Efficient operation control system and method for carbon dioxide heat pump system

Abstract

The invention discloses an efficient operation control system and method for a carbon dioxide heat pump system, and relates to the technical field of operation control, and the efficient operation control system comprises a coefficient model construction unit, a heat exchange area analysis unit, a mode switching unit, a heat supply data determination unit, a hot water parameter calculation unit and a mode operation unit. The heating effect is fully guaranteed, the heating function and the domestic hot water preparation function are integrated, multiple intelligent switching modes of heating, hot water and heating and hot water are achieved, the composite mode can preferentially meet the requirement for high-temperature domestic hot water, waste heat is efficiently recycled for heating, grade matching and gradient utilization of energy are achieved, and the energy utilization rate is increased. The system is particularly suitable for public buildings such as hotels, hospitals, schools, clubs and the like with central heating and a large amount of domestic hot water requirements, efficient cooperation and rotation operation among units are achieved through an intelligent group control strategy, and dynamic loads are accurately matched.

Description

Technical Field

[0001] This invention relates to the field of operation control technology, specifically to a high-efficiency operation control system and method for a carbon dioxide heat pump system. Background Technology

[0002] A high-efficiency operation control system for a carbon dioxide heat pump system is disclosed. This system dynamically adjusts the operating status of the equipment by real-time monitoring parameters and using optimization algorithms, enabling the system to have multiple operating modes, namely heating, hot water, and heating + hot water, while further improving energy-saving effect. Patent application number 202411200322.0 discloses "a carbon dioxide refrigeration heat pump system and a composite control method for the carbon dioxide refrigeration heat pump system." The carbon dioxide refrigeration heat pump system includes a first compressor, a second compressor, a third compressor, a water cooler, a first regenerator, a first throttling valve, a flash tank, a second throttling valve, an evaporator, a liquid storage tank, a flash bypass valve, and a second regenerator, all interconnected and coordinated. The carbon dioxide refrigeration heat pump system and composite control method disclosed in this invention are scientifically designed and can effectively achieve precise control of the operating conditions of the carbon dioxide refrigeration heat pump system, improve control accuracy, significantly improve operating energy efficiency, and ensure operating efficiency, which has significant practical significance. The composite control method for the carbon dioxide refrigeration heat pump system specifically designed in this invention is a dimension-reducing and decoupled control method for dealing with complex systems operating under varying conditions.

[0003] The aforementioned existing technology has solved the problem that the low control accuracy of complex system structures often leads to deviations from the optimal operating conditions in actual operation. However, when the system is running, the unit's energy efficiency begins to decline when the ambient temperature drops below 5°C, and it is almost unusable at -25°C, thus affecting the user experience. Furthermore, the system does not have multiple operating modes and cannot adapt to different scenarios. Summary of the Invention

[0004] The purpose of this invention is to provide a high-efficiency operation control system and method for a carbon dioxide heat pump system to solve the problems mentioned in the background art.

[0005] To achieve the above objectives, the present invention provides the following technical solution: a high-efficiency operation control system for a carbon dioxide heat pump system, including a hot water parameter calculation unit;

[0006] A coefficient model construction unit is used to build a coefficient model corresponding to the compressor's heat and power.

[0007] The heat exchange area analysis unit calculates the heat exchange area using the logarithmic mean temperature difference method and the finite volume method, and models and calculates the heat exchanger using the distributed parameter method to determine the average temperature difference.

[0008] The mode switching unit controls a three-way valve to switch between heating and hot water supply modes, and utilizes an evaporator, compressor, subcooler and condenser to complete the main circulation and auxiliary circulation.

[0009] The heating data determination unit reads known parameters, runs the main cycle first compressor model and the auxiliary cycle second compressor model, analyzes the heat exchange of the subcooler and the heat exchange of the auxiliary cycle evaporator using the known parameters, calculates the condition value through the heat exchange of the subcooler and the heat exchange of the auxiliary cycle evaporator, and outputs the subcooling degree if the condition value is less than 0.01, otherwise the subcooling degree is reset.

