Multi-split air conditioning system
By using CO2 as the refrigerant and heat transfer medium in a multi-split air conditioning system, separating the outdoor and indoor circuits and using the first heat exchanger for heat exchange, the high energy consumption, corrosion and scaling, and safety risks of traditional systems are solved, achieving efficient and safe cooling and heating.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-31
- Publication Date
- 2026-03-24
AI Technical Summary
Traditional air source heat pump chilled and hot water air conditioning heating systems suffer from high energy consumption, pipe corrosion and scaling, insensitive regulation, and difficulty in controlling low GWP refrigerant charge. In addition, multi-split systems face the safety risks of refrigerant leakage and high costs.
Using CO2 as both refrigerant and heat transfer medium, the system separates the outdoor refrigerant circuit from the indoor refrigerant circuit and utilizes a first heat exchanger for heat exchange, achieving both cooling and heating. This avoids low-GWP refrigerant from entering the room, reducing system costs and safety risks.
It improves system energy efficiency, reduces energy consumption, avoids pipe corrosion and scaling, enhances system safety and flexibility, solves the problem of controlling the charge amount of low GWP refrigerant, and reduces manufacturing costs.
Smart Images
Figure CN121720169A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of refrigeration and heating technology, and in particular to a multi-split air conditioning system. Background Technology
[0002] With increasing global demands for addressing climate change, technological innovation in air conditioning and heating systems has become a key focus. Traditional air-source heat pump chilled / hot water air conditioning systems commonly use water or antifreeze as the energy medium (i.e., the medium for distributing heat and cold). However, because this system utilizes temperature differences (sensible heat) to carry heat and cold, even with variable frequency drives for the energy medium pump, high energy consumption still exists to ensure sufficient head for unfavorable circuits, leading to reduced energy efficiency under partial load. Furthermore, the sensible heat energy medium must be kept at constant pressure. Since the constant pressure water supply device is connected to the atmosphere, problems such as pipe corrosion, scaling, clogged regulating valves, and poor adjustment sensitivity inevitably arise, making it difficult to adjust the required heat and cold as needed. This affects indoor comfort and reduces system energy efficiency.
[0003] Multi-split air conditioning systems are a typical type of air-source heat pump air conditioning system. Because they employ a direct expansion system, relying on the compressor's variable speed control to regulate cooling and heating capacity, and using electronic expansion valves to regulate the flow of phase-change refrigerant entering the indoor units, they can provide energy to rooms on demand. Due to their "partial time, partial space" energy supply characteristics, they have excellent energy-saving effects and are therefore widely used. Currently, multi-split systems have become the main form of commercial and residential air conditioning systems, accounting for approximately 50% of the output value of central air conditioning systems. However, multi-split systems currently commonly use R410A refrigerant, which, due to its Global Warming Potential (GWP) of 2100, is to be phased out according to the Kigali Amendment to the Montreal Protocol. However, many low-GWP refrigerants are flammable, increasing the difficulty of refrigerant charge management and leakage safety control in multi-split systems, making them unsuitable for large-capacity multi-split systems.
[0004] Carbon dioxide (CO2) is a high-pressure, environmentally friendly refrigerant or energy-carrying medium with a GWP of 1 and no flammability. When used as a refrigerant, its refrigeration and heat pump cycles are transcritical. Without auxiliary refrigeration and heat pump cycles, its system energy efficiency is low; moreover, the discharge pressure is as high as 10 MPa to 13 MPa, placing higher demands on the pressure-bearing capacity of pipelines, thus increasing the cost of the heat pump system. When used as an energy-carrying medium, CO2's temperature is near its critical temperature. Although its pressure is high, its specific heat or latent heat is large, its viscosity is low, and the pipeline friction resistance is small. Its energy consumption for distribution is significantly lower than that of energy-carrying media such as water or antifreeze. Furthermore, because it is a closed energy-carrying system, there are no corrosion or scaling problems in its pipeline system, effectively avoiding the problem of dirt clogging in electric or solenoid valves in its pipeline system, and improving the reliable regulation performance of valve components. Summary of the Invention
[0005] This invention provides a multi-split air conditioning system that uses CO2 as the cooling medium during cooling and as the heating medium during heating, retaining the "partial time, partial space" energy supply characteristic of multi-split systems, while reducing system costs and avoiding fire hazards.
[0006] This invention provides a multi-split air conditioning system, comprising: The first heat exchanger includes a first heat exchange channel and a second heat exchange channel; The first refrigerant circulation module has a first refrigerant circulation loop; the first refrigerant circulation loop is connected to the first heat exchange channel and is used for heat exchange with outdoor air; The second refrigerant circulation module has a carbon dioxide circulation loop; the carbon dioxide circulation loop is connected to the second heat exchange channel and is used to exchange heat with indoor air to cool or heat the room. In this process, the carbon dioxide in the carbon dioxide circulation loop exchanges heat with the first refrigerant in the first refrigerant circulation loop within the first heat exchanger.
[0007] According to the multi-split air conditioning system provided by the present invention, the first refrigerant circulation module includes: A first control valve, the first control valve having a first inlet, a first cooling port, a first heating port and a first outlet; Compressor and outdoor heat exchanger; The compressor's exhaust port is connected to the first inlet, the first cooling port is connected to the first outdoor inlet / outlet of the outdoor heat exchanger, the second outdoor inlet / outlet of the outdoor heat exchanger is connected to the first heating port through the first heat exchange channel, and the compressor's suction port is connected to the first outlet.
