Refrigerating system and oil return control method thereof

Abstract

The invention relates to a refrigerating system and an oil return control method thereof, and the refrigerating system comprises a compressor (1); an air outlet (2A) of the evaporator (2) is communicated with the air suction port (1A) of the compressor (1) through an air suction pipeline (10); an air inlet (3A) of the oil separator (3) is communicated with an exhaust port (1B) of the compressor (1), an oil outlet (3B) of the oil separator (3) is communicated with the compressor (1) through a first oil return pipeline (20), and a pump (11) is arranged on the first oil return pipeline (20); a liquid inlet (4A) of the automatic oil return device (4) is communicated with the evaporator (2) through a liquid taking pipeline (60) and used for obtaining the liquid refrigerant in the evaporator (2), an oil outlet (4B) of the automatic oil return device (4) is communicated with the air suction pipeline (10) through a second oil return pipeline (30), and at least one of the liquid taking pipeline (60) and the second oil return pipeline (30) is provided with a first on-off valve (18).

Description

Technical Field

[0001] The present disclosure relates to the technical field of refrigeration systems, and in particular to a refrigeration system and an oil return control method thereof. Background Art

[0002] Existing large-scale low-temperature refrigeration screw units only rely on suction oil return to replenish oil during operation. When the compressor frequency changes, the oil return volume changes. The compressor has more or less poor oil return problems and there is a risk of oil shortage. When the oil circuit is blocked, the unit must be shut down for maintenance, which will greatly affect production efficiency. Summary of the invention

[0003] Some embodiments of the present disclosure provide a refrigeration system and an oil return control method thereof, which can improve the oil return reliability of a compressor in the refrigeration system.

[0004] A first aspect of the present disclosure provides a refrigeration system, comprising:

[0005] A compressor having an air intake port, an air discharge port and an oil return port;

[0006] An evaporator, wherein an air outlet of the evaporator is connected to an air intake of the compressor through an air intake pipeline;

[0007] an oil separator, wherein an air inlet of the oil separator is communicated with an exhaust port of the compressor, an oil outlet of the oil separator is communicated with the compressor via a first oil return pipeline, and a pump is provided on the first oil return pipeline; and

[0008] An automatic oil return device, wherein the liquid inlet of the automatic oil return device is connected to the evaporator through a liquid extraction pipeline for obtaining liquid refrigerant in the evaporator, and the oil outlet of the automatic oil return device is connected to the air suction pipeline through a second oil return pipeline, and a first on-off valve is provided on at least one of the liquid extraction pipeline and the second oil return pipeline.

[0009] In some embodiments, at least two pumps are provided on the first oil return pipeline, and the at least two pumps are arranged in parallel.

[0010] In some embodiments, it also includes:

[0011] a coarse filter, arranged on the first oil return line and upstream of the pump; and / or

[0012] The fine filter is arranged on the first oil return pipeline and is located downstream of the pump.

[0013] In some embodiments, at least two fine filters are further included, and the at least two fine filters are arranged in parallel on the first oil return pipeline and are located downstream of the pump.

[0014] In some embodiments, it also includes:

[0015] an oil cooler, arranged in parallel with the first oil return pipeline, the oil inlet of the oil cooler being connected to the oil outlet of the oil separator, and the oil outlet of the oil cooler being connected to a position of the first oil return pipeline located upstream of the pump; and

[0016] The oil temperature control valve has a first interface, a second interface and a third interface. The first interface is connected to the oil outlet of the oil separator, and the first interface is not conductive when the oil temperature exceeds a preset high temperature threshold. The second interface is connected to the oil outlet of the oil cooler, and the third interface is connected to the pump.

[0017] In some embodiments, a first electric heater is provided in the oil separator and is configured to be turned on when the oil temperature in the oil separator is lower than a first preset low temperature threshold.

[0018] In some embodiments, it also includes:

[0019] a pressure sensor disposed on the first oil return line and between the pump and the compressor, configured to detect an outlet pressure of the pump; and

[0020] A first bypass oil circuit, a first end of the first bypass oil circuit is connected to a position of the first oil return pipeline located downstream of the pump, a second end of the first bypass oil circuit is connected to an oil inlet of the oil separator, a constant pressure valve is provided on the first bypass oil circuit, and the constant pressure valve is configured to be turned on when the detection value of the pressure sensor exceeds a preset pressure threshold.

[0021] In some embodiments, it also includes:

[0022] The second bypass oil circuit, the first end of the second bypass oil circuit is connected to the first oil return pipeline at a position downstream of the pump, the second end of the second bypass oil circuit is connected to the oil inlet of the oil separator, and a second on-off valve is arranged on the second bypass oil circuit.

[0023] In some embodiments, an oil level switch is provided in the automatic oil return device at a preset height position, and the automatic oil return device is configured to obtain liquid refrigerant from the evaporator when the oil is lower than the preset height position.

[0024] In some embodiments, a second electric heater is provided in the automatic oil return device and is configured to be turned on when the oil temperature in the automatic oil return device is lower than a second preset low temperature threshold.

[0025] In some embodiments, the compressor has an oil unloading port, which is connected to the oil inlet of the oil separator through an oil unloading pipeline. An oil unloading stop check valve is provided on the oil unloading pipeline to unidirectionally conduct the oil unloading pipeline from the compressor to the oil separator.

[0026] In some embodiments, the oil storage area of ​​the compressor is provided with a dual oil level switch, the dual oil level switch includes: a first oil level switch and a second oil level switch, the first oil level switch is set at a first height position Hmin, the second oil level switch is set at a second height position Hmax, and the second height position Hmax is higher than the first height position Hmin.

[0027] In some embodiments, the refrigeration system further comprises:

[0028] an oil cooler, arranged in parallel with the first oil return line, configured to cool the oil returned from the oil separator to the compressor; and

[0029] The air inlet of the condenser is connected to the exhaust port of the compressor through the oil separator, and the liquid refrigerant flowing out of the liquid outlet of the condenser is partially provided to the oil cooler for cooling the oil.

[0030] In some embodiments, the refrigeration system further comprises:

[0031] A siphon liquid reservoir, wherein the liquid inlet of the siphon liquid reservoir is connected to the liquid outlet of the condenser, the liquid outlet of the siphon liquid reservoir is connected to the liquid inlet of the oil cooler, the air inlet of the siphon liquid reservoir is connected to the exhaust port of the oil cooler, and the air return port of the siphon liquid reservoir is connected to the air inlet of the condenser.

[0032] In some embodiments, the refrigeration system further comprises:

[0033] The liquid reservoir has a liquid inlet connected to the overflow port of the siphon liquid reservoir, and a liquid outlet connected to the liquid inlet of the evaporator.

[0034] In some embodiments, the refrigeration system further comprises:

[0035] The subcooler is disposed between the siphon accumulator and the evaporator and is configured to subcool the liquid refrigerant in the main circulation loop.

