Titanium or titanium alloy heat exchanger

Abstract

Title of the invention: Titanium or titanium alloy heat exchanger. The invention relates to a plate and fin heat exchanger configured for heat exchange between at least one refrigerant and at least one heat transfer fluid. The heat exchanger comprises a plurality of plates (2) arranged parallel to each other and in a longitudinal direction (z) so as to define between said plates (2) a plurality of passages (3) adapted for the flow of the refrigerant or heat transfer fluid along the longitudinal direction (z). Fin-type heat exchange structures (8) (123) are arranged within at least a portion of the passages (3). The heat exchanger is characterized in that the plates (2) and the heat exchange structures (8) are formed entirely or partially of titanium or a titanium alloy. Figure for the abstract: 1

Description

Title of the invention: Titanium or titanium alloy heat exchanger

[0001] The present invention relates to a plate and fin type heat exchanger.

[0002] The present invention finds application in particular in the field of separation of gas by cryogenics, in particular of the air separation by cryogenics (known by the English acronym "ASU" for air separation unit) operated for the production of gaseous oxygen under pressure. In particular, the present invention can be applied to a heat exchanger which vaporizes a refrigerant, for example liquid oxygen, by heat exchange with a calorigenic fluid, for example nitrogen gas. If the heat exchanger is located in the bottom of a distillation column, it can constitute a vaporizer-condenser operating in thermosiphon for which the exchanger is immersed in a bath of liquid oxygen descending the column or a vaporizer operating in falling film vaporization fed directly by the liquid falling from the column and / or by a recirculation pump.

[0003] The present invention can also be applied to a heat exchanger which vaporizes at least one flow of liquid-gas mixture, in particular a flow of mixture with several constituents, for example a mixture of hydrocarbons, by heat exchange with at least one other fluid, for example natural gas.

[0004] The present invention may also find application in the field of hydrogen liquefaction. In particular, the invention may be applied to a heat exchanger, in particular a catalytic exchanger, in which a flow of gaseous hydrogen is cooled, or even liquefied in whole or in part, by heat exchange with a flow of refrigerant fluid, as well as to the cooling and / or liquefaction process using said exchanger.

[0005] The present invention also applies to on-board cryogenic exchangers in which the fluids circulating in the exchanger may comprise neon, nitrogen, hydrogen, helium, oxygen, argon, carbon monoxide, methane.

[0006] In particular, one or more exchangers according to the invention can be used in a cryogenic refrigeration device, in particular a cryogenic refrigeration device using a Brayton cycle or an Ericsson cycle.

[0007] One technology used is that of aluminum plate and fin or brazed wave exchangers, which make it possible to obtain very compact devices offering a large exchange surface. These exchangers include separating plates and a stack of passages for the different fluids to be put into exchange relation. Thermal. Heat exchange structures, generally corrugated or wave structures formed by a succession of fins or wave legs, are inserted between the plates, delimiting in the passages channels in which the fluids flow and forming additional heat exchange surfaces.

[0008] The role of heat exchange structures is to increase the contact surface between the fluids and the walls of the exchanger in order to promote heat exchange. The performance of an exchanger is linked to the heat exchange coefficient of the heat exchange structures in contact with the fluids. The heat exchange coefficient of a structure depends in particular on the geometry of the structure, the nature of the material constituting it, the porosity of this material, its roughness and the flow regime of the fluids.

[0009] Improving the thermal performance of an exchanger with constant volume and temperature difference can be achieved in particular by increasing the exchange surface area and / or by increasing the heat exchange coefficient. The increase in the exchange surface area is generally linked to the density of the corrugated interlayer element used, generally expressed in terms of the number of fins per unit length.

