CN107906777A - Heat pump unit - Google Patents

Abstract

The invention belongs to the technical field of air conditioning, and in particular relates to a heat pump unit. The invention aims to solve the problem that when a large amount of liquid heat exchange medium pours into the gas-liquid separator when the existing heat pump unit is switched from the defrosting mode to the heating mode, it is easy to cause the compressor to absorb liquid. For this reason, the heat pump unit of the present invention includes a main circulation loop and a defrosting liquid return pipeline communicated with the main circulation loop; a compressor, a first heat exchanger and a second heat exchanger communicated with each other are arranged on the main circulation loop , in the defrosting mode, the first heat exchanger is used as a condenser, and the second heat exchanger is used as an evaporator; the defrosting return line is used to exchange heat from the liquid in the first heat exchanger after defrosting The medium is directly diverted to the second heat exchanger, which effectively prevents a large amount of liquid heat exchange medium from flowing into the gas-liquid separator from the first heat exchanger after defrosting, which will cause it to overload and cause partial liquid exchange. The heat medium directly enters the compressor, causing the compressor to be damaged due to the suction of liquid.

Description

Heat pump unit

technical field

The invention belongs to the technical field of air conditioning, and in particular relates to a heat pump unit.

Background technique

With the continuous improvement of people's living standards, people have also put forward higher and higher requirements for the living environment. In order to maintain a comfortable ambient temperature, air conditioners have become an essential device in people's lives. Specifically, most of the existing air conditioners use heat pump units. When the external ambient temperature of the heat pump unit is very low, the evaporator of the heat pump unit is prone to frosting. At this time, the heat pump unit needs to defrost the evaporator. To deal with it, the technicians put forward many solutions for the defrosting of the heat pump unit.

Specifically, most existing heat pump units use the reverse cycle process of the heating mode to defrost the evaporator; although this defrosting mode can save production costs on the basis of effective defrosting; however, when the heat pump unit needs to defrost from When the mode is switched to the heating mode, the control device controls the direction of the four-way valve, and a large amount of liquid heat exchange medium suddenly flows backwards. At this time, a large amount of liquid heat exchange medium will pour into the gas-liquid separator. When the volume of the gas-liquid separator exceeds the rated workload of the gas-liquid separator, the liquid heat exchange medium is easy to directly enter the compressor, causing the danger of the compressor being sucked with liquid, which greatly shortens the life of the compressor. Affect the reliability of the heat pump unit.

Correspondingly, the field needs a new heat pump unit to solve the above problems.

Contents of the invention

In order to solve the above-mentioned problems in the prior art, that is, in order to solve the problem that when the existing heat pump unit switches from the defrosting mode to the heating mode, a large amount of liquid heat exchange medium pours into the gas-liquid separator, which can easily cause the compressor to suck liquid Problem, the present invention provides a heat pump unit, the heat pump unit includes a main circulation loop and a defrost return pipeline connected with the main circulation loop; wherein, the main circulation loop is provided with compressors communicating with each other Machine, the first heat exchanger and the second heat exchanger, in the defrosting mode, the first heat exchanger is used as a condenser, and the second heat exchanger is used as an evaporator; the defrosting liquid return line After defrosting, the liquid heat exchange medium in the first heat exchanger is directly guided into the second heat exchanger.

In the preferred technical solution of the above heat pump unit, a switching valve is arranged on the defrosting liquid return line, and the defrosting liquid return line is switched on and off through the switching valve.

In a preferred technical solution of the above heat pump unit, the on-off valve is a solenoid valve.

In a preferred technical solution of the above heat pump unit, the main circulation loop includes a first main circulation branch and a second main circulation arranged in parallel between the first heat exchanger and the second heat exchanger branch, the defrosting liquid return line communicates with the second main circulation branch.

In the preferred technical solution of the above-mentioned heat pump unit, the main circulation loop further includes a bridge branch arranged between the first main circulation branch and the second main circulation branch, and the bridge branch is set With expansion valve.

