Refrigerating system and control method thereof

Abstract

The invention provides a refrigerating system which comprises a compressor, an oil separator, an oil way electromagnetic valve, a condenser, an evaporator, a bypass pipe and a bypass electromagnetic valve. The oil separator is connected to the output end of the compressor. The oil passage solenoid valve is disposed between the oil separator and the compressor. And the condenser is connected to the oil separator. The evaporator is connected to the condenser. The bypass pipe is provided with a first end and a second end opposite to the first end, the first end is connected between the oil separator and the condenser, and the second end is connected between the evaporator and the input end of the compressor. And the bypass electromagnetic valve is arranged on the bypass pipe. The invention also provides a control method of the refrigeration system.

Description

Technical Field

[0001] The invention relates to a refrigeration system, and in particular to a refrigeration system and a control method thereof. Background Art

[0002] In the refrigeration system, the compressor extracts the low-pressure gaseous refrigerant in the evaporator, compresses the low-pressure gaseous refrigerant into high-pressure gaseous refrigerant, and then transports the high-pressure gaseous refrigerant to the condenser. The high-pressure gaseous refrigerant releases heat in the condenser to form a high-pressure liquid refrigerant. Then, the high-pressure liquid refrigerant flows through the expansion valve and is reduced in pressure to become a low-pressure liquid refrigerant. Then, the low-pressure liquid refrigerant flows into the evaporator and absorbs heat in the evaporator to form a low-pressure gaseous refrigerant, completing the refrigeration cycle.

[0003] Specifically, the high-pressure gaseous refrigerant sent from the compressor to the condenser is accompanied by lubricating oil. The high-pressure gaseous refrigerant and lubricating oil are first sent to the oil separator, where they are separated and then sent to the condenser. Therefore, the oil separator is in a high-pressure state and generates a huge pressure difference with the input end of the compressor, causing the compressor to be under a huge load after being shut down and restarted, which is not only easy to cause damage to internal parts (such as motors, bearings or other parts), but also causes the operating efficiency of the compressor to decline, resulting in increased energy consumption. Summary of the invention

[0004] The present invention is directed to a refrigeration system and a control method thereof, which are helpful to reduce the startup load of a compressor and avoid bearing damage caused by failure to lubricate the compressor smoothly during startup.

[0005] According to one embodiment of the present invention, a refrigeration system includes a compressor, an oil separator, an oil circuit solenoid valve, a condenser, an evaporator, a bypass pipe and a bypass solenoid valve. The compressor has an input end and an output end relative to the input end. The oil separator is connected to the output end of the compressor and is used to supply lubricating oil before the compressor is started. The oil circuit solenoid valve is arranged between the oil separator and the compressor. The condenser is connected to the oil separator. The evaporator is connected to the condenser. The bypass pipe has a first end and a second end relative to the first end, wherein the first end is connected between the oil separator and the condenser, and the second end is connected between the evaporator and the input end of the compressor. The bypass solenoid valve is arranged on the bypass pipe and is used to balance the pressure difference between the oil separator and the evaporator.

[0006] According to one embodiment of the present invention, the refrigeration system further comprises a first check valve and a second check valve. The first check valve is arranged between the output end of the compressor and the oil separator. The second check valve is arranged between the oil separator and the condenser, and the first end of the bypass pipe is connected between the oil separator and the second check valve.

[0007] According to an embodiment of the present invention, the refrigeration system further comprises a cooling water tower and a cooling water pump. The cooling water tower is connected to the water outlet of the condenser, and the cooling water tower is provided with a fan. The cooling water tower is connected to the water inlet of the condenser through the cooling water pump.

[0008] According to an embodiment of the present invention, the refrigeration system further comprises a liquid pipe solenoid valve, which is arranged between the condenser and the evaporator and is used to close before the compressor is shut down.

[0009] According to an embodiment of the present invention, the refrigeration system further includes an expansion valve disposed between the liquid pipe solenoid valve and the evaporator.

