Modelling and simulation of heat and mass transfer in a packed bed of solid particles having high diffusion resistance

The heat and mass transfer processes between gas phase and solid particles are studied in a fixed bed throughflow dryer. The particles have a moderate size but high heat and mass transfer resistances. To describe the drying process, simple cell model approach is used. The transport resistances of the particles are taken into account by imbedding a Luikov-type distributed parameter model into each cell.

The relationships of this model to the cell model with lumped variables for the particles, as well as to the continuous two phase model are analysed. Numerical investigations show that moisture diffusion taking place inside the particles can control the drying process even at moderate Biot numbers.