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 include 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 inner 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 provide 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 cryogenic fluid storage volume, 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 including:

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

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

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

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

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

[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 reservoir, the distal end of the circulation line is at a temperature of approximately 20 K, while the proximal end of the circulation line is at a significantly higher temperature. Upon reaching the proximal end of the circulation line, the liquid cryogenic fluid may be partially vaporized. If the distal end of the circulation line is at a higher temperature than the proximal end, the vapor rises towards the distal end and is recondensed upon contact with cold surfaces or the colder cryogenic fluid. It then flows back towards the proximal end of the circulation line.

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

[0017] This transfer is impossible if the distal circulation end of the circulation conduit(s) is located at a lower level than the proximal circulation end, since the vapor will accumulate at the higher end, i.e., the proximal circulation end. This will create a gas plug that 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 according to all technically possible combinations:

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

[0020] - the central part is horizontal;

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

[0022] - the external tube includes an external proximal part defining the end external proximal, and an external distal part connecting the external proximal part to the base plate, the external distal part being inclined downwards from the external proximal part to the base plate;

[0023] - the external proximal part is horizontal;

[0024] - the external distal part is arched;

[0025] - the circulation conduit(s) has an internal diameter greater than 21 mm

[0026] - the or each circulation conduit includes at least one compensator of thermal expansion;

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

[0028] - the proximal end portion of the circulation is not in contact with the internal tube;

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

[0030] Other features and advantages of the invention will become apparent from the detailed description given below, by way of example and not limitation, with reference to the accompanying figures, among which: - [Fig.1] The [Fig.1] is an axial section view of the cryogenic fluid storage unit; - [Fig.2] The [Fig.2] is an enlarged axial section view of part of the suspension of the storage unit of the [Fig.1]; - [Fig. 3] The [Fig. 3] is a perspective view of the heat transfer fluid circulation ducts of the suspension in [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, some welds joining the parts to each other are not shown.

[0032] The storage unit 1 shown in [Fig.1] 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 a 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 carried on board a vehicle having an electric propulsion engine, 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 reservoir 3 internally delimiting a cryogenic fluid storage volume 5, an external reservoir 7 inside which the internal reservoir 3 is housed, and a suspension 9 fixing the internal reservoir 3 to the external reservoir 7.

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

[0040] The internal reservoir 3 comprises a ferrule 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 reservoir 7 is also horizontally oriented.

[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 reservoir 3 and the external reservoir 7 delimit a space between them intermediate 19, maintained under a high vacuum.

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

[0047] A thermal insulation 21 is interposed between the inner tank 3 and the outer tank 7. The thermal insulation 21 is typically placed on the outer surface of the inner tank 3. The thermal insulation 21 comprises, for example, a plurality of metal sheets superimposed one on top of the other, with interposed layers of fibers.

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

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

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

[0051] When the storage unit 1 is mounted in a vehicle, these accelerations result from changes in the direction of the vehicle, braking applied to the vehicle or acceleration of the vehicle, roughness or irregularities of the road, or 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 from the external reservoir 7.

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

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

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

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

[0058] In other words, the link 25 allows the corresponding end of the internal reservoir 3 to slide relative to the external reservoir 7, for example because of the thermal expansion or contraction of the internal reservoir 3.

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

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

[0061] As illustrated in [Fig.2], 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 base plate 33 closing the external distal end 31;

[0064] - an inner tube 41 arranged inside the outer tube 27, having an end proximal internal 43 fixed to the external reservoir 7 and a distal internal end 45 fixed to the internal reservoir 3.

[0065] Advantageously, link 23 also includes:

[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 distal internal 45.

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

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

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

[0071] An opening 49 is provided in the bottom 13 of the internal reservoir 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 hermetic manner to the edge of the opening 49.

[0072] On a face turned towards the storage volume 5, the inner 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 external proximal end 29 is welded tightly to the external rib 53.

[0075] Similarly, the inner ring 51 has 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 tightly to the second rib 55.

[0078] The base plate 33 seals the external distal end 31. It has a base 57 extended by a raised edge 59 welded securely 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 it.

[0083] The intermediate tube 35 has over most 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 outer wall 61.

