Extremely cold environment double-working-condition heat recovery cascade type CO2 heat pump cold and heat combined supply system

Abstract

The invention relates to an extremely cold environment double-working-condition heat recovery cascade type CO2 heat pump cold and heat combined supply system. The system comprises a carbon dioxide cold and heat integrated system and an HFO cascade system. The carbon dioxide cooling and heating integrated system comprises a first evaporation end, a first compressor and a first condensation end, and the first condensation end is used for supplying heat in winter and absorbing heat in summer; the HFO cascade system comprises a second compressor, a second condensation end and an HFO unit, the carbon dioxide cooling and heating integrated system and the HFO cascade system are further jointly provided with a second evaporation end used for evaporation and heat absorption, and the HFO unit is used for recycling waste heat in the process of the carbon dioxide cooling and heating integrated system and supplying heat to the HFO cascade system. The problem that CO2 possibly enters a subcritical state in a low-temperature environment is effectively solved, so that the stability of the compressor and the heat exchange process is ensured; the HFO fluid has good heat recovery capability in a low-temperature environment, can provide extra heat for a CO2 system, and is prevented from entering an unstable state.

Description

Technical Field

[0001] The present invention relates to the field of heating technology, and in particular to a dual-operating-condition heat recovery cascade CO2 heat pump cooling and heating combined supply system for an extremely cold environment. Background Art

[0003] After searching, the Chinese patent number CN109163470B discloses an ultra-low temperature carbon dioxide hot and cold water unit, including a No. I circulation system that can obtain hot water with a higher temperature after heat exchange between No. I working fluid and water, and a No. II working circulation system that uses No. II working fluid to provide cold capacity for the condensation of No. I working fluid and improve efficiency. The No. I circulation system includes a No. I compressor, and the high-pressure gas compressed by the No. I compressor enters the gas cooler. The gas cooler is connected to a heat recovery device, and the low-temperature end of the heat recovery device is connected to the cold-end heat exchanger, and its high-temperature end is connected to the hot-end heat exchanger. This invention uses the characteristics of R744 working fluid to obtain hot water with a higher temperature after heat exchange with water, and applies it to winter heating. At the same time, a heat recovery device is added to the system, which increases the subcooling and superheating in the circulation process, and uses the R513a cycle to provide cold capacity for the condensation of R744, thereby improving the efficiency of the entire system and solving the defrosting problem of the system in winter operation.

[0004] After searching, the Chinese patent number CN109595844B discloses a self-cascading carbon dioxide air source heat pump, the key points of its technical solution include a box, a fan, an evaporator, a gas-liquid separator, a compressor, a gas cooler, a first electronic expansion valve and a second electronic expansion valve, and also includes a gas heat exchanger; the compressor medium outlet is connected to the gas cooler medium inlet, a coil is provided in the gas-liquid separator, the gas cooler medium outlet is connected to the input end of the coil in the gas-liquid separator, the coil output end is connected to the first electronic expansion valve medium inlet and the gas heat exchanger medium inlet, and the first electronic expansion valve medium outlet is connected to the gas heat exchanger. This self-cascading carbon dioxide air source heat pump changes the flow path of the carbon dioxide medium, and through the self-cascading heat exchange of the gas heat exchanger, the temperature of the carbon dioxide before entering the expansion valve is reduced, the enthalpy of the working fluid is reduced, and the loss caused by expansion is reduced, thereby improving the overall efficiency of the system in a low-temperature environment. The above-mentioned carbon dioxide heat pump relies on the supercritical state of CO2 to achieve efficient heat exchange and compression process. However, in low temperature environment, carbon dioxide may enter the subcritical state, resulting in the compressor's working pressure and temperature being unable to maintain in the supercritical state, affecting the system efficiency and stability, especially in cold areas, the system's low-temperature startup and continuous stable operation become more difficult; in addition, under low temperature conditions, the heat exchange efficiency of carbon dioxide is significantly reduced, especially when the external ambient temperature is below zero degrees, because CO2 has a higher density at low temperatures, its fluidity is reduced, resulting in poor heat exchange effect of the heat exchanger. Based on this, the present invention designs a dual-operating condition heat recovery cascade CO2 heat pump cooling and heating system for extreme cold environments to solve the above problems. Summary of the invention

