Air conditioning system and control method thereof

Abstract

The invention relates to the technical field of air conditioning systems, in particular to an air conditioning system and a control method thereof. The first end of a first refrigerant auxiliary path of the air conditioning system is connected with a pipeline between an indoor heat exchanger and a reversing valve, and the second end of the first refrigerant auxiliary path is connected with a pipeline between the indoor heat exchanger and an outdoor heat exchanger; a defrosting valve is arranged on the first refrigerant auxiliary path; the first end of the second refrigerant auxiliary path is connected with a pipeline between the outdoor heat exchanger and the second end of the first refrigerant auxiliary path, and the second end of the second refrigerant auxiliary path is connected with a pipeline between the gas-liquid separator and the four-way valve; an auxiliary path throttling device is arranged on the second refrigerant auxiliary path and located between the first end of the second refrigerant auxiliary path and the refrigerant heat exchanger. And during defrosting, the refrigerant throttled by the auxiliary path exchanges heat with the refrigerant of the main path in the refrigerant heat exchanger. During defrosting, refrigerants do not enter the indoor heat exchanger, the indoor environment temperature fluctuation is small, the second auxiliary path refrigerants absorb heat of the main path refrigerants after throttling and then are evaporated into gaseous refrigerants to return to the compressor, and liquid impact of the compressor is prevented.

Description

Technical Field

[0001] The present invention relates to the technical field of air conditioning systems, and specifically provides an air conditioning system and a control method thereof. Background Art

[0002] In winter, air conditioners need to run in a cooling mode when they are defrosting, taking heat from the room and releasing heat in the outdoor heat exchanger for defrosting. However, this defrosting mode easily causes indoor heat to dissipate quickly, exacerbating indoor ambient temperature fluctuations and affecting user experience. Therefore, in order to minimize the impact on the indoor ambient temperature and prevent excessive indoor heat exchange, which causes large indoor temperature fluctuations, the air conditioning system usually turns off the indoor fan during defrosting. However, the refrigerant will still flow in the indoor heat exchanger and absorb indoor heat, which will inevitably cause the indoor temperature to drop. After defrosting, the air conditioner switches back to heating mode, and it takes some time for the indoor temperature to return to the set temperature. This rise and fall process further affects the stability of the indoor temperature.

[0003] Moreover, in hot summer weather, the high outdoor ambient temperature will lead to poor heat dissipation of the outdoor heat exchanger. When the pressure in the air-conditioning system reaches the alarm high pressure threshold, the compressor will reduce the frequency of operation, which will lead to a decrease in the indoor cooling effect and also cause fluctuations in indoor temperature.

[0004] Accordingly, there is a need in the art for a new air conditioning system to solve the problem of large indoor temperature fluctuations caused by existing air conditioning systems during defrosting in low-temperature weather and cooling in high-temperature weather. Summary of the invention

[0005] The present invention aims to solve the above technical problem, that is, to solve the problem that the existing air-conditioning system causes large fluctuations in indoor temperature when defrosting in low-temperature weather and cooling in high-temperature weather.

[0006] In a first aspect, the present invention provides an air conditioning system, the air conditioning system of the present invention comprises a refrigerant circulation loop and a compressor, a reversing valve, an indoor heat exchanger and an outdoor heat exchanger arranged on the refrigerant circulation loop; an indoor throttling device is connected in series on the pipeline where the indoor heat exchanger is located;

[0007] The air conditioning system further includes a first refrigerant auxiliary circuit, a second refrigerant auxiliary circuit and a refrigerant heat exchanger;

[0008] The first end of the first refrigerant auxiliary circuit is connected to the pipeline between the indoor heat exchanger and the reversing valve, and the second end of the first refrigerant auxiliary circuit is connected to the pipeline between the indoor heat exchanger and the outdoor heat exchanger; a defrost valve is provided on the first refrigerant auxiliary circuit;

[0009] The first end of the second refrigerant auxiliary circuit is connected to the pipeline between the outdoor heat exchanger and the second end of the first refrigerant auxiliary circuit, a gas-liquid separator is provided between the air inlet of the compressor and the reversing valve, and the second end of the second refrigerant auxiliary circuit is connected to the pipeline between the gas-liquid separator and the reversing valve;

[0010] An auxiliary circuit throttling device is provided on the second refrigerant auxiliary circuit, and the auxiliary circuit throttling device is located between the first end of the second refrigerant auxiliary circuit and the refrigerant heat exchanger; the refrigerant after throttling in the second refrigerant auxiliary circuit and the refrigerant coming out of the outdoor heat exchanger can exchange heat in the refrigerant heat exchanger.

[0011] When the above technical solution is adopted, the indoor heat exchanger of the air-conditioning system of the present invention does not participate in heat exchange during defrosting, which means that the refrigerant does not exchange heat with the indoor environment, so the indoor environment temperature fluctuation caused by the refrigerant taking heat from the indoor environment is fundamentally avoided. In addition, the pressure and temperature of the refrigerant in the second refrigerant auxiliary circuit are reduced after throttling, and the low-temperature and low-pressure refrigerant absorbs the heat of the main circuit refrigerant, ensuring that part of the refrigerant returns to the compressor in gaseous form, preventing liquid hammer, and ensuring the safe and stable operation of the compressor.

[0012] When the air conditioning system is running in high-temperature cooling mode, the compressor is controlled to start, the reversing valve is switched to connect the compressor outlet and the outdoor heat exchanger, the indoor throttling device is opened, the defrost valve is closed, and the auxiliary throttling device is opened to a certain degree. When the outdoor temperature is high, the outdoor heat exchanger does not dissipate heat well, and the pressure in the air conditioning system will rise rapidly. At this time, the auxiliary throttling device is turned on, and the low-temperature and low-pressure refrigerant after the auxiliary throttling is used to absorb the heat of the main refrigerant. The auxiliary refrigerant directly returns to the compressor, and the heat of the main refrigerant is taken away by the auxiliary refrigerant to further reduce the temperature. The main refrigerant then enters the indoor heat exchanger to absorb heat, thereby effectively improving the cooling effect and ensuring a stable indoor temperature.

