Three-pipe heating recovery central air-conditioning system

Abstract

The invention discloses a three-pipe heat recovery central air-conditioning system which comprises an outdoor unit and a plurality of indoor units, a switching cut-off device is connected with the outdoor unit and the indoor units and is configured to switch a cold and hot mode and cut off a refrigerant when the refrigerant leaks, and the three-pipe heat recovery central air-conditioning system is characterized in that a first branch is connected with an outdoor unit side liquid pipe and an indoor unit side liquid pipe; the second branch is connected with the outdoor unit side low-pressure air pipe and the indoor unit side air pipe; the third branch is connected with the outdoor unit side high-low pressure air pipe and the second branch, and a third electronic expansion valve with the adjustable opening degree is arranged on the third branch; the unloading branch is connected with the first branch and the second branch and is configured to release the high-pressure refrigerant into the low-pressure air pipe when the refrigerant leaks; and in the cold and hot simultaneous mode, the third electronic expansion valve corresponding to the refrigeration indoor unit is opened at the set opening degree so as to prevent the refrigerant from accumulating at the third electronic expansion valve for a long time to cause liquid sealing. The switching cut-off device integrates a cold and hot mode switching function and a refrigerant cut-off function, the number of valves can be reduced, and the cost is reduced.

Description

Technical Field

[0001] This invention relates to the field of air conditioning equipment technology, and more particularly to a three-pipe heat recovery central air conditioning system. Background Technology

[0002] A three-pipe heat recovery central air conditioning system refers to a central air conditioning system in which the outdoor and indoor units are connected and refrigerant is distributed via three main refrigerant lines in the refrigerant circulation system. These three main refrigerant lines typically include: one high-pressure gas line, one low-pressure gas line, and one liquid line. The system can independently adjust the refrigerant flow direction and state according to the cooling / heating needs of each indoor unit through valves (electronic expansion valves, four-way valves, switching valves, etc.), enabling different indoor units to cool or heat simultaneously. Furthermore, the condensation heat discharged from the cooling indoor units can be directly recovered for the heating needs of the heating indoor units, thus achieving energy recovery and high energy efficiency. In other words, a three-pipe heat recovery central air conditioning system has cooling mode, heating mode, and simultaneous cooling and heating mode.

[0003] A three-pipe heat recovery central air conditioning system is currently available, which also includes a shut-off device and a cooling / heating mode switching device. The shut-off device acts as a bridge between the outdoor and indoor units, opening and closing the refrigerant circuit between them via an electronic expansion valve. The cooling / heating mode switching device, in conjunction with the outdoor unit, switches between high and low-pressure refrigerant, enabling simultaneous cooling and heating in different indoor units. The shut-off device can only cut off the refrigerant supply; it cannot simultaneously cool and heat the indoor units. The cooling / heating mode switching device can only enable simultaneous cooling and heating in the indoor units, but it cannot cut off the refrigerant supply. Furthermore, each branch of both the shut-off device and the cooling / heating mode switching device requires an electronic expansion valve for control, resulting in a large number of valves and high cost.

[0004] Therefore, it is necessary to improve the shut-off device and the hot / cold mode switching device. By integrating the functions of the two, the refrigerant shut-off and hot / cold mode switching functions can be achieved at the same time, while reducing the number of valves and lowering costs.

[0005] The information disclosed in this background section is only intended to enhance the understanding of the background technology of this application, and therefore may include prior art that is not known to those skilled in the art. Summary of the Invention

[0006] In response to the problems mentioned in the background art, the present invention proposes a three-pipe heat recovery central air conditioning system. By providing a new refrigerant switching and shut-off device, the system integrates the cooling and heating mode switching function and the refrigerant shut-off function, and can reduce the number of valves and lower costs.

[0007] To achieve the above-mentioned objectives, the present invention employs the following technical solution: In some embodiments of this application, a three-pipe heat recovery central air conditioning system is provided, including an outdoor unit and multiple indoor units. The central air conditioning system further includes a switching cut-off device connected to the outdoor unit and the indoor units. The switching cut-off device is configured to switch between cooling and heating modes and to cut off refrigerant in case of refrigerant leakage. It includes: The first branch line connects the liquid pipe on the outdoor unit side and the liquid pipe on the indoor unit side, and the first branch line is equipped with a first electronic expansion valve. The second branch connects the low-pressure gas pipe on the outdoor unit side and the gas pipe on the indoor unit side. A fourth electronic expansion valve is installed on the second branch. The third branch is connected to the high and low pressure gas pipes on the outdoor unit side and the second branch. The third branch is equipped with a third electronic expansion valve with adjustable opening. An unloading branch, which connects the first branch and the second branch, is configured to release high-pressure refrigerant into a low-pressure gas line in the event of a refrigerant leak. In the simultaneous cooling and heating mode, the third electronic expansion valve corresponding to the cooling indoor unit is opened at a set opening degree to prevent refrigerant from accumulating at the third electronic expansion valve for a long time and causing liquid sealing.

