Throttling heat exchanger for dilution refrigerator and manufacturing method

Abstract

The application discloses a throttling heat exchanger for a dilution refrigerator and a manufacturing method, and particularly relates to the field of refrigeration and cryogenic engineering, and comprises a heat exchanger outer bellows and a heat exchanger inner core arranged in the inner cavity of the heat exchanger outer bellows; the heat exchanger outer bellows comprises 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 arranged in a spiral bellows shape. The application realizes the rotational flow strengthening convection heat exchange of high-pressure and low-pressure fluids in a limited space in the form of the combination of the spiral bellows outer pipe and the spiral inner pipe, and the throttling small holes are introduced into the heat exchanger to sufficiently precool the throttling small holes in the stable stage of the dilution refrigeration system, so that the integration of the throttling small holes and the throttling heat exchanger is realized, the design of the variable aperture before and after throttling is more consistent with the change of the physical property parameters of helium at an extremely low temperature, and the optimization of the throttling heat exchange precooling process and the throttling process and the performance improvement of the dilution refrigerator have very positive significance.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of refrigeration and cryogenics, and more particularly, to a throttling heat exchanger for a dilution refrigerator and a manufacturing method. BACKGROUND

[0002] The dilution refrigerator is a research hotspot in the field of mK temperature range cryogenic refrigerators, which has the advantages of continuous refrigeration at 100 mK temperature, no electromagnetic interference and low vibration, and has broad application prospects in important fields such as quantum information technology, extreme experimental conditions construction and deep space exploration. The dilution refrigerator uses helium-3 / helium-4 mixture as the working medium, and the entire dilution refrigeration cycle includes pulse tube pre-cooling, throttling heat exchange pre-cooling, throttling, condensation heat exchange, dilution process, backflow heat exchange, evaporation process and compression process. Among them, the throttling heat exchange pre-cooling process and the throttling process are the key stages for reducing the temperature from about 4.2K to about 0.7K in the dilution refrigeration cycle, and play an important role in stabilizing the entire dilution refrigeration cycle in the system. The throttling heat exchange pre-cooling process is the prerequisite for ensuring the smooth progress of the throttling process.

[0003] The dilution refrigerator industry aims to integrate the key components of the throttling heat exchange pre-cooling process and the throttling process. In an ideal case, a throttling heat exchanger for a dilution refrigerator should achieve the following three functions:

[0004] 1) Achieve efficient and stable throttling heat exchange process in limited space. The throttling heat exchange process is actually a process of fully exchanging heat between low-pressure cold fluid (about 0.7K) and high-pressure hot fluid (about 4.2K) in a counterflow heat exchanger. Because of the throttling effect in the heat exchange process, it is called throttling heat exchange process. In the dilution refrigeration cycle, the good implementation of the throttling process requires the temperature before throttling to be lower than 1.8K, which requires the throttling heat exchanger to fully exchange heat between cold and hot fluids and fully recover the cold energy of low-pressure cold fluid to ensure the stability of the throttling process. Due to the low pressure of the cold fluid and the limited space of the entire system structure, appropriate rotation will help improve the heat exchange between cold and hot fluids in limited space, which requires the introduction of spiral corrugation and spiral tube structure to achieve stable and efficient throttling heat exchange process.

[0005] 2) Achieve stable throttling process. The throttling process is the process of converting the working medium from high-temperature liquid to low-temperature mixed gas-liquid mixture, which is the key to further reducing the temperature in the initial stage of cooling and ensuring the stability of the 0.7-4K temperature range in the cycle process. The throttling process requires micron-sized small holes and a temperature lower than 1.8K before throttling, so the size of the throttling plate and sufficient pre-cooling are extremely critical.

[0006] 3) has small heat loss. In the very low temperature area below 2K, the influence of heat loss on the performance of heat exchanger is very obvious, which requires the heat loss of the component itself to be minimized.

