Variable-frequency centrifugal air-cooled heat pump unit

Abstract

The utility model provides a variable-frequency centrifugal air-cooled heat pump unit which comprises a main circulation loop formed by connecting a compressor, a four-way valve, a first heat exchanger, a drying filter, an economizer, a second heat exchanger and a gas-liquid separator through refrigerant pipelines. The auxiliary pipeline is composed of a shutdown bypass pipeline, a hot air bypass pipeline, a motor cooling pipeline, an economizer air supply pipeline, a frequency converter cooling pipeline and an air suction bypass pipeline, and the shutdown bypass pipeline is formed by connecting pipelines arranged between the compressor and the first inlet of the gas-liquid separator; and the hot air bypass pipeline is formed by connecting a pipeline arranged between the compressor and the third inlet of the gas-liquid separator. The system does not need lubricating oil during operation, is high in heat transfer efficiency, carries an economizer system for improving unit performance and reducing exhaust temperature, and is uniform, simple and convenient in piping and stable in operation.

Description

Technical Field

[0001] The utility model belongs to the technical field of air source heat pump units, in particular to a variable frequency centrifugal air-cooled heat pump unit. Background Art

[0002] Traditional large-scale air source heat pump units are generally equipped with semi-enclosed screw compressors. Due to the presence of lubricating oil in the compressor and the two devices in the system, a layer of thermal resistance is formed between the heat exchange tubes and the medium, making the heat transfer efficiency of the unit low.

[0003] With the development of science and technology, more and more application products of magnetic suspension / gas suspension / liquid suspension variable frequency centrifugal compressors have been launched in the market recently. The units using this type of compressor do not require lubricating oil, rely on magnetic field or gaseous refrigerant to keep the compressor motor bearings in a suspended state, reduce mechanical friction and transmission loss, and greatly improve the efficiency of the compressor.

[0004] However, there are currently few air-cooled units on the market that use variable-frequency centrifugal compressors; the majority are water-cooled chillers. This is because surge in air-cooled heat pump units using variable-frequency centrifugal compressors is difficult to control and requires a large number of auxiliary piping, making the unit's piping layout more complex. Utility Model Content

[0005] In view of this, the present invention aims to provide a variable frequency centrifugal air-cooled heat pump unit to solve the above-mentioned problems.

[0006] In order to achieve the above-mentioned purpose, the technical solution of the utility model is achieved as follows:

[0007] The utility model provides a variable frequency centrifugal air-cooled heat pump unit, characterized in that the unit comprises:

[0008] A main circulation loop, wherein the main circulation loop is formed by connecting a compressor, a four-way valve, a first heat exchanger, a drying filter, an economizer, a second heat exchanger and a gas-liquid separator through a refrigerant pipeline;

[0009] Auxiliary pipeline, the auxiliary pipeline is composed of a shutdown bypass pipeline, a hot gas bypass pipeline, a motor cooling pipeline, an economizer air supply pipeline, a frequency converter cooling pipeline, and an air suction bypass pipeline;

[0010] Among them, the shutdown bypass pipeline is formed by connecting the pipeline arranged between the compressor and the first inlet of the gas-liquid separator; the hot gas bypass pipeline is formed by connecting the pipeline arranged between the compressor and the third inlet of the gas-liquid separator; the motor cooling pipeline is formed by connecting the first filter, the compressor, and the second inlet of the gas-liquid separator, and the first filter is arranged between the drying filter and the economizer; the economizer air supply pipeline is formed by connecting the pipeline arranged between the economizer and the compressor; the inverter cooling pipeline is formed by connecting the economizer, the second filter, the inverter, and the third inlet of the gas-liquid separator in sequence; the intake bypass pipeline is formed by connecting the second heat exchanger, the gas-liquid separator, and the compressor in sequence.