[0008] The above technical solution has the following advantages or beneficial effects: In the three-pipe heat recovery central air conditioning unit of this application, a switching and shut-off device is installed between the indoor and outdoor units. This switching and shut-off device integrates refrigerant switching and shut-off functions. The refrigerant switching function allows the central air conditioning unit to switch between cooling, heating, and simultaneous cooling and heating modes by controlling the opening and closing of relevant valves in the switching and shut-off device. The shut-off function allows high-pressure refrigerant to be released into the low-pressure gas pipe through an unloading branch in the event of a refrigerant leak. This achieves a compact structure and reliable function.

[0009] Furthermore, the third electronic expansion valve is a fully closing valve that controls flow rate by adjusting its opening. This allows for the use of only one third electronic expansion valve on the third branch and only one fourth electronic expansion valve on the second branch, thus reducing the number of valves and lowering costs. In other solutions, a distribution-type electronic expansion valve with a fixed bypass channel is used as the third electronic expansion valve. In this case, an additional valve capable of disconnecting the flow path is required on the pipeline where the third and second branches converge. Compared to this solution, this method uses more valves and incurs higher costs.

[0010] Other features and advantages of the present invention will become clearer after reading the detailed embodiments of the invention in conjunction with the accompanying drawings. Attached Figure Description

[0011] To more clearly illustrate the technical solutions in the embodiments of the present 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 the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0012] Figure 1 This is a structural diagram of a switching cutoff device according to some embodiments; Figure 2 This is a schematic diagram of a switching cutoff device according to some embodiments; Figure 3 A flow diagram for switching the cut-off device during cooling according to some embodiments; Figure 4 This is a flow diagram of a switching cutoff device during heating according to some embodiments; Figure 5 This is a flow diagram of a central air conditioning unit in cooling mode according to some embodiments; Figure 6 This is a flow diagram of a central air conditioning unit in heating mode according to some embodiments; Figure 7 This is a flow diagram of a central air conditioning unit in cooling mode according to some embodiments; Figure 8 This is a flow diagram of a central air conditioning unit in heating mode according to some embodiments.

[0013] Figure label: 100. Switch the cutoff device; 11. Indoor unit side liquid pipe; 12. Indoor unit side gas pipe; 13. Outdoor unit side liquid pipe; 14. High and low pressure gas pipes; 15. Low pressure gas pipe; 21. First branch road; 22. Second branch road; 23. Third branch road; 24. Unloading branch road; 31. First electronic expansion valve; 33. Third electronic expansion valve; 34. Fourth electronic expansion valve; 35. Unloading valve; 41. First filter; 42. Second filter; 43. Third filter; 44. Fourth filter; 45. Fifth filter. Detailed Implementation

[0014] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0015] Air conditioners use a compressor, condenser, expansion valve, and evaporator to perform a cooling or heating cycle. Through a series of processes such as compression, condensation, expansion, and evaporation, they cool or heat the indoor space.

[0016] Low-temperature, low-pressure refrigerant enters the compressor, which compresses it into a high-temperature, high-pressure refrigerant gas and discharges the compressed refrigerant gas. The discharged refrigerant gas flows into the condenser. The condenser condenses the compressed refrigerant into a liquid phase, and the heat is released to the surrounding environment through the condensation process.

[0017] The expansion valve expands the high-temperature, high-pressure liquid refrigerant that condenses in the condenser into a low-pressure liquid refrigerant. The evaporator evaporates the expanded refrigerant in the expansion valve and returns the low-temperature, low-pressure refrigerant gas to the compressor. The evaporator achieves its cooling effect by utilizing the latent heat of refrigerant evaporation to exchange heat with the material being cooled. Throughout the cycle, the air conditioner regulates the temperature of the indoor space.

[0018] The outdoor unit of an air conditioner refers to the part of the refrigeration cycle that includes the compressor and the outdoor heat exchanger. The indoor unit of an air conditioner includes the indoor heat exchanger, and an expansion valve can be provided in either the indoor or outdoor unit.

[0019] The indoor and outdoor heat exchangers function as either condensers or evaporators. When the indoor heat exchanger is used as a condenser, the air conditioner functions as a heater in heating mode; when the indoor heat exchanger is used as an evaporator, the air conditioner functions as a cooler in cooling mode.

