Refrigeration system

Abstract

The present disclosure relates to a refrigeration system comprising: 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. Background Art

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

[0003] Some embodiments of the present disclosure provide a refrigeration system capable of improving the oil return reliability of a compressor in the refrigeration system.

[0004] 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] Evaporator, the air outlet of the evaporator is connected to the air intake of the compressor through an air intake pipeline;

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

[0008] An automatic oil return device, the liquid inlet of the automatic oil return device is connected to the evaporator through a liquid collection pipeline, which is used to obtain liquid refrigerant in the evaporator. The oil outlet of the automatic oil return device is connected to the suction pipeline through a second oil return pipeline. A first on-off valve is provided on at least one of the liquid collection 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 further includes:

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

[0012] The fine filter is installed 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 further includes:

[0015] an oil cooler disposed 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 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 further includes:

[0019] a pressure sensor provided on the first oil return line and located between the pump and the compressor, configured to detect the 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 downstream of the pump, a second end of the first bypass oil circuit is connected to the 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 further 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 provided 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 level 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 guide 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, which 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.

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

[0028] an oil cooler, disposed 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 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 provided between the siphon accumulator and the evaporator and is configured to subcool the liquid refrigerant in the main circulation loop.

[0036] Based on the above technical solution, the present disclosure has at least the following beneficial effects:

[0037] The refrigeration system of the embodiment disclosed herein is provided with a plurality of oil return methods for the compressor, including suction oil return, forced oil return through a first oil return line and a pump, and automatic oil return through an automatic oil return device. These methods can be selected according to the actual working state of the compressor, without relying solely on a single oil return method such as suction oil return. The oil can be returned in a timely manner, making the oil return of the compressor more reliable and sufficient, preventing the phenomenon of oil shortage due to fluctuations in the return oil volume when the compressor frequency changes, and thus prolonging the service life of the compressor, thereby greatly improving the reliability of the operation of the refrigeration system. Moreover, when a certain oil return line is blocked or fails, the oil can still be returned by relying on other oil return lines, without the need to shut down the unit for maintenance. The oil return failure can be handled while the unit is running, thereby improving production efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] The drawings described herein are used to provide a further understanding of the present disclosure and constitute a part of this 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 of the present disclosure. In the drawings:

[0039] Figure 1 Schematic diagram of the system structure of some embodiments of the refrigeration system disclosed herein;

[0040] Figure 2 for Figure 1 The enlarged view of point I in FIG.

[0041] Figure 3 The flowchart of some embodiments of the oil return control method of the refrigeration system disclosed in the present invention.

[0042] It should be understood that the size of each part shown in the 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

[0043] 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, 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 convey 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 parts and steps, the composition of materials, numerical expressions, and numerical values ​​set forth in these embodiments should be interpreted as being merely exemplary and not as limiting.

[0044] The terms "first", "second" and similar terms used in this disclosure do not indicate any order, quantity or importance, but are only used to distinguish different parts. The terms "include" or "comprises" and similar terms mean that the elements before the term include the elements listed after the term, and do not exclude the possibility of also including other elements. The terms "upper", "lower", "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.

[0045] In the present disclosure, when a specific device is described as being located between a first device and a second device, an intervening device may or may not be present between the specific device and the first device or the second device. When a specific device is described as being connected to another device, the specific device may be directly connected to the other device without an intervening device, or may be not directly connected to the other device but with an intervening device.

[0046] All terms (including technical or scientific terms) used in this disclosure have the same meaning as those understood by one of ordinary skill in the art to which this disclosure belongs, unless otherwise specifically defined. It should also be understood that terms defined in, for example, general dictionaries should be interpreted as having a meaning consistent with their meaning in the context of the relevant technology, and should not be interpreted in an idealized or highly formal sense, unless explicitly defined herein.

[0047] 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.

[0048] 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.

