Transcritical CO2 heat pump system and control method thereof

Abstract

The invention discloses a transcritical CO2 heat pump system and a control method thereof.The transcritical CO2 heat pump system comprises a first loop system, the first loop system comprises a compressor, an air cooler, a heat regenerator, a flow adjusting valve, an electronic expansion valve, an evaporation assembly and a pipeline assembly, and fluid is configured to flow out of the compressor and flow out of the heat regenerator; the fluid flows to the air cooler, the flow adjusting valve, the electronic expansion valve, the evaporation assembly and the heat regenerator through the pipeline assembly and flows back to the compressor, the fluid at the outlet end of the flow adjusting valve is divided into a first line and a second line, and the fluid in the first line is converged with the fluid passing through the second line after flowing through the heat regenerator and flows to the electronic expansion valve. The first loop system provides energy for the second loop system through the air cooler. According to the method, through collaborative optimization of the actual exhaust pressure and the actual heat regeneration efficiency, it is ensured that the exhaust temperature of the compressor is appropriate, the exhaust pressure is reduced, and efficient and stable operation of the system under all working conditions is achieved.

Description

Technical Field

[0001] The present application relates to the technical field of transcritical CO2 heat pump systems, and particularly to a transcritical CO2 heat pump system and a control method thereof. Background Art

[0002] Under the requirements of a low-carbon society, heat pump refrigeration technology has been increasingly widely used in various fields due to its advantages such as high energy efficiency, no pollutant emissions, environmental friendliness, and intelligence. Commonly used refrigerants in its systems include chlorofluorocarbons (CFCs), hydrochlorofluorocarbons (HCFCs), and hydrofluorocarbons (HFCs). However, the above-mentioned fluorinated alkane refrigerants have a high global warming potential (GWP) and will cause a strong greenhouse effect. Therefore, a transcritical CO2 heat pump system using working fluids such as CO2 has emerged.

[0003] A transcritical CO2 heat pump system is a heat pump cycle using a supercritical working fluid, such as CO2. Its characteristic is that the working fluid is in a supercritical state on the high-pressure side, such as the gas cooler 20, without a traditional condensation process, and the temperature changes continuously with the heat exchange process. Compared with the subcritical cycle, the transcritical system has advantages in high-temperature heat supply (such as above 80°C) and environmental friendliness, with the ODP of CO2 working fluid being 0 and the GWP being 1, etc. However, its system efficiency is unstable and the energy loss is relatively high.

[0004] Supercritical heat exchange and compression process The loss accounts for a large proportion and multi-objective collaborative optimization is required. Existing models are often over-simplified and it is difficult to accurately guide actual operation. Summary of the Invention

[0005] The present application provides a transcritical CO2 heat pump system and a control method thereof. The transcritical CO2 heat pump system can collaboratively optimize the optimal discharge pressure and the regenerator efficiency within a wide operating condition range, reduce the optimal discharge pressure, make the discharge temperature of the compressor appropriate, improve the coefficient of performance of the system, and make the coefficient of performance (COP) of the transcritical CO2 heat pump system continuously optimal.

[0006] In a first aspect, an embodiment of the present application provides a control method for a transcritical CO2 heat pump system. The transcritical CO2 heat pump system includes a first loop system. The first loop system includes a compressor, a gas cooler, a regenerator, a flow regulating valve, an electronic expansion valve, an evaporation component, and a pipeline component. Among them, the fluid is configured to flow out of the compressor, flow through the pipeline component to the gas cooler, the flow regulating valve, the electronic expansion valve, the evaporation component, the regenerator, and then return to the compressor. And the fluid at the outlet end of the flow regulating valve is divided into a first line and a second line. The fluid in the first line flows through the regenerator and then converges with the fluid passing through the second line and flows to the electronic expansion valve. The first loop system provides energy for the second loop system through the gas cooler. The method includes:

[0007] Obtain the actual heat regeneration efficiency of the regenerator and the actual exhaust pressure of the compressor;

[0008] According to the actual heat regeneration efficiency, adjust the flow rate of the flow regulating valve flowing through the regenerator to meet the first preset condition;

[0009] According to the actual exhaust pressure, adjust the opening degree of the electronic expansion valve until the actual exhaust pressure meets the second preset condition.

[0010] When facing different working conditions and external environment changes of the transcritical CO2 heat pump system, a flow regulating valve is set in the transcritical CO2 heat pump system. By adjusting the flow rate of the working medium flowing through the regenerator, the heat regeneration efficiency of the regenerator is adjusted to reduce heat loss; the optimal exhaust pressure and the regenerator efficiency are synergistically optimized, reducing the loss of this key link of the system regenerator and compressor. For example, adjusting the actual exhaust pressure reduces the compression ratio of the compressor, and combined with real-time sensor data (such as temperature, pressure), it can respond to environmental and load changes in a timely manner, enabling the transcritical CO2 heat pump system to reduce the optimal exhaust pressure within a wide range of working conditions, making the exhaust temperature of the compressor appropriate, improving the coefficient of performance of the system, and making the coefficient of performance (COP) of the transcritical CO2 heat pump system continuously optimal. In some alternative embodiments, the transcritical CO2 heat pump system includes a temperature detector. The temperature detector includes a first temperature detector located at the fluid outlet end of the gas cooler and an ambient temperature detector. The ambient temperature detector is used to obtain the ambient temperature of the transcritical CO2 heat pump system in real time. The method further includes:

[0011] When the real-time ambient temperature of the transcritical CO2 heat pump system ≥ the first preset temperature and the detected temperature of the first temperature detector ≥ the second preset temperature, adjust the actual heat regeneration efficiency to the first preset condition and adjust the actual exhaust pressure to the second preset condition;

[0012] When the real-time ambient temperature of the transcritical CO2 heat pump system < the first preset temperature and the detected temperature of the first temperature detector < the second preset temperature, adjust the actual exhaust pressure to the second preset condition.