[0020] Three-pipe heat recovery central air conditioning refers to a central air conditioning system in which the outdoor and indoor units are connected and refrigerant is distributed via three main refrigerant lines in the refrigerant circulation system. The three main refrigerant lines include: one high-pressure gas line, one low-pressure gas line, and one liquid line. The system can independently adjust the refrigerant flow direction and state according to the cooling / heating needs of each indoor unit through valves (electronic expansion valves, four-way valves, switching valves, etc.), enabling different indoor units to cool or heat simultaneously. Furthermore, the condensation heat discharged from the cooling indoor units can be directly recovered for the heating needs of the heating indoor units, thus achieving energy recovery and high energy efficiency. In other words, three-pipe heat recovery central air conditioning has cooling mode, heating mode, and simultaneous cooling and heating mode.

[0021] A three-pipe heat recovery central air conditioning system is currently available, which also includes a shut-off device and a cooling / heating mode switching device. The shut-off device acts as a bridge between the outdoor and indoor units, opening and closing the refrigerant circuit between them via an electronic expansion valve. The cooling / heating mode switching device, in conjunction with the outdoor unit, switches between high and low-pressure refrigerant, enabling simultaneous cooling and heating in different indoor units. The shut-off device can only cut off the refrigerant supply; it cannot simultaneously cool and heat the indoor units. The cooling / heating mode switching device can only enable simultaneous cooling and heating in the indoor units, but it cannot cut off the refrigerant supply. Furthermore, each branch of both the shut-off device and the cooling / heating mode switching device requires an electronic expansion valve for control, resulting in a large number of valves and high cost.

[0022] Therefore, it is necessary to improve the shut-off device and the hot / cold mode switching device. By integrating the functions of the two, the refrigerant shut-off and hot / cold mode switching can be achieved at the same time, while reducing the number of valves and lowering costs.

[0023] In some embodiments of this application, a three-pipe heat recovery central air conditioning device is provided, including an outdoor unit and multiple indoor units. Figure 5 For example, there is one outdoor unit and four indoor units, which are referred to as indoor unit A, indoor unit B, indoor unit C and indoor unit D.

[0024] The central air conditioning unit also includes a switching cut-off device 100, which connects the outdoor unit and the indoor unit. The switching cut-off device 100 is configured to switch between cooling and heating modes and to cut off refrigerant in the event of a refrigerant leak. Figure 1 This is a structural diagram of the switching cutoff device 100. Figure 2 This is a schematic diagram of a switching cutoff device 100. Figure 3 This is a flow path diagram for switching the shut-off device 100 during cooling. Figure 4 A flow diagram for switching off the device 100 during heating.

[0025] The switching and cutting-off device 100 includes a first branch 21, a second branch 22, a third branch 23, and an unloading branch 24.

[0026] The switching cutoff device 100 includes a first branch 21, which connects the outdoor unit side liquid line 13 and the indoor unit side liquid line 11. A first electronic expansion valve 31 is provided on the first branch 21. The first electronic expansion valve 31 is configured to control the refrigerant flow of the first branch 21.

[0027] The switching cutoff device 100 includes a second branch 22, which connects the low-pressure gas pipe 15 on the outdoor unit side and the gas pipe 12 on the indoor unit side. A fourth electronic expansion valve 34 is installed on the second branch 22. The fourth electronic expansion valve 34 is configured to control the refrigerant flow of the second branch 22.

[0028] The switching cutoff device 100 includes a third branch 23, which connects to the high and low pressure gas pipes 14 on the outdoor unit side and the second branch 22. An adjustable-opening third electronic expansion valve 33 is installed on the third branch 23. The third branch 23 is connected to the side of the fourth electronic expansion valve 34 closest to the indoor unit side.

[0029] The switching cutoff device 100 includes an unloading branch 24, which connects to a first branch 21 and a second branch 22. The unloading branch 24 is configured to release high-pressure refrigerant into a low-pressure gas line 15 in the event of a refrigerant leak.

[0030] In the simultaneous cooling and heating mode, the third electronic expansion valve 33 corresponding to the cooling indoor unit opens at a set opening degree to prevent refrigerant from accumulating at the third electronic expansion valve 33 for a long time and causing liquid sealing.

[0031] The third electronic expansion valve 33 is a fully closing valve that controls flow rate by adjusting its opening. This allows only one valve (33) to be installed on the third branch 23 and only one valve (34) to be installed on the second branch 22, thus reducing the number of valves and lowering costs. In other solutions, the third electronic expansion valve 33 is a distribution-type electronic expansion valve with a fixed bypass channel. In this case, an additional valve capable of disconnecting the flow path is required on the pipeline where the third branch 23 and the second branch 22 converge. Compared to this solution, this method uses more valves and incurs higher costs.

