Throttling heat exchanger for dilution refrigerator and manufacturing method

Abstract

The invention discloses a throttling heat exchanger for a dilution refrigerator and a manufacturing method, and particularly relates to the field of refrigeration and low-temperature engineering. The throttling heat exchanger comprises a heat exchanger outer corrugated pipe and a heat exchanger inner core arranged in an inner cavity of the heat exchanger outer corrugated pipe; the heat exchanger outer corrugated pipe comprises a heat exchanger low-pressure outlet connecting pipe and a heat exchanger low-pressure inlet connecting pipe which are fixedly arranged at the top end and the bottom end, and the heat exchanger outer corrugated pipe is a spiral corrugated pipe. Rotational flow reinforced convection heat exchange of high-pressure fluid and low-pressure fluid in a limited space is achieved in the mode that the spiral corrugated outer pipe and the spiral inner pipe are combined, the throttling small holes are fully pre-cooled in the stable stage of a dilution refrigeration system in the mode that the throttling small holes are introduced into the heat exchanger, and integration of the throttling small holes and the throttling heat exchanger is achieved. The design of variable apertures before and after throttling is more consistent with the physical property parameter change of helium at extremely low temperature; the method has very positive significance in optimization of the throttling heat exchange precooling process and the throttling process and performance improvement of the dilution refrigerator.

Description

Technical Field

[0001] The present invention relates to the field of refrigeration and cryogenic engineering technology, and more particularly to a throttling heat exchanger for a dilution refrigerator and a manufacturing method thereof. Background Art

[0002] Dilution refrigerators are currently a hot research topic in the mK temperature range for cryogenic refrigerators. They offer the advantages of continuous cooling at temperatures below 100 mK, lack of electromagnetic interference, and low vibration. They hold broad application prospects in key fields such as quantum information technology, establishing extreme experimental conditions, and deep space exploration. Dilution refrigerators use a helium-3 / helium-4 mixture as the working fluid. The entire dilution refrigeration cycle includes pulse tube precooling, throttling heat exchange precooling, throttling, condensation heat exchange, dilution, reflux heat exchange, evaporation, and compression. The throttling heat exchange precooling and throttling processes are critical stages in the dilution refrigeration cycle, cooling the temperature from approximately 4.2 K to approximately 0.7 K. They play a crucial role in stabilizing the entire dilution refrigeration cycle. The throttling heat exchange precooling process is crucial for ensuring the smooth operation of the throttling process.

[0003] The dilution refrigerator industry focuses on integrating the key components of the throttling heat exchange pre-cooling process and the throttling process. Ideally, a throttling heat exchanger for a dilution refrigerator should achieve the following three functions:

[0004] 1) Realize an efficient and stable throttling heat exchange process in a limited space. The throttling heat exchange process is actually a process in which a low-pressure cold fluid (about 0.7K) and a high-pressure hot fluid (about 4.2K) are fully exchanged with each other in a countercurrent heat exchanger. Because there is a throttling effect in the heat exchange process, it is called a throttling heat exchange process. In the dilution refrigeration cycle, the good implementation of the throttling process requires that the temperature before throttling is lower than 1.8K. This requires the throttling heat exchanger to fully realize the heat exchange between the cold and hot fluids and fully recover the cold energy of the low-pressure cold fluid to ensure the stability of the throttling process. Since the cold fluid is under low-pressure conditions and considering the limited structural space of the entire system, appropriate swirl will help to improve the heat exchange between the cold and hot fluids in a limited space. This requires the introduction of spiral corrugations and spiral tube structures to achieve stability and efficiency in the throttling heat exchange process.

[0005] 2) Achieve a stable throttling process. The throttling process is the process by which the working fluid in the dilution refrigeration cycle transforms from a high-temperature liquid to a low-temperature mixed gas-liquid fluid. It is key to ensuring further reduction of the temperature throughout the cycle during the initial cooling period and ensuring stability in the 0.7-4K temperature range during the cycle. The throttling process requires micron-sized orifices and a temperature below 1.8K before throttling. Therefore, the size of the throttling plate and sufficient precooling are extremely critical.

