Oil circuit system, cascade unit, energy-saving device, refrigeration device and control method

Abstract

The application relates to an oil circuit system, a cascade unit, an energy-saving device, a refrigeration device and a control method, the oil circuit system comprising a first heat exchanger, a first oil tank and a second oil tank, the first heat exchanger being internally provided with a first channel and a second channel, heat exchange being allowed between the first channel and the second channel; the two ends of the first oil tank are respectively communicated with the first channel to form a first circulating oil circuit; and the two ends of the second oil tank are respectively communicated with the second channel to form a second circulating oil circuit. The oil circuit system provided by the application has a large temperature difference between the oil in the first oil tank and the oil in the second oil tank, and when one of the oils has an excessively low oil temperature and the other has an excessively high oil temperature or an excessively high temperature, heat exchange between the two circulating oil circuits can be realized through the first heat exchanger, and the excessively low oil temperature and the excessively high oil temperature can be simultaneously relieved, so that the normal operation of the oil circuit can be ensured. No heating component or oil cooling component needs to be additionally arranged, and the power consumption and manufacturing cost of the oil circuit system can be significantly reduced.

Description

TECHNICAL FIELD

[0001] The present application relates to the lubrication technical field, and particularly relates to an oil circuit system, a cascade unit, an energy-saving device, a refrigeration device and a control method. BACKGROUND

[0002] Since the lubricating oil can significantly reduce the friction between two relatively moving parts, reduce wear and tear, and at the same time, take away the heat generated in the friction process through the oil flow to achieve equipment cooling and prevent overheating of the equipment.

[0003] In order to realize the lubrication of multiple relative friction parts, the prior art usually realizes targeted lubrication through multiple independent oil circuits. However, due to the different relative motion conditions of different friction parts, the heat generated is also quite different, which leads to a large temperature difference between multiple independent oil circuits. When the oil temperature is too low or too high, the lubrication will be abnormal. Since multiple oil circuits are independent of each other, heat cannot be transferred and neutralized, and a one-to-one heating assembly and oil cooling assembly need to be provided for each oil circuit, which leads to an increase in the overall cost of the equipment lubrication system.

[0004] Taking the oil circuit in the cascade unit as an example, the cascade unit includes a high-temperature level refrigeration system and a low-temperature level refrigeration system. When the low-temperature level refrigeration system is started, the oil temperature of the low-temperature level lubrication system is low, the viscosity of the oil is large, and the lubricating oil has poor flowability, which will cause the low-temperature level compressor lubrication system to be abnormal. The compressor in the high-temperature level refrigeration system generates a large amount of heat during operation, which will cause the temperature of the high-temperature level lubricating oil circuit to rise rapidly, the oil temperature is high, and then the viscosity of the oil is reduced, the lubricating effect of the lubricating oil is poor, and the high-temperature level compressor lubrication system will be abnormal. SUMMARY

[0005] The present application provides an oil circuit system, a cascade unit, an energy-saving device, a refrigeration device and a control method to solve the technical problem that when multiple oil circuits are independent of each other in the prior art, a large temperature difference is easily generated due to different heat of the lubrication area, and the oil temperature of multiple oil circuits is easily too low or too high.

[0006] In a first aspect, the present application provides an oil circuit system, comprising:

[0007] A first heat exchanger, the inside of the first heat exchanger is provided with a first channel and a second channel, and the first channel and the second channel can exchange heat;

[0008] A first oil tank, both ends of the first oil tank are in communication with the first channel to form a first circulating oil circuit;

[0009] A second oil tank, both ends of the second oil tank are in communication with the second channel to form a second circulating oil circuit.

[0010] Optionally, the first oil tank and the second oil tank are each provided with a temperature detection member, and the first circulating oil path and the second circulating oil path are each provided with a valve member, and when the temperature difference between the oil temperature in the first oil tank and the oil temperature in the second oil tank is greater than a preset temperature difference threshold, the valve member is opened.

[0011] Optionally, the oil path system further comprises a second heat exchanger, and the two ends of the first oil tank are in communication with the second heat exchanger, forming a third circulating oil path.

[0012] Optionally, the first heat exchanger and the second heat exchanger are arranged in parallel at the two ends of the first oil tank.

[0013] Alternatively, the first heat exchanger and the second heat exchanger are arranged in series.

[0014] Optionally, the second heat exchanger is a flash evaporator provided with a heat exchange pipe group.

[0015] Optionally, the third circulating oil path is provided with a valve member.

[0016] In a second aspect, the application provides a complex superposition unit, comprising the oil path system provided by the first aspect of the application, and further comprising a high-temperature level refrigeration system, a low-temperature level refrigeration system, and an intermediate heat exchanger, the intermediate heat exchanger having a third passage and a fourth passage inside, the third passage being in communication with the high-temperature level refrigeration system to form a first refrigerant circulation loop, and the fourth passage being in communication with the low-temperature level refrigeration system to form a second refrigerant circulation loop.

[0017] The two ends of the first oil tank are in communication with the high-temperature level refrigeration system to form a fourth circulating oil path, and the two ends of the second oil tank are in communication with the low-temperature level refrigeration system to form a fifth circulating oil path.

[0018] Optionally, the high-temperature level refrigeration system comprises a first compressor and a high-temperature level condenser, a first exhaust pipe of the first compressor is in communication with the high-temperature level condenser, and the high-temperature level condenser is provided with a first oil separation assembly inside.

[0019] The fourth circulating oil path comprises a first oil supply pipe and a first oil return pipe, the first oil supply pipe is connected between the first oil tank and the first compressor, and the first oil return pipe is connected between the first oil separation assembly and the first oil tank.

[0020] Optionally, the high-temperature level refrigeration system further comprises a high-temperature level flash evaporator, a refrigerant outlet of the high-temperature level condenser is in communication with a refrigerant inlet of the high-temperature level flash evaporator through a first refrigerant inflow pipe, the high-temperature level flash evaporator is connected with a first refrigerant outflow pipe and a second refrigerant outflow pipe, the first refrigerant outflow pipe is in communication with an air inlet of the first compressor, the second refrigerant outflow pipe is in communication with an inlet of the third passage, and an outlet of the third passage is in communication with the air inlet of the first compressor.

[0021] Optionally, the low-temperature stage refrigeration system comprises a second compressor, a second exhaust pipeline of the second compressor being communicated with an inlet of the fourth channel, and the intermediate heat exchanger being internally provided with a second oil separation assembly communicated with the fourth channel;

[0022] The fifth circulating oil path comprises a second oil supply pipeline and a second oil return pipeline, the second oil supply pipeline being connected between the second oil tank and the second compressor, and the second oil return pipeline being connected between the second oil separation assembly and the second oil tank.

[0023] Optionally, the low-temperature stage refrigeration system further comprises a low-temperature stage flash evaporator and a low-temperature stage evaporator, an outlet of the fourth channel being communicated with a refrigerant inlet of the low-temperature stage flash evaporator through a second refrigerant inflow pipeline, the low-temperature stage flash evaporator being connected with a third refrigerant outflow pipeline and a fourth refrigerant outflow pipeline, the third refrigerant outflow pipeline being communicated with an air inlet of the second compressor, and the fourth refrigerant outflow pipeline being communicated with the low-temperature stage evaporator, and a refrigerant outlet of the low-temperature stage evaporator being communicated with the air inlet of the second compressor.

