Fresh air handling units, air conditioning systems and their control methods

Abstract

This invention provides a fresh air handling unit, an air conditioning system, and a control method thereof. The fresh air handling unit includes a housing; an indirect evaporative cooler; a water collection pan; and a surface cooler. The surface cooler is inclinedly disposed within the housing, with its lower end resting on the water collection pan, and its upper end sealed to the housing. The fresh air handling unit, air conditioning system, and control method provided by this invention utilize an indirect evaporative cooler to perform a single heat exchange between fresh air and return air. The fresh air is cooled by the indirect evaporative cooler and does not come into contact with condensate. Therefore, the dehumidification and cooling requirements at the surface cooler are relatively low, reducing the heat exchange and dehumidification demands of the surface cooler. Furthermore, by inclinedly disposing of the surface cooler, the heat exchange area is increased, thereby increasing the heat exchange effect of the surface cooler and ultimately increasing the heat exchange efficiency of the fresh air handling unit.

Description

Technical Field

[0001] This invention relates to the field of air handling equipment technology, and in particular to a fresh air handling unit, an air conditioning system and its control method. Background Technology

[0002] To improve the overall energy efficiency ratio of an air conditioning system, each degree Celsius increase in the chiller's outlet water temperature significantly improves its energy efficiency ratio. Therefore, medium-temperature water-cooled air conditioning systems (chilled water inlet / outlet temperatures of 12℃ / 17℃) offer better energy savings compared to conventional water-cooled systems (chilled water inlet / outlet temperatures of 7℃ / 12℃). However, in hot summer regions, medium-temperature water systems often fail to achieve the desired effect when handling high-temperature, high-humidity fresh air, unable to efficiently bring the air to its dew point temperature. Therefore, efficient heat recovery is the primary solution to address these issues.

[0003] In existing technologies, the working air, which is used as return air, undergoes two direct evaporative heat exchange processes with water. After each heat exchange, the air is indirectly pre-cooled by the fresh air. Then, the fresh air undergoes another direct evaporative heat exchange with water to further cool it down before finally being delivered through a surface cooler. However, the size requirements of the fresh air handling unit limit the size of the surface cooler, resulting in low heat exchange efficiency. Summary of the Invention

[0004] To address the technical problem of low heat exchange efficiency in fresh air handling units, a fresh air handling unit, an air conditioning system, and a control method thereof are provided, in which the surface cooler is tilted to increase heat exchange efficiency.

[0005] Therefore, the present invention provides a fresh air handling unit, comprising:

[0006] The housing is provided with a fresh air inlet, a fresh air outlet, a return air inlet, and a return air outlet.

[0007] An indirect evaporative cooler is disposed within the housing, and a return air duct and a fresh air duct are formed within the indirect evaporative cooler. The return air duct is connected to the return air inlet and the return air outlet, and the fresh air duct is connected to the fresh air inlet and the fresh air outlet.

[0008] The surface cooler is inclinedly disposed within the housing and is located between the indirect evaporative cooler and the fresh air outlet.

[0009] The fresh air handling unit also includes a water receiving tray, which is located between the indirect evaporative cooler and the surface cooler. The lower end of the surface cooler is disposed on the water receiving tray, and the upper end of the surface cooler is disposed on the housing.

[0010] The number of surface coolers is at least two. All surface coolers are distributed in an inverted truncated shape between the water receiving tray and the fresh air outlet. The lower end of each surface cooler is located on the water receiving tray, and the upper end of each surface cooler is located on the housing.

[0011] The number of surface coolers is four, and the four surface coolers are distributed in an inverted frustum shape between the water receiving tray and the fresh air outlet, with each surface cooler located on one side of the inverted frustum shape.

[0012] The housing has a cuboid structure, and the upper edge of the surface cooler is parallel to the inner wall of the adjacent housing.

[0013] The angle between the plane where the surface cooler is located and the horizontal plane ranges from 30° to 50°.

