A multi-connected central air-conditioning system that can perform refrigeration and heating simultaneously

Abstract

The present invention relates to a multi-connected central air-conditioning system that performs refrigeration and heating simultaneously, including a condensation module, a plurality of indoor fan coil units, a high-pressure circulation pipe, a medium-pressure circulation pipe, a low-pressure circulation pipe, and an evaporation module. The indoor fan coil units are connected to the high-pressure circulation pipe through a first branch pipe, connected to the low-pressure circulation pipe through a second branch pipe, and connected to the medium-pressure circulation pipe through a third branch pipe. Solenoid valves are respectively arranged on the first branch pipe and the second branch pipe. The beneficial effects are as follows: When heating in a local area in summer or cooling in a local room in winter, the flow of the refrigerant is realized through the switching of the solenoid valves and the medium-pressure circulation pipe, enabling the multi-connected central air-conditioning system to have multiple working modes (separate refrigeration / separate heating / simultaneous partial refrigeration and partial heating). Without adding complex refrigerant switching pipelines, the diversity of the overall operation of the air-conditioning system is improved. The condensation module and the evaporation module can also serve as balancers of the system to ensure the efficient and stable operation of the system.

Description

Technical Field

[0001] The present invention relates to the field of air conditioners, and particularly to a multi-connected central air-conditioning system that can perform refrigeration and heating simultaneously. Background Art

[0002] Central air conditioners use a refrigeration cycle to cool or heat indoor spaces, providing unified cooling in summer and unified heating in winter, which are the basic functions of air conditioners. However, this also brings a problem. Once the cooling is turned on, all air conditioners are in the cooling mode, and the same is true for heating. During the transitional season, for example, in the southern regions of China where the weather is sometimes hot and sometimes cold, different people have different requirements for temperature comfort. For example, physically stronger middle-aged and young people may feel a bit hot and need to turn on the air conditioner for cooling, while the elderly and children may feel cold and need heating. Currently, for ordinary multi-connected units on the market, most can only achieve a single cooling or heating mode. If it is required to simultaneously cool and heat different rooms in a single system, two separate air-conditioning systems need to be installed, increasing the construction cost.

[0003] With the increasingly obvious problem of energy shortage, China has put forward the national future development strategy of dual carbon goals. Energy conservation, environmental protection, and low carbon will become the mainstream direction of social development today, guiding the development direction of technological applications in all industries. Among the future choices of refrigerants, the natural refrigerant CO2 has characteristics such as large pressure difference, small viscosity, stable chemical properties, and good thermal properties, which has once again attracted the attention of technicians in the refrigeration industry. In recent years, the market share of related CO2 products has gradually increased.

[0004] Therefore, the motivation for the creation of the present invention is to provide a multi-connected central air-conditioning system that can simultaneously perform refrigeration in some independent spaces and heating in other independent spaces using a single air-conditioning system, and is convenient for switching between refrigeration and heating. Summary of the Invention

[0005] The purpose of the present invention is to overcome the deficiencies of the prior art and provide a multi-connected central air-conditioning system that can simultaneously perform refrigeration in some independent spaces and heating in other independent spaces using a single air-conditioning system, and is convenient for switching between refrigeration and heating. This is the motivation for the creation of the present invention.

[0006] What the present invention provides is as follows in its technical solution:

[0007] A multi-connected central air-conditioning system for simultaneous refrigeration and heating, comprising a condensation module, a plurality of indoor fan coil units, a high-pressure circulation pipe, a medium-pressure circulation pipe, a low-pressure circulation pipe and an evaporation module. The condensation module includes a compressor, a condenser and a liquid storage tank connected in sequence. The high-pressure circulation pipe is connected to the exhaust end of the compressor; the medium-pressure circulation pipe is connected to the liquid storage tank and the evaporation module; the low-pressure circulation pipe is connected to the suction end of the compressor and the evaporation module; the indoor fan coil unit is connected to the high-pressure circulation pipe through a first branch pipe, connected to the low-pressure circulation pipe through a second branch pipe, and connected to the medium-pressure circulation pipe through a third branch pipe. A first solenoid valve is provided on the first branch pipe, and a second solenoid valve is provided on the second branch pipe.

