Experimental and CFD-DEM numerical evaluation of flow and heat transfer characteristics in mixed pulsed fluidized beds

Abstract

Pulsed fluidized beds can make gas-solid mix and contact more uniform, therefore obviously improving heat transfer efficiency. The mixed pulsed fluidized bed, whose total gas flow is composed of stable gas flow and pulsed gas flow, is proposed in this research. Firstly, the experimental device for drying particles in a mixed pulsed fluidized bed is established. Pressure signals with different frequencies and gas flow ratios are collected, and flow pattern diagrams are obtained through a high-speed camera. Secondly, the CFD-DEM parallel numerical simulation method is constructed to research the mixed pulsed fluidized bed performance. Particle mixing, motion and heat transfer characteristics under different pulse frequencies and flow ratios are studied. Results show that particles in the mixed pulsed fluidized bed exhibit regular periodic motion, thereby promoting the mixing effect of particles. Moreover the bubble nucleation point moves to the bottom of the bed with the increasing pulse frequency. When the total gas velocity is relatively low, particle mixing effect can be enhanced by increasing the proportion of pulsed gas. However, when the velocity is relatively high,particle mixing effect will be enhanced by decreasing the proportion.