The diffusion effect (Brownian motion) of small particle size dust in a dust-free workshop is obvious, with low wind speed and longer airflow retention time in the filter material. The dust has more opportunities to collide with obstacles, resulting in high filtration efficiency. Experience has shown that for HEPA filters, reducing wind speed by half reduces the transmittance of dust by nearly an order of magnitude (efficiency value increased by 9), doubles wind speed, and increases transmittance by an order of magnitude (efficiency decreased by 9).

Dust free workshop

Similar to the diffusion effect, when the filter material carries static electricity (electret material), the longer the dust stays in the filter material, the more likely it is to be adsorbed by the material. The change in wind speed will result in a significant change in the filtration efficiency of electrostatic materials. If you are aware of static electricity on the material, you should minimize the amount of air passing through each filter when designing the air conditioning system.

For large particle dust based on inertia mechanism, according to traditional theory, when the wind speed decreases, the probability of dust colliding with fibers will decrease, and the filtration efficiency will also decrease. However, in practice, this effect is not significant because the wind speed is small, and the fiber has less rebound force against dust, making it easier for dust to adhere.

High wind speed and high resistance. If the service life of the filter is based on the final resistance, then the wind speed is high and the service life of the filter is short. It is difficult for ordinary users to actually observe the impact of wind speed on filtering efficiency, but it is much easier to observe the impact of wind speed on resistance.

For high-efficiency air filters, the airflow velocity through the filtering material is generally 0.01-0.04m/s, and within this range, the resistance of the filter is directly proportional to the amount of filtered air. For example, a 484 × four hundred and eighty-four × The 220mm high-efficiency filter has an initial resistance of 250Pa at a rated air volume of 1000m3/h. If the actual air volume used is 500m3/h, its initial resistance can be reduced to 125Pa. For general ventilation filters in air conditioning boxes, the speed of airflow passing through the filter material is within the range of 0.13-1.0m/s. The resistance is no longer linearly related to the air volume, but rather an upward arc. If the air volume increases by 30%, the resistance may increase by 50%. If the filter resistance is a very important parameter for you, you must inquire with the filter supplier about the resistance curve.