Multi-mode heat pump system and control method thereof

Abstract

The invention relates to the technical field of heat pumps, in particular to a multi-mode heat pump system and a control method thereof. The multi-mode heat pump system comprises a first heat exchanger, a second heat exchanger, a low-temperature-stage compressor, a high-temperature-stage compressor, a flash tank, a water vapor compressor and a water pump. The invention further provides a control method of the multi-mode heat pump system. According to the multi-mode heat pump system, the efficient heat pump is used for absorbing heat from underground water, free control over the flow and temperature of water vapor is achieved through the technology of series-parallel connection control of the heat pump unit and coupling of the water vapor compressor, and the requirements of different industries such as industrial heat consumption and civil heating for heat sources are met through a single thermodynamic system; the method has a profound market application prospect.

Description

Technical Field

[0001] The present invention relates to the technical field of heat pumps, and in particular to a multi-mode heat pump system and a control method thereof. Background Art

[0002] By drilling high-temperature geothermal reservoirs, the steam or hot water of geothermal fluids can be used to drive turbine generators to generate electricity. The water stored in the shallow underground layer has a low temperature, but the temperature is relatively stable, and it belongs to medium and low temperature geothermal resources. Medium and low temperature geothermal resources can be used for heating and cooling through geothermal heat pump systems, and can be directly used for heating, heating, hot water supply, etc., and are suitable for factories, schools, hospitals, residences and other places. However, high and medium temperature geothermal resources are relatively limited, and the geographical location of their distribution is relatively limited, and they cannot meet the heat needs of various industries on a large scale.

[0003] Drawing heat from shallow underground water storage and using efficient heat pumps to generate high-temperature heat for use in various industries is a practical scientific technology that will greatly promote carbon reduction and industrial energy conservation.

[0004] Therefore, a new technology is urgently needed to fully utilize medium and low temperature geothermal resources. Summary of the invention

[0005] In order to make up for the deficiencies of the prior art, the present application provides a multi-mode heat pump system and a control method thereof. The multi-mode heat pump system utilizes a high-efficiency heat pump to extract heat from groundwater, and realizes free control of water vapor flow and temperature through series-parallel control of heat pump units and coupling technology of water vapor compressors. The single thermal system meets the heat source needs of different industries such as industrial heat and civil heating, and has good market application prospects.

[0006] To achieve the above objectives, the present invention provides a multi-mode heat pump system.

[0007] The multi-mode heat pump system includes a first heat exchanger, a second heat exchanger, a low temperature compressor, a high temperature compressor, a flash tank, a water vapor compressor and a water pump. The first heat exchanger includes a first heat release pipe and a first heat absorption pipe, and the second heat exchanger includes a second heat release pipe and a second heat absorption pipe.

[0008] The inlet of the first heat-releasing pipe is connected to the geothermal, the outlet of the first heat-absorbing pipe is respectively connected to the inlets of the low-temperature compressor and the high-temperature compressor, the outlets of the low-temperature compressor and the high-temperature compressor are respectively connected to the inlet of the second heat-releasing pipe, and the outlet of the low-temperature compressor is connected to the inlet of the high-temperature compressor through a series-parallel switching pipe, and the outlet of the second heat-releasing pipe is connected to the inlet of the first heat-absorbing pipe.

[0009] A first series-parallel switching valve is arranged on the pipe connecting the outlet of the first heat absorption pipe with the inlet of the high-temperature compressor, a second series-parallel switching valve is arranged on the series-parallel switching pipe, and a third series-parallel switching valve is arranged on the pipe connecting the outlet of the low-temperature compressor with the inlet of the second heat release pipe.

[0010] The outlet of the second heat absorption tube is connected to the water inlet of the flash tank, and the inlet of the second heat absorption tube is connected to the water outlet of the flash tank, thereby forming a hot water circulation loop, and the water pump is arranged on the hot water circulation loop.

[0011] The air outlet of the flash tank is communicated with the air intake of the water vapor compressor.

