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

Abstract

The present application relates to air conditioning technical field, specifically provide a kind of outdoor unit, multi-connected air conditioning system and control method, to solve the problem of lower heat exchange efficiency of the lower part of outdoor unit heat exchanger.It is for this purpose, the outdoor unit of the present application includes heat exchanger and fan, heat exchanger is divided into n paths from top to bottom, the first path to k path is upper heat exchange pipeline, k path to n path is lower heat exchange pipeline, heat exchanger heat exchange needs total air volume Q 总 , the wind speed distribution of each aliquot of 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 upper heat exchange pipeline and lower heat exchange pipeline, required air volume and the diameter of fan of fan of the present application can uniform wind field, improve the heat exchange efficiency of the lower part of heat exchanger, to improve the overall operation efficiency of multi-connected air conditioning system.Also can improve the matching degree of air volume and refrigerant flow of heat exchanger, to improve the ability of multi-connected air conditioning system steady heating.

Description

Technical Field

[0001] This invention relates to the field of air conditioning technology, specifically providing an outdoor unit, a multi-split air conditioning system, and a control method. Background Technology

[0002] Multi-split air conditioning systems evolved from traditional air conditioners and are a type of central air conditioning system for users. Commonly known as "one-to-many," it refers to a system where one outdoor unit is connected to two or more indoor units via piping. Multi-split air conditioning systems are increasingly widely used in small and medium-sized buildings and some public buildings.

[0003] Multi-split air conditioning systems typically use top-discharge or side-discharge outdoor units. In top-discharge units, the fan is located at the top of the heat exchanger, while the lower part of the heat exchanger is farther from the fan, resulting in greater air resistance and thus lower airflow or velocity. Consequently, the airflow in the outdoor heat exchanger experiences a significant vertical reduction. This uneven airflow is particularly pronounced when the heat exchanger is tall. Existing technology reduces the resistance at the top of the heat exchanger by decreasing the tube length, thereby increasing the refrigerant flow in the higher airflow section and decreasing it in the lower section. By altering the refrigerant flow in the upper and lower parts of the heat exchanger, the uneven airflow in top-discharge outdoor units can be improved, allowing the heat exchange capacity of the upper part of the heat exchanger to be fully utilized.

[0004] However, the refrigerant flow and air volume at the bottom of the heat exchanger are small, resulting in insufficient utilization of the heat exchange area and low heat exchange efficiency. This leads to low overall heat exchange efficiency of the outdoor unit's heat exchanger, and consequently, low overall operating efficiency of the multi-split air conditioning system. Furthermore, due to the poor uniformity of the airflow in the top-discharge outdoor unit, the outdoor unit's evaporation capacity is poor while meeting condensation requirements, resulting in low steady-state heating capacity of the multi-split air conditioning system.

[0005] Accordingly, there is a need in this field for a new outdoor unit, multi-split air conditioning system, and control method to solve the above problems. Summary of the Invention

[0006] The present invention aims to solve the above-mentioned technical problems, namely, to solve the problem that when the heat exchanger is high, the uniformity of the air field of the top-discharge outdoor unit is poor, resulting in low heat exchange efficiency at the bottom of the heat exchanger, which in turn leads 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.

[0007] In a first aspect, the present invention provides an outdoor unit.

[0008] In the preferred technical solution of the outdoor unit described above, the outdoor unit includes a heat exchanger and a fan. The heat exchanger is divided into n equal channels from top to bottom. Channels 1 to k are upper heat exchange channels, and channels k to n are lower heat exchange channels. The heat exchanger requires a total air volume Q for heat exchange. 总 The wind speed distribution in each equal part of the heat exchanger is as follows: v1, v2, v3, ... v n-1 v n ;

[0009] According to n, Q 总 v1, v2, v3, ... v n-1 v n The wind speed distribution, required air volume, and fan diameter of the upper and lower heat exchange pipes are determined.

[0010] In the preferred technical solution of the outdoor unit described above, the fan is designed as a single-layer fan, and the average wind speed of the upper heat exchange pipe is:

[0011]

[0012] The average wind speed in the lower heat exchange pipeline is:

[0013]

[0014] In the preferred technical solution of the outdoor unit described above, the total air volume required for the upper heat exchange pipeline is: Q 上总 =MQ 总 / (M+N);

[0015] The total air volume required for the lower heat exchange pipeline is: Q 下总 =NQ 总 / (M+N);

[0016] When using a single-layer fan, the fan diameter is D0, and the fan diameter of the single-layer fan should satisfy the following relationship:

[0017]

[0018] Where a1, a2, a3, b1, b2, and b3 are all constants.