[0024] Optionally, the low-temperature stage flash evaporator is internally provided with a heat exchange tube group, the heat exchange tube group being communicated with an oil path of the first oil tank.

[0025] In a third aspect, the application provides an energy-saving device, comprising the cascade unit provided in the second aspect of the application, and further comprising a first working medium circulation system and a second working medium circulation system, the first working medium circulation system being connected with the high-temperature stage refrigeration system and being used for absorbing waste heat of the high-temperature stage refrigeration system, and the second working medium circulation system being connected with the low-temperature stage refrigeration system and being used for transferring waste heat to the low-temperature stage refrigeration system.

[0026] In a fourth aspect, the application further provides a refrigeration device, comprising the cascade unit provided in the second aspect of the application.

[0027] Alternatively, the refrigeration device comprises the energy-saving device provided in the third aspect of the application.

[0028] In a fifth aspect, the application further provides a control method applied to the oil path system provided in the first aspect of the application, comprising the following steps:

[0029] acquiring an actual oil temperature value T1 in the first oil tank and an actual oil temperature value T2 in the second oil tank;

[0030] judging whether to enter an oil-liquid heat exchange mode according to a comparison between the actual oil temperature values and preset oil temperature thresholds.

[0031] Optionally, the preset oil temperature thresholds comprise a first oil temperature threshold Y1 and a second oil temperature threshold Y2, and Y1>Y2;

[0032] if T1>Y2>T2, then the first circulating oil path and the second circulating oil path are started, and the oil-liquid heat exchange mode is entered;

[0033] If T1≥Y1 and T2≥Y2, the third circulating oil path is opened, and the oil liquid cooling mode is entered.

[0034] The above technical solutions provided by the embodiments of the present application have the following advantages compared with the prior art:

[0035] The oil path system provided by the embodiments of the present application communicates the first channel of the first heat exchanger and the first oil tank through the first circulating oil path, and communicates the second channel of the first heat exchanger and the second oil tank through the second circulating oil path. When there is a large temperature difference between the oil liquid temperatures in the first oil tank and the second oil tank, and one of them has an excessively low oil temperature and the other has an excessively high oil temperature or a high temperature, heat exchange between the first circulating oil path and the second circulating oil path that are independent of each other can be realized through the first heat exchanger, thereby simultaneously relieving the excessively low oil temperature and the excessively high oil temperature, and normal operation of the oil path can be ensured. The oil tank with an excessively low oil temperature does not need to be temperature-increased through an additionally arranged heating component, and the oil tank with an excessively high oil temperature does not need to be oil-cooled through an additionally arranged oil cooling component, which can significantly reduce the power consumption and manufacturing cost of the oil path system.

[0036] The cascade unit, the energy-saving device, the refrigeration device and the control method provided by the embodiments of the present application include or are applied to the above oil path system, and the oil liquid heat exchange between the two oil tanks can be realized through the oil path system. Therefore, the same technical effects as the above oil path system are also naturally obtained. BRIEF DESCRIPTION OF DRAWINGS

[0037] The accompanying drawings, which are incorporated into and form part of the specification, illustrate embodiments consistent with the present application and, together with the specification, serve to explain the principles of the application.

[0038] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the accompanying drawings needed to be used in the embodiments or the prior art description will be briefly introduced. Obviously, for those skilled in the art, other drawings can also be obtained without creative labor based on these drawings.

[0039] One or more embodiments are exemplarily illustrated by pictures in the drawings corresponding thereto, and these exemplary illustrations do not constitute a limitation on the embodiments. Elements with the same reference numerals in the drawings represent similar elements, unless otherwise specified. The drawings in the drawings do not constitute a proportional limitation.

[0040] Figure 1 The schematic diagram of the energy-saving device provided by the embodiments of the present application is shown in the following figure.

[0041] Figure 2 The connection diagram of the oil path system provided by the embodiments of the present application is shown in the following figure. Figure 1

[0042] ​Figure 3 A schematic diagram of the oil circuit system in oil heat exchange mode provided in the embodiments of this application;

[0043] Figure 4 This is a schematic diagram of the oil circuit system in oil cooling mode provided in the embodiments of this application. Figure 1 ;

[0044] Figure 5 Connection diagram of the oil circuit system provided in the embodiments of this application Figure 2 ;

[0045] Figure 6 This is a schematic diagram of the oil circuit system in oil cooling mode provided in the embodiments of this application. Figure 2 ;

[0046] Figure 7 A schematic diagram showing the connection of the high-temperature refrigeration system, the oil circuit system, and the first working fluid circulation system provided in an embodiment of this application;

[0047] Figure 8 A schematic diagram showing the connection of the cryogenic refrigeration system, the oil circuit system, and the second working fluid circulation system provided in an embodiment of this application;

[0048] Figure 9 Flowchart of the control method provided in the embodiments of this application Figure 1 ;

[0049] Figure 10 Flowchart of the control method provided in the embodiments of this application Figure 2 .

[0050] Explanation of reference numerals in the attached figures:

[0051] 1. Oil circuit system; 11. First heat exchanger; 12. First oil tank; 13. First circulating oil circuit; 131. First output oil circuit; 132. First input oil circuit; 133. First valve; 14. Second oil tank; 15. Second circulating oil circuit; 151. Second output oil circuit; 152. Second input oil circuit; 153. Second valve; 16. Third circulating oil circuit; 161. Third output oil circuit; 162. Third input oil circuit; 163. Third valve; 164. Fourth valve; 165. Oil pump; 17. Fourth circulating oil circuit; 171. First oil supply line; 172. First oil return line; 18. Fifth circulating oil circuit; 181. Second oil supply line; 182. Second oil return line;

[0052] 2. High-temperature stage refrigeration system; 21, first refrigerant circulation circuit; 211, first discharge line; 212, first refrigerant inflow line; 213, first refrigerant outflow line; 214, second refrigerant outflow line; 215, first suction line; 216, first throttling device; 217, second throttling device; 22, first compressor; 23, high-temperature stage condenser; 24, high-temperature stage flash evaporator; 25, first dry filter;

[0053] 3. Low-temperature stage refrigeration system; 31, second refrigerant circulation circuit; 311, second discharge line; 312, second refrigerant inflow line; 313, third refrigerant outflow line; 314, fourth refrigerant outflow line; 315, second suction line; 316, third throttling device; 317, fourth throttling device; 32, second compressor; 33, low-temperature stage flash evaporator; 34, low-temperature stage evaporator; 35, second dry filter;

[0054] 4. Intermediate heat exchanger. DETAILED DESCRIPTION

[0055] The technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all the other embodiments obtained by a person of ordinary skill in the art without creative work fall within the protection scope of the present application.

