Cryogenic fluid storage unit

Abstract

Cryogenic Fluid Storage Unit The storage unit (1) includes a suspension (9) attaching the inner reservoir (3) to the outer reservoir (7). The suspension (9) includes a link (23) comprising: - an outer tube (27) having an external proximal end (29) attached to the inner reservoir (3) and an external distal end (31) located inside the storage volume (5); - a bottom plate (33) closing the external distal end (31);- an inner tube (41) arranged inside the intermediate tube (35), having an inner proximal end (43) fixed to the outer reservoir (7) and an inner distal end (45) fixed to the inner reservoir (3), - at least one circulation conduit (75) extending inside the inner tube (41), the circulation conduit(s) (75) having a circulation proximal end portion (76) arranged opposite the inner proximal end (43), and a circulation distal end (77) fixed to the base plate (33) and communicating fluidly with the internal volume (5) through the base plate (33), the circulation distal end (77) being located at a level lower than the circulation proximal end portion (76) in a vertical direction. Figure for the abstract: 2;

Description

Title of the invention: Cryogenic fluid storage unit

[0001] The present invention relates generally to a cryogenic fluid storage unit.

[0002] Such a storage unit may comprise an internal tank internally delimiting a cryogenic fluid storage volume, an external tank in which the internal tank is housed and a suspension fixing the internal tank to the external tank.

[0003] In order to limit heat transfer by convection from the external reservoir to the internal reservoir, the space delimited between the internal reservoir and the external reservoir is typically maintained under a high vacuum.

[0004] Radiation transfers are limited by arranging a layer of insulating material on the internal reservoir.

[0005] Heat transfers from the external reservoir to the internal reservoir also pass through the suspension.

[0006] They can be relatively high.

[0007] In this context, the invention aims to propose a storage unit whose suspension is designed to minimize the heat flow circulating from the external reservoir to the internal reservoir through the suspension.

[0008] To this end, the invention relates to a cryogenic fluid storage unit, comprising an internal reservoir internally delimiting a storage volume for the cryogenic fluid, an external reservoir in which the internal reservoir is housed and a suspension fixing the internal reservoir to the external reservoir, the suspension comprising a connection comprising:

[0009] - an outer tube having an outer proximal end attached to the reservoir internal and an external distal end located inside the storage volume;

[0010] - a bottom plate closing the external distal end;

[0011] - an inner tube arranged inside the intermediate tube, having one end internal proximal end attached to the external reservoir and an internal distal end attached to the internal reservoir,

[0012] - at least one circulation conduit extending inside the inner tube, the or each circulation conduit having a proximal circulation end portion arranged opposite the inner proximal end, and a distal circulation end attached to the bottom plate and fluidly communicating with the inner volume through the bottom plate, the distal circulation end being located at a level lower than the proximal circulation end portion in a vertical direction.

[0013] Because the distal circulation end of the or each circulation conduit is located at a lower level than the proximal circulation end portion in a vertical direction, heat pipe effects are eliminated.

[0014] This heat pipe effect would occur if the distal circulation end of the or each circulation conduit were located at the same level or at a higher level than the proximal circulation end portion in a vertical direction.

[0015] Indeed, for a liquid hydrogen tank, the distal circulation end is at a temperature of approximately 20 K and the proximal circulation end portion is at a significantly higher temperature. The liquid cryogenic fluid upon arriving at the proximal circulation end portion may be partially vaporized. If the distal circulation end is at a higher level than the proximal circulation end portion, the vapor rises toward the distal circulation end and is recondensed upon contact with the cold surfaces or the colder cryogenic fluid. It flows again toward the proximal circulation end portion.

[0016] This loop circulation of the cryogenic fluid causes a transfer of latent heat which can be high, for example more than 100 W.

[0017] This transfer is impossible if the distal circulation end of the or each circulation conduit is located at a lower level than the proximal circulation end portion, since the vapor will accumulate at the highest end, i.e. the proximal circulation end portion. This will create a gas plug which thermally insulates the two ends of the tube from each other.

