Modeling diffusion and types I-V sorption of water vapor in heterogeneous systems

A sorption and diffusion model is developed using a mobile-immobile decomposition of the vapor con-centration. Henry's mode represents the mobile species which diffuses through the solid, while Langmuir and pooling modes represent possible immobilization processes that cause nonlinearities in sorption capacity. The model can simulate the five classical sorption types and can incorporate additional dynamics compared to models based on thermodynamic equilibrium. Additionally, the framework allows for discontinuities in material properties encountered in multi-material systems. The resulting non-linear coupled equations are solved by employing a finite element method to discretize in space, and a back-ward Euler method to discretize in time. The discretized system of equations is solved via a Newton -type iteration scheme at each time-step. Four different materials are parameterized for the model, which are then used in examples to demonstrate the model's ability to capture complex sorption processes in multi-material systems. (c) 2023 Elsevier Ltd. All rights reserved.

Automated summary

A sorption and diffusion model is developed to simulate complex sorption processes in multi-material systems. The model uses a mobile-immobile decomposition of the vapor concentration, with different modes representing mobile and immobilization processes. It can simulate five types of sorption and incorporate additional dynamics compared to thermodynamic equilibrium-based models. The model is solved using finite element method and backward Euler method, with four different materials parameterized and demonstrated in examples.