Pressure maintenance system for carbon dioxide refrigeration

Abstract

The present invention relates to the field of carbon dioxide refrigeration technology, specifically a pressure maintenance system for carbon dioxide refrigeration, comprising a cooling module and multiple carbon dioxide refrigeration modules; the carbon dioxide refrigeration module comprises a carbon dioxide unit and a liquid storage tank connected to the carbon dioxide unit, the liquid storage tank being provided with a pressure detection component and a liquid level detection component, the liquid level detection component being used to detect the carbon dioxide liquid level in the liquid storage tank; the gas outlets of the liquid storage tanks of the multiple carbon dioxide refrigeration modules are all connected to the input end of the cooling module, and the liquid inlets of the liquid storage tanks of the multiple carbon dioxide refrigeration modules are all connected to the output end of the cooling module. The present invention adjusts the operating power and operating frequency of the cooling modules by monitoring the pressure and liquid level of the carbon dioxide refrigeration modules, and simultaneously reduces the pressure of the multiple carbon dioxide refrigeration modules, so that the pressure of the carbon dioxide refrigeration modules is maintained within a safe range, thereby reducing the design cost and difficulty of the carbon dioxide refrigeration modules.

Description

Technical Field

[0001] The present invention relates to the technical field of carbon dioxide refrigeration, and in particular to a pressure maintaining system for carbon dioxide refrigeration. Background Art

[0002] Using hydrofluorocarbons (HFCs) for refrigeration can damage the ozone layer and produce a strong greenhouse effect. Carbon dioxide, on the other hand, is a natural refrigerant. It is non-toxic, non-flammable, has zero ozone depletion potential, and a global warming potential of 1. It also possesses excellent thermophysical properties. As demand for environmental performance continues to rise, CO2-based refrigeration systems are finding widespread use again in the refrigeration sector.

[0003] Existing CO2 refrigeration systems have different pressure requirements during operation and shutdown. In particular, in subcritical CO2 refrigeration systems, the compressor discharge pressure cannot exceed 5.0 MPa. However, in summer, when the CO2 refrigeration system is shut down, the liquid storage tank and refrigeration system temperatures are high. When the temperature reaches 30°C, the corresponding saturation pressure reaches 7.3 MPa. For system safety, most CO2 refrigeration systems are designed for this maximum pressure, but this significantly increases design cost and difficulty. Summary of the Invention

[0004] The present invention provides a pressure maintenance system for carbon dioxide refrigeration, which is used to solve the defects of carbon dioxide refrigeration systems in the prior art, such as being designed according to the highest pressure standard for safety, which greatly increases the design cost and difficulty. It can simultaneously reduce the pressure of multiple carbon dioxide refrigeration modules, so that the pressure of the carbon dioxide refrigeration modules is maintained within a safe range. The operating frequency of the cooling module can be adjusted in real time by monitoring the real-time status of the carbon dioxide refrigeration modules, thereby ensuring that the pressure of the carbon dioxide refrigeration modules is within the safe range and reducing the design cost and difficulty of the carbon dioxide refrigeration modules.

[0005] The present invention provides a pressure maintenance system for carbon dioxide refrigeration, comprising a cooling module and a plurality of carbon dioxide refrigeration modules;

[0006] The carbon dioxide refrigeration module includes a carbon dioxide unit and a liquid storage tank connected to the carbon dioxide unit. The liquid storage tank is provided with a pressure detection component and a liquid level detection component. The pressure detection component is used to detect the pressure in the liquid storage tank, and the liquid level detection component is used to detect the carbon dioxide liquid level in the liquid storage tank.

[0007] The gas outlets of the liquid storage tanks of the multiple carbon dioxide refrigeration modules are all connected to the input end of the cooling module, and the liquid inlets of the liquid storage tanks of the multiple carbon dioxide refrigeration modules are all connected to the output end of the cooling module.

