Refrigerating system division cooperative control method and system based on dryness physical reference

Abstract

The invention discloses a refrigeration system division cooperative control method and system based on a dryness physical reference, and is suitable for a vapor compression refrigeration system and a heat pump system. The method comprises the following steps: acquiring a dryness value x of a condenser outlet; condensing side equipment is adjusted with x approaching 0 as a target, and a first control loop is formed; independently adjusting the frequency of the compressor according to the indoor load to form a second control loop; the two loops have no signal coupling and are indirectly cooperated through a refrigerant state. And the superheat degree of the evaporator is independently adjusted by the expansion valve and is compatible with the architecture. According to the invention, traditional coupling control is decoupled, the algorithm is simplified, the hardware cost is reduced, the energy efficiency is obviously improved, and the method is suitable for various cooling modes. According to the method, the EER of the system is expected to be increased to 3.4 or above, the energy-saving rate of 15% or above is achieved, and the method cooperates with an existing dryness detection device and a basic control method to form a complete technical system.

Description

Technical Field

[0001] This invention relates to the field of refrigeration and air conditioning technology, specifically to a method and system for the division of labor and collaborative control of refrigeration systems based on the physical reference of dryness. It is applicable to vapor compression refrigeration systems using air cooling, water cooling + cooling tower, evaporative cooling, water loop heat pumps, etc., as well as CO2 transcritical refrigeration systems, including household air conditioners, commercial multi-split systems, chillers, water loop heat pumps, air source heat pumps, and CO2 heat pumps. Background Technology

[0002] The energy efficiency of a vapor compression refrigeration system is closely related to the refrigerant state at the condenser outlet. Theoretically, the system achieves maximum cooling capacity and optimal energy efficiency when the condenser outlet is saturated liquid (dryness fraction x = 0). However, in actual operation, due to factors such as load changes and ambient temperature fluctuations, the dryness fraction at the condenser outlet often deviates from 0, resulting in hidden energy losses.

[0003] The applicant has previously filed several patent applications related to physical dryness standards, such as application number 202610262063.7, "A Refrigeration System Control Method and Device Based on Physical Dryness Standard," which proposes a general method for adjusting the total flow rate of the system with the condenser outlet dryness approaching 0 as the control target, and discloses float-type and ejector-type dryness standard controllers. This application provides the theoretical basis and overarching concept for this invention. Furthermore, application number 202610274347.8, "An Online Refrigerant Dryness Tester," provides a device for real-time dryness detection.

[0004] In existing technologies, the control of vapor compression refrigeration systems typically employs a multivariable decoupling strategy: the compressor adjusts its frequency based on the load, while the condenser fan adjusts its speed based on the pressure; the two influence each other, forming a coupled control. This coupling leads to system response lag, complex adjustment, and a lack of a unified physical reference, making it difficult to ensure the system always operates under optimal conditions. For example, when the compressor frequency increases, the condensing pressure rises, and the fan accelerates accordingly; however, this fan acceleration affects the compressor inlet state, causing repeated oscillations.

[0005] Extensive research has been conducted by scholars both domestically and internationally on air source heat pump systems. Liang Kai et al. (2014) found through experiments that the evaporator outlet superheat and heat transfer coefficient increase with increasing oncoming wind speed, but tend to stabilize after the wind speed exceeds a certain value, and that there is an optimal oncoming wind speed under different ambient temperatures. [4] Experimental studies by Huang Hu et al. (2007) showed that when the ambient temperature decreases, the intake superheat is smaller, which easily leads to liquid carryover in the compressor return gas. [5] Yang Liwei (2024) studied frequency control under defrosting conditions and adopted a segmented control strategy to address the frosting problem. [6]Zhang Zhijie et al. (2026) conducted a performance analysis of an air source heat pump system in an office park in Beijing based on machine learning methods. They found that instantaneous flow rate, real-time power, and return water temperature are the core factors affecting performance, and that there is a clear "critical threshold" phenomenon in instantaneous flow rate. [7] However, none of the above studies have fundamentally solved the problem of uncertain system states, and still rely on complex feedback regulation or offline optimization.