[0014] The fresh air handling unit also includes an air valve, which is located between the upper end of the surface cooler and the housing.

[0015] There are multiple surface coolers, and each surface cooler is provided with an air valve between its upper end and the housing.

[0016] The upper ends of all the surface coolers together form a surface cooler air outlet, and the ratio of the flow area of ​​the surface cooler air outlet to the sum of the flow areas of all the air valves is in the range of 1:1 to 1:1.1.

[0017] The outlet of the water receiving tray is connected to the water inlet of the indirect evaporative cooler.

[0018] The indirect evaporative cooler includes:

[0019] shell;

[0020] An evaporative cooling core is disposed inside the outer shell, and the return air channel is formed between the evaporative cooling core and the inner surface of the outer shell, and the fresh air channel is formed inside the evaporative cooling core.

[0021] A water distributor is located above the evaporative cooling core, and the water outlet of the water distributor faces the evaporative cooling core.

[0022] The outlet of the water receiving tray is connected to the inlet of the water distributor.

[0023] The evaporative cooling core includes multiple heat exchange tubes, all of which are disposed inside the outer shell. The interior of each heat exchange tube forms the fresh air channel, and the heat exchange tube and the outer shell form the return air channel.

[0024] The fresh air handling unit also includes a fresh air fan, which is located between the fresh air outlet and the surface cooler.

[0025] The fresh air unit also includes an indoor fresh air outlet, which is connected to the fresh air outlet via a duct.

[0026] An air conditioning system comprising the aforementioned fresh air handling unit.

[0027] The air conditioning system also includes a refrigeration unit and an indoor unit. The refrigeration unit is connected to the surface cooler to form a first heat exchange cycle, and the indoor unit is connected to the refrigeration unit to form a second heat exchange cycle.

[0028] A control method for the above-mentioned air conditioning system, wherein the fresh air handling unit further includes an air valve, the air valve being disposed between the upper end of the surface cooler and the housing, the method comprising:

[0029] Obtain the gas temperature and humidity parameters of the fresh air handling unit;

[0030] The working state of the air valve is controlled according to the gas temperature parameters and the gas humidity parameters.

[0031] The gas temperature parameters include at least the indoor target temperature T0, the outdoor fresh air temperature Tw, the indoor temperature Tn, and the preset temperature difference ΔT;

[0032] The gas humidity parameters include at least the indoor target relative humidity φ0, the outdoor fresh air humidity φw, the indoor humidity φn, and the preset humidity difference △φ.

[0033] The method of controlling the operating state of the air valve based on the gas temperature parameters and the gas humidity parameters further includes:

[0034] If the gas temperature parameter and the gas humidity parameter meet the first preset condition, then control the air valve to switch to the closed state.

[0035] The first preset condition is that |Tn-T0|>△T and |φn-φ0|>△φ.

[0036] The fresh air handling unit also includes a refrigeration unit, which is connected to the surface cooler to form a first heat exchange cycle. The method further includes:

[0037] If Tn-T0>0, then increase the operating frequency of the refrigeration unit.

[0038] The fresh air handling unit further includes a fresh air fan, which is disposed between the fresh air outlet and the surface cooler. The method further includes:

[0039] If Tn-T0 < 0, then reduce the operating frequency of the fresh air fan.

[0040] The fresh air handling unit also includes a refrigeration unit, which is connected to the surface cooler to form a first heat exchange cycle. After reducing the operating frequency of the fresh air fan, it also includes:

[0041] When the operating frequency of the fresh air fan is reduced to the minimum operating frequency, if Tn-T0<0, then the operating frequency of the refrigeration unit should be reduced.

[0042] The fresh air handling unit also includes an indoor unit, and the method further includes:

[0043] If Tw > Tn, then the indoor unit will operate.

[0044] If Tw ≤ Tn, then the indoor unit will stop working.

