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CN-122015313-A - Refrigeration system division cooperative control method and system based on dryness physical reference

CN122015313ACN 122015313 ACN122015313 ACN 122015313ACN-122015313-A

Abstract

The invention discloses a refrigeration system division cooperative control method and system based on dryness physical references, which are suitable for a vapor compression refrigeration system and a heat pump system. The method comprises the steps of obtaining a dryness value x of an outlet of a condenser, adjusting condensation side equipment with the x approaching 0 as a target to form a first control loop, independently adjusting the frequency of a compressor according to indoor load to form a second control loop, and indirectly cooperating the two loops through the state of a refrigerant without signal coupling. The superheat degree of the evaporator is independently regulated by an expansion valve, and is compatible with the framework. The invention decouples the traditional coupling control, simplifies the algorithm, reduces the hardware cost, obviously improves the energy efficiency and is suitable for various cooling modes. The invention is hopeful to improve the EER of the system to more than 3.4, realize more than 15% of energy saving rate, and form a complete technical system by cooperating with the existing dryness detection device and the basic control method.

Inventors

  • ZHANG HUI

Assignees

  • 张晖

Dates

Publication Date
20260512
Application Date
20260321

Claims (12)

  1. 1. A refrigeration system division cooperative control method based on dryness physical reference is applied to a vapor compression refrigeration system, and is characterized by comprising the following steps: A first control loop, which is used for acquiring a dryness value x of the refrigerant at the outlet of the condenser, taking the dryness value approaching to 0 as a target, and adjusting the operation parameters of the condensation side adjusting equipment according to the deviation of the dryness value from the target value 0; The second control loop is used for acquiring indoor load demands and independently adjusting the operation frequency of the compressor according to the load demands; The first control loop and the second control loop are mutually independent and have no direct signal coupling, but form indirect synergy through the physical characteristics of a refrigerant system, wherein the second control loop adjusts the frequency of a compressor according to the load demand, changes the circulating flow of the system, and automatically adjusts condensation side equipment according to the dryness deviation when the dryness deviation of an outlet of a condenser is 0 caused by load change so as to enable the dryness to return to a target value; The condensation side adjusting device comprises at least one of an air-cooled condensing fan, a cooling tower fan, a cooling water pump, an evaporative cooling fan or an electromagnetic valve for adjusting the flow of refrigerant at the outlet of the condenser in a water loop heat pump system.
  2. 2. The method of claim 1, wherein the first control loop and the second control loop have different adjustment periods, the first control loop having a slower response speed than the second control loop to accommodate thermal inertia on the condensing side.
  3. 3. The method of claim 1, wherein the dryness value is obtained in real time by a refrigerant dryness on-line tester as described in prior application 202610274347.8.
  4. 4. The method of claim 1, wherein the adjustment of the first control loop is independent of a preset time period or ambient temperature threshold, such that the system always operates on a physical basis of a dryness of 0, as distinguished from existing time-rule-based mute modes and empirical temperature-based water-cooled control modes.
  5. 5. The method of claim 1, wherein the adjustment of the compressor operating frequency is targeted at indoor temperature or user set point by using a PID control algorithm in combination with variable frequency control.
  6. 6. The method of claim 1, wherein the refrigeration system is a CO 2 transcritical refrigeration system, the first control loop targets an evaporator inlet dryness fraction of 0 or targets a virtual dryness fraction of 0 based on an equivalent condenser model, and an air-cooled side conditioning apparatus is adjusted.
  7. 7. The utility model provides a refrigeration system divides work cooperative control system based on dryness fraction physical standard, is applied to vapor compression refrigeration system, characterized in that includes: -a dryness detection unit for obtaining in real time a dryness value x of the refrigerant at the condenser outlet; -a load detection unit for obtaining an indoor load demand; -a first control unit, targeting the dryness fraction value approaching 0, generating a first control signal from the deviation of the dryness fraction value from a target value of 0 and outputting to a condensation side regulating device; -a second control unit for independently generating a second control signal according to said load demand and outputting to the compressor; The first control unit and the second control unit are mutually independent and have no direct signal coupling, but form indirect synergy through the physical characteristics of the refrigerant system, wherein the second control unit adjusts the frequency of the compressor according to the load demand, changes the circulating flow of the system, and automatically adjusts condensation side equipment according to the dryness deviation to enable the dryness to return to a target value when the dryness of an outlet of a condenser deviates from 0 due to load change; -the condensation side adjusting device comprises at least one of an air cooled condensing fan, a cooling tower fan, a cooling water pump, an evaporative cooling fan or a solenoid valve in a water loop heat pump system for adjusting the condenser outlet refrigerant flow.
  8. 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. 9. The system of claim 7, wherein the first control unit and the second control unit employ different adjustment periods, the adjustment period of the first control unit being longer than the second control unit.
  10. 10. The system of claim 7, wherein the first control unit employs a PID control law to output analog quantity or PWM signals to drive the frequency converter or the speed regulating device, and the second control unit employs a PID control algorithm in combination with the frequency conversion control mode to output frequency instructions to the compressor frequency converter.
  11. 11. A vapor compression refrigeration system comprising the refrigeration system of any one of claims 7-10.
  12. 12. The method of claim 1, wherein the refrigeration system is a heat pump system and the first control loop targets an indoor side condenser outlet dryness approaching 0 to adjust an indoor side condenser conditioning apparatus.

