A processing method for a 2K negative-pressure aluminum plate-fin heat exchanger

Abstract

The present invention provides a processing method for a 2K negative pressure aluminum plate-fin heat exchanger, which includes manufacturing a core body; manufacturing a header, and the process of manufacturing the header includes integrally forging the header; connecting the core body with the header to form a heat exchanger; performing normal temperature detection on the heat exchanger; performing low temperature detection on the heat exchanger; the step of performing low temperature detection on the heat exchanger includes evacuating each heat exchange channel in the heat exchanger and the closed device where the heat exchanger is located; when the vacuum degree is less than the first preset pressure threshold, obtaining the background leakage rate of the closed device and the background leakage rate of each heat exchange channel in the heat exchanger; performing a cold shock treatment on the heat exchanger to obtain the background leakage rate and vacuum degree of each heat exchange channel in the heat exchanger during the cooling process and the background leakage rate and vacuum degree of the closed device; when the temperature is cooled to the preset temperature threshold, performing low temperature helium mass spectrometry leak detection on the heat exchanger. The present invention can obtain a heat exchanger with a micro leakage rate, high mechanical strength, compact volume, and high cleanliness, and improve the processing efficiency and the finished product rate.

Description

Technical Field

[0001] The present invention belongs to the technical field of heat exchangers, and particularly relates to a processing method for a 2K negative pressure aluminum plate-fin heat exchanger. Background Art

[0002] A 2K negative pressure heat exchanger refers to a heat exchanger operating in the temperature ranges of 4K liquid helium and 2K superfluid helium, and can be used to recover the cold energy of a cryogenic system and improve the production rate of superfluid helium. The 2K negative pressure heat exchanger operates in a deep low-temperature and negative pressure environment, with a small heat transfer temperature difference on both sides, a drastic change in the physical properties of helium, and a phase transition between two physical states of 4K liquid helium and 2K superfluid helium. Therefore, the leak rate, heat transfer performance, pressure drop performance, and volume of the 2K negative pressure heat exchanger have a great impact on the performance of the deep low-temperature system, the construction, and operation costs of the heat exchanger. The mechanical, thermal, and electrical properties of metal materials change with temperature, especially with an obvious difference between the cryogenic environment and normal temperature. These changes have important impacts in the fields of cryogenic engineering, aerospace, cryogenic storage, superconducting materials, refrigeration, and energy.

[0003] In the production and manufacturing of existing 2K negative pressure aluminum plate-fin heat exchangers, generally only visual inspection and helium mass spectrometry leak detection at normal temperature are carried out on the heat exchanger. Low-temperature detection cannot be performed, and the sealing performance of the heat exchanger in a deep low-temperature environment cannot be accurately evaluated and tested, and leak detection under the design pressure cannot be carried out. At the same time, there is a lack of relatively standardized purging treatment and cleanliness detection processes, resulting in low efficiency and low yield in the production of 2K negative pressure aluminum plate-fin heat exchangers, and a high risk of welding impurities contaminating the cryogenic system. Summary of the Invention

[0004] Therefore, the technical problem to be solved by the present invention is to provide a processing method for a 2K negative pressure aluminum plate-fin heat exchanger, which can perform various detections on the 2K negative pressure aluminum plate-fin heat exchanger, including low-temperature helium mass spectrometry leak detection, and improve the processing efficiency and yield of the 2K negative pressure aluminum plate-fin heat exchanger.

[0005] To solve the above problems, the present invention provides a processing method for a 2K negative pressure aluminum plate-fin heat exchanger, including:

[0006] Manufacturing a core body;

[0007] Manufacturing a head, and the process of manufacturing the head includes integrally forging the head;

[0008] Connecting the core body with the head to form a heat exchanger;

[0009] Performing normal temperature detection on the heat exchanger, and the temperature range of the normal temperature detection is 20°C to 30°C;

[0010] Performing low-temperature detection on the heat exchanger, and the temperature range of the low-temperature detection is below -150°C;

[0011] Among them, the steps for low-temperature detection of the heat exchanger include:

[0012] Vacuumize each heat exchange channel in the heat exchanger and the closed device where the heat exchanger is located;

[0013] When the vacuum degree is less than the first preset pressure threshold, obtain the background leakage rate of the closed device and the background leakage rate of each heat exchange channel in the heat exchanger;

[0014] Perform cold shock treatment on the heat exchanger, and obtain the background leakage rate and vacuum degree of each heat exchange channel in the heat exchanger and the background leakage rate and vacuum degree of the closed device during the cooling process;

[0015] When the temperature is cooled to the preset temperature threshold, perform low-temperature helium mass spectrometry leak detection on the heat exchanger.

[0016] Optionally, the vacuumizing of each heat exchange channel in the heat exchanger and the closed device where the heat exchanger is located includes:

[0017] Vacuumize each heat exchange channel in the heat exchanger and the closed device where the heat exchanger is located through a mechanical pump;

[0018] When the vacuum degree of each heat exchange channel in the heat exchanger and the closed device where the heat exchanger is located is less than the first intermediate pressure threshold, turn on the roots pump to vacuumize each heat exchange channel in the heat exchanger and the closed device where the heat exchanger is located;

[0019] When the vacuum degree of each heat exchange channel in the heat exchanger and the closed device where the heat exchanger is located is less than the second intermediate pressure threshold, turn on the molecular pump to vacuumize each heat exchange channel in the heat exchanger and the closed device where the heat exchanger is located, so that the vacuum degree of each heat exchange channel in the heat exchanger and the closed device where the heat exchanger is located is less than the first preset pressure threshold;

[0020] The step of obtaining the background leakage rate of the closed device and the background leakage rate of each heat exchange channel in the heat exchanger when the vacuum degree is less than the first preset pressure threshold includes:

[0021] Connect the leak detection device to the closed device, and block the connection between the leak detection device and each heat exchange channel in the heat exchanger to obtain the background leakage rate of the closed device;

[0022] Connect the leak detection device to each heat exchange channel in the heat exchanger in turn, and block the connection between the leak detection device and the closed device to obtain the background leakage rate of each heat exchange channel in the heat exchanger;

[0023] The heat exchange channels of the heat exchanger include a cold fluid channel and a hot fluid channel;

[0024] The step of performing cold shock treatment on the heat exchanger and obtaining the background leakage rate and vacuum degree of each heat exchange channel in the heat exchanger and the background leakage rate and vacuum degree of the closed device during the cooling process includes:

[0025] Select the cold fluid channel with the largest volume as the first cooling channel, introduce liquid nitrogen into the first end of the first cooling channel, and discharge it from the second end of the first cooling channel, making the second end of the first cooling channel the discharge port;

[0026] Control the cooling rate of the first cooling channel to be less than or equal to 4 °C / min;

[0027] When the temperature difference between the first end and the second end of the first cooling channel is greater than the preset temperature difference threshold and the cooling rate is less than the preset rate threshold, introduce liquid nitrogen into the second end of the first cooling channel and discharge it from the first end of the first cooling channel, making the first end of the first cooling channel the discharge port;

[0028] After the temperature of the first cooling channel is cooled to the preset temperature threshold and there is no nitrogen discharged from the exhaust port of the first cooling channel, select the hot fluid channel with the largest volume as the second cooling channel, introduce liquid nitrogen into the first end of the second cooling channel, and discharge it from the second end of the second cooling channel, making the second end of the second cooling channel the discharge port;

[0029] Control the cooling rate of the second cooling channel to be less than or equal to 4 °C / min;

[0030] When the temperature difference between the first end and the second end of the second cooling channel is greater than the preset temperature difference threshold and the cooling rate is less than the preset rate threshold, introduce liquid nitrogen into the second end of the second cooling channel and discharge it from the first end of the second cooling channel, making the first end of the second cooling channel the discharge port;

[0031] After the temperature of the second cooling channel is cooled to the preset temperature threshold and there is no nitrogen discharged from the exhaust port of the second cooling channel, perform the low-temperature helium mass spectrometry leak detection;

[0032] Or perform a cold shock treatment on the heat exchanger, and obtain the background leak rate and vacuum degree of each heat exchange channel in the heat exchanger and the background leak rate and vacuum degree of the sealing device during the cooling process, including:

[0033] Put the heat exchanger into the cooling medium and perform an immersion cold shock treatment on the heat exchanger.

[0034] Optionally, the low-temperature helium mass spectrometry leak detection of the heat exchanger includes:

[0035] Select one heat exchange channel as the charging channel, charge helium into the charging channel, and let it stand for the first period of time;

[0036] Obtain the external leak data of the charging channel and the internal leak data between adjacent heat exchange channels;

[0037] Successively switch other heat exchange channels as the charging channels, and repeat the steps of charging helium into the charging channels and standing still for the first period of time until the external leakage data of the charging channels and the internal leakage data between adjacent heat exchange channels are obtained, until the external leakage data and internal leakage data of all heat exchange channels are obtained.

[0038] Optionally, the manufacturing of the core includes:

[0039] Processing fins, partitions and seals, where the fins, partitions and seals are fittings of the core;

[0040] Cleaning the fittings;

[0041] Assembling the core;

[0042] Welding the core, where the core is welded using the process of vacuum brazing;

[0043] Checking the geometric dimensions of the core;

[0044] When the geometric dimensions of the core meet the requirements, performing water injection leak detection on the core;

[0045] The manufacturing of the head includes:

[0046] Integrally forging the head;

[0047] Cleaning the head;

[0048] Processing the steel-aluminum joint;

[0049] Cleaning the steel-aluminum joint;

[0050] Welding the steel-aluminum joint to the head;

[0051] Checking the geometric dimensions of the whole formed by the head and the steel-aluminum joint;

[0052] When the geometric dimensions of the whole formed by the head and the steel-aluminum joint meet the requirements, performing X-ray detection on the butt weld;

[0053] When both the water injection leak detection of the core and the X-ray detection of the butt weld meet the requirements, connecting the core to the head to make a heat exchanger;

[0054] The connecting the core to the head to make a heat exchanger includes:

[0055] Welding the head to the core.

[0056] Optionally, the steps of performing normal temperature detection on the heat exchanger include:

[0057] Performing penetrant detection on the fillet weld;

[0058] When the fillet weld meets the requirements, performing geometric dimension detection on the heat exchanger;

[0059] When the geometric dimensions of the heat exchanger meet the requirements, the heat exchanger is integrally immersed for leak detection.

