Single-compressor dual-temperature-zone heat pump air conditioning system with two-stage throttling pre-cooling circuit

Abstract

This invention discloses a single-compressor, dual-temperature-zone heat pump air conditioning system with a two-stage throttling pre-cooling circuit. The system includes a variable-frequency compressor with an intermediate gas injection port (b), a four-way reversing valve, a pre-cooling heat exchanger, three electronic expansion valves, and two solenoid valves. The refrigerant is distributed into a main path and a pre-cooling branch path, which exchange heat via a counter-flow pre-cooling heat exchanger. The pre-cooling branch path can be divided into return gas and injection gas paths connected to the system. The accompanying control method allows switching between six operating modes, collecting multi-dimensional operating parameters, and achieving multi-variable closed-loop regulation through independent PID control of the three-stage expansion valve, load-weighted variable-frequency compressor frequency adjustment, and differential pressure solenoid valve collaborative control. Five types of multi-level safety protection are also included. This invention achieves independent temperature control in two temperature zones, low-temperature gas injection for enthalpy increase, and simultaneous cold and heat recovery using only a single variable-frequency compressor. The system has a simplified structure, strong low-temperature heating capacity, high temperature control accuracy, and safe and reliable operation.

Description

Technical Field

[0001] This invention belongs to the field of heat pump air conditioning refrigeration cycle technology, specifically relating to a single-compressor dual-temperature zone heat pump air conditioning system with a two-stage throttling pre-cooling circuit. Background Technology

[0002] Dual-zone heat pump air conditioners can simultaneously output two different temperature levels of cooling and heating, making them core equipment for thermal management of new energy vehicles, cold chain transportation, and precision temperature control in data centers. Currently, the mainstream technology routes in the industry fall into two categories: The first is a dual-compressor dual-loop system, where two independent compression cycles correspond to two separate temperature zones, with completely independent temperature control. However, this system has high overall cost, complex piping, and large size, making it poorly adaptable to lightweight and low-cost scenarios. The second category is a single-compressor dual-zone system, which relies on a single compressor to drive multiple heat exchange loops. This mainly includes parallel dual evaporators, series evaporators, and economizer two-stage throttling solutions, and is also the mainstream R&D direction in the industry. However, existing solutions have four inherent drawbacks: 1. Strong coupling of dual temperature zones: In a parallel dual evaporator system, the two evaporators share the same suction pressure, and the evaporation temperatures of the two zones are mutually constrained. It is impossible to achieve independent temperature control for a large temperature difference of more than 30°C, and the temperature control accuracy is poor when the load fluctuates. 2. Low system energy efficiency: Ordinary single-stage throttling systems have insufficient refrigerant subcooling, resulting in more flash gas in the pipeline and large throttling losses; traditional economizers are only used for gas replenishment and enthalpy increase, and the cooling capacity of the pre-cooling branch cannot serve as an independent temperature zone cold source, resulting in energy waste. 3. Poor reliability under extreme operating conditions: The superheat of the two evaporators cannot be adjusted independently in a closed loop, which makes it easy for liquid to return and compressor liquid slugging to occur; the compressor discharge temperature soars under low temperature heating conditions, the heating output drops significantly, and the operating range is narrow. 4. Difficulty in balancing functionality and cost: The existing single-compressor architecture cannot simultaneously achieve multiple functions such as independent temperature control with large temperature difference, efficiency improvement through deep subcooling, and enthalpy increase through low-temperature gas replenishment. If multiple modes of operation are to be accommodated, the system structure will become significantly more complex.

[0003] The two closest comparison schemes are as follows: Option 1: Single compressor in parallel dual evaporator system (CN112304023A). Two expansion valves supply power to the high and low temperature evaporators respectively after the condenser, and the outlets of the two evaporators converge at the compressor suction port. This option results in pressure binding between the two evaporators, severe temperature coupling, inability to achieve independent temperature control over large temperature differences, lack of pre-cooling / subcooling and enthalpy-increasing structures, and poor low-temperature heating performance.

[0004] Option 2: Two-stage throttling heat pump system with economizer (CN209877528U). The economizer is set up to achieve subcooling of the main circuit and gas injection for the compressor. Only a single evaporator is used for heat exchange, which cannot achieve independent temperature control of the two temperature zones. The cooling capacity of the economizer is only used for gas injection and there is no additional temperature zone utilization, resulting in low energy utilization.

[0005] In summary, existing technologies cannot simultaneously achieve the requirements of decoupled independent temperature control in dual temperature zones, high energy efficiency under all operating conditions, reliable operation over a wide temperature range, and multi-mode compatibility in a compact single-compressor structure. Summary of the Invention

[0006] The present invention aims to provide a single-compressor dual-temperature zone heat pump air conditioning system with a two-stage throttling precooling circuit to solve the problems mentioned in the background art.

[0007] To achieve the above-mentioned technical objectives, the technical solution adopted by the present invention is as follows: A single-compressor dual-temperature zone heat pump air conditioning system with a two-stage throttling pre-cooling circuit includes an inverter compressor with an intermediate gas injection port b, a four-way reversing valve, an outdoor heat exchanger, a pre-cooling heat exchanger, a low-temperature zone heat exchanger, a first electronic expansion valve EV1, a second electronic expansion valve EV2, a third electronic expansion valve EV3, a return gas branch solenoid valve, a gas injection branch solenoid valve, a gas injection check valve, a liquid receiver dryer, a precision filter, and a gas-liquid separator. The variable frequency compressor is equipped with an exhaust port A, an intake port B, and an intermediate air supply port b; The four-way reversing valve is equipped with a D port, a C port, an E port, and an S port; The exhaust port A of the variable frequency compressor is connected to the D interface pipeline of the four-way reversing valve. The C port of the four-way reversing valve is connected to the first port pipe of the outdoor heat exchanger. The second interface of the outdoor heat exchanger is connected in sequence to the liquid storage dryer and the precision filter pipeline; The output of the precision filter is divided into two paths: the main pipeline and the pre-cooling branch pipeline. The precooling heat exchanger is internally equipped with a main side flow channel and a branch side flow channel that are isolated from each other. The refrigerant in the main side channel and the refrigerant in the branch side channel are arranged in a counter-current heat exchange configuration. The main pipeline is connected in series with the first electronic expansion valve EV1, the main flow channel of the precooling heat exchanger, and the second electronic expansion valve EV2, and then connected to the first interface of the low-temperature heat exchanger. The second port of the low-temperature zone heat exchanger is connected to the E port pipeline of the four-way reversing valve. The S-port of the four-way reversing valve is connected to the inlet pipe of the gas-liquid separator. The outlet of the gas-liquid separator is connected to the suction port B of the variable frequency compressor. The precooling branch pipeline is connected in series with the third electronic expansion valve EV3 and then connected to the branch flow channel inlet of the precooling heat exchanger. The outlet of the side flow channel of the precooling heat exchanger is divided into two branch pipelines: the first branch pipeline is connected to the inlet of the gas-liquid separator via the return gas branch solenoid valve, and the second branch pipeline is connected to the intermediate gas injection port b of the variable frequency compressor after being connected in series with the gas injection branch solenoid valve and the gas injection check valve.

[0008] The above technical solution employs a two-stage throttling precooling branch topology. A precision filter separates the main path and the precooling branch. A dual-channel counter-flow precooling heat exchanger enables independent heat exchange for the two refrigerants, structurally decoupling the pressure in both temperature zones and preventing interference between the high and low temperature zones. The first electronic expansion valve EV1, the second electronic expansion valve EV2, and the third electronic expansion valve EV3 independently throttle, controlling the subcooling of the main path and the superheat of the low-temperature zone and the precooling branch, respectively, precisely matching the load of the two zones. The precooling branch outlet is equipped with a dual-path solenoid valve for return gas and make-up gas, allowing switching of the refrigerant flow direction according to operating conditions. In low-temperature environments, the make-up gas branch is activated to increase enthalpy and lower temperature, enhancing low-temperature heating capacity. The entire structure can achieve six operating modes with a single compressor, combining deep subcooling loss reduction, independent dual-temperature control, make-up gas enthalpy increase, and heat recovery functions. This simplifies piping, reduces costs, and, combined with a gas-liquid separator and multiple valves, effectively prevents liquid slugging in the variable frequency compressor, expanding the system's stable operating range.

[0009] Furthermore, the control method for a single-compressor dual-temperature zone heat pump air conditioning system with a two-stage throttling precooling circuit specifically includes the following steps: S1. Receive an external mode selection command and switch between six operating modes, namely, dual-temperature zone independent cooling mode, dual-temperature zone independent heating mode, low-temperature heating gas replenishment and enthalpy enhancement mode, one cooling and one heating heat recovery mode, single low-temperature zone cooling / heating mode, and single high-temperature zone cooling / heating mode. S2. Real-time acquisition of system operating parameters, including the suction and discharge pressure and temperature of the variable frequency compressor, the intermediate gas injection pressure and temperature, the inlet and outlet temperatures and pressures of the precooling heat exchanger, the inlet and outlet temperatures and pressures of the low temperature zone heat exchanger, the set temperature and actual temperature of the dual temperature zone, the outdoor ambient temperature, the opening degree of each electronic expansion valve, the on / off status of the solenoid valve, and the operating current of the variable frequency compressor. S3. Based on the selected target operating mode, execute multi-variable collaborative closed-loop control logic to synchronously regulate the opening degree of the first electronic expansion valve EV1, the second electronic expansion valve EV2, and the third electronic expansion valve EV3, the on / off state of the return gas branch solenoid valve and the make-up gas branch solenoid valve, and the operating frequency of the variable frequency compressor. S4. Monitor system operating parameters in real time, execute multi-level safety protection control logic, and perform frequency reduction adjustment or shutdown protection when fault risks are identified.

