A CO2-R134a coupled composite heat pump heating system and its control method

Abstract

The application relates to a CO2-R134a coupled composite heat pump heating system and a control method, which comprises a CO2 circulation loop and an R134a circulation loop; the CO2 circulation loop comprises a CO2 compressor, a CO2 water heat exchanger, a first electronic expansion valve, an intermediate heat exchanger, a CO2 air-cooled evaporator and a CO2 gas-liquid separator; the R134a circulation loop comprises an R134a compressor, an R134a water heat exchanger, a thermal expansion valve and an R134a gas-liquid separator; through the deep coupling of CO2 and R134a double working media, the advantages of the high-efficiency heat transfer of the CO2 supercritical cycle and the precise regulation of the R134a system are exerted, the system COP (coefficient of performance) is increased by more than 1.5 times, and the energy-saving effect is remarkable compared with a traditional single-working-medium heat pump.

Description

Technical Field

[0001] This application relates to the field of heat source recovery technology, specifically to a CO2-R134a coupled composite heat pump heating system and control method. Background Technology

[0002] Heat pumps, as highly efficient and energy-saving heating devices, absorb low-grade heat from the air and convert it into high-grade heat energy, and have been widely used in various fields. However, traditional heat pump systems have significant technical bottlenecks: single-refrigerant heat pumps (such as Freon-based or CO2-based systems) experience a significant decrease in energy efficiency at low temperatures (≤-10℃), and may even fail to start; some heat pumps have poor environmental performance, using refrigerants that pose an ozone layer depletion risk or have high global warming potential; simultaneously, traditional heat pumps have a narrow heating temperature range and insufficient regulation stability, making it difficult to meet diverse heating needs in different scenarios (such as industrial high-temperature heating and heating in frigid regions). Existing composite heat pump systems mostly employ simple heat source superposition or single-refrigerant cycle optimization, failing to achieve deep coupling between different refrigerants and fully utilize the performance advantages of various refrigerants. This results in limited overall system energy efficiency improvement, a narrow applicable temperature range, and an inability to adapt to heating needs across all scenarios, from low-temperature frigid to high-temperature environments. Therefore, developing an environmentally friendly, efficient, wide-temperature-range adaptable, stable, and reliable composite heat pump heating system is of significant practical importance. Summary of the Invention

[0003] In order to overcome the defects in the prior art, the main objective of this invention is to provide a CO2-R134a coupled composite heat pump heating system and control method that solves the problems of low-temperature energy efficiency decay, unstable heating and narrow applicability of traditional heat pumps by deep coupling of CO2- and R134a dual working fluids, multi-mode intelligent switching and precise control logic.

[0004] To achieve the above objectives, the present invention adopts the following technical solution: a CO2-R134a coupled composite heat pump heating system, comprising: a CO2 circulation loop and an R134a circulation loop; The CO2 circulation loop includes a CO2 compressor, a CO2 water heat exchanger, a first electronic expansion valve, an intermediate heat exchanger, a CO2 air-cooled evaporator, and a CO2 gas-liquid separator. Low-pressure gaseous CO2 enters the CO2 compressor, is compressed, and then enters the CO2 water heat exchanger to exchange heat with the water entering the CO2 water heat exchanger. After heat exchange, the CO2 is throttled and depressurized by the first electronic expansion valve and then enters the intermediate heat exchanger to exchange heat with the R134a working fluid. After heat exchange with the R134a working fluid, the CO2 enters the CO2 air-cooled evaporator, where it is evaporated to obtain low-pressure gaseous CO2. The low-pressure gaseous CO2 enters the CO2 gas-liquid separator, undergoes gas-liquid separation, and then re-enters the CO2 compressor. The R134a circulation loop includes an R134a compressor, an R134a water heat exchanger, a thermostatic expansion valve, and an R134a gas-liquid separator. Low-pressure gaseous R134a enters the R134a compressor for heating and pressurization. After heating and pressurization, the R134a enters the R134a water heat exchanger to exchange heat with the medium water and cool down. After cooling, the R134a passes through the thermostatic expansion valve for throttling and pressure reduction before entering the intermediate heat exchanger to exchange heat with CO2 entering the intermediate heat exchanger. After heat exchange, the R134a enters the R134a gas-liquid separator for gas-liquid separation. The low-pressure gaseous R134a after gas-liquid separation re-enters the R134a compressor.

