A Comparative Study of Whirling- And Conventional-Fluidized Beds in Their Application to Dehydration. I. Heat and Mass Transfer Analysis

Heat and mass transfer characteristics of conventional- and whirling-flui-dized beds were compared in order to determine their suitability in dehydration applications. Results obtained for the particular case of wheat dehydration indicated that whirling beds present a better design with higher heat and mass transfer coefficients than conventional-fluidized beds. In fact, studies carried out in two-stage fluidized beds showed that whirling beds had approximately 1.9 times higher heat transfer coefficients in the first stage and 1.7 times higher in the second stage than conventional-fluidized beds. Moreover, mass transfer coefficients were 1.9 and 2.8 times higher in the first and second stages, respectively, as compared to conventional-fluidized beds. Conventional-fluidized beds were observed to exhibit a tendency for pulsating fluidization, resulting in slugging, channeling, and bubbling, factors that impair heat and mass transfer. This behavior was seldom found in whirling beds for the conditions investigated.