DE102019206904B4 - Process for cooling a fluid mixture - Google Patents

Abstract

Method for carrying out a cooling process with a fluid mixture formed with at least two components, in which (a) the fluid mixture is compressed in at least one compressor (1) from a low pressure to a high pressure and then cooled in a recooler (2),( b) the fluid mixture is successively passed through a first (3), second (4) and third (5) stage of a heat exchanger, the fluid mixture releasing heat and being cooled to a first temperature, (c) the fluid mixture in a phase separator (6 ) and a first mass partial flow of the fluid mixture is separated by condensation from a second mass partial flow of the fluid mixture,(d) the second gaseous mass partial flow of the fluid mixture is passed through the third (5) and second (4) stage of the heat exchanger, with the second gaseous mass partial flow of the fluid mixture absorbs heat and is heated to a second temperature,(e) the second gaseous mass partial flow of the fluid mixture Coming from the second (4) stage of the heat exchanger, it is expanded in an expander (7) to perform work and is thereby cooled to a third temperature, (f) the first partial mass flow of the fluid mixture is passed out of the phase separator (6) by means of a control valve (8) expanded and mixed again with the second gaseous partial mass flow of the fluid mixture coming from the expander (7),(g) the fluid mixture formed with the first and the second partial mass flow through the third (5), second (4) and first (3) stage of a heat exchanger, absorbing heat in the process and an application fluid (9) conducted countercurrently through the third stage (5) of the heat exchanger gives off heat, the application fluid (9) being cooled from an initial to an end temperature, and the fluid mixture being cooled by the first Stage (3) of the heat exchanger is passed back into the at least one compressor (1) and the cooling cycle defined by steps (a)-(g) again to be led.

Description

The invention relates to methods for carrying out a cooling process with a fluid mixture that is formed with at least two components. The methods according to the invention are particularly suitable for cooling high-temperature superconductors.

High temperature superconductors formed with copper oxide and having a critical temperature above 77 K, the condensation temperature of nitrogen at atmospheric pressure, are usually cooled with liquid nitrogen. In order to increase the current-carrying capacity of the superconductors, temperatures below 77 K are aimed for. For this task, the nitrogen can be expanded to a sub-atmospheric pressure, which lowers the temperature due to the Joule-Thomson effect. However, such systems require a continuous supply of liquid nitrogen. In addition, the efficiency is low because only the latent cooling capacity is used. The subatmospheric pressure required for this is also often assessed as a safety risk.

Brayton cycles are a possible alternative to the above-mentioned process. In a Brayton cycle, helium, neon or a mixture of these gases can be compressed as a refrigerant in a compressor, pre-cooled in a heat exchanger and then expanded in a turbine to perform work. The cooling task is then fulfilled with the cold of the expanded gas. Thus, only a temperature range between the turbine inlet temperature and the turbine outlet temperature can be used for the cooling. In the temperature range of 75 K to 65 K, which is relevant for the cooling of high-temperature superconductors, the pressure ratios with which the turbine is operated then also result. Conversely, the low turbine output means that very high mass flows of the refrigerant are required, which means that the size of the system also increases unfavorably. Alternatively, a Brayton cycle could be performed with a turbine operating at a high pressure ratio. However, given the very low temperatures to be achieved, this would have a negative effect on the efficiency of the process. The efficiency can be improved if the refrigerant flows through several turbines and is repeatedly heated up between two turbines. A disadvantage of this technical solution is that several turbines have to be operated at a comparatively low speed and a large number of expensive rotating machines are required.

In principle, a Claude cycle can also be used, in which a gas is pre-cooled with a partial flow guided through a turbine and then liquefied by adiabatic throttling. In this case, however, only nitrogen and oxygen would come into question as components with which the gas is formed. Furthermore, these circuits would require a very low pressure level after throttling and would require correspondingly large systems due to the low gas density. Usually there are also problems with sealing against the ambient pressure.

That's it DE 1 763 370 A a method is known with which an electrical device can be kept at a very low temperature.

