CN114811991B - Super-current helium refrigerator with independent load test cold box - Google Patents

Abstract

The invention relates to an overflow helium refrigerator with an independent load test cold box, which comprises a compressor unit, a refrigerator cold box, a load test cold box, a helium precooling module, a multistage turboexpander unit, a heat exchanger group, a subcooler, a cold compressor unit, a gas-liquid separator, a temperature zone load of 50-75K, a temperature zone load of 4.5-75K and a load of 2K, wherein the helium precooling module, the multistage turboexpander unit, the heat exchanger group, the subcooler, the cold compressor unit, the gas-liquid separator, the temperature zone load of 50-75K, the temperature zone load of 4.5-75K and the load of 2K are all arranged in the load test cold box.

Description

A superfluid helium refrigerator with an independent load test cold box

technical field

The invention relates to the technical field of ultra-low temperature refrigeration, in particular to a superfluid helium refrigerator with an independent load test cold box.

Background technique

Superfluid helium has a very high thermal conductivity, which is much higher than that of metals and thousands of times that of copper. Due to its excellent flow and heat transfer properties, superfluid helium is commonly used to cool superconducting magnets in many applications. Superfluid helium is nearly inviscid and easily penetrates the interior of the magnet, quickly dissipating thermal disturbances. Using superfluid helium to cool the accelerator and superconducting magnets increases stability and reduces energy consumption and operating costs. Due to the lower temperature, extremely small viscosity and high thermal conductivity of superfluid helium, a variety of cryogenic refrigeration systems and refrigerators have been established using superfluid helium. A superfluid helium refrigerator generally includes a set of 4.5K helium cryogenic system and a set of 1.8/2K superfluid helium cryogenic subsystem, which produce superfluid helium while producing liquid helium.

The superfluid helium refrigerator provides multi-temperature zone cooling capacity for external loads, such as 50-75K temperature zone cooling capacity, 4.5-75K temperature zone cooling capacity, 2K cooling capacity, etc. In order to test the cooling capacity of each temperature zone, the superfluid helium refrigerator needs to be connected to the test load of each temperature zone to test the cooling capacity. There are generally two methods for load testing, that is, the test load is placed outside the refrigerator and connected to the refrigerator through a bayonet (vacuum interface); or the test load is placed inside the refrigerator cold box. Both methods have advantages and disadvantages. When the superfluid helium refrigerator involves external cooling test loads in multiple temperature zones, it is necessary to build a load test platform outside the refrigerator, which occupies a large area and the connection lines are relatively complicated. The built-in cooling capacity test load is placed inside the cold box of the refrigerator, which is easy to arrange and does not require an external power module. However, after the cooling capacity test is completed, the test load is no longer used, and it is placed inside the cold box to become an idle heat capacity, occupying the cold box of the refrigerator. precious space.

Contents of the invention

An object of the present invention is to provide a superfluid helium refrigerator with an independent load test cold box, the superfluid helium refrigerator adopts the refrigerator cold box and the load test cold box to separate the refrigeration part and the load test part, and the load The test cold box is only used in the load cooling test stage and can be removed after the superfluid helium refrigerator is delivered to the user. This design makes the cold box of the refrigerator compact in structure and avoids the test load in each temperature zone after the load test stage. It becomes an idle heat capacity and occupies the space of the cold box of the refrigerator.

The invention provides a superfluid helium refrigerator with an independent load test cold box, including a compressor unit, a refrigerator cold box, a load test cold box, a helium precooling module all arranged in the refrigerator cold box, Multi-stage turboexpander unit, heat exchanger unit, subcooler and cold compressor unit, and the gas-liquid separator all set in the load test cold box, 50 ~ 75K temperature zone load, 4.5 ~ 75K temperature zone load and 2K load, the load test cold box is used in the load cold capacity test stage;

The compressor assembly includes a positive pressure compressor and a negative pressure compressor, the positive pressure compressor includes a medium pressure compressor and a high pressure compressor, the outlet of the negative pressure compressor and the outlet of the medium pressure compressor are connected At the suction port of the high-pressure compressor, the outlet of the high-pressure compressor is connected to the inlet of the cold box of the refrigerator, and the normal temperature and high-pressure helium gas discharged from the high-pressure compressor enters through the inlet of the cold box of the refrigerator. In the cold box of the refrigerator;

The helium pre-cooling module is arranged on the inlet side of the cold box of the refrigerator and before the multi-stage turbo-expansion unit, and is used for precooling a part of normal-temperature and high-pressure helium entering the cold box of the refrigerator ;

The multi-stage turbo-expansion unit includes a first turbo-expansion unit, a second turbo-expansion unit, a third turbo-expansion unit and a fourth turbo-expansion unit arranged in sequence, for controlling the The normal temperature and high pressure helium is used for multi-stage cooling process;

The heat exchanger group is used to perform a multi-stage heat exchange process for the normal temperature and high pressure helium entering the cold box of the refrigerator;

The superfluid helium refrigerator includes a high-pressure main gas circuit, a medium-pressure return gas circuit, a low-pressure return gas circuit, and a negative pressure return gas circuit. The inlet of the high-pressure main gas circuit is connected to the inlet and outlet of the cold box of the refrigerator. connected to the inlet of the subcooler; the inlet of the medium-pressure return gas circuit is connected to the outlet of the second turboexpander unit, and the outlet is connected to the suction port of the high-pressure compressor; the low-pressure return gas The inlet of the path is connected to the gas phase outlet of the subcooler, and the outlet is connected to the suction port of the medium pressure compressor; the inlet of the negative pressure return path is connected to the outlet of the cold compressor unit, and the outlet is connected to The suction port of the negative pressure compressor;

The liquid phase outlet of the subcooler is connected to the inlet of the load in the 4.5-75K temperature zone and the inlet of the gas-liquid separator, and the outlet of the load in the 4.5-75K temperature zone is connected to the low-pressure return gas path, The liquid phase outlet of the gas-liquid separator is connected to the 2K load, and the outlet of the 2K load and the gas phase outlet of the gas-liquid separator are connected to the inlet of the cold compressor unit;

Wherein the high-pressure compressor discharges normal temperature and high pressure helium into the refrigerator cold box through the inlet of the refrigerator cold box, and a part of the normal temperature and high pressure helium enters the helium precooling module for precooling. After the cooled helium is merged with the normal temperature and high pressure helium in the high-pressure main gas circuit, the multi-stage cooling process and the multi-stage heat exchange process are performed through the multi-stage turbo expander unit, Formation of supercritical helium;

The supercritical helium enters the subcooler through the high-pressure main gas path, the gas phase enters the low-pressure return gas path, and a part of the liquid phase enters the 4.5-75K temperature zone and returns to the low-pressure return gas after being loaded. The other part of the liquid phase is throttling into a gas-liquid two-phase, and the liquid phase enters the gas-liquid separator to collect liquid. When the liquid helium level in the gas-liquid separator reaches a preset value, the cold compressor unit Start, the helium in the gas-liquid separator is decompressed to form 2K saturated superfluid helium, and the 2K saturated superfluid helium flows out from the liquid phase outlet of the gas-liquid separator to the 2K load; the gas phase It is discharged from the gas phase outlet of the gas-liquid separator, merged with the return gas of the 2K load, enters the cold compressor unit, and enters the negative pressure return gas circuit after being boosted by the cold compressor unit. After the pressure drop, the negative pressure helium gas is formed, and the negative pressure helium gas enters the negative pressure compressor and is compressed to a medium pressure, and is combined with the medium pressure gas discharged from the medium pressure compressor and the return gas of the medium pressure return gas circuit After mixing, it enters the high-pressure compressor, and a helium cycle is completed so far.

In an embodiment of the present invention, the superfluid helium refrigerator further includes a multi-channel transfer pipeline for connecting the refrigerator cold box and the load test cold box, and the load test cold box passes through the multi-channel transfer pipeline. The channel transmission line forms a detachable connection with the cold box of the refrigerator.

In an embodiment of the present invention, the superfluid helium refrigerator also includes a load temperature conversion pipeline in a temperature range of 50-75K and a temperature conversion pipeline at the inlet of the cold compressor unit, both of which are arranged in the cold box of the refrigerator, wherein The 50-75K temperature zone load temperature conversion pipeline is connected to the first turbo expander unit, and is used to convert the temperature of the helium before entering the first turbo expander unit; wherein the inlet of the cold compressor unit The temperature exchange pipeline is arranged at the inlet side of the cold compressor unit, and is used for adjusting the temperature of the helium gas entering the cold compressor unit.

In an embodiment of the present invention, the 50-75K temperature zone load temperature conversion pipeline includes a 50K helium pipeline connected to the high-pressure main gas pipeline, a 50K helium pipeline connected to the 50-75K The load outflow pipeline of the inlet of the load in the temperature zone, the temperature conversion pipeline connected to the 50K helium pipeline, the return pipeline connected to the outlet of the load in the 50-75K temperature zone, and the return pipeline connected to the The temperature conversion pipeline and the helium gas of the first turboexpander unit pass through the pipeline, the 50K helium pipeline is provided with a 50K helium pipeline regulating valve, and the temperature conversion pipeline is provided with a temperature conversion pipeline adjustment valve. A valve and a temperature exchange pipeline heater, the return pipeline is provided with a return pipeline regulating valve, wherein the temperature exchange pipeline is used to pass through the temperature exchange pipeline regulating valve and the temperature exchange pipeline heater adjusting the temperature of the helium in the return pipeline, so that the helium entering the first turboexpander through the pipeline can meet the requirements of the inlet temperature and pressure of the first turboexpander .