[0011] Furthermore, the secondary compression exhaust port of the compressor is connected to the C port of the four-way valve through the first valve, the C port of the four-way valve is connected to each heat exchange coil of the first heat exchanger through the manifold, and each heat exchange coil of the first heat exchanger is connected to the distributor;

[0012] The distributor is connected to the second valve and the third valve respectively. The second valve is connected to the filter drier and the fifth valve respectively. The third valve is connected to the second heat exchanger through the fourth valve and is connected to the outlet of the economizer through the seventh valve and the eighth valve respectively. The other end of the fifth valve is connected to the pipeline between the fourth valve and the second heat exchanger. The filter drier is connected to the economizer through the sixth valve.

[0013] The economizer is connected to the outlet end of the gas-liquid separator and the first-stage compression suction port of the compressor.

[0014] Furthermore, the secondary compression exhaust port of the compressor is connected to the first inlet of the gas-liquid separator through a tenth valve;

[0015] The secondary compression exhaust port of the compressor is connected to the third inlet of the gas-liquid separator through the fourteenth valve.

[0016] Furthermore, the first end of the first filter is arranged between the drying filter and the sixth valve, the second end of the second filter is connected to the motor cavity of the compressor through the twelfth valve, and the motor cavity of the compressor is connected to the second inlet of the gas-liquid separator through the thirteenth valve.

[0017] Furthermore, the economizer is connected to the middle air supply port of the compressor through an eleventh valve;

[0018] The outlet of the economizer is connected to the second filter, the second filter is connected to the frequency converter through the fifteenth valve and the sixteenth valve in sequence, and the frequency converter is connected to the third inlet of the gas-liquid separator.

[0019] Furthermore, the second heat exchanger is connected to the first-stage compression suction port of the compressor through the seventeenth valve and the ninth valve in sequence, and the outlet of the gas-liquid separator is set on the pipeline between the seventeenth valve and the ninth valve.

[0020] Furthermore, the first valve is a check valve, and the ninth valve is a manual butterfly valve;

[0021] The second valve, the third valve, the fourth valve, the fifth valve and the thirteenth valve are one-way valves;

[0022] The sixth valve, the seventh valve, the eighth valve, the twelfth valve, and the sixteenth valve are electronic expansion valves;

[0023] The tenth valve, the eleventh valve, and the fifteenth valve are solenoid valves;

[0024] The fourteenth valve and the seventeenth valve are electric butterfly valves with proportional opening.

[0025] Furthermore, the seventh valve and the eighth valve constitute a parallel double main valve.

[0026] Furthermore, the compressor is a two-stage compression variable frequency centrifugal compressor with magnetic suspension / gas suspension / liquid suspension and an ECO port.

[0027] Furthermore, the first heat exchanger is an air-cooled fin-tube heat exchanger, and the heat exchanger structure is a multi-V type / inverted M type;

[0028] The second heat exchanger is a dry / flooded shell and tube heat exchanger.

[0029] Compared with the prior art, the variable frequency centrifugal air-cooled heat pump unit described in the present invention has the following beneficial effects:

[0030] The utility model describes a variable frequency centrifugal air-cooled heat pump unit, which does not require lubricating oil for system operation and has high heat transfer efficiency. It is equipped with an economizer system for improving unit performance and reducing exhaust temperature. A hot gas bypass pipeline and a shutdown bypass pipeline are specially arranged to avoid system surge, a motor cooling pipeline is used to reduce the compressor motor winding temperature, an intake bypass pipeline is used to bypass the four-way valve to reduce system pressure drop during refrigeration, an economizer air supply pipeline is used to supply air and increase enthalpy, and a frequency converter cooling circuit is used to cool the compressor frequency converter to ensure stable operation of the compressor. In addition, all of the above auxiliary pipelines are effectively combined and connected to the air inlet of the gas-liquid separator, so that the system piping is unified, simple and convenient. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] The accompanying drawings, which constitute part of the present invention, are intended to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are intended to explain the present invention and do not constitute an improper limitation of the present invention. In the accompanying drawings:

[0032] Figure 1 This is a schematic diagram of a variable frequency centrifugal air-cooled heat pump system according to an embodiment of the present utility model;

[0033] Figure 2 This is a schematic diagram of the cooling mode of a variable frequency centrifugal air-cooled heat pump unit according to an embodiment of the present utility model;

[0034] Figure 3 This is a schematic diagram of the heating mode of a variable frequency centrifugal air-cooled heat pump unit described in an embodiment of the present utility model.

