Distribution of energy dissipation rate in an agitated gas-liquid system

This contribution presents a theoretical description of the relationship between the rate of energy dissipation per unit volume and the mean kinetic energy of turbulence per unit volume in a mechanically agitated gas-liquid system. For agitated systems with standard (Rushton) turbine impellers, the effect of the aeration rate on the distribution of the rate of energy dissipation per unit volume in the system was investigated. It follows from the experiments carried out that the gas flow rate significantly affects the rate of energy dissipation per unit volume in the impeller region as well as in the bulk of the agitated batch. In the impeller region, the investigated rate of energy dissipation markedly increases with increasing gas flow rate and, in the remaining part of the agitated batch, it decreases. Moreover, the rate of energy dissipation near the impeller depends strongly on the local gas hold-up which corresponds to the regime of two-phase flow behind the impeller blades (i.e. to the occurrence of clinging of ragged cavities).