[0012] Preferably, the multi-mode heat pump system includes an economizer, which includes a main pipeline and an auxiliary pipeline, wherein the inlet of the main pipeline is connected to the outlet of the second heat-releasing pipe through a main inlet pipe, the outlet of the main pipeline is connected to the inlet of the first heat-absorbing pipe through a main outlet pipe, and a first solenoid valve is provided on the main outlet pipe. The inlet of the auxiliary pipeline is connected to the main outlet pipe through an auxiliary inlet pipe, the outlet of the auxiliary pipeline is connected to the inlet of the high-temperature compressor through an auxiliary outlet pipe, and a second solenoid valve is provided on the auxiliary inlet pipe.

[0013] Preferably, the outlet of the second heat release pipe is connected to the compression chamber of the high-temperature compressor, and a third solenoid valve is provided on the pipeline connecting the outlet of the second heat release pipe and the compression chamber of the high-temperature compressor.

[0014] Preferably, the air outlet of the flash tank is connected to the air outlet of the water vapor compressor through a bypass pipe, a first stop valve is provided on the pipe connecting the air outlet of the flash tank and the air intake of the water vapor compressor, and a second stop valve is provided on the bypass pipe.

[0015] Preferably, the multi-mode heat pump system further includes a first pressure gauge, a first temperature gauge and / or a first flow meter, the first pressure gauge and / or the first temperature gauge are arranged on the pipe connecting the outlet of the second heat absorption tube and the water inlet of the flash tank, and the first flow meter is arranged on the pipe near the water pump outlet.

[0016] Preferably, the outlet of the water vapor compressor is connected to the high-temperature water vapor outlet pipe, and the high-temperature water vapor outlet pipe is provided with a second pressure gauge, a second temperature gauge and / or a second flow meter.

[0017] Preferably, the water pump is a centrifugal pump.

[0018] The present invention also provides a control method for any of the above multi-mode heat pump systems.

[0019] Control methods include:

[0020] When the high-temperature steam demand flow is small and the temperature requirement is low, the first series-parallel switching valve is closed, the second series-parallel switching valve is closed, the third series-parallel switching valve is opened, and the low-temperature compressor is operated. The first stop valve disposed on the pipeline connecting the air outlet of the flash tank and the air intake of the water vapor compressor is closed, and the second stop valve disposed on the bypass pipeline connecting the air outlet of the flash tank and the air outlet of the water vapor compressor is opened.

[0021] When the high-temperature steam demand flow is large and the temperature requirement is low, open the first series-parallel switching valve, close the second series-parallel switching valve, open the third series-parallel switching valve, and the low-temperature compressor and the high-temperature compressor run in parallel. Close the first stop valve and open the second stop valve.

[0022] When the high-temperature steam demand flow is small and the temperature requirement is high, close the first series-parallel switching valve, open the second series-parallel switching valve, close the third series-parallel switching valve, and the low-temperature compressor and the high-temperature compressor operate in series. Close the first stop valve and open the second stop valve.

[0023] When the high-temperature steam demand flow is large and the temperature requirement is high, open the first series-parallel switching valve, close the second series-parallel switching valve, open the third series-parallel switching valve, and the low-temperature compressor and the high-temperature compressor run in parallel. Open the first stop valve, close the second stop valve, and the water vapor compressor runs.

[0024] Preferably, when the high-temperature steam demand flow is small and the temperature requirement is high, the third solenoid valve arranged on the pipeline connecting the outlet of the second heat release pipe and the compression chamber of the high-temperature stage compressor is opened.

[0025] Preferably, the multi-mode heat pump system includes a first pressure gauge, a first temperature gauge and / or a first flow meter, the first pressure gauge and / or the first temperature gauge are arranged on a pipe connecting the outlet of the second heat absorption pipe and the water inlet of the flash tank, and the first flow meter is arranged on a pipe near the outlet of the water pump. When the monitoring value of the first pressure gauge, the first temperature gauge and / or the first flow meter is greater than a preset value, the speed of the water pump is reduced, and when the monitoring value of the first pressure gauge, the first temperature gauge and / or the first flow meter is less than the preset value, the speed of the water pump is increased.

