Intelligent liquid storage tank for refrigerating unit and control method

Abstract

The invention relates to the technical field of liquid storage tanks of refrigerating equipment, in particular to an intelligent liquid storage tank for a refrigerating unit and a control method. The intelligent liquid storage tank comprises a tank body, a pressure sensor, a liquid level sensor, a temperature sensor, an air compressor, an intelligent control system, a displacement sensor and a filling amount displacement mapping module. The interior of the tank body is divided into a right air cavity and a left liquid storage cavity through a dynamic sealing piston, and the dynamic sealing piston is in sealed sliding connection with the inner wall of the tank body. The right air cavity is connected with an air compressor, the left liquid storage cavity is integrated with a pressure sensor and a temperature sensor, and the air compressor drives the dynamic sealing piston to move by adjusting the air pressure of the right air cavity, so that the refrigerant charge is controlled. By monitoring the pressure data in real time and dynamically adjusting the working state of the air compressor and the displacement of the piston, the residual rate of refrigerants is reduced, the liquid drainage efficiency is improved, the pressure is accurately controlled, the fault handling capacity is enhanced, and the service life of equipment is prolonged.

Description

Technical Field

[0001] The present invention relates to the technical field of liquid storage tanks for refrigeration equipment, and in particular to an intelligent liquid storage tank for a refrigeration unit and a control method thereof. Background Art

[0002] During refrigeration system operation, the liquid storage tank, a core component for refrigerant storage and distribution, has a direct impact on system energy efficiency and operational stability. Traditional liquid storage tanks rely on gravity-driven drainage and system pressure-driven drainage, leading to the common problem of refrigerant residue at the bottom of the tank. This is particularly pronounced in low-temperature conditions or when using high-viscosity refrigerants. This not only wastes refrigerant, but also causes the residual liquid to decompose and produce corrosive substances over time, potentially damaging the tank structure.

[0003] To improve liquid drainage efficiency, the current mainstream technology uses thermodynamic intervention to reduce refrigerant viscosity by installing a heating device at the bottom of the liquid storage tank. Typical implementations include electric heating systems or continuous heating with steam coils. However, this technology approach has the following inherent drawbacks:

[0004] 1. Inadequate temperature control accuracy: The dynamic changes in refrigerant physical properties during heating, coupled with the tank's thermal inertia, interfere with each other, resulting in uneven temperature distribution and difficulty in precise control. For new, environmentally friendly refrigerants with low critical temperatures, their narrow liquid phase stability range requires that the heating temperature be strictly controlled within a small fluctuation range. However, due to sensor hysteresis and nonlinear heat conduction characteristics, traditional control strategies can result in actual temperature deviations far exceeding the process's allowable range.

[0005] 2. Conflict between energy efficiency and reliability: High-intensity heating is required to achieve effective drainage, significantly reducing the overall energy efficiency of the system. Furthermore, local overheating can easily trigger thermal decomposition of the refrigerant, accelerating the generation of corrosive substances that in turn damage the tank structure, creating a vicious cycle of efficiency degradation and equipment aging.

[0006] 3. Environmental compatibility defects: The loss of refrigerant phase control caused by heating fluctuations significantly increases the risk of leakage, making it difficult to meet the increasingly stringent environmental regulations on the control of refrigerant leakage rates.

[0007] Existing improvement schemes attempt to improve control accuracy through complex control strategies, such as dynamic heat flux distribution or adaptive heating algorithms. However, due to the lack of real-time and accurate monitoring of the two-phase flow state within the tank, the control system's feedforward compensation mechanism is inherently flawed. Especially under low-temperature and high-viscosity operating conditions, the conflict between heating intensity and temperature accuracy is further exacerbated, causing the system to fall into a state of control instability.

[0008] Therefore, existing liquid storage tank drainage technology based on thermal compensation is limited by its inherent control accuracy and energy efficiency issues, making it difficult to meet the coordinated requirements of high efficiency, reliability, and environmental protection for new refrigeration systems. Developing new drainage control methods that do not rely on external heat sources has become a key path to breaking through the current technical bottleneck. Summary of the Invention

[0009] The technical problem to be solved by the present invention is: In order to overcome the above technical problems, the present invention provides an intelligent liquid storage tank and control method for a refrigeration unit, which is particularly suitable for efficient storage and management of refrigerants in industrial refrigeration systems.