[0060] Optionally, the step of performing normal temperature detection on the heat exchanger includes:

[0061] When the integral immersion leak detection meets the requirements, a pressure test is performed on the heat exchanger;

[0062] The pressure test includes:

[0063] Inject pressure test gas into the heat exchange channels of the heat exchanger, raise the pressure to 10% of the specified test pressure, maintain for a second duration, and detect the air leakage of all welds and connection parts;

[0064] When there is no leakage, raise the pressure to 50% of the specified test pressure, and detect the air leakage of all welds and connection parts;

[0065] When there is no leakage, raise the pressure step by step by 10% of the specified test pressure, and detect the air leakage of all welds and connection parts until the test pressure is reached, maintain for a third duration, and detect the air leakage of all welds and connection parts;

[0066] Optionally, the step of performing normal temperature detection on the heat exchanger includes:

[0067] Perform an airtightness test on the heat exchanger;

[0068] The airtightness test includes:

[0069] Inject airtightness test gas into the heat exchange channels of the heat exchanger, raise the pressure to 10% of the specified test pressure, maintain for a fourth duration, and detect the air leakage of all welds and connection parts;

[0070] When there is no leakage, raise the pressure to 50% of the specified test pressure, and detect the air leakage of all welds and connection parts;

[0071] When there is no leakage, raise the pressure step by step by 10% of the specified test pressure, maintain for a fifth duration, and detect the air leakage of all welds and connection parts until the test pressure is reached.

[0072] Optionally, the step of performing normal temperature detection on the heat exchanger includes:

[0073] When the pressure test meets the requirements, perform normal temperature helium mass spectrometry leak detection on the heat exchanger;

[0074] The normal temperature helium mass spectrometry leak detection includes:

[0075] External leakage detection and internal leakage detection;

[0076] The external leakage detection includes:

[0077] Form a hood chamber with a polyethylene plastic bag, place the heat exchanger in the hood chamber, and exhaust the air in the hood chamber;

[0078] Introduce helium into the hood chamber until it reaches one atmospheric pressure;

[0079] When the volume of the hood chamber is greater than the preset volume, let it stand for the sixth period of time;

[0080] Vacuum each heat exchange channel of the heat exchanger to be lower than the second preset pressure threshold in sequence, and detect the leakage rate data;

[0081] The internal leakage detection includes:

[0082] Select one heat exchange channel in the heat exchanger as the channel to be measured;

[0083] Introduce helium into the adjacent heat exchange channels of the channel to be measured until it reaches one atmospheric pressure;

[0084] Vacuum the channel to be measured to be lower than the third preset pressure threshold, and maintain the pressure for the seventh period of time;

[0085] Detect the leakage rate data of the channel to be measured.

[0086] Optionally, after the low-temperature detection of the heat exchanger, it further includes:

[0087] Perform blasting and purging on the heat exchanger;

[0088] The blasting and purging of the heat exchanger includes:

[0089] First step: Select a heat exchange channel for blasting and purging;

[0090] Second step: Use blasting materials to block the outlet of the selected heat exchange channel;

[0091] Third step: Inject high-pressure nitrogen through the inlet of the selected heat exchange channel;

[0092] Fourth step: Perform high-pressure blasting on the selected heat exchange channel, and detect the particle concentration at the outlet of the selected heat exchange channel after blasting;

[0093] Fifth step: When the particle concentration at the outlet of the selected heat exchange channel is greater than the preset concentration value, repeat the blasting until the particle concentration at the outlet is less than or equal to the preset concentration value;

[0094] Sixth step: Use blasting materials to block the inlet of the selected heat exchange channel;

[0095] Seventh step: Inject high-pressure nitrogen through the outlet of the selected heat exchange channel;

[0096] Eighth step: Perform high-pressure blasting on the selected heat exchange channels, and detect the particle concentration at the inlets of the selected heat exchange channels after blasting;

[0097] Ninth step: When the particle concentration at the inlets of the selected heat exchange channels is greater than the preset concentration value, repeat the blasting until the particle concentration at the inlets is less than or equal to the preset concentration value;

[0098] Tenth step: Sequentially switch to other heat exchange channels for blasting and purging, and repeat the first step to the ninth step until all heat exchange channels are completed with blasting and purging;

[0099] After the blasting and purging of the heat exchanger, it further includes:

[0100] Perform cleanliness detection on the heat exchanger;

[0101] The cleanliness detection of the heat exchanger includes:

[0102] Use an endoscope to extend into each heat exchange channel of the heat exchanger for detection.

[0103] Optionally, the method further includes:

[0104] Perform a flow and heat transfer performance test on the heat exchanger when the cleanliness detection meets the requirements;

[0105] Clean the inner and outer surfaces of the heat exchanger when the flow and heat transfer performance test meets the requirements;

[0106] Weld the nameplate;

[0107] The flow and heat transfer performance test of the heat exchanger includes:

[0108] Measure the fluid pressure drop on the cold side of the heat exchanger;

[0109] Perform an efficiency test on the heat exchanger.

[0110] Beneficial effects:

[0111] In the embodiment of the present invention, a processing method for a 2K negative pressure aluminum plate-fin heat exchanger performs various detections on the 2K negative pressure plate-fin heat exchanger, including low-temperature helium mass spectrometry leak detection. When performing low-temperature helium mass spectrometry leak detection, it can simulate the real low-temperature environment to ensure the accuracy of leak detection. Through the processing method provided in the present invention, a heat exchanger with a low leakage rate, high mechanical strength, compact volume, and high cleanliness can be obtained, greatly improving the processing efficiency and yield of the 2K negative pressure heat exchanger. Description of the drawings

[0112] Figure 1 It is a flowchart of the processing method of Embodiment 1 of the present invention;

[0113] Figure 2 It is a flowchart of the processing method according to Embodiment 3 of the present invention;

[0114] Figure 3 It is a schematic structural diagram of the cryogenic helium mass spectrometry leak detection device according to Embodiment 3 of the present invention;

[0115] Figure 4 It is a schematic structural diagram of the external leak detection device in the normal-temperature helium mass spectrometry leak detection according to Embodiment 3 of the present invention;

[0116] Figure 5 It is a schematic structural diagram of the internal leak detection device in the normal-temperature helium mass spectrometry leak detection according to Embodiment 3 of the present invention.

[0117] The reference numerals are shown as:

[0118] 1. Liquid nitrogen container; 2. Third helium mass spectrometer leak detector; 3. Vacuum pump system; 4. Chiller; 5. First helium gas cylinder; 6. First pressure reducing gauge; 7. Polyethylene plastic bag; 8. Heat exchanger; 9. First vacuum gauge; 10. First vacuum valve; 11. First vacuum pump; 12. First standard leak; 13. Second vacuum valve; 14. First helium mass spectrometer leak detector; 15. Second helium gas cylinder; 16. Second pressure reducing gauge; 17. Second vacuum gauge; 18. Third vacuum valve; 19. Second vacuum pump; 20. Second standard leak; 21. Fourth vacuum valve; 22. Second helium mass spectrometer leak detector. Detailed implementation manners

[0119] In the description of the present invention, it should be understood that the orientation or positional relationship indicated by the terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation to the present invention.

[0120] In addition, the terms "first" and "second" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include one or more of such features. In the description of the present invention, "a plurality" means two or more unless otherwise specifically defined.

[0121] In the present invention, unless otherwise clearly specified and defined, terms such as "installation", "connection", "linkage", "fixation", etc. shall be understood in a broad sense. For example, it may be a fixed connection, a detachable connection, or an integral connection; it may be a mechanical connection or an electrical connection; it may be a direct connection or an indirect connection through an intermediate medium, and it may be the communication inside two components. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0122] The preferred embodiments of the present invention will be described below in conjunction with the accompanying drawings. It should be understood that the preferred embodiments described herein are only used to illustrate and explain the present invention, and are not used to limit the present invention.

[0123] Refer to Figure 1 As shown, according to Embodiment 1 of the present invention, a processing method for a 2K negative pressure aluminum plate-fin heat exchanger is provided, including:

[0124] Step 101: Fabricate the core body.

[0125] In this step, after the fittings in the core body are assembled together, they are then welded and fixed by vacuum brazing, thereby forming the core body, ensuring that the core body has good strength.

[0126] Specifically, the fittings of the core body include flow guide plates, partition plates, heat transfer fins, seals, side plates, etc. The fittings are fixed together by an assembly tooling. Among them, heat transfer fins and seals are placed between two adjacent partition plates to form a sandwich, which is called a heat exchange channel. The sandwiches are stacked and brazed into a whole according to different fluid flow patterns to form the core body.

[0127] Among them, the fittings that need to be brazed together are welded by the process of vacuum brazing. During brazing, the core body is placed in a high-temperature brazing furnace for brazing treatment.

[0128] Step 102: Fabricate the end caps. The process of fabricating the end caps includes integral forging of the end caps.

[0129] In this step, the end caps can be integrally forged, which can reduce the number of welds, reduce the leakage risk, and increase the mechanical strength, making the end caps have the advantages of low leakage rate and high strength.

[0130] Step 103: Connect the core body with the end caps to make the heat exchanger 8.

[0131] In this step, the core body and the end caps are welded into one body, ensuring good connection strength between the core body and the end caps, and further ensuring good stability of the whole heat exchanger 8.

[0132] Among them, the core is assembled in a dust-free workshop equipped with a negative pressure and ventilation system to reduce dust pollution inside the core. The workshop is designed as a negative pressure environment to prevent dust from spreading to other areas. Before assembling the fins, the dust-free workshop is ventilated using the ventilation system. The ventilation system is reasonably planned to ensure that dust enters the dust removal equipment through the directional air flow.

[0133] Step 104: Conduct a normal temperature test on the heat exchanger 8, and the temperature range for the normal temperature test is 20°C to 30°C.

[0134] In this step, the normal temperature test can include weld inspection, appearance inspection, liquid immersion leak detection, pressure test, normal temperature helium mass spectrometry leak detection, etc.

[0135] Step 105: Conduct a low temperature test on the heat exchanger 8, and the temperature range for the low temperature test is below -150°C.

[0136] In this step, by conducting a low temperature test on the heat exchanger 8, it is possible to simulate and test the sealing performance of the heat exchanger 8 in a deep low temperature environment, ensure that the heat exchanger 8 meets the design specifications and requirements, ensure that the quality of the heat exchanger 8 reaches the standard, and guarantee the performance, stability, and reliability of the heat exchanger 8 under actual use conditions.

[0137] Embodiment 2 of the present invention is a refinement and extension of the specific implementation manner of step 105 in the above Embodiment 1, and illustrates the implementation process of step 105 in Embodiment 1.

[0138] Step 105 includes:

[0139] Step 1051: Evacuate each heat exchange channel in the heat exchanger 8 and the closed device where the heat exchanger 8 is located.

[0140] In this step, the heat exchanger 8 is placed in the closed device, and the internal space of the closed device and each heat exchange channel of the heat exchanger 8 are evacuated through the vacuum pump system 3, so that the pressure in each heat exchange channel of the heat exchanger 8 and the internal space of the closed device is less than or equal to 5 Pa.

[0141] Step 1052: When the vacuum degree is less than the first preset pressure threshold, obtain the background leak rate of the closed device and the background leak rate of each heat exchange channel in the heat exchanger 8.

