System and method for testing heat leakage of low-temperature pipeline

Abstract

The invention relates to the technical field of low temperature, in particular to a low-temperature pipeline heat leakage testing system and method. The embodiment of the invention provides a low-temperature pipeline heat leakage testing system which comprises a phase separator, a to-be-tested pipeline and a phase change pipeline. The phase separator is used for separating a low-temperature medium into a liquid phase and a gas phase, an inlet of the to-be-detected pipeline is connected with a liquid phase outlet of the phase separator, the phase change pipeline is connected to an outlet of the to-be-detected pipeline, and the phase change pipeline is provided with at least one heating device. The phase change pipeline is provided with at least one ribbon-shaped superconducting material along the axial direction, and the superconducting material is connected with a resistance testing device. The embodiment of the invention provides a system and a method for testing heat leakage of a low-temperature pipeline, which can improve the accuracy of testing a heat leakage value by an enthalpy difference method.

Description

Technical Field

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

[0002] Multi-channel cryogenic pipelines are an important part of the cryogenic distribution system. The cryogenic systems of many large scientific facilities (nuclear fusion devices, accelerator devices) often involve multi-channel cryogenic transmission pipelines of tens or even hundreds of meters to meet the transmission and distribution needs of cryogenic media. Reducing heat leakage loss is an important technical requirement for multi-channel cryogenic transmission pipelines. Accurately evaluating the heat leakage of multi-channel inner pipes is an important basis for the design and application of the entire cryogenic system. Obtaining the actual measured heat leakage value of the multi-channel cryogenic transmission pipeline can more accurately control the demand for cooling and the distribution of cooling, thereby reducing the demand for cooling capacity at the source, further controlling the scale of the cryogenic system, and effectively reducing the construction and maintenance costs of the entire cryogenic system.

[0003] In the prior art, the heat leakage value is mainly obtained by the "enthalpy difference method" (CN107238450A A low-temperature fluid transmission pipeline heat leakage test device and method, CN110017919A Low-temperature infusion pipeline heat leakage test system and measurement method), that is, by measuring the pressure and temperature at the inlet and outlet, the enthalpy value corresponding to the medium is queried or calculated, and the enthalpy difference of the two measuring points can characterize the heat leakage of the entire low-temperature pipeline; the "enthalpy difference method" needs to ensure that the medium state at the inlet and outlet is in a single-phase state (because the enthalpy value of the two-phase state is related to the pressure, temperature and gas content, and the actual enthalpy difference cannot be obtained only by the pressure and temperature parameters). However, the usual "enthalpy difference method" test process cannot judge the state change process of the low-temperature medium, and therefore cannot meet the heat leakage test requirements of the two-phase flow process in the pipe. Summary of the invention

[0004] The embodiments of the present invention provide a low-temperature pipeline heat leakage testing system and method, which can improve the accuracy of enthalpy difference method heat leakage testing.

[0005] In a first aspect, an embodiment of the present invention provides a low-temperature pipeline heat leakage test system, including a phase separator, a pipeline to be tested, and a phase change pipeline;

[0006] The phase separator is used to separate the cryogenic medium into a liquid phase and a gas phase, the inlet of the pipeline to be tested is connected to the liquid phase outlet of the phase separator, the phase change pipeline is connected to the outlet of the pipeline to be tested, the phase change pipeline is provided with at least one heating device, the phase change pipeline is provided with at least one ribbon-shaped superconducting material along its axial direction, and the superconducting material is connected to a resistance testing device;

[0007] When measuring temperature, the heating device is started to heat the fluid in the phase change pipe, and the resistance testing device monitors the resistance of the superconducting material to determine whether the fluid in the phase change pipe is gas. When the phase change pipe is gas, the liquid phase temperature and pressure (i.e., temperature and pressure) at the inlet of the pipe to be tested and the gas phase temperature and pressure at the outlet of the phase change pipe are collected to determine the heat leakage by the enthalpy difference method.

[0008] In a possible design, a plurality of superconducting materials are evenly arranged on the inner wall of the phase change pipe along the circumferential direction, and an insulating material is arranged between the superconducting material and the inner wall of the phase change pipe.

[0009] In a possible design, the superconducting material is fixed to the inner wall of the phase change pipe by a fixing structure.

[0010] In a possible design, the superconducting material is disposed at the center of the phase change pipe.

[0011] In a possible design, the superconducting material disposed at the center of the phase change pipe is fixed by a plurality of fixing ropes fixed on the phase change pipe.