[0045] The fresh air handling unit, air conditioning system and control method provided by the present invention use an indirect evaporative cooler to perform a heat exchange between fresh air and return air. The fresh air is cooled by the indirect evaporative cooler and does not come into contact with condensate. At this time, the dehumidification and cooling requirements at the surface cooler are small, reducing the heat exchange and dehumidification requirements of the surface cooler. Furthermore, by tilting the surface cooler, the heat exchange area of ​​the surface cooler is increased, thereby increasing the heat exchange effect of the surface cooler and thus increasing the heat exchange efficiency of the fresh air handling unit. Attached Figure Description

[0046] Figure 1 This is a schematic diagram of the structure of a fresh air handling unit provided in an embodiment of the present invention;

[0047] Figure 2 This is a top view of a fresh air handling unit provided in an embodiment of the present invention;

[0048] Figure 3 This is a schematic diagram of the structure of the evaporator cooling core provided in an embodiment of the present invention;

[0049] Figure 4 This is a schematic diagram of the structure of an air conditioning system provided in an embodiment of the present invention;

[0050] In the picture:

[0051] 1. Shell; 11. Fresh air inlet; 12. Fresh air outlet; 13. Return air inlet; 14. Return air outlet; 2. Indirect evaporative cooler; 21. Return air duct; 22. Fresh air duct; 3. Drain tray; 4. Surface cooler; 5. Air valve; 23. Outer shell; 24. Evaporative cooling core; 25. Water distributor; 241. Heat exchange tube; 242. Fins; 6. Fresh air fan; 7. Indoor unit. Detailed Implementation

[0052] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are for illustrative purposes only and are not intended to limit the invention.

[0053] like Figures 1 to 4 The fresh air handling unit shown includes: a housing 1, on which a fresh air inlet 11, a fresh air outlet 12, a return air inlet 13, and a return air outlet 14 are provided; an indirect evaporative cooler 2, which is disposed inside the housing 1, and a return air passage 21 and a fresh air passage 22 are formed inside the indirect evaporative cooler. The return air passage 21 is connected to the return air inlet 13 and the return air outlet 14, and the fresh air passage 22 is connected to the fresh air inlet 11 and the fresh air outlet 12. The fresh air outlet 12 is located above the indirect evaporative cooler 2; and a surface cooler 4, which is inclinedly disposed inside the housing 1 and is located between the indirect evaporative cooler 2 and the fresh air outlet 12. An indirect evaporative cooler 2 is used to perform a heat exchange between the fresh air and the return air. The fresh air is cooled by the indirect evaporative cooler 2 and does not come into contact with the condensate. At this time, the dehumidification and cooling requirements of the surface cooler 4 are small, reducing the heat exchange and dehumidification requirements of the surface cooler 4. Furthermore, by tilting the surface cooler 4, the heat exchange area of ​​the surface cooler 4 is increased, thereby increasing the heat exchange effect of the surface cooler 4 and thus increasing the heat exchange efficiency of the fresh air unit.

[0054] The fresh air handling unit also includes a water collection tray 3, which is located between the indirect evaporative cooler 2 and the surface cooler 4. The lower end of the surface cooler 4 is mounted on the water collection tray 3, and the upper end of the surface cooler 4 is mounted on the housing 1. The water collection tray 3 collects the condensate from the surface cooler 4, preventing the condensate from dripping onto the indirect evaporative cooler 2 and affecting its normal operation.