In an embodiment of the present invention, the heat exchanger group includes a circuit connected to the high-pressure main gas circuit, the medium-pressure return gas circuit, the low-pressure return gas circuit, and the negative-pressure return gas circuit in sequence. The first-stage heat exchanger, the second-stage heat exchanger, the third-stage heat exchanger, the fourth-stage heat exchanger, and the fifth-stage heat exchanger are provided, which also include connecting to the high-pressure main gas circuit, the The medium-pressure return air circuit, the sixth-stage heat exchanger of the low-pressure return air circuit, the seventh-stage heat exchanger and the eighth-stage heat exchanger connected to the high-pressure main air circuit and the low-pressure return air circuit, And the ninth-stage heat exchanger connected to the liquid phase outlet of the subcooler, the inlet and gas phase outlet of the gas-liquid separator and the outlet of the 2K load, wherein the helium discharged from the gas-liquid separator Combined with the return gas of the 2K load, it enters the ninth-stage heat exchanger for heat exchange, and the helium after heat exchange enters the cold compressor unit after being warmed through the temperature exchange pipeline at the inlet of the cold compressor unit .

In an embodiment of the present invention, the multi-channel transmission pipeline includes a first pipeline, a second pipeline, a third pipeline, a fourth pipeline, a fifth pipeline and a sixth pipeline, and the 50- The load in the 75K temperature zone is connected to the load outflow pipeline through the first pipeline, and the return pipeline is connected through the second pipeline; the load in the 4.5-75K temperature zone passes through the third pipeline Connect the liquid phase outlet of the subcooler, and connect the low-pressure return gas path through the fourth pipeline; the ninth stage heat exchanger is connected to the subcooler through the fifth pipeline The liquid phase outlet is connected to the inlet of the cold compressor unit inlet temperature conversion pipeline through the sixth pipeline.

In an embodiment of the present invention, the temperature exchange pipeline at the inlet of the cold compressor unit includes a pipeline temperature exchange module, and the pipeline temperature exchange module includes a first A temperature conversion pipeline and a first temperature conversion regulating valve arranged on the first temperature conversion pipeline.

In an embodiment of the present invention, the inlet temperature conversion pipeline of the cold compressor unit includes a heat exchanger temperature conversion module, and the heat exchanger temperature conversion module includes an outlet connected to the ninth stage heat exchanger and the The temperature conversion heat exchanger at the inlet of the cold compressor unit, the second temperature conversion pipeline connected to the high-pressure main gas circuit and the inlet of the temperature conversion heat exchanger, and the second temperature conversion pipeline arranged on the second temperature conversion pipeline The second temperature conversion regulating valve, the third temperature conversion pipeline connected to the outlet of the temperature conversion heat exchanger and the high-pressure main gas circuit, and the high-pressure main gas circuit, and located in the second temperature conversion The third temperature-converting regulating valve between the temperature-converting pipeline and the third temperature-converting pipeline.

In an embodiment of the present invention, a throttling valve group is further provided between the high-pressure main gas circuit and the subcooler, and the throttle valve group includes a first throttle valve and a second throttle valve arranged in parallel. A gas return valve is provided between the gas phase outlet of the subcooler and the low-pressure return gas circuit, and a second stage is provided between the ninth-stage heat exchanger and the inlet of the gas-liquid separator. Three throttling valves, the ninth-stage heat exchanger and the third throttling valve are both arranged in the load test cold box;

Wherein, a part of the supercritical helium output from the high-pressure main gas circuit is throttled by the first throttle valve into gas-liquid two-phase, the liquid phase accumulates liquid in the subcooler, and the gas phase enters the gas-liquid two-phase through the gas return valve. The low-pressure return gas circuit; the other part of supercritical helium enters the subcooler after being throttled by the second throttle valve, and is supercooled by the liquid helium accumulated in the subcooler to form supercooled supercritical helium , supercooled supercritical helium flows out from the bottom of the subcooler, part of which is supplied to the load in the 4.5-75K temperature zone, and the other part enters the ninth-stage heat exchanger, and is throttled into gas through the third throttle valve. Two-phase liquid, the liquid phase accumulates liquid in the gas-liquid separator, the gas phase is discharged from the gas phase outlet of the gas-liquid separator, and merges with the return gas of the 2K load into the ninth stage heat exchanger for exchange Heat, the helium gas after heat exchange enters the cold compressor unit after being warmed through the temperature exchange pipeline at the inlet of the cold compressor unit.

In an embodiment of the present invention, the cold compressor unit includes a sixth inlet regulating valve, a first cold compressor, a second cold compressor, a third cold compressor, a fourth cold compressor and a first cold compressor arranged in series. An outlet regulating valve, the superfluid helium refrigerator also includes a bypass pipeline of the cold compressor unit connected in parallel to the cold compressor unit and a bypass regulating valve arranged on the bypass pipeline of the cold compressor unit.

In an embodiment of the present invention, the superfluid helium refrigerator further includes a cold box bypass line connected to the outlet of the fourth turboexpander unit and the low-pressure return gas line, and a cold box bypass line arranged in the cold box Cold box bypass valve on the box bypass line.

In an embodiment of the present invention, the superfluid helium refrigerator further includes a low-temperature adsorber group, and the low-temperature adsorber group includes an 80K low-temperature adsorber and a 20K low-temperature adsorber for adsorbing impurity gases in helium, The 80K low-temperature adsorber and the 20K low-temperature adsorber are both arranged on the high-pressure main gas path, and the 80K low-temperature adsorber is located between the second-stage heat exchanger and the third-stage heat exchanger , the 20K cryogenic adsorber is located between the sixth-stage heat exchanger and the seventh-stage heat exchanger.

In an embodiment of the present invention, there are two 80K cryogenic adsorbers, and the two 80K cryogenic adsorbers are connected in parallel and switched for use.

In an embodiment of the present invention, the helium precooling module includes a helium passage regulating valve connected to the high-pressure main gas circuit, a liquid nitrogen precooling heat exchanger connected to the helium passage regulating valve, The liquid nitrogen inlet pipeline connected to the liquid nitrogen precooling heat exchanger and the liquid nitrogen inlet regulating valve arranged on the liquid nitrogen inlet pipeline, the outlet of the liquid nitrogen precooling heat exchanger is connected to the The high-pressure main gas circuit is located between the outlet of the second-stage heat exchanger and the inlet of the 80K cryogenic adsorber, and the liquid nitrogen fed into the helium precooling module through the liquid nitrogen inlet pipeline is The normal temperature and high pressure helium is precooled, and the amount of helium entering the liquid nitrogen precooling heat exchanger is adjusted through the helium passage regulating valve, and the amount of helium entering the liquid nitrogen precooling heat exchanger is adjusted through the liquid nitrogen inlet regulating valve. The amount of liquid nitrogen in the cold heat exchanger.

In an embodiment of the present invention, the helium pre-cooling module includes a pre-cooling turbo-expander unit composed of a first turbine, a second turbine, and a third turbine connected in series, and a A first inlet regulating valve between the outlet of the heater and the inlet of the first turbine, and the outlet of the pre-cooling turboexpander unit is connected to the medium pressure return gas circuit.

In an embodiment of the present invention, the first turboexpander unit includes a fourth turbine and a fifth turbine arranged in series, and the outlet of the third-stage heat exchanger and the fourth turbine The second inlet regulating valve between the inlets of the fourth turbine, the inlet of the fourth turbine is connected to the helium passage line of the load temperature conversion pipeline in the 50-75K temperature zone, and the outlet of the fifth turbine Connected to the medium pressure return air circuit.

In an embodiment of the present invention, the second turboexpander unit includes a sixth turbine and a seventh turbine arranged in series, and the outlet of the fifth-stage heat exchanger and the sixth turbine The third inlet regulating valve between the inlets of the turbine, the outlet of the seventh turbine is connected to the medium pressure return gas path.

In an embodiment of the present invention, the third turboexpander unit includes an eighth turbine and a ninth turbine arranged in series, and the outlet of the 20K cryogenic adsorber and the inlet of the eighth turbine The fourth inlet regulating valve between them, the outlet of the ninth turbine is connected to the low-pressure return gas path.

In an embodiment of the present invention, the fourth turboexpander unit includes a tenth turbine, a fifth inlet arranged between the outlet of the seventh-stage heat exchanger and the inlet of the tenth turbine A regulating valve and a last-stage turbine bypass valve arranged on the high-pressure main gas path and between the seventh-stage heat exchanger and the eighth-stage heat exchanger, the outlet of the tenth turbine Connected to the high-pressure main air circuit.

In an embodiment of the present invention, the superfluid helium refrigerator further includes a gas management panel, and the gas management panel includes a medium-pressure bypass valve connected to the high-pressure main gas circuit and the medium-pressure return gas circuit , the low-pressure bypass valve connecting the high-pressure main air circuit and the low-pressure return air circuit, the loading valve and buffer tank unloading valve connected to the low-pressure return air circuit and the high-pressure main air circuit, and the Load the surge tank between the valve and the surge tank unload valve.

In an embodiment of the present invention, the superfluid helium refrigerator further includes a one-way valve arranged between the negative pressure compressor and the high-pressure compressor, and the one-way valve is used to prevent the negative pressure Compressor outlet helium reverse flow.

The superfluid helium refrigerator of the present invention is composed of a refrigerator cold box and a load test cold box. The two cold boxes are connected by a multi-channel transmission pipeline, and the refrigeration part and the load are connected by the refrigerator cold box and the load test cold box. The test part is separated, and the 50-75K temperature zone load, 4.5-75K temperature zone load, 2K load, negative pressure heat exchanger and 2K helium gas-liquid separator are placed inside the load test cold box, and the load test cold box is only used for It is used in the load cooling test stage, which is separate from the refrigerator cold box function. After the superfluid helium refrigerator is delivered to the user, the load test cold box and the multi-channel transfer pipeline can be removed, and the user load is directly connected to the refrigerator cold box. This design makes the cold box of the refrigerator compact in structure, and prevents the test loads in each temperature zone from becoming idle heat capacity after the load test stage, occupying precious space in the cold box of the refrigerator.

