Heat transfer coefficients for tubes submerged in circulating fluidized bed
- Inst. for Thermo-Fluids Engineering and Science, Lehigh Univ., Bethlehem, PA (US)
Convective heat transfer coefficients were measured experimentally for a tube immersed vertically in a circulating fluidized bed. Circulating fluidized beds operate in the dilute transport regime of two-phase (solid/gas) flow. The dominant mechanism for heat transfer to surfaces is particle-induced convection. In this study, experiments were carried out in a circulating fluidized bed of 15 cm diameter and 11 m height. An instrumented tube of 9.5 mm diameter and 1.3 m length was placed vertically at the centerline of the fluidized bed to measure convection heat transfer coefficients at several different elevations in the bed. Three types of particles, with mean diameters ranging from 68 to 251 {mu}m, were used in the experiments at superficial gas velocities in the range of 1.3 to 8.2 m/s. This paper reports that results showed that the convective heat transfer coefficients with solid/gas two-phase circulation were two to three times greater than those for single-phase gas convection at the same velocity. For a given gas velocity, the coefficients increased with increasing solid mass flux, but decreased with elevation. It was demonstrated that the heat transfer coefficients for the immersed tube and for the bed wall could be correlated with different functional dependence on the two-phase suspension density.
- OSTI ID:
- 5522890
- Journal Information:
- Experimental Heat Transfer; (United States), Vol. 4:4; ISSN 0891-6152
- Country of Publication:
- United States
- Language:
- English
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