[0013] Therefore, the air conditioning system of the present invention can ensure the stability of indoor temperature whether it is defrosting in low-temperature weather or cooling in high-temperature weather.

[0014] In an optional technical solution of the above air-conditioning system, an oil-gas separator is provided between the reversing valve and the air outlet of the compressor.

[0015] When the above technical solution is adopted, the oil-gas separator is used to separate the compressor oil and the refrigerant.

[0016] In a second aspect, the present invention further provides a control method for an air conditioning system, wherein the air conditioning system of the present invention comprises a refrigerant circulation loop, and a compressor, a reversing valve, an indoor heat exchanger and an outdoor heat exchanger arranged on the refrigerant circulation loop; an indoor throttling device is connected in series on the pipeline where the indoor heat exchanger is located;

[0017] The air conditioning system further includes a first refrigerant auxiliary circuit, a second refrigerant auxiliary circuit and a refrigerant heat exchanger;

[0018] The first end of the first refrigerant auxiliary circuit is connected to the pipeline between the indoor heat exchanger and the reversing valve, and the second end of the first refrigerant auxiliary circuit is connected to the pipeline between the indoor heat exchanger and the outdoor heat exchanger; a defrost valve is provided on the first refrigerant auxiliary circuit;

[0019] The first end of the second refrigerant auxiliary circuit is connected to the pipeline between the outdoor heat exchanger and the second end of the first refrigerant auxiliary circuit, a gas-liquid separator is provided between the air inlet of the compressor and the reversing valve, and the second end of the second refrigerant auxiliary circuit is connected to the pipeline between the gas-liquid separator and the reversing valve;

[0020] The second refrigerant auxiliary circuit is provided with an auxiliary circuit throttling device, and the auxiliary circuit throttling device is located between the first end of the second refrigerant auxiliary circuit and the refrigerant heat exchanger; the refrigerant after throttling in the second refrigerant auxiliary circuit and the refrigerant coming out of the outdoor heat exchanger can exchange heat in the refrigerant heat exchanger;

[0021] The control method comprises:

[0022] Receiving a command to operate a defrost mode;

[0023] The defrost valve is controlled to open, the compressor is turned on, the reversing valve is switched to connect the compressor outlet with the outdoor heat exchanger, the auxiliary circuit throttling device is opened to a first initial opening, and the indoor throttling device is closed.

[0024] When the above technical solution is adopted, the indoor heat exchanger of the air-conditioning system of the present invention does not participate in heat exchange during defrosting, which means that the refrigerant does not exchange heat with the indoor environment, so the indoor environment temperature fluctuation caused by the refrigerant taking heat from the indoor environment is fundamentally avoided. In addition, the pressure and temperature of the refrigerant in the second refrigerant auxiliary circuit are reduced after throttling, and the low-temperature and low-pressure refrigerant absorbs the heat of the main circuit refrigerant, ensuring that part of the refrigerant returns to the compressor in gaseous form, preventing liquid hammer, and ensuring the safe and stable operation of the compressor.

[0025] In the optional technical solution of the control method of the above air-conditioning system, after the step of "controlling the defrost valve to open, the compressor to start, the reversing valve to switch to the compressor outlet to communicate with the outdoor heat exchanger, the auxiliary circuit throttling device to open the first initial opening, and the indoor throttling device to close", the control method includes:

[0026] Obtaining the low pressure Ps of the system and the refrigerant temperature T1 after throttling by the auxiliary circuit throttling device;

[0027] Obtain the corresponding evaporation saturation temperature T according to Ps;

[0028] If T≤T1, the opening of the auxiliary circuit throttling device is reduced.

[0029] When the above technical solution is adopted, T≤T1 indicates that the refrigerant in the second refrigerant auxiliary circuit is not completely vaporized, and the opening of the auxiliary circuit throttling device is reduced to reduce the refrigerant flow in the second refrigerant auxiliary circuit so that the refrigerant is completely vaporized.

[0030] In the optional technical solution of the control method of the air-conditioning system, after the step of "obtaining the corresponding evaporation saturation temperature T according to Ps", the control method includes:

[0031] If T>T1 and Ps is greater than the preset pressure value, the current opening of the auxiliary path throttling device is maintained.

[0032] When the above technical solution is adopted, T>T1 means that the refrigerant in the second refrigerant auxiliary circuit is completely gasified, and Ps is greater than or equal to the preset pressure value, which means that the current low-pressure pressure of the compressor meets the requirements and the opening of the current auxiliary circuit throttling device can be maintained.

[0033] In the optional technical solution of the control method of the air-conditioning system, after the step of “obtaining the low pressure Ps of the refrigerant”, the control method further includes:

[0034] If Ps is less than or equal to the preset pressure value, the indoor unit with the highest indoor ambient temperature among the indoor units in the closed state is selected;

[0035] The indoor throttling device corresponding to the indoor unit which is in the off state and has the highest indoor ambient temperature is opened.

[0036] When the above technical solution is adopted, if Ps is less than the preset pressure value, it means that the current low pressure is low. In order to prevent low pressure failure, the low pressure needs to be increased. When the low pressure is low, select an indoor unit with a low indoor temperature demand and a high indoor ambient temperature, and turn on the indoor throttling device of the indoor unit to allow part of the refrigerant in the main circuit to enter the indoor heat exchanger to absorb heat to increase the low pressure. The indoor temperature demand corresponding to the indoor unit in the closed state is low, so select the indoor unit with a higher indoor ambient temperature from all the indoor units in the closed state, and turn on the corresponding indoor throttling device. This can reduce the impact on the indoor temperature in the powered-on state.

