EP3511650B1 - Method and device for cooling a consumer and system with corresponding device and consumers - Google Patents

Description

The invention relates to a method and a device for cooling a consumer and a system with a corresponding device and a consumer according to the preambles of the independent patent claims.

State of the art

High and medium voltage cables and busbars can be designed as high-temperature superconductors (HTSC). Such cables and busbars can carry direct current or alternating current and are also referred to as »HTSC current guides«. They require cooling to a temperature of less than 100 K, preferably less than 80 K.

Although the present invention is described below mainly with reference to HTSC current supplies as consumers, it is also suitable in the same way for cooling other consumers that require cooling capacity at a comparable cooling temperature level, in particular superconductor materials, but also, for example, cables, current supplies and others Structures made of conventional metals such as copper and aluminum.

Different methods and devices can be used to cool corresponding consumers. These work, for example, with liquid nitrogen as a cooling medium, as explained in detail below. Devices of this type are, for example, from DE 10 2013 011 212 A1 and the EP 1 355 114 A3 known. In the DE 197 55 484 A1 describes a process in which a liquid mixture consisting of nitrogen and oxygen is used instead of nitrogen.

In the below explained in more detail DE 10 2012 016 292 A1 , which is considered to be the closest prior art, discloses a method and a device for cooling objects, in which a cooling medium is fed from a first reservoir via a first cooling medium line to an object to be cooled, brought into thermal contact with it and is then discharged via a second coolant line. After the thermal contact with the object, the cooling medium is fed to a second storage container via the second cooling medium line and stored there until a predetermined filling level is reached in the first or in the second storage container. The cooling medium is then fed from the second reservoir to the object for the purpose of cooling and brought into thermal contact with it and then fed back into the first reservoir, whereupon it is again available for cooling the object. Due to the pendulum guidance of the cooling medium between the two reservoirs, the same flow paths should be able to be used in both flow directions, at least in part. The method and the device should be particularly suitable for cooling superconducting cables.

In particular for cooling consumers over longer cooling sections, in particular along cables or HTSC power lines, conventional cooling devices sometimes prove to be unsatisfactory, for example in terms of their space requirement, especially when the liquid nitrogen used as a cooling medium is cooled at two different ends of a cooling section . Therefore systems can be used in which the liquid nitrogen is cooled at the two different ends of the cooling line, but bulky apparatuses are grouped at one end of a cooling line. A corresponding system, which is not known from the prior art, is explained in more detail below and with reference to the attached figures.

In a corresponding system, however, if a closed cooling device is used at one end of the cooling section, cooling capacity can no longer be provided by this cooling device if this cooling device fails. However, since corresponding systems, in particular for the cooling of HTSC power supply lines, must have a very high availability so that safe operation can be guaranteed over longer periods of up to several years, a corresponding failure must be avoided. For this purpose, several redundant closed cooling devices, each providing 100% of the required cooling capacity, can be used. However, this proves to be disadvantageous in terms of investment costs.

The object of the present invention is therefore to remedy this and to provide improved technical possibilities for cooling corresponding consumers using liquid nitrogen with high availability.

Disclosure of Invention

Against this background, the present invention proposes a method and a device for cooling a consumer, in particular a power supply, preferably an HTSC power supply, and a system with a corresponding device and a consumer with the features of the independent patent claims. Preferred configurations are the subject matter of the dependent patent claims and the following description.

Typically, the liquid nitrogen in the systems mentioned at the outset is conveyed by means of a pump (so-called circulation pump) and subcooled to the required cooling temperature in a subcooler. The liquid nitrogen is routed to the consumer, where it is warmed up and fed back to the circulation pump. The liquid nitrogen that is circulated in this way is also referred to as “circulated nitrogen”. The term »supercooler« is used because liquid nitrogen, after appropriate cooling, is a supercooled liquid.

In its simplest form, the heat exchanger in a subcooler is a coiled tube that is placed in a nitrogen bath ("bath nitrogen"). The warmer circulating nitrogen is guided inside the pipe coil and cooled by the colder bath nitrogen lying outside. The nitrogen in the bath evaporates continuously. As an alternative to coiled-tube heat exchangers, other types of heat exchangers can be used.

It is also possible to use circuits in which supercooling of the circulating nitrogen upstream of the circulation pump is combined with supercooling downstream of the circulation pump. Two heat exchangers are required for this and placed in a suitable way in the subcooler. A corresponding system is, for example, in the attached figure 1 illustrated. Other variants of supercooling, in particular only upstream or only downstream of the circulating pump, are also fundamentally possible.

The pressure in the cooling circuit downstream of the pump is selected in such a way that the circuit nitrogen always remains liquid and no vapor bubbles form. From a thermodynamic point of view, this means that the pressure in the circuit should always be higher than in the subcooler bath and that the circuit nitrogen must not be heated above the boiling point.

The lowest temperature of the cycle nitrogen is reached at the exit from the subcooler. This temperature is essentially determined by the temperature of the bath nitrogen used in the subcooler (and the heat transfer in the subcooler). In order to bring about supercooling, the nitrogen bath must therefore be brought to an appropriate temperature.

To lower the temperature, the pressure of the bath nitrogen can be reduced by a pressure reduction in which evaporating nitrogen is continuously pumped off using a mechanical (e.g. oil-lubricated) vacuum pump. The lower limit of the temperature that can be reached by reducing the pressure is about 63 K, which corresponds to a vapor pressure of about 0.13 bar. At lower temperatures, the nitrogen in the bath would freeze. A corresponding reduction in pressure typically leads to nitrogen and cold losses, because the pumped nitrogen and its cold can usually not be recovered or only with great effort.

