Outdoor unit, multi-split air conditioning system and control method

Abstract

The invention relates to the technical field of air conditioners, in particular to an outdoor unit, a multi-split air conditioning system and a control method, and aims to solve the problem that the heat exchange efficiency of the lower portion of an outdoor unit heat exchanger is low. In order to achieve the purpose, the outdoor unit comprises a heat exchanger and a fan, the heat exchanger is equally divided into n paths from top to bottom, the first path to the kth path are upper heat exchange pipelines, the kth path to the nth path are lower heat exchange pipelines, the total air volume required by heat exchange of the heat exchanger is Q < total >, and the air speed distribution conditions of all equal parts of the heat exchanger are v1, v2, v3,... vn-1 and vn; and according to n, Q total, v1, v2, v3,... vn-1 and vn, determining the air speed distribution condition of the upper heat exchange pipeline and the lower heat exchange pipeline, the required air volume and the diameter of the fan of the fan. The air field can be uniformized, the heat exchange efficiency of the lower portion of the heat exchanger is improved, and the overall operation efficiency of the multi-split air conditioning system is improved. And the matching degree of the air volume of the heat exchanger and the refrigerant flow can be improved, so that the steady-state heating capacity of the multi-split air conditioning system is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of air conditioning, and specifically provides an outdoor unit, a multi-split air conditioning system and a control method. Background Art

[0002] The multi-split air conditioning system is developed on the basis of the traditional air conditioner. It is a type of user central air conditioning system, commonly known as "one to many", which means that one outdoor unit is connected to two or more indoor units through piping. The multi-split air conditioning system is currently being used more and more widely in small and medium-sized buildings and some public buildings.

[0003] The outdoor unit of the multi-split air conditioning system mostly adopts top outlet or side outlet. The fan of the top outlet outdoor unit is located at the top of the heat exchanger. The lower area of ​​the heat exchanger is far away from the fan, and the wind resistance is large, so the air volume or wind speed is small. Therefore, the air volume of the outdoor heat exchanger will be greatly attenuated in the vertical direction. Especially when the height of the heat exchanger is high, the wind field in the top outlet outdoor unit is more uneven. The existing technology reduces the resistance of the upper part of the heat exchanger by reducing the pipe line of the upper part of the heat exchanger, so that the refrigerant flow rate of the upper part of the heat exchanger with a large air volume increases, and on the contrary, the refrigerant flow rate of the lower part of the heat exchanger with a small air volume is reduced. By changing the refrigerant flow rate of the upper and lower parts of the heat exchanger, the problem of uneven wind field of the top outlet outdoor unit is improved, so that the heat exchange capacity of the upper part of the heat exchanger can be fully utilized.

[0004] However, the refrigerant flow rate and air volume at the bottom of the heat exchanger are small, so the heat exchange area at the bottom of the heat exchanger is not fully utilized, and the heat exchange efficiency is low, resulting in low overall heat exchange efficiency of the outdoor unit heat exchanger, which in turn leads to low overall operating efficiency of the multi-split air conditioning system. In addition, due to the poor uniformity of the wind field of the top-outlet outdoor unit, the evaporation capacity of the outdoor unit is poor when meeting the condensing capacity requirements, resulting in low steady-state heating capacity of the multi-split air conditioning system.

[0005] Accordingly, the art needs a new outdoor unit, a multi-split air conditioning system and a control method to solve the above problems. Summary of the invention

[0001] The present invention aims to solve the above-mentioned technical problem, that is, to solve the problem that when the height of the heat exchanger is high, the wind field uniformity of the top-outlet outdoor unit is poor, resulting in low heat exchange efficiency in the lower part of the heat exchanger, leading to low overall heat exchange efficiency of the outdoor unit heat exchanger, low overall operating efficiency of the multi-split air-conditioning system and low steady-state heating capacity of the multi-split air-conditioning system.

[0002] In a first aspect, the present invention provides an outdoor unit.

