Testing device and testing method for compression and cryogenic reliquefaction of low-temperature medium

Abstract

The invention discloses a device and a method for testing compression and cryogenic reliquefaction of a low-temperature medium, and belongs to the field of energy power. The system comprises a liquefying medium storage tank, a compressor test loop, a cryogenic reliquefaction loop and a host system, an outlet of the liquefied medium storage tank is connected with an inlet of the cryogenic reliquefaction loop and an inlet of the compressor test loop, an outlet of the cryogenic reliquefaction loop is connected with an upper inlet of the liquefied medium storage tank, and an outlet of the compressor test loop is connected with the host system. The working condition of the testing device is controlled through the pump set and the valve system, and a plurality of sensors (pressure, temperature and flow sensors) are used for real-time monitoring, so that the functions of supplying gas to a host system and re-liquefying flash steam are realized; and equipment performance testing can be carried out on the cryogenic reliquefaction device and the compressor under different low-temperature medium conditions.

Description

Technical Field

[0001] The invention belongs to the field of energy and power, and in particular relates to a testing device and a testing method for low-temperature medium compression and deep-cold reliquefaction. Background Art

[0002] With the intensification of global climate change and the gradual reduction of fossil fuel resources, the development and utilization of clean energy has become the focus of global energy policy. Among them, the application technology of cryogenic media such as liquid nitrogen and liquefied natural gas plays an important role in reducing greenhouse gas emissions and improving air quality. However, since these fuels need to be stored at low temperatures, conventional materials may lose their original mechanical strength and toughness due to embrittlement in such an environment, which makes the material selection and design of storage equipment a technical difficulty. In addition, if fuels such as liquefied natural gas (LNG) are mixed with air in a certain proportion, an explosive mixture may be formed, which may cause an explosion once it encounters an ignition source.

[0003] Therefore, it is particularly important to develop a gas supply system suitable for cryogenic media. These systems need to have a high degree of sealing and reliability to prevent leakage of cryogenic media. At the same time, they also need to withstand the severe challenges of the cryogenic environment to ensure that the performance stability can be maintained under extreme conditions. Although some advanced countries in the world have established integrated test devices that can simulate the actual working conditions of cryogenic media, which has promoted the advancement and application of cryogenic technology, there are still obvious shortcomings in facilities and technologies in this regard in China. This limits the overall development of domestic cryogenic technology and its application in a wider range of fields, highlighting the urgent need and importance of building and improving relevant testing facilities. Summary of the invention

[0004] The object of the present invention is to provide a testing device and a testing method for low-temperature medium compression and deep-cold reliquefaction.

[0005] The purpose of the present invention is achieved through the following technical solutions:

[0006] A test device for low-temperature medium compression and cryogenic reliquefaction, comprising a liquefied medium storage tank, a compressor test circuit, a cryogenic reliquefaction circuit and a host system; the outlet of the liquefied medium storage tank is connected to an inlet of a cryogenic reliquefaction circuit and an inlet of a compressor test circuit, the outlet of the cryogenic reliquefaction circuit is connected to an upper inlet of the liquefied medium storage tank, and the outlet of the compressor test circuit is connected to the host system;

[0007] The cryogenic reliquefaction loop is used to reliquefy the flash gas generated by the liquefied medium storage tank and to test the equipment on the loop at the same time;

[0008] The compressor test loop compresses the gas supply medium entering the test device and tests the equipment on the loop.

[0009] Furthermore, the cryogenic reliquefaction circuit includes a reliquefaction test regulating valve, a reliquefaction transfer pump and a cryogenic reliquefaction system arranged in sequence along the liquid flow direction, and two branches are arranged at the outlet of the cryogenic reliquefaction system, one branch is connected to the cryogenic medium heater through a cryogenic heating regulating valve, the outlet of the cryogenic medium heater is connected to the upper inlet of the liquefied medium storage tank, and the other branch is connected to the outlet of the cryogenic medium heater through a cryogenic medium regulating valve; the cryogenic reliquefaction circuit performs equipment testing on the cryogenic reliquefaction system.