[0055] When the fresh air handling unit is working, return air enters the return air duct 21 through the return air inlet 13 and undergoes evaporative heat exchange with the water in the return air duct 21, thereby effectively reducing the temperature of the fresh air duct 22. The returned air after heat exchange is discharged from the casing 1 through the return air outlet 14. Fresh air enters the fresh air duct 22 through the fresh air inlet 11. After being cooled by the return air and water in the fresh air duct 22, it is further cooled by the surface cooler 4 and finally discharged from the casing 1 through the fresh air outlet 12. Since the fresh air has been cooled by the indirect evaporative cooler 2 and has not come into contact with the condensate, the dehumidification and cooling requirements at the surface cooler 4 are relatively small. That is, the required heat exchange area of ​​the surface cooler 4 is relatively small. At the same time, the surface cooler 4 is set at an angle to maximize its heat exchange area, thereby increasing the heat exchange efficiency of the fresh air handling unit while keeping the volume of the casing 1 unchanged.

[0056] The fresh air inlet 11 is located below the indirect evaporative cooler 2, the return air inlet 13 is located on one side of the indirect evaporative cooler 2, and the return air outlet 14 is located on the other side of the indirect evaporative cooler 2.

[0057] In one implementation, the number of surface coolers 4 is at least two. All surface coolers 4 are arranged in an inverted frustum shape between the water receiving tray 3 and the fresh air outlet 12, with the lower end of each surface cooler 4 positioned on the water receiving tray 3 and the upper end of each surface cooler 4 positioned on the housing 1. Without changing the size of the housing 1, the number of surface coolers 4 is increased as much as possible, thereby increasing the overall heat exchange area of ​​the surface coolers 4 and thus increasing the heat exchange efficiency of the fresh air handling unit.

[0058] The frustum shape includes a truncated pyramid shape and a frustum shape. An inverted frustum shape refers to a frustum shape where the smaller base area is used as the lower base area and the larger base area is used as the upper base area. In this embodiment, the water receiving tray 3 forms the lower surface of the frustum shape, while the upper ends of the surface coolers 4 together form the upper surface of the frustum shape.

[0059] Taking the platform shape as a frustum as an example, there are four surface coolers 4. The four surface coolers 4 are distributed in an inverted frustum shape between the water receiving tray 3 and the fresh air outlet 12, and each surface cooler 4 is located on one side of the inverted frustum shape.

[0060] Preferably, the housing 1 has a cuboid structure, and the upper edge of the surface cooler 4 is parallel to the inner wall of the adjacent housing 1. By making full use of the cuboid structure of the housing 1, the shape of the surface cooler 4 is made as compatible as possible with the shape of the housing 1, thereby increasing the size of the surface cooler 4 to increase its heat exchange area and improve the heat exchange efficiency of the fresh air unit.

[0061] The angle between the plane containing the surface cooler 4 and the horizontal plane ranges from 30° to 50°. Preferably, the angle is 40°. When the angle is less than 30°, the tilt angle of the surface cooler 4 is too small. Compared to a horizontally placed surface cooler 4, with the same cross-sectional area of ​​the shell 1, the increase in the heat exchange area of ​​the surface cooler 4 is small, and it cannot effectively improve the heat exchange efficiency of the fresh air handling unit. When the angle is greater than 50°, the tilt angle of the surface cooler 4 is too large. Compared to a horizontally placed surface cooler 4, with the same height of the shell 1, the increase in the heat exchange area of ​​the surface cooler 4 is small, and it cannot effectively improve the heat exchange efficiency of the fresh air handling unit. Only when the angle is within the range of 30° to 50° is the heat exchange area of ​​the surface cooler 4 increased significantly, which can meet the purpose of improving the heat exchange efficiency of the surface cooler 4, thereby improving the heat exchange efficiency of the fresh air handling unit.

[0062] The fresh air handling unit also includes a damper 5, which is located between the upper end of the surface cooler 4 and the housing 1. By short-circuiting the surface cooler 4 using the damper 5, the fresh air discharged from the fresh air duct 22 can flow directly through the damper 5 to the fresh air outlet 12, without passing through the surface cooler 4. When the outdoor fresh air temperature and indoor temperature at the location of the fresh air handling unit are not significantly different, fresh air can be directly introduced into the room. By opening the damper 5, the fresh air directly enters the fresh air outlet 12, achieving the purpose of supplying fresh air into the room, effectively reducing wind resistance, and thus reducing the energy consumption of the fresh air handling unit.

