JP2006234356A - Low temperature retaining device and its maintenance method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a low temperature retaining device having a constitution not needing temperature rise of a refrigerant container in the maintenance of a refrigerating machine, and not reducing much refrigerating capacity. <P>SOLUTION: This low temperature retaining device has a heat insulating container 5, a refrigerant container 13 mounted in the heat insulating container 5 for cooling and storing a refrigerant which is gas at normal temperature, in a liquid state, the refrigerating machine 30 having a cooling stage 10 mounted in the heat insulating container 5, a condenser 11 mounted over the refrigerant container 13 and in the heat insulating container 5 and thermally connected with the cooling stage 10, and a communication pipe 12 communicating the condenser 11 with the refrigerant container 13 to circulate the refrigerant. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a low temperature holding device (low temperature container) that uses a refrigerator to reduce the evaporation amount of refrigerant and a maintenance method thereof.

  A low temperature holding device using a refrigerant needs to be periodically replenished because the refrigerant evaporates due to heat penetration from outside due to conduction, radiation, or the like. Refrigerators are often used to reduce the amount of expensive refrigerant evaporated or to reduce the number of replenishment operations.

  The cryogenic holding device contains a refrigerant container for storing refrigerant in a vacuum container (insulated container) for heat insulation, and a part of the refrigerant container is thermally connected by a cooling stage of a refrigerator or is refrigerated. The cooling stage of the machine is inserted into the refrigerant container as it is (see, for example, Patent Document 1). With this refrigerator, the evaporated amount of the refrigerant is reduced by re-liquefying the evaporated and vaporized refrigerant.

An example of the object to be cooled is a superconducting coil. In order to maintain the superconducting state, it is necessary to keep the coil at a very low temperature, and the cryogenic holding is one of the important conditions of the superconducting magnet system. In recent years, the development of superconducting magnets that can be cooled and energized only by a refrigerator without using a refrigerant has been remarkable, but cooling of a large-scale coil and a magnet with a large amount of heat generation have advantages in cooling by a refrigerant. Is still in use today.
Japanese Patent No. 3347870

  In the case of the above-described conventional low temperature holding device configuration, when maintenance (also referred to as maintenance, including inspection and repair) is required due to a malfunction of the refrigerator, the refrigerator must be returned to room temperature. Also, it is necessary to raise the temperature of both the refrigerant containers that are thermally connected well. The period from expelling the refrigerant, returning the refrigerant container to room temperature, performing re-cooling and re-injection after maintenance will be several days to several tens of days depending on the size of the low temperature holding device. Inefficient in terms of cost.

  A plug-in configuration in which the refrigerator cold head is inserted into a port extending from the refrigerant container to the room temperature portion and can be removed from the refrigerant container while the cooling stage is cooled is also possible. However, in this case, during the operation of the refrigerator other than maintenance, the heat penetration from the port and the heat penetration amount of the vacuum container part of the refrigerator cold head of the plug-in configuration are added, so that the freezing capacity of the refrigerator apparently decreases. There was a problem.

  If the configuration is such that there is no need to raise the temperature of the entire low-temperature holding device during maintenance of the refrigerator and there is no increase in the amount of heat penetration due to newly added parts such as ports, it will improve the efficiency of refrigerator maintenance. . At that time, the problem is that the thermal link between the cooling stage and the refrigerant container is good when the refrigerator is in operation, but the temperature rises when the refrigerator is stopped during maintenance so that the thermal link deteriorates. And keeping the refrigerant container at a low temperature. This is a function of a thermal switch, and various thermal switches such as a mechanical type and a gas type have been developed so far. The performance required for the heat switch includes heat transfer when turned on, good heat conduction, high heat resistance when turned off, easy operation during repeated on / off, safety in handling, and reproducibility.

  Therefore, an object of the present invention is to provide a low temperature holding device having a configuration in which it is not necessary to raise the temperature of a refrigerant container during maintenance of a refrigerator and the refrigeration capacity is not significantly lowered, and a maintenance method thereof.

  The present invention achieves the above object, and the low temperature holding device according to the first aspect is disposed in the heat insulating container and the heat insulating container for cooling the gaseous refrigerant at room temperature and storing it in a liquid state. A refrigerant container, a refrigerator having a cooling stage disposed in the heat insulation container, a condenser disposed in the heat insulation container above the refrigerant container and thermally connected to the cooling stage, and And a communication pipe communicating so that the refrigerant can flow between the condenser and the refrigerant container.