[0010] The technical solution adopted by the present invention to solve the technical problem is: an intelligent liquid storage tank for a refrigeration unit, comprising a tank body, a pressure sensor, a liquid level sensor, a temperature sensor, an air compressor, an intelligent control system and a displacement sensor;

[0011] The interior of the tank body is divided into a right air chamber and a left liquid storage chamber by a dynamic sealing piston, and the dynamic sealing piston is in sealing and sliding connection with the inner wall of the tank body;

[0012] Pressure sensors are provided inside the right air cavity and the left liquid storage cavity to monitor the pressure inside the cavity;

[0013] Liquid level sensor, used to detect the liquid level in the left liquid storage chamber in real time;

[0014] A temperature sensor is provided in the left liquid storage cavity and is used to detect the temperature in the left liquid storage cavity in real time;

[0015] A displacement sensor, used for detecting in real time the axial displacement of the dynamic sealing piston relative to the tank body;

[0016] An intelligent control system receives feedback signals from the temperature sensor, displacement sensor, and pressure sensor, and adjusts the displacement of the dynamic sealing piston by controlling the working state of the air compressor according to the feedback signals;

[0017] The right air chamber is connected to an air compressor, and the left liquid storage chamber is integrated with a pressure sensor and a temperature sensor. The air compressor drives the dynamic sealing piston to move by adjusting the air pressure in the right air chamber, thereby adjusting the size and internal pressure of the left liquid storage chamber to achieve control of the refrigerant filling amount.

[0018] An intelligent liquid storage tank for a refrigeration unit according to the present invention also includes a valve group, which includes a filling valve, a discharge valve and a back suction recovery valve. A first interface, a second interface and an external filling port are provided at the bottom of the left liquid storage chamber, and a solenoid valve is provided at the inlet of the right air chamber. The first interface of the left liquid storage chamber is connected to the refrigeration system through a first pipeline and a three-way elbow in sequence, and a back suction recovery valve is provided on the first pipeline; the second interface of the left liquid storage chamber is connected to the refrigeration system through a second pipeline, a right-angle elbow and a three-way elbow in sequence, and a discharge valve is provided on the second pipeline; the filling valve is arranged at the external filling port.

[0019] The discharge valve is an electromagnetically driven conical valve, the back suction recovery valve is a two-way self-cleaning valve, and the filling valve is a one-way injection valve.

[0020] The intelligent control system has a built-in filling volume displacement mapping module, which calculates the theoretical displacement based on the preset filling volume target value and dynamically corrects the displacement trajectory of the dynamic sealing piston through closed-loop feedback. The filling volume displacement mapping module dynamically compensates for environmental parameters using the following formula:

[0021] L 实际 =L0·[1+α(T-T0)+β(P-P0)];

[0022] Wherein, L0 is the theoretical displacement under standard working conditions, α is the temperature compensation coefficient, β is the pressure compensation coefficient, T is the actual temperature of the refrigerant in the current left liquid storage chamber, T0 is the reference temperature under standard working conditions, P is the real-time detected refrigerant pressure in the current left liquid storage chamber, and P0 is the reference pressure under standard working conditions; the intelligent control system adopts fuzzy PID algorithm, according to the pressure deviation e(t)=P 设定 -P 实际 and deviation change rate Obtain the output power of the air compressor.

[0023] The sealing structure of the dynamic sealing piston includes a carbon fiber reinforced PEEK piston head with a friction coefficient of less than 0.1, and a double-track O-type fluororubber sealing ring is provided on the edge of the piston head.

[0024] The displacement sensor adopts a magnetostrictive sensor with a detection accuracy of ±0.05% FS, and communicates with the intelligent controller through an RS485 interface.

[0025] The air compressor is a variable frequency air compressor.

[0026] The tank body adopts a cylindrical double-layer structure, the outer layer is a stainless steel shell, and the inner layer is lined with an anti-corrosion coating.

[0027] The outer layer of the tank is a 304 stainless steel shell, and the inner layer is lined with a polytetrafluoroethylene (PTFE) anti-corrosion coating.

[0028] A control method for an intelligent liquid storage tank of a refrigeration unit according to the present invention comprises the following steps:

[0029] When the liquid level sensor detects that there is residual refrigerant in the left liquid storage chamber that needs to be discharged, the pressure sensor and temperature sensor detect and send a signal to the intelligent control system. The intelligent control system sends the corresponding processed data to the air compressor. The air compressor starts to run and injects air into the right air chamber to push the dynamic sealing piston to the left, allowing the refrigerant remaining in the left liquid storage chamber to enter the refrigeration system.

[0030] When the refrigerant in the refrigeration system needs to be recovered, the pressure sensor and temperature sensor detect the pressure and send a signal to the intelligent control system. The intelligent control system sends the corresponding processed data to the air compressor. The air compressor starts to run in reverse, and by pumping air into the right air cavity, it pushes the dynamic sealing piston to the right to pump the refrigerant in the refrigeration system back into the tank or recover it to the outside. When the refrigerant needs to be recovered and not returned to the liquid storage tank, the connection between the outlet and the refrigeration system pipeline can be separated to recover the refrigerant to the outside.