[0026] Compared with the prior art, the present invention has the following advantages:

[0027] Firstly, the present invention utilizes a high-efficiency heat pump to extract heat from groundwater, and realizes free control of water vapor flow and temperature through series-parallel control of heat pump units and coupling technology of water vapor compressors. The single thermal system meets the heat source needs of different industries such as industrial heat and civil heating, and has a wide range of applications.

[0028] Secondly, the thermal system of the present invention has four working modes, which can meet the needs of different industries for high-temperature steam. The present invention is particularly related to the supply of high-temperature water vapor. The system has more control modes, wider application scenarios and greater flexibility than traditional refrigerant heat pumps.

[0029] In addition, the present invention utilizes a high-efficiency heat pump system to extract heat from groundwater, transfers the heat to hot water through a second heat exchanger, and after the hot water is heated, it flashes in a flash tank to produce high-temperature steam. Based on user demand, the water vapor at the flash tank outlet is heated and pressurized and then supplied to the user, which has a huge promoting effect on carbon reduction and industrial energy conservation. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] The present application may be better understood by describing the embodiments of the present application in conjunction with the accompanying drawings, in which:

[0031] Figure 1 This is a schematic diagram of the structure of a multi-mode heat pump system of the present application.

[0032] Description of Figure Numbers:

[0033] 10. First heat exchanger; 11. First heat release pipe; 12. First heat absorption pipe; 20. Second heat exchanger; 21. Second heat release pipe; 22. Second heat absorption pipe; 30. Low temperature compressor; 32. High temperature compressor; 34. Flash tank; 36. Water vapor compressor; 38. Water pump; 40. Economizer; 50. Series-parallel switching pipe; 51. Bypass pipe; 61. First series-parallel switching valve; 62. Second series-parallel switching valve; 63. Third series-parallel switching valve; 64. First solenoid valve; 65. Second solenoid valve; 66. Third solenoid valve; 67. First stop valve; 68. Second stop valve; 71. First pressure gauge; 72. First temperature gauge; 73. First flow meter; 74. Second pressure gauge; 75. Second temperature gauge; 76. Second flow meter. DETAILED DESCRIPTION

[0034] Unless otherwise defined, technical or scientific terms used in the specification and claims shall have the common meanings understood by persons having ordinary skills in the technical field to which the present invention belongs.

[0035] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside" and "outside" etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present invention.

[0036] In addition, the terms "first", "second", etc. are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Thus, a feature defined as "first", "second", etc. may explicitly or implicitly include one or more of the features. In the description of the present invention, unless otherwise specified, "plurality" means two or more.

[0037] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood by specific circumstances.

[0038] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0039] This embodiment relates to a Figure 1 The multi-mode heat pump system shown.

[0040] The multi-mode heat pump system includes a first heat exchanger 10, a second heat exchanger 20, a low temperature stage compressor 30, a high temperature stage compressor 32, a flash tank 34, a water vapor compressor 36 and a water pump 38. Preferably, the water pump 38 is a centrifugal pump.

[0041] The first heat exchanger 10 includes a first heat-releasing tube 11 and a first heat-absorbing tube 12 , and the second heat exchanger 20 includes a second heat-releasing tube 21 and a second heat-absorbing tube 22 .

[0042] The inlet of the first heat release pipe 11 is connected to the ground heat. The outlet of the first heat absorption pipe 12 is connected to the inlets of the low temperature compressor 30 and the high temperature compressor 32 respectively, and the outlets of the low temperature compressor 30 and the high temperature compressor 32 are connected to the inlet of the second heat release pipe 21 respectively, and the outlet of the low temperature compressor 30 is connected to the inlet of the high temperature compressor 32 through the series-parallel switching pipe 50, and the outlet of the second heat release pipe 21 is connected to the inlet of the first heat absorption pipe 12.