It is therefore the object of the invention to propose efficient and reliable cooling methods with a high level of efficiency which avoid the disadvantages listed above.

According to the invention, the object is achieved with the features mentioned in claim 1 and claim 2. Advantageous variants result from the features mentioned in the dependent claims.

The invention relates to a method for carrying out a cooling process with a fluid mixture formed with at least two components, in which (a) the fluid mixture is compressed in at least one compressor from a low pressure to a high pressure and then cooled in a recooler, (b) the fluid mixture is successively passed through a first, second and third stage of a heat exchanger, the fluid mixture releasing heat and being cooled to a first temperature, (c) the fluid mixture is passed into a phase separator and a first bulk flow of the fluid mixture by condensation of a second bulk flow of the fluid mixture is separated, (d) the second gaseous mass partial flow of the fluid mixture is passed through the third and second stage of the heat exchanger, with the second gaseous mass partial flow of the fluid mixture absorbing heat and being heated to a second temperature, (e) the second gaseous mass partial flow of fluid acc ischs coming from the second stage of the heat exchanger is expanded in an expander to produce work and thereby cooled to a third temperature, (f) the first mass partial flow of the fluid mixture is passed out of the phase separator, expanded by means of a control valve and the second gaseous mass partial flow of the fluid mixture coming from the expander is mixed in again, (g) the fluid mixture formed with the first and the second mass partial flow is passed through the third, second and first stage of a heat exchanger, absorbing heat in the process and passing it countercurrently through the third stage of the heat application fluid conducted by the exchanger emits heat, the application fluid being cooled from an initial temperature to a final temperature, and the fluid mixture coming from the first stage of the heat exchanger being conducted back into the at least one compressor and which is defined by steps (a)-(g). cooling cycle is performed again.

The invention relates to a further method or a variant of the method described above for carrying out a cooling process with a fluid mixture formed with at least two components, in which (a) the fluid mixture is compressed in at least one compressor from a low pressure to a high pressure and then is cooled in a recooler, (b) the fluid mixture is passed successively through a first, second and third stage of a heat exchanger, the fluid mixture giving off heat and being cooled to a first temperature, (c) the fluid mixture passed into a phase separator and a first Mass partial flow of the fluid mixture is separated by condensation from a second mass partial flow of the fluid mixture, (d) the second gaseous mass partial flow of the fluid mixture is passed through the third and second stage of the heat exchanger, with the second gaseous mass partial flow of the fluid mixture absorbing heat and heating it to a second temperature mt, (e) the second gaseous mass partial flow of the fluid mixture coming from the second stage of the heat exchanger is expanded in an expander to produce work and thereby cooled to a third temperature, (f) the first mass partial flow of the fluid mixture is passed out of the phase separator and at least a first part of the first partial mass flow of the fluid mixture is supplied to an application, and a second part of the first partial mass flow of the fluid mixture is expanded by means of a control valve and mixed again with the second gaseous partial mass flow of the fluid mixture coming from the expander, (g) which is mixed with the second part of the first partial mass flow of the Fluid mixture and the second mass partial flow of the fluid mixture formed part of the fluid mixture is passed through the third stage of the heat exchanger, thereby absorbing heat and coming from the application first part of the first mass partial flow of the fluid mixture is mixed again and the recombined Fluidgem isch is passed through the second and the first stage of the heat exchanger and thereby absorbs heat, and the fluid mixture coming from the first stage of the heat exchanger is passed back into the at least one compressor and the cooling cycle defined by steps (a) - (g) again is carried out.

The work output obtained in the expander in step (e) can be used to compress the fluid mixture in the at least one compressor in step (a). The expander can be formed with one or more turbines. In particular, one or more turbines can be operated with a large pressure ratio. This can be achieved in that the second temperature or the turbine inlet temperature of the second mass partial flow of the fluid mixture is significantly greater than the outlet temperature of the application fluid or the third temperature.