[0035] Description of reference numerals:

[0036] 1- compressor; 2- first valve; 3- four-way valve; 4- first heat exchanger; 5- second valve; 6- third valve; 7- fourth valve; 8- fifth valve; 9- filter drier; 10- sixth valve; 11- economizer; 12- seventh valve; 13- eighth valve; 14- second heat exchanger; 15- gas-liquid separator; 16- ninth valve; 17- tenth valve; 18- eleventh valve; 19- first filter; 20- twelfth valve; 21- thirteenth valve; 22- fourteenth valve; 23- second filter; 24- fifteenth valve; 25- sixteenth valve; 26- frequency converter; 27- seventeenth valve. DETAILED DESCRIPTION

[0037] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features therein can be combined with each other.

[0038] The present invention will be described in detail below with reference to the accompanying drawings and in combination with embodiments.

[0039] See also Figure 1 As shown, this embodiment provides a variable frequency centrifugal air-cooled heat pump unit, the unit comprising:

[0040] The main circulation loop is formed by the compressor 1, the four-way valve 3, the first heat exchanger 4, the drying filter 9, the economizer 11, the second heat exchanger 14 and the gas-liquid separator 15 connected by the refrigerant pipeline;

[0041] Auxiliary pipeline, the auxiliary pipeline consists of shutdown bypass pipeline, hot gas bypass pipeline, motor cooling pipeline, economizer air supply pipeline, inverter cooling pipeline, and suction bypass pipeline;

[0042] Among them, the shutdown bypass pipeline is formed by a pipeline connection arranged between the compressor 1 and the first inlet of the gas-liquid separator 15; the hot gas bypass pipeline is formed by a pipeline connection arranged between the compressor 1 and the third inlet of the gas-liquid separator 15; the motor cooling pipeline is formed by connecting the first filter 19, the compressor 1, and the second inlet of the gas-liquid separator 15, and the first filter 19 is arranged between the drying filter 9 and the economizer 11; the economizer air supply pipeline is formed by connecting the pipeline between the economizer 11 and the compressor 1; the inverter cooling pipeline is formed by connecting the economizer 11, the second filter 23, the inverter 26, and the third inlet of the gas-liquid separator 15 in sequence; the suction bypass pipeline is formed by connecting the second heat exchanger 14, the gas-liquid separator 15, and the compressor 1 in sequence.

[0043] The air-cooled heat pump unit described in the present application does not require lubricating oil for system operation and has high heat transfer efficiency. It is equipped with an economizer 11 system for improving unit performance and reducing exhaust temperature. Special hot gas bypass pipelines and shutdown bypass pipelines are set to avoid system surge, motor cooling pipelines are used to reduce the temperature of the compressor 1 motor winding, suction bypass pipelines are used to bypass the four-way valve 3 during refrigeration to reduce system pressure drop, economizer 11 air supply pipelines are used to supply air and increase enthalpy, and inverter 26 cooling circuits are used to cool the compressor inverter 26 to ensure stable operation of the compressor, and all of the above auxiliary pipelines are effectively combined to be connected to the air inlet of the gas-liquid separator 15, so that the system piping is unified, simple and convenient.

[0044] In some embodiments, the compressor 1 of this embodiment is a two-stage compression variable frequency centrifugal compressor 1 with a magnetic suspension / gas suspension / liquid suspension and an ECO port. The secondary compression exhaust port of the compressor 1 is connected to the C port of the four-way valve 3 through the first valve 2 (the first valve 2 of this embodiment is a check valve). The four-way valve 3 is an electrically driven four-way reversing valve. The C port of the four-way valve 3 is connected to each heat exchange coil of the first heat exchanger 4 through a manifold. Each heat exchange coil of the first heat exchanger 4 is connected to the distributor. The first heat exchanger 4 of this embodiment is an air-cooled fin tube heat exchanger, and the heat exchanger structure adopts a multi-V type / inverted M type.

