Front filtering device for FFU (Fan Filter Unit)

Abstract

The utility model discloses a front filtering device for an FFU (Fan Filter Unit), which comprises a latticed frame, the frame covers an air inlet of the FFU, the frame and the air inlet of the FFU are arranged at an interval, and a filtering device for filtering air entering the air inlet of the FFU is sleeved on the frame; a sealing strip for fixing the filtering device and blocking a gap between the filtering device and the FFU is arranged at the bottom of the frame; the sealing strip is a magnetic suction strip; sealing strips are arranged on the inner and outer sides of the bottom of the frame; a base is arranged on the periphery of the FFU air inlet, and the frame is detachably connected to the base. The device can filter gas entering the FFU and avoid reduction of the air inlet amount.

Description

Technical Field

[0001] This utility model relates to an FFU filtration device, and more particularly to a pre-filter for an FFU. Background Technology

[0002] A fan filter unit (FFU) is a self-powered air supply and filtration device. It is a modular terminal air supply device with filtration capabilities. The FFU draws in air from the top, filters it through a HEPA filter, and then delivers the filtered clean air evenly across the entire outlet surface at a speed of approximately 0.45 m / s ± 20%.

[0003] Industries such as semiconductor manufacturing and precision instrument processing have extremely stringent requirements for environmental parameters such as air velocity, temperature, humidity, and particulate concentration during manufacturing and production processes. Currently commonly used cleanroom air supply systems include clean rooms with strictly controlled indoor environmental parameters. These cleanrooms have an upper mezzanine at the top and a lower mezzanine at the bottom, connected by a return air duct. The upper mezzanine houses self-powered air supply fan filter units (FFUs), while the return air duct contains dry cooling coils (DCCs) to provide sensible cooling to the cleanroom. In practice, the FFUs in the upper mezzanine filter the air and deliver it vertically downwards into the cleanroom. The indoor air flows through the lower mezzanine, is cooled by the DCC, and then mixes with fresh air treated by a makeup air unit (MAU) in the return air duct before returning to the upper mezzanine, completing the cycle. The upper mezzanine often suffers from poor air quality due to mixing with outdoor fresh air and inadequate sealing during construction. Directly introducing this poor-quality air into the FFU for filtration will rapidly shorten the lifespan of the HEPA filter. To extend the lifespan of the HEPA filter, a pre-filter can be installed in the FFU.

[0004] Chinese utility model patent CN206830537U discloses a detachable FFU coarse filter device, which is installed on the air inlet of an FFU air filtration unit. The FFU air filtration unit has a housing, and the coarse filter device includes a protective mesh, coarse filter cotton, and an iron ring. The protective mesh is vertically arranged along the airflow direction and installed on the inner wall of the air inlet. The coarse filter cotton is placed on the protective mesh and held in place by the iron ring. The iron ring is installed on a rotating shaft fixing seat fixed to the surface of the housing. The rotating shaft fixing seat is a U-shaped bent piece, and two sides of the rotating shaft fixing seat are provided with through holes for installing the iron ring and for facilitating the rotation of the iron ring. This utility model device allows for quick and effective assembly and disassembly of the FFU coarse filter device, which can be used reasonably for cleanrooms with different requirements, thereby reducing costs.

[0005] Although the above-mentioned device can pre-filter the gas entering the FFU through a coarse filter and extend the service life of the HEPA filter inside the protector, the filter material of the coarse filter in this device is attached to the air inlet of the FFU. This increases the resistance of the gas entering the FFU, reduces the air intake, and thus requires the FFU to operate at a high load to maintain the same air outlet speed. This increases the energy consumption and operating noise of the FFU and also reduces the service life of the FFU motor. Summary of the Invention

[0006] Purpose of the utility model: The purpose of this utility model is to provide a pre-filter for an FFU that can filter the gas entering the FFU and avoid reducing the air intake volume.

[0007] Technical solution: The pre-filter for FFU described in this utility model includes a mesh frame that covers the air inlet of the FFU and the two are spaced apart. A filter device for filtering the air entering the air inlet of the FFU is installed on the frame.

