Efficient heat exchange system for liquid helium closed circulation system and refrigeration method of efficient heat exchange system

Abstract

The invention relates to an efficient heat exchange system for a liquid helium closed circulation system and a refrigeration method of the efficient heat exchange system. A multi-layer thin-wall stainless steel cylinder structure; a heat exchange copper pipe assembly; the heat exchange modules comprise a first-stage heat exchange module, a second-stage heat exchange module and a third-stage heat exchange module; liquid helium is vaporized in the 4.2 K liquid helium pool, so that refrigeration power is generated; the multi-layer thin-wall stainless steel cylinder structure is used for connecting the mounting flange, the heat exchange modules and the 4.2 K liquid helium pool, the distance between the mounting flange and the 4.2 K liquid helium pool is prolonged, and the heat conduction power is reduced; the heat exchange copper pipe assembly is connected with the multi-layer thin-wall stainless steel cylinder structure or the heat exchange modules. 4.2 K helium generated by the 4.2 K liquid helium pool sequentially flows through the third-stage heat exchange module, the second-stage heat exchange module and the first-stage heat exchange module, and a 30K refrigeration environment is formed at the third-stage heat exchange module. According to the efficient heat exchange system for the liquid helium closed circulation system, by arranging the multiple stages of heat exchange modules, the temperature of cold helium is gradually increased under different temperature gradients, the 4.2 K low-temperature interface heat load is reduced, and meanwhile the precooling refrigerating capacity is provided for experiments or equipment with different temperature requirements.

Description

Technical Field

[0001] The present invention relates to the technical field of low-temperature refrigeration equipment, and in particular to a high-efficiency heat exchange system for a liquid helium closed circulation system and a refrigeration method thereof. Background Art

[0002] In surface physics analysis experiments, samples need to be cooled to extremely low temperatures (such as liquid helium 4.2K or lower), and an extremely low vibration environment is required. There are two main types of cryogenic cooling devices: the first type uses refrigerant cooling, that is, storing liquid helium in a container, or continuously transporting liquid helium through a pipeline to the part that needs to be cooled; the second type uses a 4.2K refrigerator for cooling.

[0003] The advantages of using refrigerants for refrigeration are that the operation is relatively simple, the vibration is small, and the impact on the system is small; the disadvantages are that liquid helium is a non-renewable resource and is particularly scarce in China. In recent years, as liquid helium is consumed, its price has become increasingly expensive. Moreover, when liquid helium is almost consumed, it needs to be refilled, and the experiment needs to be interrupted and discontinuous. With the invention of the 4.2K refrigerator, the method of using the 4.2K refrigerator to achieve an extremely low temperature environment has been widely used.

[0004] Among the solutions for using a 4.2K refrigerator to obtain a 4.2K low-vibration low-temperature environment, one solution is to use a continuous-flow liquid helium closed-cycle solution. This solution uses a refrigerator to liquefy helium into liquid helium, and then introduces the liquid helium to the location that needs refrigeration through a liquid helium transmission tube. After reaching the refrigeration location, the liquid helium vaporizes and absorbs heat, generating refrigeration power at the refrigeration location. The vaporized helium is pumped away by a circulating pump and then transmitted to the refrigerator location, allowing the refrigerator to liquefy the helium, and so on. This is a closed-cycle continuous-flow liquid helium refrigeration system. The advantage of using this solution is that the refrigerator can be kept away from the refrigeration interface, and the vibration generated by the refrigerator can be efficiently isolated, thereby ensuring extremely low vibration at the refrigeration interface, which is suitable for some high-demand experiments, such as scanning tunneling microscopy (STM).

[0005] However, the parameters of helium are: specific heat capacity of helium, about 3.1J / g*K (standard atmospheric pressure, 4.2K-300K, basically does not change with temperature); latent heat of helium phase change, 15.5J / g; density of liquid helium, 124.9g / L (4.2K). In other words, 1g of 4.2K liquid helium vaporizes into 4.2K gas and can absorb 15.5J of heat; 4.2K cold helium can absorb 3.1J of heat for every 1K increase in temperature. If only the vaporization refrigeration of liquid helium is used, the refrigeration power that can be obtained is very low. For example, using a 0.9W refrigerator, considering various losses, the actual effective refrigeration power that can be obtained at the 4.2K interface will be less than 0.1W, which is difficult to meet some experimental requirements that require higher refrigeration capacity, such as superconducting magnets with large magnetic fields. Summary of the invention