[0063] Optionally, there are multiple surface coolers 4, and each surface cooler 4 is provided with an air valve 5 between its upper end and the housing 1. The air valve 5 is used to short-circuit the corresponding surface cooler 4, so as to minimize the wind resistance generated when fresh air flows through the surface cooler 4, thereby increasing the air volume and air velocity of the fresh air unit and improving the heat exchange efficiency of the fresh air unit.

[0064] Preferably, the upper ends of all the surface coolers 4 together form a surface cooler air outlet, and the ratio of the flow area of ​​the surface cooler air outlet to the sum of the flow areas of all the air valves 5 is in the range of 1:1 to 1:1.1. Due to the wind resistance at the surface cooler 4, most of the airflow passes through the air valves 5, effectively reducing wind resistance and thus reducing the energy consumption of the fresh air unit.

[0065] The outlet of the water receiving pan 3 is connected to the water inlet of the indirect evaporative cooler 2, that is, the condensate from the surface cooler 4 collected in the water receiving pan 3 is used as the water source for the indirect evaporative cooler 2, reducing the use of external water sources, thereby reducing the use of driving components such as water pumps, achieving the purpose of reducing the energy consumption of the fresh air unit. The wastewater of the fresh air unit is also rationally utilized, and the low temperature advantage of the condensate can further reduce the cooling capacity required when cooling the fresh air, further reducing the energy consumption of the fresh air unit.

[0066] The indirect evaporative cooler 2 includes: a shell 23; an evaporative cooling core 24 disposed inside the shell 23, with a return air channel 21 formed between the evaporative cooling core 24 and the inner surface of the shell 23, and a fresh air channel 22 formed inside the evaporative cooling core 24; a water distributor 25 located above the evaporative cooling core 24, with the water outlet of the water distributor 25 facing the evaporative cooling core 24; and the outlet of the water receiving tray 3 connected to the inlet of the water distributor 25. Return air enters the return air channel 21 from the outside of the shell 23 and exchanges heat with the water supplied to the return air channel 21 by the water distributor 25, thereby reducing the temperature of the fresh air channel 22. The returned air, after heat exchange, is discharged from the shell 23, completing the heat exchange of the return air. Fresh air enters the fresh air channel 22 from the outside of the shell 23, is cooled within the fresh air channel 22, and is finally discharged from the shell 23, completing the fresh air cooling process.

[0067] The evaporative cooling core 24 includes multiple heat exchange tubes 241, all of which are disposed inside the outer shell 23. The interior of each heat exchange tube 241 forms the fresh air channel 22, and the heat exchange tube 241 and the outer shell 23 form the return air channel 21.

[0068] The evaporative cooling core 24 also includes multiple fins 242, all of which are disposed on the heat exchange tube 241, and a return air channel 21 is formed between two fins 242. The fins 242 are used to further increase the evaporative heat exchange effect between the return air and the water, thereby improving the cooling effect of the evaporative cooling core 24 on the fresh air.

[0069] The fresh air handling unit also includes a fresh air fan 6, which is positioned between the fresh air outlet 12 and the surface cooler 4. The fresh air fan 6 can generate negative pressure at the fresh air outlet 12, thereby forcing outdoor fresh air to flow sequentially through the fresh air inlet 11, the fresh air duct 22, and the surface cooler 4 (or the damper 5) to the fresh air fan 6, and finally exhaust it into the room through the drive of the fresh air fan 6, thus completing the supply of fresh air. Positioning the fresh air fan 6 above the surface cooler 4 allows for full utilization of the height dimension of the housing 1, thereby reducing the area occupied by the housing 1.

[0070] The fresh air unit also includes an indoor fresh air outlet, which is connected to the fresh air outlet 12 via a duct. A duct connects the indoor fresh air outlet and the fresh air outlet 12.

