(232f) The Effect of Drag Laws on the Prediction of Fluidized Bed Bubbling

Recent work has shown the significant impact drag laws have on the successful prediction of mixing and segregation in fluidized beds. A key contributor to the observed disparities may be the relative ability of the various drag laws used to accurately predict bubbling behavior, even in monodisperse systems.

In the present study, we first focus on free-bubbling monodisperse systems of Geldart B particles. A systematic characterization of bubble size, shape, speed, and frequency is made by means of a single fiber reflection probe. The void fraction in the emulsion phase is determined using the optical probe and the overall void fraction is verified by integration over the whole bed, based on the measured bed depth during operation. The same set of measurements are then taken from free-bubbling binary fluidized beds and the results are contrasted with the results from monodisperse systems.

The experimentally-obtained data are used as a test basis for evaluating predictions obtained through CFD simulations using the various drag laws tested. Specific details, including local void fraction and bubble size, shape, speed, and frequency, are all compared between the simulations and experiments. The results shed light on the ability of current constitutive relations for fluidized systems to capture the bubble-emulsion interactions in bubbling fluidized beds.