[0010] The mode operation unit obtains the current mode and controls the start and stop of each device according to the specified mode to complete the corresponding operation.

[0011] Preferably, the coefficient model in the coefficient model construction unit includes the cooling capacity of the compressor. Compressor power Overall compressor efficiency and mass flow Model, the cooling capacity of the compressor Compressor power Overall compressor efficiency and mass flow The model is as follows: , in, Indicates the evaporation temperature. This indicates the exhaust pressure.

[0012] Preferably, the average temperature difference determined in the heat exchange area analysis unit is specifically as follows:

[0013] S101. The condenser is divided into three parts: the two-phase zone, the subcooled zone, and the superheated zone.

[0014] S102. Divide the evaporator into two parts: a two-phase zone and a superheated zone.

[0015] S103. The overall heat transfer coefficient is calculated using the micro-element method, and the heat transfer area and average temperature difference of the heat exchanger are analyzed. The overall heat transfer coefficient, heat transfer area, and average temperature difference are specifically as follows:

[0016]

[0017]

[0018]

[0019] in, Indicates the total thermal resistance. Indicates the overall heat transfer coefficient. Indicates the outer surface area of ​​the tube. Indicates the inner surface area of ​​the tube. This indicates the contact resistance on the cold fluid side. Indicates the contact resistance on the hot fluid side. Indicates the inner radius of a circular pipe or conduit. Indicates the heat exchange area. This indicates the maximum temperature difference value. This represents the minimum temperature difference value. This represents the average temperature difference. This indicates heat flow.

[0020] Preferably, the main loop and auxiliary loop are completed in the mode switching unit as follows:

[0021] S201. The low-temperature, low-pressure gas generated by the evaporator is compressed by the compressor and then directly enters the air cooler to release heat.

[0022] S202. During heating, the working fluid at the outlet of the air cooler is transferred to the subcooler. The subcooled refrigerant flows through the throttling valve to reduce its pressure and is finally transferred to the evaporator for evaporation, thus completing the main cycle.

[0023] S203. In the auxiliary cycle, the subcooler acts as the evaporator of the subcooling cycle. The low-temperature and low-pressure refrigerant flowing out of the evaporator is drawn into the compressor and compressed. The high-temperature and high-pressure refrigerant at the compressor outlet enters the condenser, condenses and releases heat, and then is transferred to the expansion valve for throttling and pressure reduction.

[0024] S204. The return water flowing into the air cooler and condenser is in series, that is, the return water first flows through the condenser to be heated, and then flows into the air cooler to absorb heat.

[0025] Preferably, the known parameters in the heating data determination unit specifically include ambient temperature, evaporation temperature, inlet water temperature, outlet water temperature, superheat, narrow-point temperature difference of the air cooler, narrow-point temperature difference of the subcooler, outlet temperature of the air cooler, and exhaust pressure.

[0026] Preferably, the heat exchange capacity of the subcooler and the heat exchange capacity of the auxiliary circulation evaporator are analyzed using known parameters in the heating data determination unit as follows:

[0027] S301. Run the main cycle first compressor model and calculate the compressor's total efficiency, main cycle mass flow rate, and compressor outlet state point parameters.

[0028] S302. Analyze the heat exchange and water flow rate of the air cooler using the outlet temperature, exhaust pressure and supply and return water temperatures of the air cooler.

[0029] S303. After setting the subcooling, determine the state points of the subcooler heat exchange, subcooler outlet, and auxiliary circulation evaporator outlet.

[0030] S304. Run the auxiliary cycle second compressor model and calculate the total efficiency of the second compressor, the auxiliary cycle mass flow rate, the outlet state point parameters of the second compressor, and the heat exchange of the auxiliary cycle evaporator.