[0010] Another performance criterion of a heat exchanger concerns its embeddability. Thus, cryogenic refrigeration devices embedded for example on satellites, such as Brayton cycle refrigerating machines, require heat exchangers that combine high energy efficiency and low weight. The exchangers used for this type of application are generally shell-and-tube type tubular exchangers comprising microtubes, typically with an outside diameter of the order of 0.5 mm. The advantage of microtubes lies in their small hydraulic diameter, making it possible to achieve very high heat exchange coefficients thanks to a Reynolds number (denoted Re) which becomes laminar and a Nusselt number (denoted Nu) which is constant for a laminar Reynolds number.

[0011] However, tubular exchangers are not entirely satisfactory. Indeed, these exchangers only allow the circulation of two fluids, which may be insufficient in certain processes. In addition, these primary surface exchangers offer only a small degree of freedom to vary the exchange surface according to the characteristics of the fluids involved. Finally, the need to weld the tubes into the tube plate fixed to the end of the shell can lead to a complex and tedious manufacturing process.

[0012] The present invention aims to solve all or part of the problems mentioned above, in particular to propose a heat exchanger whose embedding and operating flexibility are improved.

[0013] The solution according to the invention is then a plate type heat exchanger and fins configured to put into heat exchange relation at least one refrigerant fluid and at least one heat-generating fluid, said exchanger comprising a plurality of plates arranged parallel to each other and in a longitudinal direction so as to define between said plates a plurality of passages adapted for the flow of the refrigerant fluid or the heat-generating fluid in the longitudinal direction, finned heat exchange structures being arranged within at least part of the passages, characterized in that the plates and the heat exchange structures are formed in whole or in part from titanium or a titanium alloy.

[0014] Depending on the case, the exchanger according to the invention may comprise one or more of the technical characteristics given below.

[0015] All of the plates and heat exchange structures are made of titanium or a titanium alloy.

[0016] The exchanger comprises inlet or outlet manifolds configured to introduce or evacuate the refrigerant or the heat-transfer fluid into or from the passages, said inlet or outlet manifolds being formed in whole or in part from titanium or a titanium alloy.

[0017] The titanium alloy comprises at least 50% by weight of titanium, more preferably at least 90% by weight of titanium, and even more preferably at least 95% by weight of titanium.

[0018] The plates and the heat exchange structures are assembled by brazing using a brazing agent comprising a eutectic copper-silver alloy.

[0019] The heat exchange structures and the plates are assembled by brazing using a brazing agent, the heat exchange structures and / or the plates having in whole or in part a surface coating formed from a material other than nickel, a nickel alloy or the brazing agent, in particular formed from a material comprising nickel.

[0020] The heat exchange structures are in the form of corrugated products comprising at least one corrugation with wave peaks and wave bases arranged against the plates and connected alternately by fins, said fins succeeding one another in a direction of corrugation of the heat exchange structures.

[0021] Said at least one corrugation has a fin density, defined as the number of fins per unit length measured along the corrugation direction, of at least 30 fins per inch or fins per inch (1 inch = 2.54 centimeters), preferably a fin density of at most 80 fins per inch or fins per inch (1 inch = 2.54 centimeters), more preferably a fin density of between 40 and 70 fins per inch or fins per inch (1 inch = 2.54 centimeters).

[0022] The heat exchange structures have a thickness ranging from 0.03 to 0.1 mm.

[0023] The passages have a height ranging from 1 to 3 mm, said height being defined as the gap between two adjacent plates measured orthogonal to the plates.

[0024] The plates have a thickness ranging from 0.05 to 0.4 mm.

[0025] The exchanger comprises a body formed by the stacking of the plates (2), said body having a length, measured parallel to the longitudinal direction (z), less than or equal to 1 m, preferably between 0.1 and 0.8 m and / or said body having a width, measured parallel to the lateral direction (x), less than or equal to 0.1 m, preferably between 0.02 and 0.08 m and / or said body having a height, measured orthogonally to the longitudinal (z) and lateral (x) directions, less than 0.06 m, preferably between 0.01 and 0.05 m.

[0026] The passages are delimited by closing bars arranged between the plates and formed entirely or partly from titanium or a titanium alloy.

