CN116710717A - Pulse tube refrigerator and superconducting magnet device - Google Patents
Pulse tube refrigerator and superconducting magnet device Download PDFInfo
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- CN116710717A CN116710717A CN202180088748.XA CN202180088748A CN116710717A CN 116710717 A CN116710717 A CN 116710717A CN 202180088748 A CN202180088748 A CN 202180088748A CN 116710717 A CN116710717 A CN 116710717A
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- pulse tube
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- 238000012546 transfer Methods 0.000 claims abstract description 9
- 239000007789 gas Substances 0.000 claims description 100
- 239000007788 liquid Substances 0.000 claims description 18
- 239000001307 helium Substances 0.000 claims description 9
- 229910052734 helium Inorganic materials 0.000 claims description 9
- SWQJXJOGLNCZEY-UHFFFAOYSA-N helium atom Chemical compound [He] SWQJXJOGLNCZEY-UHFFFAOYSA-N 0.000 claims description 9
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 claims description 8
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 claims description 4
- 229910052757 nitrogen Inorganic materials 0.000 claims description 4
- 229910052754 neon Inorganic materials 0.000 claims description 3
- GKAOGPIIYCISHV-UHFFFAOYSA-N neon atom Chemical compound [Ne] GKAOGPIIYCISHV-UHFFFAOYSA-N 0.000 claims description 3
- 229910052786 argon Inorganic materials 0.000 claims description 2
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims description 2
- 239000001257 hydrogen Substances 0.000 claims description 2
- 229910052739 hydrogen Inorganic materials 0.000 claims description 2
- 239000001301 oxygen Substances 0.000 claims description 2
- 229910052760 oxygen Inorganic materials 0.000 claims description 2
- 238000004378 air conditioning Methods 0.000 claims 2
- 125000004435 hydrogen atom Chemical class [H]* 0.000 claims 1
- 230000014759 maintenance of location Effects 0.000 abstract description 4
- 238000003860 storage Methods 0.000 abstract description 4
- 238000001816 cooling Methods 0.000 description 74
- 239000003507 refrigerant Substances 0.000 description 16
- 238000004891 communication Methods 0.000 description 12
- 238000010586 diagram Methods 0.000 description 8
- 238000005057 refrigeration Methods 0.000 description 7
- 230000007246 mechanism Effects 0.000 description 6
- 238000005481 NMR spectroscopy Methods 0.000 description 3
- 230000009471 action Effects 0.000 description 3
- 230000008859 change Effects 0.000 description 3
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- 239000007769 metal material Substances 0.000 description 3
- 230000007704 transition Effects 0.000 description 3
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 2
- 238000009835 boiling Methods 0.000 description 2
- 229910052802 copper Inorganic materials 0.000 description 2
- 239000010949 copper Substances 0.000 description 2
- 238000007599 discharging Methods 0.000 description 2
- 239000000463 material Substances 0.000 description 2
- 239000000203 mixture Substances 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 1
- 230000004323 axial length Effects 0.000 description 1
- 230000006835 compression Effects 0.000 description 1
- 238000007906 compression Methods 0.000 description 1
- 239000000470 constituent Substances 0.000 description 1
- 239000013078 crystal Substances 0.000 description 1
- 230000007423 decrease Effects 0.000 description 1
- 230000003111 delayed effect Effects 0.000 description 1
- 238000013461 design Methods 0.000 description 1
- 238000006073 displacement reaction Methods 0.000 description 1
- 230000004927 fusion Effects 0.000 description 1
- 230000005484 gravity Effects 0.000 description 1
- 238000003331 infrared imaging Methods 0.000 description 1
- 238000009413 insulation Methods 0.000 description 1
- 238000000034 method Methods 0.000 description 1
- 238000002360 preparation method Methods 0.000 description 1
- 230000005855 radiation Effects 0.000 description 1
- 238000007789 sealing Methods 0.000 description 1
- 229910001220 stainless steel Inorganic materials 0.000 description 1
- 239000010935 stainless steel Substances 0.000 description 1
- 239000011232 storage material Substances 0.000 description 1
Classifications
-
- 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
- F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
- F25B9/00—Compression machines, plants or systems, in which the refrigerant is air or other gas of low boiling point
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- Engineering & Computer Science (AREA)
- Physics & Mathematics (AREA)
- Mechanical Engineering (AREA)
- Thermal Sciences (AREA)
- General Engineering & Computer Science (AREA)
- Containers, Films, And Cooling For Superconductive Devices (AREA)
Abstract
A pulse tube refrigerator (10) of the present invention is provided with: vessels (18, 24); cold storages (16, 22) arranged in parallel with the pulse tube; and a thermal bridge (50) having a thermal switch (52), and connecting the pulse tube and the regenerator via the thermal switch (52). The thermal switch (52) functions as an adiabatic element when the regenerator side of the thermal bridge (50) is in the 1 st temperature zone and as a heat transfer element when the regenerator side of the thermal bridge (50) is in the 2 nd temperature zone, which is lower than the 1 st temperature zone.
Description
Technical Field
The present invention relates to a pulse tube refrigerator and a superconducting magnet device.
Background
Pulse tube refrigerators are often placed in a vacuum environment, but sometimes placed in a gaseous atmosphere for use in, for example, recondensing helium gas. By compressing the working gas in the pulse tube in the refrigeration cycle, the pulse tube is heated, and the regenerator is cooled to an ultra-low temperature. Pulse tube refrigerators generally employ a structure in which pulse tubes and a regenerator are arranged in parallel. The temperature difference between the pulse tube and the regenerator causes natural convection of the atmospheric gas between them, and the resultant heat input to the regenerator causes a loss of the refrigerating capacity of the pulse tube refrigerator. Therefore, the following suggestions are proposed: in such pulse tube refrigerators, the regenerator and the pulse tube are connected by a thermal bridge and the pulse tube is cooled from the regenerator by the thermal bridge so that the axial temperature distribution of the pulse tube matches the axial temperature distribution of the regenerator. This suppresses heat input from the pulse tube to the regenerator by natural convection of the atmospheric gas, and reduces the loss of the cooling capacity of the pulse tube refrigerator.