[0032] Reference Figure 3 During normal cooling, the first electronic expansion valve 31, the third electronic expansion valve 33, and the fourth electronic expansion valve 34 are in the open state, and the electronic expansion valve on the unloading branch 24 is closed. The liquid refrigerant enters the indoor unit from the outdoor unit side through the first branch 21 and the first electronic expansion valve 31, evaporates and absorbs heat to become gaseous refrigerant, and then splits into two paths through the gas pipe 12 on the indoor unit side. One path returns to the outdoor low-pressure gas pipe 15 through the second branch 22 and the fourth electronic expansion valve 34, and the other path returns to the outdoor high and low pressure gas pipe 14 through the third branch 23 and the third electronic expansion valve 33, thus completing the indoor unit refrigeration cycle.

[0033] If a refrigerant leak occurs at this time, the first electronic expansion valve 31, the third electronic expansion valve 33, and the fourth electronic expansion valve 34 will close to prevent the refrigerant from continuing to leak to the indoor unit side. The electronic expansion valve on the unloading branch 24 will open to release the high-pressure refrigerant generated at the moment the electronic expansion valve closes into the low-pressure gas pipe 15, thereby improving the safety of the device.

[0034] Reference Figure 4 During normal heating, the first electronic expansion valve 31 and the third electronic expansion valve 33 are open, the fourth electronic expansion valve 34 is closed, and the electronic expansion valve on the unloading branch 24 is closed. The gaseous refrigerant enters the indoor unit side gas pipe 12 from the high and low pressure gas pipe 14 on the outdoor unit side through the third branch 23 and the third electronic expansion valve 33. The gaseous refrigerant condenses and releases heat on the indoor unit side, and then returns to the outdoor unit side through the first branch 21 and the first electronic expansion valve 31, completing the heating cycle of the indoor unit.

[0035] If a refrigerant leak occurs at this time, the first electronic expansion valve 31, the third electronic expansion valve 33, and the fourth electronic expansion valve 34 will close to prevent the refrigerant from continuing to leak to the indoor unit side. The electronic expansion valve on the unloading branch 24 will open to release the high-pressure refrigerant generated at the moment the electronic expansion valve closes into the low-pressure gas pipe 15, thereby improving the safety of the device.

[0036] In the three-pipe heat recovery central air conditioning unit of this application, a switching and shut-off device 100 is provided between the indoor and outdoor units. The switching and shut-off device 100 integrates refrigerant switching and shut-off functions. The refrigerant switching function allows the central air conditioning unit to switch between cooling mode, heating mode, and simultaneous cooling and heating mode by controlling the opening and closing of relevant valves in the switching and shut-off device 100. The shut-off function allows high-pressure refrigerant to be released into the low-pressure gas pipe 15 through the unloading branch 24 in the event of refrigerant leakage. This achieves a compact structure and reliable function.

[0037] In some embodiments of this application, reference is made to Figure 1 and Figure 2 An unloading valve 35 is provided on the unloading branch 24. The unloading valve 35 is configured to close when the central air conditioning unit is operating normally. The unloading valve 35 is also configured to open in case of refrigerant leakage to release high-pressure refrigerant into the low-pressure gas pipe 15.

[0038] The first electronic expansion valve 31, the third electronic expansion valve 33, and the fourth electronic expansion valve 34 are configured to close in the event of a refrigerant leak.

[0039] In simultaneous cooling and heating mode, the opening degree of the third electronic expansion valve 33 corresponding to the cooling indoor unit is 25 pulses.

[0040] The fourth electronic expansion valve 34 is configured to close when its corresponding indoor unit is heating. When the indoor unit is heating, the corresponding fourth electronic expansion valve 34 is closed to prevent refrigerant from flowing between the low-pressure gas pipe 15 and the indoor unit side gas pipe 12.

[0041] Specifically, refer to Figure 3 During normal cooling, the liquid refrigerant enters the indoor unit from the outdoor unit side through the first electronic expansion valve 31, evaporates and absorbs heat to become gaseous refrigerant. The gaseous refrigerant returning from the indoor unit side gas pipe 12 is divided into two paths: one path returns to the outdoor unit side low-pressure gas pipe 15 through the fourth electronic expansion valve 34, and the other path returns to the outdoor side high and low pressure gas pipe 14 through the third electronic expansion valve 33, thus completing the indoor unit cooling cycle.

