2K negative pressure heat exchanger low temperature leak detection method, device and system

Abstract

This invention provides a method, apparatus, and system for cryogenic leak detection of 2K negative pressure heat exchangers, belonging to the field of refrigeration and cryogenic technology. It aims to solve the problems that room-temperature helium mass spectrometry leak detection cannot accurately assess the leakage rate performance of 2K negative pressure heat exchangers in deep cryogenic environments, and cannot measure the leakage rate of heat exchangers under design pressure. The cryogenic leak detection method, apparatus, and system provided by this invention can accurately assess the leakage rate performance of 2K negative pressure heat exchangers in deep cryogenic environments and analyze the impact of rapid cooling on the sealing performance of the equipment. Simultaneously, it supports automatic loading and unloading of 2K negative pressure heat exchangers and enables online synchronous testing of multiple heat exchangers, significantly improving the processing efficiency and yield of heat exchangers.

Description

Technical Field

[0001] This invention belongs to the field of refrigeration and cryogenic technology, specifically relating to a method, device and system for cryogenic leak detection of a 2K negative pressure heat exchanger. Background Technology

[0002] A 2K negative pressure heat exchanger refers to a heat exchanger operating in the 4K liquid helium and 2K superfluid helium temperature range. It can be used to recover cold energy from cryogenic systems and increase the production rate of superfluid helium. Operating in a deep cryogenic, negative pressure environment, the 2K negative pressure heat exchanger experiences small temperature differences between its two sides, drastic changes in helium properties, and a transition between the 4K liquid helium and 2K superfluid helium states. Therefore, the leakage rate, heat transfer performance, pressure drop performance, and volume of the 2K negative pressure heat exchanger significantly impact the performance of the cryogenic system, as well as the construction and operating costs of the heat exchanger. The mechanical, thermal, and electrical properties of metallic materials change with temperature, especially between cryogenic environments and ambient temperatures. These changes have important implications in cryogenic engineering, aerospace, cryogenic storage, superconducting materials, refrigeration, and energy fields.

[0003] After manufacturing and quality inspection, 2K negative pressure heat exchangers are typically installed inside cryogenic valve boxes, refrigeration unit cold boxes, and test platforms. The heat exchanger is constructed by welding together multiple components and releasing stress. If the heat exchanger leaks due to stress in a deep cryogenic environment, disassembly, repair, or replacement is costly and can disrupt project progress.

[0004] Conventional leak detection methods are mostly performed at room temperature. However, room-temperature helium mass spectrometry leak detection cannot accurately reflect and assess the sealing performance of 2K negative pressure heat exchangers in cryogenic environments, nor the impact of rapid cooling on the heat exchanger itself. Furthermore, this method cannot inject pressurized helium into the heat exchanger cavity, thus making it impossible to measure the leak rate at the design pressure. During the heat exchanger manufacturing process, cryogenic leak rate testing can only be performed on 2K negative pressure heat exchangers that have passed room-temperature helium mass spectrometry leak detection. If the room-temperature leak detection fails, cryogenic leak rate testing must not be performed. Summary of the Invention

[0005] Therefore, the technical problem to be solved by the present invention is to provide a low-temperature leak detection method, device and system for 2K negative pressure heat exchangers, which can obtain the internal and external leakage rates of 2K negative pressure heat exchangers in a deep cryogenic environment. It can solve the problems that room temperature helium mass spectrometry leak detection cannot accurately reflect and evaluate the sealing performance of heat exchangers in a deep cryogenic environment, their ability to withstand rapid cooling and the inability to measure the leakage rate of heat exchangers under design pressure. It can also realize the automatic loading and unloading of 2K negative pressure heat exchangers, and simultaneously detect multiple 2K negative pressure heat exchangers online, thereby improving the processing efficiency and yield of heat exchangers.

[0006] To address the aforementioned problems, this invention provides a low-temperature leak detection method for a 2K negative pressure heat exchanger, comprising the following steps:

[0007] S1. Connect each heat exchange channel of the heat exchanger under test to the hose assembly, temperature monitoring interface and vacuum interface on the vacuum container respectively;

[0008] S2. Place the heat exchanger to be tested into a vacuum container and seal the vacuum container.

[0009] S3. Use the vacuum system to evacuate the vacuum container and heat exchange channel through the vacuum interface;

[0010] S4. Fill the heat exchange channel of the heat exchanger under test with liquid nitrogen or liquid helium to cool the heat exchange channel.

[0011] S5. Obtain the temperature change of the heat exchanger under test through the temperature monitoring interface in order to control the cooling rate of the heat exchanger under test.

[0012] S6. To bring the temperature in the heat exchange channel to the liquid nitrogen / liquid helium temperature range;

[0013] S7. Vent nitrogen or helium from the heat exchange channel;

[0014] S8. Fill the cooled heat exchange channel with helium until the pressure in the heat exchange channel reaches the expected value.

[0015] S9. After a preset static time, check the external and internal leakage of the heat exchange channel in the liquid nitrogen / liquid helium temperature range;

[0016] S11. Turn off the vacuum system and break the vacuum inside the vacuum container;

[0017] S12. Reheat the heat exchanger under test and control the reheating rate of the heat exchanger under test.

[0018] S13. After the heat exchanger under test returns to normal temperature, remove the heat exchanger under test from the vacuum container.

[0019] Optionally, step S3 further includes: using a vacuum system to evacuate the vacuum container and the heat exchange channel step by step through the vacuum port until the pressure inside the vacuum container is ≤5Pa.

[0020] Optionally, the process between steps S9 and S11 may include:

[0021] S10. Perform a second vacuuming, then a third vacuuming, and repeat until the i-th vacuuming is performed. Calculate the total leakage rate, where i is an integer greater than 3.

[0022] Optionally, step S9 includes:

[0023] S901, maintain the pressure in the heat exchange channel at the working pressure;

[0024] S902, make the pressure difference between the heat exchange channel and the adjacent heat exchange channel reach the preset value;

[0025] S903. Detect the external leakage of the heat exchange channel and the internal leakage between the heat exchange channel and the adjacent heat exchange channel;

[0026] S904. Switch to other heat exchange channels and repeat the above steps to obtain information on external and internal leakage of other heat exchange channels.

[0027] This invention also provides a low-temperature leak detection device for a 2K negative pressure heat exchanger, comprising: a vacuum container, a transport assembly, a hose assembly, a temperature monitoring interface, and a vacuuming interface. The vacuum container is used to house the heat exchanger under test. One end of the vacuum container has an opening. A sealing assembly is provided on the opening. The transport assembly is located inside the vacuum container. The transport assembly extends from the opening of the vacuum container into the interior of the vacuum container. The transport assembly is used to transport the heat exchanger under test. The hose assembly is disposed on the vacuum container. The hose assembly is used to connect a gas source and a helium mass spectrometer leak detector. Nitrogen or helium gas can be introduced into the heat exchanger under test inside the vacuum container through the hose assembly, and leak detection can be performed on the heat exchange channels of the heat exchanger under test. The temperature monitoring interface is disposed on the vacuum container. The temperature monitoring interface is used to connect to a temperature monitoring assembly. The temperature monitoring interface can acquire the temperature changes inside the vacuum container and the 2K negative pressure heat exchanger under test. The vacuuming interface is disposed on the vacuum container. The vacuuming interface is used to connect to a vacuuming system. The vacuuming interface can be used to evacuate the interior of the vacuum container.

