Refrigerating unit capable of preventing air suction from carrying liquid

Abstract

The utility model discloses a refrigerating unit capable of preventing air suction from carrying liquid, which comprises a compressor, a condenser, a main throttling device, an evaporator and a gas-liquid separator which are sequentially connected to form a refrigerating main path, and further comprises a first-stage heat exchanger, a second-stage heat exchanger, a third-stage heat exchanger and a fourth-stage heat exchanger, an outlet of the evaporator is connected to an inlet of the gas-liquid separator through a first-stage adapter, an inlet of the first-stage bypass pipe is connected to an exhaust port of the compressor through a first-stage hot air valve, and at least part of refrigerant flowing out of the first-stage bypass pipe is conveyed to the evaporator. The refrigerating unit can also be provided with an ejector, a secondary heat exchanger and an electric heating device. By means of a multi-protection structure, air suction and liquid carrying in the unit operation process are prevented in a targeted mode, liquid impact of the compressor is effectively avoided, and the service life of the unit is prolonged.

Description

Technical Field

[0001] The utility model relates to the technical field of refrigeration units, in particular to a refrigeration unit for preventing liquid carry - over during suction. Background Art

[0002] The main function of a compressor is to boost low - pressure gas (such as air, refrigerant or other process gases) to high - pressure gas and deliver it to subsequent equipment such as condensers. Under ideal conditions, the gas inhaled by the compressor should be dry to ensure the smooth progress of the compression process. However, due to the action of various factors, liquid refrigerant may enter the compressor suction pipeline, be inhaled into the cylinder to participate in compression, forming the phenomenon of liquid carry - over during suction. As a key device widely used in the refrigeration field, a centrifugal compressor has a complex structure and a high operating speed, and has more stringent requirements for the state of the inhaled gas. Once liquid carry - over occurs during suction, it will not only affect the operating efficiency of the compressor, but may also cause serious mechanical failures.

[0003] Taking a refrigeration unit using a centrifugal compressor as an example, liquid carry - over during suction is likely to occur during the startup process and the running process. When the refrigeration unit starts up, in order to prevent surging during the startup process, the operating frequency of the compressor will be quickly increased to the startup frequency. At this time, the pressure between the condenser and the evaporator of the unit is in a balanced state, and the refrigerant is basically stored in the condenser and the evaporator, and the liquid level of the evaporator is relatively high. It is very easy to have liquid carry - over during the startup process of the compressor, resulting in faults such as over - current of the frequency converter and unstable suspension of the motor bearing, leading to the failure of the unit to start. During the running process of the refrigeration unit, especially under small - load conditions, the pressure ratio of the unit is relatively smaller and the liquid level of the evaporator is higher. Even when the operating frequency of the compressor has reached the minimum operating frequency, liquid carry - over often occurs, causing liquid hammer on the compressor impeller, seriously affecting the life of the compressor and the operating reliability of the unit.

[0004] In the prior art, an air - conditioning system with a liquid - hammer - proof function has emerged. By designing a heating device outside the gas - liquid separator and two bypass branches between the gas - liquid separator and the compressor, one bypass branch sends a part of the refrigerant discharged from the compressor into the gas - liquid separator, and the other bypass branch mixes a part of the refrigerant discharged from the compressor with the gaseous refrigerant sent out by the gas - liquid separator and returns it to the compressor, promoting the transformation of the refrigerant from liquid to gas. Although this solution can reduce the risk of liquid hammer to a certain extent, due to the obvious reduction of the refrigerant amount in the main circulation path, the evaporation heat absorption in the evaporator will decrease, there is a risk of insufficient refrigeration capacity, affecting the user experience.

[0005] Therefore, how to design a refrigeration unit that can effectively prevent the phenomenon of liquid carry - over during suction is a technical problem urgently to be solved in the industry. Summary of the Utility Model

[0006] To address the above-mentioned defects in the prior art, the present utility model proposes a refrigeration unit that prevents suction of liquid, which uses the high-temperature refrigerant led out from the compressor exhaust port to provide heat to promote the transformation of liquid refrigerant into gaseous refrigerant, and then sends the refrigerant after releasing heat back into the main refrigeration circuit to ensure the amount of refrigerant participating in refrigeration operation in the main circuit, taking into account both the safety of the compressor and the user experience.