[0010] The above technical solution enables one-click switching between six operating conditions, covering all scenarios including independent dual-temperature control, low-temperature enthalpy enhancement, heat recovery, and single-temperature zone operation. It comprehensively collects multi-dimensional parameters such as pressure, temperature, valve components, and current, providing data support for precise control. Through multi-variable collaborative closed-loop control, it links and adjusts the frequencies of three electronic expansion valves, two solenoid valves, and the variable frequency compressor. Independent PID temperature control is implemented for each loop, and precise dual-temperature zone temperature control is achieved through load-weighted frequency modulation. The solenoid valves dynamically switch flow directions based on pressure difference to improve energy efficiency. Simultaneously, a five-level safety protection mechanism is provided: frequency reduction buffering in case of abnormalities, and shutdown alarm for serious faults, balancing system control accuracy, operational efficiency, and equipment safety to ensure stable and reliable operation under all conditions.

[0011] Furthermore, the multivariable collaborative closed-loop control logic includes independent PID control of the three-stage electronic expansion valve loop, frequency regulation of the dual-temperature zone load-weighted PID variable frequency compressor, and dynamic switching logic of the solenoid valve differential pressure. The independent PID control of the three-stage electronic expansion valve is as follows: EV1 closed-loop control of the main loop subcooling, EV2 closed-loop control of the low-temperature zone heat exchanger superheat, and EV3 closed-loop control of the precooling branch heat exchanger side superheat. The dual-temperature zone load-weighted PID variable frequency compressor frequency regulation is as follows: the target operating frequency of the variable frequency compressor is calculated based on the weighted temperature deviation of the dual temperature zones. The solenoid valve differential pressure dynamic switching logic is as follows: based on the differential pressure relationship between the precooling circuit evaporation pressure and the variable frequency compressor suction pressure and intermediate gas supply pressure, the opening / closing state of the return gas branch solenoid valve and the gas supply branch solenoid valve is dynamically switched.

[0012] Using the above technical solution, the collaborative control logic can achieve precise and independent regulation of each loop. Three electronic expansion valves respectively control the subcooling of the main circuit, the superheat of the low-temperature zone, and the pre-cooling branch in a closed-loop manner, eliminating load coupling interference between the two temperature zones and significantly improving temperature control accuracy. Relying on the dual-temperature zone temperature deviation weighted PID adjustment of the inverter compressor frequency, the total cooling and heating load of the two zones can be synchronously matched, avoiding power redundancy or insufficient output of the inverter compressor. The solenoid valve automatically switches paths based on the pressure difference between the pre-cooling circuit and the suction and replenishment pressures. When the pressure is high, the refrigerant flows back to the suction port; in the low-pressure zone, it switches to replenishment to increase enthalpy, fully utilizing the cooling capacity of the pre-cooling branch, reducing throttling losses and exhaust temperature, and balancing energy efficiency, temperature control stability, and low-temperature heating performance under all operating conditions.

[0013] Furthermore, the multi-level safety protection control logic includes five types of protection mechanisms: high-pressure protection, low-pressure protection, high-temperature exhaust protection, backflow prevention protection, and variable frequency compressor overload protection. High pressure protection: When the exhaust pressure reaches the rated high pressure threshold, the frequency of the variable frequency compressor will be reduced first. If the pressure continues to exceed the limit, the compressor will shut down and alarm will be triggered. Low pressure protection: If the intake pressure is lower than the rated low pressure threshold, the corresponding electronic expansion valve will open wider. If the pressure does not recover, the machine will shut down and an alarm will sound. High exhaust temperature protection: If the exhaust temperature is ≥120℃, the gas injection solenoid valve will be opened, the throttle valve opening will be increased, and the frequency of the variable frequency compressor will be reduced. If the temperature continues to exceed the limit, the machine will be shut down immediately. Backflow prevention protection: If the superheat of any heat exchanger is ≤0℃, reduce the opening of the corresponding expansion valve. If the superheat remains negative for 5 seconds, cut off the corresponding branch and trigger a backflow warning. Overload protection: If the operating current of the variable frequency compressor is ≥ 1.2 times the rated current, the frequency of the variable frequency compressor will be reduced. If the current continues to exceed the standard, the compressor will be shut down for protection.

[0014] By adopting the above technical solution, five types of graded and progressive safety protection are set up. In the event of a fault, parameter buffering is prioritized instead of direct shutdown, thereby improving the system's continuous operation capability. High-pressure and low-pressure protection balances system pressure by adjusting the frequency of the variable frequency compressor and the opening of the expansion valve, preventing abnormal pressure from damaging components. High-temperature exhaust protection actively opens the gas supply branch to cool down, improving the overheating problem of the variable frequency compressor under low-temperature conditions. Liquid backflow prevention protection monitors the heat exchanger overheating in real time, reduces the valve opening in advance, and cuts off the branch in case of continuous liquid flow risk, preventing liquid slugging. Overload protection limits the current of the variable frequency compressor by reducing the frequency, preventing motor burnout. Multiple protections cover various fault risks such as pressure, temperature, liquid backflow, and current, providing comprehensive protection for the variable frequency compressor and valves, extending equipment life, and improving the reliability of the system under extreme operating conditions.

[0015] Furthermore, when the system operates in dual-temperature zone independent cooling mode, the following detailed control sub-steps are executed: Step 1: The system collects the actual temperature and set temperature of the high-temperature zone and the low-temperature zone in real time, and calculates the temperature deviation between the two zones. The operating frequency of the variable frequency compressor is controlled by a dual-temperature zone load-weighted PID closed-loop algorithm. Step 2: The system implements independent PID control for the three electronic expansion valves: the third electronic expansion valve EV3 is PID controlled with a target superheat of 5-8°C in the precooling heat exchanger side channel. The second electronic expansion valve EV2 is PID-regulated with the target superheat of 3-5°C for the low-temperature heat exchanger. The first electronic expansion valve EV1 is PID-regulated with a target subcooling of 15-30°C in the main flow channel of the precooling heat exchanger. Step 3: The controller compares the precooling circuit evaporation pressure, the variable frequency compressor suction pressure and the make-up gas pressure in real time, and adaptively switches the on / off state of the two branch solenoid valves: when the precooling circuit evaporation pressure ≥ suction pressure + 0.1MPa, the return gas branch solenoid valve is opened and the make-up gas branch solenoid valve is closed. When the suction pressure is less than the precooling circuit evaporation pressure and less than the suction pressure + 0.1 MPa, the two solenoid valves open synchronously and automatically distribute the refrigerant flow according to the pipeline pressure. When the suction pressure is greater than the precooling circuit evaporation pressure and greater than or equal to the intermediate gas supply pressure, the return gas branch solenoid valve is closed and the gas supply branch solenoid valve is opened. When the discharge temperature of the variable frequency compressor is ≥110℃, the solenoid valve of the gas supply branch is opened to increase the gas supply volume.

[0016] Using the above technical solution, the detailed control logic relies on a two-zone temperature difference weighted PID to accurately match the total cooling load of the inverter compressor, avoiding power waste or insufficient cooling. Three electronic expansion valves are independently controlled in a closed loop, locking preset superheat and subcooling ranges respectively, achieving complete decoupling of evaporation pressure in the high and low temperature zones, eliminating mutual load interference, and simultaneously reducing throttling flashover through deep subcooling of the main circuit, improving cooling efficiency. The solenoid valve path is automatically switched based on the pressure difference between the pre-cooling circuit and the suction and replenishment pressures. When the pressure is high, the refrigerant returns directly to the gas; when the pressure difference is insufficient, replenishment increases enthalpy; and when the exhaust temperature exceeds 110℃, forced replenishment lowers the temperature, effectively suppressing high temperatures in the inverter compressor, balancing independent temperature control accuracy in both zones, cycle efficiency, and unit operational safety.

[0017] Furthermore, when the system operates in dual-temperature zone independent heating mode, the following detailed control sub-steps are executed: Step 1: Based on the difference between the actual heating temperature and the set temperature in the high-temperature zone and the medium-temperature zone, the system uses a dual-temperature zone load-weighted PID closed-loop control algorithm to dynamically adjust the operating frequency of the variable frequency compressor and match the total heating load of the two zones. Step 2: The three electronic expansion valves are independently closed-loop controlled: the second electronic expansion valve EV2 is PID controlled with the target superheat of 3-5℃ in the main flow channel of the precooling heat exchanger. The first electronic expansion valve EV1 is PID-regulated with the target superheat of 5-8°C for the outdoor heat exchanger. The third electronic expansion valve EV3 adjusts its opening according to the temperature deviation in the mid-temperature zone to control the heating capacity. Step 3: The controller synchronously collects the outdoor ambient temperature and the discharge temperature of the variable frequency compressor, and automatically switches the working status of the two branch solenoid valves: when the outdoor ambient temperature is ≥-5℃, the return gas branch solenoid valve is opened and the make-up gas branch solenoid valve is closed. When the outdoor ambient temperature is < -5℃, close the return gas branch solenoid valve and open the make-up gas branch solenoid valve. When the discharge temperature of the variable frequency compressor is ≥115℃, the solenoid valve of the gas supply branch will be opened to reduce the discharge temperature.

