Cooling type superconducting current lead device of multi-stage serial pulse tube refrigerator

Abstract

The invention relates to a cooling type superconducting current lead device of a multi-stage serial pulse tube refrigerator, which comprises a current lead and the multi-stage serial pulse tube refrigerator, and is characterized in that the multi-stage serial pulse tube refrigerator comprises a plurality of stages of cold heads which are arranged in series and can provide cascade refrigeration temperature; and each stage of cold head sequentially cools the current lead from the room temperature section to the low temperature section from high temperature to low temperature. Compared with the prior art, the cooling type superconducting current lead of the multi-stage serial pulse tube refrigerator has the advantages that step cooling can be carried out on the superconducting current lead from the room temperature end to the low temperature end in sequence, the input work of the refrigerator can be remarkably reduced, the refrigerating efficiency of the refrigerator is improved, and electric power is greatly saved.

Description

Technical Field

[0001] The invention belongs to the technical field of superconducting current leads, and relates to a multi-stage serial pulse tube refrigerator cooling type superconducting current lead device. Background Art

[0002] In recent years, superconducting technology has developed rapidly, and the application trend and role of current leads in various superconducting devices have been continuously strengthened. The current lead is the link between the room temperature power supply and the low temperature superconducting device, and plays a transitional role in the operation of the superconducting device. Today, with the increasing shortage of energy and the increasingly severe environmental problems, the whole society has attached more and more importance to energy consumption and environmental protection. The current lead includes a large amount of Joule heat and conduction leakage heat. The resistivity of copper increases with the increase of temperature, and a large amount of Joule heat will be generated in the high temperature zone; the traditional technology of using refrigerators to cool the current lead needs to be cooled from the lowest temperature. The cooling from room temperature to low temperature requires a large temperature zone to generate a large amount of cooling load, which cannot meet the requirements of low loss. At the same time, it will cause an increase in cooling costs, which directly affects the economy and stability of the entire system. Summary of the invention

[0003] The purpose of the present invention is to provide a multi-stage series pulse tube refrigerator cooled superconducting current lead device, which adopts a multi-stage series pulse tube refrigerator to provide a cold head with multiple refrigeration temperatures, thereby performing step-by-step cooling from the room temperature end to the low-temperature end of the current lead, reducing the energy loss caused by the existing cooling technology, reducing the power consumption caused by the refrigeration equipment, and improving the economy and stability of the entire system.

[0004] The purpose of the present invention can be achieved by the following technical solutions:

[0005] A multi-stage series pulse tube refrigerator cooled superconducting current lead device comprises a current lead and a multi-stage series pulse tube refrigerator, wherein the multi-stage series pulse tube refrigerator comprises a plurality of cold heads arranged in series and capable of providing a stepped cooling temperature, and each cold head cools the current lead from a room temperature section to a low temperature section in sequence from a high temperature to a low temperature.

[0006] Furthermore, the cold heads of each stage of the multi-stage serial pulse tube refrigerator are connected in series in sequence, and the pulse tube of the cold head of the previous stage is connected to the cold head of the adjacent next stage.

[0007] Furthermore, each stage of the cold head is sequentially connected by a room temperature heat exchanger, a heat regenerator, a cold end heat exchanger, a flow equalizer and a pulse tube, which belongs to the conventional technology in this field and will not be described in detail here.

[0008] Furthermore, the expansion work of the previous stage cold head is recycled as input work of the next stage cold head.

[0009] Furthermore, the multi-stage serial pulse tube refrigerator also includes a compressor and a phase adjustment structure, wherein the compressor is a stepped piston compressor, and the stepped piston compressor generates a multi-stage compression chamber, and different stages of the multi-stage compression chamber are respectively connected to each stage of the cold head.

[0010] More preferably, the phase-adjusting structure includes an inertia tube and a phase-adjusting gas reservoir disposed at the end, and phase-adjusts with the compression chamber through the inertia tube and the phase-adjusting gas reservoir.

[0011] More preferably, an empty container is further provided at the connection between the first-stage cold head and the compressor of the multi-stage tandem pulse tube refrigerator.

[0012] Furthermore, the number of cold heads of the multi-stage tandem pulse tube refrigerator is n, and n≥2.