[0012] In a possible design, the fixing rope is made of non-metallic material.

[0013] In a possible design, the heating device is connected to a precise constant current source to adjust its heating power.

[0014] In a possible design, both the inlet of the pipeline to be tested and the outlet of the phase change pipeline are provided with temperature and pressure test components, and the inlet of the pipeline to be tested is also provided with a flow meter.

[0015] In a second aspect, an embodiment of the present invention further provides a method for testing heat leakage of a cryogenic pipeline, which is implemented according to any of the above systems, and the method includes:

[0016] When measuring the temperature, starting the heating device to heat the fluid in the phase change pipeline;

[0017] The resistance testing device monitors the resistance of the superconducting material to determine whether the fluid in the phase change pipe is gas;

[0018] When there is gas in the phase change pipeline, collecting the liquid phase temperature and pressure at the inlet of the pipeline to be tested and the gas phase temperature and pressure at the outlet of the phase change pipeline;

[0019] Calculating an inlet enthalpy value and an outlet enthalpy value according to the liquid phase temperature and pressure and the gas phase temperature and pressure respectively;

[0020] The heat leakage is calculated according to the inlet enthalpy value, the outlet enthalpy value, the power of the heating device and the mass flow rate of the low-temperature fluid flowing into the pipeline to be measured.

[0021] In a possible design, the calculation of the heat leakage according to the inlet enthalpy value, the outlet enthalpy value, the power of the heating device and the mass flow rate of the cryogenic fluid flowing into the pipeline to be measured is achieved by the following formula:

[0022] Q=m(h2-h1)-P

[0023] Wherein, Q is the amount of heat leakage, m is the mass flow rate of the low-temperature fluid flowing into the pipeline to be measured, h1 is the inlet enthalpy value, h2 is the outlet enthalpy value, and P is the power of the heating device.

[0024] Compared with the prior art, the present invention has at least the following beneficial effects:

[0025] Due to the inevitable heat leakage of multi-channel cryogenic pipelines, the cryogenic medium entering the pipeline of the cryogenic load is actually in a gas-liquid two-phase flow state. Therefore, the use of the test system of the present invention for heat leakage testing will be more in line with the actual situation, and the measured heat leakage value will have more parameter significance, greatly reducing the design redundancy of the cryogenic system, and reducing investment and operating costs. The phase change pipeline is an independent pipe section structure, which can be easily connected to the cryogenic pipeline to be tested. It has a simple structure and strong applicability. The cryogenic medium parameters of the test process can match the actual working conditions, and can perform online testing on the multi-channel cryogenic pipeline (pipeline to be tested) in normal use, and can simultaneously measure the pipeline to be tested with different operating conditions. The multi-channel cryogenic pipeline test system described in the technical solution does not need to adjust the medium in the pipeline to be tested to a single-phase flow state, and can use the actual working condition parameters for heat leakage testing. Through the coordinated use of the heating device and the superconducting material, it is possible to achieve rapid evaporation of the cryogenic medium and complete synchronous detection of the medium state. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0027] Figure 1 It is a structural schematic diagram of a low-temperature pipeline heat leakage testing system provided by an embodiment of the present invention;

[0028] Figure 2 It is a structural schematic diagram of a phase change pipeline provided by an embodiment of the present invention.

[0029] In the figure:

[0030] 100-pipeline to be tested;

[0031] 200-refrigeration system;

[0032] 300- low temperature load;

[0033] 1- Phase separator;

[0034] 2-Phase change pipeline;

[0035] 21-Superconducting materials;

[0036] 22- Heating device;

[0037] 23- low temperature connection seat;

[0038] 24-Fixed structure;

[0039] 25-Fixed rope;

[0040] 3- Temperature and pressure test components;

[0041] 4- Flow meter. DETAILED DESCRIPTION

[0042] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0043] In the description of the embodiments of the present invention, unless otherwise clearly specified and limited, the terms "first" and "second" are used for descriptive purposes only and cannot be understood as indicating or implying relative importance; unless otherwise specified or explained, the term "multiple" refers to two or more; the terms "connected" and "fixed" should be understood in a broad sense, for example, "connected" can be a fixed connection, a detachable connection, an integral connection, or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0044] In the description of this specification, it should be understood that the directional words such as "upper" and "lower" described in the embodiments of the present invention are described at the angles shown in the drawings and should not be understood as limiting the embodiments of the present invention. In addition, in the context, it should also be understood that when it is mentioned that an element is connected to another element "upper" or "lower", it can not only be directly connected to another element "upper" or "lower", but also indirectly connected to another element "upper" or "lower" through an intermediate element.