[0018] The fluid storage unit may further represent one or more of the following characteristics, considered individually or in all technically possible combinations:

[0019] - the or each circulation duct comprises a central part connected to the a proximal circulation end portion, and a distal portion connecting the central portion to the distal circulation end, the distal portion being inclined downward from the central portion to the distal circulation end;

[0020] - the central part is horizontal;

[0021] - the central part is connected to the distal part by an elbow;

[0022] - the outer tube comprises an outer proximal portion defining the end outer proximal, and an outer distal portion connecting the outer proximal portion to the bottom plate, the outer distal portion being inclined downward from the outer proximal portion to the bottom plate;

[0023] - the external proximal part is horizontal;

[0024] - the external distal part is arched;

[0025] - the or each circulation conduit has an internal diameter greater than 21 mm

[0026] - the or each circulation duct comprises at least one di compensator thermal lation;

[0027] - the or each thermal expansion compensator is a corrugated section of the conduit of traffic;

[0028] - the proximal circulation end portion is without contact with the inner tube;

[0029] - the proximal circulation end portion is a sleeve delimiting a passage internal elbow for cryogenic fluid.

[0030] Other characteristics and advantages of the invention will emerge from the detailed description given below, for information purposes only and in no way limiting, with reference to the appended figures, among which: - [Fig.l] [Fig.l] is an axial sectional view of the cryogenic fluid storage unit; - [Fig.2] [Fig.2] is an enlarged axial sectional view of part of the suspension of the storage unit of [Fig.l]; - [Fig.3]] [Fig.3] is a perspective view of the circulation ducts of heat transfer fluid of the suspension of [Fig.2]; and - [Fig.4] [Fig.4] is a view similar to that of [Fig.2], illustrating a variant embodiment,

[0031] In Figures 2 and 4, certain welds connecting the parts to each other are not shown.

[0032] The storage unit 1 shown in [Fig.l] is intended to store a cryogenic fluid.

[0033] Cryogenic fluid is understood to mean a fluid at a very low temperature, which may be at least partially in the liquid state inside the storage unit.

[0034] This fluid is typically hydrogen. Alternatively, the fluid is helium, nitrogen, a natural gas such as methane CH4, air, or any other suitable fluid.

[0035] This storage unit is typically intended to be mounted on board a vehicle having an electric propulsion motor, for example a motor vehicle, a train, a boat or any other vehicle.

[0036] The motor vehicle is for example a car, a utility vehicle, a truck, etc.

[0037] The storage unit 1 is intended to power a fuel cell. The fuel cell is configured to produce electricity and electrically power the electric propulsion motor of the vehicle.

[0038] The cryogenic fluid storage unit 1 comprises an internal tank 3 internally delimiting a cryogenic fluid storage volume 5, an external tank 7 inside which the internal tank 3 is housed, and a suspension 9 fixing the internal tank 3 to the external tank 7.

[0039] In the example shown, the internal reservoir 3 has a horizontal central axis C.

[0040] The internal reservoir 3 comprises a shell 11, closed at its two axial ends by bottoms 13.

[0041] The ferrule 11 is cylindrical, centered on the central axis C.

[0042] The external tank 7 also has a horizontal axis.

[0043] It comprises a ferrule 15, closed at its two axial ends by bottoms 17.

[0044] The ferrule 15 is cylindrical, centered on the central axis C.

[0045] The internal tank 3 and the external tank 7 delimit between them an inter space median 19, maintained under a high vacuum.

[0046] This vacuum is typically of the order of 105 mbar, so as to greatly limit the heat transfer by convection from the external reservoir 7 to the internal reservoir 3.

[0047] Thermal insulation 21 is interposed between the internal tank 3 and the external tank 7. The thermal insulation 21 is typically placed on the external surface of the internal tank 3. The thermal insulation 21 comprises, for example, a plurality of metal sheets superimposed on each other, with interposition of layers of fibers.

[0048] The suspension 9 is arranged such that the entire weight of the internal tank 3 is taken up by the external tank 7 via the suspension 9.

[0049] The weight of the internal tank 3 is understood here to include the weight of the cryogenic fluid stored in the internal tank 3.

[0050] The accelerations undergone by the internal tank 3 and the cryogenic fluid contained in the internal tank 3 are also transmitted to the external tank 7 via the suspension 9.

