Container for containing a cryofluid

Abstract

Container (1) for receiving a cryofluid, in particular cryogenic hydrogen, comprising an outer container (3) and an inner container (2), which is mounted in the outer container (3) at a distance (A) on all sides via a support structure (13), whereby an evacuable space (4) for thermal insulation is formed between the outer and inner containers (3, 2), wherein at least one magnet (20) is mounted on the inner container (2) spaced apart from the outer container (3).

Description

[0001] The present invention relates to a container for holding a cryofluid, in particular cryogenic hydrogen, comprising an outer container and an inner container, which is mounted in the outer container at all sides via a support structure, whereby an evacuable space for thermal insulation is formed between the outer and inner containers.

[0002] To increase the volumetric energy density of energy carriers that are gaseous under normal conditions, they are either compressed and stored in pressure vessels for transport and storage purposes, or cooled to low temperatures, becoming at least partially liquefied as a cryofluid and stored in temperature-insulated containers. For example, liquefied hydrogen or liquefied natural gas (LNG) are stored as cryofluids with high energy density to power vehicles, for later use in operating the vehicles' combustion engines or fuel cells.

[0003] Due to the extremely low temperatures of such cryofluids, e.g., less than -252 °C in the case of liquid hydrogen or less than -161 °C in the case of LNG, particularly good, uniform thermal insulation on all sides is essential to prevent heat loss and, consequently, overpressure in the container and / or boil-off, i.e., loss of the cryofluid. During operation, such containers, especially when used as fuel tanks for vehicles and subjected to continuous mechanical stress, occasionally suffer damage, which impairs the thermal insulation, at least locally, resulting in local thermal bridges that lead to significantly higher heat losses. Such damage is not easy to detect and locate because the containers are sealed and difficult to disassemble, and the increased losses significantly reduce the usability of the containers.

[0004] The invention aims to create a container for cryofluids which allows frequent damage leading to impaired thermal insulation to be easily and quickly detected from the outside without disassembling the container.

[0005] This objective is achieved in a container of the type mentioned in the introduction, according to the invention, by mounting at least one magnet on the inner container that is spaced apart from the outer container.

[0006] The invention is based on the understanding that a particularly frequent cause of local impairment of thermal insulation is damage to the support structure on which the inner container is mounted within the outer container, for example, due to mechanical stresses during operation as a fuel tank for a vehicle, aging or material embrittlement, and / or temperature fluctuations. Depending on the design, such stresses can lead to cracks or fractures in the support structure, causing the overall distance between the outer and inner containers to decrease significantly at one or more points, resulting in undesirable local thermal bridges and thus increased heat loss. Each magnet is mounted, for example, at a particularly vulnerable point on the inner container or at a point on the inner container where the support structure is subject to significant displacement relative to the outer container in the event of damage. Using a magnetometer, i.e.,Using a magnetic flux density measuring instrument, the magnetic flux density can be measured on the outside of the outer container, either all around or in the immediate vicinity of a magnet mounted on the inner container, for example, manually. If a predefined threshold is exceeded and / or if there is a change in the magnetic flux density compared to a previously measured undamaged (especially new) condition of the container, this indicates damage to its supporting structure and thus an impairment of the thermal insulation. This can be done quickly and easily from the outside without disassembling the container.

[0007] The at least one magnet can be, for example, an electromagnet, which is permanently powered or alternatively powered only when needed. Optionally, the electromagnet can be a superconductor, which is kept at a superconducting temperature by the inner container or the cryofluid it contains. It is particularly advantageous if the at least one magnet is a permanent magnet. Permanent magnets are easy to handle, cost-effective, and do not require electrical connecting wires, which could evaporate undesirably in the vacuum of the space between the containers.

[0008] It is particularly advantageous if, in an operating position of the container, the inner container has an underside with at least one magnet mounted on it. In a given operating position, damage to the support structure and thus increased heat loss from the container can be reliably detected with just a single magnet.

[0009] As previously described, the magnetic flux density can most easily be measured manually using a magnetometer, for example, regularly or when a problem is suspected. Alternatively or additionally, it is advantageous to attach a sensor for measuring the magnetic flux density to the outer container in close proximity to at least one magnet mounted on the inner container. With such a sensor, the magnetic flux density can be evaluated at any time, optionally automatically and continuously, so that any damage can be detected as soon as it occurs.

[0010] The container can have any shape, e.g., spherical or ellipsoidal, etc., even irregular shapes. In an advantageous embodiment, the outer container and the inner container each have a cylindrical shell, preferably a circular cylindrical shell, closed at the ends with end caps, with the inner container being mounted coaxially within the outer container. This allows for simple manufacturing, good suitability for use, e.g., as a fuel tank for vehicles, and high pressure stability of the container.

