Chaos Analysis and Contact Dynamics of Heat Transfer in a Gas-Fluidized Bed

Abstract

Abstract The present study examines fundamental aspects of the heat transfer and hydrodynamics in pulse-stabilized fluidization from a chaos perspective. The pulsed atmospheric fluidized bed combustor (PAFBC), a pulsed combustor coupled with an atmospheric bubbling fluidized bed, has technical advantages in energy efficiency and emissions. The flow in the tailpipe of the pulsed combustor was modeled in a laboratory scale fluidized bed by superimposing an oscillating component on a steady mean component. Time-varying local heat transfer was measured from a heated horizontal cylinder to the cold bed. Contact dynamics and spectral analysis of instantaneous heat flux signals clearly indicate that the bed hydrodynamics were significantly altered by the opposing secondary flow. The purpose of the present paper is to quantify these changes using chaos analysis and fractal measures. Specifically, the effect of the secondary flow on the chaotic dynamics and fractal characteristics of heat transfer were assessed by evaluating the Kolmogorov entropy and Hurst exponents, respectively, at several positions around the cylinder. The relation between chaos measures and contact dynamics was examined.