Method and device for cryogenic cooling

Abstract

Method for cryogenic cooling of a first fluid (2) by heat exchange with at least one second fluid (3) in a heat exchanger (1), the first fluid (2) and / or the second fluid (3) being at a temperature between -100°C and -273°C, characterized in that the heat exchanger (1) is of the type with polymer microtubes, i.e. comprising a plurality of microtubes (4) made of polymer and having a diameter of between 0.1 mm and 1 cm, one of the first (2) and second (3) fluids being circulated inside said microtubes (4) whilst the other fluid is circulated around said microtubes (4).

Description

[0001] The invention relates to a cryogenic cooling method and device.

[0002] The invention relates more particularly to a cryogenic cooling method for a first fluid by heat exchange with at least one second fluid in a heat exchanger, the first fluid and / or the second fluid being at a temperature between -100°C and -273°C. Such methods and devices conforming to the preambles of claims 1 and 14 are known, for example, from document FR 2 891 901A.

[0003] The structure of cryogenic heat exchangers is generally bulky, expensive, and massive. Examples include plate or tube heat exchangers made of aluminum or other metals. This type of exchanger is poorly suited for certain applications where mass or volume is critical (such as those installed in floating or flying vehicles). Other, less massive technologies exist (for example, shell-and-tube heat exchangers with polymer tubes), but they are not suitable for applications within cryogenic temperature ranges (below -100°C, for example) because these exchangers are brittle at these temperatures and cannot withstand pressure differentials and / or experience sealing and performance issues.

[0004] One aim of the present invention is to overcome all or part of the disadvantages of the prior art noted above.

[0005] To this end, the device according to the invention, which also conforms to the generic definition given in the preamble above, is essentially characterized in that the heat exchanger is of the polymer microtube type, i.e. comprising a plurality of polymer microtubes and having a diameter between 0.1mm and 1cm, one of the first and second fluids being circulated inside said microtubes while the other fluid is circulated around said microtubes.

[0006] Furthermore, embodiments of the invention may include one or more of the following characteristics: The microtubes are made of at least one of the following materials: polyetheretherketone (PEEK), polytetrafluoroethylene (PTFE), polyetherimide, polyimide(s), polyamide(s), polycarbonate(s), or any other plastic material compatible with use at said low temperatures; the microtubes are made of a material comprising a mixture of polyetherimide ("Ultem") and PEEK; the microtubes are made of a material having a density between 2700 kg / m³ and 900 kg / m³, and in particular less than 1500 kg / m³; the microtubes have a diameter between 0.1 mm and 5 mm; the pressure differential between the pressure of the fluid circulating in the microtubes and the pressure of the fluid circulating around the microtubes is between 1 bar and 100 bar, and in particular between 10 and 50 bar; the heat exchanger The heat pump includes a casing in which the microtubes are arranged.the housing comprising a first inlet communicating with a first end of the microtubes, the housing comprising a first outlet communicating with a second end of the microtubes, the housing also comprising a second inlet and a second outlet communicating with the volume surrounding the microtubes, the microtubes are arranged in a bundle along a longitudinal direction within the housing, the bundles are arranged parallel to the longitudinal direction and are preferably straight, the microtubes are wound in a helix, preferably distributed around a central support mandrel, at least one of the two longitudinal ends of the microtube bundle comprises a layer of rigid material such as a thermoset ensuring the cohesion of the microtube bundle,the housing containing at least one elastic element constrained along the longitudinal direction between a stop formed in the housing and a longitudinal end of the microtube bundle, to ensure the longitudinal maintenance of the microtube bundle while allowing expansion or contraction relative to the housing along the longitudinal direction, the elastic element comprises at least one of the following: a spring, a helical spring, one or more elastic washers, particularly of the Belleville type, the housing includes an elastic zone along the longitudinal direction such as a bellows, the process ensures heat exchange between more than two fluids, i.e., distinct portions of the microtubes and / or the volume around the microtubes accommodate distinct flows of fluid(s) for heat exchange in the heat exchanger, the cooling is achieved in a process of cryogenic refrigeration and / or liquefaction of a fluid,The heat exchanger is located within a cryogenic refrigeration and / or liquefaction device.

