Cryogenic container having a boil-off fitting

Abstract

The invention relates to a system (1) comprising a cryogenic container (2) for storing cryogenic fluid and comprising a connection line (4), which is led into the cryogenic container (2), for the extraction of cryogenic fluid from the cryogenic container (2), wherein: the connection line (4) has a fitting within the cryogenic container (2); an opening cross section (q1) of the fitting is at least 10 times, preferably 100 times or 1000 times, smaller than the internal cross section (q2) of the connection line (4) between the fitting and the connection point (7) to the cryogenic container (4); and the connection line (4) is led between the fitting and the connection point (7) to the cryogenic container (2) with a predetermined length (L) that is preferably longer than 50 cm.

Description

[0001] Cryogenic vessel with boil-off valve

[0002] The invention relates to a system comprising a cryogenic container for storing cryogenic fluid and a connecting line led into the cryogenic container for removing cryogenic fluid from the cryogenic container.

[0003] According to the current state of the art, liquefied gases can be stored in containers ("cryogenic containers") to serve as fuel for engines, for example. Cryogenic containers store gases in a cryogenically liquefied form. Gases such as methane or hydrogen, in their liquefied form, have a density 600 to 800 times higher than in their standard state (ambient temperature and pressure). This increase in density is the benefit of liquefaction and, at the same time, a risk in the protection of cryogenic containers, because the complete heating of a fully filled cryogenic container and thus evaporation of the liquefied gas would lead to pressures well over 1,000 bar, up to 2,000 bar. Such pressures would, in any case, far exceed the mechanical load-bearing capacity of the pressure container.

[0004] Pressure control in the cryogenic vessel is therefore of particular importance in this technical field. On the one hand, it is known to connect a pressure relief valve to the cryogenic vessel to release gaseous cryogenic fluid from the vessel if the pressure exceeds a permissible maximum pressure when the system is at a standstill (see, for example, WO 2022 / 204745 A1). However, it is clear that the problem still exists that releasing cryogenic fluid into the environment represents an energy loss on the one hand and also impacts the environment on the other.

[0005] The pressure in the cryogenic vessel can also be regulated by withdrawing cryogenic fluid in either the gaseous or liquid state during system operation. So-called economizers are used for this purpose; see, for example, WO 2022 / 067362 A1.

[0006] In both of the aforementioned embodiments, pressure regulation is achieved by removing gaseous cryofluid from the cryocontainer, i.e., the volume of cryofluid in the cryocontainer is reduced while the temperature remains constant. Another possibility for reducing the pressure would theoretically be to cool the cryofluid in the cryocontainer using external means such as a heat exchanger. However, this is too complex and therefore hardly feasible in many areas such as automotive engineering. US 2023067726 A1 discloses providing a pressure reducer in a connecting line within the cryocontainer in order to actively subcool the cryofluid stored in the cryocontainer. In other words, cryofluid is actively removed via this connecting line when further subcooling of the cryofluid stored in the cryocontainer is desired. The safety system of the cryocontainer is unaffected by this solution.

[0007] It is the object of the present invention to further develop the above-mentioned systems in such a way that the existing possibilities for pressure reduction in the cryogenic container are optimized.

[0008] This object is achieved by a system comprising a cryogenic container for storing cryogenic fluid and a connecting line led into the cryogenic container for withdrawing cryogenic fluid from the cryogenic container, wherein the connecting line has a fitting within the cryogenic container, wherein the fitting is a throttle, an orifice, or a nozzle, wherein an opening cross-section of the fitting is permanently or in at least one operating position at least 100 times, preferably 10,000 times or 1,000,000 times smaller than the internal cross-section of the connecting line downstream of the fitting in the withdrawal direction (e.g. between the fitting and the connection point to the cryogenic container; alternatively, the throttle cross-section could also be led to the outside, although a short throttle section is usually desired), wherein the connecting line is led between the fitting and the connection point to the cryogenic container with a predetermined length, which is preferably longer than 50 cm.Furthermore, the system comprises an outlet valve which is provided outside the cryogenic container in the connecting line, wherein the outlet valve is a pressure relief valve which is designed to open when a predetermined pressure or a predetermined pressure difference is present.

[0009] The fitting according to the invention has the advantage that the cryofluid removed from the cryogenic vessel is already expanded inside the cryogenic vessel. This expansion leads to a reduction in the temperature of the expanded cryogenic fluid. This can be exploited to cool the cryogenic fluid in the cryogenic vessel, which is why the connecting line inside the cryogenic vessel is of a predetermined length to enable sufficient heat transfer between the expanded cryogenic fluid inside the connecting line and the cryogenic fluid outside the connecting line. The temperature reduction of the cryogenic fluid during expansion and the associated pressure reduction can, depending on the design of the fitting, be regarded as an isenthalpic or isentropic process. An ideal throttle would, for example, be referred to as an isenthalpic process, in which case the temperature reduction is known as the Joule-Thomson effect.

[0010] The invention utilizes the cooling effect of pressure relief by releasing pressure within the cryogenic vessel itself. The pressure relief is achieved through the small diameter of the valve. Upstream of the valve, the pressure is essentially the vessel pressure, while downstream, the pressure is as close as possible to atmospheric ambient pressure, into which the medium flows, in order to achieve the greatest possible cooling effect through the greatest possible pressure drop.

[0011] According to the invention, the system further comprises an outlet valve, which is provided outside the cryogenic vessel in the connecting line. In this variant, the valve is located inside the cryogenic vessel and the outlet valve outside the cryogenic vessel. As long as no cryogenic fluid flows out—during the hold time—the vessel pressure in the connecting line up to the outlet valve will essentially be the same. When the outlet valve opens, the ambient pressure downstream of the valve will essentially be the same. The outlet valve generally has only a low flow resistance.

[0012] According to the invention, the outlet valve is a pressure relief valve designed to open when a predetermined pressure (e.g., an absolute pressure in the cryogenic container) or a predetermined pressure difference (e.g., a relative pressure immediately before and immediately after the pressure relief valve or a relative pressure between the container pressure and ambient pressure) is present, e.g., to release cryogenic fluid from the cryogenic container to the environment. As explained above, the flow resistance is typically negligible for this embodiment, so the combination of a valve in the cryogenic container and a pressure relief valve is particularly advantageous, especially if the valve is a rigid valve with a fixed opening cross-section.