[0018] By employing the above technical solution, relying on dual-temperature zone load-weighted PID regulation of the inverter compressor frequency, the total heating demand of the high, low, and medium temperature zones can be dynamically matched, avoiding output power imbalance. Three electronic expansion valves independently control the temperature in a closed loop, stabilizing the superheat of the pre-cooling main side and the outdoor heat exchanger respectively. The third electronic expansion valve, EV3, adjusts its opening according to the temperature difference in the medium temperature zone, achieving independent regulation of the heating capacity of the two zones. Based on the outdoor temperature threshold, the solenoid valve switches; under normal temperature conditions, the refrigerant directly returns to the gas, while in low-temperature environments, it automatically switches to the gas injection and enthalpy-increasing circuit to improve low-temperature heating capacity; when the exhaust temperature exceeds 115℃, the gas injection branch is forcibly opened to cool down, suppressing the risk of overheating. The entire control logic achieves decoupled dual-temperature heating, balancing wide ambient temperature adaptability, heating efficiency, and the operational safety of the inverter compressor.

[0019] Furthermore, when the system operates in low-temperature heating and enthalpy-increasing mode, the following detailed control sub-steps are executed: Step 1: The system maintains the original PID closed-loop control logic of the first electronic expansion valve EV1, the second electronic expansion valve EV2, and the third electronic expansion valve EV3 under the dual-temperature zone independent heating mode. When the outdoor ambient temperature is detected to be below -5℃, the controller closes the return gas branch solenoid valve and opens the gas supply branch solenoid valve. All the refrigerant in the pre-cooling circuit is introduced into the intermediate gas supply port b of the variable frequency compressor through the gas supply branch solenoid valve and the gas supply check valve. Step 2: The side flow channels of the precooling heat exchanger are synchronously connected to form a heating loop in the medium temperature zone. Step 3: When the discharge temperature of the variable frequency compressor is ≥110℃, the controller increases the opening of the solenoid valve of the gas supply branch.

[0020] Using the above technical solution, this mode retains the original expansion valve PID control logic, eliminating the need for parameter retuning and ensuring a smooth switching process without temperature fluctuations. When the outdoor temperature drops below -5℃, the return gas branch is cut off, and all refrigerant in the pre-cooling circuit enters the inverter compressor's gas injection port to complete the gas injection and enthalpy increase, effectively improving the refrigerant circulation volume of the inverter compressor and significantly mitigating the problem of low-temperature heating attenuation. The pre-cooling heat exchanger branch simultaneously acts as a heat exchange circuit in the medium-temperature zone, fully utilizing the heat from the pre-cooled refrigerant without energy waste. When the exhaust temperature exceeds 110℃, the gas injection opening is increased to quickly reduce the exhaust temperature and prevent high-temperature damage to the inverter compressor. The entire control system balances independent heating in dual-temperature zones, circulation efficiency, and the operational safety of the inverter compressor under extremely cold conditions, broadening the system's low-temperature applicability.

[0021] Furthermore, when the system operates in single-low-temperature zone cooling / heating mode, the following detailed control sub-steps are executed: Step 1: The controller closes the third electronic expansion valve EV3, the return gas branch solenoid valve, and the make-up gas branch solenoid valve, while fully opening the first electronic expansion valve EV1. Step 2: The second electronic expansion valve EV2 adopts closed-loop PID control of the superheat of the low-temperature zone heat exchanger, and the variable frequency compressor adopts single-temperature zone temperature deviation PID control frequency.

[0022] Using the above technical solution, the control logic closes all valves in the pre-cooling branch, and EV1 is fully open to eliminate pre-cooling throttling resistance, simplifying the system to a conventional single-temperature zone circulation and reducing pipeline flow losses. Only EV2 is retained for overheat closed-loop PID control of the low-temperature zone heat exchanger, accurately stabilizing the heat exchange state in the low-temperature zone and avoiding the risk of liquid return. The variable frequency compressor independently adjusts its frequency based on the temperature difference of the single low-temperature zone using PID, ensuring that the output power accurately matches the load of a single temperature zone without unnecessary energy consumption. This mode cuts off the heat exchange loop in the high-temperature zone, eliminating unnecessary heat exchange interference. The control logic is simple and stable, meeting the application scenarios that only require low-temperature cooling / heating, simplifying the control algorithm, reducing the controller's computational load, and ensuring stable temperature control and efficient operation under single-temperature conditions.

[0023] Furthermore, when the system operates in single high-temperature zone cooling / heating mode, the following detailed control sub-steps are executed: When cooling in a single high-temperature zone, the controller closes the second electronic expansion valve EV2, and the third electronic expansion valve EV3 adjusts its opening according to the temperature deviation of the high-temperature zone. When heating in a single high-temperature zone, the controller closes the first electronic expansion valve EV1, and the third electronic expansion valve EV3 adjusts its opening according to the temperature deviation of the high-temperature zone.

[0024] Under both operating conditions, the variable frequency compressor uses independent PID to adjust the operating frequency based on the temperature deviation of the single high-temperature zone. The return gas branch solenoid valve and the make-up gas branch solenoid valve switch on and off according to the pressure difference between the evaporation pressure of the precooling circuit and the suction pressure and intermediate make-up gas pressure of the variable frequency compressor.

[0025] Using the above technical solution, this mode cuts off the electronic expansion valve corresponding to the idle temperature zone, relying solely on EV3 to independently regulate the refrigerant flow in the high-temperature zone, precisely matching the heating and cooling load of the high-temperature zone, and eliminating heat exchange interference and flow losses caused by idle circuits. The variable frequency compressor adopts independent PID frequency regulation for each temperature zone, ensuring a high degree of match between power output and temperature control requirements in the high-temperature zone, reducing ineffective energy consumption. The solenoid valve still automatically switches paths based on the pre-cooling circuit, suction, and injection pressure difference, enabling injection cooling or direct return gas as needed, balancing operational energy efficiency and high-temperature protection for the variable frequency compressor. The control logic is adapted to scenarios requiring only high-temperature zone temperature control, with simple and stable mode switching, simplifying the control logic while ensuring heat exchange efficiency and unit operational reliability.

[0026] Furthermore, when the system operates in a cooling-heating heat recovery mode, the following detailed control sub-steps are executed: Step 1: The controller switches the four-way reversing valve to the heating operation position, controls the first electronic expansion valve EV1 to remain fully open, and at the same time makes the outdoor heat exchanger bypass and not participate in heat exchange. Step 2: The system refrigerant is divided into two independent heat exchangers: the pre-cooling heat exchanger branch flow channel acts as an evaporator to absorb heat and achieve cooling in the high-temperature zone, while the low-temperature heat exchanger acts as a condenser to release condensation heat and meet heating requirements. Step 3: The operating frequency of the variable frequency compressor is adjusted using a weighted PID closed-loop control based on the sum of the cooling load and the heating load; The third electronic expansion valve EV3 adjusts the cooling capacity by using the target superheat of the pre-cooled heat exchanger side channel. The second electronic expansion valve EV2 implements closed-loop control of the condensing pressure of the heat exchanger in the low-temperature zone.

[0027] Using the above technical solution, this mode switches the four-way valve and bypasses the outdoor heat exchanger. EV1 is fully open to eliminate throttling losses on the main circuit. The system achieves simultaneous heat recovery for both cooling and heating, with the pre-cooling branch providing evaporative cooling and the low-temperature heat exchanger providing condensing heating. All waste heat is recovered and utilized, significantly improving energy efficiency. The variable frequency compressor, combined with weighted PID frequency regulation based on the total cooling and heating load, precisely matches the output power to the dual-end load. EV3 uses closed-loop control to stabilize the cooling capacity by controlling the superheat on the cooling side, while EV2 regulates the condensing pressure to ensure heating performance. The two heat exchangers are independently controllable without mutual interference. No outdoor heat exchanger is required for heat exchange, reducing environmental cooling and heating losses. This system is suitable for scenarios such as computer rooms and energy storage that require both cooling and heating simultaneously, achieving cascaded energy utilization within a single system and effectively reducing overall operating energy consumption.

[0028] Compared with the prior art, the present invention has the following beneficial effects: 1. Complete decoupling of dual temperature zones to achieve independent temperature control with large temperature difference: This invention adopts a two-stage throttling and counter-current pre-cooling heat exchanger topology, dividing the system into an independent pre-cooling intermediate pressure loop and a main low-pressure loop, which completely solves the problem of temperature zone coupling in traditional single compressor parallel dual evaporator systems. It can achieve synchronous temperature control with large temperature difference, with no interference between the two zones and high temperature control accuracy.

[0029] 2. Integrated precooling heat exchanger significantly improves system energy efficiency: The precooling heat exchanger integrates three functions: deep subcooling, independent temperature zone heat exchange, and gas replenishment economizer. The main circuit achieves deep subcooling of 15 to 30°C, reducing throttling flash loss. All the cold and hot energy in the precooling branch is used in the second temperature zone, with no energy waste. The energy efficiency of both cooling and low-temperature heating cycles is significantly improved.

[0030] 3. Dynamic switching of dual-branch solenoid valves to broaden stable operating conditions: The precooling branch is equipped with dual-path solenoid valves for return gas and gas supply, which adaptively switch the flow direction according to the pressure difference, ambient temperature, and exhaust temperature. In low-temperature conditions, it automatically supplies gas to increase enthalpy and effectively suppresses high temperature of compressor exhaust. The expansion valves of each branch independently control the superheat, eliminating liquid return and liquid slugging from the source. The system can operate stably in a wide range of ambient temperatures.

