A single-stage compression liquid charging system and method for r744

Abstract

The present application belongs to the technical field of R744 refrigeration, and particularly relates to a single-stage compression liquid adding system and method for R744. The system comprises a pressurizing pipe section, a liquid storage tank and a filling pipe section directly connected to a device to be filled, which are arranged in sequence along the R744 running path. The pressurizing pipe section comprises a gas storage tank, a first switch valve V1, a cooler, a compressor, an air cooler and a second switch valve V2, which are arranged in sequence along the gas flow direction. The liquid adding system further comprises a return pipe section with a seventh switch valve V7. The inlet of the return pipe section is connected to the inlet of a sixth switch valve V6, and the outlet of the return pipe section is connected to the liquid storage tank. The present application on-line pressurizes and liquefies R744 in a single-stage compression and multi-stage cooling coupled manner, and reduces the number of high-pressure gas pipelines by artificially dividing a high-pressure gas phase area and a high-pressure liquid phase area, so that the investment cost can be greatly reduced, and the use and maintenance risks are significantly reduced.

Description

Technical Field

[0001] This invention belongs to the field of R744 refrigeration technology, specifically relating to a single-stage compression refrigerant charging system and method for R744. Background Technology

[0002] R744 is carbon dioxide, which is colorless, odorless, non-toxic, non-flammable, and non-explosive. It possesses excellent thermal properties and is considered the second most environmentally friendly substance in industrial applications after water and air. Under the same operating conditions, R744 has the highest operating pressure compared to conventional refrigerants. For example, in automotive air conditioning compressor systems, if refrigerant R134a is used, the common operating condition is evaporation at -1°C and condensation at 63°C, corresponding to an evaporation pressure of 2.82 bar and a condensation pressure of 18.04 bar. If refrigerant R410a is used, the common operating condition is evaporation at -1°C and condensation at 63°C, corresponding to an evaporation pressure of 7.73 bar and a condensation pressure of 40.94 bar. Under the same common operating conditions, refrigerant R744, evaporating at -1°C and condensing at 63°C, has an evaporation pressure of 33.9 bar and a condensation pressure exceeding 120 bar.

[0003] It is evident that R744 filling equipment places extremely high pressure requirements on all components and pipelines. Traditional filling equipment, in particular, requires multiple tanks to dispense and store R744, each enduring extremely high operating pressures. The filling pipelines directly connecting these tanks also constantly bear extremely high operating pressures. Furthermore, as the location of the equipment being filled changes, these pipelines need to extend even further, resulting in long high-pressure gas pipelines and high investment costs. Simultaneously, these filling pipelines and their components inevitably pass through areas with high ambient temperatures, passively heating the R744 inside and further increasing the pressure. For example, in one factory, an R744 filling system had a pipeline passing near a running air compressor. The local cylinder temperature of the air compressor could reach 100°C. If the filling pipeline were heated under these conditions, the already high pressure inside would further increase, potentially reaching around 150 bar, posing a risk of cracking or even explosion. This issue urgently needs to be addressed. Summary of the Invention

[0004] One objective of this invention is to overcome the shortcomings of the prior art and provide a single-stage compression-type liquefaction system for R744. This system liquefies R744 online by coupling single-stage compression with multi-stage cooling, and reduces the high-pressure gas pipeline by artificially dividing the high-pressure gas phase zone and the high-pressure liquid phase zone, thereby significantly reducing investment costs and significantly lowering the risks of use and maintenance. Another objective of this invention is to provide a method for using a single-stage compression-type liquefaction system for R744, thereby further ensuring the simplicity and efficiency of the operation process.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] A single-stage compression-type liquid filling system for R744, characterized in that it comprises a pressurization pipe section, a liquid storage tank, and a filling pipe section directly connected to the filling equipment arranged sequentially along the R744 travel path, wherein:

[0007] The pressurization section includes a gas storage tank, a first switching valve V1, a cooler, a compressor, an air cooler, and a second switching valve V2 arranged sequentially along the gas flow direction;

[0008] The filling pipe section includes a third switch valve V3, parallel pipes, a flow regulating valve LV, a flow meter L1, a temperature and pressure measuring point, and a sixth switch valve V6 arranged sequentially along the liquid flow direction; the parallel pipes include a first parallel branch with a fifth switch valve V5 and a second parallel branch with a fourth switch valve V4 and a flow pump arranged sequentially.