[0008] According to a pressure maintenance system for carbon dioxide refrigeration provided by the present invention, the carbon dioxide refrigeration module includes a first connecting member and a second connecting member, one end of the first connecting member is connected to the gas outlet of the liquid storage tank, the other end of the first connecting member is connected to the input end of the cooling module, one end of the second connecting member is connected to the liquid inlet of the liquid storage tank, and the other end of the second connecting member is connected to the output end of the cooling module, the first connecting member is provided with a first regulating valve, and the second connecting member is provided with a second regulating valve.

[0009] According to the pressure maintaining system for carbon dioxide refrigeration provided by the present invention, a first flow meter is further provided on the first connecting member, and a second flow meter is further provided on the second connecting member.

[0010] According to a pressure maintenance system for carbon dioxide refrigeration provided by the present invention, the cooling module includes a cooling unit and a heat exchanger connected to the cooling unit, one end of the heat exchanger is connected to the other end of the first connecting member, and the other end of the heat exchanger is connected to the other end of the second connecting member.

[0011] According to a pressure maintenance system for carbon dioxide refrigeration provided by the present invention, the cooling unit includes a cooling compressor, a condenser and a cooling throttle valve, one end of the cooling compressor is connected to one end of the heat exchanger, the other end of the cooling compressor is connected to one end of the condenser, the other end of the condenser is connected to one end of the cooling throttle valve, and the other end of the cooling throttle valve is connected to the other end of the heat exchanger.

[0012] According to the pressure maintenance system for carbon dioxide refrigeration provided by the present invention, a carbon dioxide working medium pump is provided between the second connecting member and the heat exchanger.

[0013] According to a pressure maintenance system for carbon dioxide refrigeration provided by the present invention, the carbon dioxide unit includes a carbon dioxide compressor, a gas cooler and an evaporator, one end of the carbon dioxide compressor is connected to one end of the gas cooler, the other end of the gas cooler is connected to the gas inlet at the upper end of the liquid storage tank, one end of the evaporator is connected to the liquid outlet at the lower end of the liquid storage tank, and the other end of the evaporator is connected to the other end of the carbon dioxide compressor.

[0014] According to a pressure maintenance system for carbon dioxide refrigeration provided by the present invention, the carbon dioxide unit also includes a first throttle valve and a second throttle valve, one end of the first throttle valve is connected to the gas cooler, and the other end of the first throttle valve is connected to the gas inlet at the upper end of the liquid storage tank, one end of the second throttle valve is connected to the evaporator, and the other end of the second throttle valve is connected to the liquid outlet of the liquid storage tank.

[0015] According to a pressure maintaining system for carbon dioxide refrigeration provided by the present invention, the pressure detection assembly includes at least one pressure sensor, and the pressure sensor is fixedly mounted on the inner wall surface of the liquid storage tank.

[0016] According to a pressure maintaining system for carbon dioxide refrigeration provided by the present invention, the liquid level detection assembly includes at least one liquid level sensor, and the liquid level sensor is fixedly mounted on the side wall of the liquid storage tank.

[0017] According to the present invention, a pressure maintenance system for CO2 refrigeration is provided. A cooling module cools gaseous CO2 to produce liquid CO2. The liquid CO2 is then transported from the cooling module's output end through the liquid inlet of the liquid storage tank into the liquid storage tank. The liquid CO2 in the liquid storage tank is then transported to the CO2 unit through the liquid outlet, thereby achieving CO2 circulation while simultaneously cooling the CO2 unit and reducing the pressure in the CO2 refrigeration module. By connecting the cooling module to the liquid storage tanks of multiple CO2 refrigeration modules simultaneously, the cooling module can simultaneously reduce the pressure of multiple CO2 refrigeration modules, maintaining the pressure of the CO2 refrigeration modules within a safe range. A pressure detection component monitors the pressure in the liquid storage tank in real time, and the operating power of the cooling module is increased or decreased based on the detected pressure value. A liquid level detection component monitors the liquid level in the liquid storage tank in real time, and the operating power of the cooling module is determined based on the CO2 liquid level in the liquid storage tank and the CO2 usage of the CO2 unit. This system enables real-time adjustment of the cooling module's operating power and frequency by monitoring the pressure and liquid level of the CO2 refrigeration module, ensuring that the pressure of the CO2 refrigeration module remains within a safe range and reducing the design cost and difficulty of the CO2 refrigeration module. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the technical solutions in the present invention or the prior art, a brief introduction is given below to the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0019] Figure 1 Schematic diagram of the structure of the pressure maintenance system for carbon dioxide refrigeration provided by the present invention;

