Control method for preventing liquid impact of air conditioning system and air conditioning system applying control method

Abstract

The invention discloses a control method for preventing liquid impact of an air conditioning system and the air conditioning system applying the control method, and relates to the technical field of heat pump air conditioners. S2, the pressure of the refrigerant flowing out of the evaporator is detected and converted into the corresponding saturation temperature, the temperature of the refrigerant flowing out of the evaporator is detected, and the superheat degree is obtained according to the saturation temperature and the temperature of the refrigerant; s3, adjusting the opening degree of an electronic expansion valve and the rotating speed of an inner fan at an evaporator according to the superheat degree so as to adjust the superheat degree; s4, stopping the system; the pressure and the temperature of the refrigerant flowing out of the evaporator are detected in real time, the pressure is converted into the saturation temperature, the superheat degree is obtained through the saturation temperature and the refrigerant temperature, then the opening degree of the electronic expansion valve and the rotating speed of the inner draught fan are adjusted in a self-adaptive mode according to the superheat degree, the purpose of regulating and controlling the superheat degree is achieved, and the liquid impact prevention effect can be effectively improved; and the stability and the safety of system operation are improved.

Description

Technical Field

[0001] The present invention relates to the technical field of heat pump air conditioners, and in particular to a control method for preventing liquid hammer in an air conditioning system and an air conditioning system using the control method. Background Art

[0002] With the rapid development of information technology, data centers have become an indispensable part of modern economic and social activities. In order to ensure the normal operation of data centers, a reliable computer room air conditioning system has become extremely important. However, traditional computer room air conditioning systems often face compressor liquid hammer problems, which not only causes equipment damage, but also affects the safe operation of the entire data center.

[0003] At present, the applicant knows the following solutions for solving the compressor hydraulic shock problem: First, a fixed-opening expansion valve is used to control the refrigerant flow rate. This method is simple and easy to implement, but it is difficult to maintain good control accuracy when the load changes greatly. Second, an additional gas-liquid separator is added to the system to separate the refrigerant that is not completely vaporized and reduce the risk of liquid hammer. Although this method can alleviate the problem to a certain extent, it increases the complexity and cost of the system. Third, a simple PID controller is used to adjust the working state of the compressor, but for a complex refrigeration cycle system, a single PID control cannot fundamentally solve the compressor liquid hammer problem. Although the above schemes can alleviate the compressor liquid hammer phenomenon to a certain extent, due to the lack of accurate real-time monitoring capabilities and adaptive adjustment mechanisms, it often leads to a slow system response and cannot effectively avoid the occurrence of liquid hammer events in a timely manner.

[0004] Therefore, people are in urgent need of a control method for preventing liquid hammer in air-conditioning systems with adaptive adjustment and good liquid hammer prevention effect. Summary of the invention

[0005] The purpose of the present invention is to provide a control method for preventing liquid hammer in an air-conditioning system and an air-conditioning system using the same, so as to solve the problems existing in the above-mentioned prior art, and to improve the anti-liquid hammer effect by real-time detection of relevant data and adaptive adjustment of system operation data.

[0006] To achieve the above object, the present invention provides the following solution: The present invention provides a control method for preventing liquid hammer in an air conditioning system, comprising the following steps: S1: System startup; S2: Detect the pressure of the refrigerant flowing out of the evaporator and convert it into the corresponding saturation temperature, detect the temperature of the refrigerant flowing out of the evaporator, and obtain the superheat according to the saturation temperature and the temperature of the refrigerant; S3: According to the superheat, the opening of the electronic expansion valve and the speed of the internal fan at the evaporator are regulated to adjust the superheat; S4: System down.

[0007] Preferably, in step S1, when the unit receives a start-up command, the internal fan at the evaporator is started and operated first, and then the electronic expansion valve runs to a preset opening before the compressor starts, and then the compressor is started and operated, and the external fan at the condenser is started and operated according to the high pressure of the refrigerant flowing out of the compressor.

[0008] Preferably, in step S2, the superheat is equal to the temperature of the refrigerant minus the saturation temperature.

