A refrigerant recovery system and its control method for testing refrigeration equipment

Abstract

This invention provides a refrigerant recovery system and its control method for testing refrigeration equipment. The system includes a condenser, an oil separator A, a first pipeline, and a second pipeline. One end of the first pipeline is connected to the oil separator A, and the other end is connected to the discharge end of compressor A. One end of the second pipeline is connected to the first pipeline, and the other end is connected to one end of the condenser. One end of an eighth pipeline is connected to the oil separator A, and the other end is connected to the inlet end of compressor B, allowing fluid to flow from the oil separator A to compressor B in the recovery mode of the system. The discharge end of compressor B is also connected to an eleventh pipeline, where the refrigerant in the eleventh pipeline heats the refrigerant in the fifth pipeline at the heat exchanger. This invention solves the problem of inconsistent refrigerant flow direction within the oil separator during normal operation of the refrigeration equipment and during the operation of the recovery system, and also solves the problem of refrigerant liquid retention in the liquid pipe.

Description

Technical Field

[0001] This invention relates to the field of refrigeration technology, specifically to a refrigerant recovery system and its control method for testing refrigeration equipment. Background Technology

[0002] The emission of Freon gas can damage the atmosphere, contribute to the greenhouse effect, and cause a series of environmental problems, including global warming. Refrigeration equipment using Freon refrigerants is used in various industries, and leaks can occur at every stage, from production and testing to user operation, after-sales maintenance, and disposal. There may even be instances of unauthorized discharges. As regulations on Freon refrigerants become increasingly stringent, strict monitoring, recycling, and reuse of Freon refrigerants at each stage of the process are necessary. Particularly during testing and maintenance, refrigerant movement within refrigeration equipment is frequently required to ensure that refrigerant does not leak into the atmosphere when connections are disconnected.

[0003] After-sales maintenance is difficult to supervise, and the use of refrigerant recovery equipment for after-sales maintenance is even rarer, especially in the case of household air conditioners, where there are numerous instances of refrigerant leaks and charges for refrigerant refills. On the other hand, some special air conditioners, especially those for computer rooms, have compressors located on the low-pressure indoor unit side. During production testing, the refrigerant used for pressure testing and leak detection differs from the unit's rated refrigerant charge. Frequent connection testing makes it difficult to accurately control the amount of refrigerant charged at the factory, essentially requiring vacuuming and recharging. This process is extremely wasteful of refrigerant and results in high production costs; vacuuming and pressure testing for refrigerant recharging also wastes production time and leads to low production efficiency.

[0004] It is necessary to develop a refrigerant recovery and adjustment device for the precise transfer of the original refrigerant within refrigeration equipment during production, testing, and after-sales maintenance, ensuring no waste or leakage. Previous patents CN202211334307.6 and CN202211333428.9 have made optimized designs and research in this area; however, when the recovery device involved in these patents is running, the refrigerant in the pipeline between the condenser and the third one-way valve (one-way valve C) is in a liquid state, preventing it from returning to the condenser and thus affecting the operating efficiency of the recovery device.

[0005] Because existing refrigeration recovery equipment suffers from technical problems such as the refrigerant being in a liquid state in the pipeline between the condenser and the third check valve, preventing it from returning to the condenser and thus affecting the operating efficiency of the recovery equipment, this invention researches and designs a refrigerant recovery system for refrigeration equipment testing and its control method. Summary of the Invention

[0006] Therefore, the technical problem to be solved by the present invention is to overcome the defect in the prior art where the refrigerant in the pipeline between the condenser and the third one-way valve is in a liquid state during operation, which prevents it from returning to the condenser and thus affects the operating efficiency of the recovery equipment. The present invention provides a refrigerant recovery system for testing refrigeration equipment and its control method.

[0007] To address the above problems, the present invention provides a refrigerant recovery system for testing refrigeration equipment, comprising:

[0008] The system includes a condenser, an oil separator A, a first pipeline, and a second pipeline. One end of the first pipeline is connected to the oil separator A, and the other end is connected to the discharge end of the compressor A. One end of the second pipeline is connected to the first pipeline, and the other end is connected to one end of the condenser.

[0009] It also includes an expansion valve and a fifth pipeline, one end of which can be connected to the other end of the condenser and the other end of which can be connected to the expansion valve.

[0010] It also includes compressor B, a heat exchanger, and an eighth pipeline. One end of the eighth pipeline is connected to the oil separator A, and the other end is connected to the inlet of compressor B, so that fluid can flow from the oil separator A to compressor B in the recovery mode of the recovery system. The outlet of compressor B is also connected to an eleventh pipeline. A portion of the fifth pipeline passes through the heat exchanger, and a portion of the eleventh pipeline passes through the heat exchanger, so that the refrigerant in the eleventh pipeline can heat the refrigerant in the fifth pipeline at the heat exchanger.

[0011] In some implementations...

[0012] When compressor A starts, it operates in refrigeration equipment test mode. At this time, the mixture of refrigerant and lubricating oil discharged from the exhaust end of compressor A enters oil separator A through the first pipeline to achieve oil-gas separation. When compressor A is turned off, it operates in recovery system recovery mode. At this time, the mixture of refrigerant and lubricating oil in the condenser can enter oil separator A through the second pipeline to achieve oil-gas separation.

[0013] In some implementations...

[0014] The heat exchanger is a shell-and-tube heat exchanger, including a shell. Parts of the fifth pipeline and the eleventh pipeline are inserted through the shell. An electric heating device A is also provided on the shell to heat the refrigerant in the fifth pipeline. And / or, an electric heating device B is also provided on the part of the fifth pipeline that does not have the heat exchanger inserted to heat the refrigerant in the fifth pipeline.

[0015] In some implementations...

[0016] It also includes a fourth pipeline, one end of which is connected to the interior of the oil separator A and the other end is connected to the second pipeline, so that fluid can flow from the oil separator A to the second pipeline during the refrigeration equipment test mode;

[0017] It also includes an eighth pipeline, one end of which is connected to the fourth pipeline and the other end of which is connected to the air inlet of the compressor B, so that fluid can flow from the oil separator A to the compressor B in the recovery mode of the recovery system. A control valve is provided on the eighth pipeline.

[0018] In some implementations...

