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Abstract: This work reports experimental results on the heat transfer between a fluidised bed of fine particles and a submerged surface. Experiments have been carried out using different bed materials (polymers, ballotini, corundum, carborundum and quartz sand) with Archimedes number between 2 and 50. Dry air at ambient pressure and temperature has been used as fluidising gas. Three different exchange surfaces, namely a sphere and two cylinders with different base diameter and same height, have been used. Experimental results show that the heat transfer coefficient increases with particle Archimedes number and is almost independent from particle thermal conductivity for K p/K g >30. Finally, the comparison of heat transfer coefficient for the different surfaces shows that the effect of the surface geometry may account for a 30% variation in the heat transfer coefficient, with higher differences occurring for coarser particles. [Copyright &y& Elsevier]

Abstract: In recent times, the possible application of fluidisation technologies to the surface treatments of engineering materials becomes a subject of growing interest both for manufacturing and chemical industries. Heat and mass transfer rates between the surface and the fluidised bed strongly influence the performance of the surface treatment. Experimental results of heat transfer between a submerged surface and a fluidised bed are presented in this article. This work is focused on the influence of bed material properties and surface geometry on heat transfer coefficient. Experimental tests show that the heat transfer coefficient is notably affected by the shape of the immersed surface resulting higher for surfaces with better aerodynamic shape. An interpretative model, based on the dimensional analysis, has been used for the description of the experimental results. [Copyright &y& Elsevier]