A refrigeration system and control method based on a three-pipe energy storage device

Abstract

This invention discloses a refrigeration system and control method based on a three-pipe energy storage device, comprising: a high-temperature stage circulation system for ice making and hot water supply; a low-temperature stage circulation system for freezing or quick-freezing; and a three-pipe energy storage device coupling the high-temperature stage circulation system and the low-temperature stage circulation system. The energy storage device includes: an evaporator cooling pipe section connected to the high-temperature stage circulation system as an evaporator; a condenser liquefaction pipe section connected to the low-temperature stage circulation system as a condenser; and a start-up pipe connected in parallel with the evaporator cooling pipe section. The inlet and outlet of the start-up pipe and the evaporator cooling pipe section are connected to anti-liquid slugging components. This invention seamlessly connects and coordinates the high- and low-temperature stage circulation systems through the evaporator cooling pipe section and the condenser liquefaction pipe section, enabling them to operate independently to meet specific needs while also working collaboratively to optimize overall performance. Furthermore, the addition of the start-up pipe and corresponding anti-liquid slugging components significantly reduces the risk of liquid refrigerant entering the compressor.

Description

Technical Field

[0001] This invention relates to the field of refrigeration technology, and in particular to a refrigeration system and control method based on a three-pipe energy storage device. Background Technology

[0002] In the CO2 refrigeration cycle, the refrigerant absorbs heat from the environment in the evaporator, gradually transforming from a low-temperature, low-pressure liquid refrigerant into a low-temperature, low-pressure gaseous refrigerant. Simultaneously, the surrounding humid air cools, achieving a refrigeration effect. Subsequently, the gaseous CO2 is sent to the compressor to complete the compression process, resulting in a significant increase in both temperature and pressure. Then, in the air cooler (condenser), the high-temperature, high-pressure CO2 refrigerant gradually cools down by exchanging heat with the cooling medium (air cooling or water cooling). Finally, after passing through the expansion valve, both temperature and pressure decrease, forming a low-temperature, low-pressure gas-liquid mixture that re-enters the evaporator to begin a new refrigeration cycle. To fully utilize peak-valley electricity differences and improve energy efficiency, an energy storage device is added to the CO2 refrigeration system to pre-store ice. Without this energy storage device, after the unit stops, the CO2 equilibrium pressure can be maintained at 5-6 MPa, with a saturation temperature of 14-22℃. This means that under normal temperature conditions, the CO2 refrigerant often remains in a gaseous state. However, after adding an energy storage device, the 5-6 MPa gaseous carbon dioxide will gradually condense in the energy storage device (such as an ice storage tank) to a gas-liquid saturation state of around 0°C. At this time, if the compressor is started directly, some refrigerant will not undergo complete phase change in the evaporator, and the unevaporated liquid refrigerant flowing back to the compressor may cause liquid slugging risk.

[0003] The Chinese patent document "An Ice Storage and Cold Storage Pool and Its Transcritical and Subcritical Cold Storage Refrigeration System," publication number CN119196971A, published on December 27, 2024, discloses an ice storage and cold storage pool. Transcritical and subcritical heat exchange tubes are arranged within the ice storage and cold storage pool. The transcritical and subcritical refrigeration units exchange heat with the ice storage and cold storage pool through these tubes. During transcritical refrigeration, the carbon dioxide refrigerant in the transcritical heat exchange tubes evaporates and stores the cooling energy as ice in the ice storage tank. During subcritical refrigeration, the subcritical refrigeration unit provides cooling energy to the subcritical refrigeration cycle by melting the ice layer, causing the gaseous carbon dioxide refrigerant in the subcritical heat exchange tubes to liquefy. The ice storage and cold storage pool effectively connects the transcritical and subcritical refrigeration units, enabling independent operation of the transcritical and subcritical refrigeration units and multi-temperature zone refrigeration. While this technology can control the system based on the amount of ice stored and the cooling demand, it lacks specific technology for determining the amount of ice stored. Furthermore, even after setting up an energy storage device, it fails to provide technology to prevent liquid slugging after the compressor stops and restarts. Summary of the Invention

[0004] The present invention aims to overcome the problem in the prior art where, after adding an energy storage device, the gaseous carbon dioxide refrigerant gradually condenses into a gas-liquid saturated state in the energy storage device, which makes the compressor prone to liquid slugging after shutdown and restart. The invention provides a refrigeration system and control method based on a three-pipe energy storage device.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: A refrigeration system based on a three-pipe energy storage device includes: a high-temperature stage circulation system for ice making and hot water supply; and a low-temperature stage circulation system for freezing or quick-freezing. A three-pipe energy storage device coupling and connecting a high-temperature stage circulation system and a low-temperature stage circulation system, the energy storage device comprising: The evaporative heat dissipation pipe section is connected to the high-temperature circulating system as an evaporator. The condensate liquefaction pipe section is connected as a condenser in the low-temperature stage circulation system; The start-up tube is connected in parallel with the evaporative cooling tube section, and the inlet and outlet connections of the start-up tube and the evaporative cooling tube section are equipped with anti-liquid hammer components.

[0006] In this invention, the three-pipe energy storage device is not only an energy storage unit but also a core hub for efficient system coupling and control. It seamlessly connects and coordinates the transcritical high-temperature stage circulation system and the subcritical low-temperature stage circulation system through evaporation and heat dissipation pipes and condensation and liquefaction pipes within the energy storage device. This allows them to operate independently to meet specific needs while also working collaboratively to optimize overall performance. Simultaneously, a closed-loop control system is constructed by adding a start-up pipe and corresponding anti-liquid slugging components. This effectively collects the liquid refrigerant condensed during compressor standby and prioritizes guiding gaseous refrigerant into the compressor via the start-up pipe during restart. Combined with dynamic pressure adjustment by the anti-liquid slugging components, this significantly reduces the risk of liquid refrigerant entering the compressor, fundamentally preventing compressor liquid slugging accidents. This greatly extends the lifespan of critical equipment and improves the overall system reliability and energy efficiency.

[0007] Preferably, the anti-liquid-smashing component includes a gas-liquid separator, the inlet of which is connected to the high-temperature stage outlet of the energy storage device, and the high-temperature stage outlet includes the outlet of the evaporative heat dissipation pipe section and the outlet of the start-up pipe. The gas outlet of the gas-liquid separator is connected to the inlet of the high-temperature compressor in the high-temperature circulating system; The liquid refrigerant in the gas-liquid separator flows out from the liquid outlet and returns to the energy storage device through the connecting microtube.

[0008] Preferably, the anti-liquid hammer assembly further includes a start valve and a high-temperature expansion valve, wherein the outlet of the high-temperature expansion valve is connected to the inlet of the start valve and the high-temperature inlet of the energy storage device, and the outlet of the start valve is connected to the high-temperature inlet of the energy storage device. The high-temperature stage inlet includes the inlet of the evaporative cooling tube section and the inlet of the start-up tube.

[0009] Preferably, the starting tube is disposed above the evaporative heat dissipation tube section, and the ratio of the number of starting tubes to the number of evaporative heat dissipation tube sections is within a preset ratio range. The vertical height of the start valve is higher than that of the high-temperature expansion valve, and the difference in horizontal distance between the two is less than the preset distance threshold.

[0010] Preferably, the refrigeration system further includes a temperature detection component to detect the temperature in the energy storage device and determine the ice storage capacity; the temperature detection component includes: The eleventh temperature sensor is installed at the high-temperature stage inlet of the energy storage device to detect the refrigerant temperature. The ninth temperature sensor is located at one end of the energy storage device near the high-temperature stage outlet to detect the internal cooling water temperature or ice layer temperature. The tenth temperature sensor is located inside the energy storage device near the outlet of the cryogenic stage to detect the water temperature at the outlet of the cryogenic stage.