The losses of bath nitrogen occurring in the subcooler as a result of evaporation are typically compensated for by topping up with fresh liquid nitrogen from a suitable reservoir, for example a cryogenic tank. The reservoir is filled, for example, using an air separation plant or a nitrogen liquefier.

The temperature of the bath nitrogen can also be reduced by incorporating one or more closed loop coolers (also known as cryocoolers) into the subcooler. The one or more refrigerating machines cool and liquefy/recondense the bath nitrogen which evaporates during cooling down to the required cooling temperature; a vacuum pump is not required in this case. In this way, nitrogen and cold losses can be reduced. When Brayton or Stirling coolers are typically used in cryocoolers. The term "closed" cooling device is understood here to mean a device in which gaseous nitrogen is not discharged from the system due to the process, but is liquefied and fed back into the system.

The use of a mechanical vacuum pump for cold generation in the subcooler is (from the point of view of investment costs) a relatively inexpensive, but energetically inefficient solution. This is mainly due to the fact that the valuable cold (since it is present at very low temperatures) of the extracted cold nitrogen vapor is not used but destroyed will. The use of chillers in the closed cooling devices is generally advantageous in terms of energy, but the corresponding devices are relatively expensive, so that their use is often not economical.

In principle, it is therefore also possible to use systems in which both techniques are used to reduce the temperature. In this way, the loss of nitrogen and cold can be reduced, but at the same time the investment outlay for closed cooling devices can be kept within limits.

It is possible to equip a sub-cooler with a corresponding vacuum pump and additionally with a closed cooling device. In particular when consumers, such as cables, are to be cooled over longer cooling sections, systems can also be used in which subcoolers are arranged at both ends of the cooling section, referred to below as the “first” and “second” end.

In such systems, the cooling section thus extends between the first end and a second end. The liquid nitrogen is in such systems in the form of a circulatory stream repeatedly (i.e. continuously circulating) subjected to a first cooling, fed to the cooling line at the first end, transported from the first end to the second end along the cooling line, the cooling line at the second end removed, subjected to a second cooling, fed back to the cooling line at the second end, transported from the second end to the first end along the cooling line and removed again from the cooling line at the first end. The first cooldown is performed using a first subcooled nitrogen bath in a subcooler and the second cooldown carried out using a second subcooled nitrogen bath in another subcooler.

In an appropriate system, such as that in the attached figure 3 is shown, the first nitrogen bath can be at least partially supercooled by means of a closed cooling device and the second nitrogen bath can be at least partially supercooled by pressure reduction to a subatmospheric pressure level. The pressure reduction takes place in that gaseous nitrogen is pumped out of a head space above the nitrogen bath from a subcooler by means of a vacuum pump, in particular a mechanical one, and is in particular discharged to the surrounding atmosphere.

As already mentioned, the nitrogen losses caused by the pumping out to reduce the pressure are compensated for by feeding in nitrogen from a reservoir, which can be filled with liquid nitrogen, for example using an air separation plant.

A disadvantage of the example in figure 3 shown arrangement is now, however, that at the first end and at the second end of the cooling section, ie in the figure 3 at the left and right end, considerable installation space claiming apparatus, namely the reservoir on the one hand and the closed cooling device on the other hand, must be arranged. This can cause problems in particular when at the second end of the cooling section, ie at the right end in the figure 3 , the space is limited.

To overcome this disadvantage, in corresponding systems the reservoir and the closed cooling device can be arranged at the first end of the cooling section, while the vacuum pump required for pressure reduction can be arranged at the other end of the cooling section. A corresponding vacuum pump represents a comparatively small unit that can be accommodated much more easily at the second end, in particular if the installation space at the second end is limited. A corresponding vacuum pump can also be connected via a line to the subcooler provided at the second end of the cooling section and does not have to be arranged in the immediate vicinity of it. This way can a further favorable adaptation to the available space can be made by repositioning.

In the systems just explained, the nitrogen losses occurring in the second nitrogen bath due to the pressure reduction caused by pumping out can also be compensated for from a reservoir, which, however, is now arranged at the opposite end of the cooling section. The nitrogen taken from the reservoir to compensate for the losses is fed into the circulatory flow at the end of the cooling section where the reservoir is located and discharged from the circulatory flow at the other end of the cooling section, where the pressure reduction takes place, and used to fill up the nitrogen bath arranged there. The circulating flow is therefore used to transport this nitrogen. The present invention is based on such a system and improves its availability without requiring full redundancy with regard to the closed cooling device.

As already mentioned, the present invention is based on a method for cooling a consumer via a cooling section that extends between a first end and a second end. In the context of the present invention, the method is carried out in at least a first time period in a first method mode and in at least a second, different time period in a second method mode.

In the process, in the first and in the second process mode, liquid nitrogen is repeated in the form of a circulatory stream, ie continuously in the circuit and in particular without intermediate storage in a container, and in each case successively subjected to a first cooling, fed to the cooling section at the first end, from the first end transported to the second end along the cooling line, removed from the cooling line at the second end, subjected to a second cooling, fed to the cooling line at the second end, transported from the second end to the first end along the cooling line, and removed from the cooling line at the first end . The circulatory flow is in particular always guided in the same direction and is not experienced, as for example in the DE 10 2012 016 292 A1 , a reversal of direction. In the first and second process modes, the first cooling is performed using a first subcooled nitrogen bath and the second cooling is performed using a second subcooled nitrogen bath, wherein the first nitrogen bath is at least partially supercooled in the first process mode by means of a closed cooling device and the second nitrogen bath is at least partially supercooled in the first and in the second process mode by pressure reduction to a subatmospheric pressure level. A quantity of nitrogen evaporating from the second nitrogen bath due to the pressure reduction to the subatmospheric pressure level in the first and in the second process mode is at least partially compensated for in the process from a reservoir.

