MODELIZATION PRINCIPLES FOR DRYING OF GELS

When one wants to understand and model the drying of high water conten t gels, one needs to gather all thermal physical parameters and to der ive a physical model based on independently measured parameters. We ch ose to work experimentally and theoretically on water diffusion and dr ying of spheres of polyacrylamide gel. We have demonstrated the strong influence of vitreous transition on the relationship of water diffusi vity with moisture content. Values of the diffusion coefficient and te mperature shift factor for diffusion have been proposed. Convective an d micro-wave drying kinetics show the presence of a drying phase purel y specific to radiation absorption. Finally, we have proposed a mathem atical model containing independent physical parameters, which not onl y predicts mass fluxes but also analyses critical physical phenomena.