[0056] The following disclosure provides many different embodiments, or examples, for implementing different structures of the present application. For the purpose of simplification, the components and arrangements of specific examples are described in the following. Of course, they are only examples, and the purpose is not to limit the present application. In addition, the present application can repeatedly refer to the reference numerals and / or letters in different examples. Such repetition is for the purpose of simplification and clarity, and it does not indicate the relationship between the various embodiments and / or arrangements discussed.

[0057] For the convenience of description, spatial relative terms can be used in the specification to describe the relative position relationship or movement condition of one element or feature with respect to another element or feature as shown in the drawings, such as "inner", "outer", "inboard", "outboard", "under", "below", "on", "above", "front", "back", etc. Such spatial relative terms are intended to include different orientations of the device in use or operation in addition to the orientation depicted in the drawings. For example, if the device in the drawings is turned over or the posture is changed or the movement state is changed, the directional indications will also change accordingly, for example: the element described as "under" or "below" another element or feature will be oriented as "above" or "above" another element or feature. Therefore, the example term "below" can include both the upper and lower positions. The device can be additionally oriented (rotated by 90 degrees or in other directions) and the spatial relative relationship descriptors used in the specification are interpreted accordingly.

[0058] To solve the technical problem that when multiple oil paths are independent of each other in the prior art, a large temperature difference is easily generated due to different heat of lubrication areas, and multiple oil paths are easily in a situation of too low or too high oil temperature. The present application provides an oil path system 1, a cascade unit, an energy-saving device, a refrigeration device and a control method, which can realize heat exchange between two circulating oil paths through a first heat exchanger 11, and when there is a large temperature difference between two independent oil paths, the temperature difference between the two oil paths can be reduced through heat exchange, thereby avoiding the situation that the two oil paths are too low or too high in temperature, and the normal operation of the oil path can be ensured.

[0059] Please refer to Figures 1 to 10 The first aspect of the embodiment of the present application provides an oil path system 1, which comprises a first heat exchanger 11, a first oil tank 12 and a second oil tank 14. The first heat exchanger 11 is internally provided with a first channel and a second channel, and heat exchange can be performed between the first channel and the second channel. Specifically, the first heat exchanger 11 can be a plate heat exchanger, a tube-in-tube heat exchanger, etc., and the first channel and the second channel can be arranged in a structure of mutual winding or nesting, etc., which can all achieve the purpose of the present application.

[0060] Please refer to Figure 1 and Figure 2The two ends of the first oil tank 12 are respectively communicated with the first channel to form a first circulating oil path 13. The oil in the first oil tank 12 enters the first channel to exchange heat and then flows back to the first oil tank 12, so that the temperature of the oil in the first circulating oil path 13 and the first oil tank 12 can be changed. The two ends of the second oil tank 14 are respectively communicated with the second channel to form a second circulating oil path 15. The oil in the second oil tank 14 enters the second channel to exchange heat and then flows back to the second oil tank 14, so that the temperature of the oil in the second circulating oil path 15 and the second oil tank 14 can be changed. When the oil temperature in the first oil tank 12 and the second oil tank 14 has a large temperature difference, and one of them has an excessively low oil temperature and the other has an excessively high oil temperature, heat exchange between the two circulating oil paths can be realized through the first heat exchanger 11, and then the excessively low oil temperature and the excessively high oil temperature can be simultaneously relieved. The oil tank with an excessively low oil temperature does not need to be heated by an additional heating component, and the oil tank with an excessively high oil temperature does not need to be cooled by an additional oil cooling component, which can significantly reduce the power consumption and manufacturing cost of the oil path system 1.

[0061] It should be noted that when one of the first oil tank 12 and the second oil tank 14 has an excessively low oil temperature, and the other has only a relatively high oil temperature (i.e., not an excessively high oil temperature), heat exchange between the two circulating oil paths can still be realized through the first heat exchanger 11. While avoiding an excessively low oil temperature in one of them, the oil in the other oil tank can be cooled to improve the cooling capacity of the cooled oil.

[0062] In some embodiments of the present application, please refer to Figure 1 , Figure 2 and Figure 5 The arrows in the figure represent the oil flow direction. In the first heat exchanger 11, the flow directions of the oil in the first channel and the oil in the second channel are opposite. By means of counter-flow heat exchange, the heat exchange path of the oil with different temperatures in the first heat exchanger 11 is prolonged, the heat exchange efficiency of the hot oil and the cold oil in the first heat exchanger 11 is improved, the temperature distribution in the first heat exchanger 11 is relatively uniform, the thermal stress caused by the temperature gradient is reduced, and the stability and service life of the first heat exchanger 11 are improved.

[0063] In some embodiments of the present application, please refer to Figure 1 , Figure 2 , Figure 3 and Figure 5The first circulating oil circuit 13 comprises a first output oil circuit 131 and a first input oil circuit 132. The first output oil circuit 131 is configured to output the oil in the first oil tank 12 into the first channel of the first heat exchanger 11. The first input oil circuit 132 is configured to input the oil in the first channel into the first oil tank 12, so as to realize the backflow of the oil after heat exchange. The second circulating oil circuit 15 comprises a second output oil circuit 151 and a second input oil circuit 152. The second output oil circuit 151 is configured to output the oil in the second oil tank 14 into the second channel of the first heat exchanger 11. The second input oil circuit 152 is configured to input the oil in the second channel into the second oil tank 14, so as to realize the backflow of the oil after heat exchange.

[0064] In some embodiments of the present application, the first oil tank 12 and the second oil tank 14 are each provided with a temperature detection member, and the first circulating oil circuit 13 and the second circulating oil circuit 15 are each provided with a valve member. When the temperature difference between the oil in the first oil tank 12 and the oil in the second oil tank 14 is greater than a preset temperature difference threshold, the valve member is opened, so as to ensure the effectiveness of the temperature neutralization of the oil in the first oil tank 12 and the oil in the second oil tank 14 through heat exchange. Specifically, when the temperature difference between the oil in the first oil tank 12 and the oil in the second oil tank 14 is large, the temperature of the oil in the first oil tank 12 and the temperature of the oil in the second oil tank 14 can both change greatly (the low-temperature oil is heated and the high-temperature oil is cooled) after heat exchange through the first heat exchanger 11, so as to ensure the effect of avoiding the low-temperature or high-temperature of the oil. When the temperature difference between the oil in the first oil tank 12 and the oil in the second oil tank 14 is small (the oil in the first oil tank 12 and the oil in the second oil tank 14 are both low-temperature or high-temperature), the temperature of the oil in the first oil tank 12 and the temperature of the oil in the second oil tank 14 will not change greatly after heat exchange through the first heat exchanger 11, and the original temperature of the oil will still be maintained, which cannot effectively alleviate the low-temperature or high-temperature of the oil.

[0065] It should be noted that the preset temperature difference threshold can be set according to actual conditions. In some preferred embodiments of the present application, the preset temperature difference threshold is greater than or equal to 20℃.

