In this paper, segregation characteristics of fluidized particles, which were the mixture of two kinds of grains having different densities and sizes, and the temperature distributions within them were experimentally examined. The dominating heat transfer mechanism was discussed from the experimental results, in order to obtain fundamental information applicable for controlling the particle segregation and/or heat transfer in practical fluidized beds. The experimental results showed that the temperature segregation was dependent on the particle segregation and that the vertical heat transfer in the segregated fluidized bed was greatly resisted by the interface layer, which was located between the jetsam and flotsam layers and had a vertically changing particle concentration. The average vertical heat transfer coefficient or apparent thermal conductivity of the interface layer increased with the excess gas velocity. When the temperature segregation occurs, the apparent thermal conductivity of the interface layer was not only much lower than that of the vigorously fluidized flotsam layer, but even lower than that of the stagnant jetsam layer.

In our previous paper, particle and temperature segregations in a fluidized bed of binary particle mixtures were experimentally examined, and heat transfer in the segregated fluidized bed was investigated. As the results, it was shown that the temperature segregation results mainly from low heat transfer coefficient through the interface layer, which exists between the flotsam-rich and jetsam-rich layers, and that the heat transfer coefficient increases rapidly with increasing the excess gas velocity. Following our previous paper, particle motion in the segregated fluidized bed was experimentally investigated in this paper, in order to make quantitative discussion on the relation between the heat transfer coefficient and particle motion in the interface layer. In the experiment, the Particle Imaging Velocimetry (PIV) method was applied to study the concentration and motion of particles in the segregated fluidized bed. A modified solid circulation model was built up to model the particle motion in the segregated fluidized bed. The experiment results showed that the vertical particle exchange rate of the interface layer increases with the excess gas velocity, and that the vertical heat transfer coefficient through the interface layer is mainly determined by the average particle exchange rate in the interface layer. Variations of the apparent thermal conductivity at different height in the particle layers were also determined by the vertical variation of the particle exchange rate. It was shown that the heat transfer coefficient or the thermal conductivity in the interface layer is influenced by the densities and specific heat capacities of the particles.