[0019] The first pipeline is connected to the second pipeline at a first position, the fourth pipeline is connected to the second pipeline at a second position, the section of the second pipeline located between the first position and the second position is the third pipeline, and a one-way valve E is provided on the third pipeline, the one-way valve E can only allow refrigerant to flow from the second pipeline to the first pipeline;

[0020] The eighth pipeline is connected to the fourth pipeline at the third position. A one-way valve D is provided on the fourth pipeline and on the section between the third position and the second position. The one-way valve D can only allow refrigerant to flow from the fourth pipeline to the second pipeline.

[0021] In some implementations...

[0022] It also includes an oil separator B, a second throttling device, a ninth pipeline, and a tenth pipeline. One end of the ninth pipeline is connected to the exhaust end of the compressor B, and the other end is connected to the interior of the oil separator B. One end of the tenth pipeline is connected to the interior of the oil separator B, and the other end is connected to the eighth pipeline. The connection position between the tenth pipeline and the eighth pipeline is the sixth position, which is located between the control valve and the compressor B. The second throttling device is installed on the tenth pipeline. The eleventh pipeline is connected to the exhaust port of the oil separator B.

[0023] In some implementations...

[0024] It also includes an evaporator, a sixth pipeline and a seventh pipeline. One end of the sixth pipeline is connected to the expansion valve and the other end is connected to the evaporator. One end of the seventh pipeline is connected to the interior of the oil separator A and the other end is connected to the fifth pipeline. The outlet of the oil separator B is connected to the seventh pipeline through the eleventh pipeline.

[0025] In some implementations...

[0026] The eleventh pipeline is connected to the seventh pipeline at the fourth position. A one-way valve B is provided on the eleventh pipeline and on the section between the heat exchanger and the fourth position. The one-way valve B can only allow refrigerant to flow from the eleventh pipeline to the seventh pipeline.

[0027] The fifth pipeline is connected to the seventh pipeline at the fifth position. A one-way valve C is provided on the section of the fifth pipeline located between the heat exchanger and the fifth position. The one-way valve C can only allow refrigerant to flow from the fifth pipeline to the expansion valve.

[0028] The seventh pipeline is equipped with a first throttling device and a one-way valve A. The first throttling device and the one-way valve are located between the oil separator A and the fourth position. The one-way valve A can only allow fluid to flow from the oil separator A to the fifth pipeline.

[0029] In some implementations...

[0030] The first pipeline is also provided with a gas valve, interface A and interface C; the fifth pipeline, located at the fifth position and between the expansion valve, is provided with a liquid valve, interface B and interface D; the second pipeline is provided with interface E; the fifth pipeline, located at the fifth position and between the condenser, is provided with interface F; and a refrigerant charging port is provided between the evaporator and the compressor A.

[0031] The present invention also provides a control method for a refrigerant recovery system for testing refrigeration equipment as described above, comprising:

[0032] The determination step involves determining whether the required operating mode for the refrigerant recovery system is the refrigeration equipment testing mode or the recovery system recovery mode.

[0033] The control steps are as follows: when the refrigerant recovery system requires operation in the refrigeration equipment test mode, the compressor A is controlled to turn on, the compressor B is controlled to turn off, and the control valve is controlled to turn off; when the refrigerant recovery system requires operation in the recovery system recovery mode, the compressor A is controlled to turn off, the compressor B is controlled to turn on, and the control valve is controlled to turn on.

[0034] The refrigerant recovery system and control method for testing refrigeration equipment provided by this invention have the following beneficial effects:

[0035] 1. This invention, by setting up first and second pipelines, an oil separator A, a compressor A, and a condenser, connects the compressor A, oil separator A, and condenser respectively through the first and second pipelines. Valve installation on the pipelines allows the refrigerant and oil mixture discharged from the compressor A to enter the oil separator A through the first pipeline for oil-gas separation during the refrigeration equipment test mode. In the recovery system recovery mode, shutting down the compressor A allows the refrigerant and oil mixture in the condenser to enter the oil separator A through the second pipeline for oil-gas separation. This effectively ensures that both test and recovery modes utilize the first pipeline for oil-gas separation. Oil-gas separation occurs in oil separator A. During normal operation of the refrigeration equipment and the recovery system, the refrigerant flow direction within the oil separator is consistent, ensuring effective oil-gas separation. This resolves the issue of inconsistent refrigerant flow direction between the two systems, thus addressing the low efficiency of existing recovery systems. When the recovery system is connected to the refrigeration equipment, different valve opening and closing combinations and the operation control of the recovery compressor B can resolve refrigerant recovery issues after online testing and the problem of mixing of refrigeration oil between the refrigeration equipment and the recovery system. No dedicated refrigerant storage pressure vessel is required, ensuring consistent refrigerant charge levels in the refrigeration equipment. Furthermore, the present invention enables the refrigerant to be powered in recovery mode by the arrangement of compressor B and the eighth pipeline, thereby promoting refrigerant recovery. The heat exchanger and eleventh pipeline located at the discharge end of compressor B allow heat exchange with the fifth pipeline at the heat exchanger, utilizing the high-temperature heat from the compressor B discharge to heat the refrigerant in the fifth pipeline. This heats the liquid refrigerant in the fifth pipeline into a gaseous state in recovery mode. The waste heat from the high-temperature discharge of the recovery compressor B and / or electric heating are used to heat the liquid refrigerant remaining in the liquid pipe, accelerating its vaporization. This allows for effective recovery of the refrigerant in this part of the pipeline, improving the recovery efficiency of the recovery equipment and its operational efficiency. It also prevents the refrigerant liquid from remaining in the liquid pipe, fully utilizing the waste heat from the high-temperature discharge of the recovery compressor, thus improving the recovery efficiency and energy efficiency of the recovery equipment.

[0036] 2. Furthermore, the present invention can further improve the heating efficiency of the refrigerant in the fifth pipeline by using an electric heating device A installed on the heat exchanger and an electric heating device B installed on the fifth pipeline, so that the refrigerant liquid retained in the fifth pipeline (liquid pipe) can be further accelerated to vaporize, further improving the recovery efficiency of this part of liquid refrigerant and further improving the recovery operation efficiency. Attached Figure Description

[0037] Figure 1 This is a structural diagram of the refrigerant recovery system for testing refrigeration equipment according to the present invention.

