Refrigeration system and oil shortage judgment method thereof

Abstract

The present invention relates to a refrigeration system and a method for determining oil shortage therefor. The method comprises the following steps: obtaining the return oil temperature of an oil separator; obtaining the ambient temperature; determining whether the return oil temperature is greater than the ambient temperature; obtaining a first difference between the return oil temperature and the ambient temperature based on the return oil temperature being greater than the ambient temperature; determining that the refrigeration system is oil-deficient based on the first difference being less than a first preset temperature value; and determining that the refrigeration system is oil-free based on the return oil temperature being less than the ambient temperature. The method for determining oil shortage according to the present invention can quickly and accurately determine whether the lubricating oil in the current compressor is oil-deficient or oil-free, so that measures such as oil replenishment can be taken in a timely manner based on the determination result, thereby preventing the compressor from operating in an oil-deficient or oil-free state and improving the reliability of the compressor's operation.

Description

Technical Field

[0001] The present invention relates to the technical field of refrigeration equipment, and in particular to a refrigeration system and an oil shortage judgment method thereof. Background Art

[0002] This section merely provides background information related to the present disclosure and is not necessarily prior art.

[0003] Refrigeration oil, commonly known as lubricating oil, is used to lubricate the moving parts of refrigeration compressors. Therefore, a certain oil level must be maintained during operation to ensure that the oil reaches all moving parts and prevent damage from friction. When there is little or no refrigerant oil at the bottom of the compressor, the moving parts of the compressor are prone to abnormal friction and damage. Oil shortage is currently one of the main causes of compressor failure.

[0004] Currently, compressor oil shortage protection relies solely on the oil return function of the air conditioner's refrigeration system. In actual operation, the oil return function is based on the compressor's cumulative operating time. However, existing equipment does not have an oil shortage detection function. If the compressor is low on oil or even completely empty, continued operation may cause damage to the compressor. Summary of the Invention

[0005] The purpose of the present invention is to at least solve the problem that existing equipment does not have the function of determining oil shortage. This purpose is achieved through the following technical solutions:

[0006] The first technical solution of the present invention proposes a method for judging oil shortage in a refrigeration system, wherein the refrigeration system includes a compressor and an oil separator, and the method for judging oil shortage includes: obtaining the return oil temperature of the oil separator; obtaining the ambient temperature; judging whether the return oil temperature is greater than the ambient temperature; obtaining a first difference between the return oil temperature and the ambient temperature based on the return oil temperature being greater than the ambient temperature; judging that the refrigeration system is short of oil based on the first difference being less than a first preset temperature value; and judging that the refrigeration system is without oil based on the return oil temperature being less than the ambient temperature.

[0007] According to the oil shortage judgment method for a refrigeration system proposed in the present invention, by comparing the return oil temperature with the ambient temperature, when the return oil temperature is greater than the ambient temperature and the first difference between the return oil temperature and the ambient temperature is less than a first preset temperature value, it can be judged that the compressor is short of oil; when the return oil temperature is less than the ambient temperature, it can be judged that the current compressor is out of oil. Based on the oil shortage judgment method proposed in the present invention, it is possible to quickly and accurately judge whether the lubricating oil in the current compressor is short of oil or out of oil, so as to take measures such as oil replenishment to the compressor in a timely manner according to the judgment result, prevent the compressor from operating in an oil shortage or oil-free state, and improve the reliability of the compressor operation.

[0008] In addition, the method for determining oil shortage in a refrigeration system according to the present invention may also have the following additional technical features:

[0009] In some embodiments of the present invention, before obtaining the return oil temperature of the oil separator, the step further includes: obtaining the startup duration of the compressor; and executing the step of determining whether the return oil temperature is greater than the ambient temperature based on the startup duration being greater than a first preset time value.

[0010] In some embodiments of the present invention, before determining whether the return oil temperature is greater than the ambient temperature, the method further includes: obtaining the exhaust temperature of the compressor; and executing the step of determining whether the return oil temperature is greater than the ambient temperature based on the return oil temperature being less than the exhaust temperature.

