TECHNICAL FIELD

[0001] The present invention relates to a heat pump unit and a multifunctional mode control method thereof, in particular to a heat pump unit with multifunctional modes such as refrigeration, heat supply, sanitary hot water supply and simultaneous refrigeration and heat supply/sanitary hot water supply and the like, and a multifunctional mode control method thereof.

BACKGROUND ART

[0002] Heat pump units designed by adopting a four-pipe system are usually applied to places such as hospitals and hotels, where two pipelines are applied to supply heat or provide sanitary hot water, and the other two pipelines may be applied to refrigeration. This type of heat pump units can provide heating and refrigeration functions for different user ends throughout the year, so as to provide relatively better user experience. At the same time, this type of heat pump units may also require more complex water system control solutions and occupy huge equipment arrangement spaces. In addition to relatively high expenses and costs of parts, pipeline arrangement complexity and labor costs also increase; and the more complex the system is, the more professional and difficult the inspection and maintenance are, and great inconvenience is caused to users.

SUMMARY OF THE INVENTION

[0003] The purpose of the present invention is to provide a heat pump unit with multifunctional modes such as refrigeration, heat supply, sanitary hot water supply and simultaneous refrigeration and heat supply/sanitary hot water supply, and the like.

[0004] The purpose of the present invention is to further provide a multifunctional mode control method for the above-described heat pump unit.

[0005] According to one aspect of the present invention, there is provided a heat pump unit, which comprises: a heat pump system comprising a compressor, a refrigeration heat exchanger, a heating heat exchanger, a first heat exchanger, a flow path switching valve which is capable of switching a flow direction of refrigerant and a throttling element, wherein the throttling element is arranged on a flow path between any two of the refrigeration heat exchanger, the heating heat exchanger and the first heat exchanger; and further comprising: a mode switching flow path, wherein a first flow path, a second flow path and a third flow path are arranged in the mode switching flow path and each flow path is controllably conducted or disconnected to realize different functional modes, wherein, under a sole refrigeration mode, a circular flow direction of the refrigerant is from a gas outlet of the compressor to a gas suction port of the compressor through the flow path switching valve, the first heat exchanger, the first flow path of the mode switching flow path and the refrigeration heat exchanger; and/or under a sole heating mode, the circular flow direction of the refrigerant is from the gas outlet of the compressor to the gas suction port of the compressor through the flow path switching valve, the heating heat exchanger, the second flow path of the mode switching flow path, the first heat exchanger and the flow path switching valve; and/or under a simultaneous refrigeration and heating mode, the circular flow direction of the refrigerant is from the gas outlet of the compressor to the gas suction port of the compressor through the flow path switching valve, the heating heat exchanger, the third flow path of the mode switching flow path and the refrigeration heat exchanger; a refrigeration water system which exchanges heat with the refrigeration heat exchanger; and a heating water system which exchanges heat with the heating heat exchanger.

[0006] According to another aspect of the present invention, there is further provided a multifunctional mode control method for a heat pump unit, wherein the heat pump unit comprises a compressor, a refrigeration heat exchanger, a heating heat exchanger, a first heat exchanger, a flow path switching valve which is capable of switching a flow direction of refrigerant and a throttling element, wherein the throttling element is arranged on a flow path between any two of the refrigeration heat exchanger, the heating heat exchanger and the first heat exchanger; and a refrigeration water system and a heating water system; and further comprises a mode switching flow path, wherein a first flow path, a second flow path and a third flow path are arranged in the mode switching flow path, wherein, during operation in a sole refrigeration mode, the first flow path of the mode switching flow path is conducted, and the second flow path and the third flow path of the mode switching flow path are disconnected; a circular flow direction of the refrigerant is from a gas outlet of the compressor to a gas suction port of the compressor through the flow path switching valve, the first heat exchanger, the first flow path of the mode switching flow path and the refrigeration heat exchanger; and at this moment, the refrigeration water system exchanges heat with the refrigeration heat exchanger; and/or during operation in a sole heating mode, the second flow path of the mode switching flow path is conducted, and the first flow path and the third flow path of the mode switching flow path are disconnected; the circular flow direction of the refrigerant is from the gas outlet of the compressor to the gas suction port of the compressor through the flow path switching valve, the heating heat exchanger, the second flow path of the mode switching flow path, the first heat exchanger and the flow path switching valve; and at this moment, the heating water system exchanges heat with the heating heat exchanger; and/or during operation in a simultaneous refrigeration and heating mode, the third flow path of the mode switching flow path is conducted, and the first flow path and the second flow path of the mode switching flow path are disconnected; the circular flow direction of the refrigerant is from the gas outlet of the compressor to the gas suction port of the compressor through the flow path switching valve, the heating heat exchanger, the third flow path of the mode switching flow path and the refrigeration heat exchanger; and at this moment, the refrigeration water system and the heating water system respectively exchange heat with the refrigeration heat exchanger and the heating heat exchanger.

