Device for transferring a cryogenic refrigerant fluid

Abstract

Device (99) for transferring a cryogenic refrigerant fluid, having a working temperature, from a first tank (101 ) to a second tank (102), wherein the device (99) comprises a first conduit (1 ) rigid made of a first material, a transport tube (2) made of a second electrically insulating material and comprising a first end (21 ) radially fitted externally to a second end (12) of the first conduit (1 ) to connect the transport tube (2) to the first conduit (1 ), and a clamping element (3) made of a third material and disposed radially externally to the transport tube (2) at the first end (21 ) of the transport tube (2) to clamp the first end (21 ) of the transport tube (2) against the first conduit (1 ), wherein the third material has a volumetric thermal expansion coefficient (a3) at the working temperature greater than a volumetric thermal expansion coefficient (ax) of the first material.

Description

[0001] DESCRIPTION

[0002] Title: DEVICE FOR TRANSFERRING A CRYOGENIC REFRIGERANT FLUID Technical field of the invention

[0003] The present invention relates to a device for transferring a cryogenic refrigerant fluid, for example from a first tank to a second tank.

[0004] State of the art

[0005] In multiple technical fields, such as for example in the field of superconductors, it is known to make use of cryogenic refrigerant fluids for cooling equipment and / or devices.

[0006] The term “radial” is used with reference to a direction perpendicular to an axis, typically of rotational symmetry, of a conduit and / or tube.

[0007] Summary of the invention

[0008] In order to clarify in the best way the problems that the present solution allows to solve, in the following specific reference will be made to the field of superconductors, and in particular to current conducting elements, also known as “current leads”, for superconductors, that is those elements that allow supplying a superconducting load, such as for example an electrical cable made of superconducting material or an electromagnet, typically by connecting the load to the electrical network. In any case, it is to be understood that the field of application of the present solution is not limited to the aforementioned field of superconductors.

[0009] In the field of superconductors, the Applicant has found it to be of fundamental importance to be able to cool with desired efficiency the current conducting element connected to the superconducting load. Indeed, the current conducting element, typically comprising metallic parts, not only is configured as a thermal bridge between the surrounding environment, typically at ambient temperature, and the superconducting load, typically at cryogenic temperature, tending to transport heat in the direction of the superconducting load, thus worsening the superconducting characteristics of the load, but moreover heats up (e.g. due to Joule effect) as a result of the passage itself of electric supply current, further contributing to the heating of the superconducting load and / or worsening the electrical conductivity properties of the current conducting element. The aforementioned cooling of the current conducting element is therefore advantageous in order to minimize such thermal bridge and counteract the heating of the current conducting element due to the passage of electriccurrent.

[0010] In the aforementioned framework, the Applicant has also realized that the cooling of the current conducting element must be carried out while keeping the current conducting element, which is typically placed at a respective electric voltage, for example of the order of 5-25 kV, electrically insulated from the tank from which the refrigerant fluid used for the cooling is taken, typically placed at ground voltage.

[0011] Furthermore, since typically the current conducting elements are placed in a vacuum atmosphere, the connection line of the refrigerant fluid between the current conducting element and the tank needs to pass through the wall of a containment body in which the current conducting element is placed, preserving during the passage the vacuum tightness properties (“leak-tight”) of the containment body, in order to preserve the aforementioned vacuum atmosphere inside the containment body. Moreover, the transfer line itself must be able to withstand the pressure difference that is established between the inside of the line, where the refrigerant fluid flows at ambient pressure or even at higher pressure, and the vacuum atmosphere in which the current conducting element is disposed.

[0012] Finally, the Applicant considers it particularly advantageous that the refrigerant fluid to be used is a cryogenic fluid. With “cryogenic fluid” it is typically meant a fluid characterized by a boiling temperature lower than -73°C at atmospheric pressure. In the aforementioned framework, the Applicant has therefore addressed the problem of transferring a cryogenic refrigerant fluid from a first tank to a second tank in order to cool the second tank, in a constructively simple and / or economical manner, and able to satisfy the aforementioned construction constraints.

[0013] According to the Applicant, the aforementioned problem is solved by a device for transferring a cryogenic refrigerant fluid in accordance with the appended claims and / or having one or more of the following characteristics.

[0014] According to one aspect the invention therefore relates to a device for transferring a cryogenic refrigerant fluid, having a working temperature, from a first tank to a second tank.