[0009] Preferably, in step S3, when the superheat is too small, the opening of the electronic expansion valve is reduced, and the speed of the internal fan is increased, and the internal fan slowly adjusts back to the normal value after the superheat is normal; when the superheat is too large, the opening of the electronic expansion valve is increased, and the speed of the internal fan is reduced, and the internal fan slowly adjusts back to the normal value after the superheat is normal; when the superheat is within a reasonable range, the electronic expansion valve maintains the current opening without adjustment, and the internal fan automatically adjusts according to the ambient temperature.

[0010] Preferably, in step S4, when the unit receives a shutdown command, the electronic expansion valve is first completely closed, and when the real-time detection shows that the pressure value of the refrigerant flowing out of the evaporator is less than or equal to the compressor shutdown value, the compressor is shut down, and then the internal fan stops running after a delay, and at the same time, the external fan at the condenser stops running according to the high pressure of the refrigerant flowing out of the compressor.

[0011] The present invention also provides an air-conditioning system with a control method for preventing liquid hammer in the above-mentioned air-conditioning system, comprising an evaporator, a compressor, a condenser and an electronic expansion valve connected in sequence, an internal fan is provided at the evaporator, an external fan is provided at the condenser, a temperature detection device and a low-pressure sensor are provided between the evaporator and the compressor, a high-pressure sensor is provided between the compressor and the condenser, and the temperature detection device, the low-pressure sensor, the high-pressure sensor, the electronic expansion valve, the driving mechanism of the internal fan, the driving mechanism of the external fan and the compressor are all electrically connected to a control system.

[0012] Preferably, along the refrigerant flow path between the evaporator and the compressor, the temperature detection device is located in front of the low pressure sensor.

[0013] Preferably, a liquid reservoir is provided between the condenser and the electronic expansion valve.

[0014] Preferably, a filter is provided between the condenser and the electronic expansion valve.

[0015] Preferably, a sight glass is provided between the condenser and the electronic expansion valve.

[0016] Compared with the prior art, the present invention mainly achieves the following technical effects: The pressure and temperature of the refrigerant flowing out of the evaporator are detected in real time, the pressure is converted into saturation temperature, and the saturation temperature and refrigerant temperature are used to obtain the superheat. Then, according to the size of the superheat, the opening of the electronic expansion valve and the speed of the internal fan are adaptively adjusted to achieve the purpose of regulating the superheat, which can effectively improve the anti-liquid hammer effect and improve the stability and safety of the system operation.

[0017] Compared with the prior art, other solutions of the present invention have achieved the following technical effects: The electronic expansion valve is closed first, and then the compressor shutdown method is controlled by detecting the numerical value of the refrigerant pressure flowing out of the evaporator to ensure that no liquid hammer occurs when the compressor is shut down or started next time. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0019] Figure 1 is a system diagram of an air conditioning system in an embodiment of the present invention; Figure 2 Flow chart of a control method for preventing liquid hammer in an air conditioning system according to an embodiment of the present invention; Among them, 1. Evaporator; 2. Compressor; 3. Condenser; 4. Electronic expansion valve; 5. Internal fan; 6. External fan; 7. Intake temperature sensing package; 8. Low pressure sensor; 9. High pressure sensor; 10. Liquid reservoir; 11. Filter; 12. Sight glass. DETAILED DESCRIPTION

[0020] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0021] The purpose of the present invention is to provide a control method for preventing liquid hammer in an air-conditioning system and an air-conditioning system using the same, so as to solve the problems existing in the prior art, and to improve the anti-liquid hammer effect by real-time detection of relevant data and adaptive adjustment of system operation data.

