic geometry with
polygonal base exhibited heat transfer coefficients higher than a
tubular geometry with circular base for example.
[0029] The surface treatment, with the microstructure elements,
makes it possible to wet all the perimeter of the primary channel
and therefore increase the exchange surface.
[0030] In most applications, the primary liquid and the secondary
fluid are cryogenic fluids. The primary liquid and the secondary
fluid introduced into the heat exchanger can be single-phase, that
is to say all liquid or all gaseous, or two-phase, that is to say
made up of liquid and gas. During their flow in the heat exchanger,
the proportions of the phases of the primary liquid and of the
secondary fluid can vary.
[0031] According to one embodiment of the invention, each polygonal
section has dimensions of between 1 mm and 10 mm, preferably
between 3 mm and 7 mm, a rectangular polygonal section having, for
example, an approximate length equal to 5 mm and an approximate
width equal to 1.5 mm.
[0032] Thus, such transverse dimensions make it possible to adapt
the heat exchanger to the primary liquid and secondary fluid flow
rates to be handled.
[0033] According to one embodiment of the invention, microstructure
elements are distributed substantially over all the internal
periphery of each rough primary channel.
[0034] Thus, such a distribution guarantees the wetting of all the
polygonal section of each rough primary channel.
[0035] According to one embodiment of the invention, for each
respective rough primary channel, the microstructure elements are
distributed over at least 80% of the surface of the rough primary
channel.
[0036] Thus, each rough primary channel is substantially covered
with microstructure elements which increase the exchange surface
area.
[0037] According to one embodiment of the invention, the
microstructure elements have mutually similar dimensions and
mutually similar forms, and in which the microstructure elements
are configured such that, for each rough primary channel:
r>1+1.310.sup.3h.epsilon.
[0038] in which: h (in m) is the mean height of the microstructure
elements.
[0039] Thus, such similar microstructure elements make it possible
to obtain a greater wettability of each rough primary channel and
to control the minimum thickness of the primary liquid film.
[0040] For example, similar dimensions of the microstructure
elements can exhibit a deviation of 20% from one microstructure
element to another. Two microstructure elements having similar
forms have all their dimensions similar.
[0041] In the present application, the term "real surface"
designates in particular the surface obtained after manufacture and
the term "geometrical surface" designates in particular a perfect
surface, therefore a smooth surface, apart from any microstructure
elements present; a geometrical surface can be fully defined
geometrically by nominal dimensions. The geometrical surface is
sometimes called "projected surface" when it is considered in a
plane.
[0042] In the present application, the term "surface" can designate
either a topological entity or the surface area of this topological
entity.
[0043] According to one embodiment of the invention, the
microstructure elements are distributed uniformly. In particular,
the microstructure elements can be similar and distributed
uniformly.
[0044] Thus, such a uniform distribution makes it possible to
guarantee a greater wettability of each rough primary channel and
to control the minimum thickness of the primary liquid film.
[0045] Alternatively to the preceding embodiment, the
microstructure elements can be similar and distributed
non-uniformly, for example randomly.
[0046] According to one embodiment of the invention, the
microstructure elements are configured such that, for each rough
primary channel:
d < 7.5 10 - 4 P ##EQU00002##
[0047] in which: [0048] d (in m) is the mean distance between the
centers of the adjacent microstructure elements, the centers being
situated on the geometrical surface of the rough primary channel,
[0049] P (in m) is the mean perimeter of the section of the
microstructure elements.
[0050] According to one embodiment of the invention, the
microstructure elements are configured such that, for each rough
primary channel:
r - 1 - 1.3 10 3 h / h + 6.7 10 - 6 / d 2 > 4.2 10 - 8
##EQU00003##
[0051] and in which the microstructure elements (30) are also
configured such that, for each rough primary channel (21):
d > S 0.4 ##EQU00004##
[0052] in which: S (in m.sup.2) is the mean surface of the section
of the microstructures.