[0066] In the following embodiments of the present application, the temperature of the oil in the first oil tank 12 is greater than the temperature of the oil in the second oil tank 14. When the oil in the second oil tank 14 is low-temperature and has poor flowability, the oil in the first oil tank 12 is high-temperature, and the oil in the first oil tank 12 can exchange heat with the oil in the second oil tank 14 through the first heat exchanger 11, so that the oil flowing back to the first oil tank 12 from the first heat exchanger 11 is cooled, and the oil flowing back to the second oil tank 14 from the first heat exchanger 11 is heated, which is beneficial to ensure the normal operation of the lubricating systems corresponding to the first oil tank 12 and the second oil tank 14.

[0067] It should be noted that in the heat exchange process, the oil in the first oil tank 12 and the second oil tank 14 will not be mixed, and the quality of the oil in the first oil tank 12 and the second oil tank 14 will not be adversely affected. The first oil tank 12 and the second oil tank 14 can select lubricating oils of different brands according to the lubrication needs, and will not affect the normal operation of the lubrication system.

[0068] In the above embodiment, if the oil temperature in the first oil tank 12 is too high, the oil in the first oil tank 12 is still at a high temperature level after heat exchange with the oil in the second oil tank 14; or, the oil temperature in the second oil tank 14 is within the normal working temperature range, and the oil in the first oil tank 12 cannot be cooled by heat exchange, which will cause the oil in the first oil tank 12 to be overheated, and the oil in the first oil tank 12 needs to be further cooled.

[0069] To solve the above technical problems, in some embodiments of the present application, please refer to Figure 2 and Figure 5 , the oil circuit system 1 further comprises a second heat exchanger, and the two ends of the first oil tank 12 are respectively communicated with the second heat exchanger, forming a third circulating oil circuit 16. The oil in the first oil tank 12 can be heat exchanged in the second heat exchanger, so that the temperature of the oil in the first oil tank 12 is within the normal working temperature range.

[0070] Specifically, in the second heat exchanger, the oil in the first oil tank 12 can exchange heat with other working medium, so that the temperature of the oil in the first oil tank 12 is reduced, and the risk of overheating of the oil in the first oil tank 12 is avoided. The normal working temperature range of the oil can be set according to the characteristics of the oil, and is usually between 10℃-50℃, and preferably between 15℃-40℃, which can not only ensure the reasonable viscosity and good flowability of the oil, but also ensure the good cooling effect of the oil on the lubricated parts.

[0071] In some embodiments of the present application, please refer to Figure 1 , Figure 2 , Figure 4 , Figure 5 and Figure 6 , the arrow indicates the flow direction of the oil, the third circulating oil circuit 16 comprises a third output oil circuit 161 and a third input oil circuit 162, the third output oil circuit 161 is used for outputting the oil in the first oil tank 12 to the heat exchange pipe group of the second heat exchanger; the third input oil circuit 162 is used for inputting the oil in the heat exchange pipe group to the first oil tank 12, so as to realize the backflow of the oil after heat exchange.

[0072] In some embodiments of the present application, please refer to Figure 2 , Figure 3 and Figure 4The first heat exchanger 11 and the second heat exchanger are arranged in parallel at two ends of the first oil tank 12, and the oil in the first oil tank 12 can be heated by the first heat exchanger 11 and the oil in the second oil tank 14 according to needs, which is referred to as an oil heating mode. The oil in the first oil tank 12 can also be cooled by the second heat exchanger through the third circulating oil path 16, which is referred to as an oil cooling mode. The oil in the first oil tank 12 can be cooled for the first time through the oil heating mode and then cooled for the second time through the oil cooling mode, so that the oil in the first oil tank 12 is fully cooled and cooled to a normal working temperature range. When the temperature of the oil in the second oil tank 14 is in the normal working temperature range, the first oil tank 12 can directly enter the oil cooling mode and be cooled by the second heat exchanger.

[0073] In some other embodiments of the present application, please refer to Figure 5 and Figure 6 The first heat exchanger 11 and the second heat exchanger are arranged in series, so that the oil in the first oil tank 12 flows through the first heat exchanger 11 and the second heat exchanger in sequence (or flows through the second heat exchanger and the first heat exchanger 11 in sequence), and the oil heating mode and the oil cooling mode are parallel. When the temperature of the oil in the second oil tank 14 is in the normal working temperature range, the second circulating oil path 15 can be closed, so that the oil in the first oil tank 12 is not heated by the oil in the second oil tank 14 in the first heat exchanger 11, and only the oil in the first oil tank 12 is cooled by the second heat exchanger, so that the oil cooling mode continues to operate.

[0074] As a specific embodiment of the present application, please refer to Figure 5 and Figure 6 When the first heat exchanger 11 and the second heat exchanger are arranged in series, the end of the first input oil path 132 is connected to the start of the third output oil path 161, so that the oil in the first oil tank 12 flows through the first heat exchanger 11 and the second heat exchanger in sequence, and is cooled twice, so that the temperature of the high-temperature oil in the first oil tank 12 is reduced to the normal working temperature range.

[0075] It should be noted that although the above two connection modes can achieve the cooling of the oil in the first oil tank 12, when the first heat exchanger 11 and the second heat exchanger are arranged in series, the oil path is relatively long, and the resistance of the oil in the flow process is also large. Therefore, in the embodiments of the present application, the first heat exchanger 11 and the second heat exchanger are preferably arranged in parallel.

[0076] In the above embodiments, the second heat exchanger can be any device that needs to absorb waste heat and achieve utilization. By absorbing the heat of the oil in the first oil tank 12, the waste heat can be recycled and utilized, and the energy utilization efficiency can be improved.

[0077] In some embodiments of the present application, please refer to Figure 1 , Figure 2 and Figure 5 , the second heat exchanger is a flash evaporator provided with a heat exchange tube group, the oil liquid in the first oil tank 12 enters the heat exchange tube group as the tube side working medium of the flash evaporator, and the refrigerant inside the flash evaporator is the shell side working medium. The heat can be transferred from the oil liquid in the heat exchange tube group to the shell side working medium, so that the liquid refrigerant inside the flash evaporator can be more quickly changed from liquid to gas, improving the gas supplement effect of the flash evaporator, and at the same time improving the gas supplement superheat of the flash evaporator, avoiding damage to the compressor caused by low gas supplement superheat of the flash evaporator.

[0078] In some embodiments of the present application, please refer to Figures 1 to 6 , the first circulating oil path 13, the second circulating oil path 15 and the third circulating oil path 16 are all provided with valve pieces, which can be used to realize the on-off control of the first circulating oil path 13, the second circulating oil path 15 and the third circulating oil path 16 respectively, and can enter the oil liquid heat exchange mode and / or the oil liquid cooling mode as needed.

[0079] Specifically, the first output oil path 131 and the first input oil path 132 of the first circulating oil path 13 are both provided with first valve pieces 133, the second output oil path 151 and the second input oil path 152 of the second circulating oil path 15 are both provided with second valve pieces 153, and the third output oil path 161 and the third input oil path 162 of the third circulating oil path 16 are both provided with third valve pieces 163. The above-mentioned valve pieces can be solenoid valves, electric valves, pneumatic valves and hydraulic valves, etc., all of which can realize the automatic on-off control of the oil path.

