Estimation and experimental validation of the circulation time in a 2D gas–solid fluidized beds

Abstract

Abstract:The circulation time is defined as the time required for a group of particles to reach the freeboard from the bottom of a fluidized bed and return to their original height. This work presents an estimation and validation of the circulation time in a 2D gas solid bubbling fluidized bed under different operating conditions. The circulation time is based on the concept of the turnover time, which was previously defined by Geldart [1] as the time required to turn the bed over once. The equation t c,est = 2 Ah′/Q b is used to calculate the circulation time, where A is the cross section of the fluidized bed, h′ is the effective fluidized bed height and Q b is the visible bubble flow. The estimation of the circulation time is based on the operating parameters and the bub ble phase properties, including the bubble diameter, bubble velocity and bed expansion. The experiments for the validation were carried out in a 2D bubbling fluidized bed. The dense phase velocity was measured with a high speed camera and non intrusive techniques such as particle image velocimetry (PIV) and digital image analysis (DIA), and the experimental circulation time was calculated for all cases. The agreement between the theoretical and experimental circulation times was satisfactory, and hence, the proposed estimation can be used to reliably predict the circulation time.

Eulerian–Eulerian simulation of dense solid–gas cylindrical fluidized beds: Impact of wall boundary condition and drag model on fluidization

“…The authors computed the solids circulation fluxes and times as well as bubbling statistics for a detailed comparison with the digital image analysis measurements reported previously by Sánchez-Delgado et al [36]. They observed significant differences in the fluidization patterns with larger and faster moving bubbles (slugs) and exponentially decreasing circulation time as φ was decreased.…”

“…U-U mf (e.g. [36][37][38]). Measuring the circulation time, however, requires optical access or the use of tracer particles limiting most studies to extremely thin beds.…”

3D Eulerian modeling of thin rectangular gas–solid fluidized beds: Estimation of the specularity coefficient and its effects on bubbling dynamics and circulation times

“…The simulation setup is based on the experimental work of Sanchez-Delgado et al [24]. The authors employed a combination of two non-intrusive techniques, namely Particle Image Velocimetry (PIV) and Digital…”

“…In addition, the authors provide time averaged solids concentration maps for a subset of the test matrix. To the best of our knowledge, this is the only study that provides circulation times in bubbling fluidized beds by means of PIV and DIA, and further details on the experimental setup are offered in [24,29].…”

“…The sensitivity of the solids circulation flux to variations of φ is studied together with detailed analysis of the differences in bubbling dynamics. Finally the appropriate values of φ for different conditions extracted from the simulations are validated with the experimental results presented in [24]. The validation procedure is a two-fold strategy since we compare circulation times, derived from the circulation fluxes, as well as solid concentration maps, indicative of the time-averaged bubble presence across the bed.…”