[0013] Furthermore, the current lead includes a room temperature section joint and a low temperature section which are connected as one body, an end of the low temperature section away from the room temperature section joint is connected to a superconducting material, and the low temperature section is provided with a plurality of levels of cooling connection units in a gradient distribution direction of temperature from high to low, and each level of cooling connection unit corresponds to a connection to a level of the cold head.

[0014] Furthermore, the cooling connection unit includes a cold head connection section connected to the low temperature section and a cooling block connected to the cold head, and the cold head connection section and the cooling block are crimped by a nut. Preferably, a G10 sleeve can be added in the screw hole to ensure electrical insulation.

[0015] More preferably, the contact interface between the cold head connection section and the cold conduction block is further provided with three layers of laminated sheets, including an aluminum nitride gasket located in the middle, and indium sheets located on the upper and lower sides (which can be divided into a first indium sheet and a second indium sheet according to different positions). The aluminum nitride gasket in the middle is used for electrical insulation while ensuring good thermal conductivity, and the first indium sheet and the second indium sheet arranged on both sides fill the gaps on the solid contact surface to increase the actual contact area, effectively reducing the interface thermal resistance and enhancing the interface heat transfer efficiency.

[0016] Through research, the present invention finds that the advantage of a multi-stage series pulse tube refrigerator is that it has a cold head that can provide multi-level cooling temperatures. The multi-stage cold head can match different temperature zones of superconducting current leads to achieve step cooling. The multi-stage series pulse tube refrigerator adopts a multi-stage stepped piston compressor that can not only output work, but also phase-adjust the cold head. The structural advantage of the multi-stage cold heads in series is that the expansion work of the previous stage cold head is also the input work of the next stage cold head, and the expansion work of the last stage is lost. Since the temperature of the last stage is the lowest and the cooling capacity is the smallest, the lost expansion work is also very small. The more series stages there are, the closer the efficiency of the whole machine will be to the Carnot efficiency, which is very beneficial for superconducting current lead cooling with large cooling capacity requirements.

[0017] At the same time, the temperature zone of the current lead spans room temperature and low temperature, and the conduction heat leakage caused by the huge temperature difference on both sides and the Joule heat of the system operation become its main cooling load. The present invention reduces the energy loss caused by the existing cooling technology by performing step-cooling from the room temperature end to the low temperature end of the current lead, reduces the power consumption caused by the refrigeration equipment, and improves the economy and stability of the entire system. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 A simple structural schematic diagram of a three-stage tandem pulse tube refrigerator for high-temperature superconducting current lead cooling provided by the present invention;

[0019] Figure 2 It is a schematic structural diagram of a two-stage tandem pulse tube refrigerator for high-temperature superconducting current lead cooling of the present invention;

[0020] Figure 3 A schematic diagram of a cooling block connecting a cold head and a superconducting current lead of the present invention;

[0021] Figure 4 It is a schematic diagram of the structure of the connection between the first-level cold head section and the first-level cooling block of the present invention.

[0022] Description of the markings in the figure:

[0023] 10-current lead; 11-copper lead; 12-superconducting material; 111-room temperature section copper joint; 112-first level cold head connection section; 113-second level cold head connection section; 114-third level cold head connection section;

[0024] 20-multi-stage tandem pulse tube refrigerator; 21-compressor; 22-first stage cold head; 23-second stage cold head; 24-third stage cold head; 25-phase adjustment mechanism;

[0025] 221- first-stage cold head cooling block; 231- second-stage cold head cooling block; 241- third-stage cold head cooling block;

[0026] 222 - a first indium sheet; 223 - an aluminum nitride ceramic gasket; 224 - a second indium sheet. DETAILED DESCRIPTION

[0027] The present invention is described in detail below in conjunction with the accompanying drawings and specific embodiments. This embodiment is implemented based on the technical solution of the present invention, and provides a detailed implementation method and specific operation process, but the protection scope of the present invention is not limited to the following embodiments.

[0028] In the description of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", and "third" are used for descriptive purposes only, and cannot be understood as indicating or implying relative importance.