[0011] Preferably, in the high-temperature stage circulation system, the refrigerant flowing out of the high-temperature stage outlet of the energy storage device sequentially passes through the high-temperature stage compressor, the high-temperature stage oil separator, the high-temperature stage condenser assembly, and the high-temperature stage expansion valve before flowing into the liquid receiver tank. From the liquid receiver tank, it is then pumped to the high-temperature stage inlet of the energy storage device via a shielded pump. The oil outlet of the high-temperature stage oil separator is connected to the high-temperature stage compressor via the high-temperature stage oil receiver tank; or The refrigerant flowing out of the high-temperature stage outlet first passes through the heat exchanger and then reaches the high-temperature stage compressor. At the same time, the refrigerant flowing out of the high-temperature stage condenser first passes through the heat exchanger and then flows into the liquid receiver tank through the high-temperature stage expansion valve.

[0012] Preferably, in the cryogenic cycle system, the refrigerant flowing out from the cryogenic stage outlet of the energy storage device passes sequentially through the cryogenic stage expansion valve, cryogenic stage evaporator, cryogenic stage compressor, and cryogenic stage oil separator to reach the cryogenic stage inlet of the energy storage device, and the oil outlet of the cryogenic stage oil separator is connected to the cryogenic stage compressor through the cryogenic stage oil storage tank.

[0013] A control method for a refrigeration system based on a three-pipe energy storage device includes: The temperature difference between the refrigerant temperature at the high-temperature stage inlet and the internal ice layer temperature, as well as the water temperature at the low-temperature stage outlet, are detected in the energy storage device. When the temperature difference is less than or equal to the first temperature difference threshold, the ice storage capacity is greater than the first upper limit. If there is a cooling demand, the low-temperature circulation system is started, and the opening of the high-temperature circulation system is determined according to the peak and off-peak electricity periods. When the temperature difference is greater than or equal to the second temperature difference threshold and the water temperature is greater than or equal to the first temperature threshold, and the ice storage capacity is less than the first lower limit, if there is a cooling demand, the low-temperature circulation system and the high-temperature circulation system will be started simultaneously; otherwise, the start of the high-temperature circulation system will be determined according to the peak and off-peak electricity periods.

[0014] Preferably, before restarting the high-temperature stage circulation system after it has been shut down for more than a preset time, the start valve is opened first, and the gaseous refrigerant flows into the gas-liquid separator through the start pipe; the gas-liquid separator introduces the gaseous refrigerant into the high-temperature stage compressor, while the liquid refrigerant flows back to the energy storage device through the connecting microtube; the suction pressure of the high-temperature stage compressor is monitored, and when the suction pressure is greater than or equal to the preset pressure threshold, the start valve is closed.

[0015] Preferably, when the compressor lubricating oil level is lower than the safe value, the solenoid valve between the oil separator and the oil tank is opened to introduce the lubricating oil into the oil tank; after closing the solenoid valve, the solenoid valve between the oil tank and the compressor is opened to allow the lubricating oil to flow back to the compressor through the oil filter; after the oil return is completed, the corresponding solenoid valve is closed and the excess pressure in the oil tank is released.

[0016] Compared with the prior art, the present invention has the following beneficial effects: 1. By setting up a parallel architecture design for energy storage devices and refrigeration / heating systems, the high-temperature refrigeration cycle system and the low-temperature refrigeration cycle system are coupled and highly integrated into the same system. This simplifies the complex structure of traditional cascade or two-stage compression systems, reduces equipment costs and maintenance difficulty, and also meets the wide-temperature range requirements for combined cooling and heating and rapid ice making, including high-temperature hot water supply (60-90℃), rapid ice making (-5℃-0℃), and low-temperature freezing and quick-freezing (-20 / -40℃).

[0017] 2. By adding a start-up pipe to the energy storage device, and forming a closed-loop control system with the start-up valve, gas-liquid separator, and connecting micro-pipe, the condensate is collected by gravity to the bottom pipe and gas-liquid separator during standby. When restarting, the gaseous refrigerant is preferentially introduced into the compressor after passing through the start-up pipe and gas-liquid separator. Combined with the start-up valve opening and closing logic control, the system pressure is dynamically regulated, thereby achieving the three core requirements of preventing liquid slugging, stabilizing pressure, and optimizing control strategy.

[0018] 3. Utilizing off-peak electricity periods for ice storage and cold storage strategies enables efficient direct expansion ice-making energy storage, effectively reducing the operating costs of low-temperature refrigeration systems during peak electricity consumption periods while meeting the demand for rapid ice making. By indirectly determining the ice storage capacity through temperature measurement and temperature difference, the process of identifying the energy state is simplified, and it is easy to embed peak and off-peak electricity periods into the system's operation control logic, thereby achieving time-shifted scheduling of energy storage resources and optimizing system economics. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the refrigeration system based on a three-pipe energy storage device in this invention.

[0020] Figure 2 This is a schematic diagram of the anti-liquid-smashing component in the energy storage device of the present invention.

[0021] Figure 3 This is a schematic diagram of the high-temperature stage circulation system in this invention.

[0022] Figure 4 This is a schematic diagram of the low-temperature stage circulation system in this invention.

[0023] Figure 5 This is a flowchart of the control method for the refrigeration system based on a three-pipe energy storage device in this invention.

[0024] Figure 6 This is a control flowchart for preventing liquid slugging during compressor restart in this invention.

[0025] Figure 7 This is the control flowchart of the high-temperature stage circulation system in this invention.

[0026] Figure 8 This is a flowchart of the oil return control process for the high-temperature circulating system in this invention.

[0027] Figure 9 This is the control flowchart of the low-temperature stage circulation system in this invention.

[0028] Figure 10 This is a flowchart of the oil return control process for the low-temperature circulating system in this invention.

[0029] In the diagram: 1. Energy storage device; 101. High-temperature stage inlet; 102. High-temperature stage outlet; 103. Low-temperature stage inlet; 104. Low-temperature stage outlet; 105. Ice-making module; 106. Low-temperature stage evaporator inlet; 107. Low-temperature stage evaporator outlet; 1011. First low-temperature stage dryer filter; 1012. First low-temperature stage expansion valve; 1013. First low-temperature stage flow meter; 1014. Second low-temperature stage dryer filter; 1015. Second low-temperature stage expansion valve; 1016. Second low-temperature stage flow meter; 2. Heat exchanger; 201. Heat exchanger inlet; 202. Heat exchanger outlet; 3. Hot water recovery unit; 31. Cold water inlet; 32. Hot water outlet; 4. Air cooler; 41. Cooling water inlet; 5. Liquid storage tank. 51. Liquid level sensor; 52. Shielded pump; 53. High-temperature flow meter; 54. Safety valve; 55. High-temperature expansion valve; 56. First high-temperature drying filter; 57. Check valve; 6. High-temperature oil separator; 7. High-temperature oil storage tank; 71. High-temperature oil filter; 8. High-temperature compressor; 9. First low-temperature oil separator; 10. Second low-temperature oil separator; 11. First low-temperature oil storage tank; 1101. First low-temperature oil filter; 12. Second low-temperature oil storage tank; 1201. Second low-temperature oil filter; 13. Low-temperature compressor; 14. Evaporator cooling pipe section; 15. Condensation liquefaction pipe section; 16. Start-up pipe; 18. Start-up valve; 19. Gas-liquid separator; 20. Connecting microtube. Detailed Implementation

[0030] The present invention will now be further described with reference to the accompanying drawings and specific embodiments.

[0031] like Figure 1 As shown, a refrigeration system based on a three-pipe energy storage device includes: a high-temperature stage circulation system for ice making and hot water supply; and a low-temperature stage circulation system for freezing or quick-freezing. A three-pipe energy storage device coupling and connecting a high-temperature stage circulation system and a low-temperature stage circulation system, the energy storage device comprising: Evaporative heat dissipation tube section 14 is connected as an evaporator in the high-temperature circulating system; The condensate liquefaction pipe section 15 is connected as a condenser in the low-temperature stage circulation system; The start-up pipe 16 is connected in parallel with the evaporative cooling pipe section 14, and the inlet and outlet of the start-up pipe 16 and the evaporative cooling pipe section 14 are connected with anti-liquid hammer components.

