Channel type pre-cooling heat exchanger

Abstract

The application discloses a channel type precooling heat exchanger, which comprises a refrigerator cold head and a heat exchanger. The refrigerator cold head comprises a base and a slit body. The slit body is a cylindrical structure, and the central hole of the slit body is a variable-diameter structure, so that the inner wall of the slit body is annular stepped, forming a large-aperture section and a small-aperture section. A plurality of slits are formed in the wall of the slit body, and the slits pass through from one end of the slit body to the other end. The small-aperture section is fixed with the base. The regenerator shell of the refrigerator is sleeved on the outer wall of the large-aperture section, and the pulse tube shell of the refrigerator is inserted into the central hole of the large-diameter section and abuts against the annular step and the inner wall of the large-diameter section. The cover plate of the heat exchanger is provided with a sink, and the base is provided with a boss matched with the sink. The base is fixed by being embedded into the sink through the boss. The precooling heat exchanger and the refrigerator cold head are integrated, the contact thermal resistance between the precooling stage cold head and the precooling heat exchanger is reduced, the heat transfer efficiency is improved, and the heat transfer temperature difference is reduced.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of low-temperature refrigeration, in particular to a channel type pre-cooling heat exchanger. BACKGROUND

[0002] For nearly half a century, space exploration technology has developed rapidly. The development of various fields such as earth observation, communication satellites and space exploration has driven the progress of related technologies. In the temperature range of 2K-4K, the throttling low-temperature refrigerator with pre-cooling has higher operating efficiency and becomes the mainstream of mechanical refrigeration technology. At the same time, as one of the key components of the throttling refrigerator, the pre-cooling heat exchanger also needs to have higher heat exchange efficiency and more compact structure arrangement.

[0003] The pre-cooling heat exchanger mentioned in the document "Research on the Principle of JT Refrigerator in Liquid Helium Temperature Range Based on Thermodynamics" (Author: Liu Dongli) is a copper square structure, which has three channels inside to increase the area of the heat exchanger. Finally, it is in contact with the refrigerator cold head through screw compression, and the contact surface uses indium sheet to reduce the contact thermal resistance. The internal channel will be bent inside the pre-cooling heat exchanger, which will enhance the heat exchange. The heat exchanger of this structure uses a live contact method to couple with the refrigerator cold head, and uses thermal grease or indium sheet to improve the heat transfer efficiency. However, due to a series of reasons such as deformation of the part material, inability to ensure the uniformity of the thermal grease or the contact condition when placing the indium sheet, there is a large temperature difference between the cold head and the pre-cooling heat exchanger, the heat transfer efficiency is greatly reduced, the working gas temperature cannot be pre-cooled to the specified value, and then the performance of the throttling refrigerator is affected. Secondly, the overall structure can only be maintained for a short time, has poor reliability, needs to be reassembled every time, the operation is more complicated, and the experimental cost is also increased.

[0004] The pre-cooling heat exchanger disclosed in the document with publication number CN110749115A is a coil type, which uses interference fit between the pipe and the spiral groove opened on the pre-cooler to realize the pre-cooling of the gas. This heat exchanger not only can directly replace the cold head of the pre-cooling machine, but also can be used as the supporting bottom plate of the cold screen. There is a slit structure in the middle to increase the heat exchange area and improve the pre-cooling efficiency. If the pre-cooling heat exchanger of this structure wants to ensure the heat exchange efficiency, it needs to use a pipe with a longer size, so the overall size is larger, and the spiral winding method also causes a larger flow resistance inside the heat exchanger, resulting in a larger flow loss. At the same time, the structure of the pre-cooling heat exchanger of this structure is relatively complex, and the interference fit at each position of the pipe and the pre-cooling heat exchanger cannot be guaranteed, and the forming is also more difficult.

[0005] Therefore, the heat transfer effect between the pre-cooling heat exchanger and the refrigerator cold head of the above two existing technologies cannot be guaranteed, and then the pre-cooling efficiency of the working gas cannot be guaranteed. SUMMARY

[0006] The technical problem to be solved by the present application is that in the prior art, the cold head and the pre-cooling heat exchanger are designed in a split type, the structure assembly is complex, and the structural stability and heat conduction cannot be guaranteed.

