Cold compressor and dilution refrigerator adopting same

Abstract

The invention relates to a cold compressor and a dilution refrigerator adopting the cold compressor, the cold compressor comprises a driving part, an air cylinder and a piston, and further comprises a precooling refrigerator, the precooling refrigerator is connected with the air cylinder, and the compressor is precooled through the precooling refrigerator. The cold compressor can be used on a dilution refrigerating machine or a space dilution refrigerating machine, and compared with the prior art, the refrigerating machine is adopted for cooling the compressor, so that the compressor becomes the cold compressor, and therefore it is ensured that helium-3 is compressed at the low temperature.

Description

Technical Field

[0001] The invention relates to a refrigerator, in particular to a cold compressor and a dilution refrigerator using the cold compressor. Background Art

[0002] The characteristics of dilution refrigerators for space are zero gravity and small cooling capacity. Patent application CN2024105341129 discloses a dilution refrigerator for space. A heating element is arranged inside the dilution refrigerator's dilution refrigerator. A high temperature zone is formed inside the dilution refrigerator through the heating element. The mixture of helium 3 and helium 4 is controlled to separate into phases, the liquid phase adheres to the inner wall of the dilution refrigerator, and the gas phase converges in the high temperature zone. The problem that the gas separation of helium 3 and helium 4 in the mixing chamber of the dilution refrigerator for space under zero gravity or microgravity becomes very difficult due to the lack of boundaries is solved. However, since the cooling capacity of the dilution refrigerator for space is very small, generally at the microwatt level, such as 1 microwatt, it is not realistic to use a conventional vacuum pump such as a molecular pump or a dry pump for a ground dilution refrigerator to compress He-3. In space, a piston compressor driven by a linear compressor is generally used to compress He-3. This is the current realistic space compressor with a long life. Since the low pressure of the dilution refrigerator is close to high vacuum, the pressure is about 100-1000Pa. The specific pressure depends on the minimum cooling temperature and the distillation chamber temperature determined according to the minimum cooling temperature. The temperature of low-pressure He3 leaving the heat exchanger of the dilution loop and entering the compressor is in the 4K temperature range, and the density is relatively large. If the linear compressor is not cooled, when the cooling capacity is in the microwatt level, such as 1 microwatt, the flow rate of He3 is very small, and the temperature difference between the room temperature end and the low temperature end of the compressor is large, and the heat leakage is also large. The temperature of the low temperature end will rise due to heat leakage, even close to room temperature, so that the average temperature of the compression chamber rises to close to room temperature. The flow rate of the inhaled He3 is small and will be heated, and its compression is even at room temperature. In this way, its density is 1-2 orders of magnitude lower than that of compression at low temperature, and the normal opening and closing of the compressor inlet valve and outlet valve cannot be guaranteed. Moreover, as the temperature rises, the density decreases, the mass density of the inhaled He3 decreases, and the compressor volume is larger. If a refrigerator is used to cool the compressor, making the compressor a cold compressor, He-3 will not be heated to a very high temperature, and the density will not change greatly, which can ensure that the compressor's inlet valve and outlet valve open and close normally at such a low pressure, and the volume can be designed to be smaller, which has an advantage in weight. So far, dry dilution refrigerators for space use have only remained in research. Summary of the invention

[0003] The purpose of the present invention is to provide a cold compressor and a dilution refrigerator using the cold compressor in order to overcome the defects of the above-mentioned prior art, so that the compressor becomes a cold compressor, thereby ensuring that the compression of helium 3 is carried out at a low temperature.

[0004] The purpose of the present invention can be achieved through the following technical scheme: a cold compressor, including a driving component, a cylinder and a piston, and also including a pre-cooling refrigerator, which is connected to the cylinder and pre-cools the compressor through the pre-cooling refrigerator.

[0005] Furthermore, the pre-cooling refrigerator is a pulse tube refrigerator, a JT refrigerator, a Stirling refrigerator or a VM refrigerator.

[0006] Furthermore, the cold compressor is a single-stage compressor or a multi-stage compressor.

[0007] Furthermore, the pre-cooling refrigerator is a single-stage or multi-stage refrigerator, including at least one stage of cold head, and the cold head is connected to the cylinder of the cold compressor through a thermal bridge.