[0009] The liquid addition system also includes a return pipe section with a seventh switching valve V7, the inlet of which is connected to the inlet of the sixth switching valve V6, and the outlet of which is connected to the storage tank.

[0010] Preferably, the liquid addition system further includes a vacuum pump section, with an eighth switch valve V8 and a ninth switch valve V9 arranged at both ends of the vacuum pump section. The end of the eighth switch valve V8 is connected to the outlet of the sixth switch valve V6, and the end of the ninth switch valve V9 is connected to a filling section between the third switch valve V3 and the fourth switch valve V4.

[0011] Preferably, the liquid filling system also includes a heat exchanger located on a section of filling pipe between the parallel pipe and the flow control valve LV.

[0012] Preferably, the heat exchanger, cooler, and air cooler are all connected to the constant temperature water tank through cooling water pipes; each cooling water pipe is equipped with a water pump, and the cooling water pipes where the cooler and air cooler are located are also equipped with an eleventh switch valve V11 and a twelfth switch valve V12, and the cooling water pipe where the heat exchanger is located is equipped with a water temperature regulator.

[0013] Preferably, the liquid addition system also includes a cooling unit, which is connected to the heat exchange coil of the liquid storage tank via a pressure pump and a tenth switch valve V10.

[0014] Preferably, a level gauge, a safety valve, and a camera for video monitoring of the liquid inside the tank are installed at the storage tank.

[0015] Preferably, the flow pump is a plunger pump.

[0016] Preferably, the return pipe section is also equipped with a one-way valve CV.

[0017] Preferably, all switching valves are automatic valves.

[0018] Preferably, a method for applying the single-stage compression dispensing system for R744 is characterized by comprising the following steps:

[0019] 1) Pressurization process:

[0020] When the pressurization line is opened, the gaseous R744 in the gas storage tank first enters the compressor through the first switch valve V1 and the cooler for pressurization. The compressor pressurizes R744 to the intermediate pressure. After that, R744 enters the air cooler for cooling, and then R744 continues to enter the liquid storage tank through the second switch valve V2 to complete the pressurization process.

[0021] 2) Vacuuming process:

[0022] Connect the equipment to be filled to the outlet of the sixth switch valve V6, open the eighth switch valve V8 and the vacuum pump, and evacuate the equipment to be filled through the evacuation pipe section. After the set vacuum requirement is reached, close the eighth switch valve V8 and the vacuum pump, and open the sixth switch valve V6 to complete the evacuation process. This process can be carried out synchronously or sequentially with the pressurization process.

[0023] 3) Filling process:

[0024] a) Open the filling pipe section. Liquid 744 passes through the third switch valve V3, the fourth switch valve V4, the flow pump, and the heat exchanger in sequence to reach the flow regulating valve LV. The flow regulating valve LV regulates the flow of R744. Then, the flow value is obtained through the flow meter L1. After obtaining the final temperature and pressure values ​​through the temperature and pressure measuring points, it enters the equipment to be filled through the sixth switch valve V6 to complete the filling process.

[0025] b) When the final temperature and pressure values ​​obtained at the temperature and pressure measuring points do not meet the requirements of the equipment to be filled, close the sixth switch valve V6 and open the seventh switch valve V7. Liquid 744 returns to the storage tank from the return pipe section until the final temperature and pressure values ​​measured at the temperature and pressure measuring points meet the temperature and pressure requirements of the equipment to be filled for R744. At this time, close the seventh switch valve V7 and reopen the sixth switch valve V6, and then proceed to the next step.

[0026] c) When the final pressure value measured at the temperature and pressure measuring point meets the temperature and pressure requirements of the equipment to be filled for R744, close the fourth switch valve V4, open the fifth switch valve V5, and then proceed to step a).

[0027] The beneficial effects of this invention are as follows:

[0028] 1) This invention provides a safe and reliable R744 filling system and filling method. By coupling single-stage compression with multi-stage cooling, it solves the problem of excessive pressure in the storage tank and the entire system when the ambient temperature is high.

[0029] 2) At the pressurization section, by adopting a single-stage compression method, the gas phase to liquid phase conversion is ensured while the entire pressurization section is simpler and maintenance costs are lower. Furthermore, since only one gas cooler is needed, the investment in the corresponding temperature control loop is further reduced. Under the above structure and operation process of this invention, the overall pipeline layout is simpler and clearer, and equipment costs are lower. Simultaneously, this invention uses a single-stage compression and multi-stage cooling coupling method to pressurize and liquefy R744 online, and relies on the artificial division of the high-pressure gas phase zone and high-pressure liquid phase zone to reduce the high-pressure gas pipeline. The diameter of the high-pressure gas pipeline is usually several times that of the high-pressure liquid pipeline, so reducing the high-pressure gas pipeline can greatly reduce the overall cost of pipeline construction and maintenance, and significantly reduce the risks of use and maintenance.

