CN107228439B - Multi-split system and control method thereof - Google Patents

Multi-split system and control method thereof Download PDF

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Publication number
CN107228439B
CN107228439B CN201710518171.7A CN201710518171A CN107228439B CN 107228439 B CN107228439 B CN 107228439B CN 201710518171 A CN201710518171 A CN 201710518171A CN 107228439 B CN107228439 B CN 107228439B
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heat exchanger
refrigerant
temperature
throttle valve
heat exchange
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CN107228439A (en
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李元阳
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Midea Group Co Ltd
GD Midea Heating and Ventilating Equipment Co Ltd
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Midea Group Co Ltd
GD Midea Heating and Ventilating Equipment Co Ltd
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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F24—HEATING; RANGES; VENTILATING
    • F24F—AIR-CONDITIONING; AIR-HUMIDIFICATION; VENTILATION; USE OF AIR CURRENTS FOR SCREENING
    • F24F5/00—Air-conditioning systems or apparatus not covered by F24F1/00 or F24F3/00, e.g. using solar heat or combined with household units such as an oven or water heater
    • F24F5/0003—Exclusively-fluid systems
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F24—HEATING; RANGES; VENTILATING
    • F24F—AIR-CONDITIONING; AIR-HUMIDIFICATION; VENTILATION; USE OF AIR CURRENTS FOR SCREENING
    • F24F13/00—Details common to, or for air-conditioning, air-humidification, ventilation or use of air currents for screening
    • F24F13/30—Arrangement or mounting of heat-exchangers
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B13/00—Compression machines, plants or systems, with reversible cycle
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B41/00—Fluid-circulation arrangements
    • F25B41/30—Expansion means; Dispositions thereof
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B49/00—Arrangement or mounting of control or safety devices
    • F25B49/02—Arrangement or mounting of control or safety devices for compression type machines, plants or systems
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02B—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS
    • Y02B30/00—Energy efficient heating, ventilation or air conditioning [HVAC]
    • Y02B30/70—Efficient control or regulation technologies, e.g. for control of refrigerant flow, motor or heating

Abstract

The invention discloses a multi-split system and a control method thereof, wherein the multi-split system comprises an outdoor unit, a plurality of indoor units, a refrigerant distribution device and a return air heat exchange device, wherein the outdoor unit comprises a compressor and an outdoor heat exchanger; the refrigerant distribution device is used for distributing refrigerants which enter and exit the plurality of indoor units; the air return heat exchange device comprises an air return heat exchanger and an air return four-way valve, and is used for establishing pressure difference between the outdoor unit and a plurality of indoor units through heat exchange between a first heat exchange flow path and a second heat exchange flow path of the air return heat exchanger when the outdoor ambient temperature is less than or equal to a first preset temperature, so that the multi-split air conditioner system can perform low-temperature refrigeration. According to the multi-split air conditioner system provided by the embodiment of the invention, the refrigerant outside the room can be smoothly delivered to the inside of the room by establishing the pressure difference between the indoor unit and the plurality of outdoor units, so that low-temperature refrigeration can be realized, and the heat recovery function and the heating and refrigerating effects of the multi-split air conditioner system are not influenced.

Description

Multi-split system and control method thereof
Technical Field
The invention relates to the technical field of multi-split air-conditioning systems, in particular to a multi-split air-conditioning system and a control method of the multi-split air-conditioning system.
Background
As shown in fig. 1, the three-pipe multi-split system in the related art may include an outdoor heat exchanger (the outdoor heat exchanger is a two-plate heat exchanger, i.e., a first heat exchanger and a second heat exchanger), a compressor, a plurality of four-way valves (e.g., ST1, ST2, and ST 3), a refrigerant distribution device, and a plurality of indoor units (e.g., a first indoor unit and a second indoor unit).
When the outdoor low temperature but indoor needs to be refrigerated, because the indoor air quality has special requirements, the multi-split system cannot directly introduce the external low temperature air into the indoor, but needs to start the refrigerating inner unit for refrigeration in the indoor, so that some problems exist in the multi-split system, for example, when the outdoor temperature is below-5 ℃, the operation of the multi-split system becomes unstable, the capacity of the multi-split system is seriously reduced, the outdoor environment temperature is low, the high condensation pressure of the outdoor heat exchanger can not be built up, and therefore, an effective pressure difference can not be formed to convey the refrigerant from the outdoor side to the indoor side, so that the quantity of the refrigerant at the indoor side is usually reduced, and the refrigerating effect and the heating effect of the indoor unit are affected.
Disclosure of Invention
The present invention aims to solve at least one of the technical problems in the above-described technology to some extent.
Therefore, an object of the present invention is to provide a multi-split system, which not only can realize low-temperature refrigeration when the outdoor environment temperature is low, but also can not affect the heat recovery function and the heating and refrigerating effects of the multi-split system.
The second object of the present invention is to provide a control method of a multi-split system.
In order to achieve the above objective, an embodiment of a first aspect of the present invention provides a multiple on-line system, including an outdoor unit, a plurality of indoor units, a refrigerant distribution device and a return air heat exchange device, wherein the outdoor unit includes a compressor and an outdoor heat exchanger, an exhaust end of the compressor is connected to one end of the outdoor heat exchanger, and the other end of the outdoor heat exchanger is connected to a first refrigerant inlet and outlet end of the refrigerant distribution device; the refrigerant distribution device is used for distributing refrigerants entering and exiting the plurality of indoor units; the air return heat exchange device comprises an air return heat exchanger and an air return four-way valve, wherein the first end of a first heat exchange flow path of the air return heat exchanger is connected to the first end of the air return four-way valve, the second end of the first heat exchange flow path of the air return heat exchanger is connected to the first refrigerant inlet and outlet end of the refrigerant distribution device, the first end of a second heat exchange flow path of the air return heat exchanger is respectively connected to the second end of the air return four-way valve and the air return end of the compressor, the second end of the second heat exchange flow path of the air return heat exchanger is connected to the second refrigerant inlet and outlet end of the refrigerant distribution device, the third end of the air return four-way valve is connected to the third refrigerant inlet and outlet end of the refrigerant distribution device, the fourth end of the air return four-way valve is connected to the air outlet end of the compressor, and the air return heat exchange device is used for establishing a multi-online refrigerating system through heat exchange between the first heat exchange flow path and the second heat exchange flow path of the air return heat exchanger when the outdoor environment temperature is smaller than or equal to a first preset temperature.
According to the multi-split system provided by the embodiment of the invention, the first end of the first heat exchange flow path of the air return heat exchanger is connected to the first end of the air return four-way valve, the second end of the first heat exchange flow path of the air return heat exchanger is connected to the first refrigerant inlet and outlet end of the refrigerant distribution device, the first end of the second heat exchange flow path of the air return heat exchanger is respectively connected to the second end of the air return four-way valve and the air return end of the compressor, the second end of the second heat exchange flow path of the air return heat exchanger is connected to the second refrigerant inlet and outlet end of the refrigerant distribution device, the third end of the air return four-way valve is connected to the third refrigerant inlet and outlet end of the refrigerant distribution device, and the fourth end of the air return four-way valve is connected to the air outlet end of the compressor, so that when the outdoor environment temperature is smaller than or equal to the first preset temperature, the pressure difference between the outdoor machine and the plurality of indoor machines is established through the heat exchange between the first heat exchange flow path of the air return heat exchanger and the second heat exchange flow path, the outdoor machine can be smoothly sent to the indoor side, the refrigerant can not be easily cooled down, and the indoor side can not be cooled down, and the refrigerating system can not be cooled down and can be cooled down and the refrigerating system can be cooled down and heated.
