Abstract
The relationship between electric capacitance of foam and the real liquid volume fraction of the foam was investigated. The foam was formed by injecting air into sodium dodecyl sulfate solution, and sent into a tube of i.d. of 12.0 mm and o.d. of 17.0 mm. The tube was placed between two parallel plate electrodes. Capacitance across the twin electrodes was measured. Foam that the passed through the tube was captured in a bag and weighed for accurate determination of the liquid volume fraction. Apparent relative electric capacity Kx, determined by factors such as the tube, was measured. When liquid volume fractions σ increases from 0 to 1, Kx increases from 0 to 1. Kx showed better correspondence to the liquid volume fraction than the dielectric constant of foam εx, in which εx was calculated. This method is suitable for measuring liquid volume fraction of dry foam since Kx is 0.9 when a is 0.057. A linear relation between a and Kx was obtained when σ increased from 0.005 to 0.05. Foam drainage was measured by this method. The flow rate of air injection is clearly shown to be affected by the shape of the foam drainage curve.