The superfluid helium refrigerator of the present invention is also provided with the 50-75K temperature zone load temperature conversion pipeline at the first turboexpander unit, and the inlet side of the cold compressor unit is provided with the The temperature conversion pipeline at the inlet of the cold compressor unit is used to control the temperature of the helium before entering the first turboexpander unit and the temperature conversion at the inlet of the cold compressor unit through the load temperature conversion pipeline in the 50-75K temperature zone, respectively. The method of exchanging the temperature of the helium gas before entering the cold compressor unit by the pipeline can make the fluid parameters entering the first turboexpander unit and the cold compressor unit reach the turbomachinery inlet design parameters, so that the turbine The impeller machinery such as the expansion unit and the cold compressor unit can operate in the best working condition, which is conducive to improving the overall performance of the superfluid helium refrigerator.

Further objects and advantages of the invention will fully appear from an understanding of the ensuing description and accompanying drawings.

Description of drawings

Fig. 1 is a schematic structural view of the superfluid helium refrigerator with an independent load test cold box according to a preferred embodiment of the present invention, wherein the direction of the arrow represents the direction of fluid flow.

Description of reference numerals: medium pressure compressor 1; high pressure compressor 2; negative pressure compressor 3; one-way valve 4; medium pressure bypass valve 5; low pressure bypass valve 6; buffer tank unloading valve 7; buffer tank 8; Loading valve 9; refrigerator cold box 10; cold box bypass line 11; cold box bypass valve 12; first throttle valve 13; second throttle valve 14; air return valve 15; third throttle valve 16 ;

High pressure main air circuit 17; medium pressure return air circuit 18; low pressure return air circuit 19; negative pressure return air circuit 20;

The first pipeline 21; the second pipeline 22; the third pipeline 23; the fourth pipeline 24; the fifth pipeline 25; the sixth pipeline 26, load test cold box 27;

Helium passage regulating valve 30; liquid nitrogen precooling heat exchanger 31; liquid nitrogen inlet pipeline 32; liquid nitrogen inlet regulating valve 33; first turbine 34; second turbine 35; third turbine 36; first Inlet regulating valve 37;

80K cryogenic adsorber 38; 20K cryogenic adsorber 39;

The fourth turbine 40; the fifth turbine 41; the second inlet regulating valve 42; the sixth turbine 43; the seventh turbine 44; the third inlet regulating valve 45; the eighth turbine 46; the ninth turbine 47; The fourth inlet regulating valve 48; the tenth turbine 49; the fifth inlet regulating valve 50; the last stage turbine bypass valve 51;

50K helium pipeline 60; 50K helium pipeline regulating valve 61; load outflow pipeline 62; temperature conversion pipeline 63; temperature conversion pipeline regulating valve 64; temperature conversion pipeline heater 65; Through pipeline 67; inlet pipeline 68 of the first turboexpander unit; return pipeline regulating valve 69;

The sixth inlet regulating valve 70; the first cold compressor 71; the second cold compressor 72; the third cold compressor 73; the fourth cold compressor 74; the first outlet regulating valve 75; ; Bypass regulating valve 77; the first exchange temperature pipeline 81; the first exchange temperature control valve 82; exchange temperature heat exchanger 83; the second exchange temperature pipeline 84; the second exchange temperature control valve 85; Pipeline 86; the third temperature control valve 87;

The first stage heat exchanger 91, the second stage heat exchanger 92, the third stage heat exchanger 93, the fourth stage heat exchanger 94; the fifth stage heat exchanger 95; the sixth stage heat exchanger 96; the seventh stage Stage heat exchanger 97; Eighth stage heat exchanger 98; Ninth stage heat exchanger 99;

50 ~ 75K temperature zone load 101; 4.5 ~ 75K temperature zone load 102; 2K load 103; subcooler 104; gas-liquid separator 105.

Detailed ways

The following description serves to disclose the present invention to enable those skilled in the art to carry out the present invention. The preferred embodiments described below are only examples, and those skilled in the art can devise other obvious variations. The basic principles of the present invention defined in the following description can be applied to other embodiments, variations, improvements, equivalents and other technical solutions without departing from the spirit and scope of the present invention.

Those skilled in the art should understand that, in the disclosure of the present invention, the terms "vertical", "transverse", "upper", "lower", "front", "rear", "left", "right", The orientations or positional relationships indicated by "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. are based on the orientation or positional relationship shown in the drawings, which are only for the convenience of describing the present invention and simplified description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operate in a specific orientation, so the above terms should not be construed as limiting the present invention.

It can be understood that the term "a" should be understood as "at least one" or "one or more", that is, in one embodiment, the number of an element can be one, while in another embodiment, the number of the element The quantity can be multiple, and the term "a" cannot be understood as a limitation on the quantity.

In the description of the present invention, it should be noted that unless otherwise specified and limited, the terms "installation", "connection" and "connection" should be understood in a broad sense, for example, it can be a fixed connection or a detachable connection. Connected, or integrally connected; it can be mechanically connected, or electrically connected, or can communicate with each other; it can be directly connected, or indirectly connected through an intermediary, and it can be the internal communication of two components or the interaction of two components relation. Those of ordinary skill in the art can understand the specific meanings of the above terms in the present invention according to specific situations.

As shown in FIG. 1 , the specific structure and working process of a superfluid helium refrigerator with an independent load test cold box according to a preferred embodiment of the present invention are specifically illustrated.

As shown in Figure 1, the superfluid helium refrigerator includes a compressor unit, a refrigerator cold box 10, a load test cold box 27, a helium precooling module all arranged in the refrigerator cold box 10, a multi-stage transparent Flat expansion unit, heat exchanger group, subcooler 104 and cold compressor unit, and gas-liquid separator 105, 50-75K temperature zone load 101, 4.5-75K temperature zone all arranged in the load test cold box 27 Load 102 and 2K load 103 .

Further, the superfluid helium refrigerator also includes a multi-channel transfer line for connecting the refrigerator cold box 10 and the load test cold box 27, and the load test cold box 27 passes through the multi-channel transfer line It forms a detachable connection with the cold box 10 of the refrigerator.

In particular, the superfluid helium refrigerator of the present invention uses the refrigerator cold box 10 and the load test cold box 27 to separate the refrigeration part from the load test part, and the load test cold box 27 is only used for load cooling. The load test cold box 27 forms a detachable connection with the refrigerator cold box 10 through the multi-channel transmission line, so the load test cold box 27 and the multi-channel transmission The pipeline can be removed after the superfluid helium refrigerator is delivered to the user. This design makes the cold box 10 of the refrigerator compact in structure, and prevents the test loads in each temperature zone from becoming idle heat capacity after the load test stage and occupying the cold box of the refrigerator. space.

Specifically, the compressor unit includes a positive pressure compressor and a negative pressure compressor 3, the positive pressure compressor includes a medium pressure compressor 1 and a high pressure compressor 2, the outlet of the negative pressure compressor 3 and the medium The outlet of the compressor 1 is connected to the suction port of the high-pressure compressor 2, the outlet of the high-pressure compressor 2 is connected to the inlet of the cold box 10 of the refrigerator, and the normal temperature and high pressure discharged by the high-pressure compressor 2 is Helium enters the refrigerator cold box 10 through the inlet of the refrigerator cold box 10, and the outlet of the cold compressor unit is connected to the suction port of the negative pressure compressor 3, and the negative pressure compressor 3 It is used to compress the superfluid helium negative pressure return gas sent by the cold compressor unit to medium pressure.

Specifically, the helium pre-cooling module is arranged on the inlet side of the refrigerator cold box 10 and before the multi-stage turboexpansion unit, and is used to cool a part of the normal temperature and high pressure gas entering the refrigerator cold box 10. Helium for precooling.

Specifically, the multi-stage turbo-expansion unit includes a first turbo-expansion unit, a second turbo-expansion unit, a third turbo-expansion unit and a fourth turbo-expansion unit, for 10 normal temperature and high pressure helium for multi-stage cooling process.

Specifically, the superfluid helium refrigerator includes a high-pressure main gas circuit 17, a medium-pressure return gas circuit 18, a low-pressure return gas circuit 19, and a negative pressure return gas circuit 20, and the inlet of the high-pressure main gas circuit 17 is connected to the The inlet and outlet of the refrigerator cold box 10 are connected to the inlet of the supercooler 104; the inlet of the medium-pressure return air circuit 18 is connected to the outlet of the second turboexpander unit, and the outlet is connected to the high-pressure compressor The suction port of the machine 2; the inlet of the low pressure return air circuit 19 is connected to the gas phase outlet of the subcooler 104, and the outlet is connected to the suction port of the medium pressure compressor 1; the negative pressure return air circuit The inlet of 20 is connected to the outlet of the cold compressor unit, and the outlet is connected to the suction port of the negative pressure compressor 3 .

Specifically, the heat exchanger group includes a first-stage heat exchanger 91, a second-stage heat exchanger 92, a third-stage heat exchanger 93, a fourth-stage heat exchanger 94, and a fifth-stage heat exchanger arranged in sequence. 95, the sixth stage heat exchanger 96, the seventh stage heat exchanger 97, the eighth stage heat exchanger 98 and the ninth stage heat exchanger 99 are used to treat the normal temperature and high pressure helium entering the cold box 10 of the refrigerator The gas undergoes a multi-stage heat exchange process.