[0007] The technical solution adopted by the present utility model is to design a refrigeration unit that prevents suction of liquid, including: a compressor, a condenser, a main throttling device, an evaporator, and a gas-liquid separator that are connected in sequence to form a main refrigeration circuit. The refrigeration unit further includes: a first-stage heat exchanger, which has a first-stage transfer pipe and a first-stage bypass pipe that exchange heat with each other. The outlet of the evaporator is connected to the inlet of the gas-liquid separator through the first-stage transfer pipe, the inlet of the first-stage bypass pipe is connected to the exhaust port of the compressor through a first-stage hot gas valve, and at least part of the refrigerant flowing out of the first-stage bypass pipe is sent to the evaporator.

[0008] Furthermore, the refrigeration unit further includes: an ejector, the first inlet of the ejector is connected to the exhaust port of the compressor through an ejector air intake valve, the second inlet of the ejector is connected to the liquid outlet of the gas-liquid separator through an ejector liquid intake valve, and the outlet of the ejector is connected to the evaporator.

[0009] Furthermore, the refrigeration unit further includes: a second-stage heat exchanger, which has a second-stage transfer pipe and a second-stage bypass pipe that exchange heat with each other. The gas outlet of the gas-liquid separator is connected to the suction port of the compressor through the second-stage transfer pipe, the inlet of the second-stage bypass pipe is connected to the exhaust port of the compressor through a second-stage hot gas valve, and at least part of the refrigerant flowing out of the second-stage bypass pipe is sent to the evaporator.

[0010] Furthermore, an electric heating device is installed inside the gas-liquid separator.

[0011] Furthermore, the refrigeration unit further includes: a flash tank, the inlet of the flash tank is connected to the condenser through a first-stage throttling device, the gas outlet of the flash tank is connected to the make-up gas port of the compressor, and the liquid outlet of the flash tank is connected to the evaporator through a second-stage throttling device.

[0012] Furthermore, the outlet of the first-stage bypass pipe and / or the outlet of the second-stage bypass pipe are connected to the flash tank.

[0013] Furthermore, the outlet of the first-stage bypass pipe and / or the outlet of the second-stage bypass pipe are connected to the evaporator.

[0014] Furthermore, the refrigeration unit further includes: a controller for controlling the working state of the refrigeration unit, and an acquisition device communicatively connected to the controller. The acquisition device includes a pressure sensor, a temperature sensor, and an electrical sensor; wherein, the pressure sensor and the temperature sensor are used to acquire the parameters on the exhaust side and / or the suction side of the compressor, and the electrical sensor is used to acquire the current and / or voltage of the compressor.

[0015] Furthermore, the collection device also includes: a liquid level sensor, which is used to collect the liquid level in the gas-liquid separator.

[0016] In some embodiments, the compressor is a centrifugal compressor.

[0017] Compared with the prior art, the present invention has the following beneficial effects:

[0018] 1. The high-temperature refrigerant drawn from the compressor exhaust port provides heat to convert the liquid refrigerant into gaseous refrigerant. At least a portion of the refrigerant after releasing heat is sent to the evaporator, ensuring the amount of refrigerant in the main circuit involved in the cooling operation, taking into account both compressor safety and user experience;

[0019] 2. Multiple protective structures such as the first-stage heat exchanger, ejector, second-stage heat exchanger and electric heating device are designed to prevent liquid from being sucked into the air during the operation of the unit, effectively avoid liquid hammer in the compressor and extend the service life of the unit. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The present invention will be described in detail below with reference to the embodiments and accompanying drawings, wherein:

[0021] Figure 1 It is a schematic structural diagram of a refrigeration unit in some embodiments of the present utility model;

[0022] Figure 2 is a schematic diagram of the refrigerant flow direction of some embodiments of the present utility model;

[0023] Figure 3 It is a schematic structural diagram of a refrigeration unit in some other embodiments of the utility model;

[0024] Figure 4 It is a schematic diagram of the refrigerant flow in other embodiments of the present invention;

[0025] Figure 5 It is a flow chart of the control method of the utility model;

[0026] Description of the drawings: 1. Compressor; 2. First-stage hot gas valve; 3. Second-stage hot gas valve; 4. Pressure sensor; 5. Temperature sensor; 6. Condenser; 7. Flasher; 8. First-stage throttling device; 9. Second-stage throttling device; 10. Main throttling device; 11. Ejector air valve; 12. Ejector; 13. Evaporator; 14. Ejector liquid valve; 15. Liquid level sensor; 16. Second-stage heat exchanger; 17. Gas-liquid separator; 18. Electric heating device; 19. First-stage heat exchanger. DETAILED DESCRIPTION

[0027] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present utility model clearer and more understandable, the present utility model will be further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present utility model and are not used to limit the present utility model.

