CN116336586A - Four-pipe air-cooled heat pump unit and control method thereof - Google Patents

Abstract

This application relates to the field of heat pump air conditioners, especially the four-pipe air-cooled heat pump unit and its control method. The four-pipe air-cooled heat pump unit includes a compressor, a four-way valve, a finned coil, a hot water side heat Heat exchanger, three-way valve, first electronic expansion valve, second electronic expansion valve, gas-liquid separator, the finned coil includes the first heat exchange circuit on the air inlet side and the second heat exchange circuit on the air outlet side circuit, the heat exchange area of the second heat exchange circuit is larger than that of the first heat exchange circuit. The four-pipe air-cooled heat pump unit of this application can use different fin coil heat exchange circuits according to the requirements of the environment and working conditions. Refrigerant will be accumulated, so that as much refrigerant as possible can participate in the circulation of the refrigeration system, preventing the evaporation temperature of the unit from dropping significantly due to the reduction of the refrigerant circulation involved in the work.

Description

Four-pipe air-cooled heat pump unit and its control method

technical field

This application relates to the field of heat pump air conditioners, in particular to a four-pipe air-cooled heat pump unit and a control method thereof.

Background technique

At present, there are more and more four-pipe air-cooled heat pump units on the market, but it is common that during winter cooling + hot water mode operation, when the ambient temperature is lower than the compressor suction saturation temperature, the refrigerant will migrate into the finned coil, As a result, the circulating volume of refrigerant involved in the work is reduced, and the evaporation temperature of the unit is significantly lowered, which affects the operating efficiency of the unit, and even affects the reliability of the unit operation in severe cases.

In view of the above problems, the existing technology mostly uses valves to control the migration of refrigerant to the finned coil. The specific solutions are as follows. Solution 1: Install an electric ball valve on the connecting pipe between the four-way valve and the finned coil, cooling + heating In water mode, close the electric ball valve to prevent the refrigerant from migrating from the gas-liquid separator to the finned coil through the four-way valve. Solution 2: Install a one-way valve on the connecting pipe between the four-way valve and the gas-liquid separator. When the pressure in the gas-liquid separator is higher than the pressure in the finned coil, the migration of the refrigerant is blocked. For example, the applicant's previous Application application publication number: CN113446756A. However, the above solution can only block the migration of the refrigerant to the finned coil to a certain extent, and it cannot drive the refrigerant that has accumulated in the finned coil back to the refrigeration system to participate in the cycle. In addition, for the second solution above, in the hot water only mode, the low-pressure return air may cause pressure loss when it passes through the one-way valve, thereby affecting the performance of the compressor.

Contents of the invention

Aiming at the technical problems existing in the prior art, the application proposes a four-pipe air-cooled heat pump unit and a control method thereof. The heat pump unit has high operating efficiency and good reliability.

On the one hand, this application proposes a four-pipe air-cooled heat pump unit, including a compressor 1, a four-way valve 2, a fin coil 3, a hot water side heat exchanger 9, a cold water side heat exchanger 7, a three-way valve 12, The first electronic expansion valve 6, the second electronic expansion valve 13, and the gas-liquid separator 8. The fin coil 3 includes a first heat exchange circuit on the air inlet side and a second heat exchange circuit on the air outlet side. The heat exchange area of the heat exchange circuit is 1.5-5 times that of the first heat exchange circuit; the outlet of the compressor 1 is connected to the interface D of the four-way valve 2, and the interface C of the four-way valve 2 is connected to the hot water side heat exchanger 9 The interface E of the four-way valve 2 is connected to one end of the second heat exchange circuit of the finned coil 3. The gas-liquid separator 8 is provided with two inlets and one outlet, and one of the two inlets is connected to the four-way valve 2 The other inlet is connected to the outlet of the cold water side heat exchanger 7, the outlet of the gas-liquid separator 8 is connected to the inlet of the compressor 1; the hot water side heat exchanger 9 is connected to the interface A of the three-way valve 12, The interface B of the three-way valve 12 is connected to one end of the first heat exchange circuit of the fin coil 3, and the other end of the first heat exchange circuit is connected to the interface C of the three-way valve 12 in parallel, and then respectively connected to the first electronic expansion valve 6 and the second electronic expansion valve 6. The expansion valve 13 is connected; the first electronic expansion valve 6 is connected to the inlet of the cold water side heat exchanger 7, the second electronic expansion valve 13 is connected to the other end of the second heat exchange circuit, and there is a bypass between them and the first electronic expansion valve. The valve 6 is connected; in different operation modes, one of the first heat exchange circuit and the second heat exchange circuit is selected as the outdoor heat exchanger.

