Effect of impeller clearance on flow structure and mixing in bioreactor with two-stage impellers

The effect of impeller clearance on flow structure and mixing time was simu lated using a commercial software package CFX 4.3 and was measured experime ntally. The mixing time calculated by simulation exhibited good agreement w ith the experimental data. The trend of forming independent flow compartmen ts by each impeller became stronger as the clearance between two impellers increased. The homogeneity in the bioreactor was affected mainly by flow ex change between the compartments by each impeller. The most efficient mixing occurred when the impeller clearance was in the range of 0.2-0.4 vessel di ameter.