[0042] If refrigerant leaks at this time, the first electronic expansion valve 31, the third electronic expansion valve 33, and the fourth electronic expansion valve 34 will close to prevent the refrigerant from continuing to leak to the indoor unit side. At the same time, the unloading valve 35 will open to release the high-pressure refrigerant generated at the moment the electronic expansion valve closes into the low-pressure gas pipe 15, thereby improving the safety of the device.

[0043] Reference Figure 4 During normal heating, the gaseous refrigerant passes through the third electronic expansion valve 33 from the outdoor unit side. At this time, the fourth electronic expansion valve 34 is in the closed state. The gaseous refrigerant enters the indoor unit side along the pipeline. The gaseous refrigerant condenses and releases heat on the indoor unit side, and then passes through the first electronic expansion valve 31 back to the outdoor unit side, completing the indoor unit heating cycle.

[0044] If a refrigerant leak occurs at this time, the first electronic expansion valve 31, the third electronic expansion valve 33, and the fourth electronic expansion valve 34 will close to prevent the refrigerant from continuing to leak to the indoor unit side. At the same time, the unloading valve 35 will open to release the high-pressure refrigerant generated at the moment the electronic expansion valve closes into the low-pressure gas pipe 15, thereby improving the safety of the device.

[0045] In some embodiments of this application, reference is made to Figure 1 and Figure 2 The first branch 21 is equipped with a first filter 41 and a second filter 42. The first electronic expansion valve 31 is located between the first filter 41 and the second filter 42. The first filter 41 is close to the liquid pipe 13 on the outdoor unit side, and the second filter 42 is close to the liquid pipe 11 on the indoor unit side.

[0046] The second branch 22 is equipped with a third filter 43 and a fourth filter 44. The third filter 43 is located on the side of the fourth electronic expansion valve 34 near the low-pressure gas pipe 15, and the fourth filter 44 is located on the side of the fourth electronic expansion valve 34 near the indoor unit side gas pipe 12.

[0047] A fifth filter 45 is installed on the third branch 23. The fifth filter 45 is located on the side of the third electronic expansion valve 33 near the high and low pressure air pipes 14.

[0048] By setting up the filters mentioned above, impurities in the refrigerant are filtered out, preventing system components from becoming clogged and worn.

[0049] The filter located upstream of the electronic expansion valve can filter out impurities, metal shavings, welding slag, oil stains and other solid particles in the refrigerant, preventing impurities from entering the electronic expansion valve and avoiding scratches, jamming or blockage of the valve needle and valve port. This ensures that the opening adjustment of the electronic expansion valve is accurate and the operation is reliable, while also protecting the throttling components from damage and extending their service life.

[0050] The filter located downstream of the electronic expansion valve can intercept tiny abrasive particles and impurities that may be generated by the electronic expansion valve itself, preventing them from entering subsequent components such as the evaporator and the compressor suction side. This avoids evaporator pipe blockage or compressor wear, and further improves the stability and safety of system operation.

[0051] In some embodiments of this application, reference is made to Figures 5 to 8 The central air conditioning unit includes multiple switching and shut-off devices 100, each corresponding to a specific indoor unit. This embodiment uses four indoor units as an example. The first branch 21 of the multiple switching and shut-off devices 100 converges and connects to the liquid pipe 13 on the outdoor unit side; the second branch 22 of the multiple switching and shut-off devices 100 converges and connects to the low-pressure gas pipe 15; and the third branch 23 of the multiple switching and shut-off devices 100 converges and connects to the high- and low-pressure gas pipes 14. This arrangement allows for a compact layout of the multiple switching and shut-off devices 100, facilitating connection to the outdoor unit and the corresponding indoor unit.

[0052] The following is a brief description of the various operating modes of a central air conditioning system. A central air conditioning system includes cooling mode, heating mode, cooling-only mode, and heating-only mode. Cooling-only mode refers to a mode where the number of indoor units performing cooling is greater than the number performing heating. Heating-only mode refers to a mode where the number of indoor units performing heating is greater than the number performing cooling.