[0031] Preferably, the hot water parameter calculation unit reads the ambient temperature, evaporation temperature, supply and return water temperature, superheat, and narrow point temperature difference of the air cooler, sets the exhaust pressure, runs the compressor model, calculates the compressor's total efficiency, mass flow rate, and compressor outlet state point parameters, divides the system into infinitesimal segments using the infinitesimal method, and calculates the condition values ​​using the supply and return water temperatures and the inlet and outlet temperatures of the air cooler. If the condition value is less than 0.01, the exhaust pressure, four state points, and COP are output; otherwise, the exhaust pressure is reset.

[0032] Preferably, the mode operation unit controls the start and stop of each device according to a specified mode as follows:

[0033] S401. When in heating mode, the second air cooler stops working. The heating return water is heated by the R134a subcooling circulation condenser. The medium-temperature hot water flowing out of the condenser enters the first air cooler for further heating. The heating supply water flows out from the first air cooler to provide heating for users.

[0034] S402. When in hot water supply mode, the first air cooler and the R134a subcooling cycle condenser stop working and transfer the hot water return water to the second air cooler for heating. The hot water flowing out of the outlet of the second air cooler is used for domestic hot water.

[0035] S403. When in heating + hot water supply mode, the refrigerant at the compressor outlet flows sequentially through the second air cooler and the first air cooler. The fluid at the outlet of the first air cooler is subcooled through the auxiliary circulation, and then passes sequentially through the safety valve, high pressure valve, dryer filter, buffer tank and throttle valve, and finally enters the evaporator to evaporate, completing the thermodynamic cycle. The heating medium and the hot water supply and return water are both configured with independent pipelines.

[0036] S404. When in defrost mode, the defrost solenoid valve is open and the electronic expansion valve is fully closed. The low-temperature, low-pressure refrigerant is compressed by the compressor and becomes a high-temperature, high-pressure state. The high-temperature, high-pressure gas flowing out of the compressor becomes a low-pressure, high-temperature gas after being throttled by the defrost electronic valve. The high-temperature refrigerant releases heat inside the evaporator to heat the frost layer. The refrigerant returns to the compressor after releasing heat, and the frost layer on the fin surface gradually melts, thus achieving the defrost function.

[0037] S405. Install a defrosting electric heater. When using the electric heater for defrosting, the solenoid valve is closed, and the compressor and air cooler fan are stopped. The switch of the heating element is turned on to start defrosting.

[0038] The efficient operation control method for a carbon dioxide heat pump system includes the following steps:

[0039] S1. Constructing a coefficient model: Building a coefficient model corresponding to the compressor's heat and power;

[0040] S2. Calculate the heat exchange area: The heat exchange area is calculated using the logarithmic mean temperature difference method and the finite volume method. The heat exchanger is modeled and calculated using the distributed parameter method to determine the average temperature difference.

[0041] S3. Determine the main circulation and auxiliary circulation: Switch between heating and hot water supply modes by controlling the three-way valve, and complete the main circulation and auxiliary circulation using the evaporator, compressor, subcooler and condenser;

[0042] S4. Determine relevant parameters: Read the known parameters, run the main cycle first compressor model and the auxiliary cycle second compressor model, analyze the heat exchange of the subcooler and the heat exchange of the auxiliary cycle evaporator using the known parameters, calculate the condition value using the heat exchange of the subcooler and the heat exchange of the auxiliary cycle evaporator, if the condition value is less than 0.01, output the subcooling degree, otherwise reset the subcooling degree, read the ambient temperature, evaporation temperature, supply and return water temperature, superheat degree and narrow point temperature difference of the air cooler, and set the discharge pressure, run the compressor model, calculate the compressor total efficiency, mass flow rate and compressor outlet state point parameters, divide the micro-element segment using the micro-element method, calculate the condition value using the supply and return water temperature and the inlet and outlet temperature of the air cooler, if the condition value is less than 0.01, output the discharge pressure, 4-point state point and COP, otherwise reset the discharge pressure;

[0043] S5. After obtaining the current mode, control the start and stop of each device according to the specified mode to complete the corresponding operation.