[0022] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0023] Please refer to Figure 1~Figure 2 As shown, a control method for preventing liquid hammer in an air conditioning system is provided, comprising the following steps: S1: System startup. When the unit receives the startup command, the internal fan 5 at the evaporator 1 is started first, and then the electronic expansion valve 4 is operated to a preset opening before the compressor 2 is started (set to the first 5 seconds in this embodiment), and then the compressor 2 is started, and the external fan 6 at the condenser 3 is started according to the high pressure of the refrigerant flowing out of the compressor 2. The start-up high pressure value of the external fan 6 can be set to control the start-up of the external fan 6; S2: Detect the pressure of the refrigerant flowing out of the evaporator 1 and convert it into the corresponding saturation temperature, detect the temperature of the refrigerant flowing out of the evaporator 1, and obtain the superheat according to the saturation temperature and the temperature of the refrigerant. The superheat is equal to the temperature of the refrigerant minus the saturation temperature; S3: According to the superheat, the opening of the electronic expansion valve 4 and the speed of the internal fan 5 at the evaporator 1 are regulated to adjust the superheat. When the superheat is too small, according to the current superheat, the high pressure of the refrigerant flowing out of the compressor 2, the low pressure of the refrigerant flowing out of the evaporator 1 and the speed of the internal fan 5, and combined with the historical operation data, a comprehensive judgment is made to reduce the opening of the electronic expansion valve 4 and increase the speed of the internal fan 5. After the superheat is normal, the internal fan 5 slowly adjusts back to the normal value; when the superheat is too large, according to the current superheat, the high pressure of the refrigerant flowing out of the compressor 2, the low pressure of the refrigerant flowing out of the evaporator 1 and the speed of the internal fan 5, and combined with the historical operation data, a comprehensive judgment is made to increase the opening of the electronic expansion valve 4 and reduce the speed of the internal fan 5. After the superheat is normal, the internal machine slowly adjusts back to the normal value; when the superheat is within a reasonable range, the electronic expansion valve 4 maintains the current opening without adjustment, and the internal fan 5 automatically adjusts according to the ambient temperature; In step S3, in this embodiment, when the superheat is lower than 6°C, it is considered as too low a superheat; when the superheat is 6-8°C, it is considered as normal a superheat; and when the superheat is higher than 8°C, it is considered as too high a superheat.

[0024] In the case where the superheat is too small in step S3, the opening of the electronic expansion valve 4 is reduced, and the speed of the internal fan 5 is increased. Under the same conditions, the greater the difference between the superheat value and the normal value, the faster the adjustment speed of the electronic expansion valve 4, and finally the opening of the electronic expansion valve 4 is reduced. When the difference is large, the opening of the electronic expansion valve 4 is smaller than the opening of the electronic expansion valve 4 when the difference is small; the greater the difference between the superheat value and the normal value, the faster the adjustment speed of the internal fan 5, the smaller the difference between the superheat value and the normal value, the slower the adjustment speed of the internal fan 5, and finally the speed of the internal fan 5 is increased. When the difference is large, the speed of the internal fan 5 is greater than the speed of the internal fan 5 when the difference is small. The rotation speed of the machine 5; the smaller the high pressure of the refrigerant flowing out of the compressor 2, the faster the adjustment speed of the electronic expansion valve 4 is, the larger the high pressure of the refrigerant flowing out of the compressor 2, the slower the adjustment speed of the electronic expansion valve 4 is, and finally the opening of the electronic expansion valve 4 is adjusted to a smaller value, and the opening of the electronic expansion valve 4 when the high pressure is large is larger than the opening of the electronic expansion valve 4 when the high pressure is small; the larger the low pressure of the refrigerant flowing out of the evaporator 1, the faster the adjustment speed of the electronic expansion valve 4 is, the smaller the low pressure of the refrigerant flowing out of the evaporator 1, the slower the adjustment speed of the electronic expansion valve 4 is, and finally the opening of the electronic expansion valve 4 is adjusted to a smaller value, and the opening of the electronic expansion valve 4 when the low pressure is large is smaller than the opening of the electronic expansion valve 4 when the low pressure is small.

[0025] In the case of a large superheat in step S3, the opening of the electronic expansion valve 4 is increased, and the speed of the internal fan 5 is reduced. Under the same conditions, the greater the difference between the superheat value and the normal value, the faster the adjustment speed of the electronic expansion valve 4 is, and finally the opening of the electronic expansion valve 4 is increased. When the difference is large, the opening of the electronic expansion valve 4 is greater than the opening of the electronic expansion valve 4 when the difference is small. The greater the difference between the superheat value and the normal value, the faster the adjustment speed of the internal fan 5 is, the smaller the difference between the superheat value and the normal value, the slower the adjustment speed of the internal fan 5 is, and finally the speed of the internal fan 5 is decreased. When the difference is large, the speed of the internal fan 5 is less than the speed of the internal fan 5 when the difference is small. 5 speed; the smaller the high pressure of the refrigerant flowing out of the compressor 2, the slower the adjustment speed of the electronic expansion valve 4, the larger the high pressure of the refrigerant flowing out of the compressor 2, the faster the adjustment speed of the electronic expansion valve 4, and finally the opening of the electronic expansion valve 4 is adjusted to a larger value, and the opening of the electronic expansion valve 4 when the high pressure is large is larger than the opening of the electronic expansion valve 4 when the high pressure is small; the smaller the low pressure of the refrigerant flowing out of the evaporator 1, the faster the adjustment speed of the electronic expansion valve 4, the larger the low pressure of the refrigerant flowing out of the evaporator 1, the smaller the adjustment speed of the electronic expansion valve 4, and finally the opening of the electronic expansion valve 4 is adjusted to a larger value, and the opening of the electronic expansion valve 4 when the low pressure is large is smaller than the opening of the electronic expansion valve 4 when the low pressure is small.