Within the scope of the method according to the invention, the liquid nitrogen is conducted in the form of the circulating stream through one or more first cooling passages, in particular during transport from the first end to the second end along the cooling section, and through one during transport from the second end to the first end along the cooling section or a plurality of second cooling passages fluidly separated from the one or more first cooling passages. One or more different cooling passages are therefore provided for guiding from the first to the second end than for guiding from the second end to the first end. A "cooling passage" refers to a fluid-guiding structure that is provided with heat-exchange surfaces. The circulatory flow is and can therefore not be performed in the same cooling passages in the context of the present invention, as in the DE 10 2012 016 292 A1 is the case due to the shuttle service there. If a "fluidic separation" of the cooling passages is mentioned here, it is of course not excluded that the cooling passages are open at their terminal ends and are connected to one another via lines that carry the circulating flow.

In other words, within the scope of the present invention, the cooling section comprises a first feed opening, a first extraction opening, a second feed opening and a second extraction opening for the liquid nitrogen, the first feed opening being connected to the first extraction opening in particular via the first Cooling passage(s) and the second feed opening are connected to the second extraction opening in particular via the mentioned second cooling passage(s). The first feed opening and the second removal opening are located at the first end, the first removal opening and the second feed opening at the second end of the cooling section. In the terminology used here, an “opening” refers to a connection of any type, for example a flange or spigot. The liquid nitrogen in the circulating stream is fed via the first feed opening at the first end of the cooling section to this cooling section or to the first cooling passage or passages and removed via the first removal opening at the second end. At the same time, i.e. not in a shuttle operation, the liquid nitrogen, if a corresponding circulatory flow is formed, is fed via the second feed opening at the second end of the cooling section to this cooling section or to the second cooling passage or passages and removed via the second removal opening at the first end.

To further clarify the measures according to the invention, the formation of the circulatory flow can also be explained by describing the existing pressure levels. A first pressure level of the liquid nitrogen supplied at the first end of the cooling section is always above a second pressure level of the liquid nitrogen removed at the second end of the cooling section. At the same time, a third pressure level of the liquid nitrogen supplied at the second end of the cooling section is always at or below the second pressure level. A fourth pressure level of the liquid nitrogen removed at the first end of the cooling section is below the third pressure level. The relationships P1>P2, P2≧P3 and P3>P4 always result for the first pressure level P1, the second pressure level P2, the third pressure level P3 and the fourth pressure level P4.

In the context of the present invention, the liquid nitrogen is advantageously not subjected to any pressure-increasing measures at the second end of the cooling section. So here is, for example, in contrast to the one mentioned several times DE 10 2012 016 292 A1 , no device for pressure build-up evaporation and no pump. A corresponding increase in pressure takes place within the scope of the present invention, in particular only at the first end of the cooling section using a circulation pump. Furthermore, within the scope of the present invention, the liquid nitrogen of the circulating stream is used, ie no switching valves are provided.

For this equalization, liquid nitrogen is taken from the reservoir and fed into the circulatory stream before the circulatory stream is fed to the cooling section at the first end, and liquid nitrogen is discharged from the circulatory stream and at least partially fed to the second nitrogen bath after the circulatory stream is fed to the cooling section taken from the second end. To this Way result in the advantages already mentioned above, in particular a reduction of the space at the second end of the cooling section.

If only one closed cooling device is provided at the first end of the cooling section, which is not redundant or not fully redundant, failure of the same will result in an intolerable drop in the cooling capacity at the first end of the cooling section. In such cases, the second method mode is therefore carried out within the scope of the present invention. In other words, in the first process mode, the closed cooling device used at the first end of the cooling section works at full power, so the first process mode represents in particular regular operation. The second process mode, on the other hand, is a process mode in which the at the first The closed cooling device used at the end of the cooling section does not work or can at least not work at full capacity. It is therefore an emergency or backup process mode, which is carried out, for example, in the event of a partial or complete unplanned failure of the closed cooling device, but also, for example, in the case of corresponding planned events, for example maintenance that is routinely required.

So if we are talking here about the first nitrogen bath being at least partially supercooled by means of the closed cooling device in the first process mode, this does not rule out the first nitrogen bath also being at least partially supercooled by means of the closed cooling device in the second process mode, although this then works with it lower performance.

The present invention makes use of the fact that, to compensate for the usual evaporation losses that occur during supercooling at the second end of the cooling section, a reservoir for liquid nitrogen is already available at the first end of the cooling section, the contents of which can now advantageously also be used to bridge periods in which the closed cooling device used at the first end of the cooling section is not working or at least not working at full power. Corresponding nitrogen is advantageously supercooled in any case in a supercooler before it is introduced into the circulation flow mentioned and can therefore be used to fill the first supercooled nitrogen bath at the first end of the cooling section. will be added while a pressure reduction in the first nitrogen bath made by means of a pump, similar to the second nitrogen bath.

In other words, the method according to the invention comprises that in the second method mode the closed cooling device is not operated or only operated to a reduced extent or with reduced power and, to compensate, further liquid nitrogen is taken from the reservoir, supercooled and fed to the first supercooled nitrogen bath, and that in the second process mode gaseous nitrogen is also pumped out of the first nitrogen bath by means of a pump under pressure reduction to a subatmospheric pressure level in the first supercooled nitrogen bath.