[0010] Furthermore, the compressor test circuit includes a compression test regulating valve, a compression test delivery pump, a low-temperature medium heater, a low-temperature gas medium storage tank, a compressor system, an air supply regulating heat exchanger and a main engine regulating valve arranged in sequence along the flow direction of gas and liquid fluids; at the outlet of the compressor system and before the inlet of the air supply regulating heat exchanger, a compression buffer tank connected through a buffer regulating valve is provided to adjust the pressure at the outlet of the compressor system; the compressor test circuit performs equipment testing on the compressor system.

[0011] Furthermore, the cryogenic reliquefaction system includes a fixed cryogenic reliquefaction device and a test cryogenic reliquefaction device, and the test cryogenic reliquefaction device serves as a test device for the cryogenic reliquefaction device; the fixed cryogenic reliquefaction device flows through a fixed reliquefaction circuit and a fixed refrigerant circuit, and the test cryogenic reliquefaction device flows through a test reliquefaction circuit and a test refrigerant circuit.

[0012] Furthermore, the inlets of the fixed reliquefaction circuit and the test reliquefaction circuit are connected to the outlet of the reliquefaction transfer pump, and the outlets of the fixed reliquefaction circuit and the test reliquefaction circuit serve as outlets of the cryogenic reliquefaction system; the fixed reliquefaction circuit includes a fixed reliquefaction regulating valve, a fixed cryogenic reliquefaction device and a fixed reliquefaction stop valve along the flow direction, and the test reliquefaction circuit includes a test reliquefaction regulating valve, a test cryogenic reliquefaction device and a test reliquefaction stop valve along the flow direction;

[0013] The inlets of the fixed refrigerant circuit and the test refrigerant circuit are connected to the refrigerant inlet, and the outlets of the fixed refrigerant circuit and the test refrigerant circuit are connected to the refrigerant outlet; the fixed refrigerant circuit includes a fixed refrigerant regulating valve, a fixed deep-cold refrigerant device and a fixed refrigerant stop valve along the flow direction, and the test refrigerant circuit includes a test refrigerant regulating valve, a test deep-cold refrigerant device and a test refrigerant stop valve along the flow direction.

[0014] Furthermore, the compressor system includes a test compressor circuit and a test compressor circuit; the inlets of the fixed compressor circuit and the test compressor circuit are connected to the outlet of the low-temperature gas medium storage tank, and the outlets of the fixed compressor circuit and the test compressor circuit are connected to the inlet of the gas supply regulating heat exchanger; the fixed compressor circuit includes a fixed compressor regulating valve, a fixed compressor and a fixed compressor stop valve along the flow direction; the test compressor circuit includes a test compressor regulating valve, a test compressor and a test compressor stop valve along the flow direction.

[0015] Furthermore, pressure, temperature and flow sensors are arranged at the inlets of the cryogenic reliquefaction system, cryogenic medium heater, low-temperature medium heater and compressor system to monitor the equipment inlet parameters of the medium, so as to control the workload of the equipment; pressure, temperature and flow sensors are arranged at the outlets of the cryogenic reliquefaction system and the compressor system to monitor the test equipment outlet parameters of the medium, so as to determine the performance of the test equipment; pressure, temperature and flow sensors are arranged at the outlet of the compressor system, and when the medium pressure at the outlet of the compressor system fluctuates too much, the opening of the buffer tank regulating valve is controlled to adjust the flow of the medium in the compression buffer tank entering the compression test circuit, thereby adjusting the medium pressure at the outlet of the compressor system.