[0028] As Figure 1 , 2 shown, the present utility model provides a refrigeration unit for preventing suction with liquid, including: a compressor 1, a condenser 6, a main throttling device 10, an evaporator 13 and a gas-liquid separator 17 that are connected in sequence to form a main refrigeration circuit. The refrigerant flow direction of the main refrigeration circuit is that the refrigerant discharged from the compressor 1 flows through the condenser 6, the main throttling device 10, the evaporator 13 and the gas-liquid separator 17, and the refrigerant flowing out of the gas-liquid separator 17 is sent back to the compressor 1.

[0029] To achieve the effect of preventing suction with liquid, the refrigeration unit of the present utility model is designed with a first-level protection structure - a primary heat exchanger 19. The primary heat exchanger 19 has a primary transfer pipe and a primary bypass pipe that exchange heat with each other. The outlet of the evaporator 13 is connected to the inlet of the gas-liquid separator 17 through the primary transfer pipe, and the inlet of the primary bypass pipe is connected to the exhaust port of the compressor 1 through a primary hot gas valve 2. At least part of the refrigerant flowing out of the primary bypass pipe is sent to the evaporator 13. Here, the sending to the evaporator 13 can be direct or indirect. For the case of directly sending to the evaporator 13, the outlet of the primary bypass pipe is connected to the evaporator 13. For the case of indirectly sending to the evaporator 13, the outlet of the primary bypass pipe is connected to an intermediate component, and after passing through the intermediate component, it is sent to the evaporator. The intermediate component includes but is not limited to a flash tank 7.

[0030] The first-level protection structure is to use the high-temperature refrigerant led out from the exhaust port of the compressor 1 to provide heat to promote the refrigerant flowing out of the evaporator 13 to be converted into gaseous refrigerant, and then after being separated by the gas-liquid separator 17, it is sent to the compressor 1. At least part of the refrigerant after releasing heat is sent to the evaporator 13. This first-level protection structure has the least impact on the main refrigeration circuit, can prevent the risk of liquid suction of the compressor 1, and can ensure the amount of refrigerant participating in the refrigeration operation in the main circuit.

[0031] As a preferred solution, the refrigeration unit of the present utility model is also designed with a second-level protection structure - an ejector 12. The first inlet of the ejector 12 is connected to the exhaust port of the compressor 1 through an ejector gas extraction valve 11, the second inlet of the ejector 12 is connected to the liquid outlet of the gas-liquid separator 17 through an ejector liquid extraction valve 14, and the outlet of the ejector 12 is connected to the evaporator 13. When the ejector gas extraction valve 11 and the ejector liquid extraction valve 14 are opened, the high-pressure gas discharged from the compressor 1 is used to eject the accumulated liquid refrigerant in the gas-liquid separator 17 back to the evaporator 13, so that the liquid level in the gas-liquid separator 17 drops, thereby reducing the risk of liquid suction of the compressor 1.

[0032] As a preferred solution, the refrigeration unit of the present utility model is also designed with a third-level protection structure - a secondary heat exchanger 16. The secondary heat exchanger 16 has a secondary transfer pipe and a secondary bypass pipe that are mutually heat-exchanged. The gas outlet of the gas-liquid separator 17 is connected to the suction port of the compressor 1 through the secondary transfer pipe, and the inlet of the secondary bypass pipe is connected to the exhaust port of the compressor 1 through the secondary hot gas valve 3. At least part of the refrigerant flowing out of the secondary bypass pipe is sent to the evaporator 13. The sending to the evaporator 13 here can be direct or indirect. For the case of directly sending to the evaporator 13, the outlet of the secondary bypass pipe is connected to the evaporator 13. For the case of indirectly sending to the evaporator 13, the outlet of the secondary bypass pipe is connected to an intermediate component, and after passing through the intermediate component, it is sent to the evaporator. The intermediate component includes but is not limited to a flash tank 7.

[0033] The principle of the third-level protection structure is similar to that of the second-level protection structure. The high-temperature refrigerant led out from the exhaust port of the compressor 1 provides heat to promote the refrigerant flowing out of the gas outlet of the gas-liquid separator 17 to be transformed into gaseous refrigerant. Since the third-level protection structure directly heats the refrigerant on the suction side of the compressor 1, it has an obvious impact on the suction temperature and exhaust temperature of the compressor 1, and it is suitable for use after the risk of liquid carry-over in suction increases.