[0020] Reference numerals:

[0021] 1: Cooling module; 2: CO2 refrigeration module; 11: Cooling unit;

[0022] 12: Heat exchanger; 21: Carbon dioxide unit; 22: Liquid storage tank;

[0023] 23: pressure detection component; 24: liquid level detection component; 25: first connecting piece;

[0024] 26: Second connecting piece; 27: First regulating valve; 28: Second regulating valve;

[0025] 111: cooling compressor; 112: condenser; 113: cooling throttle valve;

[0026] 211: CO2 compressor; 212: Gas cooler; 213: Evaporator;

[0027] 214: first throttle valve; 215: second throttle valve; 251: first flow meter;

[0028] 261: second flow meter; 262: carbon dioxide working fluid pump. DETAILED DESCRIPTION

[0029] To make the objectives, technical solutions, and advantages of the present invention more clear, the technical solutions of the present invention will be clearly and completely described below in conjunction with the accompanying drawings. Obviously, the embodiments described are only some of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts shall fall within the scope of protection of the present invention.

[0030] The following combination Figure 1 The pressure maintenance system for carbon dioxide refrigeration of the present invention is described.

[0031] As attached Figure 1 As shown, the pressure maintenance system for carbon dioxide refrigeration includes a cooling module 1 and a plurality of carbon dioxide refrigeration modules 2.

[0032] Specifically, the carbon dioxide refrigeration module 2 includes a carbon dioxide unit 21 and a liquid storage tank 22 connected to the carbon dioxide unit 21. A pressure detection component 23 and a liquid level detection component 24 are provided in the liquid storage tank 22. The pressure detection component 23 is used to detect the pressure in the liquid storage tank 22, and the liquid level detection component 24 is used to detect the carbon dioxide liquid level in the liquid storage tank 22.

[0033] The gas outlets of the liquid storage tanks 22 of the multiple carbon dioxide refrigeration modules 2 are all connected to the input end of the cooling module 1 , and the liquid inlets of the liquid storage tanks 22 of the multiple carbon dioxide refrigeration modules 2 are all connected to the output end of the cooling module 1 .

[0034] When the cooling module 1 is in use, the gas inlet at the upper end of the liquid storage tank 22 is connected to one end of the carbon dioxide unit 21, and the liquid outlet at the bottom end of the liquid storage tank 22 is connected to the other end of the carbon dioxide unit 21. The gaseous carbon dioxide from the carbon dioxide unit 21 enters the liquid storage tank 22 through the gas inlet and is then transported to the cooling module 1 through the gas outlet. The cooling module 1 cools the gaseous carbon dioxide to obtain liquid carbon dioxide. The liquid carbon dioxide is then transported from the output end of the cooling module 1 through the liquid inlet of the liquid storage tank 22 into the liquid storage tank 22. The liquid carbon dioxide in the liquid storage tank 22 is then transported to the carbon dioxide unit 21 through the liquid outlet. This achieves carbon dioxide circulation while cooling the carbon dioxide unit 21 and reducing the pressure of the carbon dioxide refrigeration module 2.

[0035] By connecting the cooling module 1 to the liquid storage tanks 22 of multiple carbon dioxide refrigeration modules 2 at the same time, the cooling module 1 can simultaneously reduce the pressure of multiple carbon dioxide refrigeration modules 2, so that the pressure of the carbon dioxide refrigeration modules 2 is maintained within a safe range.

[0036] The pressure detection component 23 monitors the pressure in the liquid storage tank 22 in real time. When the pressure detection component 23 detects that the pressure in the liquid storage tank 22 exceeds the maximum operating pressure of the CO2 refrigeration module 2, the operating power and operating frequency of the cooling module 1 are increased, so that the cooling module 1 maintains maximum power and operates, thereby reducing the pressure in the CO2 refrigeration module 2 in the shortest possible time. When the pressure detection component 23 detects that the pressure in the liquid storage tank 22 is lower than the minimum preset pressure, the cooling module 1 is suspended or operates intermittently.