[0053] Microstructure elements thus configured make it possible to
have a rate of propagation of the liquid matched to the heat
exchange method.
[0054] According to one embodiment of the invention, the
microstructure elements have irregular forms, for example with
irregular dimensions, the microstructure elements also being able
to be distributed non-uniformly, for example randomly.
[0055] In other words, the intervals between two neighboring
microstructure elements are variable, therefore not constant, over
all the real surface of the rough primary channel considered.
[0056] Thus, such a non-uniform distribution makes it possible to
obtain a constant wettability all along each rough primary channel,
by limiting the surface area of each zone without microstructure
elements.
[0057] Alternatively to this variant, each microstructure element
can have a regular form or geometry, for example in overall
cylinder, prism, cone or similar form. In this variant, the
microstructure elements of regular forms are configured such that,
for each rough primary channel:
r>1+1.310.sup.3h.epsilon.
[0058] But, in a variant in which the microstructure elements have
irregular forms, the microstructure elements are configured such
that:
r>1+1.310.sup.3R.sub.a.epsilon.
[0059] According to one embodiment of the invention, the
microstructure elements are configured such that, for each rough
primary channel:
r - 1 - 1.3 10 3 R a / R a + 1.2 10 5 > 4.2 10 - 8 .
##EQU00005##
[0060] Such microstructure elements form a roughness which
increases in particular the wettability of the surface of each
rough primary channel, which allows the liquid to wet all the
surface of the rough primary channel even in the presence of a
recess.
[0061] According to one embodiment of the invention, each rough
primary channel out of at least a part of the rough primary
channels has an overall prism form with rectangular base.
[0062] As the adjective "overall" indicates, the prism can have an
approximately rectangular base. For example, the edges of the
rectangle defining the base of the prism can be rounded, for
example by braze.
[0063] Thus, such a form of rough primary channel, with rectangular
base, makes it possible to conserve rough primary channels and
secondary channels with a conventional geometry, therefore simple
to manufacture and to implement in the assembly of the heat
exchanger.
[0064] According to one embodiment of the invention, the
microstructure elements are distributed only on the long sides of
the rectangular base.
[0065] In other words, the short sides of the rectangular perimeter
have no microstructure elements. In effect, the short sides can be
wetted because of the natural formation of the menisci in the
corners of the rectangular perimeter.
[0066] According to one embodiment of the invention, the
microstructure elements are distributed so as to define between
them passages for the flow of the primary liquid.
[0067] In other words, the microstructure elements extend overall
above the level of the geometrical surface.
[0068] Thus, the microstructure elements are distributed so as to
define a surface condition with an open roughness, that is to say a
roughness defined by peaks or locks but without narrow cavities. A
cavity is considered narrow when the peaks which surround it are
too close together to allow a circulation of the liquid.
[0069] According to one embodiment of the invention, each rough
primary channel has an arithmetic roughness R.sub.a of between 1
.mu.m and 60 .mu.m.
[0070] Thus, such an arithmetic roughness makes it possible to
obtain a great wettability of the rough primary channels.
[0071] According to one embodiment of the invention, each rough
primary channel has nanostructure elements distributed over at
least 80% of its length, each nanostructure element having
dimensions of between 1 nm and 500 nm.
[0072] Thus, such nanostructure elements make it possible to
maximize the wettability of each rough primary channel.
[0073] According to a variant of the invention, the nanostructure
elements are distributed over the surface of each rough primary
channel. Alternatively or in addition to this variant of the
invention, the nanostructure elements can be distributed over the
surfaces of the microstructure elements.
[0074] According to a variant of the invention, the coating is made
up of a metal material and/or of an inorganic material, for example
of a ceramic material. The coating can be obtained by spray
deposition (sometimes referred to as "spray") of particles and/or
of fibers on the surface of each rough primary channel.