[0037] In an optional technical solution of the control method of the air conditioning system, the control method further includes:

[0038] Receiving a command to operate a conventional cooling mode;

[0039] The defrost valve is controlled to be closed, the compressor is turned on, the reversing valve is switched to connect the compressor outlet with the outdoor heat exchanger, the auxiliary circuit throttling device is closed, and the indoor throttling device is opened.

[0040] When the above technical solution is adopted, during conventional refrigeration, the defrost valve and the auxiliary circuit throttling device are closed, the high-temperature and high-pressure gaseous refrigerant of the compressor enters the outdoor heat exchanger to dissipate heat, then enters the indoor heat exchanger to absorb heat, and finally returns to the compressor air inlet.

[0041] In an optional technical solution of the control method of the air conditioning system, the control method further includes:

[0042] Receiving an instruction to operate high temperature cooling;

[0043] The defrost valve is controlled to be closed, the compressor is turned on, the reversing valve is switched to connect the compressor outlet with the outdoor heat exchanger, the auxiliary circuit throttling device is opened to a second initial opening, and the indoor throttling device is opened.

[0044] When the above technical solution is adopted, when the air-conditioning system is cooling in high temperature weather, if the outdoor temperature is high and the heat exchange effect of the outdoor heat exchanger is poor, resulting in a substantial increase in the high-pressure pressure, the auxiliary circuit throttling device is opened to allow the refrigerant in the second refrigerant auxiliary circuit to absorb the heat of the main refrigerant, thereby increasing the supercooling of the main refrigerant. The main refrigerant then enters the indoor heat exchanger to absorb heat, thereby achieving a stable cooling effect.

[0045] In the optional technical solution of the control method of the above air-conditioning system, after the step of "controlling the defrost valve to close, the compressor to start, the reversing valve to switch to the compressor outlet to communicate with the outdoor heat exchanger, the auxiliary circuit throttling device to open the second initial opening, and the indoor throttling device to open", the control method further includes:

[0046] Obtaining the high pressure Pd of the system and the main refrigerant temperature Tliqc after heat exchange by the refrigerant heat exchanger;

[0047] Obtain the corresponding condensation saturation temperature Tpd according to Pd;

[0048] When Tpd<Tliqc, the opening of the auxiliary path throttling device is increased.

[0049] In the case of adopting the above technical solution, when high-temperature cooling is used, the outdoor ambient temperature is high, and the high pressure is correspondingly higher, resulting in the inability of the gaseous refrigerant to be completely liquefied. The high pressure is related to the condensation saturation temperature. The degree of supercooling can be adjusted by adjusting the opening of the auxiliary throttling device to completely liquefy the refrigerant passing through the main circuit. Tpd<Tliqc means that the main circuit refrigerant is not completely liquefied. Increasing the opening of the auxiliary circuit throttling device increases the amount of refrigerant entering the second refrigerant auxiliary circuit, and increases the heat exchange amount, so that the main circuit refrigerant is completely liquefied.

[0050] In the optional technical solution of the control method of the air-conditioning system, after the step of “obtaining the corresponding condensation saturation temperature Tpd according to Pd”, the control method includes:

[0051] When Tpd≥Tliqc, the current opening of the auxiliary circuit throttling device is maintained.

[0052] When the above technical solution is adopted, Tpd≥Tliqc means that the main circuit refrigerant is completely liquefied and the current opening of the auxiliary circuit throttling device can be maintained.

[0053] It can be understood by those skilled in the art that the air-conditioning system of the present invention includes a refrigerant circulation circuit and a compressor, a reversing valve, an indoor heat exchanger and an outdoor heat exchanger arranged on the refrigerant circulation circuit; the air-conditioning system also includes a first refrigerant auxiliary circuit, a second refrigerant auxiliary circuit and a refrigerant heat exchanger; and an indoor throttling device is connected in series on the pipeline where the indoor heat exchanger is located.

[0054] The first end of the first refrigerant auxiliary circuit is connected to the pipeline between the indoor heat exchanger and the reversing valve, and the second end of the first refrigerant auxiliary circuit is connected to the pipeline between the indoor heat exchanger and the outdoor heat exchanger; a defrost valve is provided on the first refrigerant auxiliary circuit;

[0055] The first end of the second refrigerant auxiliary circuit is connected to the pipeline between the outdoor heat exchanger and the second end of the first refrigerant auxiliary circuit, a gas-liquid separator is provided between the air inlet of the compressor and the reversing valve, and the second end of the second refrigerant auxiliary circuit is connected to the pipeline between the gas-liquid separator and the reversing valve;

[0056] An auxiliary circuit throttling device is provided on the second refrigerant auxiliary circuit, and the auxiliary circuit throttling device is located between the first end of the second refrigerant auxiliary circuit and the refrigerant heat exchanger; the refrigerant after throttling in the second refrigerant auxiliary circuit and the refrigerant coming out of the outdoor heat exchanger can exchange heat in the refrigerant heat exchanger.

[0057] When the above technical solution is adopted, the indoor heat exchanger of the air-conditioning system of the present invention does not participate in heat exchange during defrosting, which means that the refrigerant does not exchange heat with the indoor environment, so the indoor environment temperature fluctuation caused by the refrigerant taking heat from the indoor environment is fundamentally avoided. In addition, the pressure and temperature of the refrigerant in the second refrigerant auxiliary circuit are reduced after throttling, and the low-temperature and low-pressure refrigerant absorbs the heat of the main circuit refrigerant, ensuring that part of the refrigerant returns to the compressor in gaseous form, preventing liquid hammer, and ensuring the safe and stable operation of the compressor.

