Water source machine

Abstract

This invention belongs to the technical field of air conditioning equipment, specifically relating to a water-source heat pump unit, including a compressor, a plate heat exchanger, and a bypass branch. A four-way valve is connected to the compressor's input port via a third refrigerant main line, and to one end of the refrigerant flow path in the plate heat exchanger; the other end of the refrigerant flow path is connected to the indoor unit via a fifth refrigerant main line; a main expansion valve is installed on the fifth refrigerant main line; the bypass branch is located between the fifth and third refrigerant main lines, and a bypass expansion valve is installed on the bypass branch. The bypass expansion valve allows a portion of the throttled refrigerant to bypass the plate heat exchanger and flow into the suction side. After the refrigerant that has undergone heat exchange in the plate heat exchanger mixes with the refrigerant that has bypassed through the bypass branch, the temperature and pressure of the refrigerant drawn into the compressor can be indirectly regulated; this avoids excessively high water temperature in the plate heat exchanger and excessively high refrigerant temperature and pressure in the compressor, which can cause problems such as poor compressor stability and low energy efficiency.

Description

Technical Field

[0001] This invention belongs to the field of air conditioning equipment technology, and particularly relates to a water source unit. Background Technology

[0002] A water source heat pump is a multi-split air conditioning system that uses water as a medium for heat exchange. It exchanges heat with an auxiliary heat source through a closed circulating water pipeline. In heating mode, the refrigerant releases heat through the indoor condenser and is then transported to the plate heat exchanger to absorb heat from the circulating water. The refrigerant then returns to the compressor, where the water temperature decreases. The cooled water is then sent to an auxiliary heat source (such as a boiler, air source heat pump, or ground source heat pump) for heating and is then circulated back to provide heat to the system.

[0003] When the water temperature in a plate heat exchanger is high or fluctuates drastically, the system high pressure is prone to approaching the upper limit or triggering high-pressure protection, affecting stability and energy efficiency. Traditional countermeasures include reducing compressor frequency, optimizing electronic expansion valve (EEV) control, and increasing water-side flow rate and heat exchange area. However, in existing systems, where retrofitting is limited, or where water source fluctuations are significant, these methods are difficult to implement or have limited effectiveness. Summary of the Invention

[0004] The purpose of this invention is to provide a water source unit to solve the problems existing in the prior art, such as the system high pressure easily approaching the upper limit or triggering high pressure protection when the water temperature in the plate heat exchanger is high or fluctuates drastically, affecting stability and energy efficiency.

[0005] To achieve the above-mentioned objectives, the present invention employs the following technical solution:

[0006] This invention proposes a water source unit, which includes an indoor unit and an outdoor unit, wherein the outdoor unit includes:

[0007] The compressor has an input port and an output port.

[0008] Plate heat exchangers have internal refrigerant and water flow paths;

[0009] The four-way valve includes a first valve port, a second valve port, a third valve port, and a fourth valve port. The first valve port is connected to the output port of the compressor, the second valve port is connected to the indoor unit, the third valve port is connected to the input port of the compressor via a third refrigerant main line, and the fourth valve port is connected to one end of the refrigerant flow path. The other end of the refrigerant flow path is connected to the indoor unit via a fifth refrigerant main line. A main expansion valve is provided on the fifth refrigerant main line.

[0010] A bypass branch is provided between the fifth refrigerant main line and the third refrigerant main line, and the connection point between the bypass branch and the fifth refrigerant main line is located between the plate heat exchanger and the main expansion valve. A bypass expansion valve is provided on the bypass branch.

[0011] The controller is used to control the opening and closing of the bypass expansion valve. When the bypass expansion valve is open, part of the refrigerant that has passed through the main expansion valve flows from the bypass branch to the third refrigerant main line.

[0012] In some embodiments of this application, the input port of the compressor is provided with a suction pressure sensor and a suction temperature sensor. The suction pressure sensor is used to detect the suction pressure of the compressor, and the suction temperature sensor is used to detect the suction temperature of the compressor.

[0013] The compressor's output port is equipped with an exhaust pressure sensor and an exhaust temperature sensor. The exhaust pressure sensor is used to detect the compressor's exhaust pressure, and the exhaust temperature sensor is used to detect the compressor's exhaust temperature.

[0014] In some embodiments of this application, a first temperature sensor and a second temperature sensor are respectively provided at both ends of the refrigerant flow path of the plate heat exchanger. In the heating mode, the first temperature sensor is provided at the inlet end of the refrigerant flow path to detect the temperature of the refrigerant input to the plate heat exchanger, and the second temperature sensor is provided at the outlet end of the refrigerant flow path to detect the temperature of the refrigerant output from the plate heat exchanger.

[0015] The plate heat exchanger is equipped with an inlet water temperature sensor at the inlet end of the water flow path to detect the inlet water temperature, and an outlet water temperature sensor at the outlet end of the water flow path to detect the outlet water temperature.

[0016] In some embodiments of this application, a controller is also included. During heating operation, the controller controls the first valve port to connect with the second valve port, the third valve port to connect with the fourth valve port, and the bypass expansion valve to close. The controller controls the main expansion valve to open to a preset degree and controls the compressor to run at a preset frequency.

[0017] When the discharge pressure of the compressor is not higher than the minimum value of the high-pressure soft limit range, the controller maintains the current operating frequency of the compressor and keeps the current opening of the main expansion valve running.

[0018] In some embodiments of this application, when the discharge pressure of the compressor is higher than the minimum value of the high-pressure soft limiting range and lower than the maximum value of the high-pressure soft limiting range, the controller controls the compressor to reduce the first unit frequency, controls the main expansion valve to close the first unit opening, and controls the bypass expansion valve to open the second unit opening.

[0019] After running for a preset time, the controller re-determines the compressor's discharge pressure. If the compressor's discharge pressure is still within the high-pressure soft-limiting zone, the controller continues to control the compressor to reduce the first unit frequency, control the main expansion valve to close the first unit opening, and control the bypass expansion valve to open the second unit opening, until the compressor's discharge pressure is not higher than the minimum value of the high-pressure soft-limiting zone. Then, the controller maintains the compressor's current operating frequency and keeps the main expansion valve and the bypass expansion valve at their current openings.

[0020] In some embodiments of this application, when the discharge pressure of the compressor is not lower than the maximum value of the high-pressure soft limiting range, the controller controls the compressor to reduce the second unit frequency, controls the main expansion valve to close the third unit opening, and controls the bypass expansion valve to open the fourth unit opening.

[0021] Wherein, the second unit frequency is greater than the first unit frequency, the third unit opening is greater than the first unit opening, and the fourth unit opening is greater than the second unit opening;

[0022] After running for a preset time, the controller re-determines the compressor's discharge pressure. If the compressor's discharge pressure is still not lower than the maximum value of the high-pressure soft-limiting range, the controller continues to control the compressor to reduce the second unit frequency, control the main expansion valve to close the third unit opening, and control the bypass expansion valve to open the fourth unit opening.

[0023] Until the compressor's discharge pressure is not higher than the minimum value of the high-pressure soft limit range, the controller maintains the compressor's current operating frequency and keeps the main expansion valve and the bypass expansion valve at their current openings.

[0024] In some embodiments of this application, the bypass mass split ratio β of the bypass expansion valve satisfies: β∈[0,β_max];

[0025] Where β = m_bp / (m_bp + m_evap), 0.1 ≤ β_max ≤ 0.6;

[0026] m_bp is the refrigerant mass flow rate of the bypass branch;

[0027] m_evap is the refrigerant mass flow rate input to the plate heat exchanger.

[0028] In some embodiments of this application, a first shut-off valve and a second shut-off valve are provided between the indoor unit and the outdoor unit. The first shut-off valve is connected between the second valve port and the indoor unit, and the second shut-off valve is connected between the indoor unit and the plate heat exchanger.

[0029] A liquid storage tank is provided between the main expansion valve and the second shut-off valve, and filters are provided on both sides of the main expansion valve.