[0053] The central air conditioning system has a cooling mode. In cooling mode, the first electronic expansion valve 31, the third electronic expansion valve 33, and the fourth electronic expansion valve 34 in each switching and shut-off device are fully open. Specifically, refer to... Figure 5When the central air conditioning unit operates in cooling mode, the refrigerant reaches the first electronic expansion valve 31A / 31B / 31C / 31D through the liquid pipe 13 on the outdoor unit side. At this time, the first electronic expansion valve 31A / 31B / 31C / 31D is fully open, and the refrigerant enters indoor units A, B, C, and D for evaporation and heat absorption. In indoor unit A, the refrigerant after heat exchange is divided into two branches: one flows through the third electronic expansion valve 33A and the high / low pressure pipe 14 back to the outdoor unit, and the other flows through the fourth electronic expansion valve 34A and the low-pressure pipe 15 back to the outdoor unit. Similarly, in indoor unit B, the refrigerant after heat exchange is divided into two branches after passing through the second electronic expansion valve 32B: one flows through the third electronic expansion valve 33B and the high / low pressure pipe 14 back to the outdoor unit, and the other... One path of refrigerant flows through the fourth electronic expansion valve 34B and low-pressure pipe 15 back to the outdoor unit; after heat exchange in indoor unit C, the refrigerant is divided into two branches after passing through the second electronic expansion valve 32C. One path flows through the third electronic expansion valve 33C and high-low pressure pipe 14 back to the outdoor unit, and the other path flows through the fourth electronic expansion valve 34C and low-pressure pipe 15 back to the outdoor unit; after heat exchange in indoor unit D, the refrigerant is divided into two branches after passing through the second electronic expansion valve 32D. One path flows through the third electronic expansion valve 33D and high-low pressure pipe 14 back to the outdoor unit, and the other path flows through the fourth electronic expansion valve 34D and low-pressure pipe 15 back to the outdoor unit; at this time, the third electronic expansion valves 33A / 33B / 33C / 33D and the fourth electronic expansion valves 34A / 34B / 34C / 34D are in the fully open state.

[0054] If a refrigerant leak occurs in the system, the first electronic expansion valve 31A / 31B / 31C / 31D, the third electronic expansion valve 33A / 33B / 33C / 33D, and the fourth electronic expansion valve 34A / 34B / 34C / 34D will receive a valve closing command, and the electronic expansion valves will be in a fully closed state. At the same time, in order to prevent a sudden increase in refrigerant pressure when the electronic expansion valves close, the unloading valves 35A / 35B / 35C / 35D will be opened to release the high-pressure refrigerant into the low-pressure gas pipe 15, and then recover it into the outdoor unit.

[0055] The central air conditioning system has a heating mode. In the heating mode, the first electronic expansion valve 31 in each switching and shut-off device is fully open, the third electronic expansion valve 33 is fully open, and the fourth electronic expansion valve 34 is fully closed.

[0056] Specifically, refer to Figure 6When the central air conditioning unit is in heating mode, the refrigerant reaches the third electronic expansion valve 33A / 33B / 33C / 33D through the high and low pressure gas pipes 14. At this time, the third electronic expansion valve 33A / 33B / 33C / 33D is fully open, and the fourth electronic expansion valve 34A / 34B / 34C / 34D is fully closed. The refrigerant enters indoor units A, B, C, and D for condensation and heat release. The refrigerant after heat exchange in indoor unit A flows back to the outdoor unit through the first electronic expansion valve 31A and the outdoor unit side liquid pipe 13. The sub-expansion valve 31A is fully open; correspondingly, the refrigerant after heat exchange in indoor unit B flows through the first electronic expansion valve 31B and the liquid pipe 13 on the outdoor unit side back to the outdoor unit, with the first electronic expansion valve 31B fully open; the refrigerant after heat exchange in indoor unit C flows through the first electronic expansion valve 31C and the liquid pipe 13 on the outdoor unit side back to the outdoor unit, with the first electronic expansion valve 31C fully open; the refrigerant after heat exchange in indoor unit D flows through the first electronic expansion valve 31D and the liquid pipe 13 on the outdoor unit side back to the outdoor unit, with the first electronic expansion valve 31D fully open. If a refrigerant leak occurs in the system, the first electronic expansion valve 31A / 31B / 31C / 31D, the third electronic expansion valve 33A / 33B / 33C / 33D, and the fourth electronic expansion valve 34A / 34B / 34C / 34D will receive a valve closing command, and the electronic expansion valves will be in a fully closed state. At the same time, in order to prevent a sudden increase in refrigerant pressure when the electronic expansion valves close, the unloading valves 35A / 35B / 35C / 35D will be opened to release the high-pressure refrigerant into the low-pressure gas pipe 15, and then recover it into the outdoor unit.

[0057] The central air conditioning system has a cooling main mode. In the cooling main mode, the first electronic expansion valve 31 is fully open; the third electronic expansion valve 33 corresponding to the heating indoor unit is fully open and the fourth electronic expansion valve 34 is fully closed; the third electronic expansion valve 33 corresponding to the cooling indoor unit is opened at a set opening degree and the fourth electronic expansion valve 34 is fully open.