[0011] In some embodiments of the present invention, after determining that the refrigeration system is short of oil based on the first difference being less than a first preset temperature value, the method further includes: obtaining the return air temperature of the compressor; obtaining a first value of the sum of the return air temperature and a preset fixed value; determining whether the return oil temperature is less than or equal to the first value; determining that the refrigeration system is short of oil based on the return oil temperature being less than or equal to the first value; and determining that the refrigeration system is short of oil based on the return oil temperature being greater than the first value.

[0012] In some embodiments of the present invention, after the return oil temperature is less than or equal to the first value, before determining that the refrigeration system is oil-free, the method further includes: obtaining a second preset temperature value, and determining whether the first difference is less than the second preset temperature value; and determining that the refrigeration system is oil-free based on the first difference being less than the second preset temperature value; wherein the second preset temperature value is less than the first preset temperature value.

[0013] In some embodiments of the present invention, the oil shortage determination method further comprises: outputting an oil shortage warning signal based on determining that the refrigeration system is short of oil.

[0014] In some embodiments of the present invention, the oil shortage judgment method further includes: obtaining the operating time of the compressor based on determining that the refrigeration system has no oil; outputting a compressor shutdown signal based on the operating time being greater than a second preset time value, and controlling the compressor to shut down.

[0015] According to the second technical solution of the present invention, a refrigeration system is also proposed, which is used to implement the oil shortage judgment method in the first technical solution. The refrigeration system includes a main circuit and a compressor, an oil separator, a condenser and an evaporator connected in series on the main circuit in sequence, and the oil outlet of the oil separator is connected to the compressor through an oil return pipe; the refrigeration system also includes: a return oil temperature sensor, which is provided on the oil return pipe, and the return oil temperature sensor is used to obtain the return oil temperature; an ambient temperature sensor is used to obtain the ambient temperature; a control device, which is electrically connected to both the return oil temperature sensor and the ambient temperature sensor, and the control device judges whether the refrigeration system is short of oil based on the return oil temperature and the ambient temperature.

[0016] In some embodiments of the present invention, the refrigeration system further includes: an exhaust temperature sensor, disposed in the main circuit and close to the air inlet of the oil separator; and a return air temperature sensor, disposed in the main circuit and close to the air inlet of the compressor.

[0017] In some embodiments of the present invention, the refrigeration system further includes: a control device, which is electrically connected to the compressor, the exhaust temperature sensor, the return air temperature sensor, the return oil temperature sensor and the ambient temperature sensor, and the control device controls the operation of the compressor based on the parameters of the exhaust temperature sensor, the return air temperature sensor, the return oil temperature sensor and the ambient temperature sensor. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Various other advantages and benefits will become apparent to those skilled in the art upon reading the detailed description of the preferred embodiment below. The accompanying drawings are for illustration purposes only and are not to be considered as limiting the present invention. The same reference numerals are used throughout the accompanying drawings to denote the same components. In the accompanying drawings:

[0019] Figure 1 Schematically shows a structural diagram of a refrigeration system according to an embodiment of the present invention;

[0020] Figure 2 Schematically shows a schematic diagram of electrical connections between a control device, temperature sensors, and a compressor according to an embodiment of the present invention;

[0021] Figure 3 The following schematically shows a flow chart of a method for determining oil shortage in a refrigeration system according to one embodiment of the present invention;

[0022] Figure 4 The following schematically shows a flow chart of a method for determining oil shortage in a refrigeration system according to one embodiment of the present invention;

[0023] Figure 5 The following schematically shows a flow chart of a method for determining oil shortage in a refrigeration system according to one embodiment of the present invention;

[0024] Figure 6 The following schematically shows a flow chart of a method for determining oil shortage in a refrigeration system according to one embodiment of the present invention;

[0025] Figure 7 The flowchart of the method for determining oil shortage in a refrigeration system according to one embodiment of the present invention is schematically shown.