[0013] In the embodiment according to the invention, it is therefore provided that the throttle, orifice, or nozzle is used in combination with a pressure relief valve. Surprisingly, it has been found that this reduces the amount of passively released cryogenic fluid to maintain a constant vessel pressure. This is explained using the following practical example. According to the prior art, a conventional connecting line without a throttle, orifice, or nozzle can be led into the cryogenic vessel, and outside the cryogenic vessel, a pressure relief valve with a release pressure of 15 bar is located in the connecting line. When the vessel pressure reaches 15 bar, the pressure relief valve remains open for a short time and allows, for example, 1 m 3Gaseous cryogenic fluid (numerical values ​​assumed arbitrarily for illustrative purposes) is drawn from the cryogenic vessel to bring the pressure to 14.95 bar. Due to the continuous heat input, the pressure rises again, and the above scheme is repeated when the pressure reaches 15 bar again. However, if the connecting line within the cryogenic vessel has a throttle, an orifice, or a nozzle as described above, only 0.8 m 3Cryofluid must be drained from the cryogenic vessel to bring the pressure to 14.95 bar, which is also reduced by heat transfer. It can be seen that the arrangement according to the invention has the effect that less cryogenic fluid needs to be drained from the cryogenic vessel in order to maintain a substantially constant pressure compared to conventional boil-off systems. In other words, the pressure relief valve is designed to essentially maintain this predetermined pressure in the cryogenic vessel once a predetermined pressure has been reached (i.e. there are no “subcooling” effects). The throttle, orifice or nozzle thereby reduces the amount of cryogenic fluid that needs to be drained to maintain the pressure. “Essentially maintaining this pressure in the cryogenic vessel” can be understood to mean that the pressure is maintained in the range of + / -2%, + / -1%, + / -0.5% or + / -0.1% around a desired target pressure (15 bar in the above example).This can be implemented in particular with the variants of pressure relief valves described below.

[0014] To achieve the expansion of the cryogenic fluid, the fitting has the smallest possible opening cross-section. For the purposes of the present invention, the opening cross-section of the fitting can be assumed to be at least 100 times, preferably 10,000 times or 1,000,000 times, smaller than the internal cross-section of the connecting line between the fitting and the connection point to the cryogenic container. For example, the fitting can have an opening cross-section of 1 pm. 2 up to 9 mm 2 , especially preferred from 25 pm 2 up to 1 mm 2 or from 9:00 pm 2 up to 40,000 pm 2These measures are particularly advantageous, but deviations from them are also possible. The absolute values ​​of the opening cross-section can depend on the application, whereby in the vehicle sector or other mobile applications, opening cross-sections in the 1 / 100 mm 2 - area and in the petrol station area or other static applications opening cross-sections in mm 2 -area could be provided. However, the exact dimensioning of the opening cross-section usually also takes into account the vessel size, type of cryogenic fluid, pressure ratio, quality of the vessel insulation, and other parameters. The length of the connecting line can also depend on the application and, for example, can be 30 cm to 3 m or 1 m to 2 m between the fitting and the connection point on the cryogenic vessel.

[0015] To achieve the most efficient heat transfer possible between the cryogenic fluid inside the connecting line and outside the connecting line, the connecting line can be routed in a meandering pattern within the cryogenic container, allowing a longer line length to be accommodated within the cryogenic container. Furthermore, the connecting line within the cryogenic container can also have surface-enlarging structures, in particular cooling fins, allowing the line length to be shortened. Surface-enlarging structures also mean that the connecting line could be designed, at least in sections, as a bellows tube. The connecting line is generally made of metal, preferably of the same material as the inner tank.

[0016] According to the invention, the valve mentioned is a throttle, an orifice, or a nozzle, in particular a Laval nozzle. If the valve is designed as a throttle, an orifice, or a nozzle, it permanently has the same inner contour and thus also permanently has the same opening cross-section.

[0017] The fitting is preferably a throttle with a throttle length of preferably at least 1 mm, wherein the throttle is formed by a bore through a pipe wall of the connecting line. Such throttles have the advantage that they can be manufactured particularly easily, even with a particularly small diameter. However, the bore through the usually cylindrical pipe wall is only optional and could, for example, also run through a plug such as an end cap of the connecting line.

[0018] The throttle is preferably dimensioned such that at a predetermined pressure (e.g. a maximum vessel pressure, which can be in a range between 15 bar and 20 bar, for example), just enough flows out to prevent the pressure in the cryogenic vessel from increasing any further. The mass flow removed through the throttle is essentially dependent on the density of the fluid upstream of the valve (and thus on the state of the fluid in the tank) and is limited by the critical velocity (i.e. the speed of sound) and therefore cannot be increased any further. The mass flow cannot therefore be actively influenced without further measures. However, it has been found that the mass flow can be adjusted sufficiently precisely for an application (e.g. boil-off) by suitably dimensioning the valve. As an alternative to the throttle, the valve could also be designed as a nozzle, in particular as a Laval nozzle.A nozzle allows a velocity of the outgoing mass flow that is higher than the speed of sound.

[0019] It should be noted here that a valve with a permanently small opening cross-section is not always advantageous, as it offers high flow resistance. However, it has been found that flow resistance is not relevant, especially for so-called boil-off lines, i.e., connecting lines that are only intended to release cryogenic fluid to the environment to reduce the pressure in the cryogenic vessel and not to supply the cryogenic fluid to a consumer. In general, however, the valve can also be used for extraction lines, for example, if the obstacle of flow resistance is less important than the additional cooling provided by expansion, or if additional measures are taken to reduce flow resistance.

[0020] In a variant not claimed, the fitting could be a valve with a variable opening cross-section, wherein the valve can be moved from the first operating position, in which it has the first-mentioned opening cross-section, which is at least 100 times, preferably 10,000 times or 1,000,000 times smaller than the internal cross-section of the connecting line between the valve and the connection point to the cryogenic container, into a second operating position, in which the valve has a second opening cross-section, which is at least 100 times, preferably 10,000 times or 1,000,000 times larger than the first-mentioned opening cross-section. Particularly preferably, the second opening cross-section is the same size as the internal cross-section of the connecting line. This is particularly advantageous in the case in which the connecting line is connected to a consumer.This allows the flow resistance to be reduced during withdrawal by setting the valve to the second state. If no cryogenic fluid is actively being withdrawn from the cryogenic container, the valve can be set to the first state, allowing the cryogenic fluid to be released back into the environment, for example, via a pressure relief valve connected to the connecting line or another outlet valve. A continuously variable cross-section from "as small as possible" (ideally closed at 0 mm) is also possible. 2 , or the above mentioned 1 pm 2 up to 9 mm 2) to "as large as possible" (ideally the same size as the downstream connecting line) would be possible. In this case, the mass flow could be adapted to the requirements (e.g. required mass flow for a consumer). In the aforementioned unclaimed variant with a valve, it is further preferred if this is connected to a control unit which receives pressure measurements from a pressure measuring unit arranged in the cryogenic vessel and is designed to control the opening cross section of the valve in such a way that the pressure in the cryogenic vessel remains essentially constant, e.g. constantly corresponds to a target boil-off pressure. The control unit can, for example, open the valve just far enough to keep the vessel pressure constant. In this variant, no further outlet valve is necessary.