The heat exchanger can be designed as a countercurrent heat exchanger. The mass flow of the fluid mixture in step (b) can flow through the counterflow heat exchanger in a direction opposite to the mass flow, mass partial flow and/or part of the mass partial flow of the fluid mixture in step (g), with the mass flow of the fluid mixture giving off heat in step (b) and the Mass flow, mass partial flow and / or part of the mass partial flow of the fluid mixture in step (g) absorbs heat. The second partial mass flow of the fluid mixture in step (d) preferably also flows through the countercurrent heat exchanger in a direction opposite to the mass flow of the fluid mixture in method step (b), the mass flow of the fluid mixture giving off heat in step (b) and the second mass partial flow of the fluid mixture in step ( d) absorbs heat.

The first partial mass flow of the fluid mixture is preferably formed with components which have a condensation temperature at the high pressure which is greater than the first temperature. As a result, the component(s) forming the first partial mass flow of the fluid mixture in step (c) can at least form a large one during and/or after the flow through the first, second and/or third stage of the heat exchanger in step (b). Part condense and then present in a liquid state in the phase separator. The heat exchanger is preferably designed such that the condensation of at least one component(s) forming the first mass partial flow of the fluid mixture in step (c) begins before the fluid mixture has flowed through the third stage of the heat exchanger.

In addition, it has an advantageous effect if the second partial mass flow of the fluid mixture is formed in step (c) with at least one component that has a condensation temperature at the low pressure that is lower than the third temperature. Preferably, all of the components forming the second bulk flow of the fluid mixture have a condensation temperature at the low pressure that is lower than the third temperature. It can thereby be achieved that the component(s) of the Fluid mixture during the entire cooling process or in the entire cooling cycle does not condense / condense and is in a gaseous state / are present.

The first part of the first mass partial flow of the fluid mixture can be formed with the same component or the same components as the second part of the first mass partial flow of the fluid mixture. However, it can also prove to be advantageous if the first part of the first mass partial flow of the fluid mixture is formed with one component of the fluid mixture and the second part of the first mass partial flow of the fluid mixture is formed with another component of the fluid mixture.

The second partial mass flow of the fluid mixture can be formed with helium, neon, nitrogen and/or hydrogen as a component of the fluid mixture. The first partial mass flow of the fluid mixture can be formed with oxygen, nitrogen and/or one or more hydrocarbon(s) as component(s) of the fluid mixture.

The second partial flow by mass is preferably formed with neon with a mole fraction of 80 mol % and the first mass partial flow of the fluid mixture with nitrogen with a mole fraction of 20 mol %. The first partial flow by mass can also be formed with nitrogen with a mole fraction of 17 mol % and with oxygen with a mole fraction of 3 mol %.

The methods according to the invention can be carried out efficiently in a temperature range between 65K and 75K in particular. They are therefore particularly suitable for cooling high-temperature superconductors. In this case, the application fluid and/or the first mass partial flow of the fluid mixture is/are advantageously formed with nitrogen.

The choice of components of the fluid mixture also determines the pressure and temperature levels at which the process can be efficiently operated. For example, the low pressure may be less than or equal to 0.6 MPa and the high pressure may be greater than or equal to 1.2 MPa. The at least one compressor and/or the expander are preferably set up in such a way that the ratio between the high pressure and the low pressure is at least 3:1.

After flowing through the precooler in step (a) of the method, the temperature of the fluid mixture can be at the ambient temperature level and can be 300 K, for example. The heat exchanger can be designed in such a way that the first temperature of the fluid mixture after flowing through the heat exchanger in step (b) of the method is less than 70 K. The temperature of the fluid mixture can be less than 120 K after flowing through the first stage of the heat exchanger and less than 85 K after flowing through the second stage of the heat exchanger. The second temperature of the second partial flow by mass of the fluid mixture, which can be identical to the expander inlet temperature, can accordingly be between 85 K and 120 K. The third temperature, which can be identical to the expander outlet temperature, can be less than 70K, preferably less than 65K. Preferably, the temperature of the first mass partial flow after expansion by means of the control valve in step (f) is less than 65 K.