[0049] The present disclosure provides a refrigeration system, such as Figure 1 and Figure 2 As shown, in some embodiments, the refrigeration system includes:

[0050] The compressor 1 has an air intake port 1A, an air discharge port 1B and an oil return port 1C;

[0051] The evaporator 2, the air outlet 2A of the evaporator 2 is connected to the air intake 1A of the compressor 1 through the air intake pipe 10;

[0052] 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 via a first oil return line 20, and a pump 11 is provided on the first oil return line 20; and

[0053] Automatic oil return device 4, the liquid inlet 4A of the automatic oil return device 4 is connected to the evaporator 2 through the liquid collection pipeline 60, which is used to obtain the liquid refrigerant in the evaporator 2, and 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. At least one of the liquid collection pipeline 60 and the second oil return pipeline 30 is provided with a first on-off valve 18.

[0054] The compressor can be a screw compressor, such as a low-temperature refrigeration screw unit, or a centrifugal compressor. Large compressors are more prone to insufficient return oil supply, and the oil return system disclosed herein is more effective. The system is also applicable to small and medium-sized compressors. The compressor is powered by a drive component 39, which can be an electric motor or the like. The drive component 39 is connected to the compressor power supply via a coupling 22.

[0055] The connections of evaporator 2 within the refrigeration system are not fully illustrated. However, the outlet 2A of evaporator 2 communicates with the intake 1A of compressor 1 via an intake line 10. Intake line 10 is equipped with an intake check valve 23, which allows only gaseous refrigerant to flow from evaporator 2 to compressor 1 and prevents reverse flow. Intake line 10 may also be equipped with a first filter 19 to filter impurities from the gaseous refrigerant.

[0056] The liquid inlet 2B of the evaporator 2 is connected to the position marked "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. Thereafter, it is throttled and cooled 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 air 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.

[0057] The air inlet 3A of the oil separator 3 is connected to the exhaust port 1B of the compressor 1. After the high-temperature, high-pressure gas discharged from the compressor 1 enters the oil separator 3, it undergoes oil and gas separation. Driven by 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 line 20, enabling forced oil return in the event of insufficient oil in the compressor 1. The oil separator 3 removes lubricating oil entrained in the exhaust gas of the compressor 1, purifying the high-pressure gas refrigerant entering the condenser 6, reducing the adverse effects of the lubricating oil film on heat transfer, and lowering lubricating oil consumption. The pump 11 can provide lubricating oil to the compressor 1 before startup or during operation. The pressure differential across the pump 11 is determined by the required oil supply pressure of the compressor.

[0058] The liquid inlet 4A of the automatic oil return device 4 communicates with the evaporator 2 at the position marked "A" to retrieve liquid refrigerant from the evaporator 2. The oil outlet 4B of the automatic oil return device 4 communicates with the suction line 10 via a second oil return line 30, which may be located between the suction check valve 23 and the evaporator 2. A first on-off valve 18, such as a solenoid valve, is provided on at least one of the second oil return line 30 and the liquid extraction line 60 to control the on / off state of the automatic oil return. Automatic oil return is enabled when the valve is on, and shuts off when the valve is off. To increase the amount of automatic oil return, more than two second oil return lines 30 may be provided. Optionally, a first filter 19 may be provided on the second oil return line 30 to filter impurities from the oil.

[0059] The automatic oil return device 4 is used to take out the liquid refrigerant in the user-end evaporator 2, separate the lubricating oil melted therein and return it to the air intake 1A of the compressor 1, and control the amount of melted oil in the refrigerant in the evaporator 2 to avoid too much melted oil affecting heat exchange.

[0060] The refrigeration system of this embodiment provides compressor 1 with multiple oil return methods, including suction oil return, forced oil return through the first oil return line 20 and pump 11, and automatic oil return through the automatic oil return device 4. These methods can be selected based on the actual operating state of compressor 1, eliminating the need to rely solely on suction oil return, a single oil return method. This allows for timely oil return, making compressor 1's oil return more reliable and sufficient, preventing oil shortages due to oil return fluctuations when the compressor frequency changes, thereby extending the compressor's service life and significantly improving the reliability of the refrigeration system. Furthermore, if a particular oil return line becomes clogged or fails, oil can still be returned through other oil return lines, eliminating the need to shut down the unit for maintenance. Oil return failures can be addressed while the unit is operating, improving production efficiency.