[0010] According to one embodiment of the present invention, the refrigeration system further comprises an oil cooler, an economizer and a liquid-gas separator. The oil cooler is connected between the compressor and the oil separator. The economizer is connected to the condenser. The liquid-gas separator is connected between the evaporator and the input end of the compressor.

[0011] According to an embodiment of the present invention, the refrigeration system further includes a drying filter connected between the condenser and the economizer.

[0012] According to one embodiment of the present invention, a control method for a refrigeration system includes: receiving a start signal; starting a cooling water pump and a fan of a cooling water tower; determining a pressure difference between an oil separator and an evaporator; if the pressure difference is greater than a pressure difference setting value, opening a bypass solenoid valve to balance the pressure difference between the oil separator and the evaporator; if the pressure difference is less than or equal to the pressure difference setting value, opening an oil circuit solenoid valve to supply lubricating oil before starting a compressor; starting the compressor after a first set time has passed since the oil circuit solenoid valve was opened; and, after a second set time has passed since the compressor was started, closing the oil circuit solenoid valve.

[0013] According to an embodiment of the present invention, when the oil circuit solenoid valve is opened, a countdown is started from a first set time, and when the countdown ends, the compressor is started.

[0014] According to an embodiment of the present invention, when the compressor is started, a countdown is performed from the second set time, and when the countdown ends, the oil circuit solenoid valve is closed.

[0015] According to one embodiment of the present invention, the control method of the above-mentioned refrigeration system also includes: receiving a shutdown signal; closing the liquid pipe solenoid valve to reduce the pressure of the evaporator; detecting the pressure of the evaporator; if the pressure of the evaporator is less than or equal to the pressure setting value, turning off the compressor; and, if the pressure of the evaporator is greater than the pressure setting value, turning off the compressor after a third set time.

[0016] According to an embodiment of the present invention, when the liquid pipe solenoid valve is closed, a countdown is started from the third set time. If the pressure of the evaporator is greater than the pressure setting value, the compressor is turned off at the end of the countdown.

[0017] Based on the above, the refrigeration system and control method of the present invention can balance the pressure difference between the oil separator and the evaporator by starting the bypass solenoid valve to reduce the starting load of the compressor, which not only helps to improve the operating efficiency, but also reduces energy consumption to achieve the purpose of environmental protection and energy saving. In addition, after the pressure difference between the oil separator and the evaporator is less than or equal to the pressure difference setting value, the oil separator can supply lubricating oil to the compressor before starting to lubricate the bearings inside the compressor, and then start the compressor. The pre-lubricated bearings help to reduce the operating resistance of the compressor after starting, which not only avoids damage to internal parts (such as motors, bearings or other parts), but also helps to improve operating efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 is a schematic diagram of the architecture of a refrigeration system according to an embodiment of the present invention;

[0019] Figure 2 is a schematic diagram of a startup flow chart of a compressor of a refrigeration system according to an embodiment of the present invention;

[0020] Figure 3 The figure is a schematic diagram of a compressor shutdown process of a refrigeration system according to an embodiment of the present invention. DETAILED DESCRIPTION

[0021] Reference will now be made in detail to exemplary embodiments of the present invention, examples of which are illustrated in the accompanying drawings. Whenever possible, the same reference numerals are used in the drawings and the description to refer to the same or like parts.

[0022] Figure 1 This is a schematic diagram of the refrigeration system according to an embodiment of the present invention. Figure 1 In this embodiment, the refrigeration system 100 includes a compressor 110, an oil separator 120, an oil cooler 130, an oil circuit solenoid valve 131, a condenser 140, an economizer 150, an evaporator 160, a gas-liquid separator 170, a bypass pipe 101, and a bypass solenoid valve 102. For example, the compressor 110 may be a single-stage compressor or a two-stage compressor, which is not limited in the present invention.

