CO2 supercritical servo system

Abstract

The utility model provides a CO2 supercritical servo system which comprises a main system and an auxiliary system, the main system comprises a CO2 screw compressor, a CO2 horizontal oil separator, a CO2 precooler, a CO2 condenser and a CO2 float valve which are connected in sequence; the auxiliary system comprises a CO2 supercritical piston compressor, a CO2 supercritical oil separator and a CO2 piston compressor oil reservoir which are connected in sequence; the exhaust side of the auxiliary system is connected with a self-control valve, and a first passage of the self-control valve completes internal circulation between a CO2 circulation barrel and a CO2 precooler of the system and maintains the pressure of the system stable; the second channel is connected to a defrosting inlet of the tail end evaporator, and the third channel is connected into a CO2 oil separator exhaust pipe of the main system and enters a CO2 condenser of the main system through a CO2 precooler. Through cooperative operation of the main system and the auxiliary system, in combination with flexible distribution of the three-way reversing valve, stable, reliable, efficient and energy-saving use experience is created for a user.

Description

Technical Field

[0001] This utility model belongs to the technical field of refrigeration equipment, specifically relating to a CO2 supercritical servo system. Background Technology

[0002] Carbon dioxide (CO2), as a natural working fluid, is non-toxic, non-flammable, and has a low global warming potential (GWP), and has gained widespread attention in refrigeration, heat pump, and supercritical applications in recent years. Especially in transcritical refrigeration systems, CO2, with its excellent heat transfer performance and environmental friendliness, has become a preferred alternative to traditional Freon working fluids. However, CO2 systems also face many technical challenges, such as: high system operating pressure and complex control; CO2 operating pressure in supercritical states is typically as high as 7–12 MPa, making the system extremely sensitive to pressure fluctuations, and even slight instability can lead to a sudden drop in energy efficiency or equipment overpressure risks. Severe frosting on the terminal evaporator affects stability; especially in low-temperature environments or under frequent start-stop conditions, the terminal evaporator is prone to frosting and blockage, and traditional electric heating or hot gas bypass defrosting solutions have drawbacks such as slow response, high energy consumption, and large system disturbances. Poor load regulation capability of single-unit systems; when user demand fluctuates significantly, traditional systems require frequent start-stop of the main unit or the use of variable frequency compressors to regulate the load, which increases system complexity and cost, and may also cause frequent start-ups of the main unit, shortening its lifespan.

[0003] Existing publicly available technologies, such as patent CN204373252U, provide a conversion-type CO2 transcritical cycle refrigeration system. By switching the flow direction of the refrigerant in different heat exchangers, a single / two-stage cycle conversion can be achieved. Although this improves energy efficiency, it still has the following shortcomings in terms of system flexibility, rapid defrosting, and efficient pressure maintenance: the system structure relies on a complex heat exchanger layout and mechanical valve switching, resulting in slow adjustment response; it cannot achieve the functions of "dynamic reloading" and "servo pressure control" during operation; and it lacks a rapid defrosting path for the evaporator end, requiring external auxiliary heating methods.

[0004] In summary, existing transcritical CO2 systems are insufficient to simultaneously meet the comprehensive requirements of high efficiency, energy saving, rapid response, and stable operation. Therefore, there is an urgent need for a more integrated and functionally complex supercritical CO2 servo system to address the problems of inaccurate pressure control, delayed defrosting, and poor system flexibility in traditional solutions. Utility Model Content

[0005] In view of the above-mentioned technical problems existing in the prior art, this utility model proposes a CO2 supercritical servo system to solve the above-mentioned technical problems.

[0006] This invention proposes a CO2 supercritical servo system, including a main system and an auxiliary system;

[0007] The main system includes a CO2 screw compressor, a CO2 horizontal oil separator, a CO2 precooler, a CO2 condenser, and a CO2 float valve connected in sequence.

[0008] The auxiliary system includes a CO2 supercritical reciprocating compressor, a CO2 supercritical oil separator, and a CO2 reciprocating compressor oil reservoir connected in sequence.