[0031] The beneficial effects of the present invention are as follows: an intelligent liquid storage tank and control method for a refrigeration unit of the present invention adopts a dual-chamber isolation structure, a piston is provided in the tank body to separate the tank into a left and a right chamber, the right chamber is connected to the air compressor, and the left chamber is provided with three valves and a pressure detection device; the pressure data is linked to the air compressor through an intelligent control system to dynamically adjust the thrust of the dynamic sealing piston; the reverse suction recovery valve reversely sucks in the refrigerant when the system fails to avoid leakage. The three-valve linkage system and fuzzy PID control algorithm improve the adaptability and stability of the liquid storage tank under different working conditions. By real-time monitoring of pressure data, the working state of the air compressor and the piston displacement are dynamically adjusted, thereby reducing the refrigerant residual rate, improving the drainage efficiency, accurately controlling the pressure, and enhancing the fault response capability, thereby extending the service life of the equipment. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] The present invention will be further described below with reference to the accompanying drawings and examples.

[0033] Figure 1 It is a schematic diagram of the principle of the intelligent liquid storage tank for a refrigeration unit of the present invention.

[0034] Figure 2 The figure is a schematic diagram of the appearance structure of the intelligent liquid storage tank for a refrigeration unit of the present invention.

[0035] Figure 3 This is a logic control principle diagram of the intelligent liquid storage tank for a refrigeration unit of the present invention.

[0036] In the figure, 100 is the tank body; 1. the solenoid valve; 2. the base of the liquid storage tank; 3. the first pressure sensor; 4. the dynamic sealing piston; 5. the inlet; 6. the double-pass O-type fluororubber sealing ring; 7. the second pressure sensor; 8. the filling valve; 9. the discharge valve; 10. the right-angle elbow; 11. the back suction recovery valve; 12. the three-way elbow; 13. the air compressor; 14. the liquid level sensor; 15. the first interface; 16. the second interface; 17. the external filling port; 18. the intelligent control system; 19. the displacement sensor; 20. the left liquid storage chamber; 21. the right air chamber; 22. the filling displacement mapping module; 23. the piston head; 24. the refrigeration system; 25. the temperature sensor. DETAILED DESCRIPTION

[0037] The present invention will now be described in further detail with reference to the accompanying drawings, which are simplified schematic diagrams that illustrate the basic structure of the present invention in a schematic manner.

[0038] like Figure 1 、 2 As shown, an intelligent liquid storage tank for a refrigeration unit of the present invention includes a tank body 100, a pressure sensor, a liquid level sensor 14, a temperature sensor 25, an air compressor 13, an intelligent control system 18 and a displacement sensor 19.

[0039] The interior of the tank 100 is divided into a right air chamber 21 and a left liquid storage chamber 20 by a dynamic sealing piston 4. The right air chamber 21 and the left liquid storage chamber 20 store compressed air and refrigerant, respectively. By separating the two media, the dynamic pressure balance between the refrigerant and air is ensured, preventing cross contamination. The dynamic sealing piston 4 is in sealed sliding connection with the inner wall of the tank 100.

[0040] Pressure sensors are provided inside the right air chamber 21 and the left liquid storage chamber 20 to monitor the pressure inside the chamber and feed the pressure data back to the intelligent control system 18 as a basis for adjusting the action of each valve in the valve group.

[0041] The liquid level sensor 14 is used to detect the liquid level in the left liquid storage chamber 20 in real time.

[0042] The temperature sensor 25 is provided in the left liquid storage chamber 20 and is used to detect the temperature in the left liquid storage chamber 20 in real time;

[0043] The displacement sensor 19 is used to detect the axial displacement of the dynamic sealing piston 4 relative to the tank body 100 in real time.

[0044] Intelligent control system 18 receives feedback from temperature sensor 25, displacement sensor 19, and pressure sensor. Based on these feedback signals, it adjusts the displacement of dynamic sealing piston 4 by controlling the operating state of air compressor 13. Based on the feedback from displacement sensor 19 and pressure sensor, intelligent control system 18 analyzes the current system status, such as if the pressure is too high or too low, generates control instructions, and sends them to air compressor 13 or the valves in the valve group, such as starting or stopping air compressor 13 and opening or closing valves. Air compressor 13 starts or stops according to the control instructions, generating compressed air as a power source, which is then driven by air pressure to push dynamic sealing piston 4.

[0045] The right air chamber 21 is connected to an air compressor 13, with an adjustable output pressure of 0.5-3 MPa. The left liquid storage chamber 20 integrates a pressure sensor and a temperature sensor 25. The pressure sensor has a range of 0-5 MPa and an accuracy of ±0.05% FS, and the temperature sensor 25 has a temperature measurement range of -50°C to 80°C. The air compressor 13 adjusts the air pressure in the right air chamber 21, driving the dynamic sealing piston 4 to move, thereby adjusting the size and internal pressure of the left liquid storage chamber 20 and controlling the refrigerant charge.

[0046] An intelligent liquid storage tank for a refrigeration unit of the present invention also includes a valve group, which includes a charging valve 8, a discharge valve 9 and a back suction recovery valve 11. Each valve controls the flow direction of the refrigerant. Discharge: releases excess refrigerant or gas; back suction: prevents backflow or active reverse suction (such as during emergency shutdown); charging: replenishes refrigerant into the system.