[0005] Preferably, the CO2 circulation loop further includes a high-pressure CO2 storage tank. The inlet of the high-pressure CO2 storage tank is connected to the CO2 outlet of the intermediate heat exchanger, and the outlet of the high-pressure CO2 storage tank is connected to the inlet of the CO2 air-cooled evaporator. A second electronic expansion valve is provided between the high-pressure CO2 storage tank and the CO2 air-cooled evaporator. After heat exchange through the intermediate heat exchanger, the CO2 enters the high-pressure CO2 storage tank for buffering, and then enters the CO2 air-cooled evaporator after being throttled and depressurized by the second electronic expansion valve.

[0006] Preferably, the CO2 circulation loop further includes a CO2 regenerator, one CO2 inlet of which is connected to the CO2 outlet of an intermediate heat exchanger, and one CO2 outlet of which is connected to the inlet of a high-pressure CO2 storage tank; the other CO2 inlet of the CO2 regenerator is connected to the outlet of a CO2 gas-liquid separator, and the other CO2 outlet of the CO2 regenerator is connected to the inlet of a CO2 compressor; the CO2 after heat exchange in the intermediate heat exchanger enters the CO2 regenerator and exchanges heat with the CO2 after gas-liquid separation in the CO2 gas-liquid separator, thereby recovering the residual heat in the CO2 after separation in the CO2 gas-liquid separator.

[0007] Preferably, it also includes a hot water storage tank, which is connected to the CO2 water heat exchanger and the R134a water heat exchanger, and is used to receive heated hot water output from the CO2 water heat exchanger and the R134a water heat exchanger.

[0008] Preferably, the R134a circulation loop further includes an R134a storage tank. After passing through the R134a water heat exchanger, the R134a enters the R134a storage tank for buffering, and then enters the intermediate heat exchanger after being throttled and depressurized by the thermal expansion valve.

[0009] A control method for a CO2-R134a coupled composite heat pump heating system, comprising a CO2-R134a coupled composite heat pump heating system, the control method comprising: After the system is powered on, the R134a circulation loop is started and runs for 3 minutes. After the temperature on the R134a side of the intermediate heat exchanger stabilizes at 5℃±2℃, the CO2 circulation loop is started. After the CO2 circulation loop starts, the CO2 working fluid is compressed by the CO2 compressor and enters the CO2 water heat exchanger to release heat to the water system. Then it enters the intermediate heat exchanger to release heat to the R134a working fluid to lower its own temperature. After cooling, the CO2 working fluid is throttled by the second electronic expansion valve and enters the CO2 air-cooled evaporator to absorb heat from the ambient air. At the same time, the R134a working fluid is compressed by the R134a compressor and enters the R134a water heat exchanger to release heat to the water system. After being throttled by the thermal expansion valve, it enters the intermediate heat exchanger to absorb the heat released by the CO2 working fluid to achieve evaporation.

[0010] Preferably, it also includes shutdown control. When a shutdown command is received, the CO2 circulation loop is shut down first, and the R134a circulation loop continues to run for 2 minutes before being shut down to recover the residual cooling capacity in the intermediate heat exchanger.

[0011] Preferably, it also includes based on ambient temperature T a Operating mode switching control; When T a When the temperature is above 25℃, the control switches to evaporator fan mode, shuts off the external circulation of the air source heat pump, starts the evaporator fan and the condenser side circulation pump, and starts the R134a compressor for auxiliary heating. When 15℃≤T a When the temperature is ≤25℃, the system enters the external circulation mode of the air source heat pump, shuts down the evaporator fan, starts the air source heat pump unit and the evaporator-side circulation pump, and puts the CO2 circulation loop into standby mode. When T a When the temperature is <15℃, the system enters the CO2-R134a coupled heating mode, including start-up control and heating operation control, and enables the air source heat pump unit to provide auxiliary heat; when T a When the temperature is below -10℃, increase the operating power of the CO2 compressor to maintain the high pressure of the CO2 circuit at 8-10MPa.

[0012] Preferably, defrosting control is also included: The defrosting process is triggered when any of the following conditions are met: the CO2 compressor and evaporator fan are shut down, the CO2 air-cooled evaporator is defrosted using electric heating elements, and normal operation resumes after the evaporator temperature rises to 5°C and is maintained for 3 minutes: The temperature of the CO2 air-cooled evaporator is ≤-5℃ and the duration is ≥10 minutes; Alternatively, the difference between the ambient temperature and the temperature of the CO2 air-cooled evaporator is ≥15℃ and lasts for ≥8 minutes; Alternatively, the system may have run continuously for 2 hours without defrosting.