[0058] When the air conditioning system is running for high temperature cooling, the compressor is controlled to start, the reversing valve is switched to connect the compressor outlet with the outdoor heat exchanger, the indoor throttling device is opened, the defrost valve is closed, and the auxiliary throttling device is opened to a certain degree. When the outdoor temperature is high, the outdoor heat exchanger does not dissipate heat well, and the pressure in the air conditioning system will rise rapidly. At this time, the auxiliary throttling device is turned on, and the low-temperature and low-pressure refrigerant after the auxiliary throttling absorbs the heat of the main refrigerant. The auxiliary refrigerant directly returns to the compressor, and the heat of the main refrigerant is taken away by the auxiliary refrigerant to further reduce the temperature. The main refrigerant then enters the indoor heat exchanger to absorb heat, thereby effectively improving the cooling effect and ensuring a stable indoor temperature.

[0059] Therefore, the air conditioning system of the present invention can ensure the stability of indoor temperature whether it is defrosting in low-temperature weather or cooling in high-temperature weather. BRIEF DESCRIPTION OF THE DRAWINGS

[0060] The preferred embodiments of the present invention are described below in conjunction with the accompanying drawings, in which:

[0061] Figure 1 is a schematic diagram of a refrigerant circulation circuit of an air-conditioning system of the present invention;

[0062] Figure 2 is a schematic diagram of the refrigerant flow direction of the air conditioning system of the present invention in the defrosting mode;

[0063] Figure 3 is a schematic diagram of the refrigerant flow direction of the air-conditioning system of the present invention during conventional heating;

[0064] Figure 4 is a schematic diagram of the refrigerant flow direction during conventional refrigeration of the air-conditioning system of the present invention;

[0065] Figure 5 It is a schematic diagram of the refrigerant flow direction of the air-conditioning system of the present invention during high-temperature cooling;

[0066] Figure 6 is a flow chart of the main steps of the control method of the air conditioning system of the present invention;

[0067] Figure 7 It is a flow chart of the opening adjustment steps of the auxiliary circuit throttling device during defrosting of the air conditioning system of the present invention;

[0068] Figure 8 It is a flow chart of the opening adjustment steps of the auxiliary circuit throttling device of the air-conditioning system of the present invention during high-temperature cooling.

[0069] List of reference numerals:

[0070] 1. Refrigerant circulation circuit; 11. Compressor; 12. Reversing valve; 13. Indoor heat exchanger; 131. Indoor throttling device; 14. Outdoor heat exchanger; 15. Main circuit throttling device;

[0071] 2. First refrigerant auxiliary circuit; 21. Defrost valve;

[0072] 3. Second refrigerant auxiliary circuit; 31. Auxiliary circuit throttling device;

[0073] 4. Refrigerant heat exchanger;

[0074] 5. Gas-liquid separator;

[0075] 61. Ps sensor; 62. T1 sensor; 63. Pd sensor; 64. Tliqc sensor. DETAILED DESCRIPTION

[0076] The preferred embodiments of the present invention are described below with reference to the accompanying drawings. It should be understood by those skilled in the art that these embodiments are only used to explain the technical principles of the present invention and are not intended to limit the scope of protection of the present invention. Those skilled in the art can make adjustments to them as needed to adapt to specific application scenarios.

[0077] It should be noted that in the description of the present invention, unless otherwise clearly specified and limited, the terms "connection" and "connection" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection; it can be a direct connection between two elements, or it can be indirect connection through an intermediate medium. For those skilled in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0078] In order to solve the problem that the existing air conditioning system causes large fluctuations in indoor temperature when defrosting in low-temperature weather and cooling in high-temperature weather, the present invention proposes an air conditioning system.

[0079] The air conditioning system of the present invention comprises an outdoor unit, a plurality of indoor units and a refrigerant circulation loop 1 arranged between the indoor unit and the outdoor unit. The outdoor unit comprises an outdoor fan, an outdoor heat exchanger 14 and a variable frequency compressor. Each indoor unit comprises an indoor heat exchanger 13 and an indoor fan, and the plurality of indoor heat exchangers 13 are connected in parallel and then connected in series with the outdoor heat exchanger 14 through a pipeline. The indoor fan is used to blow air indoors, and the outdoor fan is used to dissipate heat and accelerate air flow in the outdoor unit. Of course, those skilled in the art can also set the number of indoor units according to actual needs, and it can also be set so that one indoor unit only adjusts the temperature of one room.

[0080] Reference Figure 1 The refrigerant circulation circuit 1 is provided with a compressor 11, a reversing valve 12, an indoor heat exchanger 13, a main circuit throttling device 15 and an outdoor heat exchanger 14. The main circuit throttling device 15 throttles the refrigerant in the refrigerant pipeline to adjust the flow rate.

[0081] The refrigerant circulation loop 1 is a refrigerant loop for realizing conventional refrigeration or conventional heating of the air-conditioning system. When the air-conditioning system is in conventional heating, the low-temperature and low-pressure gaseous refrigerant is compressed to become a high-temperature and high-pressure gaseous refrigerant. The high-temperature and high-pressure gaseous refrigerant releases heat in the indoor heat exchanger 13 and condenses into a high-temperature and high-pressure liquid refrigerant. The liquid refrigerant enters the outdoor heat exchanger 14 to absorb heat and evaporates into a low-temperature and low-pressure gaseous refrigerant. The gaseous refrigerant is then sucked into the compressor 11 and compressed to enter the next cycle. During the whole process, the refrigerant releases heat in the indoor heat exchanger 13 and absorbs heat in the outdoor heat exchanger 14 to achieve the purpose of heating. When the air-conditioning system is in conventional cooling, the high-temperature and high-pressure gaseous refrigerant of the compressor 11 enters the outdoor heat exchanger 14 to release heat and condense, and then enters the indoor heat exchanger 13 to absorb heat to cool the room.