In the preferred technical solution of the above-mentioned heat pump unit, the bridging branch divides the first main circulation branch and the second main circulation branch into a first part and a second part respectively, and the defrosting liquid return pipe The road is connected in parallel with the second part of the second main circulation branch; wherein, the first part of the first main circulation branch is provided with a first check valve, and the second part of the first main circulation branch is provided with There is a second one-way valve, the first part of the second main circulation branch is provided with a third one-way valve, and the second part of the second main circulation branch is provided with a fourth one-way valve; the first The one-way valve only allows the heat exchange medium to flow into the first heat exchanger, the second one-way valve only allows the heat exchange medium to flow into the second heat exchanger, and the third one-way valve only allows the heat exchange medium to out of the first heat exchanger, the fourth one-way valve only allows the heat exchange medium to flow out of the second heat exchanger.

In a preferred technical solution of the above heat pump unit, the first heat exchanger is a finned heat exchanger.

In a preferred technical solution of the above heat pump unit, the second heat exchanger is a falling film heat exchanger.

In the preferred technical solution of the above-mentioned heat pump unit, the falling film heat exchanger includes a spray element and a heat exchange element; during the defrosting process, the spray element directly sprays the liquid heat exchange medium to the on the heating element to shorten the defrost time.

In a preferred technical solution of the above heat pump unit, the compressor is a two-stage screw compressor.

Those skilled in the art can understand that, in the preferred technical solution of the present invention, the heat pump unit of the present invention includes a main circulation loop and a defrosting liquid return pipeline connected with the main circulation loop; wherein, the main circulation loop is provided with The compressor, the first heat exchanger and the second heat exchanger communicate with each other. In the defrosting mode, the first heat exchanger is used as a condenser, and the second heat exchanger is used as an evaporator; the defrosting return line is used for After defrosting, the liquid heat exchange medium in the first heat exchanger is directly guided into the second heat exchanger, thereby effectively preventing a large amount of liquid heat exchange medium from flowing into the first heat exchanger after defrosting. In the gas-liquid separator, the gas-liquid separator is overloaded, which in turn causes a part of the liquid heat exchange medium to directly enter the compressor, causing the compressor to be damaged due to the suction of liquid.

Description of drawings

Fig. 1 is a simplified schematic diagram of the heat pump unit of the present invention;

Fig. 2 is an overall schematic diagram of a preferred embodiment of the heat pump unit of the present invention.

Explanation of reference signs: 1. Compressor; 2. Oil separator; 3. Pressure maintaining valve; 4. Four-way valve; 5. Falling film heat exchanger; 61. First one-way valve; 62. Second one-way valve 63. The third one-way valve; 64. The fourth one-way valve; 7. Filter; 8. Economizer; 9. Expansion valve; 10. Finned heat exchanger; 11. Gas-liquid separator; 12. Solenoid valve; 13. Fan; 14. Oil cooler; 15. Flow meter; 16. Economizer expansion valve; 17. Oil cooling expansion valve; 18. Bypass solenoid valve; 19. Oil supply solenoid valve; 101. The first main circulation branch; 102, the second main circulation branch.

Detailed ways

Preferred embodiments of the present invention are described below with reference to the accompanying drawings. Those skilled in the art should understand that these embodiments are only used to explain the technical principles of the present invention, and are not intended to limit the protection scope of the present invention. Those skilled in the art can make adjustments as needed so as to adapt to specific applications. At the same time, although the various steps of the method of the present invention are described in a specific order in the application, these orders are not limiting, and those skilled in the art can perform the steps in different orders without departing from the basic principles of the present invention. Follow the steps described.

It should be noted that, in the description of the present invention, terms such as "upper", "lower", "left", "right" and other indicated directions or positional relationships are based on the directions or positional relationships shown in the drawings, This is for ease of description only, and does not indicate or imply that the device or element must have a particular orientation or must be constructed and operated in a particular orientation, and thus should not be construed as limiting the invention. In addition, the terms "first", "second", "third", and "fourth" are used for descriptive purposes only, and should not be construed as indicating or implying relative importance.

Most of the existing heat pump units proposed in the background technology use the reverse cycle process of the heating mode to defrost the evaporator; although this defrosting method can save production costs on the basis of effective defrosting; however, when the heat pump When the unit needs to switch from the defrosting mode to the heating mode, the control device of the heat pump unit controls the direction of the four-way valve. When the amount of the gas-liquid separator exceeds the rated workload of the gas-liquid separator, the liquid heat exchange medium is easy to directly enter the compressor, which brings the risk of suction and liquid to the compressor. Therefore, the present invention provides a new heat pump unit to solve the above-mentioned problems in the prior art.