With the method according to the invention, an application fluid can then be cooled from an initial temperature, which can be greater than or equal to 75 K, to a final temperature, which can be less than or equal to 65 K. Alternatively, the cold of a first part of the first mass partial flow of the fluid mixture with a temperature of preferably less than 65 K can be used in an application, e.g. in the cooling of high-temperature superconductors.

The invention offers, inter alia, the following additional advantages: since only the second partial mass flow is passed through the expander, the low pressures of a Claude cycle, which is operated with nitrogen as the refrigerant, can be avoided with the method according to the invention. As a result, a plant carrying out the method according to the invention can be realized in a compact design. This also enables a corresponding system to be sealed more efficiently against the ambient pressure. Since preferably only the first mass partial flow of the fluid mixture can contain nitrogen, condensation of the nitrogen on the expander or on the turbine is also avoided. This also contributes to the fact that a turbine can be operated with a high pressure ratio. Another advantage is the small number of rotating machines required to carry out the methods according to the invention. This contributes in particular to higher cost efficiency, reliability and availability.

Embodiments of the invention are illustrated in the drawings and are based on the 1 and 2 explained in more detail.

• 1 eine schematische Darstellung des erfindungsgemäßen Verfahrens, bei dem ein Anwendungsfluid gekühlt wird, und
• 2 eine schematische Darstellung einer Variante des erfindungsgemäßen Verfahrens, bei dem ein Teil des Fluidgemischs direkt der Anwendung zugeführt wird.

show:

• 1 a schematic representation of the method according to the invention, in which an application fluid is cooled, and
• 2 a schematic representation of a variant of the method according to the invention, in which part of the fluid mixture is fed directly to the application.

1 FIG. 12 shows schematically a method for performing a cooling process with a fluid mixture formed with neon as a component of the fluid mixture at a mole fraction of 80 mole % and with nitrogen as a component of the fluid mixture at a mole fraction of 20 mole %.

In step (a) of the method according to the invention, the fluid mixture, in which both nitrogen and neon are initially present in a gaseous state, is compressed in a compressor 1 as a compressor from a low pressure, which is 0.6 MPa, to a high pressure, which is 2 MPa is, compressed and then cooled in a recooler 2 by means of water or air. Before entering compressor 1 as a compressor, the temperature of the fluid mixture is 295 K. After exiting recooler 2, the temperature of the fluid mixture is 300 K.

In step (b) of the method according to the invention, the fluid mixture is passed successively through a first 3, a second 4 and a third stage 5 of the heat exchanger, which is designed as a countercurrent heat exchanger. The fluid mixture emits so much heat that the nitrogen condenses as a component of the fluid mixture and changes from the gaseous to the liquid state. After the first stage 3 of the heat exchanger, the temperature of the fluid mixture is still 105 K. After the second stage 4 of the heat exchanger, the temperature is 75 K. After flowing through the third stage 5 of the heat exchanger, the first temperature is only 66.5 K. The pressure of the fluid mixture has decreased only slightly by less than 0.02 MPa or has remained constant. Since the condensation temperature of nitrogen is about 91 K at a total pressure of about 2 MPa, the condensation of nitrogen as a component of the fluid mixture starts while the fluid mixture flows through the second stage 4 of the heat exchanger. In contrast, the condensation temperature of neon is well below 50 K at a pressure of about 2 MPa, so neon as a component of the fluid mixture remains in a gaseous state.

In step (c), the fluid mixture formed after step (b) with nitrogen in a liquid state and neon in a gaseous state is passed into a phase separator 6 . In the phase separator 6, a first partial mass flow of the fluid mixture, which is formed with liquid nitrogen, is separated from a second mass partial flow of the fluid mixture, which is formed with gaseous neon.

In step (d), the second partial mass flow of the fluid mixture, which is formed with gaseous neon, is again conducted in the opposite direction through the third 5 and second stage 4 of the heat exchanger. The second partial mass flow of the fluid mixture, which is formed with gaseous neon, absorbs heat and increases its temperature from the first temperature at 66.5 K to the second temperature at 96 K.