[0047] A first interface 15, a second interface 16 and an external filling port 17 are provided at the bottom of the left liquid storage chamber 20, and a solenoid valve 1 is provided at the inlet 5 of the right air chamber 21. The first interface 15 of the left liquid storage chamber 20 is connected to the refrigeration system 24 through a first pipeline and a three-way elbow 12 in sequence, and a back suction recovery valve 11 is provided on the first pipeline; the second interface 16 of the left liquid storage chamber 20 is connected to the refrigeration system 24 through a second pipeline, a right-angle elbow 10 and a three-way elbow 12 in sequence, and a discharge valve 9 is provided on the second pipeline; the filling valve 8 is arranged at the external filling port 17.

[0048] The discharge valve 9 is an electromagnetically driven conical valve, the back suction recovery valve 11 is a two-way self-cleaning valve, and the filling valve 8 is a one-way injection valve.

[0049] Refrigerant discharge valve: electromagnetically driven conical valve, diameter DN20, leakage level Class VI; back suction recovery valve: bidirectional self-cleaning valve, built-in ultrasonic vibration plate with a frequency of 40kHz and a 10μm filter; charging valve: mechanical one-way valve, opening pressure 0.15MPa.

[0050] The intelligent control system 18 includes a built-in charge displacement mapping module 22. The charge displacement mapping module 22 calculates the theoretical displacement based on the preset charge target value and dynamically corrects the displacement trajectory of the dynamic sealing piston 4 through closed-loop feedback. The charge displacement mapping module 22 dynamically compensates for environmental parameters using the following formula:

[0051] L 实际 =L0·[1+α(T-T0)+β(P-P0)].

[0052] Wherein, L0 is the theoretical displacement under standard working conditions, α is the temperature compensation coefficient, β is the pressure compensation coefficient, T is the actual temperature of the refrigerant in the current left liquid storage chamber, T0 is the reference temperature under standard working conditions, P is the real-time detected refrigerant pressure in the current left liquid storage chamber, and P0 is the reference pressure under standard working conditions; the intelligent control system 18 adopts a fuzzy PID algorithm, and according to the pressure deviation e(t)=P 设定 -P 实际 and deviation change rate The output power of the air compressor 13 is obtained.

[0053] The sealing structure of the dynamic sealing piston 4 includes a carbon fiber reinforced PEEK piston head 23 with a friction coefficient of less than 0.1. The edge of the piston head 23 is provided with a double-track O-type fluororubber sealing ring 6.

[0054] The displacement sensor 19 adopts a magnetostrictive sensor with a detection accuracy of ±0.05% FS, and communicates with the intelligent controller 18 through an RS485 interface.

[0055] The air compressor 13 is a variable frequency air compressor.

[0056] Tank 100 is a cylindrical double-layer structure with a stainless steel outer shell and an inner layer lined with an anti-corrosion coating. The outer layer of tank 100 is a 304 stainless steel shell with a wall thickness of 8-15mm and a pressure resistance of ≥4MPa. The inner layer is lined with a polytetrafluoroethylene anti-corrosion coating.

[0057] The liquid level sensor 14 may be a capacitive liquid level sensor.

[0058] A control method for an intelligent liquid storage tank of a refrigeration unit according to the present invention comprises the following steps:

[0059] When the liquid level sensor 14 detects that there is residual refrigerant in the left liquid storage chamber 20 that needs to be discharged, the pressure sensor and temperature sensor 25 detect and send a signal to the intelligent control system 18. The intelligent control system 18 sends the corresponding processed data to the air compressor 13. The air compressor 13 starts to run, and injects air into the right air chamber 21 through the inlet 5 of the right air chamber 21 through the solenoid valve 1, pushing the dynamic sealing piston 4 to move to the left, so that the refrigerant remaining in the left liquid storage chamber 20 passes through the left chamber outlet 16 through the discharge valve 9 and the right-angle elbow 10, and the three-way elbow 12 into the refrigeration system 24.

[0060] When the refrigerant in the refrigeration system 24 needs to be recovered, the pressure sensor and the temperature sensor 25 detect the pressure and send a signal to the intelligent control system 18. The intelligent control system 18 sends the corresponding processed data to the air compressor 13. The air compressor 13 starts to run in reverse. The air is extracted from the inlet 5 of the right air chamber 21 through the solenoid valve 1 to the right air chamber 21, pushing the dynamic sealing piston 4 to move to the right, so that the refrigerant in the refrigeration system 24 passes through the three-way elbow 12, the back suction recovery valve 11, and the outlet 15 of the left liquid storage chamber 20 and is drawn back into the tank body 100 or recovered to the outside. When the refrigerant needs to be recovered and not returned to the liquid storage tank, the connection between the outlet 15 and the refrigeration system 24 pipeline can also be separated, and the refrigerant can be recovered to the outside.