[0003] In the preferred technical solution of the outdoor unit, the outdoor unit includes a heat exchanger and a fan. The heat exchanger is evenly divided into n paths from top to bottom. The first to k paths are upper heat exchange pipes, and the kth to nth paths are lower heat exchange pipes. The total air volume Q required for heat exchange of the heat exchanger is 总 , the wind speed distribution of each equal part of the heat exchanger: v1, v2, v3, ...v n-1 , v n ;

[0004] According to n, Q 总 、v1,v2,v3,…v n-1 , v n , determine the wind speed distribution of the upper heat exchange pipeline and the lower heat exchange pipeline, the required air volume and the diameter of the fan of the fan.

[0005] In the preferred technical solution of the outdoor unit, the fan is designed as a single-layer fan, and the average wind speed of the upper heat exchange pipeline is:

[0006] The average wind speed of the lower heat exchange pipeline is:

[0007]

[0008] In the preferred technical solution of the outdoor unit, the total air volume required by the upper heat exchange pipeline is: Q 上总 =MQ 总 / (M+N);

[0009] The total air volume required for the lower heat exchange pipeline is: Q 下总 =NQ 总 / (M+N);

[0010] For a single-layer fan, the fan diameter of the single-layer fan is D0, and the fan diameter of the single-layer fan should satisfy the following relationship:

[0011] Among them, a1, a2, a3, b1, b2 and b3 are all constants.

[0012] In the preferred technical solution of the outdoor unit, the fan is designed as a double-layer fan, and the fan includes an upper fan and a lower fan;

[0013] The total air volume required for the upper heat exchange pipeline is: Q 上总 =kQ 总 / n;

[0014] The total air volume required for the lower heat exchange pipeline is: Q 下总 =(nk)Q 总 / n.

[0015] In the preferred technical solution of the outdoor unit, when there are two layers of fans, the fan diameter of the upper fan is D1, and the fan diameter of the lower fan is D2;

[0016] The fan diameters of the upper fan and the lower fan should satisfy the following relationship:

[0017] Among them, c1, c2, c3, d1, d2 and d3 are all constants.

[0018] In the preferred technical solution of the outdoor unit, the heat exchanger is surrounded to form an air duct, and when there are two layers of fans, the upper fan and the lower fan are both arranged in the air duct;

[0019] The outdoor unit further comprises a shell and a support frame, the heat exchanger is arranged in the shell, and the support frame is arranged on the shell and located in the air duct;

[0020] The support frame comprises a fan cover and a plurality of columns arranged on the fan cover, the columns are connected to the shell, and the lower fan is arranged on the fan cover.

[0021] In the preferred technical solution of the above-mentioned outdoor unit, the support frame also includes a sound insulation layer arranged on the fan cover, and the outdoor unit also includes a compressor, which is connected to the heat exchanger through a pipeline, and the compressor is located in the space formed by the sound insulation layer, the column and the shell.

[0022] In a second aspect, the present invention provides a multi-split air conditioning system.

[0023] In the preferred technical solution of the above-mentioned multi-split air-conditioning system, the multi-split air-conditioning system includes an outdoor unit.

[0024] In a third aspect, the present invention provides a control method for a multi-split air conditioning system.

[0025] In the preferred technical solution of the control method of the multi-split air conditioning system, the multi-split air conditioning system includes an outdoor unit, the outdoor unit includes a heat exchanger, an upper fan and a lower fan, the heat exchanger is surrounded to form an air duct, the upper fan and the lower fan are both arranged in the air duct, and the lower fan is located below the upper fan;

[0026] The heat exchanger comprises an upper heat exchange pipeline and a lower heat exchange pipeline, the lower heat exchange pipeline is located below the upper heat exchange pipeline, and the lower fan is located in the air duct and below the upper heat exchange pipeline;

[0027] The control method comprises the following steps:

[0028] The temperature Tdef1 of the upper heat exchange pipe and the temperature Tdef2 of the lower heat exchange pipe are obtained, and the rotation speeds of the upper fan and the lower fan are controlled according to the difference between Tdef1 and Tdef2 to adjust the wind field of the outdoor unit.