[0008] Further, an electronic expansion valve is provided on the third branch pipe.

[0009] Further, when some of the indoor fan coil units need refrigeration, the first solenoid valve of the refrigerating indoor fan coil unit is closed, and the refrigerant in the liquid storage tank sequentially passes through the medium-pressure circulation pipe, the electronic expansion valve, the indoor fan coil unit, the second solenoid valve, and the low-pressure circulation pipe to complete the refrigeration cycle;

[0010] When some of the indoor fan coil units need heating, the second solenoid valve of the heating indoor fan coil unit is closed, and the high-temperature refrigerant at the exhaust end of the compressor sequentially passes through the high-pressure circulation pipe, the first solenoid valve, the indoor fan coil unit, the electronic expansion valve, the evaporation module, and the low-pressure circulation pipe to complete the heating cycle.

[0011] Further, a temperature sensor and a pressure sensor are provided at the exhaust end of the compressor; a temperature sensor is provided at the suction end of the compressor; a temperature sensor is provided on the pipeline between the condenser and the liquid storage tank; a solenoid valve and a capillary tube are also provided on the pipeline between the liquid storage tank and the compressor; temperature sensors are provided at both the inlet end and the outlet end of the indoor fan coil unit; pressure sensors are respectively provided on the medium-pressure circulation pipe and the low-pressure circulation pipe.

[0012] Further, a first constant pressure valve is provided on the pipeline connecting the exhaust end of the compressor of the condensation module to the condenser, and a second constant pressure valve is provided on the pipeline between the condenser and the liquid storage tank.

[0013] Further, the central air-conditioning system further includes a floor heating pipe and / or a domestic hot water pipe;

[0014] The floor heating pipe is respectively connected to the high-pressure circulation pipe and the medium-pressure circulation pipe. An electronic expansion valve is provided on the connecting pipeline between the floor heating pipe and the medium-pressure circulation pipe, and a manual stop valve is provided on the connecting pipeline between the floor heating pipe and the high-pressure circulation pipe;

[0015] The domestic hot water pipe is respectively connected to the high-pressure circulation pipe and the medium-pressure circulation pipe. An electronic expansion valve is provided on the connecting pipeline between the domestic hot water pipe and the medium-pressure circulation pipe, and a manual stop valve is provided on the connecting pipeline between the domestic hot water pipe and the high-pressure circulation pipe.

[0016] Further, the evaporation module is a freeze-thaw cycle evaporator, which includes an infrared collector, a heat collection end, an energy tank, and a heat exchanger. A freeze-thaw medium is stored in the energy tank. The heat collection end and the heat exchanger are arranged in the energy tank, and both ends of the heat exchanger are respectively connected to a refrigerant circulation pipeline.

[0017] Further, the medium-pressure flow pipe is connected to the infrared heat collection plate, and a fourth control valve is arranged between the medium-pressure flow pipe and the infrared heat collection plate; the infrared heat collection plate is connected to the heat collection end, and the other end of the heat collection end is connected to the low-pressure flow pipe; the high-pressure flow pipe is connected to the first control valve, the first control valve is respectively connected to the heat exchanger and the second control valve, the other end of the second control valve is connected to the low-pressure flow pipe, the other end of the heat exchanger is connected to the third control valve, and the third control valve is connected to the medium-pressure flow pipe.

[0018] Further, the refrigerant is selected from Freon, ammonia, or carbon dioxide.

[0019] Further, carbon dioxide is selected as the single-cycle working medium for the refrigerant, and the condenser is a flash evaporator. The flash evaporator includes an enclosed housing, a negative pressure fan, and a heat exchange unit. The negative pressure fan is arranged at the top of the enclosed housing for creating a negative pressure inside the enclosed housing; multiple heat exchange units are arranged in the enclosed housing in a stacked manner. The heat exchange unit includes a water atomizer, multiple rows of coil pipes for circulating the refrigerant, and fins for fixing the multiple rows of coil pipes. The multiple rows of coil pipes and the fins are fixed by a fixing frame. Carbon dioxide flows in from the inlet end and flows out from the outlet end; the water atomizer is connected to a water source for atomizing water.