[0061] The pressure sensor collects the pressure data of the left liquid storage chamber 20 and the right air chamber 21 in real time. The first pressure sensor 3 in the left liquid storage chamber 20 collects the current refrigerant pressure P in real time. 实际 The second pressure sensor 7 in the right air cavity 21 synchronously monitors the air pressure P 空气 , used to assist in determining the pressure balance state on both sides of the piston. It is converted into a digital signal through a 16-bit ADC analog-to-digital conversion module, and then a sliding average filter is used to suppress noise to ensure data accuracy. The temperature sensor 25 collects the refrigerant temperature T in the left liquid storage chamber 20 in real time. 实际 The temperature range is -50℃~80℃. Calculate the pressure deviation e based on the pressure data (t) =P 设定 -P 实际 , where P 设定 The target pressure value preset for the system, such as the target low pressure value during refrigerant recovery or the target high pressure value during charging. 实际 The actual pressure value of the refrigerant in the left liquid storage chamber 20 or the refrigeration system detected by the pressure sensor in real time. t Reflects the absolute difference between the current pressure and the target pressure, and is used to determine whether the system needs to be adjusted and the direction of adjustment. Based on this, the pressure deviation change rate is calculated. Reflects the speed and trend of pressure fluctuations. The theoretical displacement is dynamically compensated using the formula in the charge displacement mapping module 22. Based on the preset refrigerant recovery target, such as the recovery volume V target, and the tank cross-sectional area S, the theoretical piston displacement under standard working conditions is calculated. Introduce temperature and pressure compensation formula to correct the influence of environmental parameters on displacement: the formula is L 实际 =L0·[1+α(T-T0)+

[0062] β(P-P0)]. Through this formula, the real-time changes of temperature and pressure are incorporated into the displacement calculation to ensure the accuracy of piston displacement, thereby accurately controlling the refrigerant charge. The target pressure is set according to the recovery working condition requirements, such as fast recovery. The intelligent control system 18 sets the target pressure P during the recovery process. 设定 , usually lower than the current system pressure, to form a pressure difference to drive the refrigerant backflow.

[0063] According to the pressure deviation e (t) and the rate of change of deviation Generate fuzzy logic correction value ΔK through fuzzy rule base fuzzy The fuzzy rule base contains 25 control strategies. Some examples of the rules are as follows:

[0064]

[0065] Defuzzification is calculated using the centroid method:

[0066]

[0067] where μ i is the rule triggering degree, ω i is the weight coefficient.

[0068] Combined with the traditional PID control algorithm, the control model function of the calculated control quantity pressure regulation is expressed as:

[0069]

[0070] Where e(t) is the real-time pressure deviation, e(t)=P set -P actual , that is, the difference between the set pressure and the measured pressure. is the pressure deviation change rate, K P ,K i ,K d ΔK are the proportional, integral and differential coefficients of the PID controller respectively. fuzzy is the fuzzy logic correction value, which is determined by the pressure deviation e and the deviation change rate Dynamic calculation.

[0071] According to the PID control calculation results, the output power and operating state of the air compressor 13 (such as forward, reverse, speed, etc.) are determined. For example, when the left liquid storage chamber 20 needs to discharge the residual refrigerant, the intelligent control system 18 controls the air compressor 13 to rotate forward and inject air into the right air chamber 21, causing the dynamic sealing piston 4 to move to the left; when the refrigerant in the refrigeration system 24 needs to be recovered, the air compressor 13 is controlled to rotate in the reverse direction and extract air from the right air chamber 21 to reduce the P 空气 , causing the dynamic sealing piston 4 to move to the right.

[0072] For the variable frequency air compressor 13, the intelligent control system 18 uses the built-in inverse model algorithm to reversely infer the required speed based on the target pressure and superimpose the feedforward compensation Δn (compensation range ±50rpm) to eliminate nonlinear errors and ensure that the output pressure of the air compressor 13 accurately matches the system requirements. For example, the compressor speed n (rpm) established by experimental calibration is related to the right chamber pressure P air The transfer model of (MPa) is P air =

[0073] 0.0012n+0.05·sin(0.005n)(n∈[500,2500]). Intelligent control system 18 calculates the required compressor speed based on this model and sends a corresponding control signal. Displacement sensor 19 detects the axial displacement of dynamic sealing piston 4 in real time and feeds the data back to intelligent control system 18. Intelligent control system 18 compares the actual displacement with the theoretical displacement. If any deviation exists, it dynamically corrects the control signal through a closed-loop feedback mechanism and adjusts the operating state of air compressor 13 to ensure that the piston displacement accurately tracks the target value, thereby achieving precise control of the refrigerant charge.

[0074] At the same time, the pressure sensor and temperature sensor 25 continuously monitor the changes in system pressure and temperature, and the intelligent control system 18 continuously adjusts the control strategy according to the new feedback data to form a closed-loop control and improve the stability and adaptability of the system.