[0036] A second aspect of the present disclosure provides a control method for the refrigeration system based on the above embodiment, comprising:

[0037] Detect the oil level in the oil storage area of ​​the compressor;

[0038] When the oil is between the first height position Hmin and the second height position Hmax, the air suction and oil return operation is carried out, and the automatic oil return device stops operating;

[0039] When the oil is lower than the first height position Hmin, the air suction and oil return operation is performed, the automatic oil return device is operated, and the pump is operated to operate through the first oil return pipeline;

[0040] When the oil is higher than the second height position Hmax, the air suction and oil return operation is carried out, the automatic oil return device stops running, and the compressor discharges the oil into the oil separator through the oil discharge port;

[0041] The second height position Hmax is higher than the first height position Hmin.

[0042] Based on the above technical solution, the present disclosure has at least the following beneficial effects:

[0043] The refrigeration system of the embodiment of the present disclosure is provided with a plurality of oil return modes for the compressor, including suction oil return, forced oil return through the first oil return pipeline and pump, and automatic oil return through an automatic oil return device, which can be selected and used according to the actual working state of the compressor, without relying on the single oil return mode of suction oil return, and can return oil in time, making the compressor oil return more reliable and sufficient, preventing the phenomenon of oil shortage due to fluctuation of oil return amount when the compressor frequency changes, and can increase the service life of the compressor, thereby greatly improving the reliability of the operation of the refrigeration system. Moreover, when a certain oil return pipeline is blocked or fails, other oil return pipelines can still be relied on for oil return, without stopping the unit for maintenance, and the oil return failure can be handled while the unit is running, thereby improving production efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] The drawings described herein are used to provide a further understanding of the present disclosure and constitute a part of the present application. The illustrative embodiments of the present disclosure and their descriptions are used to explain the present disclosure and do not constitute an improper limitation on the present disclosure. In the drawings:

[0045] Figure 1 Schematic diagram of the system structure of some embodiments of the refrigeration system disclosed in the present invention;

[0046] Figure 2 for Figure 1 The enlarged view at position I in FIG.

[0047] Figure 3 The flowcharts are of some embodiments of the oil return control method of the refrigeration system disclosed in the present invention.

[0048] It should be understood that the size of each part shown in the accompanying drawings is not drawn according to the actual proportional relationship. In addition, the same or similar reference numerals represent the same or similar components. DETAILED DESCRIPTION

[0049] Various exemplary embodiments of the present disclosure will now be described in detail with reference to the accompanying drawings. The description of the exemplary embodiments is merely illustrative and is in no way intended to limit the present disclosure and its application or use. The present disclosure can be implemented in many different forms and is not limited to the embodiments described herein. These embodiments are provided to make the present disclosure thorough and complete and to fully express the scope of the present disclosure to those skilled in the art. It should be noted that unless otherwise specifically stated, the relative arrangement of the components and steps, the composition of the materials, the numerical expressions and the numerical values ​​set forth in these embodiments should be interpreted as being merely exemplary and not as limiting.

[0050] The words "first", "second" and similar words used in this disclosure do not indicate any order, quantity or importance, but are only used to distinguish different parts. The words "include" or "comprise" and similar words mean that the elements before the word include the elements listed after the word, and do not exclude the possibility of including other elements. "Up", "down", "left", "right" and the like are only used to indicate relative positional relationships. When the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0051] In the present disclosure, when a specific device is described as being located between a first device and a second device, there may or may not be an intermediate device between the specific device and the first device or the second device. When a specific device is described as being connected to other devices, the specific device may be directly connected to the other device without an intermediate device, or may not be directly connected to the other device but have an intermediate device.

[0052] All terms (including technical terms or scientific terms) used in the present disclosure have the same meanings as those understood by ordinary technicians in the field to which the present disclosure belongs, unless otherwise specifically defined. It should also be understood that terms defined in general dictionaries should be interpreted as having meanings consistent with their meanings in the context of the relevant technology, and should not be interpreted in an idealized or extremely formal sense, unless explicitly defined herein.

[0053] Technologies, methods, and equipment known to ordinary technicians in the relevant art may not be discussed in detail, but where appropriate, the technologies, methods, and equipment should be considered part of the specification.

[0054] Based on the above-mentioned embodiments of the present disclosure, in the absence of explicit negation or conflict, the technical features of one embodiment may be beneficially combined with one or more other embodiments.

[0055] The present disclosure provides a refrigeration system, such as Figure 1 and Figure 2 As shown, in some embodiments, the refrigeration system includes:

[0056] The compressor 1 has an air intake port 1A, an air discharge port 1B and an oil return port 1C;

[0057] The evaporator 2, the air outlet 2A of the evaporator 2 is connected with the air intake 1A of the compressor 1 through the air intake pipeline 10;

[0058] An oil separator 3, an air inlet 3A of the oil separator 3 is connected to an exhaust port 1B of the compressor 1, an oil outlet 3B of the oil separator 3 is connected to an oil return port 1C of the compressor 1 through a first oil return pipeline 20, and a pump 11 is provided on the first oil return pipeline 20; and

[0059] An automatic oil return device 4, a liquid inlet 4A of the automatic oil return device 4 is connected to the evaporator 2 via a liquid collection pipeline 60, for obtaining liquid refrigerant in the evaporator 2, an oil outlet 4B of the automatic oil return device 4 is connected to the suction pipeline 10 via a second oil return pipeline 30, and a first on-off valve 18 is provided on at least one of the liquid collection pipeline 60 and the second oil return pipeline 30.

[0060] The compressor may be a screw compressor, such as a low-temperature refrigeration screw unit, or a centrifugal compressor. Large compressors are more likely to have insufficient return oil supply, and the oil return system disclosed herein is more effective, and is also applicable to small and medium-sized compressors. The compressor is powered by a drive component 39, which may be an electric motor or a motor, and the drive component 39 is connected to the compressor power through a coupling 22.

[0061] The connection relationship of the evaporator 2 in the refrigeration system is not fully shown. The air outlet 2A of the evaporator 2 is connected to the air intake 1A of the compressor 1 through the air intake pipeline 10. The air intake pipeline 10 is provided with an air intake check valve 23, which only allows the gaseous refrigerant to flow from the evaporator 2 to the compressor 1, and does not allow reverse flow. A first filter 19 can also be provided on the air intake pipeline 10 to filter impurities in the gaseous refrigerant.

[0062] The liquid inlet 2B of the evaporator 2 is connected to the position marked as "B" in the main circulation loop. The compressor 1, condenser 6 and evaporator 2 are arranged in the main circulation loop. After the gaseous refrigerant is discharged from the compressor 1, it enters the condenser 6 for condensation and heat exchange to form a low-temperature and high-pressure liquid refrigerant, and then throttles and cools down to form a low-temperature and low-pressure liquid refrigerant. Subsequently, it enters the evaporator 2 for evaporation and heat exchange to form a low-temperature and low-pressure gaseous refrigerant that enters the compressor 1. During the refrigerant circulation process, oil is also replenished into the compressor along with the gaseous refrigerant to realize the suction and oil return operation, and the driving force of the gaseous refrigerant is used to return a trace amount of lubricating oil to the compressor 1.