[0008] According to the multi-split air conditioning system provided by the present invention, the second refrigerant circulation module includes: The second control valve has a second inlet, a second cooling port, a second heating port, and a second outlet; Storage tank, circulating pump and indoor heat exchanger; The inlet of the liquid storage tank is connected to the second outlet, the outlet of the liquid storage tank is connected to the second inlet through the circulation pump, the second refrigeration port is connected to the first indoor inlet and outlet of the indoor heat exchanger through the second heat exchange channel, and the second indoor inlet and outlet of the indoor heat exchanger is connected to the second heating port.
[0009] The multi-split air conditioning system provided by the present invention further includes: The second heat exchanger includes a third heat exchange channel and a fourth heat exchange channel; the first heat exchange channel is connected to the first heating port through the third heat exchange channel; the second heat exchange channel is connected to the first indoor inlet and outlet through the fourth heat exchange channel.
[0010] The multi-split air conditioning system provided by the present invention further includes: The first subcooling heat exchanger includes a first subcooling heat exchange channel and a second subcooling heat exchange channel; the outlet of the liquid storage tank is connected to the circulating pump through the second subcooling heat exchange channel, and one end of the first subcooling heat exchange channel is connected to the suction port of the compressor. A first cooling check valve and a first heating check valve are provided. The inlet of the first cooling check valve is connected to the second outdoor inlet / outlet, and the inlet of the first heating check valve is connected to the first heat exchange channel. The outlets of both the first cooling check valve and the first heating check valve are connected to the other end of the first subcooling heat exchange channel via a second expansion valve.
[0011] The multi-split air conditioning system provided by the present invention further includes: The third subcooling heat exchanger includes a third subcooling heat exchange channel; the third subcooling heat exchange channel is installed inside the liquid storage tank; one end of the third subcooling heat exchange channel is connected to the suction port of the compressor. The second cooling check valve and the second heating check valve are provided. The inlet of the second cooling check valve is connected to the second outdoor inlet and outlet, and the inlet of the second heating check valve is connected to the first heat exchange channel. The outlets of the second cooling check valve and the second heating check valve are both connected to the other end of the third subcooling heat exchange channel through the second expansion valve.
[0012] According to the multi-split air conditioning system provided by the present invention, there are multiple indoor heat exchangers, and the first indoor inlet and outlet of each of the multiple indoor heat exchangers are connected to the second cooling port of the second control valve through the second heat exchange channel; the second indoor inlet and outlet of each of the indoor heat exchangers are connected to the second heating port of the second control valve through the indoor regulating valve.
[0013] According to the multi-split air conditioning system provided by the present invention, the second control valve is a four-way reversing valve.
[0014] According to the multi-split air conditioning system provided by the present invention, the second control valve is a reversing valve assembly, the reversing valve assembly comprising: A first valve body, one end of which is connected to the outlet of the circulating pump, and the other end of which is connected to the second indoor inlet and outlet of the indoor heat exchanger; The second valve body has one end connected to the second heat exchange channel and the other end connected to the inlet of the storage tank. The third valve body has one end connected to the inlet / outlet of the second chamber and the other end connected to the inlet of the storage tank. The fourth valve body has one end connected to the outlet of the circulating pump and the other end connected to the second heat exchange channel.
[0015] According to the multi-split air conditioning system provided by the present invention, the first control valve is a four-way reversing valve.
[0016] The multi-split air conditioning system provided by this invention separates the outdoor refrigerant circuit (i.e., the first refrigerant circulation circuit) from the indoor refrigerant circuit (i.e., the carbon dioxide circulation circuit). It achieves both cooling and heating of the indoor space through heat exchange between the first refrigerant and carbon dioxide in the first heat exchanger. This avoids the entry of flammable low Global Warming Potential (GWP) refrigerants into the indoor space, effectively solving the problems of charge quantity control and system capacity limitations when using low GWP refrigerants, as well as the secondary substitution challenges associated with low GWP refrigerants. It also reduces reliance on the research and development of new refrigerants and the associated environmental risks. Furthermore, this design avoids the high pressure requirements and higher costs associated with multi-split systems using carbon dioxide as the outdoor refrigerant. Attached Figure Description
[0017] To more clearly illustrate the technical solutions in this invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.
[0018] Figure 1 This is one of the structural schematic diagrams of the multi-split air conditioning system provided by the present invention.
[0019] Figure 2 This is a schematic diagram of the multi-split air conditioning system provided by the present invention in cooling mode.
[0020] Figure 3 This is a schematic diagram of the multi-split air conditioning system provided by the present invention in heating mode.
[0021] Figure 4 This is the second structural schematic diagram of the multi-split air conditioning system provided by the present invention.
[0022] Figure 5 This is the third structural schematic diagram of the multi-split air conditioning system provided by the present invention.
[0023] Figure 6 This is the fourth structural schematic diagram of the multi-split air conditioning system provided by the present invention.
[0024] Figure 7 This is a schematic diagram of the structure of the multi-split air conditioning system provided by the present invention in the safe overpressure prevention mode.
[0025] Figure 8 This is the fifth structural schematic diagram of the multi-split air conditioning system provided by the present invention.
[0026] Figure label: 100. First heat exchanger; 110. First heat exchange channel; 120. Second heat exchange channel; 200, First refrigerant circulation module; 210, Compressor; 220, Outdoor heat exchanger; 230, First control valve; 240, First expansion valve; 250, Gas-liquid separator; 260, Oil separator; 270, Oil return capillary tube; 280, Outdoor fan; 300. Second refrigerant circulation module; 310. Liquid receiver; 320. Circulation pump; 330. Indoor heat exchanger; 340. Second control valve; 341. First valve body; 342. Second valve body; 343. Third valve body; 344. Fourth valve body; 350. Indoor regulating valve; 360. Indoor fan; 400. Second heat exchanger; 410. Third heat exchange channel; 420. Fourth heat exchange channel; 510. First subcooling heat exchanger; 520. First refrigeration check valve; 530. First heating check valve; 540. Second expansion valve; 550. Third subcooling heat exchanger; 560. Second refrigeration check valve; 570. Second heating check valve. Detailed Implementation
[0027] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.