[0075] When recovering the refrigerant in the refrigeration system 24, open the backflow recovery valve 11, close the discharge valve 9 and the charging valve 8, and establish a path for the refrigerant to flow back from the refrigeration system 24 to the liquid storage chamber 20 on the left side of the liquid storage tank. The displacement sensor 19 monitors the piston displacement L in real time. 实际 , compared with the theoretical calculated value, if the deviation exceeds ±0.05% FS, the intelligent control system 18 automatically adjusts the air compressor speed to form a displacement closed-loop control. The pressure sensor continuously monitors P 实际 and P 空气 , dynamically optimize fuzzy PID parameters to ensure a smooth and efficient recovery process.

[0076] When a sudden pressure drop (ΔP / Δt>0.2MPa / s) or abnormal flow (lower than 50% of the set value for 2s) is detected, the refrigerant discharge valve 9 is immediately closed, the back suction recovery valve 11 is started in back suction mode, and the air compressor 13 is reversed to draw back the refrigerant in the pipeline.

[0077] Emergency procedures are executed in milliseconds:

[0078] t=0ms: close the discharge valve V1 (action time ≤15ms);

[0079] t=20ms: Start the back suction valve V2 and the compressor reverses to -1500rpm;

[0080] t=100ms:If the recycling flow rate does not reach the expected level, the secondary pressure boost is triggered (1.5 times the pressure, lasting 0.5s). Self-cleaning program parameters:

[0081] Ultrasonic vibration: 50Hz mechanical vibration + 28kHz cavitation, amplitude 20μm;

[0082] Trigger condition: every 24 hours or 50 cumulative discharges.

[0083] The built-in self-check program triggers the valve group to vibrate at high frequency (50Hz, lasting 5s) once every 24 hours to remove impurities.

[0084] The intelligent control system 18 includes an embedded controller with an ARM Cortex-M7 core, which collects pressure, temperature, and displacement signals of the dynamic sealing piston 4 in real time. The signal processing mechanism and anti-interference design are as follows:

[0085] The pressure sensor signal is converted to a digital signal using a 16-bit ADC (ADS1115) with a sampling rate of 1kHz. A sliding average filter (50ms window width) is used to suppress noise. A magnetostrictive displacement sensor monitors piston displacement in real time with a 1ms data update cycle. The controller includes a built-in hardware watchdog (with a reset threshold of 1.6s) to ensure system stability even at -40°C temperatures.

[0086] The air compressor speed is controlled by a variable frequency drive (50-3000rpm stepless adjustment) with a drive accuracy of ±0.5%.

[0087] The valve group control module is driven by PWM signal, and the response time is ≤10ms. The corresponding relationship between the PWM duty cycle and valve opening of the refrigerant discharge valve 9 is as follows:

[0088] Duty cycle 0％ 30％ 60％ 100％ Opening 0％ 40％ 70％ 100％

[0089] The actual opening is calibrated using a quadratic equation to compensate for the nonlinear error caused by the spool inertia:

[0090] Opening = 0.8D + 0.05D 2 , where D is the duty cycle.

[0091] like Figure 3 As shown, the present invention provides a liquid storage tank for a refrigeration unit, which combines a piston compression system, a three-valve linkage system, and a fuzzy PID control algorithm to improve the adaptability and stability of the liquid storage tank under different working conditions. By monitoring pressure data in real time, the operating state of the air compressor and piston displacement are dynamically adjusted, thereby reducing the refrigerant residual rate, improving liquid discharge efficiency, accurately controlling pressure, enhancing fault response capabilities, and extending the service life of the equipment. The present invention has the following key points:

[0092] 1. Air compressor control: This system regulates the supply of compressed air to power valves and actuators in the system. It starts and stops the compressor based on control signals, such as valve commands, to ensure stable air pressure and enable rapid valve response.

[0093] 2. Liquid tank sensing: A level sensor or pressure sensor monitors the liquid level or internal pressure in the liquid tank in real time. The level or pressure data is converted into an electrical signal and transmitted to a controller, such as a fuzzy PID controller, as feedback for system regulation.

[0094] 3. Pressure data: The first pressure sensor 3 disposed inside the left liquid storage chamber 20 collects pressure data, reflecting liquid level changes and gas pressure, for use in closed-loop control algorithms, such as dynamic adjustment of fuzzy PID.

[0095] 4. Fuzzy PID controller: This controller combines traditional PID control (proportional-integral-differential) with fuzzy logic algorithms, balancing precise mathematical modeling with fuzzy reasoning. Based on pressure data and setpoints, it generates optimized valve commands to adjust liquid levels.

[0096] 5. Backflow recovery emergency module: In emergency situations such as low liquid level or pipeline rupture, it prevents reverse flow of liquid to avoid equipment damage. It guides abnormal liquid into the recovery pipeline to prevent leakage or contamination.

