How to ensure uniform air supply with a side air inlet box equipped with ULPA? Resistance and current sharing design

Side air inlet boxWhen using ULPA filters , the air supply distribution should be coordinated through inlet layout, static pressure space and appropriate flow equalization structure. The qualified grade of the filter element does not mean that the entire air outlet surface is uniform. The airflow characteristics of side airflow and top airflow are different: the airflow of top airflow enters vertically from above and is relatively easy to distribute evenly; the airflow of side airflow enters from one side and needs to be turned and diffused in the box. There is a natural speed difference between the side near the entrance and the far end. What the current sharing design has to deal with is this speed difference. Aili Industry isIn the structural design of the side air inlet box of the EFU equipment end fan filter unit , the inlet position, static pressure space and internal diversion structure are determined on the same set of drawings.Compact models such as small-sized EFU equipment fan filter units also describe the scope of application according to the attainable uniformity level in a limited space to avoid giving only one filter element model without explaining the distribution conditions on the box side.

1. Check the side inlet airflow characteristics: where does the difference between the proximal end and the far end come from?

The entrance speed, position and rotation may increase the difference between the near end and the far end. Measure and observe the structure first. It is not advisable to judge based on the center reading alone.

After the airflow of the side air inlet box enters from the inlet, part of it rushes directly to the proximal filter surface, and the other part needs to be turned to reach the far end. The higher the inlet velocity and the larger the steering angle, the more obvious the dynamic pressure difference between the near and distal ends. If you only measure the central position, the central wind speed may be between the near-end high speed and the far-end low speed. It may seem 'about the same', but in fact both ends are not within the target range. Aili Industry isThe HEPA/ULPA filter matching solution provides corresponding structural instructions according to the air inlet mode of the box.The ultra-thin EFU 's side air inlet structure marks the entrance direction and internal space conditions during the planning stage, so that the project team can determine which locations need to be focused on testing. The relationship between grade and air supply requirements can be referred toISO cleanliness level comparison。

2. Choose between space and resistance: both static pressure space and flow-sharing components have costs

Increasing static pressure space or setting up flow equalizing components requires assessment of pressure loss, maintenance and material requirements to avoid exceeding the fan residual pressure for uniformity.

There are several ways to improve the distribution of side air inlet: enlarging the static pressure space behind the inlet to allow the airflow to spread and mix at a sufficient distance before entering the filter; setting up deflectors or flow equalizing nets to disperse the high-speed airflow to the entire cross-section; adjusting the position or direction of the inlet to allow the airflow to spread more naturally after entering. Each method brings additional resistance - increased static pressure space means increased box size, and there is a pressure drop in the flow-sharing component itself. Aili Industry isNon-standard ULPA filters andIn the EFU equipment-end fan filter unit project, the feasibility of the flow equalization scheme is evaluated based on the available space of the equipment. When the space allows, the distribution is improved through the internal structure. When the space is tight, an acceptable balance point is determined between distribution and resistance, instead of adding the flow equalization structure until the fan cannot be pushed. The resistance effect of the current equalization structure can be referred toHEPA FAQs and Selection Guide。

3. The flow equalization structure must match the filter element area and surface wind speed.

The opening ratio, layout density and position of the flow equalization components should correspond to the effective area of ​​the filter element and the design surface wind speed. If the opening ratio is too low, the resistance will increase, while if it is too high, the flow equalization effect will not be achieved.

The flow equalization design is not completed by adding a plate. The parameters of the components must be determined together with the filter element specifications and operating air volume. Aili Industry isTank seal ULPA filter andIn the side air inlet supporting scheme of the partition-less ULPA ultra-high-efficiency filter , the basic parameters of the flow equalization component are determined according to the effective area of ​​the filter element and the design surface wind speed.During the complete test of the FFU fan filter unit , the pressure drops at the inlet, flow equalization section and filter element are recorded in sections to facilitate judgment of whether the resistance ratio of the flow equalization components is reasonable. The relationship between filter element area and face wind speed can be referred toULPA ultra-high efficiency filter FAQ and selection guide。

4. Use specified measuring points for acceptance: compare the distribution of each point on the same plane and working conditions

Maintain the same measurement plane and working conditions, compare the distribution of each point with the average air volume, and simultaneously confirm the installation seal and test channel.

For the uniformity acceptance of the side air inlet box, the measuring point arrangement must cover the near end, far end and both sides of the edge, and cannot only measure the center. The measurement plane and operating conditions are determined before testing, and the same set of measuring points are used for retesting before and after rectification. Aili Industry isthe FFU fan filter unit, the air outlet distribution was recorded according to the multi-point arrangement.During the factory test of The FFU computer group control system records the operating air volume and rotation speed to facilitate matching the distribution data with actual working conditions. In terms of the test channel, there must be space for the probe to be accessible on both the inlet side and the outlet side of the side air inlet box.the fan filter unit at the EFU equipment end . The location of the detection interface is marked in the structural description of Please refer to the key points of equipment-end uniformity acceptance.EFU FAQ and technical support。

5. Related questions and answers

Will enlarging the cabinet ensure uniformity?
It is also related to the entrance, internal obstacles and wind outlet conditions, which still need to be verified after structural changes.

Is it okay to only measure the center wind speed of the side air inlet box?
Not recommended. The central wind speed may be exactly between the near high speed and the far low speed, which does not reflect the actual distribution.

How much resistance will the flow equalizer add?
Depending on the opening ratio, layout density and operating air volume, it should be calculated in sections during the planning stage to confirm that the residual pressure of the fan can be covered.

6. Related articles

ULPA ultra-high efficiency filter FAQ and selection guide

Ultra-thin EFU

Small size EFU equipment fan filter unit

HEPA FAQs and Selection Guide

7. Key points for selection and acceptance inspection

8. Product matching and technical support from Aili Industrial

Aili Industry isIn the structural design of the side air inlet box of the EFU equipment end fan filter unit , the inlet position, static pressure space and internal diversion structure are determined on the same set of drawings.The scope of application of compact models such as small-sized EFU equipment fan filter units is explained based on the achievable uniformity level in a limited space;The ultra-thin EFU side-inlet structure marks the entrance direction and internal space conditions during the planning stage.The HEPA/ULPA filter matching solution provides structural instructions according to the air inlet method of the box.Non-standard ULPA filters andThe EFU equipment end fan filter unit project evaluates the feasibility of the current equalization scheme based on the available space of the equipment.Tank seal ULPA filter andThe side air inlet package of the partition-less ULPA ultra-high efficiency filter determines the flow equalization component parameters according to the effective area of ​​the filter element and the design surface wind speed;The whole machine test of the FFU fan filter unit records the pressure drop at the inlet, flow equalization section and filter element in sections, and records the air outlet distribution at multiple points.The FFU computer group control system records the operating air volume and speed to facilitate corresponding working conditions. Provide process objectives, installation drawings, operating conditions and acceptance requirements for further communicationULPA ultra-high efficiency filters . Standard specifications, non-standard interfaces, samples and batch matching of The specific parameters and test range are based on the confirmed model and technical documents.