[0008] Based on the above technical solution, a mesh-like frame covers the FFU air inlet, and a filter device is installed on it to filter the gas entering the FFU air inlet. This pre-filters the gas entering the FFU, protecting the internal HEPA filter and extending its service life. The frame covers the FFU air inlet and is spaced out, meaning that the frame must completely cover the air inlet on its own. The spaced arrangement means that the bottom of the frame must fit against the outer wall of the FFU and cannot be located inside the air inlet, but rather on the outer edge of the air inlet. Furthermore, the entire frame must bulge to achieve the spaced arrangement with the air inlet. This structure of the frame actually increases its surface area, allowing more gas to be filtered simultaneously, thus avoiding a reduction in air intake. As long as the overall surface area of ​​the frame is set appropriately, it is possible to pre-filter the gas without reducing the air intake, which not only extends the service life of the HEPA filter but also reduces the operating noise of the FFU and extends the service life of the motor.

[0009] Preferably, the bottom of the frame is provided with a sealing strip for fixing the filter device and sealing the gap between the filter device and the FFU.

[0010] Setting a sealing strip ensures there are no gaps between the filter and the FFU, preventing gas from entering the HEPA filter through gaps without pre-filtration, thus reducing the HEPA filter's lifespan.

[0011] Preferably, the sealing strip is a magnetic strip.

[0012] The magnetic strip makes it easy to install and remove, and convenient to use.

[0013] Preferably, the frame sealing strip is provided with a handle.

[0014] The sealing strip is equipped with a handle for easy removal when the sealing strip needs to be removed.

[0015] Preferably, sealing strips are provided on both the inner and outer sides of the bottom of the frame.

[0016] Sealing strips are provided on both the inner and outer sides of the bottom of the frame to further ensure the seal between the filter device and the FFU, and to prevent gaps between the two from causing gas to enter the FFU directly without being filtered first.

[0017] Beneficial effects: Compared with the prior art, the beneficial effects of this utility model are as follows: by covering the FFU air inlet with a mesh frame and setting the two at intervals, the surface area of ​​the frame is increased, reducing the reduction of air intake; while the filter device for filtering the gas entering the FFU is installed outside the frame, the gas can be pre-filtered; therefore, this device can both pre-filter the gas and avoid reducing the air intake, reduce the operating noise of the FFU and increase the service life of the FFU. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the exploded structure of this device;

[0019] Figure 2 This is a schematic diagram of the device installed on the FFU;

[0020] Figure 3 This is a schematic diagram of the FFU structure;

[0021] Figure 4 The pressure resistance characteristic curves of a single-layer nonwoven filter device at different flow rates;

[0022] Figure 5 Vector diagram of the airflow around the FFU inlet using this device and conventional devices;

[0023] Figure 6 Pressure contour maps around the FFU inlet for devices using this apparatus and conventional apparatus;

[0024] Figure 7 The flow-speed-static pressure characteristic curves of the FFU using this device and the conventional device are shown.

[0025] Figure 8 The flow-speed-power characteristic curves of the FFU using this device and the conventional device are shown. Detailed Implementation

[0026] As shown in the figure, the pre-filter for FFU described in this utility model includes a mesh frame 1, which covers the FFU air inlet 2 and the two are spaced apart. A filter device 3 for filtering the gas entering the FFU air inlet 2 is installed on the frame 1.

[0027] The frame 1 can be a rectangular frame with an open bottom, and the rest of the surface is grid-like except for the fully open bottom. In addition to a rectangular frame, a hemispherical frame or the like can also be used, as long as the frame 1 can cover the FFU air inlet 2. The bottom of the frame 1 is located outside the FFU air inlet 2, and the rest of the frame protrudes upward away from the FFU air inlet 2. The upward protruding part can be of any shape, as long as it is ensured that no part of the frame 1 contacts the FFU air inlet 2 and that the two are spaced apart.

[0028] The shape and dimensions of the filter device 3 are designed and manufactured based on the frame 1, and its overall size is slightly larger than that of the frame 1. Its material can be made of non-woven fabric, filter cotton, glass fiber, etc., depending on actual usage needs, as long as it can perform simple pre-filtration of the gas. In this embodiment, a single-layer non-woven fabric is used, and its pressure resistance characteristic curve at different flow rates is shown in the figure. Figure 4 As shown.

[0029] The filter device 3 is mounted on the outside of the frame 1 and connected to the bottom of the frame 1. A sealing strip 4 can be installed at the bottom of the frame 1 to fix the filter device 3 and seal the gap between the filter device 3 and the FFU, so as to prevent gas from leaking from the gap and directly entering the FFU air inlet 2 without pre-filtering.

[0030] The sealing strip 4 can be set on both the inner and outer sides of the frame 1, or it can be set on only one side of the inner and outer sides; in this embodiment, the sealing strip 4 is a magnetic strip, and the sealing strip 4 can also be provided with a handle for easy gripping during disassembly and assembly.