[0007] In the conventional dilution refrigerator, the throttling heat exchanger and the throttling plate are generally arranged separately, and the throttling heat exchanger usually adopts a wave type bellows. The wave type bellows has the characteristics of certain vibration reduction, but the heat exchange strengthening ability of the heat exchanger is limited, which leads to the need to lengthen the length of the throttling heat exchanger to realize the strengthening of heat exchange. However, due to space limitations, the length of the throttling heat exchanger is difficult to reach the ideal state. For the external throttling plate structure, not only a long tube needs to be additionally introduced to fix its position, but also sufficient precooling cannot be obtained, which affects the time for the dilution refrigeration cycle to reach stability to a certain extent, and the external small hole is easily affected by heat loss, which needs sufficient precooling to avoid these problems. Therefore, the separate arrangement of the conventional throttling heat exchanger and the throttling plate has great limitations in realizing the above three requirements. SUMMARY

[0008] In order to overcome the above-mentioned defects of the prior art, embodiments of the present application provide a throttling heat exchanger for a dilution refrigerator and a manufacturing method.

[0009] To achieve the above object, the present application provides the following technical scheme: a throttling heat exchanger for a dilution refrigerator, comprising a heat exchanger outer bellows and a heat exchanger inner core arranged in the inner cavity of the heat exchanger outer bellows.

[0010] The heat exchanger outer bellows comprises 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 arranged as a spiral bellows.

[0011] The heat exchanger inner core comprises, from top to bottom, a throttling after spiral inner pipe, a throttling after seat, a throttling plate, a throttling before seat and a throttling before spiral inner pipe, the top end of the throttling after spiral inner pipe is fixedly arranged on the high pressure outlet connecting pipe, and the bottom end of the throttling before spiral inner pipe is fixedly arranged with the heat exchanger high pressure inlet connecting pipe.

[0012] In a preferred embodiment, the heat exchanger low pressure outlet connecting pipe and the heat exchanger low pressure inlet connecting pipe have equal diameters and are smaller than the inner diameter of the heat exchanger outer bellows, and the spiral bellows of the heat exchanger outer bellows is clockwise in the direction of low pressure gas flow.

[0013] The inner diameters of the heat exchanger low pressure outlet connecting pipe and the heat exchanger low pressure inlet connecting pipe are controlled to be between 16-25mm, the thread spiral angle is controlled to be between 5°-10°, the bellows wave height is controlled to be between 1.5-3mm, the bellows wavelength is controlled to be between 3-6mm, and the wave distance and the wavelength are kept 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 gas is opposite to the flow direction of the low-pressure gas in the outer corrugated pipe of the heat exchanger.

[0015] In the flow direction of the high-pressure gas, the inner diameter of the pre-throttling spiral inner tube is controlled to be between 1-1.2 mm, the wall thickness of the pre-throttling spiral inner tube is controlled to be within 0.5 mm, the corresponding spiral corrugation of the pre-throttling spiral inner tube is counterclockwise spiral, the spiral major diameter is controlled to be between 9-15 mm, and the spiral pitch is controlled to be between 3-6 mm.

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

[0017] A welding groove surface I is formed at the junction of the inner side of the pre-throttling seat and the pre-throttling spiral inner tube, and the inner side of the pre-throttling seat and the pre-throttling spiral inner tube are combined into one body by welding at the welding groove surface I.

[0018] In a preferred embodiment, a throttling small hole is formed in the center perforation of the throttling plate, the hole diameter of the throttling small hole is controlled to be between 25-40 μm, and the perforation and the post-throttling seat are installed flush.

[0019] A welding groove surface II is formed at the top end of the pre-throttling seat, and the throttling plate and the pre-throttling seat are combined into one body by welding at the welding groove surface II.

[0020] The combination of the throttling plate and the post-throttling seat is installed flush with the pre-throttling seat, a welding groove surface III is formed at the bottom end of the post-throttling seat, and the post-throttling seat and the pre-throttling seat are combined into one body by welding at the welding groove surface III.

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

[0022] The inlet of the post-throttling spiral inner tube away from the high-pressure outlet connecting pipe is inserted into the post-throttling seat, a welding groove surface IV is formed at the junction of the top end of the post-throttling seat and the post-throttling spiral inner tube, and the post-throttling seat and the post-throttling spiral inner tube are combined into one body by welding at the welding groove surface IV.

