Ultralow-vibration low-temperature system

Abstract

The invention discloses a low-temperature system with ultralow vibration. A small-sized low-temperature refrigerator is mounted in a closed damping heat exchange cavity in a vacuum manner; a sealing cavity is formed in the top of the small low-temperature refrigerating machine, and the two cavities are connected through a breather pipe to balance air pressure in the two cavities. A flow resistor and a heat exchange element are arranged in the cold box, a heat exchange pipe is arranged on the outer wall of the cavity heat exchanger, and a first inlet and a first outlet are formed in the two ends of the heat exchange pipe correspondingly. A second inlet communicated with an inner cavity of the closed damping heat exchange cavity is formed in the upper part of the closed damping heat exchange cavity; a first exhaust pipe is connected to the dilution unit; a first heat exchange coil pipe is arranged in the first exhaust pipe; the first inlet, the first outlet, the first heat exchange coil pipe, the flow resistor, the heat exchange element and the first exhaust pipe form a circulation loop; and a refrigerant is injected into the closed damping heat exchange cavity. It is guaranteed that the pressure in the damping heat exchange cavity is constant, and instability, caused by pressure fluctuation, of the heat exchange and damping effects is avoided.

Description

Technical Field

[0001] The present invention relates to the technical field of low-temperature refrigeration, and in particular to an ultra-low vibration low-temperature system. Background Art

[0002] Cryostat with liquid helium as working fluid can continuously provide low temperature environment from 4K to mK level, and is widely used in quantum physics, aerospace, basic physics research and other fields. Existing cryogenic systems mostly use Gifford-McMahon (GM) refrigerator and pulse tube refrigerator as cold source, and both types of refrigerators have corresponding mechanical parts moving during operation, which will generate vibration, which will have an adverse effect on the system thermometer measurement, so reducing system vibration is an important part of cryogenic system production.

[0003] In order to reduce the vibration generated by the cold source, Chinese patent 2022104849981 discloses a dilution refrigeration system, in which a low-temperature refrigerator is placed in a system in a damping heat exchange cavity. When the system is running, the gaseous working medium enters the damping heat exchange cavity, and is pre-cooled by the low-temperature refrigerator while also serving as a heat exchange medium between the low-temperature refrigerator and the damping heat exchange cavity. The cold capacity of the low-temperature refrigerator is exported to the wall of the damping heat exchange cavity and the pipeline surrounding the outside of the damping heat exchange cavity to pre-cool the working medium of another circuit circulating through the pipeline. However, the disadvantage of this pre-cooling method is that the pressure in the damping heat exchange cavity cannot be kept constant, because the gaseous working medium entering the damping heat exchange cavity is constantly circulating, and its circulation flow changes according to the system operating conditions. When the system circulation flow changes, the pressure inside the damping heat exchange cavity also changes accordingly. The pressure fluctuation in the shock-absorbing heat exchange cavity will produce the following adverse effects: First, the heat exchange performance is unstable. When the cooling capacity of the low-temperature refrigerator is constant, the heat exchange between the low-temperature refrigerator and the cavity wall inside the shock-absorbing heat exchange cavity depends on the mass of the gas medium involved in the heat exchange, that is, the pressure inside the shock-absorbing heat exchange cavity. When the pressure inside the shock-absorbing heat exchange cavity fluctuates, the heat exchange effect also fluctuates accordingly; Second, when the pressure inside the heat exchange cavity is low, shock absorption cannot be achieved. The low-temperature refrigerator is connected to the shock-absorbing heat exchange cavity through an elastic bellows at the top of the shock-absorbing cavity. When the system is running, the bellows will shrink or stretch due to the influence of the internal and external pressure difference. When the pressure inside the heat exchange cavity is low, the bellows will shrink significantly and lose its elasticity. At this time, the low-temperature refrigerator and the shock-absorbing heat exchange cavity are rigidly connected, and the vibration of the low-temperature refrigerator will be directly transmitted to the shock-absorbing heat exchange cavity, and then to the cold box, and the system loses its shock-absorbing effect.