The use of the method according to the invention ensures that even if the closed cooling device fails without using a corresponding, completely redundant further cooling device, there cannot be a failure of the cooling or an excessive reduction in the cooling capacity. A corresponding system can therefore be operated with significantly increased availability. In order to carry out the method according to the invention, it is provided in particular that a container used to hold the first nitrogen bath, ie the corresponding sub-cooler, is dimensioned sufficiently large. Typically, a storage volume that is two to three times that is provided compared to other systems in which no corresponding feed is provided in the second operating mode.

A closed cooling device can be used with particular advantage in the context of the present invention, in which one or more refrigerant circuits are formed with one or more refrigerants, which or in the first operating mode using a first number of compressors and in the second operating mode with a second, smaller number of compressors is or will be compressed. In particular, the first number of compressors can be two and the second number of compressors can be one. In other words, a closed cooling device can be used in which part of the compression and thus refrigeration capacity provided in the first process mode with a larger number of compressors operated can also be provided in the second operating mode, in which fewer or only one compressor be used. This lower refrigeration capacity can be compensated for by the use of liquid nitrogen according to the invention, which is drawn off from the reservoir and fed to the first nitrogen bath. By using the present invention, for example, a failure of one of two or more compressors can be tolerated as long as the reduced cooling capacity can be compensated for by means of the liquid nitrogen. In this way, a corresponding closed cooling device can be set up for emergency operation without a redundant design.

Within the scope of the method according to the invention, the liquid nitrogen taken from the reservoir and introduced into the circulatory stream is advantageously introduced into the circulatory stream using a mixing device. In this way, it is possible to avoid unequal temperature distributions and set a homogeneous mixed temperature level, particularly when the introduced nitrogen and the already present circulating nitrogen have different temperature levels.

As already mentioned, so-called circulation pumps are used in particular in methods of the type explained. In the process according to the invention, the liquid nitrogen in the form of the circulating stream is therefore advantageously passed through a circulating pump, after it has been removed at the first end of the cooling section and before it is fed in again at the first end of the cooling section, at which a suitable pressure difference can also be set.

In particular, the liquid nitrogen conducted in the form of the circulating flow can be fed to the circulating pump at a first pressure level of at least 2 bar (abs.). For example, within the scope of the present invention, the first pressure level can be about 10 bar (abs.). A corresponding pressure level results in particular from the pressure level downstream of the circulating pump, which can be above the first pressure level and, for example, at approx. 15 bar (abs.), and from the pressure losses over the cooling section.

Within the scope of the method according to the invention, the liquid nitrogen taken from the reservoir and introduced into the circulating stream is added to the reservoir, in particular at a second pressure level above the first pressure levels taken. The introduced nitrogen is in particular also fed to the circulation pump together with the circulation flow. A corresponding setting of the first and second pressure levels always results in a mandatory flow direction from the reservoir to the point of entry into the circulatory flow. The injected nitrogen is typically expanded from the second to the first pressure level by means of a suitable valve before it is introduced into the circulating stream.

Within the scope of the present invention, different variants of cooling can be used. The liquid nitrogen carried in the form of the circulating flow can be subjected to the first cooling before and/or after it is passed through the circulating pump. Details are also explained in more detail with reference to the drawings, in which the Figures 4 to 6 embodiments of the present invention shown provide cooling before and after the circulation pump.

Since the liquid nitrogen in the reservoir is typically in a non-supercooled state, while subcooled nitrogen is present in the recycle stream, if the nitrogen injected from the reservoir is not subjected to any further cooling prior to being injected into the recycle stream, a significant cooling will occur Temperature increase that must be compensated for by a corresponding cooling capacity in the assigned subcooler. Therefore, as already mentioned, it is advantageously provided within the scope of the present invention that the liquid nitrogen taken from the reservoir and introduced into the circulation stream is cooled using a third supercooled nitrogen bath before it is introduced into the circulation stream. The third supercooled nitrogen bath is also used for supercooling the liquid nitrogen fed into the first supercooled nitrogen bath in the second operating mode.

Such cooling of the liquid nitrogen introduced into the circulating flow and, in the second process mode, fed into the first supercooled nitrogen bath can therefore be carried out in particular by using a further, ie third, supercooled nitrogen bath. According to a preferred embodiment of the present invention, it is provided that the third supercooled nitrogen bath is provided in that further liquid nitrogen is removed from the reservoir at the first pressure level and expanded to a third pressure level with partial evaporation. The third pressure level can, for example, be at atmospheric pressure or slightly, ie in particular at most 0.5 bar, above atmospheric pressure. In this way, corresponding additional cold can be generated and there is a partial evaporation of the expanded nitrogen.

Advantageously, a portion of the additional liquid nitrogen from the reservoir that is not vaporized during the expansion to the third pressure level can be at least partially fed to the third nitrogen bath and a portion of the additional liquid nitrogen from the reservoir that has evaporated during the expansion to the third pressure level can be at least partially used as a coolant in the closed cooling device can be used. In this variant of the method, in which a cooling device with a Brayton cooler is used in particular as the closed cooling device, there is a further saving in energy.

The present invention also extends to a device for cooling a consumer via a cooling path that extends between a first end and a second end. The apparatus is operable in a first mode of operation for at least a first period of time and in a second mode of operation for at least a second, different period of time and comprises means adapted to supply liquid nitrogen in the form of a circulating stream, i.e. continuously, in the first and in the second mode of operation in the circuit and in particular without intermediate storage in a container, repeatedly and successively subjected to a first cooling, to be fed to the cooling section at the first end, to be transported from the first end to the second end along the cooling section, to be removed from the cooling section at the second end to subject to a second cooling, to be fed to the cooling line at the second end, to be transported from the second end to the first end along the cooling line, and to be removed from the cooling line at the first end. The means are set up in particular to always lead in the same direction, so that this is not, as for example in the DE 10 2012 016 292 A1 , experiences a reversal of direction. These means include, in particular, corresponding lines and a circulation pump.