[0019] In the preferred technical solution of the outdoor unit mentioned above, the fan is designed as a double-layer fan, which includes an upper fan and a lower fan.

[0020] The total air volume required for the aforementioned heat exchange pipeline is: Q 上总 =kQ 总 / n;

[0021] The total air volume required for the lower heat exchange pipeline is: Q 下总 =(nk)Q总 / n.

[0022] In the preferred technical solution of the outdoor unit described above, when there is a double-layer fan, the fan diameter of the upper fan is D1 and the fan diameter of the lower fan is D2.

[0023] The fan diameters of the upper and lower fans should meet the following relationship:

[0024]

[0025] Where c1, c2, c3, d1, d2 and d3 are all constants.

[0026] In the preferred technical solution of the outdoor unit mentioned above, the heat exchanger is arranged to form an air duct, and in the case of a double-layer fan, both the upper fan and the lower fan are located inside the air duct.

[0027] The outdoor unit also includes a housing and a support frame. The heat exchanger is located inside the housing, and the support frame is mounted on the housing and located inside the air duct.

[0028] The support frame includes a fan cover and several columns mounted on the fan cover. The columns are connected to the housing, and the lower fan is mounted on the fan cover.

[0029] In the preferred technical solution of the outdoor unit described above, the support frame further includes a sound insulation layer disposed on the fan cover, the outdoor unit further includes a compressor, the compressor 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.

[0030] Secondly, the present invention provides a multi-split air conditioning system.

[0031] In the preferred embodiment of the multi-split air conditioning system described above, the multi-split air conditioning system includes an outdoor unit.

[0032] Thirdly, the present invention provides a control method for a multi-split air conditioning system.

[0033] In the preferred embodiment of the control method for the above-mentioned 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 arranged to form an air duct, the upper fan and the lower fan are both located in the air duct, and the lower fan is located below the upper fan.

[0034] The heat exchanger includes an upper heat exchange pipe and a lower heat exchange pipe, the lower heat exchange pipe being located below the upper heat exchange pipe, and the lower fan being located inside the air duct and below the upper heat exchange pipe;

[0035] The control method includes the following steps:

[0036] The temperature Tdef1 of the upper heat exchange pipe and the temperature Tdef2 of the lower heat exchange pipe are obtained, and the speed of the upper fan and the lower fan is controlled according to the difference between Tdef1 and Tdef2 to adjust the air field of the outdoor unit.

[0037] In the preferred technical solution of the outdoor unit described above, "obtaining the temperature Tdef1 of the upper heat exchange pipe and the temperature Tdef2 of the lower heat exchange pipe, and controlling the speed of the upper and lower fans based on the difference between Tdef1 and Tdef2 to adjust the airflow of the outdoor unit" specifically includes the following steps:

[0038] When Tdef1-Tdef2>the first preset value, the speed of the lower fan is increased, and the air volume of the lower heat exchange pipeline is increased;

[0039] When Tdef1-Tdef2 < the second preset value, the rotation speed of the upper fan is increased, and the air volume of the upper heat exchange pipeline is increased.

[0040] When the above technical solution is adopted, during outdoor unit operation, the upper and lower fans are activated. Outside air, driven by the upper and lower fans, enters the casing through the air inlet and exchanges heat with the upper and lower heat exchange pipes. The heat-exchanged air is then discharged from the air outlet of the duct. By adding a lower fan within the duct and positioning it below the upper heat exchange pipe, the airflow in the lower heat exchange pipe is increased, the airflow becomes more uniform, and the heat exchange efficiency of the lower heat exchange pipe is improved. This, in turn, improves the overall heat exchange efficiency of the heat exchanger, thereby enhancing the overall operating efficiency of the multi-split air conditioning system.

[0041] Furthermore, by adding a lower-level fan, the airflow of the outdoor unit becomes more uniform, thereby improving the matching degree between the airflow at the bottom of the heat exchanger and the refrigerant flow in each flow path of the lower heat exchange pipe. This makes the lower heat exchange pipe less prone to frost formation, thus enhancing the steady-state heating capacity of the multi-split air conditioning system. Attached Figure Description

[0042] The preferred embodiments of the present invention are described below with reference to the accompanying drawings, in which:

[0043] Figure 1 This is a schematic diagram of the outdoor unit in Embodiment 1 of the present invention;

[0044] Figure 2 This is a flowchart of the main steps of the control method for the multi-split air conditioning system in Embodiment 2 of the present invention;

[0045] Figure 3 This is a flowchart illustrating the specific steps of the control method for the multi-split air conditioning system in Embodiment 2 of the present invention;

[0046] 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 Implementation

[0047] Preferred embodiments of the present invention will now be described with reference to the accompanying drawings. Those skilled in the art should understand that these embodiments are merely illustrative of the technical principles of the invention and are not intended to limit the scope of protection of the invention. Those skilled in the art can make adjustments as needed to adapt to specific applications.