[0051] When the storage unit 1 is mounted in a vehicle, these accelerations result from changes in direction of the vehicle, from braking applied to the vehicle or from acceleration of the vehicle, from roughness or irregularities in the road, or from shocks applied to the vehicle.

[0052] In the example shown, the suspension 9 comprises two links 23, 25.

[0053] The links 23, 25 each suspend one of the two opposite axial ends of the internal reservoir 3 to the external reservoir 7.

[0054] Links 23 and 25 are different from each other in the example shown.

[0055] The connection 23 is provided to allow the passage of the cryogenic fluid to the storage volume 5, or from the storage volume 5.

[0056] On the contrary, the connection 25 is not provided for the passage of cryogenic fluid.

[0057] The connection 23 is of the fixed type, while the connection 25 is of the sliding type.

[0058] In other words, the connection 25 allows sliding of the corresponding end weight of the internal tank 3 relative to the external tank 7, for example due to thermal expansion or contraction of the internal tank 3.

[0059] The connection 23 does not allow such sliding.

[0060] The invention relates to the non-sliding connection 23.

[0061] As illustrated in [Fig.2], the link 23 comprises:

[0062] - an external tube 27 having an external proximal end 29 fixed to the reservoir internal 3 and an external distal end 31 located inside the storage volume 5;

[0063] - a bottom plate 33 closing the external distal end 31;

[0064] - an internal tube 41 arranged inside the intermediate tube 35, having a inner proximal end 43 attached to the outer reservoir 7 and an inner distal end 45 attached to the inner reservoir 3.

[0065] Advantageously, the connection 23 also comprises:

[0066] - an intermediate tube 35 arranged between the inner tube and the outer tube 27, having an intermediate proximal end 37 fixed to the internal reservoir 3 and an intermediate distal end 39; and

[0067] - an annular ring 47 connecting the intermediate distal end 39 to the end internal distal 45.

[0068] In other words, the internal distal end 45 is fixed to the internal reservoir 3 by means of the annular ring and the intermediate tube 35.

[0069] The outer tube 27 is substantially cylindrical, and is coaxial with the central axis C.

[0070] It is located inside the storage volume 5, typically entirely inside the storage volume 5.

[0071] An opening 49 is provided in the bottom 13 of the internal tank 3. An internal ring 51 is engaged in the opening 49 and rigidly fixed to the bottom 13. The external peripheral edge of the internal ring 51 is welded in a sealed manner to the edge of the opening 49.

[0072] On a face facing the storage volume 5, the internal ring 51 has an external rib 53 of substantially cylindrical shape.

[0073] The external rib 53 is coaxial with the central axis C, and has substantially the same diameter as the external proximal end 29.

[0074] The outer proximal end 29 is welded in a sealed manner to the outer rib 53.

[0075] In the same way, the internal ring 51 carries on its face facing the storage volume 5 a second rib 55, of substantially cylindrical shape.

[0076] This second rib 55 is coaxial with the central axis C, and has the same diameter as the intermediate proximal end 37.

[0077] The intermediate proximal end 37 is welded in a sealed manner to the second rib 55.

[0078] The bottom plate 33 seals the external distal end 31 in a sealed manner. It has a bottom 57 extended by a raised edge 59 welded in a sealed manner to the external distal end 31.

[0079] The annular ring 47 is coaxial with the central axis C.

[0080] It has U-shaped sections in radial planes containing the central axis C. The annular ring 47 thus has an external cylindrical wall 61 and an internal cylindrical wall 63, connected to each other by a bottom 65.

[0081] The outer wall 61 has substantially the same diameter as the intermediate distal end 39, and is welded to this intermediate distal end 39.

[0082] The internal wall 63 has substantially the same diameter as the internal proximal end 45, and is welded to the latter.

[0083] The intermediate tube 35 has over the greater part of its length a wall thickness of between 0.5 mm and 2.5 mm, preferably between 1 and 2 mm, and for example 1.5 mm.

[0084] It is made of an austenitic stainless steel having for example an Rp 0.2 of 270 MPa. Typically, it is made of stainless steel of grade 1.4310 or type 304.