[0038] The reference numerals in the attached figures are as follows:

[0039] 1. Compressor A; 2. Heat exchanger; 3. Condenser; 4. Evaporator; 5. Expansion valve; 6. Oil separator A; 71. Check valve A; 72. Check valve B; 73. Check valve C; 74. Check valve D; 75. Check valve E; 81. First throttling device; 82. Second throttling device; 9. Compressor B; 10. Oil separator B; 11. First position; 12. Second position; 13. Third position; 14. Fourth position; 15. Fifth position; 16. Sixth position; 13'. Gas valve; 141. Interface A; 142. Interface B; 143. 144. Interface C; 145. Interface E; 146. Interface F; 15'. Liquid valve; 16'. Refrigerant inlet; 171. Gas refrigerant pipe; 172. Liquid refrigerant pipe; 18. Control valve; 191. Electric heating device A; 192. Electric heating device B; 101. First pipeline; 102. Second pipeline; 103. Third pipeline; 104. Fourth pipeline; 105. Fifth pipeline; 106. Sixth pipeline; 107. Seventh pipeline; 108. Eighth pipeline; 109. Ninth pipeline; 110. Tenth pipeline; 111. Eleventh pipeline. Detailed Implementation

[0040] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the present invention or its application or use. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0041] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the exemplary embodiments according to this application. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0042] Unless otherwise specifically stated, the relative arrangement, numerical expressions, and values ​​of the components and steps set forth in these embodiments do not limit the scope of the invention. It should also be understood that, for ease of description, the dimensions of the various parts shown in the drawings are not drawn to actual scale. Techniques, methods, and devices known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and devices should be considered part of the specification. In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limitations. Therefore, other examples of exemplary embodiments may have different values. It should be noted that similar reference numerals and letters in the following figures denote similar items; therefore, once an item is defined in one figure, it need not be further discussed in subsequent figures.

[0043] In the description of this invention, it should be understood that the orientation or positional relationship indicated by directional terms such as "front, back, up, down, left, right", "horizontal, vertical, horizontal" and "top, bottom" is generally based on the orientation or positional relationship shown in the accompanying drawings, and is only for the convenience of describing this invention and simplifying the description. Unless otherwise stated, these directional terms do not indicate or imply that the device or element referred to must have a specific orientation or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on the scope of protection of this invention; the directional terms "inner" and "outer" refer to the inner and outer contours relative to the outline of each component itself.

[0044] For ease of description, spatial relative terms such as "above," "on top of," "on the upper surface of," "above," etc., are used herein to describe the spatial positional relationship of a device or feature as shown in the figures to other devices or features. It should be understood that spatial relative terms are intended to encompass different orientations in use or operation beyond the orientation of the device as described in the figures. For example, if the device in the figures were inverted, a device described as "above" or "on top of" other devices or structures would subsequently be positioned as "below" or "under" other devices or structures. Thus, the exemplary term "above" can include both "above" and "below." The device may also be positioned in other different ways (rotated 90 degrees or in other orientations), and the spatial relative descriptions used herein will be interpreted accordingly.

[0045] Furthermore, it should be noted that the use of terms such as "first" and "second" to define components is merely for the purpose of distinguishing the corresponding components. Unless otherwise stated, the above terms have no special meaning and therefore should not be construed as limiting the scope of protection of this invention.

[0046] like Figure 1As shown, the present invention provides a refrigerant recovery system for testing refrigeration equipment, comprising:

[0047] The system includes a compressor A1, a condenser 3, an oil separator A6, a first pipeline 101, and a second pipeline 102. One end of the first pipeline 101 is connected to the oil separator A6, and the other end is connected to the discharge end of the compressor A1. One end of the second pipeline 102 is connected to the first pipeline 101, and the other end is connected to one end of the condenser 3.

[0048] It also includes an expansion valve 5 and a fifth pipeline 105, one end of which can be connected to the other end of the condenser 3 and the other end of which can be connected to the expansion valve 5.

[0049] It also includes compressor B9, heat exchanger 2, and an eighth pipe 108. One end of the eighth pipe 108 is connected to the oil separator A6, and the other end is connected to the inlet of compressor B9, so that fluid can flow from the oil separator A6 to compressor B9 in the recovery mode of the recovery system. The outlet of compressor B9 is also connected to an eleventh pipe 111. A portion of the fifth pipe 105 passes through the heat exchanger 2, and a portion of the eleventh pipe 111 passes through the heat exchanger 2, so that the refrigerant in the eleventh pipe 111 at the heat exchanger 2 can heat the refrigerant in the fifth pipe 105. (e.g.) Figure 1 As shown, the first pipeline 101 is preferably connected to the exhaust end of the compressor A1 via a refrigerant gas pipe 171.

[0050] This invention, by setting up first and second pipelines, an oil separator A, a compressor A, and a condenser, connects the compressor A, oil separator A, and condenser respectively through the first and second pipelines. Valves on the pipelines allow the refrigerant and oil mixture discharged from the compressor A to enter the oil separator A through the first pipeline for oil-gas separation during the refrigeration equipment test mode. In the recovery system recovery mode, by shutting down the compressor A, the refrigerant and oil mixture from the condenser enters the oil separator A through the second pipeline for oil-gas separation. This effectively ensures that the refrigerant and oil mixture in both test and recovery modes enters through the first pipeline. Oil-gas separation is performed in oil separator A. The refrigerant flow direction within the oil separator is consistent during both normal operation of the refrigeration equipment and the operation of the recovery system, ensuring effective oil-gas separation. This solves the problem of inconsistent refrigerant flow direction between the two systems, thereby addressing the low efficiency of existing recovery systems. When the recovery system is connected to the refrigeration equipment, different valve opening and closing combinations and the operation control of the recovery compressor B can resolve issues such as refrigerant recovery after online testing and the mixing of refrigeration oil between the refrigeration equipment and the recovery system. No dedicated refrigerant storage pressure vessel is required, ensuring consistent refrigerant charge levels in the refrigeration equipment. Furthermore, the present invention enables the refrigerant to be powered in recovery mode by the arrangement of compressor B and the eighth pipeline, thereby promoting refrigerant recovery. The heat exchanger and eleventh pipeline located at the discharge end of compressor B allow heat exchange with the fifth pipeline at the heat exchanger, utilizing the high-temperature heat from the compressor B discharge to heat the refrigerant in the fifth pipeline. This heats the liquid refrigerant in the fifth pipeline into a gaseous state in recovery mode. The waste heat from the high-temperature discharge of the recovery compressor B and / or electric heating are used to heat the liquid refrigerant remaining in the liquid pipe, accelerating its vaporization. This allows for effective recovery of the refrigerant in this part of the pipeline, improving the recovery efficiency of the recovery equipment and its operational efficiency. It also prevents the refrigerant liquid from remaining in the liquid pipe, fully utilizing the waste heat from the high-temperature discharge of the recovery compressor, thus improving the recovery efficiency and energy efficiency of the recovery equipment.