Technical literature of the prior art
Patent literature
Patent document 1: japanese patent laid-open No. 2006-214717
Disclosure of Invention
Technical problem to be solved by the invention
The present inventors have studied the pulse tube refrigerator and as a result have found the following problems. In the above-described technique, the desired object can be achieved when the pulse tube refrigerator has been cooled to an ultra-low temperature and is in a stable operation state. However, in the case of initial cooling (also referred to as cooling) from ambient temperature (e.g., room temperature) to ultra-low temperature at the start of the pulse tube refrigerator, heat conducted from the pulse tube to the regenerator through the thermal bridge increases the time required for cooling the regenerator, resulting in an increase in cooling time. The cooling is a preparation necessary for the pulse tube refrigerator to start the cooling operation, and thus it is expected to be completed in a short time as much as possible.
One of the exemplary objects of an embodiment of the present invention is to suppress an increase in the cooling time and to improve the refrigerating capacity of a pulse tube refrigerator.
Means for solving the technical problems
According to one embodiment of the present invention, a pulse tube refrigerator includes: a vessel; a regenerator arranged in parallel with the pulse tube; a thermal bridge having a thermal switch and connecting the pulse tube and the regenerator via the thermal switch. The thermal switch functions as a heat insulating element when the regenerator side of the thermal bridge is in the 1 st temperature zone and functions as a heat transfer element when the regenerator side of the thermal bridge is in the 2 nd temperature zone lower than the 1 st temperature zone.
According to one embodiment of the present invention, a superconducting magnet device includes: a superconducting coil; a cryostat having a liquid cryogen tank for accommodating the superconducting coil and the liquid cryogen together; and the pulse tube refrigerator of the above embodiment, the pulse tube refrigerator being disposed in the cryostat and recondensing the liquid cryogen.
Effects of the invention
According to the present invention, the cooling time can be suppressed from increasing and the refrigerating capacity of the pulse tube refrigerator can be improved.
Drawings
Fig. 1 is a diagram schematically showing a pulse tube refrigerator according to an embodiment.
Fig. 2 is a diagram schematically showing a refrigerant gas recondensing device and a superconducting magnet device according to an embodiment.
Fig. 3 (a) is a schematic diagram showing an example of a thermal bridge with a thermal switch according to the embodiment, and fig. 3 (b) is a graph showing exemplary characteristics of the thermal switch assembled to the thermal bridge according to the embodiment.
Fig. 4 is a schematic diagram showing another column of the thermal bridge with thermal switch according to the embodiment.
Detailed Description
Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the following description, the same elements are denoted by the same reference numerals, and overlapping description is omitted as appropriate. The following structures are examples, and are not intended to limit the scope of the present invention. In the drawings referred to in the following description, the size and thickness of each component are set appropriately for convenience of description, and do not necessarily represent actual dimensions and ratios.
Fig. 1 is a diagram schematically showing a pulse tube refrigerator 10 according to an embodiment. Fig. 2 is a diagram schematically showing the refrigerant gas recondensing device 100 and the superconducting magnet device 200 according to the embodiment.
The pulse tube refrigerator 10 serves as a cooling source for the refrigerant gas recondensing device 100, and thus can be provided in the liquid refrigerant tank 102 storing liquefied refrigerant gas. The liquid cryogen 104, for example, cools superconducting devices, sensors, or other objects to ultra-low temperatures to be vaporized. The vaporized refrigerant is condensed again by the pulse tube refrigerator 10. Helium is widely used as the refrigerant gas, for example. Thus, the helium gas is again condensed into liquid helium by pulse tube refrigerator 10. However, other suitable refrigerants such as nitrogen may be used.
The superconducting magnet device 200 shown in fig. 2 can be used as a magnetic field source of an NMR (Nuclear Magnetic Resonance: nuclear magnetic resonance) system, for example. The superconducting magnet device 200 includes a superconducting coil 202 and a cryostat 204 having a liquid cryogen tank 102. The superconducting coil 202 is housed in the liquid cryogen tank 102 together with the liquid cryogen 104. Pulse tube refrigerator 10 is positioned at cryostat 204 and recondenses liquid cryogen 104.
The superconducting magnet device 200 may be mounted on a high-magnetic-field-utilization device (not shown) as a magnetic field source of a high-energy physical system such as a single crystal pulling device, an MRI (Magnetic Resonance Imaging: magnetic resonance imaging) system, a cyclotron, or a nuclear fusion system, or other high-magnetic-field-utilization device, for example, and may generate a high magnetic field necessary for the device.
As shown in fig. 1, the pulse tube refrigerator 10 is, for example, a GM (Gifford-McMahon: gifford-maxk) type four-valve type two-stage pulse tube refrigerator.
The pulse tube refrigerator 10 includes a cold head 11 and a compressor 12. The coldhead 11 includes a main pressure switching valve 14, a stage 1 regenerator 16, a stage 1 pulse tube 18, and a stage 1 phase control mechanism optionally including a 1 st sub-pressure switching valve 20 and a 1 st flow rate adjustment element 27 a. The compressor 12 and the main pressure switching valve 14 constitute a vibration generation source of the pulse tube refrigerator 10. The coldhead 11 further includes a 2 nd-stage regenerator 22, a 2 nd-stage pulse tube 24, and a 2 nd-stage phase control mechanism optionally including a 2 nd sub-pressure switching valve 21 and a 2 nd flow rate adjustment element 27 b. The vibration generation source, the 1 st-stage phase control mechanism, and the 2 nd-stage phase control mechanism share the compressor 12.
