CN221076807U

CN221076807U - Refrigerating system

Info

Publication number: CN221076807U
Application number: CN202322637800.1U
Authority: CN
Inventors: 李庆辉; 王振; 杨伟茂; 侯志辉; 黄曙良; 薛浩; 王江南
Original assignee: Qingdao Hisense Hitachi Air Conditioning System Co Ltd
Current assignee: Qingdao Hisense Hitachi Air Conditioning System Co Ltd
Priority date: 2023-09-27
Filing date: 2023-09-27
Publication date: 2024-06-04
Anticipated expiration: 2033-09-27

Abstract

The refrigeration system comprises an outdoor unit, a first compressor and a second compressor; the device comprises a switching valve, a distributor, a first gas-liquid separator, a second gas-liquid separator, a distributing pipe, a first detection branch, a second detection branch and a control part, wherein the switching valve is respectively communicated with the first compressor and the second compressor, the distributor is communicated with the switching valve, the first gas-liquid separator and the second gas-liquid separator, the distributing pipe is provided with a regulating valve, and the first detection branch and the second detection branch are respectively communicated with the first compressor and the second compressor. The first detection branch is communicated with the first delivery pipe through a first auxiliary oil return hole, and is provided with a first pressure reducing element; the second detection branch is communicated with a second delivery pipe through a second auxiliary oil return hole, and is provided with the same second decompression element; the first auxiliary oil return hole and the second auxiliary oil return hole are the same in height; the utility model can avoid uneven oil return and liquid return.

Description

Refrigerating system

Technical Field

The utility model relates to the technical field of air conditioning, in particular to a refrigerating system.

Background

Modern residential and industrial settings require control of air parameters of indoor spaces including, but not limited to, heating, cooling, ventilation, and the like. An air conditioning system (HVAC) supplies energy through a low-temperature heat source or a high-temperature heat source so that heat-exchanged air circulates in an indoor space or introduces outdoor air to thereby adjust an ambient air parameter of an indoor space.

Modern air conditioning systems no longer limit the number of outdoor units and indoor units, for example, multiple on-line systems allow one outdoor unit to be used in match with multiple indoor units; the modular central air conditioner allows the outdoor units to be combined in a modular manner. The capacity of the current module can reach 40HP, and the combined capacity of the modules can reach 168HP. Since the multi-split air conditioning system or the modularized air conditioning system is generally required to be installed at the top of a building, a huge height drop (the drop can reach 110 meters) exists between the outdoor unit and the indoor unit in an installed state, and the length of a pipe between the outdoor unit and the indoor unit is very long (the total length of the pipe reaches 1200 meters). The huge height drop and the length of the piping need more refrigerant quantity, and compared with the traditional split type air conditioner, the refrigerant quantity of the system is improved in reply, and the current filling quantity reaches hundreds of kilograms. At the indoor end, the capacity difference of the indoor units is huge, the span can reach 15kW to 560kW, and the proportioning range of the indoor units and the outdoor units can reach 30% to 200%.

The hardware design of modern air conditioning systems has made conventional vessel components (e.g., gas-liquid separators) in refrigeration cycles, typically small pressure vessels of less than 30L, unsatisfactory for design use even in a single module.

Disclosure of Invention

When the double compressors or the multiple compressors are matched with the parallel gas-liquid separators for use, the mixture of the lubricating oil and the liquid refrigerant is in an uneven distribution state in each gas-liquid separator due to the design of the distributor and the different load of each compressor, so that the problems of poor oil return of the compressors and reduced system performance are further caused by different oil return and gas return of each compressor.

A first aspect of the present application provides a refrigeration system comprising: an outdoor unit including a plurality of outdoor units,

The outdoor unit includes:

A first compressor;

a second compressor;

a switching valve which communicates the first compressor and the second compressor, respectively;

a distributor communicating with the switching valve;

A first gas-liquid separator communicated with one outlet of the distributor, wherein a first delivery pipe communicated with the first compressor is arranged;

a second gas-liquid separator in communication with the other outlet of the distributor, wherein a second delivery line in communication with the second compressor is provided; and

The two ends of the distributing pipe are respectively communicated with the first gas-liquid separator and the second gas-liquid separator;

a regulating valve disposed on the distribution pipe;

The first detection branch is communicated with the first delivery pipe through a first auxiliary oil return hole, the first auxiliary oil return hole is higher than the bottom of the first delivery pipe, and the first detection branch is provided with a first pressure reducing element;

the second detection branch is communicated with the second delivery pipe through a second auxiliary oil return hole, the second auxiliary oil return hole is higher than the bottom of the second delivery pipe, and the second detection branch is provided with a second pressure reducing element, wherein the heights of the first auxiliary oil return hole and the second auxiliary oil return hole are the same, and the first pressure reducing element and the second pressure reducing element are the same.

In some embodiments of the application, the first gas-liquid separator has a first housing. The upper part of the first shell is provided with a first ingress pipe which is inserted into the first shell and the inlet is positioned at the upper part of the first shell; the first shell is also provided with a first delivery pipe, the first delivery pipe is close to the bottom of the first shell and is bent, and an outlet of the first delivery pipe extends outwards from the upper part of the first shell; the first delivery tube is in fluid communication with the first compressor.

In some embodiments of the application, the second gas-liquid separator has a second housing; the upper portion of the second housing is provided with a second introduction pipe into which the inlet is inserted and which is located at the upper portion of the second housing. The second shell is also provided with a second delivery pipe, the second delivery pipe is close to the bottom of the second shell and is bent, and an outlet of the second delivery pipe extends outwards from the upper part of the second shell; the second delivery tube is in fluid communication with the second compressor.

In some embodiments of the application, the first detection branch is further in fluid communication with the first compressor, further comprising:

A first inlet temperature sensor disposed at an inlet side of the first detection branch and close to the first auxiliary oil return hole;

A first outlet temperature sensor disposed on an outlet side of the first detection branch and proximate to the first compressor;

The first inlet temperature sensor, the first pressure reducing element and the first outlet temperature sensor are arranged in sequence along the flow direction of the refrigerant.

In some embodiments of the application, the second detection branch is further in fluid communication with the second compressor, further comprising:

A second inlet temperature sensor disposed at an inlet side of the second detection branch and close to the second auxiliary oil return hole;

A second outlet temperature sensor disposed on an outlet side of the second detection branch and proximate to the second compressor;

The second inlet temperature sensor, the second pressure reducing element and the second outlet temperature sensor are arranged in sequence along the flow direction of the refrigerant.

In some embodiments of the application, the regulating valve is configured to switch the distribution pipe on when the first and second gas-liquid separators are in a non-uniform liquid level state and the liquid level of the second gas-liquid separator is higher than the second auxiliary oil return hole, so as to transition the first and second gas-liquid separators from the non-uniform liquid level state to a uniform liquid level state.

In some embodiments of the application, the regulator valve is configured to: when the first gas-liquid separator and the second gas-liquid separator are in a non-uniform liquid level state, and the liquid level of the first gas-liquid separator is higher than that of the first auxiliary oil return hole, the regulating valve acts to conduct the distributing pipe so as to enable the first gas-liquid separator and the second gas-liquid separator to transition from the non-uniform liquid level state to the uniform liquid level state.