[0007] The present application solves the above technical problems by the following technical means:

[0008] A channel type pre-cooling heat exchanger, comprising a refrigerator cold head (1) and a heat exchanger (2); the refrigerator cold head (1) comprises a base (11) and a slit body (12); the slit body (12) is a cylindrical structure, the center hole of the slit body (12) is a variable diameter structure, so that the inner wall of the slit body (12) is annular stepped, forming a large aperture section (121) and a small aperture section (122); a plurality of slits are formed on the cylinder wall of the slit body (12); the slits pass through from one end to the other end of the slit body (12); the end of the small aperture section (122) is fixed to the base (11); the regenerator shell (31) of the refrigerator is sleeved on the outer wall of the large aperture section (121), and the pulse tube shell (32) of the refrigerator is inserted into the center hole of the large diameter section and abuts against the annular step and the inner wall of the large diameter section; gas enters the slits of the large aperture section (121) from the annular cavity between the regenerator shell (31) and the pulse tube shell (32) until the small aperture section (122), and then enters the inner cavity of the pulse tube shell (32) from the slits of the small aperture section (122);

[0009] The heat exchanger cover plate is provided with a sink, and the base (11) is provided with a boss (111) matched with the sink; the base (11) is fixed by embedding the boss (111) into the sink.

[0010] The pre-cooling heat exchanger and the refrigerator cold head are fixed together by the embedding of the boss and the sink, which reduces the contact thermal resistance between the pre-cooling stage cold head and the pre-cooling heat exchanger, improves the heat transfer efficiency, reduces the heat transfer temperature difference, and also optimizes the structure inside the pre-cooling heat exchanger, thereby enhancing the heat exchange effect.

[0011] Further, the outer wall of the slit body (12) and the base (11) and the base (11) form an annular groove (13), and the appearance is inserted into the annular groove (13) for fixation.

[0012] Further, the boss (111) and the sink bottom wall are welded and fixed by vacuum brazing.

[0013] Further, the heat exchanger further comprises a base body, the base body comprises an inlet (6) and an outlet (7), and the inlet (6) and the outlet (7) are connected by a serpentine channel; the cover plate covers the serpentine channel to form the side wall of the serpentine channel (23).

[0014] Further, a flow guide wire mesh (8) is fixed at the inlet (6).

[0015] Further, a threaded hole for mounting a heating resistor and a temperature measuring hole (4) for mounting a temperature sensor are further formed on the base.

[0016] Further, the slit is radially formed.

[0017] Further, the slit penetrates the inner and outer walls of the slit body (12).

[0018] Further, the slit penetrates the inner wall of the slit body (12), and the end towards the outer wall of the slit body (12) is a blind end.

[0019] Further, the refrigerator cold head (1) and the heat exchanger cover plate (21) are processed by a red copper bar and a plate lathe, and a slit is processed by wire cutting.

[0020] The advantages of the present application are that the pre-cooling heat exchanger is integrated with the refrigerator cold head, the contact thermal resistance between the pre-cooling stage cold head and the pre-cooling heat exchanger is reduced, the heat transfer efficiency is improved, the heat transfer temperature difference is reduced, the chamfered transition at the corner of the groove 23 inside the pre-cooling heat exchanger is adopted, the internal flow loss is reduced, and the heat exchange effect is enhanced. The base is embedded and fixed with the shell of the pre-cooling heat exchanger, the welding sheet is placed on the contact plane, and the welding method is plane vacuum brazing. Compared with the fillet welding for the root, the plane welding increases the welding area, improves the welding stability, makes the welding of the contact surface of the boss and the sink more firm, and the strength of the welded part is higher; at the same time, the structure form of the sink and the boss cooperation can not only ensure the assembly accuracy, but also complete the positioning of the structure before welding, reduce the welding difficulty, and reduce the risk of leakage or deformation caused by incomplete welding. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 It is a schematic diagram of the overall structure of the groove type heat exchanger in the embodiment of the present application.

[0022] Figure 2 It is a schematic diagram of the cross-sectional structure of the groove type heat exchanger in the embodiment of the present application.