[0013] In some alternative embodiments, the temperature detector includes a first temperature detector located at the fluid outlet end of the gas cooler and a second temperature detector located at the fluid outlet end of the compressor;

[0014] When the real-time ambient temperature of the transcritical CO2 heat pump system ≥ the first preset temperature and the detected temperature of the first temperature detector ≥ the second preset temperature, adjusting the actual heat regeneration efficiency to the first preset condition and adjusting the actual exhaust pressure to the second preset condition includes:

[0015]

[0016] ​When the detected temperature of the second temperature detector is less than the rated maximum temperature of the compressor, first adjust the actual regenerative efficiency to the first preset condition, and then adjust the actual discharge pressure to the second preset condition;

[0017] When the detected temperature of the second temperature detector is greater than or equal to the rated maximum temperature of the compressor, first adjust the actual discharge pressure to the second preset condition, and then adjust the actual regenerative efficiency to the first preset condition.

[0018] In some alternative embodiments, the first preset condition is |η ihx -η ihx,opt |≤ε1, where η ihx represents the actual regenerative efficiency of the regenerator, η ihx,opt represents the optimal regenerative efficiency of the regenerator, and ε1 is a preset constant.

[0019] In some alternative embodiments, the temperature detector includes a third temperature detector located at the fluid inlet end of the compressor and a fourth temperature detector located at the fluid outlet end of the evaporation assembly;

[0020] η ihx is determined by Equation (1),

[0021] where η ihx represents the actual regenerative efficiency of the regenerator, T1 represents the temperature detected by the first temperature detector; T3 represents the temperature detected by the third temperature detector; T4 represents the temperature detected by the fourth temperature detector;

[0022] η ihx,opt is determined by Equation (2),

[0023] η ihx,opt =0.4080 + 0.0099T1 - 1.3542×10 -4 T1 2 (2)

[0024] where η ihx,opt represents the optimal regenerative efficiency of the regenerator, and T3 represents the temperature detected by the third temperature detector.

[0025] In some alternative embodiments, the second preset condition is |P2 - P opt |≤ε2, P2 represents the actual discharge pressure of the transcritical CO2 heat pump system, and P opt represents the optimal discharge pressure of the transcritical CO2 heat pump system, and ε2 is a preset constant.

[0026] In some alternative embodiments, the second loop system includes a circulation pump; P opt is determined by Equation (3),

[0027]

[0028] Among them, T1 represents the temperature detected by the first temperature detector, and T wi represents the inlet water temperature at the inlet end of the circulation pump

[0029] In a second aspect, an embodiment of the present application provides a transcritical CO2 heat pump system, including:

[0030] A first circuit system, including a compressor, an air cooler, a regenerator, a flow regulating valve, an electronic expansion valve, an evaporation assembly, and a pipeline assembly; the fluid is configured to flow out of the compressor, flow through the pipeline assembly to the air cooler, the flow regulating valve, the electronic expansion valve, the evaporation assembly, the regenerator, and then flow back to the compressor, and the fluid at the outlet end of the flow regulating valve is divided into a first line and a second line. The fluid in the first line flows through the regenerator and then converges with the fluid passing through the second line, and flows to the electronic expansion valve. Among them, the first circuit system provides energy for the second circuit system through the air cooler;

[0031] A third circuit system, including

[0032] An acquisition unit, configured to acquire the actual heat regeneration efficiency of the regenerator and the actual exhaust pressure of the compressor;

[0033] A control unit, the control unit includes: a first control unit, configured to adjust the flow rate of the flow regulating valve flowing through the regenerator to meet a first preset condition according to the actual heat regeneration efficiency; a second control unit, configured to adjust the opening degree of the electronic expansion valve to make the actual exhaust pressure meet a second preset condition according to the actual exhaust pressure.

[0034] In some alternative embodiments, the third circuit system includes a driver, one end of the driver is respectively signal-connected to the compressor, the flow regulating valve, and the electronic expansion valve, and the other end of the driver is signal-connected to the control unit.

[0035] In some alternative embodiments, the second circuit system includes a water circuit assembly and a circulation pump, the circulation pump is arranged in the path of the water circuit assembly, and the second circuit system realizes heat exchange through the air cooler. Description of the Drawings

[0036] The features, advantages, and technical effects of the exemplary embodiments of the present application will be described below with reference to the drawings.

[0037] Figure 1 Shows a schematic structural diagram of a transcritical CO2 heat pump system provided by an embodiment of the present application.

[0038] Figure 2 Shows a schematic structural diagram of the structure and control method of a transcritical CO2 heat pump system provided by an embodiment of the present application.

[0039] Figure 3 The schematic diagram of the control method flow of a transcritical CO2 heat pump system provided by an embodiment of the present application is shown.

[0040] Figure 4 The schematic diagram of the control method flow of a transcritical CO2 heat pump system provided by another embodiment of the present application is shown.

[0041] Figure 5 The curve diagram of the actual exhaust pressure of the compressor and the coefficient of performance of the transcritical CO2 heat pump system provided by an embodiment of the present application is shown.

[0042] Figure 6 The curve diagram of the actual exhaust pressure and the actual exhaust temperature of the compressor provided by an embodiment of the present application is shown.

[0043] Figure 7 The curve diagram of the actual efficiency of the regenerator and the coefficient of performance of the transcritical CO2 heat pump system provided by an embodiment of the present application is shown.

[0044] The descriptions of specific reference numerals are as follows: 100, transcritical CO2 heat pump system; 10, compressor; 20, gas cooler; 30, circulation pump; 40, flow regulating valve; 50, regenerator; 60, electronic expansion valve; 70, evaporation assembly; 80, control unit. Specific embodiments

[0045] To make the objectives, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be clearly described below with reference to the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are some, but not all, of the embodiments of the present application.

[0046] The terms "first", "second", "third", etc. in the specification and claims of the present application or in the above-mentioned drawings are used to distinguish different objects, rather than to describe a specific order or primary-secondary relationship. In the embodiments of the present application, the same reference numerals represent the same components, and for the sake of brevity, in different embodiments, the detailed descriptions of the same components are omitted.

[0047] Referring to "embodiment" in the present application means that the specific features, structures or characteristics described in connection with the embodiment may be included in at least one embodiment of the present application. The phrase appears in various places in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment mutually exclusive with other embodiments.

