Heat leakage test system for low-temperature transmission pipeline

Abstract

The invention discloses a low-temperature transmission pipeline heat leakage test system, which is characterized by comprising a data processing unit, a main valve box, a rear connecting box, an exhaust measuring device and a test sample section, the main valve box is hermetically connected with the exhaust measuring device through the test sample section; low-temperature working medium input and output pipelines and cold shield medium input and output pipelines are arranged in the main valve box; a low-temperature valve, a heater, a pressure transmitter, a temperature sensor and a safety valve are arranged on the low-temperature working medium input pipeline; the low-temperature transmission pipeline to be subjected to heat leakage test in the test sample section and the low-temperature working medium loop pipeline in the rear connecting box form a low-temperature working medium transmission channel; a cold shield medium transmission channel is arranged to provide a cold shield for the low-temperature working medium transmission channel; the low-temperature working medium output pipeline is connected with the recycling air bag through the exhaust measuring device and is used for recycling the low-temperature working medium; the data processing unit calculates the enthalpy of the low-temperature working medium at the outlet and the enthalpy of the inlet of the low-temperature transmission pipeline according to the temperature and the pressure, and obtains the heat leakage value through the enthalpy difference.

Description

Technical Field

[0001] The invention belongs to the field of cryogenic engineering, and in particular relates to a low-temperature transmission pipeline heat leakage testing system. Background Art

[0002] Cryogenic transmission pipelines are widely used in various cryogenic systems to transmit cryogenic working fluids. Their main feature is low heat leakage. There is a temperature difference between the cryogenic working fluid and the environment, and heat is transferred through conduction, thermal radiation and other mechanisms. The design of cryogenic transmission pipelines is mainly to effectively reduce heat leakage by reducing heat transfer. The size of heat leakage is one of the important indicators for evaluating cryogenic transmission pipelines. Accurately measuring the heat leakage of cryogenic transmission pipelines helps to optimize the process design, system layout and selection of core equipment of the cryogenic system, so the measurement of heat leakage of cryogenic pipelines is particularly important.

[0003] Cryogenic transmission pipelines are mainly divided into single-channel transmission pipelines and multi-channel transmission pipelines. The working fluids transmitted generally include cryogenic liquids and cryogenic gases, and the working fluid states included are mainly supercooled state, saturated state, two-phase flow and gas state. Different working fluid phases have different heat leakage when flowing in multi-channel transmission pipelines. In addition, compared with single-channel transmission pipelines, the inner pipe layout, temperature gradient distribution, insulation material wrapping and cold screen layout in multi-channel transmission pipelines will also affect the heat leakage of the pipeline. Therefore, the measurement of heat leakage of cryogenic pipelines is helpful for the fluid working fluid distribution and structural design of cryogenic transmission pipelines.

[0004] Due to the importance of heat leakage testing of cryogenic transmission pipelines, it is necessary to provide a set of cryogenic transmission pipeline heat leakage testing system with accurate measurement, easy operation and wide applicability. Summary of the invention

[0005] In view of the above analysis, the present invention aims to propose a low-temperature transmission pipeline heat leakage testing system to solve the problems introduced in the above background technology.

[0006] The technical solution of the present invention is:

[0007] A low-temperature transmission pipeline heat leakage test system, characterized in that it includes a data processing unit, a main valve box 001, a rear connection box 002, an exhaust measurement device 003, and a test sample section 004; the main valve box 001 is sealedly connected to the exhaust measurement device 003 through the test sample section 004;

[0008] The main valve box 001 is provided with a cryogenic working fluid input pipeline, a cryogenic working fluid output pipeline, a cold shield medium input pipeline and a cold shield medium output pipeline; the cryogenic working fluid input pipeline is provided with a cryogenic valve 005 for controlling the flow rate q of the cryogenic working fluid transmitted in the cryogenic transmission pipeline; the cryogenic working fluid input pipeline is provided with a heater 006 for controlling the temperature of the cryogenic working fluid transmitted in the cryogenic transmission pipeline; the cryogenic working fluid input pipeline is provided with a pressure transmitter 007 for measuring the pressure P of the cryogenic working fluid transmitted in the cryogenic transmission pipeline; the cryogenic working fluid input pipeline is provided with a temperature sensor 008 for measuring the temperature T of the cryogenic working fluid transmitted in the cryogenic transmission pipeline;