[0048] It should be noted that in the description of this invention, terms such as "upper," "lower," "left," and "right," indicating directional or positional relationships, are based on the directional or positional relationships shown in the accompanying drawings. These are merely for ease of description and do not indicate or imply that the device or element must have a specific orientation, or be constructed and operated in a specific orientation; therefore, they should not be construed as limitations on this invention. Furthermore, the terms "first," "second," "third," and "fourth" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0049] Furthermore, it should be noted that, in the description of this invention, unless otherwise explicitly specified and limited, the terms "connected," "linked," and "connected" should be interpreted broadly. For example, they can refer to a fixed connection or a detachable connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0050] Example 1

[0051] To address the issue of low refrigerant flow and air volume at the bottom of the heat exchanger, resulting in low heat exchange efficiency at the bottom of the heat exchanger, which in turn leads to low overall heat exchange efficiency of the outdoor unit heat exchanger and consequently low overall operating efficiency of the multi-split air conditioning system.

[0052] like Figure 1 As shown, this embodiment discloses a multi-split air conditioning system, which includes a control system, an outdoor unit, and several indoor units. Each indoor unit is connected to the outdoor unit through pipes. The control system controls the outdoor unit and indoor units to cool or heat the indoor units. Specifically, the outdoor unit includes a casing 1, a heat exchanger, a fan, and a support frame. The casing 1 has an air inlet on its side (not shown in the figure), an air outlet on its top (not shown in the figure), and a base plate 7 fixed to the bottom of the casing 1 to form an installation space.

[0053] The heat exchanger is located within the installation space and fixed to the base 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 to the base plate 7. The upper and lower heat exchange pipes 21 and 22 form an air duct 23, the cross-section of which is rectangular, but can also be circular or other shapes. A first defrost temperature sensor (not shown in the figure) is installed on the upper heat exchange pipe 21, which can transmit the temperature Tdef1 of the upper heat exchange pipe 21 to the multi-split air conditioning system control system. A second defrost temperature sensor (not shown in the figure) is installed on the lower heat exchange pipe 22, which can transmit the temperature Tdef2 of the lower heat exchange pipe 22 to the multi-split air conditioning system control system.

[0054] like Figure 1 As shown, depending on different operating conditions, the outdoor unit's fan can be set to a single-layer or double-layer fan to improve the uniformity of the airflow inside the outdoor unit. When the overall height of the heat exchanger is low, the ratio of the wind speed at the top of the upper heat exchange pipe 21 to the wind speed at the bottom of the lower heat exchange pipe 22 is less than a preset value, and the impact on the overall heat exchange efficiency of the heat exchanger is small. In this case, the fan is set to a single layer. The single-layer fan is installed on the casing 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 casing 1 through the air inlet on the casing 1 under the action of the single-layer fan to exchange heat with the upper heat exchange pipe 21 and the lower heat exchange pipe 22. Then, the heat-exchanged air is discharged from the air outlet of the casing 1.

[0055] When the overall height of the heat exchanger is higher than a certain value, the ratio of the wind speed at the top of the upper heat exchange pipe 21 to the wind speed at the bottom of the upper heat exchange pipe is less than a preset value. At the same time, the ratio of the wind speed at the top of the upper heat exchange pipe 21 to the wind speed at the top of the lower heat exchange pipe 22 is greater than a preset value, and the ratio of the wind speed at the top of the lower heat exchange pipe 22 to the wind speed at the bottom of the lower heat exchange pipe 22 is less than or equal to a preset value. In this case, the fan is designed as a double-layer fan.

[0056] like Figure 1 As shown, the upper fan can be installed inside 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 inside the air duct 23 by a support frame, and is positioned below the upper heat exchange pipe 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. Under the action of the upper fan and the lower fan 4, the outside air enters the housing 1 through the air inlet on the housing 1 and exchanges heat with the upper heat exchange pipe 21 and the lower heat exchange pipe 22. Then, the heat-exchanged air is discharged from the air outlet of the housing 1.

