Single-stage subcritical carbon dioxide multi-connected hybrid cooling and heating balanced system and control method

Abstract

The present application relates to a single-stage subcritical carbon dioxide multi-connected machine mixed cold and heat balanced system and a control method, comprising a bidirectional evaporation heat exchanger, a compressor, a high-pressure gas refrigerant flow pipe, a medium-pressure liquid refrigerant flow pipe and a low-pressure gas refrigerant flow pipe, the communication state of the bidirectional evaporation heat exchanger with the high-pressure gas refrigerant flow pipe and the low-pressure gas refrigerant flow pipe is controlled according to the opening and closing of a control valve, the end heating assembly is communicated with the high-pressure gas refrigerant flow pipe and the medium-pressure liquid refrigerant flow pipe, and the end refrigerating assembly is communicated with the medium-pressure liquid refrigerant flow pipe and the low-pressure gas refrigerant flow pipe. The beneficial effect is that one system has the functions of single cold, single heat, partial end refrigeration and partial end heating, and the same end can be converted between refrigeration and heating modes at any time, the bidirectional evaporation heat exchanger is switched to the refrigeration or heating mode according to the cold and heat demand of the whole system, and the cold and heat demand of the whole system is balanced. The power consumption is greatly reduced, and energy saving and environmental protection are truly realized.

Description

Technical Field

[0001] This invention relates to the field of air conditioning, and in particular to a single-stage subcritical carbon dioxide multi-split air conditioning system with balanced cooling and heating and a control method thereof. Background Technology

[0002] In addressing climate change and reducing carbon emissions, the construction industry is becoming a major force. Statistics show that building energy consumption accounts for about one-third of total societal energy consumption. Reducing this portion of energy consumption will significantly improve the overall energy situation of society, and at the same time, it has a very significant effect on energy conservation, emission reduction, and environmental protection. Vigorously promoting energy-efficient buildings, through measures such as raising energy-saving standards, implementing renovation projects, strengthening supervision, and promoting renewable energy, to continuously improve building energy efficiency has become a trend. Air conditioning energy consumption accounts for a considerable proportion of building energy consumption. Every winter and summer is the peak season for air conditioning use. Given the current energy shortage, high energy consumption, and prominent environmental pollution problems, energy conservation and emission reduction are essential for sustainable social development. The main components of existing multi-split air conditioners include a compressor for heating and a condenser for cooling. Their heat exchange principle is as follows: the compressor compresses the refrigerant (ammonia or Freon) into a high-pressure saturated gas, which is then condensed by the condenser. Because condensed ammonia or Freon cannot flow quickly through pipes, it must first be throttled by a throttling device before entering the evaporator and being cooled to the set temperature before being delivered to energy-consuming components for heat exchange. This means that during heat exchange, the refrigerant must first be compressed to a temperature higher than the set temperature before cooling, significantly increasing the energy consumption of the compressor and condenser, resulting in low heat exchange efficiency. Furthermore, Freon emissions exacerbate the greenhouse effect, and ammonia is prone to explosion, contradicting the national principles of environmental protection, energy conservation, and safety.

[0003] As living standards improve, the demand for cooling and heating within the same building is also changing. Multi-split air conditioning systems utilize a cooling cycle to cool or heat indoor spaces, providing unified cooling in summer and unified heating in winter—this is the basic function of air conditioning. However, this also brings a problem: once cooling is turned on, all air conditioners are in cooling mode, and if heating is turned on, all air conditioners are in heating mode. During transitional seasons, such as in southern China where the weather fluctuates between hot and cold, different groups of people have different temperature comfort needs. For example, physically fit middle-aged and young adults may feel a bit hot and need to turn on the air conditioning for cooling, while the elderly and children may feel cold and need heating. Currently, most ordinary multi-split air conditioning units on the market can only achieve a single cooling or heating mode. If it is necessary to simultaneously cool and heat different rooms within a single system, two separate air conditioning systems must be installed, increasing construction costs.

[0004] Therefore, the motivation for this invention is to provide a single-stage subcritical carbon dioxide multi-split system that can provide cooling while also achieving convenient switching between cooling and heating, balanced utilization of cooling and heating, and energy saving and environmental protection. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide a single-stage subcritical carbon dioxide multi-split air conditioning system and control method that can provide cooling while also providing heating, convenient switching between cooling and heating, balanced utilization of cooling and heating, and energy saving and environmental protection.

[0006] The single-stage subcritical carbon dioxide multi-split air conditioning system for balanced cooling and heating provided by this invention has the following technical solution:

[0007] A single-stage subcritical carbon dioxide multi-split air conditioning system for balanced heating and cooling includes a bidirectional evaporative heat exchanger, a compressor, a high-pressure gas refrigerant circulation pipe, a medium-pressure liquid refrigerant circulation pipe, and a low-pressure gas refrigerant circulation pipe. The compressor's suction end is connected to the low-pressure gas refrigerant circulation pipe, and the compressor's discharge end is connected to the high-pressure gas refrigerant circulation pipe. The bidirectional evaporative heat exchanger is equipped with a first port and a second port. The first port is connected to both the high-pressure and low-pressure gas refrigerant circulation pipes via control valves. The connection status between the first port and the high-pressure and low-pressure gas refrigerant circulation pipes is controlled by the opening and closing of the control valves. The second port is connected to the medium-pressure liquid refrigerant circulation pipe. The terminal heating components are connected to both the high-pressure and medium-pressure liquid refrigerant circulation pipes, and the terminal cooling components are connected to both the medium-pressure liquid refrigerant circulation pipe and the low-pressure gas refrigerant circulation pipe.