[0048] In the description of the present application, it should be noted that, unless otherwise clearly specified and defined, terms such as "installation" and "connection" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be directly connected, or indirectly connected through an intermediate medium, and can be the communication inside two components. For those of ordinary skill in the art, the specific meanings of the above terms in the present application can be understood according to specific circumstances.

[0049] In the description of the embodiments of the present application, the term "a plurality of" means two or more (including two). In the description of the embodiments of the present application, technical terms such as "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc. indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing the embodiments of the present application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation to the embodiments of the present application.

[0050] In the description of the embodiments of the present application, unless otherwise clearly specified and defined, technical terms such as "installation", "connection", "joined", "fixed", etc. should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral one; it can also be a mechanical connection or an electrical connection; it can be directly connected, or indirectly connected through an intermediate medium, and can be the communication inside two components or the interaction relationship between two components. For those of ordinary skill in the art, the specific meanings of the above terms in the embodiments of the present application can be understood according to specific circumstances.

[0051] In the present application, in the structural schematic diagram, P2 represents the pressure detected by the pressure detector at that position in the figure, and can also represent the actual exhaust pressure in the specification. T1 represents the temperature detected by the first temperature detector at that position in the figure; where T represents temperature, P represents pressure, and T2, T3, T4, T5, P1, etc. are also in this situation.

[0052] With the continuous advancement of the global energy transformation and environmental protection work, the transcritical CO2 heat pump system technology has advantages such as high energy efficiency, no pollutant emissions, and environmental friendliness. It is being more and more widely applied in various fields and is continuously developing towards the trend of high capacity and large scale.

[0053] Compared with the subcritical heat pump cycle of conventional refrigerants, one of the biggest differences in the control system of the transcritical CO2 heat pump system is that there is an optimal discharge pressure in the transcritical CO2 heat pump system cycle. Therefore, during the operation of the heat pump, it is necessary to adjust the compressor discharge pressure to make the coefficient of performance (COP) of the system reach the optimal value.

[0054] On the other hand, the transcritical CO2 heat pump system can reduce energy consumption by adding a regenerator, which not only improves the system performance coefficient but also reduces the optimal discharge pressure. However, adding a regenerator will increase the compressor discharge temperature, and in actual use, the phenomenon of compressor overheating may occur, affecting the performance coefficient of the entire system.

[0055] In view of this, the embodiments of the present application provide a control method for a transcritical CO2 heat pump system, an electronic device for a transcritical CO2 heat pump system, a computer-readable storage medium, and a computer program product, which can synergistically optimize the control method of the compressor discharge pressure and the regenerator efficiency, improve the system performance, ensure that the compressor discharge temperature is within a suitable range, avoid the occurrence of overheating, and realize the efficient and stable operation of the transcritical CO2 heat pump system under all working conditions.

[0056] First, the transcritical CO2 heat pump system and the control method provided by the embodiments of the present application will be introduced with reference to the accompanying drawings.

[0057] Figure 1 The structural schematic diagram of a transcritical CO2 heat pump system provided by an embodiment of the present application is shown; please refer to Figure 1 The transcritical CO2 heat pump system 100 is a high-efficiency thermodynamic cycle device based on a supercritical working fluid (such as CO2), and its core components work together to achieve efficient energy conversion.

[0058] Specifically, the transcritical CO2 heat pump system 100 includes: a first loop system including a compressor 10 for providing a supercritical fluid; an air cooler 20 connected to the compressor 10, where the air cooler 20 is used to supply heat energy; a recuperator 50 for recovering at least part of the heat energy of the fluid in the air cooler 20 and preheating the fluid at the inlet end of the compressor 10; a flow regulating valve 40 provided at the fluid outlet end of the air cooler 20 for regulating the total amount of fluid passing through the recuperator 50; an electronic expansion valve 60 for regulating the liquid supply amount of the evaporation assembly 70; an evaporation assembly 70, where the evaporation assembly 70 is connected to the recuperator 50 and the air cooler 20 for evaporating and gasifying the collected fluid; the evaporation assembly 70 is connected to the compressor 10 for supplying the evaporated and gasified fluid to the compressor 10; a pipeline assembly for providing a flow path for the fluid; wherein, the fluid is configured to flow out of the compressor 10, flow through the pipeline assembly to the air cooler 20, the flow regulating valve 40, the electronic expansion valve 60, the evaporation assembly 70, the recuperator 50 and then return to the compressor 10, and the fluid passing through the flow regulating valve 40 flows through the first line to the recuperator 50 and then converges with the fluid passing through the flow regulating valve 40 through the second line and flows to the electronic expansion valve 60. The evaporation assembly 70 can be an evaporator.

[0059] It can be understood that: the flow rate through the flow regulating valve 40 can be divided into two paths, namely the first line and the second line; the fluid passing through the flow regulating valve 40 exchanges heat with the low-temperature and low-pressure fluid in the recuperator through the first line in the recuperator, and the fluid is cooled; after being cooled, the fluid converges or mixes with the fluid passing through the second line and then enters the electronic expansion valve 60. The flow regulating valve 40 achieves the purpose of flow splitting, and can adjust the actual heat recovery efficiency of the recuperator, making the actual heat recovery efficiency close to or consistent with the optimal recuperator efficiency.

[0060] The fluid in the transcritical CO2 heat pump system 100 is also called the working medium. The working medium can be CO2, other working media or a mixed working medium including CO2. The compressor 10 is configured to perform isentropic compression on the working medium, and the isentropically compressed working medium undergoes isobaric heat release through the air cooler 20 to provide a heat source for the second loop system. In short, it increases the temperature of the fluid in the second loop system. The working medium after isobaric heat release passes through the flow regulating valve, and part of it enters the recuperator 50. The heat in the working medium is exchanged through the recuperator, and the working medium flows out of the recuperator 50; and the working medium after isobaric heat release passes through the flow regulating valve, and the working medium that does not enter the recuperator 50 converges with the working medium flowing out of the recuperator and enters the electronic expansion valve. The liquid-phase working medium absorbs heat isobarically in the evaporation assembly. After the liquid-phase working medium evaporates, the gas-phase working medium is reheated through the recuperator 50 and returns to the inlet of the compressor 10 to form a complete cycle.