  The low temperature holding device according to the second aspect of the present invention includes a heat insulating container, a refrigerant container disposed in the heat insulating container for cooling a gaseous refrigerant at room temperature and storing it in a liquid state, and the heat insulating container. A cryogenic holding apparatus comprising: a refrigerator having a cooling stage disposed therein; and a sealed container in which a gas is enclosed and disposed outside the refrigerant container in the heat insulating container, wherein the sealed container Has a condensing part that is thermally connected to the cooling stage to liquefy the gas, and an evaporation part that is thermally connected to the refrigerant container to evaporate the gas.

  According to the present invention, it is not necessary to raise the temperature of the refrigerant container at the time of the refrigerator maintenance of the low temperature holding device, and it is possible to suppress a decrease in the refrigerating capacity.

  Hereinafter, various embodiments of the present invention will be described with reference to the drawings. In these descriptions, the same or similar parts are denoted by common reference numerals, and redundant description is omitted.

[First Embodiment]
FIG. 1 is a configuration diagram of a first embodiment of a low temperature holding apparatus according to the present invention. Here, a GM / JT (Joule Thomson) refrigerator 30 having a GM (Gifford McMahon) refrigerator 4 as a precooling refrigerator is used.

  As shown in the figure, a refrigerant container 13 is disposed in a heat insulating container (for example, a vacuum container) 5, and a superconducting coil 14 as a body to be cooled is installed in the refrigerant container 13. For example, liquid helium is used as the refrigerant. A condenser 11 is disposed above the refrigerant container 13 in the heat insulating container 5, and the top of the refrigerant container 13 and the bottom of the condenser 11 are connected by a liquid introduction pipe (communication pipe) 12. As a material of the connecting pipe 12, a material having low thermal conductivity such as stainless steel is preferable. A heater 15 that can be switched on and off is attached to the condenser 11.

  A GM / JT refrigerator is disposed above the condenser 11, and a cooling stage 10 of the GM / JT refrigerator is thermally connected to the upper portion of the condenser 11.

  The GM / JT refrigerator 30 uses the GM refrigerator 4 as a precooling refrigerator, and the GM refrigerator 4 is a two-stage GM refrigerator in the illustrated example. In the GM refrigerator 4, copper, lead or the like, or a material obtained by laminating them as a first-stage regenerator material, lead, magnetic regenerator material, or a material obtained by laminating them is used as a second-stage regenerator material. ~ 100 Kelvin, 2 stage is held at 10-20 Kelvin. The JT refrigerator is precooled through the heat exchangers 6, 7, and 8, and the JT valve 9 can obtain a low temperature of 4K level. The object to be cooled can be cooled to the 4K level by the cooling stage 10. The GM / JT refrigerator 30 includes a compressor unit 1, a JT refrigerator pipe 2, and a GM refrigerator pipe 3.

  During the operation of the refrigerator, the evaporated gas is liquefied in the condenser 11, falls due to gravity, returns to the refrigerant container 13 through the liquid introduction pipe 12. At that time, the condenser 11 and the liquid introduction pipe 12 only have a heat intrusion amount due to radiation, and there is no link due to conduction with the room temperature portion, so that a minimum heat intrusion is required. Therefore, the refrigeration capacity of the refrigerator can be utilized to the maximum.

  When maintenance is necessary, the refrigerator is stopped. At this time, liquefaction does not occur in the condenser 11, and the temperature of the cooling stage 10 of the refrigerator is forced to room temperature by natural temperature rise or a heater 15 or the like. Raise the temperature. On the other hand, if the refrigerant container 13 side is filled with the refrigerant, the temperature remains low. There is a temperature gradient between the cooling stage 10 of the refrigerator and the refrigerant container 13, and heat intrusion into the refrigerant container 13 increases. During this period, the liquid introduction pipe 12 is interposed, and this pipe has a thermal resistance. Thus, increase in heat penetration can be suppressed.

  Moreover, since the condenser 11 can be heated in a short time by using the heater 15 in particular, the time required for maintenance of the refrigerator can be shortened.

  Further, in parallel with the heating by the heater 12, in a state where the preheating GM refrigerator 4 is not operated, the JT valve 9 is opened beyond the normal opening and the JT refrigerator refrigerant is circulated to raise the temperature of the entire refrigerator, It is also possible to clean the refrigerant of the JT refrigerator or replace the parts of the GM refrigerator 4.