[0085] The intermediate proximal end 37 and the intermediate distal end 39 are thicker than the central part of the intermediate tube 35, so as to increase the rigidity respectively of the connection with the rib 55 and of the connection with the external wall 61.

[0086] In the same way, the internal tube 41 has over the greater part of its length a wall thickness of between 0.5 mm and 2.5 mm, preferably between 1 and 2 mm, and for example 1.5 mm.

[0087] It is made of an austenitic stainless steel having for example an Rp 0.2 of 270 MPa. Typically it is made of stainless steel of grade 1.4310 or type 304.

[0088] The inner proximal end 43 and the inner distal end 45 are thicker than the central part of the inner tube 41, so as to increase the rigidity respectively of the connection with the inner wall 63

[0089] The connection 23 further comprises at least one circulation conduit 75 extending inside the internal tube 4L.

[0090] The or each circulation conduit 75 has a proximal circulation end portion 76 arranged opposite the internal proximal end 43, and a distal circulation end 77 fixed to the base plate 33 and communicating fluidically with the internal volume 5 through the base plate 33.

[0091] Typically, the connection 23 comprises four circulation conduits 75.

[0092] In this case, one of the circulation conduits 75 is provided for filling the storage volume 5. Another circulation conduit 75 is provided for emptying the storage volume 5.

[0093] The other two circulation conduits 75 are provided to circulate the cryogenic fluid to a heat exchanger, in a loop.

[0094] The proximal circulation end portion 76 is arranged opposite the inner proximal end 43 in the sense that there is at least one plane perpendicular to the central axis C of the inner tube 41 intersecting both the proximal circulation end portion 76 and the inner proximal end 43.

[0095] The internal reservoir 3 also has an orifice 79 through which the internal tube 41 is connected to the external reservoir 7.

[0096] The orifice 79 is formed in the internal ring 51. The internal tube 41 passes through the orifice 79. The proximal circulation end portion 76 of the or each circulation conduit 75 also passes through the orifice 79.

[0097] Thus, the space delimited inside the external tube 27 is isolated from the storage volume 5 but communicates with the intermediate space 19 through the orifice 79.

[0098] For example, the connection 23 comprises a cup 83 of which a central part 84 is placed opposite the bottom 13 of the internal tank 3 and of which the edge 85 is rigidly fixed to the internal surface of the external tank 7. This cup is for example of the type described in the application filed under number FR2211366.

[0099] The central part 84 of the cup 83 is oriented substantially perpendicular to the central axis C. It has a central orifice 86, crossed by the internal proximal end 43.

[0100] The central portion 84 of the cup 83 is rigidly fixed directly to the internal proximal end 43.

[0101] The inner proximal end 43 is engaged through the central orifice 86 of the cup 83 and is welded to the edge of said central orifice 86.

[0102] The proximal circulation end portion 76 of each circulation conduit 75 is without contact with the inner tube 4L

[0103] According to the invention, the distal circulation end 77 of the or each given circulation conduit 75 is located at a lower level than the proximal circulation end portion 76 of the same circulation conduit 75 in a vertical direction.

[0104] The vertical direction is the direction in which the force of gravity is exerted.

[0105] The storage unit 1 is arranged such that this condition is verified.

[0106] The difference in level, in the vertical direction, is as large as possible. It is typically between 50 mm and 500 mm, preferably between 60 and 200 mm, and is for example 80 mm.

[0107] The or each circulation conduit 75 comprises a central portion 88 connected to the proximal circulation end portion 76, and a distal portion 87 connecting the central portion 88 to the distal circulation end 77.

[0108] The central portion 88 is connected to the distal portion 87 by an elbow 89.

[0109] The central part 88 is horizontal.

[0110] In the example shown, the C axis is horizontal.

[0111] The elbow 89 is configured so that the angle between the central portion 88 and the distal portion 87, at this elbow, is between 110° and 160°, preferably between 120° and 150° and more preferably between 130° and 140°.

[0112] The distal portion 87 slopes downward from the central portion 88 to the distal circulation end 77.

[0113] This means that the altitude of the distal portion 87 decreases when following the distal portion 87 from the central portion 88 to the distal circulation end 77.

[0114] In the example shown, this altitude is strictly decreasing. It decreases continuously from the central part 88 to the distal circulation end 77.