[0061] For example, the compressor 10 serves as the power core of the transcritical CO2 heat pump system 100. It adiabatically compresses the low-temperature and low-pressure gaseous working medium, approximately 0.5 - 4 MPa, to the supercritical state, such as 7 - 10 MPa, 90 - 120 °C. This process requires a specially designed high-pressure-resistant compressor 10 to adapt to the high-pressure characteristics of CO2. The gas cooler 20 replaces the traditional condenser, enabling the supercritical working medium to continuously release heat through the "temperature glide" effect while maintaining the pressure. For example, the temperature can drop from 120 °C to 40 °C, achieving efficient heat exchange with the heating medium. The flow regulating valve 40 is located at the outlet of the gas cooler 20. By precisely regulating the working medium flow rate, it maintains the system pressure balance, creates stable conditions for the subsequent throttling process, and is also beneficial for improving the energy utilization efficiency of the regenerator 50.

[0062] For example, as a key component for improving energy efficiency, the regenerator 50 adopts a countercurrent heat exchange method: the supercritical working medium on the high-pressure side, approximately 35 - 80 °C, transfers heat to the low-pressure side reflux working medium, approximately 5 - 20 °C. This process can increase the suction temperature of the compressor 10 by 10 - 25 °C while reducing the high-pressure working medium temperature by 15 - 30 °C. After the fluid flows through the regenerator 50 from the gas cooler 20, T5 is significantly lower than T1, and the regenerator 50 absorbs part of the thermal energy in the fluid. After T4 flows through the regenerator 50, T3 is significantly higher than T4, and the fluid absorbs the heat from the regenerator 50.

[0063] For example, by dynamically adjusting the opening degree of the electronic expansion valve 60, the pressure on the high-pressure side can be maintained at the optimal value. By responding to the exhaust pressure sensor signal through the PID algorithm, it avoids excessive pressure (sharp increase in energy consumption) or too low pressure (decrease in heating capacity). Through precise throttling, the high-pressure working medium of 7 - 10 MPa can be reduced to an evaporation pressure of 2 - 4 MPa, forming a low-temperature gas-liquid two-phase flow, approximately 0 - 10 °C. The evaporation component then efficiently absorbs ambient heat using the latent heat of vaporization of the working medium, approximately 150 - 300 kJ / kg, to complete the full vaporization of the working medium.

[0064] It has been found through research that by optimizing the exhaust pressure in real time throughout the cycle of the transcritical CO2 heat pump system 100, which is usually 2 - 3 times the critical pressure, and changing the efficiency of the regenerator 50, the system COP can be maintained at a relatively high level, such as 3.0 - 5.0. The transcritical CO2 heat pump system 100 is particularly suitable for occasions that require high-temperature heating (60 - 90 °C), and at the same time has excellent environmental protection characteristics. The efficient cooperation of each component enables the system to operate stably within the environmental temperature range of -20 °C to 40 °C, saving 20% - 30% or more energy compared to traditional heat pumps.

[0065] Figure 2 The schematic diagram of the heating system provided by an embodiment of the present application is shown. As Figure 2 shown, the heating system includes a transcritical CO2 heat pump system 100.

[0066] AsFigure 2 As shown, the schematic diagram shows the first loop system, the second loop system, and the third loop system of the transcritical CO2 heat pump system 100. The first loop system is as described above and will not be elaborated here.

[0067] As Figure 1 and Figure 2 shown, the transcritical CO2 heat pump system 100 includes a second loop system, which is used to receive the energy of the gas cooler 20 and provide heat to the user end. The second loop system includes a water circuit component and a circulation pump 3, and the circulation pump 30 is arranged in the path of the water circuit component. The second loop system realizes heat exchange through the gas cooler 20. The medium in the water circuit component can be a heat transfer medium such as water or oil. The fluid in the second loop system or the medium in the water circuit component and the running direction of the medium in the water circuit component are also shown in this schematic diagram. The medium flows in the water circuit component, and the circulation pump 30 provides the flow power for it, absorbs heat at the gas cooler 20, and brings the heat to the user end to provide the heat from the transcritical CO2 heat pump system 100. The outlet water temperature T wo in the water circuit component is generally much higher than the inlet water temperature T wi in the water circuit component, and the medium therein absorbs heat at the gas cooler 20.

[0068] The third loop system includes a control unit 80 (PID) and a power supply (not marked), which may include a driver. One end of the driver is respectively signal-connected to the compressor 10, the circulation pump 30, the flow regulating valve 40, and the electronic expansion valve 60, and the other end of the driver is signal-connected to the control unit 80. For example, the driver may include a first driver for regulating the compressor 10; the driver may include a second driver for regulating the circulation pump 30; the driver may include a third driver for regulating the flow regulating valve 40; the driver may include a fourth driver for regulating the electronic expansion valve 60.

[0069] The third loop system may further include an acquisition unit for acquiring the actual heat regeneration efficiency of the regenerator and the actual exhaust pressure of the compressor;

[0070] The acquisition unit may be a signal collector, and the signal collector may also collect the temperature, pressure, etc. in key components such as the compressor 10, the gas cooler 20, the flow regulating valve 40, the regenerator 50, the electronic expansion valve 60, and the evaporation component, as well as in the pipeline component and the water circuit component. One end of the signal collector is signal-connected to these components, and the other end of the signal collector is signal-connected to the control unit 80 to provide a basis for the control of the control unit 80. The control of the control unit 80 can be adjusted or realized through the above-mentioned driver.

[0071] Figure 3 shows a schematic diagram of the control method flow of the transcritical CO2 heat pump system provided by an embodiment of the present application;Figure 4 The figure shows a schematic flow chart of the control method for a transcritical CO2 heat pump system provided by another embodiment of the present application.

[0072] As Figure 3 and Figure 4 shown, the control method for the transcritical CO2 heat pump system includes: step 100 to step 300.

[0073] Step 100, obtain the actual heat recovery efficiency of the recuperator and the actual discharge pressure of the compressor.

[0074] Step 200, according to the actual heat recovery efficiency, adjust the flow rate of the flow control valve flowing through the recuperator to meet the first preset condition.