[0006] In view of some or all of the problems in the prior art, the present invention provides a high-efficiency heat exchange system for a liquid helium closed circulation system, comprising:

[0007] A mounting flange, wherein the mounting flange is at room temperature;

[0008] A multi-layer thin-wall stainless steel cylinder structure, wherein the multi-layer thin-wall stainless steel cylinder structure comprises a plurality of thin-wall stainless steel cylinders;

[0009] A heat exchange copper tube assembly, wherein the heat exchange copper tube assembly comprises a plurality of heat exchange copper tubes;

[0010] A plurality of heat exchange modules, including a primary heat exchange module, a secondary heat exchange module and a tertiary heat exchange module; and

[0011] A 4.2K liquid helium pool, in which liquid helium is vaporized to generate refrigeration power;

[0012] The multi-layer thin-wall stainless steel cylinder structure is used to connect the mounting flange, the multiple heat exchange modules and the 4.2K liquid helium pool, extend the distance between the mounting flange and the 4.2K liquid helium pool, and reduce the heat conduction power;

[0013] The heat exchange copper tube assembly is connected to the multi-layer thin-wall stainless steel cylinder structure or the plurality of heat exchange modules;

[0014] The 4.2K helium gas generated by the 4.2K liquid helium pool flows through the third-stage heat exchange module, the second-stage heat exchange module and the first-stage heat exchange module in sequence, forming a 30K refrigeration environment at the third-stage heat exchange module.

[0015] Furthermore, the multi-layer thin-walled stainless steel cylinder structure is a folded multi-layer structure, and the multi-layer thin-walled stainless steel cylinder structure includes a first thin-walled stainless steel cylinder, a second thin-walled stainless steel cylinder, a third thin-walled stainless steel cylinder, a fourth thin-walled stainless steel cylinder and a fifth thin-walled stainless steel cylinder.

[0016] Furthermore, the heat exchange copper tube assembly is connected to the multi-layer thin-wall stainless steel cylinder structure or the plurality of heat exchange modules by brazing;

[0017] The heat exchange copper tube assembly adopts a multi-circle spiral design to increase the contact area with the multi-layer thin-wall stainless steel cylinder structure or the multiple heat exchange modules.

[0018] Further, the heat exchange copper tube assembly includes a first heat exchange copper tube, a second heat exchange copper tube, a third heat exchange copper tube, a fourth heat exchange copper tube, a fifth heat exchange copper tube, a sixth heat exchange copper tube, a seventh heat exchange copper tube, an eighth heat exchange copper tube, a ninth heat exchange copper tube and a tenth heat exchange copper tube.

[0019] Furthermore, the mounting flange is connected to the secondary heat exchange module through the first thin-walled stainless steel cylinder and the second thin-walled stainless steel cylinder, and the secondary heat exchange module is connected to the 4.2K liquid helium pool through the third thin-walled stainless steel cylinder, the fourth thin-walled stainless steel cylinder and the fifth thin-walled stainless steel cylinder.

[0020] Furthermore, a groove is arranged on the three-stage heat exchange module, and the seventh heat exchange copper tube is arranged in the groove and brazed with the three-stage heat exchange module by silver brazing.

[0021] Further, the helium forms a refrigeration environment of 80K at the secondary heat exchange module, the secondary heat exchange module is connected to the secondary cold plate through a soft copper braid, and a low-temperature shielding cover is arranged on the secondary cold plate to reduce the thermal radiation load of the 4.2K liquid helium pool interface; and / or

[0022] The helium gas forms a refrigeration environment of 160K at the first-stage heat exchange module.

[0023] The present invention also provides a refrigeration method for the high-efficiency heat exchange system of the liquid helium closed circulation system, the method comprising the following steps:

[0024] Liquid helium vaporizes inside the 4.2K liquid helium pool, generating refrigeration power at the 4.2K liquid helium pool, and the helium gas generated by the vaporization of liquid helium flows out through the gas outlet exhaust pipe of the liquid helium pool;

[0025] Helium is guided to multiple heat exchange modules through the heat exchange copper tube assembly. The cooling capacity of helium during the heating process is used to provide pre-cooling refrigeration capacity for experiments or equipment with different temperature gradients, reduce the heat load at the 4.2K liquid helium pool, and improve the refrigeration power at the 4.2K liquid helium pool.