[0016] A method for testing low-temperature medium compression and cryogenic reliquefaction, using a test device for low-temperature medium compression and cryogenic reliquefaction, the test device includes four working states: cryogenic reliquefaction, cryogenic reliquefaction device test, compressed air supply, and compressor test, and the working state of the test device is controlled by controlling the opening and closing of the pump group and the valve system;

[0017] When the test device enters the "cryogenic reliquefaction device test" working state, the reliquefaction test regulating valve and the reliquefaction delivery pump are turned on, and medium flows in the cryogenic reliquefaction circuit. At the same time, the test reliquefaction regulating valve and the test reliquefaction stop valve are opened, and medium enters the test reliquefaction circuit to perform equipment testing on the test cryogenic reliquefaction device;

[0018] When the test device enters the "compressed air supply" working state, the compression test regulating valve and the compression test delivery pump are turned on, and the medium flows in the compressor test circuit. At the same time, the fixed compressor regulating valve and the fixed compressor stop valve are opened, and the medium flows in the fixed compressor circuit. In this state, the test device compresses the medium entering the host system, and the medium finally flows into the host system for air supply;

[0019] When the test device enters the "compressor test" working state, the compression test regulating valve and the compression test delivery pump are turned on, and medium flows in the compressor test circuit. At the same time, the test compressor regulating valve and the test compressor stop valve are opened, and the medium enters the test compressor circuit to perform equipment testing on the test compressor.

[0020] When the pressure in the liquid medium storage tank fluctuates, the reliquefaction test regulating valve and the reliquefaction transfer pump are turned on, and the test device enters the "cryogenic reliquefaction" working state. There is medium flow in the cryogenic reliquefaction circuit. At the same time, the fixed reliquefaction regulating valve and the fixed reliquefaction stop valve are opened. In this state, the fixed cryogenic reliquefaction device liquefies the medium to 5-8°C below the liquefaction temperature, and then transfers it to the liquefied medium storage tank through the cryogenic medium regulating valve to cool and liquefy the flash gas in the tank. When the pressure stabilizes, the cryogenic medium regulating valve is closed, the cryogenic heating regulating valve is opened, and the cryogenic medium heater heats the cryogenic medium to the liquefaction temperature and then transfers it to the liquefied medium storage tank for storage.

[0021] Furthermore, the test working fluid for the equipment test is a low-temperature gas fuel, including nitrogen, hydrogen, and natural gas.

[0022] The beneficial effects of the present invention are:

[0023] 1. The patent of this invention is applicable to different cryogenic media, including but not limited to nitrogen, hydrogen, natural gas and other gaseous fuels;

[0024] 2. The present invention utilizes a cryogenic reliquefaction method to process the flash gas generated in the liquefied medium storage tank, which effectively avoids the occurrence of excessive pressure in the tank;

[0025] 3. By installing temperature, pressure and flow sensors at key locations, the characteristic parameters of the medium can be accurately monitored and controlled, which not only improves the accuracy of the test but also ensures the safety of the system during operation;

[0026] 4. In the test loop set up by the present invention, a test equipment loop and a test equipment loop are set up to ensure that when a single device is not tested, other devices can still be tested. Through in-depth research on these devices, it is helpful to identify and solve potential problems at an early stage, ensure that the manufacturing quality of these devices meets strict standards, thereby reducing the failure rate and enhancing the overall reliability of the system. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a structural schematic diagram of a testing device and a testing method for low-temperature medium compression and deep-cold reliquefaction;

[0028] Figure 2 It is a schematic diagram of the structure of the cryogenic reliquefaction circuit described in the present invention;

[0029] Figure 3 It is a structural schematic diagram of the cryogenic reliquefaction system of the present invention;

[0030] Figure 4 It is a structural schematic diagram of the compressor test circuit described in the present invention;

[0031] Figure 5 It is a structural schematic diagram of the compressor system described in the present invention. DETAILED DESCRIPTION

[0032] The present invention is further described below in conjunction with the accompanying drawings.