[0043] A first series-parallel switching valve 61 is arranged on the pipeline connecting the outlet of the first heat absorption tube 12 and the inlet of the high-temperature stage compressor 32, a second series-parallel switching valve 62 is arranged on the series-parallel switching tube 50, and a third series-parallel switching valve 63 is arranged on the pipeline connecting the outlet of the low-temperature stage compressor 30 and the inlet of the second heat release tube 21.

[0044] The outlet of the second heat absorbing tube 22 is connected to the water inlet of the flash tank 34, and the inlet of the second heat absorbing tube 22 is connected to the water outlet of the flash tank 34, thereby forming a hot water circulation loop, and the water pump 38 is arranged on the hot water circulation loop.

[0045] The gas outlet of the flash tank 34 is communicated with the gas intake of the water vapor compressor 36 .

[0046] Preferably, the multi-mode heat pump system includes an economizer 40, and the economizer 40 includes a main pipeline and an auxiliary pipeline, the inlet of the main pipeline is connected to the outlet of the second heat release pipe 21 through the main inlet pipe, the outlet of the main pipeline is connected to the inlet of the first heat absorption pipe 12 through the main outlet pipe, and the main outlet pipe is provided with a first solenoid valve 64. The inlet of the auxiliary pipeline is connected to the main outlet pipe through the auxiliary inlet pipe, the outlet of the auxiliary pipeline is connected to the inlet of the high-temperature compressor 32 through the auxiliary outlet pipe, and the second solenoid valve 65 is provided on the auxiliary inlet pipe.

[0047] Preferably, the outlet of the second heat release pipe 21 is connected to the compression chamber of the high-temperature compressor 32 , and a third solenoid valve 66 is provided on the pipeline connecting the outlet of the second heat release pipe 21 and the compression chamber of the high-temperature compressor 32 .

[0048] Preferably, the air outlet of the flash tank 34 is connected to the air outlet of the water vapor compressor 36 through a bypass pipe 51, a first stop valve 67 is provided on the pipe connecting the air outlet of the flash tank 34 and the air intake of the water vapor compressor 36, and a second stop valve 68 is provided on the bypass pipe 51.

[0049] Preferably, the multi-mode heat pump system further includes a first pressure gauge 71, a first temperature gauge 72 and / or a first flow meter 73, the first pressure gauge 71 and / or the first temperature gauge 72 are arranged on the pipeline connecting the outlet of the second heat absorption pipe 22 and the water inlet of the flash tank 34, and the first flow meter 73 is arranged on the pipeline near the outlet of the water pump 38. The first pressure gauge 71, the first temperature gauge 72 and / or the first flow meter 73 can set the target value according to the demand. The first pressure gauge 71 and / or the first temperature gauge 72 can be connected to the first flow meter 73 through a control line, and the first flow meter 73 can be connected to the water pump 38 through a control line.

[0050] Preferably, the outlet of the water vapor compressor 36 is connected to the high-temperature water vapor outlet pipe, and the high-temperature water vapor outlet pipe is provided with a second pressure gauge 74, a second temperature gauge 75 and / or a second flow meter 76. The second pressure gauge 74, the second temperature gauge 75 and / or the second flow meter 76 can set target values ​​according to requirements, and are connected to the first series-parallel switching valve 61, the second series-parallel switching valve 62, the third series-parallel switching valve 63 and / or the water vapor compressor 36 through a control line.

[0051] In such Figure 1 In the illustrated embodiment, after the refrigerant in the heat pump system absorbs heat from the first heat exchanger 10, it is heated and pressurized by the low-temperature compressor 30 or the high-temperature compressor 32, and then condenses in the second heat exchanger 20 to release heat. The condensed refrigerant enters the first heat exchanger 10 after throttling and reducing the pressure by the economizer 40 and the first solenoid valve 64. The other refrigerant that has passed through the economizer 40 enters the economizer 40 after throttling and reducing the temperature by the second solenoid valve 65, absorbs heat, and then flows into the air intake of the high-temperature compressor 32. The hot water at the outlet of the flash tank 34 enters the second heat exchanger 20 after being pressurized by the water pump 38, and enters the flash tank 34 after absorbing heat and raising the temperature. The high-temperature hot water flashes in the flash tank 34, and the generated high-temperature water vapor leaves the outlet at the top of the flash tank 34. It can then be supplied to users through the bypass pipe 51, or it can be supplied to users after being heated and pressurized by the water vapor compressor 36.