[0051] The present invention also provides power for the recovery mode by setting up compressor B, which draws in refrigerant gas from oil separator A, thereby driving the refrigerant and oil in the condenser to flow back to oil separator A through the second pipeline for normal oil-gas separation. The setting of oil separator B can separate the oil-gas mixture at the discharge end of compressor B. The setting of the tenth pipeline can guide the oil separated in oil separator B to the inlet end of compressor B, thereby ensuring continued lubrication and cooling of the internal components of compressor B.

[0052] like Figure 1As shown, the recovery equipment has four ports: C, D, E, and F. Port C is connected to port A of the indoor unit via a gaseous refrigerant pipe, port D is connected to port B of the indoor unit via a liquid refrigerant pipe, and ports E and F are connected to the inlet and outlet of the outdoor unit, respectively. A gas valve is installed on the exhaust pipe of the indoor unit, and a liquid valve is installed on the return pipe of the indoor unit. A one-way valve E is installed on the suction pipe between port C and port E, with the flow direction from port E to port C; a one-way valve C is installed on the exhaust pipe between port D and port F, with the flow direction from port F to port D.

[0053] This invention employs a specialized recovery system to solve the aforementioned technical problems. By connecting return oil pipelines to the inlet and outlet of the refrigerant recovery system, the refrigeration oil separated from the refrigeration equipment is recovered in advance. The recovery system itself recovers refrigeration oil by connecting the high and low pressure ports of the recovery compressor to the return oil branch. A combination of control valves and check valves ensures that the refrigerant flow direction is consistent between the oil separator and the recovery system during operation, solving the problem of low oil separator efficiency in existing recovery systems. When the recovery system is connected to the refrigeration equipment, different valve opening and closing combinations and the operation control of the recovery compressor B can solve the problems of refrigerant recovery after online testing and the mixing of refrigeration oil between the refrigeration equipment and the recovery system. No special pressure vessel for refrigerant storage is required, ensuring the consistency of refrigerant charge in the refrigeration equipment.

[0054] This invention, through the combined design of two compressors, multiple pipelines, and multiple one-way valves, ensures that the refrigerant flow direction in the oil separator is consistent during the operation of the refrigeration equipment and the operation of the recovery system. This allows the oil separator to achieve efficient separation of lubricating oil in two situations: 1. during compression refrigeration, i.e., normal test mode; 2. when the compressor stops, i.e., when the test ends, operating in recovery mode.

[0055] This invention solves the following technical problems:

[0056] 1. The refrigerant flow direction within the oil separator is inconsistent between normal operation of the refrigeration equipment and operation of the recovery system. (Because when the refrigerant enters the oil separator from the outlet pipe in reverse, the outlet pipe cannot guarantee that the refrigerant will achieve centrifugal rotation inside the oil separator; without centrifugal motion, centrifugal separation cannot be achieved.)

[0057] 2. At the end of the test, issues such as the control switching problem before the recovery system starts and the control method of the recovery system were addressed.

[0058] 3. Solve the problem of refrigerant liquid retention in the liquid pipe under the recovery mode, and make full use of the waste heat of the high-temperature exhaust of the recovery compressor, which is conducive to improving the recovery efficiency and energy efficiency of the recovery equipment.

[0059] In some embodiments, when the compressor A1 is started, it operates in a refrigeration equipment test mode. At this time, the mixture of refrigerant and lubricating oil discharged from the exhaust end of the compressor A1 enters the oil separator A6 through the first pipeline 101 to achieve oil-gas separation. When the compressor A1 is turned off, it operates in a recovery system recovery mode. At this time, the mixture of refrigerant and lubricating oil in the condenser 3 can enter the oil separator A6 through the second pipeline 102 to achieve oil-gas separation.

[0060] This is a further preferred structural form of the present invention, namely, when compressor A starts, refrigerant and oil enter oil separator A from the first pipeline for oil-gas separation, and the separated gas enters the condenser through the second pipeline; while when compressor A is turned off, the flow direction of refrigerant in the second pipeline is reversed, entering oil separator A from the condenser through the second pipeline for oil-gas separation, but the flow direction entering oil separator A is the same, both entering oil separator A through the first pipeline. Therefore, it effectively ensures that the direction of fluid flowing to oil separator A is consistent in both different modes, effectively ensuring normal and efficient oil-gas separation of oil separator A.

[0061] In some implementations...

[0062] The heat exchanger 2 is a shell-and-tube heat exchanger, including a shell. Parts of the fifth pipe 105 and the eleventh pipe 111 are both inserted through the shell, and an electric heating device A191 is also provided on the shell to heat the refrigerant in the fifth pipe 105; and / or, an electric heating device B192 is also provided on the part of the fifth pipe 105 that does not have the heat exchanger 2 inserted through it to heat the refrigerant in the fifth pipe 105.

[0063] Furthermore, the present invention can further improve the heating efficiency of the refrigerant in the fifth pipeline by using an electric heating device A installed on the heat exchanger and an electric heating device B installed on the fifth pipeline, so that the refrigerant liquid retained in the fifth pipeline (liquid pipe) can be further accelerated to vaporize, further improving the recovery efficiency of this part of liquid refrigerant and further improving the recovery operation efficiency.

[0064] This invention improves recovery efficiency by adding a shell-and-tube heat exchanger, electric heating device A, and electric heating device B to the recovery equipment. It utilizes the waste heat from the high-temperature exhaust of the recovery compressor B and / or electric heating to heat the refrigerant liquid retained in the liquid pipe, accelerating its vaporization. The invention employs a shell-and-tube heat exchanger and / or electric heating to heat the refrigerant liquid retained in the liquid pipe, accelerating its vaporization. This avoids refrigerant liquid retention in the liquid pipe, fully utilizes the waste heat from the high-temperature exhaust of the recovery compressor, and improves the recovery efficiency and energy efficiency of the recovery equipment.

[0065] To address the technical problems mentioned in the background section, the present invention adds a heat source to the aforementioned recovery equipment to heat and vaporize the liquid refrigerant retained in the liquid pipe:

[0066] A shell-and-tube heat exchanger is added between interface F and the inlet of check valve C. The outlet of oil separator B is connected to the inlet of the inner tube of the shell-and-tube heat exchanger, and the outlet of the inner tube of the shell-and-tube heat exchanger is connected to the inlet of check valve B. Interface F is connected to the shell-side inlet of the shell-and-tube heat exchanger, and the inlet of check valve C is connected to the shell-side outlet of the shell-and-tube heat exchanger.