[0045] The distributor is connected to the second valve 5 and the third valve 6 (both the second valve 5 and the third valve 6 are one-way valves). The second valve 5 is connected to the filter drier 9 and the fifth valve 8 (the fifth valve 8 is a one-way valve). The third valve 6 is connected to the second heat exchanger 14 via the fourth valve 7 (the fourth valve 7 is a one-way valve) and to the outlet of the economizer 11 via the seventh valve 12 and the eighth valve 13 (the seventh valve 12 and the eighth valve 13 are electronic expansion valves and form a parallel dual main valve for expanding the capacity range of the unit). The other end of the fifth valve 8 is connected to the pipeline between the fourth valve 7 and the second heat exchanger 14. The filter drier 9 is connected to the economizer 11 via the sixth valve 10.

[0046] The economizer 11 is connected to the outlet of the gas-liquid separator 15 and the first-stage compression suction port of the compressor 1;

[0047] The secondary compression exhaust port of the compressor 1 is connected to the first inlet of the gas-liquid separator 15 through the tenth valve 17 (the tenth valve 17 is a solenoid valve. The tenth valve 17 of the shutdown bypass pipeline is opened after receiving the shutdown command to quickly balance the high and low pressure differences and avoid surge caused by excessive pressure ratio of the compressor speed reduction system);

[0048] The secondary compression exhaust port of the compressor 1 is connected to the third inlet of the gas-liquid separator 15 through the fourteenth valve 22 (the fourteenth valve 22 is an electric butterfly valve with proportional opening). The gas-liquid separator 15 has three inlets and one outlet, which are respectively connected to corresponding pipelines.

[0049] In some embodiments, the first end of the first filter 19 is arranged between the drying filter 9 and the sixth valve 10 (the sixth valve 10 is an electronic expansion valve), and the second end of the second filter 23 is connected to the motor cavity of the compressor 1 through the twelfth valve 20 (the twelfth valve 20 is an electronic expansion valve, and the twelfth valve 20 of the motor cooling pipeline is linked to the compressor 1 to open / close, and is used to control the temperature of the compressor 1 motor). The motor cavity of the compressor 1 is connected to the second inlet of the gas-liquid separator 15 through the thirteenth valve 21 (the thirteenth valve 21 is a one-way valve, and the thirteenth valve 21 of the hot gas bypass pipeline is opened 100% when the compressor is started, which is used to avoid the problem of surge that is prone to occur at the takeoff speed of the compressor 1; as the compressor speed increases, the thirteenth valve 21 gradually closes to 0; when the unit is running, if the exhaust pressure / compressor current fluctuates, the thirteenth valve 21 will also be opened by 30% on the basis of the existing opening to balance the high and low pressure differences and slow down surge).

[0050] In some embodiments, the economizer 11 of this embodiment is a flash economizer 11, and the economizer 11 is connected to the middle air supply port of the compressor 1 through the eleventh valve 18 (the eleventh valve 18 is a solenoid valve);

[0051] The outlet of the economizer 11 is connected to the second filter 23, and the second filter 23 is connected to the frequency converter 26 through the fifteenth valve 24 (the fifteenth valve 24 is a solenoid valve) and the sixteenth valve 25 (the sixteenth valve 25 is an electronic expansion valve) in sequence. The frequency converter 26 is connected to the third inlet of the gas-liquid separator 15.

[0052] Specifically, in this embodiment, the fifteenth valve 24 to the sixteenth valve 25 of the cooling pipeline of the inverter 26 are controlled to open or adjust the opening according to the set temperature inside the inverter 26, so as to avoid the inverter 26 from being overheated and to avoid condensation on the heat sink of the inverter 26.

