Variable-frequency air-cooling screw heat pump system

Abstract

The utility model provides a variable-frequency air-cooled screw heat pump system, which relates to the field of central air conditioning units and comprises a circulation main path, a motor cooling pipeline, an ECO air supply pipeline and a driver cooling branch, and the circulation main path is used for refrigerant circulation; the motor cooling pipeline and the ECO gas supplementing pipeline are connected with the circulating main path and are respectively used for forming a cooling loop of a compressor motor and a gas supplementing loop of a compressor; the driver is connected with the circulation main path through the driver cooling branch, and the driver cooling branch is used for forming a cooling loop of the driver. The screw compressor frequency converter is cooled in a refrigerant cooling mode, it is guaranteed that capacity reduction and frequency reduction are avoided under the high-temperature working condition of a unit, and the reliability of the unit is improved; a first-stage throttle valve of the flash tank is controlled by exhaust superheat, a second-stage throttle valve is controlled by a refrigerating main valve, a heating main valve and a liquid level meter, and refrigerating and heating of the unit are accurately regulated and controlled to operate efficiently and stably in cooperation with the refrigerating and heating double-loop design of the evaporator.

Description

Technical Field

[0001] The utility model belongs to the field of central air-conditioning units, in particular to a variable frequency air-cooling screw heat pump system. Background Art

[0002] Air-cooled screw units are a commonly used refrigeration equipment, widely used in large factories, hotels and other places that require refrigeration. It uses a screw compressor for refrigeration and dissipates heat through air cooling. At present, the common air-cooled screw units are generally fixed-frequency and normal-temperature types. First, the fixed-frequency units cannot follow the load changes, resulting in increased energy consumption, and second, the normal-temperature units are not suitable for heating in cold areas in the north. At present, screw compressor inverters often use air cooling to dissipate heat. This heat dissipation is often limited by the ambient temperature. When the ambient temperature is high, the capacity and frequency will be reduced, which is not conducive to the efficient operation of the unit. Furthermore, for the current common air-conditioning system, the system throttle valve is generally only one, and the cooling and heating two-way conduction throttling and the suction superheat control are all adopted. Due to the great difference in cold and hot working conditions, especially for the low ambient temperature operation of heating, the use of a throttle valve is not conducive to the precise energy adjustment and stable operation of the unit. Utility Model Content

[0003] In view of this, the utility model aims to provide a variable frequency air-cooled screw heat pump system to solve the above technical problems.

[0004] In order to achieve the above object, the technical solution of the utility model is implemented as follows:

[0005] A variable frequency air-cooled screw heat pump system, comprising a circulation main circuit, a motor cooling pipeline, an ECO air supply pipeline and a driver cooling branch circuit, wherein the circulation main circuit is used for refrigerant circulation;

[0006] The motor cooling pipeline and the ECO air supply pipeline are connected to the main circulation circuit, and are used to form a cooling circuit of the compressor motor and an air supply circuit of the compressor respectively;

[0007] The driver is connected to the main circulation circuit via the driver cooling branch, and the driver cooling branch is used to form a cooling circuit of the driver.

[0008] Furthermore, the main circulation path includes a compressor, a first heat exchanger, a second heat exchanger, a third heat exchanger, a four-way valve and a gas-liquid separator.

[0009] The exhaust port of the compressor is connected to the D port of the four-way valve through a pipeline, and a first control valve is provided on the pipeline between the compressor and the four-way valve;

[0010] The C port of the four-way valve is connected to the first heat exchanger through a pipeline, the first heat exchanger is connected to the second heat exchanger through a pipeline, and the pipeline between the first heat exchanger and the second heat exchanger is provided with a second control valve, a third control valve, a fourth control valve and a fifth control valve in sequence;

[0011] The second heat exchanger is connected to the third heat exchanger through a pipeline, and a sixth control valve and an eighth control valve are sequentially arranged between the second heat exchanger and the third heat exchanger;

[0012] The third heat exchanger is connected to the E port of the four-way valve through a pipeline, the S port of the four-way valve is connected to the return air port of the gas-liquid separator through a pipeline, and the gas outlet of the gas-liquid separator is connected to the suction port of the compressor through a pipeline.