[0030] 3) In practice, if the pressure and temperature range of the refrigerant R744 to be charged in the equipment is relatively fixed and the range is not large, and the requirements for initial investment and operating costs of the equipment are high, the operating environment has good noise control and isolation, and personnel are capable of regularly maintaining and repairing the oil circuit, then this invention can be well applied to such situations. Under the above-described structure and operating process of this invention, the overall pipeline layout is simpler and clearer, the equipment cost is lower, and the power consumption is less, effectively ensuring low-cost operation while meeting basic performance requirements. Attached Figure Description

[0031] Figure 1 This is a pipeline layout diagram of the present invention.

[0032] The actual correspondence between the reference numerals and component names in this invention is as follows:

[0033] a- Equipment requiring filling;

[0034] 10-Storage tank; 11-Heat exchange coil; 12-Level gauge; 13-Safety valve; 14-Camera;

[0035] 20 - Pressurization pipe section; 21 - Gas storage tank; 22 - Cooler; 23 - Compressor; 24 - Air cooler;

[0036] 30 - Filling section; 31 - Flow pump; 32 - Heat exchanger; 40 - Return section;

[0037] 50 - Evacuation pipe section; 51 - Vacuum pump; 60 - Constant temperature water tank; 61 - Water temperature regulator;

[0038] 70 - Cooling unit; 71 - Pressure pump Detailed Implementation

[0039] For ease of understanding, this section combines... Figure 1 The specific structure and operation of the present invention are further described below:

[0040] The specific pipeline layout of this invention is as follows: Figure 1 As shown, during actual operation, the gaseous R744 in the gas storage tank 21 first enters the compressor 23 for pressurization via the first switching valve V1 and the pipeline of the cooler 22. The compressor 23 pressurizes the R744 gas from 10 bar and 20°C to 40 bar and 90°C, reaching an intermediate pressure. Afterward, the R744 enters the gas cooler 24 for cooling, and the cooled refrigerant enters the liquid storage tank 10 via the second switching valve V2.

[0041] The outlet of the liquid storage tank 10 is connected to the third switching valve V3, then to the fourth switching valve V4 and the plunger pump (which acts as the flow pump 31), with the fifth switching valve V5 connected in parallel to the plunger pump. The refrigerant continues into the heat exchanger 32, where the flow rate of refrigerant R744 is regulated by the flow regulating valve LV, and then the specific flow rate is measured by the flow meter L1. After passing through the temperature and pressure measuring points, it passes through the sixth switching valve V6, which controls the flow rate, and then enters the charging equipment a, completing the charging process.

[0042] In the above process, the fourth switching valve V4 and the fifth switching valve V5 are used to select whether to bypass the flow pump 31 or use the flow pump 31; that is, the flow pump 31 serves as a supplement to the two-stage compressor, fine-tuning the pressure at the equipment inlet, and is used when the equipment inlet pressure fluctuates within a large range.

[0043] The auxiliary water system equipment is as follows: a constant temperature water tank 60 is configured to regulate the internal water to the required temperature. The constant temperature water tank 60 is equipped with an electric heating source and a cooling source unit. The following pipelines are also configured: cooling water pipeline and eleventh switching valve V11 for cooler 22; cooling water pipeline and twelfth switching valve V12 for air cooler 24; and cooling water pipeline and water temperature regulator 61 for heat exchanger 32. Because the control of R744 in the storage tank 10 is relatively strict, a separate cooling unit 70, a corresponding pressure pump 71, and a tenth switching valve V10 are configured for it. Furthermore, the storage tank 10 is the liquid working fluid storage component with the highest pressure in the system, so it is equipped with a level gauge 12, a safety valve 13, a camera 14 for video monitoring of the liquid inside the tank, pressure measuring points, etc. The storage tank 10 is also equipped with a heat exchange coil 11.