[0009] The test sample section 004 is provided with two sections of low-temperature transmission pipelines to be tested for heat leakage, and the rear connection box 002 is provided with a low-temperature working fluid loop pipeline; one end of the two sections of the low-temperature transmission pipelines is respectively connected to the low-temperature working fluid input pipeline and the low-temperature working fluid output pipeline, and the other ends of the two sections of the low-temperature transmission pipelines are respectively connected to the two ends of the low-temperature working fluid loop pipeline to form a low-temperature working fluid transmission channel; both ends of each section of the low-temperature transmission pipeline are provided with temperature sensors 008 for measuring the temperature difference of the low-temperature working fluid in the low-temperature transmission pipeline; the rear connection box 002 is provided with a heater 006 for controlling the temperature of the low-temperature working fluid transmitted in the low-temperature working fluid loop pipeline;

[0010] The test sample section 004 is provided with two sections of cold shield medium transmission pipelines, and the rear connection box 002 is provided with a cold shield medium loop pipeline; one end of the two sections of cold shield medium transmission pipelines is respectively connected to the cold shield medium input pipeline and the cold shield medium output pipeline, and the other ends of the two sections of cold shield medium transmission pipelines are respectively connected to the two ends of the cold shield medium loop pipeline, forming a cold shield medium transmission channel, providing a cold shield for the low-temperature working medium transmission channel;

[0011] The low-temperature working medium output pipeline is connected to the recovery air bag 014 via the exhaust measurement device 003, so as to realize the recovery of the low-temperature working medium;

[0012] The data processing unit is used to obtain the enthalpy h of the cryogenic working fluid at the outlet of the cryogenic transmission pipeline according to the temperature T and pressure P of the cryogenic working fluid in the cryogenic transmission pipeline. out , enthalpy of cryogenic medium at the entrance of cryogenic transmission pipeline h in , through the formula The heat leakage value Q of the low-temperature transmission pipeline is calculated.

[0013] Furthermore, a safety valve 009 is provided on the cryogenic working fluid input pipeline, which is used to trip when the pressure P reaches the trip pressure threshold, thereby realizing safety protection for the heat leakage test of the cryogenic transmission pipeline.

[0014] Furthermore, the cold screen medium input pipeline is provided with a low temperature valve 005, a heater 006, a pressure transmitter 007, and a temperature sensor 008.

[0015] Furthermore, the main valve box 001 is provided with a spare input pipeline and a spare output pipeline; the spare input pipeline is provided with a low-temperature valve 005, a heater 006, a pressure transmitter 007, a temperature sensor 008 and a safety valve 009; the test sample section 004 is provided with two sections of spare transmission pipelines, and the rear connection box 002 is provided with a spare loop pipeline; one end of the two sections of the spare transmission pipelines can be connected to the spare input pipeline and the spare output pipeline respectively through bellows, and the other end of the two sections of the spare transmission pipelines can be connected to the two ends of the spare loop pipeline respectively through bellows to form a spare transmission channel.

[0016] Furthermore, the exhaust measurement device 003 contains an exhaust pipeline, and the exhaust pipeline is provided with a heater 006 , a pressure transmitter 007 , a temperature sensor 008 , a normal temperature valve 013 , and a flow controller 010 .

[0017] Furthermore, the cold shield medium transmitted in the cold shield medium input pipeline is a two-phase flow or gaseous nitrogen working fluid; and the low-temperature working fluid is a low-temperature gaseous helium working fluid.

[0018] Furthermore, the heater 006 in the rear connection box 002 is arranged on the low-temperature working fluid loop pipeline; the cold shield medium loop pipeline is provided with a heater 006 for controlling the temperature of the cold shield medium transmitted in the cold shield medium loop pipeline.

[0019] Furthermore, the main valve box 001 and the rear connection box 002 are both vacuum containers.