[0026] The reference numerals are as follows:

[0027] 10-main circuit, 20-compressor, 30-oil separator, 40-oil return pipe, 50-condenser, 60-evaporator, 70-gas-liquid separator, 80-backup compressor;

[0028] 200-control device, 201-exhaust temperature sensor, 202-return air temperature sensor, 203-ambient temperature sensor, 204-return oil temperature sensor. DETAILED DESCRIPTION

[0029] Exemplary embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. Although exemplary embodiments of the present disclosure are shown in the accompanying drawings, it should be understood that the present disclosure can be implemented in various forms and should not be limited by the embodiments described herein. Rather, these embodiments are provided to enable a more thorough understanding of the present disclosure and to fully convey the scope of the present disclosure to those skilled in the art.

[0030] It should be understood that the terms used herein are for the purpose of describing specific example embodiments only and are not intended to be limiting. Unless the context clearly indicates otherwise, the singular forms "one", "an" and "said" as used herein may also be meant to include plural forms. The terms "comprise", "include", "contain" and "have" are inclusive and therefore specify the presence of stated features, steps, operations, elements and / or parts, but do not exclude the presence or addition of one or more other features, steps, operations, elements, parts, and / or combinations thereof. The method steps, processes, and operations described herein are not to be construed as necessarily requiring them to be performed in the specific order described or illustrated, unless the order of execution is clearly indicated. It should also be understood that additional or alternative steps may be used.

[0031] Although the terms first, second, third, etc. can be used in the text to describe multiple elements, components, regions, layers and / or sections, these elements, components, regions, layers and / or sections should not be limited by these terms. These terms can only be used to distinguish an element, component, region, layer or section from another region, layer or section. Unless the context clearly indicates otherwise, terms such as "first", "second" and other numerical terms do not imply order or sequence when used in the text. Therefore, the first element, component, region, layer or section discussed below can be referred to as the second element, component, region, layer or section without departing from the teaching of the example embodiments.

[0032] For ease of description, spatially relative terms may be used herein to describe the relationship of one element or feature relative to another element or feature as shown in the figures, such as "inside," "outside," "inside," "outside," "below," "beneath," "above," and the like. Such spatially relative terms are intended to include different orientations of the device in use or operation in addition to the orientation depicted in the figures. For example, if the device in the figures is flipped, an element described as "below" or "below" another element or feature would then be oriented as "above" or "above" another element or feature. Thus, the example term "below" can include both above and below orientations. The device may be otherwise oriented (rotated 90 degrees or in other orientations) and the spatially relative descriptors used herein are interpreted accordingly.

[0033] According to an embodiment of the present invention, a method for determining oil shortage in a refrigeration system is proposed.

[0034] like Figure 3 As shown, the oil shortage judgment method includes the following steps:

[0035] Step S101: obtaining the oil return temperature of the oil separator;

[0036] Step S102: Obtaining the ambient temperature:

[0037] Step S103: Determine whether the return oil temperature is greater than the ambient temperature. If so, execute step S104; otherwise, execute step S106.

[0038] Step S104: obtaining a first difference between the return oil temperature and the ambient temperature;

[0039] Step S105: determining that the refrigeration system is short of oil based on the first difference being less than a first preset temperature value;

[0040] Step S106: Determine whether the refrigeration system has no oil.

[0041] In this embodiment, the refrigeration system includes a compressor, an oil separator, and a condenser. Specifically, the air outlet of the compressor is connected to the air inlet of the oil separator, which is in turn connected to the air inlet of the condenser. The oil separator also has an oil outlet, which is connected to the return air line of the compressor via an oil return pipe. Specifically, the oil separator is used to separate the lubricating oil from the high-pressure steam discharged from the refrigeration compressor to ensure safe and efficient operation of the device. Based on the oil separation principle of reducing the air flow velocity and changing the air flow direction, the oil particles in the high-pressure steam are separated under the action of gravity. The portion above the oil separator is the refrigerant, and the portion below the oil separator is the lubricating oil. The lubricating oil flows back to the compressor via the oil return pipe to prevent the lubricating oil from flowing into the chiller and evaporator.

