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Basic principles and basic knowledge of air filter paper
Many people do not know what the principle of air filtration is, and why the dust in the air is filtered and purified by filter cotton, filters, etc. Now, I will explain to you the basic knowledge of air filtration.
The air filter paper is a kind of force that the dust material in the air receives. It uses a porous body to remove the dispersed dust particles from the gas. Some of the forces mentioned above are inertial forces, van der Waals forces, and electrostatic forces. The large particles make inertial motion in the air flow, and the air flow encounters obstacles and circles. The particles deviate from the air flow direction due to inertia and hit the obstacle. Because the diameter is larger, the inertia force is stronger, and the possibility of hitting obstacles is greater, so the dust cannot pass through. Filter material, so the filter effect is good. Small particles do irregular movements, although there is a certain direction, but mainly for diffusion movements, due to the slim fiber filter material, the van der Waals force between the two micro-molecules make them stick together, so the dust can not pass through the filter, then the filter effect is good . When we put the filter material on it and keep the electrostatic effect, due to the static energy can not hold dust, so that dust can not pass through the filter, then the filter effect is good.
During air filtration, due to the effects of inertial collisions, interception, diffusion, and static electricity, dust particles suspended in gas are allowed to sink into the porous body material. The structure is fibrous, porous, or a combination of these structures. Collectively referred to as filter material. The filter material effectively intercepts dust particles without creating excessive resistance to air flow. Air filter cotton and air filter paper meet this requirement. The disorderly interwoven fibers form innumerable barriers to the particles, and the wide space between the fibers allows the air flow to pass through smoothly.
The moving airflow hits the filter material, which causes the airflow to circulate, creating small resistance at the same time. The sum of the resistance of numerous fibers is the resistance of the filter. The resistance of the filter increases with the increase of the air flow. By increasing the area of the filter material, the relative wind speed through the filter can be reduced to reduce the filter resistance. The filter forms a resistance to the air flow, the filter accumulates ash, and the resistance increases. When the resistance increases to a specified value, the filter is scrapped. The resistance of the new filter is called "initial resistance"; the resistance value corresponding to filter scrap is called "final resistance.".
The trapped dust creates additional resistance to the air flow, so the resistance of the filter in use gradually increases. The captured dust forms new obstacles, so the filtering efficiency is slightly improved. Most of the dust that is trapped collects on the windward side of the filter material. The larger the filter area, the more dust that can be accommodated and the longer the filter life. The more dust on the filter material, the greater the resistance. When the resistance is so great that the design does not permit it, the life of the filter is at its end. Sometimes excessive resistance will cause the dust that has been trapped on the filter to fly. When this danger arises, the filter should also be scrapped. According to the above principle, in the process of manufacturing air filters, it is necessary to use excellent filter materials to meet the need of people to maintain a clean space after air filtration. This is the filtering principle that we often mention
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