[0032] In this invention Figure 1 The dashed box A represents the cryogenic cycle system. Figure 1The dashed box B represents the high-temperature stage circulation system. The three-pipe energy storage device is not only an energy storage unit but also a core hub for efficiently coupling the two circulation systems and control. It seamlessly connects and coordinates the transcritical high-temperature stage circulation system and the subcritical low-temperature stage circulation system through evaporation and liquefaction pipes within the energy storage device, enabling them to operate independently to meet specific needs while also working collaboratively to optimize overall performance. Simultaneously, a closed-loop control system is constructed by adding a start-up pipe and corresponding anti-liquid slugging components. This effectively collects the liquid refrigerant condensed during compressor standby and prioritizes guiding gaseous refrigerant into the compressor via the start-up pipe during restart. Combined with dynamic pressure adjustment by the anti-liquid slugging components, this significantly reduces the risk of liquid refrigerant entering the compressor, fundamentally preventing compressor liquid slugging accidents. This greatly extends the lifespan of critical equipment and improves the overall system reliability and energy efficiency.

[0033] As a specific example, such as Figure 2 As shown, the anti-liquid slugging component includes a gas-liquid separator 19 and a connecting microtube 20 located at the rear end of the energy storage device, and a start-up valve 18 and a high-temperature expansion valve 55 located at the front end of the energy storage device. The energy storage device is equipped with a three-pipe structure. The three-pipe structure includes several evaporative cooling pipe sections 14, several start-up pipes 16, and several condensation liquefaction pipe sections 15.

[0034] The inlet of the condensate liquefaction pipe section 15 corresponds to the cryogenic stage inlet 103 of the energy storage device 1, and the outlet of the condensate liquefaction pipe section 15 corresponds to the cryogenic stage outlet 104 of the energy storage device 1.

[0035] The outlet of the evaporator cooling pipe section 14 and the outlet of the start-up pipe 16 are connected as the high-temperature stage outlet of the energy storage device, and connected to the inlet of the gas-liquid separator 19; the inlet of the evaporator cooling pipe section 14 and the inlet of the start-up pipe 16 are connected as the high-temperature stage inlet of the energy storage device, and connected to the outlet of the high-temperature stage expansion valve 55 and the outlet of the start-up valve 18. The gas outlet of the gas-liquid separator 19 is connected to the inlet of the high-temperature stage compressor in the high-temperature stage circulation system; the liquid refrigerant in the gas-liquid separator 19 flows out from the liquid outlet and returns to the energy storage device 1 through the connecting microtube 20.

[0036] The inlet of the start valve 18 is connected to the outlet of the high-temperature expansion valve 55, and the inlet of the high-temperature expansion valve 55 is connected to the outlet of the high-temperature condenser assembly or the heat exchanger outlet according to the specific circulation path of the high-temperature circulation system.

[0037] Furthermore, the start-up pipe 16 is positioned above the evaporative heat dissipation pipe section 14, and the ratio of the number of start-up pipes 16 to the number of evaporative heat dissipation pipe sections 14 is within a preset ratio range. For example, the number of start-up pipes 16 is 15% to 20% of the number of evaporative heat dissipation pipe sections 14. The vertical height of the start-up valve 18 is higher than that of the high-temperature expansion valve 55, and the difference in horizontal distance between the two is less than a preset distance threshold.

[0038] This invention utilizes a three-pipe energy storage device to couple high-temperature and low-temperature refrigeration systems, achieving rapid ice making (energy storage) and preventing compressor liquid slugging. This is due to the multiple functions of its internal coil system. The condensation liquefaction pipe section 15 is used for heat dissipation in the low-temperature circulation system. During rapid ice making, the evaporation heat dissipation pipe section 14 and the start-up pipe 16 play two roles. First, after the refrigeration system is operating normally and stably, the refrigerant evaporation absorbs heat, dissipating heat from the cooling water outside the refrigeration pipes (including the evaporation heat dissipation pipe section and the start-up pipe) and achieving rapid freezing. Second, when the ice pool is temporarily full of ice or the high-temperature circulation system needs to be temporarily shut down, the refrigeration pipe is divided into two parts (i.e., the evaporation heat dissipation pipe section 14 and the start-up pipe 16), thereby preventing liquid slugging when the compressor needs to be restarted after a short shutdown.

[0039] The specific process is as follows: When the high-temperature stage circulation system is temporarily shut down, the remaining high-temperature, high-pressure gaseous CO2 refrigerant in the high-temperature stage compressor will slowly condense and liquefy upon encountering cold. At this time, due to the shutdown of the high-temperature stage compressor, the high-temperature stage expansion valve will also be temporarily closed (i.e., the opening of the expansion valve is adjusted to 100%, which is equivalent to a straight-through pipe). Part of the CO2 gaseous refrigerant at the heat exchanger outlet will directly pass through the high-temperature stage expansion valve (the expansion valve remains energized but its opening is 100%) and the starting valve into the starting pipe used to prevent liquid slugging when the unit is restarted, and the number of starting pipes accounts for about 15% of the total number of evaporator heat dissipation pipe sections; the other part will normally pass through the expansion valve and enter the evaporator heat dissipation pipe section. During the shutdown of the high-temperature stage circulation system, the high-temperature, high-pressure CO2 refrigerant will slowly condense after passing through the ice pool and remain in the evaporator heat dissipation pipe section.

[0040] During installation, ensure that the high-temperature expansion valve and the starting valve are located on the same vertical plane as much as possible, and that the height of the high-temperature expansion valve is lower than that of the starting valve. This arrangement facilitates the rapid entry of gaseous CO2 refrigerant into the starting pipe via the starting valve. Upon restarting the high-temperature circulation system, the gaseous CO2 refrigerant, after passing through the gas-liquid separator for gas-liquid separation, ultimately returns to the high-temperature compressor via the upper pipe, with the predominantly gaseous CO2 refrigerant. A connecting micro-tube is connected to the gas-liquid separator to return the liquid refrigerant accumulated in the separator to the energy storage device.

[0041] Furthermore, the refrigeration system of the present invention also includes a temperature detection component to detect the temperature in the energy storage device and determine the ice storage amount; the temperature detection component includes: The eleventh temperature sensor T11 is installed at the high-temperature stage inlet 101 of the energy storage device 1 to detect the refrigerant temperature; The ninth temperature sensor T9 is located inside the energy storage device 1 near the high-temperature stage outlet 102 to detect the internal cooling water temperature or ice layer temperature. The tenth temperature sensor T10 is installed in the energy storage device 1 at one end near the low temperature stage outlet 104 to detect the water temperature on the low temperature stage outlet side.

[0042] The energy storage device (acting as an evaporator and condenser, serving as the evaporator in the high-temperature stage circulation system and the condenser in the low-temperature stage circulation system) has multiple sets of start-up pipe sections arranged from top to bottom, combining low-temperature evaporation, condensation heat dissipation, and liquid slugging prevention functions. The low-temperature refrigerant flows in through the pipe at the right-side high-temperature stage inlet 101 and flows out through the pipe at the left-side high-temperature stage outlet 102. During this process, the low-temperature refrigerant, initially at -5℃, continuously absorbs heat and vaporizes, gradually increasing its temperature; after reaching saturation temperature, it continues to be heated by the water temperature, potentially leading to a superheated state at the outlet.

[0043] During this process, the energy storage device releases the most cold energy to the cooling water in the refrigerant inlet area. As the refrigerant absorbs heat along the flow direction, its temperature gradually rises, and its heat absorption gradually decreases. Therefore, the freezing process starts from the inlet and gradually expands along the refrigerant flow direction, eventually achieving complete freezing inside the energy storage device.

[0044] Conventional ice melting processes are divided into two types: external ice melting and internal ice melting. In external ice melting, the terminal chilled water circulates within the ice tank, directly exchanging heat with the ice surface. Ice melting proceeds from the outside in, with the ice layer thickness gradually decreasing. In internal ice melting, high-temperature, high-pressure refrigerant gas from the cryogenic stage compressor enters through the cryogenic stage inlet 103 and undergoes heat exchange within the condenser cooling pipes. The melting direction is from the inside out. Due to the buoyancy of the liquid water outside the coils, the ice remains in contact with the coils. Similar to the freezing process, the energy storage device releases the most heat at the cryogenic stage inlet section 103, decreasing progressively along the flow direction. This results in the ice layer in the inlet area being almost completely melted, while solid ice may still remain on the outer layer of the cryogenic stage outlet section 104.