[0037] The liquid level detection component 24 monitors the liquid level in the liquid storage tank 22 in real time. When the liquid level detection component 24 detects that the carbon dioxide liquid level in the liquid storage tank 22 is above a preset range, the operating power and operating frequency of the cooling module 1 are reduced. When the liquid level detection component 24 detects that the carbon dioxide liquid level in the liquid storage tank 22 is within the preset range, the operating power of the cooling module 1 is determined based on the carbon dioxide usage of the carbon dioxide unit 21. If the carbon dioxide flowing out of the lower end of the liquid storage tank 22 exceeds the carbon dioxide flowing in from the upper end, the power of the cooling module 1 is increased; otherwise, the power of the cooling module 1 is reduced. When the liquid level detection component 24 detects that the carbon dioxide liquid level in the liquid storage tank 22 is below the preset range, the operating power and operating frequency of the cooling module 1 are increased. This achieves real-time adjustment of the operating power and operating frequency of the cooling module 1 by monitoring the real-time conditions of the carbon dioxide refrigeration module 2, such as the pressure and liquid level, ensuring that the pressure of the carbon dioxide refrigeration module 2 is within a safe range and reducing the design cost and difficulty of the carbon dioxide refrigeration module 2.

[0038] In an optional embodiment of the present invention, the gas outlet and the liquid inlet are both located in the upper half of the liquid storage tank 22, with the gas outlet located below the liquid inlet. However, it should be understood that the gas outlet and the liquid inlet can also be located at any suitable position on the liquid storage tank 22.

[0039] Further, as attached Figure 1 As shown, the carbon dioxide refrigeration module 2 includes a first connecting member 25 and a second connecting member 26. One end of the first connecting member 25 is connected to the gas outlet of the liquid storage tank 22, and the other end of the first connecting member 25 is connected to the input end of the cooling module 1. One end of the second connecting member 26 is connected to the liquid inlet of the liquid storage tank 22, and the other end of the second connecting member 26 is connected to the output end of the cooling module 1. A first regulating valve 27 is provided on the first connecting member 25, and a second regulating valve 28 is provided on the second connecting member 26.

[0040] During operation, when the pressure detection assembly 23 detects that the pressure in the liquid storage tank 22 exceeds the maximum operating pressure of the CO2 refrigeration module 2, the first and second regulating valves 27 and 28 are fully opened, and the power of the cooling module 1 is adjusted to maximum, thereby reducing the pressure of the CO2 refrigeration module 2 in the shortest possible time. When the pressure detection assembly 23 detects that the pressure in the liquid storage tank 22 is lower than the minimum preset pressure, the openings of the first and second regulating valves 27 and 28 are adjusted to minimum, but not completely closed. At this time, the cooling module 1 can be shut down or adjusted to minimum power.

[0041] The opening degree of the first regulating valve 27 determines the amount of carbon dioxide flowing out of the liquid storage tank 22 through the first regulating valve 27, while the opening degree of the second regulating valve 28 determines the amount of carbon dioxide flowing into the liquid storage tank 22 through the second regulating valve 28. The difference between the inflow and outflow of carbon dioxide can be determined, and by adjusting this difference, the liquid level in the liquid storage tank 22 can be adjusted. The total amount of carbon dioxide required to be output by the cooling module 1 can then be determined by taking a weighted sum of the opening degrees of the second regulating valves 28 of all carbon dioxide refrigeration modules 2. This allows the operating power and operating frequency of the cooling module 1 to be adjusted according to actual conditions, ensuring that the total amount of carbon dioxide output by the cooling module 1 precisely meets the needs of all carbon dioxide refrigeration modules 2.