[0026] Further, the helium gas flows through the tenth heat exchange copper tube, the eighth heat exchange copper tube and the seventh heat exchange copper tube to form a 30K refrigeration environment at the third-stage heat exchange module;

[0027] The helium gas flows through the ninth heat exchange copper tube and the sixth heat exchange copper tube to form a refrigeration environment of 80K at the secondary heat exchange module;

[0028] The helium gas flows through the fourth heat exchange copper tube, the third heat exchange copper tube, the second heat exchange copper tube, the first heat exchange copper tube and the fifth heat exchange copper tube, forming a refrigeration environment of 160K at the primary heat exchange module.

[0029] Further, the heat loss due to heat conduction at the 4.2K liquid helium pool is 0.05W; and / or

[0030] The cooling capacity obtained at the third-stage heat exchange module is 1W; and / or

[0031] The cooling capacity obtained at the secondary heat exchange module is 2W; and / or

[0032] The cooling capacity obtained at the first-stage heat exchange module is 3W.

[0033] The technical solution provided by the present invention has the following advantages:

[0034] 1. The high-efficiency heat exchange system for a liquid helium closed-loop system provided by the present invention, by setting a multi-stage heat exchange module (the first-stage heat exchange module is about 160K, the second-stage heat exchange module is about 80K, and the third-stage heat exchange module is about 30K), allows the cold helium to gradually heat up under different temperature gradients, reduces the 4.2K low-temperature interface heat load (from 0.1W to <0.05W), and provides pre-cooling refrigeration capacity for experiments or equipment with different temperature requirements (1W at the third-stage heat exchange module, 2W at the second-stage heat exchange module, and 3W at the first-stage heat exchange module).

[0035] 2. The high-efficiency heat exchange system for the liquid helium closed circulation system provided by the present invention has a brazing connection and a long path design for the heat exchange copper tube, and the heat exchange copper tube is connected to the heat exchange module or the thin-walled stainless steel cylinder by brazing, ensuring good thermal contact between the cold helium gas and the heat exchange copper tube; and the heat exchange copper tube is designed to be longer and spiral multiple times, which increases the contact area and further improves the heat exchange efficiency.

[0036] 3. The high-efficiency heat exchange system for the liquid helium closed circulation system provided by the present invention adopts a folded multi-layer stainless steel cylinder structure, which extends the distance between the mounting flange and the 4.2K liquid helium pool, reduces the heat conduction power from the mounting flange to the 4.2K liquid helium pool, and thus reduces the heat load at the low-temperature interface of the 4.2K liquid helium pool.

[0037] 4. The high-efficiency heat exchange system for the liquid helium closed-cycle system provided by the present invention comprehensively utilizes the refrigeration capacity of the cold helium gas during heating. It not only utilizes the vaporization refrigeration of liquid helium, but also fully utilizes the refrigeration capacity of the cold helium gas during the heating process, and provides additional pre-cooling refrigeration capacity, so that some high-load experiments (such as large magnetic field superconducting magnets) can be carried out. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] To further illustrate the above and other advantages and features of various embodiments of the present invention, a more specific description of various embodiments of the present invention will be presented with reference to the accompanying drawings. It will be understood that these drawings only depict typical embodiments of the present invention and are therefore not to be considered as limiting the scope thereof. In the accompanying drawings, for clarity, identical or corresponding parts will be represented by identical or similar reference numerals.

[0039] Figure 1 A schematic structural diagram of a high-efficiency heat exchange system for a liquid helium closed circulation system according to an embodiment of the present invention is shown;

[0040] Figure 2A schematic diagram showing the structure of a three-stage heat exchange module and a heat exchange copper tube according to an embodiment of the present invention is shown;

[0041] Figure 3 A schematic diagram showing the structure of a thin-walled stainless steel cylinder and a heat exchange copper tube according to an embodiment of the present invention; and

[0042] Figure 4 A schematic flow chart of a refrigeration method for a high-efficiency heat exchange system of a liquid helium closed cycle system according to an embodiment of the present invention is shown.

