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What is the filtration principle of Shanghai air filter manufacturer?

Time: 2023-02-17

Let me introduce the principle of air filter (HEPA filter or activated carbon filter)

Five filtration methods:

The most important filtering method of air filter is interception.

1, interception (this is the most importantair filterfiltering method)

The first thing to be clear is that all kinds of dust, TVOC, formaldehyde, whether solid, liquid, bacteria, pollen, as long as they can be classified as particulate matter, the filter will treat them the same. Intercept them all.

The fibers in the fiber layer of the filter are intricately arranged, forming countless grids. (HEPA filter oractivated carbon air filter)When a particle of a certain size moves just near the fiber surface along the flow line (or inertia, or random Brownian motion, or some field force action), if the distance from the flow line (also the center line of the particle) to the fiber surface is equal to or less than the particle radius, the particle will be intercepted and deposited on the fiber surface. This effect is called the interception effect. The sieve effect is an interception effect. (Shanghai activated carbon air filter manufacturer)

A fiber screen filled with contaminants

2. Inertia

When air streams filled with various kinds of dust pass through the HEPA fiber layer, the flow lines of the air flow have to turn sharply several times due to the complex arrangement of the fibers. When the particle has a larger mass or velocity (which can be regarded as the speed of air flow), when the streamline curves, the particle has no time to follow the streamline and bypass the fiber at the same time due to inertia, so it leaves the streamline and approaches the fiber. And they collide with the fibers and they deposit on them, and if the particles collide with the fibers, instead of hitting them head-on, they collide within the range of the interception effect, then the interception effect is a combination of these two effects. (Shanghai Air Filter manufacturer)

A complex arrangement of fibers

Principle of action of inertia and diffusion collision

3. Diffusion effect

The Brownian motion of particles is caused by the collision of the thermal motion of gas molecules. The smaller the particle, the more significant the effect is. At room temperature, it is several times to tens of times larger than the distance between fibers, which makes the particles have a greater chance to move to the fiber surface and deposit. However, the Brownian motion of the particles larger than 0.3pm is weakened, which is generally not enough to make them leave the flow line and collide with the fibers. (Shanghai Air Filter manufacturer)

4. The effect of gravity

When the particles pass through the fiber layer, they shift away from the streamline under the action of gravity, that is, they deposit on the fiber due to gravity deposition. Since the time of air flow through the fiber air filter, especially through the filter paper filter, is much less than 1s, for particles with diameter less than 0.5pn, when it does not settle to the fiber, it has passed through the fiber layer, so the gravity settlement can be completely ignored.

5. Electrostatic effect

Due to a variety of causes, such as friction, positron and negative electrons in the air, fibers and particles can become charged, creating a “static effect” that attracts the particles

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