In some embodiments of the present application, the upper sides of the first and second housings are in communication via a gas communication tube, and the lower sides of the first and second housings are in communication via a liquid communication tube.

In some embodiments of the application, the tube diameter of the distribution tube is greater than the tube diameters of the gas communication tube and the liquid communication tube.

In some embodiments of the application, the regulating valve is an electronic expansion valve or a solenoid valve.

In some embodiments of the application, the first pressure relief element is a first oil return detection capillary and the second pressure relief element is a second oil return detection capillary.

In some embodiments of the present application, the first auxiliary oil gallery and the second auxiliary oil gallery are of equal height.

In some embodiments of the present application, the bottom positions of the first and second delivery pipes are further provided with first and second main oil return holes.

Through the design of the utility model, when the two gas-liquid separators are in a non-uniform liquid level state, the first pressure reducing element, the second pressure reducing element and the regulating valve are accurately regulated, so that the problems of uneven air return and liquid return caused by a set of switching valve and a distributor are effectively avoided, and the service life and the operation stability of the compressor are improved.

Other features and advantages of the present utility model will become apparent upon review of the detailed description of the utility model in conjunction with the drawings.

Drawings

In order to more clearly illustrate the embodiments of the present utility model or the technical solutions of the prior art, the drawings that are needed in the embodiments or the description of the prior art will be briefly described below, it will be obvious that the drawings in the following description are some embodiments of the present utility model, and that other drawings can be obtained according to these drawings without inventive effort to a person skilled in the art.

FIG. 1 is a schematic block diagram of a refrigeration system according to one or more embodiments of the present disclosure;

FIG. 2 is a schematic diagram of a refrigeration cycle in a refrigeration system according to one or more embodiments of the present disclosure;

Fig. 3 is a schematic view illustrating a structure of an outdoor unit refrigeration cycle in a refrigeration system according to one or more embodiments of the present application;

fig. 4 is a schematic view illustrating a structure of an outdoor unit refrigeration cycle in a refrigeration system according to one or more embodiments of the present application;

Fig. 5 is a schematic view illustrating a structure of an outdoor unit refrigeration cycle in a refrigeration system according to one or more embodiments of the present application;

FIG. 6 is an enlarged partial schematic view of portion A of FIG. 3;

Fig. 7 is a schematic view illustrating a structure of an outdoor unit refrigeration cycle in a refrigeration system according to one or more embodiments of the present application;

Fig. 8 is a schematic view illustrating an outdoor unit in a refrigeration system according to one or more embodiments of the present application;

FIG. 9 is a flow diagram of a control portion of a refrigeration system according to one or more embodiments of the present disclosure;

FIG. 10 is a flow diagram of a control portion of a refrigeration system according to one or more embodiments of the present disclosure;

Fig. 11 is a schematic view illustrating a structure of an outdoor unit refrigeration cycle in a refrigeration system according to one or more embodiments of the present application;

fig. 12 is a schematic view illustrating a structure of an outdoor unit refrigeration cycle in a refrigeration system according to one or more embodiments of the present application;

FIG. 13 is a flow diagram of a control portion of a refrigeration system according to one or more embodiments of the present disclosure;

FIG. 14 is a flow diagram of a control portion of a refrigeration system according to one or more embodiments of the present disclosure;

FIG. 15 is a graphical representation of a third set threshold versus outdoor ambient temperature for a refrigeration system according to one or more embodiments of the present application;

FIG. 16 is an exemplary graph of a first fitted curve in a refrigeration system provided in accordance with one or more embodiments of the present application;

FIG. 17 is an exemplary graph of a second fitted curve in a refrigeration system provided by one or more embodiments of the present application;

Detailed Description

The following description of the embodiments of the present application will be made clearly and completely with reference to the accompanying drawings, in which it is apparent that the embodiments described are only some embodiments of the present application, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the application without making any inventive effort, are intended to be within the scope of the application.

Fig. 1 shows a schematic diagram of a refrigeration system 1 provided by one or more embodiments of the present utility model; fig. 2 shows an example of a refrigerant circuit formed by the refrigeration system 1 according to the embodiment of the present utility model.

The refrigeration system 1 is installed in a building such as an apartment, hotel, office building, and residence. The refrigeration system 1 is configured to selectively perform a heating operation or a cooling operation.

The refrigeration system 1 has a refrigeration cycle integrated therein. A compressor, a condenser, a throttle 104, and an evaporator are used in the refrigeration cycle. The refrigeration cycle includes a series of processes involving compression, condensation, expansion, and evaporation, and refrigerating or heating an indoor space.

From the principle point of view, the low-temperature low-pressure refrigerant enters the compressor, the compressor compresses the refrigerant gas into a high-temperature high-pressure state, and the compressed refrigerant gas is discharged. The discharged refrigerant gas flows into the condenser. The condenser condenses the compressed refrigerant into a liquid phase, and heat is released to the surrounding environment through the condensation process.

The expansion device 104 expands the liquid-phase refrigerant in a high-temperature and high-pressure state formed by condensation in the condenser into a low-pressure liquid-phase refrigerant. The evaporator evaporates the refrigerant expanded in the throttle 104 and returns the refrigerant gas in a low temperature and low pressure state to the compressor. The evaporator may achieve a cooling effect by exchanging heat with a material to be cooled using latent heat of evaporation of a refrigerant. Throughout the cycle, the refrigeration system 1 may regulate the temperature of the indoor space.

The refrigeration system 1 includes an outdoor unit and an indoor unit connected to each other. Fig. 1 shows a combination of two outdoor units (10, 12) and three indoor units (20, 22, 24), and fig. 2 shows a combination of two outdoor units (10, 12) and five indoor units (20, 22, 24, 26, 28). In the present application, the number of the outdoor units and the indoor units is not particularly limited. Only one indoor unit and one outdoor unit, or a plurality of indoor units and a plurality of outdoor units, may be arranged in one set of the refrigeration system 1 according to the same manner as the indoor units and the outdoor units shown in fig. 1 and 2.

An indoor heat exchanger (shown as 200 in fig. 2) and an indoor throttle device (e.g., an indoor electronic expansion valve, shown as 201 in fig. 2) are provided in the indoor unit.

The indoor unit and the outdoor unit are connected by a liquid-side communication pipe 31 and a gas-side communication pipe 32. The liquid-side communication pipe 31 and the gas-side communication pipe 32 serve to flow the refrigerant so that the refrigerant can form a refrigerant circuit and circulate therein.

In one or more embodiments of the present application, the liquid-side communication pipe 31 is provided with a liquid-side shutoff valve 105, and the gas-side communication pipe 32 is provided with a gas-side shutoff valve 106. The liquid-side shutoff valve 105 may shut off the fluid passage in the liquid-side communication pipe 31 or close to shutting off the fluid passage in the liquid-side communication pipe 31 at the minimum opening, and the gas-side shutoff valve 106 may shut off the fluid passage in the gas-side communication pipe 32 or close to shutting off the fluid passage in the gas-side communication pipe 32 at the minimum opening.