[0006] 3) Smaller heat leakage loss. In the extremely low temperature region below 2K, the impact of heat leakage on the performance of the heat exchanger is very obvious, which requires that the heat leakage loss of the component itself be minimized.

[0007] In conventional dilution refrigerators, the throttling heat exchanger and the throttling plate are generally arranged separately, and the throttling heat exchanger usually uses a corrugated bellows. The characteristic of the corrugated bellows is that it has a certain vibration reduction effect, but the improvement of the heat exchange enhancement capacity of the heat exchanger is limited. This leads to the need to lengthen the length of the throttling heat exchanger to achieve heat exchange enhancement. However, due to space limitations, the length of the throttling heat exchanger is difficult to achieve the ideal state. As for the external throttling plate structure, not only does it require an additional long pipe to fix its position, but it cannot obtain sufficient pre-cooling, which to a certain extent affects the time it takes for the dilution refrigeration cycle to reach stability. In addition, the external small hole is easily affected by heat leakage, and sufficient pre-cooling is required to avoid these problems. Therefore, the separate placement of the conventional throttling heat exchanger and the throttling plate has great limitations in achieving the above three requirements. Summary of the Invention

[0008] In order to overcome the above-mentioned defects of the prior art, an embodiment of the present invention provides a throttling heat exchanger for a dilution refrigerator and a manufacturing method thereof.

[0009] To achieve the above-mentioned object, the present invention provides the following technical solutions: a throttling heat exchanger for a dilution refrigerator, comprising a heat exchanger outer bellows and a heat exchanger inner core disposed in an inner cavity of the heat exchanger outer bellows;

[0010] The heat exchanger outer bellows includes a heat exchanger low-pressure outlet connecting pipe and a heat exchanger low-pressure inlet connecting pipe fixedly arranged at the top and bottom ends, and the heat exchanger outer bellows is configured as a spiral corrugated pipe;

[0011] The heat exchanger core includes, from top to bottom, a post-throttling spiral inner tube, a post-throttling seat, a throttle plate, a front-throttling seat and a front-throttling spiral inner tube. The top end of the post-throttling spiral inner tube is fixedly provided on the high-pressure outlet connecting pipe, and the bottom end of the pre-throttling spiral inner tube is fixedly provided with a high-pressure inlet connecting pipe of the heat exchanger.

[0012] In a preferred embodiment, the diameters of the low-pressure outlet connecting pipe and the low-pressure inlet connecting pipe of the heat exchanger are equal and smaller than the inner diameter of the outer bellows of the heat exchanger, and the spiral corrugations of the outer bellows of the heat exchanger are clockwise along the flow direction of the low-pressure airflow;

[0013] The inner diameters of the heat exchanger low-pressure outlet connecting pipe and the heat exchanger low-pressure inlet connecting pipe are controlled between 16-25 mm, the thread helix angle is controlled between 5°-10°, the corrugation height is controlled between 1.5-3 mm, the corrugation wavelength is controlled between 3-6 mm, and the wave pitch and wavelength remain equal.

[0014] In a preferred embodiment, the inner cavity of the pre-throttling spiral inner tube is connected to the high-pressure inlet connecting pipe of the heat exchanger, and the flow direction of the high-pressure airflow is opposite to the flow direction of the low-pressure airflow in the outer bellows of the heat exchanger;

[0015] Along the flow direction of the high-pressure airflow, the inner diameter of the spiral inner tube before throttling is controlled between 1-1.2 mm, the tube wall of the spiral inner tube before throttling is controlled within 0.5 mm, the corresponding spiral corrugation of the spiral inner tube before throttling is a counterclockwise spiral, the spiral major diameter is controlled between 9-15 mm, and the spiral pitch is controlled between 3-6 mm.