[0008] Furthermore, the cylinder and piston of the multi-stage compressor are of stepped structure, forming a multi-stage compression chamber, and the side walls of each stage of the compression chamber are connected to the cold head of the pre-cooling refrigerator through a thermal bridge.

[0009] Furthermore, the phase adjustment mechanism adopted by the pulse tube refrigerator includes an inertia tube, two-way air intake, multi-way air intake or a push piston;

[0010] The pulse tube refrigerator is in the form of gas coupling, thermal coupling or a mixture of thermal coupling and gas coupling.

[0011] Furthermore, the precooling refrigerator is also connected to a cooler, and the cold compressor is cooled by the precooling refrigerator or the precooling refrigerator and the cooler, wherein the precooling refrigerator cools the cooler, and the cooler is a JT refrigerator. The cooler can also be a composite of heat exchangers with different temperatures.

[0012] The present invention also provides a dilution refrigerator, which adopts the cold compressor.

[0013] The dilution refrigerator comprises a cold compressor, a cooler, a high-temperature heat exchanger, a high-temperature throttle valve, a distillation chamber, a low-temperature heat exchanger, a low-temperature throttle valve and a cold heat exchanger which are connected in sequence.

[0014] The present invention also provides a space dilution refrigerator, which adopts the cold compressor.

[0015] The cold compressor can be used not only in space, but also in dilution refrigerators on the ground, and can also be used for other low-temperature gases that need to be compressed. The compressor can also be a combination of a cold compressor and a conventional compressor.

[0016] Compared with the prior art, the present invention has the following beneficial effects:

[0017] The present invention designs a compressor with a special structure, which is cooled by a refrigerator, so that the compressor becomes a cold compressor, thereby ensuring that the compression of helium 3 is carried out at a low temperature.

[0018] Compared with the conventional ground-based dilution refrigerator molecular pumps, dry pumps and other vacuum pumps, linear compressors can be used in space, have a long life and high reliability. The driving components of the compressor generally use linear motors, which can achieve long life. The piston is generally suspended by a leaf spring, supporting the piston to suspend in the cylinder, and maintaining a gap between the cylinder as a seal. The gap width is generally 10-20 microns. Dry friction can also be used between the piston and the cylinder, but the life is shorter. Rotary motors and crank-connecting rod mechanisms can also be used, but the life is not as long as linear motors. The cylinder and piston are generally made of low thermal conductivity materials, such as stainless steel, titanium and titanium alloys, and are made of thin walls to reduce heat leakage.

[0019] Generally, the temperature of He3 entering the cold compressor is about 4K, which will have a weak cooling effect on the wall of the compression chamber. The wall of the cylinder is controlled at about 10K by the refrigerator, so that the compression is completed at low temperature. The density of the gas does not change much, which can ensure the opening and closing of each valve.

[0020] The cold compressor can be cooled directly by the precooling refrigerator or by the precooling refrigerator plus a cooler, and the cooler is precooled by the precooling refrigerator. The cold compressor is cooled by the precooling refrigerator plus a cooler, that is, the precooling refrigerator not only cools the cold compressor, but also precools the JT refrigerator. The helium pipeline of the JT refrigerator brings part of the cold capacity to the cold compressor, further cooling the cold compressor.

[0021] The cold compressor of the driving component can be single-stage, and the single-stage compressor is connected to a single-stage pulse tube refrigerator or a multi-stage pulse tube refrigerator; each cold head of the pulse tube refrigerator is connected to the cylinder side wall of the single-stage compressor;

[0022] The cold compressor can also be multi-stage. The multi-stage compressor needs to be provided with a corresponding multi-stage pulse tube refrigerator. The cold heads of each stage of the pulse tube refrigerator are respectively connected to the compression chambers of each stage of the multi-stage compressor. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is a schematic diagram of a dilution unit using a cold compressor in Example 1;

[0024] Figure 2 This is a schematic diagram of a cold compressor of Example 1;

[0025] Figure 3 This is a schematic diagram of a cold compressor in Example 2;

[0026] Figure 4 This is a schematic diagram of a cold compressor in Example 3;

[0027] Figure 5 This is a schematic diagram of a cold compressor of Example 4;

[0028] Figure 6 This is a schematic diagram of a cold compressor in Example 5;

[0029] Figure 7 This is a schematic diagram of the cold compressor of Example 6.