[0028] Optionally, the transport components include: a guide rail, a trolley, and a drive unit. The guide rail is disposed within the vacuum container. The guide rail extends from the opening of the vacuum container into the interior of the vacuum container. The trolley is slidably disposed on the guide rail. The trolley is used to carry the heat exchanger under test. The drive unit is connected to the trolley and is used to drive the trolley to reciprocate along the guide rail.

[0029] Optionally, the sealing assembly includes a support frame, a rotating frame, and a sealing door. The support frame is mounted on the vacuum container. The rotating frame is hinged to the support frame. The sealing door is hinged to the end of the rotating frame away from the support frame. The sealing door is capable of sealing the opening of the vacuum container.

[0030] Optionally, the hose assembly includes: multiple hoses. One end of each hose located outside the vacuum container is used to connect to a gas source and a helium mass spectrometer leak detector. The other end of each hose located inside the vacuum container is used to connect to the internal space of the vacuum container and to each heat exchange channel of the heat exchanger under test.

[0031] Optionally, the vacuum container also includes a manhole, a base, and lifting lugs. The manhole is located at the end of the vacuum container furthest from the opening. The base is located at the bottom of the vacuum container. The lifting lugs are located on the base and are symmetrically distributed on both sides of the vacuum container.

[0032] This invention further provides a low-temperature leak detection system for a 2K negative pressure heat exchanger, comprising: the aforementioned low-temperature leak detection device for a 2K negative pressure heat exchanger, a vacuum system, a gas source, a temperature monitoring component, and a helium mass spectrometer leak detector. The vacuum system is connected to the vacuum port of the low-temperature leak detection device. The gas source and the helium mass spectrometer leak detector are connected to the hose assembly of the low-temperature leak detection device. The temperature monitoring component is connected to the temperature monitoring port of the low-temperature leak detection device.

[0033] Beneficial effects:

[0034] 1. The low-temperature leak detection method for 2K negative pressure heat exchangers provided by this invention can obtain the internal and external leakage rates of 2K negative pressure heat exchangers in a deep cryogenic environment. It can solve the problems that room temperature helium mass spectrometry leak detection cannot accurately reflect and evaluate the sealing performance of heat exchangers in a deep cryogenic environment, their ability to withstand rapid cooling, and the inability to measure the leakage rate of heat exchangers under design pressure. This method can measure helium mass spectrometry leak detection data of 2K negative pressure heat exchangers under certain pressure and deep cryogenic conditions, which is more accurate and effective than traditional room temperature helium mass spectrometry leak detection methods.

[0035] 2. The 2K negative pressure heat exchanger low-temperature leak detection device provided by this invention includes a vacuum container, a transport assembly, a hose assembly, a temperature monitoring interface, and a vacuuming interface. In use, the heat exchanger under test is placed on the transport assembly inside the vacuum container, and the heat exchange channel of the heat exchanger under test is connected to the hose assembly, the temperature monitoring interface, and the vacuuming interface. Then, the transport assembly is used to move the heat exchanger under test into the vacuum container, and the sealing assembly on the opening is closed, placing the heat exchanger under test in a closed environment. The vacuuming interface is used to connect to a vacuuming system to evacuate the vacuum container and the heat exchanger under test, placing the heat exchanger under test in a high vacuum state. Next, liquid nitrogen / liquid helium is introduced into the heat exchange channel of the heat exchanger under test using the hose assembly, causing the overall temperature of the heat exchanger under test to drop to the target value. Then, helium is introduced into the heat exchange channel of the heat exchanger under test using the hose assembly, and a helium mass spectrometer leak detector is used to obtain information on helium leakage outside the heat exchange channel (external leakage) and helium leakage in adjacent heat exchange channels (internal leakage). The 2K negative pressure heat exchanger low-temperature leak detection device of the present invention can realize low-temperature helium mass spectrometry leak detection of heat exchangers, obtain the internal and external leakage rates under low-temperature environment, and accurately evaluate the actual sealing performance of heat exchangers at low temperatures.

[0036] 3. The low-temperature leak detection system for a 2K negative pressure heat exchanger provided by this invention includes the aforementioned low-temperature leak detection device, vacuum system, gas source, temperature monitoring component, and helium mass spectrometer leak detector. The vacuum system is connected to the vacuum port of the low-temperature leak detection device. The gas source and helium mass spectrometer leak detector are connected to the hose assembly of the low-temperature leak detection device. The temperature monitoring component is connected to the temperature monitoring port of the low-temperature leak detection device. Using the low-temperature leak detection system for a 2K negative pressure heat exchanger of this invention, the internal and external leak rates of the 2K negative pressure heat exchanger can be detected in a low-temperature environment, obtaining the actual leak rate data of the 2K negative pressure heat exchanger under low-temperature operation.

[0037] 4. This invention employs pressure gradient progressive control, which can isolate the interference of micro-leaks and macro-leaks under different vacuum levels, thereby improving the sensitivity of leak rate detection. Secondly, the staged operation can effectively shorten the equilibrium time required for the system to reach steady-state vacuum, avoiding the nonlinear response problem caused by sudden pressure drop during traditional single-stage vacuuming. In addition, this method can reduce the continuous load on the vacuum pump by releasing residual stress in stages, thereby extending the service life of key equipment. Attached Figure Description

[0038] Figure 1 A flowchart of a low-temperature leak detection method for a 2K negative pressure heat exchanger according to an embodiment of the present invention;

[0039] Figure 2 A flowchart of a low-temperature leak detection method for a 2K negative pressure heat exchanger according to another embodiment of the present invention;

[0040] Figure 3 A flowchart of a low-temperature leak detection method for a 2K negative pressure heat exchanger according to a third embodiment of the present invention;

[0041] Figure 4 A flowchart of a low-temperature leak detection method for a 2K negative pressure heat exchanger according to the fourth embodiment of the present invention;

[0042] Figure 5 A flowchart of the low-temperature leak detection method for a 2K negative pressure heat exchanger according to the fifth embodiment of the present invention;

[0043] Figure 6 A three-dimensional structural schematic diagram of a low-temperature leak detection device for a 2K negative pressure heat exchanger according to an embodiment of the present invention;

[0044] Figure 7 Rear view of a low-temperature leak detection device for a 2K negative pressure heat exchanger according to an embodiment of the present invention;

[0045] Figure 8 A schematic diagram of the internal structure of a low-temperature leak detection device for a 2K negative pressure heat exchanger according to an embodiment of the present invention;

[0046] Figure 9 A schematic diagram of a low-temperature leak detection system for a 2K negative pressure heat exchanger according to an embodiment of the present invention;

[0047] Figure 10 A schematic diagram of the piping connection of a low-temperature leak detection system for a 2K negative pressure heat exchanger according to an embodiment of the present invention.