[0023] Specifically, the oil separator 120 is used to supply lubricating oil to the compressor 110, and the compressor 110 has an input end 111 and an output end 112 relative to the input end 111. The oil separator 120 is connected to the output end 112 of the compressor 110, and the oil separator 120 and the output end 112 of the compressor 110 are located on the high-pressure side of the system. On the other hand, the oil cooler 130 is connected between the compressor 110 and the oil separator 120, and is used to cool the lubricating oil supplied by the oil separator 120, and supply the cooled lubricating oil to the compressor 110.

[0024] like Figure 1 As shown, the oil circuit solenoid valve 131 is disposed between the oil separator 120 and the compressor 110, and the supply of lubricating oil to the compressor 110 is stopped by closing the oil circuit solenoid valve 131, and conversely, the supply of lubricating oil to the compressor 110 is stopped by opening the oil circuit solenoid valve 131. Further, the oil circuit solenoid valve 131 is disposed between the oil cooler 130 and the compressor 110, and the supply of cooled lubricating oil to the compressor 110 is stopped by closing the oil circuit solenoid valve 131.

[0025] The condenser 140 is connected to the oil separator 120, wherein the condenser 140 has a water outlet 141 and a water inlet 142, and the heat dissipation water tower 180 is connected to the water outlet 141 to receive water from the condenser 140. In addition, the heat dissipation water tower 180 is provided with a fan 181, and the heat dissipation water tower 180 is connected to the water inlet 142 through a heat dissipation water pump 182 to send cooled water to the condenser 140, thereby taking away the heat of the high-temperature refrigerant in the condenser 140, and then discharging the water with increased temperature through the water outlet 141, and then circulating in sequence.

[0026] Please refer to Figure 1 In this embodiment, the evaporator 160 is connected to the condenser 140, and the economizer 150 is connected between the condenser 140 and the evaporator 160. Further, the refrigeration system 100 further includes a filter drier 190, a liquid pipe solenoid valve 105, and an expansion valve 106, and the filter drier 190 is connected between the condenser 140 and the economizer 150. In addition, the liquid pipe solenoid valve 105 is disposed between the condenser 140 and the evaporator 160, and specifically, it can be disposed between the economizer 150 and the evaporator 160, and the expansion valve 106 is disposed between the liquid pipe solenoid valve 105 and the evaporator 160. By closing the liquid pipe solenoid valve 105, the liquid refrigerant is stopped from being sent to the evaporator 160, and conversely, by opening the liquid pipe solenoid valve 105, the liquid refrigerant is sent to the evaporator 160.

[0027] The liquid-gas separator 170 is connected between the evaporator 160 and the input end 111 of the compressor 110, wherein the evaporator 160, the liquid-gas separator 170 and the input end 111 of the compressor 110 are located on the low-pressure side of the system, and the pressures of the evaporator 160, the liquid-gas separator 170 and the input end 111 of the compressor 110 are substantially equal. On the other hand, the bypass pipe 101 is connected between the high-pressure side and the low-pressure side of the system. Specifically, the bypass pipe 101 has a first end 101a and a second end 101b opposite to the first end 101a, wherein the first end 101a is connected to the high-pressure side, and the second end 101b is connected to the low-pressure side. More specifically, the first end 101a of the bypass pipe 101 is connected between the oil separator 120 and the condenser 140 , and the second end 101b is connected between the evaporator 160 and the input end 111 of the compressor 110 , specifically, between the liquid-gas separator 170 and the input end 111 of the compressor 110 .