[0030] In some embodiments of this application, the output port of the compressor is further provided with an oil separator. The oil separator includes a separation housing, on which an air inlet port, an air outlet port, and an oil return port are formed. The air inlet port is connected to the output port of the compressor through an exhaust pipe, the air outlet port is connected to the first valve port through an air supply pipe, and the oil return port is connected to the compressor through an oil return pipe. The oil return pipe is provided with an oil return capillary tube, which is disposed inside the separation housing.

[0031] In some embodiments of this application, the input port of the compressor is further provided with a gas-liquid separator, and the effective volume V_acc of the gas-liquid separator satisfies:

[0032] V_acc≥0.8×[M_charge×χ_worst+m_total_max×t_hold×χ_dyn] / ρ_liq

[0033] Where M_charge is the system refrigerant charge;

[0034] χ_worst represents the proportion of the two most unfavorable phases;

[0035] m_total_max is the maximum total mass flow;

[0036] t_hold is the buffer time;

[0037] χ_dyn is a dynamic additional coefficient;

[0038] ρ_liq is the liquid phase density at the current temperature.

[0039] Compared with the prior art, the advantages and positive effects of the present invention are:

[0040] The water source unit proposed in this application is equipped with a bypass branch, which is equipped with a bypass expansion valve. After the bypass expansion valve is opened, part of the refrigerant after being throttled by the main expansion valve can bypass the plate heat exchanger and directly flow into the third refrigerant main line before the gas-liquid separator. After the refrigerant after heat exchange in the plate heat exchanger is mixed with the refrigerant after bypassing through the bypass branch, the temperature and pressure of the refrigerant in the suction compressor can be indirectly regulated. This avoids problems such as excessively high water temperature in the plate heat exchanger and excessively high refrigerant temperature and pressure in the suction compressor, which would lead to poor compressor stability and low energy efficiency.

[0041] 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

[0042] 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.

[0043] Figure 1 This is a system diagram of the water source unit according to an embodiment;

[0044] Figure 2 This is a schematic diagram of a four-way valve according to an embodiment;

[0045] Figure 3 This is a schematic diagram of a plate heat exchanger according to an embodiment;

[0046] Figure 4 This is a schematic diagram showing the flow of refrigerant in the water source unit under the heating mode according to an embodiment;

[0047] Figure 5 This is a schematic diagram illustrating the flow of refrigerant within the water source unit under the cooling mode according to an embodiment.

[0048] Figure 6 This is a control flowchart during operation in heating mode according to the embodiment;

[0049] Figure 7 The external structure of the oil separator according to the embodiment;

[0050] Figure 8 for Figure 7 AA section view in the middle;

[0051] Figure 9 One of the schematic diagrams showing the installation of the return capillary tube inside the oil separator;

[0052] Figure 10 Schematic diagram 2 showing the installation of the return capillary tube inside the oil separator;

[0053] Figure label:

[0054] 10. First refrigerant main road;

[0055] 20. Second refrigerant main line; 21. First shut-off valve;

[0056] 30. Third refrigerant main road;

[0057] 40. Fourth refrigerant main road;

[0058] 50. Fifth refrigerant main line; 51. Main expansion valve; 52. Second shut-off valve;

[0059] 60. Oil return line; 61. Oil return capillary tube;

[0060] 70. Bypass branch; 71. Bypass expansion valve;

[0061] 100. Compressor; 101. Discharge pressure sensor; 102. Intake pressure sensor; 103. Discharge temperature sensor; 104. Intake temperature sensor;

[0062] 200. Oil separator; 210. Separator housing; 220. Exhaust pipe; 230. Air supply pipe; 231. Air outlet pipe; 240. Oil return pipe;

[0063] 300 Plate heat exchanger; 310 Refrigerant flow path; 311 First temperature sensor; 312 Second temperature sensor; 320 Water flow path; 321 Inlet water temperature sensor; 322 Outlet water temperature sensor;

[0064] 400, Four-way valve; 410, First valve port; 420, Second valve port; 430, Third valve port; 440, Fourth valve port;

[0065] 500. Liquid storage tank; 600. Gas-liquid separator; 700. Subcooler. Detailed Implementation

[0066] 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.

[0067] In the description of this application, it should be understood that the terms "center", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application.

[0068] The terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this application, unless otherwise stated, "a plurality of" means two or more.

[0069] In the description of this application, it should be noted that, unless otherwise expressly specified and limited, the terms "installation," "connection," and "linking" 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; and they can refer to the internal connection between two components. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0070] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0071] The following disclosure provides many different embodiments or examples for implementing various structures of the invention. To simplify the disclosure, specific examples of components and arrangements are described below. These are merely examples and are not intended to limit the invention. Furthermore, reference numerals and / or letters may be repeated in different examples; such repetition is for simplification and clarity and does not in itself indicate a relationship between the various embodiments and / or arrangements discussed. In addition, examples of various specific processes and materials are provided in this invention, but those skilled in the art will recognize the application of other processes and / or the use of other materials.

[0072] Water source air conditioning units and other similar equipment execute the refrigeration cycle using a compressor, condenser, expansion valve, and evaporator. The refrigeration cycle involves a series of processes, including compression, condensation, expansion, and evaporation, to cool or heat an indoor space.

[0073] 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.

[0074] 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.

[0075] 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.

[0076] 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.

[0077] refer to Figure 1 This application proposes a water source unit, which includes an indoor unit and an outdoor unit, connected by a refrigerant pipeline, and a first shut-off valve 21 and a second shut-off valve 52 are provided between the indoor unit and the outdoor unit.

[0078] Specifically, the first shut-off valve 21 is connected between the second valve port 420 and the indoor unit, and the second shut-off valve 52 is connected between the indoor unit and the plate heat exchanger 300.

[0079] The outdoor unit includes a compressor 100, a plate heat exchanger 300, and a four-way valve 400.

[0080] The compressor 100 has an input port and an output port. The high-temperature and high-pressure refrigerant output from the compressor 100 is delivered to the indoor unit or the plate heat exchanger 300 through the four-way valve 400.

[0081] The compressor 100 can be a rotary compressor 100, a scroll compressor 100, or a reciprocating compressor 100, etc., and it stores refrigerant oil inside for lubricating the friction pairs. The compressor 100 has a refrigerant suction end and a refrigerant discharge end formed on its casing. During operation, the compressor 100 compresses the low-temperature, low-pressure gaseous refrigerant into a high-temperature, high-pressure gaseous refrigerant and discharges it. During this process, a small amount of refrigerant oil is discharged along with the refrigerant.

[0082] The compressor 100 serves as the core power source of the refrigeration cycle in the system, and the high-temperature, high-pressure gaseous refrigerant it discharges is the carrier of heat carried by the circulating working fluid. For example, in cooling mode, the compressor 100 discharges heat into the condenser; in heating mode, the flow direction is switched by the four-way valve 400, and the compressor 100 discharges heat directly into the indoor heat exchanger (which acts as the condenser in this case) to release heat.

[0083] The compressor 100's discharge temperature, pressure, and flow rate will change under different operating conditions such as startup, operation, and shutdown. For example, when starting under low-temperature heating conditions, the compressor 100's discharge temperature may rapidly rise from ambient temperature to over 80°C. Throughout the entire operating cycle, the compressor 100 continuously outputs high-temperature refrigerant, which provides a stable high-temperature thermal environment inside the oil separator 200.

[0084] The refrigerant discharged from compressor 100 has the highest temperature within the system. This high-temperature characteristic is crucial for the subsequent oil heating process within oil separator 200. In other embodiments, compressor 100 may also employ a dual-rotor or multi-cylinder structure to accommodate different capacity requirements.

[0085] Combination Figure 4 During refrigeration operation, the four-way valve 400 switches to connect the output port of the compressor 100 to the plate heat exchanger 300. The refrigerant output from the compressor 100 is transported to the plate heat exchanger 300 through the four-way valve 400 for condensation and heat exchange. After heat exchange, the refrigerant continues to be transported to the indoor heat exchanger for evaporation and heat absorption. Finally, it returns to the compressor 100.