[0013] Compared with the prior art, the present invention has the following advantages: 1. By deeply coupling CO2 and R134a as dual working fluids, the advantages of efficient heat transfer from the supercritical CO2 cycle and precise system regulation of R134a are brought into full play, resulting in a system energy efficiency ratio (COP) increase of more than 1.5 times. Compared with traditional single working fluid heat pumps, the energy saving effect is significant. 2. It is compatible with an ambient temperature range of -20℃ to 50℃, and can still provide stable heating under low temperature conditions (≤-10℃), solving the problems of energy efficiency degradation and inability to start of traditional heat pumps at low temperatures; it can output hot water at 40℃ to 90℃, meeting the temperature requirements of different scenarios such as industrial heating, commercial heating, and domestic hot water, and has extremely strong adaptability. 3. By employing logics such as fuzzy temperature regulation, coupled collaborative control, precise defrosting, and balanced compressor operation, frequent start-ups and shutdowns of the equipment are avoided, mechanical wear is reduced, and the service life of the unit is extended; at the same time, hot water temperature fluctuations are ensured to be ≤±1℃, guaranteeing heating stability. Attached Figure Description

[0014] Figure 1 This is a structural block diagram of the CO2-R134a coupled composite heat pump heating system in this invention. Detailed Implementation

[0015] To enable those skilled in the art to better understand the technical solutions of the present invention, exemplary embodiments of the present invention are described below in conjunction with the accompanying drawings, including various details of the embodiments of the present invention to aid understanding. These should be considered merely exemplary. Therefore, those skilled in the art should recognize that various changes and modifications can be made to the embodiments described herein without departing from the scope and spirit of the present invention. Similarly, for clarity and brevity, descriptions of well-known functions and structures are omitted in the following description.

[0016] Where there is no conflict, the various embodiments of the present invention and the features thereof may be combined with each other.

[0017] As used herein, the term “and / or” includes any and all combinations of one or more related enumerated entries.

[0018] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the invention. As used herein, the singular forms “a” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will also be understood that when the terms “comprising” and / or “made of” are used in this specification, the presence of the stated feature, integral, step, operation, element, and / or component is specified, but the presence or addition of one or more other features, integrals, steps, operations, elements, components, and / or groups thereof is not excluded. Terms such as “connected” or “linked” are not limited to physical or mechanical connections but can include electrical connections, whether direct or indirect.

[0019] Unless otherwise specified, all terms used herein (including technical and scientific terms) have the same meaning as commonly understood by one of ordinary skill in the art. It will also be understood that terms such as those defined in commonly used dictionaries should be interpreted as having the meaning consistent with their meaning in the context of the relevant art and the invention, and will not be interpreted as having an idealized or overly formal meaning unless expressly so defined herein. Example 1

[0020] like Figure 1 The embodiment shown provides a CO2-R134a coupled composite heat pump heating system, comprising a CO2 circulation loop and an R134a circulation loop. In this embodiment, the CO2 circulation loop serves as the core loop for high-temperature heating and includes a CO2 compressor 1, a CO2 water heat exchanger 2, a first electronic expansion valve 3, an intermediate heat exchanger 4, a CO2 air-cooled evaporator 7, and a CO2 gas-liquid separator 8 connected in series. In one embodiment, the CO2 circulation loop further includes a high-pressure CO2 storage tank 5. The inlet of the high-pressure CO2 storage tank 5 is connected to the CO2 outlet of the intermediate heat exchanger 4, and the outlet of the high-pressure CO2 storage tank 5 is connected to the inlet of the CO2 air-cooled evaporator 7. A second electronic expansion valve 6 is provided between the high-pressure CO2 storage tank 5 and the CO2 air-cooled evaporator 7. In this embodiment, the high-pressure CO2 storage tank 5 is used to stabilize the loop pressure and ensure the stability of the supercritical cycle. It can ensure that the CO2 after heat exchange in the intermediate heat exchanger 4 is buffered to avoid the stability of the entire loop pressure due to excessive or insufficient pressure. At the same time, the second electronic expansion valve 6 further throttles and reduces the pressure of the CO2 after buffering in the high-pressure CO2 storage tank 5 before it enters the CO2 air-cooled evaporator 7.