More specifically, the first stage heat exchanger 91, the second stage heat exchanger 92, the third stage heat exchanger 93, the fourth stage heat exchanger 94 and the fifth stage heat exchanger The heater 95 is connected to the high-pressure main gas circuit 17, the medium-pressure return gas circuit 18, the low-pressure return gas circuit 19, and the negative-pressure return gas circuit 20; the sixth-stage heat exchanger 96 is connected to The high-pressure main gas circuit 17, the medium-pressure return gas circuit 18, and the low-pressure return gas circuit 19; the seventh-stage heat exchanger 97 and the eighth-stage heat exchanger 98 are connected to the high-pressure main Gas path 17 and the low-pressure return gas path 19; the ninth stage heat exchanger 99 is connected to the liquid phase outlet of the subcooler 104, the inlet and gas phase outlet of the gas-liquid separator 105 and the 2K The outlet of the load 103 . It can be understood that the ninth stage heat exchanger 99 of the heat exchanger group is placed in the load test cold box 27 , and the rest of the heat exchangers are placed in the refrigerator cold box 10 .

Specifically, the liquid phase outlet of the subcooler 104 is connected to the inlet of the load 102 in the 4.5-75K temperature range and the inlet of the gas-liquid separator 105, and the outlet of the load 102 in the 4.5-75K temperature range is connected to The low-pressure gas return circuit 19, the liquid phase outlet of the gas-liquid separator 105 is connected to the 2K load 103, and the outlet of the 2K load 103 and the gas phase outlet of the gas-liquid separator 105 are connected to the Cold compressor unit.

It can be understood that the superfluid helium refrigerator provides multi-temperature zone cooling capacity for external loads, such as 50-75K temperature zone load, 4.5-75K temperature zone load, 2K load, etc. The fluid in the load return pipeline in the 50-75K temperature zone is mixed with the 75K helium of the refrigerator, and enters the first turboexpander unit for re-expansion. Whether the load return fluid in the 50-75K temperature zone can reach the inlet design parameters of the first turboexpander unit affects whether the first turboexpander unit can operate in the design working condition and reach the optimal working condition.

Therefore, in particular, in order to improve the overall performance of the superfluid helium refrigerator, the superfluid helium refrigerator further includes a 50-75K temperature range load temperature conversion pipeline arranged in the cold box 10 of the refrigerator, The load temperature conversion pipeline in the 50-75K temperature zone is connected to the first turbo expander unit, and the helium gas before entering the first turbo expander unit is passed through the load temperature conversion pipeline in the 50-75K temperature zone. Perform temperature exchange to ensure that the fluid parameters entering the first turbo-expander unit can reach the design parameters of the turbomachinery inlet, so that the multi-stage turbo-expander unit can operate in the best working condition, which is conducive to improving superfluid helium refrigeration The overall performance of the machine.

Specifically, the 50-75K temperature zone load temperature conversion pipeline includes a 50K helium pipeline 60 connected to the high-pressure main gas circuit 17, a 50K helium pipeline 60 connected to the 50-75K temperature zone load The load outflow pipeline 62 at the inlet of 101, the temperature conversion pipeline 63 connected to the 50K helium pipeline 60, the return pipeline 66 connected to the outlet of the load 101 in the 50-75K temperature zone, and the return pipeline 66 connected to the return The pipeline 66, the temperature conversion pipeline 63 and the helium of the first turboexpander unit pass through the pipeline 67, the 50K helium pipeline 60 is provided with a 50K helium pipeline regulating valve 61, and the temperature conversion pipeline Road 63 is provided with temperature exchange pipeline regulating valve 64 and temperature exchange pipeline heater 65, and said return pipeline 66 is provided with return pipeline adjustment valve 69, wherein said temperature exchange pipeline 63 is used to pass through said temperature exchange pipeline The pipeline regulating valve 64 and the temperature-exchanging pipeline heater 65 are used to adjust the temperature of the helium in the return pipeline 66, so that the helium entering the first turboexpander unit via the helium through the pipeline 67 The gas can meet the requirements of the inlet temperature and pressure of the first turboexpander unit.

It is worth mentioning that the connection between the 50K helium pipeline 60 and the high-pressure main gas pipeline 17 is located between the fourth-stage heat exchanger 94 and the fifth-stage heat exchanger 95 .

The working principle of the load temperature conversion pipeline in the 50-75K temperature zone is: when the helium temperature in the return pipeline 66 is too high, the 50K cold fluid in the temperature conversion pipeline 63 directly contacts with the return flow pipeline. The temperature of the thermal fluid in the pipeline 66, the target parameters are the inlet design temperature and design pressure of the fourth turbine 40 of the first turboexpander unit. After the temperature exchange is completed, the helium gas is mixed with the 75K helium gas in the inlet pipeline 68 of the first turboexpander unit connected to the high-pressure main gas pipeline 17 through the helium gas passage pipeline 67 and enters the first turboexpander unit. A turboexpander unit performs reexpansion. When the helium gas in the return line 66 is too low, the temperature exchange line heater 65 in the temperature exchange line 63 is activated to heat the helium in the temperature exchange line 63 to be heated. The heated hot helium is exchanged with the return cold helium in the return line 66, and the helium after the temperature exchange is passed through the helium passage line 67 and the inlet from the first turbo expander unit The 75K helium in line 68 is mixed and enters the first turboexpander unit for re-expansion.

It can be understood that the design of the load-temperature conversion pipeline in the 50-75K temperature zone enables the helium parameters in the return pipeline 66 of the load 101 in the 50-75K temperature zone to reach the design parameters of the inlet of the fourth turbine 40 (design temperature, design Pressure), so that the first turboexpander unit can operate at the design working condition and reach the optimum working condition point, which helps to improve the overall performance of the superfluid helium refrigerator.

In particular, in order to improve the overall performance of the superfluid helium refrigerator, the superfluid helium refrigerator also includes a cold compressor unit inlet temperature exchange pipeline arranged in the cold box 10 of the refrigerator, and the cold compressor The unit inlet temperature exchange pipeline is arranged on the inlet side of the cold compressor unit, and is used to adjust the temperature of the helium gas entering the cold compressor unit, so that the fluid parameters entering the cold compressor unit can reach the turbomachinery inlet design parameters, Therefore, the cold compressor unit can be operated in an optimal working condition, which is beneficial to improving the overall performance of the superfluid helium refrigerator.

Specifically, the cold compressor unit includes a sixth inlet regulating valve 70, a first cold compressor 71, a second cold compressor 72, a third cold compressor 73, a fourth cold compressor 74 and a first outlet Regulating valve 75, said superfluid helium refrigerator also includes a cold compressor unit bypass pipeline 76 parallel to said cold compressor unit and a bypass regulating valve 77 arranged on said cold compressor unit bypass pipeline 76 .

It is worth mentioning that the bypass pipeline 76 of the cold compressor unit and the bypass regulating valve 77 are used to supply and return gas helium when the liquid helium level in the gas-liquid separator 105 does not reach a certain value. Return to the negative pressure return gas end of the fifth-stage heat exchanger 95 .

In an embodiment of the present invention, the temperature exchange pipeline at the inlet of the cold compressor unit includes a pipeline temperature exchange module, and the pipeline temperature exchange module includes a pipe connected to the low-pressure return air circuit 19 and the inlet of the cold compressor unit. The first temperature conversion pipeline 81 and the first temperature conversion regulating valve 82 arranged on the first temperature conversion pipeline 81 .

It can be understood that the temperature change of the pipeline is a way of temperature change at the inlet of the cold compressor unit. Using the first temperature change pipeline 81 to directly change the temperature can quickly achieve the temperature change effect, and at the same time, in order to avoid affecting the cold compressor unit The inlet flow rate of the compressor unit and to avoid increasing the complexity of the control of the cold compressor unit, the present invention leads the first exchange temperature pipeline 81 from the low-pressure side of the superfluid helium refrigerator, that is, the first exchange temperature The inlet of the pipeline 81 is connected to the low-pressure return air circuit 19, and the outlet is connected to the inlet of the cold compressor unit, so that the inlet flow rate of the cold compressor unit changes relatively slowly, and the overall temperature of the pipeline exchange module The structure is simple, which can avoid increasing the complexity of regulation of the cold compressor unit.

In another embodiment of the present invention, the inlet temperature exchange pipeline of the cold compressor unit includes a heat exchanger temperature exchange module, and the heat exchanger temperature exchange module includes an outlet connected to the ninth stage heat exchanger 99 And the temperature conversion heat exchanger 83 of the inlet of the cold compressor unit, the second temperature conversion pipeline 84 connected to the high-pressure main gas circuit 17 and the inlet of the temperature conversion heat exchanger 83, arranged on the first The second temperature conversion regulating valve 85 on the two temperature conversion pipelines 84, the third temperature conversion pipeline 86 connected to the outlet of the temperature conversion heat exchanger 83 and the high-pressure main gas circuit 17, and the temperature conversion pipeline 86 arranged on the On the high-pressure main gas line 17 and between the second temperature conversion pipeline 84 and the third temperature conversion pipeline 86 is a third temperature conversion regulating valve 87 .

It can be understood that the temperature exchange of the heat exchanger is another way to exchange the temperature at the inlet of the cold compressor unit. The heat exchange method is adopted. Since the heat capacity of the temperature exchange heat exchanger 83 is relatively large, it is different from that of the cold compressor unit. Compared with the way of pipe temperature exchange, the temperature exchange of the heat exchanger is slower, but the temperature exchange of the heat exchanger will only affect the inlet temperature of the cold compressor unit, and will not affect the inlet flow of the cold compressor unit.