[0043] Reference numerals list

[0044] 1001 mounting flange, 1002 first thin-walled stainless steel tube, 1003 second thin-walled stainless steel tube, 1004 first heat exchange copper tube, 1005 second heat exchange copper tube, 1006 third heat exchange copper tube, 1007 fourth heat exchange copper tube, 1008 fifth heat exchange copper tube, 1009 primary heat exchange module;

[0045] 2001 Secondary heat exchange module, 2002 Sixth heat exchange copper tube, 2003 Secondary cold plate, 2004 Third thin-walled stainless steel cylinder, 2005 Fourth thin-walled stainless steel cylinder, 2006 Fifth thin-walled stainless steel cylinder;

[0046] 3001 three-stage heat exchange module, 3002 seventh heat exchange copper tube, 4001 4.2K liquid helium pool, 4002 liquid helium pool liquid helium inlet pipe, 4003 liquid helium pool gas outlet exhaust pipe, 4004 eighth heat exchange copper tube, 4005 ninth heat exchange copper tube, 4006 tenth heat exchange copper tube. DETAILED DESCRIPTION

[0047] In the following description, the present invention is described with reference to various embodiments. However, those skilled in the art will recognize that various embodiments may be implemented without one or more specific details or with other replacement and / or additional methods or components. In other cases, well-known structures or operations are not shown or described in detail to avoid obscuring the inventive point of the present invention. Similarly, for the purpose of explanation, specific numbers and configurations are set forth to provide a comprehensive understanding of embodiments of the present invention. However, the present invention is not limited to these specific details.

[0048] In the present invention, unless otherwise specified, "arranged on..." or "arranged above..." does not exclude the presence of an intermediate object between the two. In addition, "arranged on or above..." merely indicates the relative positional relationship between two components, and in certain circumstances, such as after reversing the product direction, it can also be converted to "arranged below or below...", and vice versa.

[0049] In this specification, reference to "one embodiment" or "the embodiment" means that a particular feature, structure, or characteristic described in conjunction with the embodiment is included in at least one embodiment of the present invention. The phrase "in one embodiment" appearing in various places in this specification does not necessarily all refer to the same embodiment.

[0050] It should be noted that it should also be understood that in the embodiments of the present invention, the terms "comprises", "including", "having", "includes" and / or "comprising", when used in this specification, indicate the existence of stated features, elements and / or parts, but do not exclude the existence or addition of one or more other features, elements, parts and / or combinations thereof.

[0051] In this specification, unless otherwise specified, "first" and "second" are only used for distinguishing descriptions, do not include differences in size, and cannot be understood as expressing or implying relative importance.

[0052] In this specification, the quantifiers "plurality" and "multiple" refer to one or more than one element.

[0053] The scheme of the present invention is further described below in conjunction with the accompanying drawings of the embodiments.

[0054] In this specification, the colors of components in the drawings are only used to distinguish different components, and the colors of the same components in different drawings are not necessarily the same.

[0055] The present invention provides a high-efficiency heat exchange system for a liquid helium closed-cycle system, which comprehensively utilizes the refrigeration capacity of the cold helium gas during heating, not only utilizing the vaporization refrigeration of the liquid helium, but also fully utilizing the refrigeration capacity of the cold helium gas during the heating process, thereby reducing the heat load at the low-temperature interface of a 4.2K liquid helium pool, increasing the refrigeration power at the 4.2K liquid helium pool, and providing additional pre-cooling refrigeration capacity, thereby enabling some high-load experiments (such as large-magnetic-field superconducting magnets) to be carried out.

[0056] The scheme of the present invention is further described below in conjunction with the accompanying drawings of the embodiments.

[0057] Figure 1 The schematic diagram of the structure of a high-efficiency heat exchange system for a liquid helium closed circulation system according to an embodiment of the present invention is shown. Figure 1As shown, the efficient heat exchange system for the liquid helium closed cycle system includes a mounting flange 1001, a multi-layer thin-walled stainless steel cylinder structure, a heat exchange copper tube assembly, a plurality of heat exchange modules and a 4.2K liquid helium pool 4001. The mounting flange 1001 is at room temperature. The multi-layer thin-walled stainless steel cylinder structure is used to connect the mounting flange 1001, the plurality of heat exchange modules and the 4.2K liquid helium pool 4001, extend the distance between the mounting flange 1001 and the 4.2K liquid helium pool 4001, and reduce the heat conduction power. Liquid helium vaporizes inside the 4.2K liquid helium pool 4001, thereby generating refrigeration power. The plurality of heat exchange modules include a primary heat exchange module 1009, a secondary heat exchange module 2001 and a tertiary heat exchange module 3001. The heat exchange copper tube assembly is connected to the multi-layer thin-walled stainless steel cylinder structure or the plurality of heat exchange modules.