[0027] The closing bars have a square, rectangular or U-shaped cross-section.

[0028] According to another aspect, the invention relates to an installation for separating air by distillation or liquefying hydrogen comprising at least one heat exchanger according to the invention, the heat exchanger comprising inlet or outlet collectors for distributing or discharging into or from passages of the exchanger liquid oxygen as refrigerant and gaseous nitrogen as calorigenic fluid.

[0029] Furthermore, the invention relates to a cryogenic refrigeration device intended to transfer heat from a cold source to a hot source via a working fluid circulating in a closed working circuit, the working circuit comprising in series: a substantially isothermal compression portion of the working fluid, a substantially isobaric cooling portion of the working fluid, a substantially isothermal expansion portion of the working fluid and a substantially isobaric heating portion of the working fluid, the compression portion of the working circuit comprising at least two compressors arranged in series and at least one exchanger for cooling the compressed working fluid arranged at the outlet of each compressor, the expansion portion of the working circuit comprising at least one expansion turbine and at least one exchanger for heating the expanded working fluid,wherein the exchanger for cooling the compressed working fluid and / or the exchanger for heating the expanded working fluid is according to the invention and comprises inlet or outlet manifolds for distributing or discharging into or from passages of the exchanger the compressed working fluid as a heat-transfer fluid or the expanded working fluid as a refrigerant fluid.

[0030] Furthermore, the invention relates to the use of an exchanger according to the invention in which said at least one heat-generating fluid and / or said at least one refrigerating fluid comprises at least one of: neon, krypton, xenon, nitrogen, argon, oxygen, hydrogen, helium, carbon monoxide, carbon dioxide, methane.

[0031] The present invention will now be better understood thanks to the description which follows, given solely by way of non-limiting example and made with reference to the figures mentioned below.

[0032] [Fig-1] is a partial three-dimensional view of an exchanger according to a method of rea lization of the invention.

[0033] [Fig.2] is a sectional view of a heat exchange structure in a passage exchanger according to one embodiment of the invention.

[0034] [Fig.3] is a schematic view illustrating the structure and operation of a exemplary embodiment of a refrigeration device according to the invention.

[0035] As seen in [Fig.l], a heat exchanger according to the invention comprises a set of plates 2 arranged parallel to each other with spacing and thus forming several series of passages 3 of parallelepipedal and flat shape for the flow of at least one refrigerant fluid and at least one heat-generating fluid to be put into indirect heat exchange relation via the plates 2.

[0036] The plates 2 are stacked parallel to each other and in a stacking direction y. They extend in two dimensions, length and width, respectively in the longitudinal direction z and the lateral direction x. The plates 4 thus define a plurality of passages 3 for the flow of fluids generally parallel to the longitudinal direction z. Preferably, each passage 3 has a parallelepiped and flat shape.

[0037] Over the majority of their height, the passages 3 contain heat exchange structures 8 comprising, in this example, corrugated sheets, also called exchange waves. These structures may be perforated or not. These exchange structures 8 are preferably of the vertical generator type, or so-called “easyway” arrangement. In this case, the corrugated exchange structures 8 have, in operation, an overall direction of undulation which is orthogonal to the longitudinal direction z and parallel to the lateral direction x. The exchange structures are bonded by brazing to the plates 2.

[0038] It is also conceivable that the heat exchange structures of the exchanger have directions, dimensions and / or corrugation shapes different from those of the embodiments described in the present application.

[0039] At the end of the passages 3, the exchange structures 8 may be extended respectively by so-called distribution waves used to distribute the fluids in the respective passages. All or part of the passages of the exchanger 1 may be provided with at least one heat exchange structure 8. Along their edges, the passages 3 are closed respectively by closing bars 6. The plates 2 are spaced between them by these bars 6 which do not completely block the passages 3 but leave inlet and outlet openings. The inlets and outlets of each passage used for the circulation of the same fluid are joined by collectors 4, 7 provided with pipes 5 and used for the introduction and evacuation of the fluid.

