FLUID-BED HEAT EXCHANGERS—A NEW MODEL FOR PARTICLE CONVECTIVE ENERGY TRANSFER

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Abstract
A new model is presented for the wall-to-bed heat transfer from solid surfaces immersed in fluidized beds. This model makes use of some basic ideas adopted from the kinetic theory of gases in order to describe the mechanism of energy transfer through the moving particles (“particle convection”). The parallel—and in most cases less important—gas convective and radiative contributions to the total heat transfer coefficient are calculated from well known equations from the literature. The predictions of the new model are in good agreement with many experimental observations, in particular as to the non-monotoneous variation of heat transfer coefficients with gas velocity and particle diameter. Literature data for particle diameters from 0.01 to more than 10 mm, various particle materials, some different gases, various pressures, and temperatures up to more than IOOO°C are compared with the model calculations.