Study of forces on immersed tubes in fluidized beds

Abstract

The external forces imparted by the bed material on the heat exchange tubes in a fluidized bed combustor contribute to failure of the tubes and their support systems. The objective of this investigation was to provide data on tube forces to be used in structural design. Forces on heat exchange tubes of various lengths were measured over a range of fluidization conditions. The parameters varied in the experiments were superficial gas velocity, bed media particle size, tube spacing, and tube array height above the gas distributor. Although most of the experiments were conducted in cold fluidized beds, several tests were run at high temperature. The force-time histories of the vertical component of the force on the tube consisted of a series of pulses, the magnitudes of which were approximately linearly proportional to tube length. The horizontal component of the force generally oscillated from side to side in pulses with magnitudes less than half of those of the vertical force. Spectral analyses of the time series indicated that the primary frequency composition of the load was below 25 Hz.

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