[0028] In the present embodiment, the bypass solenoid valve 102 is disposed on the bypass pipe 101 and is located between the first end 101a and the second end 101b. When the bypass solenoid valve 102 is closed, the pressure of the gaseous refrigerant in the oil separator 120 cannot be released from the high-pressure side to the low-pressure side. Conversely, when the bypass solenoid valve 102 is opened, the pressure of the gaseous refrigerant can be released from the high-pressure side to the low-pressure side. In other words, when the bypass solenoid valve 102 is closed, the pressure of the gaseous refrigerant in the oil separator 120 cannot be released from the oil separator 120 to the evaporator 160 via the bypass pipe 101. Conversely, when the bypass solenoid valve 102 is opened, the pressure of the gaseous refrigerant can be released from the oil separator 120 to the evaporator 160 via the bypass pipe 101 to perform bypass pressure relief. That is, the combination of the bypass pipe 101 and the bypass solenoid valve 102 can be used to control the pressure difference between the high-pressure side and the low-pressure side of the system, for example, the pressure difference between the oil separator 120 and the evaporator 160 .

[0029] Please refer to Figure 1 , the refrigeration system 100 further includes a first check valve 103 and a second check valve 104, wherein the first check valve 103 is disposed between the output end 112 of the compressor 110 and the oil separator 120, and the second check valve 104 is disposed between the oil separator 120 and the condenser 140. Specifically, the first check valve 103 can be used to prevent the high-pressure gaseous refrigerant and lubricating oil from flowing back to the compressor 110, or in other words, the first check valve 103 can be used to prevent the refrigerant pressure in the oil separator 120 from flowing back to the compressor 110 when the system is shut down, so as to avoid affecting the pressure in the compressor 110 and the evaporator 160.

[0030] On the other hand, the first end 101a of the bypass pipe 101 is connected between the oil separator 120 and the second check valve 104, and the second check valve 104 can be used to prevent the high-pressure gaseous refrigerant from flowing back from the condenser 140 to the oil separator 120 and the bypass pipe 101. In other words, the second check valve 104 can be used to prevent the refrigerant pressure in the condenser 140 from flowing back to the oil separator 120 and the bypass pipe 101 during bypass pressure relief, so as to avoid affecting the effect of bypass pressure relief.

[0031] like Figure 1 As shown, the refrigeration system 100 further includes an air supply solenoid valve 107, wherein the economizer 150 is connected to the compressor 110 via an air supply pipeline, and the air supply solenoid valve 107 is disposed on the air supply pipeline. When the compressor 110 is in operation or full load state, the air supply solenoid valve 107 can be opened to allow the gaseous refrigerant to be delivered to the compressor 110 via the air supply pipeline.

[0032] Figure 2 Schematic diagram of the start-up process of the compressor of the refrigeration system according to one embodiment of the present invention. Figure 1 and Figure 2 The control method of the refrigeration system 100 is described as follows. In step S10 to step S12, when the refrigeration system 100 receives a start signal, the cooling water pump 182 and the fan 181 of the cooling water tower 180 are first started, and then the pressure difference between the oil separator 120 and the evaporator 160 is determined.

[0033] In step S12 and step S13, it is determined whether the pressure difference between the oil separator 120 and the evaporator 160 is less than or equal to the pressure difference setting value. If the pressure difference between the oil separator 120 and the evaporator 160 is greater than the pressure difference setting value (e.g., 2 to 2.5 kg / cm 2 ), the bypass solenoid valve 102 is opened to balance the pressure difference between the oil separator 120 and the evaporator 160 (or the liquid-gas separator 170). That is to say, before the compressor 110 is started, if the pressure difference between the oil separator 120 and the evaporator 160 is too large, the bypass solenoid valve 102 is opened so that the pressure can be released from the oil separator 120 to the evaporator 160 (or the liquid-gas separator 170) to reduce the starting load of the compressor 110, which not only helps to improve the operating efficiency, but also reduces energy consumption to achieve the purpose of environmental protection and energy saving.

[0034] If the pressure difference between the oil separator 120 and the evaporator 160 is less than or equal to the pressure difference setting value, the oil circuit solenoid valve 131 is opened to supply lubricating oil to the compressor 110 before the compressor 110 is started. At this time, the bypass solenoid valve 102 is still opened to continuously release pressure. In steps S14 to S16, when the oil circuit solenoid valve 131 is opened, a countdown starts from a first set time (e.g., 1 to 2 seconds), and when the countdown ends, the compressor 110 is started. That is, after the oil circuit solenoid valve 131 is opened and lubricating oil is supplied to the compressor 110 for the first set time, the compressor 110 that is fully pre-lubricated is started.