[0011] It is advantageous if the support structure has at least one first support, via which the inner container is supported by one end cap against the corresponding end cap of the outer container, and at least one second support, via which the inner container is supported by its other end cap, diametrically opposite the first, against the corresponding end cap of the outer container, wherein the end caps of the inner and outer containers are penetrated by at least one connecting line, and wherein a magnet is mounted on the shell of the inner container in the region of the other end cap, e.g., on its underside, or several magnets are mounted distributed around the circumference of the shell of the inner container. The connecting lines can be, on the one hand, lines for the supply and removal of cryogenic fluid – including degassing – and, on the other hand, electrical connecting lines for pressure and level sensors and / or heating lines, etc.On this side of the aforementioned end caps, damage to the support structure is less likely due to the additional mechanical stabilization provided by the connecting cables, so that a single magnet, e.g. in the area of ​​the aforementioned other end cap on the underside of the inner container, and even more so the multiple magnets distributed around the circumference in this area, can easily and reliably detect damage to the support structure (here: to the second support).

[0012] In order to easily detect even rarer damage to the first support, it is advantageous if a magnet is also mounted on the shell of the inner container, e.g. on its underside, in the area of ​​the aforementioned end cap, or if several magnets are mounted distributed around the circumference of the shell of the inner container.

[0013] For effective thermal insulation, a heat-radiation-reflecting film is preferably placed in the space between the inner container and the at least one magnet. Particularly effective thermal insulation can be achieved if the film is a multi-layered metal foil composite with a fiberglass fabric, woven material, or fleece between the metal foil layers. Magnetometer measurements have shown that with such films or film composites, a change in magnetic flux density due to damage to the supporting structure is clearly detectable from the outside.

[0014] In an advantageous embodiment of the container, the outer container and / or the inner container is made of metal, preferably stainless steel or aluminum. Metals, especially stainless steel and aluminum, are resistant to cold and pressure and are therefore particularly suitable for cryogenic fluid containers. The outer and inner containers can be made of different materials, especially different metals or metal alloys.

[0015] The invention is explained in more detail below with reference to an embodiment illustrated in the accompanying drawings. The drawings show: Fig. 1 a container according to the invention in a longitudinal section; Fig. 2 the container of Fig. 1 in a case of damage in a schematic longitudinal section; Fig. 3 a section B of the container of Fig. 1 in a longitudinal section; and Fig. 4 a section C of the container of Fig. 2 in a longitudinal section.

[0016] Fig. 1 Figure 1 shows a container 1 for holding a cryofluid. The cryofluid can be, for example, hydrogen, which is at least partially liquefied at temperatures below -252 °C and pressures of, for example, up to 16 bar – or more, depending on the container design – or a comparable cryofluid suitable for use in internal combustion engines or fuel cells, such as liquefied natural gas (LNG) at a temperature below -161 °C. The container 1 is mounted, for example, in the manner of a conventional fuel tank, on the side of the chassis or frame of a commercial vehicle (not shown), such as a truck or passenger car.

[0017] The cryogenic fluid can also be a refrigerant, for example liquid nitrogen, used to operate the cooling system of refrigerated trucks, such as food transport vehicles. Accordingly, container 1 can also be used for storing such refrigerants on trucks or truck trailers.

[0018] For thermal insulation of the cryofluid from the external environment, the container 1 is double-walled, consisting of an inner container 2 and an outer container 3 surrounding it on all sides at a distance A. The space 4 between the inner container 2 and the outer container 3 is usually evacuated, but can alternatively or additionally be filled with a thermally insulating material.

[0019] Since the cryofluid in the inner container 2 is usually under pressure, (at least) the inner container 2 is generally designed as a pressure vessel made of metal, for example, stainless steel or aluminum. The outer container 3 can also be made of metal, especially stainless steel or aluminum, but also of plastic, since it only needs to withstand the ambient pressure against the vacuum in the space 4.

[0020] In the illustrated example, the inner container 2 has a generally cylindrical shell 5 around a central axis Z, which here corresponds to the longitudinal axis of the container 1. This shell is closed at both ends by end caps 6 and 7, each of which is, for example, convex outwards. The term "generally cylindrical" refers to a cylinder with any base or cross-sectional area, whether circular, oval, rectangular, square, square with rounded corners, or otherwise shaped. For maximum compressive strength, the shell 5, and thus the inner container 2, has a circular cross-section.

[0021] The outer container 3 is essentially adapted to the outer shape of the inner container 2 – while maintaining the all-around clearance A to create the space 4 – and the inner container 2 is optionally mounted coaxially within the outer container 3. The outer container 3 also consists, in particular, of a generally cylindrical shell 8 and two end caps 9, 10 that close off this shell at its ends, e.g., concave inwards. It is understood that the clearance A does not have to be the same on all sides of the inner container 2. The end caps 6, 7, 9, 10 are welded to the respective shell 5, 8, e.g., by means of circumferential welds 11, 12.