In particular, the outlet of the hot water side heat exchanger 9 is provided with a second one-way valve 10 , the outlet of the second one-way valve 10 is connected to the liquid reservoir 11 , and the liquid reservoir 11 is connected to the interface A of the three-way valve 12 .

Specifically, the first heat exchange circuit is connected to the interface C of the three-way valve 12 in parallel and then connected to the dry filter 5 , and the outlet of the dry filter 5 is connected to the first electronic expansion valve 6 and the second electronic expansion valve 13 respectively.

In particular, a one-way valve 4 is provided in the bypass, the outlet of the first heat exchange circuit is connected to the interface C of the three-way valve 12 , and the outlet of the first one-way valve 4 is connected to the inlet of the dry filter 5 .

In particular, the three-way valve 12 is an electric three-way valve.

On the other hand, the present application proposes a control method for the cooling + hot water mode of the four-pipe air-cooled heat pump unit. The four-pipe air-cooled heat pump unit is as described above. The one-way valve 2 is not powered, the three-way valve 12 port A is connected to the port B, the second electronic expansion valve 13 is closed, and the first electronic expansion valve 6 is connected; the compressor 1 discharges high-temperature and high-pressure gas through the four-way valve 2 port D. Interface C enters the heat exchanger 9 on the hot water side, and discharges the heat generated during the condensation process to the hot water to heat it up and then condenses into a high-pressure liquid. The high-pressure liquid refrigerant flows through the fins through the three-way valve 12 The first heat exchange circuit of the coil pipe 3 is throttled and depressurized by the first electronic expansion valve 6 to form a low-temperature and low-pressure gas-liquid two-phase refrigerant, and then enters the cold water side heat exchanger 7, and the refrigerant flows through the cold water side heat exchanger The refrigerated water in 7 absorbs heat and cools it down. After the refrigerant evaporates and exchanges heat, it returns to the suction port of the compressor through the gas-liquid separator 8 for a reciprocating cycle.

In particular, when the load demand on the cold water side is relatively large and the load demand on the hot water side is relatively small, the heat exchange fan of the fin coil 3 can be properly turned on to convect the first heat exchange circuit that flows through the fin coil 3 near the air outlet side. The high-pressure liquid refrigerant is used for heat exchange to increase its subcooling degree, increase the cooling capacity of the unit, balance the cooling and heating loads, and reduce the frequent switching of the unit’s mode.

In the third aspect, this application proposes a control method for the hot water mode of the four-pipe air-cooled heat pump unit. As mentioned above, when the unit operates in the single hot water mode, the four-way valve 2 must not Electricity, the flow direction of the three-way valve 12 is from A to C, the first electronic expansion valve 6 is closed, and the second electronic expansion valve 13 is turned on; the high-temperature and high-pressure gas discharged from the compressor 1 enters the hot water side through the four-way valve 2 The heater 9 discharges the heat to the hot water to heat it up, the refrigerant is condensed into a high-pressure liquid with a certain degree of subcooling, and then flows through the three-way valve 12 to the second electronic expansion valve 13 to be throttled into a low-temperature and low-pressure gas. The liquid two-phase refrigerant flows into the second heat exchange circuit of the finned coil 3, evaporates and exchanges heat into low-pressure gas, passes through the four-way valve 2, flows through the gas-liquid separator 8, and then returns to the suction port of the compressor, and so on. cycle.