[0020] Furthermore, one end of the two sections of low-temperature transmission pipelines are connected to the low-temperature working fluid input pipeline and the low-temperature working fluid output pipeline through bellows, and the other ends of the two sections of low-temperature transmission pipelines are connected to both ends of the low-temperature working fluid loop pipeline through bellows, forming a low-temperature working fluid transmission channel; one end of the two sections of cold shield medium transmission pipelines are connected to the cold shield medium input pipeline and the cold shield medium output pipeline through bellows, and the other ends of the two sections of cold shield medium transmission pipelines are connected to both ends of the cold shield medium loop pipeline through bellows, forming a cold shield medium transmission channel.

[0021] The low-temperature transmission pipeline heat leakage test system of the present application includes a data processing unit, a main valve box 001, a rear connection box 002, an exhaust measurement device 003, and a test sample section 004; the main valve box 001 is sealedly connected to the exhaust measurement device 003 through the test sample section 004;

[0022] The main valve box 001 is used to integrate pipelines, cryogenic valves 005, heaters 006, pressure transmitters 007, temperature sensors 008 and safety valves 009 to achieve transmission of cryogenic working fluids and control of flow, temperature (T) and pressure (P).

[0023] The main valve box 001 is provided with three cryogenic valves 005, which are respectively used to adjust the flow and pressure of the cryogenic fluid in each pipeline.

[0024] The main valve box 001 is provided with a heater 006 for adjusting and controlling the incoming flow temperature of the low-temperature fluid in the pipeline.

[0025] The main valve box 001 is provided with a pressure transmitter 007 and a temperature sensor 008 for monitoring the pressure and temperature of the cryogenic fluid in the pipeline.

[0026] The main valve box 001 is provided with a safety valve 009, which is used to trip when the pressure of the cryogenic fluid in the pipeline reaches a trip pressure threshold, thereby achieving safety protection for the system.

[0027] The main valve box 001 is provided with an injection port 012, which is used to fill the cold shield medium input pipeline with the corresponding cryogenic working fluid; the cold shield medium input pipeline adopts a pipeline with a specification of DN20, and the input port inputs liquid nitrogen (LN2) mainly as a cold shield for the test sample section. The cold shield medium output pipeline adopts a pipeline with a specification of DN40, and the outlet is emptied. The cryogenic working fluid input pipeline for testing heat leakage is a pipeline with a specification of DN32, and the cryogenic working fluid output pipeline is a pipeline with a specification of DN50, which is connected to the exhaust measurement device 003.

[0028] The main valve box 001 is provided with a spare injection port 011, and a spare input pipeline and a spare output pipeline with a specification of DN50 are used. Whether to use them is determined according to the structure of the sample section to be tested.

[0029] The rear connection box 002 is used to connect the test sample section 004, and the built-in heater 006 is used to control the return air temperature; the rear connection box 002 is provided with a heater 006 for adjusting and controlling the return temperature of the low-temperature fluid in the pipeline.

[0030] The exhaust gas measuring device 003 is used to integrate the return air pipeline, heater 006, pressure transmitter 007, temperature sensor 008, flow controller 010, and normal temperature valve 013 to achieve control of the outlet fluid.

[0031] The data processing unit is used to obtain the enthalpy h of the cryogenic working fluid at the outlet of the cryogenic transmission pipeline according to the temperature T and pressure P of the cryogenic working fluid in the cryogenic transmission pipeline. out , enthalpy of cryogenic medium at the entrance of cryogenic transmission pipeline h in , through the formula The heat leakage value Q of the low-temperature transmission pipeline is calculated.

[0032] The exhaust gas measuring device 003 is provided with a heater 006 for heating the discharged low-temperature fluid to ensure that the exhaust gas temperature is greater than zero degrees.

[0033] The exhaust gas measuring device 003 is provided with a pressure transmitter 007 and a temperature sensor 008 for monitoring the pressure and temperature of the exhaust gas.

[0034] The exhaust gas measuring device 003 is provided with a flow controller 010 and a normal temperature valve 013 for measuring, adjusting and controlling the flow of the fluid in the pipeline.

[0035] The outlet pipeline of the exhaust measurement device 003 is connected to the recovery air bag 014 for realizing the recovery of helium.

