Verification of slip flow in nanofiber filter media through pressure drop measurement at low-pressure conditions

• Published in: Separation and purification technology Vol. 159; pp. 100 - 107
• Main Authors: Bao, Li, Seki, Kazuya, Niinuma, Hitoshi, Otani, Yoshio, Balgis, Ratna, Ogi, Takashi, Gradon, Leon, Okuyama, Kikuo
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 08.02.2016
• Subjects: Drag; Fiber packing inhomogeneity; Fluororesin nanofiber filter media; Inhomogeneity; Low pressure condition; Media; Nanostructure; Polytetrafluoroethylenes; Pressure drop; Reduction; Slip flow; Slip flow; Fluororesin nanofiber filter media; Pressure drop; Fiber packing inhomogeneity; Low pressure condition
• ISSN: 1383-5866; 1873-3794
• DOI: 10.1016/j.seppur.2015.12.045

•Slip flow effect on the reduction in pressure drop was evaluated.•Pressure drop was measured at low pressure condition to verify the slip flow effect.•Slip flow effect was verified by distinguishing the effects of filter inhomogeneity.•Minimizing the beaded-fiber diameter increase the filter efficiency and extends the lifetime. Slip flow phenomena are of great concern in aerosol filtration because of their ability to develop low-pressure drops and high collection efficiency air filters by using nanofibers. However, it is a difficult task to verify the slip flow effect on the reduction in pressure drop because the inhomogeneity in fiber packing also results in a decrease in pressure drop. In the present work, we propose pressure drop measurements at low pressures to verify the slip flow effect by distinguishing the effects of filter inhomogeneity. We found that the experimental dimensionless drag at low-pressure conditions, which was obtained with correction by the inhomogeneity factor measured at atmospheric pressure, followed the theoretical prediction that includes the slip flow correction (Kirsch and Stechkina, 1978) for both conventional PTFE and newly developed fluororesin nanofiber filter media. Because the dimensionless drags of both nanofiber filters decreased inversely proportional to the Knudsen number, we concluded that these nanofiber filters have low-pressure drops because of slip flow effects.