[0005] 1. Technical issues to be resolved In view of the above-mentioned shortcomings and deficiencies of the prior art, the present invention provides a dual-operating-condition heat recovery cascade CO2 heat pump cooling and heating system for an extremely cold environment, which solves the technical problems of difficult operation and poor heat exchange effect.

[0006] (II) Technical solution In order to achieve the above object, the main technical solutions adopted by the present invention include: A dual-operating-condition heat recovery cascade CO2 heat pump cooling and heating system for an extremely cold environment, comprising a carbon dioxide cooling and heating integrated system and an HFO cascade system; The carbon dioxide cooling and heating integrated system comprises a first evaporation end, a first compressor and a first condensation end, wherein the first condensation end is used for heating in winter and absorbing heat in summer; The HFO cascade system includes a second compressor, a second condensing end and an HFO unit. The carbon dioxide cooling and heating integrated system and the HFO cascade system are also equipped with a second evaporation end for evaporation and heat absorption. The HFO unit is used to recover the waste heat in the carbon dioxide cooling and heating integrated system and to provide heat for the HFO cascade system.

[0007] Preferably, the carbon dioxide integrated cooling and heating system also includes a CO2 heat pump, the first evaporation end is installed on one side of the CO2 heat pump and connected to the outlet of the CO2 heat pump, the first compressor is installed on one side of the first evaporation end and connected to the outlet of the first evaporation end, the first condensation end is installed on one side of the first compressor and connected to the outlet of the first compressor, the second evaporation end is installed on one side of the first condensation end, the inlet of the second evaporation end is connected to the outlet of the first condensation end, and the outlet of the second evaporation end is connected to the inlet of the CO2 heat pump.

[0008] Preferably, a throttle valve is installed between the second evaporation end and the CO2 heat pump, and temperature sensors, pressure sensors and flow meters are installed between various structures of the carbon dioxide cooling and heating integrated system to monitor the operation of the carbon dioxide cooling and heating integrated system.

[0009] Preferably, the second evaporation end is installed on one side of the HFO unit and connected to the outlet of the HFO unit, the second compressor is installed on one side of the second evaporation end and connected to the outlet of the second evaporation end, the second condensation end is installed on one side of the second compressor and connected to the outlet of the second compressor, and the outlet of the second condensation end is connected to the inlet of the HFO unit.

[0010] Preferably, a control valve is installed between the second condensing end and the HFO unit, and temperature sensors, pressure sensors and flow meters are installed between the various structures of the HFO cascade system to monitor the operation of the HFO cascade system. The HFO unit uses R1234ZE refrigerant, which remains liquid at -46°C.

[0011] Preferably, the control valve is connected to the carbon dioxide heating and cooling integrated system via a pipeline and a pressure valve is installed to control the fluid pressure of the pipeline.

[0012] Preferably, the CO2 heat pump is a supercritical cycle, and the operating pressure range is set to 7.38 MPa to 10.34 MPa to ensure that the outlet temperature can reach above 60°C in the winter heating mode; at the same time, in the summer heat absorption mode, the condensation temperature is achieved to be no higher than 40°C by optimizing the cycle parameters.

[0013] Preferably, the throttle valve adopts an electronic expansion valve, which automatically adjusts the opening degree according to the real-time monitored temperature, pressure and flow data through an integrated intelligent control system to ensure stable evaporation at the second evaporation end in an extreme low temperature environment of -40°C to -10°C.