[0115] Alternatively, the distal portion comprises one or more horizontal sections of constant altitude.

[0116] The distal portions 87 of certain circulation conduits 75 are rectilinear.

[0117] The distal portion 87 of at least one circulation conduit 75 comprises at least two rectilinear sections 91 connected to each other by an elbow 93. The respective slopes of the rectilinear sections 91 increase as one moves away from the elbow 89 to approach the distal end 77.

[0118] Alternatively, the distal portion 87 comprises one or more arcuate sections, or is arcuate along its entire length.

[0119] The proximal circulation end portion 76 is a sleeve defining an internal angled passage 95 for the cryogenic fluid.

[0120] The proximal circulation end portion 76 is rectilinear, parallel to the axis C.

[0121] The proximal circulation end portion 76 is of large diameter and strong thickness, which allows a very rapid change of direction in the internal conduit 95.

[0122] The internal conduit 95 comprises an upstream section 97 parallel to the central axis C, extended by an inclined section 99 extending in a direction forming a non-zero angle with the central axis.

[0123] If the proximal circulation end portion 76 were a thin tube, it would be necessary to produce a bend to obtain the change of direction, this bend having a larger axial size.

[0124] The central portion 88 of the circulation duct 75 is connected to the internal passage 95.

[0125] To do this, the internal passage 95 has, at one end, a counterbore 101 in the extension of the upstream section 97. A connecting sleeve 103 is rigidly fixed in this 101 counterbore.

[0126] The end of the central portion 88 opposite the elbow 89 is rigidly fixed, in a sealed manner, to the connection sleeve 103, typically by welding.

[0127] The bottom plate 33 has orifices 105, in which other connecting sleeves 107 are engaged.

[0128] The distal circulation end 77 of the or each circulation conduit 75 is rigidly fixed, in a sealed manner, to one of the other connection sleeves 107, typically by welding.

[0129] The inclined section 97 of the internal passage 95 ends with a counterbore 109, provided on a flat 110 of the proximal circulation end portion 76. This counterbore is located axially beyond the cup 83, outside the internal tube 4L.

[0130] A conduit not shown is connected to the counterbore 109. This conduit is arranged in the volume delimited between the cup 83 and the bottom 17 of the external tank 7.

[0131] The or each circulation conduit 75 has an internal diameter greater than 17 mm.

[0132] This diameter is typically between 30 mm and 17 mm depending on the maximum flow rates passing through them.

[0133] The or each circulation conduit 75 has a constant internal diameter over its entire length.

[0134] The fact that the or each circulation conduit 75 is bent gives flexibility to this tube. Thus, when it is crossed by the cryogenic fluid at 20 K, it can contract axially without generating excessive stresses in the tube.

[0135] The or each circulation conduit 75 thus extends over the entire length of the internal tube 4L. It exits the internal tube 41 by passing through the center of the annular ring 47, and extends inside the external tube 27 to the bottom plate 33.

[0136] The or each circulation conduit 75 has, along the central part 88 and the distal part 87, a wall thickness of between 0.1 and 0.6 mm, preferably between 0.2 and 0.4 mm and for example 0.3 mm.

[0137] The or each circulation conduit 75 has, along the proximal circulation end portion 76, a wall thickness much greater than 0.6 mm, for example of the order of 4 to 5 mm.

[0138] The proximal circulation end portion 76 extends over a length of between 5 and 30% of the total developed length of the circulation conduit 75, preferably between 5 and 20%, more preferably between 5 and 15%.

[0139] The or each circulation conduit 75 is typically made of a type 316 L stainless steel.

[0140] The outer tube 27 comprises an outer proximal portion 111 defining the outer proximal end 29, and an outer distal portion 113 connecting the outer proximal end 29 to the outer distal end 29. external proximal 111 to the bottom plate 33

[0141] The external proximal portion 111 is horizontal.

[0142] The outer distal portion 113 is inclined downwardly from the outer proximal portion 111 to the bottom plate 33.

[0143] This means that the center line X of the outer distal portion 113 has a decreasing altitude when following the outer distal portion 113 from the outer proximal portion 111 to the bottom plate 33.