BRIEF DESCRIPTION OF THE DRAWINGS

[0007] FIG. 1 illustrates a schematic view of a heat pump unit according to one embodiment of the present invention.

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0008] As illustrated in FIG. 1, according to one embodiment of the present invention, a heat pump unit is illustrated and comprises a heat pump system 100, a refrigeration water system 200 and a heating water system 300. Here, the heat pump system 100 is a system for refrigerant working and circulation, and refrigerant is compressed by a compressor and then releases or absorbs heat at positions of different heat exchangers. The refrigeration water system 200 and the heating water system 300 are systems for water working and circulation, water in the refrigeration water system 200 and the heating water system 300 exchanges heat with each heat exchanger in the heat pump system 100 to release or absorb heat to produce cold water or hot water, so as to provide further refrigeration, heat supply or sanitary hot water supply functions.

[0009] Specifically, the heat pump system 100 comprises a compressor 110, a refrigeration heat exchanger 130, a heating heat exchanger 140, a first heat exchanger 150, a flow path switching valve 120 and a throttling element 160, wherein the throttling element 160 is arranged such that the throttling element 160 exists on a flow path between any two of the refrigeration heat exchanger 130, the heating heat exchanger 140 and the first heat exchanger 150. In order to realize this purpose, several throttling elements 160 may be arranged such that the throttling elements 160 are respectively arranged in a flow path between every two heat exchangers; and only one throttling element 160 may also be arranged, and the throttling element 160 is guaranteed to be located on the flow path between any two of the heat exchangers through flow path design. Or, a combination of above-mentioned arrangements is used.

[0010] Besides, the heat pump system should further comprise a mode switching flow path, wherein a first flow path, a second flow path and a third flow path are respectively arranged in the mode switching flow path, and all flow paths may be fully independent or have a partially overlapped common flow path. In addition, each flow path is controllably conducted or disconnected to realize different functional modes. As an example, under a sole refrigeration mode, a circular flow direction of the refrigerant is from a gas outlet of the compressor 110 to a gas suction port of the compressor 110 through the flow path switching valve 120, the first heat exchanger 150, the first flow path of the mode switching flow path and the refrigeration heat exchanger 130; and/or under a sole heating mode, the circular flow direction of the refrigerant is from the gas outlet of the compressor 110 to the gas suction port of the compressor 110 through the flow path switching valve 120, the heating heat exchanger 140, the second flow path of the mode switching flow path, the first heat exchanger 150 and the flow path switching valve 120; and/or under a simultaneous refrigeration and heating mode, the circular flow direction of the refrigerant is from the gas outlet of the compressor 110 to the gas suction port of the compressor

110 through the flow path switching valve 120, the heating heat exchanger 140, the third flow path of the mode switching flow path and the refrigeration heat exchanger 130.

[0011] Besides, the refrigeration water system 200 realizes heat exchange with the heat pump system 100 through the refrigeration heat exchanger 130 and supplies cold to a user end; and the heating water system 300 realizes heat exchange with the heat pump system 100 through the heating heat exchanger 140 and supplies heat to the user end.

[0012] Based on the above-mentioned heat pump unit, multiple modes such as refrigeration, heating and simultaneous refrigeration and heating and the like may be respectively realized. In consideration of the fact that heating may include two sub-modes: heat supply and sanitary hot water supply, the above-mentioned heat pump system may respectively fulfill five functional modes with only one set of system and only one flow path switching valve. Thus, the costs of parts are greatly reduced and the complexity of water loop control is simplified. As compared with the existing four-pipe unit using two sets of systems, the operation costs may be decreased by up to 20%.