In step (e), the second mass partial flow of the fluid mixture, which is formed with gaseous neon, coming from the second stage 4 of the heat exchanger, is expanded to perform work in an expander 7, which is designed as a turbine 7, and is thereby brought to the third temperature, the 64th .5 K, cooled. Before entry into the turbine 7, the pressure of the second partial mass flow of the fluid mixture, which is formed with gaseous neon, is still 2 MPa. After exiting the turbine 7, the pressure of the second partial mass flow of the fluid mixture, which is formed with gaseous neon, is only 0.6 MPa. Thus, the turbine 7 can be operated efficiently with a pressure ratio greater than 3:1.

In step (f), the first partial mass flow of the fluid mixture, which is formed with liquid nitrogen, is passed out of the phase separator 6 and expanded by means of a control valve 8 . Subsequently, the first mass partial flow of the fluid mixture, which is formed with liquid nitrogen, is mixed back into the second mass partial flow of the fluid mixture, which comes from the expander 7 and is formed with gaseous neon.

In step (g), the fluid mixture formed or recombined with the first and the second partial flow of mass is conducted again through the third 5, second 4 and first stage 3 of the heat exchanger. The fluid mixture absorbs heat. As it flows through the third stage 5 of the heat exchanger, the temperature of the fluid mixture increases from 63.8 K to 73 K. After further flow through the second stage 4 of the heat exchanger, the temperature of the fluid mixture is already 96 K before the fluid mixture exits the first Stage 3 of the heat exchanger has reached a temperature of 295 K and a pressure of 0.6 MPa.

A countercurrent flow through the third stage 5 of the heat exchanger application fluid 9 gives off heat to the fluid mixture, the application fluid 9 from an initial temperature of 75 K at a pressure of 0.1 MPa to a final temperature of 65 K at a pressure just below 0.1 MPa is cooled and can then be supplied to the application.

The fluid mixture coming from the first stage 3 of the heat exchanger is fed back into the compressor 1 as a compressor and the refrigeration cycle defined by steps (a)-(g) begins again.

In 2 a variant of the method according to the invention for carrying out a cooling process with a fluid mixture which is formed with at least two components is shown. Recurring features are in 2 with the same reference numbers as in 1 Mistake. The fluid mixture with neon as a component of the fluid mixture with a mole fraction of 80 mol% and with nitrogen as a component of the fluid mixture with a mole fraction of 17 mol% and with oxygen as a further component of the fluid mixture with a mole fraction of 3 mol -% educated.

In step (a) of a variant of the method according to the invention, the fluid mixture, in which both oxygen, nitrogen and neon are initially in a gaseous state, is compressed in a compressor 1 as a compressor from a low pressure, which is 0.33 MPa, to a high pressure , which is 1.2 MPa, compressed and then cooled in a recooler 2 by means of water or air. Before entering compressor 1 as a compressor, the temperature of the fluid mixture is 295.7 K. After exiting recooler 2, the temperature of the fluid mixture is 300 K.

In step (b) of a variant of the method according to the invention, the fluid mixture is passed through a first 3, a second 4 and a third stage 5 of the heat exchanger, which is designed as a countercurrent heat exchanger. The fluid mixture emits so much heat that the nitrogen and oxygen condense as components of the fluid mixture and change from the gaseous to the liquid state. After the first stage 3 of the heat exchanger, the temperature of the fluid mixture is still 113 K. After the second stage 4 of the heat exchanger, the temperature is 80 K. After flowing through the third stage 5 of the heat exchanger, the first temperature is only 65 K. The pressure of the fluid mixture has decreased only slightly by less than 0.02 MPa or has remained almost constant. Since the condensation temperature of nitrogen is about 84 K at a total pressure of about 1.2 MPa and that of oxygen is higher than 81 K, the condensation of nitrogen and oxygen as components of the fluid mixture starts while the fluid mixture passes the second stage 4 of the heat exchanger flows through. In contrast, the condensation temperature of neon is well below 50 K at a pressure of about 1.2 MPa, so neon as a component of the fluid mixture remains in a gaseous state.