[0044] Compared with the prior art, the beneficial effects of the present invention are:

[0045] This invention fully guarantees heating performance and integrates heating and domestic hot water preparation functions into one unit. It also features multiple intelligent switching modes, including "heating," "hot water," and "heating + hot water." This composite mode prioritizes meeting the demand for high-temperature domestic hot water and efficiently recovers and utilizes waste heat for heating, achieving energy quality matching and tiered utilization, thereby significantly reducing operating costs. This system is particularly suitable for public buildings such as hotels, hospitals, schools, and clubs that have both centralized heating and a large demand for domestic hot water. Through intelligent group control strategies, it achieves efficient coordination and rotation operation between units, accurately matching dynamic loads. Attached Figure Description

[0046] Figure 1 A schematic diagram of the overall system flow is provided for embodiments of the present invention;

[0047] Figure 2 The series return water two-stage compressor mechanical subcooling provided in the embodiments of the present invention Heat pump system diagram;

[0048] Figure 3 This is a general system block diagram provided for embodiments of the present invention;

[0049] Figure 4 This is a block diagram of a heating mode system provided in an embodiment of the present invention;

[0050] Figure 5 This is a block diagram of a hot water supply mode system provided in an embodiment of the present invention;

[0051] Figure 6 This is a block diagram of a heating + hot water supply system provided in an embodiment of the present invention;

[0052] Figure 7 This is a block diagram of the defrosting mode system provided in an embodiment of the present invention. Detailed Implementation

[0053] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0054] Example 1:

[0055] Please see Figures 1-7 The present invention provides a technical solution: a high-efficiency operation control system for a carbon dioxide heat pump system, including a hot water parameter calculation unit;

[0056] The coefficient model building unit constructs a coefficient model corresponding to the compressor's heat and power.

[0057] The heat exchange area analysis unit calculates the heat exchange area using the logarithmic mean temperature difference method and the finite volume method, and models and calculates the heat exchanger using the distributed parameter method to determine the average temperature difference.

[0058] The mode switching unit controls a three-way valve to switch between heating and hot water supply modes, and utilizes the evaporator, compressor, subcooler and condenser to complete the main circulation and auxiliary circulation.

[0059] The heating data determination unit reads known parameters, runs the main cycle first compressor model and the auxiliary cycle second compressor model, analyzes the heat exchange of the subcooler and the heat exchange of the auxiliary cycle evaporator using the known parameters, calculates the condition value through the heat exchange of the subcooler and the heat exchange of the auxiliary cycle evaporator, and outputs the subcooling degree if the condition value is less than 0.01, otherwise the subcooling degree is reset.

[0060] The mode operation unit obtains the current mode and controls the start and stop of each device according to the specified mode to complete the corresponding operation.

[0061] The coefficient model in the coefficient model construction unit includes the compressor's cooling capacity. Compressor power Overall compressor efficiency and mass flow Model, cooling capacity of the compressor Compressor power Overall compressor efficiency and mass flow The model is as follows: , in, Indicates the evaporation temperature. Indicates exhaust pressure;

[0062] The average temperature difference determined in the heat exchange area analysis unit is as follows:

[0063] S101. The condenser is divided into three parts: the two-phase zone, the subcooled zone, and the superheated zone.

[0064] S102. Divide the evaporator into two parts: a two-phase zone and a superheated zone.

