Heat transfer tests were conducted with an air-cooled tube in a coal-fueled fluidized-bed furnace. A 12-mm-OD (0.5-in.) tube was used, and the tests were run in a 0.5 x 0.5 m (18 x 18 in.) furnace operating at atmospheric pressure and 9,00°C (1650°F). Results were obtained for an air flow inside the tube of 10 kg/hr (23 1b/hr) and a mean bed particle size of 460 µm at fluidizing velocities of 0.2 to 0.7 msec (0.8 to 2.2 fps). The heat transfer coefficient from the bed to the tube wall increases from ∽227 W/m2-°C (40 Btu/ hr-ft2-°F) at a fluidizing velocity of 0.23 m/sec (0.76 fps) to a value of ∽483 W/m2-°C (85 Btu/hr-ft2-°F) at a velocity of 0.5 m/sec (1.6 fps). At higher velocities, the heat transfer coefficient is constant at the higher value.
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