Container for receiving a cryofluid

Abstract

A container (1) for holding a cryofluid comprises an inner container (2) with an outwardly convex cap (7) and an outer container (3) with at least one inwardly concave cap (10), wherein the inner container (2) is supported on the outer container (3) by a first support structure (13) having four rhombus-shaped struts (21-24), the ends (21", 22', 23", 24') of which are located at one of the two diagonally opposite corners (25, 27) of the rhombus are connected to the concave cap (10) and the ends (22", 23', 24", 21') of which are located at the other two diagonally opposite corners (26, 28) of the rhombus are connected to the convex cap (7), each strut (21-24) being connected at one end (21', 22', 23', 24') by a ball joint (29 - 36) and at its other end (21", 22", 23", 24") is connected to the respective cap (7, 10) via a ball or cardan joint (29 - 36).

Description

[0001] The present invention relates to a container for holding a cryofluid, comprising an inner container with at least one outwardly convex cap and an outer container with at least one inwardly concave cap, wherein the inner container is located within the outer container at a distance on all sides, the convex cap projects into the concave cap, and the inner container is supported on the outer container by a first support structure and a second support structure, which engages the inner container diametrically opposite the first support structure. Such a container is known from DE 20 2013 101162 U1.

[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, subsequently used to operate essentially conventional 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, the inner container undergoes a significant thermal expansion or contraction during filling. For a cylindrical container with a length of approximately 1 m, this expansion can be 5 mm or more. Therefore, at least one of the support structures that secure the inner container to the outer container in cryogenic tanks is designed as a floating bearing capable of accommodating these expansion and contraction of the inner container.

[0004] However, installing a loose bearing in a cryogenic container is complicated because thermal bridges between the inner and outer containers should be kept to a minimum. Furthermore, while the loose bearing must be able to accommodate changes in length, it must also permanently withstand the radial and torsional forces that occur during operation to prevent the inner container from becoming dislodged from the outer container, for example, during vibrations, accelerations, or decelerations of a vehicle, especially in the event of an impact with an obstacle.

[0005] The invention aims to create a container for cryofluids which has an improved support structure for thermally decoupled support of the inner container to the outer container.

[0006] According to the invention, this objective is achieved in a container of the type mentioned in the introduction by having the first support structure four struts forming a rhombus, the ends of which are located at one of the two diagonally opposite corners of the rhombus with the concave cap and the ends of which are located at the other two diagonally opposite corners of the rhombus with the convex cap, wherein each strut is connected at one end to the respective cap via a ball joint and at the other end via a ball or gimbal joint.

[0007] The invention thus creates a new type of axially movable, radially force-stable, and torsionally rigid support for the inner container within the outer container. Due to the ball or universal joints, the rhomboid-shaped frame formed by the struts can compensate for changes in the length of the inner container, which manifest as movement of the convex cap perpendicular to the plane of the rhomboid. The struts create a temperature gradient along their length, providing thermal insulation between the inner and outer containers. Furthermore, the strut frame engages the convex cap not at its center but around its circumference, resulting in an extremely torsionally rigid support for the inner container within the outer container.

[0008] In a particularly advantageous embodiment of the invention, the rhombus is a square. This results in a symmetrical distribution of forces and movements in the support structure on all sides.

[0009] Preferably, each strut is connected at both its ends to the respective cap via a ball joint, thereby minimizing torsional and bending forces on the struts when using the frame they form.

[0010] It is particularly advantageous if each ball or universal joint comprises a first part mounted at the respective strut end and a second part articulated to it and mounted on the respective end cap, with two second parts located at each corner of the rhombus being rigidly connected to each other and mounted together on the respective end cap. This means that only two parts need to be mounted on one end cap and two parts on the other end cap, reducing the number of parts required and significantly simplifying manufacturing.

[0011] Preferably, two rigidly connected second parts can form an angle bracket, which is screwed, pressed, or welded to the respective cap. Such an angle bracket reinforces and stabilizes the connection between the struts and the respective cap.

[0012] Preferably, the diametrical axis between the first and second support structures is a longitudinal axis of the inner container, passing through the apex of the convex cap. With an elongated inner container, the greatest thermal expansion is expected along the longitudinal axis, making the described floating support structure particularly advantageous there.