[0014] Preferably, the second compressor in the HFO cascade system adopts a high-efficiency variable frequency compressor, whose variable frequency range covers 20Hz to 60Hz, and can automatically adjust the speed according to the ambient temperature and heat load demand, and reduce wear by reducing the speed under low load conditions; the control valve in the HFO cascade system adopts a combined control strategy of solenoid valve and proportional valve, the solenoid valve is responsible for quickly responding to system start-up and shutdown instructions, and the proportional valve finely adjusts the flow rate according to the deviation between the HFO unit outlet temperature and the target temperature, ensuring that the system temperature control accuracy reaches ±0.5°C.

[0015] Preferably, the pressure valve is set to an automatic adjustment mode, and the pipeline fluid pressure is monitored and adjusted in real time through an integrated pressure sensor and a PID controller to maintain it within the range of ±0.1 MPa of the set value.

[0016] (III) Beneficial effects 1. The present invention forms a cascade heat pump system by combining HFO fluid with CO2 fluid. The present invention effectively solves the problem that CO2 may enter a subcritical state in a low-temperature environment, thereby ensuring the stability of the compressor and the heat exchange process; HFO fluid has good heat recovery capacity in a low-temperature environment and can provide additional heat for the CO2 system to prevent it from entering an unstable state due to excessively low temperature.

[0017] 2. The present invention, through the design of the HFO+CO2 cascade unit, utilizes the high fluidity of HFO refrigerant at low temperatures, effectively improves the heat transfer capacity of the heat exchanger, and alleviates the problem of poor heat exchange effect of CO2 at low temperatures; through the auxiliary heat recovery effect of the HFO fluid, the pressure ratio requirement in the CO2 expansion process is reduced, thereby avoiding the energy loss caused by excessive pressure of the condenser.

[0018] 3. The present invention, by introducing HFO fluid as a low-temperature heat recovery medium, can effectively prevent the evaporator from frosting or freezing under low-temperature conditions. HFO fluid has a lower freezing point and better fluidity, can absorb external heat at low temperatures and effectively transfer it, thereby maintaining the efficient operation of the heat pump. This design not only avoids the heating interruption problem caused by traditional defrosting devices, but also reduces system complexity and maintenance costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is the overall system diagram of the extremely cold environment dual-operating condition heat recovery cascade CO2 heat pump combined heat and cold supply system of the present invention; Figure 2 This is the structural diagram of the dual-operating heat recovery cascade CO2 heat pump combined heating and cooling system in an extremely cold environment; Figure 3 It is a flow chart of a transcritical CO2 single-stage compression cycle; Figure 4 The heating system and evaporation temperature of the HFO unit of the present invention; Figure 5 This is a table showing the improvement in heat recovery efficiency of the HFO+CO2 cascade unit of the present invention.

[0020] [Description of Reference Numerals] 1. Carbon dioxide cooling and heating integrated system; 2. HFO cascade system; 101. first evaporation end; 102. first compressor; 103. first condensation end; 104. CO2 heat pump; 105. throttle valve; 201. second compressor; 202. second condensation end; 203. HFO unit; 204. second evaporation end; 205. control valve; 206. pressure valve. DETAILED DESCRIPTION

[0021] In order to better explain the present invention and facilitate understanding, the present invention is described in detail below in conjunction with the accompanying drawings through specific embodiments. Figure 1 The orientation is used as a reference.

[0022] The technical problems of operating difficulties and poor heat exchange effects proposed in the embodiments of the present invention integrate the carbon dioxide cooling and heating integrated system 1 and the HFO cascade system 2 to achieve efficient recovery and utilization of thermal energy. In the system, the CO2 heat pump 104 serves as the core, and provides high-temperature thermal energy (≥60°C in winter) or low-temperature refrigeration (≤40°C in summer) through a supercritical cycle (working pressure 7.38 MPa to 10.34 MPa). The first evaporation end 101 receives the low-temperature and low-pressure CO2 gas at the outlet of the CO2 heat pump 104 for preliminary evaporation and heat absorption, and then is compressed into high-temperature and high-pressure gas by the first compressor 102 and enters the first condensation end 103 to supply heat or absorb heat according to seasonal demand.