[0045] Therefore, this invention installs a temperature sensor T11 at the inlet of the evaporative cooling pipe section 14 (corresponding to the high-temperature stage inlet 101) to monitor the inlet temperature of the cryogenic refrigerant in real time; simultaneously, temperature sensors T9 and T10 are arranged at both ends inside the energy storage device 1 to monitor the ice layer temperature and internal water temperature changes, respectively, to comprehensively determine the freezing and melting process. By analyzing the temperature difference between the refrigerant temperature at the high-temperature stage inlet 101 and the ice layer inside the high-temperature stage outlet 102, the amount of ice formation can be accurately assessed; based on the temperature monitoring at the cryogenic stage outlet 104 inside the energy storage device, the melting state can be effectively determined.

[0046] As a specific example, such as Figure 3 As shown, the high-temperature stage circulation system includes a high-temperature stage compressor 8, a high-temperature stage oil separator 6, a high-temperature stage condenser assembly, a high-temperature stage expansion valve 55, a liquid storage tank 5, a shielded pump 52, and related sensors and control valves.

[0047] The high-temperature stage outlet 102 of the energy storage device 1 is connected to the inlet of several parallel high-temperature stage compressors 8. A temperature sensor T3 is installed near the high-temperature stage outlet 102, and a pressure sensor P7 is installed near the inlet of each high-temperature stage compressor 8. The outlet of the high-temperature stage compressor 8 is connected to the inlet of the high-temperature stage oil separator 6, and a pressure sensor P1 is installed on the connecting pipe between the two. The gas outlet of the high-temperature stage oil separator 6 is connected to the first high-temperature stage dryer filter 56 through the high-temperature stage condenser assembly, and then connected to the first inlet of the liquid storage tank 5 through the high-temperature stage expansion valve 55. The first outlet of the liquid storage tank 5 is connected to the high-temperature stage flow meter 53 through the shielded pump 52, and then connected to the high-temperature stage inlet 101.

[0048] The high-temperature stage condenser assembly includes an air cooler 4 and a hot water recovery unit 3. The gas outlet of the high-temperature stage oil separator 6 flows into the refrigerant inlet of the hot water recovery unit via a solenoid valve YV1 and flows out from the refrigerant outlet of the hot water recovery unit to the first high-temperature stage dryer filter 56. Cold water to be heated (e.g., water at 20 degrees Celsius) enters the hot water recovery unit 3 from the cold water inlet 31 via a solenoid valve YV14, and heated water (e.g., water at 90 degrees Celsius) flows out from the hot water outlet 32. A temperature sensor T1 is installed at the hot water outlet 32. The refrigerant and the water to be heated exchange heat in the hot water recovery unit.

[0049] The gas outlet of the high-temperature oil separator 6 also enters the air cooler 4 through the solenoid valve YV2, and then flows out from the outlet of the air cooler 4 to the first high-temperature dryer filter 56. A temperature sensor T2 is installed at the outlet of the air cooler 4. The air cooler 4 adopts evaporative cooling. Cooling water entering from the cooling water inlet 41 enters the spray pipe network after passing through the solenoid valve YV15. Then, the cooling water is evenly sprayed on the outer surface of the heat exchange pipes through the precisely designed spray pipe network, forming a continuous thin water film and gradually wetting the pipe wall. Heat is carried away by the evaporation of the cooling water.

[0050] The oil outlet of the high-temperature oil separator 6 is connected to the inlet of the high-temperature oil storage tank 7 via a solenoid valve YV3. A pressure sensor P2 is installed in the high-temperature oil storage tank 7. The first outlet below the high-temperature oil storage tank 7 is connected to the high-temperature compressor 8 via a high-temperature oil filter 71 and a solenoid valve YV6. The second outlet above the high-temperature oil storage tank 7 is connected to the upper side of the liquid storage tank 5 via a solenoid valve YV4. A level sensor 51 is installed in the liquid storage tank 5. The outlet of the shielded pump 52 is connected back to the upper side of the liquid storage tank 5 via a safety valve 54. The lower side of the liquid storage tank 5 is connected to the inlet of the high-temperature flow meter 53 via a check valve 57.

[0051] All dryer filters are used to remove moisture and impurities from the refrigerant. The oil filter filters impurities to keep the lubricating oil clean. The oil separator separates the lubricating oil from the high-pressure vapor discharged from the compressor and returns it to the compressor. The oil tank is connected to the liquid receiver tank at the top via the exhaust pipe and to the compressor at the bottom via the return oil pipe.

[0052] Optionally, the high-temperature stage circulation system also includes a heat exchanger 2. The refrigerant flowing from the high-temperature stage outlet 102 first enters the heat exchanger 2 through the solenoid valve YV13, and then flows out of the heat exchanger 2 to reach the high-temperature stage compressor 8. Simultaneously, the refrigerant flowing from the high-temperature stage condenser assembly first passes through the heat exchanger 2 and then flows into the liquid receiver 5. Specifically, the refrigerant flowing from the hot water recovery unit 3 or the air cooler 4 enters the heat exchanger 2 through the solenoid valve YV5 from the heat exchanger inlet 201, and flows from the heat exchanger outlet 202 into the first high-temperature stage dryer filter 56.

[0053] The high-temperature transcritical cycle is primarily responsible for rapid ice making (-5℃ to 0℃) and industrial or domestic hot water supply (90℃), and can meet different cooling / heating supply needs through the opening and closing of solenoid valves. In the high-temperature transcritical refrigeration cycle system, the high-temperature stage compressor is a CO2 reciprocating type, the gas cooler is an evaporative cooling radiator, the high-temperature stage expansion valve is an electronic expansion valve, and a liquid level sensor is installed on the liquid storage tank. During the operation of the high-temperature stage refrigeration cycle, the energy storage device acts as the evaporator of the high-temperature stage cycle system, and the high-temperature stage inlet and outlet are connected to the outlet of the shielded pump and the inlet of the heat exchanger / high-temperature stage compressor, respectively. Inside the energy storage device, the low-temperature, low-pressure CO2 refrigerant exchanges heat with water to achieve rapid ice making, and the solid ice content exceeds 70%. In addition, the hot water recovery unit is a shell-and-tube heat exchanger, whose structure includes a cylindrical shell, heat exchange coils, and hot and cold water inlet and outlet pipes. The high-temperature and high-pressure CO2 refrigerant discharged from the high-temperature stage compressor flows in the heat exchange coils and fully exchanges heat with the municipal cold water supplied in the shell, thereby meeting the supply needs of industrial or domestic hot water and realizing the efficient recovery and utilization of waste heat.

[0054] As a specific example, such as Figure 4 In the cryogenic cycle system shown, the refrigerant flowing from the cryogenic stage outlet 104 of the energy storage device 1 passes sequentially through the cryogenic stage expansion valve, cryogenic stage evaporator, cryogenic stage compressor, and cryogenic stage oil separator to reach the cryogenic stage inlet 103 of the energy storage device. The oil outlet of the cryogenic stage oil separator is connected to the cryogenic stage compressor through a cryogenic stage oil storage tank. An ice-making module 105 is also provided in the energy storage device 1.

[0055] The cryogenic cycle system of this invention is applied to cryogenic freezing / quick freezing (minus 20 / 40°C). The cryogenic compressor is a CO2 subcritical reciprocating compressor. The energy storage device (evaporator-condenser) serves as the condenser of the cryogenic cycle system, used for refrigerant condensation and heat dissipation. Based on different application scenarios of the cryogenic cycle system, this system will have at least two cryogenic refrigeration cycle units, one for refrigeration at -20°C and the other for refrigeration at -40°C, with the two units having essentially the same configuration.