[0008] Furthermore, the compressor, bidirectional evaporator heat exchanger, and terminal components of the balanced system constitute a single-stage carbon dioxide circulation system, which operates below the critical point of the condensation temperature.

[0009] Furthermore, the terminal components that need to switch between cooling and heating modes control the connection status between the terminal components and the high-pressure gas refrigerant flow pipe and the low-pressure gas refrigerant flow pipe by controlling the opening and closing of the control valves, thereby completing the switching between cooling and heating.

[0010] Furthermore, a liquid receiver is installed between the second port of the bidirectional evaporative heat exchanger and the medium-pressure liquid refrigerant flow pipe, and a regulating valve is installed between the liquid receiver and the second port.

[0011] Furthermore, the control valve is a three-way control valve or two regulating valve assemblies installed on different pipelines.

[0012] Furthermore, the bidirectional evaporative heat exchanger includes a closed shell, a centrifugal fan, a heat exchange tube assembly, and an atomizing nozzle. A centrifugal fan is installed on one side of the closed shell, and the atomizing nozzle and the heat exchange tube assembly are installed inside the closed shell. The centrifugal fan is used to draw water vapor or air from inside the shell. The water vapor or air inside the closed shell exchanges heat with the refrigerant flowing in the heat exchange tube assembly. An electric roller shutter is installed on one side of the closed shell. The opening or closing of the electric roller shutter is used to switch the heat exchanger between heating and cooling modes.

[0013] Furthermore, a mesh panel is installed on one side of the roller shutter.

[0014] Furthermore, the terminal unit includes a fan coil unit capable of switching between cooling and heating modes. One interface of the fan coil unit is connected to a medium-pressure liquid refrigerant circulation pipe, with a regulating valve installed on the pipe. The other interface is connected to both a high-pressure gas refrigerant circulation pipe and a low-pressure gas refrigerant circulation pipe via control valves. The connection status between this port and the high-pressure and low-pressure gas refrigerant circulation pipes is controlled by the opening and closing of the control valves. A thermometer and a regulating valve are installed at the interface of the fan coil unit.

[0015] Furthermore, the terminal unit includes underfloor heating that only provides heating. The inlet of the underfloor heating system is connected to a high-pressure gaseous refrigerant pipe, and the outlet is connected to a medium-pressure liquid refrigerant pipe. A regulating valve is installed at the inlet of the underfloor heating system, and a check valve, a regulating valve, and a thermometer are installed at the outlet.

[0016] Furthermore, underfloor heating is a parallel multi-row pipe system installed in multiple rooms. The underfloor heating pipes include a gas supply pipe, a return pipe, and several branch pipes. The branch pipes bend outwards in multiple turns and coil within the floor. The floor consists of a concrete slab, a reflective layer, a wire mesh, a heat storage layer, and a tile layer laid in sequence. The branch pipes are fixed to the wire mesh by clamps and abut against the coil layer. The reflective layer is made of aluminum foil or extruded polystyrene insulation board with aluminum foil. The heat storage layer is made of a mixture of pebbles, sand, and cement.

[0017] Furthermore, the terminal includes a domestic hot water tank that only provides heating. The inlet of the domestic hot water tank is connected to a high-pressure gaseous refrigerant flow pipe, and the outlet is connected to a medium-pressure liquid refrigerant flow pipe. A regulating valve is installed at the inlet of the domestic hot water tank, and a regulating valve and a thermometer are installed at the outlet.

[0018] Furthermore, the terminal includes a cold and heat storage device capable of switching between cooling and heating modes. One interface of the cold and heat storage device is connected to a medium-pressure liquid refrigerant circulation pipe, and a regulating valve is installed on the pipe. The other interface is connected to a high-pressure gas refrigerant circulation pipe and a low-pressure gas refrigerant circulation pipe respectively through a control valve. The connection status between this port and the high-pressure gas refrigerant circulation pipe and the low-pressure gas refrigerant circulation pipe is controlled by the opening and closing of the control valve. A thermometer is installed at the interface of the cold and heat storage device.

[0019] Furthermore, the terminal includes an infrared radiation collector, the inlet of which is connected to a medium-pressure liquid refrigerant flow pipe, a regulating valve is installed on the pipe, and the outlet is connected to a low-pressure gas refrigerant flow pipe.

[0020] Furthermore, the terminal includes a wine cooler heat exchanger that only refrigerates. The inlet end of the wine cooler heat exchanger is connected to a medium-pressure liquid refrigerant flow pipe, and a regulating valve is installed on the pipe. The outlet end is connected to a low-pressure gas refrigerant flow pipe.

[0021] Furthermore, the regulating valve is a solenoid valve or an electronic expansion valve.

[0022] The control method for a single-stage subcritical CO2 multi-split air conditioning system with balanced heating and cooling involves setting the compressor's discharge and suction pressures. The discharge pressure determines the system's heating capacity, while the suction pressure determines its cooling capacity. The control module monitors whether the compressor's discharge and suction pressures are within the set range. If either the discharge or suction pressure is outside the set range, the system first checks whether the heat exchange or cooling terminal has reached its set operating state. If not, the system activates the number of heat exchange or cooling terminals to ensure the compressor's discharge and suction pressures are within the set range. If both the heat exchange and cooling terminals are in their set operating states, the system controls one or more of the following: a bidirectional evaporative heat exchanger, a cold storage heat accumulator, or an infrared radiation collector, to operate in heating mode to ensure the compressor's discharge pressure is within the set range; or it controls the bidirectional evaporative heat exchanger or the cold storage heat accumulator to operate in cooling mode to ensure the compressor's suction pressure is within the set range.

