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Volume 17, No. 4, April 2017, Pages 1052-1062 PDF(3.13 MB)  
doi: 10.4209/aaqr.2016.06.0256   

Filtration Properties of Nanofiber/Microfiber Mixed Filter and Prediction of its Performance

Hyun-Jin Choi1, Mikio Kumita1, Sho Hayashi1, Hisashi Yuasa1, Mie Kamiyama2, Takafumi Seto1, Chuen-Jinn Tsai3, Yoshio Otani1

1 School of Natural System, College of Science and Engineering, Kanazawa University, Kanazawa, Ishikawa 920-1192, Japan
2 Teijin Limited, Minohara, Ibaraki, Osaka 567-0006, Japan
3 Institute of Environmental Engineering, National Chiao Tung University, Hsinchu 30010, Taiwan


  • Investigation of filtration performance of nanofiber/microfiber mixed filter.
  • Prediction of performance by equations for bimodal distribution of fibers.
  • Optimization of nanofiber mixing fraction from viewpoint of the quality factor.



There is an increasing demand of air filters with a high collection performance, i.e., high collection efficiency and low pressure drop, for the application to indoor air cleaning. Air filters consisting of nanofibers have attracted great interests since they may have a low pressure drop because of slip flow effect and high collection efficiency due to interception. Although various nanofiber filters are available on the market, their collection performance is not as high as expected by the conventional filtration theory because non-uniform packing of fibers plays a significant role. In the present work, the collection performance of nanofiber (780 nm) and microfiber (11.2 µm) mixed filters with various mixing fractions was studied in order to maximize the quality factor of filter, qF, as a function of mixing fraction of nanofibers. The collection performance of mixed fiber filters was predicted by using theoretical equations reported by Bao et al. (1998) for bimodal distribution of fibers. As a result, it was found that the mixed fiber filters had a uniform fiber packing compared to laminated filters and that the collection efficiency was well predicted by introducing the inhomogeneity factor calculated for the filter consisting of two distinct fiber sizes. Furthermore, we found that the mixed fiber filter with the nanofiber mixing fraction of 5% in mass had the highest quality factor.



Keywords: Air filtration; Mixed fiber filter; Mixing fraction; Quality factor; Inhomogeneity factor.



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