[0058] Specifically, refer to Figure 7 When the central air conditioning unit is in cooling mode, taking indoor units A, B, and C receiving cooling commands and indoor unit D receiving heating commands as an example, the refrigerant reaches the first electronic expansion valve 31A / 31B / 31C through the liquid pipe on the outdoor unit side. At this time, the first electronic expansion valve 31A / 31B / 31C / 31D is fully open. The refrigerant flows through indoor units A, B, and C to evaporate and absorb heat. After heat exchange, the refrigerant reaches the fourth electronic expansion valve 34A / 34B / 34C. At this time, the fourth electronic expansion valve 34A / 34B / 34C is fully open, and the refrigerant then returns to the low-pressure gas pipe 15.

[0059] For indoor unit D that receives the heating command, the refrigerant reaches the third electronic expansion valve 33A / 33B / 33C / 33D through the high and low pressure gas pipes 14. At this time, the third electronic expansion valve 33D is fully open, and the fourth electronic expansion valve 34D is fully closed. The control valve opening of the third electronic expansion valve 33A / 33B / 33C is 25pls. In order to prevent the high-pressure gaseous refrigerant from accumulating at the third electronic expansion valve 33D for a long time and liquefying, the valve opening of the third electronic expansion valve 33D is controlled to be 25pls. The refrigerant enters indoor unit D to condense and release heat. The refrigerant after releasing heat reaches the first electronic expansion valve 31D. At this time, the first electronic expansion valve 31D is fully open. The refrigerant after passing through the first electronic expansion valve 31D is recirculated into indoor units A / B / C.

[0060] To prevent high-pressure gaseous refrigerant from liquefying due to prolonged accumulation at the third electronic expansion valve 33A / 33B / 33C, this application controls the valve opening of the third electronic expansion valve 33A / 33B / 33C to 25pls, and keeps the fourth electronic expansion valve 34A / 34B / 34C fully open. This allows the high-pressure refrigerant to pass through the third electronic expansion valve 33A / 33B / 33C at a very low flow rate, and then return to the low-pressure gas pipe through the fourth electronic expansion valve 34A / 34B / 34C, thereby resolving the risk of liquid seal in the outdoor unit.

[0061] If a refrigerant leak occurs in the system, the first electronic expansion valve 31A / 31B / 31C / 31D, the third electronic expansion valve 33A / 33B / 33C / 33D, and the fourth electronic expansion valve 34A / 34B / 34C / 34D will receive a valve closing command, and the electronic expansion valves will be in a fully closed state. At the same time, in order to prevent a sudden increase in refrigerant pressure when the electronic expansion valves close, the unloading valves 35A / 35B / 35C / 35D will be opened to release the high-pressure refrigerant into the low-pressure gas pipe 15, and then recover it into the outdoor unit.

[0062] The central air conditioning system has a heating main mode. In the heating main mode, the first electronic expansion valve 31 is fully open; the third electronic expansion valve 33 corresponding to the heating indoor unit is fully open and the fourth electronic expansion valve 34 is fully closed; the third electronic expansion valve 33 corresponding to the cooling indoor unit is open at a set opening degree and the fourth electronic expansion valve 34 is fully open.

[0063] Specifically, refer to Figure 8When the central air conditioning unit executes the main heating mode, taking indoor units A, B, and C receiving heating commands and indoor unit D receiving cooling commands as an example, the refrigerant reaches the third electronic expansion valve 33A / 33B / 33C / 33D through the high and low pressure gas pipes 14. At this time, the third electronic expansion valves 33A / 33B / 33C are fully open, and the valve opening of the third electronic expansion valve 33D is controlled at 25pls. In order to prevent the high-pressure gaseous refrigerant from accumulating at the third electronic expansion valve 33D for a long time and liquefying, this application controls the valve opening of the third electronic expansion valve 33D to 25pls, the fourth electronic expansion valves 34A / 34B / 34C are fully closed, and the fourth electronic expansion valve 34D is fully open. This allows the high-pressure refrigerant to pass through the third electronic expansion valve 33D at a very small flow rate, and then return to the low-pressure gas pipe through the fourth electronic expansion valve 34D, thereby solving the risk of liquid seal in the outdoor unit.

[0064] The refrigerant passing through the third electronic expansion valve 33A / 33B / 33C enters indoor unit A, indoor unit B, and indoor unit C for condensation and heat release. After heat release, the refrigerant reaches the first electronic expansion valve 31A / 31B / 31C, which is fully open at this time. Then, the refrigerant reaches the first electronic expansion valve 31D, which is also fully open. The refrigerant flows through indoor unit D for evaporation and heat absorption. After heat exchange, the refrigerant returns to the low-pressure gas pipe 15 through the fourth electronic expansion valve 34D4.