[0058] The mounting flange 1001 is at room temperature, mainly to ensure the stability and sealing of all components at normal working temperature. Through correct tightening steps and torque control, it can be ensured that the mounting flange can maintain good sealing and connection strength under various working conditions.

[0059] The multi-layer thin-walled stainless steel cylinder structure is a folded multi-layer structure, and the multi-layer thin-walled stainless steel cylinder structure includes a first thin-walled stainless steel cylinder 1002 , a second thin-walled stainless steel cylinder 1003 , a third thin-walled stainless steel cylinder 2004 , a fourth thin-walled stainless steel cylinder 2005 and a fifth thin-walled stainless steel cylinder 2006 .

[0060] The heat exchange copper tube assembly is connected to the multi-layer thin-walled stainless steel tube structure or multiple heat exchange modules by brazing. The heat exchange copper tube assembly uses a multi-circle design to increase the contact area with the multi-layer thin-walled stainless steel tube structure or multiple heat exchange modules. In one embodiment of the present invention, the material of the heat exchange copper tube assembly can be oxygen-free copper. The heat exchange copper tube assembly includes a first heat exchange copper tube 1004, a second heat exchange copper tube 1005, a third heat exchange copper tube 1006, a fourth heat exchange copper tube 1007, a fifth heat exchange copper tube 1008, a sixth heat exchange copper tube 2002, a seventh heat exchange copper tube 3002, an eighth heat exchange copper tube 4004, a ninth heat exchange copper tube 4005 and a tenth heat exchange copper tube 4006.

[0061] The mounting flange 1001 is connected to the secondary heat exchange module 2001 through the first thin-walled stainless steel cylinder 1002 and the second thin-walled stainless steel cylinder 1003 , and the secondary heat exchange module 2001 is connected to the 4.2K liquid helium pool 4001 through the third thin-walled stainless steel cylinder 2004 , the fourth thin-walled stainless steel cylinder 2005 and the fifth thin-walled stainless steel cylinder 2006 .

[0062] Figure 2 The schematic diagram of the structure of the three-stage heat exchange module and the heat exchange copper tube according to an embodiment of the present invention is shown. Figure 2As shown, the three-stage heat exchange module 3001 is provided with many grooves, and the seventh heat exchange copper tube 3002 is arranged in the grooves and brazed with the three-stage heat exchange module 3001 by silver brazing, thereby ensuring very good thermal contact between the seventh heat exchange copper tube 3002 and the three-stage heat exchange module 3001. The heat exchange copper tubes at other positions are also brazed to the thin-walled stainless steel cylinder, thereby ensuring very good thermal contact between the heat exchange copper tube and the thin-walled stainless steel tube.

[0063] The primary heat exchange module 1009 and the fifth heat exchange copper tube 1008 are also welded together by brazing.

[0064] Figure 3 FIG. 1 is a schematic diagram showing the structure of a thin-walled stainless steel cylinder and a heat exchange copper tube according to an embodiment of the present invention. Figure 3 As shown, in order to ensure good heat exchange between the cold helium and the heat exchange copper tube, the heat exchange copper tube is generally used to be relatively long, so that it is spiraled multiple times to increase the contact area.

[0065] Liquid helium enters the 4.2K liquid helium pool 4001 through the liquid helium pool inlet pipe 4002, and the liquid helium vaporizes inside the liquid helium pool, generating refrigeration power at the 4.2K liquid helium pool 4001. The helium generated by the vaporization of liquid helium flows out through the liquid helium pool outlet exhaust pipe 4003, and the 4.2K liquid helium pool 4001 generates helium. The helium flows through the tertiary heat exchange module 3001, the secondary heat exchange module 2001 and the primary heat exchange module 1009 in sequence, forming a refrigeration environment of about 30K at the tertiary heat exchange module 3001, a refrigeration environment of about 80K at the secondary heat exchange module 2001, and a refrigeration environment of about 160K at the primary heat exchange module 1009. The secondary heat exchange module 2001 is connected to the secondary cold plate 2003 through a soft copper braid, and a low-temperature shielding cover can also be arranged on the secondary cold plate 2003 to reduce the thermal radiation load of the 4.2K liquid helium pool interface.

[0066] Figure 4 The schematic diagram of the process of a refrigeration method for a high-efficiency heat exchange system of a liquid helium closed cycle system according to an embodiment of the present invention is shown. Figure 4 As shown, the present invention also provides a refrigeration method for the high-efficiency heat exchange system of the liquid helium closed circulation system, the method comprising the following steps:

[0067] First, liquid helium is vaporized inside the 4.2K liquid helium pool 4001, generating refrigeration power at the 4.2K liquid helium pool, and helium gas generated by vaporization of liquid helium flows out through the liquid helium pool outlet exhaust pipe 4003.