The basic structure and function of the outdoor unit are exemplarily described below. The number of the outdoor units may be extended to a plurality, and each of the outdoor units constitutes one module and operates in a group manner.

Fig. 3 is a schematic view of the structure of an outdoor unit; fig. 4 is a schematic view of a refrigerating cycle when the outdoor unit performs a refrigerating operation; a figure; fig. 5 is a schematic view of a refrigerating cycle when the outdoor unit performs a heating operation; fig. 6 is an enlarged view of a portion a in fig. 3.

In one or more embodiments of the present application, the outdoor unit of the refrigeration system 1 refers to a portion of the refrigeration cycle including the compressor and the outdoor heat exchanger 103, and the outdoor unit may perform a heating operation or a cooling operation on the outdoor side to supply energy for increasing the indoor temperature or energy for decreasing the indoor temperature to the indoor unit. As shown in fig. 3 to 6, the outdoor unit is provided therein with a first compressor 100a and a second compressor 100b; a greater number of compressors may be provided in the outdoor unit according to the same manner as the first and second compressors 100a and 100b shown in fig. 3 to 6. The first compressor 100a and the second compressor 100b are configured to suck and compress a refrigerant into a high temperature and high pressure state, and the types of the first compressor 100a and the second compressor 100b are not further limited herein and may be, for example, a reciprocating compressor, a screw compressor, and the like. The rotation speeds of the first compressor 100a and the second compressor 100b are controlled by the inverter, and the first compressor 100a and the second compressor 100b can be independently operated. The discharge end of the first compressor 100a is provided with a first high-voltage switch 111a, and the discharge end of the second compressor 100b is provided with a second high-voltage switch 111b. The discharge ends of the first and second compressors 100a and 100b are further provided with a high pressure sensor 110, and the suction ends of the first and second compressors 100a and 100b are further provided with a low pressure sensor 151.

The discharge end of the first compressor 100a is provided with a first compressor discharge temperature sensor 112a and the discharge end of the second compressor 100b is provided with a second compressor discharge temperature sensor 112b.

The suction side of the first compressor 100a is provided with a first gas-liquid separator 108a. The first gas-liquid separator 108a gas-liquid separates the evaporated refrigerant and guides the separated gaseous refrigerant into the first compressor 100a. The suction side of the second compressor 100b is provided with a second gas-liquid separator 108b. The second gas-liquid separator 108b gas-liquid separates the evaporated refrigerant and guides the separated gaseous refrigerant into the second compressor 100b.

An outdoor fan (not shown) and a switching valve 102 may be further provided in the outdoor unit; wherein the outdoor fan may be an axial flow fan, a cross flow fan or other alternative fan forms. The outdoor fan is disposed near the outdoor heat exchanger 103. The outdoor heat exchanger 103 may also exchange heat with other types of heat sources, such as water or the like.

The outdoor unit is further provided with a first oil separator 101a and a second oil separator 101b. The first oil separator 101a is used to separate the lubricant oil from the high temperature refrigerant vapor as the mixture of lubricant oil and refrigerant exits the compressor. The second oil separator 101b is used to separate the lubricant oil from the high temperature refrigerant vapor as the mixture of lubricant oil and refrigerant exits the compressor. The first oil separator 101a is disposed in a pipe line between the first compressor 100a and the condenser. The flow velocity of the high-pressure refrigerant in the first oil separator 101a and the second oil separator 101b decreases, so that the lubricating oil is captured in the first oil separator 101a and the second oil separator 101b. The lubricating oil having a relatively high density is separated from the refrigerant vapor and falls to the bottoms of the first oil separator 101a and the second oil separator 101b. The lubricating oil collected in the first oil separator 101a and the second oil separator 101b is returned to the first compressor 100a and the second compressor 100b through the first capillary tube 150a and the second capillary tube 150b, respectively. The tube diameters and lengths of the first and second capillaries 150a and 150b may be used to adjust the oil return amount of the lubricating oil. A solenoid valve 109 is further provided downstream of the first oil separator 101a and the second oil separator 101b.

The switching valve 102 is exemplified by a four-way valve. The switching valve 102 is a valve for switching the flow direction of the refrigerant in the refrigerant circuit, and there is one and only one switching valve 102 in one outdoor unit.

In the cooling operation, the outdoor unit may form a refrigerant circuit (hereinafter referred to as a refrigeration cycle) for the cooling operation, in which a switching valve 102 (e.g., a one-way passage of a four-way valve, illustratively, a fluid passage between the C port and the S port) and a distributor 107 are sequentially connected from the gas side communication piping 32 to the liquid side communication piping 31. The dispenser 107 (inlet shown as 107 c) is in fluid communication with the switching valve 102. Downstream of the distributor 107, that is, one outlet of the distributor 107 is sequentially connected with the first gas-liquid separator 108a and the first compressor 100a, and the other outlet of the distributor 107 is sequentially connected with the second gas-liquid separator 108b and the second compressor 100b; after the mixture of the refrigerant and the lubricating oil flowing out of the first compressor 100a enters the first oil separator 101a, and from the first oil separator 101a, the refrigerant is again introduced into the switching valve 102 (e.g., the other passage of the four-way valve, illustratively the fluid passage between the D port and the E port); the mixture of the refrigerant and the lubricating oil after exiting the second compressor 100b enters the second oil separator 101b, and after passing from the second oil separator 101b, the refrigerant is again introduced into the switching valve 102 (e.g., the other passage of the four-way valve, illustratively the fluid passage between the D and E ports); the refrigerant flowing out of the switching valve 102 enters the outdoor heat exchanger 103 again.

In the heating operation, the outdoor unit may form a refrigerant circuit (hereinafter referred to as a heating cycle) for the heating operation, in which the outdoor heat exchanger 103, the switching valve 102 (e.g., a one-way passage of a four-way valve, illustratively, a fluid passage between the E port and the S port), and the distributor 107 are connected in this order from the liquid side communication piping 31 to the gas side communication piping 32. The dispenser 107 is in fluid communication with the switching valve 102. Downstream of the distributor 107, i.e., one outlet of the distributor 107 is connected in order to the first gas-liquid separator 108a, the first compressor 100a, the first oil separator 101a, and the switching valve 102 (e.g., one path of a four-way valve, illustratively, a fluid path between ports D and C); the other outlet of the distributor 107 is connected in sequence to the second gas-liquid separator 108b, the second compressor 100b, the second oil separator 101b, and the switching valve 102 (e.g., the same path of a four-way valve, illustratively, a fluid path between ports D and C).

The design flow rates of the two outlets of distributor 107 (shown as 107a and 107 b) are the same.

The first gas-liquid separator 108a has a first housing 130a. The upper portion of the first housing 130a is provided with a first introduction pipe 131a inserted therein and having an inlet at the upper portion of the first housing 130a. The first housing 130a is further provided with a first outlet pipe 113a, wherein the first outlet pipe 113a is near the bottom of the first housing 130a and bent into a substantially U-shape, and an outlet of the first outlet pipe 113a extends out from the upper portion of the first housing 130a. The first delivery line 113a is in fluid communication with the first compressor 100a.