It should be understood that the superfluid helium refrigerator can be provided with either the pipeline temperature exchange module or the heat exchanger temperature exchange module, or two temperature exchange modules at the same time. Preferably, in this aspect of the present invention In a preferred embodiment, the inlet temperature conversion pipeline of the cold compressor unit includes the pipeline temperature conversion module and the heat exchanger temperature conversion module, that is, the superfluid helium refrigerator is provided with two temperature conversion modules. When the superfluid helium refrigerator is in operation, these two temperature changing methods can be used selectively or in combination. For example, use the pipeline to exchange temperature first, and at the same time control the second temperature exchange regulating valve 85 of the heat exchanger temperature exchange module to slowly open at a small opening, and wait until the outlet temperature of the temperature exchange heat exchanger 83 reaches the target temperature , close the pipeline temperature conversion module and switch to the heat exchanger temperature conversion mode, which is not limited in the present invention.

It is worth mentioning that the multi-channel transmission pipeline includes a first pipeline 21, a second pipeline 22, a third pipeline 23, a fourth pipeline 24, a fifth pipeline 25 and a sixth pipeline 26, so The load 101 in the 50-75K temperature zone is connected to the load outflow pipeline 62 through the first pipeline 21, and connected to the return pipeline 66 through the second pipeline 22; the 4.5-75K temperature zone The load 102 is connected to the liquid phase outlet of the subcooler 104 through the third pipeline 23, and connected to the low-pressure return gas circuit 19 through the fourth pipeline 24; the ninth stage heat exchanger 99 is connected to the The fifth pipeline 25 is connected to the liquid phase outlet of the subcooler 104 , and is connected to the inlet of the cold compressor unit inlet temperature conversion pipeline through the sixth pipeline 26 .

In addition, it is also worth mentioning that the load 101 in the 50-75K temperature range, the load 102 in the 4.5-75K temperature range, the 2K load 103, and the inlet and outlet of the ninth-stage heat exchanger 99 are all provided with Corresponding import and export regulating valves, the aforementioned import and export regulating valves are all set in the load test cold box 27, and are respectively used to adjust the load 101 in the 50-75K temperature zone, the load 102 in the 4.5-75K temperature zone, and the load in the 4.5-75K temperature zone. 2K load 103 and the gas in and out of the ninth stage heat exchanger 99 .

Further, the superfluid helium refrigerator also includes a low-temperature adsorber group, and the low-temperature adsorber group includes an 80K low-temperature adsorber 38 for adsorbing oxygen in helium, nitrogen, hydrocarbons and other impurity gases and an adsorption helium The 20K low-temperature adsorber 39 for impurity gases such as hydrogen and neon in the gas, the 80K low-temperature adsorber 38 and the 20K low-temperature adsorber 39 are all arranged on the high-pressure main gas circuit 17, and the 80K low-temperature adsorber 38 is located between the second-stage heat exchanger 92 and the third-stage heat exchanger 93, and the 20K low-temperature adsorber 39 is located between the sixth-stage heat exchanger 96 and the seventh-stage heat exchanger Between 97.

In this specific embodiment of the present invention, there are two 80K cryogenic adsorbers 38, and the two 80K cryogenic adsorbers 38 are connected in parallel and switched for use, that is to say, one of the 80K cryogenic adsorbers 38 During operation, another 80K low temperature adsorber 38 can be regenerated at the same time. The 80K cryogenic adsorber 38 is used to adsorb impurity gases in helium, such as oxygen, nitrogen, hydrocarbons and the like.

The 20K cryogenic adsorber 39 is used to adsorb impurity gases in helium, such as hydrogen, neon and other impurity gases.

It can be understood that the superfluid helium refrigerator of the present invention can also be equipped with cryogenic adsorbers corresponding to the temperature at other positions on the high-pressure main gas circuit 17, and is not limited to the 80K cryogenic adsorber 38 and the 20K cryogenic adsorption device 39, and the 20K cryogenic adsorber 39 can also adopt two parallel structures, which is not limited in the present invention.

Further, the superfluid helium refrigerator of the present invention can pre-cool the normal-temperature and high-pressure helium gas discharged into the refrigerator cold box 10 by the high-pressure compressor 2 by means of liquid nitrogen precooling or turbo expansion cooling. cold.

Specifically, in an embodiment of the present invention, the helium precooling module is a liquid nitrogen precooling device, and the liquid nitrogen precooling device includes a helium passage regulating valve 30 connected to the high-pressure main gas circuit 17 , the liquid nitrogen precooling heat exchanger 31 connected to the helium passage regulating valve 30, the liquid nitrogen inlet pipeline 32 connected to the liquid nitrogen precooling heat exchanger 31, and the liquid nitrogen inlet pipe arranged on the The liquid nitrogen inlet regulating valve 33 of the road 32, the outlet of the liquid nitrogen precooling heat exchanger 31 is connected to the high-pressure main gas circuit 17, and is located at the outlet of the second-stage heat exchanger 92 and the 80K low temperature Between the inlets of the adsorber 38, the helium precooling module precools the normal temperature and high pressure helium with the liquid nitrogen fed through the liquid nitrogen inlet pipeline 32, and passes through the helium passage regulating valve 30 Adjust the amount of helium entering the liquid nitrogen pre-cooling heat exchanger 31 , and adjust the amount of liquid nitrogen entering the liquid nitrogen pre-cooling heat exchanger 31 through the liquid nitrogen inlet regulating valve 33 .

In an embodiment of the present invention, the helium pre-cooling module is a turbo-expansion pre-cooling device, and the turbo-expansion pre-cooling device includes a first turbine 34, a second turbine 35, a third turbine 36 pre-cooling turbo-expander units in series and the first inlet regulating valve 37 arranged between the outlet of the first-stage heat exchanger 91 and the inlet of the first turbine 34, the pre-cooling turbine The outlet of the expansion unit is connected to the medium pressure return gas path 18 .

It can be understood that the superfluid helium refrigerator uses the precooling turboexpander unit composed of three turboexpanders in series to precool the normal temperature and high pressure helium to 80K. Precooling by using the precooling turboexpander unit can make the superfluid helium refrigerator suitable for occasions where there is no liquid nitrogen or liquid nitrogen is not suitable for precooling, for example, in the superfluid helium refrigerator When cooling superconducting magnets and accelerators in the tunnel, because the tunnel is a closed space, when liquid nitrogen is used for precooling, if nitrogen leaks, because the density of nitrogen is not much different from that of air, it is easy to suffocate the staff in the tunnel.

It should be understood that the superfluid helium refrigerator of the present invention is preferably provided with the liquid nitrogen precooling device and the precooling turboexpander unit, and any precooling module can be selected during use, that is, in When the precooling turboexpander unit is used for precooling, the superfluid helium refrigerator can also reserve a port for liquid nitrogen precooling, which is not limited in the present invention. By arranging two kinds of pre-cooling modules, the superfluid helium refrigerator can be applied to various application occasions, which is beneficial to expand the application range of the superfluid helium refrigerator.

It is worth mentioning that, in this specific embodiment of the present invention, the precooling turboexpander unit precools helium from 300K to 80K.

Further, the specific structure of the multi-stage turboexpander unit is as follows:

The first turboexpander unit includes a fourth turbine 40 and a fifth turbine 41 arranged in series, and is arranged between the outlet of the third-stage heat exchanger 93 and the inlet of the fourth turbine 40 The second inlet regulating valve 42 of the fourth turbine 40, the inlet of the fourth turbine 40 is connected to the helium passing through the pipeline 67 of the load temperature conversion pipeline in the 50-75K temperature zone, and the outlet of the fifth turbine 41 Connected to the medium pressure return gas circuit 18, the first turboexpander unit cools the helium gas from 75K to 50K. The reflux gas of the load 101 in the 50-75K temperature zone is mixed with the 75K helium gas in the inlet pipeline 68 of the first turboexpander unit, and then enters the first turboexpander unit for re-expansion.

The second turboexpander unit includes a sixth turbine 43 and a seventh turbine 44 arranged in series, and is arranged between the outlet of the fifth-stage heat exchanger 95 and the inlet of the sixth turbine 43 The third inlet regulating valve 45, the outlet of the seventh turbine 44 is connected to the medium pressure return gas path 18, and the second turboexpander unit cools the helium gas from 23K to 15K.

The third turboexpander unit includes an eighth turbine 46 and a ninth turbine 47 arranged in series, and a second turbine arranged between the outlet of the 20K cryogenic adsorber 39 and the inlet of the eighth turbine 46 Four inlet regulating valves 48, the outlet of the ninth turbine 47 is connected to the low-pressure return gas circuit 19, and the third turboexpander unit cools helium from 14K to 6K.

The fourth turbo-expansion unit includes a tenth turbine 49, a fifth inlet regulating valve 50 arranged between the outlet of the seventh-stage heat exchanger 97 and the inlet of the tenth turbine 49, and a fifth inlet regulating valve 50 arranged at On the high-pressure main gas circuit 17 and between the seventh-stage heat exchanger 97 and the eighth-stage heat exchanger 98, the last-stage turbine bypass valve 51, the tenth turbine 49 The outlet is connected to the high-pressure main gas path 17 . In this specific embodiment, the fourth turboexpander unit is the final turboexpander unit, and the helium gas cooled by the fourth turboexpander unit enters the eighth stage heat exchanger 98 for heat exchange , forming supercritical helium at 5.3K.

It is worth mentioning that the superfluid helium refrigerator also includes a cold box bypass line 11 connected to the outlet of the fourth turboexpansion unit and the low-pressure return gas line 19 and is arranged on the cold box The cold box bypass valve 12 on the bypass line 11 is used to realize the regulation function when the superfluid helium refrigerator 4K is partially cooled.