[0033] The present invention provides a novel testing device and method for cryogenic medium compression and deep-cold reliquefaction, which can realize the functions of storing and supplying gas fuel under different pressures for the host system, while ensuring that the equipment performance of the cryogenic medium compressor and the cryogenic medium heat exchanger are tested under different cryogenic media conditions, comprehensively testing and verifying the performance of the cryogenic medium equipment, so as to ensure its safety, reliability and economy in actual operation, reduce operating costs and extend the service life of the equipment.

[0034] Combination Figure 1 The present invention includes a medium storage system, a pump group, a heat exchange system, a cryogenic reliquefaction system 13, a compressor system 14, a valve system, a sensor system and a host system. The components in the system are connected by pipelines to form a test device, and are divided into a compressor test loop and a cryogenic reliquefaction loop.

[0035] The medium storage system includes a liquefied medium storage tank 1, a low-temperature gas medium storage tank 2 and a compression buffer tank 3, which are used to store fuel media; the pump group includes a compression test delivery pump 4 and a reliquefaction delivery pump 5, which are responsible for delivering the stored medium to different circuits; the heat exchange system includes a cryogenic medium heater 6, a low-temperature medium heater 7 and an air supply regulating heat exchanger 8, which are used to regulate the temperature of the medium; the valve system includes a reliquefaction test regulating valve 9, a compression test regulating valve 10, a buffer tank regulating valve 11 and a main engine regulating valve 12, and the switching of these valves controls the flow direction of the medium in the entire system, thereby realizing the operating condition change of the device; the outlet of the liquefied medium storage tank is connected to the inlet of the cryogenic reliquefaction circuit and the inlet of the compressor test circuit, the outlet of the cryogenic reliquefaction circuit is connected to the upper inlet of the liquefied medium storage tank, and the outlet of the compressor test circuit is connected to the inlet of the main engine system.

[0036] Specifically, the specific working process of each circuit of the present invention is as follows:

[0037] Combination Figure 2The cryogenic reliquefaction circuit includes a reliquefaction test regulating valve 9, a reliquefaction delivery pump 5, a cryogenic reliquefaction system 13, and a cryogenic medium heater 6, which are arranged in sequence along the liquid flow direction. Specifically, the liquid medium in the liquefied medium storage tank 1 is first led to the cryogenic reliquefaction system 13 by the reliquefaction delivery pump 5. Pressure, temperature, and flow sensors are arranged at the inlet of the cryogenic reliquefaction system 13 to monitor the medium parameters at the inlet of the device, so as to adjust the workload of the cryogenic reliquefaction system 13; in the cryogenic reliquefaction system 13, the temperature of the flash gas will be reduced to a cryogenic state 5-6°C lower than the liquefaction temperature. At the same time, this system can also perform equipment testing on the cryogenic reliquefaction device. The processed liquefied gas will then be sent to the cryogenic medium heater 6, where the gas is heated to the same temperature as the liquid in the liquefied medium storage tank 1. The heated gas finally flows back to the liquefied medium storage tank 1 for re-storage. This process not only keeps the pressure in the storage tank within a safe and normal range, but also ensures the energy efficiency and safety of the system.

