Numerical study of air humidity and temperature distribution in a top-spray fluidised bed coating process

• CFD model is proposed to predict flow, temperature and humidity profiles in a fluidised bed coater.
• Eulerian framework for gas/solids was combined with the Lagrangian method for the droplet phase.
• The CFD model gave good prediction of the expanded bed height of the fluidised bed.
• Thermal zones in the coater could be characterised by means of CFD.
• Further investigation to incorporate proper droplet/solids interaction in the model is needed.

The objectives of this study were to model the air temperature and humidity distributions and to determine expanded bed heights in a top-spray fluidised bed coater using computational fluid dynamics (CFD). For model validation purposes, model-predicted outlet air temperatures and expanded bed heights were compared to those reported in literature. The model-predicted outlet air temperatures at different conditions were found to be overestimated, approximately 3–5 °C higher, while good agreement was found between measured and predicted expanded bed heights. In addition, the model showed good qualitative agreement in the existence of different thermal zones in the fluidised bed with those observed in experiments. In conclusion, the CFD model could be employed to determine the expanded bed height and to characterise the thermal zones in the fluidised bed, while model development, specifically regarding implementation of droplet/particle interactions in the model is still needed to increase the consistency with the experimental air temperatures.