[0057] Compared to existing technologies that rely solely on an upper fan to promote airflow, resulting in a large airflow at the top of the heat exchanger and a small airflow at the bottom, leading to low utilization of the heat exchange tubes at the bottom, this embodiment adds a lower fan 4 below the upper heat exchange pipe 21 to the outdoor unit. This increases the airflow in the lower heat exchange pipe 22, uniforms the airflow, and improves the heat exchange efficiency of the lower heat exchange pipe 22, thereby improving the overall heat exchange efficiency of the heat exchanger and consequently the overall operating efficiency of the multi-split air conditioning system. Furthermore, the addition of the lower fan 4 makes the airflow of the outdoor unit more uniform, improving the matching degree between the airflow at the bottom of the heat exchanger and the refrigerant flow in each flow path at the bottom of the heat exchanger. This makes the bottom of the heat exchanger less prone to frost formation, thus enhancing the steady-state heating capacity of the multi-split air conditioning system.

[0058] like Figure 1 As shown, specifically, the upper fan includes a first guide ring 32 and a first fan 31 mounted on the first guide ring 32. The first fan 31 is located at the air outlet of the air duct 23. The first fan 31 draws outside air into the air duct 23 from the air inlet of the housing 1 and discharges it from the air outlet of the air duct 23, exchanging heat with the upper heat exchange pipe 21. The first guide ring 32 is detachably mounted on the housing 1 by bolts, so that the first fan 31 can be removed for maintenance.

[0059] The lower fan 4 draws outside air into the air duct 23 through the air inlet of the casing 1, where it exchanges heat with the lower heat exchange pipe 22. The heat-exchanged air is then discharged from the air outlet of the air duct 23. The lower fan 4 can be coaxially or non-coaxially arranged with the first fan 31. Both arrangements allow the first fan 31 and the lower fan 4 to form a series air outlet, increasing the speed at which outside air enters the air duct 23 and improving the heat exchanger's efficiency. Coaxial arrangement of the first fan 31 and the lower fan 4 provides better airflow guidance, reduces turbulence within the air duct 23, and lowers noise generated during outdoor unit operation.

[0060] Furthermore, the upper fan also includes a second guide ring 34 and a second fan 33 mounted on the second guide ring 34. The second fan 33 has the same installation height and blade diameter as the first fan 31. Both the second fan 33 and the first fan 31 are located at the air outlet of the air duct 23, thereby increasing the airflow through the upper heat exchange pipe 21. Depending on the actual application conditions, the designer can increase or decrease the number of upper fans. In this embodiment, two upper fans are used for explanation. Specifically, the first fan 31 and the second fan 33 are not coaxially arranged with the lower fan 4, making the airflow from the first fan 31 and the second fan 33 more uniform. The second guide ring 34 is detachably mounted on the housing 1 to facilitate the removal of the second fan 33 for maintenance.

[0061] like Figure 1As shown, within the air duct 23, the lower fan 4 is mounted below the upper fan via a support frame, and is located below the upper heat exchange pipe 21. Adding the lower fan 4 increases the airflow through the lower heat exchange pipe 22, resulting in a more uniform airflow across the outdoor unit. This more uniform airflow improves the heat exchange efficiency of the lower heat exchange pipe 22, enhancing the overall efficiency of the heat exchanger and thus improving the overall operating efficiency of the multi-split air conditioning system. Furthermore, it improves the matching between the airflow in the lower heat exchange pipe 22 and the refrigerant flow in the lower flow paths of the heat exchanger, reducing the likelihood of frost buildup on the lower heat exchange pipe 22 and further enhancing the steady-state heating capacity of the multi-split air conditioning system.

[0062] In addition, the wind speed distribution, required air volume, and fan diameter of the upper heat exchange pipe 21 and the lower heat exchange pipe 22 can be obtained by the following method:

[0063] The heat exchanger is divided into n equal sections from top to bottom. Sections 1 to k are the upper heat exchange pipes 21, and sections k to n are the lower heat exchange pipes 22. The total air volume Q required for heat exchange in the heat exchanger is... 总 The wind speed distribution in each equal part of the heat exchanger: v1, v2, v3, ... v n-1 v n The wind speed distribution in each equal part of the heat exchanger can be obtained through fluid simulation calculations or experimental tests.

[0064] According to n, Q 总 v1, v2, v3, ... v n-1 v n The wind speed distribution, required air volume, and diameter of the fan in the upper heat exchange pipe 21 and lower heat exchange pipe 22 are determined.