[0142] In this step, the first preset pressure threshold is a preset test pressure threshold, and the first preset pressure threshold can be adjusted and modified according to actual needs. When the vacuum degree is less than the first preset pressure threshold, start observing the background leak rate of the closed device and the background leak rate of each heat exchange channel in the heat exchanger 8.

[0143] Step 1053: Perform a quench treatment on the heat exchanger 8, and obtain the background leak rate and vacuum degree of each heat exchange channel in the heat exchanger 8 and the background leak rate and vacuum degree of the sealing device during the cooling process.

[0144] In this step, a way of introducing liquid nitrogen into the heat exchanger 8 can be selected to perform a quench treatment on the heat exchanger 8. During the cooling process, continuously or intermittently obtain and observe the background leak rate and vacuum degree of each heat exchange channel in the heat exchanger 8 and the background leak rate and vacuum degree of the sealing device, so as to obtain the change situation of the vacuum degree and the background leak rate.

[0145] Specifically, if obtaining and observing the background leak rate and vacuum degree of each heat exchange channel in the heat exchanger 8 and the background leak rate and vacuum degree of the sealing device intermittently, the interval duration can be the same or different, and can be flexibly set according to the actual situation.

[0146] Specifically, liquid nitrogen can be introduced into the heat exchanger 8 through the liquid nitrogen container 1, so as to perform a quench treatment on the heat exchanger 8.

[0147] Step 1054: When the temperature is cooled to a preset temperature threshold, perform a low-temperature helium mass spectrometry leak detection on the heat exchanger 8.

[0148] By performing a low-temperature helium mass spectrometry leak detection on the heat exchanger 8, it is possible to simulate a real low-temperature environment, ensure the accuracy of the leak detection, and obtain a heat exchanger 8 with a micro-leak rate, high mechanical strength, compact volume, and high cleanliness, greatly improving the processing efficiency and finished product rate of the 2K negative pressure heat exchanger 8.

[0149] Embodiment 3 of the present invention is a refinement and expansion of the specific implementation manner of the above Embodiment 1, and fully describes the specific implementation process of Embodiment 1.

[0150] As Figure 2 shown, Embodiment 3 provides a processing method for a 2K negative pressure aluminum plate-fin heat exchanger, including:

[0151] Step 2011: Process fins, baffles, and seals. Among them, the fins, baffles, and seals are fittings of the core.

[0152] In this step, process the fins, baffles, and seals respectively to obtain the fittings of the core.

[0153] Step 2012: Clean the fittings.

[0154] In this step, clean the fittings of the core. The fittings include fins, baffles, and seals, and may also include flow guide vanes and side plates, etc. By cleaning the fittings, the cleanliness inside the manufactured heat exchanger 8 is effectively improved, the internal impurity pollution during the operation of the heat exchanger 8 is reduced, and the possibility of damaging the helium low-temperature system is reduced.

[0155] Step 2013: Assemble the core body.

[0156] In this step, accessories such as fins, partitions, seals, flow guiding pieces, and side plates are assembled and fixed together through tooling. The tooling used is prior art and will not be elaborated here.

[0157] Step 2014: Weld the core body. Among them, the core body is welded using the process of vacuum brazing.

[0158] In this step, the core body can be placed in a high-temperature brazing furnace for brazing treatment.

[0159] Perform Step 2015: Check the geometric dimensions of the core body.

[0160] When the geometric dimensions of the core body meet the requirements, perform Step 2016: Inject water into the core body to detect leaks. When the geometric dimensions of the core body do not meet the requirements, remanufacture the core body.

[0161] In Step 2016, by injecting water into the core body, leak detection can be achieved, which can ensure to a certain extent that the core body has good sealing performance. When the leak detection by injecting water into the core body does not meet the requirements, remanufacture the core body.

[0162] Step 2021: Integrally forge the head.

[0163] In this step, by integrally forging the head, the number of welds can be reduced, the leakage risk can be lowered, and the mechanical strength can be increased, making the head have the advantages of low leakage rate and high strength.

[0164] The existing heads are formed by splicing and welding multiple components, having defects such as large leakage risk, low mechanical strength, and being bulky. In this embodiment, by integrally forging the head, the leakage risk is greatly reduced and the mechanical strength is increased. Since the thickness of the head can be reduced by integral forging, the volume and weight of the head are reduced, and the appearance is more beautiful.

[0165] Step 2022: Clean the head.

[0166] In this step, by cleaning the head, the cleanliness is effectively improved and impurity contamination is reduced.

[0167] When processing the head, or before and after processing the head, Step 2023: Process the steel-aluminum joint can be carried out.

[0168] Among them, the steel-aluminum joint is one of the accessories of the heat exchanger 8. The steel-aluminum joint is fixedly connected to the head and is connected to the core body together with the head.

[0169] Step 2024: Clean the steel-aluminum joint.

[0170] In this step, by cleaning the steel-aluminum joint, the cleanliness is effectively improved and impurity contamination is reduced.

[0171] Step 2025: Weld the steel-aluminum joint to the head.

[0172] In this step, the steel-aluminum joint is fixed to the head by welding to form a stable whole.

[0173] Perform Step 2026: Geometric dimension inspection on the whole formed by the head and the steel-aluminum joint.

[0174] When the geometric dimensions of the whole formed by the head and the steel-aluminum joint meet the requirements, perform Step 2027: X-ray inspection of the butt weld. When the geometric dimensions of the whole formed by the head and the steel-aluminum joint do not meet the requirements, remake the head and the steel-aluminum joint.

[0175] In Step 2027, by using X-ray to perform butt weld inspection on the whole formed by the head and the steel-aluminum joint, defects such as pores, slag inclusions, and incomplete penetration inside the weld can be accurately detected, reducing the leakage risk.

[0176] When both the core water injection leak detection and the X-ray inspection of the butt weld meet the requirements, perform Step 2028: Connect the core to the head to make the heat exchanger 8.

[0177] In the above steps, the core and the head assembly are made separately, and the processing technology and quality standards can be formulated according to their respective characteristics. When making the core, from the processing of fins, partitions, and seals to a series of processes such as cleaning, assembly, welding, geometric dimension inspection, and water injection leak detection, the internal structure and sealing performance of the core can be accurately controlled. When making the head, forging the head integrally reduces the number of welds and the leakage risk. Subsequently, the cleaning, processing, welding, geometric dimension inspection, and X-ray inspection of the butt weld of the head and the steel-aluminum joint can ensure the strength and sealing performance of the head assembly, and thus accurately control the quality of the heat exchanger 8.

[0178] Specifically, Step 2028: Connect the core to the head, including: welding the head to the core.

[0179] Step 2031: Penetrant inspection of fillet welds.

[0180] In this step, a penetrant containing a coloring dye or a fluorescent agent is applied to the surface of the fillet weld. Due to capillary action, the penetrant will penetrate into the open defects on the weld surface. Subsequently, the excess penetrant on the surface is removed, and then a developer is applied. The developer will adsorb the penetrant in the defects and expand and display it on the surface. By observing the display traces, the position, shape, and size of the defects can be judged. By using penetrant to inspect fillet welds, open defects such as microcracks and porosity on the surface of fillet welds can be accurately detected.

[0181] Specifically, in weld inspection, butt welds are inspected by X-ray, and fillet welds are inspected by penetrant.

[0182] More specifically, in X-ray inspection, before the head and the steel-aluminum joint are welded to the core body, the butt weld between the head and the steel-aluminum joint is inspected by X-ray. After the head and the steel-aluminum joint are welded to the core body, the fillet weld between the head and the core body is inspected by penetrant.

[0183] When the fillet weld meets the requirements, the heat exchanger 8 undergoes step 2032: geometric dimension inspection. When the fillet weld does not meet the requirements, the head and the core body are re-welded.

[0184] When the geometric dimensions of the heat exchanger 8 meet the requirements, step 2033: overall immersion leak detection is carried out. When the geometric dimensions of the heat exchanger 8 do not meet the requirements, the head and the core body are re-welded.

[0185] In step 2033, the heat exchanger 8 is completely immersed in the leak detection liquid, and then a certain pressure of gas is filled into the heat exchanger 8. If there are leak points in the heat exchanger 8, the gas will escape from the leak points and generate bubbles in the liquid. By observing the positions and quantities of the bubbles generated, the positions of the leak points and the severity of the leaks can be judged. Through overall immersion leak detection, the sealing performance of the heat exchanger 8 is ensured.

[0186] When the overall immersion leak detection meets the requirements, step 2034: pressure test is carried out. When the overall immersion leak detection does not meet the requirements, the core body and the head are remade and re-welded.

[0187] Specifically, step 2034: pressure test includes:

[0188] Step 20341: Introduce pressure test gas into the heat exchange channels of the heat exchanger 8, boost the pressure to 10% of the specified test pressure, maintain for a second duration, and detect the air leakage conditions of all welds and connection parts.

[0189] In this step, the pressure test gas can be dry and clean air, nitrogen or other inert gases. The second duration can be flexibly set according to actual needs. In this embodiment, the second duration is 5 - 10 minutes.

[0190] Specifically, when introducing the pressure test gas, first slowly boost the pressure to 10% of the specified test pressure, maintain for 5 - 10 minutes, and check all welds and connection parts to see if there is any air leakage.

[0191] Step 20342: When there is no leakage, boost the pressure to 50% of the specified test pressure, and detect the air leakage conditions of all welds and connection parts.

[0192] Specifically, after boosting the pressure to 50% of the specified test pressure, maintain it for 5 to 10 minutes, and inspect all welds and connection parts to check for air leakage.

[0193] Step 20343: In the case of no leakage, boost the pressure step by step by 10% of the specified test pressure, and detect the air leakage of all welds and connection parts until the pressure is boosted to the test pressure, maintain for the third duration, and detect the air leakage of all welds and connection parts.

[0194] In this step, the third duration can be flexibly set according to actual needs. In this embodiment, the third duration is 10 to 15 minutes.

[0195] Specifically, in the case of no leakage, each time the pressure is boosted step by step by 10% of the specified test pressure. That is, after each boost of the pressure by 10% of the specified test pressure, maintain it for 5 to 10 minutes, and inspect all welds and connection parts to check for air leakage. After boosting the pressure to the test pressure, maintain for 10 to 15 minutes, and inspect all welds and connection parts to check for air leakage. The pressure should remain unchanged during the inspection.

[0196] During the process of step 2034, the pressure vessel has no abnormal noise, and it is qualified only when there is no air leakage and no visible deformation after inspection with leak detection liquid.

[0197] Optionally, as a feasible implementation manner, an airtightness test can also be performed on the heat exchanger 8.

[0198] The airtightness test includes:

[0199] Inject airtightness test gas into the heat exchange channels of the heat exchanger 8, boost the pressure to 10% of the specified test pressure, maintain for the fourth duration, and detect the air leakage of all welds and connection parts.