[0016] In a preferred embodiment, the total height of the spiral cylinder of the pre-throttling spiral inner tube is controlled between 1 / 2 and 2 / 3 of the total length of the outer bellows of the heat exchanger, and the inner tube outlet of the pre-throttling spiral inner tube away from the end of the high-pressure inlet connecting pipe of the heat exchanger is inserted into the pre-throttling seat;

[0017] A welding groove surface I is provided at the connection between the inner side of the throttle front seat and the throttle front spiral inner tube, and the inner side of the throttle front seat and the throttle front spiral inner tube are combined into one body by welding at the welding groove surface I.

[0018] In a preferred embodiment, a throttling hole is formed in the central perforation of the throttling plate, and the aperture of the throttling hole is controlled between 25-40 μm, and the hole is installed flush with the throttling rear seat after being perforated;

[0019] The top of the throttle front seat is provided with a welding groove surface II, and the throttle plate and the throttle front seat are integrated into one body by welding on the welding groove surface II;

[0020] The combination of the throttle plate and the throttle rear seat is installed flush with the throttle front seat. A welding groove surface III is provided at the bottom end of the throttle rear seat, and the throttle rear seat and the throttle front seat are combined into one body by welding at the welding groove surface III.

[0021] In a preferred embodiment, the throttled spiral inner tube is connected to the high-pressure outlet connecting pipe. Along the flow direction of the high-pressure airflow, the inner diameter of the throttled spiral inner tube is controlled between 0.6-1.0 mm, the tube wall is controlled within 0.3 mm, the spiral corrugation is a counterclockwise spiral, the spiral major diameter is controlled between 9-15 mm, the spiral pitch is controlled between 2-4 mm, and the total height of the spiral cylinder is controlled between 1 / 3-1 / 2 of the total length of the outer bellows of the heat exchanger;

[0022] The inlet of one end of the throttled spiral inner tube away from the high-pressure outlet connecting pipe is inserted into the throttled rear seat, and a welding groove surface IV is provided at the connection between the top end of the throttled rear seat and the throttled spiral inner tube. The throttled rear seat and the throttled spiral inner tube are combined into one by welding on the welding groove surface IV.

[0023] The present invention also includes a method for manufacturing a throttling heat exchanger for a dilution refrigerator, and the specific manufacturing steps are as follows:

[0024] S1: The outer bellows of the heat exchanger are made of materials with low thermal conductivity. Their total length is controlled between 150-250mm. The length of the low-pressure outlet and low-pressure inlet connecting pipes is controlled between 10-15mm. The outer wall roughness of the heat exchanger outer bellows is required to be less than 0.08, the inner wall roughness is required to be less than 0.4, and the wall thickness is required to be controlled between 0.2-0.4mm. The bellows are subjected to thermal stress annealing treatment as a whole to make them have certain bendability.

[0025] S2: The spiral inner tube before throttling is made of high thermal conductivity material. The total height of the spiral cylinder is controlled between 1 / 2-2 / 3 of the total length of the heat exchanger's outer bellows. The inner diameter of the tube is controlled between 1-1.2mm. The inner wall roughness is required to be less than 0.08, and the outer wall roughness is required to be less than 0.2.

[0026] S3: The throttle plate is made of high yield strength material. The aperture is the average aperture and the aperture is as uniform as possible. Use a microscope to magnify the aperture and calculate the average aperture using the method of partition area calculation and scale conversion. The roughness of all surfaces of the throttle plate is required to be less than 0.04, and the outer diameter is controlled between 5-6mm.

[0027] S4: The throttle front seat and throttle rear seat are made of high yield strength materials. The roughness of all contact surfaces with small holes is required to be less than 0.04, and the roughness of the surface not in contact with the small holes is required to be less than 0.4;

[0028] S5: The spiral inner tube after throttling is made of high thermal conductivity material. The total height of the spiral cylinder is controlled between 1 / 3-1 / 2 of the total length of the heat exchanger outer bellows. The inner diameter of the tube is controlled between 0.6-1.0mm. The inner wall roughness is required to be less than 0.08, and the outer wall roughness is required to be less than 0.2.