[0023] Furthermore, when the bidirectional evaporative heat exchanger is used for cooling, the two ends of the bidirectional evaporative heat exchanger are connected to the high-pressure gas refrigerant flow pipe and the medium-pressure liquid refrigerant flow pipe respectively through the control valve. The electric roller shutter is closed and no air is introduced, the high-pressure atomized water is running, and the bidirectional evaporative heat exchanger is used as a flash condenser. When the bidirectional evaporative heat exchanger is used for heating, the two ends of the bidirectional evaporative heat exchanger are connected to the low-pressure gas refrigerant flow pipe and the medium-pressure liquid refrigerant flow pipe respectively through the control valve. The electric roller shutter is retracted and air is introduced, the high-pressure atomized water is closed, and the bidirectional evaporative heat exchanger is used as an evaporator.

[0024] Furthermore, when the cold storage and heat storage device is used for heat storage and cooling, the two ends of the cold storage and heat storage device are connected to the high-pressure gas refrigerant flow pipe and the medium-pressure liquid refrigerant flow pipe respectively through the control valve; when the cold storage and heat storage device is used for cooling and heating, the two ends of the cold storage and heat storage device are connected to the low-pressure gas refrigerant flow pipe and the medium-pressure liquid refrigerant flow pipe respectively through the control valve.

[0025] Furthermore, when the infrared radiation collector needs to heat, the regulating valve on the infrared radiation collector pipe opens; when it does not need to heat, the regulating valve on the infrared radiation collector pipe closes.

[0026] The implementation of this invention has the following technical effects:

[0027] This invention relates to a single-stage subcritical carbon dioxide multi-split air conditioning system with a balanced cooling and heating configuration. By incorporating high-pressure gas refrigerant, medium-pressure liquid refrigerant, and low-pressure gas refrigerant flow pipes, and by improving the connection methods of the bidirectional evaporative heat exchanger, compressor, and the high, medium, and low-pressure pipes, as well as the connection methods of the terminal heating and cooling components, this system can achieve multiple operating modes: independent cooling, independent heating, partial terminal cooling and partial terminal heating, and the ability for a single terminal to switch between cooling and heating modes at any time. This enhances the overall operational diversity of the multi-split air conditioning system without adding complex refrigerant switching pipelines, addressing the different comfort needs of different groups and the cooling and heating requirements of different terminals. In other words, a single system solves the various cooling and heating needs of a building complex. More advantageously, the heat from the cooling terminals can be used to provide heat to the heating terminals, and vice versa. The bidirectional evaporative heat exchanger switches between cooling and heating modes according to the overall system's cooling and heating needs, thus balancing the cooling and heating requirements of the entire system. By utilizing energy transfer and reuse methods, the system's efficiency is further improved, significantly reducing power consumption and truly achieving energy conservation and environmental protection. Furthermore, components such as thermal storage devices (e.g., thermal storage pools) and infrared radiation collectors can be installed to ensure the system's efficient and safe operation. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of a single-stage subcritical carbon dioxide multi-unit system for balanced cooling and heating, according to an embodiment of the present invention.

[0029] Figure 2 This is a schematic diagram of the bidirectional evaporative heat exchanger structure according to an embodiment of the present invention.

[0030] Figure 3 This is a schematic diagram showing the connection between the cooling and heating states of the bidirectional evaporative heat exchanger according to an embodiment of the present invention.

[0031] Figure 4 This is a schematic diagram showing the connection between the cooling and heating states of a fan coil unit according to an embodiment of the present invention.

[0032] Figure 5 This is a schematic diagram showing the connection between the heat storage state and the cold storage state of the heat storage device in an embodiment of the present invention.

[0033] In the diagram: 1. Two-way evaporative heat exchanger; 100. Closed shell; 101. Centrifugal fan; 102. Heat exchange tube assembly; 103. Atomizing nozzle; 104. Electric roller shutter; 105. Mesh plate; 106. First port; 107. Second port; 2. Compressor; 3. High-pressure gas refrigerant flow pipe; 4. Medium-pressure liquid refrigerant flow pipe; 5. Low-pressure gas refrigerant flow pipe; 6. Liquid receiver; 7. Regulating valve; 8. Control valve; 9. Thermometer; 10. Fan coil unit; 11. Underfloor heating; 12. Domestic hot water tank; 13. Cold and heat storage accumulator; 14. Infrared radiation collector; 15. Wine cabinet heat exchanger. Detailed Implementation

[0034] The present invention will now be described in detail with reference to the embodiments and accompanying drawings. It should be noted that the described embodiments are only intended to facilitate the understanding of the present invention and do not constitute any limitation thereof.