[0068] Next, the helium is guided to multiple heat exchange modules through the heat exchange copper tube assembly, and the cooling capacity of the helium during the heating process is used to provide pre-cooling refrigeration for experiments or equipment with different temperature gradients, reducing the heat load at the 4.2K liquid helium pool and increasing the refrigeration power at the 4.2K liquid helium pool.

[0069] The helium gas flowing out of the liquid helium pool outlet exhaust pipe 4003 passes through a thin-walled stainless steel cylinder or a thin-walled stainless steel tube (not shown in the figure) and flows into the tenth heat exchange copper tube 4006, which is brazed with the third thin-walled stainless steel cylinder 2004. The 4.2K helium gas flowing through fully exchanges heat with the tenth heat exchange copper tube 4006, thereby reducing the temperature of the third thin-walled stainless steel cylinder 2004. The cold helium gas flowing out of the tenth heat exchange copper tube 4006 is connected to the eighth heat exchange copper tube 4004 through the thin-walled stainless steel tube. After the cold helium gas fully exchanges heat with the eighth heat exchange copper tube 4004, it cools the fifth thin-walled stainless steel cylinder 2006. Compared with the case where no heat exchange copper tube is added, the heat loss caused by heat conduction at the 4.2K liquid helium pool can be reduced from about 0.1W to less than 0.05W, that is, it can be reduced by more than 50%.

[0070] The helium flowing out of the eighth heat exchange copper tube 4004 passes through the thin-walled stainless steel tube or thin-walled stainless steel cylinder and flows into the seventh heat exchange copper tube 3002 to cool the tertiary heat exchange module 3001. The temperature of the helium flowing into the seventh heat exchange copper tube 3002 is about 10K, and the temperature of the helium flowing out of the seventh heat exchange copper tube 3002 is about 30K, thereby forming a refrigeration environment of about 30K at the tertiary heat exchange module 3001, and a refrigeration capacity of about 1W can be obtained at the tertiary heat exchange module 3001, which can be used for cooling the high-temperature superconducting wire joints of superconducting magnets, or pre-cooling some cables that need to be connected to the 4.2K refrigeration interface (thereby reducing the heat load at the 4.2K refrigeration interface).

[0071] The helium gas flowing out of the seventh heat exchange copper tube 3002 flows into the ninth heat exchange copper tube 4005 through the thin-walled stainless steel tube or thin-walled stainless steel cylinder, and the cold helium gas flowing out of the ninth heat exchange copper tube 4005 flows into the sixth heat exchange copper tube 2002 through the thin-walled stainless steel tube or thin-walled stainless steel cylinder to cool the secondary heat exchange module 2001. The sixth heat exchange copper tube 2002 is brazed with the secondary heat exchange module 2001. The temperature of the helium gas flowing into the sixth heat exchange copper tube 2002 is about 40K, and the temperature of the helium gas flowing out of the sixth heat exchange copper tube 2002 is about 80K, thereby forming a refrigeration environment of about 80K at the secondary heat exchange module 2001, and a refrigeration capacity of about 2W can be obtained at the secondary heat exchange module 2001. The secondary heat exchange module 2001 is connected to the secondary cold plate 2003 through a soft copper braid. A low-temperature shielding cover can also be arranged on the secondary cold plate 2003 to wrap the 4.2K low-temperature equipment and reduce the thermal radiation load of the 4.2K liquid helium pool interface.