[0063] The air inlet 3A of the oil separator 3 is connected to the exhaust port 1B of the compressor 1. After the high-temperature and high-pressure gas discharged from the compressor 1 enters the oil separator 3, oil and gas separation is performed. Under the driving force of the pump 11, the oil flowing out of the oil outlet 3B of the oil separator 3 can enter the oil return port 1C of the compressor 1 through the first oil return pipeline 20, and forced oil return can be achieved when the oil in the compressor 1 is insufficient. The oil separator 3 separates the lubricating oil entrained in the exhaust gas of the compressor 1, so that the high-pressure gas refrigerant entering the condenser 6 is pure, reducing the adverse effect of the lubricating oil film on heat transfer and reducing the consumption of lubricating oil. The pump 11 can provide lubricating oil to the compressor 1 before the compressor 1 is started or during operation. The pressure difference before and after the pump 11 is determined by the oil supply pressure required by the compressor.

[0064] The liquid inlet 4A of the automatic oil return device 4 is connected to the evaporator 2 at the position marked as "A" to obtain the liquid refrigerant in the evaporator 2. The oil outlet 4B of the automatic oil return device 4 is connected to the suction pipeline 10 through the second oil return pipeline 30, and the connection position can be located between the suction check valve 23 and the evaporator 2. At least one of the second oil return pipeline 30 and the liquid collection pipeline 60 is provided with a first on-off valve 18, such as a solenoid valve, which is used to control the on-off of the automatic oil return, realize automatic oil return in the connected state, and cut off the automatic oil return in the disconnected state. In order to increase the automatic oil return amount, more than two second oil return pipelines 30 can also be provided. Optionally, a first filter 19 can also be provided on the second oil return pipeline 30 to filter impurities in the oil.

[0065] The automatic oil return device 4 is used to take out the liquid refrigerant in the user-side evaporator 2, separate the lubricating oil melted therein and return it to the air intake port 1A of the compressor 1, and control the amount of melted oil of the refrigerant in the evaporator 2 to avoid too much melted oil affecting heat exchange.

[0066] The refrigeration system of this embodiment is provided with a plurality of oil return modes for the compressor 1, including suction oil return, forced oil return through the first oil return pipeline 20 and the pump 11, and automatic oil return through the automatic oil return device 4, which can be selected and used according to the actual working state of the compressor 1, without relying on the single oil return mode of suction oil return, and can timely return oil, making the oil return of the compressor 1 more reliable and sufficient, preventing the phenomenon of oil shortage due to the fluctuation of the oil return amount when the compressor frequency changes, and can improve the service life of the compressor, thereby greatly improving the reliability of the operation of the refrigeration system. Moreover, when a certain oil return pipeline is blocked or fails, it can still rely on other oil return pipelines for oil return, without stopping the unit for maintenance, and can handle the oil return failure when the unit is running, thereby improving production efficiency.

[0067] In some embodiments, at least two pumps 11 are provided on the first oil return pipeline 20, and the at least two pumps 11 are arranged in parallel. The at least two pumps 11 can supply oil at the same time, or can be partially put into use to ensure that the first oil return pipeline 20 supplies oil reliably.

[0068] Optionally, only one pump 11 is provided.

[0069] In this embodiment, at least two pumps 11 are arranged in parallel on the first oil return pipeline 20, and part or all of the pumps 11 can be selected for use according to the oil return demand to provide sufficient driving pressure and ensure reliable oil supply. When a pump 11 fails, the driving pressure can still be provided by other pumps 11, and the unit can still operate normally, and can also be repaired without stopping the unit.

[0070] In some embodiments, Figure 1 As shown, the refrigeration system also includes:

[0071] A coarse filter 12 is provided on the first oil return line 20 and is located upstream of the pump 11; and / or

[0072] The fine filter 13 is disposed on the first oil return pipeline 20 and is located downstream of the pump 11 .

[0073] In this embodiment, by providing a coarse filter 12, the oil has been filtered when it is separated in the oil separator 3. After entering the coarse filter 12, larger impurity particles in the lubricating oil can be removed; by providing a fine filter 13, small-sized impurity particles in the lubricating oil can be removed. Finally, it is ensured that the lubricating oil entering the compressor is very clean, so as to ensure that the friction points of the compressor bearings, rotors, shaft seals, etc. are well lubricated, work normally, and reduce wear.

[0074] When the coarse filter 12 and the fine filter 13 are provided at the same time, after the oil is separated in the oil separator 3, the oil first enters the coarse filter 12 to remove the larger impurity particles in the lubricating oil, so that the lubricating oil entering the fine filter 13 is relatively clean, reducing the burden of the fine filter 13, so as to ensure that the oil pump and the compressor are well lubricated, work normally, and avoid wear. After leaving the pump 11, it passes through the fine filter 13 to further remove the small-sized impurity particles in the lubricating oil, and finally ensures that the lubricating oil entering the compressor is very clean, so as to ensure that the friction points of the compressor bearings, rotors, shaft seals, etc. are well lubricated, work normally, and reduce wear.

[0075] In some embodiments, the refrigeration system further includes at least two fine filters 13, which are arranged in parallel on the first oil return pipeline 20 and are located downstream of the pump 11. The at least two fine filters 13 can filter at the same time, or can be manually adjusted so that part of them are put into use and part of them are reserved, ensuring a reliable filtering effect of the first oil return pipeline 20.

[0076] In this embodiment, at least two fine filters 13 are arranged in parallel on the first oil return pipeline 20, and some or all of the fine filters 13 can be selected for use according to filtering requirements to ensure the oil filtering effect. When some fine filters 13 fail, filtering can still be performed through other fine filters 13, thereby improving the reliability of system operation, and the failed fine filters 13 can be replaced and repaired without stopping the system.

[0077] Optionally, a coarse filter 12 and at least two fine filters 13 connected in parallel are provided on the first oil return pipeline 20 to ensure the cleanliness of the oil and improve the reliability of the system operation.

[0078] In some embodiments, Figure 1 As shown, the refrigeration system also includes:

[0079] An oil cooler 5 is arranged in parallel with the first oil return pipeline 20, an oil inlet 5A of the oil cooler 5 is communicated with an oil outlet 3B of the oil separator 3, and an oil outlet 5B of the oil cooler 5 is communicated with a position of the first oil return pipeline 20 located upstream of the pump 11; and

[0080] The oil temperature control valve 37 has a first interface 37A, a second interface 37B and a third interface 37C. The first interface 37A is connected to the oil outlet 3B of the oil separator 3, and the first interface 37A is not conductive when the oil temperature exceeds a preset high temperature threshold. The second interface 37B is connected to the oil outlet 5B of the oil cooler 5, and the third interface 37C is connected to the pump 11.

[0081] The oil cooler 5 may be a fluorine-cooled oil cooler, etc. The fluorine-cooled oil cooler is a shell and tube heat exchanger, with oil on the shell side and refrigerant on the tube side. A temperature sensor may be provided on the first oil return line 20 to detect the oil temperature.

[0082] The oil temperature control valve 37 is used to control the oil temperature. It can automatically adjust the temperature of the fluid in the pipeline to maintain a stable temperature output. It is also called a thermostatic valve. The thermostatic valve is equipped with a temperature sensor to detect the fluid temperature. When the temperature exceeds the set range, the controller will control the valve opening to adjust the flow rate and opening temperature of the fluid.