[0021] Pressure relief valves located outside the cryogenic vessel can stutter because, once the pressure relief valve is opened, ambient pressure will be present on both sides. This is because the valve does not allow for immediate pressure equalization. If, for example, the pressure relief valve opens and closes due to a pressure difference upstream and downstream of the pressure relief valve, the pressure relief valve will only be open for a very short time and close again immediately. After a certain amount of time, after the pressure present in the cryogenic vessel has also returned to the connecting line, it will open again and then close again shortly afterwards, which is referred to as stuttering.

[0022] To prevent stuttering, the outlet valve can be designed as a controlled outlet valve, which receives pressure readings from a pressure measuring unit located in the cryogenic vessel and opens and / or closes based on the pressure readings received. The "reference pressure" on the basis of which the outlet valve is controlled is therefore not the pressure present directly at the outlet valve, but rather the pressure of the cryogenic fluid in the cryogenic vessel, i.e., upstream of the valve in the withdrawal direction. In other words, the pressure measuring unit measures the pressure in the cryogenic vessel upstream of the valve in the withdrawal direction.

[0023] In a further advantageous variant, the exhaust valve could receive temperature measurement values ​​from a temperature measuring unit, which preferably measures the temperature of a heat shield, wherein the exhaust valve opens and / or closes on the basis of the obtained temperature measurement values, ie the exhaust valve could, for example, remain open until an element such as a heat shield is sufficiently cooled, thereby simultaneously preventing stuttering of the exhaust valve.

[0024] In a further variant, the outlet valve could be equipped with a timer and configured to close again only after a predetermined period of time after opening. The period could, for example, be specified by a user or a control unit and selected such that a predetermined pressure reduction occurs in the cryogenic container over the period, e.g., to achieve a certain hold time, after which the outlet valve opens again.

[0025] The outlet valve could also be a purely mechanical valve, in particular a needle valve, which is preferably connected to the cryogenic container upstream of the fitting via a line. The line preferably runs directly through the fitting and opens and / or closes when a threshold pressure is exceeded. In this case, no control unit is required; instead, the outlet valve can be controlled purely mechanically, e.g., by manually actuating the outlet valve or by analog signals on the line.

[0026] At this point, however, it should also be noted that in a non-stressed version, the valve could be designed as a pressure relief valve located inside the cryogenic vessel. However, installation is more complicated and replacement, for example, in the event of a pressure relief valve failure, involves greater effort. In this case, an additional outlet valve outside the cryogenic vessel is optional.

[0027] As already explained above, the connecting line can be designed as a dedicated boil-off line, i.e. it can have a pressure relief valve or other outlet valve and is not connected to a consumer. The boil-off line can be led downstream of the outlet valve to a boil-off management system that burns the escaping fuel to reduce the danger potential when it escapes into the atmosphere, e.g. hydrogen is oxidized to water or methane to CO2 and water. Alternatively, the connecting line can also be connected to a consumer outside the cryogenic container, e.g. to an engine or a fuel cell. A T-piece can be provided in the connecting line 4, on the one hand to provide a pressure relief valve in the connecting line 4 and on the other hand to connect the connecting line to a consumer.

[0028] However, it is particularly preferred if the connecting line is designed in such a way that cryogenic fluid entering the connecting line through the fitting also passes through the outlet valve. In other words, no branch, such as a T-piece, is provided in the connecting line between the fitting and the pressure relief valve, which would prevent cryogenic fluid removed from the cryogenic container from flowing through the pressure relief valve. This solution contributes particularly to the safety aspect of the invention.

[0029] In a further preferred embodiment, the cryogenic container comprises an inner tank and an outer container. Furthermore, a heat shield is provided in a vacuum-insulated space between the inner tank and the outer container, and a thermal bridge is provided between the connecting line and the heat shield. This allows cryogenic fluid flowing out through the pressure relief valve, e.g., during a boil-off process, to cool the heat shield. The cryogenic fluid stored in the cryogenic container thus heats up more slowly, and the removed cryogenic fluid can further contribute to reducing boil-off escaping from the cryogenic container.

[0030] The solution according to the invention is particularly preferably used in cryogenic containers that store cryogenic fluid in the supercritical range. Surprisingly, it has been found that a connecting line as shown in US 2023067726 A1 can even have negative effects on cryogenic fluid in the supercritical range. After some experiments, it turned out that the relative arrangement of the connecting line within the cryogenic container was previously responsible. The reason for this is that thermal stratification can occur with cryogenic fluid in the supercritical range, i.e. there is a temperature gradient in the vertical direction, with the cryogenic fluid being warmest at the top. If the connecting line is now routed predominantly in the lower region of the cryogenic container, as taught in US 2023067726 A1, the temperature gradient is further increased.

[0031] According to the invention, the connecting line can be used to reduce thermal stratification in cryogenic fluid in the supercritical range. This is achieved by more than 50%, preferably more than 70% or more than 90%, of the length of that section of the connecting line that lies within the cryogenic vessel being located in the upper half, preferably in the upper third or upper quarter, of the cryogenic vessel. Particularly preferably, the fitting can be located in the upper half, preferably in the upper third or upper quarter, of the cryogenic vessel. Furthermore, that section of the connecting line that lies within the cryogenic vessel can be located exclusively in the upper half, preferably in the upper third or upper quarter, of the cryogenic vessel.

[0032] From the above, it follows that the use of the system mentioned for storing cryogenic fluid in the supercritical range is particularly advantageous. It is particularly noted that subcooling is not possible for cryogenic fluid in the supercritical range, making this use surprisingly advantageous.

[0033] The invention can be used in particular in vehicles, so that the vehicle can also comprise a system in one of the aforementioned embodiments, wherein the cryogenic container is preferably mounted on a vehicle frame of the vehicle. The invention is particularly advantageous for use in vehicles because the more efficient pressure reduction can reduce boil-off losses. Further measures can extend the downtime until such a boil-off event occurs, the so-called "hold time." Both lead to a reduction in fuel losses.

[0034] In a further aspect, the invention relates to the use of a system in one of the aforementioned embodiments with a cryofluid of a predetermined composition in a predetermined thermodynamic state stored in the cryogenic container, wherein the opening cross-section of the fitting is selected such that the cryofluid expands upon withdrawal from the fitting, and preferably the length of the connecting line between the fitting and the connection point is selected such that the temperature of the cryofluid in the connecting line at the connection point substantially corresponds to the temperature of the cryofluid outside the connecting line. The selection of the opening cross-section and the length can be made, in particular, by a person skilled in the art using a phase diagram for the cryofluid of the predetermined composition.After the temperature of the cryogenic fluid after expansion has been determined, the length can also be determined using the heat transfer properties of the connecting line.