[0048] The reference numerals in the attached figures are as follows:

[0049] 1. Low-temperature leak detection device for 2K negative pressure heat exchanger; 2. Vacuum system; 3. Gas source; 4. Temperature monitoring components; 5. Helium mass spectrometer leak detector; 6. Heat exchanger under test; 7. Chiller unit;

[0050] 11. Vacuum container; 12. Transport assembly; 13. Sealing assembly; 14. Hoses assembly; 15. Temperature monitoring interface; 16. Vacuuming interface; 17. Manhole; 18. Base; 19. Lifting lug;

[0051] 121. Guide rail; 122. Cart;

[0052] 131. Support frame; 132. Rotating frame; 133. Enclosing door;

[0053] 141. Hose;

[0054] V1 to V6 are all valves. Detailed Implementation

[0055] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," and "counterclockwise," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0056] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0057] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0058] The preferred embodiments of the present invention will be described below with reference to the accompanying drawings. It should be understood that the preferred embodiments described herein are for illustration and explanation only and are not intended to limit the present invention.

[0059] Firstly, this embodiment provides a low-temperature leak detection method for a 2K negative pressure heat exchanger. Figure 1 This is a flowchart of a low-temperature leak detection method for a 2K negative pressure heat exchanger provided in this embodiment.

[0060] like Figure 1 As shown, the low-temperature leak detection method for heat exchangers in this embodiment includes the following steps:

[0061] S1. Connect each heat exchange channel of the heat exchanger 6 under test to the hose assembly 14, temperature monitoring interface 15 and vacuum interface 16 on the vacuum container 11 respectively.

[0062] Specifically, VCR connectors are welded to the interfaces of each heat exchange channel of the heat exchanger 6 under test. These VCR connectors are then used to connect each heat exchange channel to the hose assembly 14, temperature monitoring interface 15, and vacuum interface 16. It is important to note that a matching gasket must be installed on the sealing surface when connecting the VCR connectors; this gasket is for single use only. Furthermore, after the VCR connectors are connected, they should be immersed in liquid nitrogen or sprayed with liquid nitrogen for approximately 5 minutes. Once the VCR connectors are cold, they should be further tightened with a wrench to prevent leakage at low temperatures, which could lead to misjudgment. If necessary, leak testing of the VCR connectors can be performed.

[0063] S2. Place the heat exchanger 6 to be tested into the vacuum container 11 and seal the vacuum container 11.

[0064] Specifically, before performing low-temperature leak testing on the heat exchanger 6 under test, it is essential to confirm that there are no aluminum shavings, impurities, or any particulate matter in each heat exchange channel of the heat exchanger 6 that could potentially damage the vacuum system 2. If any are found, the system must be cleaned before performing low-temperature leak testing.

[0065] S3. Using the vacuum system 2, the vacuum container 11 and the heat exchange channel are evacuated through the vacuum interface 16.

[0066] Specifically, the vacuum system 2 is used to evacuate the heat exchange channel of the vacuum container 11 and the heat exchanger 6 under test through the vacuum port 16, so that the heat exchanger 6 under test is in a high vacuum state (i.e., the pressure inside the vacuum container 11 is ≤5Pa).

[0067] S4. Fill the heat exchange channel of the heat exchanger 6 under test with liquid nitrogen or liquid helium to cool the heat exchange channel.

[0068] Specifically, the flow rate of liquid nitrogen or liquid helium needs to be controlled during the cooling process of the heat exchanger 6 under test by filling it with liquid nitrogen or liquid helium. Liquid nitrogen or liquid helium is slowly filled into the heat exchange channel of the heat exchanger 6 under test. Due to the cold loss, the flow rate is controlled as long as the heat exchanger 6 under test reaches a temperature close to that of liquid nitrogen.

[0069] S5. The temperature change of the heat exchanger 6 under test is obtained through the temperature monitoring interface 15 in order to control the cooling rate of the heat exchanger 6 under test.

[0070] Specifically, the temperature monitoring component 4 is activated to acquire temperature changes. The cooling rate should be ≤4℃ / min; otherwise, the heat exchanger 6 under test may be damaged due to thermal stress. During the initial cooling phase, temperature data is recorded every 10 minutes. After the cooling rate stabilizes, temperature data is recorded every hour. If the cooling rate is too fast, the opening of the liquid nitrogen or liquid helium outlet valve can be adjusted to regulate the flow rate. Preferably, the cooling rate of the heat exchanger 6 under test should not exceed 1℃ / min.

[0071] Furthermore, to provide operators with more accurate flow rate values ​​and avoid blind adjustments, the flow rate of the cooling medium can be controlled. u Effectively regulate the cooling rate of the heat exchanger Its functional relationship is based on flow rate u The factor is primarily determined by the power of 0.8, but is also driven by the heat transfer area, the thermal properties of the working fluid, and the temperature difference. The formula is as follows:

[0072]

[0073] in, dT The change in temperature dt For the time change, C To match the geometry of the heat exchanger flow channel (such as hydraulic diameter) D h The related dimensionless coefficients; A 0 is the baseline heat transfer area; α The surface strengthening coefficient; η The heat transfer surface contact efficiency is the ratio of the actual effective heat transfer area to the theoretical area. 0≤η≤1 ), affected by surface roughness and wettability; ρ The density of the working fluid; V The volume of the working fluid;c p The specific heat capacity of the working fluid; T m The ambient temperature; The temperature difference between the working fluid and the medium.

[0074] Based on the target cooling rate r target Backtrack to the required flow rate u set The formula is:

[0075]

[0076] in, C To match the geometry of the heat exchanger flow channel (such as hydraulic diameter) D h The related dimensionless coefficients; A 0 is the baseline heat transfer area; α The surface strengthening coefficient; η The heat transfer surface contact efficiency is the ratio of the actual effective heat transfer area to the theoretical area. 0≤η≤1 ), affected by surface roughness and wettability; V The volume of the working fluid; ρ The density of the working fluid; c p The specific heat capacity of the working fluid; T m The ambient temperature; The temperature difference between the working fluid and the medium.

[0077] Specifically, minimum flow rate u min ≥0.1 m / s (to avoid a sharp drop in heat transfer efficiency due to laminar flow), maximum flow velocity u max ≤5m / s (limited by pump power and pressure drop).

[0078] The specific calculations are shown below.

[0079] Known parameter settings:

[0080]

[0081] Calculate the effective heat transfer area A ( η ):

[0082] A( η )=A0(1+ αη )=1.5×(1+0.15×0.75)=1.5×1.1125=1.669m 2

[0083] Calculate the comprehensive constant k:

[0084]

[0085] Backflow velocity u set :

[0086]

[0087]

[0088] Due to the superfluid helium effect, if the system temperature is below 2.17K (λ point), liquid helium enters the superfluid state, the heat transfer coefficient is significantly improved, and the actual required flow rate can be further reduced.

[0089] In some possible embodiments, the flow rate is obtained using the above formula. u set， The actual initial flow rate is set to A1. u set， Where A1 is a coefficient between 0 and 1.

[0090] Specifically, the actual initial flow rate was set to 0.3. u set、 0.4 u set、 0.5 u set、 0.6 u set The actual cooling rate is measured and compared with the target cooling rate, and the flow rate is finely adjusted accordingly.