[0030] Markings in the figure:

[0031] 12-helium 3 flow channel, 111-high pressure helium 3 inlet, 112-high pressure helium 3 outlet, 113-cooling coil, 121-low pressure helium 3 outlet;

[0032] 21-high temperature heat exchanger, 22-cold compressor, 23-cooler, 24-high temperature throttle valve, 25-low temperature heat exchanger, 26-low temperature throttle valve;

[0033] 221-driving component, 222-cylinder, 223-piston, 224-high-pressure compression chamber, 2241-high-pressure intake valve, 2242-high-pressure exhaust valve, 2243-air outlet, 225-low-pressure compression chamber, 2251-low-pressure intake valve, 2252-low-pressure exhaust valve, 2253-air inlet, 226-gas collecting chamber;

[0034] 311-distillation chamber, 321-distillation chamber outlet;

[0035] 41-cold heat exchanger, 411-porous medium;

[0036] 50-precooling refrigerator, 51-first cold finger, 511-first cold head, 521-second cold head, 531-third cold head, 52-second cold finger, 53-third cold finger, 54-precooling refrigerator compressor, 55-common inertial tube, 551-gas reservoir, 541-first thermal bridge, 542-second thermal bridge, 543-third thermal bridge;

[0037] 60-JT refrigerator, 61-first JT heat exchanger, 62-second JT heat exchanger, 63-third JT heat exchanger, 64-final JT heat exchanger, 65-JT compressor, 651-JT low-pressure flow channel, 652-JT high-pressure flow channel, 611-first JT pre-cooling heat exchanger, 621-second JT pre-cooling heat exchanger, 631-third JT pre-cooling heat exchanger, 65-JT throttle valve, 66-JT cooling heat exchanger, 661-final JT pre-cooling heat exchanger. DETAILED DESCRIPTION

[0038] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments.

[0039] Unless otherwise specified, all components involved in the present invention are conventional commercially available components in the art.

[0040] Example 1

[0041] like Figure 1As shown, the dilution unit using a cold compressor includes a high-temperature heat exchanger 21, a cold compressor 22, a cooler 23, a high-temperature throttle valve 24, a low-temperature heat exchanger 25, a low-temperature throttle valve 26, a distillation chamber 311, a cold heat exchanger 41, and a superfluid helium flow channel 42.

[0042] The high-concentration helium 3 gas containing a small amount of helium 4 flows out from the outlet 321 of the distillation chamber, enters the high-temperature heat exchanger 21 for reheating, enters the cold compressor 22 for compression, and then is cooled by the cooler 23, enters the high-temperature heat exchanger 21 for cooling, and is throttled by the high-temperature throttle valve 24. It enters the cooling coil inside the distillation chamber 311 through the high-pressure helium 3 inlet 111 to be cooled, and then flows out from the high-pressure helium 3 outlet 112, and further enters the cooling coil 113 in thermal contact with the outside of the distillation chamber 311 for cooling, enters the helium 3 flow channel 12 of the low-temperature heat exchanger 25 for cooling, and then enters the low-temperature throttle valve 26. After throttling, the helium 3 enters the cold heat exchanger 41 to output cold energy to the outside, and then enters the distillation chamber 311 from the distillation chamber inlet 314 after being reheated in the low-temperature heat exchanger 25 along the superfluid helium flow channel 42. The mixed liquid of helium 3 and helium 4 is heated in the distillation chamber 311 , and the helium 3 evaporates from the superfluid helium and enters the gas zone of the distillation chamber 311 and then flows out from the distillation chamber outlet 321 .

[0043] Another difficulty of the dilution refrigerator for space is that the gas separation of helium 3 and helium 4 in the distillation chamber under microgravity becomes very difficult due to the absence of a gas-liquid interface. The present invention adopts a method of heating the interior of the distillation chamber to create a high-temperature area inside the distillation chamber, which is a gas phase area. The superfluid helium is stored on and near the inner wall of the distillation chamber by using the characteristics of superfluid helium crawling along the solid surface and capillary force, and porous media are added to the wall of the distillation chamber to further enhance the adsorption characteristics of superfluid helium on the wall. In this way, the center of the mixing chamber is gas and the periphery is liquid, ensuring the existence of gas phase and liquid phase areas in the absence of gravity.