[0035] See Figure 1 As shown, the single-stage subcritical carbon dioxide multi-split air conditioning system provided in this embodiment includes a bidirectional evaporative heat exchanger 1, a compressor 2, a high-pressure gas refrigerant flow pipe 3, a medium-pressure liquid refrigerant flow pipe 4, and a low-pressure gas refrigerant flow pipe 5. The suction end of the compressor 2 is connected to the low-pressure gas refrigerant flow pipe 5, and the discharge end of the compressor 2 is connected to the high-pressure gas refrigerant flow pipe 3. The bidirectional evaporative heat exchanger 1 is provided with a first port 106 and a second port 107. The first port 106 is connected to the high-pressure gas refrigerant flow pipe 3 and the low-pressure gas refrigerant flow pipe 5 respectively through a control valve 8. The connection state between the first port 106 and the high-pressure gas refrigerant flow pipe 3 and the low-pressure gas refrigerant flow pipe 5 is controlled by the opening and closing of the control valve 8. The second port 107 is connected to the medium-pressure liquid refrigerant flow pipe 4. The terminal heating components are connected to the high-pressure gas refrigerant flow pipe 3 and the medium-pressure liquid refrigerant flow pipe 4 respectively, and the terminal cooling components are connected to the medium-pressure liquid refrigerant flow pipe 4 and the low-pressure gas refrigerant flow pipe 5 respectively. The bidirectional evaporative heat exchanger 1 is a single component or a combination of multiple refrigeration and heating components capable of dynamically switching between cooling and heating modes. The terminal component requiring switching between cooling and heating modes controls the connection between the terminal component and the high-pressure gas refrigerant flow pipe 3 and the low-pressure gas refrigerant flow pipe 5 via the opening and closing of the control valve 8, thus completing the switching between cooling and heating. A liquid receiver 6 is installed between the second port 107 of the bidirectional evaporative heat exchanger 1 and the medium-pressure liquid refrigerant flow pipe 4. The liquid receiver 6 stores liquid refrigerant, and a regulating valve 7 is installed between the liquid receiver 6 and the second port 107. The control valve 8 is either a three-way control valve or two sets of regulating valves 7 installed on different pipelines.

[0036] The single-stage subcritical carbon dioxide multi-split air conditioning system of this invention, through the setting of a high-pressure gas refrigerant flow pipe 3, a medium-pressure liquid refrigerant flow pipe 4, and a low-pressure gas refrigerant flow pipe 5, and the improved connection methods of the bidirectional evaporative heat exchanger 1, compressor 2, and the high, medium, and low-pressure pipes, as well as the connection methods of the terminal heating components and terminal cooling components, can realize multiple operating modes in a single system, including independent cooling, independent heating, partial terminal cooling and partial terminal heating, and the ability for the same terminal to switch between cooling and heating modes at any time. This enhances the overall operational diversity of the multi-split air conditioning system without adding complex refrigerant switching pipelines, addressing the different comfort needs of different groups and the cooling and heating needs of different terminals. In other words, a single system solves the various cooling and heating needs of a building complex. More advantageously, the heat from the cooling terminals can be used to provide heat to the heating terminals, and vice versa. The bidirectional evaporative heat exchanger 1 switches to cooling or heating mode according to the overall system's cooling and heating needs, balancing the cooling and heating requirements of the entire system. By utilizing energy transfer and reuse, the system efficiency is further improved, and power consumption is greatly reduced, truly achieving energy saving and environmental protection. Furthermore, components such as cold and heat storage devices (e.g., cold and heat storage pool 13) and infrared radiation collectors 14 can be installed to ensure the efficient and safe operation of the system.

[0037] Furthermore, the compressor 2, bidirectional evaporator heat exchanger 1, and terminal units of the equalization system constitute a single-stage carbon dioxide circulation system. This single-stage carbon dioxide circulation system operates below the critical point of the condensation temperature (subcritical). In this embodiment, carbon dioxide is preferably used as the refrigerant for the equalization system. Utilizing carbon dioxide as the working fluid offers advantages such as large pressure differential, good fluidity, low density, and transcritical phase change, making it particularly effective for high-rise buildings. The term "single-stage" in this single-stage carbon dioxide circulation system distinguishes it from a cascade system, as it uses only carbon dioxide as the working fluid and does not require cascading. The equalization system in this embodiment, using carbon dioxide as the working fluid, can provide cooling or heating to higher floors vertically and can circulate over longer distances in horizontal applications, enabling more indoor units to operate.

[0038] A bidirectional evaporative heat exchanger refers to a device capable of switching between cooling and heating modes, or a combination of a separate cooling component and a separate heating component. Preferably, see [link to relevant documentation]. Figure 2 and Figure 3As shown, the bidirectional evaporative heat exchanger of this embodiment includes a closed shell 100, a centrifugal fan 101, a heat exchange tube assembly 102, and an atomizing nozzle 103. The centrifugal fan 101 is located on one side of the closed shell 100. The atomizing nozzle 103 and the heat exchange tube assembly 102 are disposed inside the closed shell 100. The centrifugal fan 101 is used to draw water vapor or air from the shell. The water vapor or air inside the closed shell 100 exchanges heat with the refrigerant flowing in the heat exchange tube assembly 102. An electric roller shutter 104 is located on one side of the closed shell 100. Opening or closing the electric roller shutter 104 switches the heat exchanger between heating and cooling states. By using the electric roller shutter 104 and coordinating with the refrigerant flow direction, a single device can switch between heating and cooling states, reducing equipment costs and system complexity. The atomizing nozzle 103 is connected to a high-pressure water pipe and is used to generate atomized water. Centrifugal fan 101 is a backward-curved centrifugal fan. A grid plate 105 is installed on one side of the roller shutter. In cooling mode, the water vapor after heat exchange in the bidirectional evaporative heat exchanger is not circulated or recovered, but is directly discharged into the atmosphere. Because the water droplets mainly convert heat into internal energy during decomposition, the discharged water vapor temperature is not high and will not produce a heat island effect. During cooling, heat exchange takes place within the closed shell 100 with almost no air intake. When the outside temperature and humidity are both high, the heat exchange effect is not affected by the outside temperature and humidity.