[0075] According to one embodiment of the invention, the
microstructure elements are formed by a treatment of the surface of
each primary element, for example by anodization, by sandblasting,
by shotblasting or by chemical etching or even by powder sintering,
by molten metal spraying, by laser, by photolithography or by
mechanical etching of rolling, brushing or printing type.
[0076] Furthermore, the microstructure elements can be formed by a
coating obtained by impregnation, by spray deposition by plasma
deposition, by an additive manufacturing process, for example by
three-dimensional printing.
[0077] According to a variant of the invention, the plates and/or
the spacers are composed of materials selected from the group
consisting of aluminum, copper, nickel, chrome, iron and alloys of
aluminum, an alloy of copper, of nickel, of chrome, of iron, for
example a nickel-chrome alloy or a nickel-chrome-iron alloy.
[0078] Thus, such plates and/or spacers make it possible to handle
standard primary liquids and secondary fluids in the field of
cryogenics, for example a liquid containing oxygen and a gas
containing nitrogen for separating the air gases, the acid gases
and natural gas.
[0079] According to one embodiment of the invention, the heat
exchanger is configured to form a vaporizer-condenser, the lengths
of the rough primary channels and the lengths of the secondary
channels being determined such that the exchanges of heat make it
possible to totally or partially vaporize the primary liquid and to
totally or partially condense the secondary fluid introduced in
secondary gas form.
[0080] Thus, such a vaporizer-condenser makes it possible to handle
the standard primary liquids and secondary fluids in the field of
cryogenics, for example a liquid containing oxygen and a gas
containing nitrogen for separating the components of air.
[0081] According to one embodiment of the invention, said primary
liquid inlet is placed at an altitude greater than the rough
primary channels when the heat exchanger is in service such that
the primary liquid distributor introduces the primary liquid in the
form of a film flowing by gravity through said at least one primary
liquid inlet into the rough primary channels.
[0082] According to a variant of the invention, the secondary
channels comprise rough secondary channels, each rough secondary
channel being formed in a way similar to the rough primary
channels. In particular, a rough secondary channel can have
microstructure elements which have dimensions of between 1 .mu.m
and 300 .mu.m, preferably between 1 .mu.m and 100 .mu.m, and which
satisfy the equations applicable to the rough primary channels.
More generally, each of the features mentioned above for the rough
primary channels can be applied to the rough secondary channels.
However, these features are not repeated here, so as to simplify
the reading of the present patent application.
[0083] Moreover, the subject of the present invention is a
separation unit, for separating gas by cryogenics, the separation
unit comprising at least one vaporizer-condenser-forming heat
exchanger according to the invention, the vaporizer-condenser being
configured to allow an exchange of heat between a liquid containing
oxygen and a gas containing nitrogen.
[0084] Thus, such a cryogenic gas separation unit makes it possible
to handle the standard primary liquids and secondary fluids in the
field of cryogenics, for example a liquid containing oxygen and a
gas containing nitrogen for separating the components of air.
[0085] The embodiments and the variants mentioned above can be
taken in isolation or according to any technically acceptable
combination.
BRIEF DESCRIPTION OF THE DRAWINGS
[0086] The present invention will be well understood and its
advantages will also emerge in light of the following description,
given purely as a nonlimiting example and with reference to the
attached drawings, in which:
[0087] FIG. 1 is a transverse section of a smooth primary channel
of the prior art;
[0088] FIG. 2 is a perspective schematic view of a separation unit
according to the invention and comprising a heat exchanger
according to the invention;
[0089] FIG. 3 is a transverse section of a rough primary channel
according to a first embodiment of the invention;
[0090] FIG. 4 is a perspective view illustrating microstructure
elements disposed on the rough primary channel of FIG. 1;
[0091] FIG. 5 is a perspective view illustrating microstructure
elements disposed on a rough primary channel according to a second
embodiment of the invention;
[0092] FIG. 6 is a cross-sectional schematic view of a pattern
forming microstructure elements for the rough primary channel of
FIG. 4; and
[0093] FIG. 7 is a cross-sectional schematic view of a pattern
forming microstructure elements for a rough primary channel
according to a third embodiment of the invention.
