Effect of Segment Scale in a Pore Network of Porous Materials on Drying Periods

Abstract

Drying periods of porous glass disks of nonhygroscopic MPG glass and hygroscopic Vycor glass were investigated. A simple model of dimensionless segment sizes is proposed where a dimensionless segment size is equal to the value of the tortuosity factor of gas diffusion. This model was applied to the estimation of the segment size and the drying periods of a porous Vycor glass disk. The drying rate curve of the Vycor glass disk showed that the first falling rate period appeared to be included in the constant rate period and that the second falling rate period started right after the constant rate period ended, whereas the drying rate curve of the MPG glass disk estimated from previous models showed that the first falling rate period and the second falling rate period were clearly distinguished. The difference in drying periods between two porous glass disks was caused by a large difference in the respective segment sizes.

Keywords:

• Gas diffusion
• Hygroscopic
• Nonhygroscopic
• Porous glass
• Tortuosity factor

Notes

^a Data are from Corning Inc.^{[ 23 ]}

^b Data were calculated using Eq. (2) of method 2 and average τ = 3.8.

^c Data are for diffusion in liquid.^{[ 22 ]}

^d Data are from Ise Chemical Corporation.^{[ 24 ]}

^e Data were calculated using method 1.

^f Data were calculated from the value Δ₀ in column 6 and that of d _max in column 3.

^g Data are from Shibata.^{[ 6 , 8 ]}