In this specification, for convenience of description of the positional relationship of the constituent elements of the pulse tube refrigerator 10, terms of the longitudinal direction a and the transverse direction B are used. Generally, the longitudinal and transverse directions a, B correspond to the axial and radial directions of the vessels 18, 24 and the regenerator 16, 22, respectively. However, the longitudinal direction a and the transverse direction B need not be strictly orthogonal as long as they are substantially orthogonal to each other. The marks in the longitudinal direction a and the transverse direction B are not intended to limit the posture of the pulse tube refrigerator 10 in the use position. The pulse tube refrigerator 10 may be provided in a desired posture, for example, with the longitudinal direction a and the transverse direction B oriented in the vertical direction and the horizontal direction, respectively, or with the longitudinal direction a and the transverse direction B oriented in the horizontal direction and the vertical direction, respectively. Alternatively, the longitudinal direction a and the transverse direction B may be oriented in different oblique directions.
The cold accumulators 16, 22 and the vessels 18, 24 are arranged in parallel. The two cold accumulators 16, 22 are connected in series and extend in the longitudinal direction a. The two vessels 18, 24 each extend in a longitudinal direction a. The stage 1 regenerator 16 is arranged in parallel with the stage 1 pulse tube 18 in the transverse direction B, and the stage 2 regenerator 22 is arranged in parallel with the stage 2 pulse tube 24 in the transverse direction B. The stage 1 pulse tube 18 has almost the same length as the stage 1 regenerator 16 in the longitudinal direction a, and the stage 2 pulse tube 24 has almost the same length as the total length of the stage 1 regenerator 16 and the stage 2 regenerator 22 in the longitudinal direction a. The cold reservoirs 16, 22 and the vessels 18, 24 are configured to be substantially parallel to each other.
In fig. 1, the level 1 pulse tube 18 and the level 2 pulse tube 24 are disposed on both sides of the regenerator 16, 22, but these are shown for convenience of illustration only. In general, the regenerator 16, 22, the stage 1 pulse tube 18, and the stage 2 pulse tube 24 may be configured to be triangular when viewed in the longitudinal direction a.
The compressor 12 has a compressor discharge port 12a and a compressor suction port 12b, and compresses the collected low-pressure PL working gas to generate a high-pressure PH working gas. Working gas is supplied from the compressor discharge port 12a through the stage 1 regenerator 16 to the stage 1 pulse tube 18, and the working gas is recovered from the stage 1 pulse tube 18 through the stage 1 regenerator 16 to the compressor suction port 12b. The working gas is supplied from the compressor discharge port 12a through the stage 1 regenerator 16 and the stage 2 regenerator 22 to the stage 2 pulse tube 24, and the working gas is recovered from the stage 2 pulse tube 24 through the stage 2 regenerator 22 and the stage 1 regenerator 16 to the compressor suction port 12b.
The compressor discharge port 12a and the compressor suction port 12b function as a high-pressure source and a low-pressure source of the pulse tube refrigerator 10, respectively. The working gas is also referred to as a refrigerant gas, such as helium. In addition, both the high pressure PH and the low pressure PL are typically significantly higher than atmospheric pressure.
The main pressure switching valve 14 has a main intake opening/closing valve V1 and a main exhaust opening/closing valve V2. The 1 st sub-pressure switching valve 20 has a 1 st sub-intake opening/closing valve V3 and a 1 st sub-exhaust opening/closing valve V4. The 2 nd sub-pressure switching valve 21 has a 2 nd sub-intake opening/closing valve V5 and a 2 nd sub-exhaust opening/closing valve V6.
The pulse tube refrigerator 10 is provided with a high-pressure line 13a and a low-pressure line 13b. Working gas at high pressure PH flows from the compressor 12 to the coldhead 11 through the high pressure line 13 a. Working gas of low pressure PL flows from the cold head 11 to the compressor 12 through the low pressure line 13b. The high-pressure line 13a connects the compressor discharge port 12a to the intake opening/closing valves V1, V3, V5. The low-pressure line 13b connects the compressor suction port 12b to the discharge opening and closing valves V2, V4, V6.
The 1 st stage regenerator 16 has a 1 st stage regenerator high temperature end 16a and a 1 st stage regenerator low temperature end 16b, and extends in the longitudinal direction a from the 1 st stage regenerator high temperature end 16a toward the 1 st stage regenerator low temperature end 16 b. The high-temperature end 16a and the low-temperature end 16b of the stage 1 regenerator may also be referred to as the 1 st and 2 nd ends of the stage 1 regenerator 16, respectively. Likewise, the 2 nd stage regenerator 22 has a 2 nd stage regenerator high temperature end 22a and a 2 nd stage regenerator low temperature end 22b, and extends in the longitudinal direction a from the 2 nd stage regenerator high temperature end 22a toward the 2 nd stage regenerator low temperature end 22 b. The high-temperature end 22a and the low-temperature end 22b of the 2 nd-stage regenerator may also be referred to as the 1 st and 2 nd ends of the 2 nd-stage regenerator 22, respectively. The low temperature end 16b of the stage 1 regenerator is in communication with the high temperature end 22a of the stage 2 regenerator.
The level 1 vessel 18 has a level 1 vessel high temperature end 18a and a level 1 vessel low temperature end 18b, and extends in a longitudinal direction a from the level 1 vessel high temperature end 18a toward the level 1 vessel low temperature end 18 b. The high temperature end 18a and the low temperature end 18b of the level 1 vessel may also be referred to as the 1 st and 2 nd ends, respectively, of the level 1 vessel 18.
Likewise, the level 2 vessel 24 has a level 2 vessel high temperature end 24a and a level 2 vessel low temperature end 24b, and extends in the longitudinal direction a from the level 2 vessel high temperature end 24a toward the level 2 vessel low temperature end 24 b. The level 2 vessel high temperature end 24a and the level 2 vessel low temperature end 24b may also be referred to as the 1 st and 2 nd ends of the level 2 vessel 24, respectively.
In the illustrated configuration, the cold storages 16 and 22 are cylindrical pipes filled with a cold storage material, and the vessels 18 and 24 are cylindrical pipes having cavities therein.
At both ends of the vessel 18, 24, a rectifier may be provided, which homogenizes the working gas flow velocity distribution in a plane perpendicular to the axial direction of the vessel, or adjusts it to a desired distribution. The rectifier also functions as a heat exchanger. In order to control the phase, a buffer volume may be connected to the high temperature ends of vessels 18 and 24.