[0006] In 2025, six departments jointly issued the "Action Plan for Promoting High-Quality Development of the Heat Pump Industry," which clearly proposed the goal of improving the energy efficiency of key heat pump products by more than 20% by 2030. [8] The plan emphasizes encouraging the application of air-source heat pumps in the building sector, gradually reducing the use of electric auxiliary heating devices, and improving unit energy efficiency. This policy direction places higher demands on the control technology of heat pump systems.

[0007] Furthermore, CO2, as a natural refrigerant, is increasingly widely used in the refrigeration and air conditioning fields. However, the control of CO2 transcritical cycles is more complex than that of traditional subcritical cycles: there is no phase change at the outlet of the gas cooler, and traditional control methods targeting condensing pressure or temperature are difficult to achieve optimal energy efficiency; the system needs to switch control strategies between subcritical and transcritical modes, increasing control complexity. The applicant previously proposed the concept of an "equivalent condenser" in patent 202610262063.7, virtualizing the supercritical section of the gas cooler in a CO2 transcritical system as a condenser with a phase change process, enabling the dryness-based control method to be uniformly applied to both subcritical and transcritical systems, providing a foundation for the application of this invention in CO2 systems. Based on this, the applicant further developed a specific recooling gas-liquid separation device (application number 202610336275.5), which, through two-stage throttling, a recooler, and gas-liquid separation, creates a physically locked "equivalent condensing pressure" in the transcritical cycle, achieving efficient system operation.

[0008] In existing refrigeration systems, the evaporator outlet superheat is typically regulated independently by an electronic expansion valve to ensure safe compressor return gas. This technology is mature and compatible with the control architecture of this invention: under summer refrigeration conditions, the expansion valve controls the evaporator outlet superheat (usually set to around 5K) to prevent liquid carryover during return gas; under winter heat pump conditions, the expansion valve controls the outdoor evaporator outlet superheat (also set to around 5K) to ensure safe compressor operation. The expansion valve adjustment is not signal-coupled with the first and second loops of this invention, together forming a complete refrigeration / heat pump system control system.

[0009] Therefore, the existing technology lacks a collaborative control method that can adaptively adjust the condenser-side regulating equipment based on physical quantities and achieve independent load control of the compressor. Moreover, this method should be applicable to both traditional subcritical refrigeration systems and CO2 transcritical refrigeration systems, and be compatible with existing expansion valve control. Summary of the Invention

[0010] 1. Purpose of the invention

[0011] This invention aims to solve problems such as control coupling, lack of physical reference, and unintelligent silent mode in the prior art, and provides a collaborative control method and system for refrigeration systems based on dryness physical reference, which is applicable to traditional subcritical refrigeration systems and CO2 transcritical refrigeration systems.

[0012] 2 Technical Solution

[0013] To achieve the above objectives, the present invention provides the following technical solution:

[0014] A collaborative control method for refrigeration systems based on dryness index physical reference, applied to vapor compression refrigeration systems, includes the following steps:

[0015] (1) Obtain the refrigerant dryness value x at the condenser outlet;

[0016] (2) With the goal of making the dryness value approach 0, the operating parameters of the condensing side regulating equipment are adjusted according to the deviation between the dryness value and the target value of 0, forming a first control loop;

[0017] (3) Obtain the indoor load demand, and independently adjust the operating frequency of the compressor according to the load demand to form a second control loop;

[0018] (4) The first control loop and the second control loop are independent of each other and have no direct signal coupling, but they form indirect coordination through the physical characteristics of the refrigerant system: the second control loop adjusts the compressor frequency according to the load demand and changes the system circulation flow. When the load change causes the dryness of the condenser outlet to deviate from 0, the first control loop automatically adjusts the condenser side equipment according to the dryness deviation to make the dryness return to the target value. The two loops form a closed loop at the physical level and remain independent at the control level, forming a division of labor control architecture of "condenser side controls dryness and compressor controls load".

