Modeling and simulation of liquid pulsed particulate fluidized beds

Abstract

Pulsed fluidization is of considerable interest in process engineering for improving fluidization quality. Quantitative understanding of the pulsed two-phase flow behaviors is very important for proper design and optimum operation of such contactors. The main objective of this study is to understand the mathematical models for liquid pulsed particulate fluidization and its dynamic processes. The state of the arts of the Two-Fluid Model (TFM) and its constitutive relationships are discussed and then, the Local Equilibrium Model (LEM), a simplified version of TFM, is developed and solved for liquid pulsed fluidization. LEM is proposed to describe the liquid pulsed fluidization with acceptable engineering accuracy as compared with the experimental data, and its shortcomings are also discussed at length by analyzing the relaxation processes of the two-phase flow due to a jump change of fluidizing velocity and the structure of concentration discontinuity which forms in the bed collapse process. The main shortcoming of LEM is that some detailed information in the flow fields is lost. However, errors only exist in a time interval of tens of milliseconds (several times of particle relaxation time) and a spatial span of several millimeters (several times of particle diameter).