[0015] Preferably said device comprises a first conduit made of a first material.

[0016] Preferably said first conduit is rigid.

[0017] Preferably said first conduit comprises a first end, sealingly connectable (directly or indirectly, that is by interposition of one or more further elements) to said first tank.Preferably said first conduit comprises a second end opposite to said first end.

[0018] Preferably said device comprises a transport tube made of a second material.

[0019] Preferably said second material is electrically insulating.

[0020] Preferably said transport tube comprises a first end, radially fitted externally to said second end of said first conduit to connect said transport tube to said first conduit. Preferably said transport tube comprises a second end, opposite to said first end of said transport tube, sealingly connectable (directly or indirectly) to said second tank. Preferably said device comprises a clamping element made of a third material.

[0021] Preferably said clamping element is disposed radially externally to said transport tube at said first end of the transport tube to clamp said first end of the transport tube against said second end of said first conduit.

[0022] Preferably said third material has a volumetric thermal expansion coefficient at said working temperature greater than (or equal to) a volumetric thermal expansion coefficient of said first material at said working temperature.

[0023] In the context of the present solution, with the term “end” it is meant, unless otherwise specified, an end portion of the respective conduit or tube, that is having a non-zero, arbitrary development along a main development direction of the respective conduit or tube, without necessarily extending along the entire length of the conduit or tube. With the term “opposite” referred to the ends of a conduit or tube it is meant that such ends are opposite to each other with respect to a main development of the respective conduit or tube.

[0024] With the expression “made of a material” referred to an element, it is meant that such element is substantially, more preferably entirely, composed of such material.

[0025] The volumetric thermal expansion coefficient a of a material is given by the following formula:

[0026] 1 (dp\ 1 (dV\

[0027] a = - ( — ) = H — ( — )

[0028]

[0029] p \dT)pV \dT / p

[0030] wherein p represents the density, T the temperature, V the volume and the derivatives are considered at constant pressure p, and represents the fractional change of the density of the given material as a function of the variation of the temperature at constant pressure. For example, the volumetric thermal expansion coefficient for a desired material can be obtained by interpolation of the tabulated data in the followingtechnical manual: Jack W. Ekin, “Experimental Techniques for Low-temperature Measurements”, edition 2006. As a further example, the test method ASTM E831 describes the standard test method for calculating the linear thermal expansion coefficient A of solid materials by thermomechanical analysis. For isotropic materials, the volumetric thermal expansion coefficient can be obtained directly from the linear thermal expansion coefficient by the relation a = 3A.

[0031] According to the Applicant, the first rigid conduit allows first of all to provide mechanical abutment to the clamping of the first end of the transport tube by means of the clamping element, in order to obtain the desired sealing.

[0032] Furthermore, the transport tube made of electrically insulating material allows to obtain the desired electrical insulation between the first tank and the second tank.

[0033] Finally, thanks to the first end of the transport tube radially fitted externally to the second end of the first conduit, and to the clamping element disposed radially externally to said transport tube at said first end of the transport tube to clamp said first end of the transport tube against said second end of said first conduit, together with the realization of the clamping element in the third material having a respective volumetric thermal expansion coefficient at the working temperature of the fluid greater than the volumetric thermal expansion coefficient of the first material of which the first conduit is made, it is possible to obtain the desired degree of sealing in the junction between the first conduit and the transport tube.

[0034] According to the Applicant, the aforementioned inequality between the volumetric thermal expansion coefficients respectively of the third and of the first material causes that, at the working temperature of the cryogenic refrigerant fluid (for example of about 77 K if the fluid is liquid nitrogen) the clamping element undergoes a thermal contraction greater than that undergone by the first conduit, causing that the first end of the transport tube is further clamped between the clamping element and the first conduit (the first conduit acting as a rigid abutment to the compression force exerted by the clamping element on the first portion of the transport tube), ultimately obtaining the desired sealing.

[0035] Moreover, such junction has proved particularly suitable for use in vacuum atmosphere, proving to be capable of withstanding the pressure gradient that can be established between the inside of the device, that is where the refrigerant fluid flows at ambient pressure or higher pressure, and the vacuum atmosphere.The present invention in the aforementioned aspect may have one or more of the following preferred characteristics.

[0036] Preferably one or more, more preferably all, of said first, second and third material are isotropic materials. By isotropic material it is meant a solid whose thermal expansion is equal in all directions of space.