In addition, the multi-split system provided by the embodiment of the invention can also have the following additional technical characteristics:
according to one embodiment of the invention, the outdoor heat exchanger comprises a first heat exchanger and a second heat exchanger, wherein a first end of the first heat exchanger is connected to the exhaust end of the compressor through a first four-way valve, a second end of the first heat exchanger is connected to the first refrigerant inlet and outlet end through a first throttle valve, a first end of the second heat exchanger is connected to the exhaust end of the compressor through a second four-way valve, a second end of the second heat exchanger is connected to the first refrigerant inlet and outlet end through a second throttle valve, a third throttle valve is arranged at a second end of a first heat exchange flow path of the return air heat exchanger, and the first ends of the second heat exchange flow paths of the return air heat exchanger are respectively connected to the first four-way valve and the second four-way valve.
According to one embodiment of the present invention, when the multi-split system is operated in a pure cooling mode, wherein the first throttle valve and the second throttle valve are kept in a fully opened state and the third throttle valve is in a closed state when the outdoor ambient temperature is greater than the first preset temperature; when the outdoor environment temperature is smaller than or equal to the first preset temperature, the opening of the first throttle valve and the opening of the second throttle valve are in positive correlation with the outdoor environment temperature, and the opening of the third throttle valve is in inverse correlation with the outdoor environment temperature.
According to one embodiment of the present invention, the refrigerant distribution device includes a plurality of heating control valves and a plurality of cooling control valves corresponding to a plurality of indoor units, one end of each cooling control valve is connected to the second refrigerant inlet and outlet end, the other end of each cooling control valve is connected to one end of the corresponding indoor unit, one end of each heating control valve is connected to the third refrigerant inlet and outlet end, the other end of each heating control valve is connected to one end of the corresponding indoor unit, and the other end of each indoor unit is connected to the first refrigerant inlet and outlet end.
According to one embodiment of the present invention, when the multi-split system operates in a pure refrigeration mode, each refrigeration control valve is in an open state, each heating control valve is in a closed state, the third throttle valve is in an open state, and the first heat exchanger, the second heat exchanger and the return air heat exchanger are condensers, wherein a high-temperature and high-pressure gaseous refrigerant discharged from an exhaust end of the compressor is condensed and throttled by the first heat exchanger, the second heat exchanger and the first heat exchange flow path, and then collected to the first refrigerant inlet and outlet end, and is distributed to each indoor unit by the refrigerant distribution device, and is changed into a medium-temperature and low-pressure gaseous refrigerant after being evaporated and absorbed by each indoor unit, and is collected to the second refrigerant inlet and outlet end by each refrigeration control valve, and is returned to the compressor after being subjected to heat exchange by the second heat exchange flow path.
According to one embodiment of the present invention, when the multi-split system is operated in the pure heating mode, each refrigeration control valve is in a closed state, each heating control valve is in an open state, the third throttle valve is in a closed state, and the first heat exchanger and the second heat exchanger are evaporators, wherein the high-temperature and high-pressure gaseous refrigerant discharged from the discharge end of the compressor enters the third refrigerant inlet and outlet end through the air return four-way valve, and is condensed by each heating control valve to each indoor unit respectively, and is changed into a high-temperature and high-pressure liquid refrigerant, and the high-temperature and high-pressure liquid refrigerant is collected to the first refrigerant inlet and outlet end, is changed into a low-temperature and low-pressure two-phase refrigerant after being throttled by the first throttle valve and the second throttle valve respectively, and is then changed into a low-temperature and high-temperature superheated gaseous refrigerant after being evaporated by the first heat exchanger and the second heat exchanger, and is returned to the compressor.
According to one embodiment of the present invention, when the multiple on-line system operates in a main refrigeration mode, the multiple indoor units include a refrigeration indoor unit and a heating indoor unit, the refrigeration control valves corresponding to the refrigeration indoor units are all in an open state, the heating control valves corresponding to the heating indoor units are all in an open state, and the third throttle valve is in a closed state, if the first heat exchanger is an evaporator and the second heat exchanger is a condenser, a high-temperature and high-pressure gaseous refrigerant discharged from an exhaust end of the compressor is split into two paths, one path is condensed into a first high-temperature and high-pressure liquid refrigerant by the second heat exchanger, one part of the first high-temperature and high-pressure liquid refrigerant is evaporated by the first heat exchanger and then returns to the compressor, and the other part of the first high-temperature and high-pressure liquid refrigerant enters the first refrigerant inlet and outlet end; the other path of the liquid refrigerant enters the third refrigerant inlet and outlet end through the air return four-way valve, enters the heating indoor unit through the heating control valve for condensation to become a second high-temperature high-pressure liquid refrigerant, and the second high-temperature high-pressure liquid refrigerant enters the refrigerating indoor unit for evaporation after being converged at the first refrigerant inlet and outlet end and the other part of the first high-temperature high-pressure liquid refrigerant, then enters the second refrigerant inlet and outlet end through the refrigerating control valve, and returns to the compressor through the second heat exchange flow path.
According to one embodiment of the present invention, when the multiple on-line system operates in a main heating mode, the multiple on-line system includes a refrigerating indoor unit and a heating indoor unit, the refrigerating control valves corresponding to the refrigerating indoor units are all in an open state, the heating control valves corresponding to the heating indoor units are all in an open state, the third throttle valve is in a closed state, the first heat exchanger and the second heat exchanger are both evaporators, wherein a high-temperature and high-pressure gaseous refrigerant discharged from an exhaust end of the compressor enters the third refrigerant inlet and outlet through a return air four-way valve, and is condensed by the heating control valves into the heating indoor units, and then becomes a high-temperature and high-pressure liquid refrigerant, one path of the high-temperature and high-pressure liquid refrigerant is collected into the first refrigerant inlet and outlet end and then becomes a medium-temperature and low-pressure gaseous refrigerant after being evaporated by the refrigerating indoor units, and then is collected into the second refrigerant inlet and outlet end through the refrigerating control valves, finally is collected into the compressor after being subjected to heat exchange through the second heat exchange flow passage, and the other path is changed into the high-temperature and low-pressure gaseous refrigerant after passing through the first throttle valve and the second heat exchanger.
To achieve the above objective, an embodiment of a second aspect of the present invention provides a control method of a multi-split system, where the multi-split system is the multi-split system, and the control method includes the following steps: acquiring outdoor environment temperature; when the multi-split air conditioner system is in refrigeration operation, judging whether the outdoor environment temperature is less than or equal to a first preset temperature; if the outdoor environment temperature is less than or equal to a first preset temperature, the pressure difference between the outdoor unit and the plurality of indoor units is established through heat exchange between the first heat exchange flow path and the second heat exchange flow path of the return air heat exchanger, so that the multi-split air conditioner system performs low-temperature refrigeration.
According to the control method of the multi-split system, heat exchange between the first heat exchange flow path and the second heat exchange flow path of the air return heat exchanger can be achieved through the multi-split system comprising the air return heat exchange device, so that when the multi-split system is in refrigeration operation, whether the outdoor environment temperature is smaller than or equal to the first preset temperature is judged, and when the outdoor environment temperature is smaller than or equal to the first preset temperature, the pressure difference between the outdoor unit and the plurality of indoor units is established through heat exchange between the first heat exchange flow path and the second heat exchange flow path of the air return heat exchanger, so that refrigerant outside the indoor units can be smoothly delivered to the indoor sides, low-temperature refrigeration of the multi-split system can be achieved when the outdoor environment temperature is lower, and the heat recovery function and the heating and refrigerating effects of the multi-split system are not affected.
