Vertical distributions of local void fraction and bubble size in air-water dispersion system were measured with a dual conductivity probe in a fully baffled dished base stirred vessel with the diameter T of 0.48 m

holding 0.134m

3

liquid. The impeller combination with a six parabolic blade disk turbine below two down-pumping hydrofoil propellers

identified as PDT+2CBY

was used in this study. The effects of the impeller diameter D

ranging from 0.30T to 0.40T (corresponding to D/T from 0.30 to 0.40)

on the local void fraction and bubble size were investigated by both experimental and CFD simulation methods. At low superficial gas velocity V

S

of 0.0077 m·s

-1

there is no obvious difference in the local void fraction distribution for all systems with different D/T. However

at high superficial gas velocity

the systemwith a D/T of 0.30 leads to higher local void fraction than systems with other D/T. There is no significant variation in the axial distribution of the Sauter mean bubble size for all the systems with different D/T at the same gas superficial velocity. CFD simulation based on the two-fluid model alongwith the population balancemodel (PBM)was used to investigate the effect of the impeller

diameter on the gas-liquid flows. The local void fraction predicted by the numerical simulation approach was in reasonable agreement with the experimental data.