[0013] Furthermore, the main circulation circuit also includes a liquid reservoir and a fourth pipeline.

[0014] The first end of the liquid reservoir is connected to the third heat exchanger through a pipeline, and the second end of the liquid reservoir is connected to the pipeline between the second control valve and the third control valve through a pipeline; a ninth control valve is provided on the pipeline connected to the second end of the liquid reservoir;

[0015] One end of the fourth pipeline is connected to the pipeline between the first heat exchanger and the second control valve, and the other end is connected to the pipeline between the sixth control valve and the eighth control valve; a seventh control valve is arranged on the fourth pipeline.

[0016] Furthermore, a drying filter cartridge is provided on the pipeline between the third control valve and the fourth control valve.

[0017] Furthermore, the driver cooling branch includes a first pipeline, a second pipeline and a third pipeline.

[0018] The two ends of the first pipeline are connected in parallel to the pipelines on both sides of the seventh control valve and the eighth control valve; the seventeenth control valve and the eighteenth control valve are arranged on the first pipeline;

[0019] One end of the second pipeline is connected to the first pipeline between the seventeenth control valve and the eighteenth control valve, and the other end is connected to one side of the driver; the sixteenth control valve is arranged on the second pipeline;

[0020] The other side of the driver is connected to one end of the third pipeline, and the other end of the third pipeline is connected to the pipeline between the drying filter cartridge and the second heat exchanger; the third pipeline is sequentially provided with a fifteenth control valve, a fourteenth control valve and a thirteenth control valve.

[0021] Furthermore, one end of the motor cooling pipeline is connected to the pipeline between the drying filter cartridge and the fourth control valve, and the other end is connected to the motor room of the compressor; the eleventh control valve and the tenth control valve are arranged on the motor cooling pipeline.

[0022] Furthermore, one end of the ECO air supply pipeline is connected to the second heat exchanger, and the other end is connected to the ECO port of the compressor; a twelfth control valve is provided on the ECO air supply pipeline.

[0023] Furthermore, the second heat exchanger is a flash exchanger.

[0024] Furthermore, a pressure sensor and a temperature sensor are provided on the pipeline between the first control valve and the compressor.

[0025] Furthermore, a liquid level sensor is provided on the second heat exchanger.

[0026] Compared with the prior art, the variable frequency air-cooled screw heat pump system described in the utility model has the following beneficial effects:

[0027] In the variable frequency air-cooled screw heat pump system described in the utility model, the variable frequency compressor can match the load changes in real time to achieve the effect of energy-saving operation, and the use of intermediate air supply from the flasher can effectively reduce the compressor exhaust temperature, thereby greatly expanding the operating range of the unit and meeting the heating needs of the northern region.

[0028] The variable frequency air-cooled screw heat pump system described in the utility model adopts refrigerant cooling to cool the screw compressor inverter, ensuring that the unit does not reduce capacity and frequency under high temperature conditions, thereby improving the reliability of the unit; furthermore, the first-level throttle valve of the flash unit adopts exhaust superheat control, and the second-level throttle valve adopts cooling and heating dual main valves and is controlled by a liquid level meter, and is matched with the cooling and heating dual-circuit design of the evaporator, so that the cooling and heating of the unit can be accurately controlled to operate efficiently and stably. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] The accompanying drawings constituting a part of the present invention are used to provide a further understanding of the present invention. The illustrative embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation on the present invention. In the accompanying drawings:

[0030] Figure 1 It is a structural schematic diagram of the utility model;

[0031] Figure 2 This is a schematic diagram of the refrigerant flow direction in the refrigeration mode of the utility model;

[0032] Figure 3 This is a schematic diagram of the refrigerant flow direction in the heating mode of the utility model;

[0033] Figure 4 This is a schematic diagram of the refrigerant flow direction in the defrost mode of the utility model.