[0028] In the description of this specification, it should be noted that the terms "center," "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the accompanying drawings and are used only for the convenience of describing this specification. They do not indicate or imply that the device or component referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this specification. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.
[0029] In the description of this specification, it should be noted that, unless otherwise expressly specified and limited, the terms "connected" and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms in the embodiments of this invention based on the specific circumstances.
[0030] In this specification, unless otherwise expressly specified and limited, "above" or "below" the second feature can mean that the first and second features are in direct contact, or that the first and second features are in indirect contact through an intermediate medium. Furthermore, "above," "over," and "on top" of the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.
[0031] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of the embodiments of this specification. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.
[0032] In the embodiments of this specification, "at least one" means one or more, and "more than one" means two or more. "And / or" describes the relationship between related objects, indicating that there can be three relationships. For example, A and / or B can represent three situations: A exists alone, A and B exist simultaneously, and B exists alone.
[0033] like Figures 1 to 8 As shown in the figure, a specific embodiment of the present invention provides a multi-split air conditioning system. The multi-split air conditioning system includes a first heat exchanger 100, a first refrigerant circulation module 200, and a second refrigerant circulation module 300.
[0034] The first heat exchanger 100 includes a first heat exchange channel 110 and a second heat exchange channel 120. The first refrigerant circulation module 200 has a first refrigerant circulation loop connected to the first heat exchange channel 110 for heat exchange with outdoor air. The second refrigerant circulation module 300 has a carbon dioxide circulation loop connected to the second heat exchange channel 120 for heat exchange with indoor air for cooling or heating the room. The carbon dioxide in the carbon dioxide circulation loop exchanges heat with the first refrigerant in the first refrigerant circulation loop within the first heat exchanger 100.
[0035] In other words, in this embodiment, the outdoor refrigerant circuit (i.e., the first refrigerant circulation circuit) is separated from the indoor refrigerant circuit (i.e., the carbon dioxide circulation circuit). Cooling and heating of the indoor space are achieved through heat exchange between the first refrigerant and carbon dioxide within the first heat exchanger 100. This avoids the entry of flammable low Global Warming Potential (GWP) refrigerants into the indoor space, effectively solving the problems of charge quantity control and system capacity limitations when using low GWP refrigerants, as well as the secondary substitution challenges associated with low GWP refrigerants. This reduces reliance on the research and development of new refrigerants and environmental risks. Simultaneously, this design also avoids the high pressure requirements and higher costs associated with multi-split air conditioning systems using carbon dioxide as the outdoor refrigerant.
[0036] In cooling mode, the low-temperature first refrigerant enters the first heat exchange channel 110, and the gaseous carbon dioxide enters the second heat exchange channel 120. The gaseous carbon dioxide exchanges heat with the low-temperature first refrigerant in the first heat exchanger 100, and the gaseous carbon dioxide liquefies into liquid carbon dioxide. At this time, carbon dioxide can be used as a cooling medium to cool the room.
[0037] In heating mode, the high-temperature first refrigerant enters the first heat exchange channel 110, and the liquid carbon dioxide enters the second heat exchange channel 120. The liquid carbon dioxide exchanges heat with the high-temperature first refrigerant in the first heat exchanger 100, and the liquid carbon dioxide vaporizes into gaseous carbon dioxide. At this time, carbon dioxide can be used as a heat transfer medium to heat the room.
[0038] In this embodiment, heat exchange between the first refrigerant and carbon dioxide in the first heat exchanger 100 enables the use of carbon dioxide for indoor cooling and heating. Compared to traditional air-source heat pump chilled-hot water air conditioning systems that use water or antifreeze as the energy carrier (i.e., heat and cold distribution medium), this embodiment avoids the constant pressure requirements of traditional air-source heat pump chilled-hot water air conditioning systems. Because this embodiment is a closed carbon dioxide circulation system, it reduces the risk of clogging of the indoor unit's capacity regulating valve while retaining the flexibility of multi-split systems, allowing for precise temperature adjustments in each room and improving indoor comfort. Furthermore, utilizing the latent heat of carbon dioxide phase change for heat and cold distribution reduces the energy consumption of the cooling medium compared to the sensible heat distribution using water or antifreeze.
[0039] Optionally, the first refrigerant may be a refrigerant with a relatively low Global Warming Potential (GWP). Specifically, the GWP of the first refrigerant is lower than that of R410A refrigerant.
[0040] Optionally, the first refrigerant includes, but is not limited to, one of R32 refrigerant, R290 refrigerant and R1234ze(E) refrigerant.
[0041] In some embodiments of the present invention, the first refrigerant circulation module 200 includes a first control valve 230, a compressor 210, and an outdoor heat exchanger 220.
[0042] The first control valve 230 has a first inlet d, a first cooling port c, a first heating port e, and a first outlet s. Specifically, the first control valve 230 can switch its conduction state according to cooling and heating modes. In cooling mode, the first control valve 230 is in the first conduction state, that is, the first inlet d is connected to the first cooling port c, and the first heating port e is connected to the first outlet s. In heating mode, the first control valve 230 is in the second conduction state, that is, the first inlet d is connected to the first heating port e, and the first cooling port c is connected to the first outlet s. By setting this first control valve 230, the switching between cooling and heating operation modes can be easily realized to meet the usage needs of different seasons.