[0023] In order to better understand the above technical solution, exemplary embodiments of the present invention will be described in more detail below with reference to the accompanying drawings. Although exemplary embodiments of the present invention are shown in the accompanying drawings, it should be understood that the present invention can be implemented in various forms and should not be limited by the embodiments described herein. On the contrary, these embodiments are provided to enable a clearer and more thorough understanding of the present invention and to fully convey the scope of the present invention to those skilled in the art.

[0024] Embodiment 1; See also Figure 1-Figure 5 In an embodiment of the present invention, a dual-operating-mode heat recovery cascade CO2 heat pump cooling and heating system for an extremely cold environment includes a carbon dioxide cooling and heating integrated system 1 and an HFO cascade system 2; The carbon dioxide cooling and heating integrated system 1 comprises a first evaporation end 101, a first compressor 102 and a first condensation end 103, wherein the first condensation end 103 is used for heating in winter and absorbing heat in summer; The HFO cascade system 2 includes a second compressor 201, a second condensing end 202 and an HFO unit 203. The carbon dioxide cooling and heating integrated system 1 and the HFO cascade system 2 are also jointly equipped with a second evaporation end 204 for evaporation and heat absorption. The HFO unit 203 is used to recover the waste heat in the process of the carbon dioxide cooling and heating integrated system 1 and to provide heat for the HFO cascade system 2.

[0025] The carbon dioxide cooling and heating integrated system 1 also includes a CO2 heat pump 104, a first evaporation end 101 is installed on one side of the CO2 heat pump 104 and is connected to the outlet of the CO2 heat pump 104, a first compressor 102 is installed on one side of the first evaporation end 101 and is connected to the outlet of the first evaporation end 101, a first condensation end 103 is installed on one side of the first compressor 102 and is connected to the outlet of the first compressor 102, a second evaporation end 204 is installed on one side of the first condensation end 103, an inlet of the second evaporation end 204 is connected to the outlet of the first condensation end 103, and an outlet of the second evaporation end 204 is connected to the inlet of the CO2 heat pump 104.

[0026] A throttle valve 105 is installed between the second evaporation end 204 and the CO2 heat pump 104. Temperature sensors, pressure sensors and flow meters are installed between various structures of the carbon dioxide cooling and heating integrated system 1 to monitor the operation of the carbon dioxide cooling and heating integrated system 1.

[0027] The second evaporation end 204 is installed on one side of the HFO unit 203 and connected to the outlet of the HFO unit 203, the second compressor 201 is installed on one side of the second evaporation end 204 and connected to the outlet of the second evaporation end 204, the second condensation end 202 is installed on one side of the second compressor 201 and connected to the outlet of the second compressor 201, and the outlet of the second condensation end 202 is connected to the inlet of the HFO unit 203.

[0028] A control valve 205 is installed between the second condensing end 202 and the HFO unit 203. Temperature sensors, pressure sensors and flow meters are installed between the various structures of the HFO cascade system 2 to monitor the operation of the HFO cascade system 2. The HFO unit 203 uses R1234ZE refrigerant, which remains liquid at -46°C. The control valve 205 is connected to the carbon dioxide hot and cold integrated system 1 through a pipeline and a pressure valve 206 is installed to control the fluid pressure of the pipeline.

[0029] The working principle of the embodiment of the present invention is as follows: the carbon dioxide cooling and heating integrated system 1 starts to operate, the first evaporation end 101 receives low-temperature and low-pressure CO2 gas from the outlet of the CO2 heat pump 104, performs preliminary evaporation and heat absorption, and then these gases are sent to the first compressor 102 for compression, increase their temperature and pressure, and convert them into high-temperature and high-pressure CO2 gas, which then enters the first condensation end 103 to perform heating or heat absorption operations according to seasonal requirements. In winter, the first condensation end 103 releases heat for heating; in summer, it absorbs heat for cooling.