In addition, the control method of the multi-split system according to the embodiment of the present invention may further have the following additional technical features:
according to one embodiment of the invention, the outdoor heat exchanger comprises a first heat exchanger and a second heat exchanger, a first end of the first heat exchanger is connected to the exhaust end of the compressor through a first four-way valve, a second end of the first heat exchanger is provided with a first throttle valve, a first end of the second heat exchanger is connected to the exhaust end of the compressor through a second four-way valve, a second end of the second heat exchanger is provided with a second throttle valve, a second end of a first heat exchange flow path of the return air heat exchanger is provided with a third throttle valve, and a first end of a second heat exchange flow path of the return air heat exchanger is further connected to the first four-way valve and the second four-way valve respectively, wherein when the outdoor ambient temperature is higher than the first preset temperature, the first throttle valve and the second throttle valve are controlled to be kept in a fully opened state, and the third throttle valve is controlled to be in a closed state.
According to one embodiment of the present invention, when the outdoor ambient temperature is less than or equal to the first preset temperature, the opening degree of the first throttle valve, the opening degree of the second throttle valve, and the opening degree of the third throttle valve are controlled according to the outdoor ambient temperature, respectively, wherein the opening degree of the first throttle valve and the opening degree of the second throttle valve are in positive correlation with the outdoor ambient temperature, and the opening degree of the third throttle valve is in inverse correlation with the outdoor ambient temperature.
Drawings
FIG. 1 is a system diagram of a multi-split system in the related art;
FIG. 2 is a block schematic diagram of a multi-split system according to an embodiment of the present invention;
FIG. 3 is a schematic diagram of a multi-split system according to an embodiment of the present invention;
FIG. 4 is a refrigerant flow diagram of a multi-split system operating in a pure cooling mode according to one embodiment of the present invention;
FIG. 5 is a refrigerant flow diagram when the multi-split system is operated in a pure heating mode according to an embodiment of the present invention;
FIG. 6 is a refrigerant flow diagram of a multi-split system operating in a main cooling mode according to one embodiment of the present invention;
FIG. 7 is a refrigerant flow diagram when the multi-split system is operated in a main heating mode according to an embodiment of the present invention; and
fig. 8 is a flowchart of a control method of the multi-split system according to an embodiment of the present invention.
Detailed Description
Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings, wherein like or similar reference numerals refer to like or similar elements or elements having like or similar functions throughout. The embodiments described below by referring to the drawings are illustrative and intended to explain the present invention and should not be construed as limiting the invention.
The multi-split system and the control method thereof according to the embodiment of the invention are described below with reference to the accompanying drawings.
Fig. 2 is a block schematic diagram of a multi-split system according to an embodiment of the present invention. As shown in fig. 2, the multi-split system 1 may include an outdoor unit 10, a plurality of indoor units 20, a refrigerant distribution device 30, and a return air heat exchange device 40.
The outdoor unit 10 may include a compressor 11 and an outdoor heat exchanger 12, wherein a discharge end a11 of the compressor 11 is connected to one end of the outdoor heat exchanger 12, and the other end of the outdoor heat exchanger 12 is connected to a first refrigerant inlet and outlet end a301 of the refrigerant distribution device 30. The refrigerant distribution device 30 distributes refrigerant flowing into and out of the plurality of indoor units 20. The return air heat exchanging device 40 may include a return air heat exchanger 41 and a return air four-way valve 42, wherein a first end h11 of a first heat exchanging flow path of the return air heat exchanger 41 is connected to a first end a42 of the return air four-way valve 42, a second end h12 of the first heat exchanging flow path of the return air heat exchanger 41 is connected to a first refrigerant inlet and outlet end a301 of the refrigerant distribution device 30, a first end h21 of a second heat exchanging flow path of the return air heat exchanger 41 is connected to a second end b42 of the return air four-way valve 42 and a return air end b11 of the compressor 11, respectively, a second end h22 of the second heat exchanging flow path of the return air heat exchanger 41 is connected to a second refrigerant inlet and outlet end a302 of the refrigerant distribution device 30, a third end c42 of the return air four-way valve 42 is connected to a third refrigerant inlet and outlet end a303 of the refrigerant distribution device 30, and a fourth end d42 of the return air four-way valve 42 is connected to an exhaust end a11 of the compressor 11.
The return air heat exchange device 40 is configured to establish a pressure difference between the outdoor unit 10 and the plurality of indoor units 20 by heat exchange between the first heat exchange flow path and the second heat exchange flow path of the return air heat exchanger 41 when the outdoor ambient temperature is less than or equal to a first preset temperature t1, for example, -5 ℃, so that the multi-split air conditioning system 1 performs low-temperature refrigeration. The outdoor environment temperature can be detected by the temperature sensor arranged outside the room and sent to the control part of the multi-split system. The first preset temperature t1 can be set according to actual conditions, and the set first preset temperature t1 is pre-stored in a control part in the multi-split system 1 in advance, so that the control part judges the relationship between the outdoor environment temperature and the first preset temperature t 1. For example, the first preset temperature t1 may be set to-5 ℃.
That is, when the outdoor ambient temperature is less than or equal to a first preset temperature, for example, -5 ℃, the refrigerant discharged from the compressor 11 through the discharge port a11 and the refrigerant returned to the compressor 11 through the return port b11 exchange heat between the first heat exchange flow path and the second heat exchange flow path of the return heat exchanger 41 in the return heat exchange device 40, that is, after the high-temperature and high-pressure gaseous refrigerant passing through the first heat exchange flow path is cooled and released, the low-temperature and low-pressure gaseous refrigerant passing through the second heat exchange flow path can be provided with heat, the superheat degree of the refrigerant returned to the compressor can be increased, thus the liquid return can be prevented, the refrigerant after the heat release is cooled and the refrigerant condensed and released by the outdoor heat exchanger can be combined to increase the pressure of the refrigerant flowing into the indoor side, the pressure difference between the outdoor side and the indoor side is established, so that the liquid impact of the compressor can be avoided, and the refrigerant discharged from the outdoor side can be smoothly delivered to the indoor side based on the established pressure difference between the outdoor unit and the plurality of indoor units, thereby achieving the purpose of low-temperature refrigeration of the multi-system.
In one embodiment of the present invention, as shown in fig. 3, the plurality of indoor units 20 may include a first indoor unit and a second indoor unit, the first indoor unit may include a first indoor heat exchanger 21 and a first indoor throttle valve 22, and the second indoor unit may include a second indoor heat exchanger 23 and a second indoor throttle valve 24. Wherein the first and second indoor throttle valves 22 and 24 may each be electronic expansion valves.
According to an embodiment of the present invention, as shown in fig. 3, the outdoor heat exchanger 12 may include a first heat exchanger 121 and a second heat exchanger 122, a first end of the first heat exchanger 121 is connected to the discharge end a11 of the compressor 11 through a first four-way valve ST1, a second end of the first heat exchanger 121 is connected to the first refrigerant inlet and outlet end a301 through a first throttle valve EXV1, a first end of the second heat exchanger 122 is connected to the discharge end a11 of the compressor 11 through a second four-way valve ST2, a second end of the second heat exchanger 122 is connected to the first refrigerant inlet and outlet end a301 through a second throttle valve EXV2, a second end h12 of the first heat exchange flow path of the return heat exchanger 41 is provided with a third throttle valve EXV3, and a first end h21 of the second heat exchange flow path of the return heat exchanger 41 is also connected to the first four-way valve ST1 and the second four-way valve ST2, respectively. The first throttle valve EXV1, the second throttle valve EXV2 and the third throttle valve EXV3 may be electronic expansion valves.