[0031] 4. Single compressor compatible with six operating conditions, reducing overall cost and size: A single inverter compressor can cover six operating modes: dual-temperature cooling, dual-temperature heating, low-temperature enthalpy increase, heat recovery, and single high-temperature / single low-temperature zone. It is suitable for multiple scenarios such as new energy vehicles, cold chain, and data centers. Compared with dual compressor solutions, the overall cost is lower, the pipeline structure is simplified, the overall size is reduced, and the lightweight advantage is prominent.

[0032] 5. Multi-variable collaborative control with multi-level hierarchical protection ensures high operational stability: The three-stage electronic expansion valve has independent PID control, the load-weighted variable frequency compressor adjusts its frequency, and the solenoid valve's differential pressure linkage coordinates and controls the operation. There is no pressure shock or temperature fluctuation during mode switching. It is equipped with five types of hierarchical protection: high pressure, low pressure, high exhaust temperature, backflow prevention, and overload. In case of a fault, it first adjusts and buffers before shutting down, reducing abnormal shutdowns and extending the compressor's service life. Attached Figure Description

[0033] The present invention can be further illustrated by the non-limiting embodiments given in the accompanying drawings; Figure 1 This is a schematic diagram of the overall pipeline structure of the system of the present invention; Figure 2 This is a flowchart illustrating the overall control process of the system of the present invention. Figure 3 This is a block diagram of the multivariable collaborative closed-loop control logic of the present invention; Figure 4 This is a flowchart illustrating the multi-level safety protection control process of the present invention. Figure 5 This is a schematic diagram of the refrigerant flow direction in the dual-temperature zone independent cooling mode of the present invention; Figure 6 This is a schematic diagram of the refrigerant flow direction in the dual-temperature zone independent heating mode of the present invention; Figure 7 This is a schematic diagram of the low-temperature heating gas replenishment and enthalpy increase mode of the present invention; Figure 8 This is a schematic diagram of the refrigerant flow in the heat recovery mode of the cooling and heating system of this invention. Figure 9 This is a schematic diagram of the refrigerant flow direction in the single low-temperature zone refrigeration mode of the present invention; Figure 10 This is a schematic diagram of the refrigerant flow direction in the single low-temperature zone heating mode of the present invention; Figure 11 This is a schematic diagram of the refrigerant flow direction in the single high-temperature zone refrigeration mode of the present invention; Figure 12 This is a schematic diagram of the refrigerant flow direction in the single high-temperature zone heating mode of the present invention.

[0034] The symbols for the main components are explained below: 1. Variable frequency compressor; 2. Four-way reversing valve; 3. Outdoor heat exchanger; 4. Pre-cooling heat exchanger; 5. Low temperature zone heat exchanger; 6. First electronic expansion valve EV1; 7. Second electronic expansion valve EV2; 8. Third electronic expansion valve EV3; 9. Return gas branch solenoid valve; 10. Make-up gas branch solenoid valve; 11. Make-up gas check valve; 12. Liquid receiver dryer; 13. Precision filter; 14. Gas-liquid separator; 15. High pressure switch; 16. High pressure sensor; 17. High pressure gauge; 18. Low pressure sensor; 19. Low pressure gauge. Detailed Implementation

[0035] To enable those skilled in the art to better understand the present invention, the technical solution of the present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0036] This embodiment describes a single-compressor, dual-temperature-zone heat pump air conditioning system adapted to the thermal management scenarios of new energy vehicles. The system has a rated cooling capacity of 12kW and a rated heating capacity of 15kW. In low-temperature heating (-20℃ environment), the output heating power is no less than 9kW. It can simultaneously achieve 45℃ heating in the cab + 25℃ constant temperature for the battery, and 25℃ cooling in the cab + -18℃ low-temperature cooling for the battery. The selection, specifications, and interface parameters of all structural components, parts, and interfaces of this invention are clearly defined as follows: The core power component of this system is an enthalpy-increasing variable frequency scroll compressor 1 with an intermediate air injection port. The compressor body has an exhaust port A, an intake port B, and an intermediate air injection port b. It operates in a frequency range of 10 to 120 Hz, with a rated operating current of 18 A, an overload protection threshold of 21.6 A (1.2 times the rated current), and an exhaust temperature tolerance limit of 120℃. The compressor body integrates temperature and pressure sensors, which can output real-time signals for intake and exhaust pressure and temperature, as well as the pressure and temperature of the air injection chamber. The intermediate air injection port b of the variable frequency compressor has a built-in one-way valve mounting base and is equipped with an independent air injection one-way valve 11. The one-way valve opens at a pressure of 0.02 MPa to prevent high-pressure refrigerant from flowing back into the air injection chamber of the variable frequency compressor.

[0037] The system switching component uses a four-way reversing valve 2, which has four docking ports: D, C, E, and S. Port D connects to the exhaust end of the inverter compressor 1, port C connects to the outdoor heat exchanger 3, port E connects to the low-temperature zone heat exchanger 5, and port S connects to the return gas pipeline of the gas-liquid separator 14. The valve body has a rated pressure of 4.5MPa and a built-in electromagnetic coil. It is driven by a DC 24V electromagnetic coil and the response time for switching between cooling and heating modes is no more than 0.8 seconds. The refrigerant flow direction can be switched by simply turning the coil on and off.

[0038] The outdoor heat exchange unit adopts a microchannel parallel flow outdoor heat exchanger 3, which acts as a condenser to release heat in cooling mode and as an evaporator to absorb heat in heating mode. The heat exchange area is 12㎡, the design pressure is 4.0MPa, and it is equipped with a DC brushless condenser fan with stepless speed adjustment from 0-1500rpm. The heat exchange capacity can be dynamically adjusted according to the system condensing pressure to adapt to the front installation space and heat dissipation requirements of the vehicle.

[0039] The core heat exchange unit adopts a brazed plate precooling heat exchanger 4, which is a dual-channel counter-flow high-efficiency heat exchange structure. Internally, it has independent main-side and branch-side flow channels, completely isolated from each other with no refrigerant cross-flow. The heat exchange efficiency is ≥95%, with a design pressure of 4.2 MPa and an operating temperature range of -40℃ to 120℃. The precooling heat exchanger 4 simultaneously performs three functions: deep subcooling of the main loop, independent temperature zone heat exchange, and gas injection economizer. It is the core component for achieving dual-temperature zone decoupling and energy efficiency improvement.

[0040] The low-temperature zone heat exchange unit adopts a tube-fin type low-temperature zone heat exchanger 5. In the cooling mode, it acts as an evaporator to output low-temperature cold energy, and in the heating mode, it acts as a condenser to output high-temperature heat. The heat exchange area is 8㎡, and the design pressure is 4.0MPa. It is suitable for high-load heat exchange scenarios such as low-temperature cooling of battery packs and heating of the cab. The surface is treated with anti-corrosion and hydrophilic coating to improve the heat exchange stability under low-temperature conditions.

[0041] All throttling components in the system employ stepper motor-driven electronic expansion valves. The first electronic expansion valve, EV16, is the primary throttling valve for the main circuit, with a 6mm orifice diameter and an opening adjustment range of 0-480 steps. It regulates the intermediate pressure in the main circuit and the subcooling degree of the main flow. The second electronic expansion valve, EV27, is the secondary throttling valve for the main circuit, with a 5mm orifice diameter and an opening adjustment range of 0-480 steps. It controls the refrigerant flow and evaporation pressure in the low-temperature zone heat exchanger 5. The third electronic expansion valve, EV38, is the throttling valve for the pre-cooling branch, with a 4mm orifice diameter and an opening adjustment range of 0-480 steps. It controls the refrigerant flow and heat exchange status of the branch's flow channel in the pre-cooling branch. All three electronic expansion valves support independent PID closed-loop control with an adjustment accuracy of ±1 step and a response time ≤200ms.

[0042] The branch on / off control adopts normally closed electromagnetic shut-off valves. Among them, the return gas branch electromagnetic valve 9 is installed in the return gas pipeline of the precooling branch, and the make-up gas branch electromagnetic valve 10 is installed in the make-up gas pipeline of the precooling branch. The valve body has a rated pressure of 4.5MPa, a response time of ≤1s, and a zero-leakage design. It can quickly switch on and off according to the system pressure difference and operating conditions to realize the dynamic switching of the refrigerant flow direction in the precooling branch.

[0043] The refrigerant purification and storage unit is equipped with a liquid receiver dryer 12 and a precision filter 13 in sequence. The liquid receiver dryer 12 has a volume of 1.5L and contains a molecular sieve desiccant and a multi-layer filter screen. It can store redundant refrigerant in the system and adsorb moisture and impurities in the pipeline. The precision filter 13 has a filtration accuracy of 5μm and can filter out metal debris and solid particles in the pipeline, protecting the downstream electronic expansion valve and heat exchange components from wear and blockage.

[0044] The gas-liquid separation unit adopts a vertical gas-liquid separator 14 with a volume of 2L. It has a built-in filter and a U-shaped bend structure for the outlet pipe, which can separate the liquid refrigerant entrained in the return gas, prevent the liquid refrigerant from directly entering the variable frequency compressor 1 and causing liquid slugging, and ensure the safe operation of the variable frequency compressor 1.