[0040] According to the invention, the plates 2 and the heat exchange structures 8 are formed entirely or partly from titanium or a titanium alloy.

[0041] First of all, thanks to its plate structure, the exchanger can put more than two fluids into heat exchange relation, which makes it a compact device, offering a large exchange surface and more flexible operation, in comparison with a tubular heat exchanger.

[0042] Furthermore, titanium and its alloys are characterized by low densities, lower than those of aluminum or steel, allowing the manufacture of lighter parts.

[0043] Titanium and its alloys also exhibit good mechanical strength, which is advantageous when the elements are subjected to mechanical stresses during their transport or their use in on-board devices. In addition, titanium and its alloys exhibit good corrosion resistance, which makes them materials suitable for use in corrosive atmospheres, particularly in the presence of air or oxygen.

[0044] Another advantage is that titanium or its alloys have a lower thermal conductivity than aluminum or aluminum alloys, particularly at low temperatures. This significantly reduces the phenomenon of thermal conduction from the hot end to the cold end of the exchanger, particularly through the closure bars, and known as longitudinal conduction or thermal leaks by longitudinal conduction, which is problematic for relatively short exchangers and therefore having a hot end close to the cold end.

[0045] The use of titanium or titanium alloy thus makes it possible to envisage shorter exchangers, therefore more compact and more easily embarkable. In particular, the plates 2 of the exchanger have a length, measured parallel to the longitudinal direction z, less than or equal to 1 m, preferably between 0.1 and 0.8 m. According to one embodiment, the plates 2 of the exchanger have a width, measured parallel to the lateral direction x, less than or equal to 0.1 m, preferably between 0.02 and 0.08 m.

[0046] According to one embodiment, the plates 2 have a thickness ranging from 0.05 to 0.4 mm.

[0047] According to one embodiment, the exchanger comprises a stack of a plurality of plates 2, the stack having a height, measured parallel to the stacking direction y, of between 0.01 m and 0.05 m.

[0048] In one embodiment, all of the plates 2 and the heat exchange structures 8 are formed from titanium or a titanium alloy.

[0049] Preferably, the inlet or outlet collectors 4, 7 are also formed entirely or partly from titanium or a titanium alloy. More preferably, all of the constituent elements of the exchanger are formed from titanium or a titanium alloy.

[0050] By "constituent elements of the exchanger" is meant in particular the primary parts forming the body of the exchanger, in particular the heat exchange structures, the plates, the closing bars, as well as the fluid inlet or outlet collectors assembled to said body.

[0051] The titanium alloy preferably comprises at least 50% by weight of titanium, more preferably at least 90% by weight of titanium, and even more preferably at least 95% by weight of titanium. In particular, the titanium alloy may comprise titanium and at least one component chosen from carbon, iron, vanadium, nitrogen, oxygen, hydrogen.

[0052] According to a particular embodiment, the titanium alloy may comprise from 0 to 0.08% carbon, from 0 to 0.05% nitrogen, from 0 to 0.4% oxygen, from 0 to 0.015% hydrogen and titanium for the remainder.

[0053] According to another particular embodiment, the titanium alloy may comprise from 0 to 0.1% carbon, from 0 to 0.05% nitrogen, from 0 to 0.2% oxygen, from 0 to 0.01% hydrogen, from 5.5 to 6.75% aluminum, from 3.5 to 4.5% vanadium, from 0 to 0.4% iron and titanium for the remainder.

[0054] According to another particular embodiment, the titanium alloy may comprise from 0 to 0.08% carbon, from 0 to 0.05% nitrogen, from 0 to 0.13% oxygen, from 0 to 0.012% hydrogen, from 5.5 to 6.5% aluminum, from 3.5 to 4.5% vanadium, from 0 to 0.25% iron and titanium for the remainder.