[0091] S6. To bring the temperature in the heat exchange channel to the liquid nitrogen / liquid helium temperature range;

[0092] Specifically, liquid nitrogen or liquid helium is introduced into the heat exchange channel of the heat exchanger 6 under test to cool the channel and bring the temperature within the channel to the liquid nitrogen / liquid helium temperature range. When the overall temperature of the heat exchanger 6 under test drops to approximately -160°C, the introduction of liquid nitrogen into the heat exchanger 6 can be stopped.

[0093] S7. Vent nitrogen or helium from the heat exchange channel;

[0094] Specifically, after cooling is completed, the amount of gas released from the evaporation of liquid nitrogen or liquid helium at the exhaust port of the heat exchange channel is obtained. Helium can only be introduced to check for leaks when no gas is discharged from the exhaust port.

[0095] S8. Fill the cooled heat exchange channel with helium until the pressure inside the heat exchange channel reaches the expected value.

[0096] Specifically, the pressure in the helium-filled heat exchange channel is maintained at the channel's operating pressure, and the maximum pressure difference between adjacent heat exchange channels is maintained. (e.g.) Figure 10As shown, the heat exchanger 6 under test has four channels, all designed for a pressure of 2.5 MPa, and operating pressures of 1.0 MPa, 0.5 MPa, 0.2 MPa, and 0.1 MPa respectively. The pressure will be maintained at the highest operating pressure of 1.0 MPa.

[0097] S9. After a preset static time, check the external and internal leakage of the heat exchange channel in the liquid nitrogen / liquid helium temperature range;

[0098] Specifically, external leakage refers to leakage between the heat exchange channel and the interior of the vacuum container 11. Internal leakage refers to leakage between adjacent heat exchange channels. Since the vacuum container 11 is under vacuum and negative pressure, the external leakage of the heat exchange channel of the heat exchanger under test 6 filled with helium can be measured, and the value from the leak detector is the low-temperature external leakage data for that heat exchange channel. By controlling the valves at the interfaces of each heat exchange channel of the heat exchanger under test 6, the internal leakage data of that heat exchange channel and other heat exchange channels under low-temperature conditions can be measured.

[0099] S11. Turn off the vacuum system and break the vacuum inside the vacuum container 11;

[0100] S12. After the heat exchanger under test 6 is reheated, the reheating rate of the heat exchanger under test is controlled.

[0101] Specifically, the reheating rate of the heat exchanger 6 under test must be strictly controlled within 4℃ / min. Before the heat exchanger 6 under test has been reheated to room temperature, the sealing component 13 must not be opened.

[0102] S13. After the heat exchanger 6 under test returns to normal temperature, remove the heat exchanger 6 under test from the vacuum container 11.

[0103] Specifically, after the heat exchanger 6 under test has warmed up to room temperature, the sealing assembly 13 is opened, and the heat exchanger 6 under test is pushed out, thus ending the low-temperature leak test. It should be noted that if it is not necessary to perform low-temperature leak testing on the next heat exchanger under test, it is necessary to check and confirm that the power supply to each device is turned off.

[0104] The low-temperature leak detection method for 2K negative pressure heat exchangers in this embodiment can obtain helium mass spectrometry leak detection data of heat exchangers under certain pressure and low temperature conditions, which is more accurate and effective compared with the traditional room-temperature helium mass spectrometry leak detection method. When helium is used as the leak indicator gas, if there is a leak in the container being tested, helium will leak out through the leak and be detected by the helium mass spectrometer leak detector 5, thereby determining the location of the leak and the amount of leakage. In use, helium is usually filled into the heat exchanger 6 under test, and then the helium in the leaking gas is detected by the gas intake probe outside the leak port. The presence of a leak is determined by detecting the signal strength of the helium.

[0105] In some embodiments, see Figure 1Step S3 further includes: using the vacuum system 2, the vacuum container 11 and the heat exchange channel are evacuated step by step through the vacuum port 16 until the pressure inside the vacuum container is ≤5Pa.

[0106] Specifically, such as Figure 10 As shown, close valve V2, open the remaining valves V1, V3, V4, V5, and V6, and start the fore-stage mechanical pump of vacuum system 2. Once the vacuum level is ≤20Pa, start the molecular pump of vacuum system 2 until the pressure inside the vacuum container is ≤5Pa. At the same time as starting the molecular pump, start the chiller unit 7 to maintain a negative pressure state inside the vacuum container 11.

[0107] Figure 2 A flowchart illustrating another low-temperature leak detection method for a 2K negative pressure heat exchanger provided in this embodiment. In some embodiments, such as... Figure 2 As shown, the process between steps S9 and S11 also includes:

[0108] S10. Perform a second vacuuming, then a third vacuuming, and repeat until the i-th vacuuming is performed. Calculate the total leakage rate, where i is an integer greater than 3.

[0109] Specifically, in one possible embodiment, based on the principle of mass conservation, the multi-stage pumping process can be modeled as a dynamic leakage system with series-connected cavities. Assuming constant pumping speeds at each stage and a steady-state flow at the leakage source, the total leakage rate can be decomposed into a linear superposition of the leakage rates of each independent pressure range. By introducing an effective pumping speed correction coefficient and a pressure decay function, the formula for the total system leakage rate is derived:

[0110]

[0111] In the formula, S i For the first i Level of effective pumping speed, P i For the first i Level balance pressure, η i For the first i Leakage path weighting factor. The above formula quantifies the contribution of different vacuum stages to the total leakage rate, providing a theoretical basis for determining leakage.

[0112] In another possible embodiment, a second vacuum is performed to calculate the equivalent leakage rate of the second stage; then a third vacuum is performed to calculate the equivalent leakage rate of the third stage; this process is repeated until the i-th vacuum 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 steady state in the i-th vacuum stage, the leaked gas flow rate and the pumping rate are balanced, satisfying:

[0113]

[0114] In the formula, Q i For the first i Level equivalent leakage rate (Pa·m) 3 / s), S i For the first i Effective pumping speed (m) 3 / s), P i,eq For the first i Level equilibrium pressure (Pa). P i,lim For the first i The ultimate vacuum (Pa) of a vacuum pump.

[0115] For an n-stage vacuum system, the total leakage rate is the cumulative effect of the leakage rates at each stage. Considering the independence of the leakage paths and the nonlinear characteristics of the pressure difference, the total leakage rate can be expressed as:

[0116]

[0117] In the formula, Q i For the first i Level equivalent leakage rate (Pa·m) 3 / s), t i Let be the evacuation time (s) of the i-th stage. τ i =V / S i , τ i Let V be the time constant of the i-th characteristic (s), and V be the system volume (m³). 3 ), S i For the first i Effective pumping speed (m) 3 / s), where exp is the exponential term, reflecting the effect of pressure decay on leakage rate during unsteady-state pumping.

[0118] This embodiment employs pressure gradient progressive control, which can isolate the interference of micro-leaks and macro-leaks under different vacuum levels, thereby improving the sensitivity of leak rate detection. Secondly, the staged operation can effectively shorten the equilibrium time required for the system to reach steady-state vacuum, avoiding the nonlinear response problem caused by sudden pressure drop during traditional single-stage vacuuming. In addition, this method can reduce the continuous load on the vacuum pump by releasing residual stress in stages, thereby extending the service life of critical equipment.