[0052] The present invention also provides a control method for a multi-mode heat pump system as described above. Figure 1 The control methods include:

[0053] When the high-temperature steam demand flow is small and the temperature requirement is low, the first series-parallel switching valve 61 is closed, the second series-parallel switching valve 62 is closed, the third series-parallel switching valve 63 is opened, and the low-temperature compressor 30 is operated. The first stop valve 67 provided on the pipeline connecting the air outlet of the flash tank 34 and the air intake of the water vapor compressor 36 is closed, and the second stop valve 68 provided on the bypass pipeline 51 connecting the air outlet of the flash tank 34 and the air outlet of the water vapor compressor 36 is opened. In this mode, the refrigerant in the heat pump system can absorb heat from the first heat exchanger 10, enter the low-temperature compressor 30 to increase temperature and pressure, and then condense in the second heat exchanger 20 to release heat. The hot water flowing out of the flash tank 34 is pressurized by the water pump 38 and enters the second heat exchanger 20 to absorb heat and increase temperature, and then enters the flash tank 34 for flash evaporation. The high-temperature water vapor generated by flash evaporation leaves from the outlet of the flash tank 34 and is supplied to users through the bypass pipeline 51.

[0054] When the high-temperature steam demand flow is large and the temperature requirement is low, the first series-parallel switching valve 61 is opened, the second series-parallel switching valve 62 is closed, and the third series-parallel switching valve 63 is opened, and the low-temperature compressor 30 and the high-temperature compressor 32 are operated in parallel. The first stop valve 67 is closed and the second stop valve 68 is opened. In this mode, after the refrigerant in the heat pump system absorbs heat from the first heat exchanger 10, one path enters the low-temperature compressor 30, and the other path passes through the first series-parallel switching valve 61 and enters the high-temperature compressor 32. At this time, the low-temperature compressor 30 and the high-temperature compressor 32 are operated in parallel. Subsequently, the refrigerant is heated and pressurized and condensed in the second heat exchanger 20 to release heat. The hot water flowing out of the flash tank 34 is pressurized by the water pump 38 and enters the second heat exchanger 20 to absorb heat and heat up, and then enters the flash tank 34 for flash evaporation. The high-temperature water vapor generated by flash evaporation leaves from the outlet of the flash tank 34 and is supplied to users through the bypass pipe 51.

[0055] When the high-temperature steam demand flow is small and the temperature requirement is high, the first series-parallel switching valve 61 is closed, the second series-parallel switching valve 62 is opened, and the third series-parallel switching valve 63 is closed, and the low-temperature compressor 30 and the high-temperature compressor 32 are operated in series. The first stop valve 67 is closed and the second stop valve 68 is opened. In this mode, the refrigerant in the heat pump system absorbs heat from the first heat exchanger 10 and enters the low-temperature compressor 30, and then enters the high-temperature compressor 32 through the second series-parallel switching valve 62, and condenses and releases heat in the second heat exchanger 20 after being heated and pressurized. The hot water flowing out of the flash tank 34 enters the second heat exchanger 20 after being pressurized by the water pump 38 to absorb heat and heat, and then enters the flash tank 34 for flash evaporation. The high-temperature water vapor generated by flash evaporation leaves the outlet of the flash tank 34 and is supplied to users through the bypass pipe 51. In some embodiments, when the high-temperature steam demand flow is small and the temperature requirement is high, the third solenoid valve 66 arranged on the pipe connecting the outlet of the second heat release pipe 21 and the compression chamber of the high-temperature compressor 32 is opened. At this time, part of the refrigerant flowing out of the second heat exchanger 20 enters the compression chamber of the high-temperature stage compressor 32, thereby reducing the temperature in the compression chamber.

