Mikro-Makro-Wechselwirkungen in strukturierten Medien und Partikelsystemen "Numerical Study of intraparticle heat and mass transfer during drying"

The aim of the study is to identify numerical methods that are necessary to provide accurate and efficient computations of the equations governing drying process. Drying of a porous material, i.e., removal of water from the pores by evaporation, is a complex process which involves heat and mass transfer. Porous media may be isotropic or an-isotropic. We are working with isotropic porous media at constant temperature (isothermal drying). The governing equations are strongly nonlinear, coupled diffusion equations with nonlinear boundary conditions. The laws of the variables change with different stages of drying. As an initial step, we reduced the problem by considering only the water balance equation which contains one primary variable and 17 dependent variables. Numerically the finite volume approach with explicit, semi-implicit and implicit discretizations has been studied in one dimension. Explicit scheme is studied in one and two dimensions. It has been observed that semi-implicitness is efficient and sufficient to guarantee the stability. Further we are interested in studying invariant regions and positivity of the solution. As a next step, we also consider the air balance which makes the system strongly coupled. We have results with an explicit finite volume scheme. Work is under progress in studying the implicit and semi-implicit discretizations for the coupled system.