The second gas-liquid separator 108b has a second housing 130b. The upper portion of the second housing 130b is provided with a second introduction pipe 131b inserted therein and having an inlet at the upper portion of the second housing 130b. The second housing 130b is further provided with a second outlet pipe 113b, the second outlet pipe 113b is near the bottom of the second housing 130b and bent into a substantially U-shape, and an outlet of the second outlet pipe 113b protrudes outward from the upper portion of the second housing 130b. The second delivery line 113b is in fluid communication with the second compressor 100b.

In the cooling operation or the heating operation, the evaporated refrigerant is distributed by the distributor 107, and enters the first casing 130a and the second casing 130b through the first introduction pipe 131a and the second introduction pipe 131b, respectively, to thereby generate a gas-liquid separation effect. The separated gaseous refrigerant is sucked into the first and second compressors 100a and 100b from the first and second discharge pipes 113a and 113 b; the separated liquid refrigerant is retained at the bottoms of the first and second housings 130a and 130b, gradually evaporated and gasified with the lapse of time, and then sucked by the first and second compressors 100a and 100b. The bottom of the first delivery pipe 113a is provided with a first main oil return hole 114a, the bottom of the second delivery pipe 113b is provided with a second main oil return hole 114b, and lubricating oil gathered at the bottom of the first shell 130a can flow back to the first compressor 100a through the first delivery pipe 113a through the first main oil return hole 114 a; similarly, the lubricating oil collected at the bottom of the second housing 130b through the second main oil gallery 114b may flow back to the second compressor 100b through the second delivery pipe 113 b.

In one or more embodiments of the present application, the shape and volume of the first housing 130a and the second housing 130b are the same. The first gas-liquid separator 108a and the second gas-liquid separator 108b are communicated through a distribution pipe 120, and a regulating valve 121 is provided on the distribution pipe 120. Outside of the distribution tube 120, the upper sides of the first and second housings 130a, 130b may be in communication with the gas communication tube 140, and the lower sides of the first and second housings 130a, 130b may be in communication with the liquid communication tube 150.

In one or more embodiments of the present application, the tube diameter of the distribution tube 120 is substantially larger than the tube diameters of the gas communication tube 140 and the liquid communication tube 150.

As shown in fig. 6, the first delivery pipe 113a is further provided with a first auxiliary oil return hole 115a higher than the first main oil return hole 114 a. The first auxiliary oil return hole 115a is in fluid communication with the first compressor 100a through the first detection branch 116 a. The second delivery pipe 113b is further provided with a second auxiliary oil return hole 115b higher than the second main oil return hole 114 b. The second auxiliary oil return hole 115b is in fluid communication with the second compressor 100b through a second sensing branch 116 b. The first detection branch 116a is provided with a first inlet temperature sensor 118a and a first outlet temperature sensor 117a, and a first pressure reducing element 119a is provided between the first inlet temperature sensor 118a and the second outlet temperature sensor 117b (in one or more embodiments of the present application, the first pressure reducing element 119a is a first oil return detection capillary tube), that is, the first inlet temperature sensor 118a, the first pressure reducing element 119a, and the first outlet temperature sensor 117a are sequentially provided along the flow direction of the refrigerant; the second detection branch 116b is provided with a second inlet temperature sensor 118b and a second outlet temperature sensor 117b, and a second pressure reducing element 119b (in one or more embodiments of the present application, the second pressure reducing element 119b is a second oil return detection capillary tube) is provided between the second inlet temperature sensor 118b and the second outlet temperature sensor 117b, that is, the second inlet temperature sensor 118b, the second pressure reducing element 119b, and the second outlet temperature sensor 117b are provided in this order along the flow direction of the refrigerant. The first and second return oil detection capillaries may be used to regulate the flow in the first and second detection branches 116a and 116b, respectively. The pipe diameter, the length and the relative installation positions of the first oil return detection capillary and the second oil return detection capillary are identical.

In one or more embodiments of the present application, the height difference between the first auxiliary oil gallery 115a and the first main oil gallery 114a may be determined by the difference between the maximum and minimum amounts of lubrication oil of the first compressor 100a and the maximum refrigerant volume; wherein the difference between the maximum amount of change oil and the minimum amount of lubrication oil represents the maximum capacity of lubrication oil allowed to accumulate in the first housing 130a (below the minimum amount of lubrication oil the first compressor 100a is not operating), i.e., the ratio of the difference between the maximum amount of change oil and the minimum amount of lubrication oil to the cross-sectional area of the first housing 130a (assuming the first housing 130a is cylindrical) is the maximum lubrication oil height, and the ratio of the maximum refrigerant volume to the cross-sectional area of the first housing 130a is the maximum refrigerant height. The sum of the maximum refrigerant volume height and the maximum lubricant oil height is the maximum liquid level height in the first housing 130a, and since the first main oil gallery 114a is provided at the bottom (e.g., the lowest point of the U-tube), the height difference between the first auxiliary oil gallery 115a and the first main oil gallery 114a is lower than the maximum liquid level height. For example, a relatively ideal preset refrigerant volume, which is smaller than the maximum refrigerant volume (e.g., 60% of the maximum refrigerant volume), may be set according to the capacity of the refrigeration system 1, ensuring that both the first and second compressors 100a and 100b in the refrigeration system 1 can stably operate, and a preset refrigerant height may be calculated based on a ratio of the preset refrigerant volume to the cross-sectional area of the first housing 130a, and the first auxiliary oil return hole 115a may be opened at a set position of the first delivery pipe based on a sum of the preset refrigerant height and the maximum lubricant height.

In one or more embodiments of the present application, the height difference between the second auxiliary oil gallery 115b and the second main oil gallery 114b may be determined by the difference between the maximum and minimum amounts of lubrication oil of the second compressor 100b and the maximum refrigerant volume; wherein the difference between the maximum amount of lubrication oil and the minimum amount of lubrication oil represents the maximum capacity of lubrication oil allowed to accumulate in the second housing 130b (lower than the minimum amount of lubrication oil the second compressor 100b is not operated), i.e., the ratio of the difference between the maximum amount of lubrication oil and the minimum amount of lubrication oil to the cross-sectional area of the second housing 130b (assuming that the second housing 130b is cylindrical) is the maximum lubrication oil height, and the ratio of the maximum refrigerant volume to the cross-sectional area of the second housing 130b is the maximum refrigerant height. The sum of the maximum refrigerant volume height and the maximum lubricant oil height is the maximum liquid level height in the second housing 130b, and since the second main oil gallery 114b is provided at the bottom (e.g., the lowest point of the U-tube), the difference in height between the second auxiliary oil gallery 115b and the second main oil gallery 114b is lower than the maximum liquid level height. For example, a relatively ideal preset refrigerant volume, in which both the second compressor 100b and the second compressor 100b in the refrigeration system 1 can stably operate, may be set to be smaller than the maximum refrigerant volume (for example, 60% of the maximum refrigerant volume) according to the capacity of the refrigeration system 1, a preset refrigerant height may be calculated based on a ratio of the preset refrigerant volume to the cross-sectional area of the second housing 130b, and the second auxiliary oil return hole 115b may be opened at a set position of the second delivery pipe based on a sum of the preset refrigerant height and the maximum lubricant height.

