A CFD Comparative Study of Bubbling Fluidized Bed Behavior with Thermal Effects Using the Open-Source Platforms MFiX and OpenFOAM

This work studies the performance of two open-source CFD codes, OpenFOAM and MFiX, to address bubbling fluidized bed system at different temperature and heat transfer conditions. Both codes are used to predict two parameters that are relevant for the design of fluidized units: the minimum fluidization velocity as a function of the temperature of the bed and wall-to-bed heat transfer coefficient from a lateral wall and from internal tubes. Although the CFD solvers are structuraly similar, there are some key differences (available models, meshing techniques, and balance formulations) that are often translated into differences in the fields prediction. The computational results are compared between both codes and against the experimental data. The minimum fluidization velocity can be correctly predicted with both codes at different temperatures while, in general, for the heat transfer and the fluidization patterns, MFiX shows slightly more accurate results compared to OpenFOAM but with low versatility for meshing curved geometries which might translate into higher computational costs for the same level of accuracy.

Modeling and Optimization of Gas-Solid Fluidization of Binary Mixtures using Box-Behnken Experimental Design

The influence of different factors on the fluidization of a binary mixture of red mud and aluminum was investigated. A new model was developed for predicting pressure drop through the solid bed using experimental data of other work. Statistical analysis based on response surface methodology has been used to develop correlations for bed pressure drop with three independent factors, minimum fluidization velocity (Umf), red mud to aluminum ratio (R/A), and static head (Hs). The design of experiments offers a best alternative to study the effect of factors and their response with the minimum number of experiments. The hydrodynamic characteristics of fluidization, bed pressure drop, superficial gas velocity (Umf), red mud to aluminum ratio (R/A), and initial static bed height (Hs) were modeled and optimized. ANOVA has been used to analyze the system parameters on bed pressure drop. A model of bed pressure drop was found to have a correlation coefficient of 0.98. The measured values of bed pressure drop from RSM were found to match the experimental values very well.

Effects of Coffee Form and Distributor Hole Angle on The Fluidization Behavior and Specific Energy Consumption in The Fluidized Bed Machine

The fluidized bed technique was applied to use with the Robusta coffee in this research. fluidization behavior and specific energy consumption were investigated under various coffee forms and distributor hole angles. Moreover, the minimum fluidization velocity (Vmf) was also determined. Experiments are carried out in a sample bed height of 5 cm with ambience air. In this study, two coffee forms (Ripe coffee cherries; RCC and parchment coffee; PC) and three distributor hole angles (45º, 60º and 90º) are examined. The experimental result shown that the fluidization behavior is influenced by coffee form and distributor hole angle. The RCC and distributor hole angle of 60º provided the low pressure drop throughout the superficial air velocity. The low values of Vmf and SEC were also achieved in the RCC and distributor hole angle of 60º.