[0080] When the first heat exchanger 11 and the second heat exchanger are connected in parallel, if the oil path system 1 needs to execute the oil liquid heat exchange mode, the first valve piece 133 and the second valve piece 153 are opened, the first circulating oil path 13 and the second circulating oil path 15 are opened, the third valve piece 163 is closed, and the third circulating oil path 16 is closed, so that the first oil tank 12 and the second oil tank 14 can exchange heat through the first heat exchanger 11. If the oil path system 1 needs to execute the oil liquid cooling mode, the first valve piece 133 and the second valve piece 153 are closed, the first circulating oil path 13 and the second circulating oil path 15 are closed, the third valve piece 163 is opened, and the third circulating oil path 16 is opened, so that the oil liquid in the first oil tank 12 can be cooled through the second heat exchanger.

[0081] In some embodiments of the present application, the fourth valve piece 164 can also be arranged on the first circulating oil path 13, the second circulating oil path 15 and the third circulating oil path 16. The fourth valve piece 164 is a stop valve, so as to realize the segmented start-stop control and maintenance of each oil path.

[0082] In some embodiments of the present application, please refer to Figure 1 , Figure 2 , Figure 4 ,Figure 5 and Figure 6 The third circulation oil circuit 16 is provided with an oil pump 165, which can provide driving force for the oil flow in the third circulation oil circuit 16. It should be noted that the first circulation oil circuit 13 and the second circulation oil circuit 15 can also be provided with oil pumps to provide driving force for the oil flow (not shown in the figure), which will not be described here.

[0083] In some embodiments of the present application, temperature detection members are arranged on the first circulation oil circuit 13, the second circulation oil circuit 15 and the third circulation oil circuit 16, which can be used to detect the actual oil temperature at each part of the oil circuit system 1, so as to realize intelligent adjustment of the oil temperature.

[0084] Please refer to Figures 1 to 10 , the second aspect of the embodiments of the present application provides a cascade unit, which comprises the oil circuit system 1 in the above embodiments, and further comprises a high-temperature level refrigeration system 2, a low-temperature level refrigeration system 3 and an intermediate heat exchanger 4. The intermediate heat exchanger 4 has a third passage and a fourth passage inside. The third passage is in communication with the high-temperature level refrigeration system 2 to form a first refrigerant circulation loop 21, and the fourth passage is in communication with the low-temperature level refrigeration system 3 to form a second refrigerant circulation loop 31. During the operation of the cascade unit, the intermediate heat exchanger 4 is both an evaporator in the high-temperature level refrigeration system 2 and a condenser in the low-temperature level refrigeration system 3. The high-temperature level refrigeration system 2 uses a first refrigerant with a relatively high evaporation temperature, and the low-temperature level refrigeration system 3 uses a second refrigerant with a relatively low evaporation temperature. The second refrigerant transfers heat to the first refrigerant in the intermediate heat exchanger 4, so as to realize condensation of the second refrigerant and evaporation of the first refrigerant in the intermediate heat exchanger 4.

[0085] The two ends of the first oil tank 12 are respectively in communication with the high-temperature level refrigeration system 2 to form a fourth circulation oil circuit 17, which is used to provide lubricating oil for the components to be lubricated in the high-temperature level refrigeration system 2. The two ends of the second oil tank 14 are respectively in communication with the low-temperature level refrigeration system 3 to form a fifth circulation oil circuit 18, which is used to provide lubricating oil for the components to be lubricated in the low-temperature level refrigeration system 3. Because the refrigerating capacities of the high-temperature level refrigeration system 2 and the low-temperature level refrigeration system 3 are different, the friction heat generated during the operation of the two systems is also different, which can cause a large temperature difference between the oil in the first oil tank 12 and the oil in the second oil tank 14. The oil circuit system 1 in the above embodiments can realize heat exchange between the oil in the first oil tank 12 and the oil in the second oil tank 14, so that the first oil tank 12 and the second oil tank 14 respectively deliver lubricating oil in the normal working temperature range to the high-temperature level refrigeration system 2 and the low-temperature level refrigeration system 3, as shown in Figure 1 、 Figure 7 and Figure 8 , wherein Figure 1 、 Figure 7 and Figure 8 , the dashed lines in the figure represent oil circuits, and the solid lines represent refrigerant circulation loops.

[0086] It should be noted that in the process of operation of the existing cascade unit, the following problems often exist: firstly, the lubricating oil circuit in the low-temperature stage refrigeration system 3 has the problem of low oil temperature at start-up, the viscosity of the oil is large, the flowability of the lubricating oil is poor, which can cause oil supply difficulties, and further cause the lubrication system of the compressor in the low-temperature stage refrigeration system 3 to be abnormal. Secondly, after the cascade unit has been operated for a period of time, the compressor in the high-temperature stage refrigeration system 2 has a large refrigeration capacity, and the friction heat generated in the working process is also large, which can cause the oil temperature to rise rapidly, the viscosity of the lubricating oil to decrease rapidly, the lubrication effect to be poor, and further cause the lubrication system of the compressor in the high-temperature stage refrigeration system 2 to be abnormal. The oil circuit system 1 in the present application can realize heat exchange of the oil in the first oil tank 12 and the second oil tank 14 through the first heat exchanger 11, can avoid the oil temperature in the lubricating oil circuit of the compressor in the low-temperature stage refrigeration system 3 being too low, can avoid the oil temperature in the lubricating oil circuit of the compressor in the high-temperature stage refrigeration system 2 being too high, and further ensure the normal operation of the cascade unit.

[0087] In some embodiments of the present application, please refer to Figure 1 and Figure 7 The high-temperature stage refrigeration system 2 includes a first compressor 22 and a high-temperature stage condenser 23, and a first exhaust pipe 211 of the first compressor 22 is in communication with the high-temperature stage condenser 23. During the continuous exhaust process of the first compressor 22, lubricating oil (i.e., refrigeration oil) will be discharged from the first compressor 22 together with the gaseous first refrigerant through the first exhaust pipe 211. If the discharged refrigeration oil cannot return to the first compressor 22, it will cause the first compressor 22 to be out of oil, and in severe cases, even damage the first compressor 22. Therefore, the inside of the high-temperature stage condenser 23 is provided with a first oil separation assembly, which can be used to separate the refrigeration oil and the first refrigerant.

[0088] The fourth circulating oil circuit 17 includes a first oil supply pipe 171 and a first oil return pipe 172. The first oil supply pipe 171 is connected between the first oil tank 12 and the first compressor 22, and can continuously supply refrigeration oil to the first compressor 22 through the first oil tank 12. The first oil return pipe 172 is connected between the first oil separation assembly and the first oil tank 12, and can return the refrigeration oil separated in the high-temperature stage condenser 23 to the first oil tank 12, so as to realize the circulation of the refrigeration oil between the first compressor 22 and the first oil tank 12, and avoid the first compressor 22 being out of oil.