In the fourth aspect, this application proposes 9. The control method of the cooling mode of the four-pipe air-cooled heat pump unit. As mentioned above, when the unit operates in the single cooling mode, the four-way valve 2 is powered on. The second electronic expansion valve 13 is closed, the first electronic expansion valve 6 is working, and the flow direction of the three-way valve 12 is not required; the high-temperature and high-pressure gas discharged from the compressor 1 enters the second heat exchange of the finned coil 3 through the four-way valve 2 circuit, after the heat is discharged to the atmosphere, the refrigerant condenses and heat-exchanges into a high-pressure liquid, and then flows through the bypass between the second electronic expansion valve 13 and the second heat exchange circuit to the first electronic expansion valve 6, throttling into low-temperature and low-pressure The gas-liquid two-phase refrigerant flows into the cold water side heat exchanger 7, absorbs heat from the chilled water flowing through the cold water side heat exchanger 7, and cools down the chilled water. The gas-liquid separator 8 returns to the suction port of the compressor for a reciprocating cycle.

Specifically, when the ambient temperature of the unit is lower than -10°C and the set water temperature on the hot water side has reached or there is no demand for hot water on the hot water side, the hot water flow into and out of the heat exchanger 9 on the hot water side is closed, and the four-way valve 2 When the power is off, the flow direction is from D interface to C interface, and the flow direction of three-way valve 12 is switched from A interface to B interface. The exothermic condensation is carried out in the first heat exchange circuit, the pressure in the condenser is increased, and the reliability of the single cooling operation of the unit at ultra-low temperature is guaranteed.

On the basis of conforming to common knowledge in the field, the above-mentioned preferred conditions can be combined arbitrarily to obtain the preferred examples of the present application.

The above technical solution has the following advantages or beneficial effects: the four-pipe air-cooled heat pump unit of the present application can use different finned coil heat exchange circuits according to the requirements of the environment and working conditions. When the ambient temperature is lower than the compressor suction At the saturation temperature, the refrigerant will not accumulate in the finned coil, so that as much refrigerant as possible can participate in the circulation of the refrigeration system, preventing the evaporation temperature of the unit from decreasing significantly due to the reduction of the refrigerant circulation involved in the work.

Description of drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following briefly introduces the drawings that are required in the description of the embodiments or the prior art. Obviously, for those skilled in the art, other drawings can also be obtained according to the provided drawings without creative efforts.

Fig. 1 is a schematic structural diagram of a four-pipe air-cooled heat pump unit according to the present application.

Fig. 2 is a schematic structural view of a finned coil according to the present application.

Among them, 1-compressor; 2-four-way valve; 3-finned coil; 30-first heat exchange tube; 31-aluminum foil; 32-end plate; ; 34- flute-shaped intermediate liquid pipe; 35- flute-shaped liquid outlet pipe; 312- liquid outlet interface; 36- distributor assembly; 322- liquid side interface; 313- capillary fine liquid pipe; Gas collecting pipe; 39-second heat exchange tube; 4-first one-way valve; 5-dry filter; 6-first electronic expansion valve; 7-cold water side heat exchanger; 8-gas-liquid separator; 9- Hot water side heat exchanger; 10-second one-way valve; 11-liquid reservoir; 12-three-way valve; 13-second electronic expansion valve.

Detailed ways

The technical solutions in the embodiments of the present application are clearly and completely described below in conjunction with the accompanying drawings of the present application. Apparently, the described embodiments are only some of the embodiments of the present application, and are intended to explain the inventive concept. Based on the embodiments of the present application, all other embodiments obtained by those skilled in the art without creative efforts fall within the protection scope of the present application.

The terms "first", "second" and the like used in the description are only for the purpose of description, and should not be understood as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, a feature defined as "first" and "second" may explicitly or implicitly include one or more of these features. The term "plurality" means two or more, unless otherwise clearly and specifically defined.

Unless otherwise clearly stipulated and limited, the terms "connected" and "connected" used in the description should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral body; it can be a mechanical connection or an electrical connection; it can be Directly connected, indirectly connected through an intermediary; it can be the internal communication of two elements or the interaction relationship between two elements. Those of ordinary skill in the art can understand the specific meanings of the above terms in the embodiments according to specific situations.