[0019] (5) The condenser-side regulating equipment includes at least one of the following: an air-cooled condenser fan, a cooling tower fan, a cooling water pump, an evaporative cooling fan, or a solenoid valve in a water ring heat pump system for regulating the refrigerant flow rate at the condenser outlet.

[0020] For a CO2 transcritical refrigeration system, the first control loop aims to make the dryness of the evaporator inlet approach 0, or it uses an equivalent condenser model to virtualize the supercritical section of the gas cooler as an equivalent condenser with a phase change process, and aims to make the virtual dryness of the equivalent condenser outlet approach 0, thereby adjusting the operating parameters of the gas-cooled side regulating equipment (including gas cooler fans, cooling water pumps, etc.).

[0021] Preferably, the first control loop and the second control loop have different adjustment cycles, and the response speed of the first control loop is slower than that of the second control loop, in order to adapt to the thermal inertia of the condensation side.

[0022] Preferably, the dryness value can be obtained in real time using the online refrigerant dryness tester described in prior application 202610274347.8.

[0023] Preferably, the adjustment of the first control loop is independent of the preset time period or ambient temperature threshold, so that the system always operates with a dryness of 0 as the physical reference, which is different from the existing silent mode based on time rules and the water-cooling control mode based on empirical temperature.

[0024] Preferably, the compressor operating frequency is adjusted based on the indoor temperature or a user-set value, and is achieved using a PID control algorithm combined with a variable frequency control method.

[0025] The present invention also provides a refrigeration system division of labor and cooperation control system based on dryness physical reference, comprising:

[0026] - Dryness detection unit, used to acquire the refrigerant dryness value x at the condenser outlet in real time;

[0027] - Load detection unit, used to obtain indoor load demand;

[0028] - The first control unit, with the dryness value approaching 0 as the target, generates a first control signal based on the deviation between the dryness value and the target value of 0, and outputs it to the condenser-side regulating device;

[0029] - The second control unit independently generates a second control signal based on the load demand and outputs it to the compressor;

[0030] - The first control unit and the second control unit are independent of each other and have no direct signal coupling, but they form indirect cooperation through the physical characteristics of the refrigerant system: the second control unit adjusts the compressor frequency according to the load demand and changes the system circulation flow. When the load change causes the dryness of the condenser outlet to deviate from 0, the first control unit automatically adjusts the condenser-side equipment according to the dryness deviation to bring the dryness back to the target value. The two loops form a closed loop at the physical level and remain independent at the control level, forming a division of labor control architecture of "condenser side controls dryness and compressor controls load".

[0031] - The condenser-side regulating device includes at least one of the following: an air-cooled condenser fan, a cooling tower fan, a cooling water pump, an evaporative cooling fan, or a solenoid valve in a water-ring heat pump system for regulating the refrigerant flow rate at the condenser outlet.

[0032] Preferably, the dryness detection unit is a capacitive dryness sensor or a mechanical dryness detection device based on the float principle.

[0033] Preferably, the first control unit and the second control unit use different adjustment cycles, with the adjustment cycle of the first control unit being longer than that of the second control unit.

[0034] Preferably, the first control unit adopts a PID control law and outputs analog or PWM signals to drive the frequency converter or speed control device; the second control unit adopts a PID control algorithm combined with frequency conversion control mode and outputs frequency commands to the compressor frequency converter.

[0035] The present invention further provides a vapor compression refrigeration system comprising the above-described system.

[0036] 3. Beneficial effects

[0037] Compared with the prior art, the present invention has the following beneficial effects:

[0038] 1. A division of labor control architecture of "condenser side controls dryness and compressor controls load" is proposed, which decouples the traditional coupled multivariable control into two independent loops, greatly simplifies the control algorithm and reduces the hardware cost of the controller.

