EFFECT OF SECONDARY AIR INJECTION ON BED-TO-WALL HEAT-TRANSFER IN A CIRCULATING FLUIDIZED-BED

The effects of secondary air ratio (0 similar to 50%) and injection ty pes (radial or tangential) on the bed-to wall heat transfer coefficien t have been determined in a circulating fluidized bed (0.1 m-I.D, x 5. 3 m-high). The bed-to-wall heat transfer coefficient increases with in creasing particle suspension density, The heat transfer coefficient by gas convection increases, but the overall convective heat transfer co efficient decreases with increasing the radial injection of secondary air, The convective heat transfer coefficient increases, but the parti cle convective component decreases with the tangential secondary air i njection, A model, based on the model of Basu (1990), is proposed to p redict the bed-to-wall heat transfer coefficients in a circulating flu idized bed (CFB) with the tangential secondary air injection system.