This work present. a detailed study of heat and mass transport phenomena between a large sublimable object and a gas-solid fluidized bed of either inert or adsorbent fine panicles. Heat (h) and mass (k)transfer coefficients are related to the size and adsorption capacity of the fine particles, as well as to the diameter of the spherical immersed object and to the bed temperature. Convective and conductive components are also identified, and correlations are proposed to predict all of them. The significant differences which appear for the various working conditions may be accounted for considering the particular mechanisms that prevail in every case. A simple "surface renewal" model clearly shows the leading role of the object surface temperature. For adsorbent panicles, a local overheating phenomenon at the exchange surface is demonstrated.