[0007] The invention also relates to a cryogenic cooling device for at least one first fluid by heat exchange with at least one second fluid comprising a heat exchanger ensuring heat exchange between the first fluid and the second fluid, the first and / or second fluid being at a temperature between -100°C and -273°C, the heat exchanger being of the polymer microtube type, i.e. comprising a plurality of polymer microtubes and having a diameter between 0.1mm and 10mm, the heat exchanger comprising inlets and outlets for the first and second fluid ensuring circulation of at least one fluid inside said microtubes and circulation of the other fluid around said microtubes.

[0008] Furthermore, according to possible characteristics: the exchanger includes a working circuit containing a working fluid, the working circuit comprising at least one compressor of the working gas, at least one heat exchanger for cooling the compressed fluid, at least one expansion element of the working fluid, at least one heat exchanger for reheating the expanded working fluid, the at least one cooling heat exchanger and / or the at least one reheating heat exchanger is of the polymer microtube type, i.e. comprising a plurality of polymer microtubes and having a diameter between 0.1mm and 10mm, and comprising inlets and outlets for a first flow of working fluid and another fluid having a temperature distinct from the temperature of the first flow of working fluid, to ensure heat exchange between the first flow of working fluid and the other fluid.

[0009] The invention may also relate to any alternative device or method comprising any combination of the above or below features within the scope of the claims.

[0010] Other features and advantages will become apparent upon reading the description below, which refers to the figures in which: [ Fig. 1 ] represents a schematic and partial longitudinal cross-sectional view, illustrating a first example of the structure and operation of a cooling heat exchanger according to the invention, [ Fig. 2 ] represents a schematic and partial longitudinal cross-sectional view, illustrating a second example of the structure and operation of a cooling heat exchanger according to the invention, [ Fig. 3 ] represents a schematic and partial longitudinal cross-sectional view, illustrating a third example of the structure and operation of a cooling heat exchanger according to the invention, [ Fig. 4 ] represents an enlarged detail of the heat exchanger of the [ Fig. 3 ], [ Fig. 5 ] represents a cross-sectional view of an example of an elastic element that could be used in such a heat exchanger, [ Fig. 6 ] represents a schematic and partial longitudinal cross-sectional view, illustrating a fourth example of the structure and operation of a cooling heat exchanger according to the invention, [ Fig. 7 ] represents a schematic and partial view illustrating an example of the structure and operation of a cryogenic refrigeration device that can use a cooling heat exchanger according to the invention, [ Fig. 8 ] illustrates a longitudinal cross-sectional view of another example of the implementation of such a cooling heat exchanger.

[0011] The cryogenic cooling heat exchanger 1 is shown schematically in the diagram. figure 1 The invention ensures the cooling of a first fluid 2 by heat exchange with a second fluid 3. For example, the first fluid 2 and / or the second fluid 3 may be at a temperature between -100°C and -273°C. Although optimal at cryogenic temperatures, the invention can also be used at ambient temperature or between ambient and cryogenic temperatures. The heat exchanger 1 is of the polymer microtube type, i.e., comprising a plurality of polymer microtubes 4 with a diameter between 0.1 mm and 1 cm. For example, the first fluid 2 is circulated inside said microtubes 4, while the second fluid 3 is circulated around said microtubes 4. The microtubes 4 are preferably non-porous.

[0012] Microtubes 4 are preferably made of at least one of the following materials: polyetheretherketone (PEEK), polytetrafluoroethylene (PTFE), polyetherimide, polyimides, polyamides, polycarbonates, for example, a 50% polyetherimide ("Ultem") and 50% PEEK blend, and in particular any suitable material compatible with cryogenic temperatures. This PEEK / Ultem blend can be extruded as an amorphous material with a glass transition temperature (Tv, or Tg) of approximately 180°C. Unlike the materials used in the literature, this blend does not require annealing. Furthermore, this blend is essentially non-crystalline and is quite strong and flexible as manufactured. Other crystalline materials mentioned in the literature have relatively high coefficients of thermal expansion (CTE), some exceeding 80 ppm / °C.