[0030] The HFO cascade system 2 is also running synchronously. The second evaporation end 204 is connected to the first condensation end 103, receiving the medium-temperature and medium-pressure CO2 gas discharged from the first condensation end 103, and evaporating and absorbing heat again. This process not only helps to reduce the outlet temperature of the first condensation end 103, but also realizes the effective recovery of CO2 waste heat. The evaporated HFO refrigerant gas enters the second compressor 201 for compression, and after increasing the temperature and pressure, it is sent to the second condensation end 202 for condensation and heat release.

[0031] The HFO cascade system uses R1234ZE refrigerant, which remains liquid at -46°C and has excellent low-temperature fluidity and heat recovery capabilities. The HFO unit 203 not only recovers the waste heat in the carbon dioxide hot and cold integrated system 1, but also provides a stable heat source for the HFO cascade system 2, which effectively prevents CO2 from entering a subcritical state in a low-temperature environment and ensures the stability of the compressor and heat exchange process.

[0032] The system monitors and adjusts the operating status of each component in real time through accurate temperature sensors, pressure sensors and flow meters, ensuring the safe operation of the system and improving the overall energy efficiency of the system. The throttle valve 105 adjusts the CO2 flow entering the CO2 heat pump 104 according to the outlet pressure and temperature of the second evaporation end 204, thereby optimizing the heat exchange efficiency; similarly, the coordination between the control valve 205 and the second condensation end 202 ensures the stable circulation of the HFO refrigerant in the system.

[0033] In extremely cold conditions, the low freezing point and excellent fluidity of HFO fluid play an important role. It effectively prevents the freezing and frost problems of evaporator components and ensures the continuous and efficient operation of the heat pump system. At the same time, due to the efficient heat recovery function of HFO fluid, the system not only reduces the heat energy loss caused by low temperature, but also significantly improves the overall energy efficiency and stability.

[0034] Embodiment 2; See also Figure 1-Figure 5 In the embodiment of the present invention, the CO2 heat pump 104 is a supercritical cycle, and the working pressure range is set to 7.38 MPa to 10.34 MPa to ensure that the outlet temperature can reach above 60°C in the winter heating mode; at the same time, in the summer heat absorption mode, by optimizing the cycle parameters, the condensation temperature is achieved to be no higher than 40°C.

[0035] The throttle valve 105 adopts an electronic expansion valve, which automatically adjusts the opening according to the real-time monitored temperature, pressure and flow data through an integrated intelligent control system to ensure stable evaporation at the second evaporation end 204 in an extreme low temperature environment of -40°C to -10°C.

[0036] The working principle of the embodiment of the present invention is: the CO2 heat pump 104 is designed as a supercritical circulation system, and its working pressure range is precisely set to 7.38 MPa to 10.34 MPa. This design ensures that the heat pump can output high-temperature heat energy above 60°C in the winter heating mode to meet the heating needs; at the same time, in the summer heat absorption mode, by optimizing the circulation parameters, the condensing temperature of the heat pump is controlled to be no higher than 40°C, which effectively improves the cooling efficiency of the system.

[0037] When the system is running, supercritical CO2 undergoes a cycle of compression, heating, expansion and cooling in the CO2 heat pump 104. In the compression stage, the CO2 gas is compressed to a supercritical state by the first compressor 102, and its temperature and pressure are significantly increased. Then, these high-temperature and high-pressure CO2 gases enter the first condensation end 103 to release heat. According to seasonal requirements, this heat can be used for heating or cooling. In the winter heating mode, the heat released by the first condensation end 103 is used to heat the heating medium to ensure that the outlet temperature reaches above 60°C; while in the summer heat absorption mode, the first condensation end 103 absorbs heat from the environment, and by optimizing the cycle parameters, such as adjusting the operating frequency of the compressor and the opening of the throttle valve 105, the condensation temperature is maintained below 40°C to improve the refrigeration efficiency.

