Prediction of interphase drag coefficient and bed expansion using a variational model for fluidization of small spherical particles

In this study, we applied the variational model to fluidization of small spherical particles. Fluidization experiments were carried out for spherical particles with 13 diameters between d(p) = 0.13 and 5.00 mm. We propose a generalized form of our variational model to predict the superficial velocity U and interphase drag coefficient beta by introducing an exponent n to describe the different dependences of the drag force F-d on fluid velocity for different particle sizes (different flow regimes). By comparing the predictions with the experimental results, we conclude that n=1 should be used for small particles (d(p) < 1 mm) and n = 2 for larger particles (d(p) > 1 mm). This conclusion is generalized by proposing n = 1 for particles with Re-t < 160 and n = 2 for particles with Re-t > 160. The average mean absolute error was 5.49% in calculating superficial velocity for different bed voidages using the modified variational model for all of the particles examined. The calculated values of beta were compared with values of literature models for particles with d(p) < 1.0 mm. The average mean absolute error of the modified variational model was 8.02% in calculating beta for different bed voidages for all of the particles examined. (C) 2019 Chinese Society of Particuology and Institute of Process Engineering, Chinese Academy of Sciences. Published by Elsevier B.V. All rights reserved.