[0013] Under the concept of the above-mentioned mode switching flow path, according to the understanding of one skilled in the art, multiple specific flow paths and element connection ways may be obtained. One of implementation modes is described in detail herein with reference to FIG. 1. For example, from upstream to downstream, the first flow path may comprise a conducted first one-way valve 181, a throttling element 160, a first electromagnetic valve 171 and a conducted second one-way valve 182 which are sequentially connected; and/or from upstream to downstream, the second flow path may comprise a conducted third one-way valve 183, a throttling element 160, a second electromagnetic valve 172 and a conducted fourth one-way valve 184 which are sequentially connected; and/or from upstream to downstream, the third flow path may comprise a conducted third one-way valve 183, a throttling element 160, a first electromagnetic valve 171 and a conducted second one-way valve 182 which are sequentially connected. In this implementation mode, under a sole refrigeration mode, the circular flow direction of the refrigerant is from a gas outlet of the compressor 110 to a gas suction port of the compressor 110 through the flow path switching valve 120, the first heat exchanger 150, the first one-way valve 181, the throttling element 160, the first electromagnetic valve 171, the second one-way valve 182 and the refrigeration heat exchanger 130; and/or under a sole heating mode, the circular flow direction of the refrigerant is from the gas outlet of the compressor 110 to the gas suction port of the compressor 110 through the flow path switching valve 120, the heating heat exchanger 140, the third one-way valve 183, the throttling element 160, the second electromagnetic valve 172, the fourth one-way valve 184, the first heat exchanger 150 and the flow path switching valve 120; and/or under a simultaneous refrigeration and heating mode, the circular flow direction of the refrigerant is from the gas outlet of the compressor 110 to the gas suction port of the compressor 110 through the flow path switching valve 120, the heating heat exchanger 140, the third one-way valve 183, the throttling element 160, the first electromagnetic valve 171, the second one-way valve 182 and the refrigeration heat exchanger 130.

[0014] Alternatively, in order to further complete the functions of the heat pump unit, a defrosting branch may be further arranged and is connected with a flow path between an outlet of the throttling element 160 and an outlet of the heating heat exchanger 140; and the defrosting branch is controllably opened or closed to enable or disable a defrosting function. For example, in the embodiment illustrated in FIG. 1, a third electromagnetic valve 173 and a fifth one-way valve 185 are arranged on the defrosting branch, wherein the fifth one-way valve 185 is arranged downstream of the third electromagnetic valve 173 and the fifth one-way 185 is conducted along a flow direction from the throttling element 160 to the heating heat exchanger 140. During operation in a defrosting mode, the defrosting branch is conducted by conducting the third electromagnetic valve 173 to perform defrosting on the first heat exchanger 150.

[0015] Specifically, in order to provide a condition for judging whether to operate the defrosting mode, a gas suction pressure sensor should be further arranged at the gas suction port of the compressor 110 and/or a first temperature sensor should be further arranged at the position of the first heat exchanger 150. Whether to enter the defrosting mode is judged by detecting a gas suction pressure and/or a temperature at the position of the first heat exchanger. For example, when the gas suction pressure is relatively low, it indicates that a frosting situation possibly exists in the first heat exchanger and the defrosting mode needs to be enabled. For another example, when a difference between the temperature at the position of the first heat exchanger and ambient temperature is relatively small, it also indicates that a frosting situation possibly exists in the first heat exchanger and the defrosting mode needs to be enabled.

[0016] Alternatively, as another implementation mode for completing the functions of the heat pump unit, a hot gas bypass branch may be further arranged and a fourth electromagnetic valve 174 may be arranged between the flow path switching valve 120 and a second end of the refrigeration heat exchanger 130; the hot gas bypass branch comprises a first branch section which connects the gas outlet of the compressor 110 and the second end of the refrigeration heat exchanger 130, and a second branch section which connects a first end of the refrigeration heat exchanger 130 and an inlet of the throttling element 160; and the hot gas bypass branch together with the fourth electromagnetic valve 174 is controllably conducted or disconnected to enable or disable a hot gas bypass function. For example, in the embodiment illustrated in FIG. 1, a fifth electromagnetic valve 175 is arranged on the first branch section and/or a sixth one-way valve 186 is arranged on the second branch section. During operation in a hot gas bypass mode, the hot gas bypass branch is conducted by conducting the fifth electromagnetic valve 175, and the fourth electromagnetic valve 174 and the first electromagnetic valve 171 are disconnected to block the two ends of the refrigeration heat exchanger 130, such that high-temperature gaseous refrigerant directly flows into the refrigeration heat exchanger 130 through the compressor 110 to drain liquid refrigerant accumulated in the refrigeration heat exchanger 130 out through the second branch section, thereby not only preventing the liquid refrigerant from being accumulated in the refrigeration heat exchanger 130 and being frozen, but also guaranteeing enough refrigerant to participate in working and circulation.

