Abstract
The relationship between water vapor adsorbing property and angle of repose was clarified on glass beads sample. The amount of adsorbed water was measured by the volumetric technique, and the thickness of the adsorbed layer was estimated from a water adsorption isotherm of the sample. The angle of repose of the beads under various water vapor pressures was determined by the revolving drum method.
From the avalanching number (n) in the sample bed during one revolution of drum, the difference between critical angle of repose and angle of rest, Δθ, was evaluated to be 360°/n. It was found that Δθ increased in proportion to the rotation velocity (α) of drum. The value of Δθ under a static state (Δθ0) was calculated by extrapolating the liner Δθ-α plot to α=0. Two kinds of α values were defined as follows:
pulsating flow_??_αmaxαmin continuous flow
The time dependence of Δθ was observed under a water vapor pressure where the thickness of water adsorbed was less than monomolecular layer. When the amount of water exceeded two-molecular layers, the three factors, i.e. Δθ0, αmax and αmin, were found to increase considerably. These tendencies were considered to be caused by enhancing adhesive force due to the adsorbed water molecules between the glass bead particles.
