Abstract
A series of experiments was performed on a circulating fluidized bed (CFB) in order to investigate effects of the rolling motion on gas-solid heat transfer in the riser. Superficial velocity was changed in the experiments, while amplitude of the rolling motion and rolling period were fixed at 15deg. and 6s, respectively. The following results were obtained: (1)Heat transfer at the riser walls was dominated by collision between particles and the wall. Therefore, it depends on change of the gas-solid flow near to the wall region. Namely, heat transfer is augmented by the downflow of particles in the upper/mid part of the riser, and is promoted by the particles drifting on the distributor, in the lower part. (2)When the CFB stands upright, heat transfer rate in the upper/mid part grows gradually with the increase of the superficial velocity through activation of the downflow. On the other hand, the heat transfer rate in the lower part of the riser decreases rapidly with the superficial velocity increase, which reduces the suspension density through the flow regime change. (3)When the CFB undergoes the rolling motion, the downflow along the riser walls periodically changes, and the contact between particles and the walls is promoted. As a result, the heat transfer rate in the rolling motion is larger than that at upright attitude in the upper/mid part of the riser. In the lower part of the riser, the heat transfer rate also increases notably by the rolling motion, which increases suspension density there.