[0089] In some embodiments of the present application, please refer to Figure 1 and Figure 7The high-temperature stage refrigeration system 2 further comprises a high-temperature stage flash evaporator 24, and the refrigerant outlet of the high-temperature stage condenser 23 is communicated with the refrigerant inlet of the high-temperature stage flash evaporator 24 through a first refrigerant inflow pipeline 212, so that the condensed first refrigerant can be input into the high-temperature stage flash evaporator 24 to be rapidly evaporated to form saturated gaseous refrigerant and saturated liquid refrigerant. The high-temperature stage flash evaporator 24 is connected with a first refrigerant outflow pipeline 213 and a second refrigerant outflow pipeline 214, the first refrigerant outflow pipeline 213 is communicated with the gas inlet of the first compressor 22, and the saturated gaseous refrigerant enters the high-pressure stage gas inlet of the first compressor 22 from the top of the high-temperature stage flash evaporator 24 to be subjected to two-stage compression. The second refrigerant outflow pipeline 214 is communicated with the inlet of the third channel, so that the saturated liquid refrigerant flows into the intermediate heat exchanger 4 to be subjected to heat exchange and evaporation; the outlet of the third channel is communicated with the gas inlet of the first compressor 22, and the first refrigerant circulation loop 21 comprises the first exhaust pipeline 211, the first refrigerant inflow pipeline 212, the first refrigerant outflow pipeline 213 and the second refrigerant outflow pipeline 214, so that the refrigeration cycle of the first refrigerant can be completed.

[0090] In some embodiments of the present application, referring to Figure 7 , the first refrigerant inflow pipeline 212 is provided with a first throttling element 216, which can throttle the liquid refrigerant flowing out of the high-temperature stage condenser, and the throttled first refrigerant can be rapidly evaporated in the high-temperature stage flash evaporator 24. The second refrigerant outflow pipeline 214 is provided with a second throttling element 217, which can throttle the saturated liquid refrigerant flowing out of the high-temperature stage flash evaporator 24, so that the saturated liquid refrigerant can be further subjected to pressure reduction and expansion to become low-pressure and low-temperature liquid and then enter the intermediate heat exchanger 4 to be subjected to heat exchange and evaporation.

[0091] In some embodiments of the present application, referring to Figure 1 and Figure 7 , the first refrigerant inflow pipeline 212 is provided with a first dry filter 25, which can remove impurities and moisture in the first refrigerant, so that the service life of key components (such as the first compressor 22, the first throttling element 216 and the second throttling element 217) in the high-temperature stage refrigeration system 2 can be prolonged.

[0092] In some embodiments of the present application, referring to Figure 1 and Figure 8, the low-temperature stage refrigeration system 3 comprises a second compressor 32, a second exhaust pipe 311 of the second compressor 32 is communicated with the inlet of the fourth channel, during the continuous exhaust of the second compressor 32, the refrigeration oil in the second compressor 32 will be discharged from the second compressor 32 together with the gaseous second refrigerant through the second exhaust pipe 311, if the discharged refrigeration oil cannot return to the second compressor 32, the second compressor 32 will be out of oil or damaged. Therefore, the inside of the intermediate heat exchanger 4 is provided with a second oil separation assembly communicated with the fourth channel, so that the separation of the refrigeration oil and the second refrigerant can be realized.

[0093] The fifth circulating oil circuit 18 comprises a second oil supply pipe 181 and a second oil return pipe 182, the second oil supply pipe 181 is connected between the second oil tank 14 and the second compressor 32, and the second compressor 32 can be continuously supplied with refrigeration oil through the second oil tank 14, and the second oil return pipe 182 is connected between the second oil separation assembly and the second oil tank 14, so that the separated refrigeration oil in the intermediate heat exchanger 4 can be returned to the second oil tank 14, so as to realize the circulation of the refrigeration oil between the second compressor 32 and the second oil tank 14, and the out-of-oil condition of the second compressor 32 can be avoided.

[0094] In some embodiments of the present application, referring to Figure 1 and Figure 8 , the low-temperature stage refrigeration system 3 further comprises a low-temperature stage flash evaporator 33 and a low-temperature stage evaporator 34, the outlet of the fourth channel is communicated with the refrigerant inlet of the low-temperature stage flash evaporator 33 through a second refrigerant inflow pipe 312, so that the condensed second refrigerant can be input into the low-temperature stage flash evaporator 33 for rapid evaporation, thereby forming saturated gaseous refrigerant and saturated liquid refrigerant. The low-temperature stage flash evaporator 33 is connected with a third refrigerant outflow pipe 313 and a fourth refrigerant outflow pipe 314, the third refrigerant outflow pipe 313 is communicated with the gas inlet of the second compressor 32, the saturated gaseous refrigerant enters the high-pressure stage gas inlet of the second compressor 32 from the top of the low-temperature stage flash evaporator 33, and the two-stage compression can be realized. The fourth refrigerant outflow pipe 314 is communicated with the low-temperature stage evaporator 34, so that the saturated liquid refrigerant flows into the low-temperature stage evaporator 34 for heat exchange evaporation; the refrigerant outlet of the low-temperature stage evaporator 34 is communicated with the gas inlet of the second compressor 32, and the second refrigerant circulating loop 31 comprises the second exhaust pipe 311, the second refrigerant inflow pipe 312, the third refrigerant outflow pipe 313 and the fourth refrigerant outflow pipe 314, so that the refrigerant circulation of the second refrigerant can be completed.

[0095] In the above-mentioned embodiments, since the evaporation temperature of the second refrigerant is low, the gaseous second refrigerant output from the low-temperature stage flash evaporator 33 is lower than the saturation temperature at the pressure, thereby resulting in a low superheat degree of the gas supplement of the low-temperature stage flash evaporator 33, which may cause the liquefaction of the second refrigerant in the second compressor 32 and damage the second compressor 32.

[0096] To solve the above problems, in some embodiments of the present application, a heat exchange pipe group is arranged in the low-temperature flash evaporator 33, and the heat exchange pipe group is in communication with the oil circuit of the first oil tank 12, so that the low-temperature flash evaporator 33 can be configured as a second heat exchanger in the oil circuit system 1, and the temperature of the gaseous second refrigerant input into the low-temperature flash evaporator 33 by the second compressor 32 can be increased while the temperature of the oil liquid in the first oil tank 12 is reduced, so as to increase the superheat degree of the low-temperature flash evaporator 33.

[0097] In some embodiments of the present application, a baffle plate is further arranged in the liquid storage area in the low-temperature flash evaporator 33, which can strengthen the disturbance of the second refrigerant and evaporate the second refrigerant quickly, and can also prevent the liquid refrigerant in the low-temperature flash evaporator 33 from entering the second compressor 32 when the gas flow flows, so as to improve the superheat degree of the low-temperature flash evaporator.

[0098] In some embodiments of the present application, please refer to Figure 8 , the second refrigerant inflow pipeline 312 is provided with a third throttling device 316, the fourth refrigerant outflow pipeline 314 is provided with a fourth throttling device 317, and the second refrigerant inflow pipeline 312 is provided with a second dry filter 35, which can throttle or dry filter the second refrigerant in the second refrigerant circulation loop 31, and the functions of the first throttling device 216, the second throttling device 217 and the first dry filter 25 are similar, which will not be described here.