[0036] The test sample section 004 has a low-temperature transmission pipeline to be tested for heat leakage as a core pipeline, on which a temperature sensor 008 is provided for measuring the temperature difference of the fluid in the pipeline to facilitate calculation of the pipeline heat leakage.

[0037] A cold shield medium input pipeline is also provided in the test sample section 004, which acts as a cold shield and reduces heat leakage of the core pipeline.

[0038] Two sections of spare transmission pipelines are also provided in the test sample section 004.

[0039] Furthermore, the main valve box 001 is a vacuum container that can control the temperature and flow rate of the cryogenic fluid.

[0040] Furthermore, the rear connection box 002 is a vacuum container that can control the return temperature of the cryogenic fluid.

[0041] Furthermore, the exhaust gas measuring device 003 can ensure that the exhaust gas temperature is greater than zero degrees, avoiding the phenomenon of ice and condensation, and at the same time can coordinately control the fluid flow in the pipeline.

[0042] Furthermore, the heat leakage of the cryogenic transmission pipeline to be tested is to measure the temperature and pressure to obtain the enthalpy value of the fluid, and the heat leakage of the cryogenic transmission pipeline is obtained through the enthalpy value and mass flow rate of the fluid.

[0043] Furthermore, to protect the safety of the system, too low a pressure may cause frequent tripping, and too high a pressure may cause system damage. The tripping pressure threshold of the safety valve 009 is 4.5 bara. Considering the flow range and measurement accuracy of the cryogenic transmission pipeline, the control range of the flow controller is 0-10 g / s.

[0044] Furthermore, the temperature control range of the main valve box 001 is 5-60K, and the temperature control range of the rear connection box is 40-90K. When the temperature of the main valve box 001 is greater than 5K, the cryogenic fluid is generally in a gaseous state, and there is no phase change during the transmission process, which is easy to measure; when the temperature is too high, such as greater than 90K, it is not meaningful to measure its heat leakage.

[0045] Furthermore, the outlet pipelines of the main valve box 001 and the rear connection box 002 are provided with bellows, which facilitates pipeline connection and can compensate for cold shrinkage.

[0046] Furthermore, the low-temperature transmission pipeline heat leakage test system can test a maximum of six-channel low-temperature pipelines and a minimum of a single-channel low-temperature pipeline.

[0047] Furthermore, the low-temperature pipeline transmission heat leakage testing system realizes helium recovery during the entire testing process.

[0048] In a preferred embodiment of the present invention, the heater 006 can effectively adjust and control the incoming flow temperature, the return flow temperature and the exhaust temperature of the fluid.

[0049] In a preferred embodiment of the present invention, the flow rate of the fluid can be effectively controlled and adjusted by the low-temperature valve 005, the normal temperature valve 013 and the flow controller 010.

[0050] In a preferred embodiment of the present invention, the enthalpy difference is obtained by measuring the pressure and temperature difference of the cryogenic fluid in the cryogenic transmission pipeline to be tested for heat leakage in the test sample section 004, and then the heat leakage of the cryogenic transmission pipeline to be tested for heat leakage in the test sample section can be obtained by calculation in combination with the mass flow rate of the cryogenic fluid.

[0051] In a preferred embodiment of the present invention, the pipeline interfaces of the main valve box 001 and the rear connection box 002 are both flange interfaces sealed with indium wire, which can be connected to the low-temperature test sample sections 004 of channels 1-6.

[0052] In a preferred embodiment of the present invention, a mechanical safety valve 009 is provided in the main valve box. When the pressure in the pipeline is greater than 4.5 bara, the safety valve is activated to release the pressure quickly to ensure the safety of the system.

[0053] In a preferred embodiment of the present invention, pressure transmitters 007 and temperature sensors 008 are arranged at key nodes of the entire pipeline system.

[0054] Compared with the prior art, the low-temperature transmission pipeline heat leakage test system provided by the present invention has the following advantages:

[0055] First, the heater 006 can effectively adjust and control the incoming flow temperature, return flow temperature and exhaust temperature of the fluid; second, the low temperature valve 005, the normal temperature valve 013 and the flow controller 010 can effectively control and adjust the flow of the fluid;

[0056] Third, the enthalpy difference is obtained by measuring the pressure and temperature difference of the low-temperature fluid in the low-temperature transmission pipeline to be tested for heat leakage in the test sample section 004. Then, combined with the flow rate of the low-temperature fluid, the heat leakage of the low-temperature transmission pipeline in the test sample section can be obtained by calculation, which is more accurate than conventional static evaporation heat leakage measurement.