[0042] The oil separator typically separates the lubricating oil mixed with the refrigerant gas, allowing it to drip and collect at the bottom of the oil separator's internal container. When the accumulated lubricating oil reaches a certain level, it is automatically returned to the compressor crankcase through the oil return valve. The float valve in the oil separator operates intermittently. When the accumulated lubricating oil reaches a certain level, the float valve opens, allowing the lubricating oil to flow back to the compressor through the return pipe. This process is known as the compressor's oil return. Once the oil return is complete, if the accumulated lubricating oil level falls below the set level, the float valve closes, and the compressor stops returning oil.

[0043] Understandably, because the oil separator separates the high-temperature refrigerant and lubricating oil, the separated lubricating oil that accumulates at the bottom of the oil separator container also has a higher temperature (higher than the ambient temperature). Therefore, during the oil return process, the oil return pipe is filled with the heated lubricating oil, resulting in a higher measured oil return temperature. During the oil return stop, the oil return pipe is affected by the ambient temperature and the compressor return air (the cooler refrigerant flowing back from the evaporator outlet), resulting in a lower temperature measured in the oil return pipe, close to the ambient temperature.

[0044] Based on this, in step S101, the oil return temperature of the oil separator is obtained, which is the temperature measured in the oil return pipe during the oil return process. In step S102, the ambient temperature is the air temperature of the environment in which the refrigeration system is located. In steps S103 to S105, if the oil return temperature is greater than the ambient temperature, it means that during the oil return process, there is a fluid (lubricating oil or refrigerant) with a temperature higher than the ambient temperature that continuously flows from the oil separator in the oil return pipe. Therefore, a first difference between the oil return temperature and the ambient temperature is calculated. If the first difference is less than a first preset temperature value, it means that the oil flowing in the oil return pipe is lubricating oil and the flow rate of the lubricating oil per unit time is lower than the normal value. Therefore, it can be determined that the current compressor is short of oil.

[0045] Among them, the first preset temperature value can specifically be the difference between the return oil temperature in the return oil pipe and the ambient temperature measured during the oil return process when the refrigeration system is in normal operating condition (that is, the operating condition in which the compressor is not short of oil). If the first difference is less than the first preset temperature value, it means that the current lubricating oil flow in the return oil pipe is less than the flow under normal operating condition, and therefore it can be judged that the compressor is short of oil.

[0046] It is understood that the first preset temperature value may have different values ​​based on the refrigeration system model, rated power and working environment. In an exemplary embodiment, the first preset temperature value is 10°C.

[0047] In step S106, if the return oil temperature is lower than the ambient temperature during the oil return process, it means that the return oil pipe is directly affected by the low-temperature refrigerant discharged from the air outlet of the evaporator in the return air pipe, causing the temperature in the return oil pipe to drop below the ambient temperature. It can be understood that only when there is no lubricating oil in the return oil pipe will the low-temperature refrigerant flow back into the return oil pipe, so it can be determined that the compressor is out of oil.

[0048] like Figure 4 As shown, in some embodiments of the present invention, the following steps are further included before step S101:

[0049] Step S201: Obtaining the startup time of the compressor;

[0050] Step S202: Execute step S103 according to the boot time being longer than the first preset time value.

[0051] In this embodiment, when the startup time of the compressor is greater than the first preset time value, it indicates that the compressor has entered a stable operating state, thereby avoiding errors in the detection of the return oil temperature due to too short a startup time of the compressor, which affects the accuracy of the judgment result.

[0052] In this embodiment, the first preset time value is set to 60s. In other embodiments, the first preset time value may also be set to other values, such as 70s, 90s, 120s, etc., which are not specifically limited here.