[0021] The CO2 circulation loop also includes a CO2 regenerator 9. One CO2 inlet of the CO2 regenerator 9 is connected to the CO2 outlet of the intermediate heat exchanger 4, and one CO2 outlet of the CO2 regenerator 9 is connected to the inlet of the high-pressure CO2 storage tank 5. The other CO2 inlet of the CO2 regenerator 9 is connected to the outlet of the CO2 gas-liquid separator 8, and the other CO2 outlet of the CO2 regenerator 9 is connected to the inlet of the CO2 compressor 1. In this embodiment, the CO2 regenerator 9 mainly performs further waste heat recovery of the CO2 working fluid. Specifically, the CO2 after passing through the intermediate heat exchanger 4 enters the CO2 regenerator 9 and exchanges heat with the CO2 after passing through the CO2 gas-liquid separator 8 in the CO2 regenerator 9, absorbing the waste heat of the CO2 after gas-liquid separation, ensuring that the CO2 entering the CO2 compressor 1 is in a low-pressure gaseous state.

[0022] In this embodiment, the CO2 circulation loop operates as follows: low-pressure gaseous CO2 enters the CO2 compressor 1, is compressed, and then enters the CO2-water heat exchanger 2 to exchange heat with the water entering the CO2-water heat exchanger 2. After heat exchange, the CO2 is throttled and depressurized by the first electronic expansion valve 3 before entering the intermediate heat exchanger 4 to exchange heat with the R134a working fluid. After heat exchange with the R134a working fluid, the CO2 enters the CO2 regenerator 9 to absorb the residual heat from the CO2 after passing through the CO2 gas-liquid separator 8. After absorbing heat in the CO2 regenerator 9, the CO2 enters the high-pressure CO2 storage tank 5 for buffering to ensure stable pressure. After buffering, the CO2 enters the CO2 air-cooled evaporator 7 after passing through the second electronic expansion valve 6. After evaporation in the CO2 air-cooled evaporator 7, low-pressure gaseous CO2 is obtained. The low-pressure gaseous CO2 enters the CO2 gas-liquid separator 8. After gas-liquid separation, it enters the CO2 regenerator 9 for heat exchange, forming low-pressure gaseous CO2 that re-enters the CO2 compressor 1.

[0023] The R134a circulation loop in this embodiment includes R134a via compressor 10, R134a water heat exchanger 11, thermal expansion valve 14, and R134a gas-liquid separator 13. The outlet of R134a via compressor 10 is connected to the R134a inlet in R134a water heat exchanger 11, the outlet of R134a in R134a water heat exchanger 11 is connected to the R134a inlet of intermediate heat exchanger 4 through thermal expansion valve 14, the outlet of intermediate heat exchanger 4 is connected to R134a gas-liquid separator 13, and the outlet of R134a gas-liquid separator 13 is connected to R134a via compressor 10.

[0024] In one embodiment, the R134a circulation loop further includes an R134a storage tank 12, the inlet of which is connected to the R134a outlet of the R134a water heat exchanger 11; the outlet of the R134a storage tank 12 is connected to the R134a inlet of the intermediate heat exchanger 4 via a thermal expansion valve 14. The R134a after passing through the R134a water heat exchanger 11 enters the R134a storage tank 12 for buffering, and then, after being throttled and depressurized by the thermal expansion valve 14, enters the intermediate heat exchanger 4.

[0025] In specific operation, low-pressure gaseous R134a enters the compressor 10 for heating and pressurization. After heating and pressurization, the R134a enters the R134a water heat exchanger 11 to exchange heat with the medium water and cool down. The cooled R134a enters the R134a storage tank 12 for buffering and stabilization. Then, it passes through the thermostatic expansion valve 14 for throttling and pressure reduction before entering the intermediate heat exchanger 4 to exchange heat with the CO2 entering the intermediate heat exchanger 4. After throttling and heat exchange, the R134a enters the R134a gas-liquid separator 13 for gas-liquid separation, forming low-pressure gaseous R134a, which then re-enters the compressor 1, completing the R134a cycle.

[0026] In this embodiment, the CO2 working fluid undergoes a supercritical cycle of "compression-cooling-heat exchange-expansion-evaporation" in the loop. Utilizing its critical temperature of 31.1℃ and critical pressure of 7.38MPa, it can efficiently absorb low-grade heat from the air even in low-temperature environments, adapting to a wide temperature range for heating needs. The R134a loop indirectly exchanges heat with the CO2 loop through an intermediate heat exchanger 4, providing a stable low-temperature environment for CO2 evaporation. Simultaneously, it releases the absorbed heat to the water system, achieving complementary advantages between the two working fluids and improving the overall system energy efficiency and operational stability. Through the deep coupling of CO2 and R134a as the two working fluids, leveraging the efficient heat transfer of the CO2 supercritical cycle and the precise regulation of the R134a system, the system's coefficient of performance (COP) is increased by more than 1.5 times, demonstrating significant energy savings compared to traditional single-working-fluid heat pumps.