[0013] It is particularly advantageous if the rhombus concentrically surrounds the aforementioned diametral axis. This results in a symmetrical deflection of the struts when the length of the inner container changes and a movement of the cap along the longitudinal axis, so that the distance between the inner and outer containers perpendicular to the longitudinal axis does not change.

[0014] Particularly good thermal decoupling between the inner and outer containers is achieved when the struts are made of a thermally insulating material. The struts can be advantageously manufactured from fiber-reinforced plastic, especially glass fiber-reinforced plastic. This combines high thermal insulation with additional elasticity to accommodate the thermal expansion of the inner container and excellent strength for radial force absorption and torsional stiffness of the support structure.

[0015] The second support structure, which is opposite the first support structure serving as a loose bearing, can be designed as a simple fixed bearing. Preferably, it can then be used to guide at least one connecting line leading from the outside of the container into the inner container.

[0016] The inner and outer containers can be made of any pressure- and low-temperature-resistant material, such as stainless steel. Preferably, the inner and outer containers are made of aluminum, which combines low weight with good pressure and low-temperature resistance.

[0017] The invention is explained in more detail below with reference to an embodiment illustrated in the accompanying drawings. The drawings show: Fig. 1 the container of the invention in a longitudinal section, wherein the first support structure serving as a loose bearing is only shown schematically; the Fig. 2 and3 the convex cap of the inner container and the support structure of the container serving as a loose bearing of Fig. 1 in a frontal view ( Fig. 2 ) or a perspective view ( Fig. 3 ); Fig. 4 Parts of one of the ball joints of the loose bearing of the Fig. 2 and 3 in a perspective view; and Fig. 5 one of the angle pieces of the loose bearing of the Fig. 2 and 3 with two struts shown in a perspective view, connected via ball bearings.

[0018] 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 of -252 °C and below and a pressure of 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, e.g., liquefied natural gas (LNG) at temperatures of -161 °C and below. 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), e.g., a truck or passenger car.

[0019] 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.

[0020] 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.

[0021] Since the cryofluid in the inner container 2 is usually under pressure, (at least) the inner container 2 is designed as a pressure vessel made of metal, for example, stainless steel or aluminum. The outer container 3 can also be made of metal, but also of plastic, since it only needs to withstand the ambient pressure against the vacuum in the space 4.

[0022] The inner container 2 has a general cylindrical shell 5, which is closed at both ends by an outwardly convex cap 6, 7. The term "general 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 pressure resistance, the shell 5, and thus the inner container 2, has a circular cross-section.

[0023] The outer container 3 is essentially adapted to the outer shape of the inner container 2, maintaining the all-around clearance A to create the space 4. The outer container 3 also consists, in particular, of a generally cylindrical shell 8 and two inwardly concave caps 9, 10 that close off its ends. It is understood that the clearance A does not have to be uniform on all sides of the inner container 2. The caps 6, 7, 9, 10 are welded to the respective shells 5, 8, for example, by means of circumferential welds 11, 12.

[0024] For caps 6, 7, 9, and 10, any type of convex end known from pressure vessel construction can be used, such as elliptical ends, dished ends, basket-arch ends, or the like. Diffuser ends ("reverse-dished ends") can also be used for caps 6, 7, 9, and 10. These have a centrally inwardly convex area surrounded by an outwardly convex rim. Such diffuser ends are also subsumed here under the term "outwardly convex cap" because of their convex shape, at least at the edges.

[0025] To create the all-around clearance A, the inner container 2 is supported on the outer container 3 by two support structures 13, 14, which act on diametrically opposite sides of the inner container 2. To accommodate thermal expansion of the inner container 2 in the direction of the diametrical D between the first support structure 13 and the second support structure 14, the first support structure 13 is a floating bearing in the direction of the diametrical D, i.e., it allows movement of the cap 7 in the direction of the diametrical D, while the second support structure 14 is a fixed bearing. Optionally, the second support structure 14 could also be such a floating bearing.