The term "one specific embodiment" used in the description means that a specific feature, structure, material or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the present application. In this specification, the schematic representations of the above terms are not necessarily directed to the same embodiment or example. Furthermore, the described specific features, structures, materials or characteristics may be combined in any suitable manner in any one or more embodiments or examples. In addition, those skilled in the art can combine and combine different embodiments or examples and features of different embodiments or examples described in this specification without conflicting with each other.

Referring to Fig. 1, a specific embodiment of the present application discloses a four-pipe air-cooled heat pump unit, which includes a compressor 1, a four-way valve 2, a fin coil 3, a hot water side heat exchanger 9, The cold water side heat exchanger 7, the three-way valve 12, the first electronic expansion valve 6, the second electronic expansion valve 13, and the gas-liquid separator 8, the three-way valve 12 is preferably an electric three-way valve.

The outlet of the compressor 1 is connected to the interface D of the four-way valve 2, the interface C of the four-way valve 2 is connected to the hot water side heat exchanger 9, and the interface E of the four-way valve 2 is connected to the finned coil 3. The gas-liquid separator 8 is provided with two inlets and one outlet. One of the two inlets of the gas-liquid separator 8 is connected to the interface S of the four-way valve 2, and the other inlet is connected to the outlet of the cold water side heat exchanger 7. The gas-liquid The outlet of the separator 8 is connected with the inlet of the compressor 1 .

Referring to FIG. 2 , a specific embodiment of the present application discloses a finned coil tube of a four-pipe air-cooled heat pump unit. The finned coil tube 3 includes a shell composed of an end plate 32 and an aluminum foil 31 , and one side of the shell is A heat exchange fan is provided, a first heat exchange tube 30 is provided on the air inlet side of the housing, and a second heat exchange tube 39 is provided on the air outlet side of the housing. The flute-shaped liquid inlet pipe 33 is connected in series with several first heat exchange pipes 30, flute-shaped intermediate liquid pipe 34 and flute-shaped liquid outlet pipe 35 to form a first heat exchange circuit, wherein the liquid inlet port 311 of the flute-shaped liquid inlet pipe 33 is connected to the The three-way valve 12 is connected to the interface B, and the outlet interface 312 of the flute-shaped liquid outlet pipe 35 is connected to the interface C of the three-way valve 12 and the outlet of the first one-way valve 4 and then connected to the inlet of the dry filter 5 . The second heat exchange tube 39 is connected to the elbow 37 to form a group, and the distributor assembly 36 forms a second heat exchange circuit in series with a plurality of capillary liquid pipes 313, a group of second heat exchange tubes 39, and an air collecting pipe 38, wherein the air collecting pipe The gas-side port 321 of 38 is connected to the port E of the four-way valve 2, and the liquid-side port 322 of the distributor assembly 36 is respectively connected to the second electronic expansion valve 13 and the inlet of the first one-way valve 4. The first heat exchange circuit is an auxiliary heat exchange area with a small area, and the second heat exchange circuit is a main heat exchange area with a large area. 1.5-5 times, most preferably 2-3 times.

The outlet of the hot water side heat exchanger 9 is provided with a second one-way valve 10, the outlet of the second one-way valve 10 is connected to the liquid reservoir 11, the liquid reservoir 11 is connected to the interface A of the three-way valve 12, and the three-way valve 12 The interface B is connected to one end of the first heat exchange circuit of the finned coil tube 3, and the other end of the first heat exchange circuit is connected to the interface C of the three-way valve 12, the outlet of the first one-way valve 4 and then connected to the dry filter 5 imports.

When the unit operates in the cooling+hot water mode, the four-way valve 2 is not powered, the three-way valve 12 is connected to the port A and the port B, the second electronic expansion valve 13 is closed, and the first electronic expansion valve 6 is connected.

