Power Required for Upper Impeller in Gas-Liquid Vessels Agitated by Dual Turbines with Various Designs

Abstract

The power required for the upper impeller of a dual disk turbine was measured in a 0.30 m diameter aerated vessel. The gas flow rate passing through the upper impeller was estimated with the relation between power consumption and flow rate of sparged-gas. The following results were obtained.
1) The measured power of upper impellers in the loading regime was correlated with an average absolute deviation of 4.5% by the expression (P_g/P₀) _U=1-kN_A where (P_g/P₀)_U is aerated/unaerated power ratio required for an upper impeller, N_A is gas flow number and coefficient k depends on the Froude number, vessel diameter d_T, impeller diameter d, and impeller spacing. It was successfully correlated not only for dual turbines with combination of the same diameter, but also with combinations of different diameter.
2) The ratio of gas flow rate passing through the upper impeller to lower impeller, Q_{g, U}/Q_{g, L}, in-creased with the diameter, spacing and rotation speed of the impeller. Q_{g, U}/Q_{g, L} were 1/4-1/3 for d/d_T =1/3, 1/3-3/4 for d/d_T= 5/12 and 1/2-4/5 for d/d_T= 1/2.