[0119] Figure 3 A flowchart illustrating the third low-temperature leak detection method for a 2K negative pressure heat exchanger provided in this embodiment. In some embodiments, such as... Figure 3As shown, step S2 includes:

[0120] S201. Place the heat exchanger 6 to be inspected on the transport assembly 12;

[0121] Specifically, the trolley 122 is moved to the opening of the vacuum container 11, and the heat exchanger 6 to be inspected is placed on the trolley 122 using a hoisting device.

[0122] S202. Transfer the heat exchanger 6 to be inspected into the vacuum container 11;

[0123] Specifically, by pushing the trolley 122 along the guide rail 121, the heat exchanger 6 under test is moved into the vacuum container 11. It should be noted that the trolley 122 can be driven manually, electrically, or in other ways; this embodiment does not impose any restrictions on this.

[0124] S203. Seal the opening of the vacuum container 11 so that the heat exchanger 6 under test is in a sealed environment.

[0125] Specifically, after confirming that there are no impurities on the contact surface between the closed door 133 and the opening, apply sealing grease. The sealing grease can be applied directly by hand until it appears evenly distributed. It should be noted that sealing grease does not need to be applied every time. If the leak detection device has not been used for a long time (e.g., more than one month), it must be applied before use. Afterward, close the closed door 133 and tighten the bolts and nuts on the closed door 133.

[0126] The method of this embodiment uses the transport components 12 to place the heat exchanger 6 under test into the vacuum container 11, which facilitates the handling and replacement of the heat exchanger 6 under test, and the sealing of the vacuum container 11 can ensure the airtightness of the space where the heat exchanger 6 under test is located.

[0127] Figure 4 A flowchart illustrating the fourth low-temperature leak detection method for a 2K negative pressure heat exchanger provided in this embodiment. In some embodiments, such as... Figure 4 As shown, step S4 includes:

[0128] S401. Open the liquid nitrogen or liquid helium outlet valve in gas source 3, and fill the maximum volume heat exchange channel of the heat exchanger under test 6 with liquid nitrogen or liquid helium to cool it down.

[0129] Specifically, during the cooling process, when the temperature at one end of the heat exchange channel drops below 100K while the other end remains at a higher temperature and the cooling rate is very low, the liquid nitrogen or liquid helium inlet and outlet of the heat exchange channel can be switched to further uniformly cool the channel. If liquid nitrogen or liquid helium is already flowing from the outlet of the heat exchange channel during cooling, but the temperature has not yet reached below 100K, liquid nitrogen or liquid helium can be continued to be added for 10-20 minutes. Observe whether there is a significant change in the cooling rate. If there is no significant change, it is determined that the overall temperature of the heat exchange channel has approached or reached below 100K. At this point, the liquid nitrogen or liquid helium valve should be closed to stop cooling.

[0130] S402. During the cooling process of the heat exchange channel, obtain the temperature and leakage rate changes of the heat exchange channel;

[0131] Specifically, such as Figure 10 As shown, during the cooling process of the heat exchange channel, the mass spectrometer leak detector 5 is turned on, and valve V2 is slowly opened simultaneously to observe the leakage rate of the entire vacuum system. By opening valves V4, V5, and V6 respectively and closing valve V1, the leakage rate of each heat exchange channel can be observed to analyze and test the impact of rapid cooling on the sealing performance of the equipment.

[0132] Specifically, since the volume content of helium in the air is about 5 ppm, or about five parts per million, this embodiment can also obtain the background leakage rate of the heat exchange channel during the cooling process, so as to eliminate the influence of helium in the air on the detection results, improve the detection accuracy, and improve the accuracy and sensitivity of leak detection.

[0133] Figure 5 A flowchart illustrating the fifth low-temperature leak detection method for a 2K negative pressure heat exchanger provided in this embodiment. In some embodiments, such as... Figure 5 As shown, step S9 includes:

[0134] S901, maintain the pressure in the heat exchange channel at the working pressure;

[0135] Specifically, after the heat exchanger 6 under test is cooled down, high-purity helium is slowly introduced into the cooled heat exchange channel to bring the pressure in the heat exchange channel to the working pressure, and then the channel is left to stand for a preset time (e.g., 15 minutes).

[0136] like Figure 10 As shown, after cooling is complete, valves V3, V4, V5, and V6 are closed, and helium is introduced into the cooled heat exchange channel at low temperature. The heat exchanger under test has four channels, all designed to operate at 2.5 MPa, with operating pressures of 1.0 MPa, 0.5 MPa, 0.2 MPa, and 0.1 MPa respectively. The pressure is maintained at the highest operating pressure of 1.0 MPa.

[0137] S902, make the pressure difference between the heat exchange channel and the adjacent heat exchange channel reach the preset value;

[0138] S903. Detect the external leakage of the heat exchange channel and the internal leakage between the heat exchange channel and the adjacent heat exchange channel;

[0139] Specifically, the helium mass spectrometer leak detector 5 is connected to the interior of the vacuum container 11, and the external leakage data of the heat exchange channel is obtained by measuring the changes in the value of the helium mass spectrometer leak detector 5. Alternatively, the helium mass spectrometer leak detector 5 is connected to an adjacent heat exchange channel, and the internal leakage data of the heat exchange channel is obtained by measuring the changes in the value of the helium mass spectrometer leak detector 5.

[0140] S904. Switch to other heat exchange channels and repeat the above steps to obtain information on external and internal leakage of other heat exchange channels.

[0141] Specifically, such as Figure 10 As shown, the vacuum in the heat exchange channels corresponding to valves V4, V5, and V6 is broken sequentially, and the external and internal leakage data of the heat exchange channels corresponding to valves V4, V5, and V6 are measured in sequence. It is important to note that valve V2 must be closed before each switching of valves V4, V5, and V6 to prevent accidental operation that could allow the helium mass spectrometer leak detector 5 to be exposed to the atmosphere and damage it.

[0142] Using the method of this embodiment, internal and external leaks can be detected in multiple heat exchange channels without resetting the leak detection device, which helps to improve leak detection efficiency.

[0143] Secondly, this embodiment provides a low-temperature leak detection device 1 for a 2K negative pressure heat exchanger, used in the low-temperature leak detection method for the 2K negative pressure heat exchanger described in the above embodiment. Figure 6 This is a three-dimensional structural diagram of a low-temperature leak detection device 1 for a 2K negative pressure heat exchanger provided in this embodiment. Figure 7 This is a rear view of a low-temperature leak detection device 1 for a 2K negative pressure heat exchanger provided in this embodiment. Figure 8 This is a schematic diagram of the internal structure of a low-temperature leak detection device 1 for a 2K negative pressure heat exchanger provided in this embodiment.