[0044] In this embodiment, the distillation chamber 311 is provided with a He3 cooling coil and a heater inside, and is also provided with a He3 outlet pipe extending outward, the mouth of which is the distillation chamber outlet 321. The middle of the distillation chamber 311 is mainly helium 3 gas, and the surrounding is superfluid helium (helium 4). The vapor pressure of helium 3 is higher than that of helium 4, so the gas phase is mainly helium 3, and the liquid phase is mainly helium 4. Due to the low temperature, helium 4 is superfluid. The He3 cooling coil in the middle of the distillation chamber 311 releases heat, and the He3 outlet pipe prevents the superfluid helium liquid film from creeping. The heater is also in the middle of the distillation chamber 311, so that the heat flow is directed from the middle to the surroundings, thereby ensuring that the gas phase area in the middle is slightly hot and has a temperature gradient, thereby ensuring that the middle is a gas phase area.

[0045] The cryogenic throttle valve 26 should generate enough pressure difference to prevent the superfluid helium 4 from flowing into the helium 3 flow channel 12. The cryogenic throttle valve 26 can be a capillary tube or a porous medium or a small hole.

[0046] A throttle valve can be added anywhere in the high-pressure He3 flow channel to control temperature and pressure.

[0047] Heat exchanger 41 also acts as a mixing chamber. A porous medium 411 is filled in 41, such as a porous medium made of silver powder, and superfluid He4 is attached to the surface of the porous medium. After He3 enters heat exchanger 41 through throttle valve 26, it cannot immediately mix with He4 to form a uniform mixed liquid and generate cold, but gathers into He3 micro-clusters. When He3 micro-clusters pass through the porous medium, they will penetrate into He4. Since the surface area of ​​the porous medium is large, when He3 passes through the porous medium, it will form a uniform mixed liquid with He4 to complete the refrigeration process. Here, the porous medium acts as the phase interface between the dense phase and the dilute phase of an ordinary dilution refrigerator. The He4 attached to its surface is the dilute phase, and the He3 micro-clusters are the dense phase. Moreover, compared with the traditional dilution refrigerator, the area for He3 to enter the dilute phase is huge. Moreover, the porous medium also acts as a fin, reducing the heat exchange temperature difference caused by the Kapitza thermal resistance. Therefore, it has the dual functions of the phase interface and the fin.

[0048] The compressor used in the dilution unit is a cold compressor 22, which uses a refrigerator to cool the compressor to a low temperature, thereby ensuring that compression is performed at a low temperature. The compressor can also be a combination of a cold compressor and a conventional compressor, and the cooler 23 can also be a combination of heat exchangers of different temperatures.

[0049] In this embodiment, if Figure 2 As shown, it is a schematic diagram of the structure of the cold compressor 22, including a compressor and a pre-cooling refrigerator 50 connected thereto, wherein the compressor is mainly composed of a driving component 221, a cylinder 222 and a piston 223. The cylinder and the piston are stepped (composed of several components or integral), forming a low-pressure compression chamber 225 and a high-pressure compression chamber 224. The low-pressure compression chamber 225 has a low-pressure intake valve 2251 and a low-pressure exhaust valve 2252. The high-pressure compression chamber 224 has a high-pressure intake valve 2241 and a high-pressure exhaust valve 2242. The gas enters from the intake port 2253, is sucked in from the low-pressure intake valve 2251, and is discharged into the gas collecting chamber 226 from the low-pressure exhaust valve 2252 after compression. The gas in the gas collecting chamber 226 enters the high-pressure compression chamber 224 from the high-pressure intake valve 2241, is discharged through the high-pressure exhaust valve 2242 after compression, and is discharged from the outlet port 2243.

[0050] The pre-cooling refrigerator 50 is a three-stage pulse tube refrigerator, including a first cold finger 51, a second cold finger 52, a third cold finger 53 and a first cold head 511, a second cold head 521, and a third cold head 531 connected to each cold finger respectively, and also includes a pre-cooling refrigerator compressor 54, a first heat bridge 541, a second heat bridge 542, and a third heat bridge 543.

[0051] The pre-cooling refrigerator compressor 54 supplies air to the three cold fingers, and the pulse tubes of the three cold fingers share a common inertial tube 55. The common inertial tube 55 is connected to the air reservoir 551, the first cold head 511, the second cold head 521, and the third cold head 531 for outputting cold capacity to the outside.

