Low-temperature leak detection method, device and system for 2K negative pressure heat exchanger

Abstract

The invention provides a low-temperature leakage detection method, device and system for a 2K negative-pressure heat exchanger, belongs to the technical field of refrigeration and low temperature, and aims to solve the problems that leakage rate performance of the 2K negative-pressure heat exchanger in a deep low-temperature environment cannot be accurately evaluated and the leakage rate of the heat exchanger under design pressure cannot be measured by normal-temperature helium mass spectrum leakage detection. According to the low-temperature leakage detection method, device and system for the 2K negative-pressure heat exchanger, the leakage rate performance of the 2K negative-pressure heat exchanger in a deep low-temperature environment can be accurately evaluated, and the influence of rapid cooling on the sealing performance of equipment is analyzed and tested. And meanwhile, automatic loading and unloading of the 2K negative pressure heat exchangers are supported, online synchronous detection of multiple heat exchangers can be realized, and the processing efficiency and the yield of the heat exchangers are greatly improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of refrigeration and cryogenics, and particularly relates to a low-temperature leak detection method, device and system for a 2K negative-pressure heat exchanger. Background Art

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

[0003] After the manufacture and quality inspection of the 2K negative-pressure heat exchanger, it is generally installed inside a cryogenic valve box, a refrigerator cold box and a test platform. The heat exchanger is formed by splicing and welding multiple components and releases stress. If the heat exchanger leaks under the influence of stress in the deep-low-temperature environment, the cost of unpacking, repairing or replacing it is high, and it will affect the progress of the project construction.

[0004] Most of the conventional leak detection methods are carried out at room temperature, and the normal-temperature helium mass spectrometry leak detection method cannot accurately reflect and evaluate the sealing performance of the 2K negative-pressure heat exchanger in the deep-low-temperature environment and the influence of rapid cooling on the heat exchanger body. In addition, this method cannot inject pressurized helium gas into the heat exchanger cavity, so the leak rate of the heat exchanger under the design pressure cannot be measured. During the manufacturing process of the heat exchanger, only the 2K negative-pressure heat exchanger that has passed the normal-temperature helium mass spectrometry leak detection and is confirmed to be qualified can be subjected to low-temperature leak rate detection. If the normal-temperature leak detection is unqualified, the low-temperature leak rate detection shall not be carried out. 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 a 2K negative-pressure heat exchanger, which can obtain the internal and external leak rates of the 2K negative-pressure heat exchanger in the deep-low-temperature environment, can solve the problems that the normal-temperature helium mass spectrometry leak detection cannot accurately reflect and evaluate the sealing performance of the heat exchanger in the deep-low-temperature environment, the ability to withstand rapid cooling, and the inability to measure the leak rate of the heat exchanger under the design pressure, and can realize the automatic loading and unloading of the 2K negative-pressure heat exchanger, online simultaneous detection of multiple 2K negative-pressure heat exchangers, and improve the processing efficiency and yield of the heat exchanger.

[0006] To solve the above problems, the present invention provides a low-temperature leak detection method for a 2K negative-pressure heat exchanger, including the following steps: S1. Connect each heat exchange channel of the heat exchanger to be inspected to the hose assembly, temperature monitoring interface, and vacuum pumping interface on the vacuum container respectively; S2. Place the heat exchanger to be inspected into the vacuum container and seal the vacuum container; S3. Use the vacuum pumping system to evacuate the vacuum container and the heat exchange channels through the vacuum pumping interface; S4. Fill liquid nitrogen or liquid helium into the heat exchange channels of the heat exchanger to be inspected to cool the heat exchange channels; S5. Obtain the temperature change of the heat exchanger to be inspected through the temperature monitoring interface to control the cooling rate of the heat exchanger to be inspected; S6. Make the temperature in the heat exchange channels reach the liquid nitrogen / liquid helium temperature range; S7. Drain the nitrogen or helium in the heat exchange channels; S8. Fill helium into the cooled heat exchange channels until the pressure in the heat exchange channels reaches the expected value; S9. After standing for a preset time, detect the external leakage and internal leakage of the heat exchange channels in the liquid nitrogen / liquid helium temperature range; S11. Turn off the vacuum pumping system and break the vacuum inside the vacuum container; S12. Let the heat exchanger to be inspected return to room temperature and control the rewarming rate of the heat exchanger to be inspected; S13. When the heat exchanger to be inspected returns to room temperature, take out the heat exchanger to be inspected from the vacuum container.

[0007] Optionally, step S3 further includes: using the vacuum pumping system to gradually evacuate the vacuum container and the heat exchange channels through the vacuum pumping interface until the pressure in the vacuum container ≤ 5 Pa.

[0008] Optionally, between steps S9 and S11, it further includes: S10. Perform secondary vacuum pumping, then perform tertiary vacuum pumping, and cycle until the total leakage rate is calculated after the i-th vacuum pumping, where i is an integer greater than 3.

[0009] Optionally, step S9 includes: S901. Keep the pressure in the heat exchange channels at the working pressure; S902. Make the pressure difference between the heat exchange channel and the adjacent heat exchange channel reach the preset value; S903. Detect the external leakage of the heat exchange channel and the internal leakage between this heat exchange channel and the adjacent heat exchange channel; S904. Switch to other heat exchange channels and repeat the above steps to obtain the external leakage and internal leakage of other heat exchange channels.

[0010] The present invention also provides a low-temperature leak detection device for a 2K negative pressure heat exchanger, comprising: a vacuum container, a transportation assembly, a hose assembly, a temperature monitoring interface, and a vacuum pumping interface. The vacuum container is used to accommodate the heat exchanger to be inspected. One end of the vacuum container has an opening, and a sealing assembly is provided on the opening. The transportation assembly is located in the vacuum container and extends from the opening of the vacuum container to the inside of the vacuum container. The transportation assembly is used to transfer the heat exchanger to be inspected. The hose assembly is arranged on the vacuum container and is used to connect the gas source and the helium mass spectrometer leak detector. Through the hose assembly, nitrogen or helium can be filled into the heat exchanger to be inspected inside the vacuum container, and the heat exchange channels of the heat exchanger to be inspected can be leak-detected. The temperature monitoring interface is arranged on the vacuum container and is used to connect the temperature monitoring assembly. Through the temperature monitoring interface, the temperature changes inside the vacuum container and the 2K negative pressure heat exchanger to be inspected can be obtained. The vacuum pumping interface is arranged on the vacuum container and is used to connect the vacuum pumping system. Through the vacuum pumping interface, the inside of the vacuum container can be evacuated.

[0011] Optionally, the transportation assembly includes: a guide rail, a trolley, and a driving device. The guide rail is arranged in the vacuum container and extends from the opening of the vacuum container to the inside of the vacuum container. The trolley is slidably arranged on the guide rail and is used to carry the heat exchanger to be inspected. The driving device is connected to the trolley and is used to drive the trolley to reciprocate along the guide rail.

[0012] Optionally, the sealing assembly includes: a support frame, a rotating frame, and a sealing door. The support frame is arranged 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, and the sealing door can seal the opening of the vacuum container.