[0200] Specifically, the airtightness test gas can be dry and clean air, nitrogen or other inert gases. The fourth duration can be flexibly set according to actual needs. In this embodiment, the fourth duration is 5 to 10 minutes.

[0201] More specifically, when injecting the airtightness test gas, first slowly boost the pressure to 10% of the specified test pressure, maintain for 5 to 10 minutes, and inspect all welds and connection parts to check for air leakage.

[0202] In the case of no leakage, boost the pressure to 50% of the specified test pressure, and detect the air leakage of all welds and connection parts.

[0203] Specifically, after boosting the pressure to 50% of the specified test pressure, maintain it for 5 to 10 minutes, and inspect all welds and connection parts to check for air leakage.

[0204] In the case of no leakage, boost the pressure step by step by 10% of the specified test pressure, maintain for the fifth duration, and detect the air leakage of all welds and connection parts until the pressure is boosted to the test pressure.

[0205] Specifically, the fifth duration can be flexibly set according to actual needs. In this embodiment, the fifth duration is 10 to 15 minutes.

[0206] More specifically, in the case of no leakage, each time the pressure is boosted step by step by 10% of the specified test pressure. That is, after each boost of 10% of the specified test pressure, maintain for 5 to 10 minutes, and inspect all welds and connection parts to check for air leakage. After boosting to the test pressure, maintain for 10 to 15 minutes, and inspect all welds and connection parts to check for air leakage. The pressure should remain unchanged during the inspection.

[0207] Among them, during the airtightness test, it is considered qualified if no air leakage is detected by the leak detection liquid.

[0208] In the case where the pressure test meets the requirements, perform step 2035: helium mass spectrometry leak detection at room temperature.

[0209] Specifically, step 2035: helium mass spectrometry leak detection at room temperature includes: step 20351: external leak detection and step 20352: internal leak detection.

[0210] Figure 4 Shows the external leak detection equipment in helium mass spectrometry leak detection at room temperature. The heat exchanger 8 is subjected to external leak detection through the external leak detection equipment.

[0211] Step 20351: External leak detection includes:

[0212] Step 203511: Form a hood chamber with a polyethylene plastic bag 7, place the heat exchanger 8 in the hood chamber, and evacuate the air in the hood chamber.

[0213] In this step, the air in the hood chamber is pumped out by the first vacuum pump 11. After the vacuum pumping is completed, the flow path between the first vacuum pump 11 and the hood chamber is disconnected through the first vacuum valve 10. By setting the first vacuum gauge 9 and making the first vacuum gauge 9 communicate with the heat exchanger 8 and the hood chamber respectively, the vacuum degrees of the heat exchanger 8 and the hood chamber are detected.

[0214] Step 203512: Introduce helium gas into the hood chamber until it reaches one atmospheric pressure.

[0215] In this step, after disconnecting the communication between the first vacuum pump 11 and the hood chamber through the first vacuum valve 10, helium gas is introduced into the hood chamber from the first helium gas cylinder 5 until the pressure reaches one atmosphere. The air pressure is adjusted by the first pressure reducing gauge 6 provided between the first helium gas cylinder 5 and the hood chamber.

[0216] Step 203513: When the volume of the hood chamber is greater than the preset volume, let it stand for the sixth time period.

[0217] In this step, the preset volume and the sixth time period can be flexibly set according to actual needs. In this embodiment, the preset volume is 100L and the sixth time period is 15 minutes.

[0218] Among them, when the volume of the hood chamber is less than or equal to the preset volume, the standing time can be appropriately shortened, for example, standing for 10 minutes.

[0219] Step 203514: Evacuate each heat exchange channel of the heat exchanger 8 to a pressure lower than the second preset pressure threshold in sequence, and detect the leak rate data.

[0220] In this step, the second preset pressure threshold can be flexibly set according to actual needs. In this embodiment, the second preset pressure threshold is 50Pa, that is, when each heat exchange channel of the heat exchanger 8 is evacuated to a pressure lower than 50Pa in sequence, the leak rate data is detected by the first helium mass spectrometer leak detector 14.

[0221] Among them, a branch is provided on the flow path between the first vacuum valve 10 and the first helium mass spectrometer leak detector 14, and a second vacuum valve 13 and a first standard leak hole 12 are provided on the branch, which can be used to calibrate the leak detection equipment.

[0222] Figure 5 The internal leak detection equipment in normal temperature helium mass spectrometry leak detection is shown, and the heat exchanger 8 is subjected to internal leak detection through the internal leak detection equipment.

[0223] Step 20352: Internal leak detection, including:

[0224] Step 203521: Select one heat exchange channel in the heat exchanger 8 as the measured channel.

[0225] In this step, the heat exchange channel with the largest volume in the heat exchanger 8 can be first selected as the measured channel. If there are multiple heat exchange channels with the largest volume, any one of the heat exchange channels with the largest volume in the middle position can be selected as the measured channel.

[0226] Step 203522: Introduce helium gas into the adjacent heat exchange channels of the measured channel until the pressure reaches one atmosphere.

[0227] In this step, after selecting the channel to be tested, helium is introduced into the heat exchange channel adjacent to the channel to be tested from the second helium cylinder 15 until the pressure reaches one atmosphere. The air pressure is adjusted by the second pressure reducing gauge 16 between the second helium cylinder 15 and the heat exchanger 8.

[0228] Step 203523: Evacuate the channel to be tested to a pressure lower than the third preset pressure threshold and maintain the pressure for the seventh duration.

[0229] In this step, the third preset pressure threshold and the seventh duration can be flexibly set according to actual needs. In this embodiment, the third preset pressure threshold is 50 Pa and the seventh duration is 15 minutes. That is, evacuate the channel to be tested to a pressure lower than 50 Pa and maintain the pressure for 15 minutes.

[0230] Among them, the channel to be tested is evacuated to a pressure lower than the third preset pressure threshold by the second vacuum pump 19. After the evacuation is completed, the flow path between the second vacuum pump 19 and the channel to be tested is disconnected by the third vacuum valve 18. By setting the second vacuum gauge 17 and connecting the second vacuum gauge 17 to the channel to be tested, the vacuum degree of the channel to be tested is detected.

[0231] Step 203524: Detect the leak rate data of the channel to be tested.

[0232] In this step, the leak rate data is detected by the second helium mass spectrometer leak detector 22.

[0233] If internal leak detection is required for all heat exchange channels, each heat exchange channel in the heat exchanger 8 is taken as the channel to be tested one by one, and the internal leak detection is carried out in sequence according to the above steps.

[0234] Among them, a branch is provided on the flow path between the third vacuum valve 18 and the second helium mass spectrometer leak detector 22, and a fourth vacuum valve 21 and a second standard leak hole 20 are provided on the branch, which can be used to calibrate the leak detection equipment.

[0235] The heat exchanger 8 may include two groups of heat exchange channels, such as a cold fluid channel and a hot fluid channel. In the external leak detection in step 20351 and the internal leak detection in step 20352, the external leak data of the cold fluid channel and the hot fluid channel of the heat exchanger 8, and the internal leak data between the cold fluid channel and the hot fluid channel are obtained. The worst value among the three groups of leak rate data is selected as the leak rate of the heat exchanger 8.

[0236] In the case where step 2035 does not meet the requirements, the core body and the head are remanufactured and welded again. In the case where step 2035 meets the requirements, the heat exchanger 8 is moved to a cryogenic helium mass spectrometer leak detection device, and then the heat exchanger 8 is subjected to cryogenic detection. The cryogenic helium mass spectrometer leak detection device includes the above-mentioned closed device. That is, in the case where step 2035 meets the requirements, the heat exchanger 8 is moved into the closed device of the cryogenic helium mass spectrometer leak detection device.

[0237] Specifically, three platinum resistance thermometers are respectively arranged at the inlet of the heat exchange channel with the largest volume in the heat exchanger 8, in the middle of the side plate, and at the outlet of the heat exchange channel with the largest volume in the heat exchanger 8, and are monitored after being powered on by a digital display monitor. Dry nitrogen is used to displace the air in each heat exchange channel to be detected, as well as the helium and humid air remaining during the normal temperature helium mass spectrometry leak detection process. Check again to confirm whether all joints are connected. After confirmation, push it into the closed device of the low-temperature helium mass spectrometry leak detection device. Check the sealing flange gasket of the low-temperature helium mass spectrometry leak detection device. After confirming no obvious impurities, apply sealing silicone grease. The sealing silicone grease can be directly applied by hand until it is visually uniform. Apply the sealing silicone grease as needed. Close the sealing flange and tighten the bolts and nuts at the flange.

[0238] As Figure 3 shown, the pipeline where the V1 valve is located is connected to the closed device of the low-temperature helium mass spectrometry leak detection device. The low-temperature helium mass spectrometry leak detection device includes multiple pipelines, each pipeline is connected to a heat exchange channel in the heat exchanger 8, and a valve is provided on each pipeline. In this embodiment, as Figure 3 shown, there are a total of three pipelines. One pipeline is provided with a V4 valve, one pipeline is provided with a V5 valve, and one pipeline is provided with a V6 valve. The V4 valve, V5 valve, and V6 valve are used to control the on / off of the pipeline where they are located. The V2 valve is arranged on the intake pipeline of the third helium mass spectrometry leak detector 2 and is used to control the on / off of the intake pipeline. The intake pipeline is respectively connected to the pipeline where the V1 valve is located, the pipeline where the V4 valve is located, the pipeline where the V5 valve is located, and the pipeline where the V6 valve is located. The pipeline where the vacuum pump system 3 is located is respectively connected to the pipeline where the V1 valve is located, the pipeline where the V2 valve is located, the pipeline where the V4 valve is located, the pipeline where the V5 valve is located, and the pipeline where the V6 valve is located. The V3 valve is arranged on the intake pipeline of the vacuum pump system 3 and is used to control the on / off of the intake pipeline of the vacuum pump system 3. The vacuum pump system 3 is connected to a matching chiller 4.

[0239] The vacuum pump system 3 includes a mechanical pump, a roots pump, and a molecular pump connected in sequence.

[0240] Step 2041: Use the mechanical pump to evacuate each heat exchange channel in the heat exchanger 8 and the closed device where the heat exchanger 8 is located.

[0241] In this step, refer to Figure 3 , close the V2 valve, open the V1 valve, V3 valve, V4 valve, V5 valve, and V6 valve, and start the mechanical pump to evacuate each heat exchange channel in the heat exchanger 8 and the closed device where the heat exchanger 8 is located.

[0242] Step 2042: When the vacuum degree of each heat exchange channel in the heat exchanger 8 and the closed device where the heat exchanger 8 is located is less than the first intermediate pressure threshold, start the Roots pump to evacuate each heat exchange channel in the heat exchanger 8 and the closed device where the heat exchanger 8 is located.