DETAILED DESCRIPTION OF THE INVENTION
[0094] FIGS. 2, 3 and 4 illustrate a heat exchanger 1 for producing
exchanges of heat between a primary liquid and a secondary fluid.
The heat exchanger 1 belongs to a separation unit 2 for separating
the components of air by cryogenics.
[0095] In the example of FIGS. 2 to 4, the heat exchanger 1 is
configured to form a vaporizer-condenser configured to allow an
exchange of heat between a liquid containing oxygen and a gas
containing nitrogen. The plate heat exchanger 1 can thus be used to
vaporize an oxygen-rich liquid by exchange of heat with a
nitrogen-rich gas which is concomitantly condensed.
[0096] The heat exchanger 1 comprises several plates 11, which are
disposed parallel to one another, and spacers 12, which extend
between the plates 11 and which are also disposed parallel to one
another. In the example of FIGS. 2 to 4, the plates 11 and the
spacers 12 are made of an aluminum alloy. The plates 11 are brazed
together in a manner that is known per se.
[0097] The spacers 12 are disposed so as to define:
[0098] i) primary channels conformed for the flow of the primary
liquid, in this case containing liquid dioxygen (O2L), the primary
channels comprising rough primary channels 21; and
[0099] ii) secondary channels 22 conformed for the flow of the
secondary fluid, in this case containing gaseous dinitrogen
(N2G).
[0100] Each rough primary channel 21 is arranged so as to be able
to exchange heat with two respective secondary channels 22. To this
end, the rough primary channels 21 and the secondary channels 22
follow one another alternately in a direction of stacking D of the
plates 11. The rough primary channels 21 and the secondary channels
22 are here mounted in a counter-current configuration.
Alternatively, the rough primary channels 21 and the secondary
channels 22 can be mounted in a co-current configuration.
[0101] The heat exchanger 1 also comprises a primary liquid inlet
14 which is linked fluidically to a primary liquid distributor 6
belonging to the separation unit 2. The primary liquid O2L forms a
bath above the primary liquid distributor 6.
[0102] The inlet 14 is placed at an altitude greater than the rough
primary channels 21 when the heat exchanger 1 is in service. The
altitude is measured in the usual manner with reference to an
upward vertical direction. Thus, the primary liquid distributor 6
introduces the primary liquid in the form of a film flowing by
gravity through the inlet 14 into the rough primary channels.
[0103] Moreover, each rough primary channel 21 has an overall prism
form with polygonal section and extending along a longitudinal
direction X. This prism is made up of several overall flat faces.
The edges of the rectangle defining the base of the prism are here
a little rounded by braze. Each polygonal section--or polygonal
perimeter--of the prism here has dimensions of between 1 mm and 5
mm.
[0104] As FIG. 3 shows, each rough primary channel 21 here has an
overall prism form with rectangular base and extending along the
longitudinal direction X. In this case, the rectangular section has
an approximate height H21 equal to 4.5 mm and an approximate width
W21 equal to 1.5 mm. When the heat exchanger 1 is in service, the
primary liquid flows along the prism and at right angles to the
rectangular base.
[0105] Furthermore, as FIG. 3 shows, each rough primary channel 21
has microstructure elements 30. The microstructure elements 30 are
distributed or allocated over at least 80% of the length L21 of the
rough primary channel 21 considered. To dimension the separation
unit 2, the lengths L21 of the rough primary channels 21 and the
lengths of the secondary channels 22 are determined such that the
exchanges of heat make it possible to vaporize all or part of the
primary liquid and condense all or part of the secondary fluid
introduced in secondary gas form.