[0144] The center line X is the line passing through the geometric centers of all the cross sections of the outer distal portion 113.

[0145] In the example shown, this altitude is strictly decreasing. It decreases continuously from the external proximal part 111 to the bottom plate 33.

[0146] The outer distal portion 113 is arched.

[0147] In other words, it forms an elbow whose central line X is a downward concave curve.

[0148] The central line X, at the junction with the external proximal part 111, is tangent to the horizontal.

[0149] The central line X, at the junction with the bottom plate 33, forms with the horizontal an angle of between 20° and 70°, preferably between 30° and 60° and more preferably between 40° and 50°. It is perpendicular to the bottom 57 of the bottom plate 33.

[0150] In order to compensate even better for the differential expansion between the or each circulation conduit 75 and the external tube 27, the or each circulation conduit 75 comprises, in the variant shown in [Fig. 3], at least one thermal expansion compensator 115.

[0151] Indeed, the or each circulation conduit 75 may have a temperature significantly lower than that of the external tube 27, in particular during the first filling of the storage volume 5. During this first filling, the storage volume 5 is at ambient temperature, like the external tube 27. On the other hand, the circulation conduits 75 are substantially at the same temperature as the cryogenic fluid. For a circulation conduit 75 of 420 mm length, the contraction in length of the circulation conduit 75 can then reach 1.6 mm when the cryogenic fluid is liquid hydrogen at 20 K.

[0152] In the example shown, each circulation duct 75 comprises several thermal expansion compensators 115, distributed along its length.

[0153] For example, it comprises two thermal expansion compensators 115 ([Fig.3]) or three thermal expansion compensators 115 ([Fig.4]), regularly spaced along the circulation duct 75.

[0154] The or each thermal expansion compensator 115 is advantageously a corrugated section of circulation conduit 75.

[0155] Each ringed section comprises a plurality of annular zones 117 projecting towards the outside of the circulation duct 75, each delimiting an internal groove open towards the inside of the circulation duct 75. These projecting annular zones 117 are connected to each other by at least one annular zone 119 recessed towards the outside of the circulation duct 75. The at least one recessed annular zone 119 is curved towards the inside of the circulation duct 75, and delimits between the projecting annular zones 117 a groove open towards the outside of the circulation duct 75. Considered in section in a plane containing the axis of the circulation duct 75, the ringed section has a sinuous shape.

[0156] The connection 23 preferably comprises external thermal insulation, not shown, arranged between the intermediate tube 35 and the external tube 27.

[0157] The external thermal insulation is typically of the same type as the thermal insulation 21. It comprises a plurality of aluminized metal sheets or plastic sheets (for example PET, PA, PEEK) superimposed on each other, with interposition of layers of fibers.

[0158] The connection 23 advantageously also comprises internal thermal insulation, not shown, arranged between the intermediate tube 35 and the internal tube 4L.

[0159] The internal thermal insulation is of the same type as thermal insulation 21.

[0160] According to a variant shown in [Fig.4], the proximal end circulation parts of the different circulation conduits 75 are arranged in a single distributor block 121.

[0161] More precisely, the internal passages 95 are provided in the distributor block 121.

[0162] This distributor block 121 is partially engaged in the internal tube 4L. It is not in contact with the internal tube 41, and is separated from it by an air gap.

[0163] According to a variant not shown, the connection 23 does not include an intermediate tube and an annular ring. The internal tube 41 is then directly fixed to the bottom plate 33 or to the external tube 27. The connection is for example of the type described in the application filed under number FR2207054.

[0164] The storage unit described above has multiple advantages.

[0165] When the or each circulation conduit comprises a central portion connected to the proximal circulation end portion, and a distal portion connecting the central portion to the distal circulation end, the distal portion being inclined downward from the proximal portion to the distal circulation end, the risk of forming a heat pipe inside the circulation conduit is particularly low.

[0166] When the central part is connected to the distal part by an elbow, the conduit of circulation can contract axially without generating excessive stresses in the conduit. This contraction results in flexion at the elbow.

[0167] When the outer tube comprises an outer proximal portion defining the outer proximal end, and an outer distal portion connecting the outer proximal portion to the bottom plate, the outer distal portion being inclined downwardly from the outer proximal portion to the bottom plate, it is particularly easy to arrange the or each circulation conduit in the outer tube.