[0029] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0030] In the present invention, unless otherwise specified, functional components or structures are conventional components or conventional structures used in the art to achieve corresponding functions.

[0031] The present invention is described in detail below.

[0032] In order to perform step-cooling from the room temperature end to the low temperature end of the current lead to reduce the energy loss caused by the existing cooling technology, in some embodiments, the present invention provides a multi-stage tandem pulse tube refrigerator cooled superconducting current lead, which uses a multi-stage tandem pulse tube refrigerator with several stages of cold heads (i.e., multi-stage cold heads) that can provide step-by-step cooling temperatures to cool the current lead (i.e., copper lead) from the room temperature section to the low temperature section in sequence from high temperature to low temperature.

[0033] In a specific implementation, the multi-stage cold heads are n, n ≥ 2, and the multi-stage tandem pulse tube refrigerator is connected to the compressor and is sequentially connected to the first cold head, the second cold head, and the nth cold head. According to the temperature distribution of the copper lead from room temperature to the low temperature region, the copper lead is cooled in n stages respectively.

[0034] Embodiment 1:

[0035] like Figure 1As shown, the present embodiment provides a three-stage tandem pulse tube refrigerator cooling type superconducting current lead, which includes a current lead 10 and a multi-stage tandem pulse tube refrigerator 20, wherein the current lead 10 includes a copper lead 11 and a superconducting material 12; the copper lead 11 is divided into a room temperature section copper joint 111 and a low temperature section body, and a primary cold head connection section 112, a secondary cold head connection section 113, and a tertiary cold head connection section 114 are sequentially arranged on the low temperature section body according to the direction of temperature gradient change; the multi-stage tandem pulse tube refrigerator 20 includes a compressor 21, a primary cold head 22 (i.e., a high temperature cold head), a secondary cold head 23 (i.e., a medium temperature cold head), a tertiary cold head 24 (i.e., a low temperature cold head) and a phase adjustment mechanism 25. The first-stage cold head 22 is also connected to the first-stage cold head cooling block 221, the second-stage cold head 23 is also connected to the second-stage cold head cooling block 231, and the third-stage cold head 24 is also connected to the third-stage cold head cooling block 241. The shapes of the cooling blocks at each level are as follows: Figure 3 shown.

[0036] Specifically, the primary cold head connection section 112 is connected to the primary cold head cold conduction block 221, the secondary cold head connection section 113 is connected to the secondary cold head cold conduction block 231, and the tertiary cold head connection section 114 is connected to the tertiary cold head cold conduction block 241. To perform three-stage cooling, nuts are used to tighten and press the cold head connection sections and cold conduction blocks at each level to enhance heat exchange.

[0037] Specifically, Figure 1 The three-stage serial pulse tube refrigerator comprises a compressor 21, a first-stage cold head 22, a second-stage cold head 23, a third-stage cold head 24 and a phase adjustment mechanism 25. The compressor 21 is a three-stage stepped piston compressor, and the cold heads of each stage are connected in series in sequence. The cold heads of each stage include a room temperature heat exchanger, a regenerator, a cold end heat exchanger, a pulse tube and a flow equalizer.

[0038] Embodiment 2:

[0039] like Figure 2 As shown, this embodiment provides a two-stage series pulse tube refrigerator cooled superconducting current lead. The difference from Embodiment 1 is that for low-power current lead application scenarios, two-stage cooling can be performed, which can reduce the cost of the current lead. The refrigerator part is provided with a two-stage cold head, and correspondingly, two-stage cooling is performed on the room temperature and low-temperature parts of the copper lead.

[0040] Specifically, in order to enhance thermal conductivity and electrical insulation, a multi-layer gasket is provided at the connection between each level of cold head and superconducting cable, and the multi-layer gasket is composed of three layers of gaskets, such as Figure 4As shown, from top to bottom are the first indium sheet 222, the aluminum nitride ceramic gasket 223, and the second indium sheet 224; wherein the aluminum nitride ceramic gasket can also be aluminum oxide powder or diamond film. The cold head cold block, the cold head connection section and the multi-layer gasket are crimped by nuts, and an insulating sleeve is arranged in the screw hole. The G10 insulating sleeve, whose main materials are glass fiber and epoxy resin, has excellent insulation performance, mechanical properties and low temperature resistance.