[0067] Furthermore, an electric heating device A is also wound around the outer wall of the shell-and-tube heat exchanger;

[0068] Furthermore, an electric heating device B is wound around the outer wall of the liquid pipe between the condenser liquid pipe outlet and the interface F.

[0069] The high-temperature exhaust refrigerant from compressor B outlet exchanges heat with the liquid refrigerant retained in the liquid pipe inside the shell-and-tube heat exchanger, heating and vaporizing the retained liquid refrigerant. The electric heating device A and / or electric heating device B, wound around the outer wall, can also heat and vaporize the liquid refrigerant retained inside the liquid pipe. It should be noted that electric heating device A can also be installed inside the shell side of the shell-and-tube, immersed in the retained liquid refrigerant, thus making fuller use of the heat generated by electric heating (electric heating device B can only be wound around the tube because the refrigeration equipment was not pre-installed with electric heating in the liquid pipe at the factory; electric heating device A is a component of the recycling equipment and can be designed and optimized in advance, while electric heating device B is also a component included with the recycling equipment and is wound to the position shown in the diagram during on-site use).

[0070] In some embodiments, a fourth conduit 104 is also included, one end of which is connected to the interior of the oil separator A6 and the other end is connected to the second conduit 102, so as to allow fluid to flow from the oil separator A6 to the second conduit 102 during the refrigeration equipment test mode;

[0071] It also includes an eighth pipeline 108, one end of which is connected to the fourth pipeline 104 and the other end is connected to the air inlet of the compressor B9, so that fluid can flow from the oil separator A6 to the compressor B9 in the recovery mode of the recovery system. A control valve 18 is provided on the eighth pipeline 108.

[0072] The present invention also effectively discharges the gas separated by oil separator A when compressor A starts to the second pipeline through the setting of the fourth and eighth pipelines. The eighth pipeline is used to discharge the refrigerant separated in the oil separator to compressor B when compressor A is turned off (when compressor B starts). The inlet end of oil separator A draws refrigerant from condenser 3 through the first and second pipelines, which can realize the refrigeration equipment testing mode and the recovery system recovery mode respectively. In the recovery system recovery mode, the refrigerant in the one-way valve C, condenser 3 and other structures is drawn by compressor B and discharged to the indoor unit.

[0073] In some implementations...

[0074] The first pipe 101 is connected to the second pipe 102 at a first position 11, the fourth pipe 104 is connected to the second pipe 102 at a second position 12, the pipe section of the second pipe 102 located between the first position 11 and the second position 12 is the third pipe 103, and a one-way valve E75 is provided on the third pipe 103. The one-way valve E75 can only allow refrigerant to flow from the second pipe 102 to the first pipe 101.

[0075] The eighth pipe 108 is connected to the fourth pipe 104 at the third position 13. A one-way valve D74 is provided on the fourth pipe 104 and on the pipe section located between the third position 13 and the second position 12. The one-way valve D74 can only allow refrigerant to flow from the fourth pipe 104 to the second pipe 102.

[0076] The one-way valve E of this invention is designed to prevent the gas from the exhaust port of compressor A from entering the condenser directly without passing through oil separator A when compressor A starts, thus avoiding the phenomenon of no refrigerant flowing in oil separator A. The one-way valve D is designed to prevent the refrigerant and oil returning from the condenser via the second pipeline from returning to compressor B through the fourth pipeline when compressor A is turned off (preventing the eighth pipeline 108 from bypassing oil separator A, in which case oil separator A and the eighth pipeline 108 form a parallel connection, preventing only a small amount of fluid from passing through oil separator A), and preventing the oil separator A from failing to properly separate oil and gas due to a very small fluid flow rate.

[0077] The return oil pipeline of the present invention (including the first pipeline 101, the fourth pipeline 104 and the seventh pipeline 107) includes three pipeline ports, namely the air inlet of the oil separator A6 (i.e., the first pipeline 101), the air outlet of the oil separator A6 (i.e., the fourth pipeline 104), and the return oil port of the return oil pipeline (i.e., the seventh pipeline 107). A capillary tube A (first throttling device 81) and a one-way valve A71 are connected between the return oil port and the oil outlet of the oil separator A6. The one-way valve A71 is arranged in the direction from the oil outlet of the oil separator to the return oil port.

[0078] In some implementations...

[0079] It also includes an oil separator B10, a second throttling device 82, a ninth pipe 109, and a tenth pipe 110. One end of the ninth pipe 109 is connected to the exhaust end of the compressor B9, and the other end is connected to the interior of the oil separator B10. One end of the tenth pipe 110 is connected to the interior of the oil separator B10, and the other end is connected to the eighth pipe 108. The connection position between the tenth pipe 110 and the eighth pipe 108 is the sixth position 16, which is located between the control valve 18 and the compressor B9. The second throttling device 82 is disposed on the tenth pipe 110. The eleventh pipe 111 is connected to the exhaust port of the oil separator B10.

[0080] This invention utilizes an oil separator B to separate the oil-gas mixture at the discharge end of compressor B. The tenth pipeline guides the oil separated from the oil separator B to the inlet of compressor B, ensuring continued lubrication and cooling of the internal components. The compression pipeline includes compressor B, oil separator B, and check valve B connected sequentially. The inlet of the compression pipeline, i.e., the suction port of compressor B, is connected to the pipeline between the outlet of oil separator A and the inlet of check valve D. The oil outlet of oil separator B is connected to the pipeline between compressor B and the outlet of oil separator A via capillary tube B. The outlet of the compression pipeline, i.e., the outlet of check valve B, is connected to the pipeline between interface D and check valve C.

[0081] In some implementations...

[0082] It also includes an evaporator 4, a sixth pipe 106, and a seventh pipe 107. One end of the sixth pipe 106 is connected to the expansion valve 5, and the other end is connected to the evaporator 4. One end of the seventh pipe 107 is connected to the interior of the oil separator A6, and the other end is connected to the fifth pipe 105. The outlet of the oil separator B10 is connected to the seventh pipe 107 through the eleventh pipe 111. Figure 1 As shown, the fifth pipeline 105 is connected to the expansion valve 5 via the liquid fluorine pipeline 172.