Description

Refrigeration system division cooperative control method and system based on dryness physical reference Technical Field The invention relates to the technical field of refrigeration and air conditioning, in particular to a refrigeration system labor division cooperative control method and system based on dryness physical references, which are suitable for vapor compression refrigeration systems adopting forms of air cooling, water cooling and cooling towers, evaporative cooling, water loop heat pumps and the like, and CO 2 transcritical refrigeration systems, including household air conditioners, commercial multi-split air conditioners, water chilling units, water loop heat pumps, air source heat pumps, CO 2 heat pumps and the like. Background The energy efficiency of a vapor compression refrigeration system is closely related to the condenser outlet refrigerant condition. In theory, when the outlet of the condenser is saturated liquid (dryness x=0), the unit refrigerating capacity is maximum, and the energy efficiency of the system is optimal. However, in actual operation, due to factors such as load variation, environmental temperature fluctuation, etc., the dryness of the condenser outlet often deviates from 0, resulting in hidden energy loss. The applicant submits a plurality of patent applications related to dryness physical standard, for example, application number 202610262063.7, a refrigeration system control method and device based on dryness physical standard, provides a general method for controlling the total flow of a target regulating system by taking the approach of the dryness of a condenser outlet to 0, and discloses a float type and injection type dryness standard controller. This application provides a theoretical basis and a generic concept for the present invention. In addition, the application number 202610274347.8 of the online tester for the dryness of the refrigerant provides a device for detecting the dryness in real time. In the prior art, a multivariable decoupling strategy is generally adopted for controlling a vapor compression refrigeration system, wherein a compressor adjusts frequency according to load, a condensing fan adjusts rotating speed according to pressure, and the compressor and the condensing fan are mutually influenced to form coupling control. This coupling results in a system with a lag in response, complex adjustments, and a lack of uniform physical references, making it difficult to operate the system at optimal conditions at all times. For example, as the compressor frequency increases, the condensing pressure increases, and the fan accelerates, but the fan acceleration affects the compressor inlet condition, creating repetitive oscillations. Aiming at the air source heat pump system, a great deal of researches are carried out by students at home and abroad. Liang Kai et al (2014) found through experiments that the evaporator outlet superheat and heat transfer coefficient increased with increasing head-on wind speed, but the wind speed tended to stabilize beyond a certain value, and there was an optimal head-on wind speed [4] at different ambient temperatures. Experimental researches on yellow tiger and the like (2007) show that the suction superheat degree is smaller when the ambient temperature is reduced, and the return air of the compressor is easy to carry liquid [5]. Yang Liwei (2024) explores frequency control under defrosting conditions, and adopts a sectional control strategy to cope with the frosting problem [6]. Zhang Zhijie et al (2026) perform performance analysis on an air source heat pump system in a Beijing office park based on a machine learning method, find that instantaneous flow, real-time power and backwater temperature are core factors affecting performance, and the instantaneous flow has obvious critical threshold phenomenon [7]. However, none of the above studies fundamentally solve the problem of uncertainty in the system state, and still rely on complex feedback regulation or off-line optimization. In 2025, six-door combined printing "promote high-quality development action scheme of heat pump industry" clearly proposes the goal [8] of improving energy efficiency level of important heat pump product by more than 20% in 2030. The scheme emphasizes the promotion and application of the air source heat pump in the field of construction, gradually reduces the use of the electric auxiliary heating device, and improves the energy efficiency of the unit. This policy directive places higher demands on the control technology of the heat pump system. In addition, CO 2 is increasingly used as a natural refrigerant in the field of refrigeration and air conditioning. However, the control of the CO 2 transcritical cycle is more complex than the traditional subcritical cycle, namely, the outlet of the air cooler is free of phase change, the traditional control method aiming at condensing pressure or temperature is difficult to realize optimal energy