[0023] The application also comprises a manufacturing method of the throttling heat exchanger for dilution refrigerator, and the specific manufacturing steps are as follows:

[0024] S1: the outer corrugated pipe of the heat exchanger is made of a material with low thermal conductivity, the total length is controlled to be between 150-250mm, the length of the low-pressure outlet connecting pipe and the low-pressure inlet connecting pipe is controlled to be between 10-15mm, the outer wall roughness of the outer corrugated pipe 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 to be between 0.2-0.4mm, and the whole corrugated pipe is subjected to heat stress annealing treatment, so as to have certain bendable characteristics;

[0025] S2: the spiral inner pipe before throttling is made of a material with high thermal conductivity, the total height of the spiral cylinder is controlled to be between 1 / 2-2 / 3 of the total length of the outer corrugated pipe of the heat exchanger, the inner diameter is controlled to be 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 throttling plate is made of a material with high yield strength, the hole diameter is the average hole diameter, the hole diameter is as uniform as possible, the average hole diameter is calculated by using a microscope to place the small and large holes, and using the method of calculating the average hole diameter by using the area of the partition and converting the scale, the roughness of all surfaces of the throttling plate is required to be less than 0.04, and the outer diameter is controlled to be between 5-6mm;

[0027] S4: the seat before throttling and the seat after throttling are made of a material with high yield strength, the roughness of all contact surfaces 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;

[0028] S5: the spiral inner pipe after throttling is made of a material with high thermal conductivity, the total height of the spiral cylinder is controlled to be between 1 / 3-1 / 2 of the total length of the outer corrugated pipe of the heat exchanger, the inner diameter is controlled to be 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: in the actual installation process, the inner pipe combination of the outer corrugated pipe of the heat exchanger and the spiral inner pipe before throttling, the seat before throttling, the throttling plate, the seat after throttling and the spiral inner pipe after throttling is not directly connected, the outer corrugated pipe of the heat exchanger is connected into the dilution refrigeration system through the low-pressure outlet connecting pipe and the low-pressure inlet connecting pipe of the heat exchanger, and the inner pipe combination is connected into the dilution refrigeration system through the high-pressure inlet connecting pipe and the high-pressure outlet connecting pipe, so as to jointly form a throttling heat exchanger for dilution refrigerator.

[0030] The technical effects and advantages of the application are as follows:

[0031] 1. The present application realizes efficient and stable throttling heat exchange process in limited space by the combination of spiral outer corrugated pipe and spiral inner pipe; the throttling small hole is built into the throttling heat exchanger, the throttling small hole is fully pre-cooled, and the stable throttling process is finally realized through the channels with different pipe diameters before and after throttling.

[0032] 2. The present application fully reduces the heat loss of the whole component through the surface treatment and structure of different regions, realizes the integration of the throttling heat exchanger and the throttling small hole, and has very positive significance for the structure design and optimization of the throttling heat exchanger of the dilution refrigerator and the promotion of the overall performance of the dilution refrigerator. BRIEF DESCRIPTION OF DRAWINGS

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

[0034] Figure 2 It is the heat exchanger outer corrugated pipe structure schematic diagram of the present application.

[0035] Figure 3 It is the heat exchanger outer corrugated pipe cross-section structure schematic diagram of the present application.

[0036] Figure 4 It is the heat exchanger inner core explosion structure schematic diagram of the present application.

[0037] Figure 5 It is the coupling structure cross-section diagram of the throttling plate and the high-pressure spiral inner pipe of the present application.

[0038] The figure mark is: 1, heat exchanger low-pressure outlet connecting pipe; 2, heat exchanger outer corrugated pipe; 3, heat exchanger low-pressure inlet connecting pipe; 4, heat exchanger high-pressure inlet connecting pipe; 5, spiral inner pipe before throttling; 6, throttling front seat; 7, throttling plate; 8, throttling rear seat; 9, spiral inner pipe after throttling; 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 technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0040] The present application provides a heat exchanger as follows Figures 1-3The throttling heat exchanger for a dilution refrigerator comprises a heat exchanger outer bellows 2 and a heat exchanger inner core arranged in the inner cavity of the heat exchanger outer bellows 2; 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 is arranged in a spiral bellows shape;

[0041] The heat exchanger low-pressure outlet connecting pipe 1 and the heat exchanger low-pressure inlet connecting pipe 3 have equal diameters and are smaller than the inner diameter of the heat exchanger outer bellows 2, and the spiral bellows of the heat exchanger outer bellows 2 is clockwise along the low-pressure gas flow direction; 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 to be between 16-25 mm, the thread spiral angle is controlled to be between 5°-10°, the bellows wave height is controlled to be between 1.5-3 mm, the bellows wavelength is controlled to be between 3-6 mm, and the wave distance and the wavelength are kept equal;