[0083] After the oil flows out of the oil separator 3, when the oil temperature is normal, it directly enters the coarse filter 12 through the oil temperature control valve 37, and is then sucked into the pump 11; when the oil flowing out of the oil separator 3 exceeds the preset high temperature threshold, the first interface 37A connecting the oil temperature control valve 37 and the oil separator 3 is not conductive, and the oil can only flow into the oil cooler 5. The liquid refrigerant formed by the condenser 6 can be passed into the oil cooler 5. The liquid refrigerant absorbs the heat of the oil and evaporates into a gaseous refrigerant. The oil loses heat and is cooled. The oil reaching a suitable temperature flows through the second interface 37B through the oil temperature control valve 37 into the coarse filter 12, and is then sucked into the pump 11. After the oil is discharged from the pump 11, it passes through the fine filter 13 and finally flows into the compressor 1.

[0084] If the oil temperature is detected to be too high during the operation of the refrigeration system of this embodiment, the lubricating oil separated by the oil separator 3 first passes through the oil cooler 5 to reach the viscosity and temperature required by the compressor 1, and then is sprayed into the compressor 1 for recycling, so as to prevent the high-temperature oil return from accelerating the wear of the compressor 1, thereby increasing the service life of the compressor 1.

[0085] In some embodiments, a first electric heater 36 is provided in the oil separator 3 , and is configured to be turned on when the oil temperature in the oil separator 3 is lower than a first preset low temperature threshold.

[0086] This embodiment provides a first electric heater 36 in the oil separator 3. If it is detected that the oil temperature is too low before the compressor 1 is started or during operation, the first electric heater 36 can be started to increase the oil temperature to a suitable range to prevent the low-temperature oil return from increasing the power consumption of the compressor 1.

[0087] In some embodiments, Figure 2 As shown, the refrigeration system also includes:

[0088] a pressure sensor 15 , provided on the first oil return line 20 and located between the pump 11 and the compressor 1 , configured to detect the outlet pressure of the pump 11 ; and

[0089] A first bypass oil circuit 40, a first end of the first bypass oil circuit 40 is connected to a position of the first oil return pipeline 20 located downstream of the pump 11, a second end of the first bypass oil circuit 40 is connected to an oil inlet 3C of the oil separator 3, a constant pressure valve 14 is provided on the first bypass oil circuit 40, and the constant pressure valve 14 is configured to be turned on when the detection value of the pressure sensor 15 exceeds a preset pressure threshold.

[0090] Among them, one or at least two pressure sensors 15 may be provided. Figure 2A pressure sensor 15 is respectively arranged upstream and downstream of the fine filter 13. The detection value of the pressure sensor 15 downstream of the fine filter 13 near the compressor 1 is closer to the actual pressure of the compressor 1. The pressure sensor 15 can be used as a reference when controlling the action of the constant pressure valve 14. The detection value of another pressure sensor 15 is used as an auxiliary detection. If the pressure sensor 15 near the compressor 1 fails, the detection value of another pressure sensor 15 is used to control the action of the constant pressure valve 14. This structure solves the problem of a single detection element and the need to stop production for maintenance once a component fails.

[0091] This embodiment monitors the oil pressure before entering the compressor 1 by setting a pressure sensor 15, and controls the return oil pressure of the first return oil pipeline 20 through a constant pressure valve 14 to ensure that the oil is supplied at an appropriate pressure. When the oil supply pressure of the pump 11 exceeds the preset pressure threshold, the constant pressure valve 14 opens, releases the pressure through the first bypass oil circuit 40, and part of the oil flows back to the oil separator 3 to prevent the high-pressure oil supply from causing injection noise; when the oil supply pressure of the pump 11 does not exceed the preset pressure threshold, the pump 11 continues to work to increase the oil supply pressure, ensuring that the oil is supplied at an appropriate pressure to prevent the low-pressure oil supply from causing insufficient oil supply.

[0092] In some embodiments, Figure 1 As shown, the refrigeration system also includes: a second bypass oil circuit 70, a first end of the second bypass oil circuit 70 is connected to the first oil return pipeline 20 at a position downstream of the pump 11, a second end of the second bypass oil circuit 70 is connected to the oil inlet 3C of the oil separator 3, and a second on-off valve 17 is provided on the second bypass oil circuit 70.

[0093] The second on-off valve 17 is configured to be turned on when the detection value of the pressure sensor 15 exceeds the preset pressure threshold and the constant pressure valve 14 fails, and to release pressure preferentially through the first bypass oil passage 40 when the constant pressure valve 14 is normal. For example, the second on-off valve 17 may be a solenoid valve or the like.

[0094] In this embodiment, a first bypass oil circuit 40 and a second bypass oil circuit 70 are simultaneously arranged between the outlet of the pump 11 and the oil separator 3. When the oil supply pressure of the pump 11 exceeds the preset pressure threshold, the priority constant pressure valve 14 is opened to release pressure through the first bypass oil circuit 40, so that part of the oil flows back to the oil separator 3, so that the pump 11 can maintain a stable oil supply pressure and prevent the high-pressure oil supply from causing injection noise. Moreover, in the case that the constant pressure valve 14 fails and cannot release pressure, the second on-off valve 17 can still be connected to the second bypass oil circuit 70 for pressure relief, which plays the role of standby pressure relief and improves the reliability and safety of the refrigeration system.

[0095] In some embodiments, an oil level switch 4 ′ is provided at a preset height position in the automatic oil return device 4 , and the automatic oil return device 4 is configured to obtain liquid refrigerant from the evaporator 2 when the oil is lower than the preset height position.

[0096] The automatic oil return device 4 is used to take out the liquid refrigerant in the evaporator 2, separate the lubricating oil melted therein and return it to the suction end of the compressor, control the amount of melted oil of the refrigerant in the evaporator, and avoid too much melted oil affecting heat exchange. For example, the oil level switch 4' can be a single-pole double-throw float type liquid level switch. When the first on-off valve 18 is connected, if the oil is lower than the preset height position, the oil level switch 4' opens and automatically takes liquid refrigerant from the evaporator 2; if the oil reaches the preset height position, the oil level switch 4' closes and liquid refrigerant cannot be taken from the evaporator 2. The automatic oil return device 4 can be set to switch. If there is less melted oil in the evaporator 2, the automatic oil return device 4 can be turned off.

[0097] This embodiment provides an oil level switch 4' in the automatic oil return device 4, so that liquid refrigerant can be automatically obtained from the evaporator 2 when the oil is lower than a preset height position, without the need for intervention through control, thereby reducing the control difficulty of automatic oil return, and can precipitate the lubricating oil melted therein and return it to the air intake port 1A of the compressor 1, thereby controlling the amount of melted oil of the refrigerant in the evaporator 2 to avoid too much melted oil affecting heat exchange.

[0098] In some embodiments, a second electric heater is provided in the automatic oil return device 4 and is configured to be turned on when the oil temperature in the automatic oil return device 4 is lower than a second preset low temperature threshold.

[0099] Before initial activation, a small amount of lubricating oil may be injected into the cylinder of the automatic oil return device 4 to ensure that the oil level does not exceed the second electric heater.

[0100] This embodiment provides a second electric heater in the automatic oil return device 4, so that the oil of the automatic oil return can be heated before the compressor 1 is turned on or during operation, and the oil temperature can be raised to a suitable range to prevent the low-temperature oil return from increasing the power consumption of the compressor 1.