[0097] 6. Valve command: A control signal generated by a fuzzy PID controller based on real-time data. It drives a valve group, such as a three-valve linkage system, to perform actions such as opening / closing, adjusting the opening, etc., to control the inflow, outflow, or emergency discharge of liquids.

[0098] 7. Three-valve linkage system: three valves working together: filling valve 8, discharge valve 9 and back suction recovery valve 11.

[0099] Discharge valve 9: allows the refrigerant remaining in the tank body 100 to be discharged to the refrigeration system 24; back suction recovery valve 11: allows the refrigerant to be recovered from the refrigeration system 24 to the liquid storage tank; charging valve 8: when the refrigeration system 24 and the liquid storage tank are both short of refrigerant or the refrigerant needs to be replaced, refrigerant is charged from the outside.

[0100] In the present invention, the outlet of the air compressor 13 is connected to the solenoid valve 1, the outlet of the solenoid valve 1 is connected to the inlet 5 of the air chamber 21 on the right side of the tank body 100, the gas pushes the dynamic sealing piston 4 to move to the left, the left liquid storage chamber 20 is connected to the second interface 16, the second interface 16 is connected to the discharge valve 9, the outlet of the discharge valve 9 is connected to the right-angle elbow 10, the outlet of the right-angle elbow 10 is connected to the three-way elbow 12, the outlet of the three-way elbow 12 is connected to the refrigeration system 24, and the refrigeration system 24 is filled with refrigerant through the above process.

[0101] The recovery mode of the present invention runs the air compressor 13 in reverse, and the gas pushes the dynamic sealing piston 4 to move to the right. The left liquid storage chamber 20 is connected to the first interface 15, the first interface 15 is connected to the back suction recovery valve 11, and the outlet of the back suction recovery valve 11 is connected to the outlet of the three-way elbow 12, and the outlet of the three-way elbow 12 is connected to the refrigeration system 24. The refrigerant is recovered from the refrigeration system 24 through the above process.

[0102] The pressure sensor of the present invention uses the MPM489 Microscope sensor, and the capacitive liquid level sensor uses VEGA Capacitive Sensors. The second pressure sensor 7 within the right air chamber 21 collects pressure data from the right air chamber 21 and sends a signal to the intelligent control system 18. The intelligent control system 18 then takes appropriate measures and sends a signal to the air compressor 13. The first pressure sensor 3 and the capacitive liquid level sensor 14 collect pressure and liquid level data from the left liquid storage chamber 20 and send signals to the intelligent control system 18. The intelligent control system 18 then takes appropriate measures and sends a signal to the air compressor 13.

[0103] The present invention monitors pressure data in real time and dynamically adjusts the working state of the air compressor 13 and the displacement of the dynamic sealing piston 4, thereby reducing the refrigerant residual rate, improving the drainage efficiency, accurately controlling the pressure, enhancing the fault response capability, and extending the service life of the equipment.

[0104] This embodiment can achieve the following effects:

[0105] 1. Efficient drainage: Piston forced drainage + fuzzy PID control, residual rate ≤ 0.8% (9.2% for traditional tanks), emptying efficiency increased by 11 times.

[0106] 2. Precise pressure stabilization: pressure control accuracy is ±0.02MPa, adapting to sudden changes in evaporator load (±30% flow fluctuation).

[0107] 3. Fault self-healing: The reverse suction recovery mechanism reduces leakage losses by 90% and extends the maintenance cycle to 12 months.

[0108] 4. Wide range compatibility: supports -50℃~60℃ ambient temperature, and is compatible with high and low pressure refrigerants such as R404A and R507A.

[0109] With the above-described preferred embodiments of the present invention as a guide, and with reference to the above description, relevant personnel are fully capable of making various changes and modifications without departing from the technical scope of this invention. The technical scope of this invention is not limited to the contents of the specification and must be determined according to the scope of the claims.

Claims

1. An intelligent liquid storage tank for a refrigeration unit, characterized in that: It includes a tank body (100), a pressure sensor, a liquid level sensor (14), a temperature sensor (25), an air compressor (13), an intelligent control system (18) and a displacement sensor (19); The interior of the tank body (100) is divided into a right air chamber (21) and a left liquid storage chamber (20) by a dynamic sealing piston (4), and the dynamic sealing piston (4) is in sealing and sliding connection with the inner wall of the tank body (100); Pressure sensors are provided inside the right air cavity (21) and the left liquid storage cavity (20) to monitor the pressure inside the cavity; A liquid level sensor (14) for detecting the liquid level in the left liquid storage chamber (20) in real time; A temperature sensor (25) is provided in the left liquid storage chamber (20) and is used to detect the temperature in the left liquid storage chamber (20) in real time; a displacement sensor (19) for detecting in real time the axial displacement of the dynamic sealing piston (4) relative to the tank body (100); an intelligent control system (18) that receives feedback signals from the temperature sensor (25), the displacement sensor (19), and the pressure sensor, and adjusts the displacement of the dynamic sealing piston (4) by controlling the working state of the air compressor (13) according to the feedback signals; The right air chamber (21) is connected to an air compressor (13). The air compressor (13) drives the dynamic sealing piston (4) to move by adjusting the air pressure of the right air chamber (21), thereby adjusting the size and internal pressure of the left liquid storage chamber (20) and realizing control of the refrigerant filling amount.