[0061] In some embodiments, at least two pumps 11 are provided on the first oil return line 20, and the at least two pumps 11 are arranged in parallel. The at least two pumps 11 can supply oil simultaneously or partially to ensure reliable oil supply to the first oil return line 20.

[0062] Optionally, only one pump 11 is provided.

[0063] This embodiment provides at least two pumps 11 in parallel on the first oil return line 20. Depending on the oil return demand, some or all of the pumps 11 can be selected for use to provide sufficient driving pressure and ensure reliable oil supply. If a pump 11 fails, the driving pressure can still be provided by the remaining pumps 11, allowing the unit to continue operating normally and undergo maintenance without shutting down.

[0064] In some embodiments, as Figure 1 As shown, the refrigeration system also includes:

[0065] A coarse filter 12 is provided on the first oil return line 20 and upstream of the pump 11; and / or

[0066] The fine filter 13 is provided on the first oil return pipeline 20 and is located downstream of the pump 11 .

[0067] In this embodiment, the coarse filter 12 is provided, and the oil is 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 the fine filter 13, small-sized impurity particles in the lubricating oil can be removed, and finally the lubricating oil entering the compressor is ensured to be very clean, so as to ensure that the friction points of the compressor bearings, rotors, shaft seals, etc. are well lubricated, operate normally, and reduce wear.

[0068] When both the coarse filter 12 and the fine filter 13 are provided, after the oil is separated in the oil separator 3, it first enters the coarse filter 12 to remove larger impurity particles in the lubricating oil, making the lubricating oil entering the fine filter 13 relatively clean, reducing the burden on the fine filter 13, and ensuring that the oil pump and compressor are well lubricated, operate normally, and avoid wear. After leaving the pump 11, it passes through the fine filter 13 to further remove small impurity particles in the lubricating oil, and finally ensures that the lubricating oil entering the compressor is very clean, ensuring that the friction points such as the compressor bearings, rotors, and shaft seals are well lubricated, operate normally, and reduce wear.

[0069] In some embodiments, the refrigeration system further includes at least two fine filters 13, which are arranged in parallel on the first oil return line 20 and downstream of the pump 11. The at least two fine filters 13 can filter simultaneously, or they can be manually adjusted so that some are in use and some are in standby, ensuring reliable filtering of the first oil return line 20.

[0070] This embodiment provides at least two fine filters 13 in parallel on the first oil return line 20. Depending on the filtration requirements, some or all of the fine filters 13 can be selected for use to ensure effective oil filtration. If a fine filter 13 fails, filtration can still be performed through the remaining fine filters 13, improving system reliability. Furthermore, the faulty fine filter 13 can be replaced and repaired without shutting down the system.

[0071] 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.

[0072] In some embodiments, as Figure 1 As shown, the refrigeration system also includes:

[0073] An oil cooler 5 is provided in parallel with the first oil return line 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 line 20 upstream of the pump 11; and

[0074] 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.

[0075] The oil cooler 5 can 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 can be provided on the first oil return line 20 to detect the oil temperature.

[0076] The oil temperature control valve 37 is used to control the oil temperature. It automatically adjusts 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 controls the valve opening, thereby adjusting the fluid flow rate and opening temperature.

[0077] After flowing out of the oil separator 3, if the oil temperature is normal, it flows directly through the oil temperature control valve 37 into the coarse filter 12 and is then drawn into the pump 11. If the oil flowing out of the oil separator 3 exceeds a preset high temperature threshold, the first port 37A connecting the oil temperature control valve 37 to the oil separator 3 is disconnected, and the oil can only flow into the oil cooler 5. Liquid refrigerant from the condenser 6 can flow into the oil cooler 5. The liquid refrigerant absorbs heat from the oil and evaporates into gaseous refrigerant, which loses heat and cools the oil. Once the oil reaches the appropriate temperature, it flows through the second port 37B, the oil temperature control valve 37, into the coarse filter 12, and is then drawn into the pump 11. After leaving the pump 11, the oil passes through the fine filter 13 and ultimately flows into the compressor 1.