[0038] In order to cope with the impact of extreme low temperature environment on the system, the throttle valve 105 adopts advanced electronic expansion valve technology. This technology monitors the temperature, pressure and flow data of the system in real time through an integrated intelligent control system, and automatically adjusts the opening of the throttle valve 105 according to these data. This design ensures that the second evaporation end 204 can evaporate stably in an extreme low temperature environment of -40°C to -10°C, thereby effectively recovering the waste heat in the CO2 heat pump 104.

[0039] Embodiment 3; See also Figure 1-Figure 5 In the embodiment of the present invention, the second compressor 201 in the HFO cascade system 2 adopts a high-efficiency variable frequency compressor, and its variable frequency range covers 20Hz to 60Hz. It can automatically adjust the speed according to the ambient temperature and heat load demand, and reduce wear by reducing the speed under low load conditions; the control valve 205 in the HFO cascade system 2 adopts a combined control strategy of a solenoid valve and a proportional valve. The solenoid valve is responsible for quickly responding to system start-up and shutdown instructions, and the proportional valve finely adjusts the flow rate according to the deviation between the outlet temperature of the HFO unit 203 and the target temperature, ensuring that the system temperature control accuracy reaches ±0.5°C.

[0040] The pressure valve 206 is set to the automatic adjustment mode, and the pipeline fluid pressure is monitored and adjusted in real time through the integrated pressure sensor and PID controller to maintain it within the set value ±0.1 MPa range.

[0041] The working principle of the embodiment of the present invention is as follows: the second compressor 201 in the HFO cascade system 2 adopts high-efficiency variable frequency compressor technology, which enables the compressor's variable frequency range to cover 20Hz to 60Hz, so that the speed can be automatically adjusted according to the ambient temperature and heat load demand. In winter heating mode, when the ambient temperature is low and the heat load demand is large, the compressor speed increases to increase the circulation volume and heat release of the HFO refrigerant; while in summer cooling or low-load conditions, the compressor speed decreases to reduce wear and energy consumption. This automatic adjustment mechanism not only improves the operating efficiency of the system, but also extends the service life of the compressor.

[0042] Secondly, the control valve 205 in the HFO cascade system 2 adopts a combined control strategy of a solenoid valve and a proportional valve. The solenoid valve is responsible for quickly responding to the system startup and shutdown instructions to ensure that the system can reach a stable state in a short time, while the proportional valve is finely adjusted according to the deviation between the outlet temperature of the HFO unit 203 and the target temperature, and the flow rate of the HFO refrigerant is adjusted to ensure that the system temperature control accuracy reaches ±0.5°C. This combined control strategy not only improves the temperature control accuracy of the system, but also enhances the stability and reliability of the system.

[0043] In addition, the pressure valve 206 in the HFO cascade system 2 is also set to automatic adjustment mode. By integrating the pressure sensor and PID controller, the pressure valve 206 can monitor and adjust the pipeline fluid pressure in real time to maintain it within the set value ±0.1MPa range. This design not only ensures the stability and safety of the system pressure, but also improves the operating efficiency and reliability of the system.

[0044] Working principle: The system integrates the carbon dioxide heating and cooling integrated system 1 and the HFO cascade system 2 to achieve efficient recovery and utilization of thermal energy. In the system, the CO2 heat pump 104 is the core, providing high-temperature thermal energy (≥60°C in winter) or low-temperature refrigeration (≤40°C in summer) through a supercritical cycle (working pressure 7.38 MPa to 10.34 MPa). The first evaporation end 101 receives the low-temperature and low-pressure CO2 gas at the outlet of the CO2 heat pump 104 for preliminary evaporation and heat absorption, and then is compressed into high-temperature and high-pressure gas by the first compressor 102 and enters the first condensation end 103 to provide heating or absorb heat according to seasonal demand.