Referring first to FIG. 1 , this figure is a simplified schematic diagram of the heat pump unit of the present invention. As shown in Figure 1, the heat pump unit of the present invention includes a main circulation loop and a defrosting liquid return pipeline connected with the main circulation loop; wherein, the main circulation loop is provided with a compressor 1, a fin The fin heat exchanger 10 and the falling film heat exchanger 5, in the defrosting mode, the fin heat exchanger 10 is used as a condenser, and the falling film heat exchanger 5 is used as an evaporator; the defrosting return The liquid pipeline is used to direct the liquid heat exchange medium in the finned heat exchanger 10 to the falling film heat exchanger 5 after defrosting, so as to effectively prevent a large amount of liquid heat exchange medium after defrosting Flowing from the finned heat exchanger 10 into the gas-liquid separator 11 will cause the gas-liquid separator 11 to work overloaded, and then cause part of the liquid heat exchange medium to directly enter the compressor 1, causing the compressor 1 to take suction. liquid will be damaged.

Those skilled in the art can understand that although in this preferred embodiment, the first heat exchanger is a finned heat exchanger 10, and the second heat exchanger is a falling film heat exchanger 5; However, the first heat exchanger and the second heat exchanger can obviously also be other types of heat exchangers, and the change of this type of heat exchanger does not deviate from the basic principle of the present invention, so it will all fall into the within the protection scope of the present invention.

Further, as shown in FIG. 1 , the main circulation loop includes a first main circulation branch 101 and a second main circulation branch arranged in parallel between the finned heat exchanger 10 and the falling film heat exchanger 5 Branches 102; wherein, the first main circulation branch 101 is located in the upper dotted line box, the second main circulation branch 102 is located in the lower dotted line box, and the defrosting liquid return pipeline communicates with the second main circulation branch 102 A solenoid valve 12 is arranged on the defrosting liquid return line, and the defrosting liquid return line is switched on and off through the solenoid valve 12 . It should be noted that although the on-off valve set on the defrosting liquid return pipeline described in this preferred embodiment is a solenoid valve 12, the on-off valve can obviously also be other valves that can control the on-off of the pipeline. Electrical components, as long as the on-off valve can control the on-off of the defrosting liquid return pipeline. At the same time, the main circulation circuit also includes a bridging branch arranged between the first main circulation branch 101 and the second main circulation branch 102, and an expansion valve 9 is arranged in the bridging branch, and the expansion valve 9 can control On-off between the first main circulation branch 101 and the second main circulation branch 102 .

Continuing to refer to FIG. 1, the bridging branch divides the first main circulation branch 101 and the second main circulation branch 102 into a first part and a second part respectively, wherein the defrosting liquid return line is connected to the second main circulation branch The second part of the circulation branch 102 is connected in parallel, and at the same time, the defrosting liquid return line can also communicate with the third one-way valve 63 . Specifically, the first part of the first main circulation branch 101 is provided with the first one-way valve 61, the second part of the first main circulation branch 101 is provided with the second one-way valve 62, and the second main circulation branch 102 The first part is provided with a third one-way valve 63 , and the second part of the second main circulation branch 102 is provided with a fourth one-way valve 64 . It should be noted that the first one-way valve 61 only allows the heat exchange medium to flow into the finned heat exchanger 10, the second one-way valve 62 only allows the heat exchange medium to flow into the falling film heat exchanger 5, and the third one-way valve 63 only allows the heat exchange medium to flow out of the finned heat exchanger 10 , and the fourth one-way valve 64 only allows the heat exchange medium to flow out of the falling film heat exchanger 5 .

Below in conjunction with Fig. 1, the operation process of the heating mode and the defrosting mode of the heat pump unit of the present invention will be specifically described; when the heat pump unit operates in the heating mode, the circulation process of the heat exchange medium in the heat pump unit is: compression Machine 1→oil separator 2→pressure maintenance valve 3→four-way valve 4→falling film heat exchanger 5→fourth one-way valve 64→expansion valve 9→first one-way valve 61→finned heat exchanger 10→four-way valve 4→gas-liquid separator 11→compressor 1. When the heat pump unit operates in defrosting mode, the finned heat exchanger 10 is used as a condenser, and the falling film heat exchanger 5 is used as an evaporator. At this time, the circulation process of the heat exchange medium in the heat pump unit It is: compressor 1→oil separator 2→pressure maintenance valve 3→four-way valve 4→finned heat exchanger 10→third check valve 63→expansion valve 9→second check valve 62→falling film type Heat exchanger 5→four-way valve 4→gas-liquid separator 11→compressor 1.