[0042] As Figure 4 The heat exchanger inner core comprises, from top to bottom, a throttling post-spiral inner pipe 9, a throttling post-seat 8, a throttling plate 7, a throttling pre-seat 6 and a throttling pre-spiral inner pipe 5, the throttling post-spiral inner pipe 9 is fixedly arranged at the top end of the high-pressure outlet connecting pipe 10, and the throttling pre-spiral inner pipe 5 is fixedly arranged at the bottom end of the heat exchanger high-pressure inlet connecting pipe 4;

[0043] The inner cavity of the throttling pre-spiral inner pipe 5 is connected with the heat exchanger high-pressure inlet connecting pipe 4, and the high-pressure gas flow direction is opposite to the low-pressure gas flow direction in the heat exchanger outer bellows 2; along the high-pressure gas flow direction, the inner diameter of the throttling pre-spiral inner pipe 5 is controlled to be between 1-1.2 mm, the wall thickness of the throttling pre-spiral inner pipe 5 is controlled to be less than 0.5 mm, the corresponding spiral bellows of the throttling pre-spiral inner pipe 5 is counterclockwise, the spiral major diameter is controlled to be between 9-15 mm, and the spiral pitch is controlled to be between 3-6 mm;

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

[0045] As Figure 5As shown, the inner side of the throttle front seat 6 is provided with a welding groove surface I 111 at the joint with the throttle front spiral inner tube 5, and the inner side of the throttle front seat 6 is combined with the throttle front spiral inner tube 5 in a welded manner at the welding groove surface I 111; the throttle plate 7 is provided with a throttle small hole at the center perforation, the aperture of the throttle small hole is controlled to be between 25-40 μm, the throttle plate 7 is installed flush after the perforation and the throttle rear seat 8; the throttle front seat 6 is provided with a welding groove surface II 112 at the top end, and the throttle plate 7 is combined with the throttle front seat 6 in a welded manner at the welding groove surface II 112; the combination of the throttle plate 7 and the throttle rear seat 8 is installed flush with the throttle front seat 6, and the throttle rear seat 8 is provided with a welding groove surface III 113 at the bottom end, and the throttle rear seat 8 is combined with the throttle front seat 6 in a welded manner at the welding groove surface III 113; the throttle rear spiral inner tube 9 is connected with the high-pressure outlet connecting pipe 10, along the high-pressure gas flow direction, the inner diameter of the throttle rear spiral inner tube 9 is controlled to be between 0.6-1.0 mm, the wall thickness is controlled to be less than 0.3 mm, the spiral corrugation is counterclockwise spiral, the spiral major diameter is controlled to be between 9-15 mm, the spiral pitch is controlled to be between 2-4 mm, and the spiral cylinder total height is controlled to be between 1 / 3-1 / 2 of the total length of the heat exchanger outer corrugated pipe 2; the inlet of the throttle rear spiral inner tube 9 far away from the high-pressure outlet connecting pipe 10 is inserted into the throttle rear seat 8, and the throttle rear seat 8 is provided with a welding groove surface IV 114 at the joint with the throttle rear spiral inner tube 9 at the top end, and the throttle rear seat 8 is combined with the throttle rear spiral inner tube 9 in a welded manner at the welding groove surface IV 114.

[0046] The application also includes a manufacturing method of the throttle heat exchanger for the dilution refrigerator, and the specific manufacturing steps are as follows:

[0047] S1: The heat exchanger outer corrugated pipe 2 is made of low thermal conductivity material, and the total length is controlled to be 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 to be between 10-15 mm, the outer wall roughness of the heat exchanger outer corrugated pipe 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 to be between 0.2-0.4 mm, and the whole corrugated pipe is subjected to thermal stress annealing treatment, so as to have certain bendable characteristics;

[0048] S2: The throttle front spiral inner tube 5 is made of high thermal conductivity material, the spiral cylinder total height is controlled to be between 1 / 2-2 / 3 of the total length of the heat exchanger outer corrugated pipe 2, the inner diameter is controlled to be between 1-1.2 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 high yield strength material, the small hole aperture is the average aperture, the aperture is as uniform as possible, the small and large holes are placed by using a microscope, the average aperture is calculated by using the method of calculating the area of the partition and converting the scale, the roughness of all surfaces of the throttle plate 7 is required to be less than 0.04, and the outer diameter is controlled to be between 5-6 mm;

