Design strategy for long-service-life air filters based on the stacking sequence and electrostatic charging

초록

Filter media with excellent performance and minimal replacement frequency are necessary in air purifiers. In this study, composite filters comprising nanofiber, microfiber, and coarse microfiber layers were developed and their filtration performances and dust holding capacities (DHCs) were determined. Eight composite filters with varying stacking sequences and electrostatic states were developed, and the pressure drop and DHC of each layer were measured. The pressure drop was the most pronounced when the nanofiber layer was positioned upstream, regardless of the electrostatic charge. Meanwhile, placing the nanofiber layer downstream considerably reduced the pressure drop, particularly in electrostatically charged composite filters. This result was attributed to reduced dust flux reaching the downstream nanofiber layer. Layer-specific analysis revealed that the nanofiber layer accounted for >80% of the total pressure drop under all charge conditions when placed upstream, whereas its contribution reduced to similar to 63% in charged composites when the nanofiber layer was placed downstream. These findings highlight the critical role of the upstream filtering layers relative to the nanofiber layer in modulating the pressure drop and suggest that filter service life can be extended by optimizing the stacking sequence and electrostatic charge conditions. Thus, composite filters should be designed such that the nanofiber layer is located downstream to maintain high filtration efficiency and maximize DHC.

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