A very large dilution refrigerator

Abstract

The present invention proposes an ultra-large dilution refrigerator, specifically relating to the technical field of refrigeration equipment. The ultra-large dilution refrigerator decomposes the existing pressurization and throttling refrigeration process into two circuits. One circuit pressurizes helium, pre-cools it, and liquefies it at a temperature of 0.6-0.7K through pre-cooling and throttling. The other circuit is used for the helium dilution cycle. At the same time, a circulating pump is used to overcome the pressure drop in the circulation pipeline. The ultra-large dilution refrigerator has the characteristics of large cooling capacity, high energy efficiency, and small space occupation.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of refrigeration equipment, and in particular to a super-large dilution refrigerator. BACKGROUND

[0002] With the rapid development of quantum computers, the number of qubits is increasing, and the refrigeration capacity of quantum computers at 10-100mK temperature will continue to increase. Currently, the mainstream dilution refrigerator uses a GM refrigerator or a pulse tube refrigerator as a cold source, and the maximum refrigeration capacity provided at 100mK temperature can only reach the mW level, which can only meet the heat dissipation demand of less than 2 qubits. However, future quantum computers with more than one million qubits require a refrigeration capacity of 0.5-1W or more, which means that the cooling capacity of the super-large dilution refrigerator needs to be increased by more than 1000 times compared to the current mainstream products. If the quantum computer still uses small refrigerators such as GM refrigerators or pulse tube refrigerators as a cold source, and uses a room temperature vacuum pump to circulate helium 3 in the dilution part, for quantum computers with more than one million qubits, hundreds or even thousands of small refrigerators and helium 3 room temperature vacuum pumps need to be modularly integrated. This not only has high integration difficulty, but also has high cost, low efficiency, and a large area, which is extremely difficult to achieve. Therefore, it is necessary to propose a new type of dilution refrigerator that can achieve super-large cooling capacity. SUMMARY

[0003] In order to solve the problem that the existing dilution refrigerator cannot achieve super-large cooling capacity, the present application proposes a super-large dilution refrigerator.

[0004] The present application is achieved by the following technical solutions:

[0005] The present application proposes a super-large dilution refrigerator

[0006] The present application proposes a super-large dilution refrigerator

[0007] The pre-cooling unit includes a helium 4 liquid pool, a helium 4 liquid immersion heat exchanger in the helium 4 liquid pool, a superfluid helium 4 liquid pool, a superfluid helium immersion heat exchanger in the superfluid helium 4 liquid pool, a helium 3 liquid pool, and a helium 3 liquid immersion heat exchanger in the helium 3 liquid pool. The circulating booster pump group and the circulating pump group are included in the circulating booster unit. The heat exchange unit includes a first-stage heat exchanger group and a second-stage heat exchanger group.

[0008] The outlet end of the pre-cooling booster pump group is connected to the first heat exchange side of the helium-4 liquid immersion heat exchanger, the first-stage heat exchanger group, the first heat exchange side of the superfluid helium immersion heat exchanger, the second-stage heat exchanger group, a throttle valve and the helium-3 liquid pool in sequence, and is connected back to the second-stage heat exchanger group, the second heat exchange side of the superfluid helium immersion heat exchanger, the first-stage heat exchanger group, the second heat exchange side of the liquid helium-4 liquid immersion heat exchanger and the inlet end of the pre-cooling booster pump group from the outlet of the helium-3 liquid pool in sequence to form a booster circuit; the outlet end of the circulating pump group is connected to the third heat exchange side of the liquid helium immersion heat exchanger, the first-stage heat exchanger group, the third heat exchange side of the superfluid helium immersion heat exchanger, the second-stage heat exchanger group, the helium-3 liquid immersion heat exchanger and the inlet end of the dilution unit in sequence, and is connected back to the second-stage heat exchanger group, the first-stage heat exchanger group and the inlet end of the circulating pump group from the outlet end of the dilution unit to form a circulating circuit.

[0009] Further, the pre-cooling unit further comprises a liquid helium-superfluid helium liquefier, one inlet end and outlet end of the liquid helium-superfluid helium liquefier are connected to the helium-4 liquid pool respectively, the inlet end provides liquid helium-4 for the liquid helium pool, the low-pressure helium-3 gas in the liquid helium-3 pool immersion heat exchanger is cooled to the liquid helium temperature zone by the liquid helium-4 provided by the liquid helium-superfluid helium liquefier, in the process, the heat released by the low-pressure helium-3 gas is absorbed by the liquid helium-4 in the helium-4 liquid pool, the generated saturated helium-4 vapor is discharged from the outlet end and enters the gas return circuit of the liquid helium-superfluid helium liquefier, and the cooled low-temperature low-pressure helium-3 gas then enters the first-stage heat exchanger group.