[0101] In some embodiments, the compressor 1 has an oil unloading port 1D, which is connected to the oil inlet 3C of the oil separator 3 through an oil unloading pipeline 50. The oil unloading pipeline 50 is provided with an oil unloading stop check valve 16 for unidirectionally conducting the oil unloading pipeline 50 from the compressor 1 to the oil separator 3.

[0102] The oil unloading port 1D corresponds to the high oil level in the compressor 1 . When the oil level is higher than the oil unloading port 1D, the oil flows out of the compressor 1 and flows into the oil separator 3 through the oil unloading stop check valve 16 .

[0103] The compressor 1 of this embodiment is provided with an oil discharge port 1D. When the internal oil is higher than the oil discharge port 1D, the oil can automatically flow out through the oil discharge port 1D and enter the oil separator 3 through the oil discharge pipeline 50, thereby avoiding the problem of oil compression caused by excessively high oil level in the compressor 1. Moreover, the oil discharge stop check valve 16 is unidirectional, thereby preventing the oil in the oil separator 3 from flowing back into the compressor 1, thereby improving the safety of the operation of the compressor 1.

[0104] In some embodiments, Figure 1 and Figure 3 As shown, the oil storage area of ​​the compressor 1 is provided with a double oil level switch 21, and the double oil level switch 21 includes: a first oil level switch and a second oil level switch, the first oil level switch is set at a first height position Hmin, and the second oil level switch is set at a second height position Hmax, and the second height position Hmax is higher than the first height position Hmin; wherein,

[0105] When the oil is between the first height position Hmin and the second height position Hmax, the air suction and oil return operation is performed, and the automatic oil return device 4 stops operating;

[0106] When the oil is lower than the first height position Hmin, the air suction and oil return operation is performed, the automatic oil return device 4 is operated, and the pump 11 is operated to operate through the first oil return pipeline 20; and / or

[0107] When the oil is higher than the second height position Hmax, the suction and oil return operation is performed, the automatic oil return device 4 stops operating, and the compressor 1 discharges the oil into the oil separator 3 through the oil discharge port 1D.

[0108] Among them, Hmin can be the lowest oil level allowed by the compressor, and Hmax can be the highest oil level allowed by the compressor. The oil level h in the compressor 1 is detected in real time and compared with Hmin and Hmax. According to the analysis and judgment results, the oil return combination is selected independently.

[0109] Conventional compressors decide whether to return oil based only on external parameters. When the compressor parameters change, there is a lag in the control of the oil return amount, resulting in untimely, insufficient, unreliable oil return, or even oil shortage.

[0110] This embodiment detects the liquid level height through the double oil level switch 21 of the compressor 1, and selects different oil return combinations among suction oil return, automatic oil return and forced oil return according to the actual liquid level height, so that the control can be more directly performed, so as to timely, reliably and fully perform oil return, so that the compressor 1 can reach a good lubrication state before starting or during operation, and realizes accurate control of the oil return amount of the compressor 1, thereby improving the service life and preventing the excessive oil in the compressor 1 from causing liquid compression. In addition, by setting the double oil level switch 21, compared with the single oil level switch, the reliability is high, and when the oil level switch fails, there is no need to shut down the machine for processing, which can ensure smooth production, and when the frequency of the compressor changes and the liquid level fluctuates, the double oil level switch 21 will not act frequently, which can improve the service life. When the oil level deviates from the low level or high level, it can act quickly to return or unload the oil in time.

[0111] When h<Hmin, a combination of suction oil return operation, automatic oil return operation and forced oil return operation is selected for oil return control. By opening the second oil return pipeline 30 and the first on-off valve 18 in the liquid intake pipeline 60, the automatic oil return operation can be enabled under the action of the pressure difference (the liquid column pressure in the automatic oil return device 4 and the exhaust and suction pressure difference). The forced oil return operation can be enabled when the pump 11 is working. At this time, oil can be returned simultaneously through the three oil return methods, so as to quickly replenish the lubricating oil to the compressor 1 to a suitable height range.

[0112] When Hmin≤h≤Hmax, a combination of suction oil return operation, automatic oil return operation stop, and forced oil return stop is selected for oil return control. The automatic oil return can be stopped by closing the first on-off valve 18 in the second oil return pipeline 30 and / or the liquid intake pipeline 60, and the forced oil return can be stopped by stopping the pump 11. At this time, the oil return demand of the compressor 1 can be met by returning oil using only the trace amount of lubricating oil contained in the suction air.

[0113] When h>Hmax, a combination of suction oil return operation, automatic oil return operation stop, and automatic oil unloading is selected for oil return control. Because there will still be a small amount of suction oil return when the oil in the compressor 1 exceeds the maximum allowable amount, the excess oil automatically enters the oil separator 3 through the oil unloading port 1D.

[0114] In some embodiments, Figure 1 As shown, the refrigeration system also includes:

[0115] an oil cooler 5 , arranged in parallel with the first oil return line 20 , and configured to cool the oil returned from the oil separator 3 to the compressor 1 ; and

[0116] The condenser 6 has an air inlet 6A connected to the exhaust port 1B of the compressor 1 through the oil separator 3, and a portion of the liquid refrigerant flowing out of the liquid outlet 6B of the condenser 6 is provided to the oil cooler 5 for cooling the oil.

[0117] For example, the oil cooler 5 may be a fluorine-cooled oil cooler, etc. The fluorine-cooled oil cooler is a shell and tube heat exchanger, with oil on the shell side and refrigerant on the tube side.

[0118] For example, the condenser 6 may be an evaporative condenser, which is a device that absorbs the heat of the high-temperature gaseous refrigerant in the coil when the spray water outside the coil evaporates, so that the refrigerant in the tube is gradually cooled from gas to liquid. After the gaseous refrigerant is sucked into the compressor 1, the compressed gas enters the condenser 6 and condenses into a saturated liquid with a certain degree of supercooling. A portion of the liquid refrigerant flowing out of the condenser 6 can be obtained and provided to the oil cooler 5 for heat exchange with the oil.

[0119] This embodiment can use the liquid refrigerant flowing out of the condenser 6 to cool the oil in the oil cooler 5, and can directly use the supercooled liquid refrigerant in the main circulation loop without increasing the complexity of the system. In addition, if the temperature of the lubricating oil separated by the oil separator 3 is too high, after entering the oil cooler 5 and exchanging heat with the liquid refrigerant, the oil can be cooled to the viscosity and temperature required by the compressor 1, and then sprayed into the compressor 1 for recycling, which can prevent the high-temperature oil return from accelerating the wear of the compressor 1, thereby increasing the service life of the compressor 1.

[0120] In some embodiments, the refrigeration system further includes: a siphon reservoir 7, a liquid inlet 7A of the siphon reservoir 7 being connected to a liquid outlet 6B of the condenser 6, a liquid outlet 7B of the siphon reservoir 7 being connected to a liquid inlet 5C of the oil cooler 5, an air inlet 7C of the siphon reservoir 7 being connected to an air outlet 5D of the oil cooler 5, and a return air port 7D of the siphon reservoir 7 being connected to an air inlet 6A of the condenser 6.