In one or more embodiments of the present application, the first auxiliary oil gallery 115a and the second auxiliary oil gallery 115b are the same in height.

The outdoor unit is also provided with an outdoor control circuit. The outdoor control circuit is arranged in an electric box with good sealing performance and heat dissipation function. The outdoor control circuit comprises a processor, a storage unit, an input/output interface, a communication interface and other components. The processor may be a special purpose processor, a Central Processing Unit (CPU), or the like. The processor may access the memory unit to execute instructions or applications stored in the memory unit to implement the relevant functions. The memory unit may include volatile memory and/or nonvolatile memory. The input/output interface may be communicatively connected to various sensors provided in the outdoor unit to receive detection values of the various sensors provided in the outdoor unit. The input/output interface can also be in communication connection with devices such as a frequency converter, an outdoor fan, a four-way valve and the like so as to output control instructions generated by the processor. The communication interface may support different wireless communication protocols, such as Wi-Fi, bluetooth, near field communication, NB-IoT, etc., to communicatively connect with other electronic devices, including but not limited to cloud servers, computers (kiosks), smartphones, tablets, PDAs, smart control fixtures, wearable devices, and in-vehicle devices, etc.

As well described in the background art section, the refrigerant charge in the refrigeration system 1 has reached hundreds of kilograms, and since only one switching valve 102 is provided, the switching valve 102 must be provided corresponding to the distributor 107; however, it is difficult to ensure the similarity of the length of the pipe and the diameter of the pipe during long-term use downstream of the corresponding distributor 107 (e.g., tee or three-way valve), especially in the refrigeration system 1, there may be tiny impurities and contaminants that accumulate in the pipe near the distributor 107, gradually changing the pipe diameter of the pipe; and because the output of the two compressors will vary with the load, this will aggravate the uneven distribution of the liquid in the two gas-liquid separators downstream of the distributor 107, and further cause deviation in the return oil and return air of the first and second compressors 100a and 100b due to the dissolution of the lubricating oil in the liquid refrigerant.

As shown in fig. 7 and 8, in order to solve this problem, a control part 30 is further provided in the refrigeration system 1, and in one or more embodiments of the present application, the control part 30 is implemented by an outdoor control circuit. In one or more embodiments of the present application, the control part 30 may also be implemented by a cloud server or an upper computer communicatively connected to the outdoor unit. The control unit 30 is configured to control the first compressor 100a and the second compressor 100b to operate at the same frequency, estimate whether the first gas-liquid separator 108a and the second gas-liquid separator 108b are in a non-uniform liquid level state based on temperature changes before and after the first pressure reducing element 119a and the second pressure reducing element 119b, and a temperature difference in the discharge gas temperature between the first compressor 100a and the second compressor 100b, and drive the adjustment valve 121 to operate to adjust the flow rate of the refrigerant in the distribution pipe when the non-uniform liquid level state is estimated.

More specifically, the control section is configured to control the first compressor and the second compressor to operate at the same frequency. The operating frequency may be obtained based on the total load of the refrigeration system, for example, by determining the total operating frequency required by the refrigeration system according to a PID algorithm or a fuzzy control algorithm; the total operation frequency is divided by the number of compressors, and the first compressor 100a and the second compressor 100b are controlled to operate at the calculated operation frequency, and the operation frequencies of the first compressor 100a and the second compressor 100b are the same.

Since the vaporized refrigerant enters the first and second housings 130a and 130b through the introduction pipe under the distribution of the distributor 107, a gas-liquid separation effect is generated regardless of whether the cooling operation or the heating operation is performed. The gaseous refrigerant is in an upper position and the liquid refrigerant and lubricant mixture is in a lower position.

In this case, at the same height (the opening positions of the first auxiliary oil return hole 115a and the second auxiliary oil return hole 115 b), when the fluid therein is guided through the same pressure reducing element, the temperature difference change of the gas refrigerant is much smaller than that of the liquid refrigerant (including a mixture of the liquid refrigerant and the lubricating oil). Therefore, the control unit 30 is configured to estimate whether the gas-phase substance or the liquid-phase substance flowing into the first detection branch 116a from the first auxiliary oil return hole 115a is based on the temperature change before and after the first pressure reducing element 119 a. Similarly, it is possible to estimate whether the second detection branch 116b flowing in from the second auxiliary oil return hole 115b is a gas-phase substance or a liquid-phase substance based on the temperature change before and after the second pressure reducing element 119 b.

Since the first auxiliary oil return hole 115a and the second auxiliary oil return hole 115b are of equal height, the control portion 30 can estimate whether there is a case where the liquid level of one of the gas-liquid separators is above the corresponding auxiliary oil return hole or the liquid level of the other gas-liquid separator is below the corresponding auxiliary oil return hole, that is, both are in a non-uniform liquid level state.

It is further possible to judge whether there is a load mismatch by the temperature difference between the discharge temperatures of the first compressor 100a and the second compressor 100 b.

When the non-uniform liquid level state is estimated, the control unit 30 drives the adjustment valve 121 to adjust the flow rate of the refrigerant in the distribution pipe so that the liquid levels in the two gas-liquid separators are maintained at the uniform liquid level state. In the adjustment process, the first main oil return hole 114a, the first auxiliary oil return hole 115a, the second main oil return hole 114b and the second auxiliary oil return hole 115b may all play a role in oil return simultaneously or separately.

Because the first auxiliary oil return hole 115a and the second auxiliary oil return hole 115b are both formed at positions designed according to the ideal preset refrigerant volume, the control part 30 can simultaneously count the frequencies of the liquid level higher than the first auxiliary oil return hole 115a and the second auxiliary oil return hole 115b, and optimize the overall operation and hardware design of the refrigeration system 1 accordingly, so that the matching performance of the indoor unit and the outdoor unit can be better exerted.

In one or more embodiments of the present application, a first inlet temperature sensor 118a and a first outlet temperature sensor 117a are also disposed on the first detection branch 116a that is in fluid communication with the first compressor 100a. The first inlet temperature sensor 118a is disposed at an inlet side of the first detection branch 116a and is close to the first auxiliary oil gallery 115a. The first outlet temperature sensor 117a is disposed at an outlet side of the first detection branch 116a and is close to the first compressor 100a. The first inlet temperature sensor 118a, the first pressure reducing element 119a, and the first outlet temperature sensor 117a are disposed in this order in the refrigerant flow direction.

Correspondingly, a second inlet temperature sensor 118b and a second outlet temperature sensor 117b are also disposed on the second detection branch 116b in fluid communication with the second compressor 100b. The second inlet temperature sensor 118b is disposed at an inlet side of the second detection branch 116b and near the second auxiliary oil gallery 115b. The second outlet temperature sensor 117b is disposed at an outlet side of the second detection branch 116b and near the second compressor 100b. The second inlet temperature sensor 118b, the second decompression element 119b, and the second outlet temperature sensor 117b are disposed in this order in the refrigerant flow direction.

