Machining method for improving yield of 2K negative pressure aluminum plate-fin heat exchanger

Abstract

The invention provides a machining method for improving the yield of a 2K negative pressure aluminum plate-fin heat exchanger. The machining method comprises the steps that a core body is manufactured; manufacturing an end socket; the core body is connected with the end socket to manufacture the heat exchanger; normal-temperature detection is conducted on the heat exchanger; performing low-temperature detection on the heat exchanger; the heat exchanger is subjected to cold shock treatment, and the background leakage rate and the vacuum degree of each heat exchange channel in the heat exchanger and the background leakage rate and the vacuum degree of the sealing device in the cooling process are obtained; and under the condition that the temperature is reduced to the preset temperature threshold value, low-temperature helium mass spectrum leakage detection is conducted on the heat exchanger, after low-temperature helium mass spectrum leakage detection is conducted, secondary vacuumizing is conducted, then third-time vacuumizing is conducted, the circulation is conducted till ith vacuumizing is conducted, and the total leakage rate is calculated, and i is an integer larger than 3. The heat exchanger with the micro leakage rate, high mechanical strength, compact size and high cleanliness can be obtained, and the machining efficiency and the yield are improved.

Description

[0001] The present application is a divisional application, the original application number is 202510465442.1, the original application date is April 15, 2025, and the entire contents of the original application are incorporated herein by reference. TECHNICAL FIELD

[0002] The application belongs to the technical field of heat exchangers, and particularly relates to a processing method for improving the yield of a 2K negative pressure aluminum plate-fin heat exchanger. BACKGROUND

[0003] 2K negative pressure heat exchanger refers to a heat exchanger working in the 4K liquid helium and 2K superfluid helium temperature zones, which can be used for recovering cold energy of a low-temperature system and improving the generation rate of superfluid helium. The 2K negative pressure heat exchanger operates in a deep low-temperature and negative pressure environment, has a small temperature difference between the two sides for heat exchange, a sharp change in the properties of helium, and a transition between the 4K liquid helium and 2K superfluid helium, so the leakage rate, heat transfer performance, pressure drop performance and volume of the 2K negative pressure heat exchanger have a great influence on the performance of the deep low-temperature system, the construction and operation cost of the heat exchanger. The mechanical, thermal and electrical properties of metal materials change with temperature, especially the difference between deep cooling environment and normal temperature. These changes have important influence in the fields of low-temperature engineering, aerospace, deep cooling storage, superconducting materials, refrigeration and energy.

[0004] In the existing production and manufacturing of 2K negative pressure aluminum plate-fin heat exchangers, only appearance detection and normal-temperature helium mass spectrometry leak detection are generally performed on the heat exchanger, low-temperature detection cannot be performed, the sealing performance of the heat exchanger in a deep low-temperature environment cannot be accurately evaluated and tested, and leakage detection under the design pressure cannot be performed. At the same time, there is a lack of relatively standardized purging treatment and cleanliness detection process, resulting in low efficiency and low yield of the production of 2K negative pressure aluminum plate-fin heat exchangers, and a high risk of welding impurities polluting the low-temperature system. SUMMARY

[0005] Therefore, the technical problem to be solved by the present application is to provide a processing method for improving the yield of a 2K negative pressure aluminum plate-fin heat exchanger, which can perform various detections including low-temperature helium mass spectrometry leak detection on the 2K negative pressure aluminum plate-fin heat exchanger, and improve the processing efficiency and yield of the 2K negative pressure aluminum plate-fin heat exchanger.

[0006] To solve the above problems, the present application provides a processing method for improving the yield of a 2K negative pressure aluminum plate-fin heat exchanger, comprising:

[0007] making a core body;

[0008] making a head, the process of making the head comprising integrally forging the head;

[0009] connecting the core body and the head to make a heat exchanger;

[0010] The heat exchanger is detected at normal temperature, and the temperature range of the normal temperature detection is 20-30 DEG C;

[0011] The heat exchanger is detected at low temperature, and the temperature range of the low temperature detection is below-150 DEG C;

[0012] The low temperature detection of the heat exchanger comprises:

[0013] The heat exchanger and the closed device are vacuumized;

[0014] When the vacuum degree is less than the first preset pressure threshold, the background leak rate of the closed device and the background leak rate of each heat exchange channel of the heat exchanger are obtained;

[0015] The heat exchanger is subjected to cold shock treatment, and the background leak rate and the vacuum degree of each heat exchange channel of the heat exchanger and the background leak rate and the vacuum degree of the closed device during the cooling process are obtained;

[0016] When the temperature is cooled to the preset temperature threshold, the heat exchanger is subjected to low-temperature helium mass spectrometric leak detection.

[0017] Optionally, the vacuumization of the heat exchanger and the closed device comprises:

[0018] The heat exchanger and the closed device are vacuumized by a mechanical pump;

[0019] When the vacuum degree of the heat exchanger and the closed device is less than the first intermediate pressure threshold, the Roots pump is started to vacuumize the heat exchanger and the closed device;

[0020] When the vacuum degree of the heat exchanger and the closed device is less than the second intermediate pressure threshold, the molecular pump is started to vacuumize the heat exchanger and the closed device, so that the vacuum degree of the heat exchanger and the closed device is less than the first preset pressure threshold;

[0021] The background leak rate of the closed device and the background leak rate of each heat exchange channel of the heat exchanger are obtained when the vacuum degree is less than the first preset pressure threshold, comprising:

[0022] The leak detection equipment is connected to the closed device, and the leak detection equipment is blocked from each heat exchange channel of the heat exchanger, so as to obtain the background leak rate of the closed device;

[0023] The leak detection equipment is connected to each heat exchange channel of the heat exchanger in sequence, and the leak detection equipment is blocked from the closed device, so as to obtain the background leak rate of each heat exchange channel of the heat exchanger;

[0024] The heat exchange channels of the heat exchanger include cold fluid channels and hot fluid channels;

[0025] The cold shock treatment of the heat exchanger is performed, and 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 sealing device during the cooling process are obtained, including:

[0026] The cold fluid channel with the largest volume is selected as the first cooling channel, liquid nitrogen is introduced into the first end of the first cooling channel, and the liquid nitrogen is discharged from the second end of the first cooling channel, so that the second end of the first cooling channel becomes the discharge port;

[0027] The cooling rate of the first cooling channel is controlled to be less than or equal to 4℃ / min;

[0028] In the case that the temperature difference between the first end of the first cooling channel and the second end of the first cooling channel is greater than a preset temperature difference threshold, and the cooling rate is less than a preset rate threshold, liquid nitrogen is introduced into the second end of the first cooling channel, and the liquid nitrogen is discharged from the first end of the first cooling channel, so that the first end of the first cooling channel becomes the discharge port;

[0029] After the temperature of the first cooling channel cools to a preset temperature threshold, and in the case that no nitrogen gas is discharged from the exhaust port of the first cooling channel, the hot fluid channel with the largest volume is selected as the second cooling channel, liquid nitrogen is introduced into the first end of the second cooling channel, and the liquid nitrogen is discharged from the second end of the second cooling channel, so that the second end of the second cooling channel becomes the discharge port;

[0030] The cooling rate of the second cooling channel is controlled to be less than or equal to 4℃ / min;

[0031] In the case that the temperature difference between the first end of the second cooling channel and the second end of the second cooling channel is greater than a preset temperature difference threshold, and the cooling rate is less than a preset rate threshold, liquid nitrogen is introduced into the second end of the second cooling channel, and the liquid nitrogen is discharged from the first end of the second cooling channel, so that the first end of the second cooling channel becomes the discharge port;

[0032] After the temperature of the second cooling channel cools to a preset temperature threshold, and in the case that no nitrogen gas is discharged from the exhaust port of the second cooling channel, the low-temperature helium mass spectrometric leak detection is performed;

[0033] Or the cold shock treatment of the heat exchanger is performed, and 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 sealing device during the cooling process are obtained, including:

[0034] The heat exchanger is placed in a cooling medium for immersion cold shock treatment.

[0035] Optionally, the low-temperature helium mass spectrometric leak detection of the heat exchanger includes:

[0036] Selecting one heat exchange channel as a filling channel, filling helium into the filling channel, and standing for a first time length;

[0037] Obtaining the external leakage data of the filling channel and the internal leakage data between adjacent heat exchange channels;

[0038] Switching other heat exchange channels as the filling channel in sequence, and repeating the steps of filling helium into the filling channel and standing for a first time length to the step of obtaining the external leakage data of the filling channel and the internal leakage data between adjacent heat exchange channels until the external leakage data and the internal leakage data of all heat exchange channels are obtained.

[0039] Optionally, the manufacturing of the core body comprises:

[0040] Processing the fins, the partitions and the sealing strips, wherein the fins, the partitions and the sealing strips are accessories of the core body;

[0041] Cleaning the accessories;

[0042] Assembling the core body;

[0043] Welding the core body, wherein the core body is welded by a vacuum brazing process;

[0044] Carrying out a geometric size inspection on the core body;

[0045] In the case that the geometric size of the core body meets the requirements, carrying out water injection leakage detection on the core body;

[0046] The manufacturing of the head comprises:

[0047] Integrally forging the head;

[0048] Cleaning the head;

[0049] Processing the steel-aluminum joint;

[0050] Cleaning the steel-aluminum joint;

[0051] Welding the steel-aluminum joint to the head;

[0052] Carrying out a geometric size inspection on the whole formed by the head and the steel-aluminum joint;

[0053] In the case that the geometric size of the whole formed by the head and the steel-aluminum joint meets the requirements, carrying out X-ray detection on the butt weld;

[0054] In the case that the water injection leakage detection on the core body and the X-ray detection on the butt weld both meet the requirements, connecting the core body with the head to manufacture the heat exchanger;

[0055] The connecting of the core body with the head to manufacture the heat exchanger comprises:

[0056] Welding the head to the core body.

[0057] Optionally, the step of detecting the heat exchanger at normal temperature comprises:

[0058] Detecting the corner welds of the penetrant;

[0059] In the case that the corner welds meet the requirements, detecting the geometric dimensions of the heat exchanger;

[0060] In the case that the geometric dimensions of the heat exchanger meet the requirements, performing overall immersion leak detection on the heat exchanger.

[0061] Optionally, the step of detecting the heat exchanger at normal temperature comprises:

[0062] In the case that the overall immersion leak detection meets the requirements, performing pressure testing on the heat exchanger;

[0063] The pressure testing comprises:

[0064] Passing the pressure testing gas into the heat exchange channel of the heat exchanger, increasing the pressure to 10% of the specified test pressure, keeping for a second time length, and detecting the gas leakage of all the welds and connecting parts;

[0065] In the case of no leakage, increasing the pressure to 50% of the specified test pressure, and detecting the gas leakage of all the welds and connecting parts;

[0066] In the case of no leakage, increasing the pressure by 10% of the specified test pressure step by step, keeping for a fifth time length, and detecting the gas leakage of all the welds and connecting parts, until the pressure is increased to the test pressure.