[0020] The implementation of the present invention includes the following technical effects:

[0021] The entire central air-conditioning system of the present invention uses the condenser to discharge heat and the infrared radiation collector to absorb heat; when heating a local area in summer or cooling a local room in winter, the flow of the refrigerant is realized through the solenoid valve switching and the medium-pressure flow pipe; enabling the multi-connected central air-conditioning system of the present invention to have multiple working modes (separate refrigeration / separate heating / simultaneous partial refrigeration and partial heating), improving the diversity of the overall operation of the multi-connected air-conditioning system without adding complex refrigerant switching pipelines. The system of the present invention can refrigerate and heat simultaneously, solving the different needs of different people for physical comfort at the same time. In a single system, separate refrigeration and heating of different indoor units can be achieved.

[0022] The condensation module and the evaporation module can also serve as balancers for the entire air-conditioning system, capable of balancing parameters such as the operating pressure during air-conditioning operation, ensuring the efficient and stable operation of the system, which is also an important effect of the present invention. Description of the Drawings

[0023] Figure 1Schematic diagram of a multi-connected central air-conditioning system that performs refrigeration and heating simultaneously according to an embodiment of the present invention.

[0024] Figure 2 Schematic diagram of the structure of the flash evaporator.

[0025] In the figure: 1. Condensation module; 10. Compressor; 11. Condenser; 110. Enclosed housing; 111. Negative pressure fan; 112. Heat exchange unit; 113. Water atomizer; 12. Liquid storage tank; 13. Temperature sensor; 14. First constant pressure valve; 15. Second constant pressure valve; 16. Pressure sensor; 17. Capillary tube; 2. Indoor fan coil unit; 20. First solenoid valve; 21. Second solenoid valve; 22. Electronic expansion valve; 23. First branch pipe; 24. Second branch pipe; 25. Third branch pipe; 3. High-pressure circulation pipe; 4. Medium-pressure circulation pipe; 5. Low-pressure circulation pipe; 6. Evaporation module; 60. Infrared collector; 61. Heat collection end; 62. Energy tank; 63. Heat exchanger; 64. First control valve; 65. Second control valve; 66. Third control valve; 67. Fourth control valve; 7. Floor heating pipe; 8. Domestic hot water pipe; 9. Manual stop valve. Detailed implementation manners

[0026] The present invention will be described in detail below in conjunction with embodiments and the accompanying drawings. It should be noted that the described embodiments are only intended to facilitate the understanding of the present invention and do not limit it in any way.

[0027] See Figure 1 As shown, a multi-connected central air-conditioning system that performs refrigeration and heating simultaneously provided in this embodiment includes a condensation module 1, a plurality of indoor fan coil units 2, a high-pressure circulation pipe 3, a medium-pressure circulation pipe 4, a low-pressure circulation pipe 5, and an evaporation module 6. The condensation module 1 includes a compressor 10, a condenser 11, and a liquid storage tank 12 that are connected in sequence. The high-pressure circulation pipe 3 is connected to the exhaust end of the compressor 10 and the evaporation module 6 to circulate the high-pressure and high-temperature refrigerant discharged from the compressor 10; the medium-pressure circulation pipe 4 is connected to the liquid storage tank 12 and the evaporation module 6 to circulate the medium-pressure refrigerant discharged from the plurality of indoor fan coil units 2; the low-pressure circulation pipe 5 is connected to the suction end of the compressor 10 and the evaporation module 6 to circulate the low-pressure refrigerant; the indoor fan coil unit 2 is connected to the high-pressure circulation pipe 3 through the first branch pipe 23, connected to the low-pressure circulation pipe 5 through the second branch pipe 24, and connected to the medium-pressure circulation pipe 4 through the third branch pipe 25. The first branch pipe 23 is provided with a first solenoid valve 20, the second branch pipe 24 is provided with a second solenoid valve 21, and the third branch pipe 25 is provided with an electronic expansion valve 22.