[0042] Then, based on the liquid level in the liquid storage tank 22 detected by the liquid level detection component 24, when the liquid level is above a preset range, all first regulating valves 27 and second regulating valves 28 are adjusted to their minimum openings. The openings of all second regulating valves 28 are then weighted and summed to determine the operating power of the cooling module 1. When the liquid level is within the preset range, the amount of carbon dioxide entering and exiting the carbon dioxide unit 21 is first compared. If the amount entering the carbon dioxide unit 21 is greater than the amount leaving, it indicates that the carbon dioxide liquid level in the liquid storage tank 22 is continuously decreasing and the opening of the second regulating valve 28 needs to be increased. The openings of all second regulating valves 28 are then weighted and summed to determine the operating power of the cooling module 1 and the opening of the first regulating valve 27. If the amount entering the carbon dioxide unit 21 is less than the amount leaving, it indicates that the carbon dioxide liquid level in the liquid storage tank 22 is continuously increasing and the opening of the second regulating valve 28 needs to be reduced. The openings of all second regulating valves 28 are then weighted and summed to determine the operating power of the cooling module 1 and the opening of the first regulating valve 27. When the liquid level falls below a preset range, the openings of first and second regulating valves 27 and 28 are adjusted to their maximum values. The weighted sum of the openings of all second regulating valves 28 is then used to determine the operating power of cooling module 1. This allows for real-time adjustment of the operating power and frequency of cooling module 1 by monitoring the pressure and liquid level of CO2 refrigeration module 2. This ensures that the pressure of CO2 refrigeration module 2 remains within a safe range, reducing the design cost and difficulty of CO2 refrigeration module 2.

[0043] In an optional embodiment of the present invention, the first connecting member 25 and the second connecting member 26 are, for example, connecting pipes. However, it should be understood that the first connecting member 25 and the second connecting member 26 can also be any other suitable structural members capable of transmitting carbon dioxide.

[0044] In an optional embodiment of the present invention, the first regulating valve 27 and the second regulating valve 28 are both, for example, electric regulating valves. However, it should be understood that the first regulating valve 27 and the second regulating valve 28 can also be any other suitable valves.

[0045] Among them, as attached Figure 1 As shown, the first connecting member 25 is further provided with a first flow meter 251, and the second connecting member 26 is further provided with a second flow meter 261. During use, the first flow meter 251 accurately calculates the amount of carbon dioxide passing through the first connecting member 25, and the second flow meter 261 accurately calculates the amount of carbon dioxide passing through the second connecting member 26. The difference in the amount of carbon dioxide flowing into and out of the liquid storage tank 22 can be used to accurately adjust the operating power and operating frequency of the cooling module 1 in real time, thereby achieving precise control of the liquid level in the liquid storage tank 22.

[0046] Further, as attached Figure 1 As shown, the cooling module 1 includes a cooling unit 11 and a heat exchanger 12 connected to the cooling unit 11. One end of the heat exchanger 12 is connected to the other end of the first connecting member 25, and the other end of the heat exchanger 12 is connected to the other end of the second connecting member 26. During use, the cooling unit 11 is used to cool the heat exchanger 12. The higher-temperature carbon dioxide in the liquid storage tank 22 is transported to one end of the heat exchanger 12 through the first connecting member 25, and then transported from the other end of the heat exchanger 12 to the second connecting member 26. When the carbon dioxide passes through the heat exchanger 12, heat is exchanged with the heat exchanger 12, causing the temperature of the carbon dioxide transported to the second connecting member 26 to decrease. The low-temperature carbon dioxide then returns to the liquid storage tank 22 to cool the carbon dioxide unit 21.

[0047] Among them, as attached Figure 1 As shown, a carbon dioxide working medium pump 262 is provided between the second connecting member 26 and the heat exchanger 12. When in use, the carbon dioxide working medium pump 262 is used to drive the carbon dioxide output from the other end of the heat exchanger 12 into the second connecting member 26 and then back into the liquid storage tank 22.

[0048] In an optional embodiment of the present invention, the heat exchanger 12 is, for example, a plate heat exchanger 12. However, it should be understood that the heat exchanger 12 may also be any other suitable heat exchange element.