[0067] Optionally, the step of detecting the heat exchanger at normal temperature comprises:

[0068] Performing the air tightness test on the heat exchanger;

[0069] The air tightness test comprises:

[0070] Passing the air tightness test gas into the heat exchange channel of the heat exchanger, increasing the pressure to 10% of the specified test pressure, keeping for a fourth time length, and detecting the gas leakage of all the welds and connecting parts;

[0071] In the case of no leakage, increasing the pressure to 50% of the specified test pressure, and detecting the gas leakage of all the welds and connecting parts;

[0072] In the case of no leakage, increasing the pressure by 10% of the specified test pressure step by step, keeping for a fifth time length, and detecting the gas leakage of all the welds and connecting parts, until the pressure is increased to the test pressure.

[0073] Optionally, the step of detecting the heat exchanger at normal temperature comprises:

[0074] When the pressure test meets the requirement, the heat exchanger is subjected to normal-temperature helium mass spectrometry leak detection;

[0075] The normal-temperature helium mass spectrometry leak detection comprises:

[0076] external leak detection and internal leak detection;

[0077] The external leak detection comprises:

[0078] A cover chamber is formed by a polyethylene plastic bag, and the heat exchanger is placed in the cover chamber, and air in the cover chamber is exhausted;

[0079] Helium is introduced into the cover chamber to one atmosphere pressure;

[0080] When the volume of the cover chamber is greater than a preset volume, the cover chamber is left to stand for a sixth length of time;

[0081] Each heat exchange channel of the heat exchanger is sequentially vacuumed to be lower than a second preset pressure threshold, and leak rate data is detected;

[0082] The internal leak detection comprises:

[0083] One heat exchange channel in the heat exchanger is selected as a measured channel;

[0084] Helium is introduced into an adjacent heat exchange channel of the measured channel to one atmosphere pressure;

[0085] The measured channel is vacuumed to be lower than a third preset pressure threshold, and pressure is maintained for a seventh length of time;

[0086] Leak rate data of the measured channel is detected.

[0087] Optionally, after the low-temperature detection of the heat exchanger, the method further comprises:

[0088] The heat exchanger is subjected to burst purge;

[0089] The burst purge of the heat exchanger comprises:

[0090] A first step: selecting one heat exchange channel for burst purge;

[0091] A second step: using a burst material to block the outlet of the selected heat exchange channel;

[0092] A third step: injecting high-pressure nitrogen through the inlet of the selected heat exchange channel;

[0093] A fourth step: performing high-pressure burst on the selected heat exchange channel, and detecting the particle concentration at the outlet of the selected heat exchange channel after the burst;

[0094] A fifth step: when the particle concentration at the outlet of the selected heat exchange channel is greater than a preset concentration value, repeating the burst until the particle concentration at the outlet is less than or equal to the preset concentration value.

[0095] a sixth step of plugging the inlet of the selected heat exchange channel with a blasting material;

[0096] a seventh step of injecting high pressure nitrogen gas through the outlet of the selected heat exchange channel;

[0097] an eighth step of performing high pressure blasting on the selected heat exchange channel and detecting the particle concentration at the inlet of the selected heat exchange channel after the blasting;

[0098] a ninth step of repeating the blasting when the particle concentration at the inlet of the selected heat exchange channel is greater than a preset concentration value until the particle concentration at the inlet is less than or equal to the preset concentration value;

[0099] a tenth step of switching other heat exchange channels in sequence for blasting and purging and repeating the first step to the ninth step until all heat exchange channels complete the blasting and purging;

[0100] After the blasting and purging of the heat exchanger, the method further comprises:

[0101] performing cleanliness detection on the heat exchanger;

[0102] The cleanliness detection on the heat exchanger comprises:

[0103] using an endoscope to extend into each heat exchange channel of the heat exchanger for detection.

[0104] Optionally, the method further comprises:

[0105] performing flow and heat transfer performance test on the heat exchanger when the cleanliness detection meets the requirements;

[0106] cleaning the inner and outer surfaces of the heat exchanger when the flow and heat transfer performance test meets the requirements;

[0107] welding a nameplate;

[0108] The flow and heat transfer performance test on the heat exchanger comprises:

[0109] performing cold side fluid pressure drop measurement on the heat exchanger;

[0110] performing efficiency test on the heat exchanger.

[0111] Beneficial effects:

[0112] The processing method for improving the yield of 2K negative pressure aluminum plate-fin heat exchanger provided in the embodiment of the application can detect the 2K negative pressure plate-fin heat exchanger in multiple ways, including low-temperature helium mass spectrometry leak detection. When low-temperature helium mass spectrometry leak detection is performed, the actual low-temperature environment can be simulated to ensure the accuracy of leak detection. Through the processing method provided in the application, a heat exchanger with a micro-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. BRIEF DESCRIPTION OF DRAWINGS

[0113] Figure 1 The flowchart of the processing method of the embodiment 1 of the application;

[0114] Figure 2 The flowchart of the processing method of the embodiment 3 of the application;

[0115] Figure 3 The structure diagram of the low-temperature helium mass spectrometry leak detection device of the embodiment 3 of the application;

[0116] Figure 4 The structure diagram of the external leak detection equipment in the normal-temperature helium mass spectrometry leak detection of the embodiment 3 of the application;

[0117] Figure 5 The structure diagram of the internal leak detection equipment in the normal-temperature helium mass spectrometry leak detection of the embodiment 3 of the application.

[0118] The reference signs are as follows:

[0119] 1, liquid nitrogen container; 2, third helium mass spectrometry leak detector; 3, vacuum pump system; 4, water chiller; 5, first helium bottle; 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 hole; 13, second vacuum valve; 14, first helium mass spectrometry leak detector; 15, second helium bottle; 16, second pressure reducing gauge; 17, second vacuum gauge; 18, third vacuum valve; 19, second vacuum pump; 20, second standard leak hole; 21, fourth vacuum valve; 22, second helium mass spectrometry leak detector. DETAILED DESCRIPTION

[0120] In the description of the present application, it needs to be understood that the terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise" and the like indicate the orientation or positional relationship shown in the drawings, which are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as limiting the present application.

[0121] In addition, the terms "first", "second" are only for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the technical features indicated. Therefore, the features defined with "first", "second" can explicitly or implicitly include one or more of the features. In the description of the present application, the meaning of "multiple" is two or more, unless otherwise explicitly specified and limited.

[0122] In the present application, unless otherwise explicitly specified and limited, the terms "mounting", "connecting", "connecting", "fixing" and the like should be understood broadly, for example, it can be fixedly connected, or it can be detachably connected, or integrally connected; it can be mechanically connected, or it can be electrically connected; it can be directly connected, or it can be indirectly connected through an intermediate medium; it can be the communication inside two elements. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0123] The preferred embodiments of the present application are 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 application, and are not used to limit the present application.

[0124] For reference Figure 1 As shown, according to embodiment 1 of the present application, a processing method for improving the yield of 2K negative pressure aluminum plate fin heat exchanger finished product is provided, which comprises:

[0125] Step 101: making the core.

[0126] In this step, the fittings in the core are assembled together, and then welded and fixed by vacuum brazing, so as to form the core and ensure that the core has good strength.

[0127] Specifically, the fittings of the core include flow guide vanes, partitions, heat transfer fins, sealing strips, side plates and the like. The fittings are fixed together by assembly tooling, wherein the heat transfer fins and the sealing strips are placed between the two adjacent partitions to form a sandwich, which is called a heat exchange channel. The sandwich is stacked and brazed into a whole according to different flow modes of the fluid to form the core.

[0128] Wherein, the fittings that need to be brazed together are welded by the process of vacuum brazing. When brazing, the core is placed in a high-temperature brazing furnace for brazing treatment.

[0129] Step 102: making the head, the process of making the head includes integrally forging the head.

[0130] In this step, the head can be integrally forged, which can reduce the number of welds, reduce the risk of leakage and increase the mechanical strength, so that the head has the advantages of low leakage rate and high strength.

[0131] Step 103: connecting the core with the head to make the heat exchanger 8.

[0132] In this step, the core and the head are welded together to ensure that the core and the head have good connection strength, and thus ensure that the heat exchanger 8 has good stability as a whole.

[0133] Wherein, 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 the dust enters the dust removal equipment through directional airflow.

[0134] Step 104: normal temperature detection of the heat exchanger 8, the temperature range of normal temperature detection is 20℃-30℃.

[0135] In this step, normal temperature detection can include weld detection, appearance detection, liquid immersion leak detection, pressure test, normal temperature helium mass spectrometry leak detection, etc.

[0136] Step 105: low temperature detection of the heat exchanger 8, the temperature range of low temperature detection is below-150℃.

[0137] In this step, by performing low temperature detection on the heat exchanger 8, the sealing performance of the heat exchanger 8 under deep low temperature environment can be simulated, ensuring that the heat exchanger 8 meets the design specifications and requirements, ensuring that the quality of the heat exchanger 8 meets the standards, and ensuring the performance, stability and reliability of the heat exchanger 8 under actual use conditions.

[0138] Embodiment 2 of the present application is a refinement and extension of the specific implementation of step 105 in embodiment 1 above, and describes the implementation process of step 105 in embodiment 1.

[0139] Step 105 includes:

[0140] Step 1051: vacuumizing each heat exchange channel in the heat exchanger 8 and the closed device in which the heat exchanger 8 is located.

[0141] 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 is pumped by the vacuum pump system 3 to make the pressure in each heat exchange channel of the heat exchanger 8 and the internal space of the closed device less than or equal to 5 Pa.

[0142] Step 1052: In the case where the vacuum degree is less than the first preset pressure threshold, the background leakage rate of the closed device and the background leakage rate of each heat exchange channel of the heat exchanger 8 are obtained.

[0143] In this step, the first preset pressure threshold is a preset test pressure threshold, which can be adjusted and modified according to actual needs. When the vacuum degree is less than the first preset pressure threshold, the background leakage rate of the closed device and the background leakage rate of each heat exchange channel of the heat exchanger 8 are observed.

[0144] Step 1053: The heat exchanger 8 is subjected to cold shock treatment, and the background leakage rate and the vacuum degree of each heat exchange channel of the heat exchanger 8 and the background leakage rate and the vacuum degree of the closed device during the cooling process are obtained.