[0010] Further, the other inlet end and outlet end of the liquid helium-superfluid helium liquefier are connected to the superfluid helium-4 liquid pool respectively, the inlet end provides superfluid helium-4 liquid for the superfluid helium-4 liquid pool, the low-pressure helium-3 gas in the superfluid helium immersion liquid heat exchanger is cooled to the superfluid helium temperature zone by the superfluid helium-4 liquid provided by the liquid helium-superfluid helium liquefier, in the process, the heat released by the low-pressure helium-3 gas is absorbed by the superfluid helium-4 liquid in the superfluid helium-4 liquid pool, the generated saturated helium-4 vapor is discharged from the outlet end and enters the gas return circuit of the liquid helium-superfluid helium liquefier, and the cooled low-temperature low-pressure helium-3 gas then enters the second-stage heat exchanger group.

[0011] Further, the low-pressure helium-3 gas in the liquid helium-3 pool immersion heat exchanger is cooled to about 4.5K by the liquid helium-4 provided by the liquid helium-superfluid helium liquefier, and the low-pressure helium-3 gas in the superfluid helium immersion liquid heat exchanger is cooled to about 1.2-2K by the superfluid helium-4 liquid provided by the liquid helium-superfluid helium liquefier.

[0012] Further, a throttle valve is arranged between the helium liquid pool inlet and the outlet end of the second-stage heat exchanger group.

[0013] Further, the primary heat exchanger group comprises at least one primary heat exchanger, and the secondary heat exchanger group comprises at least one secondary heat exchanger.

[0014] Further, the pressurization circuit and the circulation circuit are connected to the same primary heat exchanger and the same secondary heat exchanger, or are connected to one primary heat exchanger, one secondary heat exchanger, another primary heat exchanger and another secondary heat exchanger respectively.

[0015] Further, the negative pressure helium-3 gas in the helium-3 liquid pool is cooled by the secondary heat exchanger group, the second heat exchange side of the superfluid helium liquid heat exchanger, the primary heat exchanger group and the second heat exchange side of the helium-4 liquid immersion heat exchanger, and then enters the pre-cooling pressurization pump group, sequentially passes through the first heat exchange side of the helium-4 liquid immersion heat exchanger, the primary heat exchanger group, the first heat exchange side of the superfluid helium immersion heat exchanger and the secondary heat exchanger group, is further cooled and generates helium-3 saturated liquid by throttling of the throttle valve to the helium-3 liquid pool.

[0016] Further, the negative pressure helium-3 gas in the dilution unit is cooled by the secondary heat exchanger group and the primary heat exchanger group, and then enters the circulation pump group for compression, sequentially passes through the third heat exchange side of the helium-4 liquid immersion heat exchanger, the primary heat exchanger group, the third heat exchange side of the superfluid helium immersion heat exchanger, the secondary heat exchanger group and the first heat exchange side of the helium liquid pool for pre-cooling, and then enters the dilution unit.

[0017] The present application has the following beneficial effects:

[0018] The super-large dilution refrigerator disclosed by the present application decouples the single refrigeration multi-stage pre-cooling and multi-stage throttling circuit into two circuits, one of the two circuits pressurizes helium, pre-cools and throttles the helium to liquefy the helium at a temperature of 0.6-0.7K, and the other circuit is used for helium dilution circulation, and simultaneously uses a circulation pump to overcome the pressure drop of the circulation pipeline, so that the super-large dilution refrigerator has the characteristics of large refrigeration capacity, high energy efficiency and smaller space occupation. BRIEF DESCRIPTION OF DRAWINGS

[0019] Fig. 1 FIG. 1 is a structural diagram of the super-large dilution refrigerator of the present application;

[0020] Fig. 2 FIG. 2 is another embodiment of the structural diagram of the super-large dilution refrigerator of the present application;

[0021] In the figure: liquid helium-superfluid helium liquefier 1, dilution unit 2, pre-cooling pressurization pump group 3, circulation pump group 4, helium-4 liquid pool 5, primary heat exchanger group 6, superfluid helium-4 liquid pool 7, secondary heat exchanger group 8, throttle valve 9, helium-3 liquid pool 10;

[0022] The purpose of the present application, functional features and advantages will be further described with reference to the embodiments and the accompanying drawings. DETAILED DESCRIPTION

[0023] In order to make the technical solutions of the present application clearer and more complete, the present application will be further described below with reference to the drawings.