The coldhead 11 includes a 1 st cooling stage 28 and a 2 nd cooling stage 30. As shown in fig. 2, a neck 206 is provided above the cryostat 204 and the liquid refrigerant tank 102, and the cold head 11 of the pulse tube refrigerator 10 is inserted into the neck 206, and the 1 st cooling stage 28 and the 2 nd cooling stage 30 are disposed in the neck 206. The internal volume of the neck 206 forms a part of the liquid refrigerant tank 102, and the refrigerant vaporized in the liquid refrigerant tank 102 contacts the 2 nd cooling stage 30 and is re-condensed.
Referring again to fig. 1. The stage 1 regenerator 16 and the stage 1 pulse tube 18 extend in the same direction from the stage 1 cooling stage 28, and the stage 1 regenerator high-temperature end 16a and the stage 1 pulse tube high-temperature end 18a are disposed on the same side with respect to the stage 1 cooling stage 28. In this way, the stage 1 regenerator 16, the stage 1 pulse tube 18, and the stage 1 cooling stage 28 are arranged in a U-shape. Similarly, the 2 nd regenerator 22 and the 2 nd pulse tube 24 extend in the same direction from the 2 nd cooling stage 30, and the 2 nd regenerator high-temperature end 22a and the 2 nd pulse tube high-temperature end 24a are disposed on the same side with respect to the 2 nd cooling stage 30. In this way, the 2 nd-stage regenerator 22, the 2 nd-stage pulse tube 24, and the 2 nd cooling stage 30 are arranged in a U-shape.
The stage 1 pulse tube low temperature end 18b and the stage 1 regenerator low temperature end 16b are structurally connected together by a stage 1 cooling table 28 to be thermally connected to each other. A 1 st communication passage 29 is formed in the 1 st cooling stage 28, and the 1 st communication passage 29 communicates the 1 st regenerator low temperature end 16b and the 1 st pulse tube low temperature end 18b so that the working gas can flow between the 1 st regenerator low temperature end 16b and the 1 st pulse tube low temperature end 18 b.
Likewise, the level 2 pulse tube low temperature end 24b and the level 2 regenerator low temperature end 22b are structurally connected together by a level 2 cooling stage 30 to be thermally connected to each other. A 2 nd-stage communication path 31 is formed in the 2 nd cooling stage 30, and the 2 nd-stage communication path 31 communicates the 2 nd-stage regenerator low temperature end 22b and the 2 nd-stage pulse tube low temperature end 24b so that the working gas can flow between the 2 nd-stage regenerator low temperature end 22b and the 2 nd-stage pulse tube low temperature end 24 b.
The cooling stages 28, 30 are made of a metal material having a high thermal conductivity such as copper. The tube portions of the cold accumulators 16, 22 and the vessels 18, 24 are made of a material (for example, a metal material such as stainless steel) having a lower thermal conductivity than the cooling stages (28, 30).
The flow rate adjustment elements 27a and 27b include, for example, flow path resistances such as orifices and throttles. The flow path resistance may be fixed or adjustable.
On the other hand, the high-temperature stage 1 regenerator end 16a, the high-temperature stage 1 pulse tube end 18a, and the high-temperature stage 2 pulse tube end 24a are connected together by a flange 36. The flange 36 is attached to a support portion 38 such as a support table or a support wall on which the pulse tube refrigerator 10 is provided. The support portion 38 may be a wall material or other portion of a vacuum vessel or a heat-insulating vessel that accommodates the cooling stages 28 and 30.
The vessels 18 and 24 and the cold accumulators 16 and 22 extend from one main surface of the flange 36 toward the cooling stages 28 and 30, and a valve portion 40 is provided on the other main surface of the flange 36. The valve portion 40 accommodates the main pressure switching valve 14, the 1 st sub-pressure switching valve 20, and the 2 nd sub-pressure switching valve 21. Therefore, when the support portion 38 constitutes a part of the heat insulating container or the vacuum container, the vessels 18 and 24, the cold storages 16 and 22, and the cooling stages 28 and 30 are accommodated in the container, and the valve portion 40 is disposed outside the container when the flange portion 36 is attached to the support portion 38.
In addition, the valve portion 40 need not be directly mounted to the flange portion 36. The valve portion 40 may be disposed separately from the cold head 11 of the pulse tube refrigerator 10, and may be connected to the cold head 11 by a rigid or flexible pipe. In this way, the phase control mechanism of pulse tube refrigerator 10 may be configured separately from coldhead 11.
The main pressure switching valve 14 is configured to alternately connect the high-temperature end 16a of the stage 1 regenerator to the compressor discharge port 12a and the compressor suction port 12b in order to generate pressure vibration in the pulse tubes 18, 24. The main pressure switching valve 14 is configured such that one of the main intake opening/closing valve V1 and the main exhaust opening/closing valve V2 is closed while the other valve is open. The main pressure switching valve 14 is connected to the high-temperature side 16a of the 1 st stage regenerator via a regenerator communication passage 32. The main intake on-off valve V1 connects the compressor discharge port 12a to the high-temperature stage 1 regenerator end 16a, and the main exhaust on-off valve V2 connects the compressor suction port 12b to the high-temperature stage 1 regenerator end 16a.
While the main intake opening/closing valve V1 is open, the working gas is supplied from the compressor discharge port 12a to the regenerator 16, 22 through the high-pressure line 13a, the main intake opening/closing valve V1, and the regenerator communication passage 32. Working gas is further supplied from the level 1 regenerator 16 to the level 1 pulse tube 18 through a level 1 communication path 29, and from the level 2 regenerator 22 to the level 2 pulse tube 24 through a level 2 communication path 31. On the other hand, during the period when the main exhaust on-off valve V2 is opened, the working gas is recovered from the vessels 18 and 24 to the compressor suction port 12b through the cold accumulators 16 and 22, the main exhaust on-off valve V2, and the low pressure line 13b.
