| The heat transfer coefficient between a suspension of FCC particles and a horizontal cylindrical heat transfer probe inserted into the riser and the standpipe of a CFB has been measured. In the riser, the heat transfer coefficient ranged from 70 W/(m2.K) to 475 W/(m2.K) when the solids mass flux varied between 0 to 100 kg/(m2.s). On a plot of heat transfer coefficient versus solids flux, three zones have been identified. The heat transfer coefficient has been modeled based on an assumed mechanism of heat transfer between the particles and the heat transfer probe for each of these zones. In the downcomer, the heat transfer coefficient ranged from 70 W/(m2.K) to 310 W/(m2.K) when the downcomer solids flux varied between 3 to 45 kg/(m2.s). The heat transfer coefficient increases with increasing solids flux, is nearly independent of radial position and is negligibly affected by gas bypassing in the standpipe. The heat transfer coefficient has also been successfully modeled in the downcomer. In the riser, the flow required a shorter distance to recover from the disturbance of the introduction of the heat transfer probe at higher solids mass fluxes. |