[0039] 2. By controlling the condenser-side regulating equipment with a dryness fraction x = 0 as the physical benchmark, the condenser is always operated in its optimal state, significantly improving system energy efficiency. Literature research indicates that the energy efficiency of existing building air conditioning systems is generally low; for example, the measured EER of a system in an office building in Shenzhen was only 2.85. [9] In a Chongqing office building, air conditioning energy consumption accounts for more than 50% of the building's total energy consumption.

[10] After adopting this invention, the system's EER is expected to be improved to over 3.4, corresponding to an energy saving rate of over 15%, directly responding to the goal of "improving the energy efficiency level of key heat pump products by over 20%" proposed in the National Action Plan for Promoting High-Quality Development of the Heat Pump Industry.

[0040] 3. The compressor responds independently to load demand, avoiding mutual interference with the condenser side control and improving load response speed. At the same time, the dryness deviation caused by load changes is automatically compensated by the first loop, forming a physical closed loop of "compressor adjusting load and condenser side stabilizing dryness". The two loops perform their respective functions and complement each other, fundamentally solving the problem of mutual constraint of parameters and adjustment oscillation in traditional coupled control.

[0041] 4. System design is greatly simplified due to clear division of labor: no need for complex decoupling algorithm design, no need for multivariate coupling analysis, clear control logic, and reduced debugging and maintenance costs.

[0042] 5. Applicable to various cooling methods (air cooling, water cooling + cooling tower, evaporative cooling, water ring heat pump, air source heat pump) and various refrigerants (including traditional refrigerants and CO2), with strong versatility.

[0043] 6. In conjunction with the applicant's existing dryness detection device (202610274347.8) and basic control method (202610262063.7), form a complete dryness control technology system.

[0044] 7. Unlike existing silent modes based on time or experience rules (such as nighttime silent mode) and water-cooling control modes based on experience temperature (such as 37 / 32℃), this invention achieves adaptive adjustment based on the physical quantity of dryness, naturally reducing the fan speed while ensuring energy efficiency, thus balancing energy saving and quiet operation.

[0045] 8. Due to the simplified control, a lower-cost controller chip can be selected, further reducing the overall cost of the machine.

[0046] 9. This invention is perfectly compatible with existing expansion valve control: the expansion valve independently ensures the evaporator outlet superheat (5K in summer, 5K in winter), ensuring compressor safety; the two loops of this invention independently ensure the condenser outlet dryness is 0, ensuring system energy efficiency. The three loops are not coupled by signals and indirectly coordinate through the physical state of the refrigerant, together forming a complete refrigeration / heat pump system control system.

[0047] 10. This invention offers significant advantages under winter frosting conditions: The first control loop locks in the condenser outlet dryness (indoor condenser mode under heat pump operation), ensuring system stability. When frosting causes evaporation pressure fluctuations, the first loop automatically adjusts the condenser-side equipment to maintain a dryness baseline, indirectly suppressing further pressure drops and slowing the frosting rate. The second control loop independently adjusts the compressor frequency to prevent compressor overload under low-temperature conditions. The electronic expansion valve independently adjusts superheat, ensuring safe compressor return gas. Therefore, this invention effectively improves the reliability and energy efficiency of air source heat pump systems during winter operation.

[0048] 11. This invention is deeply integrated with the "equivalent condenser" technology of the prior patent and works in conjunction with the recooling gas-liquid separation device of application number 202610336275.5 to unify the complex control of the CO2 transcritical system into dryness-based control. It eliminates the need to distinguish between subcritical / transcritical modes and high-pressure optimization algorithms, significantly simplifies the control logic, and improves system reliability and energy efficiency. Attached Figure Description

[0049] Figure 1 This is a flowchart of the control method of the present invention.

[0050] Figure 2 This is a structural block diagram of the control system of the present invention.

[0051] Figure 3 This is a schematic diagram of an embodiment of an air-cooled unit, showing the compressor, condenser, condenser fan, and dryness detection unit. Detailed Implementation

[0053] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments.