[0027] Meanwhile, the CO2 circulation loop and the R134a circulation loop transfer heat through the intermediate heat exchanger 4. The heat extracted by the R134a system is released to the hot water storage tank through the R134a water heat exchanger. After being cooled by the intermediate heat exchanger, the CO2 system enters the CO2 air-cooled evaporator to absorb heat, thus realizing the cascade utilization of energy.

[0028] In one embodiment, a water system is also included, comprising a hot water storage tank 15, a condensate tank 16, an evaporation-side circulation pump, and a condensate-side circulation pump. The hot water storage tank serves as a heat buffer and storage unit. The condensate tank 16 provides condensate to the CO2 water heat exchanger and the R134a water heat exchanger; it also receives heated hot water output from the CO2 water heat exchanger and the R134a water heat exchanger to ensure a stable hot water temperature supplied to the user. The condensate-side circulation pump drives the hot water to circulate between the water system and the heat exchangers, ensuring heat exchange uniformity. The evaporation-side circulation pump is connected in series in the R134a circulation loop to provide power for the circulation of the R134a working fluid. The hot water storage tank 15 is connected to the CO2 water heat exchanger 2 and the R134a water heat exchanger 11, and is used to receive the heated hot water output from the CO2 water heat exchanger 2 and the R134a water heat exchanger 11. The hot water storage tank is located on the evaporator side of the system and is connected to the condenser side of the water source heat pump through a pipe. The outlets of both the CO2 water heat exchanger 2 and the R134a water heat exchanger 11 are connected to the hot water storage tank 15, forming a dual-loop heating complementary system.

[0029] In this embodiment, the intermediate heat exchanger 4 is a dedicated heat exchange device for CO2-R134a. It has independent CO2 and R134a flow channels inside. The CO2 flow channel is connected in series with the CO2 circulation loop, and the R134a flow channel is connected in series with the R134a circulation loop, so as to realize indirect heat exchange between CO2 and R134a working fluid and provide a stable low temperature environment for CO2 working fluid evaporation. Example 2

[0030] This embodiment provides a control method for a CO2-R134a coupled composite heat pump heating system, including a CO2 circulation loop, an R134a circulation loop, and a water system; pressure transmitters and temperature transmitters are installed in the inlet and outlet pipes of the CO2 water heat exchanger and the R134a water heat exchanger in the CO2 circulation loop and the R134a circulation loop to monitor the medium pressure and temperature parameters in real time. After the system is powered on, the R134a circulation loop is started first and run for 3 minutes. After the temperature on the R134a side of the intermediate heat exchanger stabilizes at 5℃±2℃, the CO2 circulation loop is started. After the CO2 circulation loop starts, the CO2 working fluid is compressed by the CO2 compressor 1 and enters the CO2 water heat exchanger 2 to release heat to the water system. Then it enters the intermediate heat exchanger 4 to release heat to the R134a working fluid to lower its own temperature. After cooling, the CO2 working fluid is throttled by the first electronic expansion valve and enters the CO2 air-cooled evaporator to absorb heat from the ambient air. At the same time, the R134a working fluid is compressed by the R134a compressor 10 and enters the R134a water heat exchanger to release heat to the water system. After being throttled by the thermal expansion valve 14, it enters the intermediate heat exchanger to absorb the heat released by the CO2 working fluid to achieve evaporation. When shutting down, first close the CO2 circulation loop, then continue running the R134a circulation loop for 2 minutes before closing it to recover the residual cooling capacity in the intermediate heat exchanger.