[0043] The discharge port of compressor 210 is connected to the first inlet d, the first refrigeration port c is connected to the first outdoor inlet and outlet of outdoor heat exchanger 220, the second outdoor inlet and outlet of outdoor heat exchanger 220 is connected to the first heating port e through the first heat exchange channel 110, and the suction port of compressor 210 is connected to the first outlet s. This connection method constitutes the first refrigerant circulation loop on the outdoor side.
[0044] In cooling mode, the first control valve 230 is in the first conducting state, and the compressor 210 discharges a high-temperature, high-pressure first refrigerant. This high-temperature, high-pressure first refrigerant passes sequentially through the first inlet d and the first cooling port c of the first control valve 230, entering the outdoor heat exchanger 220 from the first outdoor inlet / outlet. The first refrigerant discharged from the second outdoor inlet / outlet of the outdoor heat exchanger 220 enters the first heat exchange channel 110 and exchanges heat with gaseous carbon dioxide in the second heat exchange channel 120. After liquefaction and condensation, the gaseous carbon dioxide is transported indoors for cooling. The first refrigerant discharged from the first heat exchange channel 110 returns to the compressor 210's suction port via the first heating port e and the first outlet s, thus forming the first refrigerant circulation loop. In cooling mode, the entire first refrigerant circulation loop is located outdoors, avoiding the safety hazards caused by refrigerant entering the indoor space when using flammable low Global Warming Potential (GWP) refrigerants. This solves the problems of limited charging quantity and system capacity of low GWP refrigerants, improving system safety.
[0045] In heating mode, the first control valve 230 is in the second open state, and the compressor 210 discharges a high-temperature, high-pressure first refrigerant. This high-temperature, high-pressure first refrigerant passes sequentially through the first inlet d and the first heating port e of the first control valve 230 before entering the first heat exchange channel 110 to exchange heat with the liquid carbon dioxide in the second heat exchange channel 120. After heat exchange, the first refrigerant is discharged from the first heat exchange channel 110 and flows into the outdoor heat exchanger 220 through the second outdoor inlet and outlet. There, it exchanges heat with the outdoor air and finally returns to the compressor 210 through the first cooling port c and the first outlet s. Thus, the entire system, acting as a heat pump, can absorb heat from the outdoor environment and transfer it to the carbon dioxide circulation loop through the first heat exchanger 100, providing stable heating for the indoor environment and achieving efficient energy utilization.
[0046] Optionally, compressor 210 is one of a single-stage compressor, a quasi-two-stage compressor, and a two-stage compressor.
[0047] like Figures 1 to 8 As shown, optionally, the first control valve 230 is a four-way directional valve.
[0048] like Figures 1 to 8 As shown, optionally, a first expansion valve 240 is installed on the pipeline between the second outdoor inlet / outlet of the outdoor heat exchanger 220 and the first heat exchange channel 110. In other words, in cooling mode, the first refrigerant discharged from the second outdoor inlet / outlet is throttled and depressurized into a low-pressure gas-liquid two-phase first refrigerant by the first expansion valve 240, and then flows into the first heat exchange channel 110 to exchange heat with gaseous carbon dioxide in the second heat exchange channel 120. In heating mode, the first refrigerant discharged from the first heat exchange channel 110 is throttled and depressurized into a low-pressure gas-liquid two-phase first refrigerant by the first expansion valve 240, and then flows into the outdoor heat exchanger 220 from the second outdoor inlet / outlet to exchange heat with outdoor air.
[0049] In cooling mode, the refrigerant, after being throttled and cooled by the first expansion valve 240, can form a sufficiently large heat exchange temperature difference with the gaseous carbon dioxide in the second heat exchange channel 120, ensuring that the carbon dioxide can be fully condensed into liquid, thereby improving the overall cooling efficiency and capacity of the system. Simultaneously, by adjusting the opening of the first expansion valve 240, the flow rate of refrigerant entering the first heat exchanger 100 can be controlled, thereby achieving flexible adjustment of the system's cooling capacity and ensuring that the compressor 210 has appropriate superheat at the suction level, preventing liquid slugging in the compressor 210, and improving the stability and reliability of system operation.
[0050] Optionally, an outdoor fan 280 is installed on one side of the outdoor heat exchanger 220. The outdoor fan 280 is used to dissipate heat and cool the outdoor heat exchanger 220.
[0051] Optionally, the first refrigerant circulation module 200 also includes a gas-liquid separator 250 and an oil separator 260. The first outlet s of the first control valve 230 is connected to the suction port of the compressor 210 through the gas-liquid separator 250, which can be used to separate the gas and liquid of the first refrigerant, reducing the risk of liquid slugging in the compressor 210. The discharge port of the compressor 210 is connected to the first inlet d through the oil separator 260, and the oil return port of the oil separator 260 is connected to the compressor 210 through the oil return capillary tube 270. In this way, the oil separator 260 can be used to separate oil from the high-temperature and high-pressure first refrigerant discharged by the compressor 210, preventing oil from entering the first refrigerant circulation loop. The separated oil is returned to the compressor 210 to replenish the compressor 210.
[0052] like Figures 1 to 8 As shown, in some embodiments of the present invention, the second refrigerant circulation module 300 includes a second control valve 340, a liquid receiver 310, a circulation pump 320, and an indoor heat exchanger 330. This design constitutes an independent and closed carbon dioxide phase change energy-carrying circulation system, which utilizes the thermophysical properties of carbon dioxide (such as high latent heat and low viscosity) to achieve efficient distribution of indoor heating and cooling.