[0037] Preferably said volumetric thermal expansion coefficients of said first and third material satisfy the following inequality:

[0038] a3> 1.3at

[0039] more preferably the following inequality:

[0040] a3> 2at

[0041] even more preferably the following inequality:

[0042] a3> 3a

[0043] wherein a3is said volumetric thermal expansion coefficient of said third material and a±is said volumetric thermal expansion coefficient of said first material. In other terms, the Applicant has found it to be particularly advantageous for the aforementioned purposes that the volumetric thermal expansion coefficient of the third material is at least 130%, more preferably at least 200%, even more preferably at least 300%, of the volumetric thermal expansion coefficient of the first material.

[0044] Preferably said first material is a metallic material. In such way said first material is particularly suitable for realizing the first conduit, for example in order to realize the portion of the device that passes through the wall of the containment body.

[0045] Preferably said first material is chosen from the following: brass, copper, aluminum, steel (for example SS 304).

[0046] Preferably said transport tube is (elastically) flexible. In such way any insertion of the device into the aforementioned containment body in a sealing manner is facilitated. Preferably said second material is chosen from the following: polytetrafluoroethylene PTFE (Teflon™), high-density polyethylene (also known as HDPE).

[0047] By high-density polyethylene (HDPE), it is meant for example polyethylene having a density of about 0.94 g / cm3(ISO 1183).

[0048] Preferably said third material is chosen from the following: acetal resin (also known as polyoxymethylene, also called POM), acetal resin copolymer (POM-C), nylon, polytetrafluoroethylene, aluminum.

[0049] Preferably said device comprises a covering tube, more preferably made of polymericmaterial (for example polyvinyl chloride - PVC), which covers at least partially, more preferably substantially entirely, said transport tube. In such way the transport tube is protected and / or reinforced.

[0050] In a preferred embodiment, said first material is steel (for example SS 304), said second material is polytetrafluoroethylene and said third material is acetal resin copolymer. According to the Applicant the aforementioned combination of first, second and third material has proved to be particularly advantageous for the intended purposes.

[0051] Preferably said third material has a Young’s modulus greater than or equal to a Young’s modulus of said second material. Without wishing to be bound by any theory, the Applicant considers that by using a second material more elastically deformable, for a same applied action, with respect to the third material, it is possible to further facilitate the aforementioned clamping of the transport tube between the clamping element and the first conduit. Preferably the Young’s modulus is evaluated, for both said materials, at ambient temperature, for example equal to about 300 K.

[0052] Preferably said Young’s modulus of said third material is greater than or equal to 110%, more preferably greater than or equal to 115%, even more preferably greater than or equal to 120%, of said Young’s modulus of said second material. Such percentage values of difference between the Young’s moduli have proved to be particularly advantageous.

[0053] The Young’s modulus (or modulus of elasticity, expressed in SI units as N / m2) is a quantity characteristic of a material, which expresses the ratio between stress and strain in the case of uniaxial loading conditions and in the case of elastic behavior of the material. By way of example, the Young’s modulus can be obtained by means of the ASTM E111 test (standard test method for Young’s modulus), and / or by means of the ASTM E2769 test (standard test method for elastic modulus by thermomechanical analysis by three-point bending and controlled loading rate).

[0054] Preferably said device comprises an adhesive layer interposed between said first conduit and said transport tube at said first end of the transport tube. Without wishing to be bound by any theory, the Applicant considers that such adhesive layer, by filling any micro-imperfections of the external surface of the first conduit (that is the surface facing the transport tube), facilitates the realization of the sealing at the junction between the first conduit and the transport tube.Preferably said adhesive layer comprises (or consists of) a cyanoacrylic adhesive. Preferably said first end of the transport tube is radially fitted externally with mechanical interference to said second end of said first conduit. In other terms, before the mutual coupling between the transport tube and the first conduit, an internal diameter of the transport tube is less than or equal to an external diameter of the first conduit. In such way the sealing of the coupling is further facilitated. For example, the internal diameter of the transport tube is at least 3%, more preferably at least 5%, smaller than the external diameter of the first conduit. In a preferred embodiment, before the coupling, the internal diameter of the transport tube is about 6% smaller than the external diameter of the first conduit.