[0029] In the preferred technical solution of the outdoor unit, “obtaining the temperature Tdef1 of the upper heat exchange pipe and the temperature Tdef2 of the lower heat exchange pipe, and controlling the rotation speed of the upper fan and the lower fan according to the difference between Tdef1 and Tdef2, and adjusting the wind field of the outdoor unit” specifically includes the following steps:

[0030] When Tdef1-Tdef2>the first preset value, the rotation speed of the lower fan is increased to increase the air volume of the lower heat exchange pipeline;

[0031] When Tdef1-Tdef2<the second preset value, the rotation speed of the upper fan is increased to increase the air volume of the upper heat exchange pipeline.

[0032] In the case of adopting the above technical solution, when the outdoor unit is running, the upper fan and the lower fan are started, and the outside air enters the shell through the air inlet on the shell under the action of the upper fan and the lower fan to exchange heat with the upper heat exchange pipe and the lower heat exchange pipe, and then the heat exchanged air is discharged from the air outlet of the air duct. By adding a lower fan in the air duct and locating the lower fan below the upper heat exchange pipe, the air volume of the lower heat exchange pipe can be increased, the wind field can be uniform, and the heat exchange efficiency of the lower heat exchange pipe can be improved, thereby improving the overall heat exchange efficiency of the heat exchanger, and then improving the overall operation efficiency of the multi-split air conditioning system.

[0033] Moreover, since adding the lower fan makes the wind field of the outdoor unit more uniform, the matching degree between the air volume in the lower part of the heat exchanger and the refrigerant flow rate in each flow path of the lower heat exchange pipeline can be improved, making the lower heat exchange pipeline less prone to frost, thereby improving the steady-state heating capacity of the multi-split air-conditioning system. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] The preferred embodiments of the present invention are described below in conjunction with the accompanying drawings, in which:

[0035] Figure 1 is a schematic diagram of an outdoor unit in Embodiment 1 of the present invention;

[0036] Figure 2 is a flow chart of the main steps of the control method of the multi-split air conditioning system in the second embodiment of the present invention;

[0037] Figure 3 is a flowchart of specific steps of a control method for a multi-split air conditioning system in Embodiment 2 of the present invention;

[0038] 1. Shell; 21. Upper heat exchange pipe; 22. Lower heat exchange pipe; 23. Air duct; 31. First fan; 32. First guide ring; 33. Second fan; 34. Second guide ring; 4. Lower fan; 51. Fan cover; 52. Column; 53. Sound insulation layer; 6. Compressor; 7. Base plate. DETAILED DESCRIPTION

[0039] The preferred embodiments of the present invention are described below with reference to the accompanying drawings. It should be understood by those skilled in the art that these embodiments are only used to explain the technical principles of the present invention and are not intended to limit the scope of protection of the present invention. Those skilled in the art can make adjustments to them as needed to adapt to specific application scenarios.

[0040] It should be noted that in the description of the present invention, the terms "upper", "lower", "left", "right" and the like indicating directions or positional relationships are based on the directions or positional relationships shown in the drawings, which are only for the convenience of description, and do not indicate or imply that the device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", "third", and "fourth" are used for descriptive purposes only, and cannot be understood as indicating or implying relative importance.

[0041] In addition, it should be noted that in the description of the present invention, unless otherwise clearly specified and limited, the terms "connected", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection or a detachable connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the internal communication of two components. For those skilled in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0042] Embodiment 1

[0043] In order to solve the problem that the refrigerant flow and air volume in the lower part of the heat exchanger are small, the heat exchange efficiency in the lower part of the heat exchanger is low, resulting in low overall heat exchange efficiency of the outdoor unit heat exchanger, and further leading to low overall operating efficiency of the multi-split air-conditioning system.

[0044] like Figure 1 As shown, this embodiment discloses a multi-split air conditioning system, which includes a control system, an outdoor unit and a plurality of indoor units, each of which is connected to the outdoor unit through a pipeline, and the outdoor unit and the indoor unit are controlled by the control system to cool or heat the room. Specifically, the outdoor unit includes a housing 1, a heat exchanger, a fan and a support frame, an air inlet (not shown in the figure) is provided on the side of the housing 1, an air outlet (not shown in the figure) is provided on the top of the housing 1, and a bottom plate 7 is fixed to the bottom of the housing 1 to form an installation space.