[0013] Optionally, the hose assembly includes: a plurality of hoses. One ends of the plurality of hoses located outside the vacuum container are used to connect the gas source and the helium mass spectrometer leak detector. One ends of the plurality of hoses located inside the vacuum container are respectively used to connect the internal space of the vacuum container and each heat exchange channel of the heat exchanger to be inspected.

[0014] Optionally, the vacuum container further includes: a manhole, a base, and lifting lugs. The manhole is located at the end of the vacuum container away from the opening. The base is arranged at the bottom of the vacuum container. The lifting lugs are arranged on the base and are symmetrically distributed on both sides of the vacuum container.

[0015] The present invention further provides a low-temperature leak detection system for a 2K negative pressure heat exchanger, comprising: the above-mentioned low-temperature leak detection device for a 2K negative pressure heat exchanger, a vacuum pumping system, a gas source, a temperature monitoring assembly, and a helium mass spectrometer leak detector. The vacuum pumping system is connected to the vacuum pumping interface of the heat exchanger low-temperature leak detection device. The gas source and the helium mass spectrometer leak detector are connected to the hose assembly of the heat exchanger low-temperature leak detection device. The temperature monitoring assembly is connected to the temperature monitoring interface of the heat exchanger low-temperature leak detection device.

[0016] Beneficial effects: 1. The low-temperature leak detection method for the 2K negative-pressure heat exchanger provided by the present invention can obtain the internal and external leakage rates of the 2K negative-pressure heat exchanger in a deep low-temperature environment, and can solve the problems that the helium mass spectrometry leak detection at room temperature cannot accurately reflect and evaluate the sealing performance of the heat exchanger in a deep low-temperature environment, the ability to withstand rapid temperature drop, and the inability to measure the leakage rate of the heat exchanger under the design pressure. Through this method, the helium mass spectrometry leak detection data of the 2K negative-pressure heat exchanger under a certain pressure and deep low-temperature state can be measured, which is more accurate and effective compared with the traditional room-temperature helium mass spectrometry leak detection method.

[0017] 2. The low-temperature leak detection device for the 2K negative-pressure heat exchanger provided by the present invention includes a vacuum container, a transportation component, a hose component, a temperature monitoring interface, and a vacuum pumping interface. During use, the heat exchanger to be tested is placed on the transportation component inside the vacuum container, and the heat exchange channels of the heat exchanger to be tested are connected to the hose component, the temperature monitoring interface, and the vacuum pumping interface; then the transportation component is used to move the heat exchanger to be tested inside the vacuum container, and the sealing component on the opening is closed to make the heat exchanger to be tested in a closed environment; the vacuum pumping system is connected to the vacuum pumping interface to pump the vacuum container and the heat exchanger to be tested to make the heat exchanger to be tested in a high-vacuum state; then liquid nitrogen / liquid helium is filled into the heat exchange channels of the heat exchanger to be tested through the hose component to make the overall temperature of the heat exchanger to be tested drop to the target value; then helium gas is filled into the heat exchange channels of the heat exchanger to be tested through the hose component, and the helium leakage situation outside the heat exchange channels to be tested, that is, the external leakage situation, and the helium leakage situation in the adjacent heat exchange channels, that is, the internal leakage situation, are obtained through a helium mass spectrometry leak detector. The low-temperature leak detection device for the 2K negative-pressure heat exchanger of the present invention can realize the low-temperature helium mass spectrometry leak detection of the heat exchanger, obtain the internal and external leakage rates in a low-temperature environment, and accurately evaluate the actual sealing performance of the heat exchanger at low temperature.

[0018] 3. The low-temperature leak detection system for the 2K negative-pressure heat exchanger provided by the present invention includes the above-mentioned low-temperature leak detection device for the 2K negative-pressure heat exchanger, a vacuum pumping system, a gas source, a temperature monitoring component, and a helium mass spectrometry leak detector. The vacuum pumping system is connected to the vacuum pumping interface of the low-temperature leak detection device for the 2K negative-pressure heat exchanger. The gas source and the helium mass spectrometry leak detector are connected to the hose component of the low-temperature leak detection device for the 2K negative-pressure heat exchanger. The temperature monitoring component is connected to the temperature monitoring interface of the low-temperature leak detection device for the 2K negative-pressure heat exchanger. The low-temperature leak detection system for the 2K negative-pressure heat exchanger of the present invention can detect the internal and external leakage rates of the 2K negative-pressure heat exchanger in a low-temperature environment and obtain the actual leakage rate data of the 2K negative-pressure heat exchanger under low-temperature operation.

[0019] 4. The present invention adopts progressive pressure gradient control, which can isolate the interference of micro-leak holes and macroscopic leakage respectively under different vacuum degrees, thereby improving the sensitivity of leak rate detection. Secondly, the staged operation can effectively shorten the equilibrium time required for the system to reach the steady-state vacuum, avoiding the non-linear response problem caused by the sudden pressure drop during the traditional single-stage vacuum pumping process. In addition, this method can reduce the continuous load of the vacuum pump by discharging residual stress in stages, thereby extending the service life of key equipment. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a flowchart of the low-temperature leak detection method for a 2K negative-pressure heat exchanger according to an embodiment provided by the present invention; Figure 2 It is a flowchart of the low-temperature leak detection method for a 2K negative-pressure heat exchanger according to another embodiment provided by the present invention; Figure 3 It is a flowchart of the low-temperature leak detection method for a 2K negative-pressure heat exchanger according to a third embodiment provided by the present invention; Figure 4 It is a flowchart of the low-temperature leak detection method for a 2K negative-pressure heat exchanger according to a fourth embodiment provided by the present invention; Figure 5 It is a flowchart of the low-temperature leak detection method for a 2K negative-pressure heat exchanger according to a fifth embodiment provided by the present invention; Figure 6 It is a schematic perspective view of the low-temperature leak detection device for a 2K negative-pressure heat exchanger according to an embodiment provided by the present invention; Figure 7 It is a rear view of the low-temperature leak detection device for a 2K negative-pressure heat exchanger according to an embodiment provided by the present invention; Figure 8 It is a schematic internal structure view of the low-temperature leak detection device for a 2K negative-pressure heat exchanger according to an embodiment provided by the present invention; Figure 9 It is a schematic view of the low-temperature leak detection system for a 2K negative-pressure heat exchanger according to an embodiment provided by the present invention; Figure 10 It is a schematic diagram of the pipeline connection of the low-temperature leak detection system for a 2K negative-pressure heat exchanger according to an embodiment provided by the present invention.

[0021] The reference signs are represented as: 1. Low-temperature leak detection device for 2K negative-pressure heat exchanger; 2. Vacuum pumping system; 3. Gas source; 4. Temperature monitoring component; 5. Helium mass spectrometer leak detector; 6. Heat exchanger to be detected; 7. Chiller; 11. Vacuum container; 12. Transportation component; 13. Sealing component; 14. Hose component; 15. Temperature monitoring interface; 16. Vacuum pumping interface; 17. Manhole; 18. Base; 19. Lifting lug; 121. Guide rail; 122. Trolley; 131. Support frame; 132. Rotating frame; 133. Sealing door; 141. Hose; V1 to V6 are all valves. Detailed implementation manner

[0022] In the description of the present invention, it should 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", etc. indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation to the present invention.

