Study On Liquid Velocity Near Wall Region In A Solid-Liquid Stirred Tank

Solid-liquid suspension is a common mixing process . It is important to measure solid and liquid velocities in a stirred tank for the study of suspension mechanism and the law of velocity change for both solid and liquid.The experiment was carried out in a full baffled cylindrical plexiglasstank of 0.476m diameter with solid-liquid system. A new type of bi-electrode probe was used to measure liquid velocity near wall region(0.4mm from the wall) in the solid-liquid system with solid volumetric concentration (Ñ„v) from 1.0% to 5.4%. The result showed that the minimum liquid velocity to maintain particles just suspended was influenced by the properties of the solid and liquid, such as the density of the solid and liquid, the diameter and shape of the particles, etc, not by the operational conditions, such as solid volumetric concentration, type of impellor, distance of impellor from the bottom of the tank, the positions of solid particles just suspension ,etc. The relationship between impellor speed and liquid velocity is different in bottom region and up-flow wall region. Liquid velocity in up-flow wall region is not influenced by solid concentration when solid particles just uniform suspension and liquid velocity in the top of suspened liquid layer is not influenced by operating conditions.The commercial software of CFX5.5.1 has been used to numerically simulate power number Np of CBYIII impellor and liquid velocity in the solid-liquid tank agitated. The results obtained by numerically simulating are in good agreement with experimental data.