Abstract
The effect of impeller diameter for three geometrical similar impellers on solids suspension had been investigated in one of the earlier studies (Mak 1999), it was found that the smallest impeller appeared to be the most energy efficient at all clearances. This study looked further into a series of pitched bladed turbines of same blade width and an impeller diameter range between 0.3T and 0.7T (i.e. non-geometrical similar impellers, with W/D varies). Two impeller clearances, T/4 and T/8, were tested. Round grained sand and water were used as test media. It was found that the geometrical and non-geometrical similar impellers exhibited similar just suspension speed (Njs) and just suspension power (Pjs) trends and that the small diameter impellers were more energy efficient than the large ones. The effect of blade width on Njs and Pjs were found to be statistically insignificant. This work has once again confirmed that the optimum configuration is a function of both impeller diameter and clearance.