[0057] Fourth, a heater 006 is provided on the exhaust measurement device to heat the low-temperature fluid discharged from the main valve box 001 to above 0°C to prevent icing and frost in the pipeline from affecting the performance of the flow controller 010 and the normal temperature valve 013.

[0058] Fifth, the pipeline interfaces of the main valve box and the rear connection box are flange interfaces sealed with indium wire, which can connect the low-temperature test sections of 1-6 channels.

[0059] Sixth, the main valve box is equipped with a mechanical safety valve. When the pressure in the pipeline is greater than 4.5 bara, the safety valve will trip and release the pressure quickly to ensure the safety of the system.

[0060] Seventh, test the return air connection to the recovery air bag, which can be recycled after purification through the recovery purification system. BRIEF DESCRIPTION OF THE DRAWINGS

[0061] Figure 1 Schematic diagram of the low-temperature transmission pipeline heat leakage test system.

[0062] Figure markings: 001-main valve box, 002-rear connection box, 003-exhaust measurement device, 004-test sample section, 005-low temperature valve, 006-heater, 007-pressure transmitter, 008-temperature sensor, 009-safety valve, 010-flow controller, 011-spare injection port, 012-injection port, 013-normal temperature valve, 014-recovery air bag. DETAILED DESCRIPTION

[0063] In order to more clearly illustrate the technical solution of the present invention, the embodiments of the present invention will be further described below in conjunction with the accompanying drawings. Obviously, the embodiments in the following drawings are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative work.

[0064] refer to Figure 1The first embodiment of the present invention provides a low-temperature transmission pipeline heat leakage test system, including a main valve box 001, which contains three low-temperature valves 005 for controlling the flow and pressure of the fluid in the pipeline. Three heaters 006 are used to control the temperature of the fluid. Pressure transmitters 007 and temperature sensors 008 are set on the pipelines of the three fluid passages to detect the pressure and temperature of the fluid in the passage. A safety valve 009 is set in the passage with valves at both ends of the pipeline to prevent the pressure increase from causing danger to the system in an unexpected situation. The rear connection box 002 contains a heater 006 for controlling the temperature of the outlet fluid, which has achieved the purpose of testing the heat leakage of the low-temperature transmission pipeline at different temperatures. The exhaust measurement device 003 contains a heater 006, a pressure transmitter 007, a temperature sensor 008, a normal temperature valve 013, and a flow controller 010, which are used to detect the pressure and flow of the return gas and ensure that the temperature of the low-temperature fluid discharged to the recovery air bag 014 is higher than 0°C. The test sample section 004 is provided with a cryogenic transmission pipeline sample section to be measured for heat leakage, which may include 1-6 channels. Temperature sensors 008 are provided at the inlet and outlet positions of the pipe in the sample section to be tested to measure the temperature of the fluid, and the heat leakage of the cryogenic transmission pipeline is calculated in combination with the pressure and mass flow of the fluid.

[0065] In this embodiment, the test sample section with the temperature sensor installed in the helium circuit is first installed, the main valve box 001 and the rear connection box 002 are connected, and an adiabatic vacuum is established and leak detection is performed to ensure that there is no leakage and the vacuum degree is less than 5×10 -3 The temperature starts to drop after Pa, the corresponding valve is opened, and liquid nitrogen is added through the liquid nitrogen injection port to cool the nitrogen circuit. When liquid nitrogen is sprayed out of the nitrogen outlet, it is considered that the temperature has dropped to a certain level, and the opening of the valve of this circuit can be controlled to ensure that the temperature of this circuit is maintained in the liquid nitrogen temperature zone.

