화학공학소재연구정보센터
Canadian Journal of Chemical Engineering, Vol.93, No.1, 141-149, 2015
CFD Simulation of Complete Drawdown of Floating Solids in a Stirred Tank
Computational fluid dynamics (CFD) simulations were carried out to find a CFD methodology to predict the critical impeller speed (N-CS) for the complete drawdown of floating solids in a stirred tank with an up- and down-pumping pitched blade turbine (PBTU and PBTD). CFD models along with six mixing parameters predicted that N-CS was 7.5rps and 5.8rps, respectively, for PBTU and PBTD, when impeller submergence (S) was equal to half of the liquid height (H/2). Reasonable agreement was observed between CFD simulations and published empirical correlation. N-CS was smaller for PBTD relative to PBTU at S=H/2, which agreed with results in the literature. The drawdown mechanisms based on the mean drag, turbulent fluctuations or large scale eddies failed to explain the difference in N-CS between PBTU and PBTD. The flow patterns based on a simulated velocity field were further investigated and successfully accounted for this difference.