[0050] S4: The throttle front seat 6 and the throttle rear seat 8 are made of high yield strength material, the roughness of all the contact surfaces 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 throttle rear spiral inner tube 9 is made of high thermal conductivity material, the total height of the spiral cylinder is controlled to be between 1 / 3 and 1 / 2 of the total length of the outer corrugated tube 2 of the heat exchanger, the inner diameter is controlled to be between 0.6 and 1.0 mm, the roughness of the inner wall is required to be less than 0.08, and the roughness of the outer wall is required to be less than 0.2;

[0052] S6: In the actual installation process, the outer corrugated tube 2 of the heat exchanger and the inner tube combination of the throttle front spiral inner tube 5, the throttle front seat 6, the throttle plate 7, the throttle rear seat 8 and the throttle rear spiral inner tube 9 are not directly connected, the outer corrugated tube 2 of the heat exchanger is connected into the dilution refrigeration system through the low-pressure outlet connecting pipe 1 and the low-pressure inlet connecting pipe 3 of the heat exchanger, and the inner tube combination is connected into the dilution refrigeration system through the high-pressure inlet connecting pipe 4 and the high-pressure outlet connecting pipe 10, thereby forming a throttle heat exchanger for a dilution refrigerator.

[0053] The embodiment is specifically: the spiral corrugated outer tube (the outer corrugated tube 2 of the heat exchanger) and the spiral inner tube combination (the throttle front spiral inner tube 5 and the throttle rear spiral inner tube 9) realize the rotational flow strengthening convection heat exchange of high and low pressure fluids in a limited space, the throttle small holes are introduced into the heat exchanger through the throttle plate 7, thereby precooling the throttle small holes in the stable stage of the dilution refrigeration system, avoiding the influence of heat leakage on the throttling process, the coupling structure realizes the integration of the throttle small holes and the throttle heat exchanger, and the design of the variable diameter before and after throttling is more close to the change of the physical property parameters of helium at extremely low temperature, thereby being more helpful to the stable throttling heat exchange process and the realization of the throttling process.

[0054] Finally, it should be pointed out that: first, in the description of the present application, it should be pointed out that unless otherwise specified and limited, the terms “installation”, “connection”, “connection” should be understood broadly, which can be mechanical connection or electrical connection, or the communication between two elements, or direct connection, “up”, “down”, “left”, “right” and the like are only used to represent the relative positional relationship, when the absolute position of the described object changes, the relative positional relationship may change;

[0055] Secondly: the present application discloses the structure involved in the embodiment, other structures can refer to the general design, and the same embodiment and different embodiments of the present application can be combined with each other under the condition of no conflict;

[0056] Finally: the above only for the preferred embodiments of the present application, and not for limiting the present application, any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present application, should be included in the scope of protection of the present application.

Claims

1. A throttling heat exchanger for a dilution refrigeration machine, comprising an outer bellows (2) and an inner core of the heat exchanger disposed within the inner cavity of the outer bellows (2), characterized in that: The heat exchanger external corrugated pipe (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. The heat exchanger external corrugated pipe (2) is configured as a spiral corrugated pipe. The heat exchanger core consists of, from top to bottom, a throttling spiral inner tube (9), a throttling rear seat (8), a throttling plate (7), a throttling front seat (6), and a throttling front spiral inner tube (5). The top end of the throttling spiral inner tube (9) is fixed to the high-pressure outlet connecting pipe (10), and the bottom end of the throttling front spiral inner tube (5) is fixed to the high-pressure inlet connecting pipe (4) of the heat exchanger.

2. The throttling heat exchanger for a dilution refrigeration machine 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 both smaller than the inner diameter of the heat exchanger outer corrugated pipe (2). The spiral corrugations of the heat exchanger outer corrugated pipe (2) along the low-pressure airflow direction are clockwise spirals. The inner diameter of the heat exchanger low-pressure outlet connecting pipe (1) and the heat exchanger low-pressure inlet connecting pipe (3) is 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 are kept equal.

3. A throttling heat exchanger for a dilution refrigeration machine according to claim 1, characterized in that: The inner cavity of the spiral inner tube (5) before throttling 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 pipe (2) of the heat exchanger. Along the direction of high-pressure airflow, the inner diameter of the pre-throttling spiral inner tube (5) is controlled between 1 and 1.2 mm, the wall thickness of the pre-throttling spiral inner tube (5) is controlled within 0.5 mm, the corresponding spiral corrugation of the pre-throttling spiral inner tube (5) is a counterclockwise spiral, the large diameter of the spiral is controlled between 9 and 15 mm, and the spiral pitch is controlled between 3 and 6 mm.