[0029] S6: During the actual installation process, there is no direct connection between the outer bellows of the heat exchanger and the inner tube assembly of the pre-throttling spiral inner tube, the pre-throttling seat, the throttling plate, the post-throttling seat, and the post-throttling spiral inner tube. The outer bellows of the heat exchanger is connected to the dilution refrigeration system through the low-pressure outlet connecting pipe of the heat exchanger and the low-pressure inlet connecting pipe of the heat exchanger, and the inner tube assembly is connected to the dilution refrigeration system through the high-pressure inlet connecting pipe and the high-pressure outlet connecting pipe, thereby forming a throttling heat exchanger for a dilution refrigerator.

[0030] Technical effects and advantages of the present invention:

[0031] 1. The present invention realizes an efficient and stable throttling heat exchange process in a limited space by combining a spiral corrugated outer tube and a spiral inner tube. By integrating a throttling orifice into the throttling heat exchanger, the throttling orifice is fully pre-cooled, and a stable throttling process is ultimately achieved by using channels with different diameters before and after throttling.

[0032] 2. The present invention fully reduces the heat leakage loss of the entire component through surface treatment and structure of different areas, realizes the integration of the throttling heat exchanger and the throttling orifice, and has a very positive significance for the structural design and optimization of the throttling heat exchanger for the dilution refrigerator and promoting the improvement of the overall performance of the dilution refrigerator. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 It is a schematic diagram of the overall structure of the present invention.

[0034] Figure 2 This is a schematic diagram of the structure of the outer bellows of the heat exchanger of the present invention.

[0035] Figure 3 This is a schematic diagram of the cross-sectional structure of the outer bellows of the heat exchanger of the present invention.

[0036] Figure 4 This is a schematic diagram of the explosion structure of the heat exchanger inner core of the present invention.

[0037] Figure 5 It is a cross-sectional view of the coupling structure of the throttle plate and the high-pressure spiral inner tube of the present invention.

[0038] The accompanying drawings are marked as: 1 heat exchanger low-pressure outlet connecting pipe, 2 heat exchanger external bellows, 3 heat exchanger low-pressure inlet connecting pipe, 4 heat exchanger high-pressure inlet connecting pipe, 5 spiral inner pipe before throttling, 6 throttle front seat, 7 throttle plate, 8 throttle rear seat, 9 throttle rear spiral inner pipe, 10 high-pressure outlet connecting pipe, 11 welding groove surface I, 12 welding groove surface II, 13 welding groove surface III, 14 welding groove surface IV. DETAILED DESCRIPTION

[0039] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0040] The present invention provides Figure 1-3The throttling heat exchanger for a dilution refrigerator shown in the figure includes a heat exchanger outer bellows 2 and a heat exchanger inner core placed in the inner cavity of the heat exchanger outer bellows 2; the heat exchanger outer bellows 2 includes a heat exchanger low-pressure outlet connecting pipe 1 and a heat exchanger low-pressure inlet connecting pipe 3 fixed at the top and bottom ends, and the heat exchanger outer bellows 2 is configured as a spiral corrugated tube;

[0041] The diameters of the heat exchanger's low-pressure outlet connecting pipe 1 and the heat exchanger's low-pressure inlet connecting pipe 3 are equal and smaller than the inner diameter of the heat exchanger's outer bellows 2. The spiral corrugation of the heat exchanger's outer bellows 2 is clockwise along the direction of low-pressure airflow. The inner diameters of the heat exchanger's low-pressure outlet connecting pipe 1 and the heat exchanger's low-pressure inlet connecting pipe 3 are controlled between 16-25mm, the thread helix angle is controlled between 5°-10°, the corrugation height is controlled between 1.5-3mm, the corrugation wavelength is controlled between 3-6mm, and the wave pitch and wavelength remain equal.

