EP0849550B1 - Process for low temperature cooling of a load and liquefied gas refrigeration system for performing the process - Google Patents

Process for low temperature cooling of a load and liquefied gas refrigeration system for performing the process Download PDF

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Publication number
EP0849550B1
EP0849550B1 EP97111987A EP97111987A EP0849550B1 EP 0849550 B1 EP0849550 B1 EP 0849550B1 EP 97111987 A EP97111987 A EP 97111987A EP 97111987 A EP97111987 A EP 97111987A EP 0849550 B1 EP0849550 B1 EP 0849550B1
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EP
European Patent Office
Prior art keywords
liquefied gas
heat exchanger
pressure
cooling
cooling system
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EP97111987A
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German (de)
French (fr)
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EP0849550A1 (en
Inventor
Werner Konrad Diehl
Bernd Gottschlich
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Messer Griesheim GmbH
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Messer Griesheim GmbH
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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25D—REFRIGERATORS; COLD ROOMS; ICE-BOXES; COOLING OR FREEZING APPARATUS NOT OTHERWISE PROVIDED FOR
    • F25D29/00—Arrangement or mounting of control or safety devices
    • F25D29/001—Arrangement or mounting of control or safety devices for cryogenic fluid systems
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25D—REFRIGERATORS; COLD ROOMS; ICE-BOXES; COOLING OR FREEZING APPARATUS NOT OTHERWISE PROVIDED FOR
    • F25D3/00—Devices using other cold materials; Devices using cold-storage bodies
    • F25D3/10—Devices using other cold materials; Devices using cold-storage bodies using liquefied gases, e.g. liquid air