[0145] In this step, the heat exchanger 8 can be subjected to cold shock treatment by introducing liquid nitrogen into the heat exchanger 8. During the cooling process, the background leakage rate and the vacuum degree of each heat exchange channel of the heat exchanger 8 and the background leakage rate and the vacuum degree of the closed device are continuously or intermittently obtained and observed, so as to obtain the changes of the vacuum degree and the background leakage rate.

[0146] Specifically, if the background leakage rate and the vacuum degree of each heat exchange channel of the heat exchanger 8 and the background leakage rate and the vacuum degree of the closed device are intermittently obtained and observed, the interval time can be the same or different, which can be flexibly set according to actual conditions.

[0147] Specifically, the heat exchanger 8 can be subjected to cold shock treatment by introducing liquid nitrogen into the heat exchanger 8 through the liquid nitrogen container 1.

[0148] Step 1054: In the case where the temperature is cooled to a preset temperature threshold, the heat exchanger 8 is subjected to low-temperature helium mass spectrometric leak detection.

[0149] The low-temperature helium mass spectrometric leak detection of the heat exchanger 8 can simulate the actual low-temperature environment, ensure the accuracy of the leak detection, and obtain a heat exchanger 8 with a micro-leakage rate, high mechanical strength, compact volume, and high cleanliness, thereby greatly improving the processing efficiency and yield of the 2K negative pressure heat exchanger 8.

[0150] Embodiment 3 of the present application is a refinement and extension of the specific implementation of the above-mentioned embodiment 1, and fully describes the specific implementation process of embodiment 1.

[0151] As Figure 2As shown, the embodiment 3 provides a processing method for improving the yield of 2K negative pressure aluminum plate-fin heat exchanger, comprising:

[0152] Step 2011: processing fins, partitions and seals. The fins, partitions and seals are accessories of the core.

[0153] In this step, the fins, partitions and seals are processed respectively to obtain the accessories of the core.

[0154] Step 2012: cleaning the accessories.

[0155] In this step, the accessories of the core are cleaned. The accessories include fins, partitions and seals, and can also include guide vanes and side plates, etc. By cleaning the accessories, the cleanliness inside the manufactured heat exchanger 8 is effectively improved, the internal impurity pollution of the heat exchanger 8 during operation is reduced, and the possibility of damaging the helium cryogenic system is reduced.

[0156] Step 2013: assembling the core.

[0157] In this step, the accessories such as fins, partitions and seals, guide vanes and side plates are assembled and fixed together by tooling. The tooling used is prior art, which is not described here.

[0158] Step 2014: welding the core. The core is welded by vacuum brazing process.

[0159] In this step, the core can be placed in a high-temperature brazing furnace for brazing treatment.

[0160] Step 2015: geometric dimension inspection of the core.

[0161] If the geometric dimensions of the core meet the requirements, proceed to step 2016: core water injection leak detection. If the geometric dimensions of the core do not meet the requirements, the core is re-made.

[0162] In step 2016, by injecting water into the core, leak detection can be achieved, which to some extent ensures that the core has good sealing performance. If the core water injection leak detection does not meet the requirements, the core is re-made.

[0163] Step 2021: integrally forging the head.

[0164] In this step, by integrally forging the head, the number of welds can be reduced, the risk of leakage can be reduced, and the mechanical strength can be increased, so that the head has the advantages of low leakage rate and high strength.

[0165] The existing head is spliced and welded by multiple components, and has defects of high leakage risk, low mechanical strength and bulkiness. In the embodiment, the head is integrally forged, which greatly reduces the leakage risk and increases the mechanical strength. Since the head thickness can be reduced by integrally forging, the volume and weight of the head are reduced, and the appearance is more beautiful.

[0166] Step 2022: cleaning the head.

[0167] In this step, the cleanliness is effectively improved by cleaning the head, and the impurity pollution is reduced.

[0168] While the head is being processed, or before or after the head is processed, step 2023: processing the steel-aluminum joint can be performed.

[0169] 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 together with the head.

[0170] Step 2024: cleaning the steel-aluminum joint.

[0171] In this step, the cleanliness is effectively improved by cleaning the steel-aluminum joint, and the impurity pollution is reduced.

[0172] Step 2025: welding the steel-aluminum joint to the head.

[0173] In this step, the steel-aluminum joint is fixed to the head by welding to form a stable whole.

[0174] The whole formed by the head and the steel-aluminum joint is subjected to step 2026: geometric dimension inspection.

[0175] If the geometric dimensions of the whole formed by the head and the steel-aluminum joint meet the requirements, step 2027: X-ray detection of butt weld is performed. If the geometric dimensions of the whole formed by the head and the steel-aluminum joint do not meet the requirements, the head and the steel-aluminum joint are re-made.

[0176] In step 2027, the butt weld of the whole formed by the head and the steel-aluminum joint is detected by X-ray, which can accurately find defects such as pores, slag inclusion and incomplete penetration in the weld, thereby reducing the leakage risk.

[0177] If the core water injection leak detection and the X-ray detection of the butt weld both meet the requirements, step 2028: connecting the core and the head to make the heat exchanger 8 is performed.

[0178] In the above steps, the core body and the head assembly are respectively manufactured, and the processing technology and quality standard can be formulated according to the respective characteristics. When the core body is manufactured, from the processing of the fins, the partition plates and the sealing strips to the cleaning, assembly, welding and geometric size inspection and water injection leak detection and a series of processes, the internal structure and sealing performance of the core body can be accurately controlled. When the head is manufactured, the head is integrally forged to reduce the number of welds and reduce the risk of leakage. Subsequent cleaning, processing, welding, geometric size inspection and X-ray detection 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.

[0179] Specifically, step 2028: connecting the core body and the head, including: welding the head to the core body.

[0180] Step 2031: Penetrant detects the fillet weld.

[0181] In this step, the penetrant containing color dye or 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 surface of the weld. Then remove the excess penetrant on the surface, and apply a developer. The developer will adsorb the penetrant in the defects and expand it on the surface. By observing the traces, the position, shape and size of the defects can be judged. By detecting the fillet weld with penetrant, the small cracks and loose on the surface of the fillet weld can be accurately detected.

[0182] Specifically, in the weld detection, the butt weld is detected by X-ray detection, and the fillet weld is detected by penetrant.

[0183] More specifically, in the X-ray detection, the butt weld between the head and the steel-aluminum joint is detected by X-ray before the head and the steel-aluminum joint are welded to the core body. 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 detected by penetrant.

[0184] In the case where the fillet weld meets the requirements, the geometric size detection of the heat exchanger 8 is performed in step 2032. In the case where the fillet weld does not meet the requirements, the head and the core body are re-welded.

[0185] In the case where the geometric size of the heat exchanger 8 meets the requirements, the overall immersion leak detection is performed in step 2033. In the case where the geometric size of the heat exchanger 8 does not meet the requirements, the head and the core body are re-welded.

[0186] 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 is a leakage point in the heat exchanger 8, the gas will escape from the leakage point and produce bubbles in the liquid. By observing the position and number of bubbles, the position of the leakage point and the severity of the leakage can be judged. Through the overall immersion leak detection, the sealing performance of the heat exchanger 8 is guaranteed.

[0187] In the case that the overall immersion leak detection meets the requirements, step 2034: pressure test is performed. In the case that the overall immersion leak detection does not meet the requirements, the core and the head are remade and the welding is reperformed.

[0188] Specifically, step 2034: pressure test comprises:

[0189] Step 20341: pressure test gas is introduced into the heat exchange channel of the heat exchanger 8, and is increased to 10% of the specified test pressure, is maintained for a second time length, and the gas leakage of all welds and connection parts is detected.

[0190] In this step, the pressure test gas can be dry and clean air, nitrogen or other inert gas. The second time length can be flexibly set according to actual needs, and in the embodiment, the second time length is 5-10 minutes.

[0191] Specifically, when the pressure test gas is introduced, it is first slowly increased to 10% of the specified test pressure, maintained for 5-10 minutes, and all welds and connection parts are checked to see if there is gas leakage.

[0192] Step 20342: in the case of no leakage, increase to 50% of the specified test pressure, and detect the gas leakage of all welds and connection parts.

[0193] Specifically, after increasing to 50% of the specified test pressure, it is maintained for 5-10 minutes, and all welds and connection parts are checked to see if there is gas leakage.

[0194] Step 20343: in the case of no leakage, increase gradually by 10% of the specified test pressure, and detect the gas leakage of all welds and connection parts until the test pressure is reached, maintained for a third time length, and the gas leakage of all welds and connection parts is detected.

[0195] In this step, the third time length can be flexibly set according to actual needs, and in the embodiment, the third time length is 10-15 minutes.

[0196] Specifically, in the case of no leakage, each time the pressure is increased by 10% of the specified test pressure, that is, after each time the pressure is increased by 10% of the specified test pressure, it is maintained for 5-10 minutes, and all welds and connection parts are checked to see if there is gas leakage. After increasing to the test pressure, it is maintained for 10-15 minutes, and all welds and connection parts are checked to see if there is gas leakage, and the pressure should be kept constant during the inspection.

[0197] During the process of step 2034, the pressure vessel has no abnormal sound, and is qualified only after being checked by the leak detection liquid without gas leakage and no visible deformation.

[0198] Optionally, as a feasible implementation, the heat exchanger 8 can also be subjected to airtightness test.

[0199] The airtightness test includes:

[0200] The airtightness test gas is introduced into the heat exchange channel of the heat exchanger 8, and is boosted to 10% of the specified test pressure, maintained for a fourth time length, and the leakage of all welds and connection parts is detected.

[0201] Specifically, the airtightness test gas can be dry and clean air, nitrogen or other inert gases. The fourth time length can be flexibly set according to actual needs, and in the embodiment, the fourth time length is 5-10 minutes.

[0202] More specifically, when the airtightness test gas is introduced, it is first slowly boosted to 10% of the specified test pressure, maintained for 5-10 minutes, and all welds and connection parts are inspected to see if there is any leakage.

[0203] In the case of no leakage, it is boosted to 50% of the specified test pressure, and the leakage of all welds and connection parts is detected.

[0204] Specifically, after being boosted to 50% of the specified test pressure, it is maintained for 5-10 minutes, and all welds and connection parts are inspected to see if there is any leakage.

[0205] In the case of no leakage, it is gradually boosted by 10% of the specified test pressure, maintained for a fifth time length, and the leakage of all welds and connection parts is detected until it is boosted to the test pressure.

[0206] Specifically, the fifth time length can be flexibly set according to actual needs, and in the embodiment, the fifth time length is 10-15 minutes.