[0031] Specifically, the control methods include the following: 1. During the startup phase, after the system is powered on, the control module performs a fault self-check and collects the ambient temperature T through the temperature sensor. a Determine the initial operating mode; prioritize starting the R134a loop, and start the CO2 loop (under low temperature conditions) after running for 3 minutes to ensure that the intermediate heat exchanger reaches a stable low temperature state and creates favorable conditions for CO2 working fluid evaporation. 2. Heating stage: CO2 Circulation Loop: Low-pressure gaseous CO2 is compressed by the CO2 compressor, raising its pressure to 8-10 MPa (supercritical state) and significantly increasing its temperature. It then enters the CO2 water heat exchanger to release some heat to the water system, achieving initial heating. Subsequently, it flows through the intermediate heat exchanger to exchange heat with the R134a working fluid, further cooling it. After being throttled and depressurized by the second electronic expansion valve, the temperature of the CO2 working fluid drops sharply, entering the CO2 air-cooled evaporator to absorb low-grade heat from the air and evaporate into a low-pressure gaseous state. After the incompletely evaporated liquid working fluid is separated by the CO2 horizontal gas-liquid separator, it flows back to the CO2 regenerator to recover waste heat, and finally returns to the compressor to complete the cycle. R134a circulation loop: Low-pressure gaseous R134a is compressed by the R134a compressor, increasing its temperature and pressure, and then enters the R134a water heat exchanger to release heat into the water system, helping to raise the hot water temperature; after being stably supplied by the R134a storage tank, it is throttled and depressurized through the thermostatic expansion valve, and then enters the intermediate heat exchanger to absorb heat from the CO2 working fluid, evaporating into a low-pressure gaseous state; after being separated by the R134a gas-liquid separator, it returns to the compressor to complete the cycle; 3. Mode switching phase: When T a When the temperature is above 25℃, the system enters evaporator fan mode, shuts off the air source heat pump external circulation, starts the evaporator fan and condenser side circulation pump, and starts the R134a compressor for auxiliary heating; heat is extracted directly from the air through the evaporator fan. When 15℃≤T a When the temperature is ≤25℃, the system enters the external circulation mode of the air source heat pump, shuts off the evaporator fan, starts the air source heat pump unit and the evaporator-side circulation pump, and puts the CO2 circulation loop on standby; the system uses air source heat to heat the hot water storage tank. When T a When the temperature is <15℃, the system enters the CO2-R134a coupled heating mode, including start-up control and heating operation control, and enables the air source heat pump unit to provide auxiliary heat; when T a When the temperature is below -10℃, increase the operating power of the CO2 compressor to maintain the high pressure of the CO2 circuit at 8-10MPa; 4. Defrosting stage: When the temperature of the CO2 air-cooled evaporator is ≤-5℃ and lasts for ≥10 minutes, or the difference between the ambient temperature and the evaporator temperature is ≥15℃ and lasts for ≥8 minutes, or the system has been running continuously for 2 hours without defrosting, the defrosting process is triggered. During defrosting, the CO2 compressor 1 and the CO2 evaporator fan are turned off, and the electric heating tube is used to defrost. After the evaporator temperature is ≥5℃ and maintained for 3 minutes, normal operation is restored.

[0032] In this embodiment, the CO2 compressor 1 and the R134a compressor 10 have a shutdown interval of no less than 3 minutes and a continuous running time of no less than 1 minute after startup; the multi-compressor unit adopts a balanced random start strategy to ensure that the running time deviation of each compressor does not exceed 5%; In this embodiment, the hot water storage tank is located on the evaporator side of the system and is connected to the condenser side of the water source heat pump via a pipe. The outlets of both the CO2 water heat exchanger and the R134a water heat exchanger are connected to the hot water storage tank, forming a dual-loop heating complementarity. Simultaneously, in this embodiment, the evaporator fan and the CO2 air-cooled evaporator are correspondingly arranged to enhance the heat exchange efficiency between air and the CO2 working fluid, improving the heat absorption effect. A Y-type filter is installed at the front end of the water system inlet pipe to filter impurities in the water, ensuring the cleanliness of the pipes and heat exchangers and preventing blockages. A reducer is used to adapt to pipe connections of different specifications, ensuring connection sealing and compatibility, and reducing pipe resistance.

[0033] In one embodiment, the control method further includes adjustment via fuzzy temperature, specifically including: 1. Using the target temperature T_set of the hot water storage tank (default value 40℃, supports custom setting within the range of 40℃-90℃ according to actual heating needs) and the action range ΔT (default value 2℃) as the core control benchmark, combined with the real-time temperature T_wt of the hot water storage tank, four precise control zones are divided: loading zone, holding zone, unloading zone and emergency stop zone. By dynamically adjusting the number of compressors in operation and the working status of core components, precise and stable control of the hot water storage tank temperature is achieved.