[0045] The heat exchanger is located in the installation space and fixed on the bottom plate 7. The heat exchanger includes an upper heat exchange pipe 21 and a lower heat exchange pipe 22. The lower heat exchange pipe 22 is located below the upper heat exchange pipe 21 and fixed on the bottom plate 7. The upper heat exchange pipe 21 and the lower heat exchange pipe 22 are arranged to form an air duct 23. The cross section of the air duct 23 is set to be rectangular, and of course it can also be set to other shapes such as a circle. A first defrost temperature sensor (not shown in the figure) is installed on the upper heat exchange pipe 21, and the temperature Tdef1 of the upper heat exchange pipe 21 can be uploaded to the control system of the multi-split air conditioning system. A second defrost temperature sensor (not shown in the figure) is installed on the lower heat exchange pipe 22, and the temperature Tdef2 of the lower heat exchange pipe 22 can be uploaded to the control system of the multi-split air conditioning system.

[0046] like Figure 1 As shown, according to different working conditions, the fan of the outdoor unit can be set as a single-layer fan or a double-layer fan to improve the uniformity of the wind field in the outdoor unit. When the overall height of the heat exchanger is low, the ratio of the wind speed of the upper part of the upper heat exchange pipe 21 to the wind speed of the lower part of the lower heat exchange pipe 22 is less than the preset value, and the overall heat exchange efficiency of the heat exchanger is less affected. At this time, the fan is set to a single layer. The single-layer fan is installed on the shell 1 through a guide ring and is located at the air outlet of the air duct 23. During operation, the single-layer fan is started, and the outside air enters the shell 1 through the air inlet on the shell 1 under the action of the single-layer fan, and exchanges heat with the upper heat exchange pipe 21 and the lower heat exchange pipe 22, and then the air after heat exchange is discharged from the air outlet of the shell 1.

[0047] When the overall height of the heat exchanger is higher than a certain value, the ratio of the wind speed at the upper part of the upper heat exchange pipe 21 to the wind speed at the lower part of the upper heat exchange pipe 21 is less than a preset value, and at the same time, the ratio of the wind speed at the upper part of the upper heat exchange pipe 21 to the wind speed at the upper part of the lower heat exchange pipe 22 is greater than the preset value and the ratio of the wind speed at the upper part of the lower heat exchange pipe 22 to the wind speed at the lower part of the lower heat exchange pipe 22 is less than or equal to the preset value, the fan is designed as a double layer.

[0048] like Figure 1 As shown, the upper fan can be installed in the air duct 23 or at the air outlet of the air duct 23. In this embodiment, the upper fan is installed at the air outlet of the air duct 23. The lower fan 4 is installed in the air duct 23 through a support frame, and the lower fan 4 is located below the upper heat exchange pipeline 21, so that the lower fan 4 and the upper fan form a series fan. When the outdoor unit is running, the upper fan and the lower fan 4 are started, and the outside air enters the shell 1 through the air inlet on the shell 1 under the action of the upper fan and the lower fan 4, and performs heat exchange with the upper heat exchange pipeline 21 and the lower heat exchange pipeline 22, and then the heat exchanged air is discharged from the air outlet of the shell 1.

[0049] Compared with the prior art, the air flow is promoted only by the upper fan, so that the air volume at the upper part of the heat exchanger is large and the air volume at the lower part is small, resulting in a low utilization rate of the heat exchange tube at the lower part of the heat exchanger. The outdoor unit in this embodiment can increase the air volume of the lower heat exchange pipeline 22 by adding a lower fan 4 below the upper heat exchange pipeline 21, and even the wind field, thereby improving the heat exchange efficiency of the lower heat exchange pipeline 22, thereby improving the overall heat exchange efficiency of the heat exchanger, and further improving the overall operating efficiency of the multi-split air conditioning system. In addition, since the addition of the lower fan 4 makes the wind field of the outdoor unit more uniform, it can improve the matching degree between the air volume at the lower part of the heat exchanger and the refrigerant flow rate of each flow path at the lower part of the heat exchanger, so that the lower part of the heat exchanger is not easy to frost, thereby improving the steady-state heating capacity of the multi-split air conditioning system.