[0054] Example 1: Control of air-cooled condenser (including multi-split air conditioners and air source heat pumps)

[0055] like Figure 3 As shown, the air-cooled chiller unit includes a compressor, condenser, and condenser fan. An online dryness tester (using the device described in patent 202610274347.8) is installed at the condenser outlet to acquire the dryness value x in real time. The first control unit outputs a control signal to adjust the condenser fan speed with x = 0 as the target; the second control unit independently adjusts the compressor frequency according to the indoor load. The two control units use different adjustment cycles: the first unit 30s (adapting to the condenser's thermal inertia), and the second unit 5s (for rapid response to load changes). This method can stably control the dryness around 0, significantly improving system energy efficiency.

[0056] The core coordination mechanism of this invention is embodied in this embodiment as follows: when the indoor load changes, the second loop adjusts the compressor frequency to meet the load demand, at which time the dryness of the condenser outlet may deviate from 0; the first loop automatically adjusts the fan speed according to the dryness deviation to bring the dryness back to the target value. The two loops do not exchange signals directly, but form a close indirect coordination through the physical quantity of refrigerant state, avoiding the repeated oscillations caused by parameter coupling in traditional control.

[0057] In this embodiment, the electronic expansion valve independently controls the superheat of the evaporator outlet (set to 5K) to ensure the safety of compressor return gas. It has no signal coupling with the two loops of the present invention and together they form a complete control system.

[0058] This method is also applicable to multi-split air conditioning systems. In a multi-split system, the second control unit adjusts the compressor frequency according to the total load of each indoor unit, and the first control unit adjusts the outdoor unit condenser fan speed according to the dryness deviation. The control logic is exactly the same as that of air-cooled units.

[0059] Example 2: Water-cooled unit + cooling tower control

[0060] The water-cooled chiller unit is equipped with an open cooling tower. The system includes a condenser, cooling tower, and cooling water pump. A dryness meter is installed at the condenser outlet. The first control unit simultaneously adjusts the cooling tower fan speed and cooling water pump frequency based on the dryness deviation; the second control unit independently adjusts the compressor frequency. This embodiment breaks through the traditional temperature control mode based on 37 / 32℃, directly using dryness as the physical benchmark, ensuring that the condenser always operates in the optimal thermodynamic state, unaffected by fluctuations in cooling water temperature.

[0061] The electronic expansion valve independently controls the evaporator outlet superheat (set to 5K) and has no signal coupling with the two loops of this invention.

[0062] Example 3: Air Source Heat Pump Control under Winter Heat Pump Operation

[0063] This embodiment applies the present invention to an air source heat pump heating system. In winter heat pump operation, the indoor side is the condenser, and the outdoor side is the evaporator. The system configuration is the same as in Embodiment 1, with the dryness detection unit always installed at the condenser outlet (indoor condenser outlet in winter), consistent with the control logic.

[0064] The first control loop targets an indoor condenser outlet dryness fraction (x = 0) and adjusts the indoor condenser fan or water pump speed based on the dryness fraction deviation (condenser-side adjustment equipment). The second control loop independently adjusts the compressor frequency based on indoor load demand. The two control units use different adjustment cycles: the first unit for 30 seconds (adapting to condenser thermal inertia), and the second unit for 5 seconds (rapid response to load changes).

[0065] The electronic expansion valve independently controls the superheat at the outdoor evaporator outlet (set to 5K) to ensure safe return gas. It is not signal-coupled with the two loops of this invention. The three loops are independent of each other and indirectly coordinated through the physical state of the refrigerant.

[0066] When frost forms on the outdoor evaporator surface, the thickening of the frost layer reduces the evaporator's heat exchange efficiency and lowers the evaporation pressure, leading to fluctuations in the condensation pressure and causing the dryness fraction at the indoor condenser outlet to deviate from 0. Upon detecting this dryness fraction deviation, the first control loop automatically adjusts the speed of the indoor condenser-side fan or water pump to enhance heat exchange on the condenser side, restoring the condenser outlet to a saturated liquid state. This adjustment, through system thermodynamic coupling, stabilizes the condenser outlet state, indirectly suppressing further drops in evaporation pressure and slowing the frost formation rate. Simultaneously, the second loop independently adjusts the compressor frequency based on the indoor load, and the electronic expansion valve independently adjusts based on superheat; the three loops operate independently without interference.