[0031] A base 5 can be installed around the FFU air inlet 2. The frame 1 is detachably connected to the base 5 by bolting or other means. The magnetic strip on the inner side of the frame 1 can also be directly installed on the base 5 to avoid repeated disassembly and assembly. The sealing strip 4 on the outer side of the frame 1 can be installed after the filter device 3 is installed and it attracts the magnetic strip on the inner side. If the sealing strip 4 is not a magnetic strip but made of other materials, it can also be fixed by bolting or other means. Depending on the degree of dirtiness of the filter device 3, the filter device 3 can be easily disassembled and replaced by removing and installing the magnetic strip.

[0032] The energy-saving effect of this invention is illustrated through simulation. Referring to the size design and filter material arrangement of this embodiment, modeling and simulation were performed on the installation of this invention and the traditional filter placement at the FFU inlet. The modeling focuses on the resistance generated by the airflow after passing through the filter material around the FFU inlet. Therefore, other components and structures with minimal impact on the airflow are ignored. In the simulation, the FFU outlet velocity was limited to 0.4 m / s. The simulation results are as follows: Figure 5-8 As shown. The conventional device here adopts the device described in CN206830537U.

[0033] like Figure 5 The diagram shows the airflow vector diagrams around the FFU inlet under two different conditions. It can be seen that the airflow velocity change gradient around the FFU inlet of this device is slower than that of a traditional device, and the airflow velocity through this device is lower than that of a traditional device. This is because, based on fluid mechanics, when other conditions such as drag coefficient are the same, the higher the flow velocity, the greater the pressure drop, which means the greater the drag. Therefore, this device generates less drag.

[0034] like Figure 6 Pressure contour maps around the FFU inlet are shown in two scenarios. It can be seen that, compared to the traditional method of placing a filter at the FFU inlet, this device significantly reduces the pressure loss during the airflow process as it enters the FFU through the filter material. The average filtration resistance of the traditional method with a filter at the FFU inlet is 195.17 Pa, while the average filtration resistance of the device of this invention is 41.74 Pa, a reduction of 153.43 Pa, or approximately 80% of the ventilation resistance, compared to the traditional method.

[0035] like Figure 7 and 8 The diagrams shown illustrate the operating points of the FFU under two different conditions. Point A in both diagrams represents the operating point of the FFU when using the device of this invention, while point B represents the operating point of the FFU when using the conventional solution.

[0036] from Figure 7 As can be seen from the flow-speed-static pressure characteristic curve, since the ventilation resistance of the traditional solution is about 150Pa higher than that of the present invention, in order to maintain the same air volume, the fan speed of the traditional solution needs to be increased from 1113RPM to 1370RPM. At this time, its operating noise also increases from 54dB to 60dB.

[0037] from Figure 8 As can be seen from the flow-speed-power characteristic curve, in order to maintain the same air volume, the speed of the FFU fan using the traditional filtration device is increased from 1113 RPM to 1370 RPM, and the power of the fan also needs to be increased by about 160W.

[0038] In summary, the FFU energy consumption of this embodiment is only about 50% of that of the traditional solution, while reducing noise by about 10% compared to the traditional solution. Therefore, this invention significantly reduces the required air supply power and operating noise of the air supply device compared to the traditional solution, thereby reducing operating energy consumption and extending its service life.

Claims

1. A prefiltering device for an FFU, characterized by: The frame (1) is provided with a filter device (3) for filtering the gas entering the FFU air inlet (2), and the frame (1) is sleeved on the filter device (3).

2. A prefiltering device for FFUs according to claim 1, characterized in that: The frame (1) is provided with a sealing strip (4) at the bottom for fixing the filter device (3) and blocking the gap between the filter device (3) and the FFU.

3. A prefiltering device for FFUs according to claim 2, characterized in that: The sealing strip (4) is a magnetic strip.

4. A prefiltering device for FFUs according to claim 2, characterized in that: The sealing strip (4) is provided with a handle.

5. A prefiltering device for FFUs according to claim 2, characterized in that: The frame (1) is provided with a sealing strip (4) at the bottom.

6. A prefiltering device for FFUs according to claim 2, characterized in that: The FFU air inlet (2) is provided with a base (5), and the frame (1) is detachably connected to the base (5).

7. A prefiltering device for FFUs according to claim 1, characterized in that: The filter device (3) is made of non-woven fabric, filter cotton or glass fiber.

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