When the unit operates in cooling + hot water mode, the refrigerant process and its heat transfer are as follows: the high-temperature and high-pressure gas discharged from the compressor 1 enters the hot water side heat exchanger 9 through the four-way valve 2 interface D and interface C, and the A large amount of heat generated during the condensation process is discharged to the hot water to heat it up and then condensed into a high-pressure liquid. The high-pressure liquid refrigerant flows into the accumulator 11 through the second one-way valve 10, and the high-pressure liquid refrigerant flows through the three-way valve 12 through the first heat exchange circuit of the fin coil 3, the drier filter 5 to the first electronic Expansion valve 6, throttling and decompressing into low-temperature and low-pressure gas-liquid two-phase refrigerant enters the cold water side heat exchanger 7, the refrigerant absorbs heat from the chilled water flowing through the cold water side heat exchanger 7 and cools it down, and the refrigerant evaporates The heat is exchanged into a low-pressure superheated gas, and then returned to the suction port of the compressor through the gas-liquid separator 8, and the cycle is repeated.

When the ambient temperature is lower than the compressor suction saturation temperature, the high-pressure liquid refrigerant flows through the finned coil 3 and heats it, which not only prevents the refrigerant in the system from migrating to the finned coil 3 through the gas-liquid separator 8 Inside, the refrigerant accumulated in the second heat exchange tube of the fin coil 3 can also be heated to migrate to the relatively low-pressure gas-liquid separator 8, so that these refrigerants can participate in the refrigeration cycle. Further, when the load demand on the cold water side is relatively large and the load demand on the hot water side is relatively small, the heat exchange fan of the fin coil 3 can be properly turned on to cool the high-pressure liquid that flows through the first heat exchange circuit of the fin coil 3 . Heat exchange with the agent to increase its subcooling degree, increase the cooling capacity of the unit, balance the cooling and heating loads, and reduce the frequent switching of the unit’s mode.

When the unit operates in the single hot water mode, the four-way valve 2 is not powered, the flow direction of the three-way valve 12 is from A to C, the first electronic expansion valve 6 is closed, and the second electronic expansion valve 13 is on.

When the unit operates in single hot water mode, the refrigerant process and its heat transfer are as follows: the high-temperature and high-pressure gas discharged from the compressor 1 enters the hot water side heat exchanger 9 through the four-way valve 2 and discharges a large amount of heat to the hot water Heating it, the refrigerant is condensed into a high-pressure liquid with a certain degree of supercooling, and then flows into the liquid storage tank 11 through the second one-way valve 10, and then flows through the dry filter 5 through the three-way valve 12 to the second electronic expander. Valve 13, throttling into a low-temperature and low-pressure gas-liquid two-phase refrigerant, flows into the second heat exchange circuit of the fin coil 3 to evaporate and exchange heat into a low-pressure gas, and then flows through the gas-liquid separator 8 through the four-way valve 2 and returns to Compressor suction port, so reciprocating cycle.

When the temperature is low in winter, when switching from hot water only mode to cooling + hot water mode, if there is slight frost on the finned coil, the high-pressure liquid refrigerant flowing through the first heat exchange circuit of the finned coil 3 can The surface of the finned coil is heated and melts the frost layer, reducing the frequency of defrosting in the single hot water mode and improving the efficiency of heating operation.

When the unit operates in the cooling-only mode, the four-way valve 2 is energized, the second electronic expansion valve 13 is closed, the first electronic expansion valve 6 is working, and the flow direction of the three-way valve 12 is not required.

When the unit operates in single cooling mode, the refrigerant process and its heat transfer are as follows: the compressor 1 discharges high-temperature and high-pressure gas through the four-way valve 2 and enters the finned coil 3, and after the heat is discharged to the atmosphere, the refrigerant condenses The heat is converted into a high-pressure liquid, and then flows through the first one-way valve 4 to the dry filter 5, and then to the first electronic expansion valve 6, throttling into a low-temperature and low-pressure gas-liquid two-phase refrigerant, and then flows into the cold water side heat exchanger 7, And absorb heat from the chilled water flowing through the cold water side heat exchanger 7, and after cooling the chilled water, the refrigerant evaporates and exchanges heat into a low-pressure superheated gas, and then returns to the suction port of the compressor through the gas-liquid separator 8, and reciprocates .