[0004] In order to solve the influence of air pressure fluctuations, Chinese patent 2022213673527 discloses a suspended symmetrical vibration-damping low-temperature device, which is connected to the vacuum chamber of a low-temperature thermostat, and can effectively compensate for the influence of atmospheric pressure and refrigerator on the vibration-damping components after vacuuming; however, the device only places the refrigerator directly on the flange of the vacuum chamber, and the cold end of the refrigerator and the components in the cold box cannot achieve the effect of simultaneous vibration reduction and heat exchange. Summary of the invention

[0005] Purpose of the invention: The purpose of the present invention is to provide an ultra-low vibration cryogenic system based on a small cryogenic refrigerator to ensure an extremely low vibration level, while the heat exchange and shock absorption performance are not affected by the system circulating working fluid flow rate.

[0006] Technical solution: The ultra-low vibration cryogenic system of the present invention comprises a small cryogenic refrigerator, a closed shock-absorbing heat exchange cavity and a cold box. The small cryogenic refrigerator is installed in the closed shock-absorbing heat exchange cavity through a room temperature flange and a shock-absorbing bellows vacuum seal; the small cryogenic refrigerator has at least two cold ends, each cold end is connected to a cold end heat exchanger, at least two cavity heat exchangers are arranged on the cavity wall plate of the closed shock-absorbing heat exchange cavity, and there is a gap between the cavity heat exchanger and the cold end heat exchanger;

[0007] The cold box is provided with a flow resistance and a heat exchange element, the outer wall of the cavity heat exchanger is provided with a heat exchange tube, one end of the heat exchange tube extending out of the cold box is a first inlet, and the other end of the heat exchange tube is a first outlet; the upper part of the closed shock-absorbing heat exchange cavity is provided with a second inlet communicating with its inner cavity, and the heat exchange element is connected with a first exhaust pipe; the first exhaust pipe is provided with a first heat exchange coil;

[0008] The first inlet, the first outlet, the first heat exchange coil, the flow resistance, the dilution unit, and the first exhaust pipe form a circulation loop; the closed damping heat exchange cavity is filled with refrigerant.

[0009] Preferably, the refrigerant in the closed-loop vibration-damping heat exchange cavity is helium-4 gas, the circulating loop refrigerant is helium-3 or a mixture of helium-3 and helium-4. When the heat exchange element is a closed heat exchange cavity, the refrigerant is helium-3 gas, and when the heat exchange element is a dilution unit chamber, the refrigerant is a mixture of helium-3 and helium-4.

[0010] Furthermore, a top sealed cavity is arranged on the top of the small low-temperature refrigerator, and the sealed cavity includes a top sealing plate and a bottom sealing plate. The top sealing plate is fixed to the room temperature flange through a support rod, and the bottom sealing plate is fixed to the top of the small low-temperature refrigerator through a support rod. A sealed cavity is formed between the top sealing plate and the bottom sealing plate through a shock-absorbing bellows, and the sealed cavity is connected to the interior of the closed shock-absorbing heat exchange cavity through a ventilation pipe.

[0011] Furthermore, the flow resistance on the circulation loop may be located inside or outside the first exhaust pipe.

[0012] Furthermore, the closed shock-absorbing heat exchange cavity is connected to the cold box room temperature flange at the top of the cold box through the cavity room temperature flange at the top; multiple cold plates and multiple cold screens are arranged in the cold box to form a multi-layer low-temperature cavity; the cavity heat exchanger is connected to the cold plate.

[0013] Furthermore, a staggered fin, interdigitated finger or sleeve ring heat exchange structure is used between the cavity heat exchanger and the cold end heat exchanger.

[0014] Preferably, the flow resistance is a capillary tube or a cryogenic valve.