[0056] Specifically, in the -20°C refrigeration unit, the refrigerant flowing from the low-temperature stage outlet 104 of the energy storage device sequentially passes through the first low-temperature stage dryer filter 1011, the first low-temperature stage expansion valve 1012, and the first low-temperature stage flow meter 1013 before entering the evaporator through the low-temperature stage evaporator inlet 106. A temperature sensor T4 is installed in the passage between the low-temperature stage outlet 104 and the first low-temperature stage dryer filter 1011, a temperature sensor T8 is installed in the passage between the first low-temperature stage expansion valve 1011 and the first low-temperature stage flow meter 1013, and a pressure sensor P10 is installed at the outlet of the first low-temperature stage flow meter 1013. After flowing through the evaporator located in the required -20°C refrigeration space, the refrigerant flows from the low-temperature stage evaporator outlet 107 to the inlet of several parallel low-temperature stage compressors 13. A pressure sensor P9 is installed at the inlet of the low-temperature stage compressors 13. The outlet of the cryogenic compressor 13 is connected to the inlet below the first cryogenic oil separator 9, and a pressure sensor P3 is installed on the outlet of the cryogenic compressor 13. The gas outlet of the first cryogenic oil separator 9 is connected to the cryogenic inlet 103 of the energy storage device 1. The oil outlet located below the first cryogenic oil separator 9 is connected to the inlet above the first cryogenic oil storage tank 11 via a solenoid valve YV7. The outlet below the first cryogenic oil storage tank 11 is connected to the cryogenic compressor 13 via a first cryogenic oil filter 1101 and a solenoid valve YV8. The gas outlet above the first cryogenic oil storage tank 11 is connected back to the cryogenic compressor 13.

[0057] In the -40°C refrigeration unit, refrigerant flowing from the low-temperature stage outlet 104 of the energy storage device passes sequentially through the second low-temperature stage dryer filter 1014, the second low-temperature stage expansion valve 1015, and the second low-temperature stage flow meter 1016 before entering the evaporator through the low-temperature stage evaporator inlet 106. A temperature sensor T5 is installed in the passage between the low-temperature stage outlet 104 and the second low-temperature stage dryer filter 1014, and a temperature sensor T7 is installed in the passage between the second low-temperature stage expansion valve 1015 and the second low-temperature stage flow meter 1016. A pressure sensor P12 is installed at the outlet of the second low-temperature stage flow meter 1016. After flowing through the evaporator located within the required -40°C refrigeration space, the refrigerant flows from the low-temperature stage evaporator outlet 107 to the inlet of several parallel low-temperature stage compressors 13. A pressure sensor P11 is installed at the inlet of each low-temperature stage compressor 13. The outlet of the low-temperature stage compressor 13 is connected to the inlet below the second low-temperature stage oil separator 10, and a pressure sensor P4 is installed at the outlet of the low-temperature stage compressor 13. The gas outlet of the second cryogenic oil separator 10 is connected to the cryogenic inlet 103 of the energy storage device 1. The oil outlet located below the second cryogenic oil separator 10 is connected to the inlet above the second cryogenic oil storage tank 12 via a solenoid valve YV11. The outlet below the second cryogenic oil storage tank 12 is connected to the cryogenic compressor 13 via a second cryogenic oil filter 1201 and a solenoid valve YV8. The gas outlet above the second cryogenic oil storage tank 12 is connected back to the cryogenic compressor 13.

[0058] All dryer filters are used to remove moisture and impurities from the refrigerant, while the oil separator separates the lubricating oil from the high-pressure vapor discharged from the compressor and returns it to the compressor. The oil receiver is connected to the liquid receiver at the top via an exhaust pipe and to the compressor at the bottom via an oil return pipe.

[0059] In addition to providing a refrigeration system based on a three-pipe energy storage device, this invention also provides, as well as... Figure 5 The control method for a refrigeration system based on a three-pipe energy storage device, as shown, includes: At fixed intervals, the temperature difference between the refrigerant temperature at the high-temperature stage inlet and the internal ice layer temperature, as well as the water temperature at the low-temperature stage outlet, are measured. When the temperature difference is less than or equal to the first temperature difference threshold, the ice storage capacity is greater than the first upper limit. If there is a cooling demand, the low-temperature circulation system is started, and the opening of the high-temperature circulation system is determined according to the peak and off-peak electricity periods. When the temperature difference is greater than or equal to the second temperature difference threshold and the water temperature is greater than or equal to the first temperature threshold, the ice storage capacity is less than the first lower limit. If there is a cooling demand, the low-temperature circulation system and the high-temperature circulation system will be started at the same time. Otherwise, the start of the high-temperature circulation system will be determined according to the peak and off-peak electricity periods. When the temperature difference is greater than the first temperature difference threshold and less than the second temperature difference threshold, or when the temperature difference is greater than or equal to the second temperature difference threshold but the water temperature is less than the first temperature threshold, and the ice storage capacity is less than or equal to the first upper limit value, if there is a cooling demand, the low-temperature stage circulation system is started, and the opening of the high-temperature stage circulation system is determined according to the peak and off-peak electricity periods. If there is no cooling demand, the opening of the high-temperature stage circulation system is determined directly according to the peak and off-peak electricity periods.

[0060] Based on the structural diagram of the refrigeration system of the three-pipe energy storage device in this invention, the refrigerant temperature at the high-temperature stage inlet of the energy storage device is detected by temperature sensor T11, the ice layer temperature inside the energy storage device is detected by temperature sensor T9, and the water temperature at the low-temperature stage outlet of the energy storage device is detected by temperature sensor T10.

[0061] Specifically, by analyzing the temperature difference between the refrigerant at the high-temperature stage inlet and the ice layer inside the high-temperature stage outlet of the energy storage device, the amount of icing can be accurately assessed; and by monitoring the temperature at the low-temperature stage outlet inside the energy storage device, the melting state can be effectively determined.

[0062] When the temperature difference between the refrigerant at the high-temperature stage inlet and the ice layer at the high-temperature stage outlet is less than or equal to 5°C, the ice storage capacity in the energy storage device is considered to have reached 90%. At this time, if there is a demand for low-temperature freezing / quick-freezing, the low-temperature stage circulation system (subcritical low-temperature compression refrigeration cycle) is activated. At the same time, depending on whether it is a peak electricity period, it is determined whether to activate the high-temperature stage circulation system (high-temperature rapid ice making-energy storage cycle). If there is no demand for low-temperature quick-freezing / freezing, both the high-temperature stage circulation system and the low-temperature stage circulation system stop operating (both transcritical and subcritical refrigeration units stop operating). Furthermore, when the temperature at temperature sensor T10 is greater than or equal to 2°C, or the temperature difference between temperature sensors T9 and T11 is greater than or equal to 12°C, the ice storage capacity in the energy storage device is considered to be less than 20%, indicating low energy storage. Subsequently, if there is a need for low-temperature freezing / quick freezing, both the high-temperature and low-temperature circulation systems are simultaneously activated. Conversely, if there is no need for low-temperature quick freezing / freezing, the activation of the high-temperature circulation system is determined again based on whether it is during off-peak electricity hours. If there is neither a need for low-temperature quick freezing nor during peak electricity hours, both the high-temperature and low-temperature circulation systems are shut down. In addition to the above two situations, when the temperature difference between temperature sensors T9 and T11 is between 5°C and 12°C, or when the temperature difference between T9 and T11 is greater than or equal to 12°C but the temperature at T10 is less than 2°C, the ice storage capacity is between 20% and 90%. If there is a demand for low-temperature quick-freezing / freezing at this time, the low-temperature circulation system will be activated. At the same time, depending on whether it is an off-peak electricity period, it will be determined whether to activate the high-temperature circulation system. If there is no demand for low-temperature quick-freezing / freezing at this time, it will be determined whether to activate the high-temperature circulation system based on whether it is an off-peak electricity period.

