Abstract
We present a general mechanistic model of mass diffusion for a composite sphere placed in a large ambient
medium. The multi-layer problem is described by a system of diffusion equations coupled via interlayer
boundary conditions such as those imposing a finite mass resistance at the external surface of the sphere. While
the work is applicable to the generic problem of heat or mass transfer in a multi-layer sphere, the analysis and
results are presented in the context of drug kinetics for desorbing and absorbing spherical microcapsules. We
derive an analytical solution for the concentration in the sphere and in the surrounding medium that avoids any
artificial truncation at a finite distance. The closed-form solution in each concentric layer is expressed in terms of
a suitably-defined inverse Laplace transform that can be evaluated numerically. Concentration profiles and drug
mass curves in the spherical layers and in the external environment are presented and the dependency of the
solution on the mass transfer coefficient at the surface of the sphere analyzed.
Anno
2019
Autori IAC
Tipo pubblicazione
Altri Autori
G. Pontrelli, E. Carr