THE DEPENDENCY ON SCALE OF POWER NUMBERS OF RUSHTON DISK TURBINES

Extensive and very accurate power numbers have been obtained for a wide range of Rushton disk turbines using water as the working fluid in six fully baffled vessels from 0. 22 to 1. 83 m diameter. The results show that for Reynolds numbers greater than equivalent to 2 multiplied by 10**4, the average peak power number P OVER BAR o is dependent on the disk thickness (x//1) to impeller diameter (D) ratio and to the vessel diameter (T). Provided x//1/D is constant, P OVER BAR o is independent of impeller to vessel ratio in the range 0. 25 less than equivalent to D/T less than equivalent to 0. 70. An F-test shows that the inclusion of the small effect of scale, (T/T//o), is statistically significant at the 99% level. The implications of these scale and geometrical effects for mixing research, process design and scale-up are discussed.