[0042] like Figure 4 The inner core of the heat exchanger includes, from top to bottom, a post-throttling spiral inner tube 9, a post-throttling seat 8, a throttle plate 7, a front-throttling seat 6 and a front-throttling spiral inner tube 5. The top end of the post-throttling spiral inner tube 9 is fixedly provided with a high-pressure outlet connecting pipe 10, and the bottom end of the front-throttling spiral inner tube 5 is fixedly provided with a heat exchanger high-pressure inlet connecting pipe 4.

[0043] The inner cavity of the pre-throttle spiral inner tube 5 is connected to the high-pressure inlet connecting pipe 4 of the heat exchanger, and the flow direction of the high-pressure airflow is opposite to the flow direction of the low-pressure airflow in the outer corrugated tube 2 of the heat exchanger; along the flow direction of the high-pressure airflow, the inner diameter of the pre-throttle spiral inner tube 5 is controlled between 1-1.2 mm, the tube wall of the pre-throttle spiral inner tube 5 is controlled within 0.5 mm, the corresponding spiral corrugation of the pre-throttle spiral inner tube 5 is a counterclockwise spiral, the spiral major diameter is controlled between 9-15 mm, and the spiral pitch is controlled between 3-6 mm;

[0044] The total height of the spiral cylinder of the pre-throttling spiral inner tube 5 is controlled between 1 / 2 and 2 / 3 of the total length of the outer bellows 2 of the heat exchanger. The inner tube outlet of the pre-throttling spiral inner tube 5, which is away from the high-pressure inlet connecting tube 4 of the heat exchanger, is inserted into the pre-throttling seat 6.

[0045] like Figure 5As shown, a welding groove surface Ⅰ11 is provided at the connection between the inner side of the throttle front seat 6 and the throttle front spiral inner tube 5, and the inner side of the throttle front seat 6 and the throttle front spiral inner tube 5 are combined into one by welding on the welding groove surface Ⅰ11; a throttle hole is provided in the center of the throttle plate 7, and the aperture of the throttle hole is controlled between 25-40 μm. After perforation, it is installed flush with the throttle rear seat 8; a welding groove surface Ⅱ12 is provided at the top of the throttle front seat 6, and the throttle plate 7 and the throttle front seat 6 are combined into one by welding on the welding groove surface Ⅱ12; the combination of the throttle plate 7 and the throttle rear seat 8 is installed flush with the throttle front seat 6, and a welding groove surface Ⅲ13 is provided at the bottom of the throttle rear seat 8, and the throttle rear seat 8 and the throttle front seat 6 are combined into one by welding on the welding groove surface Ⅲ13. One body; the throttled spiral inner tube 9 is connected to the high-pressure outlet connecting pipe 10. Along the flow direction of the high-pressure airflow, the inner diameter of the throttled spiral inner tube 9 is controlled between 0.6-1.0mm, the tube wall is controlled within 0.3mm, the spiral corrugation is a counterclockwise spiral, the spiral major diameter is controlled between 9-15mm, the spiral pitch is controlled between 2-4mm, and the total height of the spiral cylinder is controlled between 1 / 3-1 / 2 of the total length of the outer bellows 2 of the heat exchanger; the inlet of one end of the throttled spiral inner tube 9 away from the high-pressure outlet connecting pipe 10 is inserted into the throttled rear seat 8, and a welding groove surface IV14 is provided at the connection between the top of the throttled rear seat 8 and the throttled spiral inner tube 9, and the throttled rear seat 8 and the throttled spiral inner tube 9 are combined into one body by welding on the welding groove surface IV14.

[0046] The present invention also includes a method for manufacturing a throttling heat exchanger for a dilution refrigerator, and the specific manufacturing steps are as follows:

[0047] S1: The heat exchanger's outer bellows 2 is made of a material with low thermal conductivity. Its total length is controlled between 150-250 mm. The lengths of the low-pressure outlet connecting pipe 1 and the low-pressure inlet connecting pipe 3 are controlled between 10-15 mm. The outer wall roughness of the heat exchanger's outer bellows 2 is required to be less than 0.08, the inner wall roughness is required to be less than 0.4, and the wall thickness is required to be controlled between 0.2-0.4 mm. The entire bellows is subjected to thermal stress annealing treatment to ensure a certain degree of flexibility.

