Joo Hee Han

Phase holdup characteristics in three phase fluidized beds

Abstract The bed porosity and the individual phase holdup characteristics in three phase fluidized beds with a wide range of liquid properties have been examine The liquid phase holdup increases with liquid velocity and viscosity, column diameter and liquid surface tension; it decreases with gas velocity, parti The liquid phase holdup and the bed porosity data have been combined with over 5000 points from the literature to yield dimensionless correlations.

Bubble chord length distribution in three-phase fluidized beds

Abstract Three ideal bubble chord length distributions have been derived for three different bubble shapes (spherical, ellipsoidal and spherical-cap). The measured chord length distributions in three-phase fluidized beds have been analyzed by the combined bubble length distribution model based on the ellipsoidal and spherical-cap bubble shapes. The combined bubble length distribution predicts well the measured bubble length distribution in three-phase fluidized beds. It has been found that the distribution approaches that for length distribution in three-phase fluidized beds. It has been found that the distribution approaches that for ellipsoidal-shaped bubbles in the bubble-disintegrating regime and that for spherical-cap-shaped bubbles in the bubble-coalescing regime and/or in slug flow regime. The ellipsoidal-bubble fraction increases with increasing liquid velocity and particle size, but decreases with increasing gas velocity and liquid viscosity.

Axial dispersion characteristics in three-phase fluidized beds

The effects of liquid and gas velocities, liquid viscosity and surface tension, particle size and column diameter on the axial dispersion coefficients (DZ) of liquid phase in three-phase fluidized beds have been determined in two large (0.254 and 0.376 m-I.D.) columns. Tap water, carboxymethyl cellulose (CMC), Triton X-100 and ethanol aqueous solutions were used as the liquid phase; air as the gas phase and four different sizes of glass beads as the solid phase. The coefficient increases with increasing gas and liquid velocities in three phase fluidized beds. Whereas, the effects of liquid surface tension and liquid viscosity on DZ are found to be small. The axial dispersion coefficient decreases with increasing particle size and it sharply increases with increasing column size. The axial dispersion coefficients in terms of the Peclet number in the bubble coalescing and disintegrating regimes in three phase fluidized beds have been correlated based on the isotropic turbulence theory.

BUBBLE PROPERTIES AND PRESSURE FLUCTUATIONS IN BUBBLE COLUMNS

The effects of gas (0.02-0.1 m/s) and liquid velocities (0.0-0.10 m/s) on the bubble properties and pressure fluctuations have been determined in a 0.376 m-IDx 2.1 m-high bubble column. The pressure fluctuations have been analyzed by resorting to the Fractal analysis; the time series of pressure fluctuation signals have been analyzed by means of the Rescaled range analysis and the Hurst exponent has been obtained. The bubble chord length and its rising velocity increase but the Hurst exponent decreases with increasing gas velocity. Whereas, the bubble chord length decreases, but the Hurst exponent increases with an increase in liquid velocity in the continuous bubble column (UL>0.02 m/s). The Hurst exponent has been found to have a definite relationship with the bubble chord length and its standard deviation.