Turbulence characteristics in turbine-agitated tanks of different sizes and geometries

Abstract

Velocity measurements have been conducted with constant temperature anemometry in three reactors, with diameters of 0.8, 1.88 and 2.09 m. Their impeller-to-tank-diameter ratios were 3, 2.47 and 3, and they were equipped with two three and four Rushton turbines. Turbulence parameters, intensity, turbulent kinetic energy, local energy dissipation rate and energy spectra, were calculated from the measured data. The turbulent kinetic energy was constant in the local flow situation, when scaled with the square of the convective velocity. This was independent of position, agitation rate and size of reactor, in the impeller zone. The energy spectra in the impeller zone were almost constant when scaled with the local energy dissipation length, independent of position, agitation rate and size of reactor. The local energy dissipation rate scaled with the cube of the convective velocity and impeller diameter.