[0067] Compared with traditional constant-speed fan control, under the control of this invention, the dryness of the indoor condenser outlet is stabilized near 0, the overall system operation is stable, the evaporator surface temperature fluctuation is reduced, the frosting rate is lowered, the compressor does not exhibit liquid carryover during return gas, and the system COP decrease is significantly reduced. This embodiment verifies the role of this invention in indirectly improving the operational stability of the evaporator side by stabilizing the condenser side under winter heat pump conditions, achieving "active anti-frost" rather than "passive defrosting".

[0068] Example 4: Control of a transcritical CO2 refrigeration system (based on an equivalent condenser and a recooling gas-liquid separator)

[0069] This embodiment applies the present invention in conjunction with the recooling gas-liquid separation device of application number 202610336275.5 to a CO2 transcritical refrigeration system. The system structure is shown in the accompanying drawings of that application, and mainly includes a compressor, a gas cooler, a first-stage throttling valve, a recooler, a gas-liquid separator, a second-stage throttling valve, an evaporator, and related piping.

[0070] The supercritical CO2 at the outlet of the gas cooler is throttled to an intermediate pressure (i.e., equivalent condensing pressure P) by a first-stage throttling valve. cond,eq The gas enters the two-phase region; then it enters the recooler, where it mixes with the saturated gas returning from the gas-liquid separator; the two-phase mixture at the recooler outlet enters the gas-liquid separator, where the separated saturated liquid is throttled to the evaporation pressure by a two-stage throttling valve and enters the evaporator; the separated saturated gas returns to the recooler inlet. A low-temperature saturated gas in proportion α is split from the evaporator outlet as the cold source for the recooler, and after absorbing heat, it returns to the compressor suction port.

[0071] The first control unit corresponds to a dryness fraction x = 0 (or equivalent dryness fraction x) for saturated liquid under the equivalent condensation pressure. eq With the target value of 0, the gas-liquid separator outlet is ensured to be pure saturated liquid by adjusting the speed of the air cooler fan or the frequency of the cooling water pump; the second control unit independently adjusts the compressor frequency with the target value of evaporation pressure. The two loops are not coupled by signals and cooperate indirectly through physical mechanisms.

[0072] Based on two rigid constraints (evaporation pressure reference + fixed charge amount), the equivalent condensation pressure P cond,eq The recooling ratio α is uniquely determined by the design conditions and is automatically maintained during operation. Thermodynamic simulations show that the air conditioning operating conditions ( At 5℃, the optimal recooling ratio α≈0.0288, the system COP can reach 3.038, which is 38.2% higher than the basic system.

[0073] Example 5: Energy Saving Potential Analysis

[0074] To illustrate the energy-saving potential of this invention, measured data from relevant literature are cited. Yan Tao et al.'s measurements of the air conditioning system in an office building in Shenzhen showed that the overall system energy efficiency ratio (EER) was only 2.85, the chilled water pump efficiency was only 40%, and the main unit load rate was only 38%-41%. [9] A survey conducted by Chen Gaifang of 10 office buildings in Chongqing showed that air conditioning systems accounted for 50%-60% of the building's total energy consumption.

[10] The above data indicates that existing refrigeration and air conditioning systems generally suffer from low energy efficiency and poor regulation capabilities.

[0075] The collaborative control proposed in this invention locks the condenser outlet dryness through a first control loop and independently adjusts the compressor frequency through a second control loop, ensuring the system always operates near its design conditions. This avoids the coupling oscillations and inefficient operation of traditional control systems. Based on this, it is estimated that after adopting this invention, the EER of the air conditioning system in an office building in Shenzhen can be increased from 2.85 to over 3.4, corresponding to an energy saving rate of 15%-20%, reaching or even exceeding the energy-saving retrofit potential proposed in the literature.