[0082] The air conditioning system further includes a first refrigerant auxiliary circuit 2, a second refrigerant auxiliary circuit 3 and a refrigerant heat exchanger 4. The first end of the first refrigerant auxiliary circuit 2 is connected to the pipeline between the indoor heat exchanger 13 and the reversing valve 12, and the second end of the first refrigerant auxiliary circuit 2 is connected to the pipeline between the indoor heat exchanger 13 and the outdoor heat exchanger 14; the first refrigerant auxiliary circuit 2 is provided with a defrost valve 21.

[0083] The first end of the second refrigerant auxiliary circuit 3 is connected to the pipeline between the outdoor heat exchanger 14 and the second end of the first refrigerant auxiliary circuit 2, a gas-liquid separator 5 is arranged between the compressor air inlet and the reversing valve 12, and the second end of the second refrigerant auxiliary circuit 3 is connected to the pipeline between the gas-liquid separator 5 and the reversing valve 12.

[0084] An auxiliary circuit throttling device 31 is provided on the second refrigerant auxiliary circuit 3, and the auxiliary circuit throttling device 31 is located between the first end of the second refrigerant auxiliary circuit 3 and the refrigerant heat exchanger 4; the refrigerant after throttling in the second refrigerant auxiliary circuit 3 and the main circuit refrigerant coming out of the outdoor heat exchanger 14 exchange heat in the refrigerant heat exchanger 4.

[0085] Specifically, a first heat exchange tube and a second heat exchange tube for exchanging heat with each other are arranged in the refrigerant heat exchanger 4, the first heat exchange tube is connected to the refrigerant circulation circuit 1, and the second heat exchange tube is connected to the second refrigerant auxiliary circuit 3. Of course, the present invention does not limit the structure of the refrigerant heat exchanger 4, as long as it can realize heat exchange between the two refrigerants, it falls within the protection scope of the present invention.

[0086] An indoor throttling device 131 is connected in series to the pipeline where each indoor heat exchanger 13 is located. The indoor throttling device 131 is used to control the flow rate of the refrigerant entering the indoor heat exchanger 13.

[0087] When the air conditioning system is in defrosting mode, the compressor 11 is controlled to be turned on, the reversing valve 12 is switched to connect the compressor outlet and the outdoor heat exchanger 14, the indoor throttling device 131 is closed, and the auxiliary throttling device 31 is opened for throttling. The high-temperature and high-pressure gaseous refrigerant at the compressor outlet enters the outdoor heat exchanger 14 for defrosting and condensation and liquefaction, and a part of the main liquid refrigerant enters the second refrigerant auxiliary circuit 3. After throttling by the auxiliary throttling device 31, the refrigerant temperature and refrigerant pressure of the second refrigerant auxiliary circuit 3 are lower than the main circuit, so that the refrigerant in the second refrigerant auxiliary circuit 3 absorbs the heat of the main refrigerant and evaporates to become a gaseous refrigerant. The main liquid refrigerant enters the gas-liquid separator 5 together with the gaseous refrigerant through the first refrigerant auxiliary circuit 2, and the separated gaseous refrigerant returns to the compressor 11.

[0088] When the air conditioning system of the present invention is defrosted, the indoor heat exchanger 13 does not participate in the heat exchange, which means that the refrigerant does not exchange heat with the indoor environment, so the indoor environment temperature fluctuation caused by the refrigerant taking heat from the indoor environment is fundamentally avoided. In addition, the pressure and temperature of the refrigerant in the second refrigerant auxiliary circuit 3 are reduced after throttling, and the low-temperature and low-pressure refrigerant absorbs the heat of the main circuit refrigerant, ensuring that part of the refrigerant returns to the compressor 11 in the form of gas, preventing liquid hammer, and ensuring the safe and stable operation of the compressor 11.

[0089] When the air conditioning system is running in the normal cooling mode, the compressor 11 is controlled to be turned on, the reversing valve 12 is switched to connect the compressor outlet and the outdoor heat exchanger 14, the indoor throttling device 131 is opened, the defrost valve 21 is closed, and the auxiliary throttling device 31 is closed. The high-temperature and high-pressure gaseous refrigerant at the compressor outlet enters the outdoor heat exchanger 14 for heat dissipation and condensation, and then enters the indoor heat exchanger 13 to absorb the heat from the indoor environment. The refrigerant is vaporized and returns to the compressor 11. When the outdoor temperature is high, the outdoor heat exchanger 14 does not dissipate heat well, and the pressure in the air conditioning system will rise rapidly. At this time, the auxiliary throttling device 31 is turned on, and the low-temperature and low-pressure refrigerant after the auxiliary throttling is used to absorb the heat of the main refrigerant. The auxiliary refrigerant directly returns to the compressor 11, and the heat of the main refrigerant is taken away by the auxiliary refrigerant to further reduce the temperature. The main refrigerant then enters the indoor heat exchanger 13 to absorb heat, thereby effectively improving the cooling effect and ensuring a stable indoor temperature.

[0090] Optionally, the reversing valve 12 is a four-way valve, and an oil-gas separator (not shown in the figure) is arranged between the four-way valve and the compressor outlet. The oil-gas separator is used to separate the compressor oil and the refrigerant.

[0091] The structure of the reversing valve 12 is not limited to a four-way valve, it can also be a three-way valve or a five-way valve, etc., as long as the corresponding flow direction of the refrigerant can be achieved. Technical personnel in this field can set the specific type and structure of the reversing valve 12 according to actual needs, and all of them fall within the protection scope of the present invention.

[0092] The invention also provides a control method for the air conditioning system.

[0093] Reference Figure 6 , the control method of the air conditioning system mainly includes the following steps:

[0094] Step S10: receiving an instruction to operate the defrost mode;

[0095] Step S11: Control the compressor to start, switch the four-way valve to connect the compressor outlet with the outdoor heat exchanger, close all indoor throttling devices, open all main throttling devices, open the defrost valve, and open all auxiliary throttling devices.