[0026] S4: System shutdown. When the unit receives a shutdown command, the electronic expansion valve 4 is first completely closed, and when the real-time detection pressure value of the refrigerant flowing out of the evaporator 1 is less than or equal to the shutdown value of the compressor 2 (set to 6 bar in this embodiment), the compressor 2 is shut down, and then the internal fan 5 stops running after a delay. At the same time, the external fan 6 at the condenser 3 stops running according to the high pressure of the refrigerant flowing out of the compressor 2. The shutdown of the external fan 6 can be controlled by setting the high pressure value of the external fan 6. This step can ensure that there is no liquid hammer when the compressor 2 is shut down and the next time it is started.

[0027] This method detects the pressure and temperature of the refrigerant flowing out of the evaporator 1 in real time, converts the pressure into saturation temperature, and uses the saturation temperature and the refrigerant temperature to obtain the superheat. Then, according to the size of the superheat, the opening of the electronic expansion valve 4 and the speed of the internal fan 5 are adaptively adjusted to achieve the purpose of regulating the superheat. The anti-liquid hammer effect can be effectively improved, and the stability and safety of the system operation are improved. In addition, the method has a high degree of intelligence and strong adaptability, so that the system can maintain good performance regardless of the high temperature in summer or the low temperature in winter, meeting the different needs of different types of data centers.

[0028] As the system operation time increases, the control system can continuously learn and update its own optimized parameters based on historical operation data, so that the adjustment of the electronic expansion valve 4 and the internal fan 5 becomes closer and closer to the ideal state. For example, by recording the adjustment data of the electronic expansion valve and the internal fan when the superheat was a certain value last time, and recording the time it takes for the superheat to return to a normal value, the next time the superheat is that value, the adjustment of the electronic expansion valve and the internal fan is actively optimized to shorten the time it takes for the superheat to return to a normal value.

[0029] The present invention also provides an air-conditioning system using the control method for preventing liquid hammer in the air-conditioning system, comprising an evaporator 1, a compressor 2, a condenser 3 and an electronic expansion valve 4 connected in sequence, an internal fan 5 is provided at the evaporator 1, an external fan 6 is provided at the condenser 3, a temperature detection device and a low-pressure sensor 8 are provided between the evaporator 1 and the compressor 2, the temperature detection device is used to detect the temperature of the refrigerant flowing out of the evaporator 1, the low-pressure sensor 8 is used to detect the pressure of the refrigerant flowing out of the evaporator 1, a high-pressure sensor 9 is provided between the compressor 2 and the condenser 3, the high-pressure sensor 9 is used to detect the pressure of the refrigerant flowing out of the compressor 2, and the temperature detection device, the low-pressure sensor 8, the high-pressure sensor 9, the electronic expansion valve 4, the driving mechanism of the internal fan 5, the driving mechanism of the external fan 6 and the compressor 2 are all electrically connected to the control system.

[0030] In this embodiment, the temperature detection device is an air intake temperature sensing package 7. In other embodiments, other devices capable of detecting temperature, such as a thermometer, may also be used.

[0031] In this embodiment, the temperature detection device is located in front of the low-pressure sensor 8 along the refrigerant flow path between the evaporator 1 and the compressor 2. The temperature detection device is arranged closer to the evaporator 1, which is conducive to improving the detection accuracy.

[0032] A liquid storage tank 10 is provided between the condenser 3 and the electronic expansion valve 4 to store liquid refrigerant and buffer system pressure fluctuations.

[0033] A filter 11 is provided between the condenser 3 and the electronic expansion valve 4 to filter out impurities, absorb moisture, and prevent ice blockage and dirt blockage.