[0053] like Figure 5 As shown, in some embodiments of the present invention, the following steps are further included before step S103:

[0054] Step S301: obtaining the exhaust temperature of the compressor;

[0055] Step S302: Execute step S103 based on the oil return temperature being lower than the exhaust temperature.

[0056] In this embodiment, in steps S301 and S302, the oil return temperature is compared with the exhaust temperature to determine whether the oil separator is operating normally. When the oil separator is operating normally, the oil return temperature is greater than the ambient temperature and less than the exhaust temperature. Therefore, when the oil return temperature is less than the exhaust temperature, it indicates that the oil separator is operating normally, ensuring the accuracy of the determination result. This prevents misjudgment of the oil return temperature due to abnormal oil separator operation or abnormal operating conditions (such as high temperature).

[0057] like Figure 6 As shown, in some embodiments of the present invention, the following steps are further included after step S105:

[0058] Step S401: obtaining the return air temperature of the compressor;

[0059] Step S402: obtaining a first value of the sum of the return air temperature and a preset fixed value;

[0060] Step S403: determining whether the oil return temperature is less than or equal to a first value;

[0061] Step S404: determining that the refrigeration system is oil-free based on the oil return temperature being less than or equal to the first value;

[0062] Step S405: determining that the refrigeration system is short of oil based on the oil return temperature being greater than the first value.

[0063] In this embodiment, it should be noted that after determining that the compressor is oil-free in step S105, it is necessary to further determine whether there is an oil-free situation. Specifically, when the compressor is oil-free, there is also no oil in the oil separator and the oil return pipe. Since the oil return pipe is connected to the oil separator and the return air port of the compressor, respectively, some high-temperature refrigerant can overflow into the oil return pipe through the oil separator, and some low-temperature refrigerant from the evaporator's air outlet also intrudes into the oil return pipe. Therefore, both the high-temperature refrigerant from the oil separator and the low-temperature refrigerant from the evaporator's air outlet will affect the temperature in the oil return pipe, causing the measured return oil temperature to be close to the return air temperature. Therefore, there is a situation where the return oil temperature is slightly higher than the return air temperature. The preset fixed value is that when the compressor is oil-free, the return oil temperature is higher than the upper limit of the return air temperature. Therefore, when the oil return temperature is less than or equal to the sum of the oil return temperature and a preset fixed value, it indicates that there is no oil in the oil return pipe. If the oil return temperature is lower than the ambient temperature, it can be determined that low-temperature refrigerant from the evaporator outlet has sufficiently infiltrated the oil return pipe, thus confirming that the compressor is oil-free. In this embodiment, the preset fixed value is 2°C.

[0064] like Figure 7As shown, in some embodiments of the present invention, after determining that the return oil temperature is less than or equal to the first value and before determining that the refrigeration system is oil-free, the following steps are further included:

[0065] Step S501: obtaining a second preset temperature value;

[0066] Step S502: determining whether the first difference is less than a second preset temperature value;

[0067] Step S503: determining that the refrigeration system is oil-free based on the first difference being less than the second preset temperature value.

[0068] The second preset temperature value is lower than the first preset temperature value.

[0069] In this embodiment, since the return air temperature and the ambient temperature are both floating values, the return air temperature may be greater than the ambient temperature or may be less than the ambient temperature. Therefore, in order to improve the accuracy of the oil-free state judgment, a second preset temperature value is set, and the second preset temperature value is less than the first preset temperature value. When the return oil temperature simultaneously satisfies the return oil temperature being less than or equal to the first value, and the return oil temperature being greater than the ambient temperature and the first difference being less than the second preset temperature value, it is determined that the refrigeration system is oil-free.

[0070] In this embodiment, the second preset temperature value is 8°C.

[0071] In some embodiments of the present invention, when it is determined that the compressor is short of oil, an oil shortage warning message is issued, so that maintenance personnel can promptly understand the oil shortage status and replenish lubricating oil in time.

[0072] The oil shortage warning information may be in the form of text, images, or other information, or may be issued using sound wave signals, light signals, or the like.