[0076] This method is also applicable to water-loop heat pump systems. In a water-loop heat pump system, the first control loop adjusts the opening of the solenoid valve at the outlet of each unit's condenser according to the dryness deviation, so that the refrigerant entering the evaporator remains in a saturated liquid state; the second control loop independently adjusts the compressor frequency of each unit according to the indoor load, achieving division of labor and coordinated control.

[0077] Summary of System Cooperative Control

[0078] In summary, this invention constructs a complete collaborative control system for refrigeration / heat pump systems:

[0079] - The first control loop aims to bring the dryness of the condenser outlet close to 0, independently adjusting the condenser-side equipment and locking the system into its optimal state;

[0080] - The second control loop independently adjusts the compressor frequency according to indoor load demand, quickly responding to load changes;

[0081] - An electronic expansion valve independently controls the evaporator outlet superheat (e.g., 5K) to ensure safe compressor operation.

[0082] The three control loops are independent and have no direct signal coupling. They indirectly coordinate through the physical state of the refrigerant (dryness, pressure, superheat) to form a complete system control scheme. The decoupling architecture between the first and second loops is the core contribution of this invention. The expansion valve control adopts existing mature technology and is seamlessly compatible with this architecture.

[0083] This invention, together with the applicant's prior patents (202610262063.7, 202610274347.8, 202610336275.5) filed at the same time, forms a complete technical system from the dryness reference principle, dryness detection, CO2 transcritical device to the division of labor and collaborative control architecture.

[0084] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

[0085] References

[0086] [1] Zhang Hui. A control method and device for a refrigeration system based on dryness physical reference: 202610262063.7[P]. 2026-03-05.

[0087] [2] Zhang Hui. An online refrigerant dryness tester: 202610274347.8[P]. 2026-03-08.

[0088] [3] Zhang Hui. A recooling gas-liquid separation device and method for a transcritical carbon dioxide refrigeration system: 202610336275.5 [P]. 2026-03-19.

[0089] [4] Liang Kai, Nan Xiaohong, Yue Yifeng, et al. Study on the influence of fan frequency conversion on the performance of air source heat pump water heater system [J]. Building Science, 2014, 30(8): 10-14.

[0090] [5] Huang Hu, Li Qihe, Yuan Dongxue. Experimental study on variable operating conditions of air source heat pump water heater unit [J]. Building Science, 2007, 23(12):68-71.

[0091] [6] Yang Liwei. Frequency control system of air source heat pump unit under the influence of defrosting condition [J]. Modern Electronics Technology, 2024, 47(3): 115-118.

[0092] [7] Zhang Zhijie, Hua Dongqi, Zuo Tingting, et al. Performance analysis of air source heat pump based on machine learning algorithm—a case study of an office park in Beijing [J]. Building Science, 2026 (forthcoming).

[0093] [8] National Development and Reform Commission, Ministry of Housing and Urban-Rural Development, et al. Action Plan for Promoting High-Quality Development of the Heat Pump Industry [Z]. 2025.

[0094] [9] Yan Tao, Fu Xiangzhao, Bu Zengwen, et al. Actual energy consumption measurement and energy-saving renovation potential analysis of an office building in Shenzhen [J]. Heating Ventilating & Air Conditioning, 2004, 34(3): 45-49.

[0095]

[10] Chen Gaifang. Energy consumption simulation and energy conservation research of public buildings in Chongqing [D]. Chongqing: Chongqing University, 2007.