The 1 st sub-pressure switching valve 20 alternately connects the 1 st stage pulse tube high temperature end 18a to the compressor discharge port 12a and the compressor suction port 12b via the 1 st pulse tube communication path 34. The 1 st sub-pressure switching valve 20 is configured such that one of the 1 st sub-intake opening/closing valve V3 and the 1 st sub-exhaust opening/closing valve V4 is closed while the other is opened. The 1 st sub suction on-off valve V3 connects the compressor discharge port 12a to the 1 st stage pulse tube high temperature end 18a, and the 1 st sub discharge on-off valve V4 connects the compressor suction port 12b to the 1 st stage pulse tube high temperature end 18a.
While the 1 st sub-intake on-off valve V3 is open, the working gas is supplied from the compressor discharge port 12a to the 1 st stage pulse tube 18 through the high-pressure line 13a, the 1 st sub-intake on-off valve V3, the 1 st pulse tube communication passage 34, and the 1 st stage pulse tube high temperature end 18a. On the other hand, during the period when the 1 st sub-discharge on-off valve V4 is opened, the working gas is recovered from the 1 st stage pulse tube 18 to the compressor suction port 12b through the 1 st stage pulse tube high temperature end 18a, the 1 st sub-discharge on-off valve V4, and the low pressure line 13b.
Similarly, the sub-pressure switching valve 21 alternately connects the stage 2 pulse tube high temperature end 24a to the compressor discharge port 12a and the compressor suction port 12b via the stage 2 pulse tube communication path 35. The 2 nd sub-pressure switching valve 21 is configured such that one of the 2 nd sub-intake opening/closing valve V5 and the 2 nd sub-exhaust opening/closing valve V6 is in a closed state while the other is open. The 2 nd sub suction on-off valve V5 connects the compressor discharge port 12a to the 2 nd stage pulse tube high temperature end 24a, and the 2 nd sub discharge on-off valve V6 connects the compressor suction port 12b to the 2 nd stage pulse tube high temperature end 24a. During the period when the 2 nd sub-intake opening/closing valve V5 is opened, the working gas is supplied from the compressor discharge port 12a to the 2 nd stage pulse tube 24. During the period when the 2 nd sub-discharge opening/closing valve V6 is opened, the working gas is recovered from the 2 nd stage pulse tube 24 to the compressor suction port 12b.
By adopting this structure, the pulse tube refrigerator 10 generates working gas pressure vibrations of high pressure PH and low pressure PL inside the pulse tube. The displacement vibration of the working gas (i.e., the reciprocating movement of the gas piston) is generated in the pulse tube in synchronization with the pressure vibration and delayed by an appropriate phase. The action of the working gas periodically reciprocating up and down within the pulse tube while maintaining a certain pressure is commonly referred to as a "gas piston", which is often used in the description of the action of the pulse tube refrigerator 10. When the gas piston is at or near the high temperature end of the pulse tube, the working gas expands at the low temperature end of the pulse tube to create a cold. By repeating this refrigeration cycle, the pulse tube refrigerator 10 can cool the cooling stage. The 1 st cooling stage 28 is cooled to a 1 st cooling temperature (e.g., 30K to 80K), and the 2 nd cooling stage 30 is cooled to a 2 nd cooling temperature (e.g., 3K to 20K) lower than the 1 st cooling temperature.
As described above, in the case where the pulse tube refrigerator 10 is used for recondensing refrigerant gas, the pulse tube refrigerator 10 can cool gas or liquid in contact with the 2 nd cooling stage 30. In addition, the working gas of the pulse tube refrigerator 10 and the refrigerant gas re-condensed by the pulse tube refrigerator 10 may be the same kind of gas (e.g., helium gas), but they are isolated from each other. The cold head 11 is an airtight container, and the working gas inside thereof does not leak to the outside of the cold head 11, and thus does not mix with the recondensed refrigerant gas.
In the case where the pulse tube refrigerator 10 is used for other purposes, an object (not shown) to be cooled is thermally connected to the 2 nd cooling stage 30. The object may be directly disposed on the 2 nd cooling stage 30 or may be thermally connected to the 2 nd cooling stage 30 via a rigid or flexible heat transfer member. The pulse tube refrigerator 10 is capable of cooling objects by conduction cooling from the 2 nd cooling stage 30. In addition, the object cooled by the pulse tube refrigerator 10 may be a superconducting electromagnet or other superconducting device, or an infrared imaging element or other sensor, but is not limited thereto.
It is needless to say that an object different from the object cooled by the 2 nd cooling stage 30 may be cooled by the 1 st cooling stage 28. For example, a radiation shield may be thermally coupled to cooling stage 1 at cooling stage 28 to reduce or prevent heat intrusion toward cooling stage 2 at cooling stage 30.
In this embodiment, the pulse tube refrigerator 10 is provided with at least one thermal bridge 50. The thermal bridge 50 has a thermal switch 52, which connects the pulse tube and the regenerator via the thermal switch 52. The thermal bridge 50 further includes a regenerator connecting portion 54 for connecting the thermal switch 52 to the regenerator and a pulse tube connecting portion 56 for connecting the thermal switch 52 to the pulse tube. The regenerator connection portion 54 and the pulse tube connection portion 56 are made of a metal material having a high thermal conductivity such as copper. Alternatively, one end of the thermal switch 52 may be directly connected to the pulse tube, and the other end of the thermal switch 52 may be directly connected to the regenerator.
As an example, a thermal bridge 50 may be provided that connects the level 2 pulse tube 24 and the level 2 regenerator 22. In addition to or instead of this, further thermal bridges 50 connecting the level 1 pulse tube 18 and the level 1 regenerator 16 may be provided. In addition to or instead of this, further thermal bridges 50 connecting the level 2 pulse tubes 24 and the level 1 regenerator 16 may also be provided. The thermal bridge 50 may also be located elsewhere, for example, to connect the stage 2 pulse tube 24 and the stage 1 cooling stage 28.
By compression of the gas within the pulse tube in the refrigeration cycle of the pulse tube refrigerator 10, the middle portion of the pulse tube (e.g., 1/4 to 3/4 or 1/3 to 2/3 of the axial length of the pulse tube) may be heated more strongly than the end portions of the pulse tube. Thus, the thermal bridge 50 may be connected to the middle portion of the level 1 vessel 18 or the middle portion of the level 2 vessel 24.
