Pore scale modelling of moisture transfer in building materials with the phase field method

¹ KU Leuven, Department of Civil Engineering, