关键词: off-bottom suspension;solid-liquid system;local velocity;stirred tank

Abstract: The minimum fluid velocity to maintain particles just suspended was deduced, and the
theoretical analysis shows that the minimum velocity is influenced by the properties of the
solid and liquid, not by the operational conditions. For justification, the local minimum
velocity at the bottom of the tank was measured by a bi- electrode conductivity probe, in a
square-sectioned stirred tank (0.75m×0.75m×1.0m) with the glass beads-water system.The
experiments showed that the fluid velocities for the same suspension state were identical
despite that the power dissipated per unit mass was not the same under different
configuration and operation. Both theoretical analysis and experimental results indicate
that the off-bottom suspension is controlled by the local fluid flow over the bottom of the
stirred tank.

Key words: off-bottom suspension, solid-liquid system, local velocity, stirred tank