[0086] Combination Figure 5 During heating operation, the four-way valve 400 switches to the output port of the compressor 100 and connects to the indoor unit. The refrigerant output from the compressor 100 is delivered to the indoor heat exchanger through the four-way valve 400 for condensation and heat exchange. After heat exchange, the refrigerant continues to be delivered to the plate heat exchanger 300 for evaporation and heat absorption. Finally, it returns to the compressor 100.

[0087] Combination Figure 3 Specifically, the plate heat exchanger 300 has a refrigerant flow path 310 and a water flow path 320. In the plate heat exchanger 300, the refrigerant flows in the refrigerant flow path 310 and the water flows in the water flow path 320. The fluids flow through different channels and do not mix with each other. The high-temperature fluid releases heat during the flow process, while the low-temperature fluid absorbs this heat, thereby realizing the transfer of heat.

[0088] refer to Figure 2 The four-way valve 400 includes a first valve port 410, a second valve port 420, a third valve port 430, and a fourth valve port 440. The first valve port 410 is connected to the output port of the compressor 100, the second valve port 420 is connected to the indoor unit, the third valve port 430 is connected to the input port of the compressor 100 through the third refrigerant main line 30, and the fourth valve port 440 is connected to one end of the refrigerant flow path 310.

[0089] Specifically, the first valve port 410 is connected to the output port of the compressor 100 through the first refrigerant main line 10, the second valve port 420 is connected to the indoor unit through the second refrigerant main line 20, the third valve port 430 is connected to the input port of the compressor 100 through the third refrigerant main line 30, and the fourth valve port 440 is connected to the plate heat exchanger 300 through the fourth refrigerant main line 40.

[0090] The other end of the refrigerant flow path 310 of the plate heat exchanger 300 is connected to the indoor unit through the fifth refrigerant main line 50; a main expansion valve 51 is installed on the fifth refrigerant main line 50.

[0091] The controller is used to control the opening and closing of the bypass expansion valve. When the bypass expansion valve is open, part of the refrigerant that has passed through the main expansion valve flows from the bypass branch to the third refrigerant main line.

[0092] A liquid storage tank 500 is provided between the main expansion valve 51 and the second shut-off valve 52. Filters are provided on both sides of the main expansion valve 51 to filter impurities in the refrigerant.

[0093] A subcooler 700 is also provided between the liquid receiver 500 and the second shut-off valve 52 to ensure that the refrigerant entering the main expansion valve 51 is a subcooled liquid with a temperature lower than the saturation temperature at the current pressure. This prevents "flash gas" (premature vaporization of liquid) from occurring before throttling, ensures stable operation of the expansion valve, and increases the cooling capacity per unit mass of refrigerant.

[0094] Refer again Figure 4 During cooling, the first valve port 410 is connected to the fourth valve port 440, and the second valve port 420 is connected to the third valve port 430. During heating, the first valve port 410 is connected to the second valve port 420, and the third valve port 430 is connected to the fourth valve port 440.

[0095] Filters are installed on both sides of the main expansion valve 51 to intercept metal debris, moisture or foreign objects that may be present in the refrigerant circulation, and to prevent these impurities from entering the compressor 100 and causing mechanical failures such as cylinder jamming and valve plate wear.

[0096] A bypass branch 70 is provided between the fifth refrigerant main line 50 and the third refrigerant main line 30. The connection between the bypass branch 70 and the fifth refrigerant main line 50 is located between the plate heat exchanger 300 and the main expansion valve 51. A bypass expansion valve 71 is provided on the bypass branch 70.

[0097] The controller controls the opening and closing of the bypass expansion valve 71. When the bypass expansion valve 71 is open, part of the refrigerant that has passed through the main expansion valve 51 flows from the bypass branch 70 into the third refrigerant main line 30.

[0098] Refer again Figure 5When heating, if the water temperature in the plate heat exchanger 300 is too high, in order to avoid the system high pressure easily approaching the upper limit or triggering high pressure protection, affecting stability and energy efficiency, the bypass expansion valve 71 can be opened appropriately. After the bypass expansion valve is opened, part of the refrigerant output from the indoor heat exchanger is transported to the plate heat exchanger 300 for heat exchange, and the other part is directly transported to the third refrigerant main line 30 through the bypass branch 70. After mixing with the refrigerant after heat exchange in the plate heat exchanger 300, it returns to the compressor 100.

[0099] In some embodiments of this application, the input port of the compressor 100 is provided with a suction pressure sensor 102 and a suction temperature sensor 104. The suction pressure sensor 102 is used to detect the suction pressure Ps of the compressor 100, and the suction temperature sensor 104 is used to detect the suction temperature Ts of the compressor 100.

[0100] The compressor 100 is equipped with an exhaust pressure sensor 101 and an exhaust temperature sensor 103 at its output port. The exhaust pressure sensor 101 is used to detect the exhaust pressure Pd of the compressor 100, and the exhaust temperature sensor 103 is used to detect the exhaust temperature Td of the compressor 100.

[0101] In some embodiments of this application, a first temperature sensor 311 and a second temperature sensor 312 are respectively provided at both ends of the refrigerant flow path 310 of the plate heat exchanger 300. In the heating mode, the first temperature sensor 311 is provided at the inlet end of the refrigerant flow path 310 to detect the refrigerant temperature Tr_in input to the plate heat exchanger 300, and the second temperature sensor 312 is provided at the outlet end of the refrigerant flow path 310 to detect the refrigerant temperature Tr_out output from the plate heat exchanger 300.

[0102] The inlet water temperature sensor 321 is provided at the inlet end of the water flow path 320 of the plate heat exchanger 300 to detect the inlet water temperature Tw_in, and the outlet water temperature sensor 322 is provided at the outlet end of the water flow path 320 of the plate heat exchanger 300 to detect the outlet water temperature Tw_out.

[0103] The compressor 100 is also equipped with a gas-liquid separator 600 at its input port. The gas-liquid separator 600 is a device used to separate gas and liquid mixtures. It separates liquid droplets or mists entrained in the gas or releases dissolved or entrained gases in the liquid through physical methods (such as gravity settling, centrifugal force, collision, deflection, etc.).

[0104] A gas-liquid separator 600 is typically a cylindrical container with an air inlet, an air outlet, and a bottom oil return port.

[0105] The gas-liquid separator 600 is located between the evaporator and the input port of the compressor 100. Its main function is to separate the gas flow returning from the evaporator, which may contain incompletely evaporated liquid refrigerant, to prevent liquid refrigerant from entering the compressor 100 and causing liquid slugging damage. At the same time, it can also collect and allow a small amount of oil that may have circulated here with the refrigerant to return to the compressor 100.

[0106] The inlet of the gas-liquid separator 600 is connected to the outlet of the evaporator via the fifth refrigerant line. The outlet of the gas-liquid separator 600 is connected to the input port of the compressor 100 via a pipeline. A small hole or capillary tube is typically provided at its bottom to slowly evaporate or return any accumulated small amount of liquid refrigerant or oil to the suction port of the compressor 100.

[0107] During system operation, especially in cooling or low-temperature heating mode, the refrigerant at the evaporator outlet may be in a two-phase state (gas and liquid). The gas-liquid separator 600 receives this two-phase flow; the liquid component settles at the bottom due to gravity and evaporates slowly, while the gaseous component is directly drawn into the compressor 100 from the upper outlet. This ensures that superheated vapor enters the compressor 100, guaranteeing its safe operation.

[0108] Refer again Figure 1 In some embodiments of this application, a first temperature sensor 311 and a second temperature sensor 312 are respectively provided at both ends of the refrigerant flow path 310 of the plate heat exchanger 300. In the heating mode, the first temperature sensor 311 is provided at the inlet end of the refrigerant flow path 310 to detect the temperature of the refrigerant input to the plate heat exchanger 300, and the second temperature sensor 312 is provided at the outlet end of the refrigerant flow path 310 to detect the temperature of the refrigerant output from the plate heat exchanger 300.

[0109] The inlet water temperature sensor 321 is provided at the inlet end of the water flow path 320 of the plate heat exchanger 300 to detect the inlet water temperature, and the outlet water temperature sensor 322 is provided at the outlet end of the water flow path 320 of the plate heat exchanger 300 to detect the outlet water temperature.