[0035] These and other advantageous embodiments of the system according to the invention are explained in more detail below with reference to the figures.

[0036] Figure 1 shows a system according to the invention with a cryogenic container and a connecting line which has a throttle within the cryogenic container.

[0037] Figure 2 shows the system of Figure 1 in a schematic view with the pressure relief valve closed.

[0038] Figure 3 shows the system of Figure 1 in a schematic view with the pressure relief valve open.

[0039] Figure 4 shows a variant of the system according to the invention in which the outlet valve receives measurement data from measuring units.

[0040] Figure 5 shows a possible variant for implementing the throttle. Figure 6 shows a variant of the system according to the invention with a nozzle.

[0041] Figure 7 shows a further variant of the system according to the invention, in which a pressure relief valve is arranged within the cryogenic container (not claimed). Figures 8a and 8b show a further variant with a valve in a first state (Figure 8a) and a second state (Figure 8b) (not claimed).

[0042] Figure 1 shows a system 1 comprising a cryogenic container 2 in which cryogenic fluid is stored in the gaseous and / or liquid state. The cryogenic fluid can be, for example, hydrogen, so that the cryogenic container 2 is a hydrogen container, or the cryogenic fluid can be LNG (liquefied natural gas), so that the cryogenic container 2 is an LNG container. Depending on the cryogenic fluid, the cryogenic container 2 is thus designed to store cryogenic fluid at temperatures of, for example, below 150 Kelvin, in the case of hydrogen even below 50 Kelvin or below 30 Kelvin or essentially 20 Kelvin. Depending on the application, the cryogenic container 2 could, for example, be designed to store sLH2 (subcooled liquid hydrogen) or CcH2 (cryo-compressed hydrogen) and thus also be designed for correspondingly high pressures and temporarily even higher temperatures, e.g. for maximum pressures between 5 bar and 350 bar.

[0043] The cryogenic container 2 described herein can be used, for example, as a fuel tank for a vehicle (not shown in detail) and can be mounted, for example, on the vehicle frame for this purpose. The cryogenic fluid stored in the cryogenic container 2 can, for example, be supplied as fuel to a consumer of the vehicle, such as an engine or a fuel cell. However, the cryogenic container 2 could also be used in other applications, e.g., at a gas station or another static system for storing liquefied nitrogen. The cryogenic container 2 can therefore also be installed stationary in the environment.

[0044] In order to remove cryogenic fluid from the cryogenic container 2, either to supply it to a consumer or to release it to the environment to reduce the pressure, a connecting line 4 is led into the cryogenic container and passes through it. The connecting line 4 described here is therefore expressly intended to be a withdrawal line and not a filling line, i.e. there is no check valve, for example, in the section of the connecting line 4 between the throttle 9 explained below and the outlet valve or the consumer, since the check valve would prevent the removal of cryogenic fluid from the cryogenic container 2. Conventional cryogenic containers 2 comprise an inner tank 5 and an outer container 6 which is vacuum-insulated from the inner tank 5, so that the connecting line 4 can pass through both the inner tank 5 and the outer container 6. The point at which the connecting line 4 passes through the cryogenic container 2 is referred to as the connection point 7.passes through the inner tank 5, if present.

[0045] At the beginning we will look at the case in which the connecting line 4 is intended to drain cryofluid from the cryogenic container 2 when the pressure is too high and, for example, to release it into the environment. In this case the connecting line 4 can also be colloquially referred to as a "boil-off line" and does not have to be connected to a consumer. In this case, a first end of the connecting line 4 is provided inside the cryogenic container 2 and a second end outside the cryogenic container 2. At the second end there is a pressure relief valve 8 which is triggered when a predetermined pressure in the cryogenic container 2 is reached and thus opens the connecting line 4. It is understood that in this case the pressure relief valve 8 does not have to release the cryogenic fluid drained from the cryogenic container 2 into the environment, but could also be transferred via the pressure relief valve 8 into an intermediate container or the like.

[0046] The pressure relief valve 8 thus blocks fluid flow when the pressure in the cryogenic container 2 is below a threshold value and opens when the pressure in the cryogenic container 2 exceeds the mentioned or another threshold value. The pressure relief valve 8 therefore plays a critical safety role, as it prevents the pressure in the cryogenic container 2 from becoming too high and thereby damaging the cryogenic container 2. The mentioned threshold value of the pressure relief valve 8, at which cryogenic fluid is to be released to the environment, is, for example, a so-called maximum allowable working pressure (MAWP) of the cryogenic container 2 and depends on the properties of the cryogenic container 2. This maximum allowable working pressure is, for example, 16 bar, so the pressure relief valve 8 can be designed to open from a pressure of 16 bar. As a rule, however, the threshold value of the pressure relief valve 8 can be selected arbitrarily and can, for example,depend on the external circumstances or the intended use.

[0047] Conventional connecting lines with a pressure relief valve 8 only allow the cryofluid to be transferred from the interior of the cryocontainer 2 to the exterior, i.e., the volume of cryofluid in the cryocontainer 2 is reduced, while the temperature in the cryocontainer 2 remains essentially constant. However, due to the design of the connecting line 4 according to the invention described below, the removed cryofluid is also used to cool the cryofluid in the cryocontainer 2, i.e., both the volume and the temperature of the cryofluid in the cryocontainer are to be reduced.

[0048] This is achieved by providing the connecting line 4 with a throttle 9 at the end located in the cryogenic container 2, through which the cryogenic fluid can expand. The expansion of the cryogenic fluid lowers its temperature and can thus cool the connecting line 4 and, consequently, the cryogenic fluid in the cryogenic container 2. To achieve an almost ideal expansion, the throttle 9 should have the smallest possible opening cross-section ql. In initial tests, an opening cross-section ql of essentially 2500 pm has proven successful. 2 proved to be advantageous. In general, an opening cross-section ql of 1 pm is preferred. 2 up to 9 mm 2 ; particularly preferred is an opening cross-section ql of 5 pm 2 up to 1 mm 2. However, the opening cross section ql can also be specified as a function of the internal cross section q2 of the connecting line 4, wherein the opening cross section ql of the throttle 9 is, for example, at least 100 times, preferably 10,000 times or 1,000,000 times smaller than the internal cross section q2 of the connecting line 4 between the throttle 9 and the connection point 7 to the cryogenic container 2. If the connecting line 4 has a variable diameter, the smallest internal cross section q2 of the connecting line 4 between the throttle 9 and the connection point 7 to the cryogenic container 2 can be assumed as the internal cross section q2.