[0063] When the CO2 high-temperature circulating system of this invention is applied to rapid ice making and hot water supply, the system operation process is as follows: When recovering waste heat from compressor exhaust for industrial or domestic hot water supply, the low-temperature, low-pressure CO2 refrigerant is first compressed by a high-temperature compressor (transcritical compressor) to reach a supercritical state, and then transported to a high-temperature oil separator. In the high-temperature oil separator, lubricating oil is efficiently separated from the high-pressure vapor and returned to the high-temperature compressor to ensure the normal and continuous operation of the compressor unit. Subsequently, the high-temperature, high-pressure exhaust from the high-temperature compressor is connected to a hot water recovery unit. The high-temperature, high-pressure exhaust undergoes sufficient heat exchange with municipal cold water in the hot water recovery unit, and the flow rate of cooling water entering the hot water recovery unit is controlled in real time by adjusting the opening of a solenoid valve according to actual domestic or industrial needs. After heat dissipation, the CO2 refrigerant passes through a dryer filter for impurity filtration and then flows through an expansion valve for throttling and pressure reduction. The low-temperature, low-pressure liquid CO2 refrigerant then enters a storage tank for storage.

[0064] However, when there is no demand for hot water, the high-temperature, high-pressure CO2 refrigerant, compressed by the high-temperature stage compressor, flows directly into the air cooler to complete the cooling process. When an evaporative condenser is used as the air cooler, cooling water is evenly sprayed onto the outer surface of the heat exchange pipes through a precisely designed spray system, forming a continuous thin water film that gradually wets the pipe walls. Simultaneously, an axial flow fan located at the top of the equipment activates its suction mode, driving ambient air at a set flow rate across the moistened heat exchange pipe surface. During this process, the water in the water film undergoes an evaporation phase change under the combined effects of airflow and sensible heat exchange, absorbing the heat released by the CO2 refrigerant flowing within the pipes through its latent heat of vaporization, thus lowering the CO2 refrigerant temperature. The medium-temperature, high-pressure CO2 refrigerant, after heat dissipation, flows through the heat exchanger and undergoes a reverse heat exchange with the low-temperature, low-pressure refrigerant gas from the high-temperature stage outlet of the energy storage device, which has already completed the rapid ice-making process, achieving secondary cooling. After heat exchange and with a further reduced temperature, the CO2 refrigerant then flows through a dryer filter, effectively removing impurities and moisture from the system. Subsequently, the refrigerant enters the expansion valve for throttling and pressure reduction, completing the phase change from a medium-temperature, high-pressure liquid to a low-temperature, low-pressure liquid, and finally enters the storage tank for storage.

[0065] The low-temperature, low-pressure gaseous refrigerant in the storage tank is pressurized and delivered to the energy storage device via a shielded pump. At this point, the low-temperature, low-pressure CO2 refrigerant enters the heat exchange coil through the high-temperature stage inlet on the side of the energy storage device. After absorbing heat from the water inside the energy storage device, it gradually vaporizes and flows out through the high-temperature stage outlet. As the refrigerant continuously absorbs heat, water flows continuously on the outer surface of the heat exchange coil and gradually forms an ice layer, storing the cold energy in the form of ice. Over time, the ice layer thickens, eventually forming a solid ice pool with an ice content exceeding 70%. After rapid ice-making, the low-temperature, low-pressure CO2 refrigerant absorbs waste heat from the radiator in the heat exchanger, its temperature rises, and it returns to the high-temperature stage compressor, starting a new cycle.

[0066] When the CO2 low-temperature circulating system of this invention is applied to low-temperature cold storage refrigeration, the system operation process is as follows: In the low-temperature freezing / quick-freezing cold storage, after the humid cold air flows over the surface of the goods and completes the cooling of the goods, it absorbs heat and transforms into humid hot air, which needs further cooling. At this time, the humid hot air flows in through the return air inlet at the bottom of the evaporator, and the axial flow fan promotes heat exchange between the hot humid air and the heat exchange coil in a forced convection manner. During this process, the refrigerant inside the heat exchange coil vaporizes and absorbs heat, taking away the heat from the hot humid air, thereby achieving the cooling of the humid air. Subsequently, the humid cold air flows back into the low-temperature cold storage through the air outlet on the side of the evaporator and is evenly distributed to all corners of the cold storage, ensuring that the temperature inside the cold storage is maintained in a stable and uniform state, thus completing a new round of goods cooling.

[0067] In the low-temperature stage circulation system, when the ice storage device has sufficient ice, ice making through the high-temperature stage circulation system can be temporarily stopped. Subsequently, the low-temperature, low-pressure CO2 refrigerant absorbs heat from the humid and hot air inside the cold storage in the heat exchange coil inside the evaporator and evaporates. The low-temperature, low-pressure gaseous refrigerant then flows sequentially through the low-temperature stage compressor, low-temperature stage oil separator, energy storage device, dryer filter, and expansion valve, thus completing the entire refrigeration cycle.

[0068] Specifically, the low-temperature, low-pressure gaseous CO2 refrigerant, after evaporation and vaporization, flows through the cryogenic compressor (subcritical compressor) and is compressed to a high-temperature, high-pressure state, then flows into the cryogenic oil separator. During this process, the separated lubricating oil flows back into the cryogenic compressor to ensure the normal operation of the equipment. Next, the high-temperature, high-pressure CO2 refrigerant enters the cryogenic inlet of the energy storage device, where it undergoes efficient heat exchange with the solid ice pool formed by the high-temperature circulation system, completing the condensation and heat dissipation process. At this time, based on the principle of ice-water phase change, the solid ice inside the ice pool gradually melts, creating a stable low-temperature environment, thus ensuring that the operating pressure of the cryogenic compressor remains below its critical pressure (7.38 MPa). After completing condensation and heat dissipation, the refrigerant flows through a dryer filter to remove internal moisture and impurities before flowing into the expansion valve for throttling and pressure reduction, and then evaporates and vaporizes in the heat exchange coils within the evaporator. This cycle repeats continuously to meet the refrigeration needs of goods.

[0069] Furthermore, during the condensation and heat dissipation process using the ice pool, if the ice pool's cold storage capacity is insufficient to offset the condensation and heat dissipation during the low-temperature cold storage's refrigeration process, a high-temperature circulating system can be simultaneously activated to continuously and rapidly produce ice, thereby achieving the purpose of cold storage within the energy storage device. During this operation, load fluctuations in the low-temperature cold storage are balanced solely through the transfer of cold energy from the ice pool.

[0070] As a specific example, such as Figure 6 As shown, before restarting the high-temperature stage circulation system after it has been shut down for more than a preset time, the start valve is opened first, and the gaseous refrigerant flows into the gas-liquid separator through the start pipe; the gas-liquid separator introduces the gaseous refrigerant into the high-temperature stage compressor, while the liquid refrigerant flows back to the energy storage device through the connecting microtube; the suction pressure of the high-temperature stage compressor is monitored, and when the suction pressure is greater than or equal to the preset pressure threshold, the start valve is closed.

[0071] In this invention, if the shutdown time exceeds 30 minutes during the operation of the high-temperature stage circulating system, the CO2 refrigerant will condense and liquefy within the energy storage device, forming a saturated two-phase refrigerant at 0°C. Directly starting the high-temperature stage compressor at this time would pose a risk of liquid slugging. Therefore, by installing a start-up pipe in the energy storage device, combined with a gas-liquid separator and connecting microtubes, a large amount of gaseous CO2 can be preferentially introduced into the high-temperature stage compressor during the initial restart phase. During normal stable operation, the start-up valve can be kept closed; it is opened when the high-temperature stage circulating system is shut down.