[0055] According to one embodiment, the plates 2 and the heat exchange structures 8 are assembled together by brazing using a brazing agent comprising a eutectic alloy, preferably a binary copper-silver eutectic alloy (CuAg). For example, the eutectic alloy may comprise 25% by weight of copper and 75% by weight of silver. The use of a eutectic alloy makes it possible to limit the temperature necessary for the brazing operation and therefore to limit the thermal and mechanical stresses on the constituent elements of the exchanger. The brazing agent may in particular be in the form of a coating deposited on the surfaces of the plates 2 and / or the exchange structures 18 or of one or more strips arranged between the surfaces of the plates 2 and / or the exchange structures 8 to be assembled.

[0056] According to one embodiment, all or part of the constituent elements of the exchanger, in particular the heat exchange structures 8 and / or the plates 2 and / or the closing bars 6, have in whole or in part a surface coating formed of a material distinct from nickel, a nickel alloy or the brazing agent, in particular formed from a material comprising nickel, preferably pure nickel or an alloy comprising at least 90%, or even at least 95% by weight of nickel. The surface coating is configured to limit the dissolution of the base metal forming the constituent elements of the exchanger during brazing. This limits the interaction between the brazing agent and the metal constituting the constituent elements of the exchanger so as to form as few fragile intermetallic phases as possible, which makes it possible to increase the mechanical strength of the exchanger.

[0057] Preferably, the heat exchange structures are coated before being brazed with the plates 2. Preferably, at least 90%, more preferably at least 95%, more preferably at least 98% of the surface area of ​​the exchange structures 8 is coated.

[0058] [Fig.2] schematizes an exemplary embodiment according to which the structures heat exchange 8 are in the form of corrugated products comprising at least one corrugation with wave peaks 121 and wave bases 122 alternately connected by fins 123, also called wave legs. The fins 123 follow one another in a corrugation direction D which is parallel to the plates 2 and, in the example illustrated, orthogonal to the longitudinal direction z.

[0059] In operation, the fluid circulating in the passage 3 is in indirect heat exchange relationship via a plate 2, which forms a primary exchange surface, with another fluid circulating in an adjacent passage 3. The fins 123 form secondary exchange surfaces which make it possible to intensify the heat exchanges between the fluids, as well as to stiffen the exchange passages by acting as spacers.

[0060] The structures 8 may also have other particular shapes defined according to the desired fluid flow characteristics. More generally, the term "fins" covers blades or other secondary heat exchange surfaces, which extend between the primary heat exchange surfaces, i.e. the plates of the exchanger, in the passages of the exchanger.

[0061] In the embodiment according to [Fig.2], the channels defined between each pair of consecutive fins 123 have a generally rectangular cross-section, the fins extending generally parallel to the longitudinal direction z and parallel to the stacking direction y. It is also conceivable that the fins 123 form an angle of inclination with the direction y.

[0062] Note that as a heat exchange structure 8 of the corrugated product type, it will be possible to use the different types of waves usually implemented in plate and fin type exchangers, namely straight waves, partially offset waves (of the "serrated" type in English), wave or herringbone waves (of the "herringbone" type in English), perforated or not.

[0063] Preferably, the heat exchange structure 8 has a height h, corresponding substantially to the height of the passage in which it is arranged, of between 1 and 3 mm. The heat exchange structure 8 preferably has a thickness e of less than 0.15 mm, preferably ranging from 0.03 to 0.1 mm. This makes it possible to gain in compactness and / or to reduce the weight of the exchanger. Note that the thickness of a heat exchange structure of the corrugated product type is understood to be the thickness of the flat product from which the corrugated product is formed. This thickness corresponds to the thickness of the wave legs, the wave tops and the wave bases once the corrugated product has been formed.

