EXPERIMENTAL INVESTIGATION OF HEAT TRANSFER BETWEEN A BUBBLING FLUIDIZED BED AND A LARGE PARTICLE
The results of an experimental investigation of heat transfer between a bubbling fluidized bed and a large, freely moving particle are presented in this paper. Experiments were performed with spheres of different materials (copper, aluminum, brass and graphite) and of diameter 5, 10, 15 and 20 mm, immersed in a fluidized bed of silica sand with mean particle diameter 250, 500 and 900 µm. Air and nitrogen were used as fluidization gases. Fluidization velocity was in the range 0.092 - 0.855 m/s. Investigations were performed with bed temperatures of 300, 500, 600 and 750 °C. The heat transfer coefficient was determined by measuring the center of the sphere temperature variation during its heating up in the bed. On the basis of numerous experiments, the influence of particle diameter, mean size of bed particles, bed temperature and fluidization velocity on the heat transfer coefficient was analyzed. A correlation was obtained encompassing the experimental results with an accuracy of ± 15% .