[0034] 2. Loading zone (T_wt < T_set - ΔT): Gradually increase the number of compressors in operation, maintain the electronic expansion valve opening at 80%-100%, increase heating power, and quickly approach the target temperature; 3. Holding Zone (T_set-ΔT≤T_wt≤T_set+ΔT): Maintains the current number of compressors in operation and the opening of the electronic expansion valve, making only minor adjustments based on pressure parameters (adjustment range ≤10%) to maintain stable water temperature; 4. Unloading zone (real-time temperature close to set temperature): Gradually reduce the number of compressors in operation, and simultaneously reduce the opening of the electronic expansion valve (by 10% each time) to avoid excessively high water temperature; 5. Emergency Stop Zone (T_wt≥T_set +ΔT): Unload all compressors within 5 seconds, close the electronic expansion valve, and keep only the circulation pump running at low power to ensure system safety until the water temperature drops to the lower limit of the holding zone, at which point the loading program will be restarted.

[0035] In this embodiment, the rated power of the CO2 compressor is 5kW, the rated power of the R134a compressor is 3kW, the heat exchange area of ​​the CO2 water heat exchanger is 10㎡, the heat exchange area of ​​the R134a water heat exchanger is 8㎡, the heat exchange area of ​​the intermediate heat exchanger is 6㎡, the volume of the hot water storage tank is 800L, the rated power of the air source heat pump unit is 4kW; and a dedicated controller and matching sensors for the Carrefour heat pump are also included.

[0036] In one embodiment, with the following operating parameters: target heating water temperature of 55℃ and ambient temperature of -15℃, the CO2-R134a coupled heating mode is activated. The high pressure of the CO2 circulation loop is maintained at 9MPa, and the evaporator temperature is stabilized at -3℃; the temperature of the intermediate heat exchanger side of the R134a circulation loop is maintained at 4℃, the system COP reaches 3.8, and after 10 hours of continuous operation, the heating water temperature fluctuation is ≤±0.9℃, meeting the heating needs of a 1000㎡ commercial building, and reducing energy consumption by more than 60% compared to traditional gas heating.

[0037] By employing a dual-working-fuel design of CO2 and R134a, intelligent multi-mode switching, and precise control logic, the energy efficiency, stability, and wide temperature range adaptability of the heat pump system are significantly improved, solving the technical pain points of traditional heat pumps.

[0038] The above embodiments are merely illustrative examples of the present invention and do not constitute a limitation on the scope of protection of the present invention. Any designs that are the same as or similar to the present invention are within the scope of protection of the present invention.

Claims

1. A CO2-R134a coupled compound heat pump heating system, characterized in that, include: CO2 circulation loop and R134a circulation loop; The CO2 circulation loop includes a CO2 compressor, a CO2 water heat exchanger, a first electronic expansion valve, an intermediate heat exchanger, a CO2 air-cooled evaporator, and a CO2 gas-liquid separator. Low-pressure gaseous CO2 enters the CO2 compressor, is compressed, and then enters the CO2 water heat exchanger to exchange heat with the water entering the CO2 water heat exchanger. After heat exchange, the CO2 is throttled and depressurized by the first electronic expansion valve and then enters the intermediate heat exchanger to exchange heat with the R134a working fluid. After heat exchange with the R134a working fluid, the CO2 enters the CO2 air-cooled evaporator, where it is evaporated to obtain low-pressure gaseous CO2. The low-pressure gaseous CO2 enters the CO2 gas-liquid separator, undergoes gas-liquid separation, and then re-enters the CO2 compressor. The R134a circulation loop includes an R134a compressor, an R134a water heat exchanger, a thermostatic expansion valve, and an R134a gas-liquid separator. Low-pressure gaseous R134a enters the R134a compressor for heating and pressurization. After heating and pressurization, the R134a enters the R134a water heat exchanger to exchange heat with the medium water and cool down. After cooling, the R134a passes through the thermostatic expansion valve for throttling and pressure reduction before entering the intermediate heat exchanger to exchange heat with CO2 entering the intermediate heat exchanger. After heat exchange, the R134a enters the R134a gas-liquid separator for gas-liquid separation. The low-pressure gaseous R134a after gas-liquid separation re-enters the R134a compressor.

2. The CO2-R134a coupled combined heat pump heating system according to claim 1, wherein, The CO2 circulation loop also includes a high-pressure CO2 storage tank. The inlet of the high-pressure CO2 storage tank is connected to the CO2 outlet of the intermediate heat exchanger, and the outlet of the high-pressure CO2 storage tank is connected to the inlet of the CO2 air-cooled evaporator. A second electronic expansion valve is provided between the high-pressure CO2 storage tank and the CO2 air-cooled evaporator. After heat exchange through the intermediate heat exchanger, the CO2 enters the high-pressure CO2 storage tank for buffering, and then enters the CO2 air-cooled evaporator after being throttled and depressurized by the second electronic expansion valve.