[0028] See Figure 1As shown, during the same period, when the indoor fan coils 2 of A1 - An need refrigeration and the indoor fan coils 2 of B1 - Bn need heating, the first solenoid valves 20 of the indoor fan coils 2 of A1 - An are closed. The refrigerant in the liquid storage tank 12 sequentially passes through the medium - pressure flow - through pipe 4, the electronic expansion valve 22, the indoor fan coil 2, the second solenoid valve 21, and the low - pressure flow - through pipe 5 to complete the refrigeration cycle. At this time, the second solenoid valves 21 of the indoor fan coils 2 of B1 - Bn are closed. The high - temperature refrigerant at the exhaust end of the compressor 10 sequentially passes through the high - pressure flow - through pipe 3, the first solenoid valve 20, the indoor fan coil 2, the electronic expansion valve 22, the evaporation module 6, and the low - pressure flow - through pipe 5 to complete the heating cycle.

[0029] The entire central air - conditioning system of the present invention dissipates heat through the condenser 11 and absorbs heat through the freeze - thaw cycle type evaporator. When heating in a local area in summer or cooling a local room in winter, the flow of the refrigerant is realized through the solenoid valve switching and the medium - pressure flow - through pipe 4. The multi - split central air - conditioning system of the present invention has multiple working modes (separate refrigeration / separate heating / simultaneous partial refrigeration and partial heating), which improves the diversity of the overall operation of the multi - split air - conditioning system without adding complex refrigerant switching pipelines. The system of the present invention can refrigerate and heat simultaneously, meeting the different needs of different people for physical comfort. In one system, separate refrigeration and heating of different indoor units can be achieved.

[0030] See Figure 1 As shown, a first constant - pressure valve 14 is provided on the pipeline connecting the exhaust end of the compressor 10 of the condensation module 1 to the condenser 11. The constant - pressure valve between the compressor 10 and the flash evaporator functions during winter operation to keep the exhaust pressure constantly at the pressure corresponding to the maximum COP. It is fully opened in summer to play a role in pipeline protection. A second constant - pressure valve 15 is provided on the pipeline between the condenser 11 and the liquid storage tank 12; the constant - pressure valve between the flash evaporator and the liquid storage tank 12 keeps the pressure of the liquid storage tank 12 constant within a certain range, such as 60 - 65 bar. A temperature sensor 13 and a pressure sensor 16 are provided at the exhaust end of the compressor 10; a temperature sensor 13 is provided at the suction end of the compressor 10; a temperature sensor 13 is provided on the pipeline between the condenser 11 and the liquid storage tank 12; a solenoid valve and a capillary 17 are also provided on the pipeline between the liquid storage tank 12 and the compressor 10; temperature sensors 13 are provided at both the inlet end and the outlet end of the indoor fan coil 2; pressure sensors 16 are provided on the medium - pressure flow - through pipe 4 and the low - pressure flow - through pipe 5 respectively. The capillary 17 has a throttling and pressure - reducing effect to prevent excessive evaporation of the liquid refrigerant in the liquid storage tank 12. The temperature data and pressure data of each key node are collected through the temperature sensor 13 and the pressure sensor 16, which are used as the basis for controlling the opening degrees of the compressor, the fan, the solenoid valve, and the electronic expansion valve, thereby improving the operating efficiency of the system.

[0031] See Figure 1As shown, the central air-conditioning system further includes a floor heating pipe 7. The floor heating pipe 7 is respectively connected to the high-pressure circulation pipe 3 and the medium-pressure circulation pipe 4. An electronic expansion valve 22 is provided on the connecting pipe between the floor heating pipe 7 and the medium-pressure circulation pipe 4, and a manual stop valve 9 is provided on the connecting pipe between the floor heating pipe 7 and the high-pressure circulation pipe 3. The central air-conditioning system further includes a domestic hot water pipe 8. The domestic hot water pipe 8 is respectively connected to the high-pressure circulation pipe 3 and the medium-pressure circulation pipe 4. An electronic expansion valve 22 is provided on the connecting pipe between the domestic hot water pipe 8 and the medium-pressure circulation pipe 4, and a manual stop valve 9 is provided on the connecting pipe between the domestic hot water pipe 8 and the high-pressure circulation pipe 3. When floor heating and domestic hot water production are required, the manual stop valve 9 is opened, and the high-temperature refrigerant at the exhaust end of the compressor 10 sequentially passes through the high-pressure circulation pipe 3, the manual stop valve 9, the floor heating pipe 7 / domestic hot water pipe 8, the electronic expansion valve 22, the evaporation module 6, and the low-pressure circulation pipe 5 to complete the heating cycle.

