Some studies on wall-to-bed heat transfer in a pressurized circulating fluidized bed unit

摘要

In the present work, a pressurized circulating fluidized bed (PCFB) unit of 54 mm inner diameter and riser height Of 2000 mm has been fabricated to investigate the effect of pressure on suspension density and heat transfer. The effects of blending of biomass in sand, and superficial velocity on bed hydrodynamics and heat transfer has also been studied. Experiments have been conducted at four different percentage blending of biomass such as 2.5 %, 7.5 %, 15 % and 20 % in sand with two different weight composition ratios and at a superficial velocity of 5 m/s. Operating pressure is varied from 1 to 5 bar in a step of 2 bar. Results show that, the axial heat transfer coefficient increases from the bottom to the top of heat transfer probe with the increase in operating pressure. The radial variation of heat transfer coefficient decreases from the wall to the core of the heat transfer probe. The heat transfer coefficient is also found to be higher in between the 7.5 to 15 % biomass blending in sand. The overall uncertainty in calculating heat transfer coefficient is found to be 3.90 %.