In addition, it is also worth mentioning that a throttling valve group is also provided between the high-pressure main air circuit 17 and the subcooler 104, and the throttle valve group includes a first throttle valve 13 and a The second throttle valve 14, a gas return valve 15 is also arranged between the gas phase outlet of the subcooler 104 and the low pressure return gas circuit 19, the ninth stage heat exchanger 99 and the gas-liquid separator A third throttling valve 16 is also arranged between the inlets of 105, and the ninth stage heat exchanger 99 and the third throttling valve 16 are both arranged in the load test cold box 27;

A part of the supercritical helium output from the high-pressure main gas circuit 17 is throttled by the first throttle valve 13 into a gas-liquid two-phase, the liquid phase accumulates liquid in the subcooler 104, and the gas phase passes through the return gas The valve 15 enters the low-pressure gas return circuit 19; another part of the supercritical helium enters the subcooler 104 after being throttled by the second throttle valve 14, and is filtered by the liquid helium accumulated in the subcooler 104. The supercooled supercritical helium is formed by cooling, and the supercooled supercritical helium flows out from the subcooler 104, a part of which is supplied to the load 102 in the 4.5-75K temperature zone, and the other part enters the ninth-stage heat exchanger 99 and passes through the The third throttling valve 16 throttling is a gas-liquid two-phase, the liquid phase accumulates liquid in the gas-liquid separator 105, the gas phase is discharged from the gas phase outlet of the gas-liquid separator 105, and the return with the 2K load 103 The gas merges into the ninth-stage heat exchanger 99 for heat exchange, and the helium gas after heat exchange enters the cold compressor unit after being warmed through the temperature exchange pipeline at the inlet of the cold compressor unit.

It can be understood that, in this specific embodiment, the subcooler 104 is a helium subcooler, and the gas-liquid separator 105 is a 2K gas-liquid separator.

Further, the superfluid helium refrigerator also includes a gas management panel, which is used to adjust and control the inlet and outlet pressures of the medium-pressure compressor 1 and the high-pressure compressor 2, including connecting to the high-pressure The medium pressure bypass valve 5 of the main air circuit 17 and the medium pressure return air circuit 18, the low pressure bypass valve 6 connecting the high pressure main air circuit 17 and the low pressure return air circuit 19, and the low pressure return air circuit 19 are connected to the low pressure return air circuit. The gas circuit 19 and the loading valve 9 and buffer tank unloading valve 7 of the high-pressure main gas circuit 17 , and the buffer tank 8 connected between the loading valve 9 and the buffer tank unloading valve 7 .

It is worth mentioning that the superfluid helium refrigerator also includes a one-way valve 4 arranged between the negative pressure compressor 3 and the high-pressure compressor 2, and the one-way valve 4 is used to prevent the The outlet helium of the negative pressure compressor 3 countercurrently flows.

The working process of the superfluid helium refrigerator is as follows:

(1) The normal temperature and high pressure helium discharged by the high pressure compressor 2 enters the refrigerator cold box 10;

(2) A small part of the normal temperature and high pressure helium gas entering the refrigerator cold box 10 enters the liquid nitrogen precooling heat exchanger 31 and is precooled to 80K by liquid nitrogen (liquid nitrogen precooling). Or the normal-temperature high-pressure helium gas that enters the refrigerator cold box 10 is cooled to a certain temperature by the backflow cold helium gas through the first-stage heat exchanger 91, and then a stream of fluid is separated and enters the pre-cooling turbine. The expansion unit is pre-cooled to 80K by the pre-cooling turbo-expander unit (pre-cooling of the turbo-expander unit). The return gas at the outlet of the pre-cooling turboexpander unit is at medium pressure, passes through the second-stage heat exchanger 92 and the first-stage heat exchanger 91 countercurrently, and enters the suction port of the high-pressure compressor 2 . It is worth mentioning that liquid nitrogen pre-cooling and pre-cooling turbo-expansion unit pre-cooling can be selected, and cannot be carried out at the same time;

(3) After the helium in the remaining high-pressure main gas circuit 17 is pre-cooled, it enters the 80K low-temperature adsorber 38 to remove impurity gases such as oxygen, nitrogen and hydrocarbons in the helium, and then passes through the third stage of replacement. Heater 93 is cooled by the return flow of cold helium, and a part of helium enters the first turboexpander through the inlet pipeline 68 of the first turboexpander, and is cooled from 75K to 50K. The outlet gas of the first turboexpander unit returns to the medium pressure, and passes through the fourth-stage heat exchanger 94, the third-stage heat exchanger 93, the second-stage heat exchanger 92 and all After the first-stage heat exchanger 91, it enters the suction port of the high-pressure compressor 2; another part of the helium passes through the fourth-stage heat exchanger 94 to form 50K helium, and a part of the 50K helium passes through The 50K helium pipeline 60 is divided into two strands, one strand enters the load outflow pipeline 62 and is sent to the load 101 in the 50-75K temperature zone, and the other strand enters the temperature exchange pipeline 63 and the The helium in the return line 66 is exchanged for temperature. The helium gas after the temperature exchange is completed enters the helium gas through the pipeline 67, mixes with the 75K helium gas from the inlet pipeline 68 of the first turboexpander unit, and then re-enters the first turboexpander unit for further processing. expand again;

(4) After the gas in the high-pressure main gas circuit 17 passes through the fifth-stage heat exchanger 95, part of it enters the second turboexpander unit and is cooled from 23K to 15K, and the outlet of the second turboexpander unit The helium gas is returned to medium pressure, and countercurrently passes through the sixth-stage heat exchanger 96, the fifth-stage heat exchanger 95, the fourth-stage heat exchanger 94, the third-stage heat exchanger 93, After the second-stage heat exchanger 92 and the first-stage heat exchanger 91, enter the suction port of the high-pressure compressor 2;

(5) After the gas in the remaining high-pressure main gas circuit 17 passes through the sixth-stage heat exchanger 96, it enters the 20K cryogenic adsorber 39 to remove impurity gases such as hydrogen, neon, etc. in the helium, and a part of the helium after the removal of impurities Enter the third turbo-expander unit, cool from 14K to 6K, the outlet gas of the third turbo-expander unit returns to low pressure, and passes through the seventh-stage heat exchanger 97 and the sixth-stage heat exchanger 97 countercurrently. The heat exchanger 96, the fifth stage heat exchanger 95, the fourth stage heat exchanger 94, the third stage heat exchanger 93, the second stage heat exchanger 92 and the first stage heat exchanger After the heater 91, enter the suction port of the medium pressure compressor 1;

(6) Another part of helium after the removal of impurities passes through the seventh-stage heat exchanger 97, and then enters the eighth-stage heat exchanger 98 to exchange heat with the reflux cold helium after passing through the fourth turbo-expander unit , and then the helium in the high-pressure main gas path 17 reaches a supercritical state. The 5.3K supercritical helium is divided into two parts, and a part of the supercritical helium is throttled by the first throttle valve 13 to form a gas-liquid two-phase, the liquid phase accumulates liquid in the subcooler 104, and the gas phase passes through the The air return valve 15 returns air to the low-pressure air return circuit 19 . Another part of 5.3K supercritical helium enters the subcooler 104 after being throttled by the second throttle valve 14, and is supercooled by the liquid helium accumulated in the subcooler 104 to become 4.5K@3bara supercooled. Cold supercritical helium. Supercooled supercritical helium flows out from the liquid phase outlet of the subcooler 104, and a small part is separated through the third pipeline 23 of the multi-channel transfer pipeline and enters the load test cold box 27 for supply to the The 4.5-75K temperature zone load 102, the return air of the 4.5-75K temperature zone load 102 enters the refrigerator cold box 10 through the fourth pipeline 24 of the multi-channel transmission pipeline, and returns to the first The low pressure suction side of the secondary heat exchanger 92 . Most of the rest of the subcooled supercritical helium enters the load test cold box 27 through the fifth pipeline 25 of the multi-channel transfer pipeline, passes through the ninth stage heat exchanger 99 after heat exchange, and passes through the The third throttling valve 16 throttling is a gas-liquid two-phase, the liquid phase accumulates liquid in the gas-liquid separator 105, and the gas phase returns to gas from the gas phase outlet of the gas-liquid separator 105, and passes through the ninth stage countercurrently. After the heat exchanger 99, after entering the refrigerator cold box 10 through the sixth pipeline 26 of the multi-channel transmission pipeline, it enters the cold compressor unit. When the liquid helium level in the gas-liquid separator 105 does not reach a certain value, the return gas helium returns to the fifth heat exchange stage from the cold compressor unit bypass line 76 and the bypass regulating valve 77 The negative pressure return gas end of device 95;

(7) When the liquid helium level in the gas-liquid separator 105 reaches a certain value, the cold compressor unit is started, and the helium in the gas-liquid separator 105 is decompressed to a superfluid helium saturation pressure of 0.03 bar , so that 2K saturated superfluid helium is formed in the gas-liquid separator 105 . The 2K saturated superfluid helium flows out from the liquid phase outlet of the gas-liquid separator 105 and is sent to the 2K load 103 . The return air from the 2K load 103 is mixed with the return air from the gas phase outlet of the gas-liquid separator 105, and flows back through the ninth-stage heat exchanger 99, and then passes through the sixth stage of the multi-channel transmission pipeline. The pipeline 26 enters the cold box 10 of the refrigerator, and enters the cold compressor unit after being warmed through the inlet temperature conversion pipeline of the cold compressor unit;

(8) The cold compressor unit increases the helium pressure in the downstream pipeline from 0.03 bar to 0.5 bar. The negative pressure helium gas of 0.5 bar enters the fifth stage heat exchanger 95, the fourth stage heat exchanger 94, the third stage heat exchanger 93, the second stage heat exchanger 92 and the The negative pressure channel of the first-stage heat exchanger 91 becomes 0.4 bar negative pressure helium gas after layer-by-layer pressure drop, and enters the suction port of the negative pressure compressor 3 . The negative pressure compressor 3 compresses 0.4bar negative pressure helium gas to a medium pressure of 4.05bar, and mixes it with the medium pressure gas from the outlet of the medium pressure compressor 1 and the return gas from the medium pressure return gas circuit 18, Send them into the suction port of the high-pressure compressor 2 together to complete a helium cycle.