[0013] Since the heat exchanger must operate over a very wide temperature range, it is essential that the construction materials have closely matched coefficients of thermal expansion (CTE). This is necessary so that the various components of the unit can expand and contract in unison across the operating temperature range. Close alignment of the CTEs is crucial to maintain the bond between the tubesheet material and the heat exchange tubes, as well as between the tubesheet and the structural support beam mandrel. All structural components of the module are selected for their closely aligned or similarly homogeneous CTEs.

[0014] Thus, the coefficient of thermal expansion (CTE) of PEEK is 45, the coefficient of thermal expansion of Ultem is 45 and the coefficient of thermal expansion of Epoxy resin is for example equal to 55.

[0015] This constituent material is compatible with cryogenic temperatures (down to a few degrees Kelvin for example) and can withstand significant pressure differentials (for example reaching the order of 100 bar).

[0016] Microtubes 4 are preferably made of a material having a density less than 2700kg / m3< and in particular less than 1500kg / m3< and for example between 900kg / m3 and 2700kg / m3.

[0017] The microtubes 4 preferably have a thickness between 0.01 mm and 1 mm, particularly 0.05 mm. Furthermore, the microtubes 4 preferably have a diameter on the order of 0.1 to several millimeters, particularly one millimeter.

[0018] This allows for significant heat exchange between the two fluids while limiting the volume and mass of the heat exchanger. The mechanical resistance to pressure differentials between the parts of the exchanger subjected to high pressure and the parts subjected to lower pressure is not affected; on the contrary, it is enhanced.

[0019] The pressure differential between the pressure of the fluid 2 circulating in the micro-tubes 4 and the pressure of the fluid 3 circulating around the micro-tubes 4 can be between 1 bar and 100 bar and in particular between 10 and 50 bar.

[0020] The heat exchanger 1 may include a housing 5 in which the microtubes 4 are arranged. The housing 5 includes a first inlet 6 communicating with one end of the microtubes 4 and a first outlet 7 communicating with the other end of the microtubes 4. The housing 5 also includes a second inlet 8 and a second outlet 9 communicating with the volume surrounding the microtubes. These two inlet / outlet pairs define two independent circuits for two fluids.

[0021] As illustrated, the micro-tubes 4 can be arranged in a bundle, for example parallel along a longitudinal direction in the housing 5 (and in particular straight or substantially straight), or in any other geometric configuration.

[0022] For example, the four microtubes can be wound helix and, for instance, arranged in an organized manner around a central support mandrel. This helical winding can serve not only to control the packing density of the tubes but also provides a unique mechanism to combat potential dimensional shrinkage of the tubes at low temperatures. In devices where the microtubes are oriented parallel to each other, tube shrinkage due to thermal contraction can potentially exert stress on the microtubes, which can then be transmitted to the tubesheet. This stress can lead to a breakdown of the bond between the tubesheet material and the individual tubes or, in extreme cases, to failure of the tubesheet or the manifold itself.

[0023] The helically wound microtubes 4 alleviate shrinkage stress by modifying their winding angle within the device. Therefore, the microtubes 4 are not subjected to axial tension during their shrinkage.

[0024] There [ Fig. 8 [ ] illustrates a longitudinal cross-sectional view of a possible embodiment of such a heat exchanger with microtubes 4 wound helically around a central mandrel 20. The bundle of wound microtubes 4 can thus form a tubular entity whose two ends can be mounted respectively on the shafts of two inserts 21, 22 mounted at the ends of the mandrel 20.

[0025] The peripheral surface (e.g. cylindrical) of the microtube bundle 4 can be coated with a winding or a protective and / or retaining layer 23.

[0026] The fluid 2 circulated in the micro-tubes 4 can be admitted, for example, transversely at an inlet at one longitudinal end of the exchanger and exit at the other longitudinal end, for example via passages 24 opening through the mandrel 20 and exit via a central passage of an insert 22. The cooling fluid can, on the other hand, flow longitudinally around the micro-tubes 4 in a direction opposite to the longitudinal progression of the first fluid 2.