[0075] In this step, the transcritical CO2 heat pump system 100 includes a recuperator 50, and the recuperator 50 adopts a countercurrent heat exchange method: transferring the heat in the supercritical working medium on the high-pressure side to the reflux working medium on the low-pressure side, improving the energy utilization efficiency, thereby reducing the optimal discharge pressure and also increasing the COP of the transcritical CO2 heat pump system 100.

[0076] The adjustment of the actual heat recovery efficiency is achieved by using a flow control valve to adjust the flow distribution at the fluid outlet end of the gas cooler, changing the mass flow rate entering the high-pressure pipe section in the recuperator, so as to adjust the efficiency of the recuperator.

[0077] Furthermore, by adjusting the working medium flow rate of the flow control valve 40 flowing through the recuperator 50, the subcooling degree of the liquid working medium before the electronic expansion valve 60 can be increased to avoid flashing; at the same time, ensure the superheat degree of the working medium at the suction port of the compressor 10 to prevent liquid slugging; the recuperator 50 reduces the heat transfer temperature difference between the high-temperature heat source (such as the condenser) and the low-temperature heat source (such as the evaporation module) through internal heat recovery, thereby reducing the entropy production (irreversible loss) of the cycle and improving the thermodynamic efficiency. The flow control valve 40 can dynamically adjust the flow rate of the recuperator 50 according to the system load, avoiding insufficient working medium flow rate, insufficient heat recovery, and low waste heat recovery efficiency; it can also avoid excessive working medium flow rate: the flow resistance increases and the power consumption of the compressor 10 / pump rises.

[0078] Step 300, according to the actual discharge pressure, adjust the opening degree of the electronic expansion valve until the actual discharge pressure meets the second preset condition. The superheat degree refers to the difference between the temperature of the working medium at the suction port of the compressor 10 and its saturation temperature.

[0079] In view of the fact that the transcritical CO2 heat pump system 100 includes a recuperator 50, this setting will cause the discharge temperature of the compressor 10 to rise, and in actual use, the phenomenon of overheating or excessive superheat degree of the compressor 10 may occur.

[0080] The rapid response (millisecond level) of the electronic expansion valve 60 is more precise than that of traditional thermal expansion valves, which can reduce the entropy increase during the throttling process, lower the proportion of flash gas, and reduce the heat transfer temperature difference between the evaporation component and the environment. Moreover, under varying operating conditions, the electronic expansion valve 60 adjusts its opening in real time through the PID algorithm, always maintaining the evaporation pressure close to the design value, avoiding efficiency losses on the low-pressure side and keeping the condensation pressure appropriate. By increasing the opening of the electronic expansion valve 60, the refrigerant flow rate is increased, the suction superheat is reduced, the suction state is accurately controlled, and the abnormal increase in the discharge temperature is suppressed, thereby controlling the discharge temperature within a safe range. By reducing the opening, it is ensured that the refrigerant at the outlet of the evaporation component is slightly superheated gas, completely eliminating the risk of liquid hammer.

[0081] The adjustment of the actual discharge pressure can be achieved by adjusting the opening of the electronic expansion valve, thereby changing the temperature of the fluid at the outlet end of the evaporation component 70, changing the temperature at the fluid inlet end of the compressor, and realizing the change of the temperature inside the compressor, so as to adjust the actual discharge pressure.

[0082] In the above steps, the execution order of step 200 and step 300 can be arbitrary. For example, step 200 can be executed first, and then step 300, or step 300 can be executed first, and then step 200.

[0083] According to the embodiments of the present application, when the system is under different operating conditions and the external environment changes, a flow regulating valve is set in the transcritical CO2 heat pump system. By adjusting the refrigerant flow rate through the regenerator, the regeneration efficiency of the regenerator is adjusted, and heat loss is reduced. Coordinating and optimizing the optimal discharge pressure and the regenerator efficiency reduces the losses of the key links of the system's regenerator and compressor. For example, adjusting the actual discharge pressure reduces the compression ratio of the compressor, and combined with real-time sensor data (such as temperature, pressure), it can respond to environmental and load changes in a timely manner. In a wide operating condition range, the transcritical CO2 heat pump system reduces the optimal discharge pressure, makes the discharge temperature of the compressor appropriate, improves the coefficient of performance of the system, and makes the coefficient of performance (COP) of the transcritical CO2 heat pump system continuously optimal. In some alternative embodiments, before step 100, the method further includes: step 50, the transcritical CO2 heat pump system 100 operates under given operating condition parameters.

[0084] In some alternative embodiments, the operating condition parameters include the ambient temperature, return water temperature, and inlet water temperature of the transcritical CO2 heat pump system 100; the ambient temperature can be the initial ambient temperature, as well as the ambient temperature monitored in real time subsequently or the ambient temperature updated after input.

[0085]

[0086] ​In some alternative embodiments, the transcritical CO2 heat pump system 100 includes a temperature detector. The temperature detector includes a first temperature detector located at the fluid outlet end of the gas cooler 20 and an ambient temperature detector. The ambient temperature detector is used to obtain the ambient temperature of the transcritical CO2 heat pump system 100 in real time. The method further includes:

[0087] Step 400, when the real-time ambient temperature of the transcritical CO2 heat pump system 100 ≥ the first preset temperature and the detected temperature of the first temperature detector ≥ the second preset temperature, adjust the actual regenerative efficiency to the first preset condition and adjust the actual exhaust pressure to the second preset condition; the first preset temperature can be temperatures such as -10°C, -15°C, etc.; the second preset temperature can be temperatures such as 20°C, 25°C, 30°C, etc.

[0088] In this step, when the ambient temperature and the outlet temperature of the gas cooler 20 are respectively greater than the above preset values, it is necessary to adjust the actual regenerative efficiency and the actual exhaust pressure to ensure the coefficient of performance (COP) of the transcritical CO2 heat pump system 100. The operating conditions at this time belong to normal conditions.

[0089] Step 500, when the real-time ambient temperature of the transcritical CO2 heat pump system 100 < the first preset temperature and the detected temperature of the first temperature detector < the second preset temperature, adjust the actual exhaust pressure to the second preset condition.