[0083] The present invention also enables the evaporator and expansion valve to form a refrigeration cycle loop with the condenser and compressor A through the setting of the sixth pipeline. The seventh pipeline is used to guide the oil separated from the bottom of the oil separator A to the fifth pipeline and can return to the compressor A, thereby realizing oil recovery.

[0084] In some implementations...

[0085] The eleventh pipe 111 is connected to the seventh pipe 107 at the fourth position 14. A one-way valve B72 is provided on the eleventh pipe 111 and on the pipe section located between the heat exchanger 2 and the fourth position 14. The one-way valve B72 can only allow refrigerant to flow from the eleventh pipe 111 to the seventh pipe 107.

[0086] The fifth pipe 105 is connected to the seventh pipe 107 at the fifth position 15. A one-way valve C73 is provided on the fifth pipe 105 and on the pipe section located between the heat exchanger 2 and the fifth position 15. The one-way valve C73 can only allow refrigerant to flow from the fifth pipe 105 to the expansion valve 5.

[0087] The seventh pipeline 107 is equipped with a first throttling device 81 and a one-way valve A71. The first throttling device 81 and the one-way valve A71 are located between the oil separator A6 and the fourth position 14. The one-way valve A71 can only allow fluid to flow from the oil separator A6 to the fifth pipeline 105.

[0088] The present invention also enables the refrigerant gas separated by the oil separator B to be guided to the fifth pipeline through the arrangement of the eleventh pipeline and the one-way valve B, so that it can return to the indoor unit. The one-way valve B is used to prevent the refrigerant and oil from the fifth pipeline and the like from flowing back into the oil separator B.

[0089] The present invention provides an oil return pipeline comprising three ports: an air inlet for the oil separator, an air outlet for the oil separator, and an oil return port for the oil return pipeline. A capillary tube A and a one-way valve A connect the oil return port and the oil outlet for the oil separator, with the flow direction of the one-way valve A being from the oil outlet of the oil separator to the oil return port. The air inlet for the oil separator is connected between interface C and one-way valve E; the air outlet for the oil separator is connected between interface E and one-way valve E via one-way valve D, with the flow direction of the one-way valve D being from the air outlet of the oil separator to interface E; and the oil return port for the oil return pipeline is connected between interface D and one-way valve C.

[0090] The compression pipeline includes a solenoid valve (control valve 18), compressor B, oil separator B, and check valve B connected in sequence. The oil outlet of oil separator B is connected to the pipeline between compressor B and solenoid valve through capillary tube B. The inlet of the compression pipeline, i.e. the inlet of solenoid valve, is connected to the pipeline between the outlet of oil separator A and check valve D. The outlet of the compression pipeline, i.e. the outlet of check valve B, is connected to the pipeline between interface D and check valve C.

[0091] The present invention also enables the high-pressure oil to be throttled and depressurized by the first throttling device installed on the seventh pipeline, so as to ensure the continuous flow of lubricating oil and prevent the large-scale flow of refrigerant gas. The one-way valve A can prevent the refrigerant and oil from the fifth pipeline and other pipelines from flowing back into the oil separator A.

[0092] More preferably, the first throttling device is capillary A, and the second throttling device is capillary B.

[0093] In some implementations...

[0094] The first pipeline 101 is also provided with a gas valve 13', an interface A141 and an interface C143; the fifth pipeline 105, located between the fifth position 15 and the expansion valve 5, is provided with a liquid valve 15', an interface B142 and an interface D144; the second pipeline 102 is provided with an interface E145; the fifth pipeline 105, located between the fifth position 15 and the condenser 3, is provided with an interface F146; and a refrigerant inlet 16' is provided between the evaporator 4 and the compressor A1.

[0095] like Figure 1 As shown, the indoor unit includes at least a compressor A, an evaporator, an expansion valve, a gas valve, and a liquid valve. The gas valve is connected to interface A (gas outlet), and the liquid valve is connected to interface B (liquid inlet). Typically, the gas and liquid valves also have refrigerant charging nozzles. The gas and liquid valves can be manually opened or closed. When the gas and / or liquid valves are closed, the refrigerant charging nozzles on the gas or liquid valves can only connect to either the outdoor or indoor unit. This invention assumes that when the gas or liquid valves are closed, their refrigerant charging nozzles connect to the outdoor unit but not to the indoor unit. The outdoor unit includes at least a condenser, a gas inlet, and a liquid outlet.

[0096] The present invention also enables the indoor unit, the recovery system and the outdoor unit to be effectively connected into an integrated structure through the setting of multiple valves and interfaces, and the corresponding valves and interfaces can be opened or closed as needed to ensure the normal and reliable operation of the refrigeration equipment in test mode and recovery mode.

[0097] The present invention also provides a control method for a refrigerant recovery system for testing refrigeration equipment as described above, wherein:

[0098] The determination step involves determining whether the required operating mode for the refrigerant recovery system is the refrigeration equipment testing mode or the recovery system recovery mode.

[0099] The control steps are as follows: when the refrigerant recovery system needs to operate in the refrigeration equipment test mode, the compressor A1 is controlled to open, the compressor B9 is controlled to close, and the control valve 18 is controlled to close; when the refrigerant recovery system needs to operate in the recovery system recovery mode, the compressor A1 is controlled to close, the compressor B9 is controlled to open, and the control valve 18 is controlled to open.

[0100] This invention also controls compressors A and B, and the eighth pipeline, according to different testing modes of the refrigeration equipment and the recovery mode of the recovery system. It also controls the control valves to provide power to the refrigerant in recovery mode, promoting refrigerant recovery. Furthermore, the heat exchanger and the eleventh pipeline at the discharge end of compressor B allow heat exchange with the fifth pipeline. This utilizes the high-temperature heat from the compressor B discharge to heat the refrigerant in the fifth pipeline, converting the liquid refrigerant in the fifth pipeline into a gaseous state in recovery mode. The waste heat from the high-temperature discharge of the recovery compressor B and / or electric heating further accelerate the vaporization of the liquid refrigerant remaining in the liquid pipe, thus enabling effective recovery of the refrigerant in this part of the pipeline. This improves the recovery efficiency of the recovery equipment, increases the efficiency of recovery operation, avoids the retention of liquid refrigerant in the liquid pipe, and fully utilizes the waste heat from the high-temperature discharge of the recovery compressor, which is beneficial for improving the recovery efficiency and energy efficiency of the recovery equipment.