In one or more embodiments of the present application, the first detection branch 116a and the second detection branch 116b are configured to have identical dimensions, the first inlet temperature sensor 118a is configured to have identical locations to the second inlet temperature sensor 118b, and the first outlet temperature sensor 117a is configured to have identical locations to the second outlet temperature sensor 117 b.

Specifically, as shown in fig. 9, the control section 30 is configured to sample the temperature detected by the first outlet temperature sensor 117a (as shown in step S111 in fig. 9), sample the temperature detected by the first inlet temperature sensor 118a (as shown in step S112 in fig. 9), calculate the difference between the temperature detected by the first outlet temperature sensor 117a and the temperature detected by the first inlet temperature sensor 118a (as shown in step S113 in fig. 9), determine whether the difference between the temperature detected by the first outlet temperature sensor 117a and the temperature detected by the first inlet temperature sensor 118a is lower than a first set threshold (as shown in step S114 in fig. 9), and estimate that the liquid level in the first gas-liquid separator 108a is higher than the first auxiliary oil return hole 115a (as shown in step S115 in fig. 9) when the difference is lower than the first set threshold; or when not lower than the first set threshold value, it is estimated that the liquid level in the first gas-liquid separator 108a is lower than the first auxiliary oil return hole 115a (as shown in step S116 in fig. 9).

Correspondingly, as shown in fig. 10, the control part 30 is configured to sample the temperature detected by the second outlet temperature sensor 117b (as shown in step S211 in fig. 10), sample the temperature detected by the second inlet temperature sensor 118b (as shown in step S212 in fig. 10), calculate the difference between the temperature detected by the second outlet temperature sensor 117b and the temperature detected by the second inlet temperature sensor 118b (as shown in step S213 in fig. 10), determine whether the difference between the temperature detected by the second outlet temperature sensor 117b and the temperature detected by the second inlet temperature sensor 118b is lower than a second set threshold (as shown in step S214 in fig. 10), and estimate that the liquid level in the second gas-liquid separator 108b is higher than the second auxiliary oil return hole 115b (as shown in step S215 in fig. 10) when the difference is lower than the second set threshold; or when not lower than the second set threshold value, it is estimated that the liquid level in the second gas-liquid separator 108b is lower than the second auxiliary oil return hole 115b (as shown in step S216 in fig. 10).

In one or more embodiments of the present application, the control part 30 is configured to estimate that the first gas-liquid separator 108a and the second gas-liquid separator 108b are in a non-uniform liquid level state and the liquid level of the second gas-liquid separator 108b is higher than the second auxiliary oil return hole 115b, and when the difference between the detected temperature of the first outlet temperature sensor 117a and the detected temperature of the first inlet temperature sensor 118a is not lower than the first set threshold, the difference between the detected temperature of the second outlet temperature sensor 117b and the detected temperature of the second inlet temperature sensor 118b is lower than the second set threshold, and the difference between the temperature of the exhaust gas between the first compressor 100a and the temperature of the second compressor 100b is not lower than the third set threshold, the control valve 121 is driven to operate the conduction distribution pipe 120 so that the first gas-liquid separator 108a and the second gas-liquid separator 108b rapidly transit from the non-uniform liquid level state to the uniform liquid level state in a short time, as shown in fig. 11.

In one or more embodiments of the present application, the control part 30 is configured to estimate that the first gas-liquid separator 108a and the second gas-liquid separator 108b are in a non-uniform liquid level state and the liquid level of the first gas-liquid separator 108a is higher than the first auxiliary oil return hole 115a, and the liquid level of the second gas-liquid separator 108b is lower than the second auxiliary oil return hole 115b (as shown in fig. 12), when the difference between the first outlet temperature sensor 117a detection temperature and the first inlet temperature sensor 118a detection temperature is lower than the first set threshold, the second outlet temperature sensor 117b detection temperature and the second inlet temperature sensor 118b detection temperature is not lower than the second set threshold, and the temperature difference of the exhaust gas temperature between the first compressor 100a and the second compressor 100b is not lower than the third set threshold, to quickly transition the first gas-liquid separator 108a and the second gas-liquid separator 108b from the non-uniform liquid level state to the uniform liquid level state in a short time.

In one or more embodiments of the application, a third set threshold is generated from the outdoor ambient temperature, the third set threshold being inversely related to the outdoor ambient temperature.

Illustratively, as shown in fig. 15, the third set threshold is a sum of a reference temperature (preset and stored) and a corrected temperature. When the outdoor environment temperature is lower than minus 20 ℃, the correction temperature is 5 ℃; when the outdoor environment temperature is higher than minus 20 ℃ but lower than minus 10 ℃, the correction temperature is 3 ℃; when the outdoor environment temperature is higher than minus 10 ℃ but lower than 7 ℃, the correction temperature is 1 ℃; when the outdoor ambient temperature is higher than 7 ℃, the corrected temperature is 0 ℃. That is, the lower the outdoor ambient temperature, the more relaxed the estimation condition for the active adjustment of the liquid level, because the viscosity of the lubricating oil is high at low temperature, the oil return characteristic of the refrigeration system 1 becomes worse, and the distribution of the lubricating oil needs to be balanced by the liquid equalization, and the oil return characteristic is improved.

In one or more embodiments of the application, the first set threshold and the second set threshold are the same, e.g., are both set at 5 ℃.

In one or more embodiments of the present application, the regulator valve 121 may be a solenoid valve. The control part 30 drives the regulating valve 121 to operate to conduct the distribution pipe 120 until the set conducting period is finished, so that the first gas-liquid separator 108a and the second gas-liquid separator 108b are transited from the non-uniform liquid level state to the uniform liquid level state. Wherein the duration of the set on period is obtained based on a first fitted curve generated from the temperature difference of the discharge air between the first compressor 100a and the second compressor 100 b. In the first fitted curve, the set conduction period corresponds one-to-one to the discharge temperature difference between the first compressor 100a and the second compressor 100 b. The first fitted curve is preferably measured under experimental conditions, an exemplary first fitted curve is shown in fig. 16, where Δtd represents the temperature difference of the discharge air between the first compressor 100a and the second compressor 100b, and T represents the duration of the set conduction period.

In one or more embodiments of the present application, the regulator valve 121 may be an electronic expansion valve. The control part 30 drives the regulating valve 121 to operate to conduct the distribution pipe 120 so as to make the first gas-liquid separator 108a and the second gas-liquid separator 108b transition from the uniform liquid level state to the uniform liquid level state. The operation of the control valve 121 is divided into a plurality of continuous control cycles, and the opening of the next control cycle is the sum of the opening of the current control cycle and the correction opening. The corrected opening is the product of the maximum opening and the scaling factor. The scaling factor is obtained based on a second fitted curve generated from the temperature difference of the discharge air between the first compressor 100a and the second compressor 100 b. In the second fitted curve, the scaling factor corresponds one-to-one to the temperature difference of the discharge air between the first compressor 100a and the second compressor 100 b. The second fitted curve is preferably measured under experimental conditions, an exemplary second fitted curve is shown in fig. 17, wherein Δtd represents the temperature difference of the discharge air between the first compressor 100a and the second compressor 100b, and Δev represents the scaling factor in percent.