[0073] In some embodiments of the present invention, when it is determined that the compressor is in an oil-free state and has been running continuously for a period exceeding a second preset time value, the compressor is controlled to shut down to prevent damage to the compressor from continued operation in the oil-free state. In this embodiment, the second preset time value is 180 seconds. In other embodiments, the second preset time value can also be set to other values, such as 120 seconds, 160 seconds, 190 seconds, 220 seconds, etc., which are not specifically limited here.

[0074] It should be emphasized that the sequence numbers of the steps in the present invention do not represent the order of the oil shortage determination method. For example, steps S501 to S503 are performed before step S106.

[0075] In a specific embodiment, the judgment logic of the compressor oil shortage is as follows:

[0076] When the compressor startup time is greater than 60 s, obtain the oil return temperature (T_oil), the ambient temperature (T_ambient), and the discharge temperature (T_discharge).

[0077] When the oil return temperature is greater than the ambient temperature and less than the discharge temperature, and it also needs to satisfy that the oil return temperature is less than the sum of the ambient temperature and 10 °C, then it is determined that the compressor is short of oil.

[0078] That is: T_ambient < T_oil < T_discharge; and

[0079] T_ambient < T_oil < T_ambient + 10 °C.

[0080] In a specific embodiment, the judgment logic for the compressor being oil-free is as follows:

[0081] When the compressor startup time is greater than 60 s, obtain the oil return temperature (T_oil), the ambient temperature (T_ambient), and the suction gas temperature (T_suction).

[0082] When the oil return temperature is less than or equal to the sum of the suction gas temperature and 2 °C, and it also needs to satisfy that the oil return temperature is greater than the ambient temperature minus 2 °C and less than the ambient temperature plus 8 °C, then it is determined that the compressor is oil-free.

[0083] That is: T_oil <= T_suction + 2 °C; and

[0084] T_ambient - 2 °C < T_oil < T_ambient + 8 °C.

[0085] The oil shortage judgment method for the refrigeration system proposed by the present invention can achieve automatic oil shortage warning, and the algorithm has a wide coverage, sensitive response, the refrigeration system has a simple structure, high reliability, and low production cost.

[0086] According to the embodiments of the present invention, as Figure 1 and Figure 2 shown, a refrigeration system is also proposed. The refrigeration system can implement the above-mentioned oil shortage judgment method. Specifically, the refrigeration system includes a main circuit 10 for the refrigerant to circulate, a compressor 20, an oil separator 30, a condenser 50, and an evaporator 60 that are sequentially connected in series on the main circuit 10. The oil separator 30 includes an air inlet, an air outlet, and an oil return outlet. The oil outlet is connected to the air inlet of the compressor 20 through an oil return pipe 40. Specifically, the function of the oil separator 30 is to separate the lubricating oil in the high-pressure steam discharged by the refrigeration compressor 20 to ensure the safe and efficient operation of the device. According to the oil separation principle of reducing the air flow velocity and changing the air flow direction, the oil particles in the high-pressure steam are separated under the action of gravity. The part above the oil separator 30 is the refrigerant, and the part below the oil separator 30 is the lubricating oil. The lubricating oil flows back to the compressor 20 through the oil return pipe 40 to prevent the lubricating oil from flowing into the condenser and the evaporator 60.

[0087] In this embodiment, the refrigeration system also includes: an exhaust temperature sensor 201, a return air temperature sensor 202, a return oil temperature sensor 204, an ambient temperature sensor 203 and a control device 200. In detail, an exhaust temperature sensor 201 is set in the main circuit 10 near the air inlet of the oil separator 30 to obtain the exhaust temperature. A return air temperature sensor 202 is set in the main circuit 10 near the air inlet of the compressor 20 to obtain the return air temperature. The return oil temperature sensor 204 is set in the middle area of ​​the return oil pipe 40 to obtain the return oil temperature during the oil return process. The purpose of setting the return oil temperature sensor 204 in the middle area of ​​the return oil pipe 40 is to reduce the impact of the low-temperature refrigerant in the return air pipe on the return oil pipe 40 when the compressor 20 is short of oil, so as to ensure the accuracy of the return oil temperature. The ambient temperature sensor 203 is set at the air inlet end of the condenser 50 to obtain the ambient temperature of the refrigeration system.