[0090] In this step, when the ambient temperature and the outlet temperature of the gas cooler 20 are respectively less than the above preset values, it is possible to only adjust the actual exhaust pressure, or mainly adjust the actual exhaust pressure and supplementarily adjust the actual regenerative efficiency. The reason is that at this time, the ambient temperature of the entire system and the outlet temperature of the gas cooler 20 are relatively low, and temperature is not the main consideration factor. The heat that the regenerator 50 can absorb and the regenerative efficiency are not the core problems of the system. The operating conditions at this time belong to special conditions.

[0091] In some alternative embodiments, the temperature detector includes a first temperature detector located at the fluid outlet end of the gas cooler 20 and a second temperature detector located at the fluid outlet end of the compressor 10;

[0092] Step 400, when the real-time ambient temperature of the transcritical CO2 heat pump system 100 ≥ the first preset temperature and the detected temperature of the first temperature detector ≥ the second preset temperature, adjust the actual regenerative efficiency to the first preset condition and adjust the actual exhaust pressure to the second preset condition, which specifically includes:

[0093] Step 410, when the detected temperature of the second temperature detector is less than the rated maximum temperature of the compressor 10, first adjust the actual regenerative efficiency to the first preset condition, and then adjust the actual exhaust pressure to the second preset condition;

[0094] In this step, the actual heat regeneration efficiency of the regenerator 50 directly affects T5, T4, and T3, which will cause the exhaust temperature of the compressor 10 to rise. During actual use, the phenomenon of overheating of the compressor 10 may occur. Therefore, it is necessary to balance energy recovery and the coefficient of performance of the system to avoid overheating of the compressor 10. When the detected temperature of the second temperature detector is less than the rated maximum temperature of the compressor 10, avoiding overheating of the compressor 10 is not the top priority of the system. On this basis, the actual heat regeneration efficiency is further improved, the energy utilization rate is increased, and the coefficient of performance of the system is increased.

[0095] Step 420: When the detected temperature of the second temperature detector is greater than or equal to the rated maximum temperature of the compressor 10, first adjust the actual exhaust pressure to a second preset condition, and then adjust the actual heat regeneration efficiency to a first preset condition.

[0096] In this step, when the detected temperature of the second temperature detector is greater than or equal to the rated maximum temperature of the compressor 10, in order to avoid continuous overheating of the compressor 10 and maintain the normal operation of the compressor 10, the actual exhaust pressure is preferentially adjusted, which can keep the system continuously at a relatively high coefficient of performance.

[0097] In some alternative embodiments, in any of steps 200 to 500, the first preset condition is |η ihx -η ihx,opt |≤ε1, where ηihx represents the actual heat regeneration efficiency of the regenerator 50, η ihx,opt represents the optimal heat regeneration efficiency of the regenerator 50, and ε1 is a preset constant.

[0098] For example, ε1 can be 0.01 or the like. Thus, the energy utilization efficiency can be improved, and the system can be continuously maintained at a relatively high coefficient of performance.

[0099] In some alternative embodiments, the temperature detector includes a third temperature detector (T3) located at the fluid inlet end of the compressor and a fourth temperature detector located at the fluid outlet end of the evaporation assembly;

[0100] η ihx is determined by Equation (1),

[0101] where η ihx represents the actual heat regeneration efficiency of the regenerator, T1 represents the temperature detected by the first temperature detector; T3 represents the temperature detected by the third temperature detector; T4 represents the temperature detected by the fourth temperature detector;

[0102] η ihx,opt is determined by Equation (2),

[0103] η ihx,opt= 0.4080 + 0.0099T1 - 1.3542×10 -4 T1 2 (2)

[0104] where η ihx,opt represents the optimal regenerative efficiency of the regenerator, and T3 represents the temperature detected by the third temperature detector.

[0105] The determination of the optimal regenerative efficiency of the regenerator 50 needs to combine theoretical calculation, simulation analysis and experimental verification, and be adjusted under different refrigerants and system operating conditions. Through a systematic optimization method, the best regenerative efficiency can be found to achieve an optimal balance between the energy efficiency and the system performance coefficient of the heat pump system.

[0106] In some alternative embodiments, in any of steps 200 to 500, the second preset condition is |P2 - P opt | ≤ ε2, where P2 represents the actual exhaust pressure of the transcritical CO2 heat pump system 100, and P opt represents the optimal exhaust pressure of the transcritical CO2 heat pump system 100, and ε2 is a preset constant.

[0107] For example, ε2 can be 0.01 or the like. Thus, the operating efficiency of the compressor 10 can be improved, and the system can continuously maintain a high system performance coefficient.

[0108] It can be understood that: P2 is the real-time actual exhaust pressure of the compressor 10 during the operation of the system; Popt is the optimal exhaust pressure calculated through the best pressure correlation. During the operation of the system, it is judged in real time whether the difference between P2 and Popt meets the allowable error, and based on this as the output target, the opening of the electronic expansion valve 60 is adjusted by PID.

[0109] In some alternative embodiments, the operating condition parameters include the inlet water temperature (Twi) at the inlet end of the circulation pump 30; P opt is determined by Equation (3),

[0110]

[0111] where T1 represents the temperature detected by the first temperature detector, and T wi represents the inlet water temperature at the inlet end of the circulation pump.

[0112] This optimal exhaust pressure is the core parameter of the transcritical heat pump design, which is determined through theoretical modeling and experimental verification and dynamically adjusted according to the operating conditions. For the transcritical CO2 heat pump system 100 of the present application, it is comprehensively optimized by combining the outlet temperature of the gas cooler 20, the efficiency of the compressor 10 and the load demand.

[0113] Accordingly, an embodiment of the present application provides a transcritical CO2 heat pump system 100, which may include: The control unit 80 includes: a first control module, configured to adjust the flow rate of the flow regulating valve flowing through the regenerator to meet the first preset condition according to the actual regeneration efficiency; a second control module, configured to adjust the opening degree of the electronic expansion valve according to the actual exhaust pressure until the actual exhaust pressure meets the second preset condition.