[0022] It is understood that container 1 can alternatively have a different design, e.g. a spherical or ellipsoidal shape or another geometric or irregular shape.

[0023] To create the all-around clearance A, the inner container 2 is supported on the outer container 3 by a support structure 13, i.e., mounted within it. In the illustrated example, the support structure 13 has at least one first support 13a, by which the inner container 2 is supported with one end cap 6 against the corresponding end cap 9 of the outer container 3, and at least one second support 13b, by which the inner container 2 is supported with its other end cap 7, diametrically opposite the one end cap 6, against the corresponding other end cap 10 of the outer container 3. In the illustrated example, the first and second supports 13a, 13b of the support structure 13 are coaxial with the outer and inner containers 3, 2. The first and second supports 13a, 13b are made of heat-insulating material. They are in Fig. 1 The supports are shown only schematically and can, for example, be designed as fixed bearings, or at least one of them optionally as a sliding bearing to compensate for thermal expansion. Alternatively, the support structure 13 can be formed by more than two supports and / or struts, by tension cables, or the like.

[0024] The first support 13a, if designed as a fixed bearing, can be formed, for example, by a sleeve 14 which tightly penetrates the aligned openings of the inner and outer containers 2, 3 and can be used for the sealed passage of one or more connecting lines 15 leading from the outer container into the inner container 2 and terminating there, for example, in a filling opening 16, a discharge opening 17, a degassing opening 18, and a heat exchanger 19. The connecting lines 15 may optionally also include electrical lines for, for example, sensors arranged in the container, an electric heater, or the like (not shown).

[0025] To detect damage to the support structure 13, e.g., a break in one of the supports 13a, 13b, at least one magnet 20 is mounted on the inner container 2, such that it is spaced apart from the outer container 3. In the illustrated example, the at least one magnet 20 is a permanent magnet mounted on the outside of the inner container 2. Alternatively, the at least one magnet 20 could be mounted on the inside of the inner container 2. Furthermore, the magnet 20 could be an electromagnet, in particular a superconductor carrying an electric current.

[0026] Optionally, a sheet 21 can be placed in space 4 ( Fig. 3 ) arranged, which surrounds the inner container 2 and the at least one magnet 20 and reflects the heat radiation directed from the outer container 3 towards the inner container 2 back to the outer container 3 in order to keep the inner container 2 cool.

[0027] In the example of the Fig. 1 The container 1 is shown in its operating position, i.e., the position it assumes during operation, e.g., on a truck. A magnet 20 is mounted on the inner container 2, specifically on an underside 2' of the inner container 2 in the illustrated operating position and simultaneously on the shell 5 of the inner container 2 in the area of ​​its other end cap 7.

[0028] Fig. 2 schematically shows a possible damage scenario for container 1 for the [unclear text] Fig. 1 The example shown illustrates this. In this case of damage, the second support 13b is broken. The inner container 2 sags unevenly due to its own weight and that of the cryofluid it contains, so that the distance A at this point is significantly reduced and the (here: single) magnet 20 approaches the outer container 3. This approach can be detected externally using a magnetometer 22, i.e., a device for measuring magnetic flux density, as shown below in the examples of... Fig. 3 und 4 will be explained.

[0029] Fig. 3 shows an enlarged section B from Fig. 1 , in which container 1 is undamaged. In this state, the distance A between inner and outer containers 2, 3 has the intended size.

[0030] Slide 21 is in the example of the Fig. 3 und 4 A multi-layered metal foil composite consisting of several (here: seven) layers 23 of a metal foil, between or next to which several (here also seven) layers 24 of a glass fiber fabric, woven fabric, or nonwoven fabric are located. For this purpose, for example, a large-format metal foil is laid on top of a large-format glass fiber fabric in a congruent manner and rolled up in several layers, resulting in a tubular shell that can be slid onto the inner container 2 before its assembly in the outer container 3, thus surrounding the inner container 2, including at least one magnet 20 mounted on it, at least on the outer surface.

[0031] In undamaged condition according to Fig. 3 The layers 23, 24 of the metal foil and the fiberglass fabric, woven fabric, or nonwoven fabric are hardly or not at all compressed. Concentric ellipses 25 symbolize a magnetic field surrounding the magnet 20, the flux density of which decreases with increasing distance from the magnet 20. Due to the distance A, the magnetic flux density originating from the magnet 20 is low outside the outer container 3; in the symbolic representation of the ellipses 25, these do not protrude from the space 4.