[0034] As a preferred solution, the refrigeration unit of the present utility model is also designed with a fourth-level protection structure - an electric heating device 18. The electric heating device 18 is installed inside the gas-liquid separator 17 and directly contacts and heats the refrigerant. The present utility model does not impose special restrictions on the type of the electric heating device 18. To increase the contact area between the electric heating device 18 and the refrigerant, a corrugated electric heater can be selected.

[0035] The advantage of this design is that it can prevent liquid carry-over in suction during both the startup process and the operation process of the refrigeration unit. During the startup process, when the refrigeration unit receives a startup command, the electric heating device 18 inside the gas-liquid separator 17 is simultaneously turned on to heat the internal environment of the gas-liquid separator 17, which can heat the refrigerant sucked from the evaporator 13, causing the liquid refrigerant to be transformed into gaseous state after passing through the gas-liquid separator 17, and preventing liquid hammer caused by the rapid increase in frequency within a short time during the compressor startup process. During the operation process, the electric heating device 18 can also be turned on to heat the internal environment of the gas-liquid separator 17 to transform the refrigerant into gaseous state. However, due to the relatively high energy consumption generated by the electric heating, the electric heating device 18 is usually turned on last to reduce energy waste.

[0036] Such as Figure 1 、 2As shown, in some feasible embodiments, the refrigeration unit further includes: a flash tank 7, the inlet of the flash tank 7 is connected to the condenser 6 through a primary throttling device 8, the gas outlet of the flash tank 7 is connected to the gas replenishing port of the compressor 1, the liquid outlet of the flash tank 7 is connected to the evaporator 13 through a secondary throttling device 9, and the outlet of the primary bypass pipe and / or the outlet of the secondary bypass pipe are connected to the flash tank 7.

[0037] As Figure 3 、 4 As shown, in some other feasible embodiments, the refrigeration unit further includes: a flash tank 7, the inlet of the flash tank 7 is connected to the condenser 6 through a primary throttling device 8, the gas outlet of the flash tank 7 is connected to the gas replenishing port of the compressor 1, the liquid outlet of the flash tank 7 is connected to the evaporator 13 through a secondary throttling device 9, and the outlet of the primary bypass pipe and / or the outlet of the secondary bypass pipe are connected to the evaporator 13.

[0038] Both of the above two embodiments are designed with a flash tank 7. After the primary throttling device 8 reduces the pressure of the refrigerant sent out by the condenser 6, the refrigerant in the mixed state will be separated into gas and liquid. After entering the flash tank 7, the gas phase part and the liquid phase part are processed separately. The gas phase part can be sent to the compressor 1 for intermediate gas replenishment, which helps to reduce the exhaust temperature of the compressor and improve the operating efficiency of the compressor. The liquid phase part is then decompressed through the secondary throttling device 9 and continues to enter the evaporator 13 for the evaporation process to complete the refrigeration cycle. On the basis of the refrigeration unit being designed with a flash tank 7, the outlet of the primary bypass pipe and the outlet of the secondary bypass pipe can be selectively connected to the evaporator 13 or the flash tank 7.

[0039] It should be noted that the protection structure proposed by the present utility model is applicable to refrigeration units with the risk of gas-liquid carry-over, especially refrigeration units using centrifugal compressors. The reason is that the structure of the centrifugal compressor is more complex, the operating speed is high, and the requirements for the state of the inhaled gas are more stringent. Through the multiple protection structures in the above solutions, the reliability of the centrifugal compressor can be significantly improved and the service life can be extended.

[0040] In addition, the primary heat exchanger 19 and the secondary heat exchanger 16 in the above text can adopt plate heat exchangers, the main throttling device 10 adopts a throttle valve, the primary throttling device 8 and the secondary throttling device 9 can adopt orifice plates. The throttle valve has higher flexibility and control accuracy and can meet the adjustment requirements of the refrigeration main circuit, while the orifice plate can accurately control the flow rate of the refrigerant to keep it stable within a certain range, with low cost and stable performance. The primary hot gas valve 2, the secondary hot gas valve 3, the ejector gas extraction valve 11, the ejector liquid extraction valve 14, etc. all adopt electric valves for easy automatic control.