[0101] The working principle of the recycling system is explained as follows:

[0102] 1) Refrigeration equipment test mode

[0103] In traditional refrigeration equipment production and testing, indoor and outdoor units are separate. Because the outdoor units are very simple, they don't have complex electronic control systems, while the indoor units are more complex and have electronic control systems. Therefore, the production line mainly focuses on online testing and leak detection of the indoor units. The typical practice is as follows: a small amount of refrigerant is charged into the indoor unit for leak detection, while the outdoor unit uses a test fixture with sufficient refrigerant. The indoor and outdoor units are connected, and the outdoor unit's test fixture, containing its own refrigerant, is used for testing. After testing, the liquid valve is closed, and the compressor forces all the refrigerant into the outdoor unit's test fixture, including the small amount originally used for leak detection in the indoor unit. Because the same outdoor unit's test fixture is used, after testing multiple indoor units, a large amount of refrigerant from the original indoor unit leak detection accumulates in the outdoor unit's test fixture. This leads to an increasing amount of refrigerant in the test fixture and a buildup of compressor refrigeration oil, requiring periodic drainage or transfer to other pressure vessels. This affects testing accuracy, wastes production costs, extends production time, and reduces production efficiency.

[0104] The production testing process involved in this invention differs from the traditional testing process described above, as briefly described below:

[0105] Interface E of the refrigerant recovery system connects to the air inlet of the outdoor unit, and interface F connects to the liquid outlet of the outdoor unit. After connection, the refrigerant recovery system and the outdoor unit will serve as test fixtures for online testing on the production line. Only gaseous refrigerant lines need to be connected to interfaces A and C, and liquid refrigerant lines need to be connected to interfaces B and D. Simultaneously, the indoor unit must be charged with the rated refrigerant charge or test charge amount to replace the original small amount of refrigerant used for leak detection. All valves on interfaces A / BC / D / E / F are opened. Check valves A / B / C / D automatically open or close based on the pressure difference between their ends. A vacuum pump is connected to the refrigerant charging port on the gas valve and / or liquid valve to perform a vacuuming operation on the refrigerant recovery system and the outdoor unit. After successful vacuuming, the vacuum gauge valve is closed, the vacuum pump is turned off, and then the gas valve and liquid valve are opened. The vacuum gauge is then removed shortly afterward.

[0106] There is a conversion control mechanism between starting the refrigerant recovery equipment after the refrigeration equipment stops running and before starting the refrigerant recovery equipment:

[0107] After the outdoor fan stops for t seconds, the high-temperature and high-pressure refrigerant gas discharged from the compressor will flush the liquid refrigerant in the condenser and return it to the indoor unit as soon as possible. Then, the compressor and indoor fan will stop running, and the outdoor fan will start to cool the refrigerant remaining in the condenser.

[0108] Close the gas valve and wait m seconds to allow the indoor and outdoor units to achieve pressure balance as soon as possible; turn on electric heating device A and / or electric heating device B to heat and vaporize the liquid refrigerant remaining in the liquid pipe. The vaporized refrigerant can push some of the liquid refrigerant through one-way valve C into the evaporator of the indoor unit, and can also push some of the liquid refrigerant back into the condenser.

[0109] After completing steps a) and b) above, the transition control between the refrigeration equipment's operating mode and the recovery mode is achieved. Subsequently, the recovery equipment can be started to execute the recovery mode.

[0110] 2) The recycling equipment is operating in recycling mode.

[0111] When the solenoid valve is opened and compressor B is started, the refrigerant remaining on the outdoor unit is forced back into the indoor unit through compressor B. The indoor fan speed is adjusted according to the pressure in the indoor unit, ensuring that the high-temperature, high-pressure refrigerant gas discharged from compressor B into the evaporator condenses and liquefies as quickly as possible (this prevents the evaporator from becoming completely filled with gas, ensuring maximum refrigerant recovery). The high-speed operation of the outdoor unit's fan causes the remaining liquid refrigerant in the condenser to vaporize quickly, which is then drawn into compressor B. Oil separator A separates and stores the original lubricating oil from the refrigeration equipment, achieving gas-liquid separation and preventing incompletely evaporated liquid refrigerant from returning directly to compressor B. Oil separator B separates the refrigerant and lubricating oil at compressor B's outlet, ensuring the normal flow of lubricating oil within compressor B itself. In summary, the two oil separators maximize the isolation of lubricating oil between the two compressors, preventing excessive mixing and ensuring that both compressors have sufficient lubricating oil.

[0112] In the recycling mode of the recycling equipment, the refrigerant cycle is as follows: inlet of check valve C → shell side of the casing → interface F → condenser → interface E → check valve E → oil separator A → solenoid valve → compressor B → oil separator B → shell side of the casing → check valve B → interface D → interface B → liquid valve → expansion valve → evaporator.

[0113] When the suction pressure and / or temperature of compressor B is detected to be at the critical point Low, it indicates that the refrigerant recovery meets the requirements, and the operation of the recovery mode can be stopped. Perform the following operations in sequence: close the liquid valve; close electric heating device A and / or electric heating device B; stop the operation of compressor B and the outdoor fan; close the solenoid valve; and stop the operation of the indoor fan after waiting for n seconds.

[0114] After the recycling mode ends, most of the refrigerant in the recycling equipment, outdoor unit, gas refrigerant pipe and liquid refrigerant pipe has been recovered and returned to the indoor unit. Only a small amount of refrigerant gas remains in the pipeline between the liquid valve and the outlet of the one-way valve A / B / C, which is usually within the allowable error of the indoor unit's charge amount.

[0115] It should be noted that the interfaces A / B / C / D / E / F involved in this proposal can be equipped with valves that are either manually or automatically controlled.

[0116] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention. The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present invention, and these improvements and modifications should also be considered within the protection scope of the present invention.

Claims

1. A refrigerant recovery system for testing a refrigeration appliance, characterized by: include: Compressor A (1), condenser (3), oil separator A (6), first pipeline (101) and second pipeline (102), one end of the first pipeline (101) can be connected to the oil separator A (6) and the other end can be connected to the exhaust end of the compressor A (1), one end of the second pipeline (102) can be connected to the first pipeline (101) and the other end can be connected to one end of the condenser (3); It also includes an expansion valve (5) and a fifth pipeline (105), one end of which can be connected to the other end of the condenser (3) and the other end of which can be connected to the expansion valve (5). It also includes compressor B (9), heat exchanger (2) and eighth pipeline (108), one end of which can be connected to oil separator A (6) and the other end of which can be connected to the inlet end of compressor B (9) so that fluid can flow from oil separator A (6) to compressor B (9) in the recovery mode of the recovery system. The exhaust end of compressor B (9) is also connected to eleventh pipeline (111). A section of fifth pipeline (105) is inserted in heat exchanger (2) and a section of eleventh pipeline (111) is inserted in heat exchanger (2) so that the refrigerant in eleventh pipeline (111) at heat exchanger (2) can heat the refrigerant in fifth pipeline (105).