[0055] Preferably said clamping element is disposed radially externally with mechanical interference to said transport tube. In other terms, before the mutual coupling between the clamping element and the transport tube, an internal diameter of the clamping element is less than or equal to an external diameter of the transport tube (for example when fitted on the first conduit). In such way the clamping of the transport tube is further facilitated. For example, the internal diameter of the clamping element is at least 3%, more preferably at least 5%, smaller than the external diameter of the transport tube. In a preferred embodiment, before the coupling, the internal diameter of the clamping element is about 6% smaller than the external diameter of the transport tube (for example when fitted on the first conduit).

[0056] According to one aspect, the invention relates to a system for refrigeration of a second tank by means of a cryogenic refrigerant fluid coming from a first tank.

[0057] Preferably said first and second tank are placed at a voltage difference.

[0058] Preferably said system comprises said first and second tank.

[0059] Preferably said system comprises said device for transferring said cryogenic refrigerant fluid sealingly connected (directly or indirectly) to both said first and second tank by means of respectively said first end of said first conduit and said second end of said transport tube.

[0060] Preferably said first tank is a reservoir of said cryogenic refrigerant fluid.

[0061] Preferably said second tank is an electrical current conducting element.

[0062] Preferably said electrical current conducting element has a chamber (internal) to receive said cryogenic refrigerant fluid.

[0063] Preferably said system comprises a containment body having a sealed internal cavity.Preferably said device for transferring is disposed at least partially internally to said internal cavity of said containment body.

[0064] In a preferred embodiment, said device for transferring is disposed entirely inside said internal cavity of said containment body. In such embodiment, advantageously, a further line, which penetrates inside the internal cavity of the containment body (for example passing through a suitable opening made in the containment body) connects the device, more preferably said first end of said first conduit, to the first tank (or such further line can be interpreted as belonging to the first tank).

[0065] Preferably said second tank is at least partially disposed internally to said internal cavity of said containment body.

[0066] According to a further aspect, the invention relates to a method of refrigeration of a second tank by means of a cryogenic refrigerant fluid coming from a first tank.

[0067] Preferably said first and second tank are placed at a voltage difference.

[0068] Preferably said method comprises arranging said device for transferring.

[0069] Preferably said method comprises sealingly connecting (directly or indirectly) said first end of said first conduit to said first tank.

[0070] Preferably said method comprises sealingly connecting (directly or indirectly) said second end of said transport tube to said second tank.

[0071] Preferably said method comprises introducing said cryogenic refrigerant fluid at a working temperature into said second tank from said first tank through said device for transferring.

[0072] Preferably said method comprises disposing (at least partially, more preferably entirely) said device for transferring in a vacuum atmosphere, for example by creating vacuum inside said internal cavity of said containment body. With the expression “vacuum atmosphere” it is meant a space whose pressure is lower than atmospheric pressure. Typically the vacuum atmosphere reduces the transfer of heat from the external environment towards the electrical current conducting element and / or increases the electrical insulation of the electrical current conducting element with respect to the external environment.

[0073] Preferably said introducing said cryogenic refrigerant fluid is carried out with said cryogenic refrigerant fluid subjected to ambient pressure. In such way the system architecture is simplified, for example by avoiding pumps.

[0074] Preferably said cryogenic refrigerant fluid is liquid nitrogen. Preferably said workingtemperature is comprised between 60 K and 80 K, more preferably is equal to about 77 K. Liquid nitrogen has proved to be particularly advantageous for the aforementioned purposes, for example in terms of cooling effectiveness, ease of availability, physico-chemical compatibility with a wide range of materials.

[0075] In alternative embodiments said cryogenic refrigerant fluid can be one or more of the following: liquid neon, liquid hydrogen, liquid helium.

[0076] Brief description of the figures

[0077] Figure 1 shows a detail of a longitudinal section of a device for transferring a cryogenic refrigerant fluid according to the present invention;

[0078] Figure 2 schematically shows a system for transferring a cryogenic refrigerant fluid comprising the device of Figure 1.

[0079] Detailed description of some embodiments of the invention

[0080] The features and the advantages of the present invention will be further clarified by the following detailed description of some embodiments, presented by way of example and not limiting of the present invention, with reference to the attached figures.

[0081] In the figures, with number 99 there is globally indicated a device for transferring a cryogenic refrigerant fluid (not shown) preferably liquid nitrogen, having a working temperature (for example 77K in case of liquid nitrogen), from a first tank 101 to a second tank 102 (Figure 2).