[0071] An air conditioning system comprising the aforementioned fresh air handling unit.

[0072] The air conditioning system also includes a refrigeration unit, which is connected to the surface cooler 4 to form a first heat exchange cycle. The refrigeration unit can provide chilled water to the surface cooler 4 so that the surface cooler 4 can cool the fresh air.

[0073] The fresh air handling unit also includes an indoor unit 7, which is connected to the refrigeration unit to form a second heat exchange cycle. The indoor unit 7 can directly regulate the indoor temperature and humidity without supplying fresh air.

[0074] A control method for the above-mentioned air conditioning system, wherein the fresh air handling unit further includes an air valve 5, the air valve 5 being disposed between the upper end of the surface cooler 4 and the housing 1, the method comprising:

[0075] Obtain the gas temperature and humidity parameters of the fresh air handling unit;

[0076] The operating state of the air valve 5 is controlled based on the gas temperature and humidity parameters. This allows the fresh air handling unit to adjust the operating state of the air valve 5 according to different indoor and outdoor conditions, thereby controlling whether the surface cooler 4 operates and minimizing the energy consumption of the fresh air handling unit.

[0077] The gas temperature parameters include at least the indoor target temperature T0, the outdoor fresh air temperature Tw, the indoor temperature Tn, and the preset temperature difference ΔT;

[0078] The gas humidity parameters include at least the indoor target relative humidity φ0, the outdoor fresh air humidity φw, the indoor humidity φn, and the preset humidity difference △φ.

[0079] The process of controlling the operating state of the air valve 5 based on the gas temperature parameters and the gas humidity parameters also includes:

[0080] If the gas temperature parameter and the gas humidity parameter meet the first preset condition, then control the air valve 5 to switch to the closed state.

[0081] The first preset condition is |Tn-T0|>△T and |φn-φ0|>△φ. This indicates that the outdoor fresh air condition is poor and the indoor condition is good. At this time, the fresh air unit needs to use the surface cooler 4 to cool the fresh air. Therefore, the air valve 5 is closed so that the fresh air must flow through the surface cooler 4 to achieve the cooling of the fresh air.

[0082] The fresh air handling unit also includes a refrigeration unit, which is connected to the surface cooler 4 to form a first heat exchange cycle. The method further includes:

[0083] If Tn-T0>0, it means that the indoor temperature Tn is higher than the target indoor temperature T0 and the difference is large. In this case, the operating frequency of the refrigeration unit is increased to further reduce the temperature of the chilled water, thereby further reducing the temperature of the fresh air passing through the surface cooler 4 and thus further reducing the indoor temperature.

[0084] The fresh air handling unit further includes a fresh air fan 6, which is disposed between the fresh air outlet 12 and the surface cooler 4. The method further includes:

[0085] If Tn-T0<0, it indicates that the indoor temperature Tn is lower than the target indoor temperature T0 and the difference is large. Therefore, the operating frequency of the fresh air fan 6 is reduced to gradually reduce the amount of fresh air supplied to the room, thereby reducing the cooling effect on the indoor temperature.

[0086] The fresh air handling unit also includes a refrigeration unit, which is connected to the surface cooler 4 to form a first heat exchange cycle. After reducing the operating frequency of the fresh air fan 6, it also includes:

[0087] If Tn-T0<0, it means that reducing the operating frequency of the fresh air fan 6 cannot increase the indoor temperature. Therefore, the operating frequency of the chiller is reduced, the temperature of the chilled water is increased, and the temperature of the fresh air passing through the surface cooler 4 is increased, thereby reducing the cooling effect on the indoor temperature.

[0088] In particular, when the operating frequency of the fresh air fan 6 is reduced to the minimum operating frequency, it is no longer possible to reduce the operating frequency of the fresh air fan 6, so the only option is to reduce the operating frequency of the chiller unit.