In practical use, the non-uniform liquid level state usually occurs in a transition stage of the refrigeration system 1, such as a start-up stage of the outdoor unit, a shut-down stage of the outdoor unit, and the number of corresponding working indoor units of the outdoor unit increases, the number decreases, defrosting and refrigerant charging, which may cause abrupt changes of gas and liquid in the refrigeration system 1, and may cause transient liquid level fluctuation, and at this time, small liquid level changes may cause disproportionate temperature changes, and accuracy of the exhaust gas temperature as a liquid level judgment index is reduced.

To solve this problem, in one or more embodiments of the present application, the control section 30 is configured to estimate whether the first gas-liquid separator 108a and the second gas-liquid separator 108b are in a non-uniform liquid level state based on the temperature variation before and after the first pressure reducing element 119a and the second pressure reducing element 119b, the temperature difference in the discharge temperature between the first compressor 100a and the second compressor 100b, and the operating current difference between the first compressor 100a and the second compressor 100 b; and when it is estimated that the liquid level is not uniform, the regulating valve 121 is driven to operate to regulate the flow rate of the refrigerant in the distribution pipe.

In keeping with the assumption that the temperature difference in discharge temperature between the first compressor 100a and the second compressor 100b is used as an estimated condition, a first inlet temperature sensor 118a and a first outlet temperature sensor 117a are also provided on the first detection branch 116a that is in fluid communication with the first compressor 100a fluid. The first inlet temperature sensor 118a is disposed at an inlet side of the first detection branch 116a and is close to the first auxiliary oil gallery 115a. The first outlet temperature sensor 117a is disposed at an outlet side of the first detection branch 116a and is close to the first compressor 100a. The first inlet temperature sensor 118a, the first pressure reducing element 119a, and the first outlet temperature sensor 117a are disposed in this order in the refrigerant flow direction.

In one or more embodiments of the present application, as shown in a plurality of steps in fig. 13, the control part 30 samples the detected temperatures of the first outlet temperature sensor 117a (as shown in step S311 in fig. 13), the detected temperature of the first inlet temperature sensor 118a (as shown in step S312 in fig. 13), calculates the difference between the detected temperature of the first outlet temperature sensor 117a and the detected temperature of the first inlet temperature sensor 118a (as shown in step S313 in fig. 13), and determines whether or not it is not lower than a first set threshold (as shown in step S314 in fig. 13); sampling the temperature detected by the second outlet temperature sensor 117b (as shown in step S321 in fig. 13), detecting the temperature detected by the second inlet temperature sensor 118b (as shown in step S322 in fig. 13), calculating the difference between the temperature detected by the second outlet temperature sensor 117b and the temperature detected by the second inlet temperature sensor 118b (as shown in step S323 in fig. 13), and determining whether it is lower than a second set threshold (as shown in step S324 in fig. 13); sampling the discharge temperature of the first compressor 100a (as shown in step S331 of fig. 13), calculating the discharge temperature difference between the first compressor 100a and the second compressor 100b (as shown in step S332 of fig. 13), and judging whether or not it is not lower than a third set threshold (as shown in step S334 of fig. 13); the operation current of the first compressor 100a is sampled (as shown in step S341 in fig. 13), the operation current of the second compressor 100b is sampled (as shown in step S342 in fig. 13), the operation current difference between the first compressor 100a and the second compressor 100b is calculated (as shown in step S343 in fig. 13), and it is judged whether or not it is not lower than the fourth set threshold (as shown in step S344 in fig. 13).

The control section 30 is configured to estimate that the first gas-liquid separator 108a and the second gas-liquid separator 108b are in a non-uniform liquid level state and that the liquid level of the second gas-liquid separator 108b is higher than the second auxiliary oil return hole 115b (as shown in step S35 in fig. 13), and to actuate the regulating valve 121 to turn on the distributing pipe 120 (as shown in step S36 in fig. 13) to transition the first gas-liquid separator 108a and the second gas-liquid separator 108b from a non-uniform state to a uniform liquid level state (as shown in step S37 in fig. 13) when the difference between the detected temperatures of the first outlet temperature sensor 117a and the detected temperature of the first inlet temperature sensor 118a is not lower than the first set threshold, and the detected temperature difference between the detected temperatures of the second outlet temperature sensor 117b and the detected temperature of the second inlet temperature sensor 118b is not lower than the second set threshold, and the difference between the temperature of the exhaust gas between the first compressor 100a and the second compressor 100b is not lower than the third set threshold, and the difference between the operating current between the first compressor 100a and the second compressor 100b is not lower than the fourth set threshold.

In one or more embodiments of the present application, as shown in a plurality of steps in fig. 14, the control part 30 samples the detected temperatures of the first outlet temperature sensor 117a (as shown in step S411 in fig. 14), the detected temperature of the first inlet temperature sensor 118a (as shown in step S412 in fig. 14), calculates the difference between the detected temperature of the first outlet temperature sensor 117a and the detected temperature of the first inlet temperature sensor 118a (as shown in step S413 in fig. 14), and determines whether or not it is lower than a first set threshold (as shown in step S414 in fig. 14); sampling the temperature detected by the second outlet temperature sensor 117b (as shown in step S421 in fig. 14), detecting the temperature detected by the second inlet temperature sensor 118b (as shown in step S422 in fig. 14), calculating the difference between the temperature detected by the second outlet temperature sensor 117b and the temperature detected by the second inlet temperature sensor 118b (as shown in step S423 in fig. 14), and determining whether or not it is not lower than a second set threshold (as shown in step S424 in fig. 14); sampling the discharge temperature of the first compressor 100a (as shown in step S431 in fig. 14), the discharge temperature of the second compressor 100b (as shown in step S432 in fig. 14), calculating the discharge temperature difference between the first compressor 100a and the second compressor 100b (as shown in step S433 in fig. 14), and judging whether or not it is not lower than a third set threshold (as shown in step S434 in fig. 14); the operation current of the first compressor 100a is sampled (as shown in step S441 in fig. 14), the operation current of the second compressor 100b is sampled (as shown in step S442 in fig. 14), the operation current difference between the first compressor 100a and the second compressor 100b is calculated (as shown in step S443 in fig. 14), and it is judged whether or not it is not lower than the fourth set threshold (as shown in step S444 in fig. 14).

In one or more embodiments of the present application, the control part 30 is configured to estimate that the first gas-liquid separator 108a and the second gas-liquid separator 108b are in a non-uniform liquid level state and that the liquid level of the first gas-liquid separator 108a is higher than the first auxiliary oil return hole 115a (as shown in step S45 in fig. 14), and to drive the regulating valve 121 to operate the on-distribution pipe 120 (as shown in step S46 in fig. 14) to transition the first gas-liquid separator 108a and the second gas-liquid separator 108b from a uniform liquid level state to a uniform liquid level state (as shown in step S47) when the difference between the first outlet temperature sensor 117a and the first inlet temperature sensor 118a is lower than a first set threshold, the difference between the second outlet temperature sensor 117b and the second inlet temperature sensor 118b is not lower than a second set threshold, and the temperature difference between the exhaust temperature between the first compressor 100a and the second compressor 100b is not lower than a third set threshold, and the difference between the operating current between the first compressor 100a and the second compressor 100b is not lower than a fourth set threshold.

