Experimental study of pressurized gas-fluidized bed heat transfer

This paper reports on an experimental study of the influence of operating pressure, in the range 150-1100 kPa, on wall-to-bed heat transfer coefficient in a bubbling fluidized bed. Both Geldart Group A and B solids were studied and the fluidizing gases were air and superheated steam. Fluidizing velocities were in the range 1-33 U-mf and wall temperatures in the range 125-275 degreesC. Wall-to-bed heat transfer coefficients were found to increase steadily with increasing fluidizing gas velocity and not to pass through a maximum. Increase in operating pressure was found generally to result in an increase in wall-to-bed heat transfer coefficient, although the effect is probably non-linear. In the bubbling regime, the wall-to-bed heat transfer coefficient was found to change with vertical position in the bed. Wall-to-bed heat transfer coefficients decreased when the bed entered the slugging regime. (C) 2001 Elsevier Science Ltd. All rights reserved.