[0045] The system pressure monitoring and protection components are arranged sequentially along the main pipeline: On the exhaust pipe from the discharge port A of the variable frequency compressor 1 to the interface of the four-way reversing valve 2D, a high-pressure switch 15, a high-pressure sensor 16, and a high-pressure gauge 17 are connected in series; on the suction pipe upstream of the suction port B of the variable frequency compressor 1, a low-pressure sensor 18 and a low-pressure gauge 19 are connected in series. The high-pressure switch 15 has an operating threshold of 3.2 MPa; when the pressure exceeds the limit, it directly cuts off the power supply circuit to the variable frequency compressor 1. The high-pressure sensor 16 and the low-pressure sensor 18 have a measurement accuracy of ±0.5%FS and output a 4-20mA analog signal. The high-pressure gauge 17 and the low-pressure gauge 19 are mechanical pressure gauges used for on-site visual reading of system pressure values, facilitating commissioning and maintenance.

[0046] like Figure 1 As shown, the complete pipeline connection relationship in this embodiment is as follows: The exhaust port A of the variable frequency compressor 1 leads out of the compressor exhaust pipe. After the high pressure switch 15, high pressure sensor 16, and high pressure gauge 17 are connected in series on the pipe, it is connected to the D port of the four-way reversing valve 2. The C port of the four-way reversing valve 2 is connected to the first port of the outdoor heat exchanger 3 through the pipeline. The second port of the outdoor heat exchanger 3 is connected to the input end of the liquid storage dryer 12 and the precision filter 13 in sequence. The output end pipeline of the precision filter 13 is divided into two branches, namely the main pipeline and the pre-cooling branch pipeline.

[0047] The main pipeline connects the first electronic expansion valve EV16, the main flow channel of the precooling heat exchanger 4, and the second electronic expansion valve EV27 in series along the refrigerant flow direction, and then connects to the first interface of the low-temperature zone heat exchanger 5. The second interface of the low-temperature zone heat exchanger 5 is connected to the E interface of the four-way reversing valve 2 through a pipeline. The S interface of the four-way reversing valve 2 is connected to the inlet of the gas-liquid separator 14 through a pipeline. The outlet of the gas-liquid separator 14 is connected to the suction port B of the variable frequency compressor 1 through a suction pipe. A low-pressure sensor 18 and a low-pressure gauge 19 are installed sequentially on the suction pipe.

[0048] After the precooling branch pipeline is connected in series with the third electronic expansion valve EV38 along the refrigerant flow direction, it is connected to the inlet of the branch flow channel of the precooling heat exchanger 4. The outlet pipeline of the branch flow channel of the precooling heat exchanger 4 is divided into two branches: the first branch pipeline is connected to the inlet of the gas-liquid separator 14 via the return gas branch solenoid valve 9, and the second branch pipeline is connected to the intermediate gas injection port b of the variable frequency compressor 1 after being connected in series with the gas injection branch solenoid valve 10 and the gas injection check valve 11.

[0049] Through the above pipeline topology, the system forms two independent heat exchange cycles at different pressure levels: the main loop and the pre-cooling branch. The two cycles achieve counter-current heat exchange through the pre-cooling heat exchanger 4, which structurally achieves complete decoupling of the evaporation pressure in the two temperature zones, providing a hardware foundation for multi-mode independent temperature control.

[0050] This system is equipped with a dedicated controller to achieve fully automated operation under all working conditions. The overall control process is as follows: Figure 2 As shown, the control process consists of four core steps: S1 receiving external mode selection instructions and switching the corresponding operating mode; S2 collecting the operating parameters of the entire system in real time; S3 executing multi-variable collaborative closed-loop control logic; and S4 executing multi-level safety protection control logic.

[0051] The controller collects real-time operating parameters covering all key nodes of the system, including the suction and discharge pressure and temperature of the variable frequency compressor 1, the pressure and temperature of the intermediate gas injection port b, the inlet and outlet temperatures and pressures of the precooling heat exchanger 4, the inlet and outlet temperatures and pressures of the low-temperature zone heat exchanger 5, the set temperature and actual temperature of the dual temperature zones, the outdoor ambient temperature, the opening degree of the first electronic expansion valve EV16, the second electronic expansion valve EV27, and the third electronic expansion valve EV38, the on / off status of the return gas branch solenoid valve 9 and the gas injection branch solenoid valve 10, and the operating current of the variable frequency compressor 1, providing complete data support for closed-loop control and safety protection.

[0052] like Figure 3 As shown, the system's multivariable collaborative closed-loop control logic comprises three parallel control branches: independent PID control of the three-stage electronic expansion valve loop, frequency regulation of the variable frequency compressor based on dual-temperature zone load weighted PID, and dynamic switching logic for solenoid valve differential pressure. These three control branches operate synchronously and output collaboratively, respectively regulating valve opening, compressor frequency, and solenoid valve on / off states to achieve multi-parameter linkage optimization. Specifically, the independent PID control of the three-stage electronic expansion valve independently closes loops for the main circuit subcooling, low-temperature zone superheat, and pre-cooling branch superheat, eliminating temperature zone coupling interference. The dual-temperature zone load weighted PID calculates the target frequency of variable frequency compressor 1 based on the temperature deviation between the two zones, accurately matching the total system load. The solenoid valve differential pressure switching logic dynamically switches the on / off states of solenoid valve 9 in the return gas branch and solenoid valve 10 in the replenishment gas branch based on the difference between the evaporation pressure of the pre-cooling loop and the suction pressure and intermediate replenishment gas pressure of variable frequency compressor 1, achieving optimal energy utilization.

[0053] likeFigure 4 As shown, the system is equipped with five types of multi-level safety protection mechanisms, namely high pressure protection, low pressure protection, exhaust high temperature protection, anti-return liquid protection and variable frequency compressor overload protection. All protection logic adopts a graded and progressive strategy. When a fault risk is identified, parameter adjustment buffer is executed first, and shutdown protection is executed only when the abnormality continues to deteriorate. Under the premise of ensuring equipment safety, the system's continuous operation capability is maximized.

[0054] Dual-zone independent cooling mode refrigerant flow direction as follows Figure 5 As shown, this mode can simultaneously output refrigeration capacity in the high-temperature zone and freezing capacity in the low-temperature zone, for example, enabling independent operation of the dual-temperature zones of 25°C cooling for the cab and -18°C cooling for the battery pack.

[0055] The complete workflow of the refrigeration cycle is as follows: Low-temperature, low-pressure gaseous refrigerant is compressed by the variable frequency compressor 1 and becomes high-temperature, high-pressure superheated gas. It is discharged from the exhaust port A and passes through the high-pressure switch 15, high-pressure sensor 16, and high-pressure gauge 17 in sequence before entering the D port of the four-way reversing valve 2. The four-way reversing valve 2 is switched to the refrigeration position, and the refrigerant flows out from the C port into the outdoor heat exchanger 3. In the outdoor heat exchanger 3, it exchanges heat with the outdoor air and condenses into high-pressure, medium-temperature liquid refrigerant. Then, it flows into the liquid receiver dryer 12 and the precision filter 13 in sequence to complete the drying and filtration. The filtered high-pressure liquid refrigerant is divided into the main circuit and the pre-cooling branch circuit from the outlet of the precision filter 13.

[0056] The high-pressure liquid refrigerant in the precooling branch is throttled and depressurized by the third electronic expansion valve EV38 to a medium-temperature and medium-pressure gas-liquid two-phase state. It then enters the branch flow channel of the precooling heat exchanger 4 to evaporate and absorb heat. After exchanging heat with the heat exchange medium in the high-temperature zone, it outputs cooling capacity to achieve independent refrigeration in the high-temperature zone. The evaporated medium-pressure gaseous refrigerant flows out from the outlet of the branch flow channel of the precooling heat exchanger 4. The flow direction is selected according to the system pressure difference: when the evaporation pressure of the precooling circuit is high, it flows into the gas-liquid separator 14 through the return gas branch solenoid valve 9. When the evaporation pressure of the precooling circuit is in the middle range, it enters the intermediate gas injection port b of the variable frequency compressor 1 through the gas injection branch solenoid valve 10 and the gas injection check valve 11.

[0057] The high-pressure liquid refrigerant in the main circuit is slightly throttled to the intermediate pressure by the first electronic expansion valve EV16 and enters the main flow channel of the precooling heat exchanger 4. It exchanges heat with the low-temperature refrigerant in the branch flow channel in a countercurrent manner to achieve deep subcooling of 15-30℃ and completely eliminate flash gas before throttling. After deep subcooling, the high-pressure liquid refrigerant is throttled and depressurized by the second electronic expansion valve EV27 to a low-temperature, low-pressure gas-liquid two-phase state. It enters the low-temperature zone heat exchanger 5 to evaporate and absorb heat, outputting low-temperature cooling capacity to achieve independent refrigeration in the low-temperature zone. The evaporated low-pressure gaseous refrigerant flows out from the low-temperature zone heat exchanger 5 and flows into the gas-liquid separator 14 through the E and S ports of the four-way reversing valve 2. After gas-liquid separation, it returns to the suction port B of the variable frequency compressor 1 to complete the complete refrigeration cycle. The control logic in this mode is as follows: the variable frequency compressor 1 uses a dual-temperature zone load-weighted PID algorithm to adjust the operating frequency. Based on the deviation between the actual temperature and the set temperature in the high-temperature zone and the low-temperature zone, the target frequency is calculated by weighting and synchronously matching the total cooling load of the two zones. The first electronic expansion valve EV16 performs PID closed-loop regulation with a target subcooling of 15-30℃ in the main flow channel of the precooling heat exchanger 4 to stabilize the subcooling effect of the main circuit. The second electronic expansion valve EV27 performs PID closed-loop regulation with a target superheat of 3-5℃ at the outlet of the low-temperature zone heat exchanger 5 to ensure stable evaporation in the low-temperature zone. The third electronic expansion valve EV38 performs PID closed-loop regulation with a target superheat of 5-8℃ in the branch flow channel of the precooling heat exchanger 4 to control the cooling capacity in the high-temperature zone. The return gas branch solenoid valve 9 and the make-up gas branch solenoid valve 10 are dynamically switched according to the pressure difference: when the precooling circuit evaporation pressure is ≥ suction pressure + 0.1MPa, the return gas branch solenoid valve 9 is opened and the make-up gas branch solenoid valve 10 is closed; when the suction pressure is < precooling circuit evaporation pressure < suction pressure + 0.1MPa, both valves open synchronously to automatically distribute the flow; when the suction pressure is > precooling circuit evaporation pressure ≥ intermediate make-up gas pressure, the return gas branch solenoid valve 9 is closed and the make-up gas branch solenoid valve 10 is opened; when the discharge temperature of the variable frequency compressor 1 is ≥ 110℃, the make-up gas branch solenoid valve 10 is forcibly opened to increase the make-up gas volume and reduce the discharge temperature.