Furthermore, the device has means which are set up to carry out the first cooling using a first supercooled nitrogen bath and the second cooling using a second supercooled nitrogen bath in the first and in the second operating mode. The first and the second nitrogen bath or corresponding containers are part of the device. It also has a closed cooling device that is set up to cool the first nitrogen bath in the first operating mode, and means that are set up to supercool the second nitrogen bath in the first and in the second operating mode at least partially by reducing the pressure to a subatmospheric pressure level. The latter include in particular a vacuum pump. Means are also provided which are set up in the first and in the second operating mode to at least partially compensate for the amount of nitrogen evaporating from the second nitrogen bath due to the pressure reduction to the subatmospheric pressure level from a reservoir, for which purpose the device has corresponding lines and in particular corresponding valves.

The device is characterized in particular by means that are set up to remove liquid nitrogen from the reservoir for the named equalization and introduce it into the circulatory flow before the circulatory flow is fed to the cooling section at the first end, and liquid nitrogen from the circulatory flow discharge and at least partially fed to the second nitrogen bath, after the circulatory flow of the cooling section is removed at the second end.

According to the invention, means are provided which are set up to remove further liquid nitrogen from the reservoir, to supercool it and to feed it to the first supercooled nitrogen bath whenever the closed cooling device is not operated in the second operating mode or is only operated with reduced power. Furthermore, a pump is provided which is set up to pump gaseous nitrogen out of the first nitrogen bath in the second operating mode while reducing the pressure to a subatmospheric pressure level.

Also part of the device is a control device that is set up to output a control specification to the device so that it works in the first or in the second operating mode. The control device can, for example, also be set up to recognize that the closed cooling device cannot be operated or can only be operated with reduced power and to switch from the first to the second operating mode on this basis.

According to the invention, one or more first cooling passages are provided for transporting the liquid nitrogen in the form of the circulating flow from the first end to the second end along the cooling section and one or more second cooling passages are provided for transporting from the second end to the first end along the cooling section is or are fluidly separated from the one or more first cooling passages.

With regard to the further features and advantages of the device according to the invention and its advantageous configurations, reference is expressly made to the above explanations relating to the method according to the invention and its configurations. This should explicitly apply to the feed and extraction openings, the pressure conditions, the lack of pressure increase at the second end and the lack of switching valves, which can be implemented in the device according to embodiments. It goes without saying that the method modes mentioned there correspond to corresponding operating modes of the device. A corresponding device or an embodiment thereof is advantageously set up to carry out a corresponding method or a variant thereof.

This also applies to the system also provided according to the invention with a consumer to be cooled, which is characterized according to the invention by a corresponding device.

The invention is explained in more detail below with reference to the accompanying drawings, in which embodiments of the invention are illustrated.

Brief description of the drawing

• figure 1 shows a system according to an embodiment not according to the invention in a simplified schematic representation.
• figure 2 shows a system according to an embodiment not according to the invention in a simplified schematic representation.
• figure 3 shows a system according to an embodiment not according to the invention in a simplified schematic representation.
• figure 4 shows a system according to an embodiment not according to the invention in a simplified schematic representation.
• figure 5 shows a system according to an embodiment not according to the invention in a simplified schematic representation.
• figure 6 shows a system according to an embodiment not according to the invention in a simplified schematic representation.
• Figures 7A and 7B show a system according to an embodiment of the present invention in a simplified schematic representation in a first and a second operating or method mode.
• Figures 8A and 8B show a system according to an embodiment of the present invention in a simplified schematic representation in a first and a second operating or method mode.
• figure 9 illustrates a cooling passage that may be provided in a system according to the previous figures.

In the figures, elements that are the same or functionally equivalent to one another are indicated with identical reference symbols. A repeated explanation of such elements is omitted for the sake of clarity. Liquid media are illustrated by black (filled) flow arrows, gaseous media by white (open) flow arrows.

Detailed description of the drawing

In figure 1 a system according to an embodiment not according to the invention is shown in a simplified schematic representation.

This in figure 1 The system shown comprises a consumer 1, which, as mentioned, can in particular be an (HTSL) cable system. The consumer 1 is cooled using liquid nitrogen, which is conducted in a circulatory flow 2 . After being used to cool consumer 1, the liquid nitrogen in cycle stream 2 is cooled in a heat exchanger 3 in the example shown, fed to a circulation pump 4, cooled in another heat exchanger 5 and used again to cool consumer 1. As an alternative to the representation according to figure 1 only one of the two heat exchangers 3 and 5 can also be provided.

The heat exchangers 3 and 5, if present, are each arranged in a subcooled nitrogen bath in a subcooler 6. In this way, the nitrogen in the circulating stream 2 can be cooled to a temperature level of, for example, approximately 67 K and can be used at this temperature level to cool the consumer 1 . When cooling consumer 1, it heats up to a temperature level of, for example, approx. 73 K.

The sub-cooling of the nitrogen bath in the sub-cooler 6 is effected by pressure reduction using a pump 7 which pumps out nitrogen evaporating from the nitrogen bath and in this way reduces the pressure level in the sub-cooler 6 . The nitrogen pumped out is, for example, discharged to the atmosphere (amb). Nitrogen losses caused by pumping out are compensated for by liquid nitrogen from a reservoir 8 via a valve 9 . The reservoir 8 can be fed by means of an air separation plant. The reservoir 8 is provided with a pressure build-up evaporator 10 here.

