Numerical study on spout fluidization dynamics in pulsed- spout microwave- vacuum dryer

The dynamic characteristics of gas- particle spout fluidized bed in a microwave- vacuum drying system ( PSMVD) were investigated. The spout fluidization process in a Pseudo- 2- D spouting bed was monitored by computational fluid dynamics ( CFD) using the inviscid Two- fluid theory based on Euler- Euler method.The dynamic characteristics of the spout fluidized bed and the effect of spout elevation on the particle movement were revealed, which could be used to improve the uniformity of particle mixing and microwave heating.The results revealed that mathematical model succeeded to demonstrate the dynamic characteristics of gas- particle spout fluidized bed in a microwave- vacuum drying system; the spout fluidization process includes isolated, merged and transitional jets and the fluidization at specific spout gas velocity had a start- up stage and a quasi- steady fluidization stage.The spout velocity was an important factor controlling particle status in the spout fluidized bed and a critical velocity was identified for effect transition of the flow pattern.There was an approximately linear correlation between the jet penetration depth and the spout velocity.