Heat transfer in pulse-stabilized fluidization – Part 2: local, instantaneous analysis

Enhancements in overall heat transfer from a heated, submerged horizontal cylinder in a pulse-stabilized fluidized bed were observed in Part 1 for operating conditions with low primary and secondary flow rates and low pulse frequencies. These increases in overall heat transfer were found to be a consequence of significant localized enhancements. In the present paper, through spectral and contact time analyses of local, instantaneous heat transfer, increases in both bubble phase and emulsion phase heat transfer coefficients were observed. Instantaneous measurements in a monodisperse distribution of 345 μm particles, fluidized to rates from 1.1 to 1.5 times greater than that required for minimum fluidization, are investigated. Waveforms of these time traces are characterized as exhibiting either locally or globally dominated hydrodynamic phenomena. Heat transfer with an opposing oscillatory flow exhibits characteristics of globally dominated hydrodynamics, whereas heat transfer traces acquired near minimum fluidization with no secondary flow are dominated by hydrodynamics localized at the surface of the cylinder.