[0039] Figure 3 The left frame shows a connection diagram of the bidirectional evaporative heat exchanger in cooling mode. The dotted line indicates that it is not connected, and the arrow indicates the direction of refrigerant flow. During cooling (such as in summer), the electric roller shutter 104 is closed and no air is introduced. The high-pressure atomized water is running, and the bidirectional evaporative heat exchanger is used as a flash condenser. After the electric roller shutter 104 is closed, the centrifugal fan 101 continuously discharges the water vapor in the closed shell 100 to the outside of the closed shell 100, so that the required negative pressure environment is formed in the containment chamber. The atomized water generated by the atomizing nozzle 103 exchanges heat with the high-temperature refrigerant in the heat exchange tube group 102 in the negative pressure environment of the containment chamber. The water vapor flashes rapidly, changing from water mist to steam, absorbing heat, which lowers the ambient temperature in the closed shell 100, and the refrigerant liquefies and condenses. Figure 3 The right frame shows a connection diagram of the bidirectional evaporative heat exchanger in heating mode. The dotted line indicates that it is not connected, and the arrow indicates the direction of refrigerant flow. When heating (such as in winter), the electric roller shutter 104 retracts the air intake, the high-pressure atomizing water is shut off, and the bidirectional evaporative heat exchanger is used as an evaporator. After the electric roller shutter 104 is opened and closed, the outside air exchanges heat with the low-temperature refrigerant in the heat exchange tube group 102, and the refrigerant vaporizes and evaporates.

[0040] See Figure 1 and Figure 4As shown, the terminal includes a fan coil unit 10 capable of switching between cooling and heating modes. One interface of the fan coil unit 10 is connected to a medium-pressure liquid refrigerant flow pipe 4, with a regulating valve 7 installed on the pipe. The other interface is connected to a high-pressure gas refrigerant flow pipe 3 and a low-pressure gas refrigerant flow pipe 5 via a control valve 8. The connection status between this port and the high-pressure gas refrigerant flow pipe 3 and the low-pressure gas refrigerant flow pipe 5 is controlled by the opening and closing of the control valve 8. A thermometer 9 and the regulating valve 7 are installed at the interface of the fan coil unit 10. The thermometer 9 is used to provide temperature feedback and adjust the cooling and heating capacity. Figure 4 The left frame shows a connection diagram of fan coil unit 10 in cooling mode. Dashed lines indicate disconnection, and arrows indicate the direction of refrigerant flow. Figure 4 The right frame shows a connection diagram of fan coil unit 10 in heating mode. Dashed lines indicate disconnection, and arrows indicate the direction of refrigerant flow.

[0041] See Figure 1 As shown, the terminal includes a floor heating system 11 that only provides heating. The inlet of the floor heating system 11 is connected to a high-pressure gas refrigerant flow pipe 3, and the outlet is connected to a medium-pressure liquid refrigerant flow pipe 4. A regulating valve 7 is installed at the inlet of the floor heating system 11, and a one-way valve, regulating valve 7, and thermometer 9 are installed at the outlet. The one-way valve prevents backflow of liquid refrigerant, and the thermometer 9 is used to provide temperature feedback and adjust the heating capacity. The floor heating system 11 is a parallel multi-row pipe system installed in multiple rooms. The floor heating pipes include a gas supply pipe, a liquid return pipe, and several branch pipes. The branch pipes continuously bend outwards multiple times and coil within the floor. The floor includes a concrete slab, a reflective layer, a wire mesh, a heat storage layer, and a tile layer laid in sequence. The branch pipes are fixed to the wire mesh by clamps and abut against the coil layer. Specifically, the reflective layer is made of aluminum foil or extruded insulation board with aluminum foil. The aluminum foil reflects and transfers the heat radiated by the branch pipes to the upper end of the reflective layer, achieving uniform heat conduction. The heat storage layer is composed of a mixture of pebbles, sand, and cement. The pebbles have good thermal conductivity and a smooth, non-angular surface, which helps protect the branch pipes while ensuring efficient heat transfer. Carbon dioxide is used as the heat transfer medium for the floor. Carbon dioxide has excellent thermal conductivity; during heat transfer, it enters the branch pipes from the supply pipe in gaseous form. After exchanging heat with the floor within the branch pipes, its temperature decreases, and it transforms into a liquid, flowing out through the return pipe. Compared to traditional water-based underfloor heating, carbon dioxide directly heats the floor, eliminating the intermediate step of Freon heat transfer to water, which then transfers heat to the floor. This improves heat transfer efficiency, reduces heat loss, provides a more comfortable indoor temperature, and distributes heat more evenly throughout the room, thus increasing heat utilization efficiency and reducing the operating costs of underfloor heating.

[0042] See Figure 1As shown, the terminal includes a domestic hot water tank 12 for heating only. The inlet of the domestic hot water tank 12 is connected to the high-pressure gas refrigerant flow pipe 3, and the outlet is connected to the medium-pressure liquid refrigerant flow pipe 4. A regulating valve 7 is installed at the inlet of the domestic hot water tank 12, and a regulating valve 7 and a thermometer 9 are installed at the outlet. The thermometer 9 is used to provide temperature feedback and adjust the heating capacity. During normal system operation or when hot water demand is low, the sensible heat from the exhaust of the compressor 2 is recovered for domestic hot water production. The inlet and outlet regulating valves 7 of the domestic hot water tank 12 are normally open and not adjusted. When the hot water demand is high and cannot meet the usage requirements, the inlet regulating valve 7 of the domestic hot water tank 12 is normally open, and the outlet regulating valve 7 is adjusted according to the parameter value set by the outlet temperature sensor.