[0045] like Figure 1 and Figure 2 As shown, an embodiment of the present invention provides a low-temperature pipeline heat leakage test system, including a phase separator 1, a pipeline to be tested 100, and a phase change pipeline 2;

[0046] The phase separator 1 is used to separate the cryogenic medium into a liquid phase and a gas phase. The inlet of the pipeline to be tested 100 is connected to the liquid phase outlet of the phase separator 1. The phase change pipeline 2 is connected to the outlet of the pipeline to be tested 100. The phase change pipeline 2 is provided with at least one heating device 22. The phase change pipeline 2 is provided with at least one ribbon-shaped superconducting material 21 along its axial direction. The superconducting material 21 is connected to a resistance testing device.

[0047] When measuring the temperature, the heating device 22 is started to heat the fluid in the phase change pipe 2, and the resistance testing device monitors the resistance of the superconducting material 21 to determine whether the fluid in the phase change pipe 2 is gas. When the phase change pipe 2 is gas, the liquid phase temperature and pressure at the inlet of the pipe to be tested 100 and the gas phase temperature and pressure at the outlet of the phase change pipe 2 are collected to determine the heat leakage by the enthalpy difference method.

[0048] As mentioned above, testing heat leakage under the condition of low-temperature liquid absorbing heat and evaporating and flowing is closer to the actual situation. The current enthalpy difference method cannot determine when and where it is unidirectional under the condition of low-temperature liquid absorbing heat and evaporating and flowing. In order to solve this problem, the present application first ensures that the inlet of the pipeline 100 to be tested is in liquid phase through the phase separator 1, and then sets the phase change pipeline 2 at the downstream of the pipeline 100 to be tested. The heating device 22 on the phase change pipeline 2 heats the low-temperature fluid inside. After the low-temperature fluid changes to the gas phase, the temperature rises significantly, which is higher than the critical temperature of the superconducting material 21. The change in the resistance value of the superconducting material 21 can determine whether the low-temperature fluid is transformed from gas-liquid two-phase to a single gas phase. The system provided by the present application realizes that the low-temperature fluid at both ends of the pipeline 100 to be tested is a single phase. By measuring the temperature and pressure of the gas phase and the liquid phase, the accurate heat leakage can be obtained by the enthalpy difference method.

[0049] It should be noted that, according to basic physical laws, when the cryogenic medium surrounding the superconducting material 21 is in a cryogenic liquid state or a gas-liquid two-phase flow state, its superconducting properties do not change. When the cryogenic medium vaporizes and heats up to the critical temperature, the superconducting properties of the superconducting material 21 will suddenly disappear, thereby realizing the state judgment of the cryogenic medium.

[0050] In the present application, the heating device 22 may be a heating film disposed on the phase change pipe 2 , and the heating film has a large heating surface and occupies a small space.

[0051] It should be noted that the outlet pipe at the bottom of the phase separator 1 is connected to the medium supply pipeline, and the pressure and temperature sensors at the inlet section of the pipeline 100 to be tested are located as close to the outlet pipe at the bottom of the phase separator 1 as possible.

[0052] In this embodiment, the diameters of the phase change pipeline 2 and the pipeline to be tested 100 are substantially the same, and the phase change pipeline 2 can be directly connected to the pipeline to be tested 100 .

[0053] The superconducting material 21 may be a high-temperature superconducting material or a low-temperature superconducting material 21. The high-temperature superconducting material 21 may be suitable for applications near the temperature of liquid nitrogen (80K), and the low-temperature superconducting material 21 may be suitable for applications near the temperature of liquid helium (4K). The appearance of the superconducting material 21 may be filamentary or ribbon-like. Generally, the high-temperature superconducting material 21 is ribbon-like, and the width may be selected to be less than 4 mm. The low-temperature superconducting material 21 is generally filamentary, and the diameter may be selected to be less than 0.5 mm.

[0054] Current leads and voltage leads are respectively provided at both ends of the superconducting material 21 , and the resistance at both ends of the superconducting material 21 can be measured by the conventional “four-lead method”. The leads of the superconducting material 21 can be connected to an external device through a low-temperature connection seat 23 on the phase change pipe 2 .