Specifically, when the heat pump unit is in the defrosting mode, the finned heat exchanger 10 is in a high pressure state, and the falling film heat exchanger 5 is in a low pressure state; at this time, the heat exchange in the finned heat exchanger 10 The heat released by the liquefaction of the medium during the defrosting process is used to defrost the finned heat exchanger 10 by using the heat released by the liquefaction of the heat exchange medium. It should be noted that after the defrosting of the existing heat pump unit, the four-way valve 4 is directly reversed, so that the heat pump unit starts to operate in the heating mode. After the four-way valve 4 is reversed, the finned heat exchanger The liquid heat exchange medium in 10 floods into the gas-liquid separator 11 through the four-way valve 4 in large quantities, thus causing the gas-liquid separator 11 to work overloaded, and then it is easy to cause part of the liquid heat exchange medium to directly enter the compressor 1, Cause the compressor 1 to suck liquid and be damaged.

Further, in the heat pump unit of the present invention, after the defrosting is completed, the electromagnetic valve 12 is opened before the four-way valve 4 changes direction; at this time, since the finned heat exchanger 10 is in a high pressure state, the falling film heat exchanger 5 is in a low-pressure state, and under pressure, the heat exchange medium in the fin heat exchanger 10 flows directly into the falling film heat exchanger 5 along the direction of the arrow in Figure 1, and after a predetermined time, the heat pump unit The solenoid valve 12 is controlled to close, and at the same time, the four-way valve 4 is reversed, and the heat pump unit resumes the heating mode. At this time, a large amount of liquid heat exchange medium in the finned heat exchanger 10 has flowed back into the falling film heat exchanger 5, only a small part or no liquid heat exchange medium will flow into the gas-liquid separator 11, and at the same time , the amount of this part of the liquid heat exchange medium can never exceed the rated load of the gas-liquid separator 11; therefore, under the protection of the gas-liquid separator 11, no liquid heat exchange medium will enter the compressor 1 , so that the risk of the compressor 1 being sucked with liquid is greatly reduced, thereby greatly reducing the damage rate of the compressor 1 , thereby effectively prolonging the service life of the compressor 1 .

Those skilled in the art can understand that the present invention does not impose any restrictions on the method of judging whether the defrosting is over, because the method of judging whether the defrosting is over is not within the protection scope of the present invention, therefore, technicians can make their own decisions according to the needs of actual products. The method of judging the end of defrosting in the prior art is selected, and the change of this judging method does not deviate from the basic principle of the present invention, so all will fall within the protection scope of the present invention. In addition, technicians can also set the length of the predetermined time according to the actual situation of the product and user needs and other conditions. As long as the predetermined time passes, it will flow into the gas-liquid separator 11 It is sufficient that the liquid heat exchange medium does not exceed the rated workload of the gas-liquid separator 11.

Referring to Fig. 2 below, this figure is an overall schematic diagram of a preferred embodiment of the heat pump unit of the present invention. It should be noted that the embodiment shown in Fig. 2 is only a preferred embodiment of the present invention, and is not regarded as a protection scope of the present invention. limits. As shown in Figure 2, when the heat pump unit in this preferred embodiment operates in heating mode, the circulation process of the heat exchange medium in the heat pump unit is: compressor 1 → oil separator 2 → pressure maintenance valve 3 → four-way Valve 4→falling film heat exchanger 5→fourth one-way valve 64→filter 7→economizer 8→expansion valve 9→first one-way valve 61→finned heat exchanger 10→four-way valve 4→ Gas-liquid separator 11→compressor 1. When the heat pump unit operates in heating mode, the finned heat exchanger 10 is used as an evaporator, the liquid heat exchange medium in the finned heat exchanger 10 evaporates and absorbs heat, and the falling film heat exchanger 5 is used as a condensation At the same time, the gaseous heat exchange medium in the falling film heat exchanger 5 liquefies and releases heat to heat the water. In addition, the heat exchange medium in the auxiliary path branched out from the outlet of the economizer 8 is throttled by the economizer expansion valve 16 and then returns to the economizer 8, and fully exchanges heat with the heat exchange medium in the main path. The heat exchange medium in the main path is supercooled, and at the same time, the overheated heat exchange medium in the auxiliary path is mixed with the heat exchange medium after the first stage of compression through the intermediate air supply port of compressor 1, and then the second stage of compression is performed, thereby The temperature of the heat exchange medium entering the second-stage compression is effectively reduced, and at the same time, the suction volume of the second-stage compression can be effectively increased, thereby greatly increasing the heating capacity of the heat pump unit.