[0052] The first thermal bridge 541 thermally connects the first cold head 511 with approximately the middle of the second cold finger 52 and the third cold finger 53 for pre-cooling, and is also thermally connected to approximately the middle of the cylinder 222 to pre-cool the cylinder 222, so that the heat leakage from room temperature to the pre-cooling part of the cylinder is transferred to the first cold head 511, reducing its heat leakage to the low temperature end.

[0053] The second heat bridge 542 thermally connects the second cold head 521 to the approximately middle and lower part of the third cold finger for precooling. The specific location of the heat bridge in the thermal connection between the second cold finger and the third cold finger and the compressor depends on the performance.

[0054] The third heat bridge 543 thermally connects the third cold head 531 to the high-pressure compression chamber of the cylinder 222 , so that its temperature is equal to the temperature of the third cold head 531 .

[0055] Generally, the cooling temperatures of the first cold head 511, the second cold head 521, and the third cold head 531 of the three-stage pulse tube refrigerator are approximately in the temperature range of 80K, 20K, and 10K, which can be determined according to the performance. The cooling capacity of 80K is easy to obtain and relatively large, and is used to pre-cool the approximately middle part of the cylinder 222 to compensate for the heat leakage from room temperature. The temperature difference of the cylinder from 80K to 10K is greatly reduced, and the thermal conductivity of the cylinder is generally small at low temperatures, so the heat leakage is also small. The cooling capacity of 10K is not easy to obtain, and the cooling capacity is generally small, which can compensate for the heat leakage of the cylinder 222 from 80K to 10K.

[0056] The gap between the piston 223 and the cylinder 222 is about 10-20 microns, and the helium in the gap thermally connects the two, so that the leaked heat is transferred to the cylinder 222 and taken away.

[0057] Generally, the temperature of He3 entering the cold compressor 22 is about 4K, which will have a slight cooling effect on the wall of the low-pressure compression chamber 225. Since the wall of the high-pressure compression chamber 224 is controlled at about 10K, the compression is completed at a low temperature and the density of the gas will not increase too much, so that the valves can be opened and closed to achieve compression.

[0058] like Figure 2 As shown, the pre-cooling refrigerator 50 can adopt other forms of phase adjustment mechanisms, such as ordinary inertia tubes, cold inertia tubes, two-way air intake, multi-way air intake, push pistons, etc. The common inertia tube selected in this embodiment is simple in structure and has excellent performance.

[0059] The pre-cooling refrigerator 50 may also be in the form of air coupling or a mixture of heat coupling and air coupling.

[0060] The pre-cooling refrigerator 50 can be replaced by other types of refrigerators, such as Stirling, VM, etc.

[0061] The cold compressor 22 may be single-stage or may have more stages, such as three or four stages.

[0062] The driving component 221 generally adopts a linear motor, which can achieve a long life. The piston 223 generally adopts a leaf spring suspension, which supports the piston to suspend in the cylinder 222, and maintains a gap between the piston 223 and the cylinder 222 as a seal. The gap width is generally 10-20 microns. Dry friction can also be used between the piston 223 and the cylinder 222, but the life is shorter. A rotary motor and a crank-connecting rod mechanism can also be used, but the life is not as long as a linear motor. The cylinder and the piston are generally made of low thermal conductivity materials, such as stainless steel, titanium and titanium alloys, and are made of thin walls to reduce heat leakage.

[0063] The cold compressor 22 can be used not only in space but also in dilution refrigerators on the ground, and can also be used for other low-temperature gases that need to be compressed.

[0064] Example 2

[0065] A dilution refrigerator for space use, including a dilution unit, wherein the dilution unit includes a cold compressor and a cooler. The cold compressor 22 is precooled by a precooling refrigerator 50 and a JT refrigerator 60. Figure 2 ; JT refrigerator 60 Figure 3 As shown, it includes a JT compressor 65, a first JT heat exchanger 61, a second JT heat exchanger 62, a third JT heat exchanger 63, and a final JT heat exchanger 64. The low-pressure helium in the JT low-pressure flow channel 651 is compressed by the JT compressor 65 to the JT high-pressure flow channel 652. The high-pressure helium in the JT high-pressure flow channel 652 is cooled in the first JT heat exchanger 61, enters the first JT pre-cooling heat exchanger 611 in thermal contact with the first cold head 511, enters the second JT heat exchanger 62, enters the second JT pre-cooling heat exchanger 621 in thermal contact with the second cold head 521, and enters the third JT heat exchanger 63. After cooling, it enters the third JT pre-cooling heat exchanger 631 in thermal contact with the third cold head 531 for cooling, enters the JT final stage heat exchanger 64 for cooling, and is throttled by the JT throttle valve 65. The fluid temperature drops to a low temperature of about 3-4.2K, and outputs cold energy in the JT cold energy heat exchanger 66. Thereafter, it passes through the JT final stage heat exchanger 64, the third JT heat exchanger 63, the second JT heat exchanger 62, and the first JT heat exchanger 61 in sequence for reheating and returns to the JT low-pressure flow channel 651.