[0017] Specifically, in order to provide a condition for judging whether to operate the hot gas bypass mode, a first pressure sensor should be further arranged in the refrigeration heat exchanger 130 and/or a liquid level sensor should be further arranged in the refrigeration heat exchanger 130. Whether to enter the hot gas bypass mode is judged by detecting an internal pressure of the refrigeration heat exchanger 130 and/or a liquid level in the refrigeration heat exchanger 130. For example, when the internal pressure of the refrigeration heat exchanger 130 is relatively low, it indicates that liquid refrigerant possibly starts to be accumulated in the refrigeration heat exchanger and the hot gas bypass mode needs to be enabled. For another example, when a certain liquid level exists in the refrigeration heat exchanger 130, it also indicates that liquid refrigerant possibly starts to be accumulated in the refrigeration heat exchanger 130 and the hot gas bypass mode needs to be enabled.

[0018] In addition, in order to further improve the heat pump unit provided by this embodiment, the flow path thereof may also be improved and the type of the parts thereof may be reasonably selected. Partial specific implementation modes will be described below with reference to FIG. 1.

[0019] Alternatively, the first flow path and/or the second flow path and/or the third flow path have a common flow path, and the throttling element 160 is arranged on the common flow path. This design allows that the same throttling element may be shared under various modes, the throttling effect is kept and the costs of parts are reduced at the same time. Here, as an alternative embodiment, the throttling element 160 may be an electronic expansion valve or other throttling expansion mechanisms. As a preferred solution, the electronic expansion valve can be controllably adjusted, such that throttling to different extents is provided under different functional modes or under different refrigerant flow rates to better adapt to the actual working conditions.

[0020] Alternatively, the system further comprises a drier- filter 192, and the drier- filter 192 is arranged on the common flow path and is located upstream of the throttling element 160, so as to provide drying and filtering effects for refrigerant which enters the throttling element 160 and prevent the throttling element 160 from being blocked.

[0021] Alternatively, the system further comprises a liquid reservoir 191 and the liquid reservoir 191 is arranged between a location downstream of the heating heat exchanger 140 and the third one-way valve 183. When different refrigerant amounts are needed during operation in different functional modes, excessive refrigerant may be stored in the liquid reservoir 191.

[0022] Alternatively, the system further comprises a gas-liquid separator 193 which is arranged upstream of the gas suction port of the compressor 110, so as to separate liquid refrigerant from a refrigerant flow which flows into the compressor 110, thereby avoiding the problems such as compressor liquid impact and the like.

[0023] Besides, for the type selection and design of the parts thereof, the specific implementation modes are also provided below with reference to FIG. 1 for the purpose of reference.

[0024] For example, the flow path switching valve 120 may be a four-way valve and may also be other valves which are capable of switching the flow direction of the refrigerant. Further, the flow path switching valve 120 should have a first switching position and a second switching position, so as to implement switching between at least two flow directions. Here, at the first switching position, the gas outlet of the compressor 110 is connected to the heating heat exchanger 140 through the flow path switching valve 120; and/or at the second switching position, the gas outlet of the compressor 110 is connected to the first heat exchanger 150 through the flow path switching valve 120.

[0025] Besides, jointly arranging the electromagnetic valve and the one-way valve in a certain flow path is mentioned multiple times above, mainly because a conventional electromagnetic valve is generally difficult to have an effect of reverse and full closing. As a result, in order to guarantee that a flow path can be fully disconnected when an electromagnetic valve is closed, a one-way valve with a reverse cutoff function should be further correspondingly provided. Accordingly, it is also feasible to adopt other types of valves which can fully control the conduction and disconnection of the flow path. In other words, a first valve, a second valve and a third valve which can realize two-way full closing may be used for respectively replacing the combination of the above-mentioned electromagnetic valve and the one-way valve. For example, as an alternative implementation mode, electric ball valves may be used for replacing the combination of the electromagnetic valve and the one-way valve.

[0026] More specifically, in the embodiment described above, a design may be adopted such that the first flow path comprises a first one-way valve 181, a throttling element 160 and a first electric ball valve which are sequentially connected; and/or the second flow path comprises a third one-way valve 183, a throttling element 160 and a second electric ball valve which are sequentially connected; and/or the third flow path comprises a third one-way valve 183, a throttling element 160 and a first electric ball valve which are sequentially connected. For another example, in the embodiment described above, a design may be adopted such that a third electric ball valve is arranged on the defrosting branch.

