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Air resistance
The moving airflow hits the filter material, causing the airflow to circulate, while generating minute resistance. The numerous filter fibers are the total resistance of the entire filter device at a certain wind speed and the air resistance of the filter device. When the filter device reaches a certain resistance value (final resistance value), the filter device should be replaced to ensure the filtration effect. In most cases, the final resistance value is set to 2-4 times the ancestor. The dirtier the filter device, the greater the resistance, and the smaller the corresponding wind speed.
Do not think that after the cleaning, the filter resistance is no longer increased, the filter device has been restored to filter function, in fact, the filtration efficiency is zero. Therefore, the filter equipment is a consumable item.
2. Wind speed
In most cases, the lower the wind speed, the higher the filtration efficiency. Because at low wind speeds, the diffusion of small dust is obvious. The airflow stays in the filter for a longer period of time, and the dust has more chance to hit the obstacle. The filtering effect is obvious once. For high-efficiency filters, the wind speed is reduced by half, and the chance of dust passing through the filter is reduced and the efficiency is increased by 9. Double the wind speed, double the dust rate of the filter material, and reduce the efficiency by an order of magnitude (by one). When the wind speed is low, the probability of collision of large particles with the fiber during inertia is reduced, but in practical applications, the effect is not obvious, because the wind speed is reduced, and the rebound force of the fiber against the dust is also reduced. The dust is more likely to adhere and the filtration effect is significantly improved. Therefore, as far as practical applications are concerned, reasonable low-speed filter parameters should be set. Great benefits for filtration efficiency and filtration.
3. Filter area
The resistance of the filter device increases as the gas flow rate and flow rate increase. The resistance of the trapped or adhered dust to the airflow is increased, and the air resistance of the air filter device is increased. On the other hand, since the captured dust filter medium is adhered to one body, a new filter barrier is formed, and the filtration efficiency is slightly improved. However, the overall filtration effect depends on the size of the filter unit. Therefore, the life of the filtration device is related to the filtration area.
Classification criteria.
1. European standards
European standards are based on EUROVNT4, EN779.
Main level: EU1~EU17
Particle size: 5μm, 1μm, 0.5μm, 0.3μm
2. American Standard
The US standard is based on ASHRAE, mainly DOP.
Level: initial effect: G1~G4
Medium effect: F5~F9
High efficiency: H10~H14
Ultra efficient: U15~U17
Classification method: weighting method, colorimetry
3. China's standards
There are no unified standards in the country, which are copied according to Europe and the United States, with slight modifications.
Level: initial effect, medium efficiency, high efficiency, sub-efficient, and efficient.
The primary, intermediate and high-efficiency classifications follow the European standard, using G1~G4, F5~F6, F7~F9. Sub-efficient, efficient and ultra-efficient compliance with American Standard is expressed as a percentage.
Filter equipment classification
In summary, the classification of filtration grades of domestic filter cotton and filters is based on these classifications.
Filter cotton is divided into: primary filter cotton, medium efficiency filter cotton, sub-high efficiency filter cotton
Filters are divided into: primary filter, medium efficiency filter, sub-high efficiency filter, high efficiency filter and ultra-high efficiency filter.
Concerned about surprises
Tags: Several factors that affect the efficiency of high-efficiency filters
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