[0032] As a preferred embodiment, refer to Figure 1 As shown, the evaporation module is a freeze-thaw cycle evaporator. The freeze-thaw cycle evaporator includes an infrared collector 60, a heat collection end 61, an energy storage tank 62, and a heat exchanger 63. The energy storage tank 62 stores a freeze-thaw medium. The heat collection end 61 and the heat exchanger 63 are arranged in the energy storage tank 62. Both ends of the heat exchanger 63 are respectively connected to the refrigerant circulation pipeline. After the low-temperature refrigerant passes through the heat exchanger 63, it exchanges heat with the freeze-thaw medium. The infrared collector 60 stores the absorbed solar energy in the energy storage tank 62 and extracts heat from the freeze-thaw medium as needed. The freeze-thaw medium is a phase change energy storage material. For example, the freeze-thaw medium is water. Water at 0°C releases a large amount of heat when it turns into ice at 0°C. Water is an inexpensive and environmentally friendly substance, which further reduces the cost.

[0033] Specifically, the medium-pressure circulation pipe 4 is connected to the infrared heat collection plate 60, and a fourth control valve 67 is provided between the medium-pressure circulation pipe 4 and the infrared heat collection plate 60; the infrared heat collection plate 60 is connected to the heat collection end 61, and the other end of the heat collection end 61 is connected to the low-pressure circulation pipe 5; the high-pressure circulation pipe 3 is connected to the first control valve 64, the first control valve 64 is respectively connected to the heat exchanger 63 and the second control valve 65, the other end of the second control valve 65 is connected to the low-pressure circulation pipe 5, the other end of the heat exchanger 63 is connected to the third control valve 66, and the third control valve 66 is connected to the medium-pressure circulation pipe 4.

[0034] When the heating mode is the main mode: At night, the second control valve 65, the third control valve 66, and the fourth control valve 67 are opened first, and the first control valve 64 is closed. The heat stored in the energy storage tank 62 during the day is extracted through the refrigeration mode to heat the room. When the medium in the energy storage tank 62 reaches the phase change temperature, the first control valve 64 is opened, the second control valve 65 is closed, and the third control valve 66 and the fourth control valve 67 remain open. The heat of the high-temperature exhaust gas is transferred to the suction end through the medium in the energy storage tank 62, so that the system operates stably. During the day, the first control valve 64, the second control valve 65, and the third control valve 66 are closed. The fourth control valve 67 is opened first. The overheated return air heats the low-temperature medium in the tank through the energy storage tank 62. When the return air temperature is higher than the set value, the second control valve 65 and the third control valve 66 are opened to cool the return air.

[0035] In the present invention, light energy and air energy are stored in the energy storage tank 62 body in the form of phase change through the phase change energy storage material. When the sun is sufficient, solar energy can be used for heating, which is green and environmentally friendly. When the sun is insufficient, the collector can also collect a part of the heat through the way of thermal radiation, and the air energy collector can also be used to collect heat, ensuring the heating demand.

[0036] The refrigerant can be selected from media such as Freon, ammonia, and carbon dioxide. In this embodiment, carbon dioxide medium is preferably used as the refrigeration medium of the central air conditioner. Using carbon dioxide as the circulating working medium has the advantages of large pressure difference, good fluidity, small density, and transcritical phase change, and the effect is more obvious for high-rise buildings. The refrigerant circulation pipeline is connected to a single-stage carbon dioxide circulation system using carbon dioxide as a single circulating working medium. The meaning of single-stage is to distinguish from the cascade system, and only carbon dioxide medium is used for circulation without cascading. The multi-connected central air conditioner system of this embodiment uses carbon dioxide as the working medium, and can supply cooling or heating to higher floors in the vertical height, and can circulate a longer distance in the application of the flat floor, and can drive more indoor units to work.