[0049] It should be noted that we are referring here to opening cross-sections or internal cross-sections, whereby the throttle cross-sections or pipe cross-sections are usually circular. However, the shapes of the cross-sectional areas could also be different, e.g., oval or rectangular.

[0050] In order to provide a sufficient heat transfer path, the connecting line 4 between the throttle 9 and the connection point 7 should also have a predetermined length L, e.g., more than 10 cm, more than 30 cm, more than 50 cm, or more than 100 cm. The choice of the length L of the connecting line 4 between the throttle 9 and the connection point 7 can also be optimized, e.g., by determining a temperature gradient and choosing the said length L such that the expanded cryogenic fluid at the connection point 7 has essentially the same temperature as the cryogenic fluid stored in the cryogenic container 2. If the predetermined length L is chosen to be shorter, the maximum possible heat transfer is not fully utilized (which, however, could also be implemented according to the invention, in which case at least a certain amount of heat exchange still takes place). This can be used in particular for cooling a heat shield 21, which is shown in Figure 4.In particular, a thermal bridge may be present between the connecting line 4 and the heat shield 21 to cool it when cryogenic fluid is discharged through the pressure relief valve 8. If the predetermined length L is selected to be longer, the overall weight of the system is unnecessarily increased, which can be disadvantageous, particularly in the case of cryogenic containers 2 for vehicles.

[0051] To achieve advantageous heat transfer, the connecting line 4 can also be specially designed over the predetermined length L to increase the surface area in this region. For example, the connecting line 4 can be designed with ribs or other surface-enlarging structures on the inside and / or outside of the connecting line 4 over the predetermined length L. As shown in Figure 1, the connecting line 4 can also be routed in a meandering shape within the cryogenic container, i.e., not in a straight line, so that the predetermined length L can be easily accommodated in the cryogenic container 2.

[0052] The inventive concept of additional heat transfer after expansion through the throttle 9 will now be explained in more detail below with reference to Figures 2 and 3.

[0053] Figure 2 shows a state in which the pressure relief valve 8 was closed for an extended period of time, so that equilibrium has been established in the system. In this state, cryogenic fluid with a temperature TI is present in the cryogenic vessel 2. Due to the equilibrium state, cryogenic fluid with the temperature TI is also present within the connecting line 4. Therefore, there is no heat transfer between the cryogenic fluid inside the connecting line 4 and outside the connecting line 4. Furthermore, the same pressure pl is present inside and outside the connecting line 4. However, outside the cryogenic vessel 2 and outside the connecting line 4, i.e. in the environment, there is an ambient pressure p2 (usually an air pressure of approximately 1 bar) which is lower than the pressure pl in the cryogenic vessel 2.

[0054] Figure 3 shows the condition immediately or a short period after the pressure relief valve 8 was triggered, e.g., because the pressure p2 in the cryogenic container 2 became too high, causing the pressure relief valve 8 to open. Due to the relatively small volume within the connecting line 4, the cryogenic fluid present in the connecting line 4 is discharged to the environment in a very short time. However, the throttle 9 prevents a rapid flow of cryogenic fluid into the connecting line 4, so that the ambient pressure p2 will now essentially prevail within the connecting line 4.

[0055] Due to the aforementioned change of state, a large pressure gradient occurs at the throttle 9, since there will be a pressure p1 (e.g. 16 bar) upstream at the throttle 9 and a pressure p2 (e.g. 1 bar) downstream of the throttle 9. The terms “upstream” and “downstream” refer to the direction in which the cryofluid is withdrawn. This causes the cryofluid to expand as it flows through the throttle 9. At the same time, the expansion causes the temperature to reduce. In other words, the cryofluid at the throttle 9 upstream will have a temperature TI which the cryofluid will also have at all other points around the connecting line 4. After the expansion, the fluid at the throttle 9 downstream will have a temperature T2 which is lower than the temperature TI.The exact, absolute value of the temperature T2 that the cryogenic fluid will exhibit after expansion depends on various factors, such as the pressure difference p1-p2 and the cryogenic fluid (e.g., the temperature change may be different for hydrogen than for LNG). If an exact calculation of the temperature T2 is required, the expert can use a phase diagram.

[0056] In theory, the aforementioned effect is known as the Joule-Thomson effect for an ideal throttle 9, which in turn falls under the category of isenthalpic processes. However, it should be noted that other processes may also be incorporated into the invention, particularly since the gases present are not ideal gases and changes of state and flow processes may also occur, particularly when liquid cryogenic fluid is present upstream of the throttle 9. The use of the connecting line 4 or the throttle 9 can be limited to states of the cryogenic fluid in the cryogenic container 2 from which a pressure drop causes the expanded fluid to cool, e.g., due to the Joule-Thomson effect.

[0057] If the cryogenic fluid is present downstream of the throttle 9 at temperature T2, due to the thermal gradient T2 <T1 an dieser Stelle der Anschlussleitung 4 zu einem Wärmeübergang. In anderen Worten kann das nun expandierte Kryofluid das im Kryobehälter 2 vorliegende Kryofluid weiter kühlen, wodurch der Druck im Kryobehälter 2 nicht nur durch die Volumensreduktion, (bzw. Massereduktion oder Dichtereduktion), sondern auch durch eine zusätzliche Wärmeabfuhr gesenkt werden kann. Durch die Drossel 9 wird das Überdruckventil 8 früher schließen als bei einem vergleichbaren System ohne Drossel 9, da der Druck mit einer geringeren Volumensentnahme gesenkt werden kann. Es wird daher in Summe auch weniger Kryofluid an die Umwelt abgegeben.

[0058] It is understood that the expanded cryogenic fluid now present in the connecting line 4 is heated again by the heat transfer, so that after a certain distance Li it will have a temperature Ti that lies between the temperature T2 immediately after the expansion and the temperature TI of the cryogenic fluid in the cryogenic container 2, ie T2 <Ti<Tl. Nach einer weiteren Wegstrecke Lx wird die Temperatur Ti des Kryofluids in der Anschlussleitung 4 im Wesentlichen der Temperatur TI des Kryofluids im Kryobehälter 2 entsprechen. Diese Wegstrecke Lx, nach der die Temperatur Ti des Kryofluids in der Anschlussleitung 4 zum ersten Mal im Wesentlichen der Temperatur TI des Kryofluids im Kryobehälter 2 entspricht, wäre eine optimale Länge für die vorbestimmte Länge. Es ist ersichtlich, dass es nach der Länge Lx zu keiner weiteren Wärmeübertragung kommt, da kein Temperaturgradient vorliegen wird. Bevorzugt entspricht die Länge L daher der optimalen Länge Lx.