[0099] In the above embodiments, the first compressor 22 and the second compressor 32 are screw compressors, which can realize stepless adjustment of energy, so that the cascade unit can flexibly adjust the refrigerating capacity according to actual needs during operation, thereby improving the operation efficiency.

[0100] Please refer to Figures 1 to 10 , the third aspect of the embodiments of the present application provides an energy-saving device, which comprises the cascade unit in the above embodiments, and further comprises a first working medium circulation system and a second working medium circulation system, the first working medium circulation system is connected with the high-temperature refrigeration system 2, is used for absorbing the waste heat of the high-temperature refrigeration system 2, and realizes temperature rise of the first working medium in the first working medium circulation system through the waste heat of the high-temperature refrigeration system 2, so as to realize supply of hot fluid. The second working medium circulation system is connected with the low-temperature refrigeration system 3, is used for transferring waste heat to the low-temperature refrigeration system 3, realizes temperature reduction of the second working medium in the second working medium circulation system, and thus realizes supply of cold fluid.

[0101] In the above embodiments, the first working medium and the second working medium can be water, lubricating oil and refrigerant, etc., which can realize efficient use of energy through heat exchange, so as to reduce the energy consumption caused by temperature rise or cooling of the working medium, and achieve the energy-saving effect.

[0102] As a specific embodiment of the present application, the first working fluid circulation system is a cooling water circulation system, and the second working fluid circulation system is a chilled water circulation system; wherein the cooling water circulation system exchanges heat with the high-temperature level refrigeration system 2 through the high-temperature level condenser 23, can absorb the waste heat of the high-temperature level refrigeration system 2, and can make the first refrigerant condense in the high-temperature level condenser 23. The cooling water flowing out of the high-temperature level condenser 23 can be used as hot water supply. The chilled water circulation system exchanges heat with the low-temperature level refrigeration system 3 through the low-temperature level evaporator 34, can transfer waste heat to the low-temperature level refrigeration system 3, and can make the second refrigerant evaporate in the low-temperature level evaporator 34. The chilled water realizes cooling inside the low-temperature level evaporator 34, so that the chilled water flowing out of the low-temperature level evaporator 34 can be used as cooling working fluid in the cooling circulation system.

[0103] Referring to Figures 1 to 10 The fourth aspect of the embodiment of the present application provides a refrigeration equipment, which comprises the cascade unit in the above-mentioned embodiments, such as air conditioners and refrigerators, and can realize partition refrigeration (or heating) to meet the temperature requirements of different areas.

[0104] In some other embodiments of the present application, the refrigeration equipment comprises the energy-saving equipment in the above-mentioned embodiments, which can realize the synchronous supply of hot fluid and cooling working fluid while meeting the refrigeration and heating requirements, and is beneficial to reducing the overall energy consumption of the refrigeration equipment.

[0105] Referring to Figures 1 to 10 The fifth aspect of the embodiment of the present application provides a control method, which is applied to the oil circuit system 1 in the above-mentioned embodiments and comprises the following steps:

[0106] Step one: starting the cascade unit;

[0107] Step two: obtaining the actual oil temperature value T1 in the first oil tank 12 and the actual oil temperature value T2 in the second oil tank 14; and judging whether to enter the oil heat exchange mode or the oil cooling mode according to the comparison between the actual oil temperature value and the preset oil temperature threshold value.

[0108] Since the refrigeration oil of the compressor has poor flowability when the oil temperature is too low, and has poor lubrication effect when the oil temperature is too high, the preset oil temperature threshold value comprises a first oil temperature threshold value Y1 and a second oil temperature threshold value Y2, and Y1>Y2; wherein Y1 is the minimum limit value of the oil temperature, and the oil flowability is poor when the oil temperature is lower than the first oil temperature threshold value Y1; Y2 is the maximum limit value of the oil temperature, and the lubrication effect of the oil is poor when the oil temperature is higher than the second oil temperature threshold value Y2.

[0109] As a specific embodiment of the present application, the value of the first oil temperature threshold value Y1 is 10℃, and the value of the second oil temperature threshold value Y2 is 50℃.

[0110] Step three: judge whether T2 is less than the second oil temperature threshold Y2, so as to confirm whether the low-temperature stage refrigeration system 3 exists the risk of poor flowability of the lubricating oil circuit; if T1 > Y2 > T2, open the first valve 133 and the second valve 153, open the first circulating oil circuit 13 and the second circulating oil circuit 15, and enter the oil liquid heat exchange mode; since the refrigerating capacity of the first compressor 22 is greater than that of the second compressor 32, the oil temperature in the first oil tank 12 will rise rapidly, and when the first oil tank 12 and the second oil tank 14 exchange heat through the first heat exchanger 11, the temperature of the oil in the second oil tank 14 can be raised, so that the temperature of the oil in the second oil tank 14 is raised to the normal working temperature range, and at the same time, the rising speed of the oil temperature in the first oil tank 12 is slowed down, so as to avoid the oil temperature in the first oil tank 12 being too high, thereby causing the oil temperature entering the first compressor 22 to be too high.

[0111] It should be noted that in the initial stage of the operation of the cascade unit, if the oil temperature in the first oil tank 12 is also low, the oil in the second oil tank 14 can also be heated by other heating methods first, as shown in Figure 9

[0112] Step four: after the cascade unit runs for a period of time, if the oil temperature in the second oil tank 14 reaches T2 ≥ Y2, the first valve 133 and the second valve 153 are closed, and the first circulating oil circuit 13 and the second circulating oil circuit 15 are closed.

[0113] Step five: please refer to Figure 10 After the cascade unit runs for a long time, since the oil temperature in the first oil tank 12 continues to rise, the oil in the first oil tank 12 exists the risk of overheating, judge whether T1 is greater than the first oil temperature threshold Y1, if T1 ≥ Y1 and T2 ≥ Y2, open the third valve 163, open the third circulating oil circuit 16, and enter the oil liquid cooling mode, so that the oil liquid output from the first oil tank 12 exchanges heat in the low-temperature stage flash evaporator 33 of the cascade unit, and the oil temperature is transferred to the refrigerant in the low-temperature stage flash evaporator 33, which not only can cool the oil in the first oil tank 12, but also can improve the superheat degree of the low-temperature stage flash evaporator 33.

[0114] Step six: when the oil temperature in the first oil tank 12 is reduced to the normal working temperature range, the third valve 163 is closed, and the third circulating oil circuit 16 is closed. (If the first heat exchanger 11 and the second heat exchanger are in series, the first valve 133 and the first circulating oil circuit 13 also need to be closed).