Definitions

  • the invention relates to a liquid gas cooling system for cooling a Consumer at low temperature and a method of cooling a consumer Low temperature.
  • a liquid gas cooling system of this type is known from DE 1601910 A1, in which Liquid nitrogen at Ambient pressure is filled into an insulated cooling container, around the second liquid gas circulating in the heat exchanger circuit, also to cool liquid nitrogen or another suitable gas.
  • the heat exchanger circuit has one Subcooling heat exchanger in the liquid gas bath in the Cooling container is arranged, and on the other hand, a usual Heat exchanger, which is connected to the consumer in a heat-conducting manner, to cool it.
  • a method for cooling a consumer to low temperature in which a cryogenic liquid gas is filled into a cooling container, a cryogenic gas is pumped around in a heat exchanger circuit and passed through a subcooling heat exchanger in the cooling container and then to the consumer, whereby the pressure in the heat exchanger circuit is set above the ambient pressure.
  • DE-A-29 29 709 further discloses a liquid gas cooling system with a cooling container for taking a first cryogenic liquid gas, with a pipeline system for a second cryogenic liquid gas, which comprises a subcooling heat exchanger in the cooling container and which leads to a consumer, and wherein the pressure in the piping system is set above the ambient pressure.
  • the invention solves this problem with a liquid gas cooling system with the features of claim 3 or by a method for Cooling a consumer to low temperature with the characteristics of Claim 1.
  • the liquid gas in the cooling tank always strives for its Equilibrium state (boiling point) at which pressure and temperature have a fixed relationship.
  • the internal pressure in the cooling container thus arises accordingly lower boiling temperature; for example when using Liquid nitrogen results from lowering the internal pressure to approximately 0.14 bar a boiling point of the liquid gas bath of about 64 K (liquid nitrogen changes to the solid phase at 63 K).
  • a liquid gas cooling system is for continuous use expedient, which cools the liquid gas and constantly pumped in a circuit.
  • Pressure control device provided to the pressure in the Set the heat exchanger circuit above ambient pressure.
  • the liquid gas system according to the invention has a supercooling heat exchanger device, which is arranged in the liquid gas bath to the in Heat exchanger circuit, under positive pressure, circulating second liquid gas to cool below its boiling temperature hold. Furthermore, the heat exchanger circuit has an outside of the Cooling container lying heat exchanger device, which with the object to be cooled or consumer thermally connected is.
  • the cables When cooling one or more HTSL cables as consumers can it should be expedient to put this directly into the second liquid gas to introduce leading pipe system, the cables then from the supercooled liquefied gas.
  • the Vacuum pump preferably pressure controlled to maintain a constant Set the boiling pressure of the liquid gas in the cooling tank.
  • a automatic level control For the level control of the liquid gas bath, a automatic level control provided.
  • the heat exchanger circuit preferably contains one Circulation pump, the performance of which is designed to be a uninterrupted flow of the second liquid gas with a Speed generated at which the return temperature of the Liquid gas despite the heat input by the consumer under the Boiling temperature in the heat exchanger circuit.
  • the invention is relatively simple, without large a low-temperature cooling system created with which, for example, when using Liquid nitrogen as liquid gas temperatures from below 77 K up to 64 K can be achieved by using the liquid gas bath temperature Pumping off the nitrogen gas phase using a vacuum pump is lowered.
  • the liquid gas in the heat exchanger circuit which can also be liquid nitrogen, with a pumped static pressure, which is above ambient pressure to ensure that only pure gas-free liquid nitrogen is present in the circuit is pumped, which is always in the supercooled state.
  • This supercooled liquid nitrogen can be used, for example, to cool High temperature superconductor cables are used to the to achieve and maintain superconductive state.
  • FIG. 1 shows a schematic representation of a liquid gas cooling system according to the invention, which uses liquid nitrogen (LN 2 ) as the first and second liquid gas.
  • LN 2 liquid nitrogen
  • Known safety devices of the liquid gas cooling system required have not been shown for reasons of clarity.
  • a cooling container 10 is shown, which is surrounded by a vacuum insulation jacket 12 and sealed gas-tight with a cover 14.
  • the cooling container 10 contains a liquid gas bath 16.
  • the following description relates to the use of liquid nitrogen (LN 2 ) as the liquid gas both for the liquid gas bath 16 in the cooling container 10 and for the heat exchanger circuit, which is generally designated 18.
  • the cooling principle according to the invention can also be transferred to other cryogenic liquefied gases, for example argon (Ar), neon (Ne), hydrogen (H 2 ), helium (He) or oxygen (O 2 ).
  • These liquid gases can be used in a suitable combination for the liquid gas bath 16 in the cooling container and as heat exchanger gas in the heat exchanger circuit 18.
  • Extraction line 20 for the nitrogen gas phase 22 On the cover 14 of the cooling container 10 is one Extraction line 20 for the nitrogen gas phase 22 attached.
  • a vacuum pump 24 with a vacuum pressure control device is removed 26 provided.
  • a gas heater 28 In the shown Embodiment is in the extraction line 20 in front of the vacuum pump 24 a gas heater 28 is arranged.
  • the heat exchanger circuit 18 comprises a piping system 30 which from a supercooling heat exchanger 32, which in the Liquid gas bath 16 is arranged in the cooling container 10, via a Liquefied gas pump 34 leads to a consumer 36, which via a another heat exchanger 38 is thermally conductive with the liquid gas in the Pipeline 30 is connected. If the consumer is a HTSL cable or the like, this can also directly into a pipe section of the Pipe system 30 introduced and washed around by the liquid gas are, so that then a heat exchanger 38 in the classic sense is not necessary is.
  • the heat exchanger circuit 18 further comprises a circuit pressure control device 40 to one in the piping system 30 static pressure that is above the ambient pressure. Finally, the heat exchanger circuit 18 contains one Filling device 42 for filling and refilling liquid gas in the Piping system 30.
  • a Liquid gas supply device 44 for the cooling container 10 with a level measuring device 46, which the filling level of the Liquid gas bath 16 is detected in the cooling container and a signal to controllable valve 48 can output to a feed line 50 for Open or close liquid nitrogen depending on the filling level.
  • the embodiment of the LPG cooling system according to the invention works as follows.
  • Cryogenic liquid nitrogen is supplied via line 50, usually at Ambient pressure and 77 K, filled in the cooling container 10 until a predetermined level is reached what the Level detection device 46 recognizes, and the valve 48th is closed.
  • the vacuum pump 24 pumps over the line 20 and the gas heater 28 part of the nitrogen gas phase 22 from the Cooling container 10 from.
  • the vacuum pump 24 is a vacuum pressure regulator 26 assigned to the vacuum pump 24 in Cooling container 10 generated negative pressure to a constant value, z. B. 0.1462 bar. It is important that the internal pressure in the Cooling tank is below atmospheric pressure.
  • the function of the Gas heater 28 is about to prevent the vacuum pump set 24 is damaged by the cryogenic gas masses to be pumped out. When using, for example, a cryogenic fan as Vacuum pump, the gas heater 28 can also be omitted.
  • the vacuum pump 24 By means of the vacuum pump 24 is thus by pumping the Nitrogen gas phase, the boiling pressure of the nitrogen is lowered, so that the nitrogen bath 16 below its ambient pressure Boiling temperature, ie below 77 K, cools down; at a pressure of about 0.14 bar results in a boiling bath temperature of about 64 K.
  • About the Vacuum pressure regulator 26 of the vacuum pump 24 can have the boiling pressure and thus the boiling point of the liquid nitrogen to a desired one Value can be set.
  • the automatic Level control 24 used in order to evaporation and Pumping down liquid nitrogen from a (not shown) to replenish the storage tank.
  • the Subcooling heat exchanger 32 In the liquid gas bath 16 is the Subcooling heat exchanger 32, by means of which Circulation pump 34 is also pumped liquid nitrogen.
  • the Pressure control device 40 generates a static pressure of more than 1 bar in the heat exchanger circuit 18 to ensure that the boiling point of that in the heat exchanger circuit Liquid nitrogen significantly above that of the nitrogen bath 16 in Cooling container 10 is located, so that only pure gas-free in the circuit Liquid nitrogen is pumped around, which is always in the supercooled Condition.
  • the supercooling heat exchanger 32 is like this dimensioned that the nitrogen temperature in the pipeline 30 only is slightly above the nitrogen bath temperature, d. H. that the Liquid nitrogen in the heat exchanger circuit 18 when passing through the Subcooling heat exchanger 33 essentially the temperature of the Nitrogen bath 16 adopts.
  • the delivery rate of the circulation pump 34 is designed so that the return temperature in the pipe 30 despite of the heat input by the consumer 36 under the Boiling temperature of the liquid nitrogen in the circuit 18 is.
  • the consumer 36 can use a heat exchanger 38 be connected in a heat-conducting manner to the heat exchanger circuit 18; he can also directly into a section of the piping system 30 be introduced.
  • the vacuum pump is during the operation of the invention LPG cooling system not only able to use the nitrogen bath 16 by pumping the gas phase 22 to a temperature below 77 K. cool, but it keeps the liquid gas bath 16 during the overall operation of the cooling system on a predetermined Temperature by the pressure in the cooling tank 10 on a specified value, under ambient pressure (1 bar). Pumps for this the vacuum pump 24 which due to the heat input by the Supercooling heat exchanger 32 evaporating amount of nitrogen; at the refilling of liquid nitrogen to maintain a constant Vacuum pump 24 pumps levels of the liquid gas bath 16 additionally generated gas masses and relaxes the internal pressure in the cooling container 10 to the predetermined value in order to Cool the liquid gas bath 16 back to the predetermined temperature.
  • the entire LPG cooling system can be transported in one The rack can be integrated to make it easy to handle and universal to make it usable.
  • the LPG circulation pump 34, the Liquid gas filling device 32 and the circuit pressure control device 40 can be integrated in the supercooling heat exchanger 32 in order to to make the overall system more compact.
  • cooling system according to the invention in automatic operation it is advisable to run pressure monitoring, Level and temperature measuring points with alarm signal outputs and suitable displays at different points in the overall system provided.