[0078] When the refrigeration system of this embodiment is running, if the oil temperature is detected to be too high, the lubricating oil separated by the oil separator 3 is first passed through the oil cooler 5 to reach the viscosity and temperature required by the compressor 1, and then sprayed into the compressor 1 for recycling, so as to prevent the high-temperature return oil from accelerating the wear of the compressor 1, thereby increasing the service life of the compressor 1.

[0079] 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.

[0080] This embodiment provides a first electric heater 36 in the oil separator 3. If the oil temperature is detected to be too low before the compressor 1 is started or during operation, the first electric heater 36 can be started to raise the oil temperature to a suitable range, thereby preventing the low-temperature oil return from increasing the power consumption of the compressor 1.

[0081] In some embodiments, as Figure 2 As shown, the refrigeration system also includes:

[0082] 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

[0083] The first bypass oil circuit 40 has a first end connected to the first oil return line 20 at a position downstream of the pump 11, and a second end connected to the 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.

[0084] Among them, one or at least two pressure sensors 15 can be provided. Figure 2 A pressure sensor 15 is installed upstream and downstream of the fine filter 13. The detection value of the pressure sensor 15 downstream of the fine filter 13, close to the compressor 1, is closer to the actual pressure of the compressor 1. When controlling the operation of the constant pressure valve 14, this pressure sensor 15 can be used as the reference, and the detection value of the other pressure sensor 15 is used as an auxiliary detection. If the pressure sensor 15 close to the compressor 1 fails, the detection value of the other pressure sensor 15 is used to control the operation of the constant pressure valve 14. This structure solves the problem of a single detection component, which requires production to be stopped for maintenance if a component fails.

[0085] This embodiment monitors the oil pressure before entering the compressor 1 by providing a pressure sensor 15, and controls the return oil pressure of the first return oil line 20 via a constant pressure valve 14, ensuring that the oil is supplied at an appropriate pressure. When the oil supply pressure of the pump 11 exceeds a preset pressure threshold, the constant pressure valve 14 opens, releasing pressure through the first bypass oil line 40, and partially returning the oil to the oil separator 3, preventing injection noise caused by high-pressure oil supply. When the oil supply pressure of the pump 11 does not exceed the preset pressure threshold, the pump 11 continues to operate to increase the oil supply pressure, ensuring that the oil is supplied at an appropriate pressure and preventing insufficient oil supply caused by low-pressure oil supply.

[0086] In some embodiments, as 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.

[0087] The second on-off valve 17 is configured to be closed when the detection value of the pressure sensor 15 exceeds a preset pressure threshold and the constant pressure valve 14 fails. When the constant pressure valve 14 is normal, the pressure is preferentially released through the first bypass oil passage 40. For example, the second on-off valve 17 may be a solenoid valve.

[0088] This embodiment provides both a first bypass oil passage 40 and a second bypass oil passage 70 between the outlet of the pump 11 and the oil separator 3. When the oil supply pressure of the pump 11 exceeds a preset threshold, the priority constant-pressure valve 14 opens to release pressure through the first bypass oil passage 40, allowing some oil to flow back into the oil separator 3. This maintains a stable oil supply pressure for the pump 11 and prevents jetting noise caused by high-pressure oil supply. Furthermore, if the constant-pressure valve 14 malfunctions and is unable to release pressure, the second on-off valve 17 can still be connected to the second bypass oil passage 70 for pressure relief, acting as a backup pressure relief device and improving the reliability and safety of the refrigeration system.

[0089] In some embodiments, an oil level switch 4 ′ is provided in the automatic oil return device 4 at a preset height position. 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.

[0090] The automatic oil return device 4 is used to remove liquid refrigerant from the evaporator 2, extract the lubricating oil that has been dissolved, and return it to the compressor suction port. This controls the amount of refrigerant melted in the evaporator to prevent excessive melted oil from 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 level falls below a preset height, the oil level switch 4' opens, automatically removing liquid refrigerant from the evaporator 2. If the oil level reaches the preset height, the oil level switch 4' closes, preventing liquid refrigerant from being removed from the evaporator 2. The automatic oil return device 4 can be set to on or off. If there is less melted oil in the evaporator 2, the automatic oil return device 4 can be turned off.