Continuing to refer to Fig. 2, the heat pump unit is also provided with an oil return system and an oil cooling system; specifically, the operation process of the oil return system of the heat pump unit is: the lubricating oil separated from the oil separator 2 flows through After the filter 7, the bypass solenoid valve 18, the flow meter 15 and the oil supply solenoid valve 19, it returns to the oil supply port of the compressor 1. In addition, when the discharge temperature of the compressor 1 exceeds a predetermined temperature, the operation process of the oil cooling system of the heat pump unit is: close the bypass solenoid valve 18, and at the same time, open the oil cooling expansion valve 17; at this time, the lubricating oil can The temperature is fully cooled through the oil cooler 14, and then flows through the flow meter 15 and the oil supply solenoid valve 19 in sequence, and then returns to the oil supply port of the compressor 1; in addition, the lubricating oil in the oil cooling auxiliary circuit passes through the oil cooling expansion valve 17 After throttling, it flows into the oil cooler 14 and fully exchanges heat with the lubricating oil in the main circuit, thereby effectively reducing the temperature of the lubricating oil, so that the heat pump unit can always run smoothly.

Further, when the heat pump unit in this preferred embodiment operates in the defrosting mode, the circulation process of the heat exchange medium in the heat pump unit is: compressor 1 → oil separator 2 → pressure maintenance valve 3 → four-way valve 4 → Finned heat exchanger 10→third one-way valve 63→filter 7→economizer 8→expansion valve 9→second one-way valve 62→falling film heat exchanger 5→four-way valve 4→gas-liquid separation Device 11→Compressor 1. When the heat pump unit operates in the defrosting mode, the falling film heat exchanger 5 is used as an evaporator, and the liquid heat exchange medium in the falling film heat exchanger 5 evaporates and absorbs heat, and at the same time, the finned heat exchanger 10 It is used as a condenser, and the gaseous heat exchange medium in the finned heat exchanger 10 is liquefied to release heat, so that the finned heat exchanger 10 can be effectively defrosted. At this time, the heat exchange medium in the finned heat exchanger 10 liquefies and releases heat during the defrosting process, so that the finned heat exchanger 10 can be defrosted using the heat released when the heat exchange medium is liquefied.

In the heat pump unit of the present invention, after the defrosting is completed, the electromagnetic valve 12 is opened before the four-way valve 4 changes direction. At this time, since the fin heat exchanger 10 is in a high pressure state, the falling film heat exchanger 5 is in a low pressure state. state, under pressure, the heat exchange medium in the finned heat exchanger 10 flows directly into the falling film heat exchanger 5 along the direction of the arrow in Figure 2, and after a predetermined time, the heat pump unit controls the solenoid valve 12 is closed, and at the same time, the four-way valve 4 is reversed, and the heat pump unit resumes the heating mode. At this time, a large amount of liquid heat exchange medium in the finned heat exchanger 10 has flowed back into the falling film heat exchanger 5, only a small part or no liquid heat exchange medium will flow into the gas-liquid separator 11, and The amount of this part of the liquid heat exchange medium can never exceed the rated load of the gas-liquid separator 11; therefore, under the protection of the gas-liquid separator 11, no liquid heat exchange medium will enter the compressor 1, The risk of the compressor 1 being sucked with liquid is greatly reduced, thereby greatly reducing the damage rate of the compressor 1 , thereby effectively prolonging the service life of the compressor 1 .

Those skilled in the art can understand that, in the embodiment of the present invention, the compressor 1 is preferably a two-stage screw compressor, because the use of the two-stage screw compressor and the gas supplement enthalpy increase technology can effectively reduce the compressor 1. exhaust temperature; at the same time, the oil cooler 14 can effectively stabilize the oil supply temperature of the heat pump unit, so that the oil supply temperature and exhaust temperature of the heat pump unit can also be maintained under the condition that the heat pump unit has a high outlet water temperature Maintain a stable state, so that the heat pump unit can also maintain a stable operation at all times, so that the heat pump unit of the present invention can also maintain a stable operation state when the external environment temperature is low, and can also ensure that the heat pump unit can Always deliver hot water at a predetermined temperature.