[0009] The auxiliary system's exhaust side is connected to a self-regulating valve. The first passage of the self-regulating valve connects to the inlet of the main system's CO2 precooler, the second passage connects to the defrost inlet of the terminal evaporator, and the third passage completes the internal circulation between the system's CO2 circulation tank and the CO2 precooler, maintaining stable system pressure. Through the coordinated design of the main system (CO2 screw compressor, oil separator, precooler, etc.) and the auxiliary system (supercritical piston compressor, oil separator, etc.), combined with the three-way switching of the self-regulating valve, integrated functions of refrigeration, defrosting, and load replenishment are achieved, solving the problem of the traditional system's single function and simplifying the piping structure.

[0010] In a specific embodiment, the main system also includes a CO2 oil cooling plate housing, which is disposed between the CO2 horizontal oil separator and the CO2 screw compressor. The addition of the CO2 oil cooling plate housing provides secondary cooling and purification of the lubricating oil output from the oil separator, reducing oil temperature and residual refrigerant, thereby improving the lubrication efficiency and operational stability of the screw compressor and extending its lifespan.

[0011] In a specific embodiment, a CO2 circulation tank is also included. The inlet of the CO2 circulation tank is connected to the return gas end of both the main system and the auxiliary system. The CO2 circulation tank is introduced to centrally recover the return refrigerant from the main and auxiliary systems, balance gas and liquid phase pressure fluctuations, ensure system stability during mode switching, and avoid control failures caused by sudden pressure changes.

[0012] In a specific embodiment, the suction port of the CO2 supercritical reciprocating compressor is connected to the CO2 circulation tank via a suction pipe. Direct connection of the supercritical reciprocating compressor suction port to the circulation tank ensures rapid recovery and reuse of the low-pressure gaseous refrigerant, avoiding the risk of liquid slugging caused by the compressor drawing in liquid refrigerant.

[0013] In a specific embodiment, the outlet of the terminal evaporator is connected to the CO2 circulation tank. This connection forms a closed loop, enabling directional refrigerant recovery after defrosting and automatic system pressure balancing, thus reducing refrigerant waste.

[0014] In a specific embodiment, the three-channel starting point is the outlet of the CO2 supercritical oil separator, and the gas outlet is connected to the first channel, the second channel and the third channel respectively. Switching is achieved by controlling the automatic control valve, which simplifies the pipeline layout and improves the system response speed and control reliability.

[0015] In a specific embodiment, the exhaust side of the auxiliary system is the outlet of the CO2 supercritical oil separator. This ensures efficient separation of high-pressure refrigerant and lubricating oil, prevents oil contamination from entering the downstream system, and guarantees refrigerant purity.

[0016] In a specific embodiment, the CO2 condenser, CO2 precooler, and CO2 float valve are connected in sequence to form the condensation loop of the main system, and the third passage is connected in parallel to the condensation loop. The condensation loop of the main system (condenser, precooler, float valve) is connected in parallel with the third passage of the auxiliary system to enhance the system's load replenishment capacity, improve condensation efficiency, and reduce energy consumption.

[0017] In a specific embodiment, a pressure sensor is installed on the CO2 circulation tank, and a temperature sensor is installed on the terminal evaporator. By installing pressure and temperature sensors on the circulation tank and the terminal evaporator, key parameters are monitored in real time, providing a data foundation for intelligent control and supporting automated operation.

[0018] This invention discloses a CO2 supercritical servo system, which, through structural optimization and functional integration, possesses at least the following technical advantages:

[0019] High efficiency and energy saving: The main and auxiliary systems work together, and the flexible allocation of the three-way reversing valve dynamically matches the cooling demand, improving the overall energy efficiency by 15%-20%.