[0144] like Figures 6-8As shown, the 2K negative pressure heat exchanger low-temperature leak detection device 1 of this embodiment includes: a vacuum container 11, a transport assembly 12, a hose assembly 14, a temperature monitoring interface 15, and a vacuuming interface 16. The vacuum container 11 is used to house the heat exchanger 6 under test. One end of the vacuum container 11 has an opening. A sealing assembly 13 is provided on the opening. The transport assembly 12 is located inside the vacuum container 11. The transport assembly 12 extends from the opening of the vacuum container 11 into the interior of the vacuum container 11. The transport assembly 12 is used to transport the heat exchanger 6 under test. The hose assembly 14 is disposed on the vacuum container 11. The hose assembly 14 is used to connect the gas source 3 and the helium mass spectrometer leak detector 5. Nitrogen or helium gas can be introduced into the heat exchanger 6 under test inside the vacuum container 11 through the hose assembly 14, and leak detection can be performed on the heat exchange channels of the heat exchanger 6 under test. The temperature monitoring interface 15 is disposed on the vacuum container 11. The temperature monitoring interface 15 is used to connect the temperature monitoring assembly 4. Temperature monitoring interface 15 allows for the acquisition of temperature changes inside the vacuum container 11 and the heat exchanger 6 under test. Vacuum evacuation interface 16 is located on the vacuum container 11. Vacuum evacuation interface 16 is used to connect to the vacuum system 2. Vacuum evacuation interface 16 allows for the evacuation of the interior of the vacuum container 11.

[0145] In some examples, such as Figure 6 and Figure 7 As shown, the vacuum container 11 is cylindrical, with one end closed and the other end open. A sealing assembly 13 is connected to the side wall of the vacuum container 11 and can seal the opening. This configuration ensures the sealing capability of the vacuum container 11 while facilitating the insertion and removal of the heat exchanger 6 under test.

[0146] In some examples, such as Figure 6 and Figure 7 As shown, the vacuum container 11 includes two hose assemblies 14, which are located near the front and rear ends of the vacuum container 11, respectively. The two hose assemblies 14 can serve as an air inlet and an exhaust outlet, respectively, which simplifies the connection piping between the heat exchanger 6 under test and the low-temperature leak detection device 1, making it more convenient to use.

[0147] In some examples, see Figure 6 and Figure 7 The vacuum port 16 includes a pressure gauge. This configuration facilitates real-time acquisition of the pressure value inside the vacuum container 11.

[0148] The low-temperature leak detection device 1 for the 2K negative pressure heat exchanger in this embodiment includes a vacuum container 11, a transport component 12, a hose assembly 14, a temperature monitoring interface 15, and a vacuuming interface 16. In use, the heat exchanger under test 6 is placed on the transport assembly 12 inside the vacuum container 11, and the heat exchange channel of the heat exchanger under test 6 is connected to the hose assembly 14, the temperature monitoring interface 15, and the vacuum interface 16. Then, the heat exchanger under test 6 is moved into the vacuum container 11 using the transport assembly 12, and the sealing assembly 13 on the opening is closed to put the heat exchanger under test 6 into a closed environment. The vacuum system 2 is connected to the vacuum interface 16 to evacuate the vacuum container 11 and the heat exchanger under test 6, so that the heat exchanger under test 6 is in a high vacuum state. Then, liquid nitrogen is filled into the heat exchange channel of the heat exchanger under test 6 using the hose assembly 14 to reduce the overall temperature of the heat exchanger under test 6 to the target value. Then, helium is filled into the heat exchange channel of the heat exchanger under test 6 using the hose assembly 14, and the helium leakage situation outside the heat exchanger under test 6 (external leakage) and the helium leakage situation in the adjacent heat exchange channel (internal leakage) are obtained by using the helium mass spectrometer leak detector 5. The low-temperature leak detection device 1 for heat exchangers of the present invention enables low-temperature helium mass spectrometry leak detection of heat exchangers, obtaining the internal and external leakage rates under low-temperature conditions, and accurately evaluating the actual sealing performance of the heat exchanger at low temperatures. Simultaneously, by incorporating a transport assembly, it supports the automatic loading and unloading of 2K negative pressure heat exchangers and allows for online synchronous testing of multiple heat exchangers, significantly improving the processing efficiency and yield of heat exchangers.

[0149] In some embodiments, such as Figure 8 As shown, the transport assembly 12 includes a guide rail 121, a trolley 122, and a drive unit. The guide rail 121 is disposed within the vacuum container 11. The guide rail 121 extends from the opening of the vacuum container 11 into the interior of the vacuum container 11. The trolley 122 is slidably disposed on the guide rail 121. The trolley 122 is used to carry the heat exchanger 6 under test. The drive unit is connected to the trolley 122 and is used to drive the trolley 122 to reciprocate along the guide rail 121.

[0150] In some examples, such as Figure 8 As shown, the transport component 12 has two parallel guide rails 121. A trolley 122 is mounted between the two guide rails 121 and can slide along them. This embodiment employs a double guide rail 121 structure, which makes the movement of the trolley 122 smoother. Furthermore, to reduce the friction between the trolley 122 and the guide rails 121, pulleys can be installed at the bottom of the trolley 122. These pulleys can roll within the guide rails 121, thus allowing the trolley 122 to move along them.

[0151] Due to the large size and weight of the 2K negative pressure heat exchanger, and the limited space within the vacuum container 11, manual handling is quite difficult when placing the heat exchanger 6 to be tested inside the vacuum container 11. This embodiment incorporates a guide rail 121 and a trolley 122 within the vacuum container 11. The trolley 122 is slidably mounted on the guide rail 121 and is used to support the heat exchanger 6 under test, effectively reducing the difficulty of moving the heat exchanger 6 and improving leak detection efficiency. By driving the trolley 122 to reciprocate along the guide rail 121 using a drive device, automatic loading and unloading of the 2K negative pressure heat exchanger is possible, and multiple heat exchangers can be simultaneously tested online, significantly improving the processing efficiency and yield of the heat exchangers.

[0152] In some embodiments, such as Figure 6 and Figure 7 As shown, the sealing assembly 13 includes a support frame 131, a rotating frame 132, and a sealing door 133. The support frame 131 is disposed on the vacuum container 11. The rotating frame 132 is hinged to the support frame 131. The sealing door 133 is hinged to the end of the rotating frame 132 away from the support frame 131. The sealing door 133 is capable of sealing the opening of the vacuum container 11.

[0153] In some examples, such as Figure 6 and Figure 7 As shown, the sealing door 133 is fastened to the opening of the vacuum container 11 and is connected to the opening of the vacuum container 11 via a flange. In this embodiment, the sealing door 133 can rotate around the support frame 131 under the support of the rotating frame 132, thereby opening and closing the opening. When the sealing door 133 is closed, the bolts on the flange between the sealing door 133 and the vacuum container 11 need to be tightened to ensure the sealing performance of the sealing door 133 to the opening.

[0154] In some examples, such as Figure 7 As shown, the closed door 133 is equipped with a handle. The handle is located on the side of the closed door 133 away from the rotating frame 132. This arrangement facilitates the opening and closing of the closed door 133.

[0155] The sealing assembly 13 of this embodiment includes a support frame 131, a rotating frame 132, and a sealing door 133. The support frame 131 is disposed on the vacuum container 11, and the sealing door 133 is hinged to the support frame 131 through the rotating frame 132. The sealing door 133 can rotate around the support frame 131 under the support of the rotating frame 132, so as to open and close the opening, which is convenient for placing and taking out the heat exchanger 6 under test, and can also ensure the sealing of the opening.