[0044] Other functional piping configurations are as follows:

[0045] Return pipe section 40: A return pipe section 40 is installed between the temperature and pressure measuring point and the equipment a to be charged. Because the distance from the liquid receiver 10 to the equipment a to be charged is very long, and the equipment a to be charged has very high requirements for the state of the refrigerant being charged, if the temperature and pressure of R744 are about to enter the equipment, they may fail to meet the requirements for some reason. In this case, the return pipe section 40 comes into play. Specifically: R744 returns to the liquid receiver 10 after passing through the seventh switch valve V7 and the one-way valve CV, where its temperature is readjusted by the liquid receiver 10 and its pressure is readjusted by the plunger pump until the state point measured by the temperature and pressure measuring point meets the temperature and pressure requirements of the equipment a to be charged for R744. At this point, the seventh switch valve V7 is closed, and then the aforementioned process piping is used normally.

[0046] Evacuation pipe section 50: The evacuation pipe section 50 is equipped with a vacuum pump 51, a ninth switch valve V9 that works with the vacuum pump 51 to evacuate the pump inlet pipe of the plunger pump to a vacuum, and an eighth switch valve V8 that works with the vacuum pump 51 to evacuate the pump outlet pipe of the plunger pump to a vacuum.

[0047] The evacuation process precedes the pressurization process. At this time, connect the device to be filled (a), open the eighth switch valve V8 and vacuum pump 51, and evacuate the device to be filled (a). After evacuating to the required vacuum level, close the eighth switch valve V8 and vacuum pump 51.

[0048] Further functions of each part:

[0049] The function of the air cooler 24 is to ensure that the gas entering the liquid storage tank 10 is reduced to a reasonable range, that is, to ensure that the exhaust temperature of the compressor 23 is within a safe and reasonable range.

[0050] A heat exchange coil 11 is installed at the liquid receiver 10, and the liquid receiver 10 has sufficient volume. Through the operation analysis of the compressor 23 and the plunger pump, the volume of the liquid receiver 10 is generally about 6-8 times the liquid supply of the equipment a to be charged. The large capacity, coupled with the water temperature circuit configured for the matching heat exchange coil 11, allows the refrigerant R744 in the liquid receiver 10 to be precisely regulated and controlled in temperature. Furthermore, the R744 storage, temperature, and pressure are very stable, which can withstand various changes in system flow, further improving the stability of operation.

[0051] Generally, the distance between the charging device a and the liquid storage tank 10 is relatively far, possibly hundreds to thousands of meters. Therefore, although the pressure and temperature of R744 from the third switch valve V3 are already very stable and close to the required temperature and pressure state of the charging device a, the aforementioned transmission distance of hundreds to thousands of meters may cause the charging pipe section 30 to pass through harmful heat sources, cold sources, and high-resistance pipelines, resulting in a gradual increase in temperature and pressure and deviation from the target value upon arrival at the charging device a. Therefore, the plunger pump of the charging pipe section 30 can be placed close to the charging device a to receive pressure signals from temperature and pressure measuring points for precise secondary adjustment of the refrigerant pressure state. Similarly, the heat exchanger 32 on the charging pipe section 30 is also placed close to the charging device a to receive temperature signals from temperature and pressure measuring points for precise secondary adjustment of the refrigerant temperature state. Closer proximity also allows for faster adjustment without parameter lag, resulting in more accurate refrigerant state during charging. The sixth switch valve V6 is directly located at the inlet of the charging device a, allowing for direct pipe disconnection when necessary. Meanwhile, even when exposed to harmful heat sources, heat exchanger 32 can ensure a constant temperature in the relatively high-pressure charging pipe section 30. Combined with temperature and pressure measuring points, it can ensure that unexpected pressurization problems are avoided.

[0052] The flow regulating valve LV at the outlet of heat exchanger 32 can control the flow parameters of liquid R744.

[0053] The constant temperature water tank 60 provides cooling water for various cooling and heat exchange equipment. The temperature of the constant temperature water tank 60 is precisely regulated by controlling the electric heating source and the chiller unit. Then, by adjusting the heat exchange capacity of the heat exchanger 32, cooler 22, and air cooler 24, precise control of the refrigerant temperature is achieved. More specifically, the water temperature regulator 61, by controlling the heat exchanger 32, can regulate the temperature of the refrigerant about to enter the charging equipment a. Since higher temperatures result in better refrigerant flow, it is suitable to heat the refrigerant to the required temperature here for better flow into the charging equipment a.