[0037] When carbon dioxide is selected as the refrigerant, see Figure 2As shown, the condenser 11 is preferably a flash evaporator, which includes a closed housing 110, a negative pressure fan 111 and a heat exchange unit 112. The negative pressure fan 111 is arranged at the top of the closed housing 110 to form a negative pressure inside the closed housing 110. A plurality of heat exchange units 112 are arranged in the closed housing 110 in a stacked manner. The heat exchange unit 112 includes a water atomizer 113, multiple rows of coil pipes for circulating refrigerant, and fins for fixing the multiple rows of coil pipes. The multiple rows of coil pipes and the fins are fixed by a fixing frame. Carbon dioxide flows in from the inlet end and flows out from the outlet end. The multiple rows of coil pipes of multiple heat exchange units 112 are connected in series with each other. The water atomizer 113 is connected to a water source and is used to atomize water. The atomized water fills the inner cavity of the closed housing 110. Under the action of the negative pressure, the liquid micro-masses are extracted from the closed housing 110 by the negative pressure fan 111 after completing radiative heat exchange with the carbon dioxide in the multiple rows of coil pipes. During refrigeration, when the water micro-masses in the cavity absorb the radiative heat of the carbon dioxide flowing in the multiple rows of coil pipes, they gradually decompose from large micro-masses into small micro-masses to take away the heat, and the carbon dioxide refrigerant is condensed and liquefied. The water micro-masses are dynamically and continuously decomposed into small water micro-masses to take away the heat. The ultrasonic atomized water itself has a scale removal function, which can avoid scaling on the surfaces of the heat exchange tubes and fins. The water vapor after heat exchange does not circulate or recycle, but is directly discharged into the atmosphere. Since during the decomposition process of the water micro-masses, the heat is mainly converted into internal energy, the temperature of the discharged water vapor is not high and no heat island effect will be generated. The stacked arrangement of multiple heat exchange units 112 is convenient for installation and maintenance. When a certain heat exchange unit 112 is damaged, the damaged maintenance unit can be disassembled for repair or replacement. Compared with the existing air-cooled heat exchangers, this flash evaporator conducts heat exchange inside the closed housing 110 with almost no air intake. When the external temperature and humidity are both relatively high, the heat exchange effect will not be affected by the temperature and humidity of the external natural wind.

[0038] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the protection scope of the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A multi-connected central air-conditioning system that performs refrigeration and heating simultaneously, comprising a condensation module, a plurality of indoor fan coil units, a high-pressure circulation pipe, a medium-pressure circulation pipe, a low-pressure circulation pipe, and an evaporation module, characterized in that: The condensation module includes a compressor, a condenser, and a liquid storage tank connected in sequence. The high-pressure circulation pipe is connected to the exhaust end of the compressor; the medium-pressure circulation pipe is connected to the liquid storage tank and the evaporation module; the low-pressure circulation pipe is connected to the suction end of the compressor and the evaporation module; the indoor fan coil is connected to the high-pressure circulation pipe through a first branch pipe, connected to the low-pressure circulation pipe through a second branch pipe, and connected to the medium-pressure circulation pipe through a third branch pipe. A first solenoid valve is provided on the first branch pipe, and a second solenoid valve is provided on the second branch pipe; an electronic expansion valve is provided on the third branch pipe. The evaporation module is a freeze-thaw cycle evaporator, which includes an infrared collector, a heat collection end, an energy tank, and a heat exchanger. A freeze-thaw medium is stored in the energy tank. The heat collection end and the heat exchanger are arranged in the energy tank. Both ends of the heat exchanger are respectively connected to the refrigerant circulation pipeline; the medium-pressure circulation pipe is connected to the infrared heat collection plate, and a fourth control valve is provided between the medium-pressure circulation pipe and the infrared heat collection plate; the infrared heat collection plate is connected to the heat collection end, and the other end of the heat collection end is connected to the low-pressure circulation pipe; the high-pressure circulation pipe is connected to a first control valve, the first control valve is respectively connected to the heat exchanger and a second control valve, the other end of the second control valve is connected to the low-pressure circulation pipe, the other end of the heat exchanger is connected to a third control valve, and the third control valve is connected to the medium-pressure circulation pipe.