[0088] The control device 200 is electrically connected to the compressor 20, the exhaust temperature sensor 201, the return air temperature sensor 202, the ambient temperature sensor 203 and the return oil temperature sensor 204, so that the control device 200 can obtain data such as the ambient temperature, return oil temperature, exhaust temperature and return air temperature, as well as data such as the startup and operation time of the compressor 20, and based on the obtained various temperature data, it determines whether the current compressor 20 is in an oil-deficient or oil-free state, and then controls the operation of the compressor 20 in combination with data such as the startup and operation time of the compressor 20.

[0089] In some embodiments of the present invention, the refrigeration system further includes a backup compressor 80, which is connected to the main circuit 10 in parallel with the compressor 20, and a check valve is provided on the air outlet pipe connected to the air outlet of the backup compressor 80 and the air outlet pipe connected to the air inlet of the oil separator 30. The check valve can be a variety of electric or mechanical stop valves. Of course, a mechanical check valve is preferred in this case. The backup compressor 80 connected in parallel with the compressor 20 can be of various electrical systems and structural types and is not limited to 220V / 50Hz, horizontal or vertical, piston or vortex, etc. It should be noted that by running two compressors 20 in parallel, an oil accumulation bend is set on the return pipe to prevent the oil from accumulating in the other compressor 20 when one compressor 20 stops running. At the same time, an equalizing pressure pipe and an equalizing oil pipe are installed above and below the oil surface of the crankcase to keep the pressure and oil level in the crankcase the same.

[0090] In this embodiment, a gas-liquid separator 70 is also provided in the main circuit 10. The gas-liquid separator 70 ensures the mixing of the refrigeration oil and the refrigerant at low temperatures, so that the refrigerant and the oil return to the compressor 20 at a certain ratio, maintaining the high efficiency of the system and the normal oil level of the crankcase. When the evaporator 60 is in a full liquid state under normal operation at low temperature conditions, it can also prevent the compressor 20 from "returning liquid". It can also prevent excessive refrigerant from diluting the oil in the compressor 20. Under certain operating conditions, the gas-liquid separator 70 can continuously store a certain amount of liquid. It is a liquid (oil) storage device and also a pressure vessel. The oil accumulation bend design on the return air pipeline is eliminated, simplifying the refrigeration system pipeline. The high-pressure liquid is supercooled, improving the refrigeration efficiency.

[0091] When using hot fluorine for defrosting, the necessary heat can be provided, eliminating the need to worry about a lack of heat source or the need for additional auxiliary heaters. As can be seen from the above, using multiple machines in parallel is just one of many applications. The system principle is connected to a compressor 20 and a gas-liquid separator 70 installed on the return air line. When two or more compressors 20 are operating in parallel, they can share a gas-liquid separator 70 to solve the system's oil return problem. When multiple compressors 20 operate in parallel and share a gas-liquid separator 70, not only can better oil return be achieved, but each compressor 20 in parallel operation can also operate at a relatively close suction pressure. This also simplifies the refrigeration system structure, ensuring that the refrigeration oil and refrigerant return to the compressor 20 at a sufficient ratio at low temperatures, maintaining system operating efficiency and a normal crankcase oil level.

[0092] The refrigeration system and the oil shortage judgment method of the refrigeration system proposed in the present invention can be applied to any of cold chain vehicles, cold chain containers and cold storages to provide a reliable and stable supply of cold air.

[0093] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in the present invention should be included in the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be based on the scope of protection of the claims.