[0086] Similarly, the inner tube 41 has over most 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 proximal internal end 43 and the distal internal end 45 are thicker than the central part of the internal tube 41, so as to increase the rigidity of the connection with the internal wall 63 respectively

[0089] The connection 23 further comprises at least one circulation conduit 75 extending inside the inner 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 fluidly with the internal volume 5 through the base plate 33.

[0091] Typically, the link 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 two other circulation conduits 75 are intended to circulate the cryogenic fluid to a heat exchanger, in a loop.

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

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

[0096] The orifice 79 is provided in the inner ring 51. The inner tube 41 passes through the orifice 79. The proximal circulatory end portion 76 of the or each circulatory 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 link 23 includes a cup 83 of which a central part 84 is placed opposite the bottom 13 of the inner reservoir 3 and whose edge 85 is rigidly fixed to the inner surface of the outer reservoir 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, through which the internal proximal end 43 passes.

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

[0101] The internal 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 end portion of the circulation 76 of each circulation conduit 75 is not in contact with the inner tube 4L

[0103] According to the invention, the distal circulation end 77 of the or of 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 in such a way that this condition is verified.

[0106] The difference in level, along the vertical direction, is as great 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 circulation conduit or each 75 comprises a central portion 88 connected to the proximal end portion of circulation 76, and a distal portion 87 connecting the central portion 88 to the distal end of circulation 77.

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

[0109] The central part 88 is horizontal.

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

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

[0112] The distal part 87 is inclined downwards from the central part 88 to the distal end of circulation 77.

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

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

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

[0116] The distal parts 87 of certain circulatory conduits 75 are straight.

[0117] The distal portion 87 of at least one circulatory conduit 75 comprises at least two straight sections 91 connected to each other by a bend 93. The respective slopes of the straight sections 91 increase as one moves away from the bend 89 towards the distal end 77.

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

[0119] The proximal end portion of circulation 76 is a sleeve delimiting an internal passage 95 bent for cryogenic fluid.

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

[0121] The proximal end portion of circulation 76 is of large diameter and of strong thickness, which allows for a very rapid change of direction in the internal duct 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 end part of circulation 76 was a thin tube, it would be necessary to make a bend to obtain the change of direction, this bend having an axially larger footprint.

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

[0125] To achieve 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 counterbore 101.

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

[0127] The base 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 connecting sleeves 107, typically by welding.

[0129] The inclined section 97 of the internal passage 95 terminates in a counterbore 109, formed on a flat surface 110 of the proximal end portion of the circulation 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 reservoir 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 circulation conduit or conduits 75 are bent gives flexibility to this tube. Thus, when it is traversed 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 along the entire length of the inner tube 4L II exits the inner tube 41 by passing through the center of the annular ring 47, and extends inside the outer tube 27 to the bottom plate 33.

[0136] The circulation conduit or conduits 75 have, 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 circulatory conduit or conduits 75 have along the proximal end portion of the circulatory conduit 76 a wall thickness much greater than 0.6 mm, for example on the order of 4 to 5 mm.

[0138] The proximal end portion of circulation 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 316L type stainless steel.

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

[0141] The external proximal part 111 is horizontal.

[0142] The external distal part 113 is inclined downwards from the external proximal part 111 to the base plate 33.

[0143] This means that the central line X of the external distal part 113 has a decreasing altitude when following the external distal part 113 from the external proximal part 111 to the base plate 33.

[0144] The central line X is the line passing through the geometric centers of all the straight sections of the external distal part 113.

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

[0146] The external distal part 113 is arched.

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

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

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

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

[0151] Indeed, the circulation conduit(s) 75 may have a temperature significantly lower than that of the outer tube 27, particularly during the initial filling of the storage volume 5. During this initial filling, the storage volume 5 is at ambient temperature, as is the outer tube 27. In contrast, the circulation conduits 75 are at approximately the same temperature as the cryogenic fluid. For a circulation conduit 75 with a length of 420 mm, the elongational contraction 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 has several thermal expansion compensators 115, distributed along its length.

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

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

[0155] Each corrugated section comprises a plurality of annular zones 117 projecting outwards from the circulation conduit 75, each defining an internal groove open towards the inside of the circulation conduit 75. These projecting annular zones 117 are connected to each other by at least one annular zone 119 recessed outwards from the circulation conduit 75. This at least one recessed annular zone 119 is convex towards the inside of the circulation conduit 75, and defines between the projecting annular zones 117 a groove open towards the outside of the circulation conduit 75. Considered in section in a plane containing the axis of the circulation conduit 75, the corrugated section has a sinuous shape.