[0050] like Figure 1 As shown, specifically, the upper fan includes a first guide ring 32 and a first fan 31 installed on the first guide ring 32. The first fan 31 is located at the air outlet of the air duct 23. The outside air is sucked into the air duct 23 from the air inlet of the shell 1 through the first fan 31, and discharged from the air outlet of the air duct 23 to perform heat exchange with the upper heat exchange pipeline 21. The first guide ring 32 is detachably installed on the shell 1 by bolts, so that the first fan 31 can be disassembled for maintenance.

[0051] The lower fan 4 can be used to draw outside air from the air inlet of the housing 1 into the air duct 23, and perform heat exchange with the lower heat exchange pipe 22. The air after heat exchange is discharged from the air outlet of the air duct 23. The lower fan 4 can be coaxially arranged or non-coaxially arranged with the first fan 31. Both arrangements can make the first fan 31 and the lower fan 4 form a series air outlet to increase the speed at which outside air enters the air duct 23 and improve the heat exchange efficiency of the heat exchanger. The coaxial arrangement of the first fan 31 and the lower fan 4 has a better air guiding effect, can reduce the generation of turbulence in the air duct 23, and reduce the noise generated during the operation of the outdoor unit.

[0052] Furthermore, the upper fan also includes a second guide ring 34 and a second fan 33 installed on the second guide ring 34. The second fan 33 has the same installation height and the same fan blade diameter as the first fan 31. The second fan 33 and the first fan 31 are both located at the air outlet of the air duct 23, thereby increasing the air volume flowing through the upper heat exchange pipe 21. According to the actual application conditions, the designer can increase or decrease the number of upper fans. In this embodiment, the number of upper fans is two for illustration. Specifically, the first fan 31 and the second fan 33 are both non-coaxially arranged with the lower fan 4, so that the first fan 31 and the second fan 33 guide the air more evenly. The second guide ring 34 is detachably mounted on the housing 1 to facilitate the removal of the second fan 33 for maintenance.

[0053] like Figure 1As shown, in the air duct 23, the lower fan 4 is installed below the upper fan through a support frame, and the lower fan 4 is located below the upper heat exchange pipe 21. By adding the lower fan 4, the air volume flowing through the lower heat exchange pipe 22 can be increased, making the wind field of the outdoor unit more uniform. The more uniform the wind field of the outdoor unit, on the one hand, can improve the heat exchange efficiency of the lower heat exchange pipe 22, so that the heat exchange efficiency of the heat exchanger as a whole can be improved, thereby improving the overall operating efficiency of the multi-split air-conditioning system. On the other hand, it can improve the matching degree between the air volume of the lower heat exchange pipe 22 and the refrigerant flow rate of each flow path in the lower part of the heat exchanger, so that the lower heat exchange pipe 22 is not easy to frost, thereby improving the steady-state heating capacity of the multi-split air-conditioning system.

[0054] In addition, the wind speed distribution of the upper heat exchange pipe 21 and the lower heat exchange pipe 22, the required air volume and the diameter of the fan of the fan can be obtained by the following method:

[0055] The heat exchanger is evenly divided into n paths from top to bottom. The first to k paths are upper heat exchange pipes 21, and the kth to nth paths are lower heat exchange pipes 22. The total air volume Q required for heat exchange in the heat exchanger is 总 , the wind speed distribution of each equal part of the heat exchanger: v1, v2, v3, ...v n-1 , v n The wind speed distribution of each equal part of the heat exchanger can be obtained through fluid simulation calculation or experimental testing.