[0023] Figure 3 It is Figure 2 It is a schematic diagram of the assembly structure of the regenerator shell and the pulse tube shell with the refrigerant.

[0024] Figure 4 It is a schematic diagram of the cross-sectional structure of the heat exchanger in the embodiment of the present application.

[0025] Figure 5 It is a schematic diagram of the inlet and outlet cross-sectional structure of the heat exchanger in the embodiment of the present application. DETAILED DESCRIPTION

[0026] In order to make the purposes, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be described clearly and completely below in conjunction with the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work fall within the scope of protection of the present application.

[0027] As shown in the drawings, Figure 1 The novel channel type pre-cooling heat exchanger of the present embodiment comprises a refrigerator cold head 1 and a heat exchanger 2, and the heat exchanger 2 comprises a cover plate 21 and a heat exchanger base 22. In order to strengthen heat exchange, all parts are made of high thermal conductivity material, red copper. The refrigerator cold head 1 comprises a base 11 and a slit body 12; the slit body 12 is a cylindrical structure, which is consistent with the shape of the regenerator shell 31 and the pulse tube shell 32 of the refrigerant, to ensure the installation accuracy. As shown in the drawings, Figure 2 The central hole of the slit body 12 is a variable-diameter structure, so that the inner wall of the slit body 12 is annular stepped, forming a large-aperture section 121 and a small-aperture section 122; a plurality of slits are formed on the wall of the slit body 12; the slits pass through from one end of the slit body 12 to the other end; the small-aperture section 122 is fixedly connected with the heat exchanger cover plate 21 through the base 11, and the large-aperture section 121 protrudes from the surface of the base 11. As shown in the drawings, Figure 3 The regenerator shell 31 of the refrigerator is sleeved on the outer wall of the large-aperture section 121, and the pulse tube shell 32 of the refrigerator is inserted into the central hole of the large-diameter section and abuts against the annular step and the inner wall of the large-diameter section; the gas enters the slits of the large-aperture section 121 from the annular cavity between the regenerator shell 31 and the pulse tube shell 32, and then enters the inner cavity of the pulse tube shell 32 from the slits of the small-aperture section 122.

[0028] The slits are made by wire cutting process, the width is controlled to be 0.25 mm, and the number is controlled to be 30, so as to increase the heat exchange area of the slits as much as possible; a 1 mm deep annular groove 13 is formed on the contact surface between the slit body 12 and the base 11, which is used for welding the cold head and the regenerator shell 31 of the refrigerator; two threaded holes are formed on the base 11, which are used for connecting the cold chain between the multi-stage refrigerator.

[0029] In the present embodiment, the slits are uniformly arranged. The slits pass through the inner and outer walls of the slit body 12. Or the slits pass through the inner wall of the slit body 12, and the end towards the outer wall of the slit body 12 is a blind end. For the case of passing through the inner and outer walls, when the regenerator shell 31 is sleeved on the outer wall of the large-diameter section and is sealingly welded and fixed with the annular groove, the slits can be effectively blocked to avoid gas leakage.

[0030] As shown in the drawings, Figure 2 , Figure 3As shown, the cover plate 21 is provided with a sink groove, and the side of the base 11 facing the cover plate 21 is provided with a boss 111 corresponding to the sink groove. The base 11 and the cover plate 21 are welded and fixed by vacuum brazing through embedding the boss 111 into the sink groove. The diameter of the contact part of the boss 111 is ensured to be negative tolerance, and the embedding depth is about 2mm, which can ensure the stability of welding. The cover plate 21 of the heat exchanger and the heat exchanger base 22 are welded by vacuum brazing. Figure 4 As shown, the heat exchanger base 22 is provided with a temperature measuring hole 4 for installing a rhodium iron thermometer to measure the temperature of the pre-cooling heat exchanger during the experiment. Meanwhile, the base is provided with a heating resistance mounting threaded hole 5, and a sheet type heating resistance can be pressed to the surface of the pre-cooling heat exchanger by a screw to measure the pre-cooling amount of the pre-cooling heat exchanger during the experiment, and can also be used as a heating load for rewarming after the experiment. The positions of the heating resistance mounting hole and the temperature measuring hole can be set at any position of the heat exchanger base 22 according to the needs, as long as the heating resistance and the temperature sensor can be fixed on the heat exchanger and can be ensured to be attached.

