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 m and 300 m.

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 m and 300 m, and wherein the microstructure elements are configured such that, for each rough primary channel:
r>1+1.3.Math.10.sup.3.Math.R.sub.a.Math. 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 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+1.3.Math.10.sup.3.Math.h.Math. 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: $d<\sqrt{\frac{7.5.Math.{10}^{-4}.Math.P}{\mathrm{.Math.}}}$ 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: $\frac{r-1-1.3.Math.{10}^3.Math.h.Math.\mathrm{.Math.}}{\mathrm{.Math.}/h6.7.Math.{10}^{-6}/d^2}>4.2.Math.{10}^{-8}$ and in which the microstructure elements are also configured such that, for each rough primary channel: $d>\sqrt{\frac{S}{0.4}}$ 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: $\frac{r-1-1.3.Math.{10}^3.Math.R_a.Math.\mathrm{.Math.}}{\mathrm{.Math.}/R_a+1.2.Math.{10}^5}>4.2.Math.{10}^{-8}.$

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 m and 60 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

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 sectionor polygonal perimeterof 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 m and 300 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+1.3.Math.10.sup.3.Math.R.sub.a.Math..

[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] 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+1.3.Math.10.sup.3.Math.h.Math.

[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+1.3.Math.10.sup.3.Math.h.Math.

[0116] in which:

[0117] The microstructure elements 30 are here configured such that, for each rough primary channel 21:

[00006]$d<\sqrt{\frac{7.5.Math.{10}^{-4}.Math.P}{\mathrm{.Math.}}}$

[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:

[00007]$\frac{r-1-1.3.Math.{10}^3.Math.h.Math.\mathrm{.Math.}}{\mathrm{.Math.}/h+6.7.Math.{10}^{-6}/d^2}>4.2.Math.{10}^{-8}$

[0122] Furthermore, the microstructure elements 30 are configured such that, for each rough primary channel 21:

[00008]$d>\sqrt{\frac{S}{0.4}}$

[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 m and 60 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+1.3.Math.10.sup.3.Math.R.sub.a.Math..

[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.