Principle of Air Filter
Dust particles in the air move with inertia or irregular motion along the airflow. When these particles collide with a filtering medium that can effectively trap them without creating excessive resistance to the airflow, the tangled fibers of the filtering medium form numerous barriers to the particles. The spacious gaps between the fibers allow the airflow to pass smoothly.
Inertial Effect
Larger dust particles move with inertia in the airflow. These larger particles cannot maneuver around obstacles quickly enough and thus collide directly with the fibers. Higher airflow velocity, larger particle size, finer fibers, and greater fiber quantity increase the likelihood of dust particles colliding with the fibers due to inertia.
Interception Effect
Small and light dust particles move with the airflow. When the airflow brushes against the surface of the fibers, the dust particles are intercepted. The interception effect is independent of airflow velocity but strengthened by larger particle size, finer fibers, and higher fiber density. To achieve better interception, the number of fibers in the filter material must be increased.
Diffusion Effect
Dust particles smaller than 1 micron typically undergo irregular diffusion motion due to collisions with air molecules, known as "Brownian motion." If these particles collide with the fibers, they are captured. Smaller particle size, finer fibers, and lower airflow velocity intensify diffusion motion, increasing the chances of dust particles colliding with the fibers.
Inertial Effect
Dust particles with diameters larger than the gaps between fibers are trapped. To effectively filter small dust particles, the filter material must contain a sufficient quantity of fine fibers.
Electrostatic Effect
Both filter fibers and airborne dust particles may acquire static electricity due to various factors. Dust particles are attracted to the fibers. Filters with coarse synthetic fibers often have higher initial efficiency due to inherent electrostatic charges, but their filtering effectiveness declines significantly during use.
As more dust is captured, the filtering efficiency of the layer decreases, and resistance increases. When the resistance reaches a certain value or the efficiency drops to a certain level, the filter must be replaced promptly to maintain high cleanliness requirements.
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