[0091] 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 level is lower than a preset height position, without the need for control intervention, thereby reducing the difficulty of controlling the automatic oil return. The lubricating oil melted in the evaporator 2 can be separated and returned to the air intake port 1A of the compressor 1, thereby controlling the amount of melted oil in the refrigerant in the evaporator 2 to avoid excessive melted oil affecting heat exchange.

[0092] 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.

[0093] 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.

[0094] This embodiment provides a second electric heater in the automatic oil return device 4, which can heat the oil for automatic oil return before the compressor 1 is turned on or during operation, thereby raising the oil temperature to a suitable range and preventing the low-temperature oil return from increasing the power consumption of the compressor 1.

[0095] 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.

[0096] 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 .

[0097] The compressor 1 of this embodiment is provided with an oil discharge port 1D. When the internal oil level exceeds that of the oil discharge port 1D, the oil automatically flows out through the oil discharge port 1D and into the oil separator 3 via the oil discharge pipeline 50, thereby preventing the oil level in the compressor 1 from being excessively high and causing oil compression. Furthermore, the oil discharge stop check valve 16 is unidirectional, preventing the oil in the oil separator 3 from flowing back into the compressor 1, thereby improving the safety of the compressor 1.

[0098] In some embodiments, as Figure 1 and Figure 3 As shown, the oil storage area of ​​the compressor 1 is provided with a dual oil level switch 21, which 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. The second height position Hmax is higher than the first height position Hmin.

[0099] 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 4 stops operating;

[0100] 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

[0101] When the oil level 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 unloads the oil into the oil separator 3 through the oil unloading port 1D.

[0102] 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 independently selected.

[0103] Conventional compressors decide whether to return oil based solely on external parameters. When compressor parameters change, there is a lag in the control of the oil return volume, resulting in untimely, insufficient, unreliable oil return, or even oil shortage.

[0104] This embodiment detects the liquid level of the compressor 1 via a dual oil level switch 21. Based on the actual liquid level, different oil return combinations are selected from suction return, automatic return, and forced return. This allows for more direct control, resulting in timely, reliable, and sufficient oil return. This ensures that the compressor 1 is well lubricated before startup or during operation, and precisely controls the amount of oil returned from the compressor 1, extending its service life and preventing excessive oil in the compressor 1 from causing liquid compression. Furthermore, the dual oil level switch 21 offers higher reliability than a single oil level switch. Failure of the oil level switch eliminates the need for shutdown, ensuring smooth production. Furthermore, when the compressor frequency fluctuates, causing the liquid level to fluctuate, the dual oil level switch 21 will not activate frequently, thereby extending its service life. When the oil level deviates from a low or high level, the switch can be activated quickly to promptly return or unload the oil.

[0105] 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 extraction 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), and the forced oil return operation can be enabled when the pump 11 is turned on. At this time, oil can be returned simultaneously through the three oil return modes, so that the lubricating oil of the compressor 1 can be quickly replenished to a suitable height range.

[0106] 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 extraction 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.

[0107] When h>Hmax, the combination of suction oil return operation, automatic oil return operation stop, and automatic oil unloading is selected for oil return control. Because a small amount of suction oil return will still occur when the oil in the compressor 1 exceeds the maximum allowable amount, the excess oil will automatically enter the oil separator 3 through the oil unloading port 1D.

[0108] In some embodiments, as Figure 1 As shown, the refrigeration system also includes:

[0109] an oil cooler 5 , provided in parallel with the first oil return line 20 , configured to cool the oil returned from the oil separator 3 to the compressor 1 ; and

[0110] 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.

[0111] 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.

[0112] For example, condenser 6 can be an evaporative condenser, which uses the evaporation of spray water outside the coil to absorb the heat of the high-temperature gaseous refrigerant within the coil, gradually cooling the refrigerant from gas to liquid. After the gaseous refrigerant is drawn into compressor 1, the compressed gas enters condenser 6, where it is condensed into a saturated liquid with a certain degree of subcooling. A portion of the liquid refrigerant flowing out of condenser 6 can be supplied to oil cooler 5 for heat exchange with the oil.