[0041] As Figure 1 、 2As shown in the figure, for the convenience of understanding, an application example of the present utility model is taken for illustration. The refrigeration unit is designed with the above four - layer protection structure. The outlet of the first - stage bypass pipe and the outlet of the second - stage bypass pipe are connected to the flash tank 7. The operation process of the refrigeration unit is as follows:

[0042] The refrigerant compressed by the compressor 1 is discharged to the condenser 6 through the exhaust pipe. The refrigerant coming out of the condenser 6 is divided into two paths: one path flows through the first - stage throttling device 8 and then to the flash tank 7, and then through the second - stage throttling device 9 and then to the evaporator 13; the other path flows through the main throttling device 10 and then to the evaporator 13. The gaseous refrigerant at the top of the flash tank 7 enters the gas - replenishing port of the compressor 1 through the gas - replenishing pipe. The refrigerant flowing out of the evaporator 13 first exchanges heat through the first - stage heat exchanger 19, and then enters the middle - lower part of the gas - liquid separator 17. After the refrigerant realizes gas - liquid separation in the gas - liquid separator 17, it exchanges heat through the second - stage heat exchanger 16 again, and then is sent back to the compressor 1 through the suction pipe to complete the refrigeration cycle.

[0043] The high - temperature and high - pressure gas taken out from the exhaust pipe of the compressor 1 is divided into two paths. One path passes through the first - stage hot gas valve 2 and is discharged into the first - stage heat exchanger 19, exchanges heat with the low - temperature refrigerant flowing out of the evaporator 13 in the first - stage heat exchanger 19, and then returns to the flash tank 7; the other path passes through the second - stage hot gas valve 3 and is discharged into the second - stage heat exchanger 16, exchanges heat with the low - temperature refrigerant flowing out of the gas - liquid separator 17 in the second - stage heat exchanger 16, and then returns to the flash tank 7.

[0044] Another path of the high - temperature and high - pressure gas taken out from the exhaust pipe of the compressor 1 passes through the ejector air - extraction valve 11 and then through the ejector 12. The liquid - outlet at the bottom of the gas - liquid separator 17 is connected to the ejector 12 through the ejector liquid - extraction valve 14.

[0045] After the refrigeration unit is started, by opening the first - stage hot gas valve 2 and the second - stage hot gas valve 3, the high - temperature refrigerant discharged by the compressor 1 can be used to heat the low - temperature refrigerant flowing out of the evaporator 13, promoting the transformation of the liquid refrigerant into gaseous refrigerant; by opening the ejector air - extraction valve 11 and the ejector liquid - extraction valve 14, the liquid refrigerant accumulated in the gas - liquid separator 17 can be ejected back to the evaporator 13; by opening the electric heating device 18 to heat the internal environment of the gas - liquid separator 17, the liquid refrigerant is transformed into gaseous refrigerant.

[0046] It should be noted that the first - layer protection structure to the fourth - layer protection structure can all be set independently. In actual application, on the basis of the refrigeration unit having the first - layer protection structure, at least one of the second - layer protection structure to the fourth - layer protection structure can also be selected to be added to improve the anti - liquid - carry - over - during - suction effect.

[0047] To achieve the automation of the refrigeration unit control, the refrigeration unit further includes: a controller and a collection device. The controller is used to control the working state of the refrigeration unit. The collection device is communicatively connected to the controller. The collection device includes, but is not limited to, a pressure sensor 4, a temperature sensor 5, an electrical sensor, and a liquid level sensor 15, etc. Among them, the pressure sensor 4 and the temperature sensor 5 are used to collect the exhaust side parameters and / or the suction side parameters of the compressor 1. The electrical sensor is used to collect the current and / or voltage of the compressor 1. The liquid level sensor 15 is used to collect the liquid level in the gas-liquid separator 17. The controller receives the detection data of the collection device and controls the opening or closing of the protection structure according to the detection data. For the specific control logic, please refer to the control method below.

[0048] As Figure 5 shown, the present invention also proposes a control method for the refrigeration unit, including:

[0049] Collect the working parameters during the operation of the refrigeration unit;

[0050] Judge whether the working parameters reach the preset execution conditions corresponding to any one of the protection measures;

[0051] If so, execute the protection measure;

[0052] The first protection measure is to draw out the refrigerant from the exhaust port of the compressor and exchange heat with the refrigerant on the inlet side of the gas-liquid separator. The first protection measure corresponds to the first layer of protection structure above.

[0053] The second protection measure is to draw out the liquid refrigerant from the gas-liquid separator and mix it with the gaseous refrigerant drawn out from the exhaust port of the compressor and send it to the evaporator. The second protection measure corresponds to the second layer of protection structure above.