[0121] The principle of the siphon liquid storage device 7 is based on the siphon effect of the liquid. When there is liquid inside the container, a pressure difference occurs inside the container, that is, the gas pressure at the top is lower than the vapor pressure of the liquid surface. At this time, the gas between the liquid surface and the inner wall of the container is extracted, resulting in a vacuum in the container. In this state, the liquid can be siphoned to the inlet through the inlet and outlet at the top of the container, and freely flows into the liquid storage tank under the action of gravity. When the liquid level reaches a certain level, the inside of the container will reach a state of equilibrium again, and the siphon effect at the inlet will stop.

[0122] The liquid inlet 7A and the air return port 7D may be arranged at the top of the siphon liquid reservoir 7, the liquid outlet 7B and the air inlet 7C may be arranged at the bottom of the siphon liquid reservoir 7, and the siphon liquid reservoir 7 may be arranged above the oil cooler 5 so that the liquid refrigerant can smoothly enter the oil cooler 5 by gravity. The gaseous refrigerant generated after the liquid refrigerant exchanges heat with the oil enters the air return pipe through the air exhaust port 5D of the oil cooler 5, and then enters the exhaust pipe from the air return port 7D of the siphon liquid reservoir 7, and is condensed again in the condenser 6.

[0123] Optionally, Figure 1 Two parallel condensers 6 are provided, the gaseous refrigerant drawn out from the oil separator 3 is divided into two paths and enters the air inlet 6A of the two condensers 6 respectively, the liquid refrigerant flowing out of the liquid outlet 6B of the two condensers 6 converges and enters the siphon liquid reservoir 7, part of the liquid refrigerant enters the oil cooler 5, and the gaseous refrigerant formed after heat exchange returns to the siphon liquid reservoir 7, and then is divided into two paths and enters the two condensers 6 respectively for re-condensation.

[0124] This embodiment is capable of storing and transferring liquid refrigerant formed by the condenser 6 by setting up a siphon liquid storage tank 7, and utilizing the siphon principle to supply liquid to the oil cooler 5. The supercooled liquid refrigerant in the main circulation loop can be utilized to cool the oil, and the refrigerant flow requirement of the main circulation loop can be met. The refrigerant can also achieve gas-liquid separation in the siphon liquid storage tank 7.

[0125] In some embodiments, the refrigeration system further includes: a liquid reservoir 8 , a liquid inlet 8A of the liquid reservoir 8 is connected to an overflow port 7E of the siphon liquid reservoir 7 , and a liquid outlet 8B of the liquid reservoir 8 is connected to a liquid inlet 2B of the evaporator 2 .

[0126] Among them, the function of the liquid accumulator 8 is to store and transfer liquid refrigerant. Most of the liquid refrigerant in the siphon liquid accumulator 7 enters the liquid accumulator 8, and after passing through the second filter 26 to remove impurities or moisture, it is further supercooled and then provided to the evaporator 2 at the end of the refrigeration. The refrigerant gas coming out of the evaporator 2 is sucked into the compressor 1 again to perform a refrigeration cycle. A small amount of liquid refrigerant in the siphon liquid accumulator 7 enters the oil cooler 5. For example, the liquid accumulator 8 can be arranged below the siphon liquid accumulator 7 in the height direction so that the liquid can enter the liquid accumulator 8 more smoothly.

[0127] In this embodiment, a liquid accumulator 8 is arranged downstream of the siphon liquid accumulator 7, so that most of the liquid refrigerant in the siphon liquid accumulator 7 can flow into the liquid accumulator 8 for storage in time, and the storage capacity of the liquid refrigerant can be increased to meet the situation of large load fluctuations in the refrigeration system and improve the performance of the unit; moreover, the liquid refrigerant is also mixed with gas, and after passing through the siphon liquid accumulator 7 and then entering the liquid accumulator 8, two gas-liquid separations can be performed, thereby improving the gas-liquid separation effect and increasing the content of the liquid refrigerant entering the evaporator 2.

[0128] Optionally, the siphon liquid reservoir 7 and the liquid reservoir 8 can be combined into one to form a liquid storage device, and the liquid storage device is changed to a vertical type, with the upper part being the siphon liquid reservoir and the lower part being the liquid reservoir.

[0129] In some embodiments, the refrigeration system further includes: a subcooler 9, which is disposed between the siphon liquid storage device 7 and the evaporator 2 and is configured to subcool the liquid refrigerant in the main circulation loop.

[0130] For example, the subcooler 9 may be a shell and tube economizer to subcool the refrigerant in the main circulation loop. In the embodiment where the accumulator 8 is provided, the subcooler 9 may be provided between the accumulator 8 and the evaporator 2 .

[0131] This embodiment can supercool the liquid refrigerant in the main circulation loop by providing a subcooler 9, thereby improving the economy and efficiency of the refrigeration cycle.

[0132] Below Figure 1 The refrigeration system of is taken as an example to illustrate the specific structure of the refrigeration system. There are two dotted boxes in the figure, including a compressor module 100 and a condensing module 200. The compressor module 100 is used to drive the refrigerant transfer, and the condensing module 200 plays the role of condensation heat exchange, transferring the exhaust heat of the compressor 1 to the atmosphere or cooling water. The main components of the refrigeration system include: compressor 1, evaporator 2, condenser 6, oil separator 3, automatic oil return device 4, oil cooler 5, siphon reservoir 7, reservoir 8 and subcooler 9.

[0133] The connection methods of these main components have been given in the above embodiments, and the components not mentioned are mainly described here. The compressor 1 is equipped with a solenoid valve group 22, which is used to change the working parameters of the compressor 1 and adjust the cooling capacity. A branch pipeline 80 can be set between the air outlet of the oil separator 3 and the air suction pipeline 10. The branch pipeline 80 is provided with a sight glass 31, a third solenoid valve 32 and a first filter 19. The content of liquid refrigerant in the gaseous refrigerant drawn from the oil separator 3 can be observed through the sight glass 31. When there is too much liquid refrigerant, it will have an adverse effect on the operation of the compressor 1.

[0134] Optionally, a second filter 26 may be provided between the subcooler 9 and the compressor 1. For example, such a filter may be a straight-through filter or a filter with an inclined filter element. The filter element can be directly withdrawn for easy replacement without removal. A second filter 26 and a sight glass 31 may also be provided between the liquid reservoir 8 and the subcooler 9. A safety valve 33 may be provided between the oil separator 3 and the air inlet 6A of the condenser 6. A pressure sensor 15 and a temperature sensor 41 may be provided on the pipeline between the fine filter 13 and the compressor 1.

[0135] Optionally, a plurality of stop valves are provided in the refrigeration system to facilitate the inspection and maintenance of components and pipelines. For example, the second oil return pipeline 30 and the branch pipeline 80 are both provided with a first stop valve 24, a second stop valve 35 is provided on the pipeline between the oil separator 3 and the air inlet 6A of the condenser 6, a third stop valve 34 is provided between the liquid outlet 6B of the condenser 6 and the siphon liquid reservoir 7, and a fourth stop valve 27 can be provided between the fine filter 13 and the compressor 1. In addition, the fourth stop valve 25 is used in the parts with multiple bends in the pipeline.