[0058] Dual-zone independent heating mode refrigerant flow direction Figure 6 As shown, this mode can output heat in both high-temperature and medium-temperature zones simultaneously, such as enabling independent operation of the dual-temperature zones: 45°C heating for the cab and 25°C preheating for the battery pack.

[0059] The complete working process of the heating cycle is as follows: The low-temperature, low-pressure gaseous refrigerant is compressed by the variable frequency compressor 1 and becomes a high-temperature, high-pressure superheated gas. It is discharged from the exhaust port A and passes through the high-pressure switch 15, the high-pressure sensor 16, and the high-pressure gauge 17 in sequence before entering the D port of the four-way reversing valve 2. The four-way reversing valve 2 is switched to the heating position, and the refrigerant flows out from the E port into the low-temperature zone heat exchanger 5. In the low-temperature zone heat exchanger 5, it exchanges heat with the target medium, condenses and releases heat, and outputs high-temperature heat to achieve independent heating in the high-temperature zone. The condensed high-pressure, medium-temperature liquid refrigerant flows out of the low-temperature zone heat exchanger 5 and passes through the second electronic expansion valve EV27, the main side channel of the pre-cooling heat exchanger 4, and the first electronic expansion valve EV16 in sequence before flowing into the precision filter 13 and the liquid receiver dryer 12. At this time, the refrigerant in the precooling branch is diverted and throttled by the third electronic expansion valve EV38 before entering the precooling heat exchanger 4 side channel to condense and release heat, outputting medium-temperature heat and realizing independent heating in the medium-temperature zone. The condensed refrigerant is returned to the gas-liquid separator 14 via the return gas branch solenoid valve 9 according to the operating conditions, or enters the intermediate gas injection port b of the variable frequency compressor 1 via the gas injection branch solenoid valve 10 and the gas injection check valve 11.

[0060] The main refrigerant is throttled and depressurized by the first electronic expansion valve EV16 into a low-temperature, low-pressure gas-liquid two-phase state, and enters the outdoor heat exchanger 3 to evaporate and absorb heat from the outdoor environment. The evaporated low-pressure gaseous refrigerant flows into the gas-liquid separator 14 through the C and S ports of the four-way reversing valve 2. After gas-liquid separation, it returns to the suction port B of the variable frequency compressor 1, completing the complete heating cycle.

[0061] The control logic in this mode is as follows: Variable frequency compressor 1 uses a dual-temperature zone load-weighted PID algorithm to adjust the operating frequency and match the total heating load of the two zones. The second electronic expansion valve EV27 uses PID closed-loop control with a target superheat of 3-5℃ in the main flow channel of the precooling heat exchanger 4 to stabilize the intermediate pressure of the system. The first electronic expansion valve EV16 uses PID closed-loop control with a target superheat of 5-8℃ at the outlet of the outdoor heat exchanger 3 to ensure stable evaporation on the outdoor side. The third electronic expansion valve EV38 dynamically adjusts its opening according to the temperature deviation in the middle temperature zone to control the heating capacity in the middle temperature zone. The solenoid valve switches according to the ambient temperature and exhaust temperature: when the outdoor ambient temperature is ≥-5℃, the return gas branch solenoid valve 9 is opened and the make-up gas branch solenoid valve 10 is closed; when the outdoor ambient temperature is <-5℃, the return gas branch solenoid valve 9 is closed and the make-up gas branch solenoid valve 10 is opened to start the make-up gas enthalpy increase. When the exhaust temperature of variable frequency compressor 1 is ≥115℃, the make-up gas branch solenoid valve 10 is forcibly opened to reduce the exhaust temperature.

[0062] Low-temperature heating gas replenishment and enthalpy increase mode refrigerant flow direction as follows Figure 7 As shown, this mode is designed for extreme low temperature environments below -5℃. It enhances the enthalpy increase effect of gas replenishment on the basis of dual-temperature zone heating, and solves the problems of reduced heating capacity and excessively high exhaust temperature in low temperature environments.

[0063] The basic circulation process of this mode is the same as that of the dual-temperature zone independent heating mode. The core difference is that when the controller detects that the outdoor ambient temperature is below -5℃, it closes the return gas branch solenoid valve 9 and fully opens the make-up gas branch solenoid valve 10. The refrigerant in the pre-cooling branch is throttled and evaporated by the third electronic expansion valve EV38 and becomes medium-pressure superheated gas. It enters the intermediate make-up gas port b of the variable frequency compressor 1 through the make-up gas branch solenoid valve 10 and the make-up gas check valve 11. After mixing with the main airflow in the compression chamber, it continues to be compressed, realizing the make-up gas enthalpy increase, increasing the refrigerant circulation volume of the variable frequency compressor 1, and greatly enhancing the low-temperature heating output capability.

[0064] Meanwhile, the branch flow channels of the precooling heat exchanger 4 are synchronously connected for heat exchange, continuously outputting heat in the medium temperature zone. All the energy of the precooling circuit is utilized without any additional energy loss. When the exhaust temperature of the variable frequency compressor 1 is ≥110℃, the controller further increases the opening of the solenoid valve 10 in the gas supply branch to increase the gas supply volume and quickly reduce the exhaust temperature, ensuring the safe operation of the variable frequency compressor 1 under extremely cold conditions.

[0065] In this mode, the first electronic expansion valve EV16, the second electronic expansion valve EV27, and the third electronic expansion valve EV38 maintain the original PID closed-loop control logic, and the parameters do not need to be readjusted. The mode switching process is smooth and shock-free, and the temperature in the dual temperature zones does not fluctuate significantly.

[0066] In a heat recovery mode with one cooling and one heating component, the refrigerant flow is as follows: Figure 8 As shown, in this mode, the system outputs one cooling and one heating output simultaneously, realizing energy cascade recovery and utilization. It is suitable for scenarios such as data centers and energy storage systems that have both cooling and heating needs, and can also be adapted to the combined working conditions of new energy vehicle battery cooling and cab heating.

[0067] The workflow of this mode is as follows: The controller switches the four-way reversing valve 2 to the heating operation position, controls the first electronic expansion valve EV16 to remain fully open, and simultaneously allows the outdoor heat exchanger 3 to bypass and not participate in heat exchange, so that the main system circuit does not exchange heat with the outdoor environment. After the high-temperature and high-pressure refrigerant is discharged from the discharge port A of the variable frequency compressor 1, it enters the low-temperature zone heat exchanger 5 through the four-way reversing valve 2, where it condenses and releases heat, outputting the heating capacity. The condensed liquid refrigerant flows through the second electronic expansion valve EV27 and the main flow channel of the pre-cooling heat exchanger 4 into the precision filter 13, and then all of it enters the pre-cooling branch.

[0068] After the refrigerant in the pre-cooling branch is throttled and depressurized by the third electronic expansion valve EV38, it enters the side flow channel of the pre-cooling heat exchanger 4 for evaporation and heat absorption, outputting cooling capacity. The evaporated refrigerant flows into the gas-liquid separator 14 through the return gas branch solenoid valve 9, and then returns to the suction port B of the variable frequency compressor 1 to complete the cycle. In this mode, the low-temperature zone heat exchanger 5 acts as a condenser to release condensation heat to achieve heating, while the side flow channel of the pre-cooling heat exchanger 4 acts as an evaporator to absorb heat to achieve cooling. All the condensation heat of the system is used for heating demand, and the cooling capacity is output synchronously, with an energy utilization rate of ≥95%, significantly reducing the overall operating energy consumption. In terms of control logic, the operating frequency of the variable frequency compressor 1 is adjusted by weighted PID closed-loop regulation based on the sum of the cooling load and the heating load. The third electronic expansion valve EV38 is adjusted by closed-loop regulation based on the target superheat of the side flow channel of the pre-cooling heat exchanger 4 to stabilize the cooling capacity. The second electronic expansion valve EV27 implements closed-loop regulation based on the condensation pressure of the low-temperature zone heat exchanger 5 to ensure the heating effect.

[0069] The refrigerant flow direction in single-low-temperature zone cooling and single-low-temperature zone heating modes is as follows: Figure 9 , Figure 10 As shown, in this mode, only the low-temperature zone heat exchange loop is activated, the pre-cooling branch is completely shut down, and the system is simplified to a conventional single-stage compression cycle, which is suitable for operating scenarios that only require a single low-temperature zone.