2. The refrigerant recovery system for testing refrigeration equipment according to claim 1, characterized in that: When the compressor A (1) is started, the refrigeration equipment test mode is run. At this time, the mixture of refrigerant and lubricating oil discharged from the exhaust end of the compressor A (1) enters the oil separator A (6) through the first pipeline (101) to achieve oil-gas separation. When the compressor A (1) is turned off, the recovery system recovery mode is run. At this time, the mixture of refrigerant and lubricating oil in the condenser (3) can enter the oil separator A (6) through the second pipeline (102) to achieve oil-gas separation.

3. The refrigerant recovery system for testing refrigeration equipment according to claim 1, characterized in that: The heat exchanger (2) is a shell-and-tube heat exchanger, including a shell. Parts of the fifth pipe (105) and the eleventh pipe (111) are inserted into the shell. An electric heating device A (191) is also provided on the shell to heat the refrigerant in the fifth pipe (105). And / or, an electric heating device B (192) is also provided on the part of the fifth pipe (105) where the heat exchanger (2) is not inserted to heat the refrigerant in the fifth pipe (105).

4. The refrigerant recovery system for testing refrigeration equipment according to claim 2 or 3, characterized in that: It also includes a fourth pipe (104), one end of which is connected to the interior of the oil separator A (6) and the other end is connected to the second pipe (102) so that fluid can flow from the oil separator A (6) to the second pipe (102) during the refrigeration equipment test mode. It also includes an eighth pipeline (108), one end of which is connected to the fourth pipeline (104) and the other end is connected to the air inlet of the compressor B (9) so that fluid can flow from the oil separator A (6) to the compressor B (9) in the recovery mode of the recovery system. A control valve (18) is provided on the eighth pipeline (108).

5. The refrigerant recovery system for testing refrigeration equipment according to claim 4, characterized in that: The first pipe (101) is connected to the second pipe (102) at a first position (11), the fourth pipe (104) is connected to the second pipe (102) at a second position (12), the section of the second pipe (102) located between the first position (11) and the second position (12) is the third pipe (103), and a one-way valve E (75) is provided on the third pipe (103). The one-way valve E (75) can only allow refrigerant to flow from the second pipe (102) to the first pipe (101); The eighth pipe (108) is connected to the fourth pipe (104) at the third position (13). A one-way valve D (74) is provided on the fourth pipe (104) and on the pipe section located between the third position (13) and the second position (12). The one-way valve D (74) can only allow refrigerant to flow from the fourth pipe (104) to the second pipe (102).

6. The refrigerant recovery system for testing refrigeration equipment according to claim 4, characterized in that: It also includes an oil separator B (10), a second throttling device (82), a ninth pipeline (109), and a tenth pipeline (110). One end of the ninth pipeline (109) is connected to the exhaust end of the compressor B (9), and the other end is connected to the interior of the oil separator B (10). One end of the tenth pipeline (110) is connected to the interior of the oil separator B (10), and the other end is connected to the eighth pipeline (108). The connection position between the tenth pipeline (110) and the eighth pipeline (108) is the sixth position (16). The sixth position (16) is located between the control valve (18) and the compressor B (9). The second throttling device (82) is installed on the tenth pipeline (110). The eleventh pipeline (111) is connected to the outlet of the oil separator B (10).

7. The refrigerant recovery system for testing refrigeration equipment according to claim 6, characterized in that: It also includes an evaporator (4), a sixth pipe (106) and a seventh pipe (107). One end of the sixth pipe (106) is connected to the expansion valve (5) and the other end is connected to the evaporator (4). One end of the seventh pipe (107) is connected to the interior of the oil separator A (6) and the other end is connected to the fifth pipe (105). The outlet of the oil separator B (10) is connected to the seventh pipe (107) through the eleventh pipe (111).

8. The refrigerant recovery system for testing refrigeration equipment according to claim 7, characterized in that: The eleventh pipe (111) is connected to the seventh pipe (107) at the fourth position (14). A one-way valve B (72) is provided on the eleventh pipe (111) and on the pipe section between the heat exchanger (2) and the fourth position (14). The one-way valve B (72) can only allow refrigerant to flow from the eleventh pipe (111) to the seventh pipe (107). The fifth pipe (105) is connected to the seventh pipe (107) at the fifth position (15). A one-way valve C (73) is provided on the fifth pipe (105) and on the pipe section between the heat exchanger (2) and the fifth position (15). The one-way valve C (73) can only allow refrigerant to flow from the fifth pipe (105) to the expansion valve (5). The seventh pipeline (107) is provided with a first throttling device (81) and a one-way valve A (71). The first throttling device (81) and the one-way valve A (71) are located between the oil separator A (6) and the fourth position (14). The one-way valve A (71) can only allow fluid to flow from the oil separator A (6) to the fifth pipeline (105).

9. The refrigerant recovery system for testing refrigeration equipment according to claim 8, characterized in that: The first pipeline (101) is also provided with a gas valve (13'), an interface A (141) and an interface C (143). The fifth pipeline (105) is provided with a liquid valve (15'), an interface B (142) and an interface D (144) located at the fifth position (15) and between the expansion valve (5). The second pipeline (102) is provided with an interface E (145). The fifth pipeline (105) is provided with an interface F (146) located at the fifth position (15) and between the condenser (3). The evaporator (4) is provided with a refrigerant inlet (16') between the compressor A (1).

10. A control method of a refrigerant recovery system for testing a refrigerating apparatus according to any one of claims 4 to 9, characterized by: include: The determination step involves determining whether the required operating mode for the refrigerant recovery system is the refrigeration equipment testing mode or the recovery system recovery mode. Control steps: When the required operating mode of the refrigerant recovery system is to be run in the refrigeration equipment test mode, control the compressor A (1) to open, control the compressor B (9) to close, and control the control valve (18) to close; when the required operating mode of the refrigerant recovery system is to be run in the recovery system recovery mode, control the compressor A (1) to close, control the compressor B (9) to open, and control the control valve (18) to open.

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