[0113] This embodiment utilizes the liquid refrigerant flowing out of the condenser 6 to cool the oil in the oil cooler 5, directly utilizing the supercooled liquid refrigerant in the main circulation loop without increasing the complexity of the system. Furthermore, if the lubricating oil separated by the oil separator 3 is too hot, it can be cooled to the required viscosity and temperature for the compressor 1 after entering the oil cooler 5 for heat exchange with the liquid refrigerant. The oil can then be injected into the compressor 1 for recycling, preventing high-temperature oil return from accelerating wear of the compressor 1 and thereby extending the service life of the compressor 1.

[0114] In some embodiments, the refrigeration system further includes: a siphon liquid reservoir 7, 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 exhaust port 5D of the oil cooler 5, and the return air port 7D of the siphon liquid reservoir 7 is connected to the air inlet 6A of the condenser 6.

[0115] The principle of the siphon reservoir 7 is based on the siphon effect of liquid. When liquid is present inside the container, a pressure difference occurs within the container, that is, the gas pressure at the top is lower than the vapor pressure at the liquid surface. At this time, the gas trapped 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. Under the action of gravity, it flows freely into the liquid storage tank. When the liquid level reaches a certain level, the interior of the container will return to equilibrium, and the siphon effect at the inlet will cease.

[0116] The liquid inlet 7A and the return air port 7D may be located at the top of the siphon accumulator 7, and the liquid outlet 7B and the air inlet 7C may be located at the bottom of the siphon accumulator 7. The siphon accumulator 7 may be located above the oil cooler 5 so that gravity can be used to allow the liquid refrigerant to smoothly enter the oil cooler 5. The gaseous refrigerant generated by the heat exchange between the liquid refrigerant and the oil enters the return air pipe through the exhaust port 5D of the oil cooler 5, then enters the exhaust pipe from the return air port 7D of the siphon accumulator 7, and is condensed again in the condenser 6.

[0117] Optionally, Figure 1 There are two parallel condensers 6 in the middle. 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 is gathered and enters the siphon liquid reservoir 7. Part of the liquid refrigerant enters the oil cooler 5 for heat exchange and the gaseous refrigerant formed returns to the siphon liquid reservoir 7 and is then divided into two paths and enters the two condensers 6 for re-condensation.

[0118] This embodiment is capable of storing and transferring the liquid refrigerant formed by the condenser 6 by providing a siphon liquid reservoir 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, while meeting the refrigerant flow requirements of the main circulation loop. The refrigerant can also achieve gas-liquid separation in the siphon liquid reservoir 7.

[0119] In some embodiments, the refrigeration system further includes: a liquid reservoir 8 , a liquid inlet 8A of the liquid reservoir 8 is connected to the overflow port 7E of the siphon liquid reservoir 7 , and a liquid outlet 8B of the liquid reservoir 8 is connected to the liquid inlet 2B of the evaporator 2 .

[0120] The function of accumulator 8 is to store and transfer liquid refrigerant. Most of the liquid refrigerant in siphon accumulator 7 enters accumulator 8. After exiting, it passes through second filter 26 to remove impurities and moisture, is further subcooled, and then supplied to evaporator 2 at the end of the refrigeration cycle. The refrigerant gas exiting evaporator 2 is then drawn back into compressor 1, continuing the refrigeration cycle. A small amount of liquid refrigerant in siphon accumulator 7 enters oil cooler 5. For example, accumulator 8 can be positioned below siphon accumulator 7 in height to facilitate smoother liquid flow into accumulator 8.

[0121] In this embodiment, a liquid accumulator 8 is provided 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 a timely manner, thereby increasing the storage capacity of the liquid refrigerant to meet the situation of large load fluctuations in the refrigeration system and improving the performance of the unit; moreover, the liquid refrigerant is also mixed with gas, which can be separated into gas and liquid twice after passing through the siphon liquid accumulator 7 and then entering the liquid accumulator 8, thereby improving the gas-liquid separation effect and increasing the content of the liquid refrigerant entering the evaporator 2.

[0122] 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.