[0034] Description of reference numerals:

[0035] 1-first control valve; 2-second control valve; 3-third control valve; 4-fourth control valve; 5-fifth control valve; 6-sixth control valve; 7-seventh control valve; 8-eighth control valve; 9-ninth control valve; 10-tenth control valve; 11-eleventh control valve; 12-twelfth control valve; 13-thirteenth control valve; 14-fourteenth control valve; 15-fifteenth control valve; 16-sixteenth control valve; 17-seventeenth control valve; 18 -Eighteenth control valve; 19-first heat exchanger; 20-four-way valve; 21-pressure sensor; 22-temperature sensor; 23-compressor; 24-gas-liquid separator; 25-drying filter cartridge; 26-second heat exchanger; 27-liquid level sensor; 28-third heat exchanger; 29-driver; 30-liquid reservoir; 31-motor cooling pipeline; 32-ECO air supply pipeline; 33-first pipeline; 34-second pipeline; 35-third pipeline. DETAILED DESCRIPTION

[0036] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments can be combined with each other.

[0037] In the description of the present utility model, it should be understood that the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present utility model and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present utility model. In addition, the terms "first", "second", etc. are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, features defined as "first", "second", etc. may explicitly or implicitly include one or more of the features. In the description of the present utility model, unless otherwise specified, "multiple" means two or more.

[0038] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installation", "connection" and "connection" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be an indirect connection through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood by specific circumstances.

[0039] The present invention will be described in detail below with reference to the accompanying drawings and in combination with embodiments.

[0040] The utility model provides a variable frequency air-cooled screw heat pump system, comprising a circulation main circuit, a motor cooling pipeline 31, an ECO air supply pipeline 32 and a driver 29 cooling branch circuit, wherein the motor cooling pipeline 31 is connected to the circulation main circuit, and liquid is taken from the circulation main circuit to form a cooling circuit of the motor of the compressor 23. The ECO air supply pipeline 32 is connected to the circulation main circuit to form an air supply circuit of the compressor 23. The driver 29 cooling circuit connects the driver 29 with the circulation main circuit to form a cooling circuit of the driver 29.

[0041] The main circulation path includes a compressor 23, a four-way valve 20, a first heat exchanger 19, a second heat exchanger 26 and a third heat exchanger 28. The exhaust port of the compressor 23 is connected to the D port of the four-way valve 20 through a pipeline, and a first control valve 1 is arranged on the pipeline between the compressor 23 and the D port of the four-way valve 20. The first control valve 1 is used to ensure the establishment of the pressure difference of the compressor 23 to avoid the compressor 23 being unable to return oil normally when the pressure ratio is low. The C port of the four-way valve 20 is connected to the first heat exchanger 19 through a pipeline, and the first heat exchanger 19 is connected to the drying filter cartridge 25 through a pipeline. The second control valve 2 and the third control valve 3 are arranged on the pipeline between the first heat exchanger 19 and the drying filter cartridge 25. The drying filter cartridge 25 is connected to the second heat exchanger 26 through a pipeline, and the fourth control valve 4 and the fifth control valve 5 are arranged on the pipeline between the drying filter cartridge 25 and the second heat exchanger 26. The second heat exchanger 26 is connected to the third heat exchanger 28 through a pipeline, and the sixth control valve 6 and the eighth control valve 8 are sequentially arranged on the pipeline between the second heat exchanger 26 and the third heat exchanger 28. The third heat exchanger 28 is connected to the E port of the four-way valve 20 through a pipeline, and the S port of the four-way valve 20 is connected to the return port of the gas-liquid separator 24 through a pipeline, and the gas outlet of the gas-liquid separator 24 is connected to the suction port of the compressor 23 through a pipeline.

[0042] In the refrigeration / defrost mode, the main circulation loop of the heat pump system is: the refrigerant is discharged from the compressor 23, enters the first heat exchanger 19 through the four-way valve 20D port to the C port, is discharged from the first heat exchanger 19, is filtered and dried by the filter-drying cylinder, and then flows into the second heat exchanger 26. After being discharged from the second heat exchanger 26, the refrigerant enters the third heat exchanger 28, and then passes through the four-way valve 20E port to the S port, flows through the gas-liquid separator 24, and then enters the suction port of the compressor 23.