[0026] The in Fig. 1 The first support structure 13, shown only schematically, is explained in detail below. The second support structure 14, if designed as a fixed bearing, can be formed, for example, by a sleeve 15 made of thermally insulating material, which tightly penetrates the aligned openings of the inner and outer containers 2, 3 and can be used for the sealed passage of connecting lines 16 that lead from the outside of the container into the inner container 2 and there terminate, for example, in a filling opening 17, a withdrawal opening 18, a degassing opening 19 and a heat exchanger 20.

[0027] In the example shown, the two support structures 13, 14 are arranged at the end faces of the elongated inner container 2, such that the diametral D is simultaneously the longitudinal axis of the inner container 2. If the inner container 2 is rotationally symmetric about its longitudinal axis, the longitudinal axis, or diametral D, passes through the vertex S of the caps 6, 7. However, this is not mandatory: The support structures 13, 14 could also act diametrically on other sides of the inner container 2 (provided the inner container 2 has an outwardly convex cap for the first support structure 13, as explained below), in which case the diametral D between the support structures 13, 14 no longer coincides with the longitudinal axis of the inner container 2.

[0028] The first support structure 13, serving as a loose bearing, is located in the Fig. 2 - 5 shown in detail. The construction depicted therein allows thermal expansion and contraction of the inner container 2, more precisely, a displacement of the convex cap 7 in the direction of the diametral D relative to the second support structure 14 and thus relative to the outer container 3, while simultaneously absorbing radial forces normal to the diametral D in the manner of a radial bearing. Furthermore, the support structure 13 is designed to be torsionally rigid, i.e., it prevents rotation of the cap 7 and thus of the inner container 2 about the diametral D or longitudinal axis relative to the outer container 3.

[0029] The supporting structure 13 has four struts 21-24, which are assembled in a frame-like manner to form a rhombus (here: square). Each strut 21-24 has two ends 21', 21"; 22', 22"; 23', 23"; 24', 24". The struts 21-24 form the sides of the rhombus. At the corners 25-28 of the rhombus, the opposing ends 21" / 22', 22" / 23', 23" / 24' and 24" / 21' of two adjacent struts 21-24 lie side by side.

[0030] The rhombus formed by struts 21–24 is, in the example shown, a planar rhombus, meaning that all struts 21–24 lie in a common plane and are of equal length. However, this is not mandatory; struts 21–24 might not lie in a common plane, especially in the case of irregularly shaped caps 7 and 10. In the example shown, the rhombus formed by struts 21–24 concentrically surrounds the diametral D and the apex S of cap 7.

[0031] The struts 21-24, for example, have the form of rods, bars, strips, or bands and are made of a heat-insulating material, such as plastic. Specifically, struts 21-24 are each made from a rod or strip of fiber-reinforced plastic, such as glass fiber-reinforced plastic. For example, resin-impregnated, cured fiber mats, such as woven, knitted, or non-woven fabrics, made from glass, carbon, basalt, and / or stone fibers, etc., can be used, which are punched, cut, pressed, shaped, injection-molded, etc., to form the struts 21-24.

[0032] The ends 21", 22', 23", 24' of the struts 21 - 24 located at one of the two diagonally opposite corners 25, 27 of the rhombus are connected to the concave cap 10 via a ball joint 29, 30, 33, 34, and the ends 24", 21', 22", 23' of the struts 21 - 24 located at the other two diagonally opposite corners 26, 28 of the rhombus are connected to the convex cap 7 via a ball joint 31, 32, 35, 36.

[0033] Of the two ball joints 36 / 29, 30 / 31, 32 / 33, 34 / 35, which are located at the ends 21' / 21", 22' / 22", 23' / 23", 24' / 24" of the same strut 21 - 24, one can be a universal joint (two degrees of freedom) instead of a ball joint (three degrees of freedom), if desired.

[0034] Each ball or cardan joint 29 - 36 consists of two parts connected by joints, namely a first part A mounted on the respective strut end 21' - 24', 21" - 24" and a second part B connected to it by joints on the respective cap 7 or 10.

[0035] Fig. 4 Figure 1 shows an example of a ball joint 29-39 with a first part A in the form of an eye 37 with a stem 38, which is firmly connected to the respective end 21'-24', 21"-24", e.g., clamped, pressed, glued, screwed, welded, formed in one piece, etc. The eye 37 has a spherical opening in which a ball 39 is rotatably and pivotably mounted. The ball 39 has a central bore 40 through which a bearing pin 41 of an angle piece 42 ( Fig. 5 ) or 43 ( Fig. 3 ) through it.