[0054] The third protection measure is to draw out the refrigerant from the exhaust port of the compressor and exchange heat with the refrigerant on the suction side of the compressor. The third protection measure corresponds to the third layer of protection structure above.

[0055] The fourth protection measure is to turn on the electric heating device in the gas-liquid separator. The fourth protection measure corresponds to the fourth layer of protection structure above.

[0056] The refrigeration unit can execute at least one of the above four protection measures. In practical applications, the preferred solution is to select at least two protection measures.

[0057] The advantage of this design is to design corresponding preset execution conditions for different protection measures, and execute the protection measure when the working parameters of the unit reach any one of the preset execution conditions, so as to realize the effective control of the unit during operation and improve the reliability of the unit.

[0058] In some embodiments of the present utility model, the preset execution conditions of the first protection measure, the third protection measure, and the fourth protection measure are all composed of compressor parameter conditions, and the preset execution condition of the second protection measure is composed of compressor parameter conditions and gas-liquid separator parameter conditions.

[0059] The reason for this design is that the compressor parameter conditions can reflect the working state of the compressor, and then analyze the risk level of liquid carryover in suction according to the operating conditions of the compressor. Since the first measure, the third measure, and the fourth measure all convert the refrigerant related to the gas-liquid separator into a gaseous state by heating, and the measure principles are similar, the involved parameters are the same. The second measure is to draw out the liquid refrigerant in the gas-liquid separator, and the relevant parameters of the gas-liquid separator must be increased to achieve the effect of accurate control. Otherwise, excessive drawing out of the liquid refrigerant will directly affect the separation effect and cause the gas-liquid separator to malfunction.

[0060] As a preferred solution, the compressor parameter conditions of the second protection measure include the preset execution conditions of the first protection measure, the preset execution conditions of the third protection measure include the compressor parameter conditions of the second protection measure, and the preset execution conditions of the fourth protection measure include the preset execution conditions of the third protection measure. That is to say, when the compressor parameter conditions of the second protection measure are met, the preset execution conditions of the first protection measure must be met, that is, the first protection measure has been executed; when the preset execution conditions of the third protection measure are met, the compressor parameter conditions of the second protection measure and the preset execution conditions of the first protection measure must be met, that is, the first protection measure has been executed. If the gas-liquid separator parameter conditions of the second protection measure have been achieved, the second protection measure has also been executed; when the preset execution conditions of the fourth protection measure are met, the preset execution conditions of the third protection measure, the compressor parameter conditions of the second protection measure, and the preset execution conditions of the first protection measure must be met, that is, the first protection measure and the third protection measure have both been executed. If the gas-liquid separator parameter conditions of the second protection measure have been achieved, the second protection measure has also been executed.

[0061] The advantage of this design is that the protection measures are progressive. When a single measure cannot meet the protection requirements, other protection measures are added to execute, which can not only ensure the stable operation of the unit but also minimize the additional energy consumption caused by the execution of the protection measures.

[0062] In some embodiments, the working parameters include: the current volatility D0 of the compressor, the exhaust superheat △T0 of the compressor, and the liquid level L0 of the gas-liquid separator;

[0063] The preset execution condition of the first protection measure is D0≥D1 and △T0≤△T1;

[0064] The preset execution condition for the second protection measure is D0≥D2 and △T0≤△T2 and L0≥L;

[0065] The preset execution condition for the third protection measure is D0≥D3 and △T0≤△T3;

[0066] The preset execution condition for the fourth protection measure is D0≥D4 and △T0≤△T4;

[0067] Among them, D1, D2, D3, and D4 are all set volatilities, △T1, △T2, △T3, and △T4 are all set superheats, L is the set liquid level, D1<D2<D3<D4, and △T4≤△T3≤△T2≤△T1.

[0068] The reason for this design is that when liquid is carried in the suction, the compressor requires more energy to process the liquid refrigerant, which usually causes the current to increase. Therefore, the current volatility of the compressor can, to a certain extent, reflect whether there is liquid carried in the suction of the compressor. Under normal circumstances, if liquid is carried in the suction of the compressor, the exhaust temperature may increase. If the condensation temperature remains unchanged or changes little, then the exhaust superheat may decrease accordingly. Therefore, the decrease in the exhaust superheat can also indirectly indicate whether there is liquid carried in the suction of the compressor. The utility model combines the current volatility and the exhaust superheat to achieve the effect of accurately analyzing the liquid carried in the suction of the compressor, and then executes the corresponding protection measures to effectively ensure the reliability and safety of the compressor.