[0072] The helium flowing out of the sixth heat exchange copper tube 2002 flows into the fourth heat exchange copper tube 1007 through the thin-walled stainless steel tube or thin-walled stainless steel cylinder; the helium flowing out of the fourth heat exchange copper tube 1007 flows into the third heat exchange copper tube 1006 through the thin-walled stainless steel tube or thin-walled stainless steel cylinder, and the helium flowing out of the third heat exchange copper tube 1006 flows into the second heat exchange copper tube 1005 through the thin-walled stainless steel tube or thin-walled stainless steel cylinder; the helium flowing out of the second heat exchange copper tube 1005 flows into the first heat exchange copper tube 1004 through the thin-walled stainless steel tube or thin-walled stainless steel cylinder; the helium flowing out of the first heat exchange copper tube 1004 flows into the fifth heat exchange copper tube 1008 through the thin-walled stainless steel tube or thin-walled stainless steel cylinder. The multi-layer arrangement of the first heat exchange copper tube 1004, the second heat exchange copper tube 1005, the third heat exchange copper tube 1006 and the fourth heat exchange copper tube 1007 is to reduce the heat load from the mounting flange 1001 to the secondary heat exchange module 2001. The fifth heat exchange copper tube 1008 and the first-level heat exchange module 1009 are brazed together. The temperature of the helium flowing into the fifth heat exchange copper tube 1008 is about 100K, and the temperature of the cold helium flowing out of the fifth heat exchange copper tube 1008 is about 160K, thereby forming a refrigeration environment of about 160K at the first-level heat exchange module 1009, and a refrigeration capacity of about 3W can be generated on the first-level heat exchange module 1009. A low-temperature shielding cover can be installed on the first-level heat exchange module 1009 to reduce the heat load of the room temperature cavity on the low-temperature equipment. At the same time, some pre-cooling bases can be installed on the first-level heat exchange module 1009 for pre-cooling cables connected to the second-level cold plate 2003.

[0073] The high-efficiency heat exchange system for liquid helium closed circulation system provided by the present invention is to gradually heat up the cold helium gas under different temperature gradients by setting a multi-stage heat exchange module (the first-stage heat exchange module is about 160K, the second-stage heat exchange module is about 80K, and the third-stage heat exchange module is about 30K), thereby reducing the heat load of the 4.2K low-temperature interface (from 0.1W to <0.05W), and at the same time providing pre-cooling refrigeration capacity for experiments or equipment with different temperature requirements (1W at the third-stage heat exchange module, 2W at the second-stage heat exchange module, and 3W at the first-stage heat exchange module); the brazing connection and long path design of the heat exchange copper tube connect the heat exchange copper tube to the heat exchange module or the thin-walled stainless steel cylinder by brazing, ensuring the cold There is good thermal contact between the helium and the heat exchange copper tube; the heat exchange copper tube is designed to be longer and coiled multiple times, which increases the contact area and further improves the heat exchange efficiency; the return multi-layer stainless steel cylinder structure is adopted to extend the distance between the mounting flange and the 4.2K liquid helium pool, reduce the heat conduction power from the mounting flange to the 4.2K liquid helium pool, and thus reduce the heat load at the low-temperature interface of the 4.2K liquid helium pool; the comprehensive use of the refrigeration capacity of the cold helium gas heating not only utilizes the vaporization refrigeration of liquid helium, but also makes full use of the refrigeration capacity of the cold helium gas during the heating process, and provides additional pre-cooling refrigeration capacity, so that some high-load experiments (such as large magnetic field superconducting magnets) can be carried out.

[0074] Although various embodiments of the present invention are described above, it should be understood that they are presented as examples only and not as limitations. It is obvious to those skilled in the relevant art that various combinations, modifications and changes can be made thereto without departing from the spirit and scope of the present invention. Therefore, the breadth and scope of the present invention disclosed herein should not be limited by the exemplary embodiments disclosed above, but should only be defined according to the technical solutions and their equivalents.

Claims

1. A high-efficiency heat exchange system for a liquid helium closed circulation system, characterized in that: include: A mounting flange, wherein the mounting flange is at room temperature; A multi-layer thin-wall stainless steel cylinder structure, wherein the multi-layer thin-wall stainless steel cylinder structure comprises a plurality of thin-wall stainless steel cylinders; A heat exchange copper tube assembly, wherein the heat exchange copper tube assembly comprises a plurality of heat exchange copper tubes; Multiple heat exchange modules, including a primary heat exchange module, a secondary heat exchange module and a tertiary heat exchange module; as well as A 4.2K liquid helium pool, in which liquid helium is vaporized to generate refrigeration power; The multi-layer thin-wall stainless steel cylinder structure is used to connect the mounting flange, the multiple heat exchange modules and the 4.2K liquid helium pool, extend the distance between the mounting flange and the 4.2K liquid helium pool, and reduce the heat conduction power; The heat exchange copper tube assembly is connected to the multi-layer thin-wall stainless steel cylinder structure or the plurality of heat exchange modules; The helium generated by the 4.2K liquid helium pool flows through the third-stage heat exchange module, the second-stage heat exchange module and the first-stage heat exchange module in sequence, forming a 30K refrigeration environment at the third-stage heat exchange module.