In order to adjust the pressure level of the nitrogen in the circulatory stream 2 upstream of the circulatory pump 4, a bidirectional connection, not specifically designated, to the reservoir 8 is provided in the example shown. The pressure level of the nitrogen in the circulating flow 2 upstream of the circulating pump 4 and at the same time in the reservoir is typically above 2 bar (abs.), for example approximately 10 bar (abs.). The pressure level of the nitrogen in the circulating stream 2 downstream of the Circulation pump 4 is above this, for example at about 15 bar (abs.). The pressure level in the subcooler 6 is below atmospheric pressure, in particular at 0.1 to 0.5 bar (abs.), for example at approx. 0.2 bar (abs.).

In figure 2 a system according to a further embodiment not according to the invention is shown in a simplified schematic representation.

Since the pressure reduction in the subcooler 6 by pumping out the nitrogen by means of the pump 7 leads to nitrogen and cold losses, a closed cooling device 11 can also be used, which is used in the system according to FIG figure 2 is provided in addition to the pump 7. In the cooling device 11, the nitrogen from the sub-cooler 6 is additionally cooled using a suitable refrigeration machine, which can in particular include one or more Stirling coolers and/or one or more Brayton coolers operated using neon and/or helium. The nitrogen enters the cooling device 11 in gaseous form and is returned to the subcooler 6 in liquid form.

Furthermore, in the system according to figure 2 a pressure control device 21 is provided, which instead of in the system according to figure 1 provided connection is set up with the reservoir 8 for pressure adjustment. In this way the pressure level in the reservoir 8 can be adjusted to a value which is independent of the pressure level upstream of the circulation pump 4 .

In figure 3 a system according to a further embodiment not according to the invention is shown in a simplified schematic representation.

The system according to figure 3 is particularly advantageous when a longer cooling distance is to be covered. Here, a further sub-cooler 12 with a heat exchanger 13 is arranged at one end of the consumer 1 or a corresponding cooling section of the sub-cooler 6 with the heat exchangers 3 and/or 5 and at the other end of the consumer 1 or the cooling section. The sub-cooler 6 is provided with the pump 7 , the further sub-cooler 12 is equipped with the cooling device 11 . In this way, excessive heating of the nitrogen in the circulating stream 2 over the (long) cooling section can be prevented.

In figure 4 a system according to a further embodiment not according to the invention is shown in a simplified schematic representation.

In contrast to the in figure 3 shown system are in the system according to figure 4 the cooling device 11 and the reservoir 8 at the same end of the consumer 1 or a corresponding cooling section and are assigned to the subcooler 6 arranged there. On the other hand, the subcooler 12 arranged at the other end is equipped with the pump 7 . In this way, the devices that take up a lot of space, namely the cooling device 11 and the reservoir 8, can be concentrated here. The pump 7, on the other hand, can be arranged at the other end, taking up little installation space, at which there may be a lack of space or where other devices are arranged.

To compensate for the loss of nitrogen caused by the pumping out by means of the pump 7, nitrogen is introduced from the reservoir 8 at one end into the circulating flow 2 via the valve 9 and not into a corresponding subcooler. This additionally injected nitrogen is mixed into the circulating flow 2 by means of a mixing device 14 . At the other end, this nitrogen is removed from the circulating stream 2 again and fed via a valve 15 and a corresponding line to the subcooler 12 provided there.

Contrary to the in figure 1 system shown is in accordance with the system figure 4 the nitrogen only in the direction from the reservoir 6 to the feed point, ie to the mixing device 14 provided here. There is no bidirectional flow of nitrogen provided, as in the in figure 1 system shown is basically possible. The pressure level in the reservoir 8 is therefore (slightly) higher than the pressure level of the nitrogen in the circulatory stream 2 upstream of the circulatory pump 4. The pressure difference used can in principle be higher or lower than the pressure level of the nitrogen in the circulatory stream 2 upstream of the circulatory pump 4.

In figure 5 a system according to a further embodiment not according to the invention is shown in a simplified schematic representation.

In the system according to figure 5 addresses the possible problem that the nitrogen fed in via the valve 9 has a comparatively high temperature and thus when mixing in by means of the mixing device 14 leads to a corresponding increase in temperature in the circulating stream 2.

Therefore, another sub-cooler 18 with a corresponding heat exchanger 16 is used here. The nitrogen to be fed into the circulating stream 2 is expanded by means of the valve 9 after it has been removed from the reservoir 8 and passed through the heat exchanger 16 . A nitrogen bath in the further subcooler 18 is provided by further nitrogen which is taken from the reservoir 8 and expanded to atmospheric pressure or slightly above by means of a further valve 17 . Some of the nitrogen released via the valve 17 evaporates. The vaporized portion is vented to the atmosphere (atm). The portion that remains in liquid form is supercooled and can therefore be used as a cooling medium.

The pressure level in the further sub-cooler 18 is at or slightly above atmospheric pressure, i.e. typically a maximum of 0.5 bar. As a result of the described cooling, the nitrogen to be fed into the circulating flow 2 is already at a temperature level of typically less than 80 K, so that corresponding losses during mixing in via the mixing device are avoided. The required cooling capacity of the cooling device 11 can also be reduced to a corresponding extent in this way.

In figure 6 a system according to a further embodiment not according to the invention is shown in a simplified schematic representation.

In extension to the in figure 5 In the system illustrated, gaseous nitrogen flowing out of the further subcooler 18 is also used as a cooling medium in the cooling device 11, which can have a Brayton cooler here in particular. A corresponding heat exchanger 19 is provided for this purpose. In this way, energy losses can be further reduced.