[0243] In this step, the first intermediate pressure threshold can be flexibly set according to actual needs. In this embodiment, the intermediate pressure threshold is 100 Pa. That is, when the vacuum degree of each heat exchange channel in the heat exchanger 8 and the closed device where the heat exchanger 8 is located is less than 100 Pa, start the Roots pump in the vacuum pump system 3 to evacuate each heat exchange channel in the heat exchanger 8 and the closed device where the heat exchanger 8 is located.

[0244] Step 2043: When the vacuum degree of each heat exchange channel in the heat exchanger 8 and the closed device where the heat exchanger 8 is located is less than the second intermediate pressure threshold, start the molecular pump to evacuate each heat exchange channel in the heat exchanger 8 and the closed device where the heat exchanger 8 is located, so that the vacuum degree of each heat exchange channel in the heat exchanger 8 and the closed device where the heat exchanger 8 is located is less than the first preset pressure threshold.

[0245] In this step, the second intermediate pressure threshold can be flexibly set according to actual needs. In this embodiment, the intermediate pressure threshold is 20 Pa. That is, when the vacuum degree of each heat exchange channel in the heat exchanger 8 and the closed device where the heat exchanger 8 is located is less than 20 Pa, start the molecular pump in the vacuum pump system 3 to evacuate each heat exchange channel in the heat exchanger 8 and the closed device where the heat exchanger 8 is located.

[0246] Specifically, when starting the molecular pump, start the chiller 4 at the same time. Each time the molecular pump is started, press the green "Start" button on the molecular pump control panel to start the molecular pump. When the controller shows that the rotational speed of the molecular pump reaches the rated speed, press the red "Stop" button.

[0247] When evacuating, first start the mechanical pump in the atmospheric state to obtain the low vacuum of the closed device. The Roots pump usually has a large pumping speed in the pressure range of 100 - 20 Pa, and can quickly exhaust the suddenly released gas. This pressure range is between the mechanical pump and the molecular pump. The molecular pump can transfer the momentum to the gas molecules by using the high-speed rotating rotor, so that they obtain the directional velocity, and then are compressed and driven to the exhaust port and pumped away by the fore pump. When these three vacuum pumps evacuate the closed device, they are arranged according to the start sequence and complementary functions, and can jointly complete the conversion process of the inside of the closed device from the atmospheric state to the high vacuum state.

[0248] When the vacuum degree of each heat exchange channel in the heat exchanger 8 and the closed device where the heat exchanger 8 is located is less than the first preset pressure threshold, step 2044 is performed: Connect the leak detection device to the closed device, and block the leak detection device from each heat exchange channel in the heat exchanger 8, and obtain the background leakage rate of the closed device.

[0249] In this step, the first preset pressure threshold can be flexibly set according to actual needs. For example, it can be 10 -4 Pa. Specifically, after starting the molecular pump, when the ionization silicon shows below 10 -4 Pa, that is, when it reaches 10 -4 Pa, turn on the third helium mass spectrometer leak detector 2. At this time, the V4 valve, V5 valve, and V6 valve are in the closed state. Slowly open the V1 valve and V2 valve, and then obtain the background leakage rate of the accommodation space through the third helium mass spectrometer leak detector 2.

[0250] Step 2045: Connect the leak detection device to each heat exchange channel in the heat exchanger 8 in sequence, and block the leak detection device from the closed device, and obtain the background leakage rate of each heat exchange channel in the heat exchanger 8.

[0251] In this step, open the V4 valve, V5 valve, and V6 valve in sequence, and close the V1 valve. Then, the background leakage rates of the heat exchange channels of the heat exchanger 8 corresponding to the V4 valve, the heat exchange channels of the heat exchanger 8 corresponding to the V5 valve, and the heat exchange channels of the heat exchanger 8 corresponding to the V6 valve can be obtained through the third helium mass spectrometer leak detector 2.

[0252] The heat exchange channels of the heat exchanger 8 include a cold fluid channel and a hot fluid channel.

[0253] Step 2046: Perform a cold shock treatment on the heat exchanger 8, and obtain the background leakage rate and vacuum degree of each heat exchange channel in the heat exchanger 8 and the background leakage rate and vacuum degree of the closed device during the cooling process.

[0254] In one embodiment, performing a cold shock treatment on the heat exchanger 8 includes:

[0255] Step 20461: Select the cold fluid channel with the largest volume as the first cooling channel, introduce liquid nitrogen into the first end of the first cooling channel, and discharge it from the second end of the first cooling channel, so that the second end of the first cooling channel becomes the discharge port.

[0256] In this step, open the liquid nitrogen outlet valve of the liquid nitrogen container 1, and then introduce liquid nitrogen into the first end of the cold fluid channel with the largest volume in the heat exchanger 8 for cooling.

[0257] Step 20462: Control the cooling rate of the first cooling channel to be less than or equal to 4 °C / min.

[0258] In this step, temperature changes can be detected by detection devices such as digital display monitors, and then the cooling rate of the first cooling channel can be controlled to be less than or equal to 4 °C / min. At the beginning of cooling, temperature data can be recorded every 10 minutes. After the cooling rate stabilizes, temperature data can be recorded every 1 hour. If the cooling rate is too fast, the opening of the liquid nitrogen container 1's liquid outlet valve can be adjusted to adjust the flow rate.

[0259] When the temperature difference between the first end and the second end of the first cooling channel is greater than the preset temperature difference threshold and the cooling rate is less than the preset rate threshold, step 20463 is performed: Liquid nitrogen is introduced into the second end of the first cooling channel and discharged from the first end of the first cooling channel, making the first end of the first cooling channel the discharge port.

[0260] In this step, the preset temperature difference threshold can be 10 °C. The preset rate threshold can be 1 °C / min.

[0261] Specifically, during the cooling process, when the temperature of the end where liquid nitrogen is introduced drops to the preset temperature difference threshold, the discharge port may still be in a relatively high temperature state and the cooling rate is very small. That is, when the temperature difference between the first end and the second end of the first cooling channel is greater than the preset temperature difference threshold and the cooling rate is less than the preset rate threshold, liquid nitrogen is introduced into the second end of the first cooling channel and discharged from the first end of the first cooling channel to further cool evenly.

[0262] After the temperature of the first cooling channel is cooled to the preset temperature threshold and there is no nitrogen discharged from the exhaust port of the first cooling channel, step 20464 is performed: Select the hot fluid channel with the largest volume as the second cooling channel, introduce liquid nitrogen into the first end of the second cooling channel, and discharge it from the second end of the second cooling channel, making the second end of the second cooling channel the discharge port.

[0263] In this step, the liquid outlet valve of the liquid nitrogen container 1 is opened, and then liquid nitrogen is introduced into the first end of the hot fluid channel with the largest volume in the heat exchanger 8 for cooling. The preset temperature threshold can be -173.15 °C.

[0264] Step 20465: Control the cooling rate of the second cooling channel to be less than or equal to 4 °C / min.

[0265] In this step, temperature changes can be detected by detection devices such as digital display monitors, and then the cooling rate of the second cooling channel can be controlled to be less than or equal to 4 °C / min. At the beginning of cooling, temperature data can be recorded every 10 minutes. After the cooling rate stabilizes, temperature data can be recorded every 1 hour. If the cooling rate is too fast, the opening of the liquid nitrogen container 1's liquid outlet valve can be adjusted to adjust the flow rate.

[0266] When the temperature difference between the first end and the second end of the second cooling channel is greater than a preset temperature difference threshold and the temperature reduction rate is less than a preset rate threshold, perform step 20466: Introduce liquid nitrogen into the second end of the second cooling channel and discharge it from the first end of the second cooling channel, making the first end of the second cooling channel the discharge port.

[0267] In this step, the preset temperature difference threshold can be 10 °C. The preset rate threshold can be 1 °C / min.

[0268] Specifically, during the temperature reduction process, when the temperature of the end where liquid nitrogen is introduced drops to the preset temperature difference threshold, the discharge port may still be in a relatively high temperature state and the temperature reduction rate is very small. That is, when the temperature difference between the first end and the second end of the second cooling channel is greater than the preset temperature difference threshold and the temperature reduction rate is less than the preset rate threshold, introduce liquid nitrogen into the second end of the second cooling channel and discharge it from the first end of the second cooling channel to further evenly reduce the temperature. The formula is as follows:

[0269]

[0270] In order to more accurately provide the operator with the specific flow rate value and avoid the operator's blind adjustment. The temperature reduction rate of the heat exchanger can be effectively regulated by controlling the liquid nitrogen flow rate u , and its functional relationship is dominated by the 0.8th power of the flow rate u and is simultaneously affected by the heat transfer area, the thermophysical properties of the working fluid, and the temperature difference driving force.

[0271] Among them, dT is the temperature change amount, dt is the time change amount, C is a dimensionless coefficient related to the geometric size of the heat exchanger flow channel (such as the hydraulic diameter D h ); A 0 is the reference heat transfer area; α is the surface enhancement coefficient; η is the heat transfer surface contact efficiency, that is, the ratio of the actual effective heat transfer area to the theoretical area ( 0 ≤ η ≤ 1 ), which is affected by the surface roughness and wettability; V is the working fluid volume; ρ is the working fluid density; c p is the specific heat capacity of the working fluid; T m is the ambient temperature; T is the working fluid temperature; T - T m is the working fluid-medium temperature difference.

[0272] According to the target temperature reduction rate r target Back-calculate the required flow rate u set The formula is:

[0273]

[0274] Among them, C is a dimensionless coefficient related to the geometric size of the heat exchanger flow channel (such as the hydraulic diameter D h ); A 0 is the reference heat transfer area; α is the surface enhancement coefficient; η is the heat transfer surface contact efficiency, that is, the ratio of the actual effective heat transfer area to the theoretical area ( 0 ≤ η ≤ 1 ), which is affected by surface roughness and wettability; V is the volume of the working fluid; ρ is the density of the working fluid; c p is the specific heat capacity of the working fluid; T m is the ambient temperature; T is the temperature of the working fluid; T - T m is the temperature difference between the working fluid and the medium.

[0275] Specifically, the minimum flow velocity u min ≥0.1 m / s (to avoid a sharp drop in heat transfer efficiency caused by laminar flow), and the maximum flow velocity u max ≤5 m / s (limited by pump power and pressure drop).

[0276] A specific calculation example is as follows: The known parameters are set as shown in Table 1 below:

[0277]

[0278] Calculate the effective heat transfer area A( η ):

[0279]

[0280] Calculate the comprehensive constant k:

[0281]

[0282] Back-calculate the flow velocity u set :

[0283]

[0284]

[0285] Due to the superfluid helium effect, if the system temperature is lower than 2.17 K (λ point), liquid helium enters the superfluid state, and the heat transfer coefficient increases significantly, and the actual required flow velocity can be further reduced.

[0286] In some possible embodiments, the flow rate is obtained through the above formula u set , and the actual initial flow rate is set to A1 u set， where A1 is a coefficient between 0 and 1.