According to one embodiment of the present invention, as shown in fig. 3, the refrigerant distribution device 30 may include a plurality of heating control valves (e.g., SVB1 and SVB 2) and a plurality of cooling control valves (e.g., SVA1 and SVA 2) corresponding to the plurality of indoor units 20, one end of each of the cooling control valves (e.g., SVA1 and SVA 2) is connected to the second refrigerant inlet/outlet port a302, the other end of each of the cooling control valves (e.g., SVA1 and SVA 2) is connected to one end of the corresponding indoor unit (e.g., the other end of SVA1 is connected to one end of the corresponding first indoor unit, the other end of SVA2 is connected to one end of the corresponding second indoor unit), one end of each of the heating control valves (e.g., the other end of SVB1 and SVB 2) is connected to the third refrigerant inlet/outlet port a303, the other end of each of the heating control valves (e.g., the other end of SVB1 and SVB 2) is connected to one end of the corresponding indoor unit (e.g., the other end of SVB1 is connected to one end of the corresponding first indoor unit), and the other end of each of the indoor unit is connected to the first refrigerant inlet/outlet port a301. Wherein, SVA1, SVA2, SVB1 and SVB2 can be electromagnetic valves.
According to one embodiment of the present invention, when the multi-split system 1 is operated in the pure cooling mode and the outdoor ambient temperature is greater than a first preset temperature t1, for example, -5 ℃, the first throttle valve EXV1 and the second throttle valve EXV2 are maintained in the fully opened state, and the third throttle valve EXV3 is in the closed state. That is, even if the pressure difference between the outdoor unit 10 and the plurality of indoor units 20 is not increased, the high pressure generated by the refrigerant condensed and released by the first and second heat exchangers 121 and 122 is sufficient to input a large amount of refrigerant into the plurality of indoor units 20, so that the multi-split system can be ensured to operate in a pure cooling mode, and normal cooling can be realized.
When the on-line system 1 operates in the pure refrigeration mode and the outdoor environment temperature is less than or equal to a first preset temperature t1, such as-5 ℃, the opening of the first throttle valve EXV1 and the opening of the second throttle valve EXV2 are in positive correlation with the outdoor environment temperature, and the opening of the third throttle valve EXV3 is in inverse correlation with the outdoor environment temperature. That is, the high pressure generated by the refrigerant condensed and released by the first and second heat exchangers 121 and 122 is insufficient to deliver a large amount of refrigerant to the plurality of indoor units 20, and at this time, the opening degrees of the first, second and third throttle valves EXV1, EXV2 and EXV3 may be controlled to increase the pressure difference between the outdoor unit 10 and the plurality of indoor units 20, so that the multi-split system can be ensured to operate in a pure cooling mode, thereby realizing low temperature cooling. The third throttle valve EXV3 in the multi-split air conditioner system 1 controls the opening according to the outdoor environment temperature, and the first throttle valve EXV1 and the second throttle valve EXV2 control the opening according to the outdoor environment temperature and the high pressure (or the saturation temperature corresponding to the high pressure) of the outdoor heat exchanger. For example, when the outdoor ambient temperature is lower, the opening degrees of the first throttle valve EXV1 and the second throttle valve EXV2 are controlled to be smaller, and the opening degree of the third throttle valve EXV3 is controlled to be larger. When the outdoor ambient temperature is higher, the opening degrees of the first throttle valve EXV1 and the second throttle valve EXV2 are controlled to be larger, and the opening degree of the third throttle valve EXV3 is controlled to be smaller.
The refrigerant flow direction when the multi-split system operates in different modes is described below with reference to fig. 4-7.
As shown in fig. 4, when the multi-split system 1 is operated in the pure refrigeration mode, each refrigeration control valve (e.g., SVA1 and SVA 2) is in an open state, each heating control valve (e.g., SVB1 and SVB 2) is in a closed state, the third throttle valve EXV3 is in an open state, and the first heat exchanger 121, the second heat exchanger 122 and the return air heat exchanger 41 are all condensers. The high-temperature and high-pressure gaseous refrigerant discharged from the discharge end a11 of the compressor 11 is condensed and throttled by the first heat exchanger 121, the second heat exchanger 122 and the first heat exchange flow path, and then collected to the first refrigerant inlet and outlet end a301, and is respectively distributed to each indoor unit (such as the first indoor unit and the second indoor unit) by the refrigerant distribution device 30, and is converted into a medium-temperature and low-pressure gaseous refrigerant after evaporating and absorbing heat by each indoor unit, and is collected to the second refrigerant inlet and outlet end a302 by each refrigeration control valve (such as the SVA1 and the SVA 2), and then is returned to the compressor 11 after heat exchange by the second heat exchange flow path.
Specifically, when each indoor unit in the multi-split air conditioner system 1 performs cooling operation, each cooling control valve (such as SVA1 and SVA 2) is in an open state, each heating control valve (such as SVB1 and SVB 2) is in a closed state, the third throttle valve EXV3 is in an open state, the first heat exchanger 121, the second heat exchanger 122 and the air return heat exchanger 41 may be condensers, and the first indoor heat exchanger 21 and the second indoor heat exchanger 23 may be evaporators, that is, the multi-split air conditioner system 1 operates in a pure cooling mode. Wherein the refrigerant passing through the first throttle valve EXV1, the second throttle valve EXV2 and the third throttle valve EXV3 depends on their corresponding opening degrees.
When the multi-split air conditioner system 1 operates in the pure refrigeration mode, the first four-way valve ST1, the second four-way valve ST2 and the return air four-way valve 42 are all in the power-off state, the first port a1 and the fourth port d1 of the first four-way valve ST1 are communicated, the first port a2 and the fourth port d2 of the second four-way valve ST2 are communicated, and the first port a42 and the fourth port d42 of the return air four-way valve 42 are communicated. The discharge end a11 of the compressor 11 may be directly communicated with the first heat exchange flow paths of the first heat exchanger 121, the second heat exchanger 122 and the return air heat exchanger 41 through the first four-way valve ST1, the second four-way valve ST2 and the return air four-way valve 42.
Specifically, when the multi-split air-conditioning system 1 is operated in the pure cooling mode, the high-temperature and high-pressure gaseous refrigerant discharged from the discharge end a11 of the compressor 11 may be divided into three paths.
The first path enters the first heat exchanger 121 through the first four-way valve ST1, is condensed and released into a high-temperature high-pressure liquid refrigerant through the first heat exchanger 121, and then enters the first refrigerant inlet and outlet end a301 after being throttled by the first throttle valve EXV 1.
The second path enters the second heat exchanger 122 through the second four-way valve ST2, is condensed and released into a high-temperature high-pressure liquid refrigerant through the second heat exchanger 122, and then enters the first refrigerant inlet and outlet end a301 after being throttled by the second throttle valve EXV 2.
The third path enters the return air heat exchanger 41 through the return air four-way valve 42, is condensed and released to form a medium-temperature high-pressure gaseous refrigerant through the first heat exchange flow path of the return air heat exchanger 41, and then enters the first refrigerant inlet and outlet end a301 after being throttled by the third throttle valve EXV 3.