[0106] Each microstructure element 30 has dimensions of between 1
.mu.m and 300 .mu.m. Each microstructure element 30 here has the
overall form of a narrow cylinder. As FIG. 4 shows, the
microstructure elements 30 have mutually similar dimensions and
forms. The microstructure elements 30 are configured such that, for
each rough primary channel 21:
r>1+1.310.sup.3R.sub.a.epsilon..
[0107] in which: [0108] r is the ratio of the real surface of a
respective rough primary channel 21, as numerator, to the
geometrical surface of a respective rough primary channel 21, as
denominator, [0109] R.sub.a (in m) is the arithmetic mean deviation
relative to the median line, and [0110] .epsilon. is the void
fraction of the real surface of the respective rough primary
channel 21.
[0111] In the example of FIGS. 1 to 4, the microstructure elements
30 are regular and distributed uniformly, and they are configured
such that, for each rough primary channel 21:
r>1+1.310.sup.3h.epsilon.
[0112] in which: h (in m) is the mean height of the microstructure
elements 30, the mean height being calculated from the heights H30
of each microstructure element 30.
[0113] In the example of FIG. 4, the microstructure elements 30 are
not distributed over all the rectangular section of each rough
primary channel 21. On the contrary, the microstructure elements 30
are distributed only on the long sides 44 of the rectangular
section of each rough primary channel 21, but not on the short
sides 45. In other words, the short sides 45 have no microstructure
elements 30. In effect, the short sides 45 are wetted because of
the natural formation of the menisci in the corners of the
rectangular section.
[0114] The microstructure elements 30 are distributed so as to
define between them passages for the flow of the primary liquid
O2L, which defines a surface condition with an open roughness.
Furthermore, the microstructure elements 30 are distributed
uniformly. In other words, the interval between two successive
microstructure elements 30 is substantially constant in any
direction. The microstructure elements 30 are therefore arranged
according to a uniform and ordered matrix.
[0115] The microstructure elements 30 are here configured such
that, for each rough primary channel 21:
r>1+1.310.sup.3h.epsilon.
[0116] in which:
[0117] The microstructure elements 30 are here configured such
that, for each rough primary channel 21:
d < 7.5 10 - 4 P ##EQU00006##
[0118] in which: [0119] d (in m) is the mean distance between the
centers of the adjacent microstructure elements 30, the centers
being situated on the geometrical surface of the rough primary
channel 21, the mean distance being calculated from each distance
d30 separating, two-by-two, the centers of the adjacent
microstructure elements 30, [0120] P (in m) is the mean perimeter
of the section of the microstructure elements 30, and
[0121] furthermore, the microstructure elements 30 are here
configured such that, for each rough primary channel 21:
r - 1 - 1.3 10 3 h / h + 6.7 10 - 6 / d 2 > 4.2 10 - 8
##EQU00007##
[0122] Furthermore, the microstructure elements 30 are configured
such that, for each rough primary channel 21:
d > S 0.4 ##EQU00008##
[0123] in which: S (in m.sup.2) is the mean surface of the section
of the microstructures.
[0124] Because of the presence of the microstructure elements 30,
each rough primary channel 21 has an arithmetic roughness Ra of
between 1 .mu.m and 60 .mu.m. The arithmetic roughness Ra is a
statistical parameter representing the arithmetic mean deviation
relative to the median line of the surface of a rough primary
channel 21 considered.
[0125] Furthermore, each rough primary channel 21 can have
nanostructure elements (not represented) distributed over at least
80% of its length L21. Each nanostructure element has dimensions of
between 1 nm and 100 nm. The nanostructure elements can be
distributed over the surface of each rough primary channel 21 and
over the surfaces of the microstructure elements 30.
[0126] Moreover, the microstructure elements 30 form a coating
obtained here by spray deposition (sometimes referred to by the
term "spray") of particles on the surface of each rough primary
channel 21. The particles forming this coating are here made up of
a metal material.