[0070] In single low-temperature zone cooling mode, the controller closes the third electronic expansion valve EV38, the return gas branch solenoid valve 9, and the make-up gas branch solenoid valve 10, while fully opening the first electronic expansion valve EV16. The pre-cooling heat exchanger 4 only serves as a refrigerant passage and does not perform heat exchange function. After the refrigerant condenses from the outdoor heat exchanger 3, it passes through the liquid receiver dryer 12, the precision filter 13, the fully open first electronic expansion valve EV16, and the main flow channel of the pre-cooling heat exchanger 4. Then, it is throttled by the second electronic expansion valve EV27 and enters the low-temperature zone heat exchanger 5 for evaporation and cooling. The evaporated refrigerant returns to the suction port B of the variable frequency compressor 1 through the four-way reversing valve 2 and the gas-liquid separator 14.

[0071] In the single low-temperature zone heating mode, all valves in the pre-cooling branch are closed, and the first electronic expansion valve EV16 is fully open. After the high-temperature and high-pressure refrigerant is discharged from the inverter compressor 1, it enters the low-temperature zone heat exchanger 5 to condense and release heat. Then, it passes through the second electronic expansion valve EV27, the main flow channel of the pre-cooling heat exchanger 4, the fully open first electronic expansion valve EV16, the precision filter 13, and the liquid receiver dryer 12 before entering the outdoor heat exchanger 3 to evaporate and absorb heat. Finally, it flows back to the inverter compressor 1.

[0072] In this mode, the second electronic expansion valve EV27 uses closed-loop PID control of the superheat of the low-temperature zone heat exchanger 5 to stabilize the evaporation state; the variable frequency compressor 1 uses single-temperature zone temperature deviation PID to adjust the operating frequency and accurately match the low-temperature zone load; closing the idle precooling branch can eliminate additional flow loss and heat exchange interference, simplify the control logic, and improve the single-temperature zone operation efficiency.

[0073] The refrigerant flow direction in single-high-temperature zone cooling and single-high-temperature zone heating modes is as follows: Figure 11 , Figure 12 As shown, in this mode, only the precooling branch is used as an independent temperature zone, and the low temperature zone loop of the main road is closed, which is suitable for operation scenarios that only require a single high temperature zone.

[0074] In single high-temperature zone cooling mode, the controller closes the second electronic expansion valve EV27, cutting off the main low-temperature zone circuit; after the high-pressure liquid refrigerant flows out from the precision filter 13, it all enters the pre-cooling branch, and after being throttled by the third electronic expansion valve EV38, it enters the branch flow channel of the pre-cooling heat exchanger 4 for evaporative cooling. The evaporated refrigerant flows back to the system according to the pressure difference through the return gas branch solenoid valve 9 or the make-up gas branch solenoid valve 10; the first electronic expansion valve EV16 remains fully open, and there is no refrigerant flow in the main flow channel of the pre-cooling heat exchanger 4.

[0075] In the single high-temperature zone heating mode, the controller closes the first electronic expansion valve EV16 and cuts off the outdoor main circuit. After the high-temperature and high-pressure refrigerant is discharged from the inverter compressor 1, it enters the main flow channel of the pre-cooling heat exchanger 4 through the low-temperature zone heat exchanger 5 and the second electronic expansion valve EV27. Then, it flows into the pre-cooling branch, and after being throttled by the third electronic expansion valve EV38, it condenses and releases heat in the branch flow channel, outputting the heating capacity. The refrigerant after heat exchange flows back to the inverter compressor 1 through the corresponding solenoid valve.

[0076] In the single high-temperature zone heating mode, the controller closes the first electronic expansion valve EV16 and cuts off the outdoor main circuit. After the high-temperature and high-pressure refrigerant is discharged from the inverter compressor 1, it enters the main flow channel of the pre-cooling heat exchanger 4 through the low-temperature zone heat exchanger 5 and the second electronic expansion valve EV27. Then, it flows into the pre-cooling branch, and after being throttled by the third electronic expansion valve EV38, it condenses and releases heat in the branch flow channel, outputting the heating capacity. The refrigerant after heat exchange flows back to the inverter compressor 1 through the corresponding solenoid valve.

[0077] This invention achieves complete decoupling of evaporation pressure in both temperature zones through a single compressor paired with a two-stage throttling precooling loop topology. Combined with multi-variable collaborative PID control and a six-condition seamless switching strategy, it significantly reduces overall machine cost and equipment size while offering multiple advantages such as ±0.3℃ high-precision independent temperature control, high energy efficiency under all operating conditions, stable operation in a wide environmental range from -30℃ to 45℃, and multiple safety protections against liquid slugging. It effectively solves the industry pain points of existing single-compressor dual-temperature zone heat pump systems, such as temperature zone coupling, low energy efficiency, poor reliability in low-temperature conditions, and difficulty in balancing functionality and cost. It has extremely high engineering application value and market promotion prospects.

[0078] The above provides a detailed description of a single-compressor, dual-temperature-zone heat pump air conditioning system with a two-stage throttling precooling circuit provided by the present invention. The specific embodiments described are only intended to aid in understanding the method and core ideas of the present invention. It should be noted that those skilled in the art can make various improvements and modifications to the present invention without departing from its principles, and these improvements and modifications also fall within the scope of protection of the claims of the present invention.

Claims

1. A single-compressor, dual-temperature-zone heat pump air conditioning system with a two-stage throttling pre-cooling circuit, characterized in that, It includes a variable frequency compressor with intermediate gas inlet b, a four-way reversing valve, an outdoor heat exchanger, a pre-cooling heat exchanger, a low-temperature zone heat exchanger, a first electronic expansion valve EV1, a second electronic expansion valve EV2, a third electronic expansion valve EV3, a return gas branch solenoid valve, a gas inlet branch solenoid valve, a gas inlet check valve, a liquid receiver dryer, a precision filter, and a gas-liquid separator. The variable frequency compressor is equipped with an exhaust port A, an intake port B, and an intermediate air supply port b; The four-way reversing valve is equipped with a D port, a C port, an E port, and an S port; The exhaust port A of the variable frequency compressor is connected to the D interface pipeline of the four-way reversing valve. The C port of the four-way reversing valve is connected to the first port pipe of the outdoor heat exchanger. The second interface of the outdoor heat exchanger is connected in sequence to the liquid storage dryer and the precision filter pipeline; The output of the precision filter is divided into two paths: the main pipeline and the pre-cooling branch pipeline. The precooling heat exchanger is internally equipped with a main side flow channel and a branch side flow channel that are isolated from each other. The refrigerant in the main side channel and the refrigerant in the branch side channel are arranged in a counter-current heat exchange configuration. The main pipeline is connected in series with the first electronic expansion valve EV1, the main flow channel of the precooling heat exchanger, and the second electronic expansion valve EV2, and then connected to the first interface of the low-temperature heat exchanger. The second port of the low-temperature zone heat exchanger is connected to the E port pipeline of the four-way reversing valve. The S-port of the four-way reversing valve is connected to the inlet pipe of the gas-liquid separator. The outlet of the gas-liquid separator is connected to the suction port B of the variable frequency compressor. The precooling branch pipeline is connected in series with the third electronic expansion valve EV3 and then connected to the branch flow channel inlet of the precooling heat exchanger. The outlet of the side flow channel of the precooling heat exchanger is divided into two branch pipelines: the first branch pipeline is connected to the inlet of the gas-liquid separator via the return gas branch solenoid valve, and the second branch pipeline is connected to the intermediate gas injection port b of the variable frequency compressor after being connected in series with the gas injection branch solenoid valve and the gas injection check valve.

2. The single-compressor dual-temperature zone heat pump air conditioning system with a two-stage throttling precooling circuit according to claim 1, characterized in that, The control method includes the following steps: S1. Receive an external mode selection command and switch between six operating modes, namely, dual-temperature zone independent cooling mode, dual-temperature zone independent heating mode, low-temperature heating gas replenishment and enthalpy enhancement mode, one cooling and one heating heat recovery mode, single low-temperature zone cooling / heating mode, and single high-temperature zone cooling / heating mode. S2. Real-time acquisition of system operating parameters, including the suction and discharge pressure and temperature of the variable frequency compressor, the intermediate gas injection pressure and temperature, the inlet and outlet temperatures and pressures of the precooling heat exchanger, the inlet and outlet temperatures and pressures of the low temperature zone heat exchanger, the set temperature and actual temperature of the dual temperature zone, the outdoor ambient temperature, the opening degree of each electronic expansion valve, the on / off status of the solenoid valve, and the operating current of the variable frequency compressor. S3. Based on the selected target operating mode, execute multi-variable collaborative closed-loop control logic to synchronously regulate the opening degree of the first electronic expansion valve EV1, the second electronic expansion valve EV2, and the third electronic expansion valve EV3, the on / off state of the return gas branch solenoid valve and the make-up gas branch solenoid valve, and the operating frequency of the variable frequency compressor. S4. Monitor system operating parameters in real time, execute multi-level safety protection control logic, and perform frequency reduction adjustment or shutdown protection when fault risks are identified.