[0056] When the high-temperature steam demand flow is large and the temperature requirement is high, the first series-parallel switching valve 61 is opened, the second series-parallel switching valve 62 is closed, and the third series-parallel switching valve 63 is opened, and the low-temperature compressor 30 and the high-temperature compressor 32 are operated in parallel. The first stop valve 67 is opened, the second stop valve 68 is closed, and the water vapor compressor 36 is operated. In this mode, the refrigerant in the heat pump system absorbs heat from the first heat exchanger 10, enters the low-temperature compressor 30 in one way, and enters the high-temperature compressor 32 in the other way after passing through the first series-parallel switching valve 61. Subsequently, the refrigerant is heated and pressurized and condensed in the second heat exchanger 20 to release heat. The hot water flowing out of the flash tank 34 is pressurized by the water pump 38 and enters the second heat exchanger 20 to absorb heat and heat, and then enters the flash tank 34 for flash evaporation. The high-temperature water vapor generated by flash evaporation leaves from the outlet of the flash tank 34. At this time, the second stop valve 68 is closed, the first stop valve 67 is opened, and the high-temperature water vapor generated by flash evaporation enters the air intake of the water vapor compressor 36, and is supplied to users after being heated and pressurized.

[0057] Preferably, the multi-mode heat pump system includes a first pressure gauge 71, a first temperature gauge 72 and / or a first flow meter 73. The first pressure gauge 71 and / or the first temperature gauge 72 are arranged on a pipe connecting the outlet of the second heat absorption pipe 22 and the water inlet of the flash tank 34, and the first flow meter 73 is arranged on a pipe near the outlet of the water pump 38. When the monitoring value of the first pressure gauge 71, the first temperature gauge 72 and / or the first flow meter 73 is greater than a preset value, the speed of the water pump 38 is reduced, and when the monitoring value of the first pressure gauge 71, the first temperature gauge 72 and / or the first flow meter 73 is less than the preset value, the speed of the water pump 38 is increased.

[0058] The above specific embodiments further illustrate the purpose, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above are only specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A multi-mode heat pump system, characterized in that: The multi-mode heat pump system includes a first heat exchanger, a second heat exchanger, a low-temperature compressor, a high-temperature compressor, a flash tank, a water vapor compressor and a water pump; the first heat exchanger includes a first heat release pipe and a first heat absorption pipe, and the second heat exchanger includes a second heat release pipe and a second heat absorption pipe, wherein: The inlet of the first heat-releasing pipe is connected to the ground heat, the outlet of the first heat-absorbing pipe is connected to the inlets of the low-temperature compressor and the high-temperature compressor respectively, the outlets of the low-temperature compressor and the high-temperature compressor are connected to the inlet of the second heat-releasing pipe respectively, and the outlet of the low-temperature compressor is connected to the inlet of the high-temperature compressor through a series-parallel switching pipe, and the outlet of the second heat-releasing pipe is connected to the inlet of the first heat-absorbing pipe; A first series-parallel switching valve is provided on the pipeline connecting the outlet of the first heat absorption pipe and the inlet of the high-temperature compressor, a second series-parallel switching valve is provided on the series-parallel switching pipe, and a third series-parallel switching valve is provided on the pipeline connecting the outlet of the low-temperature compressor and the inlet of the second heat release pipe; The outlet of the second heat absorption pipe is connected to the water inlet of the flash tank, and the inlet of the second heat absorption pipe is connected to the water outlet of the flash tank, so as to form a hot water circulation loop, and the water pump is arranged on the hot water circulation loop; The air outlet of the flash tank is communicated with the air intake of the water vapor compressor.

2. The multi-mode heat pump system according to claim 1, characterized in that: The multi-mode heat pump system includes an economizer, which includes a main pipeline and an auxiliary pipeline. The inlet of the main pipeline is connected to the outlet of the second heat release pipe through a main inlet pipe, and the outlet of the main pipeline is connected to the inlet of the first heat absorption pipe through a main outlet pipe, and a first solenoid valve is provided on the main outlet pipe; the inlet of the auxiliary pipeline is connected to the main outlet pipe through an auxiliary inlet pipe, and the outlet of the auxiliary pipeline is connected to the inlet of the high-temperature compressor through an auxiliary outlet pipe, and a second solenoid valve is provided on the auxiliary inlet pipe.