It can be understood that the superfluid helium refrigerator of the present invention separates the refrigeration part from the load test part through the refrigerator cold box 10 and the load test cold box 27, and loads the 50-75K temperature zone 101. The 4.5-75K temperature zone load 102, the 2K load 103, the ninth stage heat exchanger 99 and the gas-liquid separator 105 are placed inside the load test cold box 27, and the load test The cold box 27 is only used in the load cooling capacity test stage and is separated from the function of the refrigerator cold box 10 . After the superfluid helium refrigerator is delivered to the user, the load test cold box 27 and the multi-channel transfer pipeline can be removed, and the user load is directly connected to the refrigerator cold box 10 . This design makes the cold box of the refrigerator compact in structure, and prevents the test loads in each temperature zone from becoming idle heat capacity after the load test stage, occupying precious space in the cold box of the refrigerator.

In addition, the superfluid helium refrigerator of the present invention is provided with a 50-75K temperature range load temperature conversion pipeline at the first turboexpander unit, and an inlet of the cold compressor unit is provided at the inlet side of the cold compressor unit The temperature conversion pipeline enables the fluid parameters entering the first turboexpander unit and the cold compressor unit to reach the design parameters of the inlet of the turbomachinery, so that the turbomachinery such as the turboexpander unit and the cold compressor unit can operate at the optimum working condition. It is beneficial to improve the overall performance of the superfluid helium refrigerator, thereby ensuring that the superfluid helium refrigerator can be used for a long time under different operating modes such as 2K working mode, 2K standby mode, 4.5K standby mode, and heating and cooling mode. , stable and reliable operation, and can meet the cooling capacity requirements under various operating modes.

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

The above examples only express the preferred implementation of the present invention, and the descriptions thereof are relatively specific and detailed, but should not be construed as limiting the scope of the patent for the invention. It should be pointed out that those skilled in the art can make several modifications and improvements 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 patent for the present invention should be based on the appended claims.

Claims (20)