[0024] Please refer to Figs. 1-2 The present application provides an ultra-large dilution refrigerator comprising a heat exchange unit, a precooling unit, a dilution unit 2 and a circulating booster unit, wherein:

[0025] The precooling unit comprises a helium 4 liquid pool 5, a helium 4 liquid immersion heat exchanger in the helium 4 liquid pool 5, a superfluid helium 4 liquid pool 7, a superfluid helium immersion heat exchanger in the superfluid helium 4 liquid pool 7, a helium 3 liquid pool 10 and a helium 3 liquid immersion heat exchanger in the helium 3 liquid pool 10, the circulating booster unit comprises a precooling booster pump group 3 and a circulating pump group 4, and the heat exchange unit comprises a first-stage heat exchanger group 6 and a second-stage heat exchanger group 8.

[0026] The outlet end of the precooling booster pump group 3 is connected to the first heat exchange side of the helium 4 liquid immersion heat exchanger, the first-stage heat exchanger group 6, the first heat exchange side of the superfluid helium immersion heat exchanger, the second-stage heat exchanger group 8, a throttle valve 9 and the helium 3 liquid pool 10 in sequence, and the outlet end of the helium 3 liquid pool 10 is connected back to the second-stage heat exchanger group 8, the second heat exchange side of the superfluid helium immersion heat exchanger, the first-stage heat exchanger group 6, the second heat exchange side of the helium 4 liquid immersion heat exchanger and the inlet end of the precooling booster pump group 3 in sequence to form a booster circuit; the outlet end of the circulating pump group 4 is connected to the third heat exchange side of the liquid helium immersion heat exchanger, the first-stage heat exchanger group 6, the third heat exchange side of the superfluid helium immersion heat exchanger, the second-stage heat exchanger group 8, the first heat exchange side of the helium 3 liquid immersion heat exchanger and the inlet end of the dilution unit 2 in sequence, and the outlet end of the dilution unit 2 is connected back to the second-stage heat exchanger group 8, the first-stage heat exchanger group 6 and the inlet end of the circulating pump group 4 in sequence to form a circulating circuit.

[0027] In a specific embodiment, the dilution unit 2 is a distillation chamber, a heat exchanger, a mixing chamber, etc., which is similar to the structure of a traditional dilution refrigerator. In the boosting circuit, the negative pressure helium 3 gas in the helium 3 liquid pool 10 first passes through the secondary heat exchanger group 8, the superfluid helium immersion heat exchanger, the primary heat exchanger group 6 and the liquid helium pool heat exchanger to recover the cold capacity, and then the negative pressure helium 3 gas is pressurized by the pre-cooling booster pump group 3. The inlet pressure is determined by the saturation temperature of helium 4 in the helium 3 liquid pool 10 (usually 0.6-0.7K) and the pressure drop along the pipeline. The helium 3 gas pressurized by the pre-cooling booster pump group 3 first passes through the liquid helium pool for heat exchange cooling, and then enters the primary heat exchanger group 6 and is helium 3 The return gas from the liquid pool 10 is cooled, then enters the superfluid helium immersion heat exchanger for secondary cooling, and enters the secondary heat exchanger group 8 to be further cooled by the helium 3 return gas. After multiple cooling, it passes through the throttle valve 9 to produce helium saturated liquid (generally 0.6-0.7K) to cool the helium 3 in the circulation loop. The negative pressure helium 3 gas flowing out of the dilution unit 2 recovers the cold energy through the secondary heat exchanger group 8 and the primary heat exchanger group 6, then enters the circulation pump group 4 for compression, and passes through the helium 4 liquid pool 5, the first heat exchanger group, the superfluid helium immersion heat exchanger, the second heat exchanger group, and the helium 3 liquid immersion heat exchanger in sequence for gradual pre-cooling before entering the dilution unit 2 again.