[0054] When the liquid from storage tank 10, after passing through the aforementioned long pipeline, still meets the equipment requirements at pressure and no further pressure adjustment is needed, the plunger pump can be bypassed by closing the fourth switch valve V4 and opening the fifth switch valve V5, thus meeting the requirements without using the plunger pump. To use the plunger pump, simply close the fifth switch valve V5 and open the fourth switch valve V4.

[0055] In practical application, this invention also possesses the following characteristics:

[0056] 1. The single-stage pressurization structure of this invention ensures effective gas-to-liquid conversion while simplifying the entire pressurization pipeline and reducing maintenance costs. Furthermore, since only one air cooler is required, the investment in the corresponding temperature control circuit is further reduced. Even with single-stage pressurization, the pressure of gaseous R744 output from the gas storage tank 21 can be increased to 80-100 bar, and the R744 temperature can be controlled within the range of 15-20°C by the various refrigeration elements, ensuring optimal performance.

[0057] 2. The flow pump 31 used in this liquid dispensing system is preferably a plunger pump. Plunger pumps are characterized by precise liquid delivery and allow for manual or mechanical adjustment of flow rate accuracy. Once the liquid in the storage tank 10 reaches the required pressure, the plunger pump can deliver R744 to the filling equipment more accurately and quickly.

[0058] 3. The state of liquid R744 can be monitored through temperature and pressure measuring points. If the state does not meet the R744 process requirements, the supply of liquid will be stopped, and the R744 will flow back to the storage tank 10 via the return pipe section 40. After readjusting to the R744 process requirements, it will then be delivered to the equipment requiring filling via a plunger pump. The return pipe section 40 can respond and process R744 liquid quickly, making it very simple and efficient.

[0059] 4. This invention can actively partition the working fluid state of each component, using different safety protection devices for each, and focusing on monitoring the large-capacity liquid working fluid storage tank 10. This means the storage tank 10 is subject to multiple monitoring measures, including pressure, working fluid leakage, and video surveillance. When the pressure exceeds 10 MPa, the safety valve 13 can open to safely release the overflowing pressure. Simultaneously, in the high-pressure liquid phase pipeline downstream of the storage tank, due to the high density of the liquid working fluid, the required container volume for the high-pressure liquid phase is smaller than that for the high-pressure gas phase, resulting in thinner system piping and smaller valve diameters for the same flow rate. Furthermore, the filling pipe section 30 downstream of the third switching valve V3 in the relatively low-pressure zone does not need to withstand a large amount of high-pressure gas phase load for extended periods and distances, further reducing the risk of pipe bursts and cracks.

[0060] 5. The combined use of the liquid storage tank 10 and its heat exchange coil 11 enables both liquid storage and temperature control. In this system, the liquid storage tank 10 is the component storing the largest amount of R744 liquid working fluid. Precise control and monitoring of the temperature and pressure of this component is crucial for the safety and stability of the entire system. Furthermore, the stepless adjustment of the temperature and pressure of the liquid storage tank 10 can also be achieved through the cooling unit 70 and the pressurization pipe section 20.

[0061] 6. This invention can also be used with a conventional electrical control system, which mainly consists of a controller, actuators, a communication module, a power supply module, and a display unit. The controller is responsible for monitoring all electrical equipment within the system and needs to upload equipment fault information to the final assembly workshop monitoring system to assist in quickly locating faults and improving maintenance efficiency. Other underlying components need to reserve data interfaces according to the requirements of the final assembly workshop monitoring system and upload relevant information through the factory network to realize basic maintenance and automated operation functions.

[0062] Of course, those skilled in the art will recognize that the present invention is not limited to the details of the exemplary embodiments described above, but also includes the same or similar structures that can be implemented in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered illustrative and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

[0063] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

[0064] The technologies, shapes, and structures not described in detail in this invention are all known technologies.

