Trensent heat transfer in circulating fluidized bed

Abstract EN

The paper presents practical data from the experimental work on heat transfer between immersed heat transfer surface and Circulating Fluidized Bed (CFB) in special experimental rig with certain dimensions and with set of operation conditions at constant heat flux (120 W) supplied to the electrical heater.

The fluidizing medium was air at different velocities ( 4 and 5.5 m / s)and two different size of sand particles were employed (161 and 257 μm), as well as, different initial bed heights were used in the experiments (i.e, 18 and 31 cm).

Heat transfer coefficients calculated instantaneously by instant temperature of bed and heater surface are found to increase with fluidized air velocity and with heat flux, but, they show an inverse dependence on particle size, and directly proportional with initial bed height which represents the bed density.

The stabilization case depended strongly on fluidization density, where the required time to reach steady state case of heat exchange increase with increasing initial bed height as well as increasing the particle size.

The experimental heat transfer coefficient data were correlated in terms of Nusselt number with other parameters.

This correlation of the present study are assessed by comparing it with the available correlation in literature for the overall heat transfer coefficient.

Comparison shows reasonable agreements in some results and large deviation in others.

Also this correlation not to correspond with the experimental values in some conditions.