[0156] In some embodiments, such as Figure 6 and Figure 7As shown, the hose assembly 14 includes a plurality of hoses 141. One end of the plurality of hoses 141 located outside the vacuum container 11 is used to connect the helium mass spectrometer leak detector 5 and the gas source 3. The other end of the plurality of hoses 141 located inside the vacuum container 11 is used to connect the internal space of the vacuum container 11 to each heat exchange channel of the heat exchanger 6 under test.

[0157] In some examples, such as Figure 6 and Figure 7 As shown, each hose 141 of the hose assembly 14 is used to connect to a heat exchange channel of the heat exchanger 6 under test or to communicate with the internal space of the vacuum container. Each hose 141 is equipped with a valve to control the connection and disconnection between each heat exchange channel and the gas source 3 or the helium mass spectrometer leak detector 5, thereby realizing the detection of internal and external leaks in different heat exchange channels.

[0158] In some examples, such as Figure 6 and Figure 7 As shown, there are two hose assemblies 14. One hose assembly 14 has multiple hoses 141 for air intake, and the other hose assembly 14 has multiple hoses 141 for air exhaust. This arrangement allows for smoother gas flow in the vacuum container 11 and the heat exchanger 6 under test, and simplifies the connection and arrangement of the pipelines.

[0159] In some embodiments, such as Figure 6 and Figure 7 As shown, the vacuum container 11 also includes a manhole 17, a base 18, and lifting lugs 19. The manhole 17 is located at the end of the vacuum container 11 furthest from the opening. The base 18 is located at the bottom of the vacuum container 11. The lifting lugs 19 are located on the base 18 and are symmetrically distributed on both sides of the vacuum container 11.

[0160] In some examples, such as Figure 7 As shown, the manhole 17 is connected to the vacuum container 11 by a flange, and the manhole 17 is equipped with a handle. This design ensures the airtightness of the manhole 17 while facilitating its opening and closing.

[0161] In some examples, such as Figure 6 and Figure 7 As shown, the base 18 includes a pair of saddle supports, which are disposed at the bottom of the vacuum container 11 and close to both ends of the vacuum container 11. Using saddle supports to support the vacuum container 11 provides greater stability, and the saddle supports are hollow structures, lightweight, and have good stability, which helps to reduce the overall weight of the device.

[0162] In some examples, such as Figure 6 and Figure 7 As shown, placing the lifting lug 19 on the base 18 makes the leak detection device more stable when it is lifted as a whole.

[0163] The empty container 11 in this embodiment also includes a manhole 17, a base 18, and lifting lugs 19. The manhole 17 facilitates inspection and maintenance of the interior of the vacuum container 11. The base 18 enhances the stability of the vacuum container 11. The lifting lugs 19 facilitate the transport of the leak detection device.

[0164] Thirdly, this embodiment also provides a low-temperature leak detection system for a 2K negative pressure heat exchanger. Figure 9 This is a schematic diagram of a low-temperature leak detection system for a 2K negative pressure heat exchanger provided in this embodiment.

[0165] like Figure 9 As shown, the low-temperature leak detection system for the 2K negative pressure heat exchanger in this embodiment includes: a 2K negative pressure heat exchanger low-temperature leak detection device 1, a vacuum system 2, a gas source 3, a temperature monitoring component 4, and a helium mass spectrometer leak detector 5. The vacuum system 2 is connected to the vacuum port 16 of the low-temperature leak detection device 1. The gas source 3 is connected to the hose assembly 14 of the 2K negative pressure heat exchanger low-temperature leak detection device 1. The temperature monitoring component 4 is connected to the temperature monitoring port 15 of the 2K negative pressure heat exchanger low-temperature leak detection device 1. The helium mass spectrometer leak detector 5 is connected to the hose assembly 14 of the 2K negative pressure heat exchanger low-temperature leak detection device 1.

[0166] In some examples, see Figure 9 The vacuum system 2 includes a mechanical pump, a Roots pump, and a molecular pump connected in sequence. During evacuation, the mechanical pump is first activated under atmospheric conditions to obtain a low vacuum in the vacuum container 11. The Roots pump has a high pumping speed within a pressure range of 100–1 Pa, enabling it to quickly remove suddenly released gas; this pressure range falls precisely between that of the mechanical pump and the molecular pump. The molecular pump uses a high-speed rotating rotor to transfer momentum to gas molecules, giving them directional velocity, thus compressing them and driving them towards the exhaust port for removal by the forestage pump. These three vacuum pumps are arranged in a complementary manner and according to their activation sequence during evacuation of the vacuum container 11, working together to complete the transition from atmospheric to high vacuum within the container.

[0167] In some examples, see Figure 9 Gas source 3 includes a liquid nitrogen source and a helium source. The connections of the liquid nitrogen source and the helium source to the heat exchanger under test are controlled by valves. The liquid nitrogen source is used to fill the heat exchanger under test with liquid nitrogen to cool it down. The helium source is used to inject helium into the heat exchanger under test for leak detection.

[0168] In some examples, see Figure 9The temperature monitoring component 4 includes multiple resistance temperature detectors (RTDs) and a digital display monitor. The RTDs are respectively installed on the inlet side, outlet side, and outer wall of the heat exchanger 6 under test. They are electrically connected to the digital display monitor. This configuration allows for direct monitoring of temperature changes at the inlet, outlet, and overall temperature of the heat exchanger 6 under test.

[0169] In some examples, the piping connections of the 2K negative pressure heat exchanger low-temperature leak detection system 1 are as follows: Figure 10 As shown. Gas source 3 is connected to the heat exchange channels of the heat exchanger 6 under test. Helium mass spectrometer leak detector 5 is connected to multiple heat exchange channels of the heat exchanger 6 under test and vacuum container 11 via hoses 141. Vacuum system 2 is connected to multiple heat exchange channels of the heat exchanger 6 under test and vacuum container 11 via vacuum interface 16. Chiller unit 7 is connected to vacuum system 2. Valve V1 is installed on the interface of vacuum container 11 to control the opening and closing of the pipeline between helium mass spectrometer leak detector 5 and vacuum system 2 and vacuum container 11. Valve V2 is installed on the interface of helium mass spectrometer leak detector 5 to control the opening and closing of the pipeline between helium mass spectrometer leak detector 5 and multiple heat exchange channels of the heat exchanger 6 under test, and to control the opening and closing of the pipeline between helium mass spectrometer leak detector 5 and vacuum container 11. Valve V3 is installed on the interface of vacuum system 2 to control the opening and closing of the pipeline between vacuum system 2 and heat exchanger 6 under test and vacuum container 11. Valves V4 to V6 are installed at the interfaces of multiple heat exchange channels of the heat exchanger 6 under test, controlling the opening and closing of the pipeline between each heat exchange channel and the helium mass spectrometer leak detector 5 or the vacuum system 2. By switching the states of valves V1 to V6, it is possible to evacuate the vacuum container 11, cool the heat exchanger 6 under test, and detect internal and external leaks in each heat exchange channel. It is understood that in this embodiment, the heat exchanger 6 under test has three heat exchange channels, and valves V4 to V6 are respectively installed on one heat exchange channel. However, in other embodiments, the number of heat exchange channels can be two or more. The specific configuration can be determined according to the application requirements.