In step (c) of a variant of the method according to the invention, the fluid mixture formed after step (b) with nitrogen and oxygen each in a liquid state and with neon in a gaseous state is passed into a phase separator 6 . In the phase separator 6, a first partial mass flow of the fluid mixture, which is formed with liquid nitrogen and liquid oxygen, is separated from a second mass partial flow of the fluid mixture, which is formed with gaseous neon.

In step (d) of a variant of the method according to the invention, the second mass partial flow of the fluid mixture, which is formed with gaseous neon, is passed again in the countercurrent direction through the third 5 and second stage 4 of the heat exchanger. The second partial mass flow of the fluid mixture, which is formed with gaseous neon, absorbs heat and increases its temperature from the first temperature at 65 K to the second temperature at 105 K.

In step (e) of a variant of the method according to the invention, the second partial mass flow of the fluid mixture, which is formed with gaseous neon, coming from the second stage 4 of the heat exchanger, is expanded to perform work in an expander 7, which is designed as a turbine 7, and is thereby applied to the third temperature, which is 69.7 K, cooled. Before entry into the turbine 7, the pressure of the second partial mass flow of the fluid mixture, which is formed with gaseous neon, is still 1.2 MPa. After exiting the turbine 7, the pressure of the second partial mass flow of the fluid mixture, which is formed with gaseous neon, is only 0.35 MPa. Thus, the turbine 7 can be operated efficiently with a pressure ratio greater than 3:1.

In step (f) of a variant of the method according to the invention, a first part of the first mass partial flow of the fluid mixture, which is formed with liquid nitrogen and liquid oxygen, is fed to an application, and a second part of the first mass partial flow of the fluid mixture, which consists of liquid nitrogen and is formed with liquid oxygen, expanded by means of a control valve 8 and the coming from the expander 7 second partial mass flow of the fluid mixture, which is formed with gaseous neon, mixed again.

In step (g) a variant of the method according to the invention, the fluid mixture formed with the second part of the first mass partial flow and the second mass partial flow is through the third Stage 5 of the heat exchanger passed and then the first part 9 coming from the application of the first partial flow of mass, which has a temperature of 75 K, mixed again. The fluid mixture recombined in this way is then passed through the second 4 and first stage 3 of the heat exchanger, absorbing heat in the process and, after exiting the first stage 3 of the heat exchanger, reaches a temperature of 295.7 K at a pressure of 0.33 MPa.

The fluid mixture coming from the first stage 3 of the heat exchanger is fed into the compressor 1 as a compressor and the refrigeration cycle defined by steps (a) - (g) begins again.

The values cited above for pressure and temperature levels result from a numerical simulation of the method according to the invention. Realistic process losses were taken into account in the simulation. The compressor 1 as a compressor, the recooler 2, the stages 3-5 of the heat exchanger, the phase separator 6, the expander 7, and the control valve 8 are preferably set up in such a way that the process actually achieved or measured during a process carried out over several cooling cycles Values for the pressure and temperature levels do not differ by more than 10% from the simulated values quoted in the exemplary embodiments described above.

Claims (8)