[0023] In addition, the terms "first" and "second" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include one or more of such features. In the description of the present invention, "a plurality of" means two or more, unless otherwise specifically defined.

[0024] In the present invention, unless otherwise clearly defined and limited, the terms "installed", "connected", "connected", "fixed", etc. should be understood in a broad sense. For example, it may be a fixed connection, a detachable connection, or an integral connection; it may be a mechanical connection or an electrical connection; it may be directly connected or indirectly connected through an intermediate medium, and it may be the communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific situations.

[0025] The following is a description of the preferred embodiments of the present invention with reference to the drawings. It should be understood that the preferred embodiments described herein are only used to illustrate and explain the present invention and are not used to limit the present invention.

[0026] In the first aspect, this embodiment provides a low-temperature leak detection method for a 2K negative-pressure heat exchanger. Figure 1 It is a flowchart of a low-temperature leak detection method for a 2K negative-pressure heat exchanger provided in this embodiment.

[0027] As Figure 1 shown, the low-temperature leak detection method of the heat exchanger in this embodiment includes the following steps: S1. Connect each heat exchange channel of the heat exchanger 6 to be inspected to the hose assembly 14, the temperature monitoring interface 15, and the vacuum pumping interface 16 on the vacuum container 11 respectively; Specifically, VCR connectors are welded to the interfaces of each heat exchange channel of the heat exchanger 6 to be inspected. The VCR connectors are used to dock each heat exchange channel with the hose assembly 14, the temperature monitoring interface 15, and the vacuum pumping interface 16. It should be noted that when docking the VCR connectors, a matching gasket must be installed on the sealing surface, and this gasket is for single use. Also, after the VCR connectors are connected, they need to be soaked in liquid nitrogen or sprayed with liquid nitrogen at the connection for about 5 minutes. When the VCR connectors are in a cold state, use a wrench to further tighten them to prevent leakage of the VCR connectors at low temperatures, which may cause misjudgment. If necessary, leak detection can be performed on the VCR connectors.

[0028] S2. Place the heat exchanger 6 to be inspected into the vacuum container 11 and seal the vacuum container 11. Specifically, before performing low-temperature leak detection on the heat exchanger 6 to be inspected, it is necessary to confirm whether there are aluminum chips, impurities, and any particulate matter that may damage the vacuum pumping system 2 in each heat exchange channel of the heat exchanger 6 to be inspected. If any are found, they must be cleaned before performing low-temperature leak detection.

[0029] S3. Use the vacuum pumping system 2 to evacuate the vacuum container 11 and the heat exchange channels through the vacuum pumping interface 16. Specifically, use the vacuum pumping system 2 to evacuate the inside of the vacuum container 11 and the heat exchange channels of the heat exchanger 6 to be inspected through the vacuum pumping interface 16, so that the heat exchanger 6 to be inspected is in a high-vacuum state (i.e., the pressure inside the vacuum container 11 ≤ 5 Pa).

[0030] S4. Fill the heat exchange channels of the heat exchanger 6 to be inspected with liquid nitrogen or liquid helium to cool the heat exchange channels. Specifically, the flow rate of liquid nitrogen or liquid helium needs to be controlled during the process of filling liquid nitrogen or liquid helium to cool the heat exchanger 6 to be inspected. Slowly fill liquid nitrogen or liquid helium into the heat exchange channels of the heat exchanger 6 to be inspected. Due to heat loss, as long as the heat exchanger 6 to be inspected reaches a temperature close to that of liquid nitrogen.

[0031] S5. Obtain the temperature change of the heat exchanger 6 to be inspected through the temperature monitoring interface 15 to control the cooling rate of the heat exchanger 6 to be inspected. Specifically, turn on the temperature monitoring component 4 to obtain the temperature change. The cooling rate ≤ 4 °C / min, otherwise the heat exchanger 6 to be inspected may be damaged due to thermal stress. In the initial stage of cooling, record the temperature data every 10 minutes. After the cooling rate is stable, record the temperature data every 1 hour. If the cooling rate is too fast, the opening of the liquid nitrogen or liquid helium outlet valve can be adjusted to adjust the flow rate. Preferably, the cooling rate of the heat exchanger 6 to be inspected should not be faster than 1 °C / min.

[0032] Furthermore, in order to provide more accurate specific flow rate values for the operator and avoid blind adjustment by the operator. The flow rate of the cooling medium can be controlledu Effectively regulate the cooling rate of the heat exchanger , and its functional relationship is dominated by the 0.8th power of the flow velocity u , and is simultaneously affected by the heat transfer area, the thermophysical properties of the working fluid, and the temperature difference driving force. The formula is as follows:

[0033] Among them, dT is the temperature change amount, dt is the time change amount, C is a dimensionless coefficient related to the geometric size of the heat exchanger flow channel (such as the hydraulic diameter D h ); A A0 is the reference heat transfer area; α is the surface enhancement coefficient; η is the heat transfer surface contact efficiency, that is, the ratio of the actual effective heat transfer area to the theoretical area ( 0 ≤ η ≤ 1 ), which is affected by surface roughness and wettability; ρ is the density of the working fluid; V is the volume of the working fluid; c p is the specific heat capacity of the working fluid; T m is the ambient temperature; is the temperature difference between the working fluid and the medium.

[0034] According to the target cooling rate r target back-calculate the required flow velocity u set The formula is:

[0035] Among them, C is a dimensionless coefficient related to the geometric size of the heat exchanger flow channel (such as the hydraulic diameter D h ); A A0 is the reference heat transfer area; α is the surface enhancement coefficient; η is the heat transfer surface contact efficiency, that is, the ratio of the actual effective heat transfer area to the theoretical area ( 0 ≤ η ≤ 1 ), which is affected by surface roughness and wettability; V is the volume of the working fluid; ρ is the density of the working fluid; c p is the specific heat capacity of the working fluid; T m is the ambient temperature; is the temperature difference between the working fluid and the medium.

[0036] Specifically, the minimum flow velocity umin ≥0.1 m / s (to avoid a sharp drop in heat transfer efficiency caused by laminar flow), maximum flow velocity u max ≤5 m / s (limited by pump power and pressure drop).

[0037] The specific calculation is shown as follows.

[0038] Known parameter settings:

[0039] Calculate the effective heat transfer area A( η ): A( η ) = A0(1 + αη ) = 1.5×(1 + 0.15×0.75) = 1.5×1.1125 = 1.669 m 2 Calculate the comprehensive constant k:

[0040] Back-calculate the flow velocity u set :

[0041]

[0042] Due to the superfluid helium effect, if the system temperature is lower than 2.17 K (λ point), the liquid helium enters the superfluid state and the heat transfer coefficient is significantly improved, and the actual required flow velocity can be further reduced.

[0043] In some possible embodiments, the flow velocity is obtained through the above formula u set， The actual initial flow velocity is set to A1 u set， where A1 is a coefficient between 0 and 1.

[0044] Specifically, the actual initial flow velocity is set to 0.3 u set、 0.4 u set、 0.5 u set、 0.6 u set . Measure the actual cooling rate, compare it with the target cooling rate, and finely adjust the flow velocity up and down.