[0072] The operation process is as follows: After a shutdown of more than 30 minutes, the CO2 refrigerant gradually condenses into a gas-liquid two-phase state in the energy storage device and accumulates at the bottom of the evaporator cooling pipe section under the action of gravity. At this time, the start-up pipe mainly contains gaseous CO2, and liquid refrigerant will also remain at the bottom of the gas-liquid separator, while the upper part contains gaseous refrigerant. Subsequently, before starting the high-temperature stage compressor, the start-up valve must be opened first. At this time, since the start-up valve and the high-temperature stage expansion valve are on the same vertical plane, and the start-up valve and start-up pipe are both located at the top, the low-temperature, low-pressure two-phase CO2 refrigerant after being throttled by the high-temperature stage expansion valve preferentially enters the gas-liquid separator through the start-up pipe (because the gas flow channel of the start-up pipe is designed with a flow resistance much lower than that of the bottom pipe with more liquid content). After the start-up valve is opened, the system achieves pressure balance under the drive of pressure difference. The gaseous refrigerant flows to the low-pressure side along this path, and after gas-liquid separation, the gaseous CO2 enters the compressor cycle. Meanwhile, with the help of the connecting microtubes, the liquid CO2 accumulated at the bottom of the gas-liquid separator can flow back to the energy storage device, preventing excessive accumulation of liquid refrigerant there. During this process, the inlet pressure of the high-temperature stage compressor is monitored in real time by the pressure sensor P7. When the compressor suction pressure is ≥3.5MPa, the start-up valve can be closed. In addition, during the unit restart process, the system loop will prioritize flow distribution through the upper heat transfer pipe to prevent excessive liquid CO2 generated during standby from being carried to the gas-liquid separator, ensuring rapid response and stable operation during the system startup phase. Furthermore, by reducing the amount of liquid refrigerant entering the high-temperature stage compressor, the risk of liquid slugging is effectively prevented, equipment life is extended, and the overall energy efficiency and reliability of the system are improved.

[0073] Furthermore, when the compressor lubricating oil level is lower than the safe value, the solenoid valve between the oil separator and the oil tank is opened to guide the lubricating oil into the oil tank; after closing the solenoid valve, the solenoid valve between the oil tank and the compressor is opened to allow the lubricating oil to flow back to the compressor through the oil filter; after the oil return is completed, the corresponding solenoid valve is closed and the excess pressure in the oil tank is released.

[0074] Specifically, when the compressor's internal oil level monitoring system detects that the lubricating oil level is below a preset safe value, it will automatically initiate a pressure differential-driven oil return procedure. First, the first solenoid valve between the oil separator and the oil reservoir is opened. Utilizing the pressure difference between the high-pressure environment inside the oil separator (internal pressure close to the compressor's discharge pressure) and the preset low pressure in the oil reservoir, the separated lubricating oil is efficiently guided into the oil reservoir for storage. After the pressure balances, the first solenoid valve is closed, and simultaneously, the second solenoid valve between the oil reservoir and the compressor is opened. During this process, the lubricating oil stored in the oil reservoir, under the influence of gravity and pressure differential, passes through an oil filter to remove impurities and then flows back into the compressor crankcase. Finally, after the oil return operation is completed, the corresponding second solenoid valve is closed, and simultaneously, the third solenoid valve connecting the top of the oil reservoir to the receiver tank (or compressor) is opened to release excess pressure in the oil reservoir, bringing it back to a safe range, and simultaneously creating conditions for the next cycle of pressure differential oil return. Figure 8 The diagram shows the control flow chart for oil return in a high-temperature circulating system. Oil return is controlled via solenoid valves YV3, YV4, and YV6, and pressure sensor P2. Figure 10 The diagram shows the oil return control flow chart for a -20°C refrigeration unit in the cryogenic stage circulation system. Oil return control is achieved through solenoid valves YV7, YV8, and YV12, and pressure sensor 5. The oil return control flow chart for a -40°C refrigeration unit in the cryogenic stage circulation system is similar. Figure 10 The process is the same, the difference is that the return oil control is performed through solenoid valves YV9, YV10 and YV11 and pressure sensor P6.

[0075] As a specific example, such as Figure 7 The control logic of the high-temperature circulating system shown employs differentiated control strategies to optimize refrigeration and heating control for both combined cooling and heating and rapid ice-making operation modes.

[0076] First, the high-temperature stage compressor is turned on, with the number of units activated determined by the required cooling load, and at least one unit must be operational. When combined cooling and heating is required, solenoid valves YV1, YV5, and YV13 are opened, while solenoid valve YV2 is closed. The opening of the high-temperature stage expansion valve is adjusted appropriately to meet the set evaporation temperature. During operation, the temperature T1 of the hot water outlet of the hot water recovery unit (detected by temperature sensor T1) is monitored. The opening of solenoid valve YV14 is adjusted based on whether the absolute value of the difference between T1 and 90 degrees Celsius is greater than or equal to 1 degree Celsius, thereby controlling the flow of cold water into the hot water recovery unit and ensuring a stable supply of 90°C hot water. Simultaneously, the temperature T3 of the high-temperature stage outlet of the energy storage device (detected by temperature sensor T3) is monitored in real time and compared with the set maximum temperature. If T3 is higher than the set maximum temperature, solenoid valves YV5 and YV13 are closed to prevent the compressor suction temperature and pressure from becoming too high, which could lead to compressor overheating; otherwise, solenoid valves YV5 and YV13 remain open.

[0077] When the system switches to rapid ice-making mode, the high-temperature compressor remains on, with the number of units operating determined by the required cooling load, and at least one unit always operating. Solenoid valves YV2, YV5, and YV13 remain fully open. Based on the optimal discharge pressure calculation model, the theoretical optimal discharge pressure P(g) is calculated by collecting the temperature T2 at the air cooler outlet (detected by temperature sensor T2) and substituting it into the calculation formula. This calculated pressure P(g) is then compared with the actual compressor discharge pressure P1 (detected by pressure sensor P1). If the absolute value of the deviation is less than 0.05 MPa, the system is considered to be operating under optimal pressure. If the deviation exceeds this range, the opening of solenoid valve YV15 at the air cooler cooling water inlet is adjusted to change the refrigerant temperature at the air cooler outlet until the pressure deviation converges to the allowable range. If the deviation continues to increase during adjustment, the system automatically reverses the operation, ultimately achieving precise closed-loop control of the discharge pressure. At the same time, the opening of the high-temperature stage expansion valve can be adjusted in real time according to the actual required ice storage volume, thereby realizing independent adjustment of the refrigerant flow to the high-temperature stage inlet of the energy storage device and further controlling the ice-making efficiency.

[0078] It should be noted that in a CO2 refrigeration cycle system, system performance is affected by multiple parameters, primarily including compressor discharge pressure, air cooler outlet temperature, evaporation temperature, superheat, regenerator efficiency, and compressor operating characteristics. Existing research shows that optimizing compressor discharge pressure can significantly improve system refrigeration efficiency (COP); furthermore, existing operating data indicates a strong correlation between air cooler outlet temperature and discharge pressure in transcritical compression cycles, and effective control of discharge pressure can be achieved by adjusting the air cooler outlet temperature. Additionally, while ensuring the system meets cooling and heating load requirements, fine-tuning the expansion valve opening can also control discharge pressure.

[0079] When the exhaust pressure is at a specific optimal value, the system reaches its optimal cycle state, at which point the COP reaches its theoretical maximum value. This optimal pressure value is determined by thermodynamic equilibrium conditions and requires comprehensive consideration of boundary conditions such as ambient temperature, cooling medium characteristics, and load requirements. Therefore, in practical engineering applications, adaptive control algorithms can be used to adjust operating parameters in real time to ensure the system continuously operates under the optimal pressure, thereby maximizing energy efficiency. Therefore, the technical content of this optimal exhaust pressure calculation model can be directly implemented using existing technologies to achieve the technical effects of this invention, and will not be described in detail.

[0080] Furthermore, such as Figure 9The control logic of the cryogenic stage circulation system is as follows: In cryogenic refrigeration (-20℃) mode, the cryogenic compressor is turned on, and the number of compressors turned on is determined according to the required refrigeration load, with at least one compressor always in operation. The opening of the first cryogenic stage expansion valve is appropriately adjusted to meet the set evaporation temperature. At this time, based on the optimal discharge pressure calculation model, the refrigerant temperature T4 at the cryogenic stage outlet of the energy storage device (detected by temperature sensor T4) is collected and substituted into the calculation formula to calculate the theoretical optimal discharge pressure P(d), which is then compared with the actual compressor discharge pressure P3 (detected by pressure sensor P3). When the absolute value of the deviation is less than 0.05MPa, it is determined that the system is under optimal pressure conditions. If the deviation exceeds this range, the discharge pressure of the cryogenic stage compressor is controlled by appropriately adjusting parameters such as the fan speed, cooling water flow rate, compressor speed, and expansion valve opening in the air cooler (during this process, it is necessary to ensure that the CO2 refrigerant temperature after throttling and depressurization of the first cryogenic stage expansion valve meets the evaporation temperature required by the refrigeration system), until the pressure deviation converges to the allowable range. If the deviation continues to increase during the adjustment process, the reverse operation is automatically executed to ultimately achieve precise control of the discharge pressure.