Furthermore, when the ambient temperature of the unit is lower than -10°C or even lower in winter, and the set water temperature on the hot water side has reached or there is no demand for hot water on the hot water side, at this time in the single cooling mode due to The heat transfer of the finned coil is too good to maintain enough condensing pressure. When the machine may have a low pressure alarm and shut down, the following operations can be done: close the flow of hot water entering and leaving the heat exchanger 9 on the hot water side, and the four-way valve 2 will flow to D when it is powered off. Switch from the interface to the E interface to the D interface to the C interface, and the flow direction of the three-way valve 12 is switched from the A interface to the B interface. At this time, the high-temperature and high-pressure gaseous refrigerant discharged from the compressor 1 is exothermic and condensed only in the first heat exchange circuit with a small heat exchange area of the finned coil 3, and the pressure in the condenser is increased. Operational reliability is guaranteed.

Although the embodiments of the present application have been shown and described above, it should be understood that the above embodiments are exemplary and should not be construed as limitations on the present application. On the premise of not departing from the spirit and scope of the present application, there will be various changes and improvements in this application, and these changes and improvements all fall within the scope of the claimed application.

Claims (10)

1. Four-pipe air-cooled heat pump unit, including compressor (1), cross valve (2), fin coil (3), hot water side heat exchanger (9), cold water side heat exchanger (7), three-way valve (12), first electronic expansion valve (6), second electronic expansion valve (13), gas-liquid separator (8), its characterized in that: the fin coil (3) comprises a first heat exchange loop at the air inlet side and a second heat exchange loop at the air outlet side, and the heat exchange area of the second heat exchange loop is 1.5-5 times that of the first heat exchange loop; the outlet of the compressor (1) is connected with the interface D of the four-way valve (2), the interface C of the four-way valve (2) is connected with the hot water side heat exchanger (9), the interface E of the four-way valve (2) is connected with one end of the second heat exchange loop of the fin coil pipe (3), the gas-liquid separator (8) is provided with two inlets and one outlet, one of the two inlets is connected with the interface S of the four-way valve (2), the other inlet is connected with the outlet of the cold water side heat exchanger (7), and the outlet of the gas-liquid separator (8) is connected with the inlet of the compressor (1); the hot water side heat exchanger (9) is connected with a port A of the three-way valve (12), a port B of the three-way valve (12) is connected with one end of a first heat exchange loop of the fin coil pipe (3), and the other end of the first heat exchange loop is connected with a port C of the three-way valve (12) in parallel and then is respectively connected with the first electronic expansion valve (6) and the second electronic expansion valve (13); the first electronic expansion valve (6) is connected with the inlet of the cold water side heat exchanger (7), the second electronic expansion valve (13) is connected with the other end of the second heat exchange loop, and a bypass is arranged between the second electronic expansion valve and is connected with the first electronic expansion valve (6); and in different operation modes, the first heat exchange loop and the second heat exchange loop are selected as the outdoor heat exchanger.

2. The four-pipe air-cooled heat pump unit according to claim 1, wherein: the outlet of the hot water side heat exchanger (9) is provided with a second one-way valve (10), the outlet of the second one-way valve (10) is connected with a liquid reservoir (11), and the liquid reservoir (11) is connected with a three-way valve (12) interface A.

3. The four-pipe air-cooled heat pump unit according to claim 1, wherein: the first heat exchange loop is connected with the interface C of the three-way valve (12) in parallel and then is connected with the dry filter (5), and the outlet of the dry filter (5) is respectively connected with the first electronic expansion valve (6) and the second electronic expansion valve (13).

4. A four-pipe air-cooled heat pump assembly according to claim 3, wherein: the bypass is internally provided with a first one-way valve (4), and an outlet of the first heat exchange loop is connected with an interface C of the three-way valve (12) and an outlet of the first one-way valve (4) in parallel and then is connected to an inlet of the dry filter (5).

5. A four-pipe air-cooled heat pump assembly according to claim 3, wherein: the three-way valve (12) is an electric three-way valve.