[Second Embodiment]
FIG. 2 shows a second embodiment. In this embodiment, a GM refrigerator 4 using a magnetic regenerator material or a pulse tube refrigerator is used as the refrigerator. As a result, cooling to 4 Kelvin is possible, and helium gas can be liquefied similarly to the GM / JT refrigerator, and the metal superconducting coil can be cooled.

[Third Embodiment]
FIG. 3 shows a third embodiment. This embodiment is a modification of the second embodiment, and a pipe having a curved pipe portion such as a spiral pipe or a meandering pipe is used as the liquid introduction pipe 12. Thereby, even when the temperature of the condenser 11 rises for the maintenance of the refrigerator 4, the amount of heat entering the refrigerant container 13 through the liquid introduction pipe 12 can be suppressed.

  Instead of increasing the length of the liquid introduction tube 12, a bellows tube may be used to increase the heat transfer length in the longitudinal direction of the tube.

[Fourth Embodiment]
FIG. 4 shows a fourth embodiment. This embodiment is a modification of the first or second embodiment. In this figure, illustration of the heat insulation container 5, the refrigerator 4, etc. is abbreviate | omitted. In this embodiment, a gas introduction pipe (second communication pipe) 16 is provided substantially parallel to the liquid introduction pipe 12. However, the liquid introduction pipe (first communication pipe) 12 communicates the bottom of the condenser 11 and the top of the refrigerant container 13, whereas the gas introduction pipe 16 is near the upper end of the condenser 11 and the refrigerant container 13. In contact with the top. Similarly to the liquid introduction pipe 12, the gas introduction pipe 16 is preferably made of a material having low thermal conductivity such as stainless steel.

  With such a configuration, the refrigerant liquefied by the condenser 11 is led to the refrigerant container 12 through the liquid introduction pipe 12, and the evaporated gas evaporated in the refrigerant container 13 is led to the condenser 11 through the gas introduction pipe 16. Thus, the pressure loss in the pipe can be reduced by diverting the rising evaporative gas flow in the direction opposite to the flow of the falling liquid in the liquid introduction pipe 12. Therefore, a thinner and longer tube can be used, and the amount of heat penetration during maintenance can be reduced.

[Fifth Embodiment]
FIG. 5 shows a fifth embodiment. This embodiment is a modification of the fourth embodiment. In this embodiment, a condensation stage 17 is provided in the condenser 11. The condensation stage 17 is thermally connected to the cooling stage 10. Thereby, the improvement of the liquefaction performance in the condenser 11 is achieved.

[Sixth Embodiment]
FIG. 6 shows a sixth embodiment. This embodiment is a modification of the fifth embodiment. In this embodiment, the condenser, the liquid introduction pipe, and the gas introduction pipe are integrated to form a sealed container 19 independent of the refrigerant container 13. As a material of the sealed container 19, a material having low thermal conductivity such as stainless steel is preferable.

  Moreover, by making the sealed container 19 into an elongated tube, it is possible to suppress heat intrusion into the refrigerant container through the tube wall during maintenance of the refrigerator.

[Seventh Embodiment]
FIG. 7 shows a seventh embodiment. This embodiment is a modification of the sixth embodiment. In this embodiment, the sealed container 19 and the refrigerant container 13 are connected with a pressure equalizing pipe 26, and the pressure equalizing pipe 26 is provided with a pressure equalizing valve 20. Further, an air supply / exhaust pipe 21 that communicates between the sealed container 19 and the outside of the vacuum container 5 is provided.

  By closing the air supply / exhaust valve 22 and opening the pressure equalizing valve 20, the pressure in the sealed container 10 and the refrigerant container 13 can be equalized. Further, during refrigerator maintenance, heat transfer through the sealed container 19 can be suppressed by closing the pressure equalizing valve 20 and opening the air supply / exhaust valve 22 to evacuate the sealed container 19.

[Other Embodiments]
Each embodiment described above is merely an example, and the present invention is not limited thereto. The characteristic portions of the embodiments can be combined in various ways. For example, the bent pipe or the bellows pipe shown in the third embodiment (FIG. 3) can be used in the first or fourth to seventh embodiments.