[0045] S6. Make the temperature in the heat exchange channel reach the liquid nitrogen / liquid helium temperature range; Specifically, liquid nitrogen or liquid helium is filled into the heat exchange channels of the heat exchanger 6 to be inspected to cool the heat exchange channels so that the temperature in the heat exchange channels reaches the liquid nitrogen / liquid helium temperature range. When the overall temperature of the heat exchanger 6 to be inspected drops to about -160 °C, the filling of liquid nitrogen into the heat exchanger 6 to be inspected can be stopped.

[0046] S7. Drain the nitrogen or helium in the heat exchange channels; Specifically, after the temperature reduction is completed, the exhaust volume generated by the evaporation of liquid nitrogen or liquid helium at the exhaust port of the heat exchange channel is obtained, and helium can be filled for leak detection only when no gas is discharged from the exhaust port.

[0047] S8. Fill helium into the cooled heat exchange channels until the pressure in the heat exchange channels reaches the expected value; Specifically, maintain the pressure of the heat exchange channels filled with helium at the working pressure of the channels and maintain the maximum pressure difference between adjacent heat exchange channels. (As Figure 10 shown, the heat exchanger 6 to be inspected has four groups of channels, the design pressure of each group is 2.5 MPa, and the operating pressures are 1.0 MPa, 0.5 MPa, 0.2 MPa, and 0.1 MPa respectively. Then, the pressure is maintained at the highest working pressure of 1.0 MPa).

[0048] S9. After a preset time of stillness, detect the external leakage and internal leakage of the heat exchange channels in the liquid nitrogen / liquid helium temperature range; Specifically, external leakage refers to the leakage between the heat exchange channels and the inside of the vacuum vessel 11. Internal leakage refers to the leakage between adjacent heat exchange channels. Since the inside of the vacuum vessel 11 is in a vacuum negative pressure environment state, the external leakage of the heat exchange channels of the heat exchanger 6 filled with helium can be measured, and the value of the leak detector is the low-temperature external leakage data of the heat exchange channels. By controlling the valves on the interfaces of each heat exchange channel of the heat exchanger 6 to be inspected, the low-temperature internal leakage data between this heat exchange channel and other heat exchange channels can be measured.

[0049] S11. Close the vacuum pumping system and break the vacuum inside the vacuum vessel 11; S12. After the heat exchanger 6 to be inspected is rewarmed, control the rewarming rate of the heat exchanger to be inspected; Specifically, the rewarming rate of the heat exchanger 6 to be inspected must be strictly controlled within 4 °C / min. Before the heat exchanger 6 to be inspected is rewarmed to room temperature, it is prohibited to open the sealing component 13.

[0050] S13. When the heat exchanger 6 to be inspected returns to room temperature, take out the heat exchanger 6 to be inspected from the vacuum vessel 11.

[0051] Specifically, after the heat exchanger 6 to be inspected is rewarmed to room temperature, open the sealing component 13 and push out the heat exchanger 6 to be inspected, and the low-temperature leak detection ends. It should be noted that if it is not necessary to perform the low-temperature leak detection of the next heat exchanger to be inspected again, it is necessary to check and confirm whether the power supplies of all equipment are turned off.

[0052] The low-temperature leak detection method for the 2K negative-pressure heat exchanger in this embodiment can measure the helium mass spectrometry leak detection data of the heat exchanger under a certain pressure and low-temperature state, and is more accurate and effective compared with the traditional room-temperature helium mass spectrometry leak detection method. When helium is used as the leak detection gas, if there is a leak hole in the container to be detected, helium will leak out through the leak hole and be detected by the helium mass spectrometry leak detector 5, so as to know the position of the leak hole and the magnitude of the gas leakage. During use, usually helium is filled into the heat exchanger 6 to be detected, and then the suction probe outside the leakage port is used to detect helium in the leakage gas, and whether there is a leak is judged by detecting the signal intensity of helium.

[0053] In some embodiments, referring to Figure 1 , step S3 further includes: using the vacuum pumping system 2 to gradually pump the vacuum container 11 and the heat exchange channel to a vacuum through the vacuum pumping interface 16 until the pressure in the vacuum container ≤ 5 Pa.

[0054] Specifically, as Figure 10 shown, close the valve V2, open the remaining valves V1, V3, V4, V5, V6, and turn on the fore-pump of the vacuum pumping system 2. Wait until the vacuum degree ≤ 20 Pa and then turn on the molecular pump of the vacuum pumping system 2 until the pressure in the vacuum container ≤ 5 Pa. And when the molecular pump is turned on, start the chiller 7, which can keep the vacuum container 11 in a negative pressure state.

[0055] Figure 2 is a flowchart of another low-temperature leak detection method for the 2K negative-pressure heat exchanger provided in this embodiment. In some embodiments, as Figure 2 shown, between steps S9 and S11, it further includes: S10. Perform secondary vacuum pumping, then perform tertiary vacuum pumping, and cycle until the i-th vacuum pumping to calculate the total leak rate, where i is an integer greater than 3.

[0056] Specifically, in a possible embodiment, based on the principle of mass conservation, the multi-stage pumping process can be modeled as a dynamic leakage system of series cavities. Assuming that the pumping speed is constant in each stage and the leakage source is in a steady-state flow state, the total leak rate can be decomposed into a linear superposition of the leak rates in each independent pressure interval. By introducing an effective pumping speed correction coefficient and a pressure decay function, the formula for the total leak rate of the system is derived:

[0057] 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, η i is thei The weight factor of the leakage path at the first level. The above formula quantifies the contribution of different vacuum stages to the total leakage rate, providing a theoretical basis for determining leakage.

[0058] In another possible embodiment, a secondary vacuum pumping is performed to calculate the equivalent leakage rate at the second level; then a tertiary vacuum pumping is performed to calculate the equivalent leakage rate at the third level; the cycle continues until the i-th vacuum pumping is performed to calculate the equivalent leakage rate at the i-th level, and the total leakage rate is calculated, where i is an integer greater than 3. When the system reaches a steady state at the i-th vacuum stage, the leakage gas flow rate is balanced with the pumping speed, satisfying:

[0059] In the formula, Q i is the i equivalent leakage rate at the 3 -th level (Pa·m S i / s), i is the effective pumping speed at the 3 -th level (m P i,eq / s), i is the equilibrium pressure at the P i,lim -th level (Pa), i is the ultimate vacuum of the

[0060] -th level vacuum pump (Pa).

[0061] In the formula, Q i is the i equivalent leakage rate at the 3 -th level (Pa·m t i / s), τ i = V / S i is the τ i characteristic time constant at the 3 -th level (s), V is the system volume (m S i ), i is the effective pumping speed at the 3 -th level (m

[0062] / s), and exp is the exponential term, reflecting the influence of pressure decay on the leakage rate during the non-steady pumping process.This embodiment adopts pressure gradient progressive control, which can isolate the interference of micro-leak holes and macroscopic leaks at different vacuum degrees respectively, 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 and avoid the non-linear response problem caused by the sudden pressure drop during the traditional single-stage vacuum pumping process. In addition, this method can reduce the continuous load of the vacuum pump by discharging residual stress in stages, thereby extending the service life of key equipment.