[0066] In this embodiment, the heat leakage measurement of the outgoing and returning paths of the helium path in the test sample section 004 is mainly carried out. After the liquid nitrogen path is cooled to the desired level, the valve of the helium path is opened, and liquid helium is added through the liquid helium (LHe) injection port 012 for cooling. The cooling speed is controlled by the valve opening and the heater. After the temperature drops to the temperature zone to be measured, the valve and flow controller 010 are adjusted to the required flow rate, and whether the system is stable is determined by the pressure, temperature and flow curves.

[0067] In this embodiment, for the stabilized system, the pressure P, temperature T and flow value q are recorded, and the enthalpy h of the cryogenic working fluid at the outlet of the cryogenic transmission pipeline is obtained through the physical parameter library of helium. out , enthalpy of cryogenic medium at the entrance of cryogenic transmission pipeline h in ; Then calculate the heat leakage value Q by the following formula, where h is the enthalpy of the working fluid at the corresponding pressure and temperature.

[0068]

[0069] In this embodiment, a set of heat leakage measurements of temperature zones and flow rates are completed. The valve opening and the flow controller 010 can be adjusted to change the flow rate. The heat leakage test in different temperature zones can be changed by adjusting the power of the heater 006. The heat leakage of the low-temperature transmission pipeline can be evaluated by comparing multiple sets of data measurement results.

[0070] In this embodiment, various shapes of cryogenic transmission pipelines can be measured, including straight pipe sections of different lengths and angled curved pipe sections.

[0071] In this embodiment, starting from the cooling of the helium circuit, the heater 006 in the return gas measuring device 003 is turned on and automatically controls the outlet temperature to ensure that the outlet is above 0° C. to prevent ice and condensation in the normal temperature pipeline.

[0072] In this embodiment, after the test is completed, a rewarming operation needs to be completed. The nitrogen circuit is rewarmed by room temperature nitrogen, and the helium circuit is rewarmed by room temperature helium. From the beginning of cooling to the end of rewarming, the helium in the helium circuit enters the recovery airbag 014 for recovery and purification.

[0073] The above is only used to illustrate the technical solution of the present invention, and is not intended to limit the invention. Although the above embodiments are described in detail, those skilled in the art can replace, modify and simply change them without departing from the scope of the present technical solution, and these replacements, modifications and simple changes cannot cause the essence of the corresponding technical solution to deviate from the scope of the present use of new embodiments.

Claims

1. A low temperature transmission pipeline heat leakage test system, characterized in that: It comprises a data processing unit, a main valve box (001), a rear connection box (002), an exhaust gas measurement device (003), and a test sample section (004); the main valve box (001) is tightly connected to the exhaust gas measurement device (003) via the test sample section (004); The main valve box (001) is provided with a cryogenic working fluid input pipeline, a cryogenic working fluid output pipeline, a cold shield medium input pipeline and a cold shield medium output pipeline; the cryogenic working fluid input pipeline is provided with a cryogenic valve (005) for controlling the flow rate q of the cryogenic working fluid transmitted in the cryogenic transmission pipeline; the cryogenic working fluid input pipeline is provided with a heater (006) for controlling the temperature of the cryogenic working fluid transmitted in the cryogenic transmission pipeline; the cryogenic working fluid input pipeline is provided with a pressure transmitter (007) for measuring the pressure P of the cryogenic working fluid transmitted in the cryogenic transmission pipeline; The cryogenic working fluid input pipeline is provided with a temperature sensor (008) for measuring the temperature T of the cryogenic working fluid transmitted in the cryogenic transmission pipeline; The test sample section (004) is provided with two sections of low-temperature transmission pipelines to be tested for heat leakage, and the rear connection box (002) is provided with a low-temperature working fluid loop pipeline; wherein one end of the two sections of low-temperature transmission pipelines is respectively connected to a low-temperature working fluid input pipeline and a low-temperature working fluid output pipeline, and the other ends of the two sections of low-temperature transmission pipelines are respectively connected to two ends of the low-temperature working fluid loop pipeline to form a low-temperature working fluid transmission channel; Temperature sensors (008) are provided at both ends of each section of the cryogenic transmission pipeline for measuring the temperature difference of the cryogenic working fluid in the cryogenic transmission pipeline; a heater (006) is provided in the rear connection box (002) for controlling the temperature of the cryogenic working fluid transmitted in the cryogenic working fluid loop pipeline; Two sections of cold shield medium transmission pipelines are arranged in the test sample section (004), and a cold shield medium loop pipeline is arranged in the rear connection box (002); wherein one end of the two sections of cold shield medium transmission pipelines are respectively connected to a cold shield medium input pipeline and a cold shield medium output pipeline, and the other ends of the two sections of cold shield medium transmission pipelines are respectively connected to two ends of the cold shield medium loop pipeline, so as to form a cold shield medium transmission channel, and provide a cold shield for the low-temperature working medium transmission channel; The low-temperature working medium output pipeline is connected to the recovery air bag 014 via the exhaust gas measurement device (003) to realize the recovery of the low-temperature working medium; The data processing unit is used to obtain the enthalpy h of the cryogenic working fluid at the outlet of the cryogenic transmission pipeline according to the temperature T and pressure P of the cryogenic working fluid in the cryogenic transmission pipeline. out , enthalpy of cryogenic medium at the entrance of cryogenic transmission pipeline h in , through the formula The heat leakage value Q of the low-temperature transmission pipeline is calculated.