[0127] FIGS. 5 and 6 show a part of a rough primary channel 121
belonging to a heat exchanger according to a second embodiment of
the invention. Inasmuch as the rough primary channel 121 is similar
to the rough primary channel 21, the description of the heat
exchanger and of the rough primary channel 21 given hereinabove in
relation to FIGS. 1 to 4 can be transposed to the rough primary
channel 121 and to its heat exchanger, apart from the notable
differences described hereinbelow.
[0128] The rough primary channel 121 differs from the rough primary
channel 21, essentially in that the microstructure elements 130
have a relatively wide and high cylinder form and in that the
interval between two microstructure elements 130 is greater than
the interval between two microstructure elements 30.
[0129] FIG. 7 illustrates, in section, in a plane x-z, a part of a
rough primary channel 221 belonging to a heat exchanger according
to a third embodiment of the invention. Inasmuch as the rough
primary channel 221 is similar to the rough primary channel 21, the
description of the heat exchanger and of the rough primary channel
21 given hereinabove in relation to FIGS. 1 to 4 can be transposed
to the rough primary channel 221 and to its heat exchanger, apart
from the notable differences described hereinbelow.
[0130] The rough primary channel 221 differs from the rough primary
channel 21, notably in that the microstructure elements 230 have
irregular, therefore mutually dissimilar, forms and dimensions.
Furthermore, the rough primary channel 221 differs from the rough
primary channel 21, notably in that the microstructure elements 230
are distributed non-uniformly, in this case randomly. In other
words, the intervals between two neighboring microstructure
elements 230 are variable, therefore not constant, over all the
real surface of the rough primary channel 221.
[0131] The microstructure elements 230 are configured such that,
for each rough primary channel 21:
r>1+1.310.sup.3R.sub.a.epsilon..
[0132] In FIG. 7, a median line z represents the arithmetic mean of
the height z measured point-by-point, including, for example,
heights z1, z2, z3, z4 et z5. R.sub.z is the height of the highest
peak relative to the lowest point of the surface.
[0133] Obviously, the present invention is not limited to the
particular embodiments described in the present patent application,
or to embodiments within the reach of a person skilled in the art.
Other embodiments can be envisaged without departing from the scope
of the invention, from any element equivalent to an element
indicated in the present patent application.
[0134] While the invention has been described in conjunction with
specific embodiments thereof, it is evident that many alternatives,
modifications, and variations will be apparent to those skilled in
the art in light of the foregoing description. Accordingly, it is
intended to embrace all such alternatives, modifications, and
variations as fall within the spirit and broad scope of the
appended claims. The present invention may suitably comprise,
consist or consist essentially of the elements disclosed and may be
practiced in the absence of an element not disclosed. Furthermore,
if there is language referring to order, such as first and second,
it should be understood in an exemplary sense and not in a limiting
sense. For example, it can be recognized by those skilled in the
art that certain steps can be combined into a single step.
[0135] The singular forms "a", "an" and "the" include plural
referents, unless the context clearly dictates otherwise.
[0136] "Comprising" in a claim is an open transitional term which
means the subsequently identified claim elements are a nonexclusive
listing (i.e., anything else may be additionally included and
remain within the scope of "comprising"). "Comprising" as used
herein may be replaced by the more limited transitional terms
"consisting essentially of" and "consisting of" unless otherwise
indicated herein.
[0137] "Providing" in a claim is defined to mean furnishing,
supplying, making available, or preparing something. The step may
be performed by any actor in the absence of express language in the
claim to the contrary.
[0138] Optional or optionally means that the subsequently described
event or circumstances may or may not occur. The description
includes instances where the event or circumstance occurs and
instances where it does not occur.
[0139] Ranges may be expressed herein as from about one particular
value, and/or to about another particular value. When such a range
is expressed, it is to be understood that another embodiment is
from the one particular value and/or to the other particular value,
along with all combinations within said range.
[0140] All references identified herein are each hereby
incorporated by reference into this application in their
entireties, as well as for the specific information for which each
is cited.
* * * * *