[0015] Preferably, the small low-temperature refrigerator is a Gifford-McMahon refrigerator or a pulse tube refrigerator.

[0016] Preferably, a secondary cold plate and a secondary cold screen are provided in the cold box.

[0017] Beneficial effects: Compared with the prior art, the present invention has the following advantages: 1. The present invention no longer sets a separate helium-4 circuit, ensuring that the internal pressure of the vibration-damping heat exchange cavity is constant, avoiding the instability of heat exchange and vibration-damping effects caused by pressure fluctuations, and efficiently utilizing the refrigeration capacity of the small low-temperature refrigerator, greatly increasing the system pre-cooling capacity, and further improving the floor cooling capacity; 2. The present invention separates the small low-temperature refrigerator from the cold box based on the closed vibration-damping heat exchange cavity structure, and can reduce the system vibration to far below 1 micron; 3. The present invention uses the top closed cavity to balance the pressure inside the vibration-damping heat exchange cavity. When the internal pressure of the vibration-damping heat exchange cavity is low, the top closed cavity provides an upward force through the action of atmospheric pressure to offset the downward force of atmospheric pressure on the vibration-damping heat exchange cavity, thereby avoiding the metal bellows on the vibration-damping heat exchange cavity from shrinking and losing elasticity and being unable to reduce vibration. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a schematic diagram of the structure of a closed damping heat exchange cavity;

[0019] Figure 2 It is a schematic diagram of the structure of the present invention. DETAILED DESCRIPTION

[0020] The technical solution of the present invention is further described below in conjunction with the accompanying drawings.

[0021] The ultra-low vibration low temperature system of the present invention comprises a cold box 18, and a primary cold plate 19, a secondary cold plate 21, a primary cold shield 20, and a secondary cold shield 22 are arranged inside the cold box 18. A cold box room temperature flange 17 is arranged on the top of the cold box 18. A closed shock-absorbing heat exchange cavity 15 is arranged on the top of the cold box 18, and the closed shock-absorbing heat exchange cavity 15 is assembled and welded by a cavity primary heat exchanger 4, a cavity secondary heat exchanger 6, and a cavity wall plate 10, and a cavity room temperature flange 16 is arranged on the top of the closed shock-absorbing heat exchange cavity 31. The closed shock-absorbing heat exchange cavity 15 is inserted from the top of the cold box 18 from top to bottom, and is connected to the cold box room temperature flange 17 through the cavity room temperature flange 16, and the cavity primary heat exchanger 4 is connected to the primary cold plate 19, and the cavity secondary heat exchanger 6 is connected to the secondary cold plate 21, so as to form a vacuum sealed cavity in the cold box 18.

[0022] The small low-temperature refrigerator 1 is inserted into the closed damping heat exchange cavity 31 and is circumferentially connected to the closed damping heat exchange cavity 15 through the first damping bellows 2. A vacuum sealed environment is also formed in the closed damping heat exchange cavity 31. The small low-temperature refrigerator 1 has two cold ends, including a primary cold end 11 and a secondary cold end 12. The primary cold end 11 is connected to a cold end primary heat exchanger 5, and the secondary cold end 12 is connected to a cold end secondary heat exchanger 13; the cavity primary heat exchanger 4 is not in contact with the cold end primary heat exchanger 5, and the cavity secondary heat exchanger 6 is not in contact with the cold end secondary heat exchanger 138, so as to realize the vibration isolation between the small low-temperature refrigerator 1 and the cold box 18; a flow resistance 9 is also provided in the cold box 18, and heat exchange pipes are provided on the outer walls of the cavity wall panel 10, the cavity primary heat exchanger 4 and the cavity secondary heat exchanger 6. One end of the heat exchange pipe extending out of the cold box 18 is a first inlet 3, and the other end of the heat exchange pipe is a first outlet 7; a second inlet 14 communicating with its inner cavity is provided on the upper part of the closed shock-absorbing heat exchange cavity 15; a first exhaust pipe 23 is connected to the heat exchange element in the cold box 18, and a first heat exchange coil 8 is provided in the first exhaust pipe 23.