[0059] The pressure relief valve 8 described above can be implemented in a variety of ways. If the pressure relief valve is a purely mechanical pressure relief valve with a spring-loaded closure body, the pressure relief valve 8 will, for example, trigger when a pressure difference on both sides of the pressure relief valve 8 exceeds a threshold value S and close again when the pressure difference on both sides of the pressure relief valve 8 falls below the aforementioned threshold value S. However, with such a "simple" pressure relief valve 8, stuttering can occur, so that in a first variant, it could be considered that there is an upper threshold value S1 and a lower threshold value S2, where S1>S2. This "improved" pressure relief valve 8 can trigger (ieopen) when a pressure difference on both sides of the pressure relief valve 8 exceeds the upper threshold S1 and only close again when the pressure difference on both sides of the pressure relief valve 8 falls below the lower threshold S2. Such solutions are quite effective for regular pressure relief valves 8 (without throttle 9), since the actual pressure of the cryogenic fluid in the cryogenic container 2 will usually be present on the inside of the pressure relief valve 8.

[0060] However, in combination with the solution according to the invention, even the aforementioned improved pressure relief valve 8 with two threshold values ​​S1, S2 may experience stuttering, since the throttle 9 on both sides of the pressure relief valve 8 will, after a short time, essentially reach ambient pressure p2. It is difficult to set the lower threshold value S2 precisely to enable proper operation of the pressure relief valve 8 without stuttering.

[0061] Figure 4 shows that, instead of a classic mechanical pressure relief valve 8 as in Figures 2 and 3, a sensor-controlled outlet valve 8' (i.e., a different type of pressure relief valve 8) could also be used, which can effectively prevent stuttering in the solution according to the invention. In yet other embodiments, the outlet valve could also be manually operable. All of these variants make it possible to regulate the flow of cryogenic fluid from the cryogenic container 2; they are generally referred to as an outlet valve, regardless of whether it is a mechanical pressure relief valve 8, a sensor-controlled outlet valve 8' or pressure relief valve 8, or a manually operable outlet valve.

[0062] In the illustrated variant, the outlet valve 8' receives measured values ​​from a pressure measuring unit 10 designed to measure the pressure of the cryogenic fluid in the cryogenic container 2 (i.e., the pressure of the cryogenic fluid upstream of the throttle 9). For example, the outlet valve 8 can open when the pressure in the cryogenic container 2 measured by the pressure measuring unit 10 exceeds an upper threshold value S1 and only close again when the pressure in the cryogenic container 2 measured by the pressure measuring unit 10 falls below a lower threshold value S2.

[0063] If desired, the ambient pressure can be measured using a dedicated pressure measuring unit 11, and the aforementioned opening and closing can be based on a pressure difference between the measured internal pressure and the measured ambient pressure. However, as previously explained, this is not necessary, since the opening and closing of the outlet valve 8' can also be based on the absolute values ​​of the aforementioned pressure measuring unit 10. Furthermore, for safety reasons, the pressure relief valve could still be triggered mechanically, i.e., based on a pressure difference directly present at the outlet valve 8'.

[0064] Figure 4 further shows an embodiment in which a temperature measuring unit 20 is used alternatively or in addition to the pressure measuring unit 10, 11. The temperature measuring unit 20 can, for example, measure the temperature of a heat shield 21, which is arranged, for example, in the vacuum-insulated space between the inner tank 5 and the outer container 18. The outlet valve 8' can receive the measurement data from the temperature measuring unit 20 and initiate the opening and / or closing of the outlet valve 8' based on the received measured values ​​from the temperature measuring unit 20. An exemplary control can be implemented as follows. The outlet valve 8' opens when the pressure in the cryogenic container 2 reaches a predefined threshold value (which, as described above, can be determined by a pressure difference directly applied to the outlet valve 8' or by the pressure measuring unit 20).Closing only occurs when the temperature of the heat shield 21 (which is preferably in contact with the connecting line 4 via a thermal bridge and is thereby cooled when cryogenic fluid flows through the connecting line 4) reaches a predefined threshold value, which can, for example, essentially correspond to the temperature of the cryogenic fluid in the cryogenic container 2. For the sake of completeness, it should be noted that such heat shields are known per se, for example from EP 2 981 756 A1. In further embodiments, the temperature measuring unit 20 could also measure the temperature at a different location, for example on the connecting line 4 between the inner tank 5 and the outer container 6 or outside the cryogenic container 2 at a predetermined distance from the outer container 6.

[0065] A further embodiment of the outlet valve 8', which functions without stuttering in combination with the throttle 9 according to the invention, is possible with the aid of a timer device 22. In this case, the outlet valve 8' is triggered when a pressure difference, for example on both sides of the outlet valve 8', exceeds a threshold value S, i.e. the outlet valve 8' can be designed as standard for differential pressure measurement and no pressure measuring unit 10 is required to measure the pressure of the cryogenic fluid in the cryogenic container, although this could also be provided. The outlet valve 8' is not closed when the pressure falls below the threshold value, but after a predetermined period of time, which can be set, for example, on the timer device 22. For example, the outlet valve 8' closes between 5 seconds and 5 minutes after opening.The time period after which a sufficient pressure reduction has occurred can be determined by experiments or analytically.

[0066] It should be noted at this point that the outlet valve 8' can be designed purely mechanically (e.g., with a spring-loaded closure element) or electromechanically, particularly if the outlet valve 8' receives measurement data from one or more measuring units. In this context, the outlet valve 8' can also comprise a control unit or be connected to a control unit.

[0067] Furthermore, it should be noted that the variants mentioned can be provided individually or combined, e.g. by connecting a single outlet valve 8' to one or more of the following components: a first pressure measuring unit 10 for measuring the pressure in the cryogenic container 2, a second pressure measuring unit 11 for measuring the ambient pressure, a temperature measuring unit 20 and / or a timer device 22. It could also be provided that two or more outlet valves or pressure relief valves are provided parallel to one another on the connecting line 4, so that at least one of the outlet valves can trigger if other outlet valves fail.For example, a T-piece could be connected to the connecting line 4 and a first controlled outlet valve 8' with pressure measuring unit 10 is connected to a first outlet of the T-piece and a second purely mechanical pressure relief valve 8, which is triggered due to a pressure difference present thereat, is connected to a second outlet of the T-piece.

[0068] As shown in Figure 5, the throttle 9 could, for example, be formed by providing a bore in the outer wall of the connecting line 4. In this case, the wall thickness of the connecting line 4 forms the throttle length. In this variant, a plug 4' is usually provided in the connecting line 4, which seals it flush. Alternatively, the bore could also be located in the plug 4' and not in the connecting line 4.