[0020] Stable and reliable: The oil-cooled plate housing and circulation tank design optimize lubricating oil cooling and refrigerant recovery, reduce system pressure fluctuations, and lower the failure rate;

[0021] Functional integration: A single system integrates cooling, defrosting, and load replenishment functions, avoiding the complexity and cost of multi-unit configuration;

[0022] Easy maintenance: Modular structure simplifies cleaning and replacement processes, reducing operation and maintenance costs. Attached Figure Description

[0023] The accompanying drawings are included to provide a further understanding of the embodiments and are incorporated in and constitute a part of this specification. The drawings illustrate embodiments and, together with the description, serve to explain the principles of the present invention. Other embodiments and many anticipated advantages of the embodiments will be readily recognized as they become better understood through reference to the following detailed description. Elements in the drawings are not necessarily to scale. The same reference numerals refer to corresponding similar parts.

[0024] Figure 1 A schematic diagram of the system framework of a CO2 supercritical servo system according to an embodiment of the present invention is shown.

[0025] The meanings of the numbers in the diagram are as follows: 1. CO2 screw compressor; 2. CO2 horizontal oil separator; 3. CO2 oil cooler shell; 4. CO2 supercritical reciprocating compressor; 5. CO2 supercritical oil separator; 6. CO2 reciprocating compressor oil receiver; 7. CO2 precooler; 8. CO2 condenser; 9. CO2 float valve; 10. CO2 reciprocating system defrost outlet; 11. CO2 reciprocating compressor suction port. Detailed Implementation

[0026] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the relevant utility model and not intended to limit the scope of the utility model. Furthermore, it should be noted that, for ease of description, only the parts relevant to the utility model are shown in the accompanying drawings.

[0027] It should be noted that, where there is no conflict, the embodiments and features in the embodiments of this utility model can be combined with each other. The present utility model will now be described in detail with reference to the accompanying drawings and embodiments.

[0028] The specific embodiments of this utility model have been described above, but the scope of protection of this utility model is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in this utility model should be included within the scope of protection of this utility model. Therefore, the scope of protection of this utility model should be determined by the scope of the claims.

[0029] Figure 1 A schematic diagram of the system framework of a CO2 supercritical servo system according to an embodiment of the present invention is shown, as follows: Figure 1 As shown, the system comprises two main circulation paths: a main system and an auxiliary servo system. The main system consists of a refrigeration main loop comprised of a CO2 screw compressor 1, while the auxiliary servo system, centered on a CO2 supercritical reciprocating compressor 4, can be used for three modes: system pressure maintenance, terminal defrosting, and load supplementation. The two systems achieve thermodynamic coupling and loop sharing through shared components such as a CO2 circulation tank and a condenser / precooler.

[0030] In a specific embodiment, the main system includes a CO2 screw compressor 1, a CO2 horizontal oil separator 2, a CO2 oil cooling plate shell 3, a CO2 precooler 7, a CO2 condenser 8, and a CO2 float valve 9 connected in sequence. The CO2 screw compressor 1 is the driving core of the main system, used to draw in low-pressure gaseous CO2 and compress it. The CO2 horizontal oil separator 2 receives high-pressure gas from the CO2 screw compressor 1 and separates the lubricating oil therein. The CO2 oil cooling plate shell 3 is located between the CO2 horizontal oil separator 2 and the CO2 screw compressor 1, used to cool the separated lubricating oil and send it back to the CO2 screw compressor 1, closing the oil circuit circulation. The high-pressure gas in the main system flows through the CO2 precooler 7, and under the operation of the auxiliary servo system, it also receives the servo exhaust mixed flow, which has a precooling regulation function. The CO2 precooled by the CO2 condenser 8 is further cooled and partially condensed into liquid, providing a cold source for the subsequent refrigeration process. The CO2 float valve 9 connects the CO2 condenser 8 to the downstream low-pressure system (not shown in detail), controlling the flow of liquid CO2 into the liquid storage circuit.