[0287] Specifically, the actual initial flow rate is set to 0.3 u set、 0.4 u set、 0.5 u set、 0.6 u set . Measure the actual cooling rate, compare it with the target cooling rate, and finely adjust the flow rate up and down.

[0288] In another embodiment, the heat exchanger 8 is subjected to a quench treatment, including: placing the heat exchanger in a cooling medium and performing an immersion quench treatment on the heat exchanger.

[0289] Among them, an immersion quench device with a suitable size and shape is selected according to the size of the heat exchanger 8, and an appropriate amount of cooling medium is added to the immersion quench device. The heat exchanger 8 is immersed in the low-temperature cooling medium. Control the temperature and immersion time of the cooling medium. After the immersion quench is completed, the heat exchanger 8 is taken out of the cooling medium to complete the immersion quench treatment.

[0290] In the process of the above steps 20461 to 20466, the background leak rate and vacuum degree of each heat exchange channel in the heat exchanger 8 and the background leak rate and vacuum degree of the sealing device are obtained.

[0291] Specifically, the V4 valve, V5 valve, and V6 valve can be sequentially opened, and the V1 valve and V3 valve are closed, and the V2 valve is opened, so that the background leak rate and vacuum degree of the heat exchange channel of the heat exchanger 8 corresponding to the V4 valve, the heat exchange channel of the heat exchanger 8 corresponding to the V5 valve, and the heat exchange channel of the heat exchanger 8 corresponding to the V6 valve can be obtained through the third helium mass spectrometer leak detector 2. When the V1 valve and V2 valve are opened and the V3 valve, V4 valve, V5 valve, and V6 valve are closed, the background leak rate of the sealing device can be obtained through the third helium mass spectrometer leak detector 2.

[0292] After the temperature of the second cooling channel is cooled to a preset temperature threshold and there is no nitrogen discharged from the exhaust port of the second cooling channel, low-temperature helium mass spectrometry leak detection is performed. Among them, the preset temperature threshold can be -173.15 °C.

[0293] Step 2047: Perform low-temperature helium mass spectrometry leak detection on the heat exchanger 8, including:

[0294] Step 20471: Select a heat exchange channel as the charging channel, charge helium into the charging channel, and let it stand for the first period of time.

[0295] In this step, keep Figure 3 valves V3, V4, V5, and V6 in

[0296] closed, and charge helium into the charging channel.

[0297] In this step, connect the third helium mass spectrometer leak detector 2 to the closed device, and then obtain the external leakage data of the charging channel through the numerical change of the third helium mass spectrometer leak detector 2. Connect the third helium mass spectrometer leak detector 2 to the adjacent heat exchange channels of the charging channel, and then obtain the internal leakage data between the adjacent heat exchange channels through the numerical change of the third helium mass spectrometer leak detector 2.

[0298] Step 20473: Sequentially switch other heat exchange channels as the charging channel, and repeat the operations of charging helium into the charging channel and letting it stand for the first period of time; obtaining the external leakage data of the charging channel and the internal leakage data between the adjacent heat exchange channels; until the external leakage data and internal leakage data of all heat exchange channels are obtained.

[0299] In this step, other heat exchange channels can be sequentially switched as the charging channel for leak detection in the order of valves V4, V5, and V6.

[0300] Among them, before switching valves V4, V5, and V6, valve V2 must be closed to avoid introducing the atmosphere into the third helium mass spectrometer leak detector 2 and damaging the third helium mass spectrometer leak detector 2.

[0301] Among them, keep the pressure of the heat exchange channel filled with helium at the working pressure of this heat exchange channel and keep the maximum pressure difference between the adjacent heat exchange channels. For example, if the heat exchanger 8 has four groups of heat exchange channels with a design pressure of 2.5 MPa each and operating pressures of 1.0 MPa, 0.5 MPa, 0.2 MPa, and 0.1 MPa respectively, then maintain the pressure at the highest working pressure of 1.0 MPa.

[0302] The heat exchanger 8 can include two groups of heat exchange channels, such as a cold fluid channel and a hot fluid channel. In step 20472, obtain the external leakage data of the cold fluid channel and the hot fluid channel of the heat exchanger 8, and the internal leakage data between the cold fluid channel and the hot fluid channel. Select the worst value among the three sets of leak rate data as the low-temperature helium mass spectrometry leak detection data of the heat exchanger 8.

[0303] After performing low-temperature helium mass spectrometry leak detection on the heat exchanger 8 in step 2047, it further includes:

[0304] Step 2048: Perform secondary vacuum pumping, then perform tertiary vacuum pumping, and repeat the cycle until the i-th vacuum pumping is performed to calculate the total leakage rate, where i is an integer greater than 3.

[0305] Specifically, in a possible embodiment, based on the principle of mass conservation, the multi-stage pumping process can be modeled as a dynamic leakage system of series-connected cavities. Assuming that the pumping speed is constant at each stage and the leakage source is in a steady-state flow condition, the total leakage rate can be decomposed into a linear superposition of the leakage rates in each independent pressure range. By introducing an effective pumping speed correction coefficient and a pressure decay function, the formula for the total leakage rate of the system is derived:

[0306]

[0307] In the formula, is the effective pumping speed of the i-th stage, is the equilibrium pressure of the i-th stage, is the leakage path weight factor of the i-th stage. The above formula quantifies the contribution of different vacuum stages to the total leakage rate and provides a theoretical basis for determining leakage.

[0308] In another possible embodiment, perform secondary vacuum pumping, calculate the equivalent leakage rate of the second stage, then perform tertiary vacuum pumping, and calculate the equivalent leakage rate of the third stage. Repeat the cycle until the i-th vacuum pumping is performed, calculate the equivalent leakage rate of the i-th stage, and calculate the total leakage rate, where i is an integer greater than 3. When the system reaches a steady state at the i-th stage of vacuum, the leakage gas flow rate is balanced with the pumping rate, satisfying:

[0309]

[0310] In the formula, is the equivalent leakage rate of the i-th stage (Pa·m 3 / s), is the effective pumping speed of the i-th stage (m 3 / s), is the equilibrium pressure of the i-th stage (Pa), is the ultimate vacuum of the i-th stage vacuum pump (Pa).

[0311] For an n-stage vacuum pumping system, the total leakage rate is the cumulative effect of the leakage rates at each stage. Considering the independence of the leakage paths and the non-linear characteristics of the pressure difference, the total leakage rate can be expressed as:

[0312]

[0313] In the formula, is the pumping time of the i-th stage (s); =V / ; is the characteristic time constant of the i-th stage (s); V is the system volume (m 3 ); is an exponential term that reflects the influence of pressure decay on the leak rate during the unsteady pumping process.

[0314] In this embodiment, pressure gradient progressive control is adopted, which can isolate the interference of micro-leak holes and macroscopic leaks respectively under different vacuum degrees, thereby improving the sensitivity of leak rate detection; secondly, the staged operation can effectively shorten the equilibrium time required for the system to reach steady-state vacuum and avoid the non-linear response problem caused by the sudden pressure drop during the traditional single-stage vacuum pumping process; in addition, this method can reduce the continuous load of the vacuum pump by discharging residual stress in stages, thereby extending the service life of key equipment.

[0315] After step 2048, it further includes:

[0316] Step 20491: Close the vacuum pumping system and break the vacuum inside the sealed device.

[0317] Step 20492: After the heat exchanger 8 is reheated, control the reheating rate of the heat exchanger 8.

[0318] Specifically, the reheating rate of the heat exchanger 8 must be strictly controlled within 4 °C / min. Before the heat exchanger 8 is reheated to room temperature, it is prohibited to open the sealed device.

[0319] Step 20493: When the heat exchanger 8 returns to room temperature, take out the heat exchanger 8 from the sealed device.

[0320] After taking out the heat exchanger 8 from the sealed device, perform step 205: Blow and purge the heat exchanger 8 by blasting. Specifically, it includes:

[0321] The first step: Select a heat exchange channel for blow and purge by blasting.

[0322] In this step, select a heat exchange channel from all heat exchange channels and first blow and purge the selected heat exchange channel by blasting.

[0323] The second step: Use blasting materials to block the outlet of the selected heat exchange channel.

[0324] In this step, using blasting materials to block the outlet of the selected heat exchange channel can accumulate the pressure of high-pressure nitrogen in the selected heat exchange channel. When the pressure reaches a certain level, it will cause blasting, which can generate a strong impact force and effectively remove impurities in the heat exchange channel, improving the cleaning effect.

[0325] The third step: Inject high-pressure nitrogen through the inlet of the selected heat exchange channel.

[0326] In this step, high-pressure nitrogen can be used as the power source for blow and purge by blasting. High-pressure nitrogen can push the particles, impurities, etc. in the heat exchange channel out with the air flow during blasting, realizing the cleaning effect on the heat exchange channel.

[0327] Fourth step: Perform high-pressure blasting on the selected heat exchange channel, and detect the particle concentration at the outlet of the selected heat exchange channel after blasting.

[0328] Fifth step: When the particle concentration at the outlet of the selected heat exchange channel is greater than the preset concentration value, repeat the blasting until the particle concentration at the outlet is less than or equal to the preset concentration value.

[0329] In this step, through multiple high-pressure blastings, impurities that are difficult to clean in the heat exchange channel are gradually removed, ensuring that the interior of the selected heat exchange channel meets a high cleanliness standard. By comparing the particle concentration at the outlet with the preset concentration value, it provides a basis for judging whether the heat exchange channel is clean, ensuring the cleaning quality.

[0330] Among them, the particle concentration at the outlet of the selected heat exchange channel is detected by a particle counter. The detection standard is that the number of particles with a diameter greater than 5 µm is less than 10 per cm², and this detection standard is also the preset concentration value. If this standard is not met, repeat the blasting, or disassemble, transform, or even scrap and re-produce.

[0331] Sixth step: Use blasting material to block the inlet of the selected heat exchange channel.

[0332] In this step, using blasting material to block the inlet of the selected heat exchange channel can change the air flow direction during blasting and purging, further improving the comprehensiveness of cleaning.

[0333] Seventh step: Inject high-pressure nitrogen gas through the outlet of the selected heat exchange channel.

[0334] In this step, high-pressure nitrogen gas can be used as the power source for blasting and purging. When blasting, high-pressure nitrogen gas can push the particles, impurities, etc. in the heat exchange channel to be discharged with the air flow, realizing the cleaning effect of the heat exchange channel.

[0335] Eighth step: Perform high-pressure blasting on the selected heat exchange channel, and detect the particle concentration at the inlet of the selected heat exchange channel after blasting.

[0336] Ninth step: When the particle concentration at the inlet of the selected heat exchange channel is greater than the preset concentration value, repeat the blasting until the particle concentration at the inlet is less than or equal to the preset concentration value.

[0337] Among them, the particle concentration at the outlet of the selected heat exchange channel is detected by a particle counter. The detection standard is that the number of particles with a diameter greater than 5 µm is less than 10 per cm², and this detection standard is also the preset concentration value. If this standard is not met, repeat the blasting, or disassemble, transform, or even scrap and re-produce.