[0114] In some alternative embodiments, the control unit 80 may include:

[0115] a first judgment module, configured to, when the real-time ambient temperature of the transcritical CO2 heat pump system 100 ≥ the first preset temperature and the detected temperature of the first temperature detector ≥ the second preset temperature, adjust the actual regeneration efficiency to the first preset condition and adjust the actual exhaust pressure to the second preset condition;

[0116] a second judgment module, configured to, when the real-time ambient temperature of the transcritical CO2 heat pump system 100 < the first preset temperature and the detected temperature of the first temperature detector < the second preset temperature, adjust the actual exhaust pressure to the second preset condition.

[0117] In some alternative embodiments, the first judgment module may include:

[0118] a first temperature module, configured to, when the detected temperature of the second temperature detector is less than the rated maximum temperature of the compressor 10, first adjust the actual regeneration efficiency to the first preset condition, and then adjust the actual exhaust pressure to the second preset condition;

[0119] a second temperature module, configured to, when the detected temperature of the second temperature detector is greater than or equal to the rated maximum temperature of the compressor 10, first adjust the actual exhaust pressure to the second preset condition, and then adjust the actual regeneration efficiency to the first preset condition.

[0120] In some alternative embodiments, the control unit 80 includes an actual efficiency determination module, configured to determine ηihx through formula (1),

[0121] where η ihx represents the actual regeneration efficiency of the regenerator 50, T1 represents the temperature detected by the first temperature detector; T3 represents the temperature detected by the third temperature detector; T4 represents the temperature detected by the fourth temperature detector.

[0122] In some alternative embodiments, the control unit 80 includes an optimal efficiency determination module, configured to determine through formula (2),

[0123] η ihx,opt = 0.4080 + 0.0099T1 - 1.3542×10 -4 T1 2 (2)

[0124] Among them, η ihx,opt represents the optimal regenerative efficiency of the regenerator 50, and T3 represents the temperature detected by the third temperature detector.

[0125] In some alternative embodiments, the control unit 80 may include: an optimal exhaust pressure determination module for determining P through Equation (3) opt ,

[0126]

[0127] Among them, T1 represents the temperature detected by the first temperature detector, and T wi represents the water inlet temperature at the water inlet end of the circulation pump

[0128] Figure 5 shows the actual exhaust pressure of the compressor and the performance coefficient curve of the transcritical CO2 heat pump system provided by an embodiment of the present application. In the figure, the actual exhaust pressure is abbreviated as the exhaust pressure, and T e represents the ambient temperature of the transcritical CO2 heat pump system 100, and T w.gc.in represents the water inlet temperature of the transcritical CO2 heat pump system 100, and T w.gc.out represents the water outlet temperature of the transcritical CO2 heat pump system 100, and Q hot represents the heating capacity of the transcritical CO2 heat pump system 100. The curve graph of the compressor exhaust pressure and the performance coefficient of the transcritical CO2 heat pump system in this figure shows that under specific working conditions, at different exhaust pressures, the actual regenerative efficiency of the regenerator 50 is different. As the regenerative efficiency increases (several curves in the figure), the exhaust pressure of the compressor 10 will also increase accordingly, indicating that it is not the case that the greater the efficiency of the regenerator 50 corresponding to all working conditions, the better the system performance COP. Therefore, the control method of the present application is required for dynamic adjustment.

[0129] Figure 6 shows the actual exhaust pressure of the compressor and the actual exhaust temperature curve graph provided by an embodiment of the present application. In the figure, the actual exhaust pressure is abbreviated as the exhaust pressure, and the actual exhaust temperature is abbreviated as the exhaust temperature; T e represents the ambient temperature of the transcritical CO2 heat pump system 100, and T w.gc.in represents the water inlet temperature of the transcritical CO2 heat pump system 100, and T w.gc.out represents the water outlet temperature of the transcritical CO2 heat pump system 100, and Q hotIndicates the heating capacity of the transcritical CO₂ heat pump system 100. The compressor discharge pressure and discharge temperature curves in this figure illustrate that under specific operating conditions, the actual heat regeneration efficiency of the regenerator 50 is different. As the heat regeneration efficiency increases (several curves in the figure), the discharge temperature of the compressor 10 will also increase accordingly, indicating that the larger the efficiency of the regenerator 50 corresponding to all operating conditions, the better the system performance COP. Therefore, the control method of the present application is required for dynamic adjustment.

[0130] Figure 7 Shows the curve graph of the actual heat regeneration efficiency of the regenerator and the coefficient of performance of the transcritical CO₂ heat pump system provided by an embodiment of the present application. In the figure, Te represents the ambient temperature of the transcritical CO₂ heat pump system 100, Tw.gc.in represents the inlet water temperature of the transcritical CO₂ heat pump system 100, Tw.gc.out represents the outlet water temperature of the transcritical CO₂ heat pump system 100, and Qhot represents the heating capacity of the transcritical CO₂ heat pump system 100. This figure illustrates that under specific operating conditions, the coefficient of performance of the transcritical CO₂ heat pump system 100 is affected by the actual heat regeneration efficiency of the regenerator 50. Whether the efficiency of the regenerator 50 can improve the system COP depends on the dual influence of the evaporation temperature and the actual discharge pressure.

[0131] Each module in the transcritical CO₂ heat pump system provided by the embodiment of the present application can implement the above-mentioned operation and control of the transcritical CO₂ heat pump system and achieve the corresponding effects. For the sake of brevity, it will not be described in detail here.

[0132] It should be clear that the present application is not limited to the specific configurations and processes described above and shown in the figures. For the sake of brevity, the detailed description of known methods is omitted here. In the above embodiments, several specific steps are described and shown as examples. However, the method process of the present application is not limited to the specific steps described and shown. Those skilled in the art can make various changes, modifications, and additions, or change the order between steps after understanding the spirit of the present application.

[0133] It should also be noted that the exemplary embodiments mentioned in the present application describe some methods or systems based on a series of steps or devices. However, the present application is not limited to the order of the above steps. That is, the steps can be executed in the order mentioned in the embodiments, or different from the order in the embodiments, or several steps can be executed simultaneously.

[0134] Although the present application has been described with reference to preferred embodiments, various modifications can be made thereto without departing from the scope of the present application, and components therein can be replaced with equivalents. In particular, as long as there is no structural conflict, the technical features mentioned in each embodiment can be combined in any manner. The present application is not limited to the specific embodiments disclosed in the text, but includes all technical solutions falling within the scope of the claims.

