The influence of anemometer air volume and speed on air filter and its calculation method
Air filters must calculate the wind speed and volume of the product's usage location. Generally speaking, the lower the wind speed, the better the effectiveness of the air filter.
The diffusion effect (Brownian motion) of small particle size dust is obvious. When the wind speed is low, the airflow stays in the air filter material for a longer time, and the dust has more opportunities to collide with obstacles, so the filtration efficiency is higher. The experience of some air filter manufacturers shows that for high-efficiency air filters, if the wind speed is reduced by half, the dust transmission rate will decrease by nearly an order of magnitude (an increase of 9 in efficiency value), and if the wind speed is doubled, the transmission rate will increase by an order of magnitude (an decrease of 9 in efficiency).
Similar to the effect of diffusion, when the air filter material is charged with static electricity, the longer the dust stays in the air filter material, the greater the possibility of being adsorbed by the material. Changing the wind speed will significantly alter the filtration efficiency of the air filter material with static electricity. If you know that materials have static electricity, when designing an air conditioning system, you should minimize the airflow through each air filter as much as possible.
The influence of wind speed and air volume on air filters
For large particle dust mainly affected by inertia mechanism, combined with traditional theoretical knowledge, the probability of collision between dust and fibers will decrease as the wind speed decreases, and the filtration efficiency will decrease accordingly. But in practice, this effect is not significant because the wind speed is low, and the rebound force of the fibers on the dust is also small, making it easier for the dust to stick.
High wind speed leads to greater resistance. If the service life of the air filter is based on the final resistance, and the wind speed is high, the service life of the container filter will be short. It is difficult for ordinary 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 resistance.
For high-efficiency air filters, when the airflow passes through the filtering material at a speed of 0.01-0.04m/s, the resistance of the air filter is directly proportional to the filtered air volume within this range. For example, a 484mm × 484m × 220mm high-efficiency air 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 may decrease to 125Pa. For general ventilation air filters in air conditioning units, the velocity of airflow passing through the filter material is in the range of 0.13-1.0m/s, and the resistance and air volume are no longer linearly related, but an upward curve. An increase of 30% in air volume may increase the resistance by 50%. If the resistance of the air filter is a very important parameter for everyone, then we need to request the resistance curve from the air filter supplier.