[0082] Exemplarily (Figure 1) the device 99 comprises a first conduit 1 rigid, entirely made of a first material.

[0083] Exemplarily the first conduit 1 comprises a first end 11, sealingly connectable to the first tank 101 , and a second end 12, opposite to the first end 11. Exemplarily the first conduit 1 has a main development as a straight segment.

[0084] Exemplarily the device 99 further comprises a transport tube 2 entirely made of a second electrically insulating material and comprising a first end 21, radially fitted externally to the second end 12 of the first conduit 1 to connect the transport tube 2 to the first conduit 1 , and a second end 22, opposite to the first end 21 of the transport tube 2, sealingly connectable to the second tank 102.

[0085] Exemplarily the device 99 further comprises a clamping element 3 entirely made of a third material.

[0086] Exemplarily the clamping element 3 is disposed radially externally to the transport tube 2 at the first end 21 of the transport tube 2 to clamp the first end 21 of the transporttube 2 against the second end 12 of the first conduit 1.

[0087] Exemplarily the third material has a volumetric thermal expansion coefficient a3at the working temperature greater than a volumetric thermal expansion coefficient a±of the first material, with which the first conduit 1 is made, at the working temperature.

[0088] More in detail, in a preferred embodiment, the first material is stainless steel (for example SS 304) the second material is polytetrafluoroethylene (PTFE, also known as Teflon™), and the third material is acetal resin copolymer (POM-C) having a respective volumetric thermal expansion coefficient a3at the working temperature greater than more than three times the volumetric thermal expansion coefficient a±of the steel, that is in such preferred embodiment the following relation applies a3> 3a .

[0089] In embodiments, in any combination with each other, the first material can be in general any one of the following: brass, copper, aluminum, steel, the second material can be any one of the following: polytetrafluoroethylene (PTFE), high-density polyethylene (HDPE), and the third material is any one of the following: acetal resin (POM) acetal resin copolymer (POM-C), nylon, polytetrafluoroethylene, aluminum.

[0090] Exemplarily (Figure 1), the device 99 further comprises a covering tube 4, made of polymeric material (for example polyvinyl chloride, PVC), which covers substantially entirely the transport tube 2. More in detail, the covering tube 4 leaves exemplarily at least partially free the first end portion 21 of the transport tube 2 to facilitate the positioning of the clamping element 3.

[0091] Exemplarily furthermore the third material has a Young’s modulus (at 300K) greater than or equal to a Young’s modulus (at 300K) of the second material. More in detail, in the aforementioned preferred embodiment, the Young’s modulus of the third material is for example equal to about 120% of the Young’s modulus of the second material. Exemplarily the device 99 comprises an adhesive layer (not shown) interposed between the first conduit 1 and the transport tube 2 at the first end 21 of the transport tube 2 to uniform the surface roughness of an external surface (that is facing the transport tube 2) of the first conduit 1 by filling any micro-imperfections of the external surface. Exemplarily the adhesive layer consists of a cyanoacrylic adhesive.

[0092] Exemplarily the first end 21 of the transport tube 2 is radially fitted externally with mechanical interference to the second end 12 of the first conduit 1. More precisely, before the mutual coupling between the transport tube 2 and the first conduit 1, an internal diameter of the transport tube 2 is less than or equal to an external diameterof the first conduit 1. Exemplarily, before the aforementioned mutual coupling, the internal diameter of the transport tube 2 is about 6% smaller than the external diameter of the first conduit 1.

[0093] Exemplarily furthermore the clamping element 3 is disposed radially externally with mechanical interference to the transport tube 2. More in detail, before the mutual coupling, the internal diameter of the clamping element 3 is exemplarily about 6% smaller than the external diameter of the transport tube 2 (for example when fitted on the first conduit).

[0094] With reference to Figure 2, Figure 2 shows a refrigeration system 100 of a second tank 102 by means of a cryogenic refrigerant fluid (not shown) coming from a first tank 101. Exemplarily the system 100 comprises first of all the first 101 and the second tank 102, preferably placed at a voltage difference.

[0095] By way of example only, the first tank 101 is a reservoir of the cryogenic refrigerant fluid, typically distinct and separate from the second tank 102, whereas the second tank 102 is an electrical current conducting element, such as for example of known type, used for supplying electric power to a superconducting load (not shown) such as for example a superconducting cable or an electromagnet.

