Does the higher the filtration efficiency of the ULPA filter, the greater the wind resistance?

uncertain.

If you only say half of this sentence, it is easy for people to think that 'high efficiency means low resistance.' That is the other extreme. The real situation is: there is no fixed correspondence between efficiency and resistance. The resistance also depends on the filter material, area, pleat pitch, thickness and test air volume.

When the grade is upgraded from U15 to U16, if the product structure and filter material area remain unchanged, the resistance will most likely increase. However, if the two products use different filter materials, different pleat designs, or even just replace the structure with a larger effective filtration area, the resistance performance may be completely different. Therefore, to compare resistance, the premise is to align the conditions first.

Unify the conditions before comparing

This is the step that's most likely to go wrong.

Frame size and thickness should be aligned. A 600×600×292 filter element and a 600×600×150 filter element, even if they have the same grade, have different resistance and air volume characteristics and cannot be directly compared.

The effective filter area must be aligned. Under the same dimensions, the effective filtration area may be different by adjusting the pleat density or structural form. For products with a large area, the passing wind speed of the filter material is lower under the same air volume, and the resistance is often smaller. This difference is sometimes greater than the difference caused by level.

The test air volume should be aligned. Resistance changes with flow, and readings at different air volumes cannot be directly compared. Some manufacturers' samples give the resistance under rated air volume, and some give data under a specific working condition. If the conditions are not unified, there will be no comparison.

Detection objects must be aligned. The resistance reported on the filter material and the resistance of the finished product are not the same thing. Structures such as pleats, edge sealing, and protective nets will affect the resistance of the entire machine.

Why high efficiency does not necessarily mean high resistance

There are several reasons behind this.

There are different types of filter media. Fiberglass and PTFE have different resistance characteristics. At the same grade, PTFE membrane materials may show lower resistance under certain structures, but this is not determined by the name of the material and depends on the design of the specific product. For specific material selection, please refer to the relevant instructions for filter material selection.

The effective area can be compensated. If the increase in efficiency level causes the resistance of the filter material to increase, the passing wind speed can be reduced by increasing the effective filtration area. The resistance of the final product may not be much higher than that of lower-level products.

Structural design optimization. The pleat pitch, channel shape, and support method will all affect the energy loss when air flows through the filter material. Properly designed, there is not necessarily a linear relationship between high efficiency and high resistance.

Therefore, the statement 'the higher the efficiency, the greater the resistance' is only true when other conditions are exactly the same. In actual products, other conditions are often different.

How to use this data when selecting a model

After getting several candidate products, the recommended order of comparison is:

First align the dimensions of the outer frame, effective area, and air volume, and then compare the resistance. If the conditions do not match, first ask the supplier for data of the same caliber.

Use complete curves rather than single point data. The resistance curve can reflect the performance under different air volumes, and single-point data can only be used under specific working conditions. The value of the curve is more obvious when the operating range of the equipment changes.

Look at the initial resistance and final resistance. The initial resistance is used to check the initial working point, and the final resistance is used to evaluate the fan's margin in the later stage of filter element dust accumulation. Just looking at the initial resistance may not be enough. For details, please refer to the relevant explanation on the difference between initial resistance and final resistance.

Put resistance into the system and see. It is meaningless to look at the resistance of the filter element alone. It also depends on the resistance of the air duct, box and other filter sections, as well as the available static pressure of the fan. Supporting For the FFU fan filter unit system, the filter element resistance and unit working point must be checked together; the equipment end application is as follows: The internal space of the EFU equipment-end fan filter unit is limited, and the final resistance conditions need to be taken into account when calculating.

Model selection should not only pursue low resistance

Low resistance is beneficial, but it is not the only indicator.

Local performance should be looked at together. The overall resistance is low, but if there is a leak somewhere, the actual filtration effect will still not meet the requirements. Resistance and integrity are two dimensions.

Sealing and mechanical stability. Some low-drag designs are achieved by reducing supports or reducing the sealing surface, which may affect long-term seal reliability. When selecting, confirm the structural strength and sealing method.

The test conditions should be clear. If a product only gives a low resistance number and does not explain the test air volume and detection objects, this number cannot be directly used for fan selection.

Lifespan and dust holding capacity are also variables. Low resistance does not mean long life. Products with large filter media area and high dust holding capacity may have lower long-term use costs. involving For HEPA/ULPA air filter products of different grades, these dimensions must be considered together.

Project judgment example

A certain U15 model made of PTFE has lower resistance than a certain H14 model made of fiberglass.

Seeing this data, we cannot conclude that 'U15 resistance is lower than H14'. It is more likely that the PTFE model has a larger effective filter area or a different pleat structure, resulting in a lower passing wind speed.

If the project wants to use this data as a basis for selection, what needs to be done is to confirm whether the size, area, and test air volume of the two products are comparable, and then judge based on the available static pressure of the system fan. A simple comparison of resistance numbers cannot tell which solution is more suitable.

Selection and Acceptance Checklist

About Aili Industrial’s resistance accounting cooperation

The mismatch between the filter element resistance and the fan operating point is a common problem in renovation projects. After replacing the filter element and changing the air volume, the problem was exposed.

Aili Industrial's manufacturing system covers filters, motors, fans, control systems and complete machine assembly, and can provide ULPA ultra-high efficiency filter and supporting air supply equipment. filter with When the FFU fan filter unit and EFU are matched in the same system, the filter element resistance and fan operating point can be calculated together at the planning stage, instead of being purchased separately and then adjusted on site.

When enquiring, provide the design air volume, available static pressure and installation space to help confirm the appropriate resistance solution. The specific performance is subject to the testing data of the corresponding model, and no unfounded resistance promises are made.