[0036] The ball 39 with its opening 40, and if applicable the respective angle piece 42, 43 with the bearing bolt 41, forms in the example shown the second part B of the ball joint 29 - 36.

[0037] In the case of ball joints 29, 30, 33, 34, the angle piece 42 is firmly connected to the concave cap 10, for example by clamping, pressing, gluing, screwing, welding, forming a single piece, etc. For example, the angle piece 42 has a bore 44 through which it can be screwed to the cap 10 by means of screws (not shown). In the case of ball joints 31, 32, 35, 36, the angle piece 43 is firmly connected to the convex cap 7, for example by clamping, pressing, gluing, screwing, welding, forming a single piece, etc. In the example shown, the angle pieces 43 are welded to the convex cap 7.

[0038] In the example shown, each pair of ball joints 29 / 30, 31 / 32, 33 / 34, 35 / 36 shares a common second part B, i.e., (at corners 25 and 27) an angled piece 42 with two bearing pins 41 attached at an angle to it, or (at corners 26 and 27) an angled piece 43 with two bearing pins 41 attached at an angle to it. It is understood that, alternatively, each ball joint 29-36 could have its own second part B, i.e., it could connect to the respective cap 7, 10 via its own angled piece 42, 43.

[0039] The invention is not limited to the embodiments shown, but includes all variants, modifications and combinations thereof that fall within the scope of the attached claims.

Claims

1. A container for receiving a cryogenic fluid, comprising an inner container (2) having at least one outwardly convex cap (7) and an outer container (3) having at least one inwardly concave cap (10), the inner container (2) being located in the outer container (3) spaced a distance (A) apart on all sides, the convex cap (7) protruding into the concave cap (10), and the inner container (2) being supported on the outer container (3) by way of a first support structure (13) and a second support structure (14), which engages on the inner container (2) in a manner that is diametrically opposed from the first support structure (13), characterised in that the first support structure (13) comprises four struts (21 - 24) forming a rhombus, the ends (21", 22', 23", 24') of which struts located at the one set of two diagonally opposed corners (25, 27) of the rhombus are connected to the concave cap (10), and the ends (22", 23', 24", 21') of which struts located at the other set of two diagonally opposed corners (26, 28) of the rhombus are connected to the convex cap (7), each strut (21 - 24) being connected to the respective cap (7, 10) at its one end (21', 22', 23', 24') by way of a ball joint (29 - 36) and at its other end (21", 22", 23", 24") by way of a ball or universal joint (29 - 36).

2. The container according to claim 1, characterised in that the rhombus is a square.

3. The container according to claim 1 or 2, characterised in that each strut (21 - 24) is connected at both of its ends (21', 21", 22', 22", 23', 23", 24', 24") to the respective cap (7, 10) by way of a ball joint (29 - 36).

4. The container according to any one of claims 1 to 3, characterised in that each ball or universal joint (29 - 36) comprises a first part (A) that is mounted on the respective strut end (21', 21", 22', 22", 23', 23", 24', 24") and a second part (B) that is connected to the first part in an articulated manner and mounted on the respective cap (7, 10), two second parts (B) at a time, located at a corner (25 - 28) of the rhombus, being rigidly connected to each other and mounted together on the respective cap (7, 10).

5. The container according to claim 4, characterised in that two rigidly connected second parts (B) respectively form an angle piece (42, 43) that is screwed, pressed or welded to the respective cap (7, 10).

6. The container according to any one of claims 1 to 5, characterised in that the diametrical line (D) between the first and second support structures (13, 14) is the longitudinal axis of the inner container (2), which extends through the apex (S) of the convex cap (7).

7. The container according to claim 6, characterised in that the rhombus surrounds the diametrical line (D) concentrically.

8. The container according to any one of claims 1 to 7, characterised in that the struts (21 - 24) are made of a thermally insulating material.

9. The container according to claim 8, characterised in that the struts (21 - 24) are made of fibre-reinforced plastic material, and preferably glass fibre-reinforced plastic material.

10. The container according to any one of claims 1 to 9, characterised in that the inner container (2) and the outer container (3) are made of aluminium.

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