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

[0157] External thermal insulation is typically of the same type as thermal insulation 21. It comprises a plurality of metallic or plastic sheets (for example PET, PA, PEEK) aluminized superimposed on one another, with interposed layers of fibers.

[0158] The connection 23 advantageously includes further internal thermal insulation (not shown) arranged between the intermediate tube 35 and the inner 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 portions of the circulation of the various circulation conduits 75 are provided in a single distributing block 121.

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

[0162] This distributor block 121 is partially engaged in the inner tube 4L II is without contact with the inner tube 41, and is separated from it by an air gap.

[0163] According to an alternative not shown, the connection 23 does not include an intermediate tube and an annular ring. The inner tube 41 is then directly attached to the base plate 33 or to the outer tube 27. The connection is, for example, of the type described in application number FR2207054.

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

[0165] Where the circulation conduit or conduits comprise a central portion connected to the proximal end portion of the circulation, and a distal portion connecting the central portion to the distal end of the circulation, the distal portion being inclined downwards From the proximal part to the distal end of the circulation, the risk of heat pipe formation inside the circulation conduit is particularly low.

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

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

[0168] An arcuate shape is particularly well suited for the external distal part, due to the fact that it has a relatively high diameter.

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

[0170] The Taconis effect, which is a thermoacoustic effect. Taconis waves are generated when a tube is partially immersed in a cryogenic fluid bath, particularly liquid hydrogen. The temperature difference between the part immersed in the fluid (cold) and the warmer part produces an acoustic wave that travels back and forth within the tube. This sound production is accompanied by heat transfer towards the bath. This heat transfer can be significant and lead to substantial vaporization of the cryogenic fluid.

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

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

[0173] The fact that the proximal end portion of circulation is not in contact with the inner tube means that there is no thermal path for heat from the proximal end portion of circulation to the inner reservoir via the inner tube.

[0174] Because the proximal end portion of the circulation is a sleeve delimiting 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.

Claims

Demands

1. Cryogenic fluid storage unit (1), comprising an internal reservoir (3) internally delimiting a cryogenic fluid storage volume (5), an external reservoir (7) in which the internal reservoir (3) is housed, and a suspension (9) attaching the internal reservoir (3) to the external reservoir (7), the suspension (9) comprising a link (23) having: - an external tube (27) having an external proximal end (29) attached 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 outer tube (27), 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 duct (75) extending inside the inner tube (41), the circulation duct or ducts (75) having a circulation proximal end portion (76) arranged opposite the inner proximal end (43), and a circulation distal end (77) fixed to the bottom plate (33) and communicating fluidly with the internal volume (5) through the bottom plate (33), the circulation distal end (77) being located at a level lower than the circulation proximal end portion (76) in a vertical direction; wherein the circulation duct or ducts (75) comprise at least one thermal expansion compensator (115).

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

3. Storage unit according to claim 2, wherein the central part (88) is horizontal.

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

5. Storage unit according to any one of the preceding claims, wherein the outer tube (27) comprises an outer proximal part (111) defining the outer proximal end (29), and an outer distal part (113) connecting the outer proximal part (111) to the bottom plate (33), the outer distal part (113) being inclined downwards from the outer proximal part (111) to the bottom plate (33).

6. Storage unit according to claim 5, wherein the outer proximal part (111) is horizontal.

7. Storage unit according to claim 5 or 6, wherein the external distal part (113) is arched.

8. Storage unit according to any one of the preceding claims, wherein the or each circulation conduit (75) has an internal diameter greater than 21 mm.

9. Storage unit according to any one of the preceding claims, wherein the or each thermal expansion compensator (115) is a corrugated section of the circulation conduit (75).

10. Storage unit according to any one of the preceding claims, wherein the proximal circulating end portion (76) is not in contact with the inner tube (41).

11. Storage unit according to any one of the preceding claims, wherein the proximal circulating end portion (76) is a sleeve delimiting an internal angled passage (95) for the cryogenic fluid.

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