3. The CO2-R134a coupled composite heat pump heating system according to claim 2, characterized in that, The CO2 circulation loop also includes a CO2 regenerator. One CO2 inlet of the CO2 regenerator is connected to the CO2 outlet of the intermediate heat exchanger, and one CO2 outlet of the CO2 regenerator is connected to the inlet of the high-pressure CO2 storage tank. The other CO2 inlet of the CO2 regenerator is connected to the outlet of the CO2 gas-liquid separator, and the other CO2 outlet of the CO2 regenerator is connected to the inlet of the CO2 compressor. After heat exchange in the intermediate heat exchanger, the CO2 enters the CO2 regenerator and exchanges heat with the CO2 that has undergone gas-liquid separation in the CO2 gas-liquid separator, thereby recovering the residual heat in the CO2 after separation in the CO2 gas-liquid separator.

4. The CO2-R134a coupled composite heat pump heating system according to claim 1, characterized in that, It also includes a hot water storage tank, which is connected to the CO2 water heat exchanger and the R134a water heat exchanger, and is used to receive heated hot water output from the CO2 water heat exchanger and the R134a water heat exchanger.

5. The CO2-R134a coupled composite heat pump heating system according to claim 1, characterized in that, The R134a circulation loop also includes an R134a storage tank. After passing through the R134a water heat exchanger, the R134a enters the R134a storage tank for buffering, and then enters the intermediate heat exchanger after being throttled and depressurized by the thermal expansion valve.

6. A control method for a CO2-R134a coupled composite heat pump heating system, comprising any one of the CO2-R134a coupled composite heat pump heating systems according to claims 1-5, characterized in that, The control method includes: After the system is powered on, the R134a circulation loop is started and runs for 3 minutes. After the temperature on the R134a side of the intermediate heat exchanger stabilizes at 5℃±2℃, the CO2 circulation loop is started. After the CO2 circulation loop starts, the CO2 working fluid is compressed by the CO2 compressor and enters the CO2 water heat exchanger to release heat to the water system. Then it enters the intermediate heat exchanger to release heat to the R134a working fluid to lower its own temperature. After cooling, the CO2 working fluid is throttled by the second electronic expansion valve and enters the CO2 air-cooled evaporator to absorb heat from the ambient air. At the same time, the R134a working fluid is compressed by the R134a compressor and enters the R134a water heat exchanger to release heat to the water system. After being throttled by the thermal expansion valve, it enters the intermediate heat exchanger to absorb the heat released by the CO2 working fluid to achieve evaporation.

7. The control method for a CO2-R134a coupled composite heat pump heating system according to claim 6, characterized in that, It also includes shutdown control. When a shutdown command is received, the CO2 circulation loop is shut down first, and the R134a circulation loop continues to run for 2 minutes before being shut down to recover the residual cooling capacity in the intermediate heat exchanger.

8. The control method for a CO2-R134a coupled composite heat pump heating system according to claim 6, characterized in that, Also included is operating mode switching control based on ambient temperature T a of the engine 1. When T a At > 25℃, control to enter the evaporative fan mode, turn off the air source heat pump outer circulation, start the evaporative fan and the condensation side circulation pump, and start the R134a compressor auxiliary heating. When 15℃≤T a When 15℃≤T a When 15℃≤T a When 15℃≤T a When 15℃≤T a When 15℃≤T a When 15℃≤T a When 15℃≤T a When 15℃≤T a When 15℃≤T a When 15℃≤T <000000 When T a When T a When T 9. The control method for a CO2-R134a coupled composite heat pump heating system according to claim 6, characterized in that, It also includes defrost control: The defrosting process is triggered when any of the following conditions are met: the CO2 compressor and evaporator fan are shut down, the CO2 air-cooled evaporator is defrosted using electric heating elements, and normal operation resumes after the evaporator temperature rises to 5°C and is maintained for 3 minutes: The temperature of the CO2 air-cooled evaporator is ≤-5℃ and the duration is ≥10 minutes; Alternatively, the difference between the ambient temperature and the temperature of the CO2 air-cooled evaporator is ≥15℃ and lasts for ≥8 minutes; Alternatively, the system may have run continuously for 2 hours without defrosting.

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