The use of pressure fluctuations in the monitoring of fluidized bed hydrodynamic

Perusing the hydrodynamic changes of fluidized bed is important for online monitoring of the drying process. The hydrodynamic changes occur because of a variety of reasons such as change of air velocity and change in physical features of particles. So in this research, fluidized bed dryer was considered to evaluate the effect of shrinkage and increasing particle density on hydrodynamic changes due to moisture loss. Therefore, wet rice particles were dried in fluidized bed with 15cm internal diameter and bed pressure fluctuations during this period were recorded in appropriate frequency. Data survey in the time domain showed that bubble size becomes smaller and more numerous by reducing the particle size. Evaluating data in the frequency domain also confirmed this trend of hydrodynamic changes. Also with the help of wavelet analysis, part of the signal related precisely to the bed hydrodynamic was evaluated and it was found that large bubbles energy is transferred into smaller bubbles and clusters by decreasing bed volume