[0045] To further improve energy efficiency, the system is designed with a second evaporation end 204, which is connected to the first condensation end 103 and uses medium-temperature and medium-pressure CO2 gas to evaporate and absorb heat again, effectively recovering waste heat. During this process, the electronic expansion valve intelligently adjusts the throttling to ensure that the second evaporation end 204 evaporates stably at extremely low temperatures of -40°C to -10°C. The recovered waste heat is used by the HFO unit 203 to provide a stable heat source for the HFO cascade system 2, using R1234ZE refrigerant, which remains liquid at -46°C, enhancing low-temperature fluidity and heat recovery capabilities.

[0046] In the HFO cascade system 2, the second compressor 201 (frequency range 20Hz to 60Hz) automatically adjusts the speed according to the ambient temperature and heat load to optimize energy consumption and performance. The control valve 205 combines the solenoid valve and the proportional valve to quickly respond to system instructions and finely adjust the HFO refrigerant flow to ensure a temperature control accuracy of ±0.5°C. At the same time, the pressure valve 206 automatically adjusts the pipeline fluid pressure to maintain it within the range of ±0.1 MPa to ensure stable operation of the system.

[0047] In the description of the present invention, it should be understood that the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0048] In the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like 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 a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium; it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0049] In the present invention, unless otherwise clearly specified and limited, when a first feature is “on” or “below” a second feature, it may be that the first and second features are in direct contact, or that the first and second features are in indirect contact through an intermediate medium. Moreover, when a first feature is “above”, “above” or “above” a second feature, it may be that the first feature is directly above or obliquely above the second feature, or it may simply mean that the first feature is higher in level than the second feature. When a first feature is “below”, “below” or “below” a second feature, it may be that the first feature is directly below or obliquely below the second feature, or it may simply mean that the first feature is lower in level than the second feature.

[0050] In the description of this specification, the description of the terms "one embodiment", "some embodiments", "embodiment", "example", "specific example" or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, unless they are contradictory.

[0051] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations of the present invention. A person skilled in the art may alter, modify, replace and modify the above embodiments within the scope of the present invention.

Claims

1. A dual-operating heat recovery cascade CO2 heat pump cooling and heating system for an extremely cold environment, characterized in that: It includes a carbon dioxide cooling and heating integrated system (1) and an HFO cascade system (2); The carbon dioxide cooling and heating integrated system (1) comprises a first evaporation end (101), a first compressor (102) and a first condensation end (103); the first condensation end (103) is used for heating in winter and absorbing heat in summer; The HFO cascade system (2) comprises a second compressor (201), a second condensing end (202) and an HFO unit (203); the carbon dioxide cooling and heating integrated system (1) and the HFO cascade system (2) are also jointly equipped with a second evaporation end (204) for evaporation and heat absorption; the HFO unit (203) is used to recover waste heat in the process of the carbon dioxide cooling and heating integrated system (1) and to provide heat for the HFO cascade system (2).

2. According to claim 1, a dual-operating-mode heat recovery cascade CO2 heat pump cooling and heating system for an extremely cold environment, characterized in that: The carbon dioxide cooling and heating integrated system (1) further comprises a CO2 heat pump (104), wherein the first evaporation end (101) is installed on one side of the CO2 heat pump (104) and is connected to an outlet of the CO2 heat pump (104), the first compressor (102) is installed on one side of the first evaporation end (101) and is connected to an outlet of the first evaporation end (101), the first condensation end (103) is installed on one side of the first compressor (102) and is connected to an outlet of the first compressor (102), the second evaporation end (204) is installed on one side of the first condensation end (103), the inlet of the second evaporation end (204) is connected to an outlet of the first condensation end (103), and the outlet of the second evaporation end (204) is connected to an inlet of the CO2 heat pump (104).