[0028] Traditional dilution refrigerators mainly use room temperature vacuum pumps to realize the circulation of helium and the decompression and cooling of the distillation chamber. In order to ensure the required temperature of 0.6-0.7K in the distillation chamber, it is generally first pressurized by a room temperature pump or a low temperature pump, and then the helium is decompressed and throttled through multi-stage pre-cooling and multi-stage throttling. In order to achieve this function, the outlet pressure of the circulation pump generally needs to reach 0.5-1bar, and the pressure ratio of the room temperature vacuum pump needs to reach more than 10,000. In this application, this function is decoupled into two circuits, one circuit is used for helium pressurization, and after pre-cooling and one-stage throttling, the helium is liquefied at a temperature of 0.6-0.7K. The other circuit is used for helium dilution circulation, and the circulation pump overcomes the pressure drop of the pipeline, so that the entire refrigerator has a large cooling capacity and high energy efficiency while being simpler in structure and occupying a smaller area.

[0029] Further, the pre-cooling unit further comprises a liquid helium- superfluid helium liquefier 1, an inlet end and an outlet end of the liquid helium- superfluid helium liquefier 1 are connected to the helium 4 liquid pool 5 respectively, the inlet end provides the helium 4 liquid pool 5 with helium 4 liquid, the low-pressure helium 3 gas in the liquid helium 3 pool immersion heat exchanger is cooled to the liquid helium temperature zone by the helium 4 liquid provided by the liquid helium- superfluid helium liquefier, in the process, the heat released by the low-pressure helium 3 gas is absorbed by the helium 4 liquid in the helium 4 liquid pool 5, the generated saturated helium 4 steam is discharged from the outlet end and enters the gas return path of the liquid helium- superfluid helium liquefier; the low-temperature low-pressure helium 3 gas after cooling then enters the primary heat exchanger group 6. The liquid helium- superfluid helium liquefier 1 The liquid helium- superfluid helium liquefier 1 The liquid helium- superfluid helium liquefier 1 In a specific embodiment, the liquid helium- superfluid helium liquefier 1 (refrigerator) is the cold source of the entire system, the helium 4 liquid pool 5 is filled with liquid helium, and part of the liquid helium will be converted into helium gas when heat exchange is performed in the circulating loop and the pressure increasing loop, the helium gas enters the liquid helium- superfluid helium refrigerator to be liquefied and converted into liquid helium, and the liquid helium enters the helium 4 liquid pool 5 to continuously provide pre-cooling for the circulating loop and the pressure increasing loop.

[0030] Further, another inlet end and outlet end of the liquid helium- superfluid helium liquefier 1 are connected to the superfluid helium 4 liquid pool 7 respectively, the inlet end provides the superfluid helium 4 liquid pool 7 with superfluid helium 4 liquid, the low-pressure helium 3 gas in the superfluid helium immersion liquid heat exchanger is cooled to the superfluid helium temperature zone by the superfluid helium 4 liquid provided by the liquid helium- superfluid helium liquefier 1, in the process, the heat released by the low-pressure helium 3 gas is absorbed by the superfluid helium 4 liquid in the superfluid helium 4 liquid pool 7, the generated saturated helium 4 steam is discharged from the outlet end and enters the gas return path of the liquid helium- superfluid helium liquefier; the low-temperature low-pressure helium 3 gas after cooling then enters the secondary heat exchanger group 8.

[0031] The liquid helium- superfluid helium liquefier 1 The liquid helium- superfluid helium liquefier 1

[0032] In a specific embodiment, the superfluid helium 4 liquid pool 7 is filled with superfluid helium 4 liquid, and part of the superfluid helium 4 liquid will be converted into helium 4 gas when heat exchange is performed in the circulating loop and the pressure increasing loop, the helium 4 gas enters the liquid helium- superfluid helium liquefier 1 to be liquefied and converted into superfluid helium 4 liquid, and the superfluid helium 4 liquid reenters the superfluid helium 4 liquid pool 7 to further provide pre-cooling.

[0033] Further, the low-pressure helium 3 gas in the liquid helium 3 pool immersion heat exchanger is cooled to about 4.5K by the helium 4 liquid provided by the liquid helium- superfluid helium liquefier 1, and the low-pressure helium 3 gas in the superfluid helium immersion liquid heat exchanger 1 is cooled to about 1.2-2K by the superfluid helium 4 liquid provided by the liquid helium- superfluid helium liquefier 1. Further, the primary heat exchanger group 6 comprises at least one primary heat exchanger, and the secondary heat exchanger group 8 comprises at least one secondary heat exchanger;

[0034] The pressurization loop and the circulation loop are connected to the same primary heat exchanger and the same secondary heat exchanger, or are connected to one primary heat exchanger, one secondary heat exchanger and another primary heat exchanger, another secondary heat exchanger respectively.