[0123] In some embodiments, the refrigeration system further includes: a subcooler 9, which is provided between the siphon liquid reservoir 7 and the evaporator 2 and is configured to subcool the liquid refrigerant in the main circulation loop.

[0124] For example, the subcooler 9 can be a shell and tube economizer to subcool the refrigerant in the main circulation loop. In the embodiment where the liquid reservoir 8 is provided, the subcooler 9 can be provided between the liquid reservoir 8 and the evaporator 2.

[0125] This embodiment can supercool the liquid refrigerant in the main circulation loop by providing the subcooler 9, thereby improving the economy and efficiency of the refrigeration cycle.

[0126] Below Figure 1 The refrigeration system in Figure 1 is used as an example to illustrate its specific structure. The figure shows two dashed boxes, representing a compressor module 100 and a condensing module 200. Compressor module 100 drives the refrigerant, while condensing module 200 performs condensation heat exchange, transferring exhaust heat from 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 accumulator 7, accumulator 8, and subcooler 9.

[0127] The connection methods for these major components have been described in the previous embodiments; this section will focus on components not mentioned. Compressor 1 is equipped with a solenoid valve assembly 22, which is used to change compressor 1's operating parameters and adjust cooling capacity. A branch line 80 can be provided between the outlet of the oil separator 3 and the suction line 10. This branch line 80 is equipped with a sight glass 31, a third solenoid valve 32, and a first filter 19. The sight glass 31 allows the content of liquid refrigerant in the gaseous refrigerant drawn from the oil separator 3 to be observed. Excessive liquid refrigerant can adversely affect the operation of compressor 1.

[0128] Optionally, a second filter 26 may be provided between the subcooler 9 and the compressor 1. For example, this filter may be a straight-through filter or a filter with an inclined filter element, which can be directly removed for 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.

[0129] Optionally, multiple shutoff valves are provided in the refrigeration system to facilitate component and pipeline maintenance. For example, a first shutoff valve 24 is provided on both the second oil return line 30 and the branch line 80. A second shutoff valve 35 is provided on the line between the oil separator 3 and the air inlet 6A of the condenser 6. A third shutoff valve 34 is provided between the liquid outlet 6B of the condenser 6 and the siphon reservoir 7. A fourth shutoff valve 27 may be provided between the fine filter 13 and the compressor 1. Furthermore, a fourth shutoff valve 25 is provided at various locations within the line where there are bends.

[0130] Figure 1 The refrigeration system shown works as follows:

[0131] The refrigerant circulation path is as follows: gaseous refrigerant from evaporator 2 is drawn into compressor 1. The compressed gas enters condenser 6, condensing it into a saturated liquid with a certain degree of subcooling. The subcooled liquid enters siphon accumulator 7, feeding oil cooler 5. The resulting gaseous refrigerant after heat exchange enters the exhaust pipe through the return air pipe and is further condensed in condenser 6. Most of the liquid in siphon accumulator 7 enters accumulator 8, where it passes through a filter or filter drier to remove impurities and moisture. It then enters economizer 9 for further subcooling before being supplied to evaporator 2. The gaseous refrigerant evaporated from evaporator 2 is again drawn into compressor 1, continuing the refrigeration cycle.

[0132] The lubricating oil circulation in the refrigeration system includes three flow paths, namely: the suction return oil 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.

[0133] The suction and oil return flow path is: compressor 1 - oil separator 3 - condenser 6 - siphon accumulator 7 - accumulator 8 - subcooler 9 - evaporator 2 - compressor 1. Tiny oil droplets entrained in the refrigerant circulate with the refrigerant, and each component operates according to the refrigerant cycle requirements, requiring no special control.

[0134] The automatic oil return flow path is: evaporator 2 - first on-off valve 18 of liquid extraction line 60 - automatic oil return device 4 - first on-off valve 18 of second oil return line 30 - first filter 19 - first shut-off valve 24 of second oil return line 30 - suction check valve 23 - compressor 1. During automatic oil return operation, the first on-off valve 18 of liquid extraction line 60 and second oil return line 30 is open. Automatic oil return removes liquid refrigerant from evaporator 2, extracts the lubricating oil, and returns it to the compressor suction port. This controls the amount of refrigerant melted in the evaporator to prevent excessive melted oil from affecting heat exchange.