[0338] In this step, through multiple high-pressure blasting, the impurities that are difficult to clean in the heat exchange channel are gradually removed to ensure that the selected heat exchange channel meets a high cleanliness standard. By comparing the particle concentration at the entrance with the preset concentration value, it provides a basis for judging whether the heat exchange channel is clean and ensures the cleaning quality.

[0339] Step 10: Switch other heat exchange channels in turn for blasting and blowing, and repeat steps 1 to 9 until all heat exchange channels have completed blasting and blowing.

[0340] All heat exchange channels are blasted and purged one by one to ensure that each heat exchange channel of the heat exchanger 8 meets high cleanliness standards to avoid affecting the overall performance and operating stability of the heat exchanger 8 due to incomplete cleaning of some heat exchange channels.

[0341] Specifically, in one embodiment, during the blasting and purging process, an air compressor or a nitrogen cylinder injects high-pressure nitrogen, generally at a pressure of 0.6 to 1.0 MPa. Highland barley paper blasting discs are used as blasting materials, with a thickness of 0.3 to 0.5 mm, and the compressive strength needs to be designed according to the purging pressure. A pressure gauge can be provided to monitor the purging pressure in real time, and the pressure gauge range is 0 to 1.5 MPa. A safety valve or a pressure relief valve can be provided on the flow path to prevent overpressure.

[0342] In this embodiment, preparations are made before blasting and purging. Close the inlet and outlet valves of the heat exchanger to ensure isolation from other systems. Open the drain valve to drain the internal medium and confirm that the pressure returns to zero. Remove the original inlet and outlet flanges of the heat exchanger and install a temporary flange with a bursting disc interface. After the preparations are completed, install the bursting disc and select the thickness of the highland barley paper according to the purge pressure. For example, 0.4mm can withstand a bursting pressure of about 0.8MPa. During installation, clean the flange sealing surface to ensure that there are no burrs. Cut the highland barley paper into flange size and place it in the center. Apply high-temperature sealant, tighten the bolts evenly, and tighten them diagonally to avoid bias. Then connect the gas source system and connect the air compressor or nitrogen bottle to the inlet flange of the heat exchanger with a rubber hose. Install a pressure gauge on the inlet pipeline and calibrate the range. Install a safety valve at the outlet of the gas source and set the pressure to 1.1 times the purge pressure. During blasting and purging, perform low-pressure pre-purging first. Open the gas source and slowly pressurize it to 0.2MPa, maintain it for 10 minutes, loosen the impurities initially, and observe whether there are obvious foreign objects discharged from the outlet. Then perform high-pressure blasting and purge, gradually increase the pressure to the design pressure, such as 0.8MPa, until the highland barley paper bursting piece breaks. At the moment of blasting, the airflow rushes out at high speed, carrying the impurities out, and achieving blasting and purge.

[0343] After step 205, the method further includes:

[0344] Step 206: Perform cleanliness inspection on the heat exchanger 8, which specifically includes: using an endoscope to extend into each heat exchange channel of the heat exchanger 8 for inspection.

[0345] In this step, an endoscope is used to extend into each heat exchange channel of the heat exchanger 8 for inspection, and it is possible to directly observe whether there are impurities, foreign objects, etc. in the heat exchange channel. If there are impurities, it may cause blockage of the heat exchange channel in a low-temperature environment, affecting fluid flow and even damaging the equipment. Through cleanliness detection, impurities can be detected and cleared in a timely manner, effectively avoiding these problems and ensuring the safe and stable operation of the equipment.

[0346] When the cleanliness detection meets the requirements, step 207: flow and heat transfer performance test is carried out. Specifically, it includes:

[0347] Step 2071: Measure the pressure drop of the cold-side fluid of the heat exchanger 8.

[0348] Among them, the pressure drop of the cold-side fluid is an important indicator to measure the performance of the heat exchanger 8. In this step, by measuring the pressure drop of the cold-side fluid, the resistance of superfluid helium flowing in the heat exchanger 8 is evaluated.

[0349] Before measurement, prepare a stable cold fluid source, such as a 2K negative pressure heat exchanger test device, to ensure that it can provide cold fluid with stable temperature and flow rate in the superfluid helium temperature range. Install a high-precision pressure sensor on each of the cold fluid inlet and outlet pipes of the heat exchanger 8 to measure the pressure difference of the cold-side fluid before and after entering the heat exchanger 8. At the same time, install a flow measurement device, such as a turbine flowmeter, on each of the cold-side inlet and hot-side inlet pipes to analyze the cold-side pressure drop at different flow rates. Start the cold fluid source to make the cold fluid flow stably in the pipeline and the heat exchanger 8 for a period of time to make the system reach a thermal stable state, avoiding affecting the measurement accuracy due to temperature fluctuations. According to the design parameters of the heat exchanger 8 and the actual operating conditions, adjust the cold fluid flow rate to the design condition and keep the flow rate stable. After the system is stable, read and record the readings measured by the cold-side inlet and cold-side outlet pressure sensors and the pressure value measured by the outlet pressure sensor. The cold-side fluid pressure drop value is the difference between the pressure value measured by the inlet pressure sensor and the pressure value measured by the outlet pressure sensor.

[0350] Step 2072: Test the heat transfer efficiency of the heat exchanger 8.

[0351] In this step, by measuring the relevant parameters of the cold-side fluid and the hot-side fluid, the heat transfer amount is obtained using the heat calculation formula, and then the efficiency of the heat exchanger 8 is calculated.

[0352] Specifically, high-precision temperature sensors are installed on the inlet and outlet pipes of the cold and hot fluids of the heat exchanger 8 to measure the inlet and outlet temperatures of the cold and hot fluids in real time. At the same time, a flow measurement device, such as a mass flowmeter, is installed on the pipe to accurately measure the mass flow rates of the cold and hot fluids. According to the thermodynamic principle, the heat transfer amounts of the cold and hot fluids are calculated respectively. Based on the design parameters of the heat exchanger 8, the maximum possible heat transfer amount is calculated, and the heat transfer efficiency of the heat exchanger 8 is calculated based on the actual heat transfer amount and the maximum possible heat transfer amount of the heat exchanger 8.

[0353] Specifically, according to the law of conservation of energy, the heat transfer amounts of the cold and hot fluids should be equal.

[0354] Among them, the calculation formula for the heat transfer amount on the cold side is:

[0355]

[0356] In the formula, 、 : The inlet / outlet temperature of the cold fluid (measured by a high-precision temperature sensor);

[0357] : The mass flow rate of the cold fluid (measured by a turbine flowmeter or a mass flowmeter);

[0358] : The specific heat capacity at constant pressure of the cold fluid (known physical property parameter);

[0359] Among them, the calculation formula for the pressure drop on the cold side is:

[0360]

[0361] is the inlet pressure of the cold fluid, is the outlet pressure of the cold fluid, and can be measured by a pressure sensor.

[0362] Among them, the calculation formula for the heat transfer amount on the hot side is:

[0363]

[0364] In the formula, 、 : The inlet / outlet temperature of the hot fluid (measured by a high-precision temperature sensor);

[0365] : The mass flow rate of the hot fluid (measured by a mass flowmeter);

[0366] : The specific heat capacity at constant pressure of the hot fluid (known physical property parameter);

[0367] Determine the minimum heat capacity rate, the formula is:

[0368]

[0369] In the formula, is the minimum heat capacity rate;

[0370] : Mass flow rate of the cold fluid (measured by a turbine flowmeter or a mass flowmeter);

[0371] : Specific heat capacity at constant pressure of the cold fluid (known physical property parameter);

[0372] : Mass flow rate of the hot fluid (measured by a mass flowmeter);

[0373] : Specific heat capacity at constant pressure of the hot fluid (known physical property parameter).

[0374] Determine the maximum heat capacity rate, the formula is:

[0375]

[0376] In the formula, is the maximum heat capacity rate;

[0377] : Mass flow rate of the cold fluid (measured by a turbine flowmeter or a mass flowmeter);

[0378] : Specific heat capacity at constant pressure of the cold fluid (known physical property parameter);

[0379] : Mass flow rate of the hot fluid (measured by a mass flowmeter);

[0380] : Specific heat capacity at constant pressure of the hot fluid (known physical property parameter).

[0381] The maximum heat transfer amount, the formula is:

[0382]

[0383] Heat transfer efficiency is defined as the ratio of the actual heat transfer amount to the maximum possible heat transfer amount. Based on the number of transfer units (NTU) method, assuming the overall heat transfer coefficient is related to the pressure drop on the cold side P c :

[0384] Heat transfer coefficient correlation:

[0385] , where

[0386] The NTU expression is:

[0387]

[0388] Assume , and is a constant, which is combined into the coefficient .

[0389] When the heat exchanger is a counter-current heat exchanger, The ratio of to satisfies the formula:

[0390]

[0391] Then the efficiency formula is:

[0392]

[0393] Specifically, the formula is:

[0394]

[0395] Among them, is a fitting constant, which comprehensively considers factors such as heat transfer area and fluid physical properties.

[0396] In some possible embodiments = 0.023, then the formula is:

[0397]

[0398] When the requirements for the flow and heat transfer performance test are met, step 208 is performed: cleaning the inner and outer surfaces of the heat exchanger 8.

[0399] In this step, by cleaning the inner and outer surfaces of the heat exchanger 8 again, the cleanliness of the heat exchanger 8 is further improved.

[0400] Step 209: Weld the nameplate. After welding the nameplate, the processing of the 2K negative pressure aluminum plate-fin heat exchanger is completed.

[0401] It is easy for those skilled in the art to understand that, on the premise of no conflict, the above advantageous ways can be freely combined and superimposed.

[0402] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention. The above is only the preferred implementation manner of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the technical principle of the present invention, several improvements and variations can be made, and these improvements and variations should also be regarded as within the protection scope of the present invention.