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  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Physics & Mathematics (AREA)
  • Mechanical Engineering (AREA)
  • Thermal Sciences (AREA)
  • General Engineering & Computer Science (AREA)
  • Filling Or Discharging Of Gas Storage Vessels (AREA)

Description

Die Erfindung betrifft ein Flüssiggas-Kühlungssystem zur Kühlung eines Verbrauchers auf Tieftemperatur und ein Verfahren zum Kühlen eines Verbrauchers auf Tieftemperatur.The invention relates to a liquid gas cooling system for cooling a Consumer at low temperature and a method of cooling a consumer Low temperature.

Aus der DE 1601910 A1 ist ein Flüssiggas - Kühlsystem dieser Art bekannt, bei dem Flüssigstickstoff bei Umgebungsdruck in einen isolierten Kühlungsbehälter eingefüllt wird, um das in dem Wärmetauscherkreislauf umlaufende zweite Flüssiggas, ebenfalls Flüssigstickstoff oder ein anderes geeignetes Gas, zu kühlen. Der Wärmetauscherkreislauf hat einerseits einen Unterkühlungswärmetauscher, der im Flüssiggasbad in dem Kühlungsbehälter angeordnet ist, und andererseits einen üblichen Wärmetauscher, der mit dem Verbraucher wärmeleitend verbunden ist, um diesen zu kühlen.A liquid gas cooling system of this type is known from DE 1601910 A1, in which Liquid nitrogen at Ambient pressure is filled into an insulated cooling container, around the second liquid gas circulating in the heat exchanger circuit, also to cool liquid nitrogen or another suitable gas. The heat exchanger circuit has one Subcooling heat exchanger in the liquid gas bath in the Cooling container is arranged, and on the other hand, a usual Heat exchanger, which is connected to the consumer in a heat-conducting manner, to cool it.

Aus der DE-A-1 601 910 ist auch ein Verfahren zur Kühlung eines Verbrauchers auf Tieftemperatur bekannt, bei dem
ein tiefkaltes Flüssiggas in einen Kühlungsbehälter gefüllt wird,
ein tiefkaltes Gas in einem Wärmetauscherkreislauf umgepumpt und durch einen Unterkühlungswärmetauscher im Kühlungsbehälter sowie anschließend zu dem Verbraucher geführt wird, wobei
der Druck im Wärmetauscherkreislauf über dem Umgebungsdruck eingestellt wird.From DE-A-1 601 910 a method for cooling a consumer to low temperature is known, in which
a cryogenic liquid gas is filled into a cooling container,
a cryogenic gas is pumped around in a heat exchanger circuit and passed through a subcooling heat exchanger in the cooling container and then to the consumer, whereby
the pressure in the heat exchanger circuit is set above the ambient pressure.

Die DE-A-29 29 709 offenbart weiterhin ein Flüssiggas-Kühlungssystem
mit einem Kühlungsbehälter zum Autnehmen eines ersten tiefkalten Flüssiggases,
mit einem Rohrleitungssystem für ein zweites tiefkaltes Flüssiggas, das einen Unterkühlungswärmetauscher im Kühlungsbehälter umfasst und das zu einem Verbraucher führt, und wobei
der Druck im Rohrleitungssystem über dem Umgebungsdruck eingestellt ist.DE-A-29 29 709 further discloses a liquid gas cooling system
with a cooling container for taking a first cryogenic liquid gas,
with a pipeline system for a second cryogenic liquid gas, which comprises a subcooling heat exchanger in the cooling container and which leads to a consumer, and wherein
the pressure in the piping system is set above the ambient pressure.

Bei den bekannten Kühlsystemen dieser Art tritt das Problem auf, daß beispielsweise Flüssigstickstoff bei Umgebungsdruck (1 bar) eine Siedetemperatur von 77 K hat, so daß sich selbst bei Einfüllung von unterkühltem Flüssiggas mit der Zeit im Flüssiggasbad eine Temperatur von 77 K einstellt, und daß das in dem Wärmetauscherkreislauf umlaufende Flüssiggas zur Kühlung des Verbrauchers nicht unter diese Temperatur abgekühlt werden kann.In the known cooling systems of this type occurs the problem that, for example, liquid nitrogen Ambient pressure (1 bar) has a boiling temperature of 77 K, so that itself when filling in supercooled liquefied gas over time Liquid gas bath sets a temperature of 77 K, and that in the Circulating liquefied gas for cooling the heat exchanger circuit Consumer cannot be cooled below this temperature.

Bei gewissen Anwendungen (zum Beispiel HTSL-Kabeln) sollte jedoch zum Erreichen und Aufrechterhalten des supraleitenden Zustands auf Temperaturen von weniger als 77 K abgekühlt werden. Auch andere Anwendungen bzw. Verbraucher des Flüssiggas-Kühlungssystems können eine Abkühlung auf Temperaturen unter 77 K bzw. unter die jeweilige Siedetemperatur (bei Umgebungsdruck) des verwendeten Flüssiggases erforderlich machen.For certain applications (e.g. HTSL cables), however, should to achieve and maintain the superconducting state Temperatures of less than 77 K can be cooled. Others too Applications or consumers of the liquid gas cooling system can cool down to temperatures below 77 K or below respective boiling temperature (at ambient pressure) of the used Make liquid gas necessary.

Es ist daher eine Aufgabe der Erfindung ein Flüssiggas-Kühlungssystem anzugeben, mit dem tiefere Temperaturen als beim Stand der Technik erzielt werden können, insbesondere Temperaturen unter der dem Umgebungsdruck entsprechenden Siedetemperatur.It is therefore an object of the invention to provide a liquid gas cooling system specify at which lower temperatures than in the prior art can be achieved, especially temperatures below that Ambient boiling temperature.

Die Erfindung löst diese Aufgabe durch ein Flüssiggas-Kühlungssystem mit den Merkmalen von Anspruch 3 bzw. durch ein Verfahren zur Kühlung eines Verbrauchers auf Tieftemperatur mit den Merkmalen von Anspruch 1. The invention solves this problem with a liquid gas cooling system with the features of claim 3 or by a method for Cooling a consumer to low temperature with the characteristics of Claim 1.