2. The high-efficiency heat exchange system for a liquid helium closed circulation system according to claim 1, characterized in that: The multi-layer thin-wall stainless steel cylinder structure is a folded multi-layer structure, and the multi-layer thin-wall stainless steel cylinder structure includes a first thin-wall stainless steel cylinder, a second thin-wall stainless steel cylinder, a third thin-wall stainless steel cylinder, a fourth thin-wall stainless steel cylinder and a fifth thin-wall stainless steel cylinder.

3. The high-efficiency heat exchange system for a liquid helium closed circulation system according to claim 1, characterized in that: The heat exchange copper tube assembly is connected to the multi-layer thin-wall stainless steel cylinder structure or the plurality of heat exchange modules by brazing; The heat exchange copper tube assembly adopts a multi-circle spiral design to increase the contact area with the multi-layer thin-wall stainless steel cylinder structure or the multiple heat exchange modules.

4. The high-efficiency heat exchange system for a liquid helium closed circulation system according to claim 1, characterized in that: The heat exchange copper tube assembly includes a first heat exchange copper tube, a second heat exchange copper tube, a third heat exchange copper tube, a fourth heat exchange copper tube, a fifth heat exchange copper tube, a sixth heat exchange copper tube, a seventh heat exchange copper tube, an eighth heat exchange copper tube, a ninth heat exchange copper tube and a tenth heat exchange copper tube.

5. The high-efficiency heat exchange system for a liquid helium closed circulation system according to claim 1 or 2, characterized in that: The mounting flange is connected to the secondary heat exchange module through the first thin-walled stainless steel cylinder and the second thin-walled stainless steel cylinder, and the secondary heat exchange module is connected to the 4.2K liquid helium pool through the third thin-walled stainless steel cylinder, the fourth thin-walled stainless steel cylinder and the fifth thin-walled stainless steel cylinder.

6. The high-efficiency heat exchange system for a liquid helium closed circulation system according to claim 4, characterized in that: The three-stage heat exchange module is provided with a groove, and the seventh heat exchange copper tube is arranged in the groove and brazed with the three-stage heat exchange module by silver brazing.

7. The high-efficiency heat exchange system for a liquid helium closed circulation system according to claim 1, characterized in that: The helium forms a refrigeration environment of 80K at the secondary heat exchange module, the secondary heat exchange module is connected to the secondary cold plate through a soft copper braid, and a low-temperature shielding cover is arranged on the secondary cold plate to reduce the thermal radiation load of the 4.2K liquid helium pool interface; and / or The helium forms a refrigeration environment of 160K at the first-stage heat exchange module.

8. A refrigeration method for a high-efficiency heat exchange system for a liquid helium closed circulation system according to any one of claims 1 to 7, characterized in that: include: Liquid helium vaporizes inside the 4.2K liquid helium pool, generating refrigeration power at the 4.2K liquid helium pool, and the helium gas generated by the vaporization of liquid helium flows out through the gas outlet exhaust pipe of the liquid helium pool; Helium is guided to multiple heat exchange modules through the heat exchange copper tube assembly. The cooling capacity of helium during the heating process is used to provide pre-cooling refrigeration capacity for experiments or equipment with different temperature gradients, reduce the heat load at the 4.2K liquid helium pool, and improve the refrigeration power at the 4.2K liquid helium pool.

9. The refrigeration method for a liquid helium closed cycle system according to claim 8, characterized in that: The helium gas flows through the tenth heat exchange copper tube, the eighth heat exchange copper tube and the seventh heat exchange copper tube to form a 30K cooling environment at the third-stage heat exchange module; The helium gas flows through the ninth heat exchange copper tube and the sixth heat exchange copper tube to form a refrigeration environment of 80K at the secondary heat exchange module; The helium gas flows through the fourth heat exchange copper tube, the third heat exchange copper tube, the second heat exchange copper tube, the first heat exchange copper tube and the fifth heat exchange copper tube, forming a refrigeration environment of 160K at the primary heat exchange module.

10. The refrigeration method for a liquid helium closed cycle system according to claim 8, characterized in that: The heat loss due to heat conduction in the 4.2K liquid helium pool is 0.05W; and / or The cooling capacity obtained at the third-stage heat exchange module is 1W; and / or The cooling capacity obtained at the secondary heat exchange module is 2W; and / or The cooling capacity obtained at the first-stage heat exchange module is 3W.

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