[0065] S103. The overall heat transfer coefficient is calculated using the micro-segment method, and the heat transfer area and average temperature difference of the heat exchanger are analyzed. A plate heat exchanger with compact structure, small footprint, high heat transfer efficiency, high pressure resistance, and reliable operation is selected. The specific overall heat transfer coefficient, heat transfer area, and average temperature difference are as follows:

[0066]

[0067]

[0068]

[0069] in, Indicates the total thermal resistance. Indicates the overall heat transfer coefficient. Indicates the outer surface area of ​​the tube. Indicates the inner surface area of ​​the tube. This indicates the contact resistance on the cold fluid side. Indicates the contact resistance on the hot fluid side. Indicates the inner radius of a circular pipe or conduit. Indicates the heat exchange area. This indicates the maximum temperature difference value. This represents the minimum temperature difference value. This represents the average temperature difference. Indicates heat flow;

[0070] The main loop and auxiliary loop are completed in the mode switching unit as follows:

[0071] S201. The low-temperature, low-pressure gas generated by the evaporator is compressed by the compressor and then directly enters the air cooler to release heat.

[0072] S202. During heating, the working fluid at the outlet of the air cooler is transferred to the subcooler. The subcooled refrigerant flows through the throttling valve to reduce its pressure and is finally transferred to the evaporator for evaporation, thus completing the main cycle.

[0073] S203. In the auxiliary cycle, the subcooler acts as the evaporator of the subcooling cycle. The low-temperature and low-pressure refrigerant flowing out of the evaporator is drawn into the compressor and compressed. The high-temperature and high-pressure refrigerant at the compressor outlet enters the condenser, condenses and releases heat, and then is transferred to the expansion valve for throttling and pressure reduction.

[0074] S204. The return water flowing into the air cooler and condenser is in series, that is, the return water first flows through the condenser to be heated, and then flows into the air cooler to absorb heat.

[0075] The known parameters in the heating data determination unit specifically include ambient temperature, evaporation temperature, inlet water temperature, outlet water temperature, superheat, narrow point temperature difference of air cooler, narrow point temperature difference of subcooler, outlet temperature of air cooler, and exhaust pressure.

[0076] The heat exchange capacity of the subcooler and the auxiliary circulation evaporator are specifically analyzed using known parameters in the heating data determination unit as follows:

[0077] S301. Run the main cycle first compressor model and calculate the compressor's total efficiency, main cycle mass flow rate, and compressor outlet state point parameters.

[0078] S302. Analyze the heat exchange and water flow rate of the air cooler using the outlet temperature, exhaust pressure and supply and return water temperatures of the air cooler.

[0079] S303. After setting the subcooling, determine the state points of the subcooler heat exchange, subcooler outlet, and auxiliary circulation evaporator outlet.

[0080] S304. Run the auxiliary cycle second compressor model and calculate the total efficiency of the second compressor, the auxiliary cycle mass flow rate, the outlet state point parameters of the second compressor, and the heat exchange of the auxiliary cycle evaporator.

[0081] The hot water parameter calculation unit reads the ambient temperature, evaporation temperature, supply and return water temperature, superheat, and narrow point temperature difference of the air cooler. After setting the exhaust pressure, it runs the compressor model and calculates the compressor's total efficiency, mass flow rate, and compressor outlet state point parameters. It divides the system into infinitesimal segments using the infinitesimal method and calculates the condition values ​​using the supply and return water temperatures and the inlet and outlet temperatures of the air cooler. If the condition value is less than 0.01, it outputs the exhaust pressure, four state points, and COP; otherwise, it resets the exhaust pressure.

[0082] The mode operation unit controls the start and stop of each device according to the specified mode, specifically as follows:

[0083] S401. When in heating mode, the second air cooler stops working. The heating return water is heated by the R134a subcooling circulation condenser. The medium-temperature hot water flowing out of the condenser enters the first air cooler for further heating. The heating supply water flows out from the first air cooler to provide heating for users.

[0084] S402. When in hot water supply mode, the first air cooler and the R134a subcooling cycle condenser stop working and transfer the hot water return water to the second air cooler for heating. The hot water flowing out of the outlet of the second air cooler is used for domestic hot water.