Claims

1. A method for determining oil shortage in a refrigeration system, wherein the refrigeration system comprises a compressor and an oil separator, wherein: The oil shortage judgment method includes: Obtaining the return oil temperature of the oil separator; Get the ambient temperature; determining whether the oil return temperature is greater than the ambient temperature; Obtaining a first difference between the oil return temperature and the ambient temperature based on the oil return temperature being greater than the ambient temperature; Determining that the refrigeration system is short of oil based on the first difference being less than a first preset temperature value; Determining that the refrigeration system is oil-free based on the oil return temperature being lower than the ambient temperature; The first preset temperature value is the difference between the return oil temperature in the return oil pipe and the ambient temperature, measured during the oil return process when the refrigeration system is in normal operation; After determining that the refrigeration system is short of oil based on the first difference being less than a first preset temperature value, the method further includes: Obtaining the return air temperature of the compressor; Obtaining a first value of the sum of the return air temperature and a preset fixed value; determining whether the oil return temperature is less than or equal to the first value; The refrigeration system is judged to be oil-free if the return oil temperature is less than or equal to the first value; the refrigeration system is judged to be oil-deficient if the return oil temperature is greater than the first value. The preset fixed value is that when the compressor is oil-free, the return oil temperature is greater than the upper limit value of the return air temperature.

2. The method for determining oil shortage in a refrigeration system according to claim 1, wherein: Before obtaining the oil return temperature of the oil separator, the method further includes: Obtaining the startup time of the compressor; The step of determining whether the oil return temperature is greater than the ambient temperature is performed according to the startup duration being greater than a first preset time value.

3. The method for determining oil shortage in a refrigeration system according to claim 1, wherein: Before determining whether the oil return temperature is greater than the ambient temperature, the method further includes: Obtaining the exhaust temperature of the compressor; The step of determining whether the oil return temperature is greater than the ambient temperature is performed based on the oil return temperature being less than the exhaust temperature.

4. The method for determining oil shortage in a refrigeration system according to claim 1, wherein: After the oil return temperature is less than or equal to the first value, and before determining that the refrigeration system is oil-free, the method further includes: Obtaining a second preset temperature value; Determining whether the first difference is less than the second preset temperature value; Determining that the refrigeration system is oil-free based on the first difference being less than the second preset temperature value; Wherein, the second preset temperature value is lower than the first preset temperature value.

5. The method for determining oil shortage in a refrigeration system according to claim 1, wherein: The oil shortage judgment method further includes: An oil shortage warning signal is outputted based on determining that the refrigeration system is short of oil.

6. The method for determining oil shortage in a refrigeration system according to claim 1, wherein: The oil shortage judgment method further includes: Obtaining the operating time of the compressor based on determining that the refrigeration system is oil-free; According to the running time being greater than a second preset time value, a compressor shutdown signal is output, and the compressor is controlled to shut down.

7. A refrigeration system for implementing the oil shortage judgment method according to any one of claims 1 to 6, wherein the refrigeration system comprises a main circuit and a compressor, an oil separator, a condenser, and an evaporator connected in series to the main circuit, wherein the oil outlet of the oil separator is connected to the compressor via an oil return pipe; The refrigeration system further comprises: an oil return temperature sensor, provided on the oil return pipe, for obtaining the oil return temperature; Ambient temperature sensor, used to obtain ambient temperature; A control device is electrically connected to the oil return temperature sensor and the ambient temperature sensor, and the control device determines whether the refrigeration system is short of oil based on the oil return temperature and the ambient temperature.

8. The refrigeration system according to claim 7, characterized in that The refrigeration system further comprises: an exhaust temperature sensor, disposed in the main circuit and close to the air inlet of the oil separator; The return air temperature sensor is arranged in the main circuit and close to the air inlet of the compressor.

9. The refrigeration system according to claim 8, characterized in that The control device is electrically connected to the compressor, the exhaust temperature sensor, the return air temperature sensor, the return oil temperature sensor and the ambient temperature sensor, and the control device controls the operation of the compressor based on parameters of the exhaust temperature sensor, the return air temperature sensor, the return oil temperature sensor and the ambient temperature sensor.

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