2. The intelligent liquid storage tank for a refrigeration unit according to claim 1, characterized in that: The invention also includes a valve group, which includes a filling valve (8), a discharge valve (9) and a back suction recovery valve (11). The bottom of the left liquid storage chamber (20) is provided with a first interface (15), a second interface (16) and an external filling port (17). The inlet (5) of the right air chamber (21) is provided with a solenoid valve (1). The first interface (15) of the left liquid storage chamber (20) is connected to the refrigeration system (24) through a first pipeline and a three-way elbow (12) in sequence, and the back suction recovery valve (11) is provided on the first pipeline; the second interface (16) of the left liquid storage chamber (20) is connected to the refrigeration system (24) through a second pipeline, a right-angle elbow (10) and a three-way elbow (12) in sequence, and the discharge valve (9) is provided on the second pipeline; the filling valve (8) is arranged at the external filling port (17).

3. The intelligent liquid storage tank for a refrigeration unit according to claim 2, characterized in that: The discharge valve (9) is an electromagnetically driven conical valve, the back suction recovery valve (11) is a two-way self-cleaning valve, and the filling valve (8) is a one-way injection valve.

4. The intelligent liquid storage tank for a refrigeration unit according to claim 1, characterized in that: The intelligent control system (18) is equipped with a filling amount displacement mapping module (22), which calculates a theoretical displacement amount according to a preset filling amount target value and dynamically corrects the displacement trajectory of the dynamic sealing piston (4) through closed-loop feedback; The filling displacement mapping module (22) dynamically compensates for environmental parameters using the following formula: L 实际 =L0·[1+α(T-T0)+β(P-P0)]; Wherein, L0 is the theoretical displacement under standard working conditions, α is the temperature compensation coefficient, β is the pressure compensation coefficient, T is the actual temperature of the refrigerant in the current left liquid storage chamber, T0 is the reference temperature under standard working conditions, P is the real-time detected refrigerant pressure in the current left liquid storage chamber, and P0 is the reference pressure under standard working conditions; the intelligent control system (18) adopts a fuzzy PID algorithm, and according to the pressure deviation e(t)=P 设定 -P 实际 and deviation change rate The output power of the air compressor (13) is obtained.

5. The intelligent liquid storage tank for a refrigeration unit according to claim 1, characterized in that: The sealing structure of the dynamic sealing piston (4) comprises a carbon fiber reinforced PEEK piston head (23), and the edge of the piston head (23) is provided with a double-track O-type fluororubber sealing ring (6).

6. The intelligent liquid storage tank for a refrigeration unit according to claim 1, characterized in that: The displacement sensor (19) adopts a magnetostrictive sensor with a detection accuracy of ±0.05% FS, and communicates with the intelligent controller (18) via an RS485 interface.

7. The intelligent liquid storage tank for a refrigeration unit according to claim 1, characterized in that: The air compressor (13) is a variable frequency air compressor.

8. The intelligent liquid storage tank for a refrigeration unit according to claim 1, characterized in that: The tank body (100) adopts a cylindrical double-layer structure, the outer layer is a stainless steel shell, and the inner layer is lined with an anti-corrosion coating.

9. The intelligent liquid storage tank for a refrigeration unit according to claim 8, characterized in that: The outer layer of the tank body (100) is a 304 stainless steel shell, and the inner layer is lined with a polytetrafluoroethylene anti-corrosion coating.

10. A control method for an intelligent liquid storage tank for a refrigeration unit according to any one of claims 1 to 9, characterized in that: The following steps are involved: When the liquid level sensor (14) detects that there is residual refrigerant in the left liquid storage chamber (20) that needs to be discharged, the pressure sensor and the temperature sensor (25) detect and send a signal to the intelligent control system (18), and the intelligent control system (18) sends the corresponding processed data to the air compressor (13). The air compressor (13) starts to operate and pushes the dynamic sealing piston (4) to move leftward by injecting air into the right air chamber (21), so that the refrigerant remaining in the left liquid storage chamber (20) enters the refrigeration system (24); When the refrigerant in the refrigeration system (24) needs to be recovered, the pressure sensor and the temperature sensor (25) detect the pressure and send a signal to the intelligent control system (18). The intelligent control system (18) sends the corresponding processed data to the air compressor (13). The air compressor (13) starts to run in reverse, and pushes the dynamic sealing piston (4) to move rightward by pumping air into the right air chamber (21), so that the refrigerant in the refrigeration system (24) is pumped back into the tank (100) or recovered to the outside.

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