1 is a schematic configuration diagram of a first embodiment of a low temperature holding device according to the present invention. The schematic block diagram of 2nd Embodiment of the low temperature holding | maintenance apparatus which concerns on this invention. The schematic block diagram of 3rd Embodiment of the low temperature holding | maintenance apparatus which concerns on this invention. The schematic block diagram which shows the principal part of 4th Embodiment of the low temperature holding | maintenance apparatus which concerns on this invention. The schematic block diagram which shows the principal part of 5th Embodiment of the low temperature holding | maintenance apparatus which concerns on this invention. The schematic block diagram which shows the principal part of 6th Embodiment of the low temperature holding | maintenance apparatus which concerns on this invention. The schematic block diagram which shows the principal part of 7th Embodiment of the low temperature holding | maintenance apparatus which concerns on this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Compressor unit, 2 ... JT refrigerator piping, 3 ... GM refrigerator piping, 4 ... GM refrigerator, 5 ... Thermal insulation container, 6 ... Heat exchanger, 7 ... Heat exchanger, 8 ... Heat exchanger, DESCRIPTION OF SYMBOLS 9 ... JT valve, 10 ... Cooling stage, 11 ... Condenser, 12 ... Liquid introduction pipe (1st connecting pipe), 13 ... Refrigerant container, 14 ... Superconducting coil, 15 ... Heater, 16 ... Gas introduction pipe (2nd 17 ... condensing stage, 18 ... condensing stage in refrigerant container, 19 ... sealed container, 20 ... pressure equalizing valve, 21 ... air supply / exhaust pipe, 22 ... air supply / exhaust valve, 26 ... pressure equalizing pipe, 30 ... refrigerator

Claims (13)

An insulated container;
A refrigerant container disposed in the heat insulating container for cooling the gaseous refrigerant at room temperature and storing it in a liquid state;
A refrigerator having a cooling stage disposed in the heat insulating container;
A condenser disposed in the heat insulating container above the refrigerant container and thermally connected to the cooling stage;
A communication pipe communicating so that the refrigerant can flow between the condenser and the refrigerant container;
A low temperature holding apparatus characterized by comprising:   The low-temperature holding device according to claim 1, wherein the communication pipe has at least one curved pipe portion.   The low-temperature holding device according to claim 1 or 2, wherein the connecting pipe has a bellows pipe portion having a wave shape in a longitudinal direction.   The communication pipe includes a first communication pipe that communicates between the lower part of the condenser and the refrigerant container, and a second communication pipe that communicates between the upper part of the condenser and the refrigerant container; The low temperature holding device according to any one of claims 1 to 3.   The low temperature holding device according to any one of claims 1 to 4, wherein a heater is attached to at least one of the condenser and the cooling stage. An insulated container;
A refrigerant container disposed in the heat insulating container for cooling the gaseous refrigerant at room temperature and storing it in a liquid state;
A refrigerator having a cooling stage disposed in the heat insulating container;
Gas sealed inside, a sealed container disposed outside the refrigerant container in the heat insulating container,
A low temperature holding device comprising:
The sealed container includes a condensing unit that is thermally connected to the cooling stage to liquefy the gas, and an evaporation unit that is thermally connected to the refrigerant container to evaporate the gas.
Low temperature holding device characterized by.   The low temperature holding device according to claim 6, wherein at least a part of the sealed container excluding the condensing part and the evaporating part is formed to be narrower than the condensing part and the evaporating part.   The low-temperature holding device according to claim 5 or 7, further comprising a pressure equalizing pipe that connects the sealed container and the refrigerant container.   A pressure equalizing valve provided in the middle of the pressure equalizing pipe, an intake / exhaust pipe connecting the sealed container and the outside of the heat insulating container, and an intake / exhaust valve provided in the middle of the intake / exhaust pipe. 9. The low temperature holding device according to claim 8, wherein   The low temperature holding device according to any one of claims 6 to 9, wherein a heater is attached to at least one of the condensing unit and the cooling stage.   The low-temperature holding device according to any one of claims 1 to 10, wherein the refrigerator is a GM / JT refrigerator or a GM refrigerator using a magnetic regenerator material.   The maintenance method of the low temperature holding device according to claim 5 or 10, wherein the inside of the refrigerator is heated to about room temperature by the heater, and then the refrigerator in the state of about room temperature is maintained. Low temperature holding device maintenance method characterized by the above. The refrigerator is a GM / JT refrigerator having a JT refrigerator including a JT valve and a GM refrigerator for pre-cooling,
In parallel with the heating by the heater, the temperature of the entire refrigerator is increased by opening the JT valve of the JT refrigerator beyond the normal opening and circulating the refrigerant of the JT refrigerator without operating the precooling GM refrigerator. And then performing maintenance on the refrigerator,
The method for maintaining a low temperature holding device according to claim 12.

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