[0207] More specifically, in the case of no leakage, each time the pressure is gradually increased by 10% of the specified test pressure, that is, after each time the pressure is increased by 10% of the specified test pressure, it is maintained for 5-10 minutes, and all welds and connection parts are inspected to see if there is any leakage. After being boosted to the test pressure, it is maintained for 10-15 minutes, and all welds and connection parts are inspected to see if there is any leakage, and the pressure should be kept constant during the inspection.

[0208] During the airtightness test, no leakage is detected by the leak detection liquid, which is qualified.

[0209] In the case that the pressure test meets the requirements, step 2035: normal temperature helium mass spectrometry leak detection is performed.

[0210] Specifically, step 2035: normal-temperature helium mass spectrometry leak detection, comprising: step 20351: external leak detection and step 20352: internal leak detection.

[0211] Figure 4 An external leak detection device in normal-temperature helium mass spectrometry leak detection is shown, and the heat exchanger 8 is subjected to external leak detection by the external leak detection device.

[0212] Step 20351: external leak detection, comprising:

[0213] Step 203511: a cover chamber is formed by the polyethylene plastic bag 7, the heat exchanger 8 is placed in the cover chamber, and air in the cover chamber is excluded.

[0214] In this step, the air in the cover 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 cover chamber is disconnected by the first vacuum valve 10. The first vacuum gauge 9 is arranged to communicate the heat exchanger 8 and the cover chamber, respectively, and thus the vacuum degrees of the heat exchanger 8 and the cover chamber are detected.

[0215] Step 203512: helium is introduced into the cover chamber to one atmosphere.

[0216] In this step, after the communication between the first vacuum pump 11 and the cover chamber is disconnected by the first vacuum valve 10, helium is introduced into the cover chamber to one atmosphere by the first helium bottle 5. The first pressure reducing table 6 arranged between the first helium bottle 5 and the cover chamber is used to adjust the gas pressure.

[0217] Step 203513: when the volume of the cover chamber is greater than a preset volume, the sixth time length is set.

[0218] In this step, the preset volume and the sixth time length can be flexibly set according to actual needs. In this embodiment, the preset volume is 100 L, and the sixth time length is 15 minutes.

[0219] In this step, when the volume of the cover chamber is less than or equal to the preset volume, the standing time can be appropriately shortened, for example, standing for 10 minutes.

[0220] Step 203514: each heat exchange channel of the heat exchanger 8 is sequentially pumped to be lower than a second preset pressure threshold, and leak rate data is detected.

[0221] 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 50 Pa, that is, when each heat exchange channel of the heat exchanger 8 is sequentially pumped to be lower than 50 Pa, the leak rate data is detected by the first helium mass spectrometry leak detector 14.

[0222] The branch is provided on a flow path between the first vacuum valve 10 and the first helium mass spectrometer leak detector 14, and the second vacuum valve 13 and the first standard leak hole 12 are arranged on the branch, which can be used for calibrating the leak detection equipment.

[0223] Figure 5 The internal leakage detection equipment in normal temperature helium mass spectrometer leak detection is shown, and the heat exchanger 8 is subjected to internal leakage detection by the internal leakage detection equipment.

[0224] Step 20352: internal leakage detection, comprising:

[0225] Step 203521: selecting one heat exchange channel in the heat exchanger 8 as a measured channel.

[0226] In this step, the heat exchange channel with the largest volume in the heat exchanger 8 can be selected as the measured channel first, and if there are multiple heat exchange channels with the largest volume, any heat exchange channel with the largest volume at the middle position can be selected as the measured channel.

[0227] Step 203522: introducing helium into the adjacent heat exchange channels of the measured channel to one atmosphere.

[0228] In this step, after the measured channel is selected, helium is introduced into the heat exchange channels adjacent to the measured channel to one atmosphere by the second helium cylinder 15. The gas pressure is adjusted by the second pressure reducing gauge 16 between the second helium cylinder 15 and the heat exchanger 8.

[0229] Step 203523: vacuumizing the measured channel to below a third preset pressure threshold and maintaining the pressure for a seventh time length.

[0230] In this step, the third preset pressure threshold and the seventh time length can be flexibly set according to actual needs. In this embodiment, the third preset pressure threshold is 50 Pa, and the seventh time length is 15 minutes. That is, the measured channel is vacuumized to below 50 Pa and maintained for 15 minutes.

[0231] In this step, the measured channel is vacuumized to below the third preset pressure threshold by the second vacuum pump 19. After vacuumization is completed, the flow path between the second vacuum pump 19 and the measured channel is disconnected by the third vacuum valve 18. The vacuum degree of the measured channel is detected by arranging the second vacuum gauge 17 and connecting the second vacuum gauge 17 with the measured channel.

[0232] Step 203524: detecting the leakage rate data of the measured channel.

[0233] In this step, the leakage rate data is detected by the second helium mass spectrometer leak detector 22.

[0234] If all the heat exchange channels need to be subjected to internal leakage detection, each heat exchange channel in the heat exchanger 8 is sequentially taken as the measured channel, and the internal leakage detection is sequentially performed according to the above steps.

[0235] Among them, a branch is set in 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 set in the branch, which can be used to calibrate the leak detection equipment.

[0236] The heat exchanger 8 may include two sets of heat exchange channels, such as a cold fluid channel and a hot fluid channel. In steps 20351 (external leakage detection) and 20352 (internal leakage detection), external leakage data of the cold fluid channel and the hot fluid channel of the heat exchanger 8, as well as internal leakage data between the cold fluid channel and the hot fluid channel, are acquired. The worst value among the three sets of leakage rate data is selected as the leakage rate of the heat exchanger 8.

[0237] If the requirements of step 2035 are not met, the core and end cap are remanufactured and re-welded. If the requirements of step 2035 are met, the heat exchanger 8 is moved to the cryogenic helium mass spectrometry leak detection device for cryogenic testing. The cryogenic helium mass spectrometry leak detection device includes the aforementioned sealing device. That is, if the requirements of step 2035 are met, the heat exchanger 8 is moved to the sealing device of the cryogenic helium mass spectrometry leak detection device.

[0238] Specifically, three platinum resistance thermometers are installed at the inlet, the middle of the side plate, and the outlet of the largest heat exchange channel in heat exchanger 8, respectively, and monitored using a digital display monitor after being powered on. Dry nitrogen is used to replace the air in each tested heat exchange channel, as well as any residual helium and humid air from the room-temperature helium mass spectrometry leak detection process. All connections are checked again to ensure they are complete. After confirmation, the device is pushed into the sealed enclosure of the cryogenic helium mass spectrometry leak detection device. The sealing flange gasket of the cryogenic helium mass spectrometry leak detection device is checked, and after confirming there are no obvious impurities, sealing grease is applied. The sealing grease can be applied directly by hand until it appears visually uniform. Sealing grease is applied as needed. The sealing flange is closed, and the bolts and nuts at the flange are tightened.

[0239] like Figure 3 As shown, the pipe containing valve V1 is connected to the sealing device of the cryogenic helium mass spectrometry leak detection device. The cryogenic helium mass spectrometry leak detection device includes multiple pipes, each connected to a heat exchange channel within heat exchanger 8, and each pipe is equipped with a valve. In this embodiment, as... Figure 3As shown, three pipelines are provided, one of which is provided with a V4 valve, one of which is provided with a V5 valve, and one of which is provided with a V6 valve. The V4 valve, the V5 valve and the V6 valve are used to control the on-off of the pipelines. The V2 valve is arranged on the gas inlet pipeline of the third helium mass spectrometer leak detector 2 and is used to control the on-off of the gas inlet pipeline. The gas inlet pipeline is in communication with the pipeline where the V1 valve is arranged, the pipeline where the V4 valve is arranged, the pipeline where the V5 valve is arranged and the pipeline where the V6 valve is arranged. The pipeline where the vacuum pump system 3 is arranged is in communication with the pipeline where the V1 valve is arranged, the pipeline where the V2 valve is arranged, the pipeline where the V4 valve is arranged, the pipeline where the V5 valve is arranged and the pipeline where the V6 valve is arranged. The V3 valve is arranged on the gas inlet pipeline of the vacuum pump system 3 and is used to control the on-off of the gas inlet pipeline of the vacuum pump system 3. The vacuum pump system 3 is connected with a matching water chiller 4.

[0240] The vacuum pump system 3 comprises a mechanical pump, a Roots pump and a molecular pump connected in sequence.

[0241] Step 2041: The mechanical pump is used to pump the heat exchange channels in the heat exchanger 8 and the closed device where the heat exchanger 8 is arranged.

[0242] In this step, referring to Figure 3 , the V2 valve is closed, the V1 valve, the V3 valve, the V4 valve, the V5 valve and the V6 valve are opened, and the mechanical pump is used to pump the heat exchange channels in the heat exchanger 8 and the closed device where the heat exchanger 8 is arranged.

[0243] Step 2042: When the vacuum degree of the heat exchange channels in the heat exchanger 8 and the closed device where the heat exchanger 8 is arranged is less than a first intermediate pressure threshold, the Roots pump is started to pump the heat exchange channels in the heat exchanger 8 and the closed device where the heat exchanger 8 is arranged.

[0244] 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 the heat exchange channels in the heat exchanger 8 and the closed device where the heat exchanger 8 is arranged is less than 100 Pa, the Roots pump in the vacuum pump system 3 is started to pump the heat exchange channels in the heat exchanger 8 and the closed device where the heat exchanger 8 is arranged.

[0245] Step 2043: When the vacuum degree of the heat exchange channels in the heat exchanger 8 and the closed device where the heat exchanger 8 is arranged is less than a second intermediate pressure threshold, the molecular pump is started to pump the heat exchange channels in the heat exchanger 8 and the closed device where the heat exchanger 8 is arranged, so that the vacuum degree of the heat exchange channels in the heat exchanger 8 and the closed device where the heat exchanger 8 is arranged is less than a first preset pressure threshold.

[0246] In this step, the second intermediate pressure threshold value can be flexibly set according to actual needs. In the embodiment, the intermediate pressure threshold value is 20 Pa. That is, in the case where the vacuum degree of each heat exchange channel in the heat exchanger 8 and the closed device in which the heat exchanger 8 is located is less than 20 Pa, the molecular pump in the vacuum pump system 3 is started to vacuumize each heat exchange channel in the heat exchanger 8 and the closed device in which the heat exchanger 8 is located.

[0247] Specifically, the water chiller 4 is started at the same time when the molecular pump is started. Each time the molecular pump is started, the green "start" button on the molecular pump control panel is pressed to start the molecular pump. When the controller displays that the rotation speed of the molecular pump reaches the rated rotation speed, the red "stop" button is pressed.