[0168] An arcuate shape is particularly well suited for the outer distal portion, because it has a relatively large diameter.

[0169] When the or each circulation conduit has an internal diameter greater than 21 mm, it is possible to limit the Taconis effect.

[0170] The Taconis effect which is a thermo-acoustic effect. So-called Taconis waves are generated when a tube is partially immersed in a bath of cryogenic fluid, in particular liquid hydrogen. The temperature difference between the part immersed in the fluid (cold) and the hotter part produces an acoustic wave which goes back and forth in this tube. This production of sound is accompanied by a transport of heat towards the bath. This contribution can be significant and lead to significant vaporization of the cryogenic fluid.

[0171] When the or each circulation duct comprises at least one thermal expansion compensator, the circulation duct can contract axially without generating excessive stresses in the duct.

[0172] When the or each thermal expansion compensator is a corrugated section of the circulation duct, the thermal path for the conduction of heat along the duct is elongated.

[0173] The fact that the circulation proximal end portion is without contact with the inner tube means that there is no thermal path for heat from the circulation proximal end portion to the inner reservoir via the inner tube.

[0174] Because the proximal circulation end portion is a sleeve defining an internal angled passage for the cryogenic fluid, it is possible to create a change of direction for the circulation of the cryogenic fluid in a reduced axial space requirement.

Claims

Claims

1. Storage unit (1) for cryogenic fluid, comprising an internal reservoir (3) internally delimiting a volume (5) for storing the cryogenic fluid, an external reservoir (7) in which the internal reservoir (3) is housed and a suspension (9) fixing the internal reservoir (3) to the external reservoir (7), the suspension (9) comprising a connection (23) comprising: - an external tube (27) having an external proximal end (29) fixed to the internal reservoir (3) and an external distal end (31) located inside the storage volume (5); - a bottom plate (33) closing the external distal end (31);- an inner tube (41) arranged inside the intermediate tube (35), having an inner proximal end (43) fixed to the outer reservoir (7) and an inner distal end (45) fixed to the inner reservoir (3), - at least one circulation conduit (75) extending inside the inner tube (41), the or each circulation conduit (75) having a proximal circulation end portion (76) arranged opposite the inner proximal end (43), and a distal circulation end (77) fixed to the bottom plate (33) and fluidly communicating with the inner volume (5) through the bottom plate (33), the distal circulation end (77) being located at a level lower than the proximal circulation end portion (76) in a vertical direction.;

2. A storage unit according to claim 1, wherein the or each circulation conduit (75) comprises a central portion (88) connected to the circulation proximal end portion (76), and a distal portion (87) connecting the central portion (88) to the circulation distal end (77), the distal portion (87) being inclined downwardly from the central portion (88) to the circulation distal end (77).

3. A storage unit according to claim 2, wherein the central portion (88) is horizontal.

4. A storage unit according to claim 2 or 3, wherein the central portion (88) is connected to the distal portion (87) by an elbow (89).

5. A storage unit according to any preceding claim, wherein the outer tube (27) comprises an outer proximal portion (111) defining the outer proximal end (29),

6.

7.

8.

9.

10.

11.

12. and an outer distal portion (113) connecting the outer proximal portion (111) to the bottom plate (33), the outer distal portion (113) being inclined downward from the outer proximal portion (111) to the bottom plate (33). Storage unit according to claim 5, wherein the outer proximal portion (111) is horizontal. A storage unit according to claim 5 or 6, wherein the outer distal portion (113) is arcuate. Storage unit according to any one of the preceding claims, in which the or each circulation conduit (75) has an internal diameter greater than 21 mm. A storage unit according to any preceding claim, wherein the or each circulation conduit (75) comprises at least one thermal expansion compensator (115). A storage unit according to claim 9, wherein the or each thermal expansion compensator (115) is a corrugated section of the circulation conduit (75). A storage unit according to any preceding claim, wherein the proximal circulation end portion (76) is non-contacting the inner tube (41). A storage unit according to any preceding claim, wherein the proximal circulation end portion (76) is a sleeve defining an internal angled passage (95) for the cryogenic fluid.

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