The convective heat and mass transfers from a single particle, surrounded by a flowing fluid,
have important practical applications in Chemical Engineering. Among them are process component
cooling, adsorption, distillation, catalytic reactions, extraction, and drying in fixed and fluidized beds.
This chapter is intended to provide a concise vision of the phenomena emerging during the drying of
single particles. A case study is presented with the proposition of a mathematical model for the drying
process of spherical gel systems considering the effect of fluid flow on mass transfer and shape
evolution. The experimental results presented were evaluated under a laminar fluid flow with different
particle diameters and fluid velocities. Shrinkage of the samples was observed through digital images,
and it was used for the calculations of the shape factors and apparent specific mass. The mathematical
model considers two-dimensional mass transfer inside the samples, variable effective diffusivity, linear
shrinkage, and non-uniform mass transfer by convection. The results confirmed that the major factor for
the mechanical alterations of the spherical gel particles was the non-uniform drying owing to the fact
that the mass transfer rates over the forward surface of the sphere are greater than those at the rear
hemisphere. The proposed mathematical model represented the two-dimensional moisture profiles
inside the sample and their consequent shape evolutions. This chapter attests the need for the
consideration of the fluid flow effect on the mathematical modeling and contributes to a better
understanding and the technological development of the drying processes.
Keywords: Shrinkage, boundary layer, convection, moisture profiles, mathematical modeling.
