Suspension‐to‐Surface heat transfer in a circulating‐fluidized‐bed combustor

Abstract

Abstract Heat transfer coefficients were measured for ciculating beds of sand particles of mean size 222 to 299 μm at temperatures of 340–880° C. Transfer coefficients were obtained for both a 1.22‐m‐long, 12.7‐mm‐OD vertical tube and a 1.59‐m‐long, 148‐mm‐wide membrane wall near the top of a 152‐mm‐square by 7.32‐m‐tall combustion column. For both surfaces and all temperatures, average heat transfer coefficients increased almost linearly with local suspension density which ranged from 0 to 70 kg/m 3 . Radiation played a significant role, especially at high temperatures and low suspension densities. Heat transfer coefficients also varied significantly with the lateral position of the tube. The vertical length of heat transfer surface is shown to be an important parameter allowing seemingly discrepant published results to be reconciled.