Claims

1. A control method for a transcritical CO2 heat pump system, characterized in that, The transcritical CO2 heat pump system includes a first loop system, and the first loop system includes a compressor, an air cooler, a regenerator, a flow regulating valve, an electronic expansion valve, an evaporation component and a pipeline component; the fluid flows out of the compressor, flows through the pipeline component to the air cooler, the flow regulating valve, the electronic expansion valve, the evaporation component, the regenerator and then returns to the compressor, and the fluid at the outlet end of the flow regulating valve is divided into a first line and a second line, and the fluid in the first line flows through the regenerator and then converges with the fluid passing through the second line and flows to the electronic expansion valve; wherein, the first loop system provides energy for the second loop system through the air cooler; The method includes: Obtaining the actual heat regeneration efficiency of the regenerator and obtaining the actual exhaust pressure of the compressor; Adjusting the flow rate of the flow regulating valve flowing through the regenerator according to the actual heat regeneration efficiency to meet a first preset condition; Adjusting the opening degree of the electronic expansion valve according to the actual exhaust pressure until the actual exhaust pressure meets a second preset condition.

2. The method according to claim 1, wherein The transcritical CO2 heat pump system includes a temperature detector, and the temperature detector includes an ambient temperature detector and a first temperature detector located at the fluid outlet end of the air cooler. The ambient temperature detector is used to obtain the ambient temperature of the transcritical CO2 heat pump system in real time. The method further includes: When the real-time ambient temperature of the transcritical CO2 heat pump system ≥ a first preset temperature and the detected temperature of the first temperature detector ≥ a second preset temperature, adjusting the actual heat regeneration efficiency to a first preset condition and adjusting the actual exhaust pressure to a second preset condition; When the real-time ambient temperature of the transcritical CO2 heat pump system < a first preset temperature and the detected temperature of the first temperature detector < a second preset temperature, adjusting the actual exhaust pressure to a second preset condition.

3. The method according to claim 2, characterized in that, The temperature detector includes a first temperature detector located at the fluid outlet end of the air cooler and a second temperature detector located at the fluid outlet end of the compressor; The step of when the real-time ambient temperature of the transcritical CO2 heat pump system ≥ a first preset temperature and the detected temperature of the first temperature detector ≥ a second preset temperature, adjusting the actual heat regeneration efficiency to a first preset condition and adjusting the actual exhaust pressure to a second preset condition includes: When the detected temperature of the second temperature detector is less than the rated maximum temperature of the compressor, first adjusting the actual heat regeneration efficiency to the first preset condition, and then adjusting the actual exhaust pressure to the second preset condition; When the detected temperature of the second temperature detector is greater than or equal to the rated maximum temperature of the compressor, first adjusting the actual exhaust pressure to the second preset condition, and then adjusting the actual heat regeneration efficiency to the first preset condition.

4. The method according to any one of claims 1 to 3, characterized in that The first preset condition is |η ihx -η ihx,opt | ≤ ε1, where ηihx represents the actual heat regeneration efficiency of the regenerator, and η ihx,opt represents the optimal heat regeneration efficiency of the regenerator, and ε1 is a preset constant.

5. The method according to claim 3, wherein The temperature detector includes a third temperature detector located at the fluid inlet end of the compressor and a fourth temperature detector located at the fluid outlet end of the evaporation component; η ihx Determined by Equation (1), where η ihx represents the actual heat regeneration efficiency of the regenerator, T1 represents the temperature detected by the first temperature detector; T3 represents the temperature detected by the third temperature detector; T4 represents the temperature detected by the fourth temperature detector; η ihx,opt Determined by formula (2). η ihx,opt = 0.4080 + 0.0099T1 - 1.3542×10 -4 T1 2 (2) Among them, η ihx,opt represents the optimal regenerative efficiency of the regenerator, and T3 represents the temperature detected by the third temperature detector.

6. The method according to any one of claims 1 to 3, characterized in that, The second preset condition is |P2 - P opt | ≤ ε2, where P2 represents the actual exhaust pressure of the transcritical CO2 heat pump system, and P opt represents the optimal exhaust pressure of the transcritical CO2 heat pump system, and ε2 is a preset constant.

7. The method according to claim 6, wherein The second loop system includes a circulation pump; P opt Determined by Equation (3), Among them, T1 represents the temperature detected by the first temperature detector, and T wi represents the inlet water temperature at the inlet end of the circulation pump.

8. A transcritical CO2 heat pump system, characterized in that, Includes: The first circuit system includes a compressor, an air cooler, a recuperator, a flow regulating valve, an electronic expansion valve, an evaporation assembly, and a pipeline assembly; the fluid is configured to flow out of the compressor, flow through the pipeline assembly to the air cooler, the flow regulating valve, the electronic expansion valve, the evaporation assembly, the recuperator, and then return to the compressor, and the fluid at the outlet end of the flow regulating valve is divided into a first line and a second line, the fluid in the first line flows through the recuperator and then converges with the fluid passing through the second line and flows to the electronic expansion valve; wherein, the first circuit system provides energy for the second circuit system through the air cooler; The third circuit system includes: An acquisition unit for acquiring the actual recuperation efficiency of the recuperator and the actual exhaust pressure of the compressor; A control unit, the control unit includes: A first control unit for adjusting the flow rate of the flow regulating valve flowing through the recuperator to meet a first preset condition according to the actual recuperation efficiency; A second control unit for adjusting the opening degree of the electronic expansion valve to make the actual exhaust pressure meet a second preset condition according to the actual exhaust pressure.

9. The transcritical CO2 heat pump system according to claim 8, characterized in that, The third circuit system includes a driver, one end of the driver is respectively signal-connected to the compressor, the flow regulating valve, and the electronic expansion valve, and the other end of the driver is signal-connected to the control unit.

10. The transcritical CO2 heat pump system according to claim 8, characterized in that, The second circuit system includes a water circuit assembly and a circulation pump, the circulation pump is arranged in the path of the water circuit assembly, and the second circuit system realizes heat exchange through the air cooler.

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