[0085] S403. When in heating + hot water supply mode, the refrigerant at the compressor outlet flows sequentially through the second air cooler and the first air cooler. The fluid at the outlet of the first air cooler is subcooled through the auxiliary circulation, and then passes sequentially through the safety valve, high pressure valve, dryer filter, buffer tank and throttle valve, and finally enters the evaporator to evaporate, completing the thermodynamic cycle. The heating medium and the hot water supply and return water are both configured with independent pipelines.

[0086] S404. When in defrost mode, the defrost solenoid valve is open and the electronic expansion valve is fully closed. The low-temperature, low-pressure refrigerant is compressed by the compressor and becomes a high-temperature, high-pressure state. The high-temperature, high-pressure gas flowing out of the compressor becomes a low-pressure, high-temperature gas after being throttled by the defrost electronic valve. The high-temperature refrigerant releases heat inside the evaporator to heat the frost layer. The refrigerant returns to the compressor after releasing heat, and the frost layer on the fin surface gradually melts, thus achieving the defrost function.

[0087] S405. Install a defrosting electric heater. When using the electric heater for defrosting, the solenoid valve is closed, and the compressor and air cooler fan are stopped. The switch of the heating element is turned on to start defrosting.

[0088] A method for efficient operation control of a carbon dioxide heat pump system includes the following steps:

[0089] S1. Constructing a coefficient model: Building a coefficient model corresponding to the compressor's heat and power;

[0090] S2. Calculate the heat exchange area: The heat exchange area is calculated using the logarithmic mean temperature difference method and the finite volume method. The heat exchanger is modeled and calculated using the distributed parameter method to determine the average temperature difference.

[0091] S3. Determine the main circulation and auxiliary circulation: Switch between heating and hot water supply modes by controlling the three-way valve, and complete the main circulation and auxiliary circulation using the evaporator, compressor, subcooler and condenser;

[0092] S4. Determine relevant parameters: Read the known parameters, run the main cycle first compressor model and the auxiliary cycle second compressor model, analyze the heat exchange of the subcooler and the heat exchange of the auxiliary cycle evaporator using the known parameters, calculate the condition value using the heat exchange of the subcooler and the heat exchange of the auxiliary cycle evaporator, if the condition value is less than 0.01, output the subcooling degree, otherwise reset the subcooling degree, read the ambient temperature, evaporation temperature, supply and return water temperature, superheat degree and narrow point temperature difference of the air cooler, and set the discharge pressure, run the compressor model, calculate the compressor total efficiency, mass flow rate and compressor outlet state point parameters, divide the micro-element segment using the micro-element method, calculate the condition value using the supply and return water temperature and the inlet and outlet temperature of the air cooler, if the condition value is less than 0.01, output the discharge pressure, 4-point state point and COP, otherwise reset the discharge pressure;

[0093] S5. After obtaining the current mode, control the start and stop of each device according to the specified mode to complete the corresponding operation.

[0094] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0095] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A high-efficiency operation control system for a carbon dioxide heat pump system, comprising a hot water parameter calculation unit, characterized in that: A coefficient model construction unit is used to build a coefficient model corresponding to the compressor's heat and power. The heat exchange area analysis unit calculates the heat exchange area using the logarithmic mean temperature difference method and the finite volume method, and models and calculates the heat exchanger using the distributed parameter method to determine the average temperature difference. The mode switching unit controls a three-way valve to switch between heating and hot water supply modes, and utilizes an evaporator, compressor, subcooler and condenser to complete the main circulation and auxiliary circulation.

2. Heating data determination unit: The heating data determination unit reads known parameters, runs the main cycle first compressor model and the auxiliary cycle second compressor model, analyzes the heat exchange of the subcooler and the heat exchange of the auxiliary cycle evaporator using the known parameters, calculates the condition value through the heat exchange of the subcooler and the heat exchange of the auxiliary cycle evaporator, and outputs the subcooling degree if the condition value is less than 0.01; otherwise, the subcooling degree is reset. The mode operation unit obtains the current mode and controls the start and stop of each device according to the specified mode to complete the corresponding operation.

