Heat transfer to horizontal cylinders immersed in fluidized beds has been extensively studied, but mainly in the context of heat transfer to boiler tubes in coal-fired beds. As a result, most correlations in the literature have been derived for cylinders of 25–50mm diameter in vigorously fluidizing beds. In recent years, fluidized bed heat treating furnaces fired by natural gas have become increasingly popular, particularly in the steel wire manufacturing industry. These fluidized beds typically operate at relatively low fluidizing rates (G/Gmf < 5) and with small diameter wires (1–6mm). Nusselt number correlations developed based on boiler tube studies do not extrapolate down to these small size ranges and low fluidizing rates. In order to obtain reliable Nusselt number data for these size ranges, an experimental investigation has been undertaken using two heat treating fluidized beds; one a pilot-scale industrial unit and the other a lab-scale (300mm diameter) unit. Heat transfer measurements were obtained using resistively heated cylindrical samples ranging from 1.3 mm to 9.5 mm in diameter at fluidizing rates ranging from approximately 0.5 × Gmf (packed bed condition) to over 10 × Gmf using aluminum oxide sand particles ranging from dp = 145–330 μm (50 to 90 grit). It has been found that for all cylinder sizes tested, the Nusselt number reaches a maximum near 2 × Gmf, then remains relatively steady (± 5–10%) to the maximum fluidizing rate tested, typically 8–12 × Gmf. A correlation for maximum Nusselt number is developed.
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18th International Conference on Fluidized Bed Combustion
May 22–25, 2005
Toronto, Ontario, Canada
Conference Sponsors:
- Advanced Energy Systems
ISBN:
0-7918-4183-9
PROCEEDINGS PAPER
Heat Transfer to Small Cylinders Immersed in a Fluidized Bed Available to Purchase
Jacob Friedman,
Jacob Friedman
Ryerson University, Toronto, ON, Canada
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Polo Koundakjian,
Polo Koundakjian
University of Waterloo, Waterloo, ON, Canada
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Dennis Rosero
Dennis Rosero
Ryerson University, Toronto, ON, Canada
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Jacob Friedman
Ryerson University, Toronto, ON, Canada
Polo Koundakjian
University of Waterloo, Waterloo, ON, Canada
Dennis Rosero
Ryerson University, Toronto, ON, Canada
Paper No:
FBC2005-78038, pp. 263-269; 7 pages
Published Online:
October 7, 2008
Citation
Friedman, J, Koundakjian, P, & Rosero, D. "Heat Transfer to Small Cylinders Immersed in a Fluidized Bed." Proceedings of the 18th International Conference on Fluidized Bed Combustion. 18th International Conference on Fluidized Bed Combustion. Toronto, Ontario, Canada. May 22–25, 2005. pp. 263-269. ASME. https://doi.org/10.1115/FBC2005-78038
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