[0056] According to n, Q 总 、v1,v2,v3,…v n-1 , v n , determine the wind speed distribution of the upper heat exchange pipeline 21 and the lower heat exchange pipeline 22, the required air volume and the diameter of the fan of the fan.

[0057] When the fan is designed as a single-layer fan, the average wind speed of the upper heat exchange pipeline 21 is:

[0058] The average wind speed of the lower heat exchange pipeline 22 is:

[0059] k is any value from 1 to n.

[0060] Furthermore, the wind speed distribution of the upper heat exchange pipeline 21 and the lower heat exchange pipeline 22 is known, and the total air volume required by the upper heat exchange pipeline 21 and the lower heat exchange pipeline 22 can be calculated.

[0061] The total air volume required for the upper heat exchange pipe 21 is: Q 上总 =MQ 总 / (M+N);

[0062] The total air volume required for the lower heat exchange pipe 22 is: Q下总 =NQ 总 / (M+N); when this air volume is reached, the heat exchange efficiency of the upper heat exchange pipe 21 and the lower heat exchange pipe 22 is higher, thereby improving the heat exchange efficiency of the entire heat exchanger.

[0063] For a single-layer fan, the fan diameter of the single-layer fan is D0, and the fan diameter of the single-layer fan should satisfy the following relationship:

[0064] Among them, a1, a2, a3, b1, b2 and b3 are all constants and can be calculated through fluid simulation. By determining the fan diameter of the single-layer fan through the formula, the fan of the single-layer fan can be made to better meet the operating requirements and improve the air intake efficiency, thereby further improving the heat exchange efficiency of the heat exchanger.

[0065] When the fan is designed as a double-layer fan, the total air volume required by the upper heat exchange pipe 21 is: Q 上总 =kQ 总 / n;

[0066] The total air volume required for the lower heat exchange pipeline is: Q 下总 =(nk)Q 总 / n; When this air volume is reached, the heat exchange efficiency of the upper heat exchange pipe 21 and the lower heat exchange pipe 22 is higher, thereby improving the heat exchange efficiency of the entire heat exchanger.

[0067] Further, when the fan is designed as a double-layer fan, the fan includes an upper fan and a lower fan 4, the fan diameter of the upper fan is D1, and the fan diameter of the lower fan 4 is D2;

[0068] The fan diameters of the upper fan and the lower fan 4 should satisfy the following relationship:

[0069] Among them, c1, c2, c3, d1, d2 and d3 are all constants and can be calculated through fluid simulation. By determining the fan diameters of the upper and lower fans through the formula, the fans of the upper and lower fans can be made more in line with the operation requirements, and the air intake efficiency can be improved, thereby further improving the heat exchange efficiency of the heat exchanger.

[0070] like Figure 1 As shown, further, the outdoor unit also includes a compressor 6, a gas-liquid separator, an oil separator, a four-way valve and a refrigerant pipeline, which are necessary components for realizing the basic functions of the multi-split air-conditioning system. The compressor 6, the gas-liquid separator, the oil separator and the four-way valve are all located in the space between the support frame and the base plate 7 to reduce the internal space occupied by the shell 1.

[0071] The support frame includes a fan cover 51, a sound insulation layer 53 fixed on the fan cover 51, and a plurality of columns 52. The lower fan 4 is installed on the fan cover 51. One end of the column 52 away from the fan cover 51 is fixed on the bottom plate 7, so that the lower fan 4 can be more stably installed in the air duct 23. The sound insulation layer 53 is bonded to the fan cover 51. The sound insulation layer 53 can be a layered structure made of polyester fiber cotton sound insulation cotton, centrifugal glass wool or damping sound-absorbing material. The noise emitted by the compressor 6, the gas-liquid separator and the oil separator is reduced by the sound insulation layer 53, so as to reduce the noise transmitted to the environment during the operation of the outdoor unit.

[0072] As another preferred embodiment, a sound insulation layer 53 may be bonded to the outer walls of the compressor 6, the gas-liquid separator and the oil separator to reduce vibration and noise transmission, thereby further reducing the noise generated by the outdoor unit during operation.