[0063] Figure 3 It is a flowchart of the third low-temperature leak detection method for a 2K negative pressure heat exchanger provided in this embodiment. In some embodiments, as Figure 3 shown, step S2 includes: S201. Place the heat exchanger 6 to be inspected on the transportation component 12; Specifically, move the trolley 122 to the opening of the vacuum container 11, and place the heat exchanger 6 to be inspected on the trolley 122 through a hoisting device.

[0064] S202. Transfer the heat exchanger 6 to be inspected inside the vacuum container 11; Specifically, move the heat exchanger 6 to the inside of the vacuum container 11 by pushing the trolley 122 along the guide rail 121. It should be noted that the trolley 122 can adopt driving methods such as manual or electric, and this embodiment does not limit it too much.

[0065] S203. Seal the opening of the vacuum container 11 so that the heat exchanger 6 to be inspected is in a sealed environment.

[0066] Specifically, after confirming that there are no impurities on the contact surface between the closing door 133 and the opening, apply sealing silicone grease. The sealing silicone grease can be directly applied by hand until it is visually uniform. It should be noted that the sealing silicone grease does not need to be applied every time. If the leak detection device has not been used for a long time (for example, more than 1 month), it must be applied before use again. Then close the closing door 133 and tighten the bolts and nuts on the closing door 133.

[0067] The method of this embodiment will use the transportation component 12 to place the heat exchanger 6 to be inspected in the vacuum container 11, which is convenient for the handling and replacement of the heat exchanger 6 to be inspected, and sealing the vacuum container 11 can ensure the tightness of the space where the heat exchanger 6 to be inspected is located.

[0068] Figure 4 It is a flowchart of the fourth low-temperature leak detection method for a 2K negative pressure heat exchanger provided in this embodiment. In some embodiments, as Figure 4 shown, step S4 includes: S401. Open the liquid outlet valve of liquid nitrogen or liquid helium in the gas source 3, and fill liquid nitrogen or liquid helium in the heat exchange channels with the largest volume of the heat exchanger 6 to be inspected for cooling.

[0069] Specifically, during the cooling process, when the temperature at one end of the heat exchange channel drops below 100 K, while the other end is still at a relatively high temperature and the cooling rate is very small, the liquid nitrogen or liquid helium inlet and the exhaust port of the heat exchange channel can be swapped to further evenly cool down. During the cooling process, if liquid nitrogen or liquid helium has flowed out of the exhaust port of the heat exchange channel but the temperature has not reached below 100 K, liquid nitrogen or liquid helium can be continuously filled for 10 - 20 minutes, and observe whether there is an obvious change in the cooling rate. If there is no obvious change, it is judged that the overall temperature of the heat exchange channel has approached or reached below 100 K. At this time, close the liquid nitrogen or liquid helium valve to stop the cooling.

[0070] S402. During the cooling process of the heat exchange channel, obtain the temperature and leak rate changes of the heat exchange channel; Specifically, as Figure 10 shown, during the cooling process of the heat exchange channel, turn on the mass spectrometer leak detector 5. At the same time, slowly open the valve V2 to observe the leak rate of the entire vacuum system. By opening the valves V4, V5, and V6 respectively and closing the valve V1, the leak rate of each heat exchange channel can be observed to analyze the influence of rapid cooling on the sealing performance of the equipment.

[0071] Specifically, since the volume content of helium in the air is about 5 ppm, that is, about five parts per million, in this embodiment, during the cooling process, the background leak rate of the heat exchange channel can also be obtained to exclude the influence of helium in the air on the detection results, improve the detection accuracy, and improve the accuracy and sensitivity of leak detection.

[0072] Figure 5 This is the flowchart of the fifth 2K negative pressure heat exchanger low-temperature leak detection method provided by this embodiment. In some embodiments, as Figure 5 shown, step S9 includes: S901. Keep the pressure in the heat exchange channel at the working pressure; Specifically, after the heat exchanger 6 to be inspected is cooled down, slowly fill the cooled heat exchange channel with high-purity helium gas to make the pressure in the heat exchange channel reach the working pressure, and then keep it static for a preset time (such as 15 min).

[0073] As Figure 10 shown, after the cooling is completed, close the valves V3, V4, V5, and V6, and fill the cooled heat exchange channel with helium gas at a low temperature. The heat exchanger to be inspected has four groups of channels, and the design pressure of each group is 2.5 MPa, and the operating pressures are 1.0 MPa, 0.5 MPa, 0.2 MPa, and 0.1 MPa respectively. Then, keep the pressure at the highest working pressure of 1.0 MPa.

[0074] 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 this heat exchange channel and adjacent heat exchange channels. Specifically, connect the helium mass spectrometer leak detector 5 to the inside of the vacuum container 11, and obtain the external leakage data of this heat exchange channel through the change in the value of the helium mass spectrometer leak detector 5. Or, connect the helium mass spectrometer leak detector 5 to an adjacent heat exchange channel, and obtain the internal leakage data of this heat exchange channel through the change in the value of the helium mass spectrometer leak detector 5.

[0075] S904. Switch to other heat exchange channels and repeat the above steps to obtain the external leakage and internal leakage conditions of other heat exchange channels.

[0076] Specifically, as Figure 10 shown, break the vacuum of the heat exchange channels corresponding to the valves V4, V5, and V6 in sequence, and measure the external leakage and internal leakage data of the heat exchange channels corresponding to the valves V4, V5, and V6 in sequence. It should be noted that before each switch of the valves V4, V5, and V6, the valve V2 must be closed to avoid accidentally operating to let the helium mass spectrometer leak detector 5 access the atmosphere and damaging the helium mass spectrometer leak detector 5.

[0077] Using the method of this embodiment, the internal leakage and external leakage of multiple heat exchange channels can be detected without resetting the leak detection device, which is beneficial to improving the leak detection efficiency.

[0078] In a second aspect, this embodiment provides a 2K negative pressure heat exchanger low-temperature leak detection device 1 for the 2K negative pressure heat exchanger low-temperature leak detection method of the above embodiment. Figure 6 FIG. is a schematic three-dimensional structure diagram of a 2K negative pressure heat exchanger low-temperature leak detection device 1 provided by this embodiment. Figure 7 FIG. is a rear view of a 2K negative pressure heat exchanger low-temperature leak detection device 1 provided by this embodiment. Figure 8 FIG. is a schematic internal structure diagram of a 2K negative pressure heat exchanger low-temperature leak detection device 1 provided by this embodiment.

[0079] As Figures 6 - 8As shown in the figure, the low-temperature leak detection device 1 of the 2K negative pressure heat exchanger in this embodiment includes: a vacuum container 11, a transportation component 12, a hose component 14, a temperature monitoring interface 15, and a vacuum pumping interface 16. The vacuum container 11 is used to accommodate the heat exchanger 6 to be inspected. One end of the vacuum container 11 has an opening. A sealing component 13 is provided on the opening. The transportation component 12 is located in the vacuum container 11. The transportation component 12 extends from the opening of the vacuum container 11 to the inside of the vacuum container 11. The transportation component 12 is used to transfer the heat exchanger 6 to be inspected. The hose component 14 is arranged on the vacuum container 11. The hose component 14 is used to connect the gas source 3 and the helium mass spectrometer leak detector 5. Through the hose component 14, nitrogen or helium can be filled into the heat exchanger 6 inside the vacuum container 11, and the heat exchange channels of the heat exchanger 6 can be leak-tested. The temperature monitoring interface 15 is arranged on the vacuum container 11. The temperature monitoring interface 15 is used to connect the temperature monitoring component 4. Through the temperature monitoring interface 15, the temperature changes inside the vacuum container 11 and the heat exchanger 6 to be inspected can be obtained. The vacuum pumping interface 16 is arranged on the vacuum container 11. The vacuum pumping interface 16 is used to connect the vacuum pumping system 2. Through the vacuum pumping interface 16, the inside of the vacuum container 11 can be evacuated.