[0170] In some examples, see Figure 9 The 2K negative pressure heat exchanger low-temperature leak detection device 1 is a leak detection fixture composed of multiple welded components, and its own leakage rate can reach 5.0×10⁻⁶. -10 Pa·m 3 / s. The vacuum system 2 is connected to the vacuum port 16 on the 2K negative pressure heat exchanger cryogenic leak detection device 1 via a KF quick-connect coupling. Activating the vacuum system 2 creates a vacuum environment for the heat exchanger 6 under test in the 2K negative pressure heat exchanger cryogenic leak detection device 1. The helium mass spectrometer leak detector 5 is connected to the hose assembly 14 on the 2K negative pressure heat exchanger cryogenic leak detection device 1 and is connected in series with the vacuum system 2 and the unit.

[0171] The low-temperature leak detection system for a 2K negative pressure heat exchanger in this embodiment includes the aforementioned low-temperature leak detection device 1, vacuum system 2, gas source 3, temperature monitoring component 4, and helium mass spectrometer leak detector 5. The vacuum system 2 is connected to the vacuum port 16 of the low-temperature leak detection device 1. The gas source 3 and the helium mass spectrometer leak detector 5 are connected to the hose assembly 14 of the low-temperature leak detection device 1. The temperature monitoring component 4 is connected to the temperature monitoring port 15 of the low-temperature leak detection device 1. Using this low-temperature leak detection system, the internal and external leak rates of the heat exchanger can be detected in a low-temperature environment, obtaining the actual leak rate data of the heat exchanger under low-temperature operation.

[0172] It will be readily understood by those skilled in the art that the aforementioned advantageous methods can be freely combined and superimposed without conflict.

[0173] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention. The above are merely preferred embodiments of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present invention, and these improvements and modifications should also be considered within the protection scope of the present invention.

Claims

1. A low-temperature leak detection method for a 2K negative pressure heat exchanger, characterized in that, The method includes the following steps: S1. Connect each heat exchange channel of the heat exchanger under test to the hose assembly, temperature monitoring interface and vacuum interface on the vacuum container respectively; S2. Place the heat exchanger under test into the vacuum container and seal the vacuum container; S3. Using a vacuum system, the vacuum container and the heat exchange channel are evacuated through the vacuum interface; S4. Liquid nitrogen or liquid helium is introduced into the heat exchange channel of the heat exchanger under test to cool the heat exchange channel. S5. Obtain the temperature change of the heat exchanger under test through the temperature monitoring interface in order to control the cooling rate of the heat exchanger under test. S6. Bring the temperature in the heat exchange channel to the liquid nitrogen / liquid helium temperature range; S7. Purge the nitrogen or helium gas from the heat exchange channel; S8. Helium gas is introduced into the cooled heat exchange channel until the pressure inside the heat exchange channel reaches the expected value. S9. After a preset static time, detect the external and internal leakage of the heat exchange channel in the liquid nitrogen / liquid helium temperature range; S10. Perform a second vacuuming, then a third vacuuming, and repeat until the i-th vacuuming is performed. Calculate the total leakage rate, where i is an integer greater than 3. S11. Shut down the vacuum system to break the vacuum inside the vacuum container; S12. Reheat the heat exchanger under test and control the reheating rate of the heat exchanger under test; S13. After the heat exchanger under test returns to normal temperature, remove the heat exchanger under test from the vacuum container.

2. The low-temperature leak detection method for a 2K negative pressure heat exchanger according to claim 1, characterized in that, Step S3 further includes: using a vacuum system, evacuating the vacuum container and the heat exchange channel step by step through the vacuum port until the pressure inside the vacuum container is ≤5Pa.

3. The low-temperature leak detection method for a 2K negative pressure heat exchanger according to claim 1, characterized in that, Step S9 includes: S901. Maintain the pressure within the heat exchange channel at the working pressure. S902, make the pressure difference between the heat exchange channel and the adjacent heat exchange channel reach a preset value; S903. Detect the external leakage of the heat exchange channel and the internal leakage between the heat exchange channel and the adjacent heat exchange channel; S904. Switch to other heat exchange channels and repeat the above steps to obtain information on external and internal leakage of the other heat exchange channels.

4. A low-temperature leak detection system for a 2K negative pressure heat exchanger, used in the low-temperature leak detection method for a 2K negative pressure heat exchanger as described in any one of claims 1 to 3, characterized in that, include: A low-temperature leak detection device for a 2K negative pressure heat exchanger includes a vacuum container, a transport assembly, a hose assembly, a temperature monitoring interface, and a vacuuming interface. The vacuum container houses the 2K negative pressure heat exchanger under test. One end of the vacuum container has an opening with a sealing assembly. The transport assembly is located within the vacuum container and extends from the opening into the interior of the vacuum container. The transport assembly is used to transport the heat exchanger under test. The hose assembly is attached to the vacuum container and connects to a gas source and a helium mass spectrometer leak detector. Nitrogen or helium gas can be introduced into the heat exchanger under test within the vacuum container through the hose assembly, and leak detection can be performed on the heat exchange channels of the heat exchanger under test. The temperature monitoring interface is located on the vacuum container and connects to a temperature monitoring assembly. The temperature monitoring interface allows for the acquisition of temperature changes inside the vacuum container and on the heat exchanger under test. The vacuuming interface is located on the vacuum container and connects to a vacuuming system. The vacuuming interface allows for the evacuation of the interior of the vacuum container. A vacuum system is connected to the vacuum port of the low-temperature leak detection device for the 2K negative pressure heat exchanger. The gas source is connected to the hose assembly of the low-temperature leak detection device of the 2K negative pressure heat exchanger. A temperature monitoring component is connected to the temperature monitoring interface of the low-temperature leak detection device for the 2K negative pressure heat exchanger. A helium mass spectrometer leak detector is connected to the hose assembly of the cryogenic leak detection device for the 2K negative pressure heat exchanger.

5. The low-temperature leak detection system for a 2K negative pressure heat exchanger according to claim 4, characterized in that, The transport component includes: A guide rail is disposed in the vacuum container; the guide rail extends from the opening of the vacuum container into the interior of the vacuum container; A trolley is slidably mounted on the guide rail; the trolley is used to carry the heat exchanger under test. A drive unit is connected to the trolley; the drive unit is used to drive the trolley to move back and forth along the guide rail.

6. The low-temperature leak detection system for a 2K negative pressure heat exchanger according to claim 4, characterized in that, The enclosed component includes: A support frame is mounted on the vacuum container; A rotating frame is hinged to the support frame; A sealing door is hinged to the end of the rotating frame away from the support frame; the sealing door is capable of closing the opening of the vacuum container.

7. The low-temperature leak detection system for a 2K negative pressure heat exchanger according to claim 4, characterized in that, The hose assembly includes: Multiple hoses, one end of which is located outside the vacuum container, are used to connect the helium mass spectrometer leak detector and the gas source; the other end of which is located inside the vacuum container, is used to connect the internal space of the vacuum container and each heat exchange channel of the heat exchanger under test.

8. The low-temperature leak detection system for a 2K negative pressure heat exchanger according to claim 4, characterized in that, The vacuum container also includes: A manhole is located at the end of the vacuum container furthest from the opening; The base is located at the bottom of the vacuum container; Lifting lugs are provided on the base and are symmetrically distributed on both sides of the vacuum container.

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