[0089] The fresh air handling unit also includes an indoor unit 7, which is connected to the refrigeration unit to form a second heat exchange cycle. The indoor unit 7 can regulate the indoor temperature and humidity without supplying fresh air into the room. The method further includes:

[0090] If Tw > Tn, the temperature of the outdoor fresh air is too high, and the indoor unit 7 needs to participate in cooling the indoor air. In this case, the indoor unit 7 will be controlled to work.

[0091] If Tw≤Tn, the outdoor fresh air temperature is low, and indoor unit 7 is not needed to cool the indoor air. Therefore, indoor unit 7 is controlled to stop working.

[0092] The process of controlling the operating state of the air valve 5 based on the gas temperature parameters and the gas humidity parameters also includes:

[0093] If the gas temperature parameter and the gas humidity parameter meet the second preset conditions, then control the air valve 5 to switch to the open state.

[0094] The second preset condition includes Tw≤Tn and |Tn-T0|<△T and |φn-φ0|<△φ. At this time, the outdoor temperature is low, and the indoor load can be dissipated through the gaps in the room and other structures. At this time, the surface cooler 4 does not need to work, and the outdoor fresh air can be directly introduced into the room. At this time, the air valve 5 is opened, and the fresh air flows directly through the air valve 5 to the fresh air outlet 12 and is sent into the room, thereby completing the supply of indoor fresh air.

[0095] To avoid frequent adjustments to the fresh air handling unit, the unit should be monitored at set intervals for outdoor fresh air temperature Tw, indoor temperature Tn, outdoor fresh air humidity φw, and indoor humidity φn, and adjustments should be made accordingly based on the monitoring results.

[0096] The preferred time setting is 30 minutes.

[0097] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention. Therefore, the scope of protection of this patent should be determined by the appended claims.

Claims

1. A fresh air handling unit, characterized in that: include: The housing (1) is provided with a fresh air inlet (11), a fresh air outlet (12), a return air inlet (13) and a return air outlet (14). An indirect evaporative cooler (2) is disposed inside the housing (1), and a return air passage (21) and a fresh air passage (22) are formed inside the indirect evaporative cooler (2). The return air passage (21) is connected to the return air inlet (13) and the return air outlet (14), and the fresh air passage (22) is connected to the fresh air inlet (11) and the fresh air outlet (12). The surface cooler (4) is inclinedly disposed inside the housing (1) and the surface cooler (4) is located between the indirect evaporative cooler (2) and the fresh air outlet (12). The fresh air unit also includes a water receiving tray (3), which is located between the indirect evaporative cooler (2) and the surface cooler (4). The lower end of the surface cooler (4) is disposed on the water receiving tray (3), and the upper end of the surface cooler (4) is disposed on the housing (1). The number of surface coolers (4) is four. The four surface coolers (4) are distributed in the shape of an inverted truncated pyramid between the water receiving tray (3) and the fresh air outlet (12). Each surface cooler (4) is located on one side of the inverted truncated pyramid shape. The angle between the plane where the surface cooler (4) is located and the horizontal plane is in the range of 30° to 50°; The fresh air unit also includes a damper (5), which is located between the upper end of the surface cooler (4) and the housing (1). There are multiple surface coolers (4), and each surface cooler (4) is provided with a wind valve (5) between its upper end and the housing (1). The upper ends of all the surface coolers (4) together form a surface cooler air outlet, and the ratio of the flow area of ​​the surface cooler air outlet to the sum of the flow areas of all the air valves (5) is in the range of 1:1 to 1:1.

1.

2. The fresh air handling unit according to claim 1, characterized in that: The housing (1) has a cuboid structure, and the upper edge of the surface cooler (4) is parallel to the inner wall of the adjacent housing (1).

3. The fresh air handling unit according to claim 1, characterized in that: The outlet of the water receiving tray (3) is connected to the water inlet of the indirect evaporative cooler (2).