[0080] In some examples, such as Figure 6 and Figure 7 shown, the vacuum container 11 is cylindrical, one end of the vacuum container 11 is closed, and the other end has an opening. The sealing component 13 is connected to the side wall of the vacuum container 11 and can be sealed on the opening. With such a setting, the sealing ability of the vacuum container 11 can be guaranteed, and at the same time, it is convenient to put in and take out the heat exchanger 6 to be inspected.

[0081] In some examples, such as Figure 6 and Figure 7 shown, the vacuum container 11 includes two hose components 14, and the two hose components 14 are respectively close to the front and rear ends of the vacuum container 11. By setting two hose components 14, they can be used as the air inlet and the exhaust port respectively, which is beneficial to simplifying the connection pipeline between the heat exchanger 6 to be inspected and the low-temperature leak detection device 1 of the heat exchanger, and is more convenient to use.

[0082] In some examples, referring to Figure 6 and Figure 7 , the vacuum pumping interface 16 includes a pressure gauge. With such a setting, it is convenient to obtain the pressure value inside the vacuum container 11 in real time.

[0083] The low-temperature leak detection device 1 of the 2K negative-pressure heat exchanger in this embodiment includes a vacuum container 11, a transportation component 12, a hose component 14, a temperature monitoring interface 15, and a vacuum pumping interface 16. During use, the heat exchanger 6 to be inspected is placed on the transportation component 12 inside the vacuum container 11, and the heat exchange channels of the heat exchanger 6 to be inspected are connected to the hose component 14, the temperature monitoring interface 15, and the vacuum pumping interface 16. Then, the heat exchanger 6 to be inspected is moved into the vacuum container 11 by using the transportation component 12, and the sealing component 13 on the opening is closed to make the heat exchanger 6 to be inspected in a closed environment. The vacuum pumping system 2 is connected to the vacuum pumping interface 16 to pump the vacuum container 11 and the heat exchanger 6 to be inspected to make the heat exchanger 6 to be inspected in a high-vacuum state. Then, liquid nitrogen is filled into the heat exchange channels of the heat exchanger 6 by using the hose component 14 to make the overall temperature of the heat exchanger 6 drop to the target value. Then, helium is filled into the heat exchange channels of the heat exchanger 6 by using the hose component 14, and the helium leakage situation outside the heat exchanger 6, that is, external leakage, and the helium leakage situation in adjacent heat exchange channels, that is, internal leakage, are obtained through the helium mass spectrometer leak detector 5. The low-temperature leak detection device 1 of the heat exchanger of the present invention can realize the low-temperature helium mass spectrometry leak detection of the heat exchanger, obtain the internal and external leakage rates under low-temperature conditions, and accurately evaluate the actual sealing performance of the heat exchanger at low temperature. At the same time, by setting the transportation component, the automatic loading and unloading of the 2K negative-pressure heat exchanger are supported, and the online synchronous detection of multiple heat exchangers can be realized, greatly improving the processing efficiency and finished product rate of the heat exchanger.

[0084] In some embodiments, as Figure 8 shown, the transportation component 12 includes: a guide rail 121, a trolley 122, and a driving device. The guide rail 121 is arranged in the vacuum container 11. The guide rail 121 extends from the opening of the vacuum container 11 to the inside of the vacuum container 11. The trolley 122 is slidably arranged on the guide rail 121. The trolley 122 is used to carry the heat exchanger 6 to be inspected. The driving device is connected to the trolley 122 and is used to drive the trolley 122 to reciprocate along the guide rail 121.

[0085] In some examples, as Figure 8 shown, there are two guide rails 121 of the transportation component 12, and the two guide rails 121 are parallel to each other. The trolley 122 is mounted between the two guide rails 121 and can slide along the two guide rails 121. The double-guide-rail 121 structure is adopted in this embodiment, which can make the movement of the trolley 122 more stable. In addition, in order to reduce the friction between the trolley 122 and the guide rail 121, pulleys can also be arranged at the bottom of the trolley 122, and the pulleys can roll in the guide rail 121, so that the trolley 122 can move along the guide rail 121.

[0086] Since the 2K negative pressure heat exchanger has a large volume and weight, and the space in the vacuum container 11 is limited, it is difficult to manually carry the heat exchanger 6 to be inspected when placing it in the vacuum container 11. In this embodiment, a guide rail 121 and a trolley 122 are arranged in the vacuum container 11. The trolley 122 is slidably arranged on the guide rail 121, and the trolley 122 is used to carry the heat exchanger 6 to be inspected, effectively reducing the difficulty of moving the heat exchanger 6 to be inspected and improving the leak detection efficiency. By driving the trolley 122 to reciprocate along the guide rail 121, it is possible to support the automatic loading and unloading of the 2K negative pressure heat exchanger, and online synchronous detection of multiple heat exchangers can be achieved, greatly improving the processing efficiency and yield of the heat exchanger.

[0087] In some embodiments, as Figure 6 and Figure 7 shown, the closing assembly 13 includes: a support frame 131, a rotating frame 132 and a closing door 133. The support frame 131 is arranged on the vacuum container 11. The rotating frame 132 is hinged to the support frame 131. The closing door 133 is hinged to one end of the rotating frame 132 far from the support frame 131. The closing door 133 can close the opening of the vacuum container 11.

[0088] In some examples, as Figure 6 and Figure 7 shown, the closing door 133 is buckled on the opening of the vacuum container 11 and is connected to the opening of the vacuum container 11 by a flange. In this embodiment, the closing door 133 can rotate around the support frame 131 under the support of the rotating frame 132 to open and close the opening. When the closing door 133 is closed, the bolts on the flange between the closing door 133 and the vacuum container 11 need to be tightened to ensure the sealing of the opening by the closing door 133.

[0089] In some examples, as Figure 7 shown, a handle is provided on the closing door 133. The handle is located on the side of the closing door 133 far from the rotating frame 132. With such a setting, it is convenient to open and close the closing door 133.

[0090] The closing assembly 13 of this embodiment includes a support frame 131, a rotating frame 132 and a closing door 133. The support frame 131 is arranged on the vacuum container 11. The closing door 133 is hinged to the support frame 131 through the rotating frame 132. The closing door 133 can rotate around the support frame 131 under the support of the rotating frame 132 to open and close the opening, which is convenient for placing and taking out the heat exchanger 6 to be inspected and can ensure the sealing of the opening.

[0091] In some embodiments, 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. One end of the plurality of hoses 141 located inside the vacuum container 11 is respectively used to connect the internal space of the vacuum container 11 and each heat exchange channel of the heat exchanger 6 to be inspected.