[0032] In contrast, it shows Fig. 4 as section C of Fig. 2 The damage case in detail. Due to the (here: unilateral) sinking of the inner container 2, the mutual distance A between the inner and outer containers 2, 3 is reduced to an undesirably small distance A', thereby compressing the multilayer film 21. As a result, the magnetic flux density detectable by the magnetometer 22 on the outside of the outer container 3 increases compared to the undamaged case. Fig. 1 and 3 measurable, for example by 10% to 50%, depending on the design of container 1, so that the damage to the support structure 13 (here: to the second support 13b) is easily detectable from the outside. This is illustrated in Fig. 4 through the ellipses 25 projecting beyond the outer container 3.

[0033] The detection of damage can be based on exceeding a predetermined threshold value of the magnetic flux density and / or on a change exceeding a threshold value compared to a preliminary measurement in the undamaged state of the container 1. It is further understood that the at least one magnet 20 can be of any shape and orientation for this purpose.

[0034] In addition (or alternatively) to the one magnet 20, at least one further magnet can be, for example, on the underside 2' of the inner container 2 and on its shell 5 in the area of ​​one end cap 6 or distributed around the circumference of its shell 5, for example, in the area of ​​one and / or the other end cap 6, 7, or even mounted elsewhere (not shown), so that additional detection possibilities exist, for example, the detection of a local displacement of the relatively highest measured magnetic flux density when a magnet 20 mounted on a lateral side of the inner container 2 has sunk as a result of a break in a support 13a, 13b inside the outer container 3.

[0035] Furthermore, instead of manually measuring the magnetic flux density with a portable magnetometer 22, a sensor (not shown) for measuring the magnetic flux density, e.g., a Hall sensor or the like, can be permanently attached to the outer container 3 in the vicinity of at least one magnet 20 mounted on the inner container 2. In the case of multiple magnets 20, a separate sensor can optionally be used for each magnet 20, and the reading can be automatically read and displayed. The "nearby vicinity" refers in particular to the area of ​​the outer container 3 lying immediately radially outside the magnet 20.

[0036] The invention is not limited to the embodiments shown, but includes all variants, modifications and their combinations that fall within the scope of the attached claims.

Claims

1. Container for holding a cryofluid, in particular cryogenic hydrogen, comprising an outer container (3) and an inner container (2), which is mounted in the outer container (3) at all sides distance (A) via a support structure (13), whereby an evacuable space (4) for thermal insulation is formed between the outer and inner containers (3, 2), characterized by the fact that at least one magnet (20) is mounted on the inner container (2) and is spaced apart from the outer container (3).

2. Container according to claim 1, characterized by the fact that at least one magnet (20) is a permanent magnet.

3. Container according to claim 1 or 2, characterized by the fact that In an operating position of the container (1) the inner container (2) has a bottom surface (2') with at least one magnet (20) mounted on it.

4. Container according to any one of claims 1 to 3, characterized by the fact thata sensor for measuring the magnetic flux density is attached to the outer container (3) in the vicinity of at least one magnet (20) mounted on the inner container (2).

5. Container according to any one of claims 1 to 4, characterized by the fact that the outer container (3) and the inner container (2) each have a cylindrical shell (8, 5) closed at the end faces with end caps (9, 10; 6, 7), preferably a circular cylindrical shell (8, 5), wherein the inner container (2) is mounted coaxially in the outer container (3).

6. Container according to claim 5, characterized by the fact thatthe support structure (13) has at least a first support (13a) over which the inner container (2) with its one end cap (6) is supported on the corresponding one end cap (9) of the outer container (3), and at least a second support (13b) over which the inner container (2) with its other end cap (7) diametrically opposite the aforementioned one is supported on the corresponding other end cap (10) of the outer container (3), wherein the aforementioned one end caps (6, 9) of the inner and outer containers (2, 3) are penetrated by at least one connecting line (15), wherein in the area of ​​the aforementioned other end cap (7) a magnet (20) is mounted on the shell (5) of the inner container (2) or several magnets (20) are mounted distributed over the circumference of the shell (5) of the inner container (2).

7. Container according to claim 6, characterized by the fact thatfurthermore, in the area of ​​the aforementioned end cap (6) a magnet (20) is mounted on the shell (5) of the inner container (2) or several magnets (20) are mounted distributed over the circumference of the shell (5) of the inner container (2).

8. Container according to any one of claims 1 to 7, characterized by the fact that Furthermore, in the space (4) there is a heat radiation reflecting film (21) surrounding the inner container (2) and the at least one magnet (20).

9. Container according to claim 8, characterized by the fact that the film (21) is a multilayer metal foil composite with a glass fiber fabric, woven or nonwoven (24) between the metal foil layers (23) 10. Container according to any one of claims 1 to 9, characterized by the fact that the outer container (3) and / or the inner container (2) is made of metal, preferably stainless steel or aluminium.

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