[0248] During vacuumization, the mechanical pump is first started in an atmospheric state to obtain 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 remove the suddenly released gas, which is in the pressure range between the mechanical pump and the molecular pump. The molecular pump can use the high-speed rotating rotor to transfer momentum to the gas molecules, so that they obtain directional speed, and are compressed and driven to the exhaust port to be removed by the previous stage. When the three kinds of vacuum pumps are arranged in the order of starting and complementary function during vacuumization of the closed device, they can jointly complete the conversion process of the closed device from atmospheric state to high vacuum state.

[0249] In the case where the vacuum degree of each heat exchange channel in the heat exchanger 8 and the closed device in which the heat exchanger 8 is located is less than the first preset pressure threshold value, step 2044 is performed: the leak detection equipment is connected to the closed device, and the leak detection equipment is blocked from each heat exchange channel in the heat exchanger 8, to obtain the background leakage rate of the closed device.

[0250] In this step, the first preset pressure threshold value can be flexibly set according to actual needs. For example, it can be 10 -4 Pa. Specifically, after the molecular pump is started, when the ionized silicon shows 10 -4 Pa or below, that is, reaches 10 -4 Pa, the third helium mass spectrometric leak detector 2 is started, at this time, the V4 valve, the V5 valve and the V6 valve are in a closed state, the V1 valve and the V2 valve are slowly opened, and then the background leakage rate of the containing space is obtained through the third helium mass spectrometric leak detector 2.

[0251] Step 2045: The leak detection equipment is sequentially connected to each heat exchange channel in the heat exchanger 8, and the leak detection equipment is blocked from the closed device, to obtain the background leakage rate of each heat exchange channel in the heat exchanger 8.

[0252] In this step, the V4 valve, the V5 valve and the V6 valve are opened in sequence respectively, and the V1 valve is closed, so that the background leak rate 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 by the third helium mass spectrometer leak detector 2.

[0253] The heat exchange channel of the heat exchanger 8 includes a cold fluid channel and a hot fluid channel.

[0254] Step 2046: The heat exchanger 8 is subjected to cold shock treatment, and 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 cooling are obtained.

[0255] In one embodiment, the cold shock treatment of the heat exchanger 8 includes:

[0256] Step 20461: Select the cold fluid channel with the largest volume as the first cooling channel, and 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.

[0257] 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 cold fluid channel with the largest volume in the heat exchanger 8 for cooling.

[0258] Step 20462: Control the cooling rate of the first cooling channel to be less than or equal to 4℃ / min.

[0259] In this step, the temperature change can be detected by a digital display monitoring instrument and other detection equipment, and then the cooling rate of the first cooling channel is controlled to be less than or equal to 4℃ / min. At the beginning of cooling, temperature data can be recorded every 10 minutes, and after the cooling rate is stable, temperature data can be recorded every 1 hour. If the cooling rate is too fast, the opening degree of the liquid outlet valve of the liquid nitrogen container 1 can be adjusted to adjust the flow rate.

[0260] In the case where the temperature difference between the first end of the first cooling channel and the second end of the first cooling channel is greater than a preset temperature difference threshold value, and the cooling rate is less than a preset rate threshold value, 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, so that the first end of the first cooling channel becomes the discharge port.

[0261] In this step, the preset temperature difference threshold value can be 10℃. The preset rate threshold value can be 1℃ / min.

[0262] Specifically, in the cooling process, when the temperature of the end through which liquid nitrogen is introduced decreases to the preset temperature difference threshold, the discharge port can still be in a state of higher temperature, 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, so as to further uniformly cool.

[0263] After the temperature of the first cooling channel cools to the preset temperature threshold, and in the case that there is no nitrogen gas discharged from the exhaust port of the first cooling channel, step 20464 is performed: the largest volume of the heat fluid channel is selected as the second cooling channel, liquid nitrogen is introduced into the first end of the second cooling channel, and discharged from the second end of the second cooling channel, so that the second end of the second cooling channel becomes the discharge port.

[0264] 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 largest volume of the heat fluid channel in the heat exchanger 8 to cool. The preset temperature threshold can be -173.15°C.

[0265] Step 20465: control the cooling rate of the second cooling channel to be less than or equal to 4°C / min.

[0266] In this step, the temperature change can be detected by a digital display monitoring instrument or other detection equipment, and then the cooling rate of the second cooling channel is controlled to be less than or equal to 4°C / min. At the beginning of cooling, temperature data can be recorded every 10 minutes, and after the cooling rate is stable, temperature data can be recorded every 1 hour. If the cooling rate is too fast, the opening of the liquid outlet valve of the liquid nitrogen container 1 can be adjusted to adjust the flow.

[0267] In the case that the temperature difference between the first end of the second cooling channel 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, step 20466 is performed: liquid nitrogen is introduced into the second end of the second cooling channel, and discharged from the first end of the second cooling channel, so that the first end of the second cooling channel becomes the discharge port.

[0268] In this step, the preset temperature difference threshold can be 10°C. The preset rate threshold can be 1°C / min.

[0269] Specifically, in the cooling process, when the temperature of the end through which liquid nitrogen is introduced decreases to the preset temperature difference threshold, the discharge port can still be in a state of higher temperature, and the cooling 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 cooling rate is less than the preset rate threshold, liquid nitrogen is introduced into the second end of the second cooling channel and discharged from the first end of the second cooling channel, so as to further uniformly cool. The formula is as follows:

[0270]

[0271] In order to provide more accurate specific flow value for the operator, avoid the operator blind adjustment. The heat exchanger cooling rate can be effectively controlled by controlling the flow rate u of liquid nitrogen The function relationship is dominated by the 0.8 power of flow rate u, and is also affected by heat transfer area, working medium thermal property and temperature difference.

[0272] Wherein, dT is the temperature change, dt is the time change, C is the dimensionless coefficient related to the geometric size of the heat exchanger flow passage (such as the hydraulic diameter D h ), A0 is the reference heat transfer area, α is the surface strengthening coefficient, η is the contact efficiency of heat transfer surface, that is, the ratio of actual effective heat transfer area to theoretical area (0≤η≤1), which is affected by surface roughness and wettability, V is the volume of working medium, ρ is the density of working medium, c p is the specific heat capacity of working medium, T m is the ambient temperature, T is the working medium temperature, and T-T m is the working medium-medium temperature difference.

[0273] According to the target cooling rate r target , the required flow rate u set is calculated as follows:

[0274]

[0275] Wherein, C is the dimensionless coefficient related to the geometric size of the heat exchanger flow passage (such as the hydraulic diameter D h ), A0 is the reference heat transfer area, α is the surface strengthening coefficient, η is the contact efficiency of heat transfer surface, that is, the ratio of actual effective heat transfer area to theoretical area (0≤η≤1), which is affected by surface roughness and wettability, V is the volume of working medium, ρ is the density of working medium, c p is the specific heat capacity of working medium, T m is the ambient temperature, T is the working medium temperature, and T-T m is the working medium-medium temperature difference.

[0276] Specifically, the minimum flow rate u min ≥0.1m / s (to avoid the sudden drop of heat transfer efficiency caused by laminar flow), and the maximum flow rate u max ≤5m / s (limited by pump power and pressure drop).

[0277] Specific calculation example: the known parameter settings are as shown in the following table 1:

[0278] Table 1

[0279]

[0280] Calculate the effective heat transfer area A (η):

[0281] A(η) = A0(1 + αη) = 1.5 x (1 + 0.15 x 0.75) = 1.5 x 1.1125 = 1.669 m 2

[0282] Calculate the comprehensive constant k:

[0283]

[0284] Backflow velocity u set :

[0285]

[0286] u set = 2.504 1.25 ≈ 2.504 1 x 2.504 0.25 ≈ 2.504 x 1.274 ≈ 3.19 m / s

[0287] Due to the superfluid helium effect, if the system temperature is lower than 2.17K (lambda point), the liquid helium enters the superfluid state, and the heat transfer coefficient is significantly improved, so the actual required flow rate can be further reduced.

[0288] In some possible embodiments, the flow rate u set is obtained by the above formula, and the actual initial flow rate is set as A1u set， , wherein A1 is a coefficient between 0 and 1.

[0289] Specifically, the actual initial flow rate is set as 0.3u set , 0.4u set , 0.5u set , 0.6u set . The actual cooling rate is measured and compared with the target cooling rate to make fine adjustment of the flow rate.

[0290] In another embodiment, the heat exchanger 8 is subjected to a cold shock treatment, including: placing the heat exchanger into a cooling medium, and immersing the heat exchanger in the cooling medium for cold shock treatment.

[0291] In the above step 20461 to step 20466, 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 sealing device are obtained.

[0292] In the above step 20461 to step 20466, 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 sealing device are obtained.

[0293] Specifically, the V4 valve, the V5 valve and the V6 valve can be opened in sequence, the V1 valve and the V3 valve can be closed, and the V2 valve can be opened, so that the third helium mass spectrometer 2 can obtain the background leakage rate and the 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. The V1 valve and the V2 valve can be opened, the V3 valve, the V4 valve, the V5 valve and the V6 valve can be closed, and the third helium mass spectrometer 2 can obtain the background leakage rate of the closed device.

[0294] After the temperature of the second cooling channel is cooled to a preset temperature threshold, and in the case that no nitrogen gas is discharged from the exhaust port of the second cooling channel, low-temperature helium mass spectrometric leak detection is performed. The preset temperature threshold can be -173.15℃.

[0295] Step 2047: performing low-temperature helium mass spectrometric leak detection on the heat exchanger 8, including:

[0296] Step 20471: selecting one heat exchange channel as a filling channel, filling helium into the filling channel, and standing for a first time length.

[0297] In this step, the V3 valve, the V4 valve, the V5 valve and the V6 valve in the closed device are kept closed, and helium is filled into the filling channel. Figure 3

[0298] Step 20472: obtaining the external leakage data of the filling channel and the internal leakage data between adjacent heat exchange channels.

[0299] In this step, the third helium mass spectrometer 2 is connected to the closed device, and then the external leakage data of the filling channel is obtained through the numerical change of the third helium mass spectrometer 2. The third helium mass spectrometer 2 is connected to the adjacent heat exchange channels of the filling channel, and then the internal leakage data between the adjacent heat exchange channels is obtained through the numerical change of the third helium mass spectrometer 2.

[0300] Step 20473: sequentially switching other heat exchange channels as the filling channel, repeatedly filling helium into the filling channel and standing for a first time length, obtaining the external leakage data of the filling channel and the internal leakage data between adjacent heat exchange channels, until the external leakage data and the internal leakage data of all heat exchange channels are obtained.

