Theoretical and experimental study for enhancement of filtration performance of nonwoven fibrous media by nonuniform compression

In this study, the effect of uniform and nonuniform compression on the quality factor of filtration of nonwoven fibrous media has been investigated theoretically and experimentally. Given that the effect of nonuniform compression on filtration has not been reported, it is a new way for enhancement the performance of filters. The "quality factor", which includes filtration efficiency and pressure drop, has been used to compare different types of filter media compression. Theoretical calculations have been performed using the classical single fiber efficiency theory. The results showed that with compression, the filtration efficiency increases only for a range of particle sizes. Experiments were carried out on 10 polypropylene fibrous filters with different compression ratios and types. For each sample, the efficiency and pressure drop were measured. It was found that the trend of changes in filtration efficiency due to compression is the same for the theoretical and experimental results. The experimental of uniform and nonuniform compression results showed that the filtration efficiency increases only for particles smaller than 3 mu m. For particles smaller than 3 mu m, the effect of compression on increasing efficiency increases. The increase is lower in nonuniform compression because some particles can escape from uncompressed spaces. Due to the lower pressure drop in nonuniform compression an increase in the quality factor is achieved in comparison to the uniform compression. The increase in the quality factor of the PP1 filter is up to 25.83%, and for the PP2 filter is up to 25.93%. It was also observed that with the increase of the compression ratio, the quality factor of the filter decreases.