As shown in fig. 1, the thermal bridge 50 connects the pulse tube and the regenerator at the same position in the axial direction (longitudinal direction a in fig. 1). The temperature at the axial location of the connection by the thermal bridge 50 can be made close to (or equal to) in the pulse tube and regenerator, which is advantageous in matching the axial temperature profiles of the pulse tube and regenerator.
Alternatively, the thermal bridge 50 may connect the pulse tube and the regenerator at different positions in the axial direction. Thus, for example, the axial temperature distribution of the pulse tube and the regenerator can be adjusted. Alternatively, the mounting position of the thermal bridge 50 may be different between the pulse tube and the regenerator in order to select a portion where the thermal bridge 50 is easily mounted.
The thermal switch 52 is configured to function as a heat insulating element when the regenerator side is in the 1 st temperature zone T1, and to function as a heat transfer element when the regenerator side is in the 2 nd temperature zone T2 which is lower than the 1 st temperature zone T1. The thermal switch 52 is operated to switch on and off according to a temperature change, and thermally connects the regenerator and the pulse tube (i.e., on) at a relatively low temperature (i.e., the 2 nd temperature zone T2), and cuts off the thermal connection (i.e., off) of the regenerator and the pulse tube at a relatively high temperature (i.e., the 1 st temperature zone T1).
Pulse tube refrigerator 10 is capable of performing steady state operation and a cool down operation performed prior to steady state operation. As described above, the cool down operation may also be referred to as initial cooling. The cooling operation is an operation mode in which the pulse tube refrigerator 10 is rapidly cooled from the initial temperature to the ultra-low temperature when the pulse tube refrigerator 10 is started, and the steady-state operation is an operation mode in which the pulse tube refrigerator 10 is maintained in a state cooled to the ultra-low temperature by the cooling operation. The initial temperature may be ambient temperature (e.g., room temperature). The pulse tube refrigerator 10 is cooled to the standard cooling temperature by the cooling operation, and in the steady-state operation, is maintained within the allowable temperature range including the ultralow temperature of the standard cooling temperature. The standard cooling temperature varies depending on the use and setting of the pulse tube refrigerator 10, for example, in the cooling use of the superconducting device, typically about 4.2K or less. In other cooling applications, the standard cooling temperature may be, for example, about 10K to 20K, or less than 10K. The switching from the cooling operation to the steady-state operation may be performed by controlling the valve portion 40 to change the number of refrigeration cycles per unit time (the frequency of the refrigeration cycles). For example, pulse tube refrigerator 10 may operate with a high frequency refrigeration cycle in a cool down operation and with a low frequency refrigeration cycle below it in a steady state operation.
In this embodiment, the 1 st temperature zone T1 is a temperature range higher than the set temperature Tc, the 2 nd temperature zone T2 is a temperature range lower than the set temperature Tc, and the set temperature Tc is selected from, for example, a temperature range of 4K to 100K. The set temperature Tc may be determined based on the 1 st cooling temperature (target cooling temperature of the 1 st cooling stage 28) described above, and may be determined to be a temperature higher than the 1 st cooling temperature by a predetermined temperature (for example, within 5K or within 10K).
Thus, the thermal switch 52 can be turned off at the start of the cooling operation of the pulse tube refrigerator 10, and the thermal switch 52 can be switched from off to on during the cooling operation (for example, last) or when transitioning from the cooling operation to the steady-state operation. In steady state operation, the thermal switch 52 can be turned on.
Fig. 3 (a) is a schematic diagram showing an example of the thermal bridge 50 with the thermal switch 52 according to the embodiment, and fig. 3 (b) is a graph showing exemplary characteristics of the thermal switch 52 assembled to the thermal bridge 50 according to the embodiment.
As shown in fig. 3 (a), the heat bridge 50 has a heat pipe as the heat switch 52, and a working gas 60 that is gasified in the 1 st temperature zone T1 and liquefied in the 2 nd temperature zone T2 is enclosed in the heat pipe. One end of the heat pipe is connected to a regenerator connection 54, which is thermally connected to a regenerator (e.g., a stage 2 regenerator 22) via the regenerator connection 54. And the other end of the heat pipe is connected to the vessel connecting portion 56, which is thermally connected to the vessel (e.g., the level 2 vessel 24) via the vessel connecting portion 56.
As shown in fig. 3 (b), the thermal switch 52 has a 1 st thermal conductivity α1 in a 1 st temperature zone T1 and a 2 nd thermal conductivity α2 greater than the 1 st thermal conductivity α1 in a 2 nd temperature zone T2 lower than the 1 st temperature zone T1. The set temperature Tc that becomes the boundary between the 1 st temperature zone T1 and the 2 nd temperature zone T2 corresponds to the boiling point of the enclosed working gas 60. In the 1 st temperature zone T1 and the 2 nd temperature zone T2, the change in the thermal conductivity is small and stable as compared with the intermediate transition temperature zone (including the set temperature Tc). In the transition temperature zone, the thermal conductivity α1 varies greatly from the 1 st thermal conductivity α1 toward the 2 nd thermal conductivity α2. In fig. 3 (b), the 1 st thermal conductivity α1 in the 1 st temperature zone T1 and the 2 nd thermal conductivity α2 in the 2 nd temperature zone T2 are each illustrated as a constant value for convenience, but the values of these thermal conductivities may vary somewhat depending on the temperature.
When both ends of the thermal switch 52 (i.e., the heat pipe) are in the 1 st temperature zone T1, the enclosed working gas 60 is entirely gaseous, and thus the thermal switch 52 does not substantially conduct heat. Ideally, the 1 st thermal conductivity α1 is zero, but in fact takes a certain small value corresponding to the thermal conductivity of the working gas 60 in the gaseous state. The thermal conductivity of the wall of the thermal switch 52 in which the working gas 60 is enclosed also contributes to the 1 st thermal conductivity α1. However, since the 1 st thermal conductivity α1 is sufficiently smaller than the 2 nd thermal conductivity α2, the thermal switch 52 can be regarded as an insulating element for shutting off the heat input from the pulse tube to the regenerator in the 1 st temperature zone T1.