Since the non-uniform liquid level condition generally occurs in a transient stage of the refrigeration system 1, such as a start-up stage of the outdoor unit, a shut-down stage of the outdoor unit, an increase in the number of corresponding working indoor units of the outdoor unit, a decrease in the number, defrosting, refrigerant charging, etc., this may result in abrupt changes in gas and liquid in the refrigeration system 1, which may lead to instantaneous liquid level fluctuations that are difficult to discriminate (even high-precision sensors cannot discriminate). In contrast, in the present application, the control unit 30 discriminates the distribution of the gas-phase refrigerant and the liquid-phase refrigerant in the first gas-liquid separator 108a and the second gas-liquid separator 108b based on the temperature change of the first detection branch 116a and the temperature change of the second detection branch 116 b; on the other hand, the influence of the working load of the first compressor 100a and the second compressor 100b on the liquid level is discriminated based on the complementary exhaust temperature difference and the running current difference of the compressors, so that the disproportionate temperature change caused by small liquid level change is avoided, and the accuracy of the temperature serving as a liquid level judgment index is reduced. The running current of the compressor is directly related to the working load of the compressor, particularly in the start-stop stage, the current can respond to the change, the detection is more accurate, and the exhaust temperature of the compressor can further judge whether the compressor has faults or not. The multi-parameter method has better robustness, can process the change under different transitional work adjustment, and can further cope with load change, environmental change and even sensor faults. Systems with a head above 100m are particularly useful for above 100 HP.

For example, the first set threshold and the second set threshold may each be set to 5 ℃, the third set threshold may be generated based on the outdoor environment temperature, and the fourth set threshold may be 1A.

In one or more embodiments of the present application, the regulator valve 121 may be a solenoid valve. The control part 30 drives the regulating valve 121 to operate to conduct the distribution pipe 120 until the set conducting period is finished, so that the first gas-liquid separator 108a and the second gas-liquid separator 108b are transited from the non-uniform liquid level state to the uniform liquid level state. Wherein the duration of the set on period is obtained based on a first fitted curve generated from the temperature difference of the discharge air between the first compressor 100a and the second compressor 100 b. In the first fitted curve, the set conduction period corresponds one-to-one to the discharge temperature difference between the first compressor 100a and the second compressor 100 b. The first fitted curve is preferably measured under experimental conditions, an exemplary first fitted curve is shown, where ΔTd represents the temperature difference of the discharge air between the first compressor 100a and the second compressor 100b, and T represents the duration of the set conduction period.

In one or more embodiments of the present application, the regulator valve 121 may be an electronic expansion valve. The control part 30 drives the regulating valve 121 to operate to conduct the distribution pipe 120 so as to make the first gas-liquid separator 108a and the second gas-liquid separator 108b transition from the uniform liquid level state to the uniform liquid level state. The operation of the control valve 121 is divided into a plurality of continuous control cycles, and the opening of the next control cycle is the sum of the opening of the current control cycle and the correction opening. The corrected opening is the product of the maximum opening and the scaling factor. The scaling factor is obtained based on a second fitted curve generated from the temperature difference of the discharge air between the first compressor 100a and the second compressor 100 b. In the second fitted curve, the scaling factor corresponds one-to-one to the temperature difference of the discharge air between the first compressor 100a and the second compressor 100 b. The second fitted curve is preferably measured under experimental conditions, an exemplary second fitted curve is shown, wherein ΔTd represents the temperature difference of the discharge air between the first compressor 100a and the second compressor 100b, ΔEV represents the scaling factor in percent.

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

The foregoing is merely illustrative of the present utility model, and the present utility model is not limited thereto, and any changes or substitutions easily contemplated by those skilled in the art within the scope of the present utility model should be included in the scope of the present utility model. Therefore, the protection scope of the utility model is subject to the protection scope of the claims.

Claims

1. A refrigeration system, comprising: an outdoor unit including a plurality of outdoor units,

The outdoor unit includes:

A first compressor;

a second compressor;

a distributor communicating with the switching valve;

a regulating valve disposed on the distribution pipe;

2. A refrigeration system as set forth in claim 1 wherein:

the first gas-liquid separator has a first housing; the upper part of the first shell is provided with a first ingress pipe which is inserted into the first shell and the inlet is positioned at the upper part of the first shell; the first shell is also provided with a first delivery pipe, the first delivery pipe is close to the bottom of the first shell and is bent, and an outlet of the first delivery pipe extends outwards from the upper part of the first shell; the first delivery tube is in fluid communication with the first compressor;

The second gas-liquid separator has a second housing; the upper part of the second shell is provided with a second ingress pipe which is inserted into the second shell and the inlet is positioned at the upper part of the second shell; the second shell is also provided with a second delivery pipe, the second delivery pipe is close to the bottom of the second shell and is bent, and an outlet of the second delivery pipe extends outwards from the upper part of the second shell; the second delivery tube is in fluid communication with the second compressor.

3. A refrigeration system as set forth in claim 1 wherein:

The first detection branch is also in fluid communication with the first compressor, further comprising:

The first inlet temperature sensor, the first pressure reducing element and the first outlet temperature sensor are sequentially arranged along the flowing direction of the refrigerant;

The second detection branch is also in fluid communication with the second compressor, further comprising:

4. A refrigeration system as set forth in claim 1 wherein:

The regulating valve is configured to conduct the distributing pipe when the first gas-liquid separator and the second gas-liquid separator are in a non-uniform liquid level state and the liquid level of the second gas-liquid separator is higher than the second auxiliary oil return hole so as to enable the first gas-liquid separator and the second gas-liquid separator to transition from the non-uniform liquid level state to the uniform liquid level state.

5. A refrigeration system as set forth in claim 1 wherein:

The regulator valve is configured to: when the first gas-liquid separator and the second gas-liquid separator are in a non-uniform liquid level state, and the liquid level of the first gas-liquid separator is higher than that of the first auxiliary oil return hole, the regulating valve acts to conduct the distributing pipe so as to enable the first gas-liquid separator and the second gas-liquid separator to transition from the non-uniform liquid level state to the uniform liquid level state.

6. A refrigeration system as set forth in claim 2 wherein:

the upper sides of the first and second housings are in communication through the gas communication tube, and the lower sides of the first and second housings are in communication through the liquid communication tube.

7. A refrigeration system as set forth in claim 5 wherein:

the pipe diameter of the distributing pipe is larger than the pipe diameters of the gas communicating pipe and the liquid communicating pipe.

8. A refrigeration system as set forth in claim 1 wherein:

the regulating valve is an electronic expansion valve or an electromagnetic valve.

9. A refrigeration system as set forth in claim 1 wherein:

the first pressure reducing element is a first oil return detection capillary, and the second pressure reducing element is a second oil return detection capillary.

10. A refrigeration system as set forth in claim 1 wherein:

The bottom positions of the first delivery pipe and the second delivery pipe are also provided with a first main oil return hole and a second main oil return hole.