[0136] Figure 1 The refrigeration system shown works as follows:

[0137] The circulation path of the refrigerant is as follows: the gaseous refrigerant from the evaporator 2 is sucked into the compressor 1, and the compressed gas enters the condenser 6 to be condensed into a saturated liquid with a certain degree of supercooling. The supercooled liquid enters the siphon accumulator 7 to supply the oil cooler 5. The gaseous refrigerant generated after heat exchange enters the exhaust pipe through the return pipe and is condensed again in the condenser 6. Most of the liquid in the siphon accumulator 7 enters the accumulator 8, and then passes through a filter or a drying filter to remove impurities and moisture, enters the economizer 9 for further supercooling, and is supplied to the evaporator 2. The gaseous refrigerant evaporated from the evaporator 2 is sucked into the compressor 1 again to carry out the refrigeration cycle.

[0138] The lubricating oil circulation in the refrigeration system includes three flow paths, namely: the suction oil return operation flow path, the automatic oil return operation flow path and the forced oil return operation flow path. The lubricating oil is supplied to the compressor 1 for lubrication, sealing, noise reduction and removal of part of the compression heat, which will be explained separately below.

[0139] The suction and oil return operation flow path is: compressor 1 - oil separator 3 - condenser 6 - siphon liquid storage 7 - liquid storage 8 - subcooler 9 - evaporator 2 - compressor 1. The tiny oil droplets mixed in the refrigerant circulate with the refrigerant cycle, and each component operates according to the refrigerant cycle requirements without special control.

[0140] The flow path of automatic oil return operation is: evaporator 2—first on-off valve 18 of liquid extraction pipeline 60—automatic oil return device 4—first on-off valve 18 of second oil return pipeline 30—first filter 19—first stop valve 24 of second oil return pipeline 30—intake check valve 23—compressor 1. When automatic oil return operation is in progress, the first on-off valve 18 of liquid extraction pipeline 60 and second oil return pipeline 30 is connected. The function of automatic oil return operation is to take out the liquid refrigerant in evaporator 2, precipitate the lubricating oil melted therein and return it to the suction end of the compressor, control the amount of melted oil of the refrigerant in the evaporator, and avoid too much melted oil to affect heat exchange.

[0141] The forced oil return operation flow path is: compressor 1-oil separator 3-oil cooler 5-oil temperature control valve 37-coarse filter 12-pump 11-fine filter 13-compressor 1. During forced oil return operation, the oil temperature control valve 37 is turned on and off according to the temperature. After the oil flows out of the oil separator 3, when the oil temperature is normal, it directly enters the coarse filter 12 through the oil temperature control valve 37, and then is sucked into the pump 11; when the oil flowing out of the oil separator 3 is at a high temperature, the first interface 37A connecting the oil temperature control valve 37 and the oil separator 3 is not conductive, and the oil can only flow into the oil cooler 5. In it, the liquid refrigerant from the siphon accumulator 7 absorbs the heat of the oil and evaporates into a gaseous refrigerant, and the oil is cooled due to the loss of heat. The oil that reaches the appropriate temperature passes through the oil temperature control valve 37, flows into the coarse filter 12, and is then sucked into the pump 11. After being discharged from the pump 11, it passes through the fine filter 13 and finally flows into the compressor 1.

[0142] The refrigeration system disclosed in the present invention has timely, sufficient and reliable oil return, which prevents oil shortage, avoids liquid compression and ensures the service life of the compressor; it also has high oil return reliability, and adopts three oil return methods: suction oil return, automatic oil return and forced oil return, which greatly improves the operating reliability of the system; it can also improve production efficiency and handle oil return faults when the unit is in operation; in addition, the oil return quality is high, and the oil temperature, oil pressure and cleanliness are precisely controlled, which greatly improves the oil return quality.

[0143] In some embodiments of the large-scale low-temperature refrigeration screw unit system, the refrigeration capacity is 1800kW, and the shell and tube economizer liquid outlet temperature is -18°C.

[0144] Secondly, the present disclosure provides an oil return control method for a refrigeration system based on the above embodiment. In some embodiments, such as Figure 3 As shown, the control method includes:

[0145] Detecting the oil level position in the oil storage area of ​​the compressor 1;

[0146] When the oil is between the first height position Hmin and the second height position Hmax, the air suction and oil return operation is performed, and the automatic oil return device 4 stops operating;

[0147] When the oil is lower than the first height position Hmin, the air suction and oil return operation is performed, the automatic oil return device 4 is operated, and the pump 11 is operated to operate through the first oil return pipeline 20; and / or

[0148] When the oil is higher than the second height position Hmax, the air suction and oil return operation is carried out, the automatic oil return device 4 stops running, and the compressor 1 discharges the oil into the oil separator 3 through the oil discharge port 1D;

[0149] The second height position Hmax is higher than the first height position Hmin.

[0150] For example, the oil storage area of ​​the compressor 1 is provided with a dual oil level switch 21 to detect the height position of the oil. The dual oil level switch 21 includes: a first oil level switch and a second oil level switch. The first oil level switch is set at a first height position Hmin, and the second oil level switch is set at a second height position Hmax.

[0151] After the unit is running, this embodiment selects different oil return combinations among suction oil return, automatic oil return and forced oil return according to the actual liquid level height in the compressor 1, so that the oil return can be carried out in a timely, reliable and sufficient manner, so that the compressor 1 can reach a good lubrication state before starting or during operation, and the oil return amount of the compressor 1 can be accurately controlled, thereby improving the service life and preventing the excessive oil in the compressor 1 from causing liquid compression.

[0152] When h<Hmin, a combination of suction oil return operation, automatic oil return operation and forced oil return operation is selected for oil return control. By opening the second oil return pipeline 30 and the first on-off valve 18 in the liquid intake pipeline 60, the automatic oil return operation can be enabled under the action of the pressure difference (the pressure difference includes the liquid column pressure in the automatic oil return device 4, and the exhaust and suction pressure difference). The forced oil return operation can be enabled when the pump 11 is working. At this time, oil can be returned simultaneously through the three oil return methods, so as to quickly replenish the lubricating oil to the compressor 1 to a suitable height range.

[0153] When Hmin≤h≤Hmax, a combination of suction oil return operation, automatic oil return operation stop, and forced oil return stop is selected for oil return control. The automatic oil return can be stopped by closing the first on-off valve 18 in the second oil return pipeline 30 and / or the liquid intake pipeline 60, and the forced oil return can be stopped by stopping the pump 11. At this time, the oil return demand of the compressor 1 can be met by returning oil using only the trace amount of lubricating oil contained in the suction air.

[0154] When h>Hmax, a combination of suction oil return operation, automatic oil return operation stop, and automatic oil unloading is selected for oil return control. Because there will still be a small amount of suction oil return when the oil in the compressor 1 exceeds the maximum allowable amount, the excess oil automatically enters the oil separator 3 through the oil unloading port 1D.

[0155] Although some specific embodiments of the present disclosure have been described in detail by way of examples, it should be understood by those skilled in the art that the above examples are for illustration only and are not intended to limit the scope of the present disclosure. It should be understood by those skilled in the art that the above embodiments may be modified or some technical features may be replaced by equivalents without departing from the scope and spirit of the present disclosure. The scope of the present disclosure is defined by the appended claims.