[0055] It should be noted that the low-temperature pipeline system in the related technology includes a refrigeration machine system 200, a low-temperature pipeline (including the pipeline to be tested 100) and a low-temperature load 300. The fluid output by the refrigeration machine system 200 flows into the low-temperature load 300 through the low-temperature pipeline for refrigeration, and the refrigerated fluid then flows back to the refrigeration machine system 200 through the low-temperature pipeline for refrigeration again.

[0056] In some embodiments of the present invention, a plurality of superconducting materials 21 are uniformly arranged on the inner wall of the phase change pipe 2 along the circumferential direction, and an insulating material is arranged between the superconducting material 21 and the inner wall of the phase change pipe 2 .

[0057] In this embodiment, the plurality of superconducting materials 21 arranged circumferentially on the phase change pipe 2 can more comprehensively determine whether the pipe 100 to be tested has completely changed into the gas phase. In addition, a layer of polytetrafluoroethylene film can be sprayed on the inner wall of the pipe to achieve insulation.

[0058] In some embodiments of the present invention, the superconducting material 21 is fixed on the inner wall of the phase change pipe 2 by a fixing structure 24 .

[0059] In some embodiments of the present invention, a superconducting material 21 is disposed in the center of the phase change pipe 2. In this way, in combination with the superconducting material 21 on the pipe wall, it is possible to determine in all directions whether the cryogenic fluid in the pipe is transformed into a gas phase.

[0060] In some embodiments of the present invention, the superconducting material 21 disposed at the center of the phase change pipe 2 is fixed by a plurality of fixing ropes 25 fixed on the phase change pipe 2 .

[0061] In some embodiments of the present invention, the fixing rope 25 is made of non-metallic material. The main body of the fixing rope 25 is made of non-metallic material (such as glass fiber, cotton thread, etc.), and the end is welded or bonded to the pipeline wall through the transition fixing structure 24.

[0062] In some embodiments of the present invention, the heating device 22 is connected to a precise constant current source to adjust its heating power.

[0063] In some embodiments of the present invention, both the inlet of the pipeline to be tested 100 and the outlet of the phase change pipeline 2 are provided with a temperature and pressure test assembly 3 , and the inlet of the pipeline to be tested 100 is also provided with a flow meter 4 .

[0064] The embodiment of the present invention further provides a method for testing heat leakage of a cryogenic pipeline, which is implemented according to any of the above systems, and includes:

[0065] When measuring the temperature, the heating device 22 is started to heat the fluid in the phase change pipe 2;

[0066] The resistance testing device monitors the resistance of the superconducting material 21 to determine whether the fluid in the phase change pipe 2 is gas;

[0067] When there is gas in the phase change pipeline 2, the liquid phase temperature and pressure at the inlet of the pipeline 100 to be tested and the gas phase temperature and pressure at the outlet of the phase change pipeline 2 are collected;

[0068] Calculate the inlet enthalpy and outlet enthalpy values ​​according to the liquid phase temperature and pressure and the gas phase temperature and pressure respectively;

[0069] The heat leakage is calculated by the mass flow meter 4 according to the inlet enthalpy value, the outlet enthalpy value, the power of the heating device 22 and the mass flow meter 4 of the cryogenic fluid flowing into the pipeline 100 to be measured.

[0070] In some embodiments of the present invention, the heat leakage is calculated by the mass flow meter 4 according to the inlet enthalpy value, the outlet enthalpy value, the power of the heating device 22 and the mass flow meter 4 of the cryogenic fluid flowing into the pipeline 100 to be tested by the following formula:

[0071] Q=m(h2-h1)-P

[0072] Wherein, Q is the amount of heat leakage, m is the mass flow rate of the low-temperature fluid flowing into the pipeline 100 to be tested, h1 is the inlet enthalpy value, h2 is the outlet enthalpy value, and P is the power of the heating device 22 .

[0073] Specifically, before the test, the cryogenic medium provided by the refrigeration system 200 is separated into the required cryogenic liquid by the phase separator 1, and the cryogenic liquid enters the multi-test pipeline 100 and the phase change pipeline 2 after passing through the regulating valve, and the inside of the pipeline is filled with the normally flowing cryogenic medium. Along the flow direction, due to the heat leakage from the outside transferred to the cryogenic medium, the cryogenic medium changes from a single-phase liquid flow state to a gas-liquid two-phase flow state. The cryogenic medium in the test pipeline 100 close to the phase separator 1 in the valve box is in a single-phase liquid state, and the enthalpy value h1 can be obtained through the pressure and temperature measured at the test pipeline 100.