[0027] Alternatively, the first heat exchanger 150 may be a water-refrigerant heat exchanger or an air-refrigerant heat exchanger. When the first heat exchanger 150 is an air- refrigerant heat exchanger, the first heat exchanger 150 may comprise a V-shaped heat exchange coil, so as to achieve better heat exchange efficiency. Only when the first heat exchanger 150 is an air-refrigerant heat exchanger, there is a need for defrosting.

[0028] Alternatively, the compressor 110 may be a scroll compressor 110 or a screw compressor 110.

[0029] The water system of the heat pump unit will be further described below with reference to FIG. 1.

[0030] The water system in this embodiment comprises a refrigeration water system 200 and a heating water system 300. The refrigeration water system 200 comprises a first water loop which is connected between a refrigeration end 240 and the refrigeration heat exchanger 130. The first water loop comprises a first water inlet pipeline 210, a first water return pipeline 220 and a first water pump 230 which drives water to circulate therein.

[0031] In addition, the heating water system 300 comprises a second water loop which is connected between a heating end 340 and the heating heat exchanger 140; and the second water loop comprises a second water inlet pipeline 310, a second water return pipeline 320 and a second water pump 330 which drives water to circulate in the water loop. In this embodiment, in consideration of demands of hotels, hospitals or other application places, the heating end 340 is required to be capable of providing heating or sanitary hot water. Thus, the heating end 340 should comprise a heat supply end and/or a sanitary hot water end.

[0032] One embodiment of the heat pump unit is described in detail above with reference to FIG. 1. A multifunctional mode control method suitable for the heat pump unit will be further described below in combination with the heat pump unit.

[0033] With respect to the most fundamental heat pump unit, in other words, the heat pump unit comprises a compressor 110, a refrigeration heat exchanger 130, a heating heat exchanger 140, a first heat exchanger 150, a flow path switching valve 120 which is capable of switching a flow direction of refrigerant and a throttling element 160, wherein the throttling element 160 is arranged on a flow path between any two of the refrigeration heat exchanger 130, the heating heat exchanger 140 and the first heat exchanger 150; and a refrigeration water system and a heating water system; and further comprises a mode switching flow path, wherein a first flow path, a second flow path and a third flow path are arranged in the mode switching flow path. In such a case, during operation in a sole refrigeration mode, the first flow path of the mode switching flow path is conducted, and the second flow path and the third flow path of the mode switching flow path are disconnected; a circular flow direction of the refrigerant is from a gas outlet of the compressor 110 to a gas suction port of the compressor 110 through the flow path switching valve 120, the first heat exchanger 150, the first flow path of the mode switching flow path and the refrigeration heat exchanger 130; and at this moment, the refrigeration water system exchanges heat with the refrigeration heat exchanger 130; and/or during operation in a sole heating mode, the second flow path of the mode switching flow path is conducted, and the first flow path and the third flow path of the mode switching flow path are disconnected; the circular flow direction of the refrigerant is from the gas outlet of the compressor 110 to the gas suction port of the compressor 110 through the flow path switching valve 120, the heating heat exchanger 140, the second flow path of the mode switching flow path, the first heat exchanger 150 and the flow path switching valve 120; and at this moment, the heating water system exchanges heat with the heating heat exchanger 140; and/or during operation in a simultaneous refrigeration and heating mode, the third flow path of the mode switching flow path is conducted, and the first flow path and the second flow path of the mode switching flow path are disconnected; the circular flow direction of the refrigerant is from the gas outlet of the compressor 110 to the gas suction port of the compressor 110 through the flow path switching valve 120, the heating heat exchanger 140, the third flow path of the mode switching flow path and the refrigeration heat exchanger 130; and at this moment, the refrigeration water system and the heating water system respectively exchange heat with the refrigeration heat exchanger 130 and the heating heat exchanger 140.

[0034] More specifically, when the heating water system further comprises a heat supply end and/or a sanitary hot water end, a sole heating mode is further divided into a heat supply mode and/or a sanitary hot water mode. During operation in the heat supply mode, the heat supply end exchanges heat with the heating heat exchanger 140; and/or during operation in the sanitary hot water mode, the sanitary hot water end exchanges heat with the heating heat exchanger 140. As an alternative implementation mode, when the heating water system further comprises a heat supply end and/or a sanitary hot water end, the simultaneous refrigeration and heating mode further comprises a simultaneous refrigeration and heat supply mode and/or a simultaneous refrigeration and sanitary hot water mode. During operation in the simultaneous refrigeration and heat supply mode, the heat supply end exchanges heat with the heating heat exchanger 140; and/or during operation in the simultaneous refrigeration and sanitary hot water mode, the sanitary hot water end exchanges heat with the heating heat exchanger 140. Under this situation, heating or sanitary hot water can be respectively or simultaneously provided for a user end.