[0065] When the fan is designed as a single-layer fan, the average air velocity of the upper heat exchange pipe 21 is:

[0066]

[0067] The average wind speed of the lower heat exchange pipe 22 is:

[0068]

[0069] k can be any value from 1 to n.

[0070] Furthermore, given the wind speed distribution of the upper heat exchange pipe 21 and the lower heat exchange pipe 22, the total air volume required for the upper heat exchange pipe 21 and the lower heat exchange pipe 22 can be calculated.

[0071] The total air volume required for the upper heat exchange pipe 21 is: Q 上总 =MQ 总 / (M+N);

[0072] 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.

[0073] When using a single-layer fan, the fan diameter is D0, and the fan diameter of the single-layer fan should satisfy the following relationship:

[0074]

[0075] Where a1, a2, a3, b1, b2, and b3 are all constants that can be obtained through fluid simulation calculations. Determining the fan diameter of a single-layer fan using the formula allows the fan to better meet operational requirements, improves air intake efficiency, and thus further enhances the heat exchanger's heat exchange efficiency.

[0076] When the fan is designed as a double-layer fan, the total air volume required for the upper heat exchange pipe 21 is: Q 上总 =kQ 总 / n;

[0077] The total air volume required for the 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 overall heat exchange efficiency of the heat exchanger.

[0078] Furthermore, 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.

[0079] The fan diameters of the upper fan and the lower fan 4 should meet the following relationship:

[0080]

[0081] Where c1, c2, c3, d1, d2, and d3 are all constants that can be obtained through fluid simulation calculations. Determining the fan diameters of the upper and lower fans using the formula allows the fans of the upper and lower fans to better meet operational requirements, improve air intake efficiency, and thus further enhance the heat exchanger's heat exchange efficiency.

[0082] like Figure 1 As shown, the outdoor unit further includes compressor 6, gas-liquid separator, oil separator, four-way valve and refrigerant piping, which are essential components for realizing the basic functions of the multi-split air conditioning system. Compressor 6, gas-liquid separator, oil separator and 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 casing 1.

[0083] The support frame includes a fan cover 51, a sound insulation layer 53 fixed to the fan cover 51, and several columns 52. The lower fan 4 is installed on the fan cover 51, and the end of the column 52 away from the fan cover 51 is fixed to the base plate 7, which allows the lower fan 4 to be installed more stably 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 sound insulation cotton, centrifugal glass wool, or damping sound-absorbing material. The sound insulation layer 53 reduces the noise emitted by the compressor 6, gas-liquid separator, and oil separator, thereby reducing the noise transmitted to the environment by the outdoor unit during operation.

[0084] As another preferred embodiment, a sound insulation layer 53 can also be adhered to the outer wall 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.

[0085] Example 2

[0086] This embodiment discloses a control method for a multi-split air conditioning system, wherein the multi-split air conditioning system is the one described in Embodiment 1. Figure 2 As shown, the control method for a multi-split air conditioning system includes the following steps:

[0087] 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 speed of the upper fan and the lower fan 4 are controlled according to the difference between Tdef1 and Tdef2 to adjust the air field of the outdoor unit.

[0088] This allows the refrigerant volume and air volume passing through the upper heat exchange pipe 21 and the lower heat exchange pipe 22 to be better matched, thus enabling both the upper heat exchange pipe 21 and the lower heat exchange pipe 22 to 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 operate more efficiently.

[0089] like Figure 3 As shown, the control method includes the following specific steps:

[0090] The temperature Tdef1 of the upper heat exchange pipe 21 and the temperature Tdef2 of the lower heat exchange pipe 22 are obtained. The speed of the upper fan and the lower fan 4 is controlled based on the difference between Tdef1 and Tdef2 to adjust the airflow of the outdoor unit and make the airflow more uniform. In the initial state, the upper fan and the lower fan 4 are started and rotated at the set speed. The first fan 31 and the second fan 33 of the upper fan start and stop simultaneously and rotate at the same speed.

[0091] When Tdef1-Tdef2>1℃, in this embodiment, the first preset value is selected as 1℃. That is, when Tdef1-Tdef2>1℃, the temperature of the upper heat exchange pipe 21 is higher than that of the lower heat exchange pipe 22. In other words, the refrigerant flow rate and air volume of the lower heat exchange pipe 22 are not well matched. Therefore, the speed of the lower fan 4 is increased to increase the air volume flowing through the lower heat exchange pipe 22, so as to improve the matching degree of refrigerant flow rate and air volume of the lower heat exchange pipe 22 and improve the heat exchange efficiency of the lower heat exchange pipe 22.