[0069] It should be understood that in practical applications, relevant electrical parameters such as the voltage volatility of the compressor can also be used to replace the current volatility, and relevant operating parameters such as the suction superheat can also be used to replace the exhaust superheat. The design principle is similar as long as it can reflect the changes of the compressor when liquid is carried in the suction.

[0070] In order to prevent the situation that the above four protection measures still cannot achieve the ideal effect under extreme working conditions, in some embodiments of the present utility model, the control method further includes:

[0071] Judging whether the working parameters of the refrigeration unit reach the preset shutdown condition;

[0072] If so, it indicates that the current operating state of the refrigeration unit is poor, and the refrigeration unit is controlled to shut down;

[0073] Among them, the preset shutdown condition is D0≥D and △T0≤△T, D is the set volatility, △T is the set superheat, D4<D, and △T≤△T4.

[0074] This design can prevent the refrigeration unit from malfunctioning due to long-term operation under poor conditions. By setting preset shutdown conditions, the unit can automatically shut down before approaching poor conditions, avoiding failures and improving the stability and reliability of the refrigeration unit.

[0075] It should be understood that the current volatility D0 above is the change rate of the compressor operating current within the judgment period T. The exhaust superheat △T0 and the current volatility D0 are detected within the same period T. The exhaust superheat = exhaust temperature - exhaust saturation temperature. Generally, the value range of the set volatility is 0% - 100%, the value range of the set superheat is 0 - 10°C, and the value range of L is 0% - 100% of the gas-liquid separator capacity. The specific values of the set volatility, the set superheat, and the set liquid level can all be designed according to actual needs. For example, in some feasible embodiments, D1 is taken as 5%, D2 is taken as 10%, D3 is taken as 15%, D4 is taken as 20%, D is taken as 25%, △T1 is taken as 6°C, △T2 is taken as 5°C, △T3 is taken as 4°C, △T4 is taken as 3°C, △T is taken as 2.5°C, and L is taken as 10% of the gas-liquid separator capacity.

[0076] In some feasible embodiments of the present invention, to achieve effective protection during the startup process of the refrigeration unit, the control method includes: turning on the electric heating device in the gas-liquid separator when the refrigeration unit starts, turning off the electric heating device after the refrigeration unit completes the startup process, and then collecting the working parameters during the operation of the refrigeration unit and determining whether to execute protective measures based on the working parameters.

[0077] The advantage of this design is to turn on the electric heater simultaneously when the compressor starts. By using the electric heating method, the internal environment temperature of the gas-liquid separator can be quickly increased, the refrigerant sucked from the evaporator can be heated, and the liquid refrigerant can be changed into a gaseous state after passing through the gas-liquid separator, preventing liquid hammer caused by the rapid increase in frequency within a short time during the compressor startup process. After the compressor completes the startup process (for example, after the unit has been turned on for a certain time, it is defaulted to complete the startup process and enter the operation process), the electric heating device is turned off, and protective measures are reasonably executed according to the operating state of the unit to reduce the energy consumption of the unit.

[0078] Such as Figure 5 As shown, for easy understanding, an application example of the present invention is used for illustration. The above four-fold protective measures are formulated for the operation process of the refrigeration unit:

[0079] If the current volatility D0 ≥ D1 and the exhaust superheat △T0 ≤ △T1 within the judgment period T, the first-stage hot gas valve is opened. If the current volatility D0 < D1 or the exhaust superheat △T0 >

[0080] △T1 in the next period T, the first-stage hot gas valve is closed;

[0081] During the judgment period T, determine whether the current volatility D0≥D2 and the exhaust superheat △T0≤△T2. If the liquid level L0 of the gas-liquid separator is ≥L, continue to open the ejector gas extraction valve and the ejector liquid extraction valve to eject the liquid refrigerant in the gas-liquid separator back to the evaporator; if the current volatility D0<D2 or the exhaust superheat △T0>△T2 in the next period T, close the ejector gas extraction valve and the ejector liquid extraction valve.

[0082] During the judgment period T, determine whether the current volatility D0≥D3 and the exhaust superheat △T0≤△T3, then continue to open the second-stage hot gas valve; if the current volatility D0<D3 or the exhaust superheat △T0>△T3 in the next period T, close the second-stage hot gas valve.

