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

Abstract

In this study, we applied the variational model to fluidization of small spherical particles. Fluidizationexperiments were carried out for spherical particles with 13 diameters between dp= 0.13 and 5.00 mm.We propose a generalized form of our variational model to predict the superficial velocity U and inter-phase drag coefficient ˇ by introducing an exponent n to describe the different dependences of the dragforce Fdon fluid velocity for different particle sizes (different flow regimes). By comparing the predictionswith the experimental results, we conclude that n=1 should be used for small particles (dp< 1 mm) andn = 2 for larger particles (dp> 1 mm). This conclusion is generalized by proposing n = 1 for particles withRet< 160 and n = 2 for particles with Ret> 160. The average mean absolute error was 5.49% in calculatingsuperficial velocity for different bed voidages using the modified variational model for all of the particlesexamined. The calculated values of ˇ were compared with values of literature models for particles withdp< 1.0 mm. The average mean absolute error of the modified variational model was 8.02% in calculatingˇ for different bed voidages for all of the particles examined.