Claims

1. A refrigeration system, characterized in that: include: A compressor (1) having an air intake port (1A), an air discharge port (1B) and an oil return port (1C); An evaporator (2), wherein an air outlet (2A) of the evaporator (2) is connected to an air intake (1A) of the compressor (1) via an air intake pipeline (10); an oil separator (3), wherein an air inlet (3A) of the oil separator (3) is in communication with an exhaust port (1B) of the compressor (1), and an oil outlet (3B) of the oil separator (3) is in communication with the compressor (1) via a first oil return pipeline (20), wherein a pump (11) is provided on the first oil return pipeline (20); and An automatic oil return device (4), wherein a liquid inlet (4A) of the automatic oil return device (4) is connected to the evaporator (2) via a liquid collection pipeline (60) for obtaining liquid refrigerant in the evaporator (2), and an oil outlet (4B) of the automatic oil return device (4) is connected to the air intake pipeline (10) via a second oil return pipeline (30), and a first on-off valve (18) is provided on at least one of the liquid collection pipeline (60) and the second oil return pipeline (30).

2. The refrigeration system according to claim 1, characterized in that: At least two pumps (11) are arranged on the first oil return pipeline (20), and the at least two pumps (11) are arranged in parallel.

3. The refrigeration system according to claim 1, characterized in that: Also includes: a coarse filter (12) disposed on the first oil return pipeline (20) and located upstream of the pump (11); and / or A fine filter (13) is arranged on the first oil return pipeline (20) and is located downstream of the pump (11).

4. The refrigeration system according to claim 1, characterized in that: It also comprises at least two fine filters (13), wherein the at least two fine filters (13) are arranged in parallel on the first oil return pipeline (20) and are located downstream of the pump (11).

5. The refrigeration system according to claim 1, characterized in that: Also includes: an oil cooler (5) arranged in parallel with the first oil return pipeline (20), the oil inlet (5A) of the oil cooler (5) being in communication with the oil outlet (3B) of the oil separator (3), and the oil outlet (5B) of the oil cooler (5) being in communication with a position of the first oil return pipeline (20) located upstream of the pump (11); and The oil temperature control valve (37) comprises a first interface (37A), a second interface (37B) and a third interface (37C), wherein the first interface (37A) is connected to the oil outlet (3B) of the oil separator (3), and the first interface (37A) is not connected when the oil temperature exceeds a preset high temperature threshold, the second interface (37B) is connected to the oil outlet (5B) of the oil cooler (5), and the third interface (37C) is connected to the pump (11).

6. The refrigeration system according to claim 1, characterized in that: A first electric heater (36) is provided in the oil separator (3) and is configured to be turned on when the oil temperature in the oil separator (3) is lower than a first preset low temperature threshold.

7. The refrigeration system according to claim 1, characterized in that: Also includes: a pressure sensor (15), arranged on the first oil return pipeline (20) and located between the pump (11) and the compressor (1), and configured to detect the outlet pressure of the pump (11); and A first bypass oil circuit (40), wherein a first end of the first bypass oil circuit (40) is connected to a position of the first oil return pipeline (20) located downstream of the pump (11), and a second end of the first bypass oil circuit (40) is connected to an oil inlet (3C) of the oil separator (3). A constant pressure valve (14) is provided on the first bypass oil circuit (40), and the constant pressure valve (14) is configured to be conductive when a detection value of the pressure sensor (15) exceeds a preset pressure threshold.

8. The refrigeration system according to claim 7, characterized in that: Also includes: A second bypass oil circuit (70), wherein a first end of the second bypass oil circuit (70) is in communication with a position of the first oil return pipeline (20) located downstream of the pump (11), a second end of the second bypass oil circuit (70) is in communication with an oil inlet (3C) of the oil separator (3), and a second on-off valve (17) is provided on the second bypass oil circuit (70).

9. The refrigeration system according to claim 1, characterized in that: An oil level switch (4') is provided at a preset height position in the automatic oil return device (4), and the automatic oil return device (4) is configured to obtain liquid refrigerant from the evaporator (2) when the oil level is lower than the preset height position.

10. The refrigeration system according to claim 1, wherein: A second electric heater is provided in the automatic oil return device (4) and is configured to be turned on when the oil temperature in the automatic oil return device (4) is lower than a second preset low temperature threshold.

11. The refrigeration system according to any one of claims 1 to 10, characterized in that: The compressor (1) has an oil discharge port (1D), the oil discharge port (1D) being connected to the oil inlet (3C) of the oil separator (3) via an oil discharge pipeline (50), and the oil discharge pipeline (50) is provided with an oil discharge stop check valve (16) for unidirectionally conducting the oil discharge pipeline (50) from the compressor (1) to the oil separator (3).

12. The refrigeration system according to any one of claims 1 to 10, characterized in that: The oil storage area of ​​the compressor (1) is provided with a dual oil level switch (21), the dual oil level switch (21) comprising: a first oil level switch and a second oil level switch, the first oil level switch being set at a first height position Hmin, the second oil level switch being set at a second height position Hmax, the second height position Hmax being higher than the first height position Hmin.

13. The refrigeration system according to any one of claims 1 to 10, characterized in that: Also includes: an oil cooler (5), arranged in parallel with the first oil return pipeline (20), and configured to cool the oil returned from the oil separator (3) to the compressor (1); and A condenser (6), wherein an air inlet (6A) of the condenser (6) is connected to an exhaust port (1B) of the compressor (1) via the oil separator (3), and a portion of the liquid refrigerant flowing out of a liquid outlet (6B) of the condenser (6) is provided to the oil cooler (5) for cooling the oil.

14. The refrigeration system according to claim 13, characterized in that: Also includes: A siphon liquid reservoir (7), wherein the liquid inlet (7A) of the siphon liquid reservoir (7) is connected to the liquid outlet (6B) of the condenser (6), the liquid outlet (7B) of the siphon liquid reservoir (7) is connected to the liquid inlet (5C) of the oil cooler (5), the air inlet (7C) of the siphon liquid reservoir (7) is connected to the air outlet (5D) of the oil cooler (5), and the air return port (7D) of the siphon liquid reservoir (7) is connected to the air inlet (6A) of the condenser (6).

15. The refrigeration system according to claim 14, characterized in that Also includes: A liquid reservoir (8), wherein a liquid inlet (8A) of the liquid reservoir (8) is connected to an overflow port (7E) of the siphon liquid reservoir (7), and a liquid outlet (8B) of the liquid reservoir (8) is connected to a liquid inlet of the evaporator (2).

16. The refrigeration system according to claim 14, wherein: Also includes: The subcooler (9) is arranged between the siphon liquid accumulator (7) and the evaporator (2) and is configured to subcool the liquid refrigerant in the main circulation loop.

17. An oil return control method for a refrigeration system according to any one of claims 1 to 16, characterized in that: include: Detecting the oil level in the oil storage area of ​​the compressor (1); When the oil is between the first height position Hmin and the second height position Hmax, the air suction and oil return operation is performed, and the automatic oil return device (4) stops operating; When the oil is lower than the first height position Hmin, the air suction and oil return operation is performed, the automatic oil return device (4) is operated, and the pump (11) is operated to operate through the first oil return pipeline (20); When the oil level is higher than the second height position Hmax, the air suction and oil return operation is performed, the automatic oil return device (4) stops running, and the compressor (1) discharges the oil into the oil separator (3) through the oil discharge port (1D); The second height position Hmax is higher than the first height position Hmin.

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