Das Flüssiggas in dem Kühlungsbehälter strebt stets seinem Gleichgewichtszustand (Siedepunkt) zu, bei dem Druck und Temperatur in einem festen Verhältnis stehen. Durch das Absenken des Innendrucks im Kühlungsbehälter stellt sich somit eine entsprechend tiefere Siedetemperatur ein; beispielsweise bei Verwendung von Flüssigstickstoff ergibt sich durch Absenken des Innendrucks auf etwa 0,14 bar eine Siedetemperatur des Flüssiggasbades von etwa 64 K (Flüssigstickstoff geht bei 63 K in die feste Phase über).The liquid gas in the cooling tank always strives for its Equilibrium state (boiling point) at which pressure and temperature have a fixed relationship. By lowering the The internal pressure in the cooling container thus arises accordingly lower boiling temperature; for example when using Liquid nitrogen results from lowering the internal pressure to approximately 0.14 bar a boiling point of the liquid gas bath of about 64 K (liquid nitrogen changes to the solid phase at 63 K).

Durch das Absenken der Temperatur des Flüssiggasbades im Kühlungsbehälter auf unter 77 K kann in dem Wärmetauscherkreislauf ein unterkühlter Flüssiggasstrom, insbesondere Flüssigstickstoffstrom, erzeugt werden, wenn der Druck im Wärmetauscherkreislauf höher ist als im Kühlungsbehälter. Für den Dauereinsatz ist ein Flüssiggas-Kühlsystem zweckmäßig, welches das Flüssiggas unterkühlt und ständig im Kreislauf umpumpt.By lowering the temperature of the liquid gas bath in the Cooling tanks below 77 K can be in the heat exchanger circuit a supercooled liquid gas flow, in particular liquid nitrogen flow, are generated when the pressure in the heat exchanger circuit is higher than in the cooling tank. A liquid gas cooling system is for continuous use expedient, which cools the liquid gas and constantly pumped in a circuit.

Um zu gewährleisten, daß das Flüssiggas im Wärmetauscherkreislauf stets in der Flüssigphase bleibt, wird eine Druckregeleinrichtung vorgesehen, um den Druck im Wärmetauscherkreislauf über Umgebungsdruck einzustellen. Durch Erhöhung des Drucks ergibt sich eine entsprechende Erhöhung der Siedetemperatur des umlaufenden Flüssiggases.To ensure that the liquefied gas in the heat exchanger circuit remains in the liquid phase at all times Pressure control device provided to the pressure in the Set the heat exchanger circuit above ambient pressure. By An increase in pressure results in a corresponding increase in Boiling temperature of the circulating liquid gas.

Das erfindungsgemäße Flüssiggassystem weist eine Unterkühlungs-Wärmetauschereinrichtung auf, welche im Flüssiggasbad angeordnet ist, um das im Wärmetauscherkreislauf, unter Überdruck, umlaufende zweite Flüssiggas unter seine Siedetemperatur abzukühlen bzw. zu halten. Ferner hat der Wärmetauscherkreislauf eine außerhalb des Kühlungsbehälters liegende Wärmetauschereinrichtung, welche mit dem zu kühlenden Gegenstand oder Verbraucher wärmeleitend verbunden ist. Bei Kühlung eines oder mehrerer HTSL-Kabel als Verbraucher kann es zweckmäßig sein, diese unmittelbar in ein das zweite Flüssiggas führendes Rohrsystem einzubringen, wobei die Kabel dann von dem unterkühlten Flüssiggas umspült werden.The liquid gas system according to the invention has a supercooling heat exchanger device, which is arranged in the liquid gas bath to the in Heat exchanger circuit, under positive pressure, circulating second liquid gas to cool below its boiling temperature hold. Furthermore, the heat exchanger circuit has an outside of the Cooling container lying heat exchanger device, which with the object to be cooled or consumer thermally connected is. When cooling one or more HTSL cables as consumers can it should be expedient to put this directly into the second liquid gas to introduce leading pipe system, the cables then from the supercooled liquefied gas.

Um die Flüssiggastemperatur im Flüssiggasbad abzusenken, wird also bei der vorliegenden Erfindung der Innendruck und somit der Siededruck des Flüssiggases, insbesondere des Flüssigstickstoffs, im Kühlungsbehälter abgesenkt. Dies geschieht durch Abpumpen der Gasphase mittels der Vakuumpumpe. Die Vakuumpumpe ist in der Lage,

  • 1.
    soviel Flüssiggas aus der Gasphase in dem Kühlungsbehälter abzupumpen, daß eine Absenkung des Innendrucks unter Umgebungsdruck zur Abkühlung des Flüssiggasbades und zur Aufrechterhaltung einer Temperatur, welche unter der Siedetemperatur bei Umgebungsdruck liegt, erreicht wird (für Flüssigstickstoff beispielsweise unter 77 K);
  • 2.
    die aufgrund des Wärmeeintrags durch den Unterkühlungswärmetauscher verdampfende Gasmenge abzupumpen;
  • 3.
    die zusätzliche Gasmasse abzupumpen, welche bei der Nachfüllung von Flüssiggas zur Niveauhaltung des Flüssiggasbades im Kühlungsbehälter entsteht; und
  • 4.
    die zur Niveauhaltung nachgefüllte Flüssiggasmenge auf einen Druck unter Umgebungsdruck zu entspannen, um deren Abkühlung auf eine Temperatur, welche unter der Siedetemperatur bei Umgebungsdruck (z.B. 77 K) liegt, zu erreichen.
    • In order to lower the liquid gas temperature in the liquid gas bath, the internal pressure and thus the boiling pressure of the liquid gas, in particular of the liquid nitrogen, in the cooling container are reduced in the present invention. This is done by pumping off the gas phase using the vacuum pump. The vacuum pump is able
  • 1.
    pumping out so much liquid gas from the gas phase in the cooling container that a reduction in the internal pressure below ambient pressure for cooling the liquid gas bath and for maintaining a temperature which is below the boiling temperature at ambient pressure is achieved (for liquid nitrogen, for example, below 77 K);
  • Second
    pump out the amount of gas evaporating due to the heat input through the supercooling heat exchanger;
  • Third
    pumping out the additional mass of gas which arises during the refilling of liquid gas to maintain the liquid gas bath in the cooling tank; and
  • 4th
    to relax the amount of liquid gas refilled to maintain a pressure below ambient pressure in order to cool it down to a temperature which is below the boiling point at ambient pressure (for example 77 K).