[0027] Furthermore, one and preferably both longitudinal ends of the microtube bundle 4 comprise a layer 13 of rigid material such as a thermosetting resin (epoxy resin or other) ensuring the cohesion of the microtube bundle and resistance to cryogenic temperatures. This rigid zone can notably be used to ensure a seal between the two fluid circuits (for example via one or more seals 18, in particular O-rings interposed between the housing 5 and the resin layer 13 (as illustrated in the [ Fig. 3 ]).

[0028] This mass or layer 13 of solid resinous material bonds the microtubes 4 at their ends to prevent the high-pressure fluid from communicating with the low-pressure fluid when the module is operating. The resin used for this part bonds reliably with the constituent material of the microtubes 4 and also has a high glass transition temperature (Tg) (e.g., on the order of 150 °C).

[0029] The adhesion between the resin and the microtubes 4 is improved by using the aforementioned materials that constitute the microtubes 4. Indeed, PEEK is a crystalline material with a relatively "slippery" surface due to its low coefficient of friction. Consequently, it is generally difficult to bond it to an adhesive resin. The incorporation of polyetherimide (Ultem) or an equivalent material, as mentioned above, into the microtube composition 4 produces an amorphous structure.

[0030] The alloy therefore gives the resin more "bonding" possibilities for better adhesion.

[0031] As illustrated in the [ Fig. 3 ] or the [ Fig. 4 The housing 5 can accommodate at least one elastic element 11 constrained along the longitudinal direction between a stop formed in the housing 5 and a longitudinal end of the microtube bundle, to ensure the longitudinal stability of the microtube bundle while allowing its expansion or contraction relative to the housing 5 along the longitudinal direction. Thus, one longitudinal end of the microtube bundle can be longitudinally constrained while the other can be longitudinally free and held by the elastic element 11. This allows the microtube bundle to absorb contractions / expansions when subjected to temperature variations while maintaining its seal.

[0032] As illustrated in the [ Fig. 3 ] or the [ Fig. 4 ], the elastic element may comprise or be made up of a spring 11, in particular a helical one. Of course, one or more stacked elastic washers 12, in particular of the Belleville type, may be considered as schematically shown in the [ Fig. 5 ].

[0033] The first fluid 2 (gas or liquid, for example, at high pressure between 5 bar and 100 bar) can enter via the inlet 6 (on the left at the [ Fig. 1 ]), enter the micro-tubes 4 and exit at the other end via outlet 7. Simultaneously, the second fluid 3 (gas or liquid, for example, at low pressure between 1 bar and 99 bar) enters the housing 5 via an inlet (in the upper part of the [ Fig. 1 ]), circulates around the micro-tubes 4 and exits via outlet 9 (in the lower part of the [ Fig. 1 ]).

[0034] The method of implementation of the [ Fig. 2 ] differs from that of the [ Fig. 1 ] only in that transverse deflectors 19 are provided in the housing 5 to force the second fluid to meander around the micro-tubes 4 between the inlet 8 and the outlet 9. This improves the efficiency of the heat exchange.

[0035] The casing 5 can be made of composite material, epoxy resin with glass fibers, polymer, metal or any other suitable material and in particular the same material as that constituting the micro-tubes 4. This minimizes the contraction differentials between the casing 5 and the micro-tubes 4.

[0036] The pressure differential between the pressure of the fluid flowing in the microtubes 4 (e.g., at high pressure) and the pressure of the fluid flowing around the microtubes (e.g., at low pressure) can be on the order of a few bars or several tens of bars, for example, on the order of one hundred bars. As illustrated in [ Fig. 6 ], the housing 5 may include an elastic zone 14 along the longitudinal direction such as a bellows to absorb dimensional variations due to temperature changes.

[0037] Such a cryogenic heat exchanger 11 is particularly efficient, compact, and lightweight compared to known cryogenic exchangers. This type of exchanger can be used, in particular, as a cooling exchanger in a refrigeration and / or liquefaction system.

[0038] Heat exchanger 1 can in particular be used in a "Turbo Brayton" type liquefier cooler. The [ Fig. 7 ] illustrates an example of a cooling device 10. This includes a working circuit 15 containing a working fluid (helium and / or hydrogen and / or argon and / or nitrogen and / or any other gas).

