Impact of wind speed in clean room
The diffusion effect (Brownian motion) of small-sized particles is obvious, the wind speed is low, the air stays in the filter material for a longer time, and the dust has more opportunities to hit the obstacle, so the filtration efficiency is high. Experience has shown that for high-efficiency filters, when the wind speed is reduced by half, the dust transmission rate is reduced by nearly an order of magnitude (the efficiency value is increased by a factor of 9), when the wind speed is doubled, the transmission rate is increased by an order of magnitude (the efficiency is reduced by a factor of 9).
Similar to the effect of diffusion, when the filter material is electrostatically charged (electret material), the longer the dust stays in the filter material, the more likely it is to be adsorbed by the material. By changing the wind speed, the filtration efficiency of static-charged materials will change significantly. If you know that there is static electricity on the material, you should design the air conditioning system to reduce the amount of air passing through each filter as much as possible.
For large-particle dust mainly dominated by inertial mechanism, according to the traditional theory, after the wind speed is reduced, the probability of the dust colliding with the fiber will be reduced, and the filtration efficiency will be reduced accordingly. However, in practice, this effect is not obvious, because the wind speed is smaller, the fiber's rebound force to the dust is also smaller, and the dust is more likely to be stuck.
The higher the wind speed, the greater the resistance. If the life of the filter is based on the final resistance and the wind speed is high, the life of the filter will be short. It is difficult for general users to actually observe the effect of wind speed on filtration efficiency, but it is much easier to observe the effect of wind speed on drag.
For high-efficiency air filters, the velocity of air passing through the filter material is generally 0.01 to 0.04 m / s. Within this range, the resistance of the filter is proportional to the amount of filtering air. For example, a 484 × 484 × 220mm high-efficiency filter has an initial resistance of 250Pa at a rated air volume of 1000m3 / h. If the actual air volume in use is 500m3 / h, its initial resistance can be reduced to 125Pa. For a general ventilation filter in an air-conditioning box, the velocity of air passing through the filter material is in the range of 0.13 to 1.0 m / s, and the resistance and air volume are no longer a linear relationship, but an upward arc, the air volume is increased by 30%, and the resistance May increase by 50%. If the filter resistance is a very important parameter for you, you need to ask the filter supplier for the resistance curve.