[0069] Although it has been discussed so far that the inventive effect of additional heat transfer through the expanded cryogenic fluid is brought about by a throttle 9, other fittings could also be provided to achieve this effect. For example, Figure 6 shows that a nozzle such as a Laval nozzle could also be used. A Laval nozzle is particularly advantageous because mass flows at supersonic speeds can be achieved. A comparison of the detailed views in Figures 1 and 6 also clearly shows the difference between a throttle 9 and a nozzle 9'. A throttle 9 has a constant contour in the longitudinal direction and thus only a single opening cross-section. A nozzle 9', on the other hand, has a longitudinally variable (but temporally constant) contour, with the narrowest area being regarded as the opening cross-section, particularly with regard to the dimensions described herein.The valve could, for example, also be an orifice plate, which is understood to mean a throttle 9 with a throttle length of, for example, < 0.5 mm. The throttle described herein could, for example, have a throttle length of 0.5 mm to 3 cm, or even be longer. In a further variant, the valve could also be a turbine. In all of the aforementioned embodiments, the throttle 9 could also be replaced by another valve such as an orifice plate, a nozzle, a valve (in particular a pressure relief valve), or a turbine.

[0070] Figure 7 shows a variant not claimed, in which no stuttering occurs. The pressure relief valve 8 is not provided outside the cryogenic container 2 as shown in the embodiments of Figures 1 to 4, but inside the cryogenic container 2 ("inside" and "outside" refer here to the connection point 7). The pressure relief valve 8 can itself form a fitting with a variable cross-section and assume a first state in which it closes the connecting line 4 and a second state in which it opens the connecting line 4, but only with a small size corresponding to the aforementioned opening cross-section. The pressure relief valve 8 can be designed with one or two threshold values, as explained above. The advantage is that no additional measures for the pressure relief valve 8, such as a timer device 22 or additional measuring units, need to be taken.The disadvantage, however, is that such a pressure relief valve 8 is difficult to install inside the cryogenic container 2 and can only be replaced with great effort.

[0071] However, the invention is not limited to boil-off lines in which cryogenic fluid is to be released into the environment so that a maximum pressure is not exceeded. As already mentioned above, the connecting line 4 can also be part of a withdrawal line which is led to a consumer, for example, via a pressure relief valve 8. In this case too, a rigid throttle 9 as in Figures 1 to 4, an orifice plate or a nozzle could be used, but in a variant not claimed, provision can be made for a valve 9" with a variable cross-section to be used as the fitting, as shown in Figures 8a and 8b. It should be emphasized that the valve 9" shown in Figures 8a and 8b is only shown schematically and the actual structure may look different.

[0072] Figure 8a shows the valve 9" with variable cross-section, wherein the valve 9" is in a state (ie in a first operating position) in which it has a first opening cross-section ql. In Figure 8b, the valve 9" is shown in a second state (i.e. in a second operating position), in which it has a second opening cross-section qx. The first opening cross-section ql is so small that an expansion of the cryogenic fluid can take place as explained above for the rigid throttle 9 in Figures 1 to 4. The second opening cross-section qx is, for example, at least 10 times, preferably 100 times or 1000 times, larger than the first opening cross-section ql and has the aim of minimizing the flow resistance. The valve 9" can, for example, be connected by means of a control line 12 (or wirelessly) to a control unit 13, which can control the valve 9" in order to change it from the first state into the second state orfrom the second state to the first state. Instead of a control unit 13, the valve 9" could also be adjusted manually, e.g., using a manually operated switch.

[0073] In this embodiment, the first opening cross-section ql is set when the aforementioned throttling effect is to be achieved. In this state, essentially the same function as explained above can be achieved if, for example, a pressure relief valve 8 is arranged in the withdrawal path by means of a T-piece 14, which can release cryogenic fluid to the environment. The valve 9" can, for example, be set to the first state when no cryogenic fluid is to be actively withdrawn from the cryogenic container 2.

[0074] However, for active withdrawal of cryogenic fluid from cryogenic container 2, i.e., when cryogenic fluid is to flow toward consumer V, connecting line 4 should have the lowest possible flow resistance, so that valve 9" should be placed in the second state during active withdrawal. In the second state, valve 9" is therefore preferably opened to its maximum so that it can also completely release the cross-section of connecting line 4.

[0075] An advantage over the variants shown in Figures 1 to 4 is that no separate pipeline is required for withdrawal into the cryogenic container 2, thus eliminating one thermal bridge. However, a disadvantage is that the 9" valve should be controlled to reduce flow resistance.

[0076] In addition to the states in Figures 8a and 8b, the valve 9" can also optionally be placed in a third state in which the valve 9" is completely closed. Alternatively, however, a valve could also be provided in the connecting line 4, which is located outside the cryogenic container 2 in the connecting line 4 to shut off fluid flow.

[0077] It is understood that the valve 9" can also assume all states between the first and the second state, ie is continuously adjustable.

[0078] The aforementioned valve 9" could, for example, also be formed by connecting a throttle with the aforementioned opening cross-section ql and an on / off valve in parallel. When the on / off valve is closed, the entire mass flow flows through the throttle, thereby achieving the aforementioned expansion and the associated temperature reduction of the withdrawn cryogenic fluid. However, when the on / off valve is opened, essentially the entire mass flow of cryogenic fluid will flow through the on / off valve, since this has a lower flow resistance than the throttle.

[0079] The previously described control unit 13 could, if necessary in combination with one of the previously described controls via a measured pressure, temperature or time, also be connected to the valve 9". In this case, the control unit 13 can also be connected to the previously described outlet valve 8, although this is not mandatory. The control unit 13 can, for example, receive the pressure from the cryogenic container 2 and control the valve 9" such that the pressure in the cryogenic container 2 remains essentially constant. For example, the valve 9" can remain closed until the pressure in the cryogenic container corresponds to a desired boil-off pressure and then open. After opening, the opening cross-section ql of the valve 9" is, for example, between 1 pm 2 up to 9 mm 2 . Now the control unit 13 can adjust the opening cross section ql within the range 1 pm 2 up to 9 mm 2(or a portion thereof) so that the pressure in the cryogenic vessel remains constant. Alternatively or additionally, the control unit 13 can also control the valve 9" in a different way, e.g., to continuously reduce the vessel pressure and / or to cool a cooling shield (heat shield) to a desired temperature, after which the valve 9" can be closed again.

[0080] In all of the aforementioned embodiments, the connecting line 4 can be provided for the withdrawal of either liquid cryofluid or gaseous cryofluid. For the withdrawal of liquid cryofluid, the end of the connecting line 4 located in the cryocontainer 2 is typically arranged in the lower half, in particular in the lower quarter, of the cryocontainer 2. For the withdrawal of gaseous cryofluid, the end of the connecting line 4 located in the cryocontainer 2 is typically arranged in the upper half, in particular in the upper quarter, of the cryocontainer 2.