[0035] Specifically, after the pressure difference between the oil separator 120 and the evaporator 160 is less than or equal to the pressure difference setting value, the oil separator 120 first supplies lubricating oil to the compressor 110 before starting to lubricate the bearings inside the compressor 110, and then starts the compressor 110. The pre-lubricated bearings help reduce the operating resistance of the compressor 110 after starting, which can not only avoid damage to internal parts (such as motors, bearings or other parts), but also help improve operating efficiency.

[0036] Please continue to refer to Figure 1 and Figure 2 In step S16 to step S18, when the compressor 110 is started, the countdown starts from the second set time (e.g., 5 to 6 seconds), and when the countdown ends, the bypass solenoid valve 102 is closed to stop the pressure release. In other words, the bypass solenoid valve 102 is closed after the second set time has passed since the compressor 110 was started. In the early stage after the compressor 110 is started (i.e., within the second set time), the bypass solenoid valve 102 is continuously opened to release pressure to reduce the pressure difference, thereby achieving the purpose of reducing the starting load.

[0037] Figure 3 This is a schematic diagram of the process of shutting down the compressor of a refrigeration system according to an embodiment of the present invention. Figure 1 and Figure 3 , the control method of the refrigeration system 100 is described as follows. In step S20 to step S22, when the refrigeration system 100 receives the shutdown signal, the liquid pipe solenoid valve 105 is first closed to stop sending the liquid refrigerant to the evaporator 160 and the liquid-gas separator 170. At this time, the compressor 110 continues to operate, and the refrigerant in the evaporator 160 and the compressor 110 is discharged to reduce the pressure of the evaporator 160. Next, the pressure of the evaporator 160 is detected, and it is determined whether the pressure of the evaporator 160 (or the liquid-gas separator 170) is less than or equal to the pressure setting value. In addition, when the liquid pipe solenoid valve 105 is closed, the countdown starts from the third set time (for example, 30 to 60 seconds).

[0038] In step S22 to step S24, if the pressure of the evaporator 160 is less than or equal to the pressure setting value, the compressor 110 is directly turned off. If the pressure of the evaporator 160 (or the liquid-gas separator 170) is greater than the pressure setting value, the compressor 110 will continue to operate, discharge the gaseous refrigerant in the evaporator 160 and the compressor 110 to reduce the refrigerant pressure in both, and during the countdown process, the pressure of the evaporator 160 is continuously judged to determine whether to directly turn off the compressor 110 or turn off the compressor 110 at the end of the countdown. That is, before turning off the compressor 110, if the pressure of the evaporator 160 is greater than the pressure setting value, the compressor 110, which can continue to operate for up to the third set time after closing the liquid pipe solenoid valve 105, can extract the low-pressure gaseous refrigerant in the liquid-gas separator 170, so that the pressure of the evaporator 160 is reduced.

[0039] Before shutting down the compressor 110, the liquid refrigerant has stopped being sent from the condenser 140 to the evaporator 160 and the liquid-gas separator 170, so that the pressure of the evaporator 160 is greatly reduced, and its surface pressure is approximately equal to 0 kg / cm 2 Since the pressure of the evaporator 160 drops to an extremely low level and the refrigerant is concentrated in the condenser 140 , the pressure difference between the oil separator 120 and the evaporator 160 increases, which not only helps to accelerate the process of balancing the pressure difference between the oil separator 120 and the evaporator 160 , but also helps to reduce the average value of the pressure of the oil separator 120 and the pressure of the evaporator 160 .