[0092] When Tdef1-Tdef2 < the second preset value, in this embodiment the second preset value is selected as -1℃. That is, when Tdef1-Tdef2 < -1℃, the temperature of the upper heat exchange pipe 21 is lower than the temperature of the lower heat exchange pipe 22. In other words, the refrigerant flow rate and air volume of the upper heat exchange pipe 21 are not well matched. Therefore, the speed of the upper fan is increased to increase the air volume flowing through the upper heat exchange pipe 21, so as to improve the matching degree of refrigerant flow rate and air volume of the upper heat exchange pipe 21 and improve the heat exchange efficiency of the upper heat exchange pipe 21.

[0093] The technical solution of the present invention has been described above with reference to the preferred embodiments shown in the accompanying drawings. However, it will be readily understood by those skilled in the art that the scope of protection of the present invention is obviously not limited to these specific embodiments. Without departing from the principles 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 such changes or substitutions will all fall within the scope of protection of the present invention.

Claims

1. An outdoor unit characterized by comprising: The heat exchanger and the fan are included, the heat exchanger is divided into n paths from top to bottom, the first path to the kth path are upper heat exchange paths (21), the kth path to the nth path are lower heat exchange paths (22), the heat exchanger exchanges heat with total air volume Q 总 , the air velocity distribution of each aliquot 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; the fan is designed as a single-layer fan, and the average wind speed of the upper heat exchange pipeline (21) is: The average air speed of the lower heat exchange pipeline (22) is: The total air amount required by the upper heat exchange pipeline (21) is Q 上总 = MQ 总 / (M+N); The total air required for the lower heat exchanger line (22) is: Q 下总 = NQ 总 / (M+N); When the fan is 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: Wherein, a1, a2, a3, b1, b2 and b3 are constants.

2. The outdoor unit according to claim 1, characterized by The fan is designed as a double-layer fan, and the fan includes an upper fan and a lower fan (4); The total air amount required for the upper heat exchange pipeline (21) is Q 上总 = kQ 总 / n; The total air required for the lower heat exchanger line (22) is: Q 下总 = (n - k)Q 总 / n; The fan diameter of the upper fan is D1, and the fan diameter of the lower fan (4) is D2; The fan diameter of the upper fan and the lower fan (4) should satisfy the following relationship: Wherein, c1, c2, c3, d1, d2 and d3 are constants.

3. The outdoor unit according to claim 2, characterized by The heat exchanger surrounds to form an air duct (23), and when the fan is a double-layer fan, the upper fan and the lower fan (4) are both arranged in the air duct (23); The outdoor unit further includes 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 includes a fan cover (51) and a plurality of stand columns (52) arranged on the fan cover (51), the stand columns (52) are connected to the shell (1), and the lower fan (4) is arranged on the fan cover (51).

4. The outdoor unit according to claim 3, characterized by The support frame further includes a sound insulation layer (53) arranged on the fan cover (51), and the outdoor unit further includes a compressor (6), the compressor (6) is communicated with the heat exchanger through a pipeline, and the compressor (6) is located in a space surrounded by the sound insulation layer (53), the stand columns (52) and the shell (1).

5. A multi-split air conditioning system, characterized in that, The outdoor unit includes the outdoor unit according to any one of claims 1-4.

6. A control method of a multi VRF system, characterized by, The multi-connected air conditioning system includes the outdoor unit according to any one of claims 2-4. The control method includes the following steps: Obtaining the temperature Tdef1 of the upper heat exchange pipeline (21) and the temperature Tdef2 of the lower heat exchange pipeline (22), and controlling the rotating speed of the upper fan and the lower fan (4) according to the difference between Tdef1 and Tdef2 to adjust the wind field of the outdoor unit.

7. The control method of a multi VRF air conditioning system according to claim 6, wherein, "Obtaining the temperature Tdef1 of the upper heat exchange pipeline (21) and the temperature Tdef2 of the lower heat exchange pipeline (22), and controlling the rotating speed of the upper fan and the lower fan (4) according to the difference between Tdef1 and Tdef2 to adjust the wind field of the outdoor unit" specifically includes the following steps: When Tdef1-Tdef2>the first preset value, the rotating speed of the lower fan (4) is increased to increase the air volume of the lower heat exchange pipeline (22); When Tdef1-Tdef2<the second preset value, the rotating speed of the upper fan is increased to increase the air volume of the upper heat exchange pipeline (21).

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