[0064] According to one embodiment, the heat exchange structure 8 has at least 40 fins per inch (1 inch = 2.54 centimeters), preferably a fin density of at most 70 fins per inch (1 inch = 2.54 centimeters). Since titanium or its alloys have a lower density than aluminum, it is possible to use higher fin densities without increasing the weight of the exchanger too significantly. As in the example of [Fig. 2], the fins 123 preferably follow one another periodically with a pitch p between two successive fins. The fin density n, i.e. the number of fins per unit length, expressed by the relationship n = l / p.

[0065] According to one embodiment, the passages 3 are delimited by closure bars 6 which may have a square, rectangular or U-shaped cross-section. The closure bars 6 with a U-shaped section make it possible to mechanically reinforce the exchanger and limit the collapse of the waves during the brazing operation at temperature. Indeed, in order to obtain quality brazed joints, that is to say continuous, it is imperative to apply a load to the assembly during brazing. In addition, the closure bars serve to isolate the fluids contained in the exchanger from the external atmosphere. The use of closure bars 6 with a U-shaped section makes it possible to gain in passage section for the fluid circulating in the passages of the exchanger, thanks to the additional volume released in the hollow of the U, and contributes to minimizing the size of the exchanger.

[0066] Preferably, all or part of the bars 6 are arranged so that the hollow of the U of the bars 6 is oriented towards the inside of the passages of the exchanger.

[0067] The hollow of the U can possibly be oriented towards the face of one of the plates located on either side of a bar.

[0068] Note that the closure bars 6 may also be formed in whole or in part from titanium or a titanium alloy. The bars 6 may also be assembled by brazing using a brazing agent comprising a eutectic copper-silver alloy.

[0069] [Fig.3] schematizes an embodiment according to which at least one exchanger according to the invention is integrated into a cryogenic refrigeration device of the type using a Brayton cycle. These refrigeration devices are generally used for the reliquefaction of methane vapors or the liquefaction of hydrogen or even for cooling superconducting elements. They may be devices on board ships or satellites. The integration of one or more exchangers according to the invention has the advantage of reducing the mass and dimensions of the refrigeration devices. Referring to the exemplary embodiment of [Fig. 3], the refrigeration device according to the invention is intended to transfer heat from a cold source 35 at a cryogenic temperature to a hot source 21, at ambient temperature for example.

[0070] The cold source 35 may be, for example, liquid nitrogen to be cooled and the hot source 21 water or air. To achieve this heat transfer, the refrigeration device illustrated in [Fig.3] uses a working circuit 200 of a working fluid comprising the components listed below.

[0071] The circuit 200 comprises at least two centrifugal compressors 23, 25, 27 arranged in series and operating at ambient temperature. The circuit 200 comprises several heat exchangers 22, 24, 26 operating at ambient temperature arranged respectively at the outlet of the compressors 23, 25, 27. The temperatures of the working fluid at the inlet and outlet of each compression stage (i.e. at the inlet and outlet of each compressor 23, 25, 27) are maintained by the heat exchanges at a substantially identical level.

[0072] The inlet and outlet temperatures of each compression stage are substantially the same.

[0073] The exchangers 22, 24, 26 may be separate or consist of separate portions of the same exchanger in heat exchange with the hot source 21. At least one of the exchangers 26, 24, 22 for cooling the compressed working fluid is according to the invention.

[0074] Downstream of the compression portion comprising the compressors in series, the refrigerator comprises a heat exchanger 28, preferably of the counter-current plate type, separating the elements at ambient temperature (in the upper part of the circuit 200 shown in [Fig. 3]) from the elements at cryogenic temperature (in the lower part of the circuit 200). The fluid is cooled. The cooling of the gas from ambient temperature to cryogenic temperature is carried out by counter-current exchange with the same working fluid at cryogenic temperature which returns from the expansion portion after heat exchange with the cold source 35. Downstream of this cooling portion constituted by the plate exchanger 28, the circuit comprises one or more expansion turbines 29, 31, 33, preferably of the centripetal type, arranged in series. The turbines 29, 31, 33 operate at cryogenic temperature, the tem The inlet and outlet temperatures of each expansion stage (turbine inlet and outlet) are maintained substantially identical by one or more cryogenic heat exchangers 30, 32, 34 arranged at the outlet of the turbine(s). This arrangement makes it possible to approximate isothermal expansion. The inlet and outlet temperatures of each expansion stage are substantially the same.