[0023] The first inlet 3, the first outlet 7, the first heat exchange coil 8, the flow resistance 9, the heat exchange element 31, and the first exhaust pipe 23 form a circulation loop. The refrigerant is helium-3 or a mixture of helium-3 and helium-4. It enters the cold box 18 from the first inlet 3, and after heat exchange through the heat exchange tubes at the outer wall 10 of the vibration-damping heat exchange cavity, the first-stage heat exchanger 4 of the cavity, and the outer wall of the second-stage heat exchanger 6 of the cavity, it is partially liquefied and passes through the first heat exchange coil 8 in the first exhaust pipe 23. It is then throttled by the flow resistance 9 and flows into the heat exchange element 31. It is then extracted from the first exhaust pipe 23 through a circulation pump and returns to the first inlet 3.

[0024] In the closed damping heat exchange cavity, the helium 4 loop no longer circulates, but the helium 4 gas is filled into the closed damping heat exchange cavity through the second inlet 16, and remains in the damping cavity after heat exchange at the primary cold end 11, the secondary cold end 12, the cold end primary heat exchanger 4 and the cold end secondary heat exchanger 5, acting as a heat exchange medium between the primary cold end 11, the secondary cold end 12, the cold end primary heat exchanger 5, the cold end secondary heat exchanger 13 and the wall 10 and the cavity primary heat exchanger 4 and the cavity secondary heat exchanger 6. In this embodiment, the temperature of the primary cold plate 19 is between 30 and 70K, and the temperature of the secondary cold plate 217 is between 2 and 5K.

[0025] Furthermore, a top sealed cavity 230 is arranged on the top of the small low-temperature refrigerator 1, and the sealed cavity 30 includes a top sealing plate 26 and a bottom sealing plate 27. The top sealing plate 26 is fixed to the room temperature flange 16 through a first support rod 24, and the bottom sealing plate 27 is fixed to the top of the small low-temperature refrigerator 1 through a second support rod 25. A sealed cavity is formed between the top sealing plate 26 and the bottom sealing plate 27 through a second shock-absorbing bellows 28, and the sealed cavity is connected to the inside of the closed shock-absorbing heat exchange cavity 30 through a ventilation pipe 29 to ensure that the pressure of the two is always maintained constant. The main function of the top sealed cavity 30 is: when the vibration-damping heat exchange cavity without such a structure is cooled, the air pressure inside the vibration-damping heat exchange cavity will gradually decrease due to the continuous decrease in the temperature of the refrigerator. At this time, the atmospheric pressure acts on the top of the refrigerator, pressing down the refrigerator, causing the first vibration-damping bellows 2 of the vibration-damping heat exchange cavity to be continuously compressed, lose its elasticity, and thus lose its vibration-damping function; while for the vibration-damping heat exchange cavity with such a structure, when the temperature is cooled, although the pressure inside the vibration-damping heat exchanger cavity is reduced, causing the atmospheric pressure to press down the refrigerator, at the same time, the pressure of the top opposite cavity is also reduced, and the atmospheric pressure will act on the bottom sealing plate 27, compressing the second vibration-damping bellows 28, forming an upward force, which offsets the force acting on the vibration-damping heat exchanger cavity, thereby avoiding the compression of the first vibration-damping bellows 2 on the vibration-damping heat exchange cavity and losing its vibration-damping effect.

[0026] The present invention is based on this special closed shock-absorbing heat exchange cavity. On the one hand, it can construct multi-level high-efficiency heat conduction to pre-cool the refrigerant gas; on the other hand, it can achieve non-contact vibration isolation between a small low-temperature refrigerator and a cold box to ensure the refrigeration effect.