[0043] The circulation main line also includes a liquid reservoir 30 and a fourth pipeline. The first end of the liquid reservoir 30 is connected to the third heat exchanger 28 through a pipeline, and the second end of the liquid reservoir 30 is connected to the pipeline between the second control valve 2 and the third control valve 3 through a pipeline bypass. The ninth control valve 9 is installed on the pipeline connected to the second end of the liquid reservoir 30. One end of the fourth pipeline is connected to the pipeline between the first heat exchanger 19 and the second heat exchanger 26, and the other end is connected to the pipeline between the sixth control valve 6 and the eighth control valve 8. The seventh control valve 7 is arranged on the fourth pipeline.

[0044] In the heating mode, the main circulation loop of the heat pump system is: the refrigerant is discharged from the exhaust port of the compressor 23, and is introduced into the third heat exchanger 28 through the four-way valve 20D port to the E port. After being discharged from the third heat exchanger 28, it passes through the liquid storage tank 30 and the drying filter cartridge 25 in sequence to enter the second heat exchanger 26, and then enters the first heat exchanger 19 through the sixth control valve 6 and the seventh control valve 7. After passing through the first heat exchanger 19, it flows from the four-way valve 20C port to the S port through the gas-liquid separator 24 and enters the suction port of the compressor 23.

[0045] Furthermore, a pressure sensor 21 and a temperature sensor 22 are provided on the pipeline between the first control valve 1 and the compressor 23. A liquid level sensor 27 is provided on the second heat exchanger 26. The pressure sensor 21 is controlled by a voltage signal, with a measuring range of -0.1 to 1.6Mpa, and an interface of NPT1 / 4. The temperature sensor 22 is a PT1000 type. The liquid level sensor 27 is controlled by a current signal, which is connected to the refrigerant inside the second heat exchanger 26 through a pipeline, and is used to monitor the liquid level of the second heat exchanger 26 in real time. The exhaust superheat is calculated by the pressure sensor 21 and the temperature sensor 22, which is used to control the action of the fourth valve, and the liquid level sensor 27 is used to control the action of the seventh and eighth valves. Preferably, the exhaust superheat is controlled between 20°C and 25°C, and the liquid level height of the liquid level sensor 27 is controlled between 150mm and 180mm. The above control principle is the prior art.

[0046] Specifically, the compressor 23 is an integral twin-screw variable frequency compressor 23, and the operating speed is 25 to 70HZ. The first control valve 1 is a pressure maintaining valve, which detects the high and low pressures at both ends of the compressor, and is preferably conducted when the high and low pressure difference is greater than 2bar, otherwise it is not conducted. The four-way valve 20 is a mechanical / electric four-way valve 20. The first heat exchanger 19 is an inverted M / multi-V fin tube heat exchanger. The second heat exchanger 26 is a flasher. The third heat exchanger 28 is a dry shell and tube heat exchanger, and its refrigeration and heating liquid pipes are separated, and the heating liquid pipe is located below the refrigeration liquid pipe. The second control valve 2, the ninth control valve 9, the seventeenth control valve 17, and the eighth control valve 8 are piston-type one-way valves. The third control valve 3, the fifth control valve 5, and the sixth control valve 6 are ball valves, which are used to close other pipelines when inspecting the drying filter cartridge 25 and the second heat exchanger 26. The fourth control valve 4, the seventh control valve 7, and the eighth control valve 8 are direct-through electronic expansion valves, and their fully open steps are 2000 pulses. The tenth control valve 10 and the thirteenth control valve 13 are right-angle electronic expansion valves, and their fully open steps are 500 pulses. The fourth control valve 4 is a primary throttle valve, the seventh control valve 7 is a secondary heating throttle valve, and the eighth control valve 8 is a secondary cooling throttle valve. The eleventh control valve 11, the twelfth control valve 12, and the fourteenth control valve 14 are normally closed solenoid valves, which are turned on when energized and closed when de-energized. The fifteenth control valve 15 and the sixteenth control valve 16 are right-angle valves, which are used to isolate from other refrigerant circuits when inspecting the driver 29.