[0073] Embodiment 2

[0074] This embodiment discloses a control method for a multi-split air conditioning system, and the multi-split air conditioning system is the multi-split air conditioning system in the first embodiment. Figure 2 As shown, the control method of the multi-split air conditioning system includes the following steps:

[0075] The temperature Tdef1 of the upper heat exchange pipe 21 and the temperature Tdef2 of the lower heat exchange pipe 22 are obtained, and the rotation speeds of the upper fan and the lower fan 4 are controlled according to the difference between Tdef1 and Tdef2 to adjust the wind field of the outdoor unit.

[0076] In this way, the amount of refrigerant and the air volume passing through the upper heat exchange pipe 21 and the lower heat exchange pipe 22 are more matched, so that the upper heat exchange pipe 21 and the lower heat exchange pipe 22 can better exert their heat exchange capacity, improve the overall heat exchange efficiency of the heat exchanger, and thus make the multi-split air-conditioning system more efficient.

[0077] like Figure 3 As shown, the control method includes the following specific steps:

[0078] The temperature Tdef1 of the upper heat exchange pipe 21 and the temperature Tdef2 of the lower heat exchange pipe 22 are obtained, and the rotation speed of the upper fan and the lower fan 4 is controlled according to the difference between Tdef1 and Tdef2, and the wind field of the outdoor unit is adjusted to make the wind field of the outdoor unit more uniform. In the initial state, the upper fan and the lower fan 4 are started to rotate at the set speed, wherein the first fan 31 and the second fan 33 of the upper fan are started and stopped at the same time, and the rotation speed is the same.

[0079] When Tdef1-Tdef2>the first preset value, in this embodiment, the first preset value is selected as 1°C, that is, when Tdef1-Tdef2>1°C, the temperature of the upper heat exchange pipe 21 is higher than the temperature of the lower heat exchange pipe 22, that is, the refrigerant flow and air volume of the lower heat exchange pipe 22 are not sufficiently matched. The rotation speed of the lower fan 4 is increased, and the air volume flowing through the lower heat exchange pipe 22 is increased to improve the matching degree of the refrigerant flow and air volume of the lower heat exchange pipe 22 and improve the heat exchange efficiency of the lower heat exchange pipe 22.

[0080] When Tdef1-Tdef2<the second preset value, in this embodiment, the second preset value is selected as -1°C, that is, when Tdef1-Tdef2<-1°C, the temperature of the upper heat exchange pipe 21 is lower than the temperature of the lower heat exchange pipe 22, that is, the refrigerant flow and air volume of the upper heat exchange pipe 21 are not sufficiently matched. The rotation speed of the upper fan is increased, and the air volume flowing through the upper heat exchange pipe 21 is increased to improve the matching degree of the refrigerant flow and air volume of the upper heat exchange pipe 21 and improve the heat exchange efficiency of the upper heat exchange pipe 21.

[0081] So far, the technical solutions of the present invention have been described in conjunction with the preferred embodiments shown in the accompanying drawings. However, it is easy for those skilled in the art to understand that the protection scope of the present invention is obviously not limited to these specific embodiments. Without departing from the principle of the present invention, those skilled in the art can make equivalent changes or substitutions to the relevant technical features, and the technical solutions after these changes or substitutions will fall within the protection scope of the present invention.

Claims

1. An outdoor unit, characterized in that: The heat exchanger comprises a heat exchanger and a fan. The heat exchanger is evenly divided into n paths from top to bottom. The first to k paths are upper heat exchange pipes (21), and the kth to nth paths are lower heat exchange pipes (22). The heat exchanger requires a total air volume Q 总 , the wind speed distribution of each equal part of the heat exchanger: v1, v2, v3, ...v n-1 , v n ; According to n, Q 总 、v1,v2,v3,…v n-1 , v n , determine the wind speed distribution of the upper heat exchange pipeline (21) and the lower heat exchange pipeline (22), the required air volume and the diameter of the fan of the fan.