[0110] refer to Figure 6 In some embodiments of this application, a controller is also included. During heating operation, the controller controls the first valve port 410 to connect with the second valve port 420, the third valve port 430 to connect with the fourth valve port 440, and the bypass expansion valve 71 to close. The controller controls the main expansion valve 51 to open to a preset degree and controls the compressor 100 to run at a preset frequency.

[0111] Define the discharge pressure Pd of compressor 100, and the high-pressure soft limiting range [Pd_warn, Pd_set_lim]; Pd_warn is the high-pressure warning threshold, which is also the minimum value of the high-pressure soft limiting range. It is the warning pressure before entering the soft limiting control, in MPa.

[0112] Among them, the value range of Pd_warn is 2.5 - 2.9 MPa, and the value range of Pd_set_lim is 3.0 - 3.9 MPa.

[0113] When the discharge pressure of the compressor 100 is not higher than the minimum value of the high-pressure soft limit range, that is, when Pd ≤ Pd_warn, the controller maintains the current operating frequency of the compressor 100 and continues to operate with the current opening degree of the main expansion valve 51.

[0114] In some embodiments of the present application, when the discharge pressure of the compressor 100 is higher than the minimum value of the high-pressure soft limit range and lower than the maximum value of the high-pressure soft limit range, that is, when the discharge pressure of the compressor 100 is within the high-pressure soft limit range Pd_warn < Pd < Pd_set_lim, the controller controls the compressor 100 to reduce the first unit frequency, controls the main expansion valve 51 to close the first unit opening degree, and controls the bypass expansion valve 71 to open the second unit opening degree;

[0115] After continuing to operate for a preset time, the controller re-determines the discharge pressure of the compressor 100. If the discharge pressure of the compressor 100 is still within the high-pressure soft limit range, that is, Pd_warn < Pd < Pd_set_lim, the controller continues to control the compressor 100 to reduce the first unit frequency, controls the main expansion valve 51 to close the first unit opening degree, and controls the bypass expansion valve 71 to open the second unit opening degree.

[0116] Through cyclic control, until the discharge pressure of the compressor 100 is not higher than the minimum value of the high-pressure soft limit range, the controller maintains the current operating frequency of the compressor 100 and continues to operate with the current opening degrees of the main expansion valve 51 and the bypass expansion valve 71.

[0117] In some embodiments of the present application, when the discharge pressure of the compressor 100 is not lower than the maximum value of the high-pressure soft limit range, that is, when Pd ≥ Pd_set_lim, the corresponding discharge pressure of the compressor 100 is in the forced pressure limit area, and an emergency avoidance action is immediately executed. The controller controls the compressor 100 to reduce the second unit frequency, controls the main expansion valve 51 to close the third unit opening degree, and controls the bypass expansion valve 71 to open the fourth unit opening degree;

[0118] Among them, the second unit frequency is greater than the first unit frequency, the third unit opening degree is greater than the first unit opening degree, and the fourth unit opening degree is greater than the second unit opening degree; safety and reliability are guaranteed first.

[0119] After running for the preset time, the controller re-determines the discharge pressure of the compressor 100. If the discharge pressure of the compressor 100 is still not lower than the maximum value of the high-pressure soft limit range, the controller continues to control the compressor 100 to reduce the second unit frequency, control the main expansion valve 51 to close the third unit opening, and control the bypass expansion valve 71 to open the fourth unit opening;

[0120] Until the discharge pressure of the compressor 100 is not higher than the minimum value of the high-pressure soft limit range, that is, Pd ≤ Pd_warn, the controller maintains the current operating frequency of the compressor 100 and keeps the current openings of the main expansion valve 51 and the bypass expansion valve 71 to continue running.

[0121] Since there is a positive correlation between the discharge pressure and the suction pressure of the compressor 100, in addition to monitoring the discharge pressure of the compressor 100, the controller can also directly monitor the suction pressure of the compressor 100, and adjust the frequency of the compressor 100, the opening of the bypass expansion valve 71, and the opening of the main expansion valve 51 through the suction pressure of the compressor 100.

[0122] Define the frequency converter f of the compressor 100, the step valve position N_main of the main electronic expansion valve (EVO), and the step valve position N_bp of the bypass electronic expansion valve BEEV;

[0123] The main physical quantities involved in the control process include:

[0124] Suction superheat: SH = Ts - Tsat(Ps)

[0125] Where, Ts: the actual temperature of the refrigerant measured by the suction temperature sensor 104;

[0126] Tsat(Ps): the saturation temperature of the refrigerant at the pressure Ps.

[0127] High-pressure soft limit range: Pd_warn < Pd < Pd_set_lim (set parameter, example of R410A: the value range of Pd_warn is 2.5 - 2.9 MPa, and the value range of Pd_set_lim is 3.0 - 3.9 MPa)

[0128] Where, warn: high-pressure warning threshold, the warning pressure before entering the soft limit control, unit MPa.

[0129] Pd_set_lim: high-pressure soft limit upper limit (pressure limit setting value), unit MPa.

[0130] Typical control logic and actions (mode switching):

[0131] Pd ≤ Pd_warn: normal control (prioritize load and efficiency).

[0132] Pd_warn < Pd < Pd_set_lim: Soft pressure limit area, mild suppression (reduce frequency a little, close the main valve, open a small amount of bypass, etc.).

[0133] Pd ≥ Pd_set_lim: Forced pressure limit area, immediately execute risk avoidance actions, and prioritize ensuring safety and reliability.

[0134] Bypass mass flow ratio: β = m_bp / (m_bp + m_evap), β ∈ [0, β_max]

[0135] The bypass mass flow ratio indicates what proportion of the total mass flow rate goes through the bypass branch 70, reflecting the "shunt intensity" of the bypass on the liquid supply / suction state of the evaporation side.

[0136] m_bp: Mass flow rate of the bypass branch 70;

[0137] m_evap: Mass flow rate in the refrigerant flow path through the plate heat exchanger;

[0138] β ∈ [0, β_max], β = 0: No bypass flow;

[0139] β → β_max: The maximum shunt ratio allowed by the system / valve capacity (determined jointly by the valve, pipeline, and working conditions), with a value range of 0.1 - 0.6.

[0140] Control objectives and priorities:

[0141] Main objective: Keep Pd ≤ Pd_set_lim and avoid protection actions; Td does not exceed the limit.

[0142] Sub-objective: Maintain SH ≥ SHmin (set parameter, example: 5 - 10K configurable) and limit it within SHmax (set parameter, example: 15K) to ensure stable energy efficiency.

[0143] Auxiliary objective: Suppress valve position oscillation, reduce pressure and flow fluctuations, and ensure oil return and liquid level safety.

[0144] Priority: Safety over-limit protection > High-pressure soft amplitude limiting (limit frequency first) > Superheat closed-loop (bypass + main EEV coordination) > Energy efficiency optimization.

[0145] Control methods include:

[0146] Water temperature feedforward:

[0147] ΔT_w = Tw_in − Tw_ref

[0148] Δf_ff = kf·sat(ΔT_w, −ΔTw_max, ΔTw_max)

[0149] ΔN_bp_ff=kb·sat(ΔT_w,−ΔTw_max,ΔTw_max)

[0150] Wherein, Tw_in: the current inlet water temperature of the heat exchanger, which is measured in real time by the inlet water temperature sensor.

[0151] Tw_ref: Reference inlet water temperature, which can be a set value or an adaptive reference based on operating conditions. The reference setting range is 20-30℃.

[0152] ΔT_w = Tw_in − Tw_ref: Water temperature deviation. A positive value indicates that the inlet water temperature is higher than the reference temperature (heavier load or hotter ambient temperature), while a negative value indicates that it is lower (lighter load).

[0153] sat(x,xmin,xmax): Saturation function that restricts x to the interval [xmin,xmax], and truncates it if it exceeds the interval.

[0154] Δf_ff: Feedforward correction (Hz) for compressor frequency f at 100. Positive values ​​increase the frequency, negative values ​​decrease it.