3. The high-efficiency operation control system for a carbon dioxide heat pump system according to claim 1, characterized in that: The coefficient model in the coefficient model construction unit includes the cooling capacity of the compressor. Compressor power Overall compressor efficiency and mass flow Model, the cooling capacity of the compressor Compressor power Overall compressor efficiency and mass flow The model is as follows: ， in, Indicates the evaporation temperature. This indicates the exhaust pressure.

4. The high-efficiency operation control system for a carbon dioxide heat pump system according to claim 1, characterized in that: The average temperature difference determined in the heat exchange area analysis unit is as follows: S101. The condenser is divided into three parts: the two-phase zone, the subcooled zone, and the superheated zone. S102. Divide the evaporator into two parts: a two-phase zone and a superheated zone. S103. The overall heat transfer coefficient is calculated using the micro-segment method, and the heat transfer area and average temperature difference of the heat exchanger are analyzed.

5. The high-efficiency operation control system for a carbon dioxide heat pump system according to claim 1, characterized in that: The main loop and auxiliary loop are completed in the mode switching unit as follows: S201. The low-temperature, low-pressure gas generated by the evaporator is compressed by the compressor and then directly enters the air cooler to release heat. S202. During heating, the working fluid at the outlet of the air cooler is transferred to the subcooler. The subcooled refrigerant flows through the throttling valve to reduce its pressure and is finally transferred to the evaporator for evaporation, thus completing the main cycle. S203. In the auxiliary cycle, the subcooler acts as the evaporator of the subcooling cycle. The low-temperature and low-pressure refrigerant flowing out of the evaporator is drawn into the compressor and compressed. The high-temperature and high-pressure refrigerant at the compressor outlet enters the condenser, condenses and releases heat, and then is transferred to the expansion valve for throttling and pressure reduction. S204. The return water flowing into the air cooler and condenser is in series, that is, the return water first flows through the condenser to be heated, and then flows into the air cooler to absorb heat.

6. The high-efficiency operation control system for a carbon dioxide heat pump system according to claim 1, characterized in that: The known parameters in the heating data determination unit specifically include ambient temperature, evaporation temperature, inlet water temperature, outlet water temperature, superheat, narrow-point temperature difference of the air cooler, narrow-point temperature difference of the subcooler, outlet temperature of the air cooler, and exhaust pressure.

7. The high-efficiency operation control system for a carbon dioxide heat pump system according to claim 1, characterized in that: The heating data determination unit analyzes the heat exchange capacity of the subcooler and the heat exchange capacity of the auxiliary circulation evaporator using known parameters, specifically as follows: S301. Run the main cycle first compressor model and calculate the compressor's total efficiency, main cycle mass flow rate, and compressor outlet state point parameters. S302. Analyze the heat exchange and water flow rate of the air cooler using the outlet temperature, exhaust pressure and supply and return water temperatures of the air cooler. S303. After setting the subcooling, determine the state points of the subcooler heat exchange, subcooler outlet, and auxiliary circulation evaporator outlet. S304. Run the auxiliary cycle second compressor model and calculate the total efficiency of the second compressor, the auxiliary cycle mass flow rate, the outlet state point parameters of the second compressor, and the heat exchange of the auxiliary cycle evaporator.

8. The high-efficiency operation control system for a carbon dioxide heat pump system according to claim 1, characterized in that: The hot water parameter calculation unit reads the ambient temperature, evaporation temperature, supply and return water temperature, superheat, and narrow-point temperature difference of the air cooler. It then sets the exhaust pressure, runs the compressor model, calculates the compressor's total efficiency, mass flow rate, and compressor outlet state point parameters, divides the system into infinitesimal segments using the infinitesimal method, and calculates the condition values ​​using the supply and return water temperatures and the air cooler's inlet and outlet temperatures. If the condition value is less than 0.01, it outputs the exhaust pressure, four state points, and COP; otherwise, it resets the exhaust pressure.

