Dry air

Fig. 4 Lea and Nurse permeability apparatus with manometer and flowmeter

Manometer Flowmeter

Fig. 5 Fisher subsieve sizer operation

A simplified version of the air permeameter, known as the Blaine permeameter (Fig. 6) (Ref 23), relied on a variable pressure technique (Ref 24). A vacuum was used to displace the oil in a U-tube connected in series with the powder cell. The resultant pressure caused air to flow through the powder bed, and the time required for the displaced oil to fall back to its equilibrium position was measured. This method resulted in a measured specific surface area, which decreased with porosity. Usui (Ref 25) showed that log t and the void fraction exhibited a linear relationship and that a plot of these parameters gave a value for surface area.

Fig. 6 Blaine air permeability apparatus. Source Ref 23
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