X-ray imaging for flow characterization and investigation of invasive probe interference in travelling fluidized bed

Abstract

X-ray imaging was employed to visualize the internal flow structures of the travelling fluidized bed (TFB), operating in the bubbling and turbulent flow regimes. The degree of interference of a 4-mm diameter intrusive probe inserted in the gas-fluidized bed was investigated by comparing the time-average voidage in a region of the bed operated with and without the probe being present. Transition from bubbling to the turbulent fluidization regime was visually inspected from images obtained by the X-ray system and quantitatively characterized in terms of statistical parameters associated with grayscale intensity probability distribution functions (PDF). Voidage data obtained by different measurement techniques are compared with time-average voidages obtained by X-rays and borescopic imaging. The hydrodynamic data provided by this study extend the benchmark database produced from the experiments performed on the TFB for validation of CFD and other models.