[0301] In this step, other heat exchange channels can be sequentially switched as the filling channel for leak detection in the order of the V4 valve, the V5 valve and the V6 valve.

[0302] Before switching the V4 valve, the V5 valve and the V6 valve, the V2 valve must be closed to avoid the third helium mass spectrometer 2 from being connected to the atmosphere and damaged.

[0303] ​The pressure of the heat exchange channel filled with helium is kept at the working pressure of the heat exchange channel and the maximum pressure difference between adjacent heat exchange channels. For example, the heat exchanger 8 has four groups of heat exchange channels, and the design pressure is 2.5 MPa, and the operating pressure is 1.0 MPa, 0.5 MPa, 0.2 MPa, and 0.1 MPa, respectively. The pressure is kept at the highest working pressure of 1.0 MPa.

[0304] The heat exchanger 8 can include two groups of heat exchange channels, such as cold fluid channels and hot fluid channels. In step 20472, the external leakage data of the cold fluid channels and the external leakage data of the hot fluid channels of the heat exchanger 8 are obtained, and the internal leakage data between the cold fluid channels and the hot fluid channels is obtained. The worst value in the three groups of leakage rate data is selected as the low-temperature helium mass spectrometry leakage detection data of the heat exchanger 8.

[0305] In step 2047, after the low-temperature helium mass spectrometry leakage detection of the heat exchanger 8, the following steps are further included:

[0306] Step 2048: Perform secondary vacuum pumping, and then perform three times of vacuum pumping, and cycle until the total leakage rate is calculated after the i-th time of vacuum pumping, where i is an integer greater than 3.

[0307] Specifically, in one possible embodiment, based on the principle of mass conservation, a multi-stage pumping process can be modeled as a dynamic leakage system of a series of cavities. Assuming that the pumping speed of each stage is constant and the leakage source is in a steady flow state, the total leakage rate can be decomposed into the linear superposition of the leakage rate of each independent pressure interval. By introducing an effective pumping speed correction coefficient and a pressure decay function, the total leakage rate formula of the system is derived:

[0308]

[0309] In the formula, S i is the effective pumping speed of the i-th stage, P i is the equilibrium pressure of the i-th stage, and η i 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, providing a theoretical basis for leakage determination.

[0310] In another possible embodiment, secondary vacuum pumping is performed, the equivalent leakage rate of the second stage is calculated, and then three times of vacuum pumping is performed, the equivalent leakage rate of the third stage is calculated. Cycle until the i-th time of vacuum pumping is performed, the equivalent leakage rate of the i-th stage is calculated, and the total leakage rate is calculated, where i is an integer greater than 3. When the system reaches a steady state in the i-th vacuum stage, the leakage gas flow and the pumping speed are balanced, and satisfy:

[0311] Q i = S i · (P i,5q -P i,lim )

[0312] In the formula, Qi The equivalent leak rate of the i-th stage (Pa·m 3 / s), S i The effective pumping speed of the i-th stage (m 3 / s), P i,eq The equilibrium pressure of the i-th stage (Pa), P i,lim The ultimate vacuum of the i-th stage (Pa).

[0313] For an n-stage pumping system, the total leak rate is the cumulative effect of the leak rates of each stage. Considering the independence of the leakage paths and the non-linear characteristics of the pressure difference, the total leak rate can be expressed as:

[0314]

[0315] Where t i is the i-th stage pumping time (s); τ i = V / S i ; τ i is the i-th stage characteristic time constant (s); V is the system volume (m 3 ); and exp is the exponential term, reflecting the influence of pressure decay on leak rate during the unsteady pumping process.

[0316] The present embodiment adopts pressure gradient progressive control, which can isolate the interference of micro leaks and macro leaks at 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 a steady state vacuum, avoiding the problem of non-linear response caused by sudden pressure drop in the traditional single-stage pumping process. In addition, this method can reduce the continuous load of the vacuum pump by releasing residual stress in stages, thereby prolonging the service life of the key equipment.

[0317] After step 2048, it further includes:

[0318] Step 20491, close the vacuum pumping system to break the vacuum inside the sealed device;

[0319] Step 20492, after the heat exchanger 8 is warmed up, control the warming rate of the heat exchanger 8;

[0320] Specifically, the warming rate of the heat exchanger 8 must be strictly controlled within 4℃ / min, and the sealed device must not be opened before the heat exchanger 8 is warmed up to room temperature.

[0321] Step 20493, when the heat exchanger 8 returns to room temperature, remove the heat exchanger 8 from the sealed device.

[0322] After removing the heat exchanger 8 from the sealed device, step 205 is performed: performing a burst purge on the heat exchanger 8. Specifically, it includes:

[0323] First step: select a heat exchange channel for burst purge.

[0324] In this step, one of the heat exchange channels is selected, and the selected heat exchange channel is first subjected to explosive purging.

[0325] The second step is to block the outlet of the selected heat exchange channel using explosive materials.

[0326] In this step, the outlet of the selected heat exchange channel is blocked using explosive materials, which can accumulate the pressure of high-pressure nitrogen gas in the selected heat exchange channel. When the pressure reaches a certain level, it can trigger an explosion, generating a powerful impact force that can effectively remove impurities in the heat exchange channel and improve the cleaning effect.

[0327] The third step is to inject high-pressure nitrogen gas through the inlet of the selected heat exchange channel.

[0328] In this step, high-pressure nitrogen gas can serve as the power source for explosive purging. When the explosion occurs, the high-pressure nitrogen gas can push the particles, impurities, and other substances in the heat exchange channel out with the gas flow, achieving the cleaning effect of the heat exchange channel.

[0329] The fourth step is to 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 the blasting.

[0330] The fifth step is to repeat the blasting when the particle concentration at the outlet of the selected heat exchange channel is greater than the preset concentration value, until the particle concentration at the outlet is less than or equal to the preset concentration value.

[0331] In this step, through multiple high-pressure blasting, the difficult-to-clean impurities in the heat exchange channel are gradually removed, ensuring that the interior of the selected heat exchange channel meets the higher cleanliness standard. By comparing the particle concentration at the outlet with the preset concentration value, a basis is provided for determining whether the heat exchange channel is clean, ensuring the cleaning quality.

[0332] 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 cm 2 , which is the preset concentration value. If this standard is not met, repeated blasting or disassembly and modification or even scrapping and re-production is performed.

[0333] The sixth step is to block the inlet of the selected heat exchange channel using explosive materials.

[0334] In this step, the inlet of the selected heat exchange channel is blocked using explosive materials, which can change the direction of the gas flow during explosive purging, further improving the comprehensiveness of the cleaning.

[0335] The seventh step is to inject high-pressure nitrogen gas through the outlet of the selected heat exchange channel.

[0336] In this step, high-pressure nitrogen gas can be used as the power source for the blasting purge. When the blasting occurs, the high-pressure nitrogen gas can push the particles, impurities, and the like in the heat exchange channel out with the airflow, thereby achieving the cleaning effect on the heat exchange channel.

[0337] The eighth step is to 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 the blasting.

[0338] The ninth step is to repeat the blasting when the particle concentration at the inlet of the selected heat exchange channel is greater than the preset concentration value, until the particle concentration at the inlet is less than or equal to the preset concentration value.

[0339] In this step, 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 pm is less than 10 per cm 2 , which is the preset concentration value. If this standard is not met, the blasting is repeated, or the heat exchange channel is disassembled, modified, or even scrapped and re-produced.

[0340] In this step, the impurities that are difficult to clean in the heat exchange channel are gradually removed through multiple high-pressure blasting, so as to ensure that the interior of the selected heat exchange channel reaches a high cleanliness standard. By comparing the particle concentration at the inlet with the preset concentration value, a basis is provided for judging whether the heat exchange channel is clean, thereby ensuring the cleaning quality.

[0341] The tenth step is to switch other heat exchange channels for blasting and purging in turn, and repeat the first step to the ninth step until all the heat exchange channels are completed.

[0342] All the heat exchange channels are blasted and purged one by one to ensure that each heat exchange channel of the heat exchanger 8 reaches a high cleanliness standard, thereby avoiding the influence of incomplete cleaning of part of the heat exchange channels on the overall performance and operation stability of the heat exchanger 8.

[0343] Specifically, in an embodiment, during the blasting and purging process, a compressor or a nitrogen cylinder injects high-pressure nitrogen gas, and the general pressure is 0.6-1.0 MPa. The highland barley paper burst disc is used as the blasting material, and the thickness is 0.3-0.5 mm. The pressure resistance strength needs to be designed according to the purging pressure. A pressure gauge can be arranged to realize real-time monitoring of the purging pressure, and the pressure gauge range is 0-1.5 MPa. A safety valve or a pressure relief valve can be arranged on the flow path to prevent overpressure.

[0344] In this embodiment, preparation work is done before the burst purge. Close the heat exchanger inlet and outlet valves to ensure isolation from other systems. Open the blowdown valve to drain the internal medium and confirm that the pressure is zero. Remove the original heat exchanger inlet and outlet flanges and install temporary flanges with burst disc interfaces. After the preparation work is completed, install the burst disc, select the thickness of the barley paper according to the purge pressure, for example, 0.4mm can withstand about 0.8MPa burst pressure. When installing, clean the flange sealing surface to ensure that there are no burrs. Cut the barley paper to the size of the flange and place it in the center. Apply high-temperature sealant and tighten the bolts evenly and diagonally to avoid bias. Then connect the gas source system, connect the air compressor or nitrogen cylinder to the heat exchanger inlet flange with rubber hose. Install a pressure gauge on the inlet pipeline and calibrate the range. Install a safety valve on the gas source outlet and set the pressure to 1.1 times the purge pressure. When burst purging, first perform low-pressure pre-purging. Turn on the gas source and slowly pressurize to 0.2MPa, maintain for 10 minutes, loosen the impurities initially, and observe whether there are obvious foreign matters discharged from the outlet. Then perform high-pressure burst purging, gradually pressurize to the design pressure, for example, 0.8MPa, until the barley paper burst disc breaks. The gas flow is high-speed at the moment of burst, carrying impurities out, realizing burst purging.

[0345] After step 205, further comprising:

[0346] Step 206: Perform cleanliness detection on the heat exchanger 8. Specifically, use an endoscope to extend into each heat exchange channel of the heat exchanger 8 for detection.

[0347] In this step, use an endoscope to extend into each heat exchange channel of the heat exchanger 8 for detection, which can directly observe whether there are impurities, foreign matters, etc. in the heat exchange channel. If there are impurities, it may cause the heat exchange channel to be blocked in a low-temperature environment, affecting fluid flow, and even damaging the equipment. Through cleanliness detection, impurities can be found and cleaned in time, which can effectively avoid these problems and ensure the safe and stable operation of the equipment.