[0035] Specifically, under a situation that a first electromagnetic valve 171 and a second electromagnetic valve 172 are arranged in the mode switching flow path, a control method for conducting each flow path is provided in detail herein. When the first electromagnetic valve 171 is conducted, the second electromagnetic valve 172 is disconnected and the flow path switching valve 120 is switched to a second switching position, the first flow path of the mode switching flow path is conducted and the second flow path and the third flow path of the mode switching flow path are disconnected; and/or when the second electromagnetic valve 172 is conducted, the first electromagnetic valve 171 is disconnected and the flow path switching valve 120 is switched to a first switching position, the second flow path of the mode switching flow path is conducted and the first flow path and the third flow path of the mode switching flow path are disconnected; and/or when the first electromagnetic valve 171 is conducted, the second electromagnetic valve 172 is disconnected and the flow path switching valve 120 is switched to a first switching position, the third flow path of the mode switching flow path is conducted and the first flow path and the second flow path of the mode switching flow path are disconnected.

[0036] Alternatively, in order to improve the defrosting function of the heat pump unit, the heat pump unit further comprises a defrosting branch which is connected between an outlet of the throttling element 160 and an outlet of the heating heat exchanger 140. In this implementation mode, when a defrosting mode is enabled, the defrosting branch is conducted, the circular flow direction of the refrigerant is from the gas outlet of the compressor 110 to the gas suction port of the compressor 110 through the flow path switching valve 120, the first heat exchanger 150, the throttling element 160, the defrosting branch, the heating heat exchanger 140 and the flow path switching valve 120; and at this moment, high-temperature gaseous refrigerant flows to the first heat exchanger 150 to perform defrosting on the first heat exchanger 150.

[0037] Specifically, a control method for operating the defrosting mode is provided in detail herein. That is, when the defrosting mode is enabled, the third electromagnetic valve 173 is conducted, the first electromagnetic valve 171 and the second electromagnetic valve 172 are disconnected, and the flow path switching valve 120 is switched to the second switching position.

[0038] In order to clearly know whether or when to operate the defrosting mode, a plurality of conditions for judging whether to conduct the defrosting branch is provided in this embodiment. As an implementation mode, the heat pump unit comprises a gas suction pressure sensor which is arranged at the gas suction port of the compressor 110; and when the gas suction pressure is smaller than a first pressure threshold, a frosting phenomenon may probably occur in the first heat exchange 150 and at this moment the defrosting mode needs to be enabled. As another implementation mode, the heat pump unit comprises a first temperature sensor which is arranged at the position of the first heat exchanger 150; and when a difference between the first temperature and ambient temperature is small than a first temperature threshold, a frosting phenomenon may probably occur in the first heat exchanger 150 and the defrosting mode needs to be enabled.

[0039] Alternatively, in order to prevent the refrigeration heat exchanger 130 from having a risk of being frozen during operation in the heating mode and prevent the refrigerant from having a risk of imbalance in a mode switching process, the heat pump unit further comprises a fourth electromagnetic valve 174 which is arranged between the flow path switching valve 120 and a second end of the refrigeration heat exchanger 130, and a hot gas bypass branch; the hot gas bypass branch comprises a first branch section which connects the gas outlet of the compressor 110 and the second end of the refrigeration heat exchanger 130, and a second branch section which connects a first end of the refrigeration heat exchanger 130 and an inlet of the throttling element 160. In this implementation mode, when a hot gas bypass mode is enabled, the hot gas bypass branch is conducted, and the circular flow direction of the refrigerant is from the gas outlet of the compressor 110 to the gas suction port of the compressor 110 through the first branch section, the refrigeration heat exchanger 130, the second branch section, the throttling element 160, the first heat exchanger 150 and the flow path switching valve 120; and at this moment, high-temperature gaseous refrigerant flows to the refrigeration heat exchanger 130 and squeezes out liquid refrigerant in the refrigeration heat exchanger 130. [0040] Specifically, when the heat pump unit comprises a fifth electromagnetic valve

175 which is arranged on the first branch section and/or a sixth one-way valve 186 which is arranged on the second branch section, a control method for enabling the hot gas bypass mode is provided in detail herein. That is, when the hot gas bypass mode is enabled, the fifth electromagnetic valve 175 and the second electromagnetic valve 172 are conducted, the first electromagnetic valve 171 and the fourth electromagnetic valve 174 are disconnected, and the flow path switching valve is switched to the second switching position.