[0053] In some embodiments, the second heat exchanger 14 is connected to the first-stage compression suction port of the compressor 1 through the seventeenth valve 27 (the seventeenth valve 27 is an electric butterfly valve with a proportional opening. The seventeenth valve 27 of the suction bypass line is opened during cooling and closed during heating. It is used to bypass the pressure drop of the four-way valve 3 and the gas-liquid separator 15 during cooling operation, thereby increasing the evaporation temperature and thus improving the system energy efficiency) and the ninth valve 16 (the ninth valve 16 is a manual butterfly valve). The outlet of the gas-liquid separator 15 is arranged on the pipeline between the seventeenth valve 27 (the seventeenth valve 27 is an electric butterfly valve with a proportional opening) and the ninth valve 16. The second heat exchanger 14 of this embodiment adopts a dry / full liquid shell and tube heat exchanger.

[0054] Since the centrifugal compressor 1 rotates at a high speed, the defrosting method of the unit is to stop the compressor 1 and then restart the refrigeration mode for defrosting. In the defrosting mode, the eleventh valve 18 and the seventeenth valve 27 are closed.

[0055] When this unit is implemented:

[0056] like Figure 2 As shown, in the cooling mode, the four-way valve 3 must not be electrically closed and the seventeenth valve 27 must be electrically opened. The low-temperature and low-pressure superheated gaseous refrigerant enters from the suction port of the compressor 1, is compressed in two stages, and is discharged from the secondary exhaust port of the compressor 1 to become a high-temperature and high-pressure superheated gaseous refrigerant. Then, it passes through the first valve 2 and the four-way valve 3 and enters the first heat exchanger 4 for condensation and heat dissipation, becoming a medium-temperature and high-pressure liquid refrigerant. Then, the main liquid refrigerant passes through the second valve 5, the drying filter 9, and the sixth valve 10 in sequence to enter the economizer 11 for flashing to increase the supercooling degree of the main refrigerant, thereby improving the refrigeration capacity of the unit.

[0057] A portion of the main refrigerant flashes to form the auxiliary superheated gaseous refrigerant, which is then passed through the top outlet of the economizer 11, the eleventh valve 18, and the middle air supply port of the compressor 1, thereby facilitating motor cooling of the compressor 1 and reducing its exhaust temperature.

[0058] Another part of the main refrigerant is supercooled to become saturated liquid refrigerant and discharged from the bottom of the economizer 11, then flows through the seventh valve 12 & the eighth valve 13 for throttling, and becomes a low-temperature and low-pressure two-phase gas-liquid two-phase refrigerant, and then flows through the fourth valve 7 to enter the second heat exchanger 14 for evaporation and heat absorption, which is used to produce chilled water. The low-temperature and low-pressure gaseous refrigerant evaporates and absorbs heat in the second heat exchanger 14 to become a low-temperature and low-pressure superheated gaseous refrigerant, and then flows through the seventeenth valve 27. Then the main refrigerant returns to the suction port of the compressor 1 through the ninth valve 16, completing a complete refrigeration cycle.

[0059] During the refrigeration cycle, a part of the medium-temperature and high-pressure liquid refrigerant is branched off from the downstream of the drying filter 9 and flows into the motor cavity of the compressor 1 to cool the motor of the compressor 1. Then, under the action of the pressure difference, it is discharged into the gas-liquid separator 15 on the low-pressure side to complete the motor cooling circuit.

[0060] When the refrigeration cycle is started or the unit is predicted to surge, the hot gas bypass pipeline needs to be opened to reduce the pressure ratio of the system. At this time, a part of the high-temperature and high-pressure gaseous refrigerant is drawn out from the pipeline between the first valve 2 and the four-way valve 3. Under the action of the pressure difference, this part of the refrigerant is discharged to the gas-liquid separator 15 on the low-pressure side, and then returns to the suction port of the compressor 1, completing the effect of reducing the pressure ratio and avoiding surge.

[0061] The inverter cooling circuit is as follows: a portion of medium-temperature and high-pressure liquid refrigerant is drawn out from the main lower outlet of the economizer 11 and passes through the second filter 23-the fifteenth valve 24-the sixteenth valve 25 in sequence to the inverter 26 for cooling the heat sink temperature of the inverter 26 to ensure that it is within the normal operating temperature range. Then, under the action of the pressure difference, this portion of the refrigerant returns to the gas-liquid separator 15 on the low-pressure side to complete the cooling of the inverter 26.

