Numerical simulation on characteristics of hydrodynamics, interphase and wall to bed heat transfer in a pseudo 2D spouted bed using supercritical CO2 as fluidizing agent

Abstract

By employing the Eulerian-Eulerian Two Fluid Model, the effect of different particle size, supercritical CO₂ (scCO₂) velocity at slit jet (U_jet) and initial bed height on the macroscopic characteristics (i.e., fountain morphology, profiles of particle velocity, momentum transfer characteristics among particles, transient temperature evolutions of particles, interphase heat transfer coefficient and wall to bed heat transfer characteristics) in the pseudo 2D rectangular spouted bed using scCO₂ as fluidizing agent is numerically studied in detail herein. Considering there are currently no relevant visualized experiments reported using scCO₂ as a fluidized agent due to the extreme operating pressure of CO₂ (25 MPa in this paper) under supercritical conditions, present numerical model was validated with experimental data by using air as the fluidizing agent, confirming simulated instantaneous volume fraction distribution of air and transient temperature evolutions of particles basically consistent with the experiments. Numerical results reveal some of the internal relations among hydrodynamics characteristics in bed, momentum transfer characteristics among particles and relevant heat transfer behaviours. Results show larger U_jet and smaller particle size will accelerate the particles' translational motion in spout, spout core and fountain core zone. Larger particle concentration will promote inter-particle collisions while suppress the kinetic motion of particles in above zones. Decrease the particle size will enhance interphase convective heat transfer coefficient, while increasing U_jet results insignificant impacts. Finally, we also observe the transition zone between annular and periphery zone has a certain enhancing effect on the wall to bed heat transfer coefficient.