[0031] In a specific embodiment, the auxiliary servo system includes a CO2 supercritical reciprocating compressor 4, a CO2 supercritical oil separator 5, and a CO2 reciprocating compressor oil reservoir 6 connected in sequence. The CO2 supercritical reciprocating compressor 4 is the driving core of the auxiliary system and can be started independently as a servo control source. The CO2 supercritical oil separator 5 receives high-pressure exhaust gas from the CO2 supercritical reciprocating compressor 4 and separates the lubricating oil therein. The CO2 reciprocating compressor oil reservoir 6 is connected to the CO2 supercritical oil separator 5 and is used to store and return the separated lubricating oil to complete the closed loop of the auxiliary compressor oil circuit. The auxiliary servo system is also equipped with a CO2 reciprocating compressor suction port 11 for drawing back low-pressure refrigerant from the circulation tank.

[0032] In a specific embodiment, a CO2 circulation tank is also provided to receive liquid or gaseous reflux from the main / auxiliary system, serving as a pressure balance or system buffer.

[0033] In a specific embodiment, the exhaust gas from the CO2 supercritical reciprocating compressor 4 passes through the CO2 supercritical oil separator 5 and then enters the three-way assembly (not separately numbered, but represented by multiple branches in the figure). This valve distributes the airflow to the following three paths:

[0034] First path (pressure maintenance mode): Automatic control valve → Main system CO2 precooler 7 outlet 1 → CO2 circulation tank → CO2 condenser 8 inlet, used to assist the system in participating in the main circulation condensation and maintain the system pressure stability;

[0035] Second path (defrosting mode): Automatic control valve → CO2 piston system defrosting outlet 10 in the upper right corner, then sent to the terminal evaporator; the evaporator outlet gas not shown is recovered to the circulation tank.

[0036] Third path (load supplement mode): Automatic control valve → CO2 precooler 7 → CO2 condenser 8 → floating CO2 ball valve 9, supplementing the refrigeration load.

[0037] In a specific embodiment, a pressure sensor is also included in the CO2 circulation tank, and a temperature sensor is included in the terminal evaporator. In a preferred embodiment, automatic switching can be achieved by means of a controller (such as a 32-bit ARM architecture microcontroller or other controller unit), which automatically switches the passage of the self-control valve and starts and stops the CO2 supercritical piston compressor 4 according to the signals collected by the temperature sensor and pressure sensor, and automatically switches between three servo modes. The specific principle is as follows;

[0038] Real-time monitoring of pressure data from the CO2 circulation tank of the refrigerant returned by the main system and auxiliary system, as well as temperature data from the terminal evaporator;

[0039] When the CO2 circulation tank pressure exceeds the preset upper limit, the unit mode is activated to maintain operation. The auxiliary system exhaust is introduced into the main system's CO2 condenser via the gas regulating valve until the pressure drops to the lower limit. Specifically, when the CO2 circulation tank pressure exceeds the preset upper limit, the CO2 supercritical piston compressor is started, and the gas regulating valve is switched to the first passage to introduce the auxiliary system exhaust into the main system's CO2 condenser.

[0040] When the terminal evaporator temperature falls below the defrost threshold, the defrost mode is activated. An automatic control valve directs exhaust gas from the auxiliary system to the terminal evaporator, and the defrosted gaseous refrigerant is recovered to the CO2 circulation tank. Specifically, when the temperature remains below the defrost threshold for a preset duration, the CO2 supercritical reciprocating compressor is started, and the automatic control valve switches to the second passage, directing high-pressure exhaust gas to the defrost inlet of the terminal evaporator. After defrosting, the second passage is closed, and the CO2 supercritical reciprocating compressor stops. The recovered gaseous refrigerant returns to the CO2 circulation tank through the suction port. This setup clearly defines the control logic for over-limit start-up and return-to-shutdown, enabling the auxiliary unit to maintain system pressure more precisely and control energy consumption more effectively.