[0039] The working circuit 15 includes at least one compressor 16 for the working gas, at least one heat exchanger 1 for cooling the compressed fluid, at least one expansion device 17 for the working fluid, and at least one heat exchanger 117 for reheating the expanded working fluid. The expansion device may include, for example, at least one of the following: a turbine, a Joule-Thomson valve, or at least one orifice...

[0040] For example, at least one cooling heat exchanger 1 and / or at least one heating heat exchanger 1 may be a heat exchanger 1 of the aforementioned type with polymer microtubes.

[0041] For example, such a heat exchanger 1 can be used in such a device as a counter-current heat exchanger to exchange the working fluid in two distinct states of the cycle.

[0042] For example, at one end of heat exchanger 1 (on the right at the [ Fig. 7 ]) the fluid temperature is decreased in heat exchanger 1 (for example from non-cryogenic ambient temperature to a cryogenic temperature, in particular between 130K and 4K) while at the other end (on the left of the [ Fig. 7 ]) a stream of this fluid is heated (e.g. from a cryogenic temperature to a non-cryogenic temperature).

[0043] Of course, the heat exchanger 1 is not limited to the examples above. Thus, for example, the heat exchanger can be configured to perform heat exchange between more than two fluids (three, four, or more). That is to say, distinct portions of the microtubes 4 and / or the volume around the microtubes 4 can accommodate distinct fluid flows (different fluids or fluids of the same type but at different or similar temperatures) for heat exchange within the heat exchanger 1.

[0044] Such a heat exchanger 1 can, where appropriate, ensure heat exchange with another fluid (liquid nitrogen for example).

[0045] Such a heat exchanger 1 can in particular be used to ensure pre-cooling of the fluid with a cold heat transfer fluid (liquid nitrogen, or any other fluid).

[0046] Such a heat exchanger 1 can also be used to cool the working fluid at the outlet of a compressor. In this case, the working fluid can exchange heat with a heat transfer fluid such as water. While the fluids in heat exchange are not necessarily at cryogenic temperatures and could be replaced by a more conventional heat exchanger, the advantages of the aforementioned heat exchanger 1 remain significant. Such a heat exchanger 1 can also be used to heat a cryogenic fluid contained in a storage tank. The heat exchanger 1 is, for example, located outside the storage tank and provides heat exchange between the cryogenic fluid drawn from the tank and a warmer fluid (air, water, or another heat transfer fluid) to vaporize it.

[0047] As an example, such a heat exchanger 1 can be used to cool and / or heat nitrogen, helium, hydrogen, argon or a mixture of all or part of these components in cryogenic form by heat exchange with a cryogenic or non-cryogenic fluid: nitrogen, helium, hydrogen, argon or a mixture of all or part of these and / or water.

Claims

1. A method for cryogenic cooling of a first fluid (2) by thermal exchange with at least a second fluid (3) in a heat exchanger (1), the first fluid (2) and / or the second fluid (3) being at a temperature comprised between -100°C and -273°C, characterized in that the heat exchanger (1) is of the polymeric micro-tube type, i.e. comprising a plurality of polymeric micro-tubes (4) and having a diameter comprised between and 0.1mm and 1mm, one of the first (2) and second (3) fluids being put into circulation inside said micro-tubes (4) while the other fluid is put into circulation around said micro-tubes (4), and in that the heat exchanger (1) comprises a casing (5) in which the micro-tubes (4) are arranged, the casing (5) comprising a first inlet (6) communicating with a first end of the micro-tubes (4), the casing (5) comprising a first outlet (7) communicating with a second end of the micro-tubes (4), the casing (5) also comprising a second inlet (8) and a second outlet (9) communicating with the volume situated around the micro-tubes (4).

2. The method according to claim 1, characterized in that the micro-tubes (4) are constituted by at least one of the following materials: polyetheretherketone (PEEK), Polytetrafluoroethylene (PTFE), Polyetherimide, polyimides, polyamides, polycarbonates or any other plastic material compatible with use at said low temperatures.

3. The method according to claim 1 or 2, characterized in that the micro-tubes (4) are constituted by a material comprising a mixture of polyetherimide ("Ultem") and Peek.

