Jet mixing in tall tanks: Comparison of methods for predicting blend times

Grenville and Tilton (1996) presented a simple model that correlates blend time data from jet mixed vessels up to 12,000 m3 in volume. The model is based on the idea that the turbulent kinetic energy dissipation rate at the end of the jet's free path determines the mixing rate for the whole vessel. Maruyama et al. (1982) and Revill (1992) had previously proposed that the blend time should be proportional to the circulation time of the fluid entrained by the jet. Grenville and Tilton (1997) compared their proposed Jet Turbulence model with the Circulation Time model and found that, over the range of the data studied, both can be used to accurately predict blend times. Extrapolation of the models showed that their predictions diverge as the ratio of fluid depth to vessel diameter increases. In this paper blend time data taken in vessels with aspect ratios of 2, 3 and 4 are included in the analysis. The results show that the Grenville and Tilton (1996) Jet Turbulence model fits all data for 0.2 < H/T < 3. The ratio of blend time to the circulation time is dependent on the ratio of fluid depth to vessel diameter.