[0092] In some examples, as Figure 6 and Figure 7 shown, each hose 141 of the hose assembly 14 is used to connect a heat exchange channel of the heat exchanger 6 to be inspected or communicate with the internal space of the vacuum container, and a valve is correspondingly arranged on each hose 141 to facilitate controlling 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 leakage and external leakage of different heat exchange channels.

[0093] In some examples, as Figure 6 and Figure 7 shown, there are two hose assemblies 14. The plurality of hoses 141 of one hose assembly 14 are used for air intake, and the plurality of hoses 141 of the other hose assembly 14 are used for exhaust. With such an arrangement, the gas flow in the vacuum container 11 and the heat exchanger 6 to be inspected can be made smoother, and the connection and arrangement of the pipelines are more convenient.

[0094] In some embodiments, as Figure 6 and Figure 7 shown, the vacuum container 11 further includes: a manhole 17, a base 18, and a lifting lug 19. The manhole 17 is located at one end of the vacuum container 11 far from the opening. The base 18 is arranged at the bottom of the vacuum container 11. The lifting lug 19 is arranged on the base 18, and the lifting lugs 19 are symmetrically distributed on both sides of the vacuum container 11.

[0095] In some examples, as Figure 7 shown, the closing door of the manhole 17 is flange-connected to the vacuum container 11, and a handle is provided on the closing door of the manhole 17. With such an arrangement, the sealing performance of the manhole 17 can be ensured, and at the same time, it is convenient to open and close the manhole 17.

[0096] In some examples, as Figure 6 and Figure 7 shown, the base 18 includes a pair of saddle supports arranged at the bottom of the vacuum container 11 and respectively close to both ends of the vacuum container 11. Supporting the vacuum container 11 with saddle supports is more stable, and the saddle supports are of a hollow structure, with light weight and good stability, which is beneficial to reducing the overall weight of the device.

[0097] In some examples, as Figure 6 and Figure 7 shown, setting the lifting lug 19 on the base 18 can make the overall lifting of the leak detection device more stable.

[0098] The empty container 11 of this embodiment further includes a manhole 17, a base 18, and a lifting lug 19. The manhole 17 is provided to facilitate the maintenance of the interior of the vacuum container 11. The base 18 is provided to make the vacuum container 11 more stable. The lifting lug 19 is provided to facilitate the handling of the leak detection device.

[0099] In a third aspect, this embodiment also provides a 2K negative pressure heat exchanger low-temperature leak detection system. Figure 9 It is a schematic diagram of a 2K negative pressure heat exchanger low-temperature leak detection system provided for this embodiment.

[0100] As Figure 9 shown, the 2K negative pressure heat exchanger low-temperature leak detection system of this embodiment includes: the 2K negative pressure heat exchanger low-temperature leak detection device 1, a vacuum pumping system 2, a gas source 3, a temperature monitoring component 4, and a helium mass spectrometer leak detector 5 of the above embodiment. The vacuum pumping system 2 is connected to the vacuum pumping interface 16 of the heat exchanger 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 interface 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.

[0101] In some examples, referring to Figure 9 , the vacuum pumping system 2 includes a mechanical pump, a Roots pump, and a molecular pump connected in sequence. When pumping vacuum, first start the mechanical pump in the atmospheric state to obtain a low vacuum in the vacuum container 11. The Roots pump has a large pumping speed in the pressure range of 100 to 1 Pa and can quickly discharge the suddenly released gas. This pressure range is exactly between the mechanical pump and the molecular pump. The molecular pump can transfer the momentum to the gas molecules by using a high-speed rotating rotor, so that they obtain a directional velocity, and thus are compressed and driven towards the exhaust port and then pumped away by the fore pump. These three vacuum pumps are arranged in the starting order and in a complementary function manner when pumping the vacuum container 11, and can jointly complete the conversion process of the interior of the vacuum container 11 from the atmospheric state to the high vacuum state.

[0102] In some examples, referring to Figure 9 , the gas source 3 includes a liquid nitrogen source and a helium gas source. The connection between the liquid nitrogen source and the helium gas source and the heat exchanger to be inspected is controlled by a valve. The liquid nitrogen source is used to fill liquid nitrogen into the heat exchanger to be inspected to cool the heat exchanger to be inspected. The helium gas source is used to inject helium gas into the heat exchanger to be inspected for leak detection.

[0103] In some examples, referring to Figure 9, the temperature monitoring component 4 includes a plurality of thermal resistors and a digital display monitor. The plurality of thermal resistors are respectively arranged on the inlet side, the outlet side of the heat exchange channels of the heat exchanger 6 to be inspected and the outer wall of the heat exchanger 6 to be inspected, and are electrically connected to the digital display monitor. With such an arrangement, the temperature changes at the inlet and outlet of the heat exchanger 6 to be inspected and the overall temperature can be intuitively obtained.

[0104] In some examples, the pipeline connection of the 2K negative pressure heat exchanger low-temperature leak detection system 1 is as Figure 10 shown. The gas source 3 is connected to the heat exchange channels of the heat exchanger 6 to be inspected. The helium mass spectrometer leak detector 5 is respectively connected to a plurality of heat exchange channels of the heat exchanger 6 to be inspected and the vacuum container 11 through the hose 141. The vacuum pumping system 2 is connected to a plurality of heat exchange channels of the heat exchanger 6 to be inspected and the vacuum container 11 through the vacuum pumping interface 16. The chiller 7 is connected to the vacuum pumping system 2. The valve V1 is arranged on the interface of the vacuum container 11 and is used to control the on-off of the pipeline between the helium mass spectrometer leak detector 5 and the vacuum pumping system 2 and the vacuum container 11. The valve V2 is arranged on the interface of the helium mass spectrometer leak detector 5 and is used to control the on-off of the pipeline between the helium mass spectrometer leak detector 5 and a plurality of heat exchange channels of the heat exchanger 6 to be inspected and the on-off of the pipeline between the helium mass spectrometer leak detector 5 and the vacuum container 11. The valve V3 is arranged on the interface of the vacuum pumping system 2 and is used to control the on-off of the pipeline between the vacuum pumping system 2 and the heat exchanger 6 to be inspected and the vacuum container 11. The valves V4-V6 are arranged on the interfaces of a plurality of heat exchange channels of the heat exchanger 6 to be inspected and respectively control the on-off of the pipeline between each heat exchange channel and the helium mass spectrometer leak detector 5 or the vacuum pumping system 2. By switching the states of the valves V1-V6, the vacuum pumping of the vacuum container 11, the cooling of the heat exchanger 6 to be inspected, and the detection of internal and external leaks of each heat exchange channel can be realized. It can be understood that in this embodiment, the heat exchanger 6 to be inspected has three heat exchange channels, and the valves V4-V6 are respectively arranged on one heat exchange channel. However, in other embodiments, the number of heat exchange channels can be two or more than three. Specifically, it can be set according to the use requirements.

