Bubble behavior and void fraction fluctuation in vertical tube banks immersed in a gas-solid fluidized-bed model

摘要

Heat transfer characteristics of tube-banks immersed in a fluidized bed are dominated by the time averaged as well as fluctuating characteristics of fluidized-particle movement especially in the neighboring region of heat transfer tube. Quantitative flow visualization of the fluidized bed installed vertical tube-banks has been successfully conducted using neutron radiography and image processing technique. The quantitative data of void fraction distribution as well as the fluctuation data are presented. The bubbles formed in the bed rise along by the vertical tubes and observed bubble size is smaller than that in a free bubbling bed without tube-banks. The bubble diameter is well correlated by the modified Mori and Wen's correlation. The bubble rise velocity is also well correlated by applying the drift-flux model. These results are consistent for both tested bed materials of Geldard's B- and A- particles, while the bubble size is significantly different between two kinds of particles. (C) 2002 Elsevier Science Inc. All rights reserved. [References: 25]