4. The method according to any one of claims 1 to 3, characterized in that the micro-tubes (4) are constituted by a material having a volume mass comprised between 2700kg / m3 and 900kg / m3 and notably lower than 1500kg / m3.

5. The method according to any one of claims 1 to 4, characterized in that the micro-tubes (4) have a diameter comprised between 0.1mm and 5mm.

6. The method according to any one of claims 1 to 5, characterized in that the pressure differential between the pressure of the fluid (2) put into circulation inside the micro-tubes (4) and the pressure of the fluid (3) put into circulation around the micro-tubes (4) is comprised between 1 bar and 100bar and notably comprised between 10 and 50bar.

7. The method according to any one of claims 1 to 6, characterized in that the micro-tubes (4) are arranged in a bundle according to a longitudinal direction in the casing (5).

8. The method according to any one of claims 1 to 6, characterized in that the micro-tubes (4) are wound helically, preferably distributed around a central support mandrel (20).

9. The method according to claim 7 or 8, characterized in that at least one of the two longitudinal ends of the micro-tube bundle (4) comprises a layer (13) of rigid material such as a thermoset ensuring the cohesion of the micro-tube bundle, the casing (5) housing at least one elastic member (11, 12) constrained according to the longitudinal direction between an abutment formed in the casing (5) and a longitudinal end of the micro-tube bundle, to ensure the longitudinal maintenance of the micro-tube bundle while allowing a dilation or a contraction relative to the casing (5) according to the longitudinal direction.

10. The method according to claim 9, characterized in that the elastic member comprises at least one of: a spring (11), a helical spring, one or several washers (12) being elastic, notably of the Belleville type.

11. The method according to claim 9 or 10, characterized in that the casing (5) comprises an elastic zone (14) according to the longitudinal direction such as a bellows.

12. The method according to any one of claims 1 to 11, characterized in that it ensures a heat exchange between more than two fluids, i.e. distinct portions of the micro-tubes (4) and / or the volume around the micro-tubes (4) accommodate distinct fluid flows (s) for thermal exchanges in the heat exchanger (1).

13. The method according to any one of claims 1 to 12, characterized in that the cooling is realized in a cryogenic refrigeration and / or liquefaction process of a fluid, the heat exchanger (1) being situated in a cryogenic refrigeration and / or liquefaction device.

14. A cryogenic cooling device for at least a first fluid by thermal exchange with at least a second fluid comprising a heat exchanger (1) ensuring a heat exchange between the first fluid and the second fluid, the first and / or the second fluid being at a temperature comprised between -100°C and -273°C, the heat exchanger (1) being characterized in that it is of the polymeric micro-tube type, i.e. comprising a plurality of polymeric micro-tubes (4) and having a diameter comprised between and 0.1mm and 1mm, and in that the heat exchanger (1) comprises a casing (5) in which the micro-tubes (4) are arranged, the casing (5) comprising a first inlet (6) communicating with a first end of the micro-tubes (4), the casing (5) comprising a first outlet (7) communicating with a second end of the micro-tubes (4), the casing (5) also comprising a second inlet (8) and a second outlet (9) communicating with the volume situated around the micro-tubes (4), to ensure a circulation of at least one fluid inside said micro-tubes (4) and a circulation of the other fluid around said micro-tubes.

15. The cooling device according to claim 14, characterized in that it comprises a working circuit (15) containing a working fluid, the working circuit (15) comprising at least a compressor (16) for the working gas, at least one heat exchanger (1) for cooling the compressed fluid, at least one expansion member (17) for the working fluid, at least one heat exchanger (1) for reheating the expanded working fluid, characterized in that the at least one cooling heat exchanger (1) and / or the at least one reheating heat exchanger (1) is of the polymeric micro-tube type, i.e. comprising a plurality of polymeric micro-tubes (4) and having a diameter comprised between and 0.1mm and 10mm, and comprising inlets (6, 8) and outlets (7, 9) for a first flow of working fluid and another fluid having a temperature distinct from the temperature of the first flow of working fluid, to ensure a thermal exchange between the first flow of working fluid and the other fluid.

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