Turbulent flow and gas-liquid mass transfer in gas-injected system

The fluid flow and gas-liquid mass transfer in a water model of gas-injected ladle were analyzed by a numerical simulation of turbulent flow and mathematical models on mass transfer. In the fluid flow simulation, a single-phase model was adopted, in which the turbulent diffusion of bubbles was assumed. The computed average dissipation rates agreed well with the energy-input rates due to the work done by bubbles. The volumetric coefficients in the bubble dispersion zone and free surface zone were estimated by the eddy-cell model and penetration model, and compared with the observed results. The eddy-cell model gave better prediction of volumetric coefficients in the bubble-dispersion zone than the penetration model. On the other hand, both models did not predict well the volumetric coefficients at the free surface; the eddy-cell model gave larger values and the penetration model gave smaller values than the observed values. This was thought to be attributable to the fluctuating motion of the free surface, which consumed turbulence energy and decreased the energy dissipation rate required for the surface renewal.