부산대학교 도서관

The present study examines the effect of an opposing oscillatory flow on local, instantaneous heat transfer and pressure in a laboratory scale gas-fluidized bed. The experimental facility models a Pulsed Atmospheric Fluidized Bed Combustor (PAFBC), a hybrid combustor concept that couples a pulsed combustor with an atmospheric bubbling fluidized bed. Time-varying data were acquired at eight angular positions around a horizontal cylinder submerged in a monodisperse distribution of particles having a weight mean diameter of 345 {micro}m. Total flow rates employed in the present study ranged from 10 to 40% greater than the flow required for minimum fluidization. Spectral analyses of local, instantaneous heat flux and pressure clearly indicate that the bed hydrodynamics were significantly altered by the opposing secondary flow. The behavior of time-varying local pressure and heat transfer in fluidized beds in the absence of a secondary flow is consistent with deterministic chaos. Kolmogorov entropy estimates from local, instantaneous pressure suggest that the degree of chaotic behavior was substantially suppressed for operating conditions with low primary and secondary flow rates, and a secondary flow forcing frequency of 15 Hz. In contrast, entropy estimates from measurements of local, instantaneous heat transfer suggest no clear indication of chaos suppression for these operating conditions.