[0066] Among them, the high-pressure flow channel of the JT final stage heat exchanger 64 can be high-flow resistance, and the high-pressure helium completes most of the throttling therein, so that the pressure drop of the JT throttle valve 65 is very small, and it only plays a regulating role. In this way, the diameter of the JT throttle valve 65 is larger and not easy to be blocked, thereby improving the reliability of the system.

[0067] Among them, the cooling capacity of the JT cooling heat exchanger 66 is used to provide Figure 1 The cooler 23 of the dilution loop shown provides cooling in the liquid helium temperature zone, and the temperature is generally 4.2-4.5 K, and the lowest can be lower than 1 K. If the temperature of He3 in the cooler 23 is very high, the cooling required by the cooler 23 can be first provided by the first cold head 511, the second cold head 521, the third cold head 531, etc. according to the required temperature, and then provided by the JT cooling heat exchanger 66.

[0068] The helium in the JT refrigerator 60 and the pre-cooling refrigerator 50 is preferably He4, and He3 may also be selected, wherein He3 is more expensive.

[0069] In this embodiment, the thermal connection between the pre-cooling refrigerator 50 and the JT refrigerator 60 is a helium tube, which is flexible and has low thermal stress. The thermal connection between the pre-cooling refrigerator 50 and the cold compressor 22 is a thermal bridge, which can be made of copper braid made of copper wire, but it is relatively heavy. If solid copper or aluminum is used, the thermal stress is large.

[0070] The cooling of the cold compressor 22 can also be achieved by using the helium pipeline of the JT refrigerator 60 to bring cold energy to the cold compressor for cooling the cold compressor, thereby achieving a flexible connection between the pre-cooling refrigerator 50 and the cold compressor 22.

[0071] If the precooling refrigerator is two-stage, the third JT heat exchanger of the JT refrigerator and the third precooling heat exchanger are not.

[0072] Example 3

[0073] A dilution refrigerator for space use, such as Figure 4 As shown, the difference from Example 2 is that the low-pressure compression chamber 225 is directly cooled to 4K by the final-stage JT pre-cooling heat exchanger 661, thereby ensuring that the inhaled He3 is at low temperature, thereby ensuring compression at low temperature. Although this will cause additional cold loss and increase input work, this structure can achieve higher compression efficiency.

[0074] Among them, 4K refers to the temperature in the 4K temperature zone, which generally depends on the situation. The same is true for other temperatures, and it does not refer to a specific temperature.

[0075] Example 4

[0076] A dilution refrigerator for space use, such as Figure 5As shown, the cold compressor 22 is a single-stage structure, and its cylinder 222 and piston 223 are single-stage structures. The piston 223 is placed in the cylinder 222 to form a high-pressure compression chamber 224. The high-pressure compression chamber 224 has a high-pressure air inlet valve 2241 and a high-pressure exhaust valve 2242. The gas enters the high-pressure compression chamber 224 from the air inlet 2253, is discharged from the high-pressure exhaust valve 2242, and is discharged from the air outlet 2243. The rest is the same as in Example 1. Its advantage is that the structure is simple. The low pressure of He3 in the dilution refrigerator is generally on the order of 100Pa. If a single-stage cold compressor is used for compression, the pressure can reach hundreds of Pa or even exceed 1000Pa. The problem of too low low pressure is skipped, and the conventional compressor can continue to compress.

[0077] Example 5

[0078] A dilution refrigerator for space use, such as Figure 6 As shown, the difference from Example 4 is that the cold compressor 22 is single-stage, and the precooling refrigerator 50 is double-stage, that is, the precooling refrigerator 50 includes a first cold finger 51, a second cold finger 52, and a first cold head 511 and a second cold head 521 connected to each cold finger, respectively, and also includes a precooling refrigerator compressor 54, a first heat bridge 541, and a second heat bridge 542. The first heat bridge 541 thermally connects the first cold head 511 and the second cold finger 52 at approximately the middle for precooling, and is thermally connected to the cylinder 222 at approximately the middle to precool the cylinder 222, and the second heat bridge 542 is thermally connected to the high-pressure compression chamber 224, and the high-pressure compression chamber 224 is cooled by the second cold head 521.