[0096] Reference Figure 2 During defrosting, the indoor fan and indoor throttling device are closed, and the refrigerant does not enter the indoor heat exchanger 13 to exchange heat with the indoor room, so the indoor ambient temperature fluctuates less, and the high-temperature and high-pressure gaseous refrigerant of the compressor directly enters the outdoor heat exchanger 14 for defrosting. The high-temperature liquid refrigerant after defrosting does not pass through the main throttling device 15 for throttling, and a part of it returns to the compressor 11 through the second refrigerant auxiliary line 3, and the other part returns to the compressor 11 through the first refrigerant auxiliary line 2 to prevent the low pressure from being too low. In order to ensure the low pressure in the system at the beginning of defrosting, the auxiliary throttling device 31 is fully opened at the beginning of defrosting, and then the opening of the auxiliary throttling device 31 is adjusted according to the low pressure, so that the low pressure is in a suitable range while meeting the defrosting requirements, to prevent the compressor 11 from reporting a low pressure fault. It should be noted that the rate of system pressure rise is different under different working conditions. If it is determined based on past experience that a large flow of auxiliary refrigerant is not required to participate in heat exchange, then in step S11, the auxiliary throttling device 31 does not need to be fully opened, and its opening degree can be less than the full opening degree. Technical personnel in this field can set its first initial opening degree according to their needs.

[0097] Reference Figure 7 After step S11, the control method further includes:

[0098] Step S12: Obtain the low pressure Ps of the system and the refrigerant temperature T1 after throttling by the auxiliary circuit throttling device.

[0099] The low pressure Ps is measured by the Ps sensor 61 on the main line, and the refrigerant temperature T1 after throttling by the auxiliary line throttling device is measured by the T1 sensor 62 on the second refrigerant auxiliary line. The low pressure of the refrigerant is the pressure of the refrigerant on the low pressure side of the system in the air conditioning refrigerant system, that is, the refrigerant pressure of the part of the pipeline from the four-way valve to the compressor inlet. The present invention does not set any detection position of the low pressure side pressure.

[0100] Step S13: Obtain the corresponding evaporation saturation temperature T according to Ps;

[0101] Step S14: Determine whether T>T1 holds.

[0102] If step S14 is established, step S15 is executed; if not, step S16 is executed.

[0103] If T>T1, it means that the refrigerant in the second refrigerant auxiliary circuit 3 is completely vaporized, and T≤T1, it means that the refrigerant in the second refrigerant auxiliary circuit 3 is not completely vaporized.

[0104] The corresponding evaporation saturation temperature T is obtained according to the low pressure Ps. The calculation can be performed based on an empirical formula fitted according to the experimental data, or it can be queried based on a refrigerant pressure-temperature comparison table. Those skilled in the art can set the calculation method of the evaporation saturation temperature T according to their needs, and all of them fall within the protection scope of the present invention.

[0105] Step S15: Determine whether Ps is greater than or equal to a preset pressure value.

[0106] If step S15 is established, then execute step S151, if step S15 is not established, then execute step S152;

[0107] Step S151: Maintain the current opening of the auxiliary circuit throttling device.

[0108] It is determined whether the low pressure Ps reaches the preset pressure value. If Ps is greater than or equal to the preset pressure value, it means that the current low pressure of the compressor meets the requirement and the opening of the current auxiliary circuit throttling device 31 can be maintained.

[0109] Step S152: Selecting the indoor unit with the highest indoor ambient temperature among the indoor units in the turned-off state;

[0110] Step S153: Open the indoor throttling device corresponding to the indoor unit which is in the closed state and has the highest indoor ambient temperature.

[0111] If Ps is less than the preset pressure value, it means that the current low pressure is low. In order to prevent low pressure failure, the low pressure needs to be increased.

[0112] When the low pressure is low, select the indoor unit with low indoor temperature demand and high indoor ambient temperature, open the indoor throttling device of the indoor unit, so that part of the refrigerant in the main circuit enters the indoor heat exchanger to absorb heat, so as to increase the low pressure. The indoor temperature demand corresponding to the indoor unit in the closed state is low, so select the indoor unit with high indoor ambient temperature from all the indoor units in the closed state, and open the corresponding indoor throttling device. This can reduce the impact on the indoor temperature in the turned-on state.

[0113] Step S16: Reduce the opening of the auxiliary circuit throttling device.

[0114] If T≤T1, it means that the refrigerant in the low-pressure pipeline has not been completely vaporized, and the opening of the auxiliary circuit throttling device 31 is reduced to reduce the refrigerant flow in the second refrigerant auxiliary circuit 3 so that the refrigerant is completely vaporized.

[0115] After step S16, the process returns to step S12.

[0116] Reference Figure 6 , the control method of the air conditioning system further comprises the following steps:

[0117] Step S20: receiving an instruction to operate a conventional heating mode;

[0118] Step S21: Control the defrost valve to close, the compressor to start, the four-way valve to connect the compressor outlet and the indoor heat exchanger, the main throttling device to open, the defrost valve to close, the auxiliary throttling device to close, and the indoor throttling device to open.

[0119] Reference Figure 3 During conventional heating, the defrost valve 21 and the auxiliary circuit throttling device 31 are both in the closed state. The high-temperature and high-pressure gaseous refrigerant of the compressor 11 enters the indoor heat exchanger 13 to dissipate heat, then enters the outdoor heat exchanger 14 to absorb heat, and finally returns to the compressor air inlet.

[0120] Step S30: receiving an instruction to operate a conventional cooling mode;

[0121] Step S31: Control the defrost valve to close, the compressor to start, the four-way valve to connect the compressor outlet and the outdoor heat exchanger, the main throttling device to open, the defrost valve to close, the auxiliary throttling device to close, and the indoor throttling device to open.

[0122] Reference Figure 4 During conventional cooling, the defrost valve 21 and the auxiliary circuit throttling device 31 are closed, and the high-temperature and high-pressure gaseous refrigerant of the compressor 11 enters the outdoor heat exchanger 14 to dissipate heat, then enters the indoor heat exchanger 13 to absorb heat, and finally returns to the compressor air inlet.

