A critical comparison between local heat and mass transfer coefficients of horizontal cylinders immersed in bubbling fluidised beds

摘要

Heat and mass transfer coefficients between bubbling fluidised beds and immersed surfaces are analysed in light of recent findings that clarify the properties of the emulsion phase in proximity of immersed surfaces. The correlation between heat and mass transfer in fluidised beds is not straightforward since the two phenomena obey to different transport mechanisms, so that the classical Chilton-Colburn analogy is not valid any longer. Therefore, the link between the two phenomena can be achieved only through a deeper understanding of the fluid dynamic and morphological characteristics of the granular flow in proximity of the exchange surface. In this paper, results available in the pertinent literature are critically compared and used to provide a simple methodology to correlate the average and local heat and mass transfer coefficient with the fluid dynamic field for the case of a horizontal cylinder immersed in a bubbling fluidised bed.