[0031] As shown in Figure 5 As shown, the pre-cooling heat exchanger base 22 is provided with an inlet 6 and an outlet 7, and the inlet 6 and the outlet 7 are connected by a serpentine channel 23. The cover plate 21 covers the serpentine channel 23 to form the side wall of the serpentine channel 23. The inlet hole 6 is stepped, and several copper guide wire meshes 8 are placed on the step, and then fixed by pressing the inlet tube 9. The mesh number of the guide wire mesh 8 is 100, which is to improve the flow of the gas entering the pre-cooling heat exchanger and enhance the heat exchange effect. The inlet tube 9 is inserted into the inlet hole by about 3mm, and the vacuum brazing is performed at the connection 13 to realize the connection between the inlet tube and the pre-cooling heat exchanger base 22. The outlet tube 10 is inserted into the outlet 7 by about 3mm, and the vacuum brazing is performed at the connection 14 to realize the connection between the pre-cooling heat exchanger base 22 and the outlet tube 10. In this embodiment, the corners of the channel 23 are chamfered to transition smoothly, reducing internal flow loss.

[0032] The manufacturing process of the new channel type pre-cooling heat exchanger is as follows: the refrigerator cold head 1 and the heat exchanger cover plate 21 are processed by red copper bar and plate, and the slit is processed by wire cutting; the heat exchanger base is first processed into a shape by a plate lathe, and then the internal channel is processed by numerical milling; then the wire mesh is placed at the inlet hole 6, and the refrigerator shell, the heat exchanger cover plate 21, the heat exchanger base 22, the inlet tube 9 and the outlet tube 10 are assembled and fixed, the solder is applied at the welding point, and the solder sheet is placed at the welding surface, and finally it is put into the vacuum brazing furnace for welding, thereby forming the new channel type pre-cooling heat exchanger.

[0033] In use, first, the cooling machine is cooled, the cooling head 1 of the cooling machine reaches the lowest temperature through the heat exchange of the slit, and then the temperature is transmitted to the cover plate 21 of the heat exchanger. Since the cooling head 1 and the cover plate 21 and the base 22 are welded as a whole, the heat transfer temperature difference is small, and the heat transfer efficiency is high. The temperature of the heat exchanger base 22 is approximately equal to the temperature of the cooling head 1 of the cooling machine. The working gas is connected to the gas inlet pipe 9 of the pre-cooling heat exchanger, and the pre-cooling effect is achieved through the heat exchange with the internal channel of the heat exchanger base 22. Finally, the cooled working gas is discharged through the gas outlet pipe 10, and the next process is continued.

[0034] The specific operation steps of the application in use are as follows:

[0035] (1) The new channel type pre-cooling heat exchanger is installed in the whole machine system, and the thermometer and the heating resistance are installed. In order to reduce the radiation heat loss of the whole pre-cooling heat exchanger, the surface needs to be polished clean and wrapped with multiple layers of materials.

[0036] (2) In order to reduce the heat loss caused by the convection heat exchange between the cooling machine and the room temperature, the whole system needs to be evacuated after the heat exchanger is installed in the whole machine system, and the vacuum degree needs to be maintained at 1x10 -3 Then the internal pipeline is replaced with gas for 2-3 times to ensure that there is no impurity gas in the pipeline.

[0037] (3) Turn on the cooling machine and observe the value of the thermometer on the cooling head of the cooling machine. Let the cooling machine first drop to the lowest temperature. When the cooling machine is working, the pre-cooling heat exchanger is also pre-cooled and cooled.

[0038] (4) After the temperatures of the cooling head of the cooling machine and the pre-cooling heat exchanger are stable and approximately equal, a certain amount of helium is filled into the pipeline, the compressor in the circuit is turned on, and the gas flows in the pipeline. The gas is pre-cooled and cooled by the pre-cooling heat exchanger. The temperature of the gas can be inferred by monitoring the temperature values of the heat exchanger, the inlet and outlet gas pipes of the heat exchanger, and the pre-cooling efficiency of the pre-cooling heat exchanger can be obtained.