[0041] When the main system load demand exceeds a preset threshold, the cooling load supplementation mode is activated. This mode dynamically supplements cooling capacity by adjusting the mixing ratio of auxiliary system exhaust and main system refrigerant via an automatic control valve. Specifically, when the main system load demand exceeds the preset threshold, the system starts a CO2 supercritical reciprocating compressor and switches the gas regulating valve to the third passage, ensuring the auxiliary system exhaust mixes with the main system refrigerant in the correct proportion. The mixed refrigerant is then cooled by the CO2 condenser and delivered to the downstream system until the load demand drops below the threshold. A closed-loop definition is implemented for start-up conditions, flow path switching, defrosting completion, and unit shutdown, enabling rapid and controllable completion of the terminal defrosting process and avoiding overheating or prolonged occupation of the refrigeration circuit. The system can automatically supplement cooling capacity based on real-time load, improving the main unit's response speed and reducing frequent start-stop cycles.

[0042] The CO2 supercritical servo system of this application is equipped with groundbreaking CO2 supercritical servo compressor technology. Through the coordinated operation of the main and auxiliary systems and the flexible allocation of automatic control valves, it dynamically matches the cooling demand and improves the overall energy efficiency. The single system integrates cooling, defrosting, and load supplementation functions, avoiding the complexity and cost of multi-unit configuration, and can create a stable, reliable, efficient and energy-saving user experience.

[0043] In the description of this utility model, it should be understood that the terms "upper," "lower," "inner," "outer," etc., indicating the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, are only for the convenience of describing this utility model and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this utility model. The word "comprising" does not exclude the presence of elements or steps not listed in the claims. The word "a" or "an" preceding an element does not exclude the presence of a plurality of such elements. The simple fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used for improvement. Any reference signs in the claims should not be construed as limiting the scope.

Claims

1. A CO2 supercritical servo system, characterized in that, Includes main system and auxiliary system; The main system includes a CO2 screw compressor, a CO2 horizontal oil separator, a CO2 precooler, a CO2 condenser, and a CO2 float valve connected in sequence. The auxiliary system includes a CO2 supercritical reciprocating compressor, a CO2 supercritical oil separator, and a CO2 reciprocating compressor oil reservoir connected in sequence. The auxiliary system is connected to a self-controlled valve on the exhaust side. The first passage of the self-controlled valve completes the internal circulation between the system's CO2 circulation tank and the CO2 precooler to maintain stable system pressure. The second passage is connected to the defrost inlet of the terminal evaporator, and the third passage is connected to the exhaust pipe of the main system's CO2 oil separator, which then enters the main system's CO2 condenser via the CO2 precooler.

2. The CO2 supercritical servo system according to claim 1, characterized in that, The main system also includes a CO2 oil cooling plate housing, which is disposed between the CO2 horizontal oil separator and the CO2 screw compressor.

3. The CO2 supercritical servo system according to claim 1, characterized in that, It also includes a CO2 circulation tank, the inlet of which is connected to the return gas end of the main system and the auxiliary system.

4. The CO2 supercritical servo system according to claim 3, characterized in that, The intake port of the CO2 supercritical piston compressor is connected to the CO2 circulation tank through an intake pipe.

5. The CO2 supercritical servo system according to claim 3, characterized in that, The outlet of the terminal evaporator is connected to the CO2 circulation tank.

6. The CO2 supercritical servo system according to claim 1, characterized in that, The three-channel system starts at the outlet of the CO2 supercritical oil separator, and the gas outlet is connected to the first, second, and third channels respectively. Switching is achieved by controlling the automatic valve.

7. The CO2 supercritical servo system according to claim 1, characterized in that, The exhaust side of the auxiliary system is the outlet of the CO2 supercritical oil separator.

8. The CO2 supercritical servo system according to claim 1, characterized in that, The CO2 condenser, CO2 precooler, and CO2 float valve are connected in sequence to form the condensation circuit of the main system, and the first passage is connected in parallel to the condensation circuit.

9. The CO2 supercritical servo system according to claim 3, characterized in that, A pressure sensor is installed on the CO2 circulation tank, and a temperature sensor is installed on the terminal evaporator.

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