Specific Surface Area Measurement by Air Permeability with Consideration for the Molecular Flow Effect [Translated]†

• Main Authors: Akira Suganuma, Yu Matsumoto, Egure Murata, Toshitaka Hamada
• Format: Article
• Language: English
• Published: Hosokawa Powder Technology Foundation 2014-05-01
• Series: KONA Powder and Particle Journal
• Online Access: https://www.jstage.jst.go.jp/article/kona/18/0/18_2000030/_pdf/-char/en

Because gas permeation through a powder bed is affected by molecular flow, applicability of the Kozeny-Carman equation, which neglects this effect, is limited to powders coarser than about 10 μm. ΦB=ΦV + δΦM is a general expression in some permeability equations for finer powders, where ΦB denotes the permeability of a bed, ΦV is a viscous flow term, and ΦM is a molecular flow term. δ is a constant that adjusts for the molecular flow effect. It has been more than 40 years since δ=0.515 was proposed by Rigden, 0.97 by Lea and Nurse, and 1.215 by Carman. It is because of these large differences in δ that the Kozeny-Carman equation is still used. In this paper δ=0.82 is proposed as a reasonable value based on a least squares analysis of Rigden's data and with reference to Knudsen's equation of capillary permeation. The use of δ=0.82 allows the more reasonable measurement of powders down to about 1 μm. † This report was originally printed in J. Soc. Powder Technology, Japan. 35(9), 649-654 (1998) in Japanese, before being translated into English by KONA Editorial Committee with the permission of the editorial committee of the Soc. Powder Technology, Japan.