[0047] The pipeline between the drying filter cartridge 25 and the fourth control valve 4 is connected to one end of the motor cooling pipeline 31 in a bypass manner, and the other end of the motor cooling pipeline 31 is connected to the motor room of the compressor 23. The eleventh control valve 11 and the tenth control valve 10 are arranged on the motor cooling pipeline 31. The motor cooling pipeline 31 takes liquid from the main circulation line to form a cooling circuit for the motor of the compressor 23.

[0048] One end of the ECO air supply pipeline 32 is connected to the second heat exchanger 26, and the other end is connected to the ECO port of the compressor 23. The twelfth control valve 12 is provided on the ECO air supply pipeline 32. The ECO air supply pipeline 32 is connected between the second heat exchanger 26 of the main circulation path and the compressor 23, and is used to form an air supply circuit for the compressor 23.

[0049] The cooling branch of the driver 29 is connected to the driver 29, and includes a first pipeline 33, a second pipeline 34 and a third pipeline 35. The two ends of the first pipeline 33 are connected in parallel to the pipelines on both sides of the seventh control valve 7 and the eighth control valve 8. The first pipeline 33 is provided with a seventeenth control valve 17 and an eighteenth control valve 18. The second pipeline 34 is connected to the pipeline between the seventeenth control valve 17 and the eighteenth control valve 18 in a bypass manner. The other end of the second pipeline 34 is connected to one side of the driver 29. The second pipeline 34 is provided with a sixteenth control valve 16. The other side of the driver 29 is connected to the third pipeline 35. The other end of the third pipeline 35 is connected to the pipeline between the drying filter cartridge 25 and the fourth control valve 4 in a bypass manner. The third control valve 3 is provided with a fifteenth control valve 15, a fourteenth control valve 14 and a thirteenth control valve 13 in sequence.

[0050] In the refrigeration / defrost mode, the third pipeline 35 takes liquid from the pipeline between the drying filter cartridge 25 and the fourth control valve 4, flows through the driver 29 and the second pipeline 34 into the third pipeline 35, and flows through the eighteenth control valve 18 into the main circulation path.

[0051] In the heating mode, the third pipeline 35 takes liquid from the pipeline between the drying filter cartridge 25 and the fourth control valve 4, flows through the driver 29 and the second pipeline 34 into the third pipeline 35, and flows through the seventeenth control valve 17 into the main circulation path.

[0052] It should be noted that the refrigerant flow direction of the main circulation loop of the defrost mode is the same as that of the refrigeration mode. The system is unstable when used for defrosting, so the ECO air supply loop should be closed. On the other hand, during the defrosting switching process, that is, during the switching from the heating mode to the cooling mode, the eighth control valve 813 should be opened 5-10 seconds in advance to avoid the system circulation being blocked and jumping to low pressure when the four-way valve 203 is switched to the cooling mode. Similarly, when the defrosting is completed and the four-way valve 203 is switched from the cooling mode to the heating mode, the seventh control valve 712 should be opened 5-10 seconds in advance to avoid the system circulation being blocked and jumping to low pressure when the four-way valve 203 is switched to the heating mode.

[0053] The variable frequency compressor in the utility model can match the load changes in real time to achieve the effect of energy-saving operation, and the use of intermediate air supply from the flasher can effectively reduce the compressor exhaust temperature, thereby greatly expanding the operating range of the unit and meeting the heating needs of the northern region.

[0054] The utility model adopts refrigerant cooling to cool the screw compressor inverter, ensuring that the unit does not reduce capacity and frequency under high temperature conditions, thereby improving the reliability of the unit; furthermore, the first-level throttle valve of the flash unit adopts exhaust superheat control, and the second-level throttle valve adopts cooling and heating dual main valves and is controlled by a liquid level meter, and is matched with the cooling and heating dual-circuit design of the evaporator, so that the cooling and heating of the unit can be accurately controlled to operate efficiently and stably.

[0055] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the utility model, rather than to limit it. Although the utility model has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. These modifications or replacements do not deviate the essence of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the utility model, and they should all be included in the scope of the claims and specification of the utility model.