[0048] S2: The inner spiral tube 5 before throttling is made of a material with high thermal conductivity. The total height of the spiral cylinder is controlled between 1 / 2 and 2 / 3 of the total length of the outer bellows 2 of the heat exchanger. The inner diameter of the tube is controlled between 1 and 1.2 mm. The inner wall roughness is required to be less than 0.08, and the outer wall roughness is required to be less than 0.2.

[0049] S3: The throttle plate 7 is made of a material with high yield strength. The aperture is the average aperture and the aperture is as uniform as possible. The aperture is magnified using a microscope and the average aperture is calculated using the method of partition area calculation and scale conversion. The roughness of all surfaces of the throttle plate 7 is required to be less than 0.04, and the outer diameter is controlled between 5-6 mm.

[0050] S4: The throttle front seat 6 and the throttle rear seat 8 are made of high yield strength materials. The roughness of all surfaces in contact with the small holes is required to be less than 0.04, and the roughness of the surfaces not in contact with the small holes is required to be less than 0.4;

[0051] S5: The throttled spiral inner tube 9 is made of a material with high thermal conductivity. The total height of the spiral cylinder is controlled between 1 / 3 and 1 / 2 of the total length of the heat exchanger outer bellows 2. The inner diameter of the tube is controlled between 0.6 and 1.0 mm. The inner wall roughness is required to be less than 0.08, and the outer wall roughness is required to be less than 0.2.

[0052] S6: During the actual installation process, there is no direct connection between the outer bellows 2 of the heat exchanger and the inner tube assembly of the pre-throttling spiral inner tube 5, the pre-throttling seat 6, the throttle plate 7, the post-throttling seat 8 and the post-throttling spiral inner tube 9. The outer bellows 2 of the heat exchanger is connected to the dilution refrigeration system through the low-pressure outlet connecting pipe 1 of the heat exchanger and the low-pressure inlet connecting pipe 3 of the heat exchanger, and the inner tube assembly is connected to the dilution refrigeration system through the high-pressure inlet connecting pipe 4 and the high-pressure outlet connecting pipe 10, thereby forming a throttling heat exchanger for a dilution refrigerator.

[0053] The specific implementation method is as follows: by combining a spiral corrugated outer tube (heat exchanger outer corrugated tube 2) and a spiral inner tube (spiral inner tube 5 before throttling, and spiral inner tube 9 after throttling), swirl-enhanced convective heat exchange of high and low pressure fluids in a limited space is realized, and by introducing the throttling holes corresponding to the throttling plate 7 into the interior of the heat exchanger, the throttling holes are fully pre-cooled in the stable stage of the dilution refrigeration system, thereby avoiding the throttling process from being affected by heat leakage. The coupling structure realizes the integration of the throttling holes and the throttling heat exchanger. The design of variable aperture before and after throttling is also closer to the changes in the physical properties of helium at extremely low temperatures, which is more conducive to a stable throttling heat exchange process and the realization of a throttling process.

[0054] Finally, a few points should be explained: First, in the description of this application, it should be noted that, unless otherwise specified or limited, the terms "mounted," "connected," and "connected" should be understood in a broad sense, and may refer to mechanical or electrical connections, internal communication between two components, or direct connection. "Up," "down," "left," and "right" are only used to indicate relative positional relationships. When the absolute positions of the objects being described change, the relative positional relationships may also change.

[0055] Secondly: The drawings of the embodiments disclosed in the present invention only involve structures related to the embodiments disclosed in the present invention. Other structures may refer to conventional designs. The same embodiment and different embodiments of the present invention may be combined with each other without conflict.

