How to choose a central air-conditioning filter reasonably to extend the service life of the filter. Under normal circumstances, the last-level central air-conditioning filter determines the degree of air purification. The upstream filters at all levels only play a protective role. It protects the downstream filter to extend Its service life or protect the air conditioning system to ensure its normal operation.
In the air-conditioning design, the efficiency of the last-level central air-conditioning filter should be determined first according to the user’s cleanliness requirements, and then a protective filter should be selected. If this level of the filter also needs to be protected, a filter should be added to its upper wind side. Device. Protective filters are collectively referred to as "pre-filters".
The efficiency of central air conditioning filters at all levels should be properly matched. If the efficiency specifications of the adjacent two-stage filters are too different, the previous stage will not be able to protect the latter stage; if the difference between the two stages is small, the latter stage will have a too little burden. The service life of the high-efficiency filter at the end of the cleanroom should be 5-15 years. The most important factor affecting the service life is the quality of the pre-filter. When using the "G～F～H～U" efficiency specification classification, it is convenient to estimate the efficiency of the required levels of filters. In G2～H12, one filter is set every 2～4 steps. For example, G4→F7→H10, where the end H10 (sub-high efficiency) filter determines the cleanliness level of the air supply, F7 protects H10, G4 protects F7. Before the HEPA filter at the end of the cleanroom, a filter with an efficiency specification of not less than F8 should be used for protection; the ultra-high efficiency (ULPA) filter can choose F9～H11 filters. The central air conditioner itself should be protected by a filter with an efficiency specification no lower than F5.
The service life of the central air-conditioning filter also depends on the filter area and filter material selection. The unfolded area of the filter material in the filter is often several times, dozens of times, and sometimes up to 100 times the windward surface of the filter. The filter area is large, the dust that can be contained is more, and the service life of the filter is long. With a large filtering area, the speed of airflow through the material is low, and the resistance of the filter is small. Increasing the filter area is the most effective way to extend the service life of the filter.
Experience has shown that for filters with the same structure and the same filter material when the final resistance is determined, the filter area will increase by 50%, and the service life of the filter will be prolonged by 70% to 80%; when the area is doubled, the service life of the filter will be increased. About three times the original.
The extension of the service life also means the reduction of maintenance labor costs and the reduction of risks. In addition, the initial resistance will decrease after the filter area increases, and the energy consumption of the air conditioning system will be less. For the end-user, it is certainly cost-effective to choose a filter with a large filtering area.
Most filters used in general ventilation and clean rooms are disposable. They may not be cleaned, or they are not worth cleaning from an economic point of view. High-efficiency filters are very particular about use occasions. Even if the filters are not damaged, it is best not to wash them unless you are sure that they are thoroughly cleaned and the performance does not change after cleaning, and there are test methods to prove this.