[0096] Exemplarily, the electrical current conducting element has an internal chamber 103 to receive the cryogenic refrigerant fluid (which typically evaporates upon contact with the walls of the internal chamber 103 and is discharged in the form of vapor).

[0097] Exemplarily the system 100 further comprises the device for transferring 99 of the cryogenic refrigerant fluid sealingly connected to both the first 101 and the second tank 102 by means of respectively the first end 11 of the first conduit 1 and the second end 22 of the transport tube 2.

[0098] For example, as schematically shown in Figure 2, the first end 11 of the first conduit 1 can be sealingly connected to the first tank 101 by connection, for example by welding or other known sealing connection method, for example by flange, with a duct T1 , for example also made of metallic material, coming from (or belonging to) the first tank 101.

[0099] As regards the sealing connection between the second end 22 of the transport tube 2 and the second tank 102, such connection can for example be realized by radially fitting the second end 22 onto a respective end of a further conduit T2 (shown only schematically in Figure 2) in turn connected to the second tank 102, for example to theelectrical current conducting element, and more in detail connected to the internal chamber 103 of the electrical current conducting element. Advantageously such further conduit can be rigid (for example made also of the first material, which can coincide with the same material of which the electrical current conducting element is made, typically copper), and the second end 22 of the transport tube 2 can be radially fitted, preferably with mechanical interference, onto such respective end of the further conduit T2.

[0100] For such purpose, the system 100 can further comprise a further clamping element (not shown) disposed radially externally to the transport tube 2 at the second end 22 of the transport tube 2 to clamp the second end 22 of the transport tube 2 against said respective end of the further conduit T2.

[0101] Advantageously the further clamping element is made of a respective material having preferably one or more of, more preferably all, the characteristics described above with reference to the third material, which, when referred to the first material and / or to the second material, are to be referred respectively to the respective material of the further conduit T2 (for example copper or steel), and to the second material itself.

[0102] For example, therefore, advantageously the respective material of the further clamping element has a respective volumetric thermal expansion coefficient, at the working temperature, greater than a respective volumetric thermal expansion coefficient of the material of the further conduit T2 at the working temperature. In such way the same considerations apply as above with reference to the sealing achievable between the transport tube and the further conduit T2.

[0103] In the aforementioned embodiment, the covering tube 4 can leave at least partially free the second end portion 22 of the transport tube 2 to facilitate the positioning of the further clamping element.

[0104] Exemplarily furthermore the system 100 comprises a containment body 104 having a sealed internal cavity 105.

[0105] Exemplarily the device for transferring 99 is disposed internally to the internal cavity 105 of the containment body 104, with the duct T1 which penetrates (not shown) into the internal cavity 105 through a suitable opening (not shown) in the wall of the containment body 104 in order to be connected to the first conduit 1. In such example the maintenance of the vacuum tightness of the containment body is also provided at said opening of the wall of the containment body (for example by known methods).Exemplarily the second tank 102 is at least partially disposed internally to the internal cavity 105 of the containment body 104.

[0106] Optionally, as for example schematically shown in Figure 2, electrical connection poles P1, P2 of the electrical current conducting element can partially protrude from the internal cavity 105 of the containment body 104 in order to allow the connection with the superconducting load and with the electrical network.

[0107] In use, the device for transferring 99 allows to carry out a method of refrigeration of the second tank 102 by means of the cryogenic refrigerant fluid coming from the first tank 101.

[0108] Exemplarily the method comprises sealingly connecting the first end 11 of the first conduit 1 to the first tank 101 and sealingly connecting the second end 22 of the transport tube 2 to the second tank 102, for example as described above.

[0109] Exemplarily the method then comprises introducing the cryogenic refrigerant fluid at the working temperature into the second tank 102 from the first tank 101 through the device for transferring 99.

[0110] In a preferred embodiment, the method comprises disposing the device for transferring 99 in a vacuum atmosphere, for example by creating vacuum inside the internal cavity 105 of the containment body 104.

[0111] Advantageously, introducing the cryogenic refrigerant fluid is carried out with the cryogenic refrigerant fluid subjected to ambient pressure. In other terms, the driving force that sets the fluid in motion is provided only by the head of the refrigerant liquid in the reservoir 101.

[0112] In a particularly preferred embodiment the cryogenic refrigerant fluid is liquid nitrogen at the working temperature of about 77K.