[0105] In some examples, refer to Figure 9 , the 2K negative pressure heat exchanger low-temperature leak detection device 1 is a leak detection tooling composed of a plurality of components welded together, and its own leak rate can reach 5.0×10 -10 Pa·m 3 / s. The vacuum pumping system 2 is connected to the vacuum pumping interface 16 on the 2K negative pressure heat exchanger low-temperature leak detection device 1 through a KF quick connector. Starting the vacuum pumping system 2 can make the heat exchanger 6 to be detected in the 2K negative pressure heat exchanger low-temperature leak detection device 1 in a vacuum negative pressure environment. The helium mass spectrometer leak detector 5 is connected to the hose assembly 14 on the 2K negative pressure heat exchanger low-temperature leak detection device 1 and is connected in series with the vacuum pumping system 2 and the unit.

[0106] The low-temperature leak detection system for the 2K negative-pressure heat exchanger in this embodiment includes the above-mentioned low-temperature leak detection device 1 for the 2K negative-pressure heat exchanger, a vacuum pumping system 2, a gas source 3, a temperature monitoring component 4, and a helium mass spectrometer leak detector 5. The vacuum pumping system 2 is connected to the vacuum pumping interface 16 of the low-temperature leak detection device 1 for the 2K negative-pressure heat exchanger. 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 for the heat exchanger. The temperature monitoring component 4 is connected to the temperature monitoring interface 15 of the low-temperature leak detection device 1 for the heat exchanger. Using the heat exchanger low-temperature leak detection system of the present invention, the internal and external leak rates of the heat exchanger can be detected in a low-temperature environment, and the actual leak rate data of the heat exchanger under low-temperature operation can be obtained.

[0107] It is easily understood by those skilled in the art that, on the premise of no conflict, the above-mentioned advantageous ways can be freely combined and superimposed.

[0108] The above are only the preferred embodiments of the present invention, and are not intended to limit the present invention. Any modifications, equivalent replacements, and improvements made within the spirit and principle of the present invention shall be included in the protection scope of the present invention. The above is only the preferred implementation manner of the present invention. It should be noted that for those of ordinary skill in the art in the technical field of the present invention, several improvements and modifications can be made without departing from the technical principle of the present invention, and these improvements and modifications should also be regarded as 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 to be inspected to the hose assembly, temperature monitoring interface, and vacuum pumping interface on the vacuum container respectively; S2. Place the heat exchanger to be inspected into the vacuum container and seal the vacuum container; S3. Use a vacuum pumping system to evacuate the vacuum container and the heat exchange channels through the vacuum pumping interface; S4. Fill the heat exchange channels of the heat exchanger to be inspected with liquid nitrogen or liquid helium to cool the heat exchange channels; S5. Obtain the temperature change of the heat exchanger to be inspected through the temperature monitoring interface to control the cooling rate of the heat exchanger to be inspected; S6. Make the temperature in the heat exchange channels reach the liquid nitrogen / liquid helium temperature range; S7. Evacuate the nitrogen or helium gas in the heat exchange channels; S8. Fill the cooled heat exchange channels with helium gas until the pressure in the heat exchange channels reaches the expected value; S9. After standing for a preset duration, detect the external leakage and internal leakage conditions of the heat exchange channels in the liquid nitrogen / liquid helium temperature range; S10. Perform secondary vacuum pumping, then perform tertiary vacuum pumping, and cycle until the total leakage rate is calculated after the i-th vacuum pumping, where i is an integer greater than 3; S11. Shut down the vacuum pumping system and break the vacuum inside the vacuum container; S12. Reheat the heat exchanger to be inspected and control the reheating rate of the heat exchanger to be inspected; S13. When the heat exchanger to be inspected returns to normal temperature, take out the heat exchanger to be inspected from the vacuum container.

2. The low-temperature leak detection method for the 2K negative pressure heat exchanger according to claim 1, wherein Step S3 further includes: using a vacuum pumping system to gradually evacuate the vacuum container and the heat exchange channels through the vacuum pumping interface until the pressure in the vacuum container ≤ 5 Pa.

3. The low-temperature leak detection method of the 2K negative pressure heat exchanger according to claim 1, characterized in that Step S9 includes: S901. Keep the pressure in the heat exchange channels 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 condition of the heat exchange channel and the internal leakage condition 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 the external leakage and internal leakage conditions of other heat exchange channels.

4. A 2K negative pressure heat exchanger low-temperature leak detection system, which is used for the 2K negative pressure heat exchanger low-temperature leak detection method described in any one of claims 1 to 3, and is characterized in that, including: 2K Negative Pressure Heat Exchanger Low Temperature Leak Detection Device, comprising a vacuum container, a transportation component, a hose component, a temperature monitoring interface and a vacuum pumping interface; the vacuum container is used to accommodate the heat exchanger to be detected under 2K negative pressure; one end of the vacuum container has an opening; a sealing component is provided on the opening; the transportation component is located in the vacuum container; the transportation component extends from the opening of the vacuum container to the inside of the vacuum container; the transportation component is used to transfer the heat exchanger to be detected; the hose component is arranged on the vacuum container; the hose component is used to connect the gas source and the helium mass spectrometer leak detector; through the hose component, nitrogen or helium can be filled into the heat exchanger to be detected inside the vacuum container, and the heat exchange channels of the heat exchanger to be detected can be leak detected; the temperature monitoring interface is arranged on the vacuum container; the temperature monitoring interface is used to connect the temperature monitoring component; through the temperature monitoring interface, the temperature changes inside the vacuum container and the heat exchanger to be detected can be obtained; the vacuum pumping interface is arranged on the vacuum container; the vacuum pumping interface is used to connect the vacuum pumping system; through the vacuum pumping interface, the inside of the vacuum container can be evacuated. The vacuum pumping system is connected to the vacuum pumping interface of the 2K negative pressure heat exchanger low temperature leak detection device. The gas source is connected to the hose component of the 2K negative pressure heat exchanger low temperature leak detection device. The temperature monitoring component is connected to the temperature monitoring interface of the 2K negative pressure heat exchanger low temperature leak detection device. The helium mass spectrometer leak detector is connected to the hose component of the 2K negative pressure heat exchanger low temperature leak detection device.

5. The 2K negative pressure heat exchanger low-temperature leak detection system according to claim 4, wherein, The transportation component includes: A guide rail is arranged in the vacuum container; the guide rail extends from the opening of the vacuum container to the inside of the vacuum container. A trolley is slidably arranged on the guide rail; the trolley is used to carry the heat exchanger to be detected. A driving device is connected to the trolley; the driving device is used to drive the trolley to reciprocate 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 sealing component includes: A support frame is arranged 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 can seal the opening of the vacuum container.

7. The low-temperature leak detection system for a 2K negative-pressure heat exchanger according to claim 4, wherein The hose component includes: A plurality of hoses, one ends of the plurality of hoses located outside the vacuum container are used to connect the helium mass spectrometer leak detector and the gas source; one ends of the plurality of hoses located inside the vacuum container are respectively used to connect the internal space of the vacuum container and each heat exchange channel of the heat exchanger to be detected.

8. The 2K negative pressure heat exchanger low-temperature leak detection system according to claim 4, wherein The vacuum container further includes: A manhole is located at the end of the vacuum container away from the opening. A base is arranged at the bottom of the vacuum container. Lifting lugs are arranged on the base, and the lifting lugs are symmetrically distributed on both sides of the vacuum container.

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