Claims

1. A processing method of a 2K negative pressure aluminum plate-fin heat exchanger, characterized in that, Including: Manufacturing the core body; Manufacturing the head, and the process of manufacturing the head includes integrally forging the head; Connecting the core body with the head to form a heat exchanger; Performing normal temperature detection on the heat exchanger, and the temperature range of the normal temperature detection is 20°C to 30°C; Performing low temperature detection on the heat exchanger, and the temperature range of the low temperature detection is below -150°C; Among them, the step of performing low temperature detection on the heat exchanger includes: Vacuumizing each heat exchange channel in the heat exchanger and the closed device where the heat exchanger is located. The heat exchange channels of the heat exchanger include a cold fluid channel and a hot fluid channel; When the vacuum degree is less than the first preset pressure threshold, obtaining the background leakage rate of the closed device and the background leakage rate of each heat exchange channel in the heat exchanger; Performing a cold shock treatment on the heat exchanger, and obtaining the background leakage rate and vacuum degree of each heat exchange channel in the heat exchanger and the background leakage rate and vacuum degree of the closed device during the cooling process; When the temperature is cooled to the preset temperature threshold, performing a low temperature helium mass spectrometry leak detection on the heat exchanger; Among them, performing a cold shock treatment on the heat exchanger includes: Selecting the cold fluid channel with the largest volume as the first cooling channel, introducing liquid nitrogen into the first end of the first cooling channel, and discharging it from the second end of the first cooling channel, so that the second end of the first cooling channel becomes the discharge port; When the temperature difference between the first end and the second end of the first cooling channel is greater than the preset temperature difference threshold and the cooling rate is less than the preset rate threshold, introducing liquid nitrogen into the second end of the first cooling channel and discharging it from the first end of the first cooling channel, so that the first end of the first cooling channel becomes the discharge port; After the temperature of the first cooling channel is cooled to the preset temperature threshold and there is no nitrogen discharged from the exhaust port of the first cooling channel, selecting the hot fluid channel with the largest volume as the second cooling channel, introducing liquid nitrogen into the first end of the second cooling channel and discharging it from the second end of the second cooling channel, so that the second end of the second cooling channel becomes the discharge port; Controlling the cooling rate of the first cooling channel and the second cooling channel to be less than or equal to 4°C / min; When the temperature difference between the first end and the second end of the second cooling channel is greater than the preset temperature difference threshold and the cooling rate is less than the preset rate threshold, introducing liquid nitrogen into the second end of the second cooling channel and discharging it from the first end of the second cooling channel, so that the first end of the second cooling channel becomes the discharge port; After the temperature of the second cooling channel is cooled to the preset temperature threshold and there is no nitrogen discharged from the exhaust port of the second cooling channel, performing the low temperature helium mass spectrometry leak detection; The cooling rate of the heat exchanger is regulated by controlling the flow rate u of liquid nitrogen, and the required flow rate u set is given by the formula: where r target is the target cooling rate, C is a dimensionless coefficient related to the geometric dimensions of the heat exchanger flow channel; A 0 is the reference heat transfer area; α is the surface enhancement coefficient; η is the heat transfer surface contact efficiency, i.e., the ratio of the actual effective heat transfer area to the theoretical area ( 0 ≤ η ≤ 1 ), affected by surface roughness and wettability; V is the working fluid volume; ρ is the working fluid density; c p is the specific heat capacity of the working fluid; T m is the ambient temperature; T is the working fluid temperature; T - T m is the working fluid - medium temperature difference.

2. The processing method of the 2K negative pressure aluminum plate-fin heat exchanger according to claim 1, wherein, The vacuumizing of each heat exchange channel in the heat exchanger and the closed device where the heat exchanger is located includes: Vacuumizing each heat exchange channel in the heat exchanger and the closed device where the heat exchanger is located through a mechanical pump; When the vacuum degree of each heat exchange channel in the heat exchanger and the closed device where the heat exchanger is located is less than the first intermediate pressure threshold, starting a Roots pump to vacuumize each heat exchange channel in the heat exchanger and the closed device where the heat exchanger is located; When the vacuum degree of each heat exchange channel in the heat exchanger and the vacuum degree of the closed device where the heat exchanger is located are less than the second intermediate pressure threshold, turn on the molecular pump to evacuate each heat exchange channel in the heat exchanger and the closed device where the heat exchanger is located, so that the vacuum degree of each heat exchange channel in the heat exchanger and the closed device where the heat exchanger is located is less than the first preset pressure threshold; When the vacuum degree is less than the first preset pressure threshold, obtaining the background leakage rate of the closed device and the background leakage rate of each heat exchange channel in the heat exchanger includes: Connect the leak detection device to the closed device and block the leak detection device from each heat exchange channel in the heat exchanger to obtain the background leakage rate of the closed device; Connect the leak detection device to each heat exchange channel in the heat exchanger in turn and block the leak detection device from the closed device to obtain the background leakage rate of each heat exchange channel in the heat exchanger.

3. The processing method of the 2K negative pressure aluminum plate-fin heat exchanger according to claim 2, characterized in that, Performing low-temperature helium mass spectrometry leak detection on the heat exchanger includes: Select one heat exchange channel as the charging channel, charge helium into the charging channel, and let it stand for the first period of time; Obtain the external leakage data of the charging channel and the internal leakage data between adjacent heat exchange channels; Switch other heat exchange channels as the charging channel in turn, and repeat the steps of charging helium into the charging channel and letting it stand for the first period of time to the steps of obtaining the external leakage data of the charging channel and the internal leakage data between adjacent heat exchange channels until the external leakage data and internal leakage data of all heat exchange channels are obtained.

4. The processing method of the 2K negative pressure aluminum plate-fin heat exchanger according to claim 1, characterized in that, Manufacturing the core includes: Processing fins, partitions and seals, where the fins, partitions and seals are the accessories of the core; Clean the accessories; Assemble the core; Weld the core, where the core is welded using the process of vacuum brazing; Check the geometric dimensions of the core; When the geometric dimensions of the core meet the requirements, perform water injection leak detection on the core; Manufacturing the head includes: Integrally forge the head; Clean the head; Process the steel-aluminum joint; Clean the steel-aluminum joint; Weld the steel-aluminum joint to the head; Check the geometric dimensions of the whole formed by the head and the steel-aluminum joint; When the geometric dimensions of the whole formed by the head and the steel-aluminum joint meet the requirements, perform X-ray detection on the butt weld; When both the water injection leak detection of the core and the X-ray detection of the butt weld meet the requirements, connect the core to the head to make a heat exchanger; Connecting the core to the head to make a heat exchanger includes: Weld the head to the core.

5. The processing method of the 2K negative pressure aluminum plate-fin heat exchanger according to claim 1, characterized in that, The steps of performing normal temperature detection on the heat exchanger include: Detect the fillet weld with penetrant; When the fillet weld meets the requirements, perform geometric dimension detection on the heat exchanger; When the geometric dimensions of the heat exchanger meet the requirements, perform overall immersion leak detection on the heat exchanger.

6. The processing method of the 2K negative pressure aluminum plate-fin heat exchanger according to claim 5, characterized in that, The steps of performing normal temperature detection on the heat exchanger include: When the overall immersion leak detection meets the requirements, perform a pressure test on the heat exchanger; The pressure test includes: Inject pressure test gas into the heat exchange channels of the heat exchanger, raise the pressure to 10% of the specified test pressure, keep it for the second period of time, and detect the air leakage of all welds and connection parts; When there is no leakage, raise the pressure to 50% of the specified test pressure and detect the air leakage of all welds and connection parts; In the case of no leakage, increase the pressure step by step in increments of 10% of the specified test pressure, and detect the air leakage of all welds and connection parts until the pressure is increased to the test pressure, maintain for the third duration, and detect the air leakage of all welds and connection parts.

7. The processing method of the 2K negative pressure aluminum plate-fin heat exchanger according to claim 1, characterized in that The steps for performing normal temperature detection on the heat exchanger include: Perform an airtightness test on the heat exchanger; The airtightness test includes: Introduce airtightness test gas into the heat exchange channels of the heat exchanger, increase the pressure to 10% of the specified test pressure, maintain for the fourth duration, and detect the air leakage of all welds and connection parts; In the case of no leakage, increase the pressure to 50% of the specified test pressure, and detect the air leakage of all welds and connection parts; In the case of no leakage, increase the pressure step by step in increments of 10% of the specified test pressure, maintain for the fifth duration, and detect the air leakage of all welds and connection parts until the pressure is increased to the test pressure.

8. The processing method of the 2K negative pressure aluminum plate-fin heat exchanger according to claim 6, characterized in that, The steps for performing normal temperature detection on the heat exchanger include: Perform normal temperature helium mass spectrometry leak detection on the heat exchanger when the pressure test meets the requirements; The normal temperature helium mass spectrometry leak detection includes: External leak detection and internal leak detection; The external leak detection includes: Form a covering chamber with a polyethylene plastic bag, place the heat exchanger in the covering chamber, and remove the air in the covering chamber; Introduce helium gas into the covering chamber until it reaches one atmospheric pressure; When the volume of the covering chamber is greater than the preset volume, let it stand for the sixth duration; Evacuate each heat exchange channel of the heat exchanger to be lower than the second preset pressure threshold in sequence, and detect the leak rate data; The internal leak detection includes: Select one heat exchange channel inside the heat exchanger as the channel to be tested; Introduce helium gas into the adjacent heat exchange channels of the channel to be tested until it reaches one atmospheric pressure; Evacuate the channel to be tested to be lower than the third preset pressure threshold, and maintain the pressure for the seventh duration; Detect the leak rate data of the channel to be tested.

9. The processing method of the 2K negative pressure aluminum plate-fin heat exchanger according to claim 1, characterized in that After performing low temperature detection on the heat exchanger, it further includes: Perform blasting and purging on the heat exchanger; The blasting and purging of the heat exchanger includes: The first step: Select one heat exchange channel for blasting and purging; The second step: Use blasting materials to block the outlet of the selected heat exchange channel; The third step: Inject high-pressure nitrogen gas through the inlet of the selected heat exchange channel; The fourth step: Perform high-pressure blasting on the selected heat exchange channel, and detect the particle concentration at the outlet of the selected heat exchange channel after blasting; The fifth step: When the particle concentration at the outlet of the selected heat exchange channel is greater than the preset concentration value, repeat the blasting until the particle concentration at the outlet is less than or equal to the preset concentration value; The sixth step: Use blasting materials to block the inlet of the selected heat exchange channel; The seventh step: Inject high-pressure nitrogen gas through the outlet of the selected heat exchange channel; The eighth step: Perform high-pressure blasting on the selected heat exchange channel, and detect the particle concentration at the inlet of the selected heat exchange channel after blasting; The ninth step: When the particle concentration at the inlet of the selected heat exchange channel is greater than the preset concentration value, repeat the blasting until the particle concentration at the inlet is less than or equal to the preset concentration value; The tenth step: Sequentially switch to other heat exchange channels for blasting and purging, and repeat the first step to the ninth step until all heat exchange channels are completed with blasting and purging; After the blasting purge of the heat exchanger, it further includes: Conducting cleanliness detection on the heat exchanger; The cleanliness detection of the heat exchanger includes: Using an endoscope to extend into each heat transfer channel of the heat exchanger for detection.

10. The processing method of the 2K negative pressure aluminum plate-fin heat exchanger according to claim 9, characterized in that, The method further includes: Conducting a flow and heat transfer performance test on the heat exchanger when the cleanliness detection meets the requirements; Cleaning the inner and outer surfaces of the heat exchanger when the flow and heat transfer performance test meets the requirements; Welding the nameplate; The flow and heat transfer performance test of the heat exchanger includes: Measuring the pressure drop of the cold-side fluid of the heat exchanger; Conducting an efficiency test on the heat exchanger.

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