Method for carrying out a cooling process with a fluid mixture which is formed with at least two components, in which (a) the fluid mixture is compressed in at least one compressor (1) from a low pressure to a high pressure and then cooled in a dry cooler (2), (b) the fluid mixture is passed sequentially through a first (3), second (4) and third (5) stage of a heat exchanger, wherein the fluid mixture releases heat and is cooled to a first temperature, (c) the fluid mixture is fed into a phase separator (6) and a first partial flow by mass of the fluid mixture is separated by condensation from a second partial flow by mass of the fluid mixture, (d) the second gaseous mass partial flow of the fluid mixture is passed through the third (5) and second (4) stage of the heat exchanger, the second gaseous mass partial flow of the fluid mixture absorbing heat and being heated to a second temperature, (e) the second gaseous mass partial flow of the fluid mixture coming from the second (4) stage of the heat exchanger is expanded to perform work in an expander (7) and thereby cooled to a third temperature, (f) the first partial mass flow of the fluid mixture is passed out of the phase separator (6), expanded by means of a control valve (8) and mixed again with the second gaseous mass partial flow of the fluid mixture coming from the expander (7), (g) the fluid mixture formed with the first and the second partial mass flow is passed through the third (5), second (4) and first (3) stage of a heat exchanger, absorbing heat in the process and passing a countercurrent flow through the third stage (5) of the The application fluid (9) conducted by the heat exchanger emits heat, the application fluid (9) being cooled from an initial temperature to a final temperature, and the fluid mixture coming from the first stage (3) of the heat exchanger being conducted back into the at least one compressor (1) and the cooling cycle defined by steps (a) - (g) is performed again. Method for carrying out a cooling process with a fluid mixture formed with at least two components, in which (a) the fluid mixture is compressed in at least one compressor (1) from a low pressure to a high pressure and then cooled in a recooler (2), ( b) the fluid mixture is successively passed through a first (3), second (4) and third (5) stage of a heat exchanger, the fluid mixture releasing heat and being cooled to a first temperature, (c) the fluid mixture in a phase separator (6 ) and a first mass partial flow of the fluid mixture is separated by condensation from a second mass partial flow of the fluid mixture, (d) the second gaseous mass partial flow of the fluid mixture is passed through the third (5) and second (4) stage of the heat exchanger, with the second gaseous mass partial flow of the fluid mixture absorbs heat and is heated to a second temperature, (e) the second gaseous mass partial flow of the fluid id mixture coming from the second stage of the heat exchanger (4) in an expander (7) to perform work and is thereby cooled to a third temperature, (f) the first partial mass flow of the fluid mixture is passed out of the phase separator (6) and at least a first part of the first Partial mass flow of the fluid mixture is supplied to an application, and a second part of the first partial mass flow of the fluid mixture is expanded by means of a control valve (8) and mixed again with the second gaseous mass partial flow of the fluid mixture coming from the expander (7), (g) the one with the second part the part of the fluid mixture formed by the first partial mass flow of the fluid mixture and the second partial mass flow of the fluid mixture is passed through the third stage of the heat exchanger (5), heat in the process and is remixed with the first part of the first mass partial flow of the fluid mixture coming from the application and the recombined fluid mixture is passed through the second (4) and the first (3) stage of the heat exchanger and thereby absorbs heat, and the fluid mixture from the first stage of the heat exchanger (3) is fed back into the at least one compressor (1) and the cooling cycle defined by steps (a)-(g) is carried out again. Method according to one of the preceding claims, characterized in that the work output obtained in the expander (7) in step (e) is used to compress the fluid mixture in the at least one compressor (1) in step (a). Method according to one of the preceding claims , characterized in that the first partial mass flow of the fluid mixture is formed with components which have a condensation temperature at the high pressure which is greater than the first temperature and the second mass partial flow of the fluid mixture is formed with components which have a condensation temperature at the Have low pressure that is lower than the third temperature. Method according to one of the preceding claims , characterized in that the second partial mass flow of the fluid mixture is formed with helium, neon, nitrogen and/or hydrogen as a component of the fluid mixture and the first mass partial flow of the fluid mixture is formed with oxygen, nitrogen and/or one or more hydrocarbons ) is formed as a component of the fluid mixture. Method according to one of the preceding claims , characterized in that the second mass partial flow of the fluid mixture with neon as a component of the fluid mixture with a mole fraction of 80 mol% and the first mass partial flow of the fluid mixture with nitrogen as a component of the fluid mixture with a mole fraction of 20 mol% formed or the first partial mass flow of the fluid mixture is formed with nitrogen as a component of the fluid mixture with a mole fraction of 17 mol% and with oxygen as a component of the fluid mixture with a mole fraction of 3 mol%. Method according to one of the preceding claims , characterized in that the at least one compressor (1) and/or the expander (7) is/are set up in such a way that the ratio between the high pressure and the low pressure is at least 3:1. Method according to one of the preceding claims, characterized in that high-temperature superconductors are cooled with the application fluid or with the first part of the first mass partial flow of the fluid mixture.

Images