Study of bed-to-wall heat transfer with twisted tape at the upper splash region of a pressurized circulating fluidized bed unit

In the present investigation, bed-to-wall heat transfer coefficient was studied at the upper splash region of a pressurized circulating fluidized bed (PCFB) riser of internal diameter 54 mm and height of 2000 mm. The experiments were carried out at three different temperatures. At each temperature, experiments were performed at three different operating pressures viz. 1, 3 and 5 bar to investigate the influence of operating pressure. At each pressure condition, bed temperature distributions along the height of the riser were investigated. The superficial velocity was maintained constant throughout the experiment at 7 m/s. The effect of twisted tape inserts on heat transfer at the upper splash region of the riser was studied at three different solid inventories of 400, 600 and 800 g and the results obtained are compared without twisted tape inserts. The average particle size of sand used in the experiment was of 307 μm. The overall uncertainty in calculating the heat transfer coefficient was found to be ±12.3%.