Heat transfer in cross-flow tube-banks immersed in a fluidized bed with normal and down-flow mode operations

摘要

Fluidized-bed boiler of bubbling-type and/or circulating-type is an important technology for coal and/or incineration firing. To meet the limitation for the environmental importance, it is essential to control the bed temperature precisely at a predetermined level so as to less produce emissions. Provided the bed materials of moderate diameter, the heat transfer performance immersed in the bed is a function of the time-averaged void fraction, the residence time of solids in the thermal boundary layer and the solid convection between the boundary layer and the bulk. This paper describes the flow pattern around the tube-banks observed by using neutron radiography, and the heat transfer characteristics are discussed with respect to the flow pattern.