    • Um eine Beschädigung der Vakuumpumpe durch die tiefkalten abzupumpenden Gasmassen zu vermeiden, kann zwischen der Vakuumpumpe und dem Kühlungsbehälter eine Gasanwärmeinrichtung angeordnet sein.In order to damage the vacuum pump by the cryogenic avoiding gas masses to be pumped out can occur between the Vacuum pump and the cooling tank a gas heating device be arranged.

    Zur Sicherstellung einer konstanten Flüssiggasbadtemperatur wird die Vakuumpumpe vorzugsweise druckgeregelt, um einen konstanten Siededruck des Flüssiggases im Kühlungsbehälter einzustellen.To ensure a constant liquid gas bath temperature, the Vacuum pump preferably pressure controlled to maintain a constant Set the boiling pressure of the liquid gas in the cooling tank.

    Zur Niveauregelung des Flüssiggasbades wird vorzugsweise eine automatische Füllstandsregelung vorgesehen.For the level control of the liquid gas bath, a automatic level control provided.

    Schließlich enthält der Wärmetauscherkreislauf vorzugsweise eine Umwälzpumpe, deren Leistung so ausgelegt ist, daß sie eine ununterbrochene Strömung des zweiten Flüssiggases mit einer Geschwindigkeit erzeugt, bei der die Rücklauftemperatur des Flüssiggases trotz des Wärmeeintrags durch den Verbraucher unter der Siedetemperatur im Wärmetauscherkreislauf liegt.Finally, the heat exchanger circuit preferably contains one Circulation pump, the performance of which is designed to be a uninterrupted flow of the second liquid gas with a Speed generated at which the return temperature of the Liquid gas despite the heat input by the consumer under the Boiling temperature in the heat exchanger circuit.

    Durch die Erfindung wird auf relativ einfache Weise, ohne großen zusätzlichen Energieaufwand ein Tieftemperatur-Kühlsystem geschaffen, mit dem beispielsweise bei Verwendung von Flüssigstickstoff als Flüssiggas Temperaturen von unter 77 K bis zu 64 K erzielt werden können, indem die Flüssiggasbadtemperatur durch Abpumpen der Stickstoff-Gasphase mittels einer Vakuumpumpe abgesenkt wird. Das Flüssiggas im Wärmetauscherkreislauf, welches ebenfalls Flüssigstickstoff sein kann, wird mit einem statischen Druck umgepumpt, der über Umgebungsdruck liegt, um sicherzustellen, daß im Kreislauf nur reiner gasfreier Flüssigstickstoff umgepumpt wird, der sich stets im unterkühlten Zustand befindet. Dieser unterkühlte Flüssigstickstoff kann beispielsweise zum Kühlen von Hochtemperatursupraleiterkabeln verwendet werden, um den supraleitfähigen Zustand zu erreichen und aufrechtzuerhalten.The invention is relatively simple, without large a low-temperature cooling system created with which, for example, when using Liquid nitrogen as liquid gas temperatures from below 77 K up to 64 K can be achieved by using the liquid gas bath temperature Pumping off the nitrogen gas phase using a vacuum pump is lowered. The liquid gas in the heat exchanger circuit, which can also be liquid nitrogen, with a pumped static pressure, which is above ambient pressure to ensure that only pure gas-free liquid nitrogen is present in the circuit is pumped, which is always in the supercooled state. This supercooled liquid nitrogen can be used, for example, to cool High temperature superconductor cables are used to the to achieve and maintain superconductive state.

    Eine bevorzugte Ausführungsform der Erfindung ist im folgenden mit Bezug auf die einzige Figur näher erläutert. Diese zeigt eine schematische Darstellung eines Flüssiggas-Kühlungssystems gemäß der Erfindung, welches Flüssigstickstoff (LN2) als erstes und zweites Flüssiggas verwendet. Erforderliche bekannte Sicherheitseinrichtungen des Flüssiggas-Kühlungssystems wurden aus Übersichtsgründen nicht dargestellt.A preferred embodiment of the invention is explained in more detail below with reference to the single figure. This shows a schematic representation of a liquid gas cooling system according to the invention, which uses liquid nitrogen (LN 2 ) as the first and second liquid gas. Known safety devices of the liquid gas cooling system required have not been shown for reasons of clarity.

    In der Figur ist ein Kühlungsbehälter 10 dargestellt, welcher von einem Vakuumisolationsmantel 12 umgeben und mit einer Abdeckung 14 gasdicht verschlossen ist. Der Kühlungsbehälter 10 enthält ein Flüssiggasbad 16. Die folgende Beschreibung bezieht sich auf die Verwendung von Flüssigstickstoff (LN2) als Flüssiggas sowohl für das Flüssiggasbad 16 im Kühlungsbehälter 10 als auch für den Wärmetauscherkreislauf, der allgemein mit 18 bezeichnet ist. Das erfindungsgemäße Kühlungsprinzip kann jedoch auch auf andere tiefkalt verflüssigte Gase übertragen werden, z.B. Argon (Ar), Neon (Ne), Wasserstoff (H2), Helium (He) oder Sauerstoff (O2). Diese Flüssiggase können in geeigneter Kombination für das Flüssiggasbad 16 im Kühlungsbehälter und als Wärmetauschergas im Wärmetauscherkreislauf 18 verwendet werden. In the figure, a cooling container 10 is shown, which is surrounded by a vacuum insulation jacket 12 and sealed gas-tight with a cover 14. The cooling container 10 contains a liquid gas bath 16. The following description relates to the use of liquid nitrogen (LN 2 ) as the liquid gas both for the liquid gas bath 16 in the cooling container 10 and for the heat exchanger circuit, which is generally designated 18. However, the cooling principle according to the invention can also be transferred to other cryogenic liquefied gases, for example argon (Ar), neon (Ne), hydrogen (H 2 ), helium (He) or oxygen (O 2 ). These liquid gases can be used in a suitable combination for the liquid gas bath 16 in the cooling container and as heat exchanger gas in the heat exchanger circuit 18.