[0056] Finally: The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A throttling heat exchanger for a dilution refrigerator, comprising an outer bellows (2) of the heat exchanger and an inner core of the heat exchanger disposed in an inner cavity of the outer bellows (2), characterized in that: The heat exchanger outer bellows (2) comprises a heat exchanger low-pressure outlet connecting pipe (1) and a heat exchanger low-pressure inlet connecting pipe (3) fixedly arranged at the top and bottom ends, and the heat exchanger outer bellows (2) is configured as a spiral corrugated pipe; The heat exchanger inner core comprises, from top to bottom, a post-throttling spiral inner tube (9), a post-throttling seat (8), a throttle plate (7), a front-throttling seat (6) and a front-throttling spiral inner tube (5). The top end of the post-throttling spiral inner tube (9) is fixedly arranged on a high-pressure outlet connecting pipe (10), and the bottom end of the front-throttling spiral inner tube (5) is fixedly arranged on a high-pressure inlet connecting pipe (4) of the heat exchanger.

2. A throttling heat exchanger for a dilution refrigerator according to claim 1, characterized in that: The diameters of the heat exchanger low-pressure outlet connecting pipe (1) and the heat exchanger low-pressure inlet connecting pipe (3) are equal and smaller than the inner diameter of the heat exchanger outer bellows (2), and the spiral corrugations of the heat exchanger outer bellows (2) along the flow direction of the low-pressure airflow are clockwise. The inner diameters of the heat exchanger low-pressure outlet connecting pipe (1) and the heat exchanger low-pressure inlet connecting pipe (3) are controlled between 16-25 mm, the thread helix angle is controlled between 5°-10°, the corrugation height is controlled between 1.5-3 mm, the corrugation wavelength is controlled between 3-6 mm, and the wave pitch and wavelength are kept equal.

3. The throttling heat exchanger for a dilution refrigerator according to claim 1, characterized in that: The inner cavity of the pre-throttling spiral inner tube (5) is connected to the high-pressure inlet connecting pipe (4) of the heat exchanger, and the flow direction of the high-pressure airflow is opposite to the flow direction of the low-pressure airflow in the outer bellows (2) of the heat exchanger; Along the flow direction of the high-pressure airflow, the inner diameter of the spiral inner tube (5) before throttling is controlled between 1 and 1.2 mm, the tube wall of the spiral inner tube (5) before throttling is controlled within 0.5 mm, the corresponding spiral corrugation of the spiral inner tube (5) before throttling is a counterclockwise spiral, the spiral major diameter is controlled between 9 and 15 mm, and the spiral pitch is controlled between 3 and 6 mm.

4. The throttling heat exchanger for a dilution refrigerator according to claim 3, characterized in that: The total height of the spiral cylinder of the pre-throttling spiral inner tube (5) is controlled to be between 1 / 2 and 2 / 3 of the total length of the outer bellows (2) of the heat exchanger, and the inner tube outlet of the pre-throttling spiral inner tube (5) away from the end of the high-pressure inlet connecting tube (4) of the heat exchanger is inserted into the pre-throttling seat (6); A welding groove surface I (11) is provided at the connection between the inner side of the throttle front seat (6) and the throttle front spiral inner tube (5), and the inner side of the throttle front seat (6) and the throttle front spiral inner tube (5) are integrated by welding at the welding groove surface I (11).

5. The throttling heat exchanger for a dilution refrigerator according to claim 1, characterized in that: The throttle plate (7) is perforated at the center to form a throttling hole, the aperture of which is controlled to be between 25-40 μm, and after being perforated, it is installed flush with the throttling rear seat (8); The top of the throttle front seat (6) is provided with a welding groove surface II (12), and the throttle plate (7) and the throttle front seat (6) are integrated into one body by welding on the welding groove surface II (12); The combination of the throttle plate (7) and the throttle rear seat (8) is installed flush with the throttle front seat (6). A welding groove surface III (13) is provided at the bottom end of the throttle rear seat (8). The throttle rear seat (8) and the throttle front seat (6) are combined into one body by welding at the welding groove surface III (13).