It can be seen that the above three refrigerants enter the high pressure liquid pipe together, and the high pressure liquid refrigerant collected into a high pressure liquid refrigerant with a certain supercooling degree enters the first refrigerant inlet and outlet end a301 and enters the first indoor unit and the second indoor unit. Then the liquid refrigerant is throttled by the first indoor throttle valve 22 and the second indoor throttle valve 24 respectively, becomes low-pressure liquid refrigerant, and enters the first indoor heat exchanger 21 and the second indoor heat exchanger 23 respectively. The first indoor heat exchanger 21 and the second indoor heat exchanger 23 are used for evaporating and absorbing heat to form low-pressure gaseous refrigerants, and the low-pressure gaseous refrigerants are collected to the second refrigerant inlet and outlet end a302 after passing through the refrigeration control valves SVA1 and SVA2 respectively. Further, the refrigerant enters the second heat exchange flow path of the return air heat exchanger 41 through the second refrigerant inlet and outlet end a302, and the second heat exchange flow path of the return air heat exchanger 41 absorbs the heat released by cooling of the first heat exchange flow path, so that the refrigerant returns to the compressor 11 with higher superheat. Therefore, liquid return can be prevented, simultaneously, the cooled and exothermic refrigerant can be converged with the refrigerant condensed and released by the outdoor heat exchanger to improve the pressure of the refrigerant flowing into the indoor side, and the pressure difference between the outdoor side and the indoor side is established, so that the liquid impact of the compressor can be avoided, and the refrigerant discharged from the outdoor side can be smoothly delivered to the indoor side based on the established pressure difference between the outdoor unit and a plurality of indoor units, thereby realizing the aim of low-temperature refrigeration of the multi-split air conditioner system.
According to the multi-split system provided by the embodiment of the invention, the first end of the first heat exchange flow path of the air return heat exchanger is connected to the first end of the air return four-way valve, the second end of the first heat exchange flow path of the air return heat exchanger is connected to the first refrigerant inlet and outlet end of the refrigerant distribution device, the first end of the second heat exchange flow path of the air return heat exchanger is respectively connected to the second end of the air return four-way valve and the air return end of the compressor, the second end of the second heat exchange flow path of the air return heat exchanger is connected to the second refrigerant inlet and outlet end of the refrigerant distribution device, the third end of the air return four-way valve is connected to the third refrigerant inlet and outlet end of the refrigerant distribution device, and the fourth end of the air return four-way valve is connected to the air outlet end of the compressor, so that when the outdoor environment temperature is smaller than or equal to the first preset temperature, the pressure difference between the outdoor machine and the plurality of indoor machines is established through the heat exchange between the first heat exchange flow path of the air return heat exchanger and the second heat exchange flow path, the outdoor machine can be smoothly sent to the indoor side, the refrigerant can not be easily cooled down, and the indoor side can not be cooled down, and the refrigerating system can not be cooled down and can be cooled down and the refrigerating system can be cooled down and heated.
As shown in fig. 5, when the multi-split system 1 is operated in the pure heating mode, each of the refrigeration control valves (e.g., SVA1 and SVA 2) is in a closed state, each of the heating control valves (e.g., SVB1 and SVB 2) is in an open state, the third throttle valve EXV3 is in a closed state, and the first heat exchanger 121 and the second heat exchanger 122 are evaporators. The high-temperature and high-pressure gaseous refrigerant discharged from the discharge end a11 of the compressor 11 enters the third refrigerant inlet and outlet end a303 through the air return four-way valve 42, is condensed into a high-temperature and high-pressure liquid refrigerant through each heating control valve (such as SVB1 and SVB 2) to each indoor unit, is collected into the first refrigerant inlet and outlet end a301, is throttled by the first throttle valve EXV1 and the second throttle valve EXV2, is changed into a low-temperature and low-pressure gas-liquid two-phase refrigerant, is evaporated by the first heat exchanger 121 and the second heat exchanger 122, and is changed into a low-temperature and overheated gaseous refrigerant to return to the compressor 11.
Specifically, when each indoor unit in the multi-split air conditioner system 1 heats and operates, each refrigeration control valve (such as SVA1 and SVA 2) is in a closed state, each heating control valve (such as SVB1 and SVB 2) is in an open state, the third throttle valve EXV3 is in a closed state, the first heat exchanger 121 and the second heat exchanger 122 are both evaporators, the first indoor heat exchanger 21 and the second indoor heat exchanger 23 are both condensers, and the air return heat exchanger 41 does not operate, i.e. the multi-split air conditioner system 1 operates in a pure heating mode. Wherein the refrigerant passing through the first throttle valve EXV1, the second throttle valve EXV2 and the third throttle valve EXV3 depends on their corresponding opening degrees.
When the multi-split air conditioner system 1 operates in a pure heating mode, the first four-way valve ST1, the second four-way valve ST2 and the return air four-way valve 42 are all in a power-on state, the first port a1 and the second port b1 of the first four-way valve ST1 are communicated, the first port a2 and the second port b2 of the second four-way valve ST2 are communicated, and the third port c42 and the fourth port d42 of the return air four-way valve 42 are communicated. The discharge end a11 of the compressor 11 may be directly communicated with the first indoor heat exchanger 21 and the second indoor heat exchanger 23 through the return air four-way valve 42.
Specifically, when the multi-split system 1 is operated in the pure heating mode, the high-temperature and high-pressure gaseous refrigerant discharged from the discharge end a11 of the compressor 11 may be split into two paths.
The first path enters the first indoor heat exchanger 21 through the air return four-way valve 42 and the heating control valve SVB1, is condensed and released into a high-temperature high-pressure liquid refrigerant through the first indoor heat exchanger 21, and then enters the first refrigerant inlet and outlet end a301 after being throttled by the first indoor throttle valve 22.
The second path flows to the second indoor throttle valve 24 through the air return four-way valve 42 and the heating control valve SVB2, is condensed and released into a high-temperature high-pressure liquid refrigerant through the second indoor heat exchanger 23, and then enters the first refrigerant inlet and outlet end a301 after being throttled by the second indoor throttle valve 24.
It can be seen that the above two refrigerants enter the high pressure liquid pipe together and are collected to the first refrigerant inlet/outlet end a301. Then the refrigerant is throttled by a first throttle valve EXV1 and a second throttle valve EXV2 respectively and then becomes a low-temperature low-pressure gas-liquid two-phase refrigerant. Finally, the refrigerant is evaporated and absorbed by the first heat exchanger 121 and the second heat exchanger 122 to become low-temperature superheated gaseous refrigerant, and the low-temperature superheated gaseous refrigerant returns to the compressor 11 through the first four-way valve ST1 and the second four-way valve ST 2. Therefore, when the multi-split system operates in a pure heating mode, the heating effect of the multi-split system can be ensured.
It should be noted that, when the multi-split system 1 is in the pure heating mode, the first heat exchanger 121 and the second heat exchanger 122 in the outdoor unit 10 operate as an evaporator for a period of time, and then frosting may occur.
When the multi-split air conditioner system 1 operates in the pure heating mode under the frosting working condition of the first heat exchanger 121 and the second heat exchanger 122, the frosting of the first heat exchanger 121 and the second heat exchanger 122 increases the heat transfer resistance between the surface and the air, and increases the flow resistance, so that the air flow passing through the first heat exchanger 121 and the second heat exchanger 122 is reduced, the heat exchange efficiency is obviously reduced, the heat exchange amount between the outdoor environment and the refrigerant is reduced, and the air outlet temperature is reduced.