In the Figures 7A and 7B 1 shows a system according to an embodiment of the present invention in a simplified schematic representation in a first and a second operating or method mode and is denoted by 100 .

The first operating or process mode, which is Figure 7A is shown corresponds essentially to the (single) operating or method mode in the system according to FIG figure 6 is possible. As a supplement is in the system 100 according to Figure 7A and 7B a compressor that compresses one or more refrigerants in one or more refrigeration circuits in the closed cooling device 11, shown explicitly and denoted by 20. Such a compressor can also be used in the cooling device of the system according to FIG figure 6 be provided. Whether the vaporized nitrogen from the subcooler 15 is not, partially or fully used as a cooling medium in the closed cooling device 11 or is instead discharged to the atmosphere (atm) is basically optional.

In the Figures 7A and 7B a valve 22 and a pump 23 are also shown, which in accordance with the first mode of operation Figure 7A are closed or not in operation. This is additionally illustrated by dashed flow arrows. According to the first mode of operation Figure 7A the entire cooling capacity for cooling the nitrogen bath in the subcooler 6 is provided by the closed cooling device 11. Occurs in the system 100 according to the Figures 7A and 7B If the closed cooling device 11 is at least partially switched off or is at least partially switched off, the second operating or method mode according to FIG Figure 7B carried out or initiated. The inactivation of the closed cooling device 11 in the second operating mode is indicated by corresponding dashed elements in FIG Figure 7B illustrated. As can be seen from this, in the second method mode according to Figure 7B the closed cooling device 11 is not operated or is only operated with reduced power and further liquid nitrogen is removed from the reservoir 8, supercooled via the valve 22 and fed to the first supercooled nitrogen bath, ie the subcooler 6. In the second process mode, gaseous nitrogen is also pumped out of the first nitrogen bath, ie from the subcooler 6, by means of the pump 19 by means of the pump 23, with the pressure being reduced to a subatmospheric pressure level.

In the Figures 8A and 8B a system according to a further embodiment of the present invention is shown in a simplified schematic representation in a first and a second operating or method mode and is denoted by 200 .

The system 200 differs from the system 100 essentially in that the closed cooling device 11 is provided with two compressors or compressor stages of a compressor, denoted here by 20a and 20b. If one of them fails, as with regard to the second operating mode in Figure 8B shown, the correspondingly reduced cooling capacity can be compensated for by feeding in the nitrogen from the reservoir 8 .

In the Figures 8A and 8B a control device 50 is also illustrated in a highly simplified manner, which is set up to output a control specification to the device so that it works in the first or in the second operating mode. The control device 50 can also be set up, for example, to recognize that the closed cooling device 11 cannot be operated or can only be operated with reduced power and to switch from the first to the second operating mode on this basis.

Supplementary is in figure 9 illustrates a cooling line that can be provided in a system according to the previous figures. This is summarized here with 1000. As before, a consumer is indicated by 1 and a circulating stream by 2. Cooling passages are illustrated at 1010 and 1020 separated by a dashed line 1100 . The cooling passages 1010 and 1020 are for transporting the liquid nitrogen in the form of the circulating stream 2 from the first end to the second end along the cooling line on the one hand ("first cooling passage" 1010) and for transporting it from the second end to the first end along the cooling line on the other hand ("second cooling passage" 1020) provided and fluidically separated from each other in the sense explained above.

The first end of the cooling section 1000 has the reference number 1001, the second end of the cooling section has the reference number 1002. A feed opening (for the circulating flow 2 at the first end 1001 into the cooling section 1000 or the first cooling passage 1010) is denoted by 1011 ("first feed opening"). A removal opening (for the circuit stream 2 at the second end 1002 from the cooling section 1000 or the first cooling passage 1010) is denoted by 1012 ("first removal opening"). A feed opening (for the circuit stream 2 at the second end 1002 in the cooling section 1000 or the second cooling passage 1020) is denoted by 1021 ("second feed opening"). A bleed port (for the recycle flow 2 at the first end 1001 from the cooling section 1000 or the second cooling passage 1020) is denoted by 1022 ("second removal opening").

Claims (13)

1. Method for cooling a consumer (1) via a cooling zone extending between a first end and a second end, wherein

   - the method is performed in a first method mode in at least one first time period and in a second method mode in at least one second, different time period,

   - in the first and in the second method mode, liquid nitrogen in the form of a circulating flow (2) is continuously and repeatedly subjected to a first cooling in the circuit; supplied to the cooling zone at the first end; transported from the first end to the second end along the cooling zone; removed from the cooling zone at the second end; subjected to a second cooling; supplied to the cooling zone at the second end; transported from the second end to the first end along the cooling zone; and removed from the cooling zone at the first end,

   - in the first and in the second method mode, the first cooling is performed using a first, supercooled nitrogen bath, and the second cooling is performed using a second, supercooled nitrogen bath, wherein, in the first method mode, the first nitrogen bath is supercooled at least partially by means of a closed cooling device (11), and, in the first and in the second method mode, the second nitrogen bath is supercooled at least partially through pressure reduction to a sub-atmospheric pressure level,

   - in the first and in the second method mode, an amount of nitrogen evaporating from the second nitrogen bath due to the pressure reduction to the sub-atmospheric pressure level is at least partially compensated for from a reservoir (8) in that liquid nitrogen is removed from the reservoir (8), supercooled, and introduced into the circulating flow (2) before the circulating flow (2) is supplied to the cooling zone at the first end, and in that liquid nitrogen is discharged from the circulating flow (2) and at least partially supplied to the second nitrogen bath after the circulating flow (2) is removed from the cooling zone at the second end,