[0053] The second control valve 340 has a second inlet d', a second cooling port c', a second heating port e', and a second outlet s'. Specifically, the second control valve 340 switches its conduction state according to the cooling mode and the heating mode. In cooling mode, the second control valve 340 is in the third conduction state, that is, the second inlet d' is connected to the second heating port e', and the second cooling port c' is connected to the second outlet s'. In heating mode, the second control valve 340 is in the fourth conduction state, that is, the second inlet d' is connected to the second cooling port c', and the second heating port e' is connected to the second outlet s'. By switching the second control valve 340, the flow path of carbon dioxide in the indoor circulation loop (i.e., the carbon dioxide circulation loop) can be reliably and conveniently changed, thereby realizing the switching between cooling and heating modes and improving the operational flexibility and automation level of the system.
[0054] The inlet of the liquid storage tank 310 is connected to the second outlet s', and the outlet of the liquid storage tank 310 is connected to the second inlet d' via the circulation pump 320. The second refrigeration port c' is connected to the first indoor inlet and outlet of the indoor heat exchanger 330 via the second heat exchange channel 120, and the second indoor inlet and outlet of the indoor heat exchanger 330 is connected to the second heating port e'. This connection design constitutes an indoor carbon dioxide circulation loop. The liquid storage tank 310 can effectively store and buffer liquid carbon dioxide, adapt to changes in refrigeration demand under different loads, and ensure stable system operation. The circulation pump 320 is used to transport liquid carbon dioxide, which can pressurize the liquid carbon dioxide and has lower energy consumption than gas compression, thereby reducing energy consumption in the heat and cold distribution process and improving system energy efficiency.
[0055] like Figure 2 As shown, in the cooling mode, the second control valve 340 is in the third conducting state; the circulation pump 320 starts to pump out the liquid carbon dioxide stored in the liquid storage tank 310. The high-pressure liquid carbon dioxide discharged from the circulation pump 320 passes through the second inlet d' and the second heating port e' of the second control valve 340 in sequence, and flows into the indoor heat exchanger 330 from the second indoor inlet and outlet. In the indoor heat exchanger 330, it absorbs heat and evaporates into gaseous carbon dioxide. After being discharged from the first indoor inlet and outlet of the indoor heat exchanger 330, the gaseous carbon dioxide flows into the second heat exchange channel 120. In the second heat exchange channel 120, it exchanges heat with the low-temperature first refrigerant in the first heat exchange channel 110. The gaseous carbon dioxide releases heat and condenses into liquid in the first heat exchanger 100. The liquid carbon dioxide discharged from the second heat exchange channel 120 passes through the second cooling port c' and the second outlet s' of the second control valve 340 in sequence and returns to the liquid storage tank 310, thus forming a carbon dioxide circulation loop in the cooling mode. The entire circulation process is completed in a closed indoor piping system, completely isolating the first refrigerant from the outside. This eliminates the safety risk of the first refrigerant (especially flammable refrigerants with low GWP values) leaking into the room, thus improving the safety of the system.
[0056] like Figure 3As shown, in heating mode, the second control valve 340 is in the fourth conducting state; the circulation pump 320 starts, pumping out the liquid carbon dioxide in the storage tank 310. The high-pressure liquid carbon dioxide discharged from the circulation pump 320 flows into the second heat exchange channel 120 after passing through the second inlet d' and the second refrigeration port c' of the second control valve 340. The liquid carbon dioxide exchanges heat with the high-temperature and high-pressure first refrigerant in the first heat exchange channel 110 in the second heat exchange channel 120. The liquid carbon dioxide absorbs heat and evaporates into gaseous carbon dioxide in the first heat exchanger 100. The gaseous carbon dioxide discharged from the second heat exchange channel 120 enters the indoor heat exchanger 330 from the first indoor inlet and outlet, and releases heat and cools into liquid carbon dioxide in the indoor heat exchanger 330 to achieve indoor heating. The liquid carbon dioxide discharged from the second indoor inlet and outlet of the indoor heat exchanger 330 returns to the storage tank 310 after passing through the second heating port e' and the second outlet s' of the second control valve 340. The heating cycle is also fully enclosed and uses carbon dioxide as a medium, which avoids the risk of freezing that may exist in traditional water systems in winter. It eliminates the need to add antifreeze, simplifies the system, and reduces maintenance costs and environmental risks.
[0057] Optionally, the second indoor inlet and outlet of the indoor heat exchanger 330 are connected to the second heating port e' of the second control valve 340 via an indoor regulating valve 350. The indoor regulating valve 350 is used to regulate the flow rate of carbon dioxide, and can adjust the flow rate of carbon dioxide flowing through each indoor heat exchanger 330 to match the actual heating and cooling load requirements of the room.
[0058] Optionally, an indoor fan 360 is provided on one side of the indoor heat exchanger 330, which is used to blow the air around the indoor heat exchanger 330 into the room.
[0059] Optionally, there may be multiple indoor heat exchangers 330; the second indoor inlet and outlet of each indoor heat exchanger 330 are connected to the second heating port e' of the second control valve 340 via an indoor regulating valve 350. The first indoor inlet and outlet of the multiple indoor heat exchangers 330 are connected to the second cooling port c' of the second control valve 340 via a second heat exchange channel 120. In other words, multiple indoor heat exchangers 330 are arranged in parallel, and an indoor regulating valve 350 is installed at the second indoor inlet and outlet of each indoor heat exchanger 330.
[0060] Optionally, the indoor regulating valve 350 can be an electric electronic expansion valve, a solenoid electronic expansion valve, or an automatic control valve with flow regulation and shut-off functions.