[0043] See Figure 1 and Figure 5 As shown, the terminal includes a cold storage / heat storage unit 13 capable of switching between cooling and heating modes. One interface of the cold storage / heat storage unit 13 is connected to a medium-pressure liquid refrigerant flow pipe 4, with a regulating valve 7 installed on the pipe. The other interface is connected to a high-pressure gas refrigerant flow pipe 3 and a low-pressure gas refrigerant flow pipe 5 via a control valve 8. The connection status between this port and the high-pressure gas refrigerant flow pipe 3 and the low-pressure gas refrigerant flow pipe 5 is controlled by the opening and closing of the control valve 8. A thermometer 9 is installed at the interface of the cold storage / heat storage unit 13. The thermometer 9 is used to provide temperature feedback and adjust the cooling and heating capacity. Figure 5 The left frame shows a connection diagram of the cold and heat storage unit 13 in its heat storage state. Dashed lines indicate disconnection, and arrows indicate the direction of refrigerant flow. Figure 5 The right frame shows a connection diagram of the cold and heat storage unit 13 in its cold storage state. Dashed lines indicate disconnections, and arrows indicate the direction of refrigerant flow. The cold and heat storage unit can be a swimming pool. The system not only heats the pool water to a suitable swimming temperature but also stores cold and heat. When the room's cooling demand is high and the system cannot meet the needs, the pool acts as a condenser, releasing heat from the room. When the room's heating demand is high and the system cannot meet the needs, the pool acts as an evaporator, extracting heat from the pool to supply the room.

[0044] See Figure 5 As shown, the terminal includes an infrared radiation collector 14. The inlet of the infrared radiation collector 14 is connected to a medium-pressure liquid refrigerant flow pipe 4, and a regulating valve 7 is installed on the pipe. The outlet is connected to a low-pressure gas refrigerant flow pipe 5. According to the system's heat demand, the connection state of the infrared radiation collector 14 is controlled by the regulating valve 7 to provide heat to the system. The infrared radiation collector 14 can collect a portion of the heat through thermal radiation and can also utilize an air-source heat pump to collect heat, ensuring the system's heating requirements are met. In this embodiment, the infrared radiation collector 14 includes a protective plate, a heat-absorbing plate, and a core. The heat-absorbing plate is located between the core and the protective plate. The core includes a heat exchange medium inlet and a heat exchange medium outlet. The heat-absorbing plate is used to transfer the absorbed heat to the refrigerant circulating within the core.

[0045] See Figure 1 As shown, the terminal includes a wine cooler heat exchanger 15 that only provides cooling. The inlet of the wine cooler heat exchanger 15 is connected to a medium-pressure liquid refrigerant flow pipe 4, and a regulating valve 7 is installed on the pipe. The outlet is connected to a low-pressure gaseous refrigerant flow pipe 5. The refrigerant flow rate is controlled by the regulating valve 7 according to the cooling demand of the wine cooler heat exchanger 15 to achieve cooling.

[0046] In this embodiment, the regulating valve 7 can be either a solenoid valve or an electronic expansion valve.

[0047] This embodiment also provides a control method for a single-stage subcritical carbon dioxide multi-split air conditioning system with balanced heating and cooling. The system sets the discharge pressure and suction pressure of compressor 2. The discharge pressure determines the heating capacity of the balanced system, and the suction pressure determines the cooling capacity. The control module monitors whether the compressor's discharge pressure and suction pressure are within the set range. If the discharge pressure or suction pressure of compressor 2 is not within the set range, it first determines whether the heat exchange terminal or cold exchange terminal has reached the set operating state (i.e., whether the set terminal temperature has been reached). If the operating state has not been reached, the number of heat exchange terminals or cold exchange terminals is increased to ensure that the compressor's discharge pressure and suction pressure are within the set range. If both the heat exchange terminals and cold exchange terminals are in the set operating state, one or more of the bidirectional evaporative heat exchanger 1, the cold storage heat storage unit 13, and the infrared radiation collector 14 are controlled to be in heating mode to ensure that the compressor's discharge pressure is within the set range. Alternatively, the bidirectional evaporative heat exchanger 1 or the cold storage heat storage unit 13 is controlled to be in cooling mode to ensure that the compressor's suction pressure is within the set range. Multiple cooling and heating terminals can be assigned priority weights, ensuring that the cooling and heating terminals ranked higher reach their set temperatures first, thus improving user comfort. The system maintains thermal equilibrium by controlling the cooling and heating states of equalization devices such as the bidirectional evaporative heat exchanger 1, the cold and heat storage tank 2, and the infrared radiation collector 14. Specifically, the system ensures that the suction and discharge pressures of compressor 2 remain constant, maintaining high-efficiency operation throughout. If either the suction or discharge pressure of compressor 2 is within the set range, the balanced system's operating state remains unchanged.

[0048] The balanced system prioritizes the use of a bidirectional evaporative heat exchanger to ensure that the compressor's suction and discharge pressures remain within the set range during switching between cooling and heating modes. Furthermore, a thermal storage device plays a crucial balancing role. This storage device can be a swimming pool, utilizing the high latent heat of water for thermal storage, which is economical and convenient. The swimming pool can be set to a desired temperature range. When the balanced system has excess heat, it supplements the pool to heat it; when it has excess cooling, it supplements the pool to cool it. As needed, heat and cold can also be extracted from the pool for utilization. This ensures efficient operation of the balanced system without wasting excess heat or cold, allowing for the extraction of heat and cold as required. It can fully utilize off-peak electricity at night, reducing the impact on the local power grid. Infrared radiation collectors can also fully utilize daytime solar energy for heating.

[0049] Furthermore, when the bidirectional evaporative heat exchanger 1 is cooling, the two ends of the bidirectional evaporative heat exchanger 1 are connected to the high-pressure gas refrigerant flow pipe 3 and the medium-pressure liquid refrigerant flow pipe 4 respectively through the control valve. The electric roller shutter 104 is closed and no air is introduced. The high-pressure atomized water is running, and the bidirectional evaporative heat exchanger 1 is used as a flash condenser. When heating, the two ends of the bidirectional evaporative heat exchanger 1 are connected to the low-pressure gas refrigerant flow pipe 5 and the medium-pressure liquid refrigerant flow pipe 4 respectively through the control valve. The electric roller shutter 104 is retracted and air is introduced. The high-pressure atomized water is shut off, and the bidirectional evaporative heat exchanger 1 is used as an evaporator.