Claims

1. A method for a single-stage compression-type dispensing system for R744, characterized in that: The single-stage compression filling system for R744 includes a pressurization pipe section (20), a storage tank (10), and a filling pipe section (30) directly connected to the filling equipment, arranged sequentially along the R744 travel path, wherein: The pressurization section (20) includes a gas storage tank (21), a first switching valve (V1), a cooler (22), a compressor (23), a gas cooler (24) and a second switching valve (V2) arranged sequentially along the gas flow direction. The filling pipe section (30) includes a third switch valve (V3), parallel pipes, flow regulating valve (LV), flow meter (L1), temperature and pressure measuring point and a sixth switch valve (V6) arranged in sequence along the liquid flow direction; the parallel pipes include a first parallel branch with a fifth switch valve (V5) and a second parallel branch with a fourth switch valve (V4) and a flow pump (31) arranged in sequence; The liquid addition system also includes a return pipe section (40) with a seventh switch valve (V7), the inlet of which is connected to the inlet of the sixth switch valve (V6), and the outlet of which is connected to the storage tank (10). The liquid filling system also includes a vacuum section (50) with a vacuum pump (51), with an eighth switch valve (V8) and a ninth switch valve (V9) arranged at both ends of the vacuum section (50). The end of the eighth switch valve (V8) is connected to the outlet of the sixth switch valve (V6), and the end of the ninth switch valve (V9) is connected to a filling section between the third switch valve (V3) and the fourth switch valve (V4). The liquid filling system also includes a heat exchanger (32), which is located on a section of filling pipe between the parallel pipe and the flow control valve (LV); Includes the following steps: 1) Pressurization process: When the pressurization pipe section (20) is opened, the gaseous R744 in the gas storage tank (21) first enters the compressor (23) for pressurization after passing through the first switch valve (V1) and the cooler (22). The compressor (23) pressurizes the R744 to the intermediate pressure. After that, the R744 enters the air cooler (24) for cooling, and then the R744 continues to enter the liquid storage tank (10) through the second switch valve (V2) to complete the pressurization process. 2) Vacuuming process: Connect the equipment to be filled to the outlet of the sixth switch valve (V6), open the eighth switch valve (V8) and the vacuum pump (51), and evacuate the equipment to be filled through the evacuation pipe section (50). After the set vacuum requirement is reached, close the eighth switch valve (V8) and the vacuum pump (51), open the sixth switch valve (V6), and complete the evacuation process. This process is carried out synchronously or sequentially with the pressurization process. 3) Filling process: a) Open the filling pipe section (30). Liquid 744 passes through the third switch valve (V3), the fourth switch valve (V4), the flow pump (31), and the heat exchanger (32) in sequence to reach the flow regulating valve (LV). The flow regulating valve (LV) regulates the flow of R744. Then, the flow value is obtained through the flow meter (L1). After obtaining the final temperature and pressure values ​​through the temperature and pressure measuring point, it enters the equipment to be filled through the sixth switch valve (V6) to complete the filling process. b) When the final temperature and pressure values ​​obtained at the temperature and pressure measuring points do not meet the requirements of the equipment to be filled, close the sixth switch valve (V6) and open the seventh switch valve (V7). Liquid 744 returns from the return pipe section (40) to the storage tank (10) until the final temperature and pressure values ​​measured at the temperature and pressure measuring points meet the requirements of the equipment to be filled for the temperature and pressure of R744. At this time, close the seventh switch valve (V7) and reopen the sixth switch valve (V6), and then proceed to the next step. c) When the final pressure value measured at the temperature and pressure measuring point meets the temperature and pressure requirements of the equipment to be filled for R744, close the fourth switch valve (V4), open the fifth switch valve (V5), and then proceed to step a).

2. The method for a single-stage compression-type liquid dispensing system for R744 according to claim 1, characterized in that: The heat exchanger (32), cooler (22) and air cooler (24) are all connected to the constant temperature water tank (60) through cooling water pipes; each cooling water pipe is equipped with a water pump, and the cooling water pipes where the cooler (22) and air cooler (24) are located are also equipped with an eleventh switch valve (V11) and a twelfth switch valve (V12), and the cooling water pipe where the heat exchanger (32) is located is equipped with a water temperature regulator (61).

3. The method for a single-stage compression-type liquid dispensing system for R744 according to claim 1, characterized in that: The liquid addition system also includes a cooling unit (70), which is connected to the heat exchange coil (11) of the liquid storage tank (10) via a pressure pump (71) and a tenth switch valve (V10).

4. The method for a single-stage compression-type liquid dispensing system for R744 according to claim 3, characterized in that: A level gauge (12), a safety valve (13), and a camera (14) for video monitoring of the liquid inside the tank are installed at the storage tank (10).

5. The method for a single-stage compression-type dispensing system for R744 according to claim 1, characterized in that: The flow pump (31) is a plunger pump.

6. The method for a single-stage compression-type dispensing system for R744 according to claim 1, characterized in that: The return pipe section (40) is also equipped with a one-way valve (CV).

7. The method for a single-stage compression-type dispensing system for R744 according to claim 1, characterized in that: All switching valves are automatic valves.

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