1. A superfluid helium refrigerator with independent load test cold box, is characterized in that, comprises compressor unit, refrigerator cold box, load test cold box, the helium pre-cooling that is all arranged in described refrigerator cold box module, multi-stage turboexpander unit, heat exchanger unit, subcooler and cold compressor unit, and the gas-liquid separator all set in the load test cold box, 50~75K temperature zone load, 4.5~75K temperature zone load, 4.5~75K temperature Zone load and 2K load, the load test cold box is used for use in the load cold capacity test stage; The superfluid helium refrigerator also includes a multi-channel transfer line for connecting the refrigerator cold box and the load test cold box, and the load test cold box is connected to the refrigerator cold box through the multi-channel transfer line. The box forms a detachable connection; The compressor assembly includes a positive pressure compressor and a negative pressure compressor, the positive pressure compressor includes a medium pressure compressor and a high pressure compressor, the outlet of the negative pressure compressor and the outlet of the medium pressure compressor are connected At the suction port of the high-pressure compressor, the outlet of the high-pressure compressor is connected to the inlet of the cold box of the refrigerator, and the normal temperature and high-pressure helium gas discharged from the high-pressure compressor enters through the inlet of the cold box of the refrigerator. In the cold box of the refrigerator; The helium pre-cooling module is arranged on the inlet side of the cold box of the refrigerator and before the multi-stage turbo-expansion unit, and is used for precooling a part of normal-temperature and high-pressure helium entering the cold box of the refrigerator ; The multi-stage turbo-expansion unit includes a first turbo-expansion unit, a second turbo-expansion unit, a third turbo-expansion unit and a fourth turbo-expansion unit arranged in sequence, for controlling the The normal temperature and high pressure helium is used for multi-stage cooling process; The heat exchanger group is used to perform a multi-stage heat exchange process for the normal temperature and high pressure helium entering the cold box of the refrigerator; The superfluid helium refrigerator includes a high-pressure main gas circuit, a medium-pressure return gas circuit, a low-pressure return gas circuit, and a negative pressure return gas circuit. The inlet of the high-pressure main gas circuit is connected to the inlet and outlet of the cold box of the refrigerator. connected to the inlet of the subcooler; the inlet of the medium-pressure return gas circuit is connected to the outlet of the second turboexpander unit, and the outlet is connected to the suction port of the high-pressure compressor; the low-pressure return gas The inlet of the path is connected to the gas phase outlet of the subcooler, and the outlet is connected to the suction port of the medium pressure compressor; the inlet of the negative pressure return path is connected to the outlet of the cold compressor unit, and the outlet is connected to The suction port of the negative pressure compressor; The liquid phase outlet of the subcooler is connected to the inlet of the load in the 4.5~75K temperature zone and the inlet of the gas-liquid separator, and the outlet of the load in the 4.5~75K temperature zone is connected to the low pressure return gas path, The liquid phase outlet of the gas-liquid separator is connected to the 2K load, and the outlet of the 2K load and the gas phase outlet of the gas-liquid separator are connected to the inlet of the cold compressor unit; Wherein the high-pressure compressor discharges normal temperature and high pressure helium into the refrigerator cold box through the inlet of the refrigerator cold box, and a part of the normal temperature and high pressure helium enters the helium precooling module for precooling. After the cooled helium is merged with the normal temperature and high pressure helium in the high-pressure main gas circuit, the multi-stage cooling process and the multi-stage heat exchange process are performed through the multi-stage turbo expander unit, Formation of supercritical helium; The supercritical helium enters the subcooler through the high-pressure main gas circuit, the gas phase enters the low-pressure return gas circuit, and a part of the liquid phase enters the 4.5-75K temperature zone and returns to the low-pressure return gas The other part of the liquid phase is throttling into a gas-liquid two-phase, and the liquid phase enters the gas-liquid separator to collect liquid. When the liquid helium level in the gas-liquid separator reaches a preset value, the cold compressor unit Start, the helium in the gas-liquid separator is decompressed to form 2K saturated superfluid helium, and the 2K saturated superfluid helium flows out from the liquid phase outlet of the gas-liquid separator to the 2K load; the gas phase It is discharged from the gas phase outlet of the gas-liquid separator, merged with the return gas of the 2K load, enters the cold compressor unit, and enters the negative pressure return gas circuit after being boosted by the cold compressor unit. After the pressure drop, the negative pressure helium gas is formed, and the negative pressure helium gas enters the negative pressure compressor and is compressed to a medium pressure, and is combined with the medium pressure gas discharged from the medium pressure compressor and the return gas of the medium pressure return gas circuit After mixing, it enters the high-pressure compressor, and a helium cycle is completed so far. 2. The superfluid helium refrigerator with independent load test cold box according to claim 1, characterized in that, the superfluid helium refrigerator also includes 50 ~ 75K temperature thermostats all arranged in the cold box of the refrigerator. Zone load temperature conversion pipeline and cold compressor unit inlet temperature conversion pipeline, wherein the load temperature conversion pipeline in the 50~75K temperature zone is connected to the first turboexpander unit for The helium gas before the expansion unit is exchanged for temperature; wherein the temperature exchange pipeline at the inlet of the cold compressor unit is arranged on the inlet side of the cold compressor unit, and is used to adjust the temperature of the helium gas entering the cold compressor unit. 3. The superfluid helium refrigerator with independent load test cold box according to claim 2, characterized in that, said 50-75K temperature zone load temperature conversion pipeline comprises 50K helium connected to said high-pressure main gas circuit Gas pipeline, load discharge pipeline connected to the 50K helium pipeline and the inlet of the load in the 50~75K temperature zone, temperature exchange pipeline connected to the 50K helium pipeline, connected to the 50~75K temperature zone The return line of the outlet of the load, and the helium passage line connected to the return line, the temperature exchange line and the first turboexpander unit, the 50K helium line is provided with a 50K helium pipe The temperature conversion pipeline is provided with a temperature conversion pipeline regulating valve and a temperature conversion pipeline heater, and the return pipeline is provided with a return pipeline regulation valve, wherein the temperature conversion pipeline is used for passing through the temperature conversion pipeline. The temperature exchange pipeline regulating valve and the temperature exchange pipeline heater are used to adjust the temperature of the helium in the return pipeline, so that the helium gas that enters the first turboexpander unit via the helium gas pipeline It can meet the requirements of the inlet temperature and pressure of the first turboexpander unit. 4. the superfluid helium refrigerator with independent load test cold box according to claim 3, is characterized in that, described heat exchanger group comprises and is connected with described high-pressure main gas circuit, described medium pressure return gas circuit, The first-stage heat exchanger, the second-stage heat exchanger, the third-stage heat exchanger, the fourth-stage heat exchanger, and the fifth-stage heat exchanger of the low-pressure return air circuit and the negative-pressure return air circuit are arranged in sequence. The heat exchanger also includes a sixth-stage heat exchanger connected to the high-pressure main gas circuit, the medium-pressure return gas circuit, and the low-pressure return gas circuit, connected to the high-pressure main gas circuit and the low-pressure return gas circuit The seventh-stage heat exchanger and the eighth-stage heat exchanger of the gas circuit, and the first stage connected to the liquid phase outlet of the subcooler, the inlet and gas phase outlet of the gas-liquid separator, and the outlet of the 2K load Nine-stage heat exchanger, wherein the helium gas discharged from the gas-liquid separator and the return gas of the 2K load are combined and then enter the ninth-stage heat exchanger for heat exchange, and the helium gas after heat exchange passes through the The inlet temperature conversion pipeline of the cold compressor unit enters the cold compressor unit after being warmed. 5. The superfluid helium refrigerator with independent load test cold box according to claim 4, characterized in that, the multi-channel transfer pipeline comprises a first pipeline, a second pipeline, a third pipeline, a fourth pipeline Pipeline, fifth pipeline and sixth pipeline, the load in the 50~75K temperature zone is connected to the load outflow pipeline through the first pipeline, and the return pipe is connected through the second pipeline road; the 4.5~75K temperature zone load is connected to the liquid phase outlet of the subcooler through the third pipeline, and connected to the low-pressure return gas circuit through the fourth pipeline; the ninth-stage replacement The heater is connected to the liquid phase outlet of the subcooler through the fifth pipeline, and connected to the inlet of the cold compressor unit inlet temperature conversion pipeline through the sixth pipeline. 6. The superfluid helium refrigerator with independent load test cold box according to claim 4, characterized in that, the inlet temperature exchange pipeline of the cold compressor unit includes a pipeline temperature exchange module, and the pipeline temperature exchange module includes a connecting The first temperature conversion pipeline between the low-pressure return air circuit and the inlet of the cold compressor unit, and the first temperature conversion regulating valve arranged on the first temperature conversion pipeline. 7. The superfluid helium refrigerator with an independent load test cold box according to claim 4 or 6, wherein the inlet temperature exchange pipeline of the cold compressor unit includes a heat exchanger temperature exchange module, and the heat exchange The temperature exchange module includes a temperature exchange heat exchanger connected to the outlet of the ninth stage heat exchanger and the inlet of the cold compressor unit, and connected to the high-pressure main gas circuit and the inlet of the temperature exchange heat exchanger The second temperature conversion pipeline, the second temperature conversion regulating valve arranged on the second temperature conversion pipeline, the third temperature conversion tube connected to the outlet of the temperature conversion heat exchanger and the high-pressure main gas circuit road, and a third temperature-converting regulating valve arranged on the high-pressure main gas circuit and between the second temperature-converting pipeline and the third temperature-converting pipeline. 8. The superfluid helium refrigerator with an independent load test cold box according to any one of claims 4 to 6, characterized in that, a joint is also arranged between the high-pressure main gas circuit and the subcooler A throttling valve group, the throttling valve group includes a first throttle valve and a second throttle valve arranged in parallel, and a gas return valve is also arranged between the gas phase outlet of the subcooler and the low pressure return gas circuit, A third throttling valve is also set between the ninth stage heat exchanger and the inlet of the gas-liquid separator, and both the ninth stage heat exchanger and the third throttling valve are set at the load Test in the cold box; Wherein, a part of the supercritical helium output from the high-pressure main gas circuit is throttled by the first throttle valve into gas-liquid two-phase, the liquid phase accumulates liquid in the subcooler, and the gas phase enters the gas-liquid two-phase through the gas return valve. The low-pressure return gas circuit; another part of supercritical helium enters the subcooler after being throttled by the second throttle valve, and is supercooled by the liquid helium accumulated in the subcooler to form supercooled supercritical helium, Supercooled supercritical helium flows out from the subcooler, part of which is supplied to the load in the 4.5-75K temperature zone, and the other part enters the ninth-stage heat exchanger, and is throttled by the third throttle valve into gas-liquid phase, the liquid phase accumulates liquid in the gas-liquid separator, the gas phase is discharged from the gas phase outlet of the gas-liquid separator, merges with the return gas of the 2K load and enters the ninth stage heat exchanger for heat exchange, The heat-exchanged helium enters the cold compressor unit after being warmed through the temperature exchange pipeline at the inlet of the cold compressor unit. 9. The superfluid helium refrigerator with independent load test cold box according to claim 8, characterized in that, the cold compressor unit comprises the sixth inlet regulating valve, the first cold compressor, the second cold compressor arranged in series compressor, the third cold compressor, the fourth cold compressor, and the first outlet regulating valve, and the superfluid helium refrigerator also includes a cold compressor unit bypass line connected in parallel with the cold compressor unit and arranged on the The bypass regulating valve on the bypass line of the cold compressor unit. 10. The superfluid helium refrigerator with independent load test cold box according to claim 9, characterized in that, the superfluid helium refrigerator also includes an outlet connected to the fourth turboexpander unit and the The cold box bypass line of the low-pressure return air circuit and the cold box bypass valve arranged on the cold box bypass line. 11. The superfluid helium refrigerator with an independent load test cold box according to any one of claims 4 to 6, characterized in that, the superfluid helium refrigerator also includes a low-temperature adsorber group, and the low-temperature adsorption The device group includes an 80K cryogenic adsorber and a 20K cryogenic adsorber for adsorbing impurity gases in helium, the 80K cryogenic adsorber and the 20K cryogenic adsorber are both arranged on the high-pressure main gas path, and the 80K The low-temperature adsorber is located between the second-stage heat exchanger and the third-stage heat exchanger, and the 20K low-temperature adsorber is located between the sixth-stage heat exchanger and the seventh-stage heat exchanger . 12. The superfluid helium refrigerator with an independent load test cold box according to claim 11, wherein there are two 80K cryogenic adsorbers, and the two 80K cryogenic adsorbers are connected in parallel and switched for use. 13. The superfluid helium refrigerator with independent load test cold box according to claim 11, characterized in that, the helium precooling module comprises a helium passage regulating valve connected to the high-pressure main gas circuit, a connection The liquid nitrogen pre-cooling heat exchanger connected to the liquid nitrogen pre-cooling heat exchanger of the helium passage regulating valve, the liquid nitrogen inlet pipeline connected to the liquid nitrogen pre-cooling heat exchanger, and the liquid nitrogen inlet adjustment set on the liquid nitrogen inlet pipeline Valve, the outlet of the liquid nitrogen pre-cooling heat exchanger is connected to the high-pressure main gas circuit, and is located between the outlet of the second-stage heat exchanger and the inlet of the 80K cryogenic adsorber, and the helium The precooling module precools the normal temperature and high pressure helium by the liquid nitrogen fed through the liquid nitrogen inlet pipeline, and adjusts the amount of helium entering the liquid nitrogen precooling heat exchanger through the helium passage regulating valve , and adjust the amount of liquid nitrogen entering the liquid nitrogen precooling heat exchanger through the liquid nitrogen inlet regulating valve. 14. The superfluid helium refrigerator with independent load test cold box according to claim 13, characterized in that, the helium precooling module comprises a first turbine, a second turbine, and a third turbine connected in series A pre-cooling turbo-expansion unit composed of a first inlet regulating valve arranged between the outlet of the first-stage heat exchanger and the inlet of the first turbine, the outlet of the pre-cooling turbo-expander unit is connected to In the medium pressure return air circuit. 15. The superfluid helium refrigerator with independent load test cold box according to claim 11, characterized in that, the first turboexpander unit comprises a fourth turbine and a fifth turbine arranged in series, and is arranged at A second inlet regulating valve between the outlet of the third-stage heat exchanger and the inlet of the fourth turbine, the inlet of the fourth turbine is connected to the load temperature conversion pipeline in the 50~75K temperature zone The helium gas passes through the pipeline, and the outlet of the fifth turbine is connected to the medium pressure return gas circuit. 16. The superfluid helium refrigerator with independent load test cold box according to claim 15, characterized in that, the second turboexpander unit includes the sixth turbine and the seventh turbine arranged in series, and is arranged at A third inlet regulating valve between the outlet of the fifth-stage heat exchanger and the inlet of the sixth turbine, and the outlet of the seventh turbine is connected to the medium-pressure return gas path. 17. The superfluid helium refrigerator with independent load test cold box according to claim 16, characterized in that, the third turboexpander unit includes the eighth turbine and the ninth turbine arranged in series, and is arranged at The fourth inlet regulating valve is between the outlet of the 20K cryogenic adsorber and the inlet of the eighth turbine, and the outlet of the ninth turbine is connected to the low-pressure return gas path. 18. The superfluid helium refrigerator with an independent load test cold box according to claim 17, characterized in that, the fourth turboexpansion unit includes a tenth turbine arranged in the seventh stage heat exchanger The fifth inlet regulating valve between the outlet of the tenth turbine and the inlet of the tenth turbine is set on the high-pressure main gas path, and is located between the seventh-stage heat exchanger and the eighth-stage heat exchanger The last-stage turbine bypass valve, the outlet of the tenth turbine is connected to the high-pressure main gas path. 19. The superfluid helium refrigerator with an independent load test cold box according to any one of claims 4 to 6, wherein the superfluid helium refrigerator further comprises a gas management panel, the gas management panel It includes a medium-pressure bypass valve connected to the high-pressure main air circuit and the medium-pressure return air circuit, a low-pressure bypass valve connected to the high-pressure main air circuit and the low-pressure return air circuit, and a low-pressure bypass valve connected to the low-pressure return air circuit. A loading valve and a buffer tank unloading valve of the gas circuit and the high-pressure main gas circuit, and a buffer tank connected between the loading valve and the buffer tank unloading valve. 20. The superfluid helium refrigerator with independent load test cold box according to any one of claims 4 to 6, characterized in that, the superfluid helium refrigerator also includes A one-way valve between the high-pressure compressors, the one-way valve is used to prevent backflow of helium at the outlet of the negative-pressure compressor.

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