[0050] When the cold storage and heat storage device 13 is used for heat storage and cooling, the two ends of the cold storage and heat storage device 13 are connected to the high-pressure gas refrigerant flow pipe 3 and the medium-pressure liquid refrigerant flow pipe 4 respectively by the control valve; when the cold storage and heat storage device is used for cooling and heating, the two ends of the cold storage and heat storage device 13 are connected to the low-pressure gas refrigerant flow pipe 5 and the medium-pressure liquid refrigerant flow pipe 4 respectively by the control valve.

[0051] When the infrared radiation collector 14 needs to heat, the regulating valve on the pipe of the infrared radiation collector 14 is opened; when it does not need to heat, the regulating valve on the pipe of the infrared radiation collector 14 is closed.

[0052] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A single-stage subcritical carbon dioxide multi-split air conditioning system for balanced cooling and heating, characterized in that: The system includes a bidirectional evaporative heat exchanger, a compressor, a high-pressure gas refrigerant circulation pipe, a medium-pressure liquid refrigerant circulation pipe, and a low-pressure gas refrigerant circulation pipe. The compressor's suction end is connected to the low-pressure gas refrigerant circulation pipe, and the compressor's discharge end is connected to the high-pressure gas refrigerant circulation pipe. The bidirectional evaporative heat exchanger has a first port and a second port. The first port is connected to both the high-pressure and low-pressure gas refrigerant circulation pipes via control valves. The connection status between the first port and the high-pressure and low-pressure gas refrigerant circulation pipes is controlled by the opening and closing of the control valves. The second port is connected to the medium-pressure liquid refrigerant circulation pipe. Terminal heating components are connected to both the high-pressure and medium-pressure liquid refrigerant circulation pipes, and terminal cooling components are connected to both the medium-pressure liquid refrigerant circulation pipe and the low-pressure gas refrigerant circulation pipe.

2. The single-stage subcritical carbon dioxide multi-unit mixed cooling and heating equilibrium system according to claim 1, characterized in that: The compressor, bidirectional evaporator heat exchanger, and terminal components of the balanced system constitute a single-stage carbon dioxide circulation system, which operates below the critical point of the condensation temperature.

3. The single-stage subcritical carbon dioxide multi-unit mixed cooling and heating equilibrium system according to claim 1, characterized in that: Terminal components that need to switch between cooling and heating modes control the connection between the terminal component and the high-pressure gas refrigerant flow pipe and the low-pressure gas refrigerant flow pipe by controlling the opening and closing of control valves, thereby completing the switching between cooling and heating modes.

4. The single-stage subcritical carbon dioxide multi-unit mixed cooling and heating equilibrium system according to claim 1, characterized in that: A liquid receiver is provided between the second port of the bidirectional evaporative heat exchanger and the medium-pressure liquid refrigerant flow pipe, and a regulating valve is provided between the liquid receiver and the second port.

5. The single-stage subcritical carbon dioxide multi-unit mixed cooling and heating equilibrium system according to claim 1, characterized in that: The control valve is a three-way control valve or two regulating valve groups installed on different pipelines.

6. The single-stage subcritical carbon dioxide multi-unit mixed cooling and heating equilibrium system according to claim 1, characterized in that: The bidirectional evaporative heat exchanger includes a closed shell, a centrifugal fan, a heat exchange tube assembly, and an atomizing nozzle. A centrifugal fan is installed on one side of the closed shell, and the atomizing nozzle and the heat exchange tube assembly are installed inside the closed shell. The centrifugal fan is used to draw water vapor or air from inside the shell. The water vapor or air inside the closed shell exchanges heat with the refrigerant flowing in the heat exchange tube assembly. An electric roller shutter is installed on one side of the closed shell. Opening or closing the electric roller shutter is used to switch the heat exchanger between heating and cooling modes.

7. The single-stage subcritical carbon dioxide multi-unit mixed cooling and heating equilibrium system according to claim 6, characterized in that: A grid panel is installed on one side of the roller shutter.

8. The single-stage subcritical carbon dioxide multi-unit mixed cooling and heating equilibrium system according to claim 1, characterized in that: The terminal unit includes a fan coil unit capable of switching between cooling and heating modes. One interface of the fan coil unit is connected to a medium-pressure liquid refrigerant circulation pipe, and a regulating valve is installed on the pipe. The other interface is connected to a high-pressure gas refrigerant circulation pipe and a low-pressure gas refrigerant circulation pipe respectively through a control valve. The connection status of this port with the high-pressure gas refrigerant circulation pipe and the low-pressure gas refrigerant circulation pipe is controlled by the opening and closing of the control valve. A thermometer and a regulating valve are installed at the interface of the fan coil unit.

9. The single-stage subcritical carbon dioxide multi-unit mixed cooling and heating equilibrium system according to claim 1, characterized in that: The terminal includes underfloor heating that only provides heating. The inlet of the underfloor heating system is connected to a high-pressure gas refrigerant circulation pipe, and the outlet is connected to a medium-pressure liquid refrigerant circulation pipe. The inlet of the underfloor heating system is equipped with a regulating valve, and the outlet is equipped with a check valve, a regulating valve, and a thermometer.