    An der Abdeckung 14 des Kühlungsbehälters 10 ist eine Entnahmeleitung 20 für die Stickstoffgasphase 22 angebracht. Für die Entnahme ist eine Vakuumpumpe 24 mit einer Vakuum-Druckregeleinrichtung 26 vorgesehen. Bei der gezeigten Ausführungsform ist in der Entnahmeleitung 20 vor der Vakuumpumpe 24 ein Gasanwärmer 28 angeordnet.On the cover 14 of the cooling container 10 is one Extraction line 20 for the nitrogen gas phase 22 attached. For the A vacuum pump 24 with a vacuum pressure control device is removed 26 provided. In the shown Embodiment is in the extraction line 20 in front of the vacuum pump 24 a gas heater 28 is arranged.

    Der Wärmetauscherkreislauf 18 umfaßt ein Rohrleitungssystem 30, das von einem Unterkühlungswärmetauscher 32, welcher in dem Flüssiggasbad 16 im Kühlungsbehälter 10 angeordnet ist, über eine Flüssiggaspumpe 34 zu einem Verbraucher 36 führt, der über einen weiteren Wärmetauscher 38 wärmeleitend mit dem Flüssiggas in der Rohrleitung 30 verbunden ist. Wenn der Verbraucher ein HTSL-Kabel oder dergleichen ist, kann dieser auch direkt in ein Rohrstück des Rohrleitungssystems 30 eingebracht und von dem Flüssiggas umspült werden, so daß dann ein Wärmetauscher 38 im klassischen Sinne nicht notwendig ist.The heat exchanger circuit 18 comprises a piping system 30 which from a supercooling heat exchanger 32, which in the Liquid gas bath 16 is arranged in the cooling container 10, via a Liquefied gas pump 34 leads to a consumer 36, which via a another heat exchanger 38 is thermally conductive with the liquid gas in the Pipeline 30 is connected. If the consumer is a HTSL cable or the like, this can also directly into a pipe section of the Pipe system 30 introduced and washed around by the liquid gas are, so that then a heat exchanger 38 in the classic sense is not necessary is.

    Der Wärmetauscherkreislauf 18 umfaßt ferner eine Kreislauf-Druckregeleinrichtung 40, um in dem Rohrleitungssystem 30 einen statischen Druck einzustellen, der über dem Umgebungsdruck liegt. Schließlich enthält der Wärmetauscherkreislauf 18 noch eine Fülleinrichtung 42 zum Ein- und Nachfüllen von Flüssiggas in das Rohrleitungssystem 30.The heat exchanger circuit 18 further comprises a circuit pressure control device 40 to one in the piping system 30 static pressure that is above the ambient pressure. Finally, the heat exchanger circuit 18 contains one Filling device 42 for filling and refilling liquid gas in the Piping system 30.

    In der Figur ebenfalls dargestellt ist eine Flüssiggasversorgungseinrichtung 44 für den Kühlungsbehälter 10 mit einer Füllstandsmeßeinrichtung 46, welche das Füllniveau des Flüssiggasbades 16 im Kühlbehälter erfaßt und ein Signal an ein steuerbares Ventil 48 ausgeben kann, um eine Speiseleitung 50 für Flüssigstickstoff abhängig vom Füllniveau zu öffnen oder zu schließen. Also shown in the figure is a Liquid gas supply device 44 for the cooling container 10 with a level measuring device 46, which the filling level of the Liquid gas bath 16 is detected in the cooling container and a signal to controllable valve 48 can output to a feed line 50 for Open or close liquid nitrogen depending on the filling level.

    Die Ausführungsform des erfindungsgemäßen Flüssiggas-Kühlungssystems arbeitet wie folgt.The embodiment of the LPG cooling system according to the invention works as follows.

    Tiefkalter Flüssigstickstoff wird über die Leitung 50, in der Regel bei Umgebungsdruck und 77 K, in den Kühlungsbehälter 10 eingefüllt, bis ein vorgegebenes Niveau erreicht ist, was die Füllstandserfassungseinrichtung 46 erkennt, und das Ventil 48 geschlossen wird. Die Vakuumpumpe 24 pumpt über die Leitung 20 und den Gasanwärmer 28 einen Teil der Stickstoffgasphase 22 aus dem Kühlungsbehälter 10 ab. Der Vakuumpumpe 24 ist ein Vakuum-Druckregler 26 zugeordnet, um den von der Vakuumpumpe 24 im Kühlungsbehälter 10 erzeugten Unterdruck auf einen konstanten Wert, z. B. 0,1462 bar, einzustellen. Wichtig ist, daß der Innendruck im Kühlungsbehälter unter Atmosphärendruck liegt. Die Funktion des Gasanwärmers 28 ist dabei, zu verhindern, daß der Vakuumpumpensatz 24 durch die tiefkalten abzupumpenden Gasmassen beschädigt wird. Bei Verwendung beispielsweise eines kryotauglichen Gebläses als Vakuumpumpe kann der Gasanwärmer 28 auch weggelassen werden.Cryogenic liquid nitrogen is supplied via line 50, usually at Ambient pressure and 77 K, filled in the cooling container 10 until a predetermined level is reached what the Level detection device 46 recognizes, and the valve 48th is closed. The vacuum pump 24 pumps over the line 20 and the gas heater 28 part of the nitrogen gas phase 22 from the Cooling container 10 from. The vacuum pump 24 is a vacuum pressure regulator 26 assigned to the vacuum pump 24 in Cooling container 10 generated negative pressure to a constant value, z. B. 0.1462 bar. It is important that the internal pressure in the Cooling tank is below atmospheric pressure. The function of the Gas heater 28 is about to prevent the vacuum pump set 24 is damaged by the cryogenic gas masses to be pumped out. When using, for example, a cryogenic fan as Vacuum pump, the gas heater 28 can also be omitted.