2. The multi-connected central air-conditioning system for simultaneous refrigeration and heating according to claim 1, wherein: When some of the indoor fan coils need to be cooled, the first solenoid valve of the cooling indoor fan coil is closed, and the refrigerant in the liquid storage tank sequentially passes through the medium-pressure circulation pipe, the electronic expansion valve, the indoor fan coil, the second solenoid valve, and the low-pressure circulation pipe to complete the cooling cycle. When some of the indoor fan coils need to be heated, the second solenoid valve of the heating indoor fan coil is closed, and the high-temperature refrigerant at the exhaust end of the compressor sequentially passes through the high-pressure circulation pipe, the first solenoid valve, the indoor fan coil, the electronic expansion valve, the evaporation module, and the low-pressure circulation pipe to complete the heating cycle.

3. The multi-connected central air-conditioning system capable of simultaneous refrigeration and heating according to claim 1, wherein: Temperature sensors and pressure sensors are provided at the exhaust end of the compressor; temperature sensors are provided at the suction end of the compressor; temperature sensors are provided on the pipeline between the condenser and the liquid storage tank; a solenoid valve and a capillary tube are also provided on the pipeline between the liquid storage tank and the compressor; temperature sensors are provided at both the inlet end and the outlet end of the indoor fan coil; pressure sensors are respectively provided on the medium-pressure circulation pipe and the low-pressure circulation pipe.

4. A multi-connected central air-conditioning system for simultaneous refrigeration and heating according to claim 3, characterized in that: A first constant pressure valve is provided on the pipeline connecting the exhaust end of the compressor of the condensation module to the condenser, and a second constant pressure valve is provided on the pipeline between the condenser and the liquid storage tank.

5. A multi-connected central air-conditioning system for simultaneous refrigeration and heating according to claim 1, characterized in that: The central air-conditioning system further includes a floor heating pipe and / or a domestic hot water pipe. The floor heating pipe is respectively connected to the high-pressure circulation pipe and the medium-pressure circulation pipe. An electronic expansion valve is provided on the connecting pipeline between the floor heating pipe and the medium-pressure circulation pipe, and a manual stop valve is provided on the connecting pipeline between the floor heating pipe and the high-pressure circulation pipe. The domestic hot water pipe is respectively connected to the high-pressure circulation pipe and the medium-pressure circulation pipe. An electronic expansion valve is provided on the connecting pipeline between the domestic hot water pipe and the medium-pressure circulation pipe, and a manual stop valve is provided on the connecting pipeline between the domestic hot water pipe and the high-pressure circulation pipe.

6. The multi-connected central air-conditioning system for simultaneous refrigeration and heating according to claim 1, wherein: The refrigerant is selected from Freon, ammonia, or carbon dioxide.

7. A multi-connected central air-conditioning system for simultaneous refrigeration and heating according to claim 1, characterized in that: The refrigerant selects carbon dioxide as the single-cycle working fluid, and the condenser is a flash evaporator. The flash evaporator includes a closed shell, a negative pressure fan, and a heat exchange unit. The negative pressure fan is arranged at the top of the closed shell and is used to form a negative pressure in the closed shell. Multiple heat exchange units are arranged in the closed shell in a stacked manner. The heat exchange unit includes a water atomizer, multiple rows of coil pipes for circulating the refrigerant, and fins for fixing the multiple rows of coil pipes. The multiple rows of coil pipes and the fins are fixed by a fixing frame. Carbon dioxide flows in from the inlet end and flows out from the outlet end. The water atomizer is connected to a water source and is used to atomize water.

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