[0081] It should be noted that several connecting lines 4 could also be routed into the cryogenic container 2, each of which has a throttle 9 or another corresponding fitting. For example, two connecting lines 4 could be provided, each of which has one of the aforementioned fittings, one for withdrawing liquid cryogenic fluid and one for withdrawing gaseous cryogenic fluid.

[0082] Figures 9 and 10 show variants which are particularly advantageous when cryogenic fluid is present in the supercritical range in the cryogenic vessel 2. In this case, the cryogenic fluid in the cryogenic vessel 2 will essentially be in a single-phase state, i.e. no liquid phase and a gas phase clearly separated from this will form. With cryogenic fluid in the supercritical range, thermal stratification will form, so that the temperature of the cryogenic fluid in the upper region (“top” is understood here to be an operating position; the influence of gravity defines the thermal stratification and thus also the arrangement described below) is considerably higher than at the bottom. In these cases, it is advantageous to route the part of the connecting line 4 located within the cryogenic vessel, in particular the heat exchanger defined by it, predominantly in the upper half.In other words, for cryogenic containers in which cryogenic fluid is to be stored in the supercritical range, it is preferred if more than 50%, preferably more than 70% or more than 90%, of the length of the section of the connecting line located within the cryogenic container is located in the upper half, preferably in the upper third or in the upper quarter, of the cryogenic container.

[0083] Figure 9 shows that the connecting line 4 can be routed exclusively in the upper half of the cryogenic vessel 2. In this case, the fitting will also be located in the upper half.

[0084] Figure 10 shows that the fitting could also be located in the lower half of the cryogenic container 2, wherein it is further preferred that the majority of the connecting line 4 routed within the cryogenic container can be located in the upper half.

Claims

Claims:

1. System (1) comprising a cryogenic container (2) for storing cryogenic fluid and a connecting line (4) led into the cryogenic container (2) for removing cryogenic fluid from the cryogenic container (2), wherein the connecting line (4) has a fitting inside the cryogenic container (2), wherein the fitting is a throttle (9), an orifice plate, or a nozzle (9'), wherein the system (1) comprises an outlet valve (8, 8') which is provided outside the cryogenic container (2) in the connecting line (4), characterized in that the fitting permanently has an opening cross-section (ql) which is at least 100 times, preferably 10,000 times or 1,000.000 times smaller than an internal cross section (q2) of the connecting line (4) downstream of the fitting in the withdrawal direction, wherein the connecting line (4) is guided between the fitting and the connection point (7) on the cryogenic container (2) with a predetermined length (L), which is preferably longer than 50 cm, wherein the outlet valve (8) is a pressure relief valve which is designed to open when a predetermined pressure or a predetermined pressure difference is present.

2. System according to claim 1, wherein said opening cross-section (ql) has a size of 1 pm 2 up to 9 mm 2 , especially preferred from 25 pm 2 up to 1 mm 2 , has.

3. System according to claim 1 or 2, wherein the connecting line (4) is guided between the fitting and the connection point (7) to the cryogenic container (2) with a length of 1 m to 3 m.

4. System according to one of claims 1 to 3, wherein the connecting line (4) is guided in a meandering manner within the cryogenic container (2) and / or wherein the connecting line (4) has surface-enlarging structures, in particular cooling fins, within the cryogenic container (2).

5. System according to one of claims 1 to 4, wherein the fitting is a throttle (9) with a throttle length of preferably at least 1 mm and is formed by a bore through a pipe wall of the connecting line (4).

6. System according to one of claims 1 to 4, wherein the fitting is a nozzle (9') which is designed as a Laval nozzle.

7. System according to one of claims 1 to 6, wherein the outlet valve (8) is a mechanical valve, in particular a needle valve, which is connected via a line to the cryogenic container upstream of the fitting, wherein the line is preferably led directly through the fitting, and opens and / or closes when a threshold value of the pressure applied there is exceeded.

8. System according to one of claims 1 to 7, wherein the outlet valve (8') receives pressure measurement values ​​from a pressure measuring unit (10) arranged in the cryogenic container (2) and opens and / or closes on the basis of the pressure measurement values ​​received, or wherein the outlet valve (8') receives temperature measurement values ​​from a temperature measuring unit (20), which preferably measures the temperature of a heat shield (21), wherein the outlet valve (8') opens and / or closes on the basis of the temperature measurement values ​​received.

9. System according to one of claims 1 to 8, wherein the outlet valve (8') is equipped with a timer device (22) and is designed to close again after opening only after a predetermined period of time.

10. System according to one of claims 1 to 9, wherein the connecting line (4) is connected to a consumer outside the cryogenic container (2).

11. System according to one of claims 1 to 10, wherein the connecting line (4) is designed such that cryogenic fluid which penetrates through the fitting into the connecting line (4) also passes through the outlet valve (8).

12. System according to one of claims 1 to 11, wherein the cryogenic container has an inner tank (5) and an outer container (6) and wherein a heat shield (21) is further provided in a vacuum-insulated space between the inner tank (5) and the outer container (6) and a heat bridge is present between the connecting line (4) and the heat shield (21).

13. System according to one of claims 1 to 12, wherein the pressure relief valve is designed to essentially maintain this pressure in the cryogenic container (2) after the predetermined pressure has been reached.

14. System according to one of claims 1 to 13, wherein more than 50%, preferably more than 70% or more than 90%, of the length of that section of the connecting line (4) which is within of the cryogenic container (2), in the upper half, preferably in the upper third or in the upper quarter, of the cryogenic container (2).

15. System according to claim 14, wherein the fitting is located in the upper half, preferably in the upper third or upper quarter, of the cryogenic container (2).

16. System according to claim 14 or 15, wherein that section of the connecting line (4) which lies within the cryogenic container (2) lies exclusively in the upper half, preferably in the upper third or in the upper quarter, of the cryogenic container (2).

17. A vehicle comprising a system (1) according to any one of claims 1 to 16, wherein the cryogenic container (2) is preferably mounted on a vehicle frame of the vehicle.

18. Use of a system (1) according to one of claims 1 to 16 with a cryogenic fluid of a predetermined composition in a predetermined thermodynamic state stored in the cryogenic container (2), wherein the opening cross-section (ql) of the fitting is selected such that the cryogenic fluid expands when removed from the fitting and preferably the length of the connecting line (4) between the fitting and the connection point (7) is selected such that the temperature of the cryogenic fluid in the connecting line (4) at the connection point (4) substantially corresponds to the temperature of the cryogenic fluid in the cryogenic container (2) outside the connecting line (4).

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