[0041] In order to clearly know whether or when to operate the hot gas bypass mode, a plurality of conditions for judging whether to conduct the hot gas bypass branch is provided in this embodiment. As an implementation mode, the heat pump unit comprises a first pressure sensor which is arranged in the refrigeration heat exchanger 130; and when an internal pressure of the refrigeration heat exchanger 130 is smaller than a second pressure threshold, liquid refrigerant probably starts to be accumulated in the refrigeration heat exchanger 130 and at this moment the hot gas bypass mode is enabled. Specifically, in this implementation mode, if a saturated temperature of refrigerant in the refrigeration heat exchanger 130 is lower than a freezing point temperature of water (or other secondary refrigerant which exchanges heat with the refrigerant), at this moment the refrigeration heat exchanger has a risk of being frozen and thus a hot gas bypass is needed. As another implementation mode, the heat pump unit comprises a liquid level sensor which is arranged in the refrigeration heat exchanger 130; and when a liquid level in the refrigeration heat exchanger 130 is greater than a first liquid level threshold, liquid refrigerant probably starts to be accumulated in the refrigeration heat exchanger 130 and at this moment the hot gas bypass mode is enabled.

[0042] After the embodiments of the heat pump unit and the control method thereof provided by the present invention are described in detail above, a working process of the heat pump unit provided by the present invention will be comprehensively and integrally described below with reference to FIG. 1.

[0043] During operation in a sole refrigeration mode, the flow path switching valve 120 is switched to the second position and the first electromagnetic valve 171 and the fourth electromagnetic valve 174 are conducted; the second electromagnetic valve 172, the third electromagnetic valve 173 and the fifth electromagnetic valve 175 are disconnected; and at this moment, the circular flow direction of the refrigerant is from the gas outlet of the compressor 110 to the gas suction port of the compressor 110 through the flow path switching valve 120, the first heat exchanger 150, the first one-way valve 181, the drier- filter 192, the throttling element 160, the first electromagnetic valve 171, the second one-way valve 182, the refrigeration heat exchanger 130, the fourth electromagnetic valve 174 and the gas-liquid separator 193. Here, the refrigerant releases heat at the position of the first heat exchanger 150 and absorbs heat at the position of the refrigeration heat exchanger 130. Water flowing through the refrigeration heat exchanger 130 via the refrigeration water system 200 is cooled thereby and flows to the refrigeration end 240 under the drive of the first water pump 230 to provide cold for a user.

[0044] During operation in a sole heating mode, the four- way valve 120 is switched to the first position and the second electromagnetic valve 172 is conducted; the first electromagnetic valve 171, the third electromagnetic valve 173, the fourth electromagnetic valve 174 and the fifth electromagnetic valve 175 are disconnected; and the circular flow direction of the refrigerant is from the gas outlet of the compressor 110 to the gas suction port of the compressor 110 through the flow path switching valve 120, the heating heat exchanger 140, the liquid reservoir 191, the third one-way valve 183, the drier-filter 192, the throttling element 160, the second electromagnetic valve 172, the fourth one-way valve 184, the first heat exchanger 150, the flow path switching valve 120 and the gas-liquid separator 193. Here, the refrigerant releases heat at the position of the heating heat exchanger 140 and absorbs heat at the position of the first heat exchanger 150. Water flowing through the heating heat exchanger 140 via the heating water system 300 is heated thereby and flows to the heating end 340 under the drive of the second water pump 330 for heating. Specifically, the heating end 340 may be a heat supply end and/or a sanitary hot water end. When the heating end 340 is a heat supply end, heating may be provided to the user; and when the heating end 340 is a sanitary hot water end, sanitary hot water may be provided to the user. Of course, the heating end 340 may be simultaneously the both, and at this moment water pipelines for heat supply and sanitary hot water supply should be isolated since heat supply hot water is only used as a heat transfer medium and the requirement on water quality is not high while sanitary hot water is directly used by the user and the water quality thereof needs to satisfy corresponding standards.