[0041] At the same time, the room temperature section copper joint 111 in this embodiment is connected to the room temperature end side of the copper lead 11 by soldering. The cold head conduction blocks of each level are connected to the cold head by soldering.

[0042] It should be pointed out that the various embodiments described above in detail for the concept of the present invention may be implemented individually or in any combination of two or more.

[0043] In combination with the above content, the multi-stage tandem pulse tube refrigerator cooling superconducting current lead device provided by the present invention has a compact structure, realizes efficient energy utilization, and greatly reduces the refrigerator input work on the basis of meeting the cooling of the superconducting current lead. The device has a wide range of applications and can be applied to superconducting current lead devices, and has good development prospects.

[0044] The above description of the embodiments is to facilitate the understanding and use of the invention by those skilled in the art. It is obvious that those skilled in the art can easily make various modifications to these embodiments and apply the general principles described herein to other embodiments without creative work. Therefore, the present invention is not limited to the above embodiments, and improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the present invention should be within the scope of protection of the present invention.

Claims

1. A multi-stage tandem pulse tube refrigerator cooling type superconducting current lead device, characterized in that: It comprises a current lead and a multi-stage series pulse tube refrigerator, wherein the multi-stage series pulse tube refrigerator comprises a plurality of cold heads arranged in series and capable of providing a stepped cooling temperature, and each cold head cools the current lead from a room temperature section to a low temperature section in sequence from a high temperature to a low temperature.

2. A multi-stage tandem pulse tube refrigerator-cooled superconducting current lead device according to claim 1, characterized in that: The cold heads of each stage of the multi-stage serial pulse tube refrigerator are connected in series in sequence, and the pulse tube of the cold head of the previous stage is connected to the cold head of the adjacent next stage.

3. A multi-stage tandem pulse tube refrigerator cooling type superconducting current lead device according to claim 2, characterized in that: The expansion work of the previous stage cold head is recycled as the input work of the next stage cold head.

4. A multi-stage tandem pulse tube refrigerator cooling type superconducting current lead device according to claim 2, characterized in that: The multi-stage serial pulse tube refrigerator also includes a compressor and a phase adjustment structure, wherein the compressor is a stepped piston compressor, the stepped piston compressor generates a multi-stage compression chamber, and different stages of the multi-stage compression chamber are respectively connected to each stage of the cold head.

5. A multi-stage tandem pulse tube refrigerator cooling type superconducting current lead device according to claim 4, characterized in that: The phase adjustment structure comprises an inertia tube and a phase adjustment gas reservoir arranged at the end, and phase adjustment is performed together with the compression chamber through the inertia tube and the phase adjustment gas reservoir.

6. A multi-stage tandem pulse tube refrigerator-cooled superconducting current lead device according to claim 4, characterized in that: An empty container is also provided at the connection between the first-stage cold head and the compressor of the multi-stage serial pulse tube refrigerator.

7. A multi-stage tandem pulse tube refrigerator-cooled superconducting current lead device according to claim 1, characterized in that: The number of cold heads of the multi-stage tandem pulse tube refrigerator is n, and n≥2.

8. The multi-stage tandem pulse tube refrigerator cooling type superconducting current lead device according to claim 1, characterized in that: The current lead includes a room temperature section joint and a low temperature section which are connected as one body. One end of the low temperature section away from the room temperature section joint is connected to a superconducting material. The low temperature section is provided with a plurality of levels of cold conduction connection units in a temperature gradient distribution direction from high to low. Each level of cold conduction connection unit is connected to a corresponding level of the cold head.

9. A multi-stage tandem pulse tube refrigerator-cooled superconducting current lead device according to claim 8, characterized in that: The cooling connection unit includes a cold head connection section connected to the low temperature section and a cooling block connected to the cold head. The cold head connection section and the cooling block are crimped by a nut.

10. A multi-stage tandem pulse tube refrigerator-cooled superconducting current lead device according to claim 9, characterized in that: The contact interface between the cold head connecting section and the cold conducting block is also provided with three layers of laminated sheets, including an aluminum nitride gasket located in the middle and indium sheets located on the upper and lower sides.

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