10. The single-stage subcritical carbon dioxide multi-unit mixed cooling and heating equilibrium system according to claim 9, characterized in that: Underfloor heating is a parallel multi-row pipe system installed in multiple rooms. The underfloor heating pipes include a gas supply pipe, a return pipe, and several branch pipes. The branch pipes bend outwards in multiple turns and coil inside the floor. The floor consists of a concrete slab, a reflective layer, a wire mesh, a heat storage layer, and a tile layer laid in sequence. The branch pipes are fixed to the wire mesh with clamps and abut against the coil layer. The reflective layer is made of aluminum foil or extruded polystyrene insulation board with aluminum foil. The heat storage layer is made of a mixture of pebbles, sand, and cement.

11. The single-stage subcritical carbon dioxide multi-unit mixed cooling and heating equilibrium system according to claim 1, characterized in that: The terminal includes a domestic hot water tank that only provides heating. The inlet of the domestic hot water tank is connected to a high-pressure gas refrigerant flow pipe, and the outlet is connected to a medium-pressure liquid refrigerant flow pipe. A regulating valve is installed at the inlet of the domestic hot water tank, and a regulating valve and a thermometer are installed at the outlet.

12. The single-stage subcritical carbon dioxide multi-unit mixed cooling and heating equilibrium system according to claim 1, characterized in that: The terminal includes a cold and heat storage device capable of switching between cooling and heating modes. One interface of the cold and heat storage device is connected to a medium-pressure liquid refrigerant circulation pipe, and a regulating valve is installed on the pipe. The other interface is connected to a high-pressure gas refrigerant circulation pipe and a low-pressure gas refrigerant circulation pipe respectively through a control valve. The connection status of this port with the high-pressure gas refrigerant circulation pipe and the low-pressure gas refrigerant circulation pipe is controlled by the opening and closing of the control valve. A thermometer is installed at the interface of the cold and heat storage device.

13. The single-stage subcritical carbon dioxide multi-unit mixed cooling and heating equilibrium system according to claim 1, characterized in that: The terminal includes an infrared radiation collector. The inlet of the infrared radiation collector is connected to a medium-pressure liquid refrigerant flow pipe. A regulating valve is installed on the pipe, and the outlet is connected to a low-pressure gas refrigerant flow pipe.

14. The single-stage subcritical carbon dioxide multi-unit mixed cooling and heating equilibrium system according to claim 1, characterized in that: The terminal includes a wine cooler heat exchanger that only refrigerates. The inlet end of the wine cooler heat exchanger is connected to a medium-pressure liquid refrigerant flow pipe, and a regulating valve is installed on the pipe. The outlet end is connected to a low-pressure gas refrigerant flow pipe.

15. The single-stage subcritical carbon dioxide multi-unit mixed cooling and heating equilibrium system according to claim 4, characterized in that: The regulating valve is either a solenoid valve or an electronic expansion valve.

16. A control method for a single-stage subcritical carbon dioxide multi-unit mixing and heating balanced system, characterized in that: The discharge pressure and suction pressure of the compressor are set for the equalization system. The discharge pressure determines the heating capacity of the equalization system, and the suction pressure determines the cooling capacity of the equalization system. The control module monitors whether the discharge pressure and suction pressure of the compressor are within the set range. If the compressor's discharge pressure or suction pressure is not within the set range, first determine whether the heat exchange terminal or cold exchange terminal has reached the set operating state. If it has not reached the operating state, then increase the number of heat exchange terminals or cold exchange terminals to ensure that the compressor's discharge pressure and suction pressure are within the set range. If both the heat exchange terminal and cold exchange terminal are in the set operating state, then control one or more of the bidirectional evaporative heat exchanger, cold storage heat storage unit, and infrared radiation collector to be in heating mode to ensure that the compressor's discharge pressure is within the set range, or control the bidirectional evaporative heat exchanger or cold storage heat storage unit to be in cooling mode to ensure that the compressor's suction pressure is within the set range.

17. The control method for a single-stage subcritical carbon dioxide multi-unit mixed cooling and heating balanced system according to claim 16, characterized in that: When the bidirectional evaporative heat exchanger is used for cooling, the two ends of the bidirectional evaporative heat exchanger are connected to the high-pressure gas refrigerant flow pipe and the medium-pressure liquid refrigerant flow pipe respectively through the control valve. The electric roller shutter is closed and no air is introduced. The high-pressure atomized water is running, and the bidirectional evaporative heat exchanger is used as a flash condenser. When the bidirectional evaporative heat exchanger is used for heating, the two ends of the bidirectional evaporative heat exchanger are connected to the low-pressure gas refrigerant flow pipe and the medium-pressure liquid refrigerant flow pipe respectively through the control valve. The electric roller shutter is retracted and air is introduced. The high-pressure atomized water is closed, and the bidirectional evaporative heat exchanger is used as an evaporator.

18. The control method for a single-stage subcritical carbon dioxide multi-unit hybrid cooling and heating balanced system according to claim 16, characterized in that: When the cold storage and heat storage device is used for heat storage and cooling, the two ends of the cold storage and heat storage device are connected to the high-pressure gas refrigerant flow pipe and the medium-pressure liquid refrigerant flow pipe respectively by the control valve; when the cold storage and heat storage device is used for cooling and heating, the two ends of the cold storage and heat storage device are connected to the low-pressure gas refrigerant flow pipe and the medium-pressure liquid refrigerant flow pipe respectively by the control valve.

19. The control method for a single-stage subcritical carbon dioxide multi-unit mixed cooling and heating balanced system according to claim 16, characterized in that: When the infrared radiation collector needs to heat, the regulating valve on the infrared radiation collector pipe is opened; when it does not need to heat, the regulating valve on the infrared radiation collector pipe is closed.

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