[0061] like Figure 8As shown, in some embodiments of the present invention, the second control valve 340 is a four-way directional valve. Using a single four-way directional valve as the switching element makes the structure of the carbon dioxide circulation loop more compact and simplified. This design reduces the number of components and connection points in the system, which not only helps to reduce manufacturing costs and installation complexity but also reduces potential leakage risks. At the same time, the control logic is relatively simple; rapid switching between cooling and heating modes can be achieved by controlling a single valve, improving the system's response speed and operational reliability.
[0062] like Figures 1 to 7 As shown, in some other embodiments of the present invention, the second control valve 340 includes a reversing valve assembly. The reversing valve assembly includes a first valve body 341, a second valve body 342, a third valve body 343, and a fourth valve body 344.
[0063] One end of the first valve body 341 is connected to the outlet of the circulating pump 320, and the other end is connected to the second indoor inlet / outlet of the indoor heat exchanger 330. One end of the second valve body 342 is connected to the second heat exchange channel 120, and the other end is connected to the inlet of the liquid storage tank 310. One end of the third valve body 343 is connected to the second indoor inlet / outlet, and the other end is connected to the inlet of the liquid storage tank 310. One end of the fourth valve body 344 is connected to the outlet of the circulating pump 320, and the other end is connected to the second heat exchange channel 120. By using a combination of four independent valve bodies (e.g., solenoid valves) to achieve flow path switching, greater design flexibility and maintainability are provided.
[0064] like Figure 2 As shown, in cooling mode, the reversing valve assembly is in the third conducting state. At this time, the third valve body 343 and the fourth valve body 344 are closed, and the first valve body 341 and the second valve body 342 are open, ensuring that the second inlet d' is connected to the second heating port e' and the second cooling port c' is connected to the second outlet s'.
[0065] like Figure 3 As shown, in heating mode, the reversing valve group is in the fourth conducting state. At this time, the third valve body 343 and the fourth valve body 344 are open, and the first valve body 341 and the second valve body 342 are closed, ensuring that the second inlet d' is connected to the second cooling port c' and the second heating port e' is connected to the second outlet s'.
[0066] Compared to a single integrated four-way directional control valve, in this embodiment, each valve body in the directional control valve group can be a simple on / off valve, typically offering higher operational reliability and a longer service life. Furthermore, if one valve body fails, the cost and difficulty of diagnosing and replacing that single valve body are far lower than replacing the entire four-way directional control valve, thereby improving system maintainability and overall lifecycle economics.
[0067] like Figures 4 to 7 As shown, in some embodiments of the present invention, the multi-split air conditioning system further includes a second heat exchanger 400. The second heat exchanger 400 includes a third heat exchange channel 410 and a fourth heat exchange channel 420; the first heat exchange channel 110 is connected to the first heating port e through the third heat exchange channel 410; the second heat exchange channel 120 is connected to the first indoor inlet / outlet through the fourth heat exchange channel 420. This is equivalent to connecting the first heat exchanger 100 and the second heat exchanger 400 in series to increase the heat exchange time between the first refrigerant and carbon dioxide. This series connection increases the total heat exchange area and heat exchange time between the first refrigerant and carbon dioxide, resulting in more thorough heat exchange and thus improving the overall system's heat exchange efficiency and energy utilization.
[0068] In cooling mode, the low-temperature liquid refrigerant flowing out of the first heat exchange channel 110 enters the third heat exchange channel 410, where it undergoes preliminary heat exchange with the gaseous carbon dioxide entering the fourth heat exchange channel 420. The carbon dioxide flowing out of the fourth heat exchange channel 420 then enters the second heat exchange channel 120 for secondary heat exchange with the refrigerant in the first heat exchange channel 110. This increases the subcooling degree of the liquid carbon dioxide before entering the second control valve 340. This two-stage counter-current heat exchange method achieves deep subcooling of carbon dioxide, increasing the cooling capacity of the liquid carbon dioxide. Greater subcooling means that more indoor heat can be absorbed after being delivered to the indoor heat exchanger 330, thereby increasing the total cooling capacity of the system with the same circulation volume. Simultaneously, this also reduces the amount of flash vapor of carbon dioxide after throttling at the indoor regulating valve 350, improving refrigerant utilization efficiency and the system's coefficient of performance (COP).
[0069] In heating mode, the high-temperature, high-pressure refrigerant discharged from the first heating port e first enters the third heat exchange channel 410, where it exchanges heat with the gaseous carbon dioxide discharged from the second heat exchange channel 120 and entering the fourth heat exchange channel 420. The refrigerant discharged from the third heat exchange channel 410 then enters the first heat exchange channel 110, where it exchanges heat with the liquid carbon dioxide in the second heat exchange channel 120, thus increasing the heat carrying capacity of the gaseous carbon dioxide. This two-stage counter-current heat exchange method ensures that the liquid carbon dioxide is fully vaporized after primary heat exchange in the first heat exchanger 100 and further heated during auxiliary heat exchange in the second heat exchanger 400, thereby increasing the heat carrying capacity and superheat of the gaseous carbon dioxide delivered to the room. The higher superheat not only increases the heat released into the room, improving the system's heating capacity and efficiency, but also ensures that the carbon dioxide entering the indoor heat exchanger 330 is in a pure gaseous state, avoiding noise and uneven heat exchange problems that may be caused by gas-liquid two-phase flow, thus guaranteeing heating stability and comfort.
[0070] It is understandable that both the first heat exchanger 100 and the second heat exchanger 400 are counter-current heat exchangers.
[0071] like Figure 5 As shown, in some embodiments of the present invention, the multi-split air conditioning system further includes a first subcooling heat exchanger 510, a first cooling check valve 520, and a first heating check valve 530.