9. The high-efficiency operation control system for a carbon dioxide heat pump system according to claim 1, characterized in that: The specific steps of controlling the start and stop of each device according to the specified mode in the mode operation unit are as follows: S401. When in heating mode, the second air cooler stops working. The heating return water is heated by the R134a subcooling circulation condenser. The medium-temperature hot water flowing out of the condenser enters the first air cooler for further heating. The heating supply water flows out from the first air cooler to provide heating for users. S402. When in hot water supply mode, the first air cooler and the R134a subcooling cycle condenser stop working and transfer the hot water return water to the second air cooler for heating. The hot water flowing out of the outlet of the second air cooler is used for domestic hot water. S403. When in heating + hot water supply mode, the refrigerant at the compressor outlet flows sequentially through the second air cooler and the first air cooler. The fluid at the outlet of the first air cooler is subcooled through the auxiliary circulation, and then passes sequentially through the safety valve, high pressure valve, dryer filter, buffer tank and throttle valve, and finally enters the evaporator to evaporate, completing the thermodynamic cycle. The heating medium and the hot water supply and return water are both configured with independent pipelines. S404. When in defrost mode, the defrost solenoid valve is open and the electronic expansion valve is fully closed. The low-temperature, low-pressure refrigerant is compressed by the compressor and becomes a high-temperature, high-pressure state. The high-temperature, high-pressure gas flowing out of the compressor becomes a low-pressure, high-temperature gas after being throttled by the defrost electronic valve. The high-temperature refrigerant releases heat inside the evaporator to heat the frost layer. The refrigerant returns to the compressor after releasing heat, and the frost layer on the fin surface gradually melts, thus achieving the defrost function. S405. Set up a defrosting electric heater. When using the electric heater for defrosting, the solenoid valve is closed, and the compressor and air cooler fan are stopped. The switch of the heating element is turned on to start defrosting.

10. A method for efficient operation control of a carbon dioxide heat pump system, characterized in that, The operation control method is applicable to the high-efficiency operation control system of a carbon dioxide heat pump system as described in any one of claims 1-8, and includes the following steps: S1. Constructing a coefficient model: Building a coefficient model corresponding to the compressor's heat and power; S2. Calculate the heat exchange area: The heat exchange area is calculated using the logarithmic mean temperature difference method and the finite volume method. The heat exchanger is modeled and calculated using the distributed parameter method to determine the average temperature difference. S3. Determine the main circulation and auxiliary circulation: Switch between heating and hot water supply modes by controlling the three-way valve, and complete the main circulation and auxiliary circulation using the evaporator, compressor, subcooler and condenser; S4. Determine relevant parameters: Read the known parameters, run the main cycle first compressor model and the auxiliary cycle second compressor model, analyze the heat exchange of the subcooler and the heat exchange of the auxiliary cycle evaporator using the known parameters, calculate the condition value using the heat exchange of the subcooler and the heat exchange of the auxiliary cycle evaporator, if the condition value is less than 0.01, output the subcooling degree, otherwise reset the subcooling degree, read the ambient temperature, evaporation temperature, supply and return water temperature, superheat degree and narrow point temperature difference of the air cooler, set the discharge pressure, run the compressor model, calculate the compressor total efficiency, mass flow rate and compressor outlet state point parameters, divide the infinitesimal segment using the infinitesimal element method, calculate the condition value using the supply and return water temperature and the inlet and outlet temperature of the air cooler, if the condition value is less than 0.01, output the discharge pressure, 4-point state point and COP, otherwise reset the discharge pressure; S5. After obtaining the current mode, control the start and stop of each device according to the specified mode to complete the corresponding operation.

Images