[0075] These heating exchangers 30, 32, 34 may be separate or consist of separate portions of the same exchanger in heat exchange with the cold source 35. At least one of the exchangers 30, 32, 34 for heating the expanded working fluid is in accordance with the invention.

[0076] Downstream of the expansion portion and the heat exchange with the cold source 35, the working fluid exchanges heat again with the plate heat exchanger 28. The fluid exchanges heat in the exchanger 8 counter-currently to its passage after the compression portion. After reheating, the fluid returns to the compression portion and can start a cycle again.

[0077] The refrigerator preferably uses as working fluid a fluid in the gas phase circulating in a closed circuit. This consists, for example, of a pure gas or a mixture of pure gases. The gases best suited to this technology include: helium, neon, nitrogen, oxygen and argon. Carbon monoxide and methane, or any other fluid having a gas phase at the temperature of the cold source, can also be used.

[0078] According to one embodiment, the refrigerator is designed and controlled in such a way as to obtain a fluid working cycle approaching the Ericsson cycle, i.e. isothermal compression, isobaric cooling, isothermal expansion and isobaric heating.

[0079] According to another embodiment, the refrigerator is designed and controlled in such a way as to obtain a fluid working cycle approaching the Brayton cycle, i.e. adiabatic compression, isobaric cooling, adiabatic expansion and isobaric heating.

[0080] According to an advantageous feature, the refrigerator uses several so-called high-speed motors 70 for driving at least the compressors 23, 25, 27 (i.e. for driving the compressor wheels). A high-speed motor is usually understood to mean motors whose rotational speed allows direct coupling with a centrifugal compression stage or a centripetal expansion stage. High-speed motors preferably use magnetic or dynamic gas bearings. A high-speed motor typically rotates at a rotational speed of 10,000 revolutions per minute or several tens of thousands of revolutions per minute. A low-speed motor usually rotates at a speed of a few thousand revolutions per minute.

Claims

Claims

1. A plate and fin heat exchanger configured to bring into heat exchange relation at least one refrigerant and at least one heat-transfer fluid, said exchanger comprising a plurality of plates (2) arranged parallel to each other and in a longitudinal direction (z) so as to define between said plates (2) a plurality of passages (3) adapted for the flow of the refrigerant or the heat-transfer fluid in the longitudinal direction (z), heat exchange structures (8) with fins (123) being arranged within at least a portion of the passages (3), characterized in that the plates (2) and the heat exchange structures (8) are formed in whole or in part from titanium or a titanium alloy.

2. Exchanger according to claim 1, characterized in that all of the plates (2) and the heat exchange structures (8) are formed from titanium or a titanium alloy.

3. Exchanger according to one of claims 1 or 2, characterized in that it comprises inlet or outlet manifolds (4, 7) configured to introduce or evacuate the refrigerant or the heat-generating fluid into or from the passages (3), said inlet or outlet manifolds (4, 7) being formed in whole or in part from titanium or a titanium alloy.

4. Exchanger according to one of the preceding claims, characterized in that the titanium alloy comprises at least 50% by weight of titanium, more preferably at least 90% by weight of titanium, and even more preferably at least 95% by weight of titanium.

5. Exchanger according to one of the preceding claims, characterized in that the heat exchange structures (8) and the plates (2) are assembled by brazing using a brazing agent, the heat exchange structures (8) and / or the plates (2) having in whole or in part a surface coating formed from a material other than nickel, a nickel alloy or the brazing agent, in particular formed from a material comprising nickel.