[0072] The first subcooling heat exchanger 510 includes a first subcooling heat exchange channel and a second subcooling heat exchange channel. The outlet of the liquid storage tank 310 is connected to the circulating pump 320 through the second subcooling heat exchange channel, and one end of the first subcooling heat exchange channel is connected to the suction port of the compressor 210. The inlet of the first refrigeration check valve 520 is connected to the second outdoor inlet and outlet, the inlet of the first heating check valve 530 is connected to the first heat exchange channel 110, and the outlets of both the first refrigeration check valve 520 and the first heating check valve 530 are connected to the other end of the first subcooling heat exchange channel through the second expansion valve 540. This forms a subcooling circulation loop, which can further optimize the thermodynamic state of carbon dioxide, thereby improving the operating efficiency and reliability of the entire system. By subcooling the carbon dioxide liquid at the inlet of the circulating pump 320, its subcooling degree can be effectively increased, and the liquid density can be improved. This prevents the liquid from flashing before the circulating pump 320 due to pressure fluctuations or local temperature rises, avoiding cavitation damage to the circulating pump 320. This enhances the stability and service life of the circulating pump 320 and reduces operating noise.
[0073] In other words, the first refrigeration check valve 520 and the first heating check valve 530 are arranged in parallel. This allows the check valves to automatically select the flow path, drawing a small stream of liquid first refrigerant from the first refrigerant circulation loop. Subcooling can be achieved in both refrigeration and heating modes without the need for additional complex switching valves, simplifying the system structure and improving reliability.
[0074] In cooling mode, the first heating check valve 530 is closed and the first cooling check valve 520 is open. The first refrigerant flowing out from the second outdoor inlet and outlet of the outdoor heat exchanger 220, a small portion of the first refrigerant flows into the other end of the first subcooling heat exchange channel after being throttled by the first cooling check valve 520 and the second expansion valve 540. The first refrigerant in the first subcooling heat exchange channel exchanges heat with the liquid carbon dioxide in the second subcooling heat exchange channel to subcool the liquid carbon dioxide entering the circulation pump 320. The first refrigerant flowing out from one end of the first subcooling heat exchange channel returns to the suction port of the compressor 210 through the gas-liquid separator 250.
[0075] In heating mode, the first cooling check valve 520 is closed, and the first heating check valve 530 is open. A small portion of the first refrigerant from the first heat exchange channel 110 passes through the first heating check valve 530 and is then throttled by the second expansion valve 540 before entering the first subcooling heat exchange channel. The first refrigerant in the first subcooling heat exchange channel exchanges heat with the carbon dioxide in the second subcooling heat exchange channel to subcool the liquid carbon dioxide entering the circulating pump 320. The first refrigerant, after heat exchange in the first subcooling heat exchange channel, is then reabsorbed by the compressor 210.
[0076] like Figure 7 As shown, when the multi-split air conditioning system is shut down for a long time and the indoor temperature is high, the compressor 210 starts the low-frequency operation mode. The first subcooling heat exchange channel of the first subcooling heat exchanger 510 cools and condenses the carbon dioxide in the liquid storage tank 310, which can reduce the pressure of carbon dioxide in the circulation system, prevent overpressure in the carbon dioxide circulation loop, ensure the pressure safety of the unit, and prevent cavitation of the circulation pump 320, prevent the indoor regulating valve 350 from malfunctioning, and prevent overpressure in the carbon dioxide pipeline system.
[0077] The outlet of the liquid storage tank 310 is connected to the circulating pump 320 through a second subcooling heat exchange channel. Since the first subcooling heat exchanger 510 is an independent component, its specifications and form can be flexibly selected according to design requirements, without being limited by the structure of the liquid storage tank 310, simplifying the manufacturing and procurement process. When system maintenance is required, the first subcooling heat exchanger 510 can be inspected, repaired, or replaced separately without operating the liquid storage tank 310, reducing maintenance difficulty and cost, and shortening system downtime.
[0078] Optionally, one end of the second subcooling heat exchange channel is connected to the second outlet s' of the second control valve 340, and the other end is connected to the inlet of the liquid storage tank 310. In other words, the first subcooling heat exchanger 510 can be positioned between the inlet of the liquid storage tank 310 and the second outlet s' of the second control valve 340. One end of the first subcooling heat exchange channel is connected to the suction port of the compressor 210, and the other end is connected to the outlet of the first refrigeration check valve 520 and the outlet of the first heating check valve 530. In other words, this achieves subcooling of the liquid carbon dioxide entering the liquid storage tank 310.
[0079] like Figure 6 and Figure 7 As shown, in some other embodiments of the present invention, the multi-split air conditioning system includes a third subcooling heat exchanger 550, a second cooling check valve 560, and a second heating check valve 570.
[0080] The third subcooling heat exchanger 550 includes a third subcooling heat exchange channel, which is installed inside the liquid storage tank 310. In other words, the liquid storage tank 310 and the third subcooling heat exchanger 550 are integrated into one unit, which makes the system structure more compact. One end of the third subcooling heat exchange channel is connected to the suction port of the compressor 210. The inlet of the second refrigeration check valve 560 is connected to the second outdoor inlet and outlet, the inlet of the second heating check valve 570 is connected to the first heat exchange channel 110, and the outlets of the second refrigeration check valve 560 and the second heating check valve 570 are both connected to the other end of the third subcooling heat exchange channel through the second expansion valve 540.