[0034] A sight glass 12 is provided between the condenser 3 and the electronic expansion valve 4, which can be used to observe the flow condition of the refrigerant and detect the water vapor content.

[0035] Adaptive changes made according to actual needs are all within the protection scope of the present invention.

[0036] It should be noted that it is obvious to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the present invention can be implemented in other specific forms without departing from the spirit or essential features of the present invention. Therefore, the embodiments should be regarded as exemplary and non-restrictive from any point of view, and the scope of the present invention is defined by the appended claims rather than the above description, and it is intended that all changes falling within the meaning and scope of the equivalent elements of the claims are included in the present invention. Any reference numerals in the claims should not be regarded as limiting the claims involved.

[0037] The present invention uses specific examples to illustrate the principles and implementation methods of the present invention. The above examples are only used to help understand the method and core ideas of the present invention. At the same time, for those skilled in the art, according to the ideas of the present invention, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as limiting the present invention.

Claims

1. A control method for preventing liquid hammer in an air conditioning system, characterized in that: The following steps are involved: S1: System startup; S2: Detect the pressure of the refrigerant flowing out of the evaporator and convert it into the corresponding saturation temperature, detect the temperature of the refrigerant flowing out of the evaporator, and obtain the superheat according to the saturation temperature and the temperature of the refrigerant; S3: According to the superheat, the opening of the electronic expansion valve and the speed of the internal fan at the evaporator are regulated to adjust the superheat; S4: System down.

2. The control method for preventing liquid hammer in an air conditioning system according to claim 1, characterized in that: In step S1, when the unit receives a start-up command, the internal fan at the evaporator starts running first, and then the electronic expansion valve runs to a preset opening before the compressor starts, and then the compressor starts running, and the external fan at the condenser starts running according to the high pressure of the refrigerant flowing out of the compressor.

3. The control method for preventing liquid hammer in an air conditioning system according to claim 1, characterized in that: In step S2, the superheat degree is equal to the temperature of the refrigerant minus the saturation temperature.

4. The control method for preventing liquid hammer in an air conditioning system according to claim 1, characterized in that: In step S3, when the superheat is too small, the opening of the electronic expansion valve is reduced, and the speed of the internal fan is increased. After the superheat is normal, the internal fan slowly adjusts back to the normal value; when the superheat is too large, the opening of the electronic expansion valve is increased, and the speed of the internal fan is reduced. After the superheat is normal, the internal fan slowly adjusts back to the normal value; when the superheat is within a reasonable range, the electronic expansion valve maintains the current opening without adjustment, and the internal fan automatically adjusts according to the ambient temperature.

5. The control method for preventing liquid hammer in an air conditioning system according to claim 1, characterized in that: In step S4, when the unit receives a shutdown command, the electronic expansion valve is first completely closed, and when the real-time detection shows that the pressure value of the refrigerant flowing out of the evaporator is less than or equal to the compressor shutdown value, the compressor is shut down, and then the internal fan stops running after a delay. At the same time, the external fan at the condenser stops running according to the high pressure of the refrigerant flowing out of the compressor.

6. An air conditioning system, characterized in that: A control method for preventing liquid hammer in an air-conditioning system according to any one of claims 1 to 5 is applied, comprising an evaporator, a compressor, a condenser and an electronic expansion valve connected in sequence, an internal fan being provided at the evaporator, an external fan being provided at the condenser, a temperature detection device and a low-pressure sensor being provided between the evaporator and the compressor, a high-pressure sensor being provided between the compressor and the condenser, and the temperature detection device, the low-pressure sensor, the high-pressure sensor, the electronic expansion valve, a driving mechanism of the internal fan, a driving mechanism of the external fan and the compressor are all electrically connected to a control system.

7. The air conditioning system according to claim 6, characterized in that: Along the refrigerant flow path between the evaporator and the compressor, the temperature detection device is located in front of the low pressure sensor.

8. The air conditioning system according to claim 6, characterized in that: A liquid reservoir is arranged between the condenser and the electronic expansion valve.

9. The air conditioning system according to claim 6, characterized in that: A filter is arranged between the condenser and the electronic expansion valve.

10. The air conditioning system according to claim 6, characterized in that: A sight glass is arranged between the condenser and the electronic expansion valve.

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