[0065] If a refrigerant leak occurs in the system, the first electronic expansion valve 31A / 31B / 31C / 31D, the third electronic expansion valve 33A / 33B / 33C / 33D, and the fourth electronic expansion valve 34A / 34B / 34C / 34D will receive a valve closing command, and the electronic expansion valves will be in a fully closed state. At the same time, in order to prevent a sudden increase in refrigerant pressure when the electronic expansion valves close, the unloading valves 35A / 35B / 35C / 35D will be opened to release the high-pressure refrigerant into the low-pressure gas pipe 15, and then recover it into the outdoor unit.

[0066] In the description of the above embodiments, specific features, structures, materials, or characteristics may be combined in any suitable manner in one or more embodiments or examples.

[0067] The above are merely specific embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A three-pipe heat recovery central air conditioning system, comprising an outdoor unit and multiple indoor units, characterized in that, The central air conditioning unit further includes a switching cutoff device connected to the outdoor unit and the indoor unit. The switching cutoff device is configured to switch between cooling and heating modes and to cut off refrigerant supply in case of refrigerant leakage. It includes: The first branch line connects the liquid pipe on the outdoor unit side and the liquid pipe on the indoor unit side, and the first branch line is equipped with a first electronic expansion valve. The second branch connects the low-pressure gas pipe on the outdoor unit side and the gas pipe on the indoor unit side. A fourth electronic expansion valve is installed on the second branch. The third branch is connected to the high and low pressure gas pipes on the outdoor unit side and the second branch. The third branch is equipped with a third electronic expansion valve with adjustable opening. An unloading branch, which connects the first branch and the second branch, is configured to release high-pressure refrigerant into a low-pressure gas line in the event of a refrigerant leak. In the simultaneous cooling and heating mode, the third electronic expansion valve corresponding to the cooling indoor unit is opened at a set opening degree to prevent refrigerant from accumulating at the third electronic expansion valve for a long time and causing liquid sealing.

2. The central air conditioning system according to claim 1, characterized in that, The first electronic expansion valve, the third electronic expansion valve, and the fourth electronic expansion valve are configured to close in the event of a refrigerant leak.

3. The central air conditioning system according to claim 1, characterized in that, The fourth electronic expansion valve is configured to close when its corresponding indoor unit is heating.

4. The central air conditioning system according to claim 1, characterized in that, An unloading valve is provided on the unloading branch. The unloading valve is configured to close when the central air conditioning unit is operating normally. The unloading valve is also configured to open when the refrigerant leaks to release the high-pressure refrigerant into the low-pressure gas pipe.

5. The central air conditioning system according to claim 1, characterized in that, In simultaneous cooling and heating mode, the opening degree of the third electronic expansion valve corresponding to the cooling indoor unit is 25 pulses.

6. The central air conditioning system according to any one of claims 1 to 5, characterized in that, The central air conditioning unit includes multiple switching and shut-off devices, each corresponding to one of the multiple indoor units. The first branches of the multiple switching and shut-off devices are connected to the liquid pipe on the outdoor unit side after being joined together. The second branches of the multiple switching and shut-off devices are connected to the low-pressure gas pipe after being joined together. The third branches of the multiple switching and shut-off devices are connected to the high- and low-pressure gas pipes after being joined together.

7. The central air conditioning system according to claim 6, characterized in that, The central air conditioning system has a heating mode. In the heating mode, the first electronic expansion valve in each of the switching and shut-off devices is fully open, the third electronic expansion valve is fully open, and the fourth electronic expansion valve is fully closed.

8. The central air conditioning system according to claim 6, characterized in that, The central air conditioning system has a cooling mode. In the cooling mode, the first electronic expansion valve, the third electronic expansion valve, and the fourth electronic expansion valve in each of the switching and shut-off devices are fully open.

9. The central air conditioning system according to claim 6, characterized in that, The central air conditioning system has a heating main mode. In the heating main mode, the first electronic expansion valve is fully open; the third electronic expansion valve corresponding to the heating indoor unit is fully open and the fourth electronic expansion valve is fully closed; the third electronic expansion valve corresponding to the cooling indoor unit is open at a set opening degree and the fourth electronic expansion valve is fully open.

10. The central air conditioning system according to claim 6, characterized in that, The central air conditioning system has a cooling main mode. In the cooling main mode, the first electronic expansion valve is fully open; the third electronic expansion valve corresponding to the heating indoor unit is fully open and the fourth electronic expansion valve is fully closed; the third electronic expansion valve corresponding to the cooling indoor unit is opened to a set degree and the fourth electronic expansion valve is fully open.

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