In contrast, in the 2 nd temperature zone T2, the working gas 60 is liquefied. When one end (regenerator connection part 54 side) of the thermal switch 52 is in the 2 nd temperature zone T2, the working gas 60 in contact with the inner wall surface thereof is cooled by applying heat to the wall surface, and becomes liquid. The droplet 62 of the working gas 60 is transported toward the other end (the vessel connecting portion 56 side) in the thermal switch 52 by, for example, the action of gravity or by utilizing capillary phenomenon. The transported droplets 62 absorb heat and are vaporized again. Thus, the thermal switch 52 functions as a heat transfer element that transfers heat from the pulse tube connection portion 56 side to the regenerator connection portion 54 side, and thus functions as the thermal bridge 50. Thereby, the other end (the vessel connecting portion 56 side) of the thermal switch 52 can be cooled to the set temperature Tc.
The set temperature Tc is selected by selecting the type of gas of the working gas 60 enclosed in the thermal switch 52. The working gas 60 may comprise, for example, at least 1 of helium (about 4.2K), hydrogen (about 20.4K), neon (about 27.1K), nitrogen (about 77.4K), oxygen (about 90.2K), and argon (about 87.3K). Here, the portion indicated by brackets after the gas species is the boiling point of each gas species at atmospheric pressure. Therefore, for example, when neon is enclosed as the working gas 60 in the air to the thermal switch 52, the set temperature Tc can be set to about 27.1K. The working gas 60 may be enclosed in the thermal switch 52 at a high pressure (e.g., within 5 atmospheres or within 10 atmospheres) above atmospheric pressure. The set temperature Tc can be adjusted by adjusting the sealing pressure of the working gas 60.
The working gas 60 may be, for example, air (about 78.8K), other mixed gas containing nitrogen, mixed gas containing helium, or other mixed gas. The set temperature Tc can be adjusted by adjusting the composition of the mixed gas.
As described at the beginning of the present specification, the regenerator and the pulse tube are connected by the thermal bridge 50, and the pulse tube is cooled from the regenerator through the thermal bridge 50, so that the axial temperature distribution of the pulse tube matches the axial temperature distribution of the regenerator (i.e., the temperature difference between the pulse tube and the regenerator at the same axial position is reduced), and the loss of the refrigerating capacity of the pulse tube refrigerator 10 due to natural convection of the atmospheric gas can be reduced. The effect of such a thermal bridge 50 is effectively exerted by the thermal switch 52 being rendered conductive during steady state operation of the pulse tube refrigerator 10.
In the cooling operation of the pulse tube refrigerator 10, initially, the thermal switch 52 is in an off state, and the thermal bridge 50 becomes an insulating element that cuts off the heat input from the pulse tube to the regenerator through the thermal bridge 50. The pulse tube refrigerator 10 can cool the regenerator and the cooling table more quickly than in the case where heat is input from the pulse tube to the regenerator through the heat bridge 50 without the heat bridge 50 being disconnected, and can reduce the time required for cooling. As the temperature of the regenerator decreases as described above, the thermal switch 52 switches from off to on, the thermal bridge 50 switches from the adiabatic condition to the heat transfer condition, and the pulse tube refrigerator 10 can transition to steady state operation.
Therefore, according to the embodiment, the cooling capacity of the pulse tube refrigerator 10 can be improved while suppressing an increase in the cooling time.
Fig. 4 is a schematic diagram showing another row of the thermal bridge 50 with the thermal switch 52 according to the embodiment. The thermal bridge 50 has a thermal switch 52 that connects a pulse tube (e.g., stage 2 pulse tube 24) and a regenerator (e.g., stage 2 regenerator 22) via the thermal switch 52. The thermal bridge 50 further includes a regenerator connecting portion 54 for connecting the thermal switch 52 to the regenerator and a pulse tube connecting portion 56 for connecting the thermal switch 52 to the pulse tube.
The thermal switch 52 includes an airtight container 64, a gas supply unit 66 for supplying gas to the airtight container 64, and a gas discharge unit 68 for discharging gas from the airtight container 64. The gas supplied to the airtight container 64 may be, for example, the same gas as the working gas sealed in the heat pipe, or any other suitable gas may be used.
The airtight container 64 is a cylindrical pressure container, and one end thereof is connected to the regenerator connecting portion 54 and the other end thereof is connected to the pulse tube connecting portion 56. The gas supply unit 66 includes a gas supply source 66a, a supply valve 66b, and a supply pipe 66c. The gas supply source 66a is connected to the airtight container 64 through a supply pipe 66c. The supply valve 66b is provided in the supply pipe 66c, and when the supply valve 66b is opened, gas is supplied from the gas supply source 66a to the airtight container 64. The gas discharge portion 68 includes a discharge pump 68a, a discharge valve 68b, and a discharge pipe 68c. The discharge pump 68a is connected to the airtight container 64 through a discharge pipe 68c. The discharge valve 68b is provided in the discharge pipe 68c, and when the discharge pump 68a is operated and the discharge valve 68b is opened, the gas is discharged from the airtight container 64 to the discharge pump 68a, whereby the airtight container 64 can be set to a vacuum. The gas supply source 66a, the supply valve 66b, the discharge pump 68a, and the discharge valve 68b may be disposed outside the vacuum vessel in which the pulse tube refrigerator 10 is provided.
The thermal switch 52 can be switched on and off by supplying gas to the airtight container 64 and discharging gas from the airtight container 64. When gas is supplied to the airtight container 64, the thermal switch 52 is turned on by heat conduction of the gas. When the airtight container 64 is evacuated to a vacuum state, the thermal switch 52 is turned off by vacuum insulation.
Therefore, the thermal switch 52 can be operated to function as a heat insulating element when the regenerator side is in the 1 st temperature zone T1 and as a heat transfer element when the regenerator side is in the 2 nd temperature zone T2 which is lower than the 1 st temperature zone T1. The thermal switch 52 may have, for example, a temperature sensor 70 that measures the temperature of the regenerator connection 54, regenerator, or cooling table, and may be turned on and off manually or by automatic control according to the measured temperature.
