Macroscopic description of adsorption-diffusion processes in porous media (Q2771724)

To describe theoretically practically relevant environmental problems by using field equations, the author formulates some continuum mechanics notions, and then derives balance equations for one- and multicomponent bodies. Boundary conditions and initial values are analyzed in order to close the problem. The author considers classical kinematic and dynamic conditions as well as a mixed condition which reflects the mass transport out of the body. The mass transfer rate is assumed to be proportional to the pressure difference between the body and external medium. The boundary condition contains also a surface parameter related to the boundary layer. Boundary conditions for porous materials are compared with boundary conditions in the presence of heat conduction.NEWLINENEWLINENEWLINEThe complete system is first illustrated by examples without mass exchange. After this the author introduces an adsorption-diffusion model. The source in the mass balance consists of two parts. The first is the Langmuir part in which a change of partial pressure in the absorbate yields an isothermal change of the fluid volume fraction on the surface, leading to a new phase equilibrium. The second part describes the change of internal surface coupled with the source of porosity. Properties of the model are demonstrated on two examples. Both are solved by use of perturbation method.