3. According to claim 2, a dual-operating-mode heat recovery cascade CO2 heat pump cooling and heating system for an extremely cold environment, characterized in that: A throttle valve (105) is installed between the second evaporation end (204) and the CO2 heat pump (104), and temperature sensors, pressure sensors and flow meters are installed between various structures of the carbon dioxide cooling and heating integrated system (1) for monitoring the operation of the carbon dioxide cooling and heating integrated system (1).

4. According to claim 1, a dual-operating-mode heat recovery cascade CO2 heat pump cooling and heating system for an extremely cold environment, characterized in that: The second evaporation end (204) is installed on one side of the HFO unit (203) and is connected to the outlet of the HFO unit (203); the second compressor (201) is installed on one side of the second evaporation end (204) and is connected to the outlet of the second evaporation end (204); the second condensation end (202) is installed on one side of the second compressor (201) and is connected to the outlet of the second compressor (201); and the outlet of the second condensation end (202) is connected to the inlet of the HFO unit (203).

5. According to claim 1, a dual-operating-mode heat recovery cascade CO2 heat pump cooling and heating system for an extremely cold environment, characterized in that: A control valve (205) is installed between the second condensing end (202) and the HFO unit (203); temperature sensors, pressure sensors and flow meters are installed between the various structures of the HFO cascade system (2) for monitoring the operation of the HFO cascade system (2); the HFO unit (203) uses R1234ZE refrigerant, which remains in a liquid state at -46°C.

6. The extremely cold environment dual-operating condition heat recovery cascade CO2 heat pump combined heating and cooling system according to claim 5, characterized in that: The control valve (205) is connected to the carbon dioxide cooling and heating integrated system (1) via a pipeline, and a pressure valve (206) is installed to control the fluid pressure of the pipeline.

7. The extremely cold environment dual-operating condition heat recovery cascade CO2 heat pump combined heating and cooling system according to claim 1, characterized in that: The CO2 heat pump (104) is a supercritical cycle, and the operating pressure range is set to 7.38 MPa to 10.34 MPa, so as to ensure that in the winter heating mode, the outlet temperature can reach above 60°C; at the same time, in the summer heat absorption mode, by optimizing the cycle parameters, the condensation temperature is achieved to be no higher than 40°C.

8. The extremely cold environment dual-operating condition heat recovery cascade CO2 heat pump combined heating and cooling system according to claim 3, characterized in that: The throttle valve (105) adopts an electronic expansion valve, which automatically adjusts the opening according to the real-time detected temperature, pressure and flow data through an integrated intelligent control system, thereby ensuring stable evaporation at the second evaporation end (204) in an extreme low temperature environment of -40°C to -10°C.

9. The extremely cold environment dual-operating condition heat recovery cascade CO2 heat pump combined heating and cooling system according to claim 6, characterized in that: The second compressor (201) in the HFO cascade system (2) adopts a high-efficiency variable frequency compressor, whose variable frequency range covers 20 Hz to 60 Hz, and can automatically adjust the speed according to the ambient temperature and heat load demand, and reduce wear by reducing the speed under low load conditions; the control valve (205) in the HFO cascade system (2) adopts a combined control strategy of a solenoid valve and a proportional valve, wherein the solenoid valve is responsible for quickly responding to system start-up and shutdown instructions, and the proportional valve finely adjusts the flow rate according to the deviation between the outlet temperature of the HFO unit (203) and the target temperature, thereby ensuring that the system temperature control accuracy reaches ±0.5°C.

10. The extremely cold environment dual-operating condition heat recovery cascade CO2 heat pump cooling and heating system according to claim 6, characterized in that: The pressure valve (206) is set to an automatic adjustment mode, and monitors and adjusts the pipeline fluid pressure in real time through an integrated pressure sensor and a PID controller to maintain it within the range of ±0.1 MPa of the set value.

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