[0062] In addition, in the cooling mode, an air suction bypass line is provided to bypass the four-way valve 3 and the gas-liquid separator 15. This reduces the system pressure drop and increases the evaporation temperature of the air suction port of the compressor 1, thereby improving the performance of the unit.

[0063] like Figure 3 As shown, in heating mode, the main circulation refrigerant flows as follows: compressor 1, first valve 2, four-way valve 3, second heat exchanger 14, fifth valve 8, filter drier 9, sixth valve 10, economizer 11, seventh valve 12 & eighth valve 13, third valve 6, first heat exchanger 4, four-way valve 3, gas-liquid separator 15, ninth valve 16, and first stage compression suction port of compressor 1.

[0064] In the heating mode, the four-way valve 3 is powered on and opened to switch the refrigerant flow direction, and the seventeenth valve 27 is powered off and closed. The low-temperature and low-pressure superheated gaseous refrigerant enters from the suction port of the compressor 1, is compressed in two stages, and is discharged from the secondary exhaust port of the compressor 1 to become a high-temperature and high-pressure superheated gaseous refrigerant. It passes through the four-way valve 3 and is diverted to the second heat exchanger 14 to transfer heat to the cooling water for producing hot water. The high-temperature and high-pressure gaseous refrigerant is condensed in the second heat exchanger 14 to become a medium-temperature and high-pressure supercooled liquid refrigerant, and then flows through the fifth valve 8, the drying filter 9, and the sixth valve 10 in sequence to enter the economizer 11.

[0065] A portion of the main refrigerant flashes to form an auxiliary path, and the superheated gaseous refrigerant is discharged from the top outlet of the economizer 11 - the eleventh valve 18 - the intermediate air supply port of the compressor 1, which is convenient for cooling the motor of the compressor 1 and thereby reducing its exhaust temperature; furthermore, the intermediate air supply increases the refrigerant circulation volume of the compressor, thereby increasing the amount of refrigerant entering the second heat exchanger 14, thereby improving the heating capacity of the unit.

[0066] The other part of the main refrigerant is supercooled to become saturated liquid refrigerant and discharged from the bottom of the economizer 11. It then flows through the seventh valve 12 & the eighth valve 13 for throttling and flows through the third valve 6 to enter the first heat exchanger 4 for evaporation and heat absorption, becoming a low-temperature and low-pressure superheated gaseous refrigerant. It then flows through the four-way valve 3 and reverses to flow to the gas-liquid separator 15 for secondary gas-liquid separation. The main refrigerant then returns to the suction port of the compressor 1 through the ninth valve 16, completing a complete heating cycle.

[0067] In heating mode, the flow direction of the auxiliary refrigerant is the same as that in cooling mode, except that the suction bypass line is closed.

[0068] In defrost mode, the system refrigerant flow direction is the same as that of refrigeration, except that the economizer air supply line and suction bypass line are closed.

[0069] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or make equivalent replacements for some or all of the technical features therein. 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 present invention, and they should all be included in the scope of the claims and description of the present invention.

[0070] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A variable frequency centrifugal air-cooled heat pump unit, characterized in that: The unit comprises: A main circulation loop, wherein the main circulation loop is formed by connecting a compressor, a four-way valve, a first heat exchanger, a drying filter, an economizer, a second heat exchanger and a gas-liquid separator through a refrigerant pipeline; Auxiliary pipeline, the auxiliary pipeline is composed of a shutdown bypass pipeline, a hot gas bypass pipeline, a motor cooling pipeline, an economizer air supply pipeline, a frequency converter cooling pipeline, and an air suction bypass pipeline; Among them, the shutdown bypass pipeline is formed by connecting the pipeline arranged between the compressor and the first inlet of the gas-liquid separator; the hot gas bypass pipeline is formed by connecting the pipeline arranged between the compressor and the third inlet of the gas-liquid separator; the motor cooling pipeline is formed by connecting the first filter, the compressor, and the second inlet of the gas-liquid separator, and the first filter is arranged between the drying filter and the economizer; the economizer air supply pipeline is formed by connecting the pipeline arranged between the economizer and the compressor; the inverter cooling pipeline is formed by connecting the economizer, the second filter, the inverter, and the third inlet of the gas-liquid separator in sequence; the intake bypass pipeline is formed by connecting the second heat exchanger, the gas-liquid separator, and the compressor in sequence.