3. The multi-mode heat pump system according to claim 1, characterized in that: The outlet of the second heat release pipe is connected to the compression chamber of the high-temperature compressor, and a third solenoid valve is arranged on the pipeline connecting the outlet of the second heat release pipe and the compression chamber of the high-temperature compressor.

4. The multi-mode heat pump system according to claim 1, characterized in that: The air outlet of the flash tank is connected to the air outlet of the water vapor compressor through a bypass pipe, a first stop valve is arranged on the pipe connecting the air outlet of the flash tank and the air intake of the water vapor compressor, and a second stop valve is arranged on the bypass pipe.

5. The multi-mode heat pump system according to claim 1, characterized in that: The multi-mode heat pump system further includes a first pressure gauge, a first temperature gauge and / or a first flow meter. The first pressure gauge and / or the first temperature gauge are arranged on a pipe connecting the outlet of the second heat absorption tube and the water inlet of the flash tank. The first flow meter is arranged on a pipe near the water pump outlet.

6. The multi-mode heat pump system according to claim 1, characterized in that: The outlet of the water vapor compressor is connected to the high-temperature water vapor outlet pipe, and the high-temperature water vapor outlet pipe is provided with a second pressure gauge, a second temperature gauge and / or a second flow meter.

7. The multi-mode heat pump system according to claim 1, characterized in that: The water pump is a centrifugal pump.

8. A control method for a multi-mode heat pump system according to any one of claims 1 to 7, characterized in that: The control method comprises: When the high-temperature steam demand flow is small and the temperature requirement is low, the first series-parallel switching valve is closed, the second series-parallel switching valve is closed, the third series-parallel switching valve is opened, and the low-temperature compressor is operated; the first stop valve provided on the pipeline connecting the air outlet of the flash tank and the air intake of the water vapor compressor is closed, and the second stop valve provided on the bypass pipeline connecting the air outlet of the flash tank and the air outlet of the water vapor compressor is opened; When the high-temperature steam demand flow is large and the temperature requirement is low, the first series-parallel switching valve is opened, the second series-parallel switching valve is closed, and the third series-parallel switching valve is opened, so that the low-temperature compressor and the high-temperature compressor are operated in parallel; the first stop valve is closed and the second stop valve is opened; When the high-temperature steam demand flow is small and the temperature requirement is high, the first series-parallel switching valve is closed, the second series-parallel switching valve is opened, the third series-parallel switching valve is closed, and the low-temperature compressor and the high-temperature compressor are operated in series; the first stop valve is closed, and the second stop valve is opened; When the high-temperature steam demand flow is large and the temperature requirement is high, open the first series-parallel switching valve, close the second series-parallel switching valve, open the third series-parallel switching valve, and the low-temperature stage compressor and the high-temperature stage compressor operate in parallel; open the first stop valve, close the second stop valve, and the water vapor compressor operates.

9. The control method of the multi-mode heat pump system according to claim 8, characterized in that: The third solenoid valve disposed on the pipeline connecting the outlet of the second heat release pipe and the compression chamber of the high-temperature compressor is opened.

10. The control method of the multi-mode heat pump system according to claim 8, characterized in that: The multi-mode heat pump system includes a first pressure gauge, a first temperature gauge and / or a first flow meter, wherein the first pressure gauge and / or the first temperature gauge are arranged on a pipe connecting the outlet of the second heat absorption tube and the water inlet of the flash tank, and the first flow meter is arranged on a pipe near the water pump outlet; when the monitoring value of the first pressure gauge, the first temperature gauge and / or the first flow meter is greater than a preset value, the water pump speed is reduced, and when the monitoring value of the first pressure gauge, the first temperature gauge and / or the first flow meter is less than the preset value, the water pump speed is increased.

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