Particularly, when the multi-split system 1 is operated in a pure heating mode under some working conditions of low temperature and high humidity, the evaporation effect of the refrigerant in the first heat exchanger 121 and the second heat exchanger 122 is gradually deteriorated due to severe frosting of the first heat exchanger 121 and the second heat exchanger 122, and the operation condition of the multi-split system 1 is deteriorated, so that the liquid return of the multi-split system 1 is caused when severe frosting occurs.
Therefore, when the multi-split system 1 is operated in the pure heating mode, the defrosting mode may be turned on to remove frost formed on the first heat exchanger 121 and the second heat exchanger 122, and the refrigerant flow path in the defrosting mode may be as in the refrigerant flow path in the pure cooling mode of fig. 4. In a specific embodiment of the present invention, when the multi-split system 1 is operated in the defrosting mode, the first heat exchanger 121 and the second heat exchanger 122 may be defrosted at the same time, and the first heat exchanger 121 and the second heat exchanger 122 may be defrosted separately, which is not limited herein.
As shown in fig. 6, when the refrigeration energy requirement of the multi-split air-conditioning system 1 is greater than the heating energy requirement, and the multi-split air-conditioning system operates in the main refrigeration mode, the plurality of indoor units 20 may include a refrigeration indoor unit, such as a second indoor unit, and a heating indoor unit, such as a first indoor unit, where the refrigeration control valves, such as SVA2, corresponding to the refrigeration indoor units are all in an open state, the heating control valves, such as SVB1, corresponding to the heating indoor units are all in an open state, and the third throttle valve EXV3 is in a closed state.
When the multi-split air conditioner system 1 operates in the main refrigeration mode, the first four-way valve ST1 is in a power-on state, the first port a1 and the second port b1 of the first four-way valve ST1 are communicated, the second four-way valve ST2 is in a power-off state, the first port a2 and the fourth port d2 of the second four-way valve ST2 are communicated, the air return four-way valve 42 is in a power-on state, and the third port c42 and the fourth port d42 of the air return four-way valve 42 are communicated.
When the multi-split system 1 is operated in the main cooling mode, the return air heat exchanger 41 does not work, and the first heat exchanger 121 and the second heat exchanger 122 can both be condensers, but if the high pressure of the high pressure liquid pipe of the multi-split system 1 is too low, the amount of refrigerant entering the second indoor unit is small, the first heat exchanger 121 can be switched to an evaporator. When the first heat exchanger 121 is an evaporator and the second heat exchanger 122 is a condenser, the high-temperature and high-pressure gaseous refrigerant discharged from the discharge end a11 of the compressor 11 may be divided into two paths.
One path of the refrigerant is condensed and released through the second heat exchanger 122 to become a first high-temperature high-pressure liquid refrigerant, one part of the first high-temperature high-pressure liquid refrigerant is evaporated and absorbed through the first heat exchanger 121 to return to the compressor 11, and the other part of the first high-temperature high-pressure liquid refrigerant enters the first refrigerant inlet and outlet end a301, so that the area of the evaporator can be increased to increase the flow of the refrigerant passing through the evaporator to absorb heat of the outdoor environment, the low pressure of the refrigerant returned to the compressor by the multi-split air conditioner can be improved, and the high pressure of the refrigerant discharged from the compressor by the multi-split air conditioner can be improved.
The other path of the refrigerant enters a third refrigerant inlet and outlet end a303 through a return air four-way valve 42, enters a heating indoor unit such as a first indoor unit through a heating control valve SVB1 to perform condensation and heat release so as to be changed into a second high-temperature high-pressure liquid refrigerant, and enters a refrigerating indoor unit such as a second indoor unit to perform evaporation and heat absorption after the second high-temperature high-pressure liquid refrigerant is converged at the first refrigerant inlet and outlet end a301 and the other part of the first high-temperature high-pressure liquid refrigerant, enters a second refrigerant inlet and outlet end a302 through a refrigerating control valve SVA2 and returns to the compressor 11 through a second heat exchange flow path.
Therefore, when the multi-split system operates in the main refrigeration mode, the heat absorbed from the heating indoor unit can be used in the refrigerating indoor unit to complete the heat recovery function of the multi-split system and ensure the heating effect of the multi-split system.
As shown in fig. 7, when the heating energy requirement of the multi-split air conditioning system 1 is greater than the cooling energy requirement and the multi-split air conditioning system operates in the main heating mode, the plurality of indoor units 20 may include a cooling indoor unit, such as a second indoor unit, and a heating indoor unit, such as a first indoor unit, where the cooling control valves, such as SVA2, corresponding to the second indoor unit, are all in an open state, the heating control valves, such as SVB1, corresponding to the first indoor unit, and the third throttle valve EXV3 is in a closed state.
When the multi-split air conditioner system 1 operates in the main heating mode, the first four-way valve ST1, the second four-way valve ST2 and the return air four-way valve 42 are all in the power-on state, the first port a1 and the second port b1 of the first four-way valve ST1 are communicated, the first port a2 and the second port b2 of the second four-way valve ST2 are communicated, and the third port c42 and the fourth port d42 of the return air four-way valve 42 are communicated.
When the multi-split system 1 is operated in the main heating mode, both the first heat exchanger 121 and the second heat exchanger 122 may be evaporators, and the return air heat exchanger 41 does not operate. The high-temperature and high-pressure gaseous refrigerant discharged from the discharge end a11 of the compressor 11 enters the third refrigerant inlet and outlet end a303 through the return air four-way valve 42, and is condensed and released to the heating indoor unit such as the first indoor unit through the heating control valve SVB1 to be changed into a high-temperature and high-pressure liquid refrigerant, and the high-temperature and high-pressure liquid refrigerant is collected to the first refrigerant inlet and outlet end a301 and is divided into two paths.
One path of the refrigerant is evaporated and absorbed by a refrigerating indoor unit such as a second indoor unit to be changed into a medium-temperature low-pressure gaseous refrigerant, and then the medium-temperature low-pressure gaseous refrigerant is collected to a second refrigerant inlet and outlet end a302 through a refrigerating control valve SVA2, and finally the medium-temperature low-pressure gaseous refrigerant is returned to the compressor 11 after heat exchange is carried out through a second heat exchange flow path.
The other path is throttled by a first throttle valve EXV1 and a second throttle valve EXV2 respectively and then becomes a low-temperature low-pressure gas-liquid two-phase refrigerant, and then is evaporated and absorbed by a first heat exchanger 121 and a second heat exchanger 122 and then becomes a low-temperature overheated gaseous refrigerant to return to the compressor 11.
Therefore, when the multi-split system operates in the main heating mode, the cold quantity absorbed from the heating indoor unit can be used in the refrigerating indoor unit to complete the heat recovery function of the multi-split system, and the redundant high-temperature high-pressure liquid refrigerant can be throttled into the first heat exchanger and the second heat exchanger through the first throttle valve and the second throttle valve to be evaporated and absorbed, and then is changed into the low-temperature overheated gaseous refrigerant to return to the compressor.
Based on the embodiment, the invention further provides a control method of the multi-split system.
Fig. 8 is a flowchart of a control method of the multi-split system according to an embodiment of the present invention.