[0135] The forced oil return 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 switched on and off based on temperature. After oil flows out of the oil separator 3 and is at normal temperature, it flows directly through the oil temperature control valve 37 into the coarse filter 12 and is then drawn into the pump 11. If the oil flows out of the oil separator 3 and is at a high temperature, the first port 37A connecting the oil temperature control valve 37 to the oil separator 3 is blocked, and the oil can only flow into the oil cooler 5. Within the oil cooler 5, liquid refrigerant from the siphon reservoir 7 absorbs heat from the oil and evaporates into gaseous refrigerant, cooling the oil as it loses heat. Once the oil reaches the appropriate temperature, it passes through the oil temperature control valve 37, flows into the coarse filter 12, and is then drawn into the pump 11. After exiting the pump 11, it passes through the fine filter 13 and ultimately flows into the compressor 1.

[0136] The refrigeration system disclosed herein 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.

[0137] In some embodiments of the large-scale low-temperature refrigeration screw unit system, the cooling capacity is 1800 kW, and the shell and tube economizer liquid outlet temperature is -18°C.

[0138] 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:

[0139] Detecting the oil level in the oil storage area of ​​the compressor 1;

[0140] 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 4 stops operating;

[0141] 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

[0142] When the oil level is higher than the second height position Hmax, the air suction and oil return operation is started, the automatic oil return device 4 stops running, and the compressor 1 unloads the oil into the oil separator 3 through the oil unloading port 1D;

[0143] The second height position Hmax is higher than the first height position Hmin.

[0144] 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.

[0145] 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, which can timely, reliably and fully return oil, so that the compressor 1 reaches a good lubrication state before starting or during operation, and realizes precise control of the oil return amount of the compressor 1, thereby improving the service life and preventing excessive oil in the compressor 1 from causing liquid compression.

[0146] 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 extraction 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 by the operation of the pump 11. At this time, oil can be returned simultaneously through the three oil return modes, so that the lubricating oil of the compressor 1 can be quickly replenished to a suitable height range.

[0147] 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 extraction 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.

[0148] When h>Hmax, the combination of suction oil return operation, automatic oil return operation stop, and automatic oil unloading is selected for oil return control. Because a small amount of suction oil return will still occur when the oil in the compressor 1 exceeds the maximum allowable amount, the excess oil will automatically enter the oil separator 3 through the oil unloading port 1D.

[0149] Although some specific embodiments of the present disclosure have been described in detail through examples, those skilled in the art will understand that the above examples are for illustration only and are not intended to limit the scope of the present disclosure. Those skilled in the art will understand that the above embodiments may be modified or some technical features may be replaced with 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 line (20), wherein a pump (11) is provided on the first oil return line (20); and An automatic oil return device (4) is provided, 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); 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, wherein: 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.

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

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

5. The refrigeration system according to claim 1, wherein: 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) has a first interface (37A), a second interface (37B) and a third interface (37C), wherein the first interface (37A) is in communication with the oil outlet (3B) of the oil separator (3), and the first interface (37A) is closed when the oil temperature exceeds a preset high temperature threshold, the second interface (37B) is in communication with the oil outlet (5B) of the oil cooler (5), and the third interface (37C) is in communication with the pump (11).

6. The refrigeration system according to claim 1, wherein: 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, wherein: Also includes: 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 A first bypass oil circuit (40) is provided, wherein a first end of the first bypass oil circuit (40) is connected to a position of the first oil return line (20) 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, wherein: 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 line (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, wherein: 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), and the oil discharge port (1D) is connected to the oil inlet (3C) of the oil separator (3) via an oil discharge pipeline (50). 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, wherein: 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 line (20), and configured to cool the oil returned from the oil separator (3) to the compressor (1); and A condenser (6), wherein the air inlet (6A) of the condenser (6) is connected to the exhaust port (1B) of the compressor (1) through the oil separator (3), and the liquid refrigerant flowing out of the liquid outlet (6B) of the condenser (6) is partially provided to the oil cooler (5) for cooling the oil.

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

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

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

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