Filtration principle/Medium efficiency filter

1.Inertia and diffusion

Dust particles in the air is moving with the airflow in inertial or irregular Brownian motion or under the action of a certain field force. When the the particles hits other objects, the Van Der Waals forces makes the particles stick to the surface of the fiber. 

The larger the particle, the easier it is to hit, and the better the effect.

Small particles of dust make irregular Brownian motion. The smaller the particles, the more violent the irregular movement, the more chances of hitting obstacles, and the better the filtering effect.

The particles smaller than 0.1 micron in the air mainly make Brownian motion, the particles are small, and the filtering effect is good.

Particles larger than 0.3 microns are mainly used for inertial motion, and the larger the particle, the higher the efficiency.

Diffusion and inertia are not obvious, and particles are the most difficult to filter out. When measuring the performance of high-efficiency filters, people

It is often specified to measure the dust efficiency value that is the most difficult to measure.

2.Electrostatic effect.

For some reason, fibers and particles may be charged with  electrostatic effect. The filtering effect of electrostatically charged filter materials can be significantly improved. Reason: Static electricity makes the dust change its trajectory and hit obstacles, and static electricity makes the dust stick to the medium more firmly. Materials that can charge static electricity for a long time are also called 'electret' materials. After the material is charged with static electricity, the resistance will not change, and the filtering effect will be significantly improved.

3. Chemical filter

The chemical filter mainly selectively adsorbs harmful gas molecules.

There are a large number of invisible micropores in the activated carbon material, and the museum's effective air-conditioning filterwind bag has a larger adsorption area. In activated carbon the size of rice grains, the area of the micropores is more than ten square meters. After the free molecules contact the activated carbon, they condense into liquid in the micropores and stay in the micropores due to the capillary principle. The medium-efficiency air-conditioning filter wind sock, and some are integrated with the material. The adsorption without obvious chemical reaction is called physical adsorption.

Some processes the activated carbon, and the adsorbed particles react with the material to produce solid matter or harmless gas, which is called Huai Xue adsorption. The adsorption capacity of the activated carbon material is constantly weakened during the use process, and when it weakens to a certain degree, the filter will be scrapped.