In an embodiment of the present invention, the outdoor heat exchanger may include a first heat exchanger and a second heat exchanger, a first end of the first heat exchanger is connected to the exhaust end of the compressor through a first four-way valve, a second end of the first heat exchanger is provided with a first throttle valve, a first end of the second heat exchanger is connected to the exhaust end of the compressor through a second four-way valve, a second end of the second heat exchanger is provided with a second throttle valve, a second end of the first heat exchange flow path of the return air heat exchanger is provided with a third throttle valve, and a first end of the second heat exchange flow path of the return air heat exchanger is further connected to the first four-way valve and the second four-way valve, respectively, wherein when the outdoor ambient temperature is greater than a first preset temperature, the first throttle valve and the second throttle valve are controlled to maintain a fully opened state, and the third throttle valve is controlled to be in a closed state. The foregoing is specific and will not be described in detail herein.
As shown in fig. 8, the control method of the multi-split system according to the embodiment of the present invention may include the following steps:
s1, acquiring outdoor environment temperature.
Specifically, the outdoor ambient temperature may be detected by a temperature sensor provided at the outdoor side and transmitted to the control part of the multi-split system.
S2, judging whether the outdoor environment temperature is less than or equal to a first preset temperature t1 when the multi-split air conditioner system is in refrigeration operation.
Specifically, the first preset temperature t1 may be set according to an actual situation, and the set first preset temperature t1 is pre-stored in the control part of the multi-split system 1 in advance, so that the control part determines a relationship between the outdoor environment temperature and the first preset temperature t1. For example, the first preset temperature t1 may be set to-5 ℃.
S3, if the outdoor environment temperature is less than or equal to a first preset temperature t1, the pressure difference between the outdoor unit and the plurality of indoor units is established through heat exchange between the first heat exchange flow path and the second heat exchange flow path of the return air heat exchanger, so that the multi-split air conditioner system performs low-temperature refrigeration.
According to one embodiment of the present invention, when the outdoor ambient temperature is less than or equal to a first preset temperature t1, the opening of the first throttle valve, the opening of the second throttle valve and the opening of the third throttle valve are controlled according to the outdoor ambient temperature, respectively, wherein the opening of the first throttle valve and the opening of the second throttle valve are in positive correlation with the outdoor ambient temperature, and the opening of the third throttle valve is in inverse correlation with the outdoor ambient temperature.
It should be noted that, for details not disclosed in the control method of the multi-split system according to the embodiment of the present invention, please refer to details disclosed in the multi-split system according to the embodiment of the present invention, and details thereof will not be described in detail herein.
According to the control method of the multi-split system, heat exchange between the first heat exchange flow path and the second heat exchange flow path of the air return heat exchanger can be achieved through the multi-split system comprising the air return heat exchange device, so that when the multi-split system is in refrigeration operation, whether the outdoor environment temperature is smaller than or equal to the first preset temperature is judged, and when the outdoor environment temperature is smaller than or equal to the first preset temperature, the pressure difference between the outdoor unit and the plurality of indoor units is established through heat exchange between the first heat exchange flow path and the second heat exchange flow path of the air return heat exchanger, so that refrigerant outside the indoor units can be smoothly delivered to the indoor sides, low-temperature refrigeration of the multi-split system can be achieved when the outdoor environment temperature is lower, and the heat recovery function and the heating and refrigerating effects of the multi-split system are not affected.
In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc. indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings are merely for convenience in describing the present invention and simplifying the description, and do not indicate or imply that the device or element being referred to must have a specific orientation, be configured and operated in a specific orientation, and therefore should not be construed as limiting the present invention.
Furthermore, the terms "first," "second," and the like, are used for descriptive purposes only and are not to be construed as indicating or implying a relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defining "a first" or "a second" may explicitly or implicitly include at least one such feature. In the description of the present invention, the meaning of "plurality" means at least two, for example, two, three, etc., unless specifically defined otherwise.
In the present invention, unless explicitly specified and limited otherwise, the terms "mounted," "connected," "secured," and the like are to be construed broadly, and may be, for example, fixedly connected, detachably connected, or integrally formed; can be mechanically or electrically connected; either directly or indirectly, through intermediaries, or both, may be in communication with each other or in interaction with each other, unless expressly defined otherwise. The specific meaning of the above terms in the present invention can be understood by those of ordinary skill in the art according to the specific circumstances.
In the present invention, unless expressly stated or limited otherwise, a first feature "up" or "down" a second feature may be the first and second features in direct contact, or the first and second features in indirect contact via an intervening medium. Moreover, a first feature being "above," "over" and "on" a second feature may be a first feature being directly above or obliquely above the second feature, or simply indicating that the first feature is level higher than the second feature. The first feature being "under", "below" and "beneath" the second feature may be the first feature being directly under or obliquely below the second feature, or simply indicating that the first feature is less level than the second feature.
In the description of the present specification, a description referring to terms "one embodiment," "some embodiments," "examples," "specific examples," or "some examples," etc., means that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the present invention. In this specification, schematic representations of the above terms are not necessarily directed to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples. Furthermore, the different embodiments or examples described in this specification and the features of the different embodiments or examples may be combined and combined by those skilled in the art without contradiction.
While embodiments of the present invention have been shown and described above, it will be understood that the above embodiments are illustrative and not to be construed as limiting the invention, and that variations, modifications, alternatives and variations may be made to the above embodiments by one of ordinary skill in the art within the scope of the invention.

Claims (11)

1. A multi-split air conditioner system is characterized by comprising an outdoor unit, a plurality of indoor units, a refrigerant distribution device and a return air heat exchange device, wherein,
The outdoor unit comprises a compressor and an outdoor heat exchanger, wherein the exhaust end of the compressor is connected to one end of the outdoor heat exchanger, and the other end of the outdoor heat exchanger is connected with a first refrigerant inlet and outlet end of the refrigerant distribution device;
the refrigerant distribution device is used for distributing refrigerants entering and exiting the plurality of indoor units;
the air return heat exchange device comprises an air return heat exchanger and an air return four-way valve, wherein the first end of a first heat exchange flow path of the air return heat exchanger is connected to the first end of the air return four-way valve, the second end of the first heat exchange flow path of the air return heat exchanger is connected to the first refrigerant inlet and outlet end of the refrigerant distribution device, the first end of a second heat exchange flow path of the air return heat exchanger is respectively connected to the second end of the air return four-way valve and the air return end of the compressor, the second end of the second heat exchange flow path of the air return heat exchanger is connected to the second refrigerant inlet and outlet end of the refrigerant distribution device, the third end of the air return four-way valve is connected to the third refrigerant inlet and outlet end of the refrigerant distribution device, the fourth end of the air return four-way valve is connected to the air outlet end of the compressor, and the air return heat exchange device is used for establishing a multi-online refrigerating system through heat exchange between the first heat exchange flow path and the second heat exchange flow path of the air return heat exchanger when the outdoor environment temperature is smaller than or equal to a first preset temperature.
2. The multiple on-line system of claim 1, wherein the outdoor heat exchanger includes a first heat exchanger and a second heat exchanger, a first end of the first heat exchanger is connected to an exhaust end of the compressor through a first four-way valve, a second end of the first heat exchanger is connected to the first refrigerant inlet and outlet end through a first throttle valve, a first end of the second heat exchanger is connected to the exhaust end of the compressor through a second four-way valve, a second end of the second heat exchanger is connected to the first refrigerant inlet and outlet end through a second throttle valve, a second end of the first heat exchange flow path of the return air heat exchanger is provided with a third throttle valve, and a first end of the second heat exchange flow path of the return air heat exchanger is also connected to the first four-way valve and the second four-way valve, respectively.