[0113] In alternative embodiments the cryogenic refrigerant fluid can be one or more of the following: liquid neon, liquid hydrogen, liquid helium.

Claims

CLAIMS1. Device (99) for transferring a cryogenic refrigerant fluid, having a working temperature, from a first tank (101 ) to a second tank (102), said device (99) comprising: - a first rigid conduit (1 ) made of a first material, said first conduit (1 ) comprising a first end (11), sealingly connectable to said first tank (101 ), and a second end (12) opposite to said first end (11);- a transport tube (2) made of a second electrically insulating material and comprising a first end (21 ), radially fitted externally to said second end (12) of said first conduit (1 ) to connect said transport tube (2) to said first conduit (1), and a second end (22), opposite to said first end (21) of said transport tube (2), sealingly connectable to said second tank (102);- a clamping element (3) made of a third material, said clamping element (3) being disposed radially externally to said transport tube (2) at said first end (21) of the transport tube (2) to clamp said first end (21) of the transport tube (2) against said second end (12) of said first conduit (1), wherein said third material has a volumetric thermal expansion coefficient (a3) at said working temperature greater than a volumetric thermal expansion coefficient (tri) of said first material at said working temperature.

2. Device (99) according to claim 1, wherein said volumetric thermal expansion coefficients (alta3) of said first and third materials satisfy the following inequality:a3> 1.3atwherein a3is the volumetric thermal expansion coefficient of said third material and a±is the volumetric thermal expansion coefficient of said first material.

3. Device (99) according to any one of the previous claims, wherein said first material is a metallic material chosen from the following: brass, copper, aluminum, steel, wherein said transport tube (2) is flexible and said second material is chosen from the following: polytetrafluoroethylene, high-density polyethylene, and wherein said third material is chosen from the following: acetal resin, acetal resin copolymer, nylon, polytetrafluoroethylene, aluminum.

4. Device (99) according to any one of the previous claims, wherein said first material is steel, wherein said second material is polytetrafluoroethylene, and wherein said third material is acetal resin copolymer.

5. Device (99) according to any one of the previous claims, wherein said third material has a Young's modulus greater than or equal to the Young's modulus of said second material.

6. Device (99) according to any one of the previous claims, comprising an adhesive layer interposed between said first conduit (1) and said transport tube (2) at said first end (21) of the transport tube (2), wherein said first end (21) of the transport tube (2) is radially fitted with mechanical interference to said second end (12) of said first conduit (1), and wherein said clamping element (3) is disposed radially externally with mechanical interference to said transport tube (2).

7. Refrigeration system (100) of a second tank (102) by means of a cryogenic refrigerant fluid from a first tank (101), said first (101) and second tanks (102) being placed at a voltage difference, said system (100) comprising said first (101 ) and second tanks (102) and said device (99) for transferring the cryogenic refrigerant fluid according to any one of claims 1 to 6, sealingly connected to both said first (101) and second tanks (102) via said first end (11 ) of said first conduit (1 ) and said second end (22) of said transport tube (2).

8. System (100) according to claim 7, wherein said first tank (101 ) is a reservoir of said cryogenic refrigerant fluid, wherein said second tank (102) is an electrical conductor element having a chamber (103) to receive said cryogenic refrigerant fluid, wherein said system (100) comprises a containment body (104) having a sealed internal cavity (105), wherein said device (99) for transferring is at least partially disposed within said internal cavity (105) of said containment body (104), and wherein said second tank (102) is at least partially disposed within said internal cavity (105) of said containment body (104).

9. Method of refrigeration of a second tank (102) by means of a cryogenic refrigerant fluid coming from a first tank (101), said first (101) and second tank (102) being placed at a voltage difference, said method comprising the steps of:- arranging the device (99) for transferring said cryogenic refrigerant fluid according to any one of claims 1 to 6;- sealingly connecting said first end (11 ) of said first conduit (1 ) to said first tank (101 ); - sealingly connecting said second end (22) of said transport tube (2) to said second tank (102);- introducing said cryogenic refrigerant fluid at a working temperature into said secondtank (102) from said first tank (101) through said device (99) for transferring.

10. Method according to claim 9, comprising arranging said device (99) for transferring in a vacuum atmosphere, wherein said introducing of said refrigerant fluid is performed with said fluid subjected to ambient pressure, and wherein said refrigerant fluid is liquid nitrogen.

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