4. A throttling heat exchanger for a dilution refrigeration machine according to claim 3, characterized in that: 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) at the end away from the high pressure inlet connecting pipe (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 throttling front seat (6) and the throttling front spiral inner tube (5). The inner side of the throttling front seat (6) and the throttling front spiral inner tube (5) are combined into one piece by welding on the welding groove surface I (11).

5. A throttling heat exchanger for a dilution refrigeration machine according to claim 1, characterized in that: The throttling plate (7) has a throttling hole in the center. The diameter of the throttling hole is controlled between 25-40μm. After the hole is perforated, it is flush with the throttling seat (8). The top of the throttling front seat (6) is provided with a welding groove surface II (12), and the throttling plate (7) and the throttling front seat (6) are combined into one piece by welding on the welding groove surface II (12); The throttling plate (7) and the throttling rear seat (8) are mounted flush with the throttling front seat (6). The bottom end of the throttling rear seat (8) is provided with a welding groove surface Ⅲ (13), and the throttling rear seat (8) and the throttling front seat (6) are combined into one piece by welding on the welding groove surface Ⅲ (13).

6. A throttling heat exchanger for a dilution refrigeration machine according to claim 1, characterized in that: The throttling spiral inner tube (9) is connected to the high-pressure outlet connecting pipe (10). Along the high-pressure airflow direction, the inner diameter of the throttling 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 counterclockwise spiral, the spiral large 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 and 1 / 2 of the total length of the heat exchanger outer corrugated tube (2). The inlet of the throttling spiral inner tube (9) away from the high pressure outlet connecting pipe (10) is inserted into the throttling seat (8). A welding groove surface Ⅳ (14) is opened at the connection between the top of the throttling seat (8) and the throttling spiral inner tube (9). The throttling seat (8) and the throttling spiral inner tube (9) are combined into one piece by welding on the welding groove surface Ⅳ (14).

7. A method for manufacturing a throttling heat exchanger for a dilution refrigeration machine as described in any one of claims 1-6, characterized in that, The specific manufacturing steps are as follows: S1: The heat exchanger outer corrugated pipe (2) is made of a material with low thermal conductivity. Its total length is controlled between 150-250mm. The lengths of the low-pressure outlet connecting pipe (1) and the low-pressure inlet connecting pipe (3) are controlled between 10-15mm. The outer wall roughness of the heat exchanger outer corrugated pipe (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 0.2-0.4mm. The corrugated pipe is subjected to thermal stress annealing treatment to give it certain bendability. S2: The spiral inner tube (5) before throttling is made of a material with high thermal conductivity. The total height of its spiral cylinder is controlled between 1 / 2 and 2 / 3 of the total length of the outer corrugated tube (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 throttling plate (7) is made of a material with high yield strength. The aperture of the small hole is the average aperture. The aperture should be as uniform as possible. The small hole is magnified with a microscope. The average aperture is calculated by calculating the area of ​​the partition and converting the scale. The surface roughness of all surfaces of the throttling plate should be less than 0.

04. The outer diameter should be controlled between 5-6 mm. S4: The throttling front seat (6) and the throttling rear seat (8) are made of high yield strength material. The surface roughness of all surfaces in contact with the orifice is required to be less than 0.04, and the surface roughness of surfaces not in contact with the orifice is required to be less than 0.

4. S5: The spiral inner tube (9) after throttling is made of a material with high thermal conductivity. The total height of its spiral cylinder is controlled between 1 / 3 and 1 / 2 of the total length of the outer corrugated tube (2) of the heat exchanger. 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: In actual installation, there is no direct connection between the heat exchanger outer corrugated pipe (2) and the inner tube assembly of the throttling front spiral inner tube (5), throttling front seat (6), throttling plate (7), throttling rear seat (8) and the throttling rear spiral inner tube (9). The heat exchanger outer corrugated pipe (2) is connected to the dilution refrigeration system through the heat exchanger low-pressure outlet connecting pipe (1) and the heat exchanger low-pressure inlet connecting pipe (3). 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), thus forming a throttling heat exchanger for a dilution refrigeration machine.

Images