3. The multi-split system of claim 2, wherein when the multi-split system is operated in a pure cooling mode, wherein,
when the outdoor environment temperature is higher than the first preset temperature, the first throttle valve and the second throttle valve are kept in a full-open state, and the third throttle valve is in a closed state;
when the outdoor environment temperature is smaller than or equal to the first preset temperature, the opening of the first throttle valve and the opening of the second throttle valve are in positive correlation with the outdoor environment temperature, and the opening of the third throttle valve is in inverse correlation with the outdoor environment temperature.
4. The multi-split system according to claim 2, wherein the refrigerant distribution device includes a plurality of heating control valves and a plurality of cooling control valves corresponding to the plurality of indoor units, one end of each cooling control valve is connected to the second refrigerant inlet/outlet port, the other end of each cooling control valve is connected to one end of the corresponding indoor unit, one end of each heating control valve is connected to the third refrigerant inlet/outlet port, the other end of each heating control valve is connected to one end of the corresponding indoor unit, and the other end of each indoor unit is connected to the first refrigerant inlet/outlet port.
5. The multi-split system of claim 4, wherein each refrigeration control valve is in an open state, each heating control valve is in a closed state, the third throttle valve is in an open state, the first heat exchanger, the second heat exchanger, and the return air heat exchanger are all condensers when the multi-split system is operated in a pure refrigeration mode,
the high-temperature high-pressure gaseous refrigerant discharged from the exhaust end of the compressor is condensed and throttled through the first heat exchanger, the second heat exchanger and the first heat exchange flow path respectively and then converged to the first refrigerant inlet and outlet end, is respectively distributed to each indoor unit through the refrigerant distribution device, is changed into medium-temperature low-pressure gaseous refrigerant after being evaporated and absorbed by each indoor unit, is converged to the second refrigerant inlet and outlet end through each refrigeration control valve, and is returned to the compressor after being subjected to heat exchange through the second heat exchange flow path.
6. The multi-split system of claim 4, wherein each of the refrigeration control valves is in a closed state, each of the heating control valves is in an open state, the third throttle valve is in a closed state, and the first heat exchanger and the second heat exchanger are evaporators when the multi-split system is operated in a pure heating mode,
the high-temperature high-pressure gaseous refrigerant discharged from the exhaust end of the compressor enters the third refrigerant inlet and outlet end through the air return four-way valve, and is condensed into a high-temperature high-pressure liquid refrigerant after passing through each heating control valve to each indoor unit, the high-temperature high-pressure liquid refrigerant is converged into the first refrigerant inlet and outlet end, is throttled into a low-temperature low-pressure gas-liquid two-phase refrigerant through the first throttle valve and the second throttle valve respectively, and is evaporated into a low-temperature overheated gaseous refrigerant after passing through the first heat exchanger and the second heat exchanger to return to the compressor.
7. The multi-split system according to claim 4, wherein when the multi-split system is operated in a main cooling mode, the plurality of indoor units comprise a cooling indoor unit and a heating indoor unit, the cooling control valves corresponding to the cooling indoor units are all in an open state, the heating control valves corresponding to the heating indoor units are all in an open state, the third throttle valve is in a closed state, if the first heat exchanger is an evaporator and the second heat exchanger is a condenser, wherein the high-temperature and high-pressure gaseous refrigerant discharged from the exhaust end of the compressor is divided into two paths,
One path of the refrigerant is condensed into a first high-temperature high-pressure liquid refrigerant through the second heat exchanger, one part of the first high-temperature high-pressure liquid refrigerant is evaporated through the first heat exchanger and then returns to the compressor, and the other part of the first high-temperature high-pressure liquid refrigerant enters the first refrigerant inlet and outlet end;
the other path of the liquid refrigerant enters the third refrigerant inlet and outlet end through the air return four-way valve, enters the heating indoor unit through the heating control valve for condensation to become a second high-temperature high-pressure liquid refrigerant, and the second high-temperature high-pressure liquid refrigerant enters the refrigerating indoor unit for evaporation after being converged at the first refrigerant inlet and outlet end and the other part of the first high-temperature high-pressure liquid refrigerant, then enters the second refrigerant inlet and outlet end through the refrigerating control valve, and returns to the compressor through the second heat exchange flow path.
8. The multi-split system according to claim 4, wherein when the multi-split system is operated in a main heating mode, the plurality of indoor units include a cooling indoor unit and a heating indoor unit, the cooling control valves corresponding to the cooling indoor units are all in an open state, the heating control valves corresponding to the heating indoor units are all in an open state, the third throttle valve is in a closed state, the first heat exchanger and the second heat exchanger are both evaporators,
The high-temperature high-pressure gaseous refrigerant discharged from the exhaust end of the compressor enters the third refrigerant inlet and outlet end through the air return four-way valve, is condensed into a high-temperature high-pressure liquid refrigerant through the heating control valve to the heating indoor unit, is divided into two paths after being collected into the first refrigerant inlet and outlet end, one path is evaporated and absorbed by the cooling indoor unit to become a medium-temperature low-pressure gaseous refrigerant, is collected into the second refrigerant inlet and outlet end through the cooling control valve, is finally subjected to heat exchange through the second heat exchange flow path and is returned to the compressor, and the other path is respectively throttled through the first throttle valve and the second throttle valve and becomes a low-temperature low-pressure gas-liquid two-phase refrigerant, and is evaporated through the first heat exchanger and the second heat exchanger and then becomes a low-temperature overheated gaseous refrigerant to return to the compressor.
9. A control method of the multi-split system as claimed in any one of claims 1 to 8, comprising the steps of:
acquiring outdoor environment temperature;
when the multi-split air conditioner system is in refrigeration operation, judging whether the outdoor environment temperature is less than or equal to a first preset temperature;
if the outdoor environment temperature is less than or equal to a first preset temperature, the pressure difference between the outdoor unit and the plurality of indoor units is established through heat exchange between the first heat exchange flow path and the second heat exchange flow path of the return air heat exchanger, so that the multi-split air conditioner system performs low-temperature refrigeration.
10. The method for controlling a multiple on-line system according to claim 9, wherein the outdoor heat exchanger comprises a first heat exchanger and a second heat exchanger, a first end of the first heat exchanger is connected to an exhaust end of the compressor through a first four-way valve, a second end of the first heat exchanger is provided with a first throttle valve, a first end of the second heat exchanger is connected to the exhaust end of the compressor through a second four-way valve, a second end of the second heat exchanger is provided with a second throttle valve, a second end of a first heat exchanging flow path of the return air heat exchanger is provided with a third throttle valve, and a first end of a second heat exchanging flow path of the return air heat exchanger is further connected to the first four-way valve and the second four-way valve, respectively,
when the outdoor environment temperature is higher than the first preset temperature, the first throttle valve and the second throttle valve are controlled to be kept in a full-open state, and the third throttle valve is controlled to be in a closed state.
11. The method for controlling a multi-split system according to claim 10, wherein when the outdoor ambient temperature is less than or equal to the first preset temperature, the opening degree of the first throttle valve, the opening degree of the second throttle valve, and the opening degree of the third throttle valve are controlled according to the outdoor ambient temperature, respectively, wherein the opening degree of the first throttle valve and the opening degree of the second throttle valve are in positive correlation with the outdoor ambient temperature, and the opening degree of the third throttle valve is in inverse correlation with the outdoor ambient temperature.
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