[0049] Among them, as attached Figure 1As shown, the cooling unit 11 includes a cooling compressor 111, a condenser 112 and a cooling throttle valve 113. One end of the cooling compressor 111 is connected to one end of the heat exchanger 12, and the other end of the cooling compressor 111 is connected to one end of the condenser 112. The other end of the condenser 112 is connected to one end of the cooling throttle valve 113, and the other end of the cooling throttle valve 113 is connected to the other end of the heat exchanger 12. When in use, the condenser 112 delivers a low-temperature working medium to the cooling throttle valve 113. The cooling throttle valve 113 is adjusted according to actual demand to control the amount of low-temperature working medium flowing to the heat exchanger 12 through the cooling throttle valve 113. When the low-temperature working medium flows through the heat exchanger 12, it takes away the heat of the heat exchanger 12 and is then delivered to the cooling compressor 111. The cooling compressor 111 compresses the working medium and then delivers it to the condenser 112, thereby forming a working medium cycle and achieving cooling of the heat exchanger 12.

[0050] Further, as attached Figure 1 As shown, the carbon dioxide unit 21 includes a carbon dioxide compressor 211, a gas cooler 212, and an evaporator 213. One end of the carbon dioxide compressor 211 is connected to one end of the gas cooler 212, and the other end of the gas cooler 212 is connected to the gas inlet at the upper end of the liquid storage tank 22. One end of the evaporator 213 is connected to the liquid outlet at the lower end of the liquid storage tank 22, and the other end of the evaporator 213 is connected to the other end of the carbon dioxide compressor 211. During use, the gas cooler 212 transports carbon dioxide gas into the liquid storage tank 22 through the gas inlet, and then transports it to the cooling module 1 for cooling to obtain liquid carbon dioxide, which is then returned to the liquid storage tank 22. The liquid carbon dioxide in the liquid storage tank 22 is then transported to the evaporator 213. The evaporator 213 evaporates the carbon dioxide and then transports it to the carbon dioxide compressor 211. The carbon dioxide compressor 211 compresses the carbon dioxide and then transports it to the gas cooler 212. This reduces the pressure in the carbon dioxide unit 21 and the liquid storage tank 22 while realizing the carbon dioxide refrigeration cycle.

[0051] Among them, as attached Figure 1As shown, the carbon dioxide unit 21 also includes a first throttle valve 214 and a second throttle valve 215. One end of the first throttle valve 214 is connected to the gas cooler 212, and the other end of the first throttle valve 214 is connected to the gas inlet at the upper end of the liquid storage tank 22. One end of the second throttle valve 215 is connected to the evaporator 213, and the other end of the second throttle valve 215 is connected to the liquid outlet of the liquid storage tank 22. When in use, the first throttle valve 214 can control the amount of carbon dioxide gas entering the liquid storage tank 22, and the amount of carbon dioxide entering the liquid storage tank 22 can be known through the opening of the first throttle valve 214. The second throttle valve 215 can throttle and flow control the carbon dioxide flowing from the liquid storage tank 22 to the evaporator 213, and the amount of carbon dioxide flowing from the liquid storage tank 22 to the evaporator 213 can be known through the opening of the first throttle valve 214. The difference between the amount of carbon dioxide entering the carbon dioxide unit 21 and the amount of carbon dioxide discharged from the carbon dioxide unit 21 can be obtained, so as to determine whether the carbon dioxide liquid level in the liquid storage tank 22 needs to be increased, and the working power of the cooling module 1 can be determined.

[0052] Furthermore, the pressure detection assembly 23 includes at least one pressure sensor fixedly mounted on the inner wall of the liquid storage tank 22. During use, the pressure sensor detects the pressure in the liquid storage tank 22 in real time, thereby determining the pressure value of the CO2 refrigeration module 2. This allows the cooling module 1 to adjust its operating power and operating frequency in real time based on the pressure value of the CO2 refrigeration module 2.

[0053] Furthermore, the liquid level detection assembly 24 includes at least one liquid level sensor, which is fixedly mounted on the side wall of the liquid storage tank 22. During use, the liquid level sensor detects the carbon dioxide liquid level in the liquid storage tank 22 in real time. Based on the carbon dioxide liquid level in the liquid storage tank 22, the openings of the first regulating valve 27 and the second regulating valve 28 are adjusted. The openings of all the second regulating valves 28 are then weighted and summed to determine the operating power and operating frequency of the cooling module 1.

