Parametric studies and effect of scale-up on wall-to-bed heat transfer characteristics of circulating fluidized bed risers

Abstract: In the present work a comparative study of steady state wall-to-bed heat transfer was conducted along the risers of height 2.85m of three different circulating fluidized beds (CFBs) with bed cross sections of 0.15m×0.15m, 0.20m×0.20m, and 0.25m×0.25m, respectively. Experiments were conducted on each CFB unit for five superficial air velocities (U =2.5m/s, 2.75m/s, 3m/s, 3.3m/s, and 4m/s) and two different weights of sand inventory per unit area of the distributor plate (P =1750N/m2 and P =3050N/m2) with average sand particle size of 460μm. Bed temperature distributions across the three risers were measured and compared at different heights (1.04m, 1.64m, and 2.24m above the distributor plate). Axial distribution of heat transfer coefficient along the height of riser was evaluated and compared for the three bed cross sections. Effect of superficial velocity of air, sand inventory, and bed cross section on bed temperature and heat transfer coefficient was investigated. An empirical correlation was developed for the bed Nusselt number as a function of various non-dimensional parameters based on the parametric study. The correlation was compared with available literatures. [ABSTRACT FROM AUTHOR]