[0079] The lower the number of pulse tube refrigerator stages, the simpler the structure and the easier it is to manufacture, but the minimum refrigeration temperature is slightly higher. In this way, the suction density of He3 is reduced and the requirements for the valve manufacturing of the compressor are increased.

[0080] Example 6

[0081] A dilution refrigerator for space use, such as Figure 7 As shown, the difference from Example 5 is that the pre-cooling refrigerator 50 is single-stage, that is, the pre-cooling refrigerator 50 includes a first cold finger 51 and a first cold head 511 connected thereto, and the first cold head 511 is thermally connected to the pre-cooling cylinder 222 at approximately the middle of the cylinder 222 through a first thermal bridge 541.

[0082] The lower the number of stages of the pulse tube refrigerator (i.e., the precooling refrigerator 50), the simpler the structure and the easier it is to manufacture, but the lowest refrigeration temperature is Figure 6 Compared with He3, the suction density of He3 is reduced, which increases the requirements for valve manufacturing of the compressor.

[0083] The advantage of this solution is that it is very simple, but the cooling temperature at which a single-stage pulse tube refrigerator can effectively provide cooling capacity is currently about 35 K. From 35 K to 4 K, the thermal conductivity of metal materials such as stainless steel is greatly reduced compared to room temperature. If the flow rate of He3 is large enough, the cylinder 224 can be further cooled to a lower temperature by the cold He3.

[0084] The thermal bridge 541 may also cool the compression chamber 224 .

[0085] The technical features of the above embodiments may be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0086] The above embodiments only express the preferred implementation modes of the present invention, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for those of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the attached claims.

Claims

1. A cold compressor, comprising a driving component, a cylinder and a piston, characterized in that: It also includes a pre-cooling refrigerator, which is connected to the cylinder and pre-cools the compressor through the pre-cooling refrigerator.

2. A cold compressor according to claim 1, characterized in that: The precooling refrigerator is a pulse tube refrigerator, a JT refrigerator, a Stirling refrigerator or a VM refrigerator.

3. A cold compressor according to claim 1 or 2, characterized in that: The cold compressor is a single-stage compressor or a multi-stage compressor.

4. A cold compressor according to claim 3, characterized in that: The pre-cooling refrigerator is a single-stage or multi-stage refrigerator, including at least one stage of cold head, and the cold head is connected to the cylinder of the cold compressor through a thermal bridge.

5. A cold compressor according to claim 2, characterized in that: The phase adjustment mechanism used in the pulse tube refrigerator includes an inertia tube, two-way air intake, multi-way air intake or a push piston; The pulse tube refrigerator is in the form of gas coupling, thermal coupling or a mixture of thermal coupling and gas coupling.

6. A cold compressor according to claim 1, characterized in that: The precooling refrigerator is also connected to a cooler, and the cold compressor is cooled by the precooling refrigerator or the precooling refrigerator and the cooler together, wherein the precooling refrigerator cools the cooler.

7. A dilution refrigerator, characterized in that: A cold compressor as described in any one of claims 1-6 is used.

8. The dilution refrigerator according to claim 7, characterized in that The invention comprises a cold compressor, a cooler, a high-temperature heat exchanger, a high-temperature throttle valve, a distillation chamber, a low-temperature heat exchanger, a low-temperature throttle valve and a cold heat exchanger which are connected in sequence.

9. The cold compressor according to claim 7, characterized in that: The cold compressor adopts a pulse tube refrigerator, or the pulse tube refrigerator and the JT refrigerator are cooled together, wherein each stage of the cold head of the pulse tube refrigerator is connected to the cylinder of the cold compressor, each stage of the pre-cooling heat exchanger of the JT refrigerator is connected to each stage of the cold head, or at least one stage of the pre-cooling heat exchanger of the JT refrigerator is directly connected to the cylinder of the cold compressor.

10. A space dilution refrigerator, characterized in that: A cold compressor as described in any one of claims 1-6 is used.

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