3. A single-compressor dual-temperature zone heat pump air conditioning system with a two-stage throttling precooling circuit according to claim 2, characterized in that, In the control method, the multi-variable collaborative closed-loop control logic includes independent PID control of the three-stage electronic expansion valve circuit, frequency regulation of the dual-temperature zone load-weighted PID variable frequency compressor, and dynamic switching logic of the solenoid valve differential pressure. The independent PID control of the three-stage electronic expansion valve circuit is as follows: the first electronic expansion valve EV1 controls the subcooling of the main circuit in a closed loop; the second electronic expansion valve EV2 controls the superheat of the heat exchanger in the low-temperature zone in a closed loop; and the third electronic expansion valve EV3 controls the superheat of the heat exchange side of the precooling branch in a closed loop. The dual-temperature zone load-weighted PID variable frequency compressor frequency regulation is as follows: the target operating frequency of the variable frequency compressor is calculated based on the weighted temperature deviation of the dual temperature zones. The solenoid valve differential pressure dynamic switching logic is as follows: based on the differential pressure relationship between the precooling circuit evaporation pressure and the variable frequency compressor suction pressure and intermediate gas supply pressure, the opening / closing state of the return gas branch solenoid valve and the gas supply branch solenoid valve is dynamically switched.

4. A single-compressor dual-temperature zone heat pump air conditioning system with a two-stage throttling precooling circuit according to claim 3, characterized in that, In the control method, the multi-level safety protection control logic includes five types of protection mechanisms: high-pressure protection, low-pressure protection, high-temperature exhaust protection, anti-return protection, and variable frequency compressor overload protection. High pressure protection: When the exhaust pressure reaches the rated high pressure threshold, the frequency of the variable frequency compressor is reduced first. If the pressure continues to exceed the limit, the compressor will shut down and alarm. Low pressure protection: If the intake pressure is lower than the rated low pressure threshold, the corresponding electronic expansion valve will open wider. If the pressure does not recover, the machine will shut down and an alarm will sound. High exhaust temperature protection: If the exhaust temperature is ≥120℃, the gas injection solenoid valve will be opened, the throttle valve opening will be increased, and the frequency of the variable frequency compressor will be reduced. If the temperature continues to exceed the limit, the machine will be shut down immediately. Backflow prevention protection: If the superheat of any heat exchanger is ≤0℃, reduce the opening of the corresponding expansion valve. If the superheat remains negative for 5 seconds, cut off the corresponding branch and trigger a backflow warning. Overload protection: If the operating current of the variable frequency compressor is ≥ 1.2 times the rated current, the frequency of the variable frequency compressor will be reduced. If the current continues to exceed the standard, the compressor will be shut down for protection.

5. A single-compressor dual-temperature zone heat pump air conditioning system with a two-stage throttling precooling circuit according to claim 4, characterized in that, In the control method, when the system operates in dual-temperature zone independent cooling mode, the following detailed control sub-steps are executed: Step 1: The system collects the actual temperature and set temperature of the high-temperature zone and the low-temperature zone in real time, and calculates the temperature deviation between the two zones. The operating frequency of the variable frequency compressor is controlled by a dual-temperature zone load-weighted PID closed-loop algorithm. Step 2: The system implements independent PID control for the three electronic expansion valves: the third electronic expansion valve EV3 is PID controlled with a target superheat of 5-8°C in the precooling heat exchanger side channel. The second electronic expansion valve EV2 is PID-regulated with the target superheat of 3-5°C for the low-temperature heat exchanger. The first electronic expansion valve EV1 is PID-regulated with a target subcooling of 15-30°C in the main flow channel of the precooling heat exchanger. Step 3: The controller compares the precooling circuit evaporation pressure, the variable frequency compressor suction pressure and the make-up gas pressure in real time, and adaptively switches the on / off state of the two branch solenoid valves: when the precooling circuit evaporation pressure ≥ suction pressure + 0.1MPa, the return gas branch solenoid valve is opened and the make-up gas branch solenoid valve is closed. When the suction pressure is less than the precooling circuit evaporation pressure and less than the suction pressure + 0.1 MPa, the two solenoid valves open synchronously and automatically distribute the refrigerant flow according to the pipeline pressure. When the suction pressure is greater than the precooling circuit evaporation pressure and greater than or equal to the intermediate gas supply pressure, the return gas branch solenoid valve is closed and the gas supply branch solenoid valve is opened. When the discharge temperature of the variable frequency compressor is ≥110℃, the solenoid valve of the gas supply branch is opened to increase the gas supply volume.

6. A single-compressor dual-temperature zone heat pump air conditioning system with a two-stage throttling precooling circuit according to claim 5, characterized in that, In the control method, when the system is operating in dual-temperature zone independent heating mode, the following detailed control sub-steps are executed: Step 1: Based on the difference between the actual heating temperature and the set temperature in the high-temperature zone and the medium-temperature zone, the system uses a dual-temperature zone load-weighted PID closed-loop control algorithm to dynamically adjust the operating frequency of the variable frequency compressor and match the total heating load of the two zones. Step 2: The three electronic expansion valves are independently closed-loop controlled: the second electronic expansion valve EV2 is PID controlled with the target superheat of 3-5℃ in the main flow channel of the precooling heat exchanger. The first electronic expansion valve EV1 is PID-regulated with the target superheat of 5-8°C for the outdoor heat exchanger. The third electronic expansion valve EV3 adjusts its opening according to the temperature deviation in the mid-temperature zone to control the heating capacity. Step 3: The controller synchronously collects the outdoor ambient temperature and the discharge temperature of the variable frequency compressor, and automatically switches the working status of the two branch solenoid valves: when the outdoor ambient temperature is ≥-5℃, the return gas branch solenoid valve is opened and the make-up gas branch solenoid valve is closed. When the outdoor ambient temperature is < -5℃, close the return gas branch solenoid valve and open the make-up gas branch solenoid valve. When the discharge temperature of the variable frequency compressor is ≥115℃, the solenoid valve of the gas supply branch will be opened to reduce the discharge temperature.

7. A single-compressor dual-temperature zone heat pump air conditioning system with a two-stage throttling precooling circuit according to claim 6, characterized in that, In the control method, when the system is operating in low-temperature heating and enthalpy-increasing mode, the following detailed control sub-steps are executed: Step 1: The system maintains the original PID closed-loop control logic of the first electronic expansion valve EV1, the second electronic expansion valve EV2, and the third electronic expansion valve EV3 under the dual-temperature zone independent heating mode. When the outdoor ambient temperature is detected to be below -5℃, the controller closes the return gas branch solenoid valve and opens the gas supply branch solenoid valve. All the refrigerant in the pre-cooling circuit is introduced into the intermediate gas supply port b of the variable frequency compressor through the gas supply branch solenoid valve and the gas supply check valve. Step 2: The side flow channels of the precooling heat exchanger are synchronously connected to form a heating loop in the medium temperature zone. Step 3: When the discharge temperature of the variable frequency compressor is ≥110℃, the controller increases the opening of the solenoid valve of the gas supply branch.

8. A single-compressor dual-temperature zone heat pump air conditioning system with a two-stage throttling precooling circuit according to claim 7, characterized in that, In the control method, when the system is operating in a single low-temperature zone cooling / heating mode, the following detailed control sub-steps are executed: Step 1: The controller closes the third electronic expansion valve EV3, the return gas branch solenoid valve, and the make-up gas branch solenoid valve, while fully opening the first electronic expansion valve EV1. Step 2: The second electronic expansion valve EV2 adopts closed-loop PID control of the superheat of the low-temperature zone heat exchanger, and the variable frequency compressor adopts single-temperature zone temperature deviation PID control frequency.

9. A single-compressor dual-temperature zone heat pump air conditioning system with a two-stage throttling precooling circuit according to claim 8, characterized in that, In the control method, when the system is operating in a single high-temperature zone cooling / heating mode, the following process is executed: When cooling in a single high-temperature zone, the controller closes the second electronic expansion valve EV2, and the third electronic expansion valve EV3 adjusts its opening according to the temperature deviation of the high-temperature zone. When heating in a single high-temperature zone, the controller closes the first electronic expansion valve EV1, and the third electronic expansion valve EV3 adjusts its opening according to the temperature deviation of the high-temperature zone. Under both operating conditions, the variable frequency compressor uses independent PID to adjust the operating frequency based on the temperature deviation of the single high-temperature zone. The return gas branch solenoid valve and the make-up gas branch solenoid valve switch on and off according to the pressure difference between the evaporation pressure of the precooling circuit and the suction pressure and intermediate make-up gas pressure of the variable frequency compressor.

10. A single-compressor dual-temperature zone heat pump air conditioning system with a two-stage throttling precooling circuit according to claim 9, characterized in that, In the control method, when the system operates in a cooling-heating heat recovery mode, the following detailed control sub-steps are executed: Step 1: The controller switches the four-way reversing valve to the heating operation position, controls the first electronic expansion valve EV1 to remain fully open, and at the same time makes the outdoor heat exchanger bypass and not participate in heat exchange. Step 2: The system refrigerant is divided into two independent heat exchangers: the pre-cooling heat exchanger branch flow channel acts as an evaporator to absorb heat and achieve cooling in the high-temperature zone, while the low-temperature heat exchanger acts as a condenser to release condensation heat and meet heating requirements. Step 3: The operating frequency of the variable frequency compressor is adjusted using a weighted PID closed-loop control based on the sum of the cooling load and the heating load; The third electronic expansion valve EV3 adjusts the cooling capacity by using the target superheat of the pre-cooled heat exchanger side channel. The second electronic expansion valve EV2 implements closed-loop control of the condensing pressure of the heat exchanger in the low-temperature zone.

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