   - in the second method mode, the closed cooling device (11) is not operated or operated only at reduced power, and further liquid nitrogen is removed from the reservoir (8), supercooled, and supplied to the first supercooled nitrogen bath, and

   - furthermore, in the second method mode, by means of a pump (19), gaseous nitrogen is pumped out of the first nitrogen bath under pressure reduction to a sub-atmospheric pressure level, characterized in that

   - that in which the liquid nitrogen, in the form of the circulating flow (2), is conducted, during transport from the first end to the second end, along the cooling zone through one or more first cooling passages, and, during transport from the second end to the first end, along the cooling zone through one or more second cooling passages, which is or are fluidically separated from the one or more first cooling passages.
2. Method according to Claim 1, in which, as the closed cooling device (11), a closed cooling device (11) is used in which one or more refrigerant circuits having one or more refrigerants are formed, which is or are compressed in the first operating mode using a first number of compressors (20a, 20b) and in the second operating mode with a second, smaller number of compressors (20a).
3. Method according to one of the preceding claims, in which the liquid nitrogen conducted in the form of the circulating flow (2), after its removal at the first end of the cooling zone and before being resupplied to the first end of the cooling zone, is conducted through a circulating pump (4).
4. Method according to Claim 3, in which the liquid nitrogen conducted in the form of the circulating flow (2) is supplied to the circulating pump (4) at a first pressure level of at least 2 bar (abs.).
5. Method according to Claim 4, in which the liquid nitrogen removed from the reservoir (8) and introduced into the circulating flow (2) is removed from the reservoir (8) at a second pressure level above the first.
6. Method according to Claim 5, in which the liquid nitrogen conducted in the form of the circulating flow (2) is subjected to the first cooling before and/or after it is conducted through the circulating pump (4).
7. Method according to one of Claims 3 through 6, in which the liquid nitrogen removed from the reservoir (8) and introduced into the circulating flow (2) is introduced into the circulating flow (2) before the circulating flow (2) is conducted through the circulating pump (4).
8. Method according to one of Claims 3 through 7, in which the liquid nitrogen removed from the reservoir (8) in the first and in the second method mode and introduced into the circulating flow (2), as well as the further liquid nitrogen removed from the reservoir (8) in the second method mode and supplied to the first, supercooled nitrogen bath, are cooled using a third, supercooled nitrogen bath before being introduced into the circulating flow (2).
9. Method according to Claim 8, in which the the third, supercooled nitrogen bath is provided by further liquid nitrogen being removed from the reservoir (8) at the first pressure level and expanded to a third pressure level with partial evaporation.
10. Method according to Claim 9, in which a portion of the further liquid nitrogen from the reservoir (8) that was not evaporated in the expansion to the third pressure level is supplied at least partially to the third nitrogen bath, and a portion of the further liquid nitrogen from the reservoir (8) that evaporated in the expansion to the third pressure level is used at least partially as a coolant in the closed cooling device (11).
11. Method according to Claim 10, in which a cooling device with a Brayton cooler is used as the closed cooling device (11).
12. Device for cooling a consumer (1) via a cooling zone, which extends between a first end and a second end, wherein the device can be operated in a first operating mode in at least one first time period and in a second operating mode in at least one second, different time period, and has:

    - means, comprising heat exchangers (3, 5, 13) and a circulating pump (4), which are configured so that, in the first and second operating modes, liquid nitrogen in the form of a circulating flow (2) is continuously and repeatedly subjected in the circuit to a first cooling; supplied to the cooling zone at the first end; transported from the first end to the second end along the cooling zone; removed from the cooling zone at the second end; subjected to a second cooling; supplied to the cooling zone at the second end; transported from the second end to the first end along the cooling zone; and removed from the cooling zone at the first end,

    - means which are configured to perform, in the first and second operating modes, the first cooling using a first, supercooled nitrogen bath and the second cooling using a second, supercooled nitrogen bath; a closed cooling device (11) configured, in the first operating mode, to cool the first nitrogen bath; and means, comprising a vacuum pump (7), which are configured to supercool the second nitrogen bath in the first and second operating modes at least partially by pressure reduction to a sub-atmospheric pressure level, and

    - means which are configured to at least partially compensate from a reservoir (8) for an amount of nitrogen evaporating from the second nitrogen bath due to the pressure reduction to the sub-atmospheric pressure level, in that they remove liquid nitrogen from the reservoir and introduce it into the circulating flow (2) before the circulating flow (2) is supplied to the cooling zone at the first end, and in that they discharge liquid nitrogen from the circulating flow (2) and at least partially supply it to the second nitrogen bath after the circulating flow (2) is removed from the cooling zone at the second end,

    - means which are configured to remove further liquid nitrogen from the reservoir (8), to supercool and to supply it to the first, supercooled nitrogen bath whenever, in the second operating mode, the closed cooling device (11) is not operated or is operated only at reduced power,

    - a pump (19) which is configured to pump, in the second operating mode, gaseous nitrogen out of the first nitrogen bath under pressure reduction to a sub-atmospheric pressure level, and

    - a control device (50) which is configured to output a control specification to the device so that it operates in the first or in the second operating mode, characterized in that, in which, for transporting the liquid nitrogen in the form of the circulating flow from the first end to the second end along the cooling zone, one or more first cooling passage(s) is or are provided, and, for transporting from the second end to the first end along the cooling zone, one or more second cooling passage(s) that is or are fluidically separated from the one or more first cooling passage(s) is or are provided.
13. System (100, 200) having a consumer (1) to be cooled, characterized by a device according to Claim 12.

Images