[0081] By integrating the third subcooling heat exchanger 550 into the liquid receiver 310, internal installation space is saved, reducing the overall footprint of the unit and making the entire system more compact. Furthermore, this design reduces external connecting pipes and welding points, simplifying the assembly process and lowering the risk of primary refrigerant leakage, thereby enhancing the long-term operational reliability and environmental performance of the system. Simultaneously, the third subcooling heat exchanger 550, immersed in liquid carbon dioxide, subcools all the liquid in the liquid receiver 310, ensuring sufficient subcooling of the liquid reaching the inlet of the circulating pump 320, resulting in higher heat exchange efficiency.
[0082] It should be noted that when switching system operating modes, the second control valve 340 should be started no later than the first control valve 230.
[0083] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.
Claims
1. A multi-split air conditioning system, characterized in that, include: The first heat exchanger (100) includes a first heat exchange channel (110) and a second heat exchange channel (120). The first refrigerant circulation module (200) has a first refrigerant circulation loop; the first refrigerant circulation loop is connected to the first heat exchange channel (110) for heat exchange with outdoor air; The second refrigerant circulation module (300) has a carbon dioxide circulation loop; the carbon dioxide circulation loop is connected to the second heat exchange channel (120) for heat exchange with indoor air to cool or heat the room. In this process, the carbon dioxide in the carbon dioxide circulation loop exchanges heat with the first refrigerant in the first refrigerant circulation loop within the first heat exchanger (100).
2. The multi-split air conditioning system according to claim 1, characterized in that, The first refrigerant circulation module (200) includes: The first control valve (230) has a first inlet, a first cooling port, a first heating port and a first outlet; Compressor (210) and outdoor heat exchanger (220); The exhaust port of the compressor (210) is connected to the first inlet, the first cooling port is connected to the first outdoor inlet and outlet of the outdoor heat exchanger (220), the second outdoor inlet and outlet of the outdoor heat exchanger (220) is connected to the first heating port through the first heat exchange channel (110), and the suction port of the compressor (210) is connected to the first outlet.
3. The multi-split air conditioning system according to claim 2, characterized in that, The second refrigerant circulation module (300) includes: The second control valve (340) has a second inlet, a second cooling port, a second heating port and a second outlet; Storage tank (310), circulation pump (320) and indoor heat exchanger (330); The inlet of the liquid storage tank (310) is connected to the second outlet, the outlet of the liquid storage tank (310) is connected to the second inlet through the circulation pump (320), the second refrigeration port is connected to the first indoor inlet and outlet of the indoor heat exchanger (330) through the second heat exchange channel (120), and the second indoor inlet and outlet of the indoor heat exchanger (330) is connected to the second heating port.
4. The multi-split air conditioning system according to claim 3, characterized in that, Also includes: The second heat exchanger (400) includes a third heat exchange channel (410) and a fourth heat exchange channel (420); the first heat exchange channel (110) is connected to the first heating port through the third heat exchange channel (410); the second heat exchange channel (120) is connected to the first indoor inlet and outlet through the fourth heat exchange channel (420).
5. The multi-split air conditioning system according to claim 3, characterized in that, Also includes: The first subcooling heat exchanger (510) includes a first subcooling heat exchange channel and a second subcooling heat exchange channel; the outlet of the liquid storage tank (310) is connected to the circulating pump (320) through the second subcooling heat exchange channel, and one end of the first subcooling heat exchange channel is connected to the suction port of the compressor (210). The first cooling check valve (520) and the first heating check valve (530) are connected. The inlet of the first cooling check valve (520) is connected to the second outdoor inlet and outlet, and the inlet of the first heating check valve (530) is connected to the first heat exchange channel (110). The outlets of the first cooling check valve (520) and the first heating check valve (530) are both connected to the other end of the first subcooling heat exchange channel through the second expansion valve (540).
6. The multi-split air conditioning system according to claim 3, characterized in that, Also includes: The third subcooling heat exchanger (550) includes a third subcooling heat exchange channel; the third subcooling heat exchange channel is installed inside the liquid storage tank (310); one end of the third subcooling heat exchange channel is connected to the suction port of the compressor (210). The second cooling check valve (560) and the second heating check valve (570) are connected. The inlet of the second cooling check valve (560) is connected to the second outdoor inlet and outlet, and the inlet of the second heating check valve (570) is connected to the first heat exchange channel (110). The outlets of the second cooling check valve (560) and the second heating check valve (570) are both connected to the other end of the third subcooling heat exchange channel through the second expansion valve (540).
7. The multi-split air conditioning system according to claim 3, characterized in that, The number of indoor heat exchangers (330) is multiple, and the first indoor inlet and outlet of each of the multiple indoor heat exchangers (330) are connected to the second refrigeration port of the second control valve (340) through the second heat exchange channel (120); the second indoor inlet and outlet of each of the indoor heat exchangers (330) are connected to the second heating port of the second control valve (340) through the indoor regulating valve (350).
8. The multi-split air conditioning system according to claim 3, characterized in that, The second control valve (340) is a four-way directional valve.
9. The multi-split air conditioning system according to claim 3, characterized in that, The second control valve (340) is a directional valve assembly, which includes: The first valve body (341) has one end connected to the outlet of the circulating pump (320) and the other end connected to the second indoor inlet and outlet of the indoor heat exchanger (330). The second valve body (342) has one end connected to the second heat exchange channel (120) and the other end connected to the inlet of the liquid storage tank (310). The third valve body (343) has one end connected to the inlet / outlet of the second chamber and the other end connected to the inlet of the liquid storage tank (310). The fourth valve body (344) is connected at one end to the outlet of the circulating pump (320) and at the other end to the second heat exchange channel (120).
10. The multi-split air conditioning system according to any one of claims 2 to 7, characterized in that, The first control valve (230) is a four-way directional valve.