[0083] During the judgment period T, determine whether the current volatility D0≥D4 and the exhaust superheat △T0≤△T4, then continue to turn on the electric heating device in the gas-liquid separator; if the current volatility D0<D4 or the exhaust superheat △T0>△T4 in the next period T, turn off the electric heating device.

[0084] During the judgment period T, determine whether the current volatility D0≥D and the exhaust superheat △T0≤△T, then the unit reports an alarm of "liquid carry-over at the compressor suction" and performs a fault shutdown to prompt the user to troubleshoot and repair the unit.

[0085] It should be noted that the terms used above are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present invention. When the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or their combinations. For the actions and steps in the devices and methods shown in the specification and drawings, as long as there is no specific limitation on the execution order, and as long as the output of the previous process is not used in the subsequent process, they can be implemented in any order. The similar sequential terms used for convenience of description do not mean that they must be implemented in such an order.

[0086] For technologies, methods, and devices known to those of ordinary skill in the relevant art, they may not be discussed in detail, but in appropriate cases, the said technologies, methods, and devices should be regarded as part of the authorization specification. In all the examples shown and discussed here, any specific value should be interpreted as merely exemplary and not as a limitation. Therefore, other examples of the exemplary embodiments may have different values. It should be noted that similar reference numerals and letters represent similar items in the following drawings. Therefore, once an item is defined in one drawing, it does not need to be further discussed in the subsequent drawings.

[0087] The above are only the preferred embodiments of the present utility model and are not intended to limit the present utility model. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present utility model shall be included within the protection scope of the present utility model.

Claims

1. Refrigeration unit preventing suction of liquid, comprising: A compressor, a condenser, a main throttling device, an evaporator, and a gas-liquid separator that are sequentially connected to form a main refrigeration circuit, characterized in that it further includes: a primary heat exchanger having a primary transfer pipe and a primary bypass pipe that exchange heat with each other, an outlet of the evaporator is connected to an inlet of the gas-liquid separator through the primary transfer pipe, an inlet of the primary bypass pipe is connected to an exhaust port of the compressor through a primary hot gas valve, and at least part of the refrigerant flowing out of the primary bypass pipe is sent to the evaporator.

2. The refrigeration unit according to claim 1, characterized in that, It further includes: An ejector, a first inlet of the ejector is connected to the exhaust port of the compressor through an ejector gas extraction valve, a second inlet of the ejector is connected to a liquid outlet of the gas-liquid separator through an ejector liquid extraction valve, and an outlet of the ejector is connected to the evaporator.

3. The refrigeration unit according to claim 1, wherein, It further includes: A secondary heat exchanger having a secondary transfer pipe and a secondary bypass pipe that exchange heat with each other, an outlet of the gas-liquid separator is connected to a suction port of the compressor through the secondary transfer pipe, an inlet of the secondary bypass pipe is connected to the exhaust port of the compressor through a secondary hot gas valve, and at least part of the refrigerant flowing out of the secondary bypass pipe is sent to the evaporator.

4. The refrigeration unit according to claim 1, characterized in that, An electric heating device is installed in the gas-liquid separator.

5. The refrigeration unit according to claim 3, characterized in that, The refrigeration unit further includes: a flash tank, an inlet of the flash tank is connected to the condenser through a primary throttling device, an outlet of the flash tank is connected to a gas supplement port of the compressor, and a liquid outlet of the flash tank is connected to the evaporator through a secondary throttling device.

6. The refrigeration unit according to claim 5, characterized in that, An outlet of the primary bypass pipe and / or an outlet of the secondary bypass pipe are connected to the flash tank.

7. The refrigeration unit according to claim 3, characterized in that, An outlet of the primary bypass pipe and / or an outlet of the secondary bypass pipe are connected to the evaporator.

8. The refrigeration unit according to claim 1, characterized in that, It further includes: A controller for controlling the working state of the refrigeration unit, and a collection device communicatively connected to the controller, the collection device includes a pressure sensor, a temperature sensor, and an electrical sensor; Wherein, the pressure sensor and the temperature sensor are used to collect exhaust side parameters and / or suction side parameters of the compressor, and the electrical sensor is used to collect current and / or voltage of the compressor.

9. The refrigeration unit according to claim 8, characterized in that, The collection device further includes: a liquid level sensor for collecting the liquid level in the gas-liquid separator.

10. The refrigeration unit according to any one of claims 1 to 9, characterized in that, The compressor is a centrifugal compressor.

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