    Mittels der Vakuumpumpe 24 wird also durch Abpumpen der Stickstoffgasphase der Siededruck des Stickstoffs abgesenkt, so daß das Stickstoffbad 16 unter seine dem Umgebungsdruck entsprechende Siedetemperatur, also unter 77 K, abkühlt; bei einem Druck von etwa 0,14 bar ergibt sich eine Siedebadtemperatur von etwa 64 K. Über den Vakuum-Druckregler 26 der Vakuumpumpe 24 kann der Siededruck und somit die Siedetemperatur des Flüssigstickstoffs auf einen gewünschten Wert eingestellt werden.By means of the vacuum pump 24 is thus by pumping the Nitrogen gas phase, the boiling pressure of the nitrogen is lowered, so that the nitrogen bath 16 below its ambient pressure Boiling temperature, ie below 77 K, cools down; at a pressure of about 0.14 bar results in a boiling bath temperature of about 64 K. About the Vacuum pressure regulator 26 of the vacuum pump 24 can have the boiling pressure and thus the boiling point of the liquid nitrogen to a desired one Value can be set.

    Zur Niveauregelung des Stickstoffbades 16 wird die automatische Füllstandsregelung 24 eingesetzt, um in Folge der Verdampfung und Abpumpung verlorengegangenen Flüssigstickstoff aus einem (nicht gezeigten) Vorratstank nachzuspeisen.For the level control of the nitrogen bath 16, the automatic Level control 24 used in order to evaporation and Pumping down liquid nitrogen from a (not shown) to replenish the storage tank.

    In dem Flüssiggasbad 16 befindet sich der Unterkühlungswärmetauscher 32, durch welchen mittels der Umwälzpumpe 34 ebenfalls flüssiger Stickstoff gepumpt wird. Die Druckregeleinrichtung 40 erzeugt dabei einen statischen Druck von mehr als 1 bar in dem Wärmetauscherkreislauf 18, um sicherzustellen, daß die Siedetemperatur des im Wärmetauscherkreislauf befindlichen Flüssigstickstoffs deutlich über der des Stickstoffbades 16 im Kühlungsbehälter 10 liegt, so daß im Kreislauf nur reiner gasfreier Flüssigstickstoff umgepumpt wird, der sich stets im unterkühlten Zustand befindet. Der Unterkühlungswärmetauscher 32 ist so dimensioniert, daß die Stickstofftemperatur in die Rohrleitung 30 nur geringfügig über der Stickstoffbadtemperatur liegt, d. h. daß der Flüssigstickstoff im Wärmetauscherkreislauf 18 bei Durchlaufen des Unterkühlungswärmertauschers 33 im wesentlichen die Temperatur des Stickstoffbades 16 annimmt. Die Förderleistung der Umwälzpumpe 34 ist so ausgelegt, daß die Rücklauftemperatur in der Rohrleitung 30 trotz des Wärmeeintrags durch den Verbraucher 36 unter der Siedetemperatur des Flüssigstickstoffs im Kreislauf 18 liegt.In the liquid gas bath 16 is the Subcooling heat exchanger 32, by means of which Circulation pump 34 is also pumped liquid nitrogen. The Pressure control device 40 generates a static pressure of more than 1 bar in the heat exchanger circuit 18 to ensure that the boiling point of that in the heat exchanger circuit Liquid nitrogen significantly above that of the nitrogen bath 16 in Cooling container 10 is located, so that only pure gas-free in the circuit Liquid nitrogen is pumped around, which is always in the supercooled Condition. The supercooling heat exchanger 32 is like this dimensioned that the nitrogen temperature in the pipeline 30 only is slightly above the nitrogen bath temperature, d. H. that the Liquid nitrogen in the heat exchanger circuit 18 when passing through the Subcooling heat exchanger 33 essentially the temperature of the Nitrogen bath 16 adopts. The delivery rate of the circulation pump 34 is designed so that the return temperature in the pipe 30 despite of the heat input by the consumer 36 under the Boiling temperature of the liquid nitrogen in the circuit 18 is.

    Der Verbraucher 36 kann, wie gesagt, über einen Wärmetauscher 38 wärmeleitend mit dem Wärmetauscherkreislauf 18 verbunden sein; er kann auch direkt in einen Abschnitt des Rohrleitungssystems 30 eingebracht werden.As stated, the consumer 36 can use a heat exchanger 38 be connected in a heat-conducting manner to the heat exchanger circuit 18; he can also directly into a section of the piping system 30 be introduced.

    Die Vakuumpumpe ist während des Betriebs des erfindungsgemäßen Flüssiggas-Kühlungssystems nicht nur in der Lage, das Stickstoffbad 16 durch Abpumpen der Gasphase 22 auf eine Temperatur unter 77 K abzukühlen, sondern sie hält das Flüssiggasbad 16 während des gesamten Betriebs des Kühlungssystems auf einer vorgegebenen Temperatur, indem sie den Druck im Kühlungsbehälter 10 auf einem vorgegebenen Wert, unter Umgebungsdruck (1 bar), hält. Hierfür pumpt die Vakuumpumpe 24 die aufgrund des Wärmeeintrags durch den Unterkühlungswärmetauscher 32 verdampfende Stickstoffmenge ab; bei der Nachfüllung von Flüssigstickstoff zur Einhaltung eines konstanten Niveaus des Flüssiggasbades 16 pumpt die Vakuumpumpe 24 zusätzlich entstehende Gasmassen ab und entspannt den Innendruck in dem Kühlungsbehälter 10 auf den vorgegebenen Wert, um das Flüssiggasbad 16 wieder auf die vorgegebene Temperatur abzukühlen.The vacuum pump is during the operation of the invention LPG cooling system not only able to use the nitrogen bath 16 by pumping the gas phase 22 to a temperature below 77 K. cool, but it keeps the liquid gas bath 16 during the overall operation of the cooling system on a predetermined Temperature by the pressure in the cooling tank 10 on a specified value, under ambient pressure (1 bar). Pumps for this the vacuum pump 24 which due to the heat input by the Supercooling heat exchanger 32 evaporating amount of nitrogen; at the refilling of liquid nitrogen to maintain a constant Vacuum pump 24 pumps levels of the liquid gas bath 16 additionally generated gas masses and relaxes the internal pressure in the cooling container 10 to the predetermined value in order to Cool the liquid gas bath 16 back to the predetermined temperature.