[0155] ΔN_bp_ff: Feedforward correction (steps or percentage) for the bypass valve position N_bp. A positive value increases the bypass opening, and a negative value decreases it. Used to define the opening degree of an electronic expansion valve at the moment of opening, or applied to situations with slow disturbances in the operating conditions.

[0156] ΔTw_max is an "amplitude cap" that saturates and limits the inlet water temperature deviation, preventing excessive feedforward action caused by abnormal measurements or sudden disturbances. For conventional plate heat exchanger and water systems: ΔTw_max ≈ 2–6K.

[0157] Kf and kb are correction coefficients, determined based on empirical values.

[0158] Calculation example:

[0159] Define Tw_ref=30°C, the current Tw_in=33°C⇒ΔT_w=+3K.

[0160] Let ΔTw_max = 4K, kf = 1.5Hz / K, and kb = 12 steps / K (electronic expansion valve with 0–480 steps).

[0161] Then Δf_ff = 1.5 × 3 = +4.5 Hz; ΔN_bp_ff = 12 × 3 = +36 steps.

[0162] The frequency control of compressor 100 will be described in detail below:

[0163] Compressor 100 frequency control (high-pressure soft limiting outer loop):

[0164] 1) Target high voltage setting: Pdo=min(Pd_set_nom,Pd_set_lim)

[0165] Among them, Pd_set_nom: the control target Pd for normal operation, used to achieve the optimal balance between efficiency, capability, and stability. It is usually derived from experience and ranges from 2 to 3 MPa.

[0166] Pd_set_lim: This is the upper limit threshold for safety or protection, usually close to but below the high-voltage protection operating point, with a value range of 3.0-3.9 MPa.

[0167] 2) PI regulation (water-side feedforward Δf_ff):

[0168] Δf=Kp_HP·(Pdo−Pd)+Ki_HP·∫(Pdo−Pd)dt+Δf_ff

[0169] f_cmd=sat(f_prev+Δf,f_min,f_max)

[0170] f_cmd: The calculated target frequency of compressor 100;

[0171] f_prev: Current actual frequency (Note: Frequency calculated in the previous control cycle).

[0172] Δf: The frequency increment calculated for this period, which is calculated by the PI control formula and consists of multiple superimposed components.

[0173] sat(x, xmin, xmax): A saturation function that limits x to the interval [xmin, xmax]. If x exceeds the upper limit, xmax is used; if x falls below the lower limit, xmin is used; within the interval, xmax is retained.

[0174] f_min: The minimum frequency to ensure oil return / heating capacity, or the minimum stable frequency of the inverter, is usually taken as 10-20Hz.

[0175] f_max: The maximum permissible frequency that is dynamically adjusted by factors such as current, exhaust temperature, high voltage limit, and noise constraints, and is usually taken as 60-120Hz.

[0176] 3) Limiting and protection triggering:

[0177] Condition: Pd ≥ Pd_set_lim

[0178] As mentioned earlier, when Pd≥Pd_set_lim, the system enters the protection zone (e.g., the high pressure is too high), and it is necessary to quickly reduce the compressor frequency by 100, but it cannot be reduced too low to avoid instability or oil return risk.

[0179] Derating mode: f_cmd = max(f_min, f_prev - k_drop)

[0180] f_cmd: The calculated target frequency of the compressor 100;

[0181] f_prev: The current actual frequency (Note: the frequency calculated in the previous control cycle).

[0182] k_drop: The maximum step-down rate in this cycle (Hz). It reflects "speed-limited descent" to prevent system shock caused by sudden frequency drop; usually takes a value of 0.5 - 2 Hz / S.

[0183] f_min: The minimum frequency to ensure oil return / heating capacity, or the minimum stable frequency of the frequency converter, usually takes a value of 10 - 20 Hz.

[0184] Superheat closed-loop and bypass / main EEV coordination:

[0185] I. Generation of target superheat

[0186] SH_target = clamp(SH_base + k_HP·max(0, Pd - Pd_warn), SHmin, SHmax)

[0187] SH_target refers to the suction target superheat;

[0188] SH_base: The nominal / reference superheat target, the set value under normal conditions (no high-pressure pressure), with a value range of 6 - 15 K.

[0189] Pd: The current condensing pressure (high-pressure side pressure), the pressure collected by the pressure sensor.

[0190] Pd_warn is the condensing pressure warning threshold, indicating the starting point where "it is considered that the high pressure is tightening and suppression measures need to be taken". The above formula moderately raises the superheat target when Pd > Pd_warn to suppress the mass flow rate and relieve the high pressure.

[0191] SHmin / SHmax sets the upper and lower limits for the target, avoiding too low to cause wet compression or too high to cause efficiency drop / noise.

[0192] clamp(a, lo, hi): Clamping function, which limits a within the interval [lo, hi]. If a < lo, then take lo; if a > hi, then take hi; otherwise take a.

[0193] II. Bypass valve position control (mainly for pressure limit, taking into account SH to avoid liquid hammer or liquid carryover in suction caused by pressure limit action):

[0194] ① Define the comprehensive error

[0195] $e_{mix}=w_P·(P_d - P_{d\_ref}) - w_{SH}·(SH_{target} - SH), w_P \geq w_{SH}$

[0196] $P_d$: Current condensation pressure (high - side pressure), the pressure collected by the pressure sensor.

[0197] $P_{d\_ref}$ (target condensation pressure / reference line): An empirical set value, the "desired" or "benchmark" pressure for pressure - limit control. Higher than it indicates that bypass unloading is required. The value range is 2.7 - 3.3 MPa (higher values can be taken in medium - high ambient conditions).

[0198] $SH$ (actual superheat): It is recorded previously that $SH = T_s - T_{sat}(P_s)$

[0199] The first - term promotes pressure - limit: When $P_d > P_{d\_ref}$, $e_{mix}$ increases, prompting the bypass to open wider for unloading / pressure reduction.

[0200] The second - term "taking $SH$ into account": When $SH$ (the $SH$ at the current moment) is lower than the target ($SH < SH_{target}$), $(SH_{target} - SH)$ is positive. Subtracting this term will reduce $e_{mix}$, thus suppressing the bypass from opening wider and avoiding further reducing $SH$ to cause the risk of liquid slugging.

[0201] $w_P$ and $w_{SH}$ are coefficients. $w_P \geq w_{SH}$ reflects "pressure - limit priority", but still retains the weight of $SH$ protection, which is obtained through empirical values.

[0202] ② Bypass expansion valve opening conditions:

[0203] When $P_d \geq P_{d\_on}$ and $T_d < T_{d\_soft}$;

[0204] Close when $P_d \leq P_{d\_off}$ or when the risk of too - low superheat occurs;

[0205] $P_d \geq P_{d\_on}$: The high pressure reaches the opening threshold, indicating that unloading / pressure - limit is required, and only then is the bypass allowed to participate. This avoids mistakenly opening the bypass when the high pressure is normal or low, reducing energy - efficiency loss and system disturbance.

[0206] $T_d < T_{d\_soft}$: The exhaust temperature does not exceed the soft limit before the bypass is allowed to open. The bypass action will change the system flow rate and pressure ratio. If the exhaust temperature is already at a relatively high level, first limit the freedom of the bypass and prefer to use other means (such as reducing the frequency of compressor 100) to handle it.

[0207] ③ Command (PI regulation):

[0208] $N_{bp\_cmd}=sat[N_{bp\_base}+dN_{bp\_ff}+K_{p\_bp}*e_{mix}+K_{i\_bp}*\int e_{mix}dt]$

[0209] N_bp_cmd: The bypass target instruction (valve opening) will eventually be limited to the allowable range by the saturation function sat.

[0210] sat[·]: Saturation function, which limits the output to [N_bp_min, N_bp_max].

[0211] N_bp_base: Base bias / starting value, a value that varies with operating conditions. If the system requires more bypass when under medium load, take 40-60%; if the main path is usually expected to handle more, take 20-40%.

[0212] dN_bp_ff: Bypass change feedforward quantity (formerly ΔN_bp_ff, introduced in Chapter 5.1), which is the prior compensation estimated from the known disturbance.