[0056] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A variable frequency air-cooled screw heat pump system, characterized in that: It includes a circulation main circuit, a motor cooling pipeline, an ECO air supply pipeline and a driver cooling branch circuit, wherein the circulation main circuit is used for refrigerant circulation; The motor cooling pipeline and the ECO air supply pipeline are connected to the main circulation circuit, and are used to form a cooling circuit of the compressor motor and an air supply circuit of the compressor respectively; The driver is connected to the main circulation circuit via the driver cooling branch, and the driver cooling branch is used to form a cooling circuit of the driver.

2. The variable frequency air-cooled screw heat pump system according to claim 1, characterized in that: The main circulation path includes a compressor, a first heat exchanger, a second heat exchanger, a third heat exchanger, a four-way valve and a gas-liquid separator. The exhaust port of the compressor is connected to the D port of the four-way valve through a pipeline, and a first control valve is provided on the pipeline between the compressor and the four-way valve; The C port of the four-way valve is connected to the first heat exchanger through a pipeline, the first heat exchanger is connected to the second heat exchanger through a pipeline, and the pipeline between the first heat exchanger and the second heat exchanger is provided with a second control valve, a third control valve, a fourth control valve and a fifth control valve in sequence; The second heat exchanger is connected to the third heat exchanger through a pipeline, and a sixth control valve and an eighth control valve are sequentially arranged between the second heat exchanger and the third heat exchanger; The third heat exchanger is connected to the E port of the four-way valve through a pipeline, the S port of the four-way valve is connected to the return air port of the gas-liquid separator through a pipeline, and the gas outlet of the gas-liquid separator is connected to the suction port of the compressor through a pipeline.

3. The variable frequency air-cooled screw heat pump system according to claim 2, characterized in that: The main circulation circuit also includes a liquid reservoir and a fourth pipeline. The first end of the liquid reservoir is connected to the third heat exchanger through a pipeline, and the second end of the liquid reservoir is connected to the pipeline between the second control valve and the third control valve through a pipeline; a ninth control valve is arranged on the pipeline connected to the second end of the liquid reservoir; One end of the fourth pipeline is connected to the pipeline between the first heat exchanger and the second control valve, and the other end is connected to the pipeline between the sixth control valve and the eighth control valve; a seventh control valve is arranged on the fourth pipeline.

4. The variable frequency air-cooled screw heat pump system according to claim 3, characterized in that: A drying filter cartridge is arranged on the pipeline between the third control valve and the fourth control valve.

5. The variable frequency air-cooled screw heat pump system according to claim 4, characterized in that: The driver cooling branch includes a first pipeline, a second pipeline and a third pipeline. The two ends of the first pipeline are connected in parallel to the pipelines on both sides of the seventh control valve and the eighth control valve; the seventeenth control valve and the eighteenth control valve are arranged on the first pipeline; One end of the second pipeline is connected to the first pipeline between the seventeenth control valve and the eighteenth control valve, and the other end is connected to one side of the driver; A sixteenth control valve is arranged on the second pipeline; the other side of the driver is connected to one end of the third pipeline, and the other end of the third pipeline is connected to the pipeline between the drying filter cartridge and the second heat exchanger; a fifteenth control valve, a fourteenth control valve and a thirteenth control valve are arranged in sequence on the third pipeline.

6. The variable frequency air-cooled screw heat pump system according to claim 4, characterized in that: One end of the motor cooling pipeline is connected to the pipeline between the drying filter cartridge and the fourth control valve, and the other end is connected to the motor room of the compressor; the eleventh control valve and the tenth control valve are arranged on the motor cooling pipeline.

7. The variable frequency air-cooled screw heat pump system according to claim 2, characterized in that: One end of the ECO air supply pipeline is connected to the second heat exchanger, and the other end is connected to the ECO port of the compressor; a twelfth control valve is arranged on the ECO air supply pipeline.

8. The variable frequency air-cooled screw heat pump system according to claim 2, characterized in that: The second heat exchanger is a flash heat exchanger.

9. The variable frequency air-cooled screw heat pump system according to claim 2, characterized in that: A pressure sensor and a temperature sensor are arranged on the pipeline between the first control valve and the compressor.

10. The variable frequency air-cooled screw heat pump system according to claim 2, characterized in that: The second heat exchanger is provided with a liquid level sensor.

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