[0040] Please refer to Figure 1 and Figure 2 After the refrigeration system 100 receives the start signal, it must first determine the pressure difference between the high-pressure side and the low-pressure side, specifically, determine the pressure difference between the oil separator 120 and the evaporator 160. When the aforementioned pressure difference does not meet the set conditions, the bypass solenoid valve 102 is opened to release the pressure from the high-pressure side to the low-pressure side, specifically, to release the pressure from the oil separator 120 to the evaporator 160, so that the aforementioned pressure difference meets the set conditions. Once the aforementioned pressure difference meets the set conditions, the oil circuit solenoid valve 131 is opened to lubricate the bearings and / or the compression chamber of the compressor 110. After the bearings of the compressor 110 are lubricated for a period of time, the compressor 110 is started again, so that the compressor 110 is injected with lubricating oil before and after starting to reduce the loss of the bearings.

[0041] Please refer to Figure 1 and Figure 3After receiving the shutdown signal, the refrigeration system 100 directly closes the liquid pipe solenoid valve 105 and determines the pressure of the evaporator 160 within a period of time. Once the pressure of the evaporator 160 meets the set condition, the compressor 110 is directly shut down. On the contrary, once the pressure of the evaporator 160 does not meet the set condition, the compressor 110 continues to operate during the period of time to reduce the pressure of the evaporator 160, and continues to determine the pressure of the evaporator 160, or the compressor 110 stops operating after the period of time.

[0042] Please refer to Figure 1 and Figure 3 Before the compressor 110 stops running, the liquid pipe solenoid valve 105 is closed to stop sending the refrigerant from the condenser 140 to the evaporator 160, the liquid-gas separator 170 and the compressor 110. At this time, the compressor 110 continues to discharge the refrigerant on the low-pressure side to the oil separator 120 and the condenser 140, so that the refrigerant pressure in the evaporator 160, the liquid-gas separator 170 and the compressor 110 is reduced.

[0043] In contrast, after the compressor 110 stops operating, the first check valve 103 can prevent the refrigerant pressure in the oil separator 120 from flowing back into the compressor 110, so that the evaporator 160, the liquid-gas separator 170 and the compressor 110 can maintain a relatively low pressure when the compressor 110 stops operating. Therefore, when the compressor 110 is restarted, since the average pressure of the evaporator 160 and the oil separator 120 is low, the starting load of the compressor 110 is relatively reduced, thereby reducing the load of the components of the compressor 110. On the other hand, since the average pressure between the evaporator 160 and the oil separator 120 is low, when the compressor 110 starts, the refrigerant easily pushes open the first check valve 103, so that the gas in the compressor 110 can be discharged smoothly.

[0044] In addition, since the pressure difference between the oil separator 120 and the compressor 110 is relatively high, when the bypass solenoid valve 102 is opened, the bypass effect of releasing the refrigerant pressure from the high-pressure side to the low-pressure side is better, and before the compressor 110 is started, there is sufficient pressure difference to drive the lubricating oil from the oil separator 120 to be smoothly injected into the compressor 110, so as to achieve the purpose of pre-lubrication of the bearings before the compressor 110 is started, which can not only reduce the starting resistance of the components, but also avoid bearing damage.

[0045] In summary, the refrigeration system and control method of the present invention can balance the pressure difference between the oil separator and the evaporator by starting the bypass solenoid valve to reduce the starting load of the compressor, which not only helps to improve the operating efficiency, but also reduces energy consumption to achieve the purpose of environmental protection and energy saving. In addition, after the pressure difference between the oil separator and the evaporator is less than or equal to the pressure difference setting value, the oil separator can supply lubricating oil to the compressor before starting to lubricate the bearings inside the compressor, and then start the compressor. The pre-lubricated bearings help to reduce the operating resistance of the compressor after starting, which can not only avoid damage to internal parts (such as motors, bearings or other parts), but also help to improve operating efficiency.