Further, the falling film heat exchanger 5 includes a spray element and a heat exchange element, and during the defrosting process of the heat pump unit, the spray element can directly spray the heat exchange medium onto the heat exchange element , so that the falling film heat exchanger 5 can quickly enter the heat absorption state, and at the same time, enable the finned heat exchanger 10 to quickly enter the heat release state, thereby effectively shortening the defrosting time of the heat pump unit. In addition, this spray heat exchange method can also effectively reduce the amount of heat exchange medium required for defrosting, so that the amount of heat exchange medium required by the heat pump unit in the heating mode can be compared with that in the defrosting mode. The amount of heat exchange medium required is equal, so that the heat pump unit of the present invention can cancel the arrangement of the liquid reservoir, thereby effectively simplifying the structure of the heat pump unit.

Finally, it should be noted that the above examples are all preferred implementations of the present invention, and are not intended to limit the protection scope of the present invention. When actually using the present invention, those skilled in the art may appropriately add or delete some steps as required, or exchange the order of different steps. This change does not go beyond the basic principles of the present invention and belongs to the protection scope of the present invention.

So far, the preferred embodiments of the present invention have been described with reference to the accompanying drawings, but those skilled in the art will easily understand that the protection scope of the present invention is obviously not limited to these specific embodiments. Without departing from the principles of the present invention, those skilled in the art can make equivalent changes or substitutions to relevant technical features, and the technical solutions after these changes or substitutions will all fall within the protection scope of the present invention.

Claims (10)

1. A kind of 1. heat pump unit, it is characterised in that the heat pump unit include main circulation loop and with the main circulation loop The defrosting liquid back pipe road being connected；

   Wherein, the compressor to communicate with each other, First Heat Exchanger and the second heat exchanger are provided with the main circulation loop, is being defrosted Under pattern, the First Heat Exchanger is used as condenser, and second heat exchanger is used as evaporator；

   The defrosting liquid back pipe road is used for after defrosting, by the direct water conservancy diversion of liquid heat transferring medium in the First Heat Exchanger Into second heat exchanger.
2. 2. heat pump unit according to claim 1, it is characterised in that switch valve is provided with the defrosting liquid back pipe road, The break-make on the defrosting liquid back pipe road is realized by the switch valve in the defrosting liquid back pipe road.
3. 3. heat pump unit according to claim 2, it is characterised in that the switch valve is solenoid valve.
4. 4. heat pump unit according to any one of claim 1 to 3, it is characterised in that the main circulation loop include with Parallel way is arranged on the first major cycle branch and the second major cycle between the First Heat Exchanger and second heat exchanger Branch, the defrosting liquid back pipe road are connected with the second major cycle branch.
5. 5. heat pump unit according to claim 4, it is characterised in that the main circulation loop, which further includes, is arranged on described Bridge joint branch between one major cycle branch and the second major cycle branch, described bridge in branch are provided with expansion valve.
6. 6. heat pump unit according to claim 5, it is characterised in that the branch that bridges is by the first major cycle branch Part I and Part II, the defrosting liquid back pipe road and the described second master are respectively divided into the second major cycle branch The Part II of circulation branch road is in parallel；

   Wherein, the Part I of the first major cycle branch is provided with the first check valve, and the of the first major cycle branch Two parts are provided with the second check valve, and the Part I of the second major cycle branch is provided with the 3rd check valve, and described second The Part II of major cycle branch is provided with the 4th check valve；

   First check valve only allows heat transferring medium to flow into the First Heat Exchanger, and second check valve only allows heat exchange to be situated between Mass flow enters second heat exchanger, and the 3rd check valve only allows heat transferring medium to flow out the First Heat Exchanger, and the described 4th Check valve only allows heat transferring medium to flow out second heat exchanger.
7. 7. heat pump unit according to claim 1, it is characterised in that the First Heat Exchanger is finned heat exchanger.
8. 8. heat pump unit according to claim 1, it is characterised in that second heat exchanger is falling-film heat exchanger.
9. 9. heat pump unit according to claim 8, it is characterised in that the falling-film heat exchanger includes spray element and changes Thermal element；

   During defrosting, liquid heat transferring medium is directly sprayed on the heat exchange element by the spray element, to shorten Defrosting time.
10. 10. heat pump unit according to claim 1, it is characterised in that the compressor is two-stage screw compressor.