Prediction of interphase drag coefficient and bed expansion using avariational model for fluidization of small spherical particles
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tIn 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 v...alues 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.
Keywords:Calculus of variations / Isoperimetric problem / Bed expansion / Drag coefficient / Fluidization / Spherical particles
Source:Particuology, 2020, 51, 184-192