[0035] In the specific embodiment, the number of heat exchangers in the primary heat exchanger group 6 and the secondary heat exchanger group 8 can be one or two according to actual conditions, when the primary heat exchanger group 6 and the secondary heat exchanger group 8 have two heat exchangers; the outlet group of the pre-cooling pressurization pump group 3 is connected to the first heat exchange side of the helium 4 liquid immersion heat exchanger, the first primary heat exchanger, the first heat exchange side of the superfluid helium immersion heat exchanger in the superfluid helium 4 liquid pool, the first secondary heat exchanger, the helium 3 liquid pool 10, the first secondary heat exchanger, the second heat exchange side of the superfluid helium immersion heat exchanger, the first primary heat exchanger, the second heat exchange side of the helium 4 liquid immersion heat exchanger and the inlet of the pre-cooling pressurization pump group 3 in sequence to form a pressurization loop, while the outlet of the circulation pump group 4 is connected to the third heat exchange side of the helium 4 liquid immersion heat exchanger, the second primary heat exchanger, the third heat exchange side of the superfluid helium immersion heat exchanger, the second secondary heat exchanger, the first heat exchange side of the helium 3 liquid pool 10, the dilution unit 2, the second secondary heat exchanger, the second primary heat exchanger and the inlet of the circulation pump group 4 in sequence to form a circulation loop.

[0036] Further, the negative pressure helium 3 gas in the helium 3 liquid pool 10 is cooled by the secondary heat exchanger group 8, the second heat exchange side of the superfluid helium liquid heat exchanger, the primary heat exchanger group 6 and the second heat exchange side of the helium 4 liquid immersion heat exchanger, and then enters the pre-cooling pressurization pump group 3 to be pressurized, and then passes through the first heat exchange side of the helium 4 liquid immersion heat exchanger, the primary heat exchanger group 6, the first heat exchange side of the superfluid helium immersion heat exchanger and the secondary heat exchanger group 8 in sequence to be further cooled, and then passes through the throttle valve 9 to generate helium 3 saturated liquid into the helium 3 liquid pool 10.

[0037] Further, the negative pressure helium 3 gas in the dilution unit 2 is cooled by the secondary heat exchanger group 8 and the primary heat exchanger group 6 to recover cold energy, and then enters the circulation pump group 4 to be compressed, and then passes through the third heat exchange side of the helium 4 liquid immersion heat exchanger, the primary heat exchanger group 6, the third heat exchange side of the superfluid helium immersion heat exchanger, the secondary heat exchanger group 8 and the first heat exchange side of the helium 3 liquid pool 10 in sequence to be pre-cooled, and then enters the dilution unit 2.

[0038] Of course, the present application can have other various embodiments, and based on the present embodiment, other embodiments obtained by those skilled in the art without any creative labor shall fall within the scope of the present application.

Claims

1. An ultra-large dilution refrigerator, characterized in that: It includes heat exchange unit, pre-cooling unit, dilution unit and circulation pressurization unit, among which: The pre-cooling unit includes a helium-4 liquid pool, a helium-4 liquid immersed heat exchanger in the helium-4 liquid pool, a superfluid helium-4 liquid pool, a superfluid helium immersed heat exchanger in the superfluid helium-4 liquid pool, a helium-3 liquid pool, and a helium-3 liquid immersed heat exchanger in the helium-3 liquid pool; the circulating boosting unit includes a pre-cooling boosting pump group and a circulating pump group; the heat exchange unit includes a primary heat exchanger group and a secondary heat exchanger group; The outlet end of the pre-cooling booster pump group is sequentially connected to the first heat exchange side of the helium-4 liquid immersed heat exchanger, the first heat exchanger group, the first heat exchange side of the superfluid helium immersed heat exchanger, the second heat exchanger group, the throttle valve and the helium-3 liquid pool, and is sequentially connected from the outlet of the helium-3 liquid pool back to the second heat exchanger group, the second heat exchange side of the superfluid helium immersed heat exchanger, the first heat exchanger group, the second heat exchange side of the helium-4 liquid immersed heat exchanger and the inlet end of the pre-cooling booster pump group to form a booster circuit; the outlet end of the circulation pump group is sequentially connected to the third heat exchange side of the helium-4 liquid immersed heat exchanger, the first heat exchanger group, the third heat exchange side of the superfluid helium immersed heat exchanger, the second heat exchanger group, the helium-3 liquid immersed heat exchanger and the inlet end of the dilution unit, and is sequentially connected from the outlet of the dilution unit back to the second heat exchanger group, the first heat exchanger group and the inlet end of the circulation pump group to form a circulation circuit. The dilution unit includes a distillation chamber, a heat exchanger and a mixing chamber.