Claims

1. A collaborative control method for a refrigeration system based on a dryness index physical reference, applied to a vapor compression refrigeration system, characterized in that, include: First control loop: Obtain the refrigerant dryness value x at the condenser outlet, aim for the dryness value to approach 0, and adjust the operating parameters of the condenser-side regulating equipment according to the deviation between the dryness value and the target value of 0; Second control loop: Obtain indoor load demand and independently adjust the compressor's operating frequency according to the load demand; The first control loop and the second control loop are independent of each other and have no direct signal coupling, but they form indirect cooperation through the physical characteristics of the refrigerant system: the second control loop adjusts the compressor frequency according to the load demand and changes the system circulation flow. When the load change causes the dryness of the condenser outlet to deviate from 0, the first control loop automatically adjusts the condenser-side equipment according to the dryness deviation to bring the dryness back to the target value. The two loops form a closed loop at the physical level and remain independent at the control level, forming a division of labor control architecture of "condenser side controls dryness and compressor controls load". The condenser-side regulating equipment includes at least one of the following: an air-cooled condenser fan, a cooling tower fan, a cooling water pump, an evaporative cooling fan, or a solenoid valve in a water-ring heat pump system for regulating the refrigerant flow rate at the condenser outlet.

2. The method according to claim 1, characterized in that, The first control loop and the second control loop have different adjustment cycles. The response speed of the first control loop is slower than that of the second control loop to adapt to the thermal inertia of the condenser side.

3. The method according to claim 1, characterized in that, The dryness value can be obtained in real time using the online refrigerant dryness tester described in prior application 202610274347.

8.

4. The method according to claim 1, characterized in that, The adjustment of the first control loop is independent of the preset time period or ambient temperature threshold, so that the system always operates with a dryness of 0 as the physical reference, which is different from the existing silent mode based on time rules and the water-cooling control mode based on empirical temperature.

5. The method according to claim 1, characterized in that, The compressor's operating frequency is adjusted based on the indoor temperature or a user-defined value, using a PID control algorithm combined with variable frequency control.

6. The method according to claim 1, characterized in that, The refrigeration system is a CO2 transcritical refrigeration system. The first control loop aims to make the dryness of the evaporator inlet approach 0, or to make the virtual dryness approach 0 based on an equivalent condenser model, and adjusts the air-cooled side regulating equipment.

7. A refrigeration system division of labor and collaborative control system based on dryness index physical reference, applied to a vapor compression refrigeration system, characterized in that, include: - Dryness detection unit, used to acquire the refrigerant dryness value x at the condenser outlet in real time; - Load detection unit, used to obtain indoor load demand; - The first control unit, with the dryness value approaching 0 as the target, generates a first control signal based on the deviation between the dryness value and the target value of 0, and outputs it to the condenser-side regulating device; - The second control unit independently generates a second control signal based on the load demand and outputs it to the compressor; - The first control unit and the second control unit are independent of each other and have no direct signal coupling, but they form indirect cooperation through the physical characteristics of the refrigerant system: the second control unit adjusts the compressor frequency according to the load demand and changes the system circulation flow. When the load change causes the dryness of the condenser outlet to deviate from 0, the first control unit automatically adjusts the condenser-side equipment according to the dryness deviation to bring the dryness back to the target value. The two loops form a closed loop at the physical level and remain independent at the control level, forming a division of labor control architecture of "condenser side controls dryness and compressor controls load". - The condenser-side regulating device includes at least one of the following: an air-cooled condenser fan, a cooling tower fan, a cooling water pump, an evaporative cooling fan, or a solenoid valve in a water-ring heat pump system for regulating the refrigerant flow rate at the condenser outlet.

8. The system according to claim 7, characterized in that, The dryness detection unit is a capacitive dryness sensor or a mechanical dryness detection device based on the float principle.

9. The system according to claim 7, characterized in that, The first control unit and the second control unit use different adjustment cycles, with the adjustment cycle of the first control unit being longer than that of the second control unit.

10. The system according to claim 7, characterized in that, The first control unit uses a PID control law to output analog or PWM signals to drive the frequency converter or speed control device; the second control unit uses a PID control algorithm combined with frequency conversion control to output frequency commands to the compressor frequency converter.

11. A vapor compression refrigeration system, characterized in that, The refrigeration system division of labor and coordination control system as described in any one of claims 7-10.

12. The method according to claim 1, characterized in that, The refrigeration system is a heat pump system. The first control loop aims to make the dryness of the indoor condenser outlet approach 0 and adjusts the indoor condenser regulating device.

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