[0039] (5) At the end of the operation, the pre-cooling heat exchanger still has a low temperature, and the cooling machine needs to be turned off, the heating resistance is connected, and the pre-cooling heat exchanger is heated. After the temperature value returns to room temperature, the heating is turned off to protect the system components.

[0040] In this embodiment, the pre-cooling heat exchanger and the cooling head of the cooling machine are integrated, the contact thermal resistance between the pre-cooling stage cooling head and the pre-cooling heat exchanger is reduced, the heat transfer efficiency is improved, the heat transfer temperature difference is reduced, and the chamfered transition at the corner of the channel 23 in the pre-cooling heat exchanger is adopted to reduce the internal flow loss and enhance the heat exchange effect. The base is embedded in the shell of the pre-cooling heat exchanger, which can ensure the assembly accuracy and make the convex and the concave contact surface more firm.

[0041] The above examples are only used to illustrate the technical solutions of the present application, but not to limit the present application; although the present application has been described in detail with reference to the foregoing examples, those ordinarily skilled in the art should understand: the technical solutions recorded in the foregoing examples can still be modified, or some technical features can be replaced equivalently; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A channel type precooling heat exchanger, characterized by, The application relates to a refrigeration machine cold head (1) and a heat exchanger (2), wherein the refrigeration machine cold head (1) comprises a base (11) and a slit body (12); the slit body (12) is in a cylindrical structure, the central hole of the slit body (12) is in a variable-diameter structure, the inner wall of the slit body (12) is annular and stepped, a large-aperture section (121) and a small-aperture section (122) are formed, a plurality of slits are formed on the wall of the slit body (12), the slits pass through from one end of the slit body (12) to the other end, the end of the small-aperture section (122) is fixed to the base (11), the regenerator shell (31) of the refrigeration machine is sleeved on the outer wall of the large-aperture section (121), the pulse tube shell (32) of the refrigeration machine is inserted into the central hole of the large-diameter section and abuts against the annular step and the inner wall of the large-diameter section, gas enters the slits of the large-aperture section (121) from the annular cavity between the regenerator shell (31) and the pulse tube shell (32) and then enters the small-aperture section (122), and then enters the inner cavity of the pulse tube shell (32) from the slits of the small-aperture section (122); The heat exchanger (2) further comprises a heat exchanger cover plate (21), the heat exchanger cover plate (21) is provided with a sink, the base (11) is provided with a boss (111) matched with the sink, and the base (11) is fixed by being embedded into the sink through the boss (111).

2. A channel type pre-cooling heat exchanger according to claim 1, characterized in that, A ring groove (13) is formed on the contact surface between the periphery of the slit body (12) and the base (11).

3. A channel type pre-cooling heat exchanger according to claim 1 or 2, characterized in that, The boss (111) and the bottom wall of the sink are welded and fixed by vacuum brazing.

4. The channel type pre-cooling heat exchanger according to claim 1 or 2, characterized in that, The heat exchanger further comprises a base body, the base body comprises an inlet (6) and an outlet (7), and the inlet (6) and the outlet (7) are communicated through a serpentine channel; the cover plate covers the serpentine channel to form the side wall of the serpentine channel (23).

5. A channel type pre-cooling heat exchanger according to claim 4, wherein A flow guide wire net (8) is fixed at the inlet (6).

6. A channel type pre-cooling heat exchanger according to claim 4, wherein A threaded hole for mounting a heating resistor and a temperature measuring hole (4) for mounting a temperature sensor are further formed on the base body.

7. A channel type pre-cooling heat exchanger according to claim 1 or 2, characterized in that, The slits are formed by radiation.

8. The channel type pre-cooling heat exchanger according to claim 1 or 2, characterized in that, The slits pass through the inner and outer walls of the slit body (12).

9. The channel type pre-cooling heat exchanger according to claim 1 or 2, characterized in that, The slits pass through the inner wall of the slit body (12), and one end of the slits towards the outer wall of the slit body (12) is a blind end.

10. The channel type pre-cooling heat exchanger according to claim 1 or 2, characterized in that, The refrigeration machine cold head (1) and the heat exchanger cover plate (21) are processed by a red copper bar and a plate lathe, and the slits are processed by wire cutting.

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