[0348] If the cleanliness detection meets the requirements, proceed to step 207: flow and heat transfer performance test. Specifically, it includes:

[0349] Step 2071: Measure the cold side fluid pressure drop of the heat exchanger 8.

[0350] Among them, the cold side fluid pressure drop 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.

[0351] Before measurement, prepare a stable cold fluid source, such as a 2K negative pressure heat exchanger test device, to ensure that superfluid helium temperature zone and stable cold fluid flow can be provided. A high-precision pressure sensor is installed on the cold fluid inlet and outlet pipe of the heat exchanger 8 for measuring the pressure difference before and after the cold side fluid enters the heat exchanger 8. At the same time, a flow measuring device, such as a turbine flowmeter, is installed on the cold side inlet and hot side inlet pipe for analyzing the cold side pressure drop under different flow rates. Start the cold fluid source and make the cold fluid flow stably in the pipe and heat exchanger 8 for a period of time to make the system reach a thermal steady state, avoiding the influence of temperature fluctuations on the accuracy of measurement. According to the design parameters of the heat exchanger 8 and the actual working conditions, adjust the cold fluid flow to the design working condition and keep the flow stable. After the system is stable, read and record the readings of the cold side inlet and 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.

[0352] Step 2072: Perform heat exchange efficiency test on the heat exchanger 8.

[0353] In this step, by measuring the relevant parameters of the cold side fluid and the hot side fluid, the heat exchange amount is obtained by using the heat calculation formula, and then the efficiency of the heat exchanger 8 is calculated.

[0354] Specifically, high-precision temperature sensors are installed on the inlet and outlet pipes of the cold fluid and hot fluid 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, flow measuring devices, such as mass flow meters, are installed on the pipes to accurately measure the mass flow of the cold and hot fluids. According to the principles of thermodynamics, the heat exchange amounts of the cold fluid and the hot fluid are calculated respectively. According to the design parameters of the heat exchanger 8, the maximum possible heat exchange amount is calculated, and the heat exchange efficiency of the heat exchanger 8 is calculated based on the actual heat exchange amount of the heat exchanger 8 and the maximum possible heat exchange amount.

[0355] Specifically, according to the law of conservation of energy, the heat exchange amounts of the cold and hot fluids should be equal.

[0356] The calculation formula of the cold side heat exchange amount is:

[0357] Q c = m c · c c · (T c,out -T c,in )

[0358] T c,out , T c,in : cold fluid inlet / outlet temperature (measured by high-precision temperature sensor);

[0359] m c : cold fluid mass flow (measured by turbine flowmeter or mass flowmeter);

[0360] c c : specific heat capacity of cold fluid at constant pressure (known property parameter);

[0361] Wherein, the calculation formula of cold side pressure drop is:

[0362] ΔP c = P c,in - P c,out

[0363] P c,in : cold fluid inlet pressure, P c,out : cold fluid outlet pressure, P c,in and P c,out can be measured by pressure sensor.

[0364] Wherein, the calculation formula of heat side heat exchange amount is:

[0365] Q h = m h · c h · (T h,in - T h,out )

[0366] In the formula, T h,in , T h,out : hot fluid inlet / outlet temperature (measured by high-precision temperature sensor);

[0367] m h : hot fluid mass flow (measured by mass flow meter);

[0368] c h : specific heat capacity of hot fluid at constant pressure (known property parameter);

[0369] Determine the minimum heat capacity rate, the formula is:

[0370] C min = min(m c c c , m h c h )

[0371] In the formula, C min is the minimum heat capacity rate;

[0372] m c : cold fluid mass flow (measured by turbine flow meter or mass flow meter);

[0373] c c : specific heat capacity of cold fluid at constant pressure (known property parameter);

[0374] m h : hot fluid mass flow (measured by mass flow meter);

[0375] c h : specific heat capacity at constant pressure of hot fluid (known property parameter).

[0376] The maximum heat capacity rate is determined by the formula:

[0377] C max = max(m c c c , m h c h )

[0378] where C max is the maximum heat capacity rate;

[0379] m c : mass flow rate of cold fluid (measured by turbine flow meter or mass flow meter);

[0380] c c : specific heat capacity at constant pressure of cold fluid (known property parameter);

[0381] m h : mass flow rate of hot fluid (measured by mass flow meter);

[0382] c h : specific heat capacity at constant pressure of hot fluid (known property parameter).

[0383] The maximum heat exchange rate is determined by the formula:

[0384] Q max = C min ·(T h,in -T c,in )

[0385] The heat exchange efficiency η is defined as the ratio of actual heat exchange rate to the maximum possible heat exchange rate, based on the number of transfer units (NTU) method, assuming that the overall heat transfer coefficient U and the cold side pressure drop ΔP c are related as:

[0386] The heat transfer coefficient correlation is:

[0387] U∝(ΔP) α , where α ≈ 0.4

[0388] The expression for NTU is:

[0389]

[0390] Assuming C min = m c c c , and A is a constant, which is combined into the coefficient k.

[0391] When the heat exchanger is a counterflow heat exchanger, C minThe ratio C max of the heat transfer coefficient of the heat transfer surface of the heat exchanger 8 to the heat transfer coefficient of the heat transfer surface of the heat exchanger 8 r satisfies the formula:

[0392] C r = C min / C max <<1

[0393] The efficiency formula is:

[0394]

[0395] Specifically, the formula is:

[0396]

[0397] Wherein, k is a fitting constant, which comprehensively considers the heat transfer area, fluid properties and other factors.

[0398] In some possible embodiments, k = 0.023, and the formula is:

[0399]

[0400] In the case that the flow heat transfer performance test meets the requirements, step 208 is performed: cleaning the inner and outer surfaces of the heat exchanger 8.

[0401] In this step, the cleanliness of the heat exchanger 8 is further improved by cleaning the inner and outer surfaces of the heat exchanger 8 again.

[0402] Step 209: welding the nameplate. After welding the nameplate, the processing of the 2K negative pressure aluminum finned heat exchanger is completed.

[0403] It is easy for those skilled in the art to understand that the above advantageous modes can be freely combined and superimposed without conflict.

[0404] The above is only a preferred embodiment of the present application, and is not intended to limit the present application. Any modification, equivalent replacement and improvement made within the spirit and principle of the present application shall be included in the protection scope of the present application. The above is only a preferred embodiment of the present application, and it should be pointed out that, for ordinary skilled in the art, without departing from the technical principles of the present application, a number of improvements and modifications can be made, and these improvements and modifications should be regarded as the protection scope of the present application.

Claims

1. A processing method for improving the yield of 2K negative pressure aluminum plate-fin heat exchangers, characterized in that, The method comprises the following steps: manufacturing a core; manufacturing a head, the manufacturing process of the head comprising integrally forging the head; connecting the core and the head to form a heat exchanger; performing normal-temperature detection on the heat exchanger, the temperature range of the normal-temperature detection being 20-30℃; performing low-temperature detection on the heat exchanger, the temperature range of the low-temperature detection being below-150℃; wherein the step of performing low-temperature detection on the heat exchanger comprises: performing vacuumization on each heat exchange channel in the heat exchanger and a closed device in which the heat exchanger is located, the heat exchange channels of the heat exchanger comprising cold fluid channels and hot fluid channels; in the case where the vacuum degree is less than a 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 cold stimulation treatment on the heat exchanger, and obtaining the background leakage rate and the vacuum degree of each heat exchange channel in the heat exchanger and the background leakage rate and the vacuum degree of the closed device during the cooling process; in the case where the temperature cools to a preset temperature threshold, performing low-temperature helium mass spectrometry leak detection on the heat exchanger; wherein the cold stimulation treatment on the heat exchanger comprises: selecting a cold fluid channel with the largest volume as a first cooling channel, introducing liquid nitrogen into a first end of the first cooling channel, and discharging the liquid nitrogen from a second end of the first cooling channel, so that the second end of the first cooling channel becomes a discharge port; in the case where the temperature difference between the first end of the first cooling channel and the second end of the first cooling channel is greater than a preset temperature difference threshold, and the cooling rate is less than a preset rate threshold, introducing liquid nitrogen into the second end of the first cooling channel, and discharging the liquid nitrogen from the first end of the first cooling channel, so that the first end of the first cooling channel becomes a discharge port; after the temperature of the first cooling channel cools to a preset temperature threshold, and in the case where no nitrogen gas is discharged from the exhaust port of the first cooling channel, selecting a hot fluid channel with the largest volume as a second cooling channel, introducing liquid nitrogen into a first end of the second cooling channel, and discharging the liquid nitrogen from a second end of the second cooling channel, so that the second end of the second cooling channel becomes a discharge port; controlling the cooling rate of the first cooling channel and the second cooling channel to be less than or equal to 4℃ / min; in the case where the temperature difference between the first end of the second cooling channel and the second end of the second cooling channel is greater than a preset temperature difference threshold, and the cooling rate is less than a preset rate threshold, introducing liquid nitrogen into the second end of the second cooling channel, and discharging the liquid nitrogen from the first end of the second cooling channel, so that the first end of the second cooling channel becomes a discharge port; after the temperature of the second cooling channel cools to a preset temperature threshold, and in the case where no nitrogen gas is discharged from the exhaust port of the second cooling channel, performing the low-temperature helium mass spectrometry leak detection; The heat exchanger cooling rate is regulated by controlling the liquid nitrogen flow rate u, the required flow rate u set The formula is: wherein r target is the target cooling rate, C is a dimensionless coefficient related to the heat exchanger flow passage geometry; A0 is the reference heat transfer area; a 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), which is affected by the surface roughness and wettability; V is the working medium volume; p is the working medium density; c p is the specific heat capacity of the working medium; T m is the ambient temperature; T is the working medium temperature; T-T m is the working medium-medium temperature difference; after the low-temperature helium mass spectrometry leak detection on the heat exchanger, further comprising: performing secondary vacuumization, and then performing tertiary vacuumization, and repeating the process until the ith vacuumization is performed to calculate the total leakage rate, wherein i is an integer greater than 3.

2. The processing method for improving the yield of 2K negative pressure aluminum finned heat exchanger according to claim 1, characterized in that, the process of performing secondary vacuumization, and then performing tertiary vacuumization, and repeating the process until the ith vacuumization is performed to calculate the total leakage rate, wherein i is an integer greater than 3, comprises: based on the principle of mass conservation, modeling the multi-stage air extraction process as a dynamic leakage system of series-connected cavities; the extraction speed of each stage is constant, and the leakage source is in a steady flow state, and the total leakage rate is decomposed into the linear superposition of the leakage rates of each independent pressure interval; the effective extraction speed correction coefficient and the pressure decay function are introduced, and the total leakage rate formula of the system is: In the formula, S i is the i-th stage effective pumping speed, P i is the i-th stage equilibrium pressure, η i is the i-th stage leakage path weight factor.