[0038] Combination Figure 3 There are two routes for the medium in the cryogenic reliquefaction system 13, including a fixed reliquefaction circuit 13-a and a test reliquefaction circuit 13-b. Specifically, when the fixed reliquefaction circuit 13-a enters the working state, the fixed reliquefaction regulating valve 13-1, the fixed reliquefaction stop valve 13-2, the fixed refrigerant regulating valve 13-3 and the fixed refrigerant stop valve 13-4 are opened, and the flash gas flows to the fixed cryogenic reliquefaction device, where it is liquefied and cooled to a cryogenic state 5-6°C lower than the liquefaction temperature, and flows to the cryogenic medium heater 6 through the fixed reliquefaction stop valve 13-2. At the same time, pressure, temperature and flow sensors are arranged at the inlet of the cryogenic reliquefaction system 13 to monitor the medium parameters at the inlet of the device, and the fixed refrigerant regulating valve 13-1 is controlled to adjust the temperature of the medium. The opening of valve 13-3 controls the flow rate of refrigerant in the fixed refrigerant circuit 13-c, thereby adjusting the heat exchange load of the fixed cryogenic reliquefaction device; when the test reliquefaction circuit 13-b enters the working state, the test reliquefaction regulating valve 13-5, the test reliquefaction stop valve 13-6, the test refrigerant regulating valve 13-7 and the test refrigerant stop valve 13-8 are opened, and the flash gas flows to the test cryogenic reliquefaction device for equipment testing. At the same time, pressure, temperature and flow sensors are arranged at the inlet of the cryogenic reliquefaction system 13 to monitor the medium parameters at the inlet of the device. By controlling the opening of the test refrigerant regulating valve 13-7, the flow rate of refrigerant in the test refrigerant circuit 13-d is controlled, thereby adjusting the heat exchange load of the test cryogenic reliquefaction device;

[0039] Combination Figure 4The compressor test circuit includes a compression test regulating valve 10, a compression test delivery pump 4, a low-temperature medium heater 7, a low-temperature gas medium storage tank 2, a compressor system 14, a medium buffer tank and a host regulating valve 12 arranged in sequence along the flow direction of gas and liquid fluids. The circuit is designed to provide compressed gas for the host system or to perform equipment testing on the compressor and the low-temperature medium heater 7.

[0040] Specifically, the liquid medium in the liquefied medium storage tank 1 is first delivered by the compression test delivery pump 4, and a pressure, temperature, and flow sensor are arranged at the inlet of the low-temperature medium heater 7 to monitor the medium parameters at the inlet of the device, so as to adjust the workload of the low-temperature medium heater 7. After being heated to the tank temperature of the low-temperature gas medium storage tank 2 by the low-temperature medium heater 7, it enters the low-temperature gas medium storage tank 2 for storage. After the storage volume reaches a certain amount, the medium enters the compressor to compress the gas supply medium, and the compressor performance can also be tested. Pressure, temperature, and flow sensors are arranged at the inlet of the compressor system 14 to monitor the medium parameters at the inlet of the device, so as to adjust the workload of the compressor; pressure, temperature, and flow sensors are set at the outlet of the compressor system 14 to monitor the outlet parameters of the medium test equipment to determine the performance of the test equipment. At the same time, when the medium pressure at the outlet of the compressor system 14 fluctuates too much, the flow of the medium in the compression buffer tank 3 entering the compressor test circuit b is adjusted by controlling the opening of the buffer tank regulating valve 11 to change the medium pressure at the outlet of the compressor system 14. After the pressure is regulated, the high-temperature and high-pressure medium enters the air supply regulating heat exchanger 8 for heat exchange and temperature adjustment to the air supply temperature, and finally enters the main engine system through the main engine regulating valve 12.

[0041] Combination Figure 5 The compressor system 14 includes a fixed compressor circuit 14-a and a test compressor circuit 14-b. The inlets of the fixed compressor circuit 14-a and the test compressor circuit 14-b are connected to the outlet of the low-temperature gas medium storage tank 2, and the outlets of the fixed compressor circuit 14-a and the test compressor circuit 14-b are connected to the inlet of the gas supply regulating heat exchanger 8. Specifically, when the fixed compressor circuit 14-a enters the working state, the fixed compressor regulating valve 14-1 and the fixed compressor stop valve 14-2 are opened, and the low-temperature gas medium enters the fixed compressor through the fixed compressor regulating valve 14-1, and the medium is compressed to the gas supply pressure in the fixed compressor, and then flows out of the compressor system 14 through the fixed compressor stop valve 14-2; when the test compressor circuit 14-b enters the working state, the test compressor regulating valve 14-3 and the test compressor stop valve 14-4 are opened, and the low-temperature gas medium enters the test compressor through the test compressor regulating valve 14-3, and the medium performs a compressor equipment performance test in the test compressor, and then flows out of the compressor system 14 through the test compressor stop valve 14-4.