6. The control method of the four-pipe air-cooled heat pump unit in the cooling and hot water modes is characterized in that: when the heat pump unit operates in a refrigerating and hot water mode, the four-way valve (2) is not electrified, the interface A and the interface B of the three-way valve (12) are communicated, the second electronic expansion valve (13) is closed, and the first electronic expansion valve (6) is communicated; the high-temperature high-pressure gas discharged by the compressor (1) enters the hot water side heat exchanger (9) through the interface D and the interface C of the four-way valve (2), heat generated in the condensation process is discharged to hot water to heat the hot water, the hot water is condensed into high-pressure liquid, the high-pressure liquid refrigerant flows through a first heat exchange loop of the fin coil (3) through the three-way valve (12) after flowing through the fin coil, the high-pressure liquid refrigerant is throttled and depressurized into low-temperature low-pressure gas-liquid two-phase refrigerant by the first electronic expansion valve (6) and then enters the cold water side heat exchanger (7), the refrigerant absorbs heat from chilled water flowing through the cold water side heat exchanger (7) and cools the chilled water, and the refrigerant returns to the air inlet of the compressor through the gas-liquid separator (8) after evaporating and exchanging heat and circulates reciprocally.

7. The control method of the four-pipe air-cooled heat pump unit in the cooling and hot water mode as set forth in claim 6, wherein: when the load demand on the cold water side is larger and the load demand on the hot water side is relatively smaller, the heat exchange air quantity of the fin coil (3) is increased, and the high-pressure liquid refrigerant flowing through the first heat exchange loop on the air outlet side of the fin coil (3) exchanges heat so as to improve the supercooling degree of the high-pressure liquid refrigerant.

8. The control method of the hot water mode of the four-pipe air-cooled heat pump unit, wherein the four-pipe air-cooled heat pump unit is as set forth in claim 1, and is characterized in that: when the unit operates in a single hot water mode, the four-way valve (2) is not electrified, the flowing direction of the three-way valve (12) is A to C, the first electronic expansion valve (6) is closed, and the second electronic expansion valve (13) is conducted; the high-temperature high-pressure gas discharged by the compressor (1) enters the hot water side heat exchanger (9) through the four-way valve (2) to discharge heat to the hot water for heating, the refrigerant is condensed into high-pressure liquid with a certain supercooling degree, then flows to the second electronic expansion valve (13) through the three-way valve (12) to be throttled into low-temperature low-pressure gas-liquid two-phase refrigerant, then flows into the second heat exchange loop of the fin coil pipe (3), is evaporated and heat-exchanged into low-pressure gas, and then flows through the gas-liquid separator (8) through the four-way valve (2) to return to the air inlet of the compressor, and thus the reciprocating circulation is realized.

9. The control method of the refrigerating mode of the four-pipe air-cooled heat pump unit, wherein the four-pipe air-cooled heat pump unit is as set forth in claim 1, and is characterized in that: when the unit operates in a single refrigeration mode, the four-way valve (2) is powered on, the second electronic expansion valve (13) is closed, and the first electronic expansion valve (6) works; the high-temperature high-pressure gas discharged by the compressor (1) enters a second heat exchange loop of the fin coil (3) through the four-way valve (2), heat is discharged to the atmosphere, the refrigerant is condensed and exchanges heat to form high-pressure liquid, then the high-pressure liquid flows through a bypass between the second electronic expansion valve (13) and the second heat exchange loop to the first electronic expansion valve (6), is throttled to form low-temperature low-pressure gas-liquid two-phase refrigerant, then flows into the cold water side heat exchanger (7), absorbs heat from chilled water flowing through the cold water side heat exchanger (7), cools the chilled water, and then the refrigerant is evaporated and exchanges heat to form low-pressure superheated gas, and then returns to the air suction port of the compressor through the gas-liquid separator (8) to reciprocate.

10. The control method for the cooling mode of the four-pipe air-cooled heat pump unit according to claim 9, wherein: when the ambient temperature of the unit is lower than-10 ℃ and the set water temperature of the hot water side reaches or the hot water side has no hot water demand, the hot water flow entering and exiting the hot water side heat exchanger (9) is closed, the four-way valve (2) loses electricity, namely the flow direction is from the D interface to the C interface, the flow direction of the three-way valve (12) is switched to from the A interface to the B interface, and the high-temperature high-pressure gaseous refrigerant discharged by the compressor (1) is only subjected to heat release condensation in the first heat exchange loop with smaller heat exchange area of the fin coil (3).

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