[0115] ​It is to be understood that the terminology used herein is for the purpose of describing particular example embodiments only and is not intended to be limiting. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. The terms "comprises", "comprising", "includes", "including" and "has" are inclusive and therefore specify the presence of stated features, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, steps, operations, elements, components, and / or groups thereof. The method steps, processes, and operations described herein are not to be construed as necessarily requiring their performance in the particular order

[0116] Although the terms first, second, third, etc. can be used herein to describe various 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 be only used to distinguish one element, component, region, layer or section from another region, layer or section. Terms such as "first", "second", and other numerical terms when used herein do not imply a sequence or order unless clearly indicated by the context. Thus, a first element, component, region, layer or section discussed below could be termed a second element, component, region, layer or section without departing from the teachings of the example embodiments.

[0117] The specific embodiments described herein have been chosen for purposes of illustration and discussion. Those of ordinary skill in the art will realize that the general principles of the teachings herein can be applied to other embodiments as readily apparent. Thus, the present application is not to be limited to the specific embodiments disclosed herein, but to include all such as are encompassed within the spirit and scope of the invention as defined by the appended claims.

Claims

1. An oil circuit system (1), characterized in that, include: The first heat exchanger (11) has a first channel and a second channel inside. Heat exchange can be carried out between the first channel and the second channel. The oil in the first channel and the oil in the second channel flow in opposite directions. The first oil tank (12) has two ends connected to the first channel to form a first circulating oil circuit (13). The second oil tank (14) is connected to the second channel at both ends to form the second circulating oil circuit (15). The second heat exchanger is connected to both ends of the first oil tank (12) to form a third circulating oil circuit (16). Temperature detection devices are provided in both the first oil tank (12) and the second oil tank (14). Valves are provided on the first circulating oil circuit (13) and the second circulating oil circuit (15). When the difference between the oil temperature in the first oil tank (12) and the oil temperature in the second oil tank (14) is greater than the preset temperature difference threshold, the valve opens.

2. The oil circuit system (1) according to claim 1, characterized in that, The first heat exchanger (11) and the second heat exchanger are connected in parallel at both ends of the first oil tank (12); Alternatively, the first heat exchanger (11) and the second heat exchanger may be connected in series.

3. The oil circuit system (1) according to claim 1, characterized in that, The second heat exchanger is a flash evaporator equipped with heat exchange tubes.

4. The oil circuit system (1) according to claim 1, characterized in that, The third circulating oil circuit (16) is equipped with valves.

5. A cascade generator unit, characterized in that, The system includes the oil circuit system (1) as described in any one of claims 1 to 4, and further includes a high-temperature refrigeration system (2), a low-temperature refrigeration system (3), and an intermediate heat exchanger (4). The intermediate heat exchanger (4) has a third channel and a fourth channel inside. The third channel is connected to the high-temperature refrigeration system (2) to form a first refrigerant circulation loop (21), and the fourth channel is connected to the low-temperature refrigeration system (3) to form a second refrigerant circulation loop (31). The two ends of the first oil tank (12) are respectively connected to the high-temperature refrigeration system (2) to form a fourth circulating oil circuit (17), and the two ends of the second oil tank (14) are respectively connected to the low-temperature refrigeration system (3) to form a fifth circulating oil circuit (18).

6. The cascade unit according to claim 5, characterized in that, The high-temperature refrigeration system (2) includes a first compressor (22) and a high-temperature condenser (23). The first exhaust pipe (211) of the first compressor (22) is connected to the high-temperature condenser (23). The high-temperature condenser (23) is provided with a first oil separation component inside. The fourth circulating oil circuit (17) includes a first oil supply line (171) and a first oil return line (172). The first oil supply line (171) is connected between the first oil tank (12) and the first compressor (22), and the first oil return line (172) is connected between the first oil separation assembly and the first oil tank (12).

7. The cascade unit according to claim 6, characterized in that, The high-temperature refrigeration system (2) further includes a high-temperature flash evaporator (24). The refrigerant outlet of the high-temperature condenser (23) and the refrigerant inlet of the high-temperature flash evaporator (24) are connected through a first refrigerant inflow pipe (212). The high-temperature flash evaporator (24) is connected to a first refrigerant outflow pipe (213) and a second refrigerant outflow pipe (214). The first refrigerant outflow pipe (213) is connected to the air inlet of the first compressor (22). The second refrigerant outflow pipe (214) is connected to the inlet of the third channel. The outlet of the third channel is connected to the air inlet of the first compressor (22).

8. The cascade unit according to any one of claims 5 to 7, characterized in that, The low-temperature refrigeration system (3) includes a second compressor (32), the second exhaust pipe (311) of the second compressor (32) is connected to the inlet of the fourth channel, and the interior of the intermediate heat exchanger (4) is provided with a second oil separation component connected to the fourth channel; The fifth circulating oil circuit (18) includes a second oil supply line (181) and a second oil return line (182). The second oil supply line (181) is connected between the second oil tank (14) and the second compressor (32), and the second oil return line (182) is connected between the second oil separation assembly and the second oil tank (14).

9. The cascade unit according to claim 8, characterized in that, The low-temperature refrigeration system (3) further includes a low-temperature flash evaporator (33) and a low-temperature evaporator (34). The outlet of the fourth channel is connected to the refrigerant inlet of the low-temperature flash evaporator (33) through a second refrigerant inflow pipe (312). The low-temperature flash evaporator (33) is connected to a third refrigerant outflow pipe (313) and a fourth refrigerant outflow pipe (314). The third refrigerant outflow pipe (313) is connected to the air inlet of the second compressor (32). The fourth refrigerant outflow pipe (314) is connected to the low-temperature evaporator (34). The refrigerant outlet of the low-temperature evaporator (34) is connected to the air inlet of the second compressor (32).

10. The cascade unit according to claim 9, characterized in that, The low-temperature flash evaporator (33) is equipped with a heat exchange tube assembly inside, which is connected to the oil circuit of the first oil tank (12).

11. An energy-saving device, characterized in that, The cascade unit includes any one of claims 5 to 10, and further includes a first working fluid circulation system and a second working fluid circulation system, wherein the first working fluid circulation system is connected to the high-temperature stage refrigeration system (2) and is used to absorb the waste heat of the high-temperature stage refrigeration system (2); The second working fluid circulation system is connected to the low-temperature stage refrigeration system (3) and is used to transfer waste heat to the low-temperature stage refrigeration system (3).

12. A refrigeration device, characterized in that, Including the cascade unit as described in any one of claims 5 to 10; Alternatively, it may include the energy-saving device as described in claim 11.

13. A control method, characterized in that, The method applied to the oil circuit system (1) as described in any one of claims 1 to 4 includes the following steps: Obtain the actual oil temperature value T1 in the first oil tank (12) and the actual oil temperature value T2 in the second oil tank (14); The system determines whether to enter the oil heat exchange mode by comparing the actual oil temperature with the preset oil temperature threshold.

14. The control method according to claim 13, characterized in that, The preset oil temperature threshold includes a first oil temperature threshold Y1 and a second oil temperature threshold Y2, where Y1 > Y2; If T1 > Y2 > T2, then the first circulating oil circuit (13) and the second circulating oil circuit (15) are opened, and the oil heat exchange mode is entered; If T1≥Y1 and T2≥Y2, then the third circulation oil circuit (16) is activated, and the oil cooling mode is entered.

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