[0042] The control method of the test device of the present invention is as follows:

[0043] In the "cryogenic reliquefaction device test" state, the valve opening and closing conditions on the test device are as follows: the reliquefaction test regulating valve 9 is opened, the reliquefaction delivery pump 5 enters the working state, and the liquid medium in the liquefied medium storage tank 1 enters the cryogenic reliquefaction circuit; in the cryogenic reliquefaction system 13, the fixed reliquefaction regulating valve 13-1, the fixed reliquefaction stop valve 13-2, the fixed refrigerant regulating valve 13-3 and the fixed refrigerant stop valve 13-4 are opened, the fixed reliquefaction circuit 13-a and the fixed refrigerant circuit 13-c enter the working state, and the medium enters the fixed cryogenic reliquefaction device for equipment testing; the tested medium is heated to the temperature of the liquefied medium storage tank 1 by the cryogenic medium heater 6, and then enters the liquefied medium storage tank 1 for storage;

[0044] When entering the "compressed air supply" state, the valve opening and closing conditions on the test device are as follows: the compression test regulating valve 10 is opened, the compression test delivery pump 4 is turned on, the liquid medium flows into the compressor test circuit, and in the compressor system 14, the fixed compressor regulating valve 14-1 and the fixed compressor stop valve 14-2 are opened, and the low-temperature gas medium enters the fixed compressor for compression processing. After compression, the medium passes through the compression buffer tank 3 and the air supply regulating heat exchanger 8 for temperature and pressure adjustment and leads to the host system;

[0045] In the "compressor test" state, the operation is similar, but at this time in the compressor system 14, the test compressor regulating valve 14-3 and the test compressor stop valve 14-4 are opened, and the low-temperature gas medium is transported to the test compressor for equipment testing. After the test, the medium passes through the compression buffer tank 3 and the gas supply regulating heat exchanger 8 for temperature and pressure adjustment and leads to the host system;

[0046] When the pressure in the liquid medium storage tank increases sharply, it automatically switches to the "cryogenic reliquefaction state", the reliquefaction test regulating valve 9 and the cryogenic medium delivery pump are started, and in the cryogenic reliquefaction system 13, the test reliquefaction regulating valve 13-5, the test reliquefaction stop valve 13-6, the test refrigerant regulating valve 13-7 and the test refrigerant stop valve 13-8 are opened, and the test reliquefaction circuit 13-b and the test refrigerant circuit 13-d enter the working state. The medium is liquefied and cooled to a cryogenic state 5-8°C lower than the liquefaction temperature inside the fixed cryogenic reliquefaction device, and then enters the liquefied medium storage tank 1 through the cryogenic medium regulating valve 16 to cool and liquefy the flash gas in the tank. When the pressure is stable, the cryogenic medium regulating valve 16 is closed, the cryogenic heating regulating valve 15 is opened, and the cryogenic medium enters the cryogenic medium heater 6, is heated to the liquefaction temperature, and then is transported to the liquefied medium storage tank for storage.

[0047] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A test device for low-temperature medium compression and cryogenic reliquefaction, characterized in that: It comprises a liquefied medium storage tank (1), a compressor test circuit, a cryogenic reliquefaction circuit and a host system; the outlet of the liquefied medium storage tank (1) is connected to the inlet of the cryogenic reliquefaction circuit and the inlet of the compressor test circuit, the outlet of the cryogenic reliquefaction circuit is connected to the upper inlet of the liquefied medium storage tank (1), and the outlet of the compressor test circuit is connected to the host system; The cryogenic reliquefaction loop is used to reliquefy the flash gas generated by the liquefied medium storage tank (1) and to test the equipment on the loop at the same time; The compressor test loop compresses the gas supply medium entering the test device and tests the equipment on the loop.