6. The throttling heat exchanger for a dilution refrigerator according to claim 1, characterized in that: The throttled spiral inner tube (9) is connected to the high-pressure outlet connecting tube (10). Along the flow direction of the high-pressure airflow, the inner diameter of the throttled spiral inner tube (9) is controlled between 0.6-1.0 mm, the tube wall is controlled within 0.3 mm, the spiral corrugation is a counterclockwise spiral, the spiral major diameter is controlled between 9-15 mm, the spiral pitch is controlled between 2-4 mm, and the total height of the spiral cylinder is controlled between 1 / 3-1 / 2 of the total length of the outer bellows (2) of the heat exchanger; The inlet of one end of the throttle rear spiral inner tube (9) away from the high-pressure outlet connecting tube (10) is inserted into the throttle rear seat (8). A welding groove surface IV (14) is provided at the connection between the top end of the throttle rear seat (8) and the throttle rear spiral inner tube (9). The throttle rear seat (8) and the throttle rear spiral inner tube (9) are integrated into one body by welding at the welding groove surface IV (14).

7. A method for manufacturing a throttling heat exchanger for a dilution refrigerator according to any one of claims 1 to 6, characterized in that: The specific manufacturing steps are as follows: S1: The outer bellows (2) of the heat exchanger is made of a material with low thermal conductivity, and its total length is controlled between 150-250 mm, wherein the length of the low-pressure outlet connecting pipe (1) and the low-pressure inlet connecting pipe (3) is controlled between 10-15 mm, the outer wall roughness of the outer bellows (2) of the heat exchanger is required to be less than 0.08, the inner wall roughness is required to be less than 0.4, and the wall thickness is required to be controlled between 0.2-0.4 mm. The bellows are subjected to thermal stress annealing treatment as a whole to make it have certain bendability characteristics; S2: The inner spiral tube (5) before throttling is made of a material with high thermal conductivity. The total height of the spiral cylinder is controlled between 1 / 2 and 2 / 3 of the total length of the outer bellows (2) of the heat exchanger. The inner diameter of the tube is controlled between 1 and 1.2 mm. The inner wall roughness is required to be less than 0.08 and the outer wall roughness is required to be less than 0.

2. S3: The throttle plate (7) is made of a material with high yield strength. The aperture is the average aperture and the aperture is as uniform as possible. The aperture is magnified using a microscope and the average aperture is calculated using the method of calculating the area of the partition and converting the scale. The roughness of all surfaces of the throttle plate is required to be less than 0.04, and the outer diameter is controlled between 5-6 mm. S4: The throttle front seat (6) and the throttle rear seat (8) are made of high yield strength materials. The roughness of all contact surfaces with the small holes is required to be less than 0.04, and the roughness of the surface not in contact with the small holes is required to be less than 0.4; S5: The throttled spiral inner tube (9) is made of a material with high thermal conductivity. The total height of the spiral cylinder is controlled between 1 / 3 and 1 / 2 of the total length of the heat exchanger outer bellows (2). The inner diameter of the tube is controlled between 0.6 and 1.0 mm. The inner wall roughness is required to be less than 0.08 and the outer wall roughness is required to be less than 0.

2. S6: During the actual installation process, there is no direct connection between the outer bellows (2) of the heat exchanger and the inner tube combination of the pre-throttling spiral inner tube (5), the pre-throttling seat (6), the throttling plate (7), the post-throttling seat (8) and the post-throttling spiral inner tube (9). The outer bellows (2) of the heat exchanger is connected to the dilution refrigeration system through the low-pressure outlet connecting pipe (1) of the heat exchanger and the low-pressure inlet connecting pipe (3) of the heat exchanger, and the inner tube combination is connected to the dilution refrigeration system through the high-pressure inlet connecting pipe (4) and the high-pressure outlet connecting pipe (10), thereby forming a throttling heat exchanger for a dilution refrigerator.

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