MEAN HEAT-TRANSFER COEFFICIENT AROUND A H ORIZONTAL SINGLE PIPE IN A FAST CIRCULATING FLUIDIZED-BED

Mean heat transfer coefficient h(s) around a single, horizontal pipe s ettled in a fast circulating fluidized bed was measured under various fluidizing condition. The heat transfer coefficient could be correlate d well with the solid fraction in gas-solid mixture flow, being a func tion of solid circulating rate, gas velocity and riser position. The v alue of h(s) increased as the solid circulating rate became high. Howe ver, it was found that there was a critical solid fraction, ranged fro m 0.01 to 0.02, over which the increasing ratio dropped to a smaller o ne. This phenomenon was considered to be due to a characteristic chang e of the particle behavior around pipe.