2. A testing device for low-temperature medium compression and deep-cold reliquefaction according to claim 1, characterized in that: The cryogenic reliquefaction circuit comprises a reliquefaction test regulating valve (9), a reliquefaction delivery pump (5) and a cryogenic reliquefaction system (13) arranged in sequence along the liquid flow direction, and two branches are arranged at the outlet of the cryogenic reliquefaction system (13), one branch is connected to the cryogenic medium heater (6) through a cryogenic heating regulating valve (15), the outlet of the cryogenic medium heater (6) is connected to the upper inlet of the liquefied medium storage tank (1), and the other branch is connected to the outlet of the cryogenic medium heater (6) through a cryogenic medium regulating valve (16); the cryogenic reliquefaction circuit performs equipment testing on the cryogenic reliquefaction system (13).

3. A testing device for low-temperature medium compression and deep-cold reliquefaction according to claim 1, characterized in that: The compressor test circuit comprises a compression test regulating valve (10), a compression test delivery pump (4), a low-temperature medium heater (7), a low-temperature gas medium storage tank (2), a compressor system (14), an air supply regulating heat exchanger (8) and a main engine regulating valve (12) which are arranged in sequence along the flow direction of gas and liquid fluids; at the outlet of the compressor system (14) and before the inlet of the air supply regulating heat exchanger (8), a compression buffer tank (3) is connected through a buffer regulating valve (11) to regulate the pressure at the outlet of the compressor system (14); the compressor test circuit performs equipment testing on the compressor system (14).

4. A testing device for low-temperature medium compression and deep-cold reliquefaction according to claim 2, characterized in that: The cryogenic reliquefaction system (13) comprises a fixed cryogenic reliquefaction device and a test cryogenic reliquefaction device, wherein the test cryogenic reliquefaction device serves as a test device for the cryogenic reliquefaction device; the fixed cryogenic reliquefaction device flows through a fixed reliquefaction circuit and a fixed refrigerant circuit, and the test cryogenic reliquefaction device flows through a test reliquefaction circuit and a test refrigerant circuit.

5. A testing device for low-temperature medium compression and deep-cold reliquefaction according to claim 4, characterized in that: The inlets of the fixed reliquefaction circuit and the test reliquefaction circuit are connected to the outlet of the reliquefaction delivery pump (5), and the outlets of the fixed reliquefaction circuit and the test reliquefaction circuit serve as outlets of the cryogenic reliquefaction system (13); the fixed reliquefaction circuit includes a fixed reliquefaction regulating valve (13-1), a fixed cryogenic reliquefaction device and a fixed reliquefaction stop valve (13-2) along the flow direction, and the test reliquefaction circuit includes a test reliquefaction regulating valve (13-5), a test cryogenic reliquefaction device and a test reliquefaction stop valve (13-6) along the flow direction; The fixed refrigerant circuit and the test refrigerant circuit inlet are connected to the refrigerant inlet, and the fixed refrigerant circuit and the test refrigerant circuit outlet are connected to the refrigerant outlet; the fixed refrigerant circuit includes a fixed refrigerant regulating valve (13-3), a fixed deep-cold refrigerant device and a fixed refrigerant stop valve (13-4) along the flow direction, and the test refrigerant circuit includes a test refrigerant regulating valve (13-7), a test deep-cold refrigerant device and a test refrigerant stop valve (13-8) along the flow direction.

6. A testing device for low-temperature medium compression and deep-cold reliquefaction according to claim 3, characterized in that: The compressor system comprises a test compressor circuit and a test compressor circuit; the inlets of the fixed compressor circuit and the test compressor circuit are connected to the outlet of the low-temperature gas medium storage tank (2), and the outlets of the fixed compressor circuit and the test compressor circuit are connected to the inlet of the gas supply regulating heat exchanger (8); the fixed compressor circuit comprises a fixed compressor regulating valve (14-1), a fixed compressor and a fixed compressor stop valve (14-2) along the flow direction; the test compressor circuit comprises a test compressor regulating valve (14-3), a test compressor and a test compressor stop valve (14-4) along the flow direction.