2. The ultra-large dilution refrigerator according to claim 1, characterized in that: The pre-cooling unit also includes a liquid helium-superfluid helium liquefier, an inlet end and an outlet end of the liquid helium-superfluid helium liquefier are respectively connected to the helium-4 liquid pool, the inlet end provides helium-4 liquid to the helium-4 liquid pool, and the low-pressure helium-3 gas in the helium-4 liquid immersion heat exchanger is cooled to the liquid helium temperature zone by the helium-4 liquid provided by the liquid helium-superfluid helium liquefier. During this process, the heat released by the low-pressure helium-3 gas is absorbed by the helium-4 liquid in the helium-4 liquid pool, and the generated saturated helium-4 vapor is discharged from the outlet end and enters the return gas path of the liquid helium-superfluid helium liquefier; the cooled low-temperature and low-pressure helium-3 gas then enters the first-stage heat exchanger group.

3. The ultra-large dilution refrigerator according to claim 2, characterized in that: The other inlet end and outlet end of the liquid helium-superfluid helium liquefier are respectively connected to the superfluid helium 4 liquid pool, and the inlet end provides superfluid helium 4 liquid to the superfluid helium 4 liquid pool. The low-pressure helium 3 gas in the superfluid helium immersion heat exchanger is cooled to the superfluid helium temperature zone by the superfluid helium 4 liquid provided by the liquid helium-superfluid helium liquefier. During this process, the heat released by the low-pressure helium 3 gas is absorbed by the superfluid helium 4 liquid in the superfluid helium 4 liquid pool, and the generated saturated helium 4 vapor is discharged from the outlet end and enters the return gas path of the liquid helium-superfluid helium liquefier; the cooled low-temperature and low-pressure helium 3 gas then enters the secondary heat exchanger group.

4. The ultra-large dilution refrigerator according to claim 3, characterized in that: The low-pressure helium-3 gas in the helium-4 liquid immersion heat exchanger is cooled to about 4.5K by the helium-4 liquid provided by the liquid helium-superfluid helium liquefier, and the low-pressure helium-3 gas in the superfluid helium immersion heat exchanger is cooled to about 1.2-2K by the superfluid helium-4 liquid provided by the liquid helium-superfluid helium liquefier.

5. The ultra-large dilution refrigerator according to claim 4, characterized in that: The primary heat exchanger group includes at least one primary heat exchanger, and the secondary heat exchanger group includes at least one secondary heat exchanger.

6. The ultra-large dilution refrigerator according to claim 1, characterized in that: The boosting loop and the circulation loop are connected to the same primary heat exchanger and the same secondary heat exchanger, or are respectively connected to a primary heat exchanger, a secondary heat exchanger and another primary heat exchanger, another secondary heat exchanger.

7. The ultra-large dilution refrigerator according to claim 1, characterized in that: The negative pressure helium-3 gas in the helium-3 liquid pool is cooled by passing through the secondary heat exchanger group, the second heat exchange side of the superfluid helium immersion heat exchanger, the primary heat exchanger group and the second heat exchange side of the helium-4 liquid immersion heat exchanger, and then enters the pre-cooling booster pump group for pressurization and passes through the first heat exchange side of the helium-4 liquid immersion heat exchanger, the primary heat exchanger group, the first heat exchange side of the superfluid helium immersion heat exchanger and the secondary heat exchanger group in sequence for further cooling and throttling through the throttle valve to produce helium-3 saturated liquid into the helium-3 liquid pool.

8. The ultra-large dilution refrigerator according to claim 7, characterized in that: The negative pressure helium-3 gas in the dilution unit recovers cold energy through the secondary heat exchanger group and the primary heat exchanger group, enters the circulation pump group for compression, and sequentially passes through the third heat exchange side of the helium-4 liquid immersed heat exchanger, the primary heat exchanger group, the third heat exchange side of the superfluid helium immersed heat exchanger, the secondary heat exchanger group and the helium-3 liquid immersed heat exchanger for pre-cooling, and then enters the dilution unit.

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