Claims

1. An ultra-low vibration cryogenic system, comprising a small cryogenic refrigerator (1), a closed vibration-damping heat exchange cavity (15) and a cold box (18), wherein the small cryogenic refrigerator (1) is installed in the closed vibration-damping heat exchange cavity (15) by means of a room temperature flange and a vibration-damping bellows in a vacuum seal; characterized in that: The small low-temperature refrigerator (1) has at least two cold ends, each cold end is connected to a cold end heat exchanger, and at least two cavity heat exchangers are provided on the cavity wall plate (10) of the closed shock-absorbing heat exchange cavity (15), and there is a gap between the cavity heat exchanger and the cold end heat exchanger; A flow resistor (9) and a heat exchange element (31) are provided in the cold box (18); a heat exchange tube is provided on the outer wall of the cavity heat exchanger; one end of the heat exchange tube extending out of the cold box (18) is a first inlet (3); the other end of the heat exchange tube is a first outlet (7); a second inlet (14) communicating with the inner cavity of the closed damping heat exchange cavity (15) is provided at the upper part; a first exhaust pipe (23) is connected to the heat exchange element; and a first heat exchange coil (8) is provided in the first exhaust pipe (23); The first inlet (3), the first outlet (7), the first heat exchange coil (8), the flow resistance (9), the heat exchange element (10), and the first exhaust pipe (23) form a circulation loop, and the circulation loop and the closed damping heat exchange cavity (15) are filled with refrigerant.

2. The ultra-low vibration cryogenic system according to claim 1, characterized in that: The heat exchange element (10) is a closed heat exchange cavity or a dilution unit.

3. The ultra-low vibration cryogenic system according to claim 1, characterized in that: The refrigerant in the closed vibration-damping heat exchange cavity is helium-4 gas; when the heat exchange element (10) is a closed heat exchange cavity, the refrigerant in the circulation loop is helium-3 gas; when the heat exchange element (10) is a dilution unit, the refrigerant in the circulation loop is a mixed gas of helium-3 and helium-4.

4. The ultra-low vibration cryogenic system according to claim 1, characterized in that: A top sealed cavity (30) is arranged at the top of the small low-temperature refrigerator (1), and the sealed cavity comprises a top sealing plate (26) and a bottom sealing plate (27), the top sealing plate (26) is fixed to the room temperature flange via a first support rod (24), the bottom sealing plate (6) is fixed to the top of the small low-temperature refrigerator (1) via a second support rod (25), a sealed cavity is formed between the top sealing plate (26) and the bottom sealing plate (27) via a second shock-absorbing bellows (28), and the sealed cavity is connected to the inside of the closed shock-absorbing heat exchange cavity (30) via a vent pipe (29).

5. The ultra-low vibration cryogenic system according to claim 1, characterized in that: The closed damping heat exchange cavity (15) is connected to the cold box room temperature flange (17) at the top of the cold box (18) via the cavity room temperature flange (16) at the top; a multi-stage cold plate and a multi-stage cold screen are arranged in the cold box (18) to form a multi-layer low-temperature cavity; and the cavity heat exchanger is connected to the cold plate.

6. The ultra-low vibration cryogenic system according to claim 1, characterized in that: The flow resistance (9) is located inside or outside the first exhaust pipe (23).

7. The ultra-low vibration cryogenic system according to claim 1, characterized in that: A staggered fin, interdigitated finger or sleeve ring heat exchange structure is used between the cavity heat exchanger and the cold end heat exchanger.

8. The ultra-low vibration cryogenic system according to claim 1, characterized in that: The flow resistance (9) is a capillary tube or a cryogenic valve.

9. The ultra-low vibration cryogenic system according to claim 1, characterized in that: The small low-temperature refrigerator (1) adopts a Gifford-McMahon refrigerator or a pulse tube refrigerator.

10. The ultra-low vibration dilution refrigeration system according to claim 5, characterized in that: The cold box (18) is provided with a secondary cold plate and a secondary cold screen.

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