[0045] During operation in a simultaneous refrigeration and heating mode, the four-way valve 120 is switched to the first position and the first electromagnetic valve 171 and the fourth electromagnetic valve 174 are conducted; the second electromagnetic valve 172, the third electromagnetic valve 173 and the fifth electromagnetic valve 175 are disconnected; the circular flow direction of the refrigerant is from the gas outlet of the compressor 110 to the gas suction port of the compressor 110 through the flow path switching valve 120, the heating heat exchanger 140, the liquid reservoir 191, the third one-way valve 183, the drier-filter 192, the throttling element 160, the first electromagnetic valve 171, the second one-way valve 182, the refrigeration heat exchanger 130, the fourth electromagnetic valve 174 and the gas-liquid separator 193. Here, the refrigerant releases heat at the position of the heating heat exchanger 140 and absorbs heat at the position of the refrigeration heat exchanger 130. At this moment, on one hand, water flowing through the refrigeration heat exchanger 130 via the refrigeration water system 200 is cooled thereby and flows to the refrigeration end 240 under the drive of the first water pump 230 to provide cold for the user; and on the other hand, water flowing through the heating heat exchanger 140 via the heating water system 300 is heated thereby and flows to the heating end 340 under the drive of the second water pump 330 for heating. Specifically, the heating end 340 may be a heat supply end and/or a sanitary hot water end. When the heating end 340 is a heat supply end, heating may be provided to the user; and when the heating end 340 is a sanitary hot water end, sanitary hot water may be provided to the user. Of course, the heating end 340 may be simultaneously the both, and at this moment water pipelines for heat supply and sanitary hot water supply should be isolated since heat supply hot water is only used as a heat transfer medium and the requirement on water quality is not high while sanitary hot water is directly used by the user and the water quality thereof needs to satisfy corresponding standards.

[0046] During operation in a defrosting mode, the four-way valve 120 is switched to the second position and the third electromagnetic valve 173 is conducted; the first electromagnetic valve 171, the second electromagnetic valve 172, the fourth electromagnetic valve 174 and the fifth electromagnetic valve 175 are disconnected; and the circular flow direction of the refrigerant is from the gas outlet of the compressor 110 to the gas suction port of the compressor 110 through the flow path switching valve 120, the first heat exchanger 150, the first one-way valve 181, the drier-filter 192, the throttling element 160, the third electromagnetic valve 173, the fifth one-way valve 185, the liquid reservoir 191, the heating heat exchanger 140, the flow path switching valve 120 and the gas-liquid separator 193. Here, the refrigerant releases heat at the position of the first heat exchanger 150 and absorbs heat at the position of the heating heat exchanger 140. At this moment, the first heat exchanger 150 which is at low temperature for a long time and is possibly frosted will achieve a defrosting effect under the circulation of high- temperature gaseous refrigerant, and thereby the performance of the heat exchanger and the system is prevented from being influenced.

[0047] When a hot gas bypass function is enabled, the second electromagnetic valve 172 and the fifth electromagnetic valve 175 are conducted; the first electromagnetic valve 171, the third electromagnetic valve 173 and the fourth electromagnetic valve 174 are disconnected; and the circular flow direction of the refrigerant is from the gas outlet of the compressor 110 to the gas suction port of the compressor 110 through the fifth electromagnetic valve 175, the refrigeration heat exchanger 130, the sixth one-way valve 186, the drier- filter 192, the throttling element 160, the second electromagnetic valve 172, the fourth one-way valve 184, the first heat exchanger 150, the flow path switching valve 120 and the gas-liquid separator 193. At this moment, the refrigeration heat exchanger 130 which possibly is at low temperature and accumulates a number of liquid refrigerant in winter will drain the liquid refrigerant to the heat pump system under the circulation of high-temperature gaseous refrigerant to participate in normal working and circulation, and thereby is prevented from being frozen.

[0048] In the description of the present invention, it needs to be understood that direction or position relationships indicated by terms "above", "below", "front", "rear", "left", "right" and the like are direction or position relationships illustrated in the drawings, and are only used for facilitating the description of the present invention and simplifying the description instead of indicating or implying that the indicated devices or features must have specific directions and be constructed and operated in specific directions, and thus shall not be understood as limitations to the present invention.

[0049] The above-mentioned examples mainly describe the heat pump unit and the control method thereof provided by the present invention. Although only some implementation modes of the present invention are described, one skilled in the art shall understand that the present invention may be implemented in many other forms without departing from the essence and scope of the present invention. Therefore, the described examples and implementation modes shall be considered as exemplary instead of restrictive. The present invention may cover various modifications and replacements without going beyond the spirit and scope of the present invention as defined by the attached claims.