[0074] During the test, the heating program is started to heat the low-temperature medium at the outlet of the pipeline 100 to be tested, and the heating power P is adjusted by a precise constant current source; along the flow direction of the low-temperature medium, the low-temperature medium evaporates rapidly until it completely turns into a gaseous state, and the temperature will gradually rise after turning into a gaseous state, and the superconducting material 21 at the downstream will gradually lose its superconducting properties along the length direction from downstream to upstream, and the resistance will also increase linearly synchronously. The state of the medium around the superconducting material 21 can be determined by the change in resistance. When the superconducting material 21 completely loses its superconducting properties, or the superconducting material 21 corresponding to the downstream length completely loses its superconducting properties, it can be determined that the medium in the phase change pipeline 2 is completely vaporized. At this time, the outlet enthalpy value h2 of the low-temperature medium can be obtained by the pressure and temperature at the outlet of the corresponding pipeline 100 to be tested.

[0075] According to the principle of conservation of energy, the heat leakage of the entire length of the pipeline 100 to be measured is Q=m(h2-h1)-P, where m is the mass flow rate of the cryogenic liquid measured by the flowmeter 4.

[0076] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A low temperature pipeline heat leakage test system, characterized in that: Including phase separator, pipeline to be tested, and phase change pipeline; The phase separator is used to separate the cryogenic medium into a liquid phase and a gas phase, the inlet of the pipeline to be tested is connected to the liquid phase outlet of the phase separator, the phase change pipeline is connected to the outlet of the pipeline to be tested, the phase change pipeline is provided with at least one heating device, the phase change pipeline is provided with at least one ribbon-shaped superconducting material along its axial direction, and the superconducting material is connected to a resistance testing device; When measuring the temperature, the heating device is started to heat the fluid in the phase change pipe, and the resistance testing device monitors the resistance of the superconducting material to determine whether the fluid in the phase change pipe is gas. When the phase change pipe is gas, the liquid phase temperature and pressure at the inlet of the pipe to be tested and the gas phase temperature and pressure at the outlet of the phase change pipe are collected to determine the heat leakage by the enthalpy difference method.

2. The system according to claim 1, characterized in that The inner wall of the phase change pipe is evenly provided with a plurality of superconducting materials along the circumferential direction, and an insulating material is provided between the superconducting material and the inner wall of the phase change pipe.

3. The system according to claim 1, characterized in that The superconducting material is fixed on the inner wall of the phase change pipe through a fixing structure.

4. The system according to claim 1, characterized in that The superconducting material is arranged at the center of the phase change pipeline.

5. The system according to claim 4, characterized in that The superconducting material arranged at the center of the phase change pipe is fixed by a plurality of fixing ropes fixed on the phase change pipe.

6. The system according to claim 5, characterized in that The fixing rope is made of non-metallic material.

7. The system according to claim 1, characterized in that The heating device is connected to a precise constant current source to adjust its heating power.

8. The system according to claim 1, characterized in that The inlet of the pipeline to be tested and the outlet of the phase change pipeline are both provided with temperature and pressure test components, and the inlet of the pipeline to be tested is also provided with a flow meter.

9. A method for testing heat leakage of a cryogenic pipeline, characterized in that: According to the system implementation according to any one of claims 1 to 8, the method comprises: When measuring the temperature, starting the heating device to heat the fluid in the phase change pipeline; The resistance testing device monitors the resistance of the superconducting material to determine whether the fluid in the phase change pipe is gas; When there is gas in the phase change pipeline, collecting the liquid phase temperature and pressure at the inlet of the pipeline to be tested and the gas phase temperature and pressure at the outlet of the phase change pipeline; Calculating an inlet enthalpy value and an outlet enthalpy value according to the liquid phase temperature and pressure and the gas phase temperature and pressure respectively; The heat leakage is calculated according to the inlet enthalpy value, the outlet enthalpy value, the power of the heating device and the mass flow rate of the low-temperature fluid flowing into the pipeline to be measured.

10. The method according to claim 9, characterized in that The calculation of the heat leakage according to the inlet enthalpy value, the outlet enthalpy value, the power of the heating device and the mass flow rate of the low-temperature fluid flowing into the pipeline to be measured is achieved by the following formula: Q=m(h2-h1)-P Wherein, Q is the amount of heat leakage, m is the mass flow rate of the low-temperature fluid flowing into the pipeline to be measured, h1 is the inlet enthalpy value, h2 is the outlet enthalpy value, and P is the power of the heating device.

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