3. The processing method for improving the yield of 2K negative pressure aluminum plate-fin heat exchangers according to claim 1, characterized in that, The secondary vacuum is performed, and the third vacuum is performed, and the cycle is repeated until the total leakage rate is calculated by performing the i-th vacuum, wherein i is an integer greater than 3, including: The secondary vacuum is performed, and the third vacuum is performed, and the cycle is repeated until the total leakage rate is calculated by performing the i-th vacuum, wherein i is an integer greater than 3, including: Q i = S i · (P i,5q - P i,lim ) wherein Q i is the equivalent pumping speed of the i-th stage (Pa·m 3 / s), S i is the effective pumping speed of the i-th stage (m 3 / s), P i,eq is the equilibrium pressure of the i-th stage (Pa), and P i,lim is the ultimate vacuum of the i-th stage (Pa). For an n-stage vacuum system, the total leakage rate is the cumulative effect of the leakage rates of each stage, considering the independence of the leakage paths and the non-linear characteristics of the pressure difference, and the total leakage rate can be expressed as: where t i is the i-th stage evacuation time (s); τ i = V / S i ; τ i is the i-th stage characteristic time constant (s); V is the system volume (m 3 ); and exp is an exponential term reflecting the influence of pressure decay on the leak rate during the non-steady state evacuation.

4. The processing method for improving the yield of 2K negative pressure aluminum plate-fin heat exchangers according to claim 1, characterized in that, After the secondary vacuum is performed, and the third vacuum is performed, and the cycle is repeated until the total leakage rate is calculated by performing the i-th vacuum, wherein i is an integer greater than 3, including: The vacuum system is closed, and the vacuum inside the sealed device is broken; After the heat exchanger is warmed up, the warming rate of the heat exchanger is controlled; the warming rate of the heat exchanger is controlled to be within 4℃ / min; After the heat exchanger returns to normal temperature, the heat exchanger is removed from the sealed device.

5. The processing method for improving the yield of 2K negative pressure aluminum plate-fin heat exchangers according to claim 1, characterized in that, After the heat exchanger is detected at low temperature, the heat exchanger is also subjected to a burst purge; After the heat exchanger is subjected to a burst purge, the heat exchanger is also subjected to a cleanliness detection; If the cleanliness detection meets the requirements, the heat exchanger is subjected to a flow heat transfer performance test; The flow heat transfer performance test of the heat exchanger includes a cold side fluid pressure drop measurement of the heat exchanger; The cold side fluid pressure drop measurement of the heat exchanger includes: A high-precision pressure sensor is installed on each of the heat exchanger cold fluid inlet and outlet pipelines to measure the pressure difference before and after the cold side fluid enters the heat exchanger, and a flow measurement device is installed on each of the cold side inlet and hot side inlet pipelines to analyze the cold side pressure drop at different flow rates; Start the cold fluid source and make the cold fluid flow stably in the pipeline and the heat exchanger for a period of time to make the system reach a thermal steady state, adjust the cold fluid flow to the design condition, and keep the flow stable; After the system stabilizes, read and record the readings measured by the cold side inlet and 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.

6. The processing method for improving the yield of 2K negative pressure aluminum plate-fin heat exchangers according to claim 5, characterized in that, The flow heat transfer performance test of the heat exchanger also includes an efficiency test of the heat exchanger; The efficiency test of the heat exchanger includes: High-precision temperature sensors are installed on the inlet and outlet pipelines of the cold fluid and hot fluid of the heat exchanger to measure the inlet and outlet temperatures of the cold and hot fluids in real time; Flow measurement devices such as mass flow meters are installed on the pipelines to accurately measure the mass flow of the cold and hot fluids; According to the principles of thermodynamics, the heat transfer amounts of the cold fluid and the hot fluid are calculated respectively; According to the design parameters of the heat exchanger, the maximum possible heat transfer amount is calculated, and the heat transfer efficiency of the heat exchanger is calculated based on the actual heat transfer amount and the maximum possible heat transfer amount of the heat exchanger; According to the law of conservation of energy, the heat transfer amounts of the cold and hot fluids should be equal; The calculation formula of the cold side heat exchange amount is: Q c = m c · c c · (T c,out - T c,in ) wherein T c,out , T c,in : cold fluid inlet / outlet temperature (high precision temperature sensor measurement); m c : cold fluid mass flow (measured by turbine flow meter or mass flow meter) c c : Constant pressure specific heat capacity of cold fluid (known property parameter) The calculation formula of the cold side pressure drop is: ΔP c = P c,in - P c,out P c,in is the cold fluid inlet pressure, P c,out is the cold fluid outlet pressure, P c,in and P c,out may be measured by pressure sensors; The calculation formula of the hot side heat exchange amount is: Q h = m h · c h · (T h,in - T h,out ) wherein T h,in , T h,out : hot fluid inlet / outlet temperature (high precision temperature sensor measurement); m h : Hot fluid mass flow (measured by mass flow meter); c h : Constant pressure specific heat capacity of hot fluid (known property parameter) The minimum heat capacity rate is determined, and the formula is: C min = min(m c c c ,m h c h ) In the formula, C min is the minimum heat capacity rate; m c : cold fluid mass flow (measured by turbine flow meter or mass flow meter) c c : Constant pressure specific heat capacity of cold fluid (known property parameter) m h : Hot fluid mass flow (measured by mass flow meter); c h : Constant pressure specific heat capacity of hot fluid (known property parameter) The maximum heat capacity rate is determined, and the formula is: C max = max(m c c c ,m h c h ) In the formula, C max is the maximum heat capacity rate; m c : cold fluid mass flow (measured by turbine flow meter or mass flow meter) c c : Constant pressure specific heat capacity of cold fluid (known property parameter) m h : Hot fluid mass flow (measured by mass flow meter); c h : Constant pressure specific heat capacity of hot fluid (known property parameter) The maximum heat exchange amount is determined, and the formula is: Q max = C min ·(T h,in -T c,in ) The heat exchange efficiency η is defined as the ratio of the actual heat exchange quantity to the maximum possible heat exchange quantity, based on the heat transfer unit number (NTU) method, assuming that the total heat transfer coefficient U and the cold side pressure drop ΔP c Related: The heat transfer coefficient correlation is: U ∝ (ΔP) α where a ~ 0.4 The NTU expression is: Assume c min = m c c c , and A is a constant, merged into the coefficient k; When the heat exchanger is a counterflow heat exchanger, C min The ratio C max of C r satisfies the formula: C r = C min / C max < 1 The efficiency formula is: Specifically, the formula is: Wherein, k is a fitting constant, which comprehensively considers the heat transfer area, fluid properties and other factors; In some possible embodiments, k = 0.023, and the formula is:

7. The method of claim 1, wherein the method is characterized by: Minimum flow rate u of the flow rate u of the liquid nitrogen min Maximum flow rate u of the flow rate u of the liquid nitrogen max ≤ 5 m / s.

8. The processing method for improving the yield of 2K negative pressure aluminum plate-fin heat exchangers according to claim 1, characterized in that, The pipeline where the V1 valve is located is connected to the closed device of the low-temperature helium mass spectrometric leak detection device. The low-temperature helium mass spectrometric leak detection device includes a plurality of pipelines. Each pipeline is connected to a heat exchange channel in the heat exchanger, and a valve is arranged on each pipeline. There are three pipelines in total. A V4 valve is arranged on one of the pipelines, a V5 valve is arranged on one of the pipelines, and a V6 valve is arranged on one of the pipelines. The V4 valve, the V5 valve, and the V6 valve are used to control the on-off of the pipelines where they are located. The V2 valve is arranged on the gas inlet pipeline of the third helium mass spectrometric leak detector and is used to control the on-off of the gas inlet pipeline. The gas inlet pipeline is 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 is located is 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 gas inlet pipeline of the vacuum pump system and is used to control the on-off of the gas inlet pipeline of the vacuum pump system. The vacuum pump system is connected to a matching water chiller 4. The vacuum is drawn on each heat exchange channel in the heat exchanger and the closed device where the heat exchanger is located, including: The V2 valve is closed, and the V1 valve, the V3 valve, the V4 valve, the V5 valve, and the V6 valve are opened. The mechanical pump is started to draw vacuum on each heat exchange channel in the heat exchanger and the closed device where the heat exchanger is located. In the case 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 100 Pa, the Roots pump in the vacuum pump system is started to draw vacuum on each heat exchange channel in the heat exchanger and the closed device where the heat exchanger is located. In the case 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 20 Pa, the molecular pump in the vacuum pump system is started to draw vacuum on each heat exchange channel in the heat exchanger and the closed device where the heat exchanger is located.

9. The processing method for improving the yield of 2K negative pressure aluminum plate-fin heat exchangers according to claim 8, characterized in that, In the case that the vacuum degree is less than the first preset pressure threshold, the background leak rate of the closed device and the background leak rate of each heat exchange channel in the heat exchanger are obtained, including: After the molecular pump is opened, 10 -4 Pa, the third helium mass spectrometer leak detector is opened, at this time, the V4 valve, the V5 valve and the V6 valve are in a closed state, the V1 valve and the V2 valve are opened, and the background leakage rate of the containing space is obtained through the third helium mass spectrometer leak detector; The V4 valve, the V5 valve, and the V6 valve are opened in sequence, and the V1 valve is closed. The background leak rates of the heat exchange channels of the heat exchanger corresponding to the V4 valve, the V5 valve, and the V6 valve are obtained by the third helium mass spectrometric leak detector.

10. The processing method for improving the yield of 2K negative pressure aluminum finned heat exchanger according to claim 8, characterized in that, The low-temperature helium mass spectrometric leak detection is performed on the heat exchanger, including: The V3 valve, the V4 valve, the V5 valve, and the V6 valve are kept closed, and helium gas is filled into the filling channel. The third helium mass spectrum leak detector is connected with the closed device, the outside leakage data of the filling channel is obtained through the numerical change of the third helium mass spectrum leak detector, the third helium mass spectrum leak detector is connected with the adjacent heat exchange channels of the filling channel, and the internal leakage data between the adjacent heat exchange channels is obtained through the numerical change of the third helium mass spectrum leak detector. Other heat exchange channels are switched as the filling channel in sequence to carry out leak detection.

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