Let’s talk about the filter efficiency, surface velocity and filter velocity of hepa filters. Hepa filters and ulpa filters are used at the end of the clean room. Their structural forms can be divided into: mini pleat hepa filter and deep pleat hepa filter.
Among them, the performance parameters of hepa filters determine their high-efficiency filtration performance, so the study of performance parameters of hepa filters has far-reaching significance. The following is a brief introduction to the filtration efficiency, surface velocity, and filter velocity of hepa filters:
Surface velocity and filter velocity
The surface velocity and filter velocity of a hepa filter can reflect the air flow capacity of the hepa filter. The surface velocity refers to the airflow velocity on the section of the hepa filter, generally expressed in m/s, V=Q/F*3600. The surface velocity is an important parameter that reflects the structural characteristics of the hepa filter. The filter velocity refers to the velocity of air flow over the area of the filter material, generally expressed in L/cm2.min or cm/s. The filter velocity reflects the passing capacity of the filter material and the filtration performance of the filter material. The filtration rate is low, generally speaking, higher efficiency can be obtained. The filtration rate allowed to pass through is low and the resistance of the filter material is large.
Filter efficiency
The "filter efficiency" of a hepa filter is the ratio of the amount of dust captured to the dust content in original air: filter efficiency = amount of dust captured by the hepa filter/dust content in the upstream air = 1-dust content in downstream air/upstream. The meaning of air dust efficiency seems simple, but its meaning and value vary greatly depending on different test methods. Among the factors that determine filter efficiency, the "amount" of dust has various meanings, and the efficiency values of hepa filters calculated and measured are also varied.
In practice, there are the total weight of dust and the number of dust particles; sometimes it is the amount of dust of a certain typical particle size, sometimes it is the amount of all dust; there is also the amount of light that indirectly reflects the concentration using a specific method, fluorescence quantity; there is an instantaneous quantity of a certain state, and there is also a weighted average quantity of the efficiency value of the whole process of dust generation.
If the same hepa filter is tested using different methods, the measured efficiency values will be different. The test methods used by various countries and manufacturers are not uniform, and the interpretation and expression of hepa filter efficiency are very different. Without test methods, filter efficiency is impossible to talk about.
Post time: Dec-05-2023