[0054] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A pressure maintenance system for carbon dioxide refrigeration, characterized in that: It includes a cooling module and multiple carbon dioxide refrigeration modules; The carbon dioxide refrigeration module includes a carbon dioxide unit and a liquid storage tank connected to the carbon dioxide unit. The liquid storage tank is provided with a pressure detection component and a liquid level detection component. The pressure detection component is used to detect the pressure in the liquid storage tank, and the liquid level detection component is used to detect the carbon dioxide liquid level in the liquid storage tank. The gas outlets of the liquid storage tanks of the multiple carbon dioxide refrigeration modules are all connected to the input end of the cooling module, and the liquid inlets of the liquid storage tanks of the multiple carbon dioxide refrigeration modules are all connected to the output end of the cooling module; On the liquid storage tank, the gas outlet is located below the liquid inlet.

2. The pressure maintenance system for carbon dioxide refrigeration according to claim 1, characterized in that: The carbon dioxide refrigeration module includes a first connecting member and a second connecting member. One end of the first connecting member is connected to the gas outlet of the liquid storage tank, and the other end of the first connecting member is connected to the input end of the cooling module. One end of the second connecting member is connected to the liquid inlet of the liquid storage tank, and the other end of the second connecting member is connected to the output end of the cooling module. A first regulating valve is provided on the first connecting member, and a second regulating valve is provided on the second connecting member.

3. The pressure maintenance system for carbon dioxide refrigeration according to claim 2, characterized in that: The first connecting member is further provided with a first flow meter, and the second connecting member is further provided with a second flow meter.

4. The pressure maintenance system for carbon dioxide refrigeration according to claim 2 or 3, characterized in that: The cooling module includes a cooling unit and a heat exchanger connected to the cooling unit, one end of the heat exchanger is connected to the other end of the first connecting member, and the other end of the heat exchanger is connected to the other end of the second connecting member.

5. The pressure maintenance system for carbon dioxide refrigeration according to claim 4, characterized in that: The cooling unit includes a cooling compressor, a condenser and a cooling throttle valve. One end of the cooling compressor is connected to one end of the heat exchanger, the other end of the cooling compressor is connected to one end of the condenser, the other end of the condenser is connected to one end of the cooling throttle valve, and the other end of the cooling throttle valve is connected to the other end of the heat exchanger.

6. The pressure maintenance system for carbon dioxide refrigeration according to claim 4, characterized in that: A carbon dioxide working medium pump is provided between the second connecting member and the heat exchanger.

7. The pressure maintenance system for carbon dioxide refrigeration according to any one of claims 1 to 3, characterized in that: The carbon dioxide unit includes a carbon dioxide compressor, a gas cooler and an evaporator. One end of the carbon dioxide compressor is connected to one end of the gas cooler, and the other end of the gas cooler is connected to the gas inlet at the upper end of the liquid storage tank. One end of the evaporator is connected to the liquid outlet at the lower end of the liquid storage tank, and the other end of the evaporator is connected to the other end of the carbon dioxide compressor.

8. The pressure maintenance system for carbon dioxide refrigeration according to claim 7, characterized in that: The carbon dioxide unit also includes a first throttle valve and a second throttle valve, one end of the first throttle valve is connected to the gas cooler, and the other end of the first throttle valve is connected to the gas inlet at the upper end of the liquid storage tank, one end of the second throttle valve is connected to the evaporator, and the other end of the second throttle valve is connected to the liquid outlet of the liquid storage tank.

9. The pressure maintenance system for carbon dioxide refrigeration according to any one of claims 1 to 3, characterized in that: The pressure detection assembly includes at least one pressure sensor, and the pressure sensor is fixedly mounted on the inner wall surface of the liquid storage tank.

10. The pressure maintenance system for carbon dioxide refrigeration according to any one of claims 1 to 3, characterized in that: The liquid level detection assembly includes at least one liquid level sensor, and the liquid level sensor is fixedly mounted on the side wall of the liquid storage tank.

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