[0123] Step S32: When the air conditioning system is operating in the normal cooling mode, upon receiving an instruction to operate in the high-temperature cooling mode, the auxiliary circuit throttling device is controlled to open to the second initial opening.

[0124] Reference Figure 5 When the air conditioning system is cooling in high temperature weather, if the outdoor temperature is high and the heat exchange effect of the outdoor heat exchanger 14 is poor, resulting in a significant increase in the high-pressure pressure, the auxiliary circuit throttling device 31 is opened to allow the refrigerant in the second refrigerant auxiliary circuit 3 to absorb the heat of the main refrigerant, increase the supercooling of the main refrigerant, and then the main refrigerant enters the indoor heat exchanger 13 to absorb heat to achieve a stable cooling effect.

[0125] Reference Figure 8 , after step S32, execute step S33.

[0126] Step S33: Obtain the high pressure Pd of the system and the main refrigerant temperature Tliqc after heat exchange in the refrigerant heat exchanger.

[0127] Reference Figure 2 The high pressure Pd is measured by the Pd sensor 63 on the main line, and the main line refrigerant temperature Tliqc after heat exchange in the refrigerant heat exchanger is measured by the Tliqc sensor 64 on the main line. The high pressure of the refrigerant is the pressure of the refrigerant in the high pressure side pipeline of the air conditioning refrigerant system, that is, the refrigerant pressure of the pipeline from the compressor outlet to the four-way valve. Those skilled in the art can set the detection position according to actual needs.

[0128] Step S34: Obtain the corresponding condensation saturation temperature Tpd according to Pd.

[0129] The corresponding condensation saturation temperature Tpd obtained according to Pd can be calculated based on an empirical formula fitted according to experimental data, or can be queried based on a refrigerant pressure-temperature comparison table. Those skilled in the art can set the calculation method of the condensation saturation temperature Tpd according to their needs, and all of them fall within the protection scope of the present invention.

[0130] Step S35: Determine whether Tpd≥Tliqc holds.

[0131] If step S35 is established, then execute step S351;

[0132] Step S351: maintaining the current opening of the auxiliary circuit throttling device;

[0133] During high-temperature cooling, the outdoor ambient temperature is high, and the high pressure is correspondingly higher, which causes the gaseous refrigerant to be unable to be completely liquefied. The high pressure is related to the condensation saturation temperature. The degree of subcooling can be adjusted by adjusting the opening of the auxiliary throttling device to completely liquefy the refrigerant passing through the main circuit. Tpd ≥ Tliqc means that the main circuit refrigerant is completely liquefied, and the current opening of the auxiliary circuit throttling device 31 can be maintained.

[0134] If step S35 is not established, execute step S352;

[0135] Step S352: Increase the opening of the auxiliary circuit throttling device.

[0136] After step S352, return to step S33.

[0137] Tpd<Tliqc means that the main refrigerant is not completely liquefied. By increasing the opening of the auxiliary throttling device 31, the amount of refrigerant entering the second refrigerant auxiliary circuit 3 increases, and the heat exchange amount increases, so that the main refrigerant is completely liquefied.

[0138] During high-temperature cooling, the auxiliary circuit throttling device 31 is initially opened to a relatively small degree, and then the degree of opening of the auxiliary circuit throttling device 31 is adjusted according to the system high pressure so that the high pressure is always maintained within a suitable range.

[0139] As stated in the first paragraph of this section, the above implementation mode is only used to illustrate the principles of the present invention and is not intended to limit the scope of protection of the present invention. Without departing from the principles of the present invention, those skilled in the art can adjust the above structure so that the present invention can be applied to more specific application scenarios.

[0140] Those skilled in the art can understand that the above-mentioned air conditioning system also includes some other well-known structures, such as processors, controllers, memories, etc., wherein the memories include but are not limited to random access memory, flash memory, read-only memory, programmable read-only memory, volatile memory, non-volatile memory, serial memory, parallel memory or registers, etc., and the processor includes but is not limited to CPLD / FPGA, DSP, ARM processor, MIPS processor, etc. In order to unnecessarily obscure the embodiments of the present disclosure, these well-known structures are not shown in the drawings.

[0141] Although the various steps in the above embodiment are described in the above order, those skilled in the art can understand that in order to achieve the effect of the present embodiment, different steps do not have to be executed in such an order, and they can be executed simultaneously (in parallel) or in a reverse order. Those skilled in the art can set the order of the steps as needed, and all of them fall within the protection scope of the present invention.

[0142] So far, the technical solutions of the present invention have been described in conjunction with the preferred embodiments shown in the accompanying drawings. However, it is easy for those skilled in the art to understand that the protection scope of the present invention is obviously not limited to these specific embodiments. Without departing from the principle of the present invention, those skilled in the art can make equivalent changes or substitutions to the relevant technical features, and the technical solutions after these changes or substitutions will fall within the protection scope of the present invention.

