Influences of Nano Particle Addition on Hydrodynamics and Heat Transfer in Gas-Solid Fluidized Beds

Abstract

Nano particles (7 nm TiO2) added coarse particle (100 μm Al2O3) fluidization was carried out in a 2-D column. Influences of nano particle addition on hydrodynamics and heat transfer in gas–solid fluidized beds were investigated. The flow behavior and heat transfer were evaluated with Kolmogorov entropy (K) of the pressure fluctuation and heat transfer coefficient (h), respectively. It was found that K is drastically increased as the ratio of nano particle addition increased, whereas h is exponentially decreased in accordance with the unstable flow behaviors. From SEM images, the sizes of nano agglomerates fragmented and the nano agglomerates on the surface of coarse particle were observed. The flow regimes with the variation of nano particle ratio were classified into a fragmented agglomerate flow and a surface dispersed agglomerate flow. It was also found that the agglomerate film around the surface of heater and coarse particles acted as a dominant resistance source of the heat transfer.