The thermal switch 52 of the heat pipe type is more advantageous in the case where it is expected to increase the difference in thermal conductivity by turning on and off the thermal switch 52, but the gas supply/discharge type thermal switch 52 is advantageous in that the operating temperature (set temperature Tc) of the thermal switch 52 for switching on and off can be arbitrarily determined.
The present invention has been described above with reference to examples. It should be understood by those skilled in the art that the present invention is not limited to the above embodiments, and various design changes may be made, and various modifications are possible and are included in the scope of the present invention. Various features described in one embodiment may be applied to other embodiments as well. The new embodiments produced by the combination have the effects of the combined embodiments.
In the above-described embodiment, the four-valve type two-stage pulse tube refrigerator of GM system was described as an example, but the thermal bridge with thermal switch according to the present invention can be applied to various pulse tube refrigerators in which pulse tubes and cold storages are arranged in parallel. The heat bridge with the heat switch can also be applied to a single-stage or three-pole multi-stage pulse tube refrigerator. The thermal bridge with the thermal switch can be applied to, for example, a pulse tube refrigerator of GM type having a phase control mechanism of a different type from a four-valve type, such as a two-way intake type and an active buffer type. The thermal bridge with the thermal switch can be applied to, for example, a pulse tube refrigerator having a vibration generation source of a different type from the GM type such as the stirling type.
The present invention has been described above by using specific terms based on the embodiments, but the embodiments merely represent one side of the principle and application of the present invention, and in the embodiments, various modifications and arrangement changes are allowed without departing from the scope of the idea of the present invention defined in the claims.
Industrial applicability
The present invention can be used in the field of pulse tube refrigerators and superconducting magnet devices.
Symbol description
10-pulse tube refrigerator, 16-1 st stage regenerator, 18-1 st stage pulse tube, 22-2 nd stage regenerator, 24-2 nd stage pulse tube, 50-heat bridge, 52-heat switch, 60-working gas, 64-airtight container, 66-gas supply part, 68-gas discharge part, 200-superconducting magnet device, 202-superconducting coil, 204-cryostat.
Claims (7)
1. A pulse tube refrigerator is characterized by comprising:
a vessel;
a regenerator disposed in parallel with the pulse tube: a kind of electronic device with high-pressure air-conditioning system
A thermal bridge having a thermal switch and connecting the pulse tube and the regenerator via the thermal switch,
the thermal switch functions as a heat insulating element when the regenerator side of the thermal bridge is in the 1 st temperature zone and functions as a heat transfer element when the regenerator side of the thermal bridge is in the 2 nd temperature zone lower than the 1 st temperature zone.
2. A pulse tube refrigerator according to claim 1, wherein,
the heat bridge has a heat pipe as the heat switch, and a working gas that is gasified in the 1 st temperature zone and liquefied in the 2 nd temperature zone is enclosed in the heat pipe.
3. A pulse tube refrigerator according to claim 2, wherein,
the working gas comprises at least 1 of helium, hydrogen, neon, nitrogen, oxygen, and argon.
4. A pulse tube refrigerator according to claim 2 or 3, wherein,
the working gas is a mixed gas.
5. A pulse tube refrigerator according to claim 1, wherein,
the thermal switch is provided with: an airtight container provided to the thermal bridge and connecting the pulse tube and the regenerator; a gas supply unit that is operated to supply gas to the airtight container when the regenerator side of the thermal bridge is in the 2 nd temperature zone; and a gas discharge unit that operates to discharge the gas from the airtight container when the regenerator side of the thermal bridge is in the 1 st temperature zone.
6. A pulse tube refrigerator according to any one of claims 1-5, wherein,
the 1 st temperature zone is a temperature range higher than a set temperature, the 2 nd temperature zone is a temperature range lower than the set temperature, and the set temperature is selected from a temperature range of 4K to 100K.
7. A superconducting magnet device is characterized by comprising:
a superconducting coil;
a cryostat having a liquid cryogen tank for accommodating the superconducting coil and liquid cryogen together; a kind of electronic device with high-pressure air-conditioning system
The pulse tube refrigerator of any one of claims 1 to 6, disposed at the cryostat and recondensing the liquid cryogen.
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2021-003930 | 2021-01-14 | ||
| JP2021003930 | 2021-01-14 | ||
| PCT/JP2021/044504 WO2022153713A1 (en) | 2021-01-14 | 2021-12-03 | Pulse tube freezer and superconductive magnet apparatus |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CN116710717A true CN116710717A (en) | 2023-09-05 |
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| Application Number | Title | Priority Date | Filing Date |
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| CN202180088748.XA Pending CN116710717A (en) | 2021-01-14 | 2021-12-03 | Pulse tube refrigerator and superconducting magnet device |
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| CN (1) | CN116710717A (en) |
| WO (1) | WO2022153713A1 (en) |
Family Cites Families (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH09312210A (en) * | 1996-03-18 | 1997-12-02 | Toshiba Corp | Cooling device and cooling method |
| JP3835912B2 (en) * | 1997-12-17 | 2006-10-18 | 三菱重工業株式会社 | Pulse tube refrigerator |
| JP3589401B2 (en) * | 2000-02-24 | 2004-11-17 | 住友重機械工業株式会社 | Pulse tube refrigerator |
| US7568351B2 (en) * | 2005-02-04 | 2009-08-04 | Shi-Apd Cryogenics, Inc. | Multi-stage pulse tube with matched temperature profiles |
| JP2020031160A (en) * | 2018-08-23 | 2020-02-27 | 住友重機械工業株式会社 | Superconducting magnet cooling device and superconducting magnet cooling method |
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2021
- 2021-12-03 WO PCT/JP2021/044504 patent/WO2022153713A1/en active Application Filing
- 2021-12-03 CN CN202180088748.XA patent/CN116710717A/en active Pending
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| WO2022153713A1 (en) | 2022-07-21 |
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