    Das gesamte Flüssiggas-Kühlsystem kann in einem transportablen Gestell integriert werden, um es gut handhabbar und universell einsetzbar zu machen. Die Flüssiggas-Umwälzpumpe 34, die Flüssiggas-Fülleinrichtung 32 und die Kreislauf-Druckregeleinrichtung 40 können in dem Unterkühlungswärmetauscher 32 integriert sein, um das Gesamtsystem kompakter zu gestalten.The entire LPG cooling system can be transported in one The rack can be integrated to make it easy to handle and universal to make it usable. The LPG circulation pump 34, the Liquid gas filling device 32 and the circuit pressure control device 40 can be integrated in the supercooling heat exchanger 32 in order to to make the overall system more compact.

    Wenn das erfindungsgemäße Kühlsystem im automatischen Betrieb laufen soll, ist es zweckmäßig, zur Prozeßüberwachung Druck-, Füllstands- und Temperaturmeßstellen mit Alarmsignalausgängen und geeigneten Anzeigen an unterschiedlichen Stellen des Gesamtsystems vorzusehen.If the cooling system according to the invention in automatic operation it is advisable to run pressure monitoring, Level and temperature measuring points with alarm signal outputs and suitable displays at different points in the overall system provided.

    Claims (11)

    1. Method for cooling a consumer to a low temperature, in which
      a first cryogenic liquefied gas is introduced into a cooling vessel (10), and the internal pressure in the cooling vessel (10) is reduced to below the ambient pressure, in order to reduce the boiling point of the first liquefied gas,
      a second cryogenic liquefied gas is pumped around a heat exchanger circuit (18) and is guided through a supercooling heat exchanger (32) in the cooling vessel (10) and then to the consumer (36), in which method
      the pressure in the heat exchanger circuit (18) is set at above the ambient pressure, in order for the liquefied gas in the heat exchanger circuit (18) always to be kept in the liquid phase.
    2. Method according to Claim 1, characterized in that an uninterrupted flow of the second liquefied gas is effected in the heat exchanger circuit (18).
    3. Liquefied-gas cooling system for carrying out the method according to Claim 1 or 2,
      having a cooling vessel (10) for receiving a first cryogenic liquefied gas,
      having a heat exchanger circuit (18) for a second cryogenic liquefied gas, which comprises a supercooling heat exchanger (32) in the cooling vessel (10) and is thermally conductively connected to the consumer (36) or has been introduced into that of the consumers,
      having a vacuum pump (24) for pumping gaseous first liquefied gas out of the cooling vessel (10), in order to reduce the internal pressure in the cooling vessel to below ambient pressure or to hold the internal pressure in the cooling vessel below ambient pressure,
      and having a circuit pressure-control device (40) for the heat exchanger circuit (18), in order to set the pressure in the heat exchanger circuit (18) to above ambient pressure.
    4. Liquefied gas cooling system according to Claim 3, characterized in that the first and second liquefied gases are selected from the following group of gases: nitrogen, argon, neon, hydrogen, helium, oxygen.
    5. Liquefied gas cooling system according to Claim 3 or 4, characterized in that the first and second liquefied gases are identical.
    6. Liquefied gas cooling system according to one of Claims 3 to 5, characterized by a vacuum pressure control device (26) for the vacuum pump.
    7. Liquefied gas cooling system according to one of Claims 3 to 6, characterized in that the heat exchanger circuit (18) has a pipeline system (30) which carries the second liquefied gas and into which the consumer is fitted.
    8. Liquefied gas cooling system according to one of Claims 3 to 7, characterized in that a heating device (28) is provided between the vacuum pump (24) and the cooling vessel (10) in order to heat the gas before it enters the vacuum pump.
    9. Liquefied gas cooling system according to one of Claims 3 to 8, characterized by a level-control device (44) for the first cryogenic liquefied gas in the cooling vessel (10).
    10. Liquefied gas cooling system according to one of Claims 3 to 9, characterized in that the heat exchanger circuit (18) has a recirculation pump (34), in order produce an uninterrupted flow of the second liquefied gas at a rate which is such [lacuna].
    11. Liquefied gas cooling system according to one of Claims 3 to 10, characterized in that the first and second liquefied gases are liquid nitrogen, and in that the vacuum pump (24) generates a subatmospheric pressure of between approximately 0.14 and 1 less than bar [sic], in order to cool the liquid nitrogen to approximately 64 K to less than 77 K.
    EP97111987A 1996-12-18 1997-07-15 Process for low temperature cooling of a load and liquefied gas refrigeration system for performing the process Expired - Lifetime EP0849550B1 (en)

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    DE19652764A DE19652764A1 (en) 1996-12-18 1996-12-18 Liquid gas cooling system for cooling a consumer to low temperature
    DE19652764 1996-12-18

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    EP0849550A1 EP0849550A1 (en) 1998-06-24
    EP0849550B1 true EP0849550B1 (en) 2003-08-20

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    DE102017216015A1 (en) 2017-09-12 2019-03-14 Robert Bosch Gmbh Hand tool
    CN110332762A (en) * 2019-08-08 2019-10-15 兰州真空设备有限责任公司 Gas nitrogen cycle method for regulating temperature and system
    CN114111082A (en) * 2021-11-02 2022-03-01 深圳供电局有限公司 Supercooled liquid nitrogen circulating system based on GM refrigerator

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    EP0849550A1 (en) 1998-06-24
    DE59710611D1 (en) 2003-09-25

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