2. The low temperature transmission pipeline heat leakage test system according to claim 1, characterized in that: The low-temperature working fluid input pipeline is provided with a safety valve (009) for tripping when the pressure P reaches a trip pressure threshold, thereby achieving safety protection for the heat leakage test of the low-temperature transmission pipeline.

3. The low temperature transmission pipeline heat leakage test system according to claim 1, characterized in that: The cold screen medium input pipeline is provided with a low temperature valve (005), a heater (006), a pressure transmitter (007) and a temperature sensor (008).

4. The low temperature transmission pipeline heat leakage test system according to claim 1, characterized in that: The main valve box (001) is provided with a spare input pipeline and a spare output pipeline; the spare input pipeline is provided with a low-temperature valve (005), a heater (006), a pressure transmitter (007), a temperature sensor (008) and a safety valve (009); the test sample section (004) is provided with two sections of spare transmission pipelines, and the rear connection box (002) is provided with a spare loop pipeline; one end of the two sections of the spare transmission pipelines is connected to the spare input pipeline and the spare output pipeline respectively through a bellows, and the other end of the two sections of the spare transmission pipelines is connected to the two ends of the spare loop pipeline respectively through a bellows to form a spare transmission channel.

5. The low temperature transmission pipeline heat leakage test system according to claim 1, characterized in that: The exhaust gas measuring device (003) contains an exhaust gas pipeline, and the exhaust gas pipeline is provided with a heater (006), a pressure transmitter (007), a temperature sensor (008), a normal temperature valve (013), and a flow controller (010).

6. The low temperature transmission pipeline heat leakage test system according to any one of claims 1 to 5, characterized in that: The cold shield medium transmitted in the cold shield medium input pipeline is a two-phase flow or gaseous nitrogen working fluid; the low-temperature working fluid is a low-temperature gaseous helium working fluid.

7. The low temperature transmission pipeline heat leakage test system according to any one of claims 1 to 5, characterized in that: The heater (006) in the rear connection box (002) is arranged on the low-temperature working fluid loop pipeline; the cold shield medium loop pipeline is provided with a heater (006) for controlling the temperature of the cold shield medium transmitted in the cold shield medium loop pipeline.

8. The low temperature transmission pipeline heat leakage test system according to any one of claims 1 to 5, characterized in that: The main valve box (001) and the rear connection box (002) are both vacuum containers.

9. The low temperature transmission pipeline heat leakage test system according to any one of claims 1 to 5, characterized in that: One end of the two sections of low-temperature transmission pipelines are connected to the low-temperature working medium input pipeline and the low-temperature working medium output pipeline through bellows, and the other ends of the two sections of low-temperature transmission pipelines are connected to the two ends of the low-temperature working medium loop pipeline through bellows to form a low-temperature working medium transmission channel; One end of the two sections of cold screen medium transmission pipelines are connected to the cold screen medium input pipeline and the cold screen medium output pipeline through bellows respectively, and the other ends of the two sections of cold screen medium transmission pipelines are connected to the two ends of the cold screen medium loop pipeline through bellows respectively, to form a cold screen medium transmission channel.

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