7. A testing device for low-temperature medium compression and deep-cold reliquefaction according to claim 2 or 3, characterized in that: Pressure, temperature and flow sensors are arranged at the inlets of the cryogenic reliquefaction system (13), the cryogenic medium heater (6), the low-temperature medium heater (7) and the compressor system (14) to monitor the equipment inlet parameters of the medium, so as to control the equipment workload; pressure, temperature and flow sensors are arranged at the outlets of the cryogenic reliquefaction system (13) and the compressor system (14) to monitor the test equipment outlet parameters of the medium, so as to determine the performance of the test equipment; pressure, temperature and flow sensors are arranged at the outlet of the compressor system (14). When the medium pressure at the outlet of the compressor system (14) fluctuates too much, the flow of the medium in the compression buffer tank (3) entering the compression test circuit is adjusted by controlling the opening of the buffer tank regulating valve (11), thereby adjusting the medium pressure at the outlet of the compressor (14) system.

8. A test method for low temperature medium compression and cryogenic reliquefaction, characterized in that: A test device for low-temperature medium compression and cryogenic reliquefaction as described in any one of claims 1 to 7 is used, wherein the test device includes four working states: cryogenic reliquefaction, cryogenic reliquefaction device test, compressed air supply, and compressor test, and the working state of the test device is controlled by controlling the opening and closing of the pump group and the valve system; When the test device enters the "cryogenic reliquefaction device test" working state, the reliquefaction test regulating valve (9) and the reliquefaction delivery pump (5) are opened, and medium flows in the cryogenic reliquefaction circuit. At the same time, the test reliquefaction regulating valve (13-5) and the test reliquefaction stop valve (13-6) are opened, and medium enters the test reliquefaction circuit to perform equipment testing on the test cryogenic reliquefaction device. When the test device enters the "compressed air supply" working state, the compression test regulating valve (10) and the compression test delivery pump (4) are opened, and medium flows in the compressor test circuit. At the same time, the fixed compressor regulating valve (14-1) and the fixed compressor stop valve (14-2) are opened, and medium flows in the fixed compressor circuit. In this state, the test device compresses the medium entering the host system, and the medium finally flows into the host system for air supply; When the test device enters the "compressor test" working state, the compression test regulating valve (10) and the compression test delivery pump (4) are opened, and medium flows in the compressor test circuit. At the same time, the test compressor regulating valve (14-3) and the test compressor stop valve (14-4) are opened, and medium enters the test compressor circuit, and the test compressor is tested; When the pressure of the liquid medium storage tank fluctuates, the reliquefaction test regulating valve (9) and the reliquefaction delivery pump (5) are opened, and the test device enters the "cryogenic reliquefaction" working state. The medium flows in the cryogenic reliquefaction circuit. At the same time, the fixed reliquefaction regulating valve (13-1) and the fixed reliquefaction stop valve (13-2) are opened. In this state, the fixed cryogenic reliquefaction device liquefies the medium to 5-8°C below the liquefaction temperature, and then delivers it to the liquefied medium storage tank (1) through the cryogenic medium regulating valve (16), cools down and liquefies the flash gas in the tank. When the pressure stabilizes, the cryogenic medium regulating valve (16) is closed, the cryogenic heating regulating valve (15) is opened, and the cryogenic medium heater (6) heats the cryogenic medium to the liquefaction temperature and then delivers it to the liquefied medium storage tank for storage.

9. A method for testing low-temperature medium compression and cryogenic reliquefaction according to claim 8, characterized in that: The test working fluid for the equipment test is low-temperature gas fuel, including nitrogen, hydrogen, natural gas, etc.

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