6. Exchanger according to one of the preceding claims, characterized in that the plates (2) and the heat exchange structures (8) are assembled by brazing using a brazing agent comprising a eutectic copper-silver alloy.

7. Exchanger according to one of the preceding claims, characterized in that the heat exchange structures (8) are in the form of corrugated products comprising at least one corrugation with corrugation peaks (121) and corrugation bases (122) arranged against the plates (2) and connected alternately by fins (123), said fins (123) succeeding one another in a direction of corrugation (D) of the heat exchange structures (8).

8. Exchanger according to claim 7, characterized in that said at least one corrugation has a fin density, defined as the number of fins per unit of length measured along the corrugation direction (D), of at least 30 fins per inch or fins per inch (1 inch = 2.54 centimeters), preferably a fin density of at most 80 fins per inch or fins per inch (1 inch = 2.54 centimeters), more preferably a fin density of between 40 and 70 fins per inch or fins per inch (1 inch = 2.54 centimeters).

9. Exchanger according to one of the preceding claims, characterized in that the heat exchange structures (8) have a thickness ranging from 0.03 to 0.1 mm.

10. Exchanger according to one of the preceding claims, characterized in that the passages (3) have a height ranging from 1 to 3 mm, said height being defined as the gap between two adjacent plates (2) measured orthogonally to the plates (2).

11. Exchanger according to one of the preceding claims, characterized in that the plates (2) have a thickness ranging from 0.05 to 0.4 mm.

12. Exchanger according to one of the preceding claims, characterized in that it comprises a body formed by the stacking of the plates (2), said body having a length, measured parallel to the longitudinal direction (z), less than or equal to 1 m, preferably between 0.1 and 0.8 m and / or said body having a width, measured parallel to the lateral direction (x), less than or equal to 0.1 m, preferably between 0.02 and 0.08 m and / or said body having a height, measured orthogonally to the longitudinal (z) and lateral (x) directions, less than 0.06 m, preferably between 0.01 and 0.05 m.

13. Exchanger according to one of the preceding claims, characterized in that the passages (3) are delimited by closing bars (6) arranged between the plates (2) and formed entirely or partly from titanium or a titanium alloy, in particular the closing bars (6) have a square, rectangular or U-shaped cross-section.

14. Installation for separating air by distillation or liquefaction of hydrogen comprising at least one heat exchanger according to one of claims 1 to 12, the heat exchanger comprising inlet or outlet collectors for distributing or discharging into or from passages of the exchanger liquid oxygen as refrigerant and gaseous nitrogen as calorigenic fluid.

15. Cryogenic refrigeration device intended to transfer heat from a cold source (35) to a hot source (21) via a working fluid circulating in a closed working circuit (200), the working circuit (200) comprising in series: a substantially isothermal compression portion of the working fluid, a substantially isobaric cooling portion of the working fluid, a substantially isothermal expansion portion of the working fluid and a substantially isobaric heating portion of the working fluid, the compression portion of the working circuit (200) comprising at least two compressors (27, 25, 23) arranged in series and at least one exchanger (26, 24, 22) for cooling the compressed working fluid arranged at the outlet of each compressor (27, 25, 23), the expansion portion of the working circuit (200) comprising at least one expansion turbine (29, 31, 33) and at least one exchanger (30, 32,34) for heating the expanded working fluid, wherein the exchanger (26, 24, 22) for cooling the compressed working fluid and / or the exchanger (30, 32, 34) for heating the expanded working fluid is as defined according to one of claims 1 to 12 and comprises inlet or outlet manifolds for distributing or discharging into or from passages of the exchanger the compressed working fluid as a heat-transfer fluid or the expanded working fluid as a refrigerant fluid.,

16. Use of an exchanger according to one of claims 1 to 13 in which said at least one heat-generating fluid and / or said at least one refrigerating fluid comprises at least one of: neon, krypton, xenon, nitrogen, argon, oxygen, hydrogen, helium, carbon monoxide, carbon dioxide, methane.

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