[0046] In addition, before shutting down the compressor, close the liquid pipe solenoid valve to stop delivering liquid refrigerant to the evaporator and liquid-gas separator, and then continue to operate the compressor to discharge the refrigerant on the low-pressure side, which greatly reduces the pressure of the evaporator. Because the pressure of the evaporator drops to an extremely low level, the pressure difference between the oil separator and the evaporator increases, so that the bypass procedure at the next startup can accelerate the process of balancing the pressure difference between the oil separator and the evaporator.

[0047] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A refrigeration system, characterized in that: include: A compressor having an input and an output opposite to the input; an oil separator connected to the output end of the compressor and used to supply lubricating oil before starting the compressor; An oil circuit solenoid valve is arranged between the oil separator and the compressor; a condenser connected to the oil separator; an evaporator connected to the condenser; a bypass pipe having a first end and a second end opposite to the first end, wherein the first end is connected between the oil separator and the condenser, and the second end is connected between the evaporator and the input end of the compressor; and A bypass solenoid valve is arranged on the bypass pipe and is used to balance the pressure difference between the oil separator and the evaporator.

2. The refrigeration system according to claim 1, characterized in that: Also includes: a first check valve, disposed between the output end of the compressor and the oil separator; as well as The second check valve is disposed between the oil separator and the condenser, and the first end of the bypass pipe is connected between the oil separator and the second check valve.

3. The refrigeration system according to claim 1, characterized in that: Also includes: A heat dissipation water tower connected to the water outlet of the condenser, and the heat dissipation water tower is provided with a fan; as well as A cooling water pump, wherein the cooling water tower is connected to the water inlet of the condenser through the cooling water pump.

4. The refrigeration system according to claim 1, characterized in that: Also includes: The liquid pipe solenoid valve is arranged between the condenser and the evaporator, and is used for closing before the compressor is shut down.

5. The refrigeration system according to claim 4, characterized in that: Also includes: The expansion valve is arranged between the liquid pipe solenoid valve and the evaporator.

6. The refrigeration system according to claim 1, characterized in that: Also includes: an oil cooler connected between the compressor and the oil separator; an economizer connected between the condenser and the evaporator; as well as A liquid-gas separator is connected between the evaporator and the input end of the compressor.

7. The refrigeration system according to claim 6, characterized in that: Also includes: A drying filter is connected between the condenser and the economizer.

8. A method for controlling a refrigeration system, characterized in that: include: receiving a start signal; Start the cooling water pump and the cooling tower fan; Determine the pressure difference between the oil separator and the evaporator; If the pressure difference is greater than the pressure difference setting value, the bypass solenoid valve is opened to balance the pressure difference between the oil separator and the evaporator; If the pressure difference is less than or equal to the pressure difference setting value, the oil circuit solenoid valve is opened to supply lubricating oil before the compressor is started; After the oil circuit solenoid valve is opened for a first set time, starting the compressor; as well as After the second set time has passed since the compressor started, the bypass solenoid valve is closed.

9. The control method of the refrigeration system according to claim 8, characterized in that: When the oil circuit solenoid valve is opened, a countdown is started from the first set time, and when the countdown ends, the compressor is started.

10. The control method of the refrigeration system according to claim 8, characterized in that: When the compressor is started, a countdown is started from the second set time, and when the countdown ends, the bypass solenoid valve is closed.

11. The control method of a refrigeration system according to claim 8, characterized in that: Also includes: Receive a shutdown signal; Closing the liquid pipe solenoid valve to reduce the pressure of the evaporator; detecting the pressure of the evaporator; If the pressure of the evaporator is less than or equal to the pressure setting value, shutting down the compressor; and If the pressure of the evaporator is greater than the pressure setting value, the compressor is turned off after a third set time.

12. The control method of the refrigeration system according to claim 11, characterized in that: When the liquid pipe solenoid valve is closed, a countdown is started from the third set time. If the pressure of the evaporator is greater than the pressure setting value, the compressor is turned off at the end of the countdown.

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