[0081] Control process under low-temperature quick-freezing (-40℃) mode and Figure 9 Similarities exist, but the differences lie in the specific expansion valves controlled and the sensors used to collect data. Specifically, the cryogenic compressor is started, with the number of units activated determined by the required refrigeration load, and at least one unit must be operational. The opening of the second cryogenic stage expansion valve is appropriately adjusted to meet the set evaporation temperature. At this point, based on the optimal discharge pressure calculation model, the refrigerant temperature T5 at the cryogenic stage outlet of the energy storage device (detected by temperature sensor T5) is collected and substituted into the calculation formula to calculate the theoretical optimal discharge pressure P(d)', which is then compared with the actual compressor discharge pressure P4 (detected by pressure sensor P4). When the absolute value of the deviation is less than 0.05 MPa, it is determined that the optimal pressure condition has been reached. If the deviation exceeds this range, the discharge pressure of the cryogenic stage compressor is controlled by appropriately adjusting parameters such as the fan speed in the air cooler, the cooling water flow rate, the compressor speed, and the opening of the expansion valve (during this process, it is necessary to ensure that the CO2 refrigerant temperature after throttling and depressurization of the second cryogenic stage expansion valve meets the evaporation temperature required by the quick-freezing system), until the pressure deviation converges to the allowable range. If the deviation continues to increase during the adjustment process, the reverse operation is automatically executed, ultimately achieving precise control of the discharge pressure.

[0082] The above embodiments are further elaborations and descriptions of the present invention to facilitate understanding, and are not intended to limit the present invention in any way. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A refrigeration system based on a three-pipe energy storage device, characterized in that, include: A high-temperature circulating system for ice making and hot water supply; A low-temperature circulating system for freezing or quick-freezing; A three-pipe energy storage device coupling and connecting a high-temperature stage circulation system and a low-temperature stage circulation system, the energy storage device comprising: The evaporative heat dissipation pipe section is connected to the high-temperature circulating system as an evaporator. The condensate liquefaction pipe section is connected as a condenser in the low-temperature stage circulation system; The start-up tube is connected in parallel with the evaporative cooling tube section, and the inlet and outlet connections of the start-up tube and the evaporative cooling tube section are equipped with anti-liquid hammer components.

2. The refrigeration system based on a three-pipe energy storage device according to claim 1, characterized in that, The anti-liquid-sinking component includes a gas-liquid separator, the inlet of which is connected to the high-temperature stage outlet of the energy storage device. The high-temperature stage outlet includes the outlet of the evaporative heat dissipation pipe section and the outlet of the start-up pipe. The gas outlet of the gas-liquid separator is connected to the inlet of the high-temperature compressor in the high-temperature circulating system; The liquid refrigerant in the gas-liquid separator flows out from the liquid outlet and returns to the energy storage device through the connecting microtube.

3. A refrigeration system based on a three-pipe energy storage device according to claim 1 or 2, characterized in that, The anti-liquid hammer assembly also includes a start valve and a high-temperature expansion valve. The outlet of the high-temperature expansion valve is connected to the inlet of the start valve and the high-temperature inlet of the energy storage device, respectively. The outlet of the start valve is connected to the high-temperature inlet of the energy storage device. The high-temperature stage inlet includes the inlet of the evaporative cooling tube section and the inlet of the start-up tube.

4. A refrigeration system based on a three-pipe energy storage device according to claim 3, characterized in that, The starting tube is positioned above the evaporative heat dissipation tube section, and the ratio of the number of starting tubes to the number of evaporative heat dissipation tube sections is within a preset ratio range. The vertical height of the start valve is higher than that of the anti-liquid hammer expansion valve, and the difference in horizontal distance between the two is less than the preset distance threshold.

5. A refrigeration system based on a three-pipe energy storage device according to claim 1, 2, or 4, characterized in that, The refrigeration system also includes a temperature detection component to detect the temperature in the energy storage device and determine the ice storage capacity; the temperature detection component includes: The eleventh temperature sensor is installed at the high-temperature stage inlet of the energy storage device to detect the refrigerant temperature. The ninth temperature sensor is located at one end of the energy storage device near the high-temperature stage outlet to detect the internal cooling water temperature or ice layer temperature. The tenth temperature sensor is located inside the energy storage device near the outlet of the cryogenic stage to detect the water temperature at the outlet of the cryogenic stage.

6. A refrigeration system based on a three-pipe energy storage device according to claim 1, 2, or 4, characterized in that, In the high-temperature stage circulation system, the refrigerant flowing out from the high-temperature stage outlet of the energy storage device passes sequentially through the high-temperature stage compressor, high-temperature stage oil separator, high-temperature stage condenser assembly, and high-temperature stage expansion valve before flowing into the liquid storage tank. It is then transported from the liquid storage tank to the high-temperature stage inlet of the energy storage device through a shielded pump. The oil outlet of the high-temperature stage oil separator is connected to the high-temperature stage compressor through the high-temperature stage oil storage tank. or The refrigerant flowing out of the high-temperature stage outlet first passes through the heat exchanger and then reaches the high-temperature stage compressor. At the same time, the refrigerant flowing out of the high-temperature stage condenser first passes through the heat exchanger and then flows into the liquid receiver tank through the high-temperature stage expansion valve.

7. A refrigeration system based on a three-pipe energy storage device according to claim 1, 2, or 4, characterized in that, In the cryogenic cycle system, the refrigerant flowing out of the cryogenic stage outlet of the energy storage device passes sequentially through the cryogenic stage expansion valve, cryogenic stage evaporator, cryogenic stage compressor, and cryogenic stage oil separator to reach the cryogenic stage inlet of the energy storage device. The oil outlet of the cryogenic stage oil separator is connected to the cryogenic stage compressor through the cryogenic stage oil storage tank.

8. A control method for a refrigeration system based on a three-pipe energy storage device, applicable to the refrigeration system as described in any one of claims 1-7, characterized in that, include: The temperature difference between the refrigerant temperature at the high-temperature stage inlet and the internal ice layer temperature, as well as the water temperature at the low-temperature stage outlet, are detected in the energy storage device. When the temperature difference is less than or equal to the first temperature difference threshold, the ice storage capacity is greater than the first upper limit. If there is a cooling demand, the low-temperature circulation system is started, and the opening of the high-temperature circulation system is determined according to the peak and valley periods. When the temperature difference is greater than or equal to the second temperature difference threshold and the water temperature is greater than or equal to the first temperature threshold, and the ice storage capacity is less than the first lower limit, if there is a cooling demand, the low-temperature circulation system and the high-temperature circulation system will be started; otherwise, the start of the high-temperature circulation system will be determined according to the peak and valley periods.

9. The control method for a refrigeration system based on a three-pipe energy storage device according to claim 8, characterized in that, Before restarting the high-temperature stage circulating system after it has been shut down for more than a preset time, the start valve is opened first, and the gaseous refrigerant flows into the gas-liquid separator through the start pipe; the gas-liquid separator introduces the gaseous refrigerant into the high-temperature stage compressor, while the liquid refrigerant flows back to the energy storage device through the connecting microtube; the suction pressure of the high-temperature stage compressor is monitored, and when the suction pressure is greater than or equal to the preset pressure threshold, the start valve is closed.

10. A control method for a refrigeration system based on a three-pipe energy storage device according to claim 8 or 9, characterized in that, When the compressor lubricating oil level is lower than the safe value, open the solenoid valve between the oil separator and the oil tank to introduce the lubricating oil into the oil tank; after closing the solenoid valve, open the solenoid valve between the oil tank and the compressor to allow the lubricating oil to flow back to the compressor through the oil filter; after the oil return is completed, close the corresponding solenoid valve and release the excess pressure in the oil tank.

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