Claims

1. An air conditioning system, characterized in that: The air conditioning system of the present invention comprises a refrigerant circulation circuit (1) and a compressor (11), a reversing valve (12), an indoor heat exchanger (13) and an outdoor heat exchanger (14) arranged on the refrigerant circulation circuit (1); an indoor throttling device (131) is connected in series to the pipeline where the indoor heat exchanger (13) is located; The air conditioning system further comprises a first refrigerant auxiliary circuit (2), a second refrigerant auxiliary circuit (3) and a refrigerant heat exchanger (4); The first end of the first refrigerant auxiliary circuit (2) is connected to the pipeline between the indoor heat exchanger (13) and the reversing valve (12), and the second end of the first refrigerant auxiliary circuit (2) is connected to the pipeline between the indoor heat exchanger (13) and the outdoor heat exchanger (14); a defrost valve (21) is provided on the first refrigerant auxiliary circuit (2); The first end of the second refrigerant auxiliary circuit (3) is connected to the pipeline between the outdoor heat exchanger (14) and the second end of the first refrigerant auxiliary circuit (2), a gas-liquid separator (5) is provided between the air inlet of the compressor (11) and the reversing valve (12), and the second end of the second refrigerant auxiliary circuit (3) is connected to the pipeline between the gas-liquid separator (5) and the reversing valve (12); An auxiliary circuit throttling device (31) is provided on the second refrigerant auxiliary circuit (3), and the auxiliary circuit throttling device (31) is located between the first end of the second refrigerant auxiliary circuit (3) and the refrigerant heat exchanger (4); the refrigerant after throttling in the second refrigerant auxiliary circuit (3) and the refrigerant coming out of the outdoor heat exchanger (14) can exchange heat in the refrigerant heat exchanger (4).

2. The air conditioning system according to claim 1, characterized in that: An oil-gas separator is provided between the reversing valve (12) and the gas outlet of the compressor (11).

3. A control method for an air conditioning system, characterized in that: The air conditioning system of the present invention comprises a refrigerant circulation circuit (1) and a compressor (11), a reversing valve (12), an indoor heat exchanger (13) and an outdoor heat exchanger (14) arranged on the refrigerant circulation circuit (1); an indoor throttling device (131) is connected in series to the pipeline where the indoor heat exchanger (13) is located; The air conditioning system further comprises a first refrigerant auxiliary circuit (2), a second refrigerant auxiliary circuit (3) and a refrigerant heat exchanger (4); The first end of the first refrigerant auxiliary circuit (2) is connected to the pipeline between the indoor heat exchanger (13) and the reversing valve (12), and the second end of the first refrigerant auxiliary circuit (2) is connected to the pipeline between the indoor heat exchanger (13) and the outdoor heat exchanger (14); a defrost valve (21) is provided on the first refrigerant auxiliary circuit (2); The first end of the second refrigerant auxiliary circuit (3) is connected to the pipeline between the outdoor heat exchanger (14) and the second end of the first refrigerant auxiliary circuit (2), a gas-liquid separator (5) is provided between the air inlet of the compressor (11) and the reversing valve (12), and the second end of the second refrigerant auxiliary circuit (3) is connected to the pipeline between the gas-liquid separator (5) and the reversing valve (12); The second refrigerant auxiliary circuit (3) is provided with an auxiliary circuit throttling device (31), and the auxiliary circuit throttling device (31) is located between the first end of the second refrigerant auxiliary circuit (3) and the refrigerant heat exchanger (4); the refrigerant after throttling in the second refrigerant auxiliary circuit (3) and the refrigerant coming out of the outdoor heat exchanger (14) can exchange heat in the refrigerant heat exchanger (4); The control method comprises: Receiving a command to operate a defrost mode; The defrost valve is controlled to open, the compressor is turned on, the reversing valve is switched to connect the compressor outlet with the outdoor heat exchanger, the auxiliary circuit throttling device is opened to a first initial opening, and the indoor throttling device is closed.

4. The control method of the air conditioning system according to claim 3, characterized in that: After the step of "controlling the defrost valve to open, the compressor to start, the reversing valve to switch to the compressor outlet to communicate with the outdoor heat exchanger, the auxiliary circuit throttling device to open the first initial opening, and the indoor throttling device to close", the control method includes: Obtaining the low pressure Ps of the system and the refrigerant temperature T1 after throttling by the auxiliary circuit throttling device; Obtain the corresponding evaporation saturation temperature T according to Ps; If T≤T1, the opening of the auxiliary circuit throttling device is reduced.

5. The control method of the air conditioning system according to claim 4, characterized in that: After the step of "obtaining the corresponding evaporation saturation temperature T according to Ps", the control method includes: If T>T1 and Ps is greater than the preset pressure value, the current opening of the auxiliary path throttling device is maintained.

6. The control method of the air conditioning system according to claim 4, characterized in that: After the step of "obtaining the low pressure Ps of the refrigerant", the control method further includes: If Ps is less than or equal to the preset pressure value, the indoor unit with the highest indoor ambient temperature among the indoor units in the closed state is selected; The indoor throttling device corresponding to the indoor unit which is in the off state and has the highest indoor ambient temperature is opened.

7. The control method of the air conditioning system according to claim 3, characterized in that: The control method further comprises: Receiving a command to operate a conventional cooling mode; The defrost valve is controlled to be closed, the compressor is turned on, the reversing valve is switched to connect the compressor outlet with the outdoor heat exchanger, the auxiliary circuit throttling device is closed, and the indoor throttling device is opened.

8. The control method of the air conditioning system according to claim 3, characterized in that: The control method further comprises: Receiving an instruction to operate high temperature cooling; The defrost valve is controlled to be closed, the compressor is turned on, the reversing valve is switched to connect the compressor outlet with the outdoor heat exchanger, the auxiliary circuit throttling device is opened to a second initial opening, and the indoor throttling device is opened.

9. The control method of the air conditioning system according to claim 8, characterized in that: After the step of "controlling the defrost valve to close, the compressor to start, the reversing valve to switch to the compressor outlet to communicate with the outdoor heat exchanger, the auxiliary circuit throttling device to open the second initial opening, and the indoor throttling device to open", the control method further includes: Obtaining the high pressure Pd of the system and the main refrigerant temperature Tliqc after heat exchange by the refrigerant heat exchanger; Obtain the corresponding condensation saturation temperature Tpd according to Pd; When Tpd<Tliqc, the opening of the auxiliary path throttling device is increased.

10. The control method of the air conditioning system according to claim 9, characterized in that: After the step of "obtaining the corresponding condensation saturation temperature Tpd according to Pd", the control method includes: When Tpd≥Tliqc, the current opening of the auxiliary circuit throttling device is maintained.

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