2. The variable frequency centrifugal air-cooled heat pump unit according to claim 1, characterized in that: The secondary compression exhaust port of the compressor is connected to the C port of the four-way valve through the first valve, and the C port of the four-way valve is connected to the heat exchange coils of the first heat exchanger through the manifold, and the heat exchange coils of the first heat exchanger are connected to the distributor; The distributor is connected to the second valve and the third valve respectively. The second valve is connected to the filter drier and the fifth valve respectively. The third valve is connected to the second heat exchanger through the fourth valve and is connected to the outlet of the economizer through the seventh valve and the eighth valve respectively. The other end of the fifth valve is connected to the pipeline between the fourth valve and the second heat exchanger. The filter drier is connected to the economizer through the sixth valve. The economizer is connected to the outlet end of the gas-liquid separator and the first-stage compression suction port of the compressor.

3. The variable frequency centrifugal air-cooled heat pump unit according to claim 2, characterized in that: The secondary compression exhaust port of the compressor is connected to the first inlet of the gas-liquid separator through the tenth valve; The secondary compression exhaust port of the compressor is connected to the third inlet of the gas-liquid separator through the fourteenth valve.

4. The variable frequency centrifugal air-cooled heat pump unit according to claim 2, characterized in that: The first end of the first filter is arranged between the drying filter and the sixth valve, the second end of the second filter is connected to the motor cavity of the compressor through the twelfth valve, and the motor cavity of the compressor is connected to the second inlet of the gas-liquid separator through the thirteenth valve.

5. The variable frequency centrifugal air-cooled heat pump unit according to claim 2, characterized in that: The economizer is connected to the middle air supply port of the compressor through the eleventh valve; The outlet of the economizer is connected to the second filter, the second filter is connected to the frequency converter through the fifteenth valve and the sixteenth valve in sequence, and the frequency converter is connected to the third inlet of the gas-liquid separator.

6. The variable frequency centrifugal air-cooled heat pump unit according to claim 2, characterized in that: The second heat exchanger is connected to the first-stage compression suction port of the compressor through the seventeenth valve and the ninth valve in sequence, and the outlet of the gas-liquid separator is arranged on the pipeline between the seventeenth valve and the ninth valve.

7. A variable frequency centrifugal air-cooled heat pump unit according to claim 2, 3, 4, 5 or 6, characterized in that: The first valve is a check valve, and the ninth valve is a manual butterfly valve; The second valve, the third valve, the fourth valve, the fifth valve and the thirteenth valve are one-way valves; The sixth valve, the seventh valve, the eighth valve, the twelfth valve, and the sixteenth valve are electronic expansion valves; The tenth valve, the eleventh valve, and the fifteenth valve are solenoid valves; The fourteenth valve and the seventeenth valve are electric butterfly valves with proportional opening.

8. The variable frequency centrifugal air-cooled heat pump unit according to claim 2, characterized in that: The seventh valve and the eighth valve constitute a parallel double main valve.

9. The variable frequency centrifugal air-cooled heat pump unit according to claim 1, characterized in that: The compressor is a two-stage compression variable frequency centrifugal compressor with magnetic suspension / gas suspension / liquid suspension and ECO port.

10. The variable frequency centrifugal air-cooled heat pump unit according to claim 1, characterized in that: The first heat exchanger is an air-cooled fin-tube heat exchanger with a multi-V / inverted M-shaped structure; The second heat exchanger is a dry / flooded shell and tube heat exchanger.

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