4. The fresh air handling unit according to claim 3, characterized in that: The indirect evaporative cooler (2) includes: Outer shell (23); An evaporative cooling core (24) is disposed inside the outer shell (23), and the return air channel (21) is formed between the evaporative cooling core (24) and the inner surface of the outer shell (23), and the fresh air channel (22) is formed inside the evaporative cooling core (24). Water distributor (25) is located above the evaporative cooling core (24), and the water outlet of the water distributor (25) is directed toward the evaporative cooling core (24). The outlet of the water receiving tray (3) is connected to the inlet of the water distributor (25).

5. The fresh air handling unit according to claim 4, characterized in that: The evaporative cooling core (24) includes multiple heat exchange tubes (241), all of which are located inside the outer shell (23). The interior of the heat exchange tubes (241) forms the fresh air channel (22), and the heat exchange tubes (241) and the outer shell (23) form the return air channel (21).

6. The fresh air handling unit according to claim 1, characterized in that: The fresh air unit also includes a fresh air fan (6), which is located at the fresh air outlet (12).

7. The fresh air handling unit according to claim 1, characterized in that: The fresh air unit also includes an indoor fresh air outlet, which is connected to the fresh air outlet (12) via a duct.

8. An air conditioning system, characterized in that: The fresh air handling unit includes any one of claims 1 to 7.

9. The air conditioning system according to claim 8, characterized in that: The air conditioning system also includes a refrigeration unit and an indoor unit (7). The refrigeration unit is connected to the surface cooler (4) to form a first heat exchange cycle, and the indoor unit (7) is connected to the refrigeration unit to form a second heat exchange cycle.

10. A control method for an air conditioning system according to claim 8 or 9, characterized in that: The fresh air handling unit also includes a damper (5), which is disposed between the surface cooler (4) and the housing (1). The method includes: Obtain the gas temperature and humidity parameters of the fresh air handling unit; The working state of the air valve (5) is controlled according to the gas temperature parameters and the gas humidity parameters.

11. The method according to claim 10, characterized in that: The gas temperature parameters include at least the indoor target temperature T0, the outdoor fresh air temperature Tw, the indoor temperature Tn, and the preset temperature difference ΔT; The gas humidity parameters include at least the indoor target relative humidity φ0, the outdoor fresh air humidity φw, the indoor humidity φn, and the preset humidity difference △φ.

12. The method according to claim 11, characterized in that: In controlling the working state of the air valve (5) according to the gas temperature parameters and the gas humidity parameters, the following is also included: If the gas temperature parameter and the gas humidity parameter meet the first preset conditions, then control the air valve (5) to switch to the closed state.

13. The method according to claim 12, characterized in that: The first preset condition is that |Tn-T0|>△T and |φn-φ0|>△φ.

14. The method according to claim 13, characterized in that: The fresh air handling unit also includes a refrigeration unit, which is connected to the surface cooler (4) to form a first heat exchange cycle. The method further includes: If Tn-T0>0, then increase the operating frequency of the refrigeration unit.

15. The method according to claim 13, characterized in that: The fresh air handling unit also includes a fresh air fan (6), which is located at the fresh air outlet (12). The method further includes: If Tn-T0<0, then reduce the operating frequency of the fresh air fan (6).

16. The method according to claim 15, characterized in that: The fresh air handling unit also includes a refrigeration unit, which is connected to the surface cooler (4) to form a first heat exchange cycle. After reducing the operating frequency of the fresh air fan (6), it also includes: When the operating frequency of the fresh air fan (6) is reduced to the minimum operating frequency, if Tn-T0<0, then the operating frequency of the refrigeration unit is reduced.

17. The method according to any one of claims 12 to 16, characterized in that: The fresh air handling unit also includes an indoor unit (7), and the method further includes: If Tw > Tn, then control the indoor unit (7) to work; If Tw≤Tn, then control the indoor unit (7) to stop working.

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