TURBULENT PROPERTIES IN BUBBLE-FLOW REGION IN EXTERNAL-LOOP AIRLIFT BUBBLE-COLUMN

Turbulent properties of the bubble flow region in an airlift bubble co lumn were examined using an anemometer for water and CMC solutions. Th e turbulent structures of the gas-liquid system in these liquids were evaluated by the power spectrum of turbulent eddies. The power spectru ms of the liquids decayed with decrease in the size of eddies with a s lope of -5/3 to -2. This is almost comparable to that of Kolmogoroff's spectrum law for an isotropic turbulence. The radial distributions of turbulent intensity, u'(l), macro-scale of turbulent eddies, LAMBDA(f ) bubble diameter, d(B), and bubble rise velocity, u(B), were measured . The influence of the media on these properties was examined. The tur bulent viscosity, v(t), was evaluated from the values of u'(l) and LAM BDA(f) for the liquids. It was found that v(t) of gas-liquid two-phase flow was five times higher than that of a single-phase flow of water. Using these turbulent properties, the liquid superficial velocity, U( L), slip velocity of bubble, U(BS), and bubble diameter (Sauter diamet er), d(BS), in the riser were estimated theoretically. The estimated v alues agreed with those obtained experimentally.