2. The outdoor unit according to claim 1, characterized in that: The fan is designed as a single-layer fan, and the average wind speed of the upper heat exchange pipeline (21) is: The average wind speed of the lower heat exchange pipeline (22) is:

3. The outdoor unit according to claim 2, characterized in that: The total air volume required by the upper heat exchange pipeline (21) is: Q 上总 =MQ 总 / (M+N); The total air volume required by the lower heat exchange pipeline (22) is: Q 下总 =NQ 总 / (M+N); For a single-layer fan, the fan diameter of the single-layer fan is D0, and the fan diameter of the single-layer fan should satisfy the following relationship: Among them, a1, a2, a3, b1, b2 and b3 are all constants.

4. The outdoor unit according to claim 1, characterized in that: The fan is designed as a double-layer fan, comprising an upper-layer fan and a lower-layer fan (4); The total air volume required by the upper heat exchange pipeline (21) is: Q 上总 =kQ 总 / n; The total air volume required by the lower heat exchange pipeline (22) is: Q 下总 =(nk)Q 总 / n.

5. The outdoor unit according to claim 4, characterized in that: In the case of a double-layer fan, the fan diameter of the upper fan is D1, and the fan diameter of the lower fan (4) is D2; The fan diameters of the upper fan and the lower fan (4) should satisfy the following relationship: Among them, c1, c2, c3, d1, d2 and d3 are all constants.

6. The outdoor unit according to claim 1, characterized in that: The heat exchanger is surrounded to form an air duct (23), and in the case of a double-layer fan, the upper fan and the lower fan (4) are both arranged in the air duct (23); The outdoor unit further comprises a shell (1) and a support frame, the heat exchanger is arranged in the shell (1), and the support frame is arranged on the shell (1) and located in the air duct (23); The support frame comprises a fan cover (51) and a plurality of columns (52) arranged on the fan cover (51), the columns (52) are connected to the housing (1), and the lower fan (4) is arranged on the fan cover (51).

7. The outdoor unit according to claim 6, characterized in that: The support frame further comprises a sound insulation layer (53) arranged on the fan cover (51), and the outdoor unit further comprises a compressor (6), the compressor (6) is connected to the heat exchanger through a pipeline, and the compressor (6) is located in a space formed by the sound insulation layer (53), the column (52) and the shell (1).

8. A multi-split air conditioning system, characterized in that: Comprising an outdoor unit as described in any one of claims 1-7.

9. A control method for a multi-split air conditioning system, characterized in that: The multi-split air conditioning system comprises an outdoor unit, the outdoor unit comprises a heat exchanger, an upper fan and a lower fan (4), the heat exchanger is surrounded to form an air duct (23), the upper fan and the lower fan (4) are both arranged in the air duct (23), and the lower fan (4) is located below the upper fan; The heat exchanger comprises an upper heat exchange pipeline (21) and a lower heat exchange pipeline (22), wherein the lower heat exchange pipeline (22) is located below the upper heat exchange pipeline (21), and the lower fan (4) is located in the air duct (23) and below the upper heat exchange pipeline (21); The control method comprises the following steps: The temperature Tdef1 of the upper heat exchange pipe (21) and the temperature Tdef2 of the lower heat exchange pipe (22) are obtained, and the rotation speeds of the upper fan and the lower fan (4) are controlled according to the difference between Tdef1 and Tdef2 to adjust the wind field of the outdoor unit.

10. The control method of the multi-split air conditioning system according to claim 9, characterized in that: "obtaining the temperature Tdef1 of the upper heat exchange pipe (21) and the temperature Tdef2 of the lower heat exchange pipe (22), and controlling the rotation speeds of the upper fan and the lower fan (4) according to the difference between Tdef1 and Tdef2, thereby adjusting the wind field of the outdoor unit" specifically comprises the following steps: When Tdef1-Tdef2>the first preset value, the rotation speed of the lower fan (4) is increased, and the air volume of the lower heat exchange pipeline (22) is increased; When Tdef1-Tdef2<the second preset value, the rotation speed of the upper fan is increased, thereby increasing the air volume of the upper heat exchange pipeline (21).

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