Effect of pressure fluctuations on the heat transfer characteristics in a pressurized slurry bubble column

Abstract

The hydrodynamics and heat transfer characteristics were investigated in a slurry bubble column reactor whose diameter was 0.0508 m (ID) and 1.5 m in height. Effects of gas velocity (0.025-0.1 m/s), pressure (0.1-0.7 MPa), solid concentration (0-20 vol%) and liquid viscosity (1.0-38.0 mPa s) on the hydrodynamics and heat transfer characteristics were examined. The pressure difference fluctuations were analyzed by means of attractor trajectories and correlation dimension to characterize the hydrodynamic behavior in the column. The gas holdup increased with increasing gas velocity or pressure, but decreased with increasing solid concentration or liquid viscosity. It was found that the attractor trajectories and correlation dimension of pressure fluctuations were effective tools to describe the hydrodynamic behaviors in the slurry bubble column. The heat transfer coefficient increased with increasing pressure or gas velocity, but decreased with increasing solid concentration or viscosity of slurry phase in the slurry bubble column. The heat transfer coefficient value was well correlated in terms of operating variables and correlation dimension of pressure fluctuations in the slurry bubble column.

Flow behavior of wakes in a three-phase slurry bubble column with viscous liquid medium

“…In addition, the wake regions could also coalesce with each other whenever bubble coalescence could occur. It has been reported that the bubble rising velocity increases with increasing gas velocity [14][15][16]; thus, the rising velocity of the wake region can also increase with increasing gas velocity, since the rising bubbles are tailed by wakes.…”

“…It is noted that the bubble frequency decreases but the rising velocity of bubbles increases, with increasing liquid viscosity. These can be due to the fact that the bubble coalescence could increase with increasing liquid viscosity [14][15][16]. Since the buoyancy force acting on the bubbles, which is due to the difference of density between the bubble and slurry phase, increases with increasing bubble size, the rising velocity of wakes as well as bubbles could increase with increasing liquid viscosity.…”

“…The size of glass bead was in the range of 40-70 µm and solid content in the slurry phase was 0-20 wt%. Filtered, oil-free compressed air, which was used as a gas phase, was admitted at the bottom of the column through the gas distributor [12][13][14].…”

Multiple effects of operating variables on heat transfer in three-phase slurry bubble columns

“…The total acquisition time was 10 s having 5000 data points. This combination of sampling rate and time can detect the full spectrum of temperature fluctuation signals in a multiphase flow system [13][14][15][16].…”

Chaotic behavior of in-line bubbles rising with coalescences in non-Newtonian fluids: A multiscale analysis

“…Recently, the multiresolution signal decomposition [6] has been widely applied to analyze pressure fluctuation signals with multiscale features and unsteady characteristics in fluidization and bubble columns in chemical engineering [7][8][9][10][11][12]. Another technique, the chaotic time series analysis, has also shown great advantages in studying the nonlinear dynamics of bubble columns [4,13,14]. In the present work, both the multiresolution signal decomposition and chaotic time series analysis were simultaneously employed to analyze the temporary signals of bubble passages in non-Newtonian fluids and then to characterize qualitatively and quantitatively the nonlinear dynamics of in-line bubbles rising with coalescences.…”