[0213] Kp_bp: Proportional gain.

[0214] Ki_bp: Integral gain.

[0215] e_mix: Comprehensive error (usually a weighted error mainly based on pressure limiting, while also taking into account superheat), the calculation method of which has been given above.

[0216] ∫e_mixdt: Error integral term.

[0217] 3. Main EEV Valve Position Control (Main control SH, to avoid conflict with the bypass. The main EEV primarily controls the evaporator outlet superheat SH, and coordinates with the bypass expansion valve to prevent excessive SH oscillation caused by both valves operating in the same direction. The two valves use a coupling coordination strategy to prevent "fighting": the bypass is fast and has a hard pressure limit; the main valve is slower and has a stable SH.)

[0218] ① Error calculation e_SH=SH_target−SH

[0219] ②PI adjustment:

[0220] N_main_cmd=sat[N_main_ff+Kp_main·e_SH+Ki_main·∫e_SHdt]

[0221] N_main_cmd: The final opening command (output) of the main electronic expansion valve (EVO), which is limited to the allowable range by the saturation function.

[0222] sat[·]: Saturation / limiting function, prevents commands from exceeding hardware / safety boundaries, and can add rate limiting and soft limit logic.

[0223] N_main_ff: Feedforward baseline opening, derived from operating condition mapping (load, environment, pressure ratio, speed, etc.), used to offset most steady-state demands and reduce the burden on the PI.

[0224] Kp_main: Proportional gain, which determines the strength of the response to instantaneous errors; too large a value can easily cause oscillations, while too small a value will result in a slow response.

[0225] Ki_main: Integral gain, used to eliminate steady-state bias.

[0226] IV. Coordination strategy between main electronic expansion valve EVO and bypass electronic expansion valve BEEV:

[0227] When the bypass opening increases (ΔN_bp>threshold), the EVO integral of the main electronic expansion valve is briefly reduced or the integral is frozen, and then restored after a time τ_couple, to prevent the SH oscillation caused by large simultaneous movements of the two valves.

[0228] ΔN_bp: The increment of bypass opening within a certain time window, used to determine whether a "significant increase" has occurred. ΔN_bp value = the difference between N_bp_cmd at two consecutive moments.

[0229] Threshold: The minimum bypass increment that triggers integral coordination, an empirical value (e.g., 2–5% for electronic expansion valve opening, or 10–24 steps for a 480-step electronic expansion valve).

[0230] Reduce the EVO integral of the main electronic expansion valve or freeze the integral, that is, reduce the value of Ki_main or set it to 0.

[0231] τ_couple: The time window during which the bypass action and the main valve coupling have a significant impact; after this period, normal integration resumes. It can be a constant or a coupling function.

[0232] τ_couple=a+b·|ΔN_bp|.

[0233] The controller coordinates the frequency of compressor 100, the opening degree of main expansion valve 51, and the opening degree of bypass expansion valve 71 based on the discharge pressure or suction pressure of compressor 100. It adjusts the amount of refrigerant that bypasses plate heat exchanger 300 and flows directly into gas-liquid separator 600, thereby indirectly regulating the temperature and pressure of refrigerant drawn into compressor 100. After the suction pressure of compressor 100 is adjusted, the discharge pressure of compressor 100 can be adjusted in a targeted manner, thereby avoiding excessively high water temperature in plate heat exchanger 300 and excessively high temperature and pressure of refrigerant drawn into compressor 100, which would lead to problems such as poor stability and low energy efficiency of compressor 100.

[0234] refer to Figure 7 , Figure 8 In some embodiments of this application, the input port of the compressor 100 is also provided with a gas-liquid separator 600, which is typically a cylindrical container with an air inlet, an air outlet and a bottom oil return port.

[0235] The gas-liquid separator 600 is located between the evaporator and the input port of the compressor 100. Its main function is to separate the gas flow returning from the evaporator, which may contain incompletely evaporated liquid refrigerant, to prevent liquid refrigerant from entering the compressor 100 and causing liquid slugging damage. At the same time, it can also collect and allow a small amount of oil that may have circulated here with the refrigerant to return to the compressor 100.

[0236] The inlet of the gas-liquid separator 600 is connected to the outlet of the evaporator via a four-way valve 400. The outlet of the gas-liquid separator 600 is connected to the input port of the compressor 100 via a pipeline. A small hole or capillary tube is typically provided at its bottom to slowly evaporate or return any accumulated small amount of liquid refrigerant or oil to the suction port of the compressor 100.

[0237] During system operation, especially in cooling or low-temperature heating mode, the refrigerant at the evaporator outlet may be in a two-phase state (gas and liquid). The gas-liquid separator 600 receives this two-phase flow; the liquid component settles at the bottom due to gravity and evaporates slowly, while the gaseous component is directly drawn into the compressor 100 from the upper outlet. This ensures that superheated vapor enters the compressor 100, guaranteeing its safe operation.

[0238] The effective volume V_acc of the gas-liquid separator 600 satisfies:

[0239] V_acc≥0.8×[M_charge×χ_worst+m_total_max×t_hold×χ_dyn] / ρ_liq

[0240] V_acc can be understood as the space inside the gas separator where refrigerant can be placed;

[0241] M_charge is the system refrigerant charge; it is determined through simulation calculations and experiments, and the specific method of obtaining it is existing technology and will not be described in detail.

[0242] χ_worst represents the proportion of the two most unfavorable phases, which is obtained through simulation. The specific method used is also an existing technology.

[0243] m_total_max represents the maximum total mass flow rate. There are three methods to obtain the maximum mass flow rate: first, by testing with a flow meter during experiments; second, by calculating based on the compressor speed (100 rpm), displacement, and refrigerant density; and third, by calculating based on the heat exchanger capacity: maximum mass flow rate = capacity / enthalpy difference.

[0244] t_hold is the buffer time;

[0245] χ_dyn is a dynamic additional coefficient;

[0246] ρ_liq is the liquid phase density at the current temperature.

[0247] The parameters involved in the above calculation of the effective volume V_acc of the gas-liquid separator 600 can all be obtained using existing calculation, simulation, or experimental methods.

[0248] The gas-liquid separator 600 of suitable volume is obtained by using the above method.

[0249] The output port of the compressor 100 is also provided with an oil separator 200. The oil separator 200 includes a separation housing 210, on which an air inlet port, an air outlet port, and an oil return port are formed. The first refrigerant main line 10 includes an exhaust pipe 220 and an air supply pipe 230. The air inlet port is connected to the output port of the compressor 100 through the exhaust pipe 220, the air outlet port is connected to the first valve port 410 through the air supply pipe 230, and the oil return port is connected to the compressor 100 through the oil return pipe 240. The oil return pipe 240 is provided with an oil return capillary tube 61.

[0250] In extended operating conditions such as low-temperature heating, the ambient temperature can drop as low as -30℃, which places higher demands on the reliability of the oil return system under extreme conditions. Because the viscosity characteristics of refrigeration oil exhibit a strong temperature dependence, in low-temperature environments, the oil temperature at the inlet of the oil return capillary 61 may be close to the ambient temperature. This results in poor oil flow in the oil return capillary 61, leading to problems such as oil shortage in the system.

[0251] refer to Figure 9 , Figure 10 To address the aforementioned issues, this application includes a return capillary tube 61 installed within the separation housing 210.

[0252] The gas-liquid separator 600 and the oil separator 200 together provide dual protection for the compressor 100. The oil separator 200 primarily handles oil separation on the discharge side of the compressor 100, preventing excessive oil from entering the system piping. The gas-liquid separator 600 primarily handles liquid refrigerant separation on the suction side of the compressor 100, preventing liquid slugging. These two components ensure the long-term reliable operation of the compressor 100 from different perspectives. The significantly improved oil separator 200 in this design ensures effective oil return, reducing oil retention in the system. This indirectly reduces the burden on the gas-liquid separator 600, which might need to handle oil buildup, resulting in a more balanced and efficient overall system operation.

[0253] Since the oil return capillary 61 is located inside the separator housing 210, the oil return capillary 61 built into the oil separator 200 is always in a high-temperature exhaust environment throughout the process, and the oil inside is continuously heated, ensuring that the oil return passage remains smooth and the system operates stably even under harsh conditions such as the compressor 100 starting at low temperature.

[0254] The air inlet port on the oil separator 200 is connected to the output port of the compressor 100; the oil return port extends to one end outside the separator housing 210 and is connected to the input port of the compressor 100 through the oil return line 240.

[0255] The oil return port extends to one end of the separator housing 210 and is connected to the oil return capillary 61. The oil return capillary 61 is fixed on the inner wall of the separator housing 210, and a gap is formed between the oil return capillary 61 and the air inlet port.

[0256] In other words, the position of the oil return capillary tube 61 is staggered from that of the air intake port to prevent the refrigerant input from the air intake port from directly impacting the oil return capillary tube 61 and causing vibration impact on it.

[0257] The oil separated in the oil separator 200 collects at the bottom of the separator cavity. The other end of the oil return capillary tube 61 extends into the oil at the bottom of the separator cavity. The oil in the separator cavity is transported outward through the oil return capillary tube 61 and returned to the compressor 100 through the oil return line 240.

[0258] The oil return capillary 61 on the oil separator 200, which is used to output the separated oil, is set on the inner wall of the separator housing 210. This helps to reduce the vibration of the oil return capillary 61 during operation and avoids it from colliding with other working parts on the surrounding side and causing damage.

[0259] In addition, the oil return capillary tube 61 absorbs part of the heat from the high-temperature refrigerant input from the intake port, thereby reducing the viscosity of the oil in the oil return capillary tube 61, improving the flow effect of the oil, and allowing the oil to flow smoothly back to the input port of the compressor 100, avoiding the risk of oil shortage.

[0260] In some embodiments of this application, the air outlet is located at the top of the separator housing 210, and an air outlet pipe 231 is formed inside the oil separator 200. One end of the air outlet pipe 231 is connected to the air supply pipeline through the air outlet port, and the other end extends into the separator cavity and forms a gap with the bottom of the separator cavity.

[0261] The refrigerant and oil mixture entering from the intake port is separated in the separator chamber. The oil collects at the bottom of the separator chamber, while the refrigerant is output to the condenser through the outlet pipe 231.

[0262] In some embodiments of this application, a filter is provided at the bottom of the separation chamber, and the oil return capillary 61 is connected to the oil outlet port of the filter through an oil supply line. The filter is configured to filter the engine oil separated in the separation chamber.

[0263] After being filtered by the filter, the separated oil is output from the oil outlet port through the oil supply line and the oil return capillary 61, and finally returns to the input port of the compressor 100 through the oil return line 240.

[0264] Specifically, the filter is located at the bottom of the separator chamber. The gaseous refrigerant mixed with engine oil is introduced into the separator chamber from the air inlet port. After being separated by the oil separator 200, the engine oil and refrigerant are separated. The refrigerant is output to the circulation system through the air outlet port for heat exchange, and the engine oil is collected at the bottom of the separator chamber.

[0265] The filter is used to filter the oil flowing to the bottom of the separator chamber, and after separating the impurities, it is transported to the return capillary 61 through the oil delivery pipeline.

[0266] The small diameter of the oil return capillary 61 helps to prevent refrigerant from mixing in during the oil delivery process. However, it also has the characteristic of being relatively weak. In this application, the oil return capillary 61 is fixed to the inner wall of the separation cavity, which helps to ensure the structural strength of the oil return capillary 61.

[0267] In the solution described in this application, if oil blockage occurs in the return capillary tube 61, the high-temperature exhaust gas from the compressor 100 will quickly heat the entire capillary tube, reducing the viscosity of the refrigerant oil in the capillary tube, and the capillary tube can be quickly unblocked.

[0268] In addition, by placing the oil return capillary 61 inside the oil separator 200, this application can also avoid the problem of the oil return capillary 61 breaking due to vibration during the operation of the outdoor unit when it is placed outside the oil separator 200. In this respect, it provides protection for the oil return capillary 61.

[0269] In some embodiments of this application, the air inlet port is disposed on the side wall of the separation housing 210, the oil return capillary 61 is disposed below the air inlet port, and the height of the oil return port is adapted to the height of the oil return capillary 61.

[0270] In some embodiments of this application, the air intake port is located on the upper side wall of the separator housing 210, and the air outlet pipe 231 extends to the lower part of the separator cavity, so that the refrigerant input from the air intake port can more thoroughly separate the oil mixed inside it.

[0271] The height of the oil return capillary 61 is matched with the height of the outlet pipe 231 extending into the separation cavity, so as to make full use of the temperature of the refrigerant to heat the oil return capillary 61 and increase the fluidity of the oil in the oil return capillary 61.

[0272] In addition, the oil return capillary 61 is located below the air inlet port, which helps to prevent the airflow input from the air inlet port from impacting the oil return capillary 61, reduces the vibration of the oil return capillary 61, and prevents the airflow from impacting the oil return capillary 61 and causing damage to the oil return capillary 61.

[0273] refer to Figure 9In some embodiments of this application, the return capillary 61 includes a spiral section.

[0274] Specifically, the bottom of the return capillary 61 is connected to the filter located at the bottom of the separation chamber via an oil supply line. The spiral section of the return capillary 61 is connected to the return port via a portion of the capillary straight tube. The return port is externally connected to the return line 240.

[0275] The spiral tube section design increases the length of the return capillary 61, allowing full use of the heat in the refrigerant to heat the oil in the return capillary 61 and improve its flow smoothness.

[0276] In some embodiments, the spiral tube segment can be fixed to the inner wall of the separated inner cavity by welding.

[0277] For example, but not limited to, the spiral tube segment is arranged spirally upward along the height direction of the separation cavity, and one end of the spiral tube segment is fixed to the inner wall of the separation cavity by spot welding or other welding methods.

[0278] In other embodiments, the spiral tube segment extends radially and spirally along the separation cavity, and one spiral tube segment that is in close contact with the separation cavity is fixed to the inner wall of the separation cavity by spot welding or other welding methods.

[0279] In other embodiments, the spiral tube segment is detachably connected to the inner wall of the separation housing 210 via a hook-on portion.

[0280] In some embodiments, the hooking part is L-shaped, and the hooking part includes a hooking horizontal part and a hooking vertical part arranged at an angle to the hooking horizontal part. The hooking vertical part extends upward, and a hooking groove is formed between the hooking vertical part, the hooking horizontal part and the side wall of the separation inner cavity. The spiral tube section is hooked on the hooking groove.

[0281] In some embodiments, the mounting portion has a welding conformal surface that is adapted to the shape of the inner wall of the separation cavity. The welding conformal surface is in contact with the inner wall of the separation cavity, and the mounting portion is fixed to the inner wall of the separation cavity by welding.

[0282] The horizontal part of the hanging section is welded to the inner wall of the separation cavity, and the return capillary tube 61 is directly hung on the hanging groove, which is convenient for operation and plays a restrictive role on the entire spiral tube section.

[0283] Specifically, the size of the hanging slot is not less than the overall height of the spiral pipe section. The spiral pipe section is fitted on the top of the hanging stand and moves from the hanging slot to the bottom of the hanging slot.

[0284] In other embodiments, the spiral section of the oil return capillary 61 is located at the bottom of the separation inner cavity, the oil return port is located at a lower position of the separation housing 210, the height of the oil return port is flush with the spiral section, and the oil return port is connected to the external oil return pipeline 240.

[0285] In some embodiments, the spiral tube segment can be fixed to the inner wall of the separated inner cavity by welding.

[0286] For example, but not limited to, the spiral tube segment is arranged spirally upward along the height direction of the separation cavity, and one end of the spiral tube segment is fixed to the inner wall of the separation cavity by spot welding or other welding methods.

[0287] In other embodiments, the spiral tube segment extends radially and spirally along the separation cavity, and one spiral tube segment that is in close contact with the separation cavity is fixed to the inner wall of the separation cavity by spot welding or other welding methods.

[0288] refer to Figure 10 In some embodiments of this application, the oil return capillary 61 is a straight pipe structure, the air outlet is located at the upper position of the separation housing 210, the oil return capillary 61 is welded to the side wall of the separation inner cavity, the bottom of the oil return capillary 61 is connected to the oil pipeline and the filter, and the top of the oil return capillary 61 is connected to the air outlet.

[0289] Specifically, one end of the oil return capillary 61 extends to the bottom of the separation chamber and connects to the filter, while the other end extends upward along the inner wall of the separation chamber to the air outlet.

[0290] The air outlet is located at the upper part of the separator housing 210 so that the length of the oil return capillary 61 in the separator cavity is sufficient. The oil return capillary 61 absorbs heat from the refrigerant to improve the flow of oil in the oil return capillary 61.

[0291] In addition, the straight-tube-structured return capillary 61 is evenly distributed along the inner wall of the separation shell 210, which reduces the risk of breakage of the return capillary 61.

[0292] By employing a specific technical approach of embedding and fixing the oil return capillary 61 within the inner wall of the housing and staggering it from the high-temperature air inlet port, the oil return capillary 61 can achieve stable support through the housing, significantly reducing the risk of operational vibration and collision. On the other hand, it can continuously absorb the exhaust heat of the compressor 100 through non-contact heat exchange, effectively reducing the viscosity of the refrigeration oil inside the pipe. This solves the technical problem of oil blockage in the oil return capillary 61 under low-temperature conditions leading to system oil shortage, versus increasing the capillary diameter to avoid oil blockage, which would reduce system energy efficiency. Thus, it achieves the technical effect of simultaneously improving the reliability of system oil return, operational energy efficiency, and mechanical stability without adding additional complex components.

[0293] Whenever possible, the various aspects and features described and shown in the specification can be applied individually, and these individual aspects can serve as the subject of a divisional application.

[0294] 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.

[0295] 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 water source machine, characterized in that, Includes an indoor unit and an outdoor unit, wherein the outdoor unit includes: The compressor has an input port and an output port. Plate heat exchangers have internal refrigerant and water flow paths; The four-way valve includes a first valve port, a second valve port, a third valve port, and a fourth valve port. The first valve port is connected to the output port of the compressor, the second valve port is connected to the indoor unit, the third valve port is connected to the input port of the compressor via a third refrigerant main line, and the fourth valve port is connected to one end of the refrigerant flow path. The other end of the refrigerant flow path is connected to the indoor unit via a fifth refrigerant main line. A main expansion valve is provided on the fifth refrigerant main line. A bypass branch is provided between the fifth refrigerant main line and the third refrigerant main line, and the connection point between the bypass branch and the fifth refrigerant main line is located between the plate heat exchanger and the main expansion valve. A bypass expansion valve is provided on the bypass branch. A controller is used to control the opening and closing of the bypass expansion valve. When the bypass expansion valve is open, a portion of the refrigerant that has passed through the main expansion valve flows from the bypass branch into the third refrigerant main line. It also includes a controller. When heating is running, the controller controls the main expansion valve to open to a preset degree and controls the compressor to run at a preset frequency. When the discharge pressure of the compressor is higher than the minimum value of the high-pressure soft limiting range but lower than the maximum value of the high-pressure soft limiting range, the controller controls the compressor to reduce the first unit frequency, controls the main expansion valve to close the first unit opening, and controls the bypass expansion valve to open the second unit opening. After running for a preset time, the controller re-determines the compressor's discharge pressure. If the compressor's discharge pressure is still within the high-pressure soft-limiting zone, the controller continues to control the compressor to reduce the first unit frequency, control the main expansion valve to close the first unit opening, and control the bypass expansion valve to open the second unit opening, until the compressor's discharge pressure is not higher than the minimum value of the high-pressure soft-limiting zone. Then, the controller maintains the compressor's current operating frequency and keeps the main expansion valve and the bypass expansion valve at their current openings.

2. The water source machine according to claim 1, characterized in that, The compressor's input port is equipped with a suction pressure sensor and a suction temperature sensor. The suction pressure sensor is used to detect the suction pressure of the compressor, and the suction temperature sensor is used to detect the suction temperature of the compressor. The compressor's output port is equipped with an exhaust pressure sensor and an exhaust temperature sensor. The exhaust pressure sensor is used to detect the compressor's exhaust pressure, and the exhaust temperature sensor is used to detect the compressor's exhaust temperature.

3. The water source machine according to claim 1, characterized in that, The plate heat exchanger has a first temperature sensor and a second temperature sensor installed at both ends of the refrigerant flow path. In heating mode, the first temperature sensor is installed at the inlet end of the refrigerant flow path to detect the temperature of the refrigerant input to the plate heat exchanger, and the second temperature sensor is installed at the outlet end of the refrigerant flow path to detect the temperature of the refrigerant output from the plate heat exchanger. The plate heat exchanger is equipped with an inlet water temperature sensor at the inlet end of the water flow path to detect the inlet water temperature, and an outlet water temperature sensor at the outlet end of the water flow path to detect the outlet water temperature.

4. The water source machine according to claim 2, characterized in that, The controller controls the first valve port to connect with the second valve port, the third valve port to connect with the fourth valve port, and the bypass expansion valve to close; When the discharge pressure of the compressor is not higher than the minimum value of the high-pressure soft limit range, the controller maintains the current operating frequency of the compressor and keeps the current opening of the main expansion valve running.

5. The water source machine according to claim 1, characterized in that, When the discharge pressure of the compressor is not lower than the maximum value of the high-pressure soft limit range, the controller controls the compressor to reduce the second unit frequency, controls the main expansion valve to close the third unit opening, and controls the bypass expansion valve to open the fourth unit opening. Wherein, the second unit frequency is greater than the first unit frequency, the third unit opening is greater than the first unit opening, and the fourth unit opening is greater than the second unit opening; After running for a preset time, the controller re-determines the compressor's discharge pressure. If the compressor's discharge pressure is still not lower than the maximum value of the high-pressure soft-limiting range, the controller continues to control the compressor to reduce the second unit frequency, control the main expansion valve to close the third unit opening, and control the bypass expansion valve to open the fourth unit opening. Until the compressor's discharge pressure is not higher than the minimum value of the high-pressure soft limit range, the controller maintains the compressor's current operating frequency and keeps the main expansion valve and the bypass expansion valve at their current openings.

6. The water source machine according to claim 1, characterized in that, The bypass mass split ratio β of the bypass expansion valve satisfies: β∈[0,β_max]; Where β = m_bp / (m_bp + m_evap), 0.1 ≤ β_max ≤ 0.6; m_bp is the refrigerant mass flow rate of the bypass branch; m_evap is the refrigerant mass flow rate input to the plate heat exchanger.

7. The water source machine according to claim 1, characterized in that, A first shut-off valve and a second shut-off valve are provided between the indoor unit and the outdoor unit. The first shut-off valve is connected between the second valve port and the indoor unit, and the second shut-off valve is connected between the indoor unit and the plate heat exchanger. A liquid storage tank is provided between the main expansion valve and the second shut-off valve, and filters are provided on both sides of the main expansion valve.

8. The water source machine according to claim 1, characterized in that, The compressor's output port is also equipped with an oil separator, which includes a separation housing. The separation housing has an inlet port, an outlet port, and an oil return port. The inlet port is connected to the compressor's output port through an exhaust pipe. The outlet port is connected to the first valve port through an air supply pipe. The oil return port is connected to the compressor through an oil return pipe. The oil return pipe is equipped with an oil return capillary tube, which is located inside the separation housing.

9. The water source machine according to claim 1, characterized in that, The compressor's input port is also equipped with a gas-liquid separator, and the effective volume V_acc of the gas-liquid separator satisfies: V_acc≥0.8×[M_charge×χ_worst+m_total_max×t_hold×χ_dyn] / ρ_liq Where M_charge is the system refrigerant charge; χ_worst represents the proportion of the two most unfavorable phases; m_total_max is the maximum total mass flow; t_hold is the buffer time; χ_dyn is a dynamic additional coefficient; ρ_liq is the liquid phase density at the current temperature.

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