HEAT-TRANSFER BETWEEN A SURFACE AND A FLUIDIZED-BED - CONSIDERATION OF PRESSURE AND TEMPERATURE EFFECTS

A two-zone model of heat transfer between a fluidized bed and an immersed surface (J. Engng Phys. 56(5), 767-773 (1989) is used to correctly take into account the effect of the fluidized gas pressure and of the surface and bed temperatures on the overall heat transfer coefficient considered as the sum of conductive (h(cond)), convective (h(conv)) and radiative (h(r)) components. The quantity h(cond) represents the effect of contact thermal conductivity of solid particles and also their convection near the heat transfer surface, h(r) takes account of the effect of the bed non-isothermicity near the surface on its effective emissivity. Based on the model used, correlations are obtained for computing the overall heat transfer coefficient. Comparison with the literature data shows that these correlations are valid over a wide range of experimental conditions: 0.1 less-than-or-equal-to d less-than-or-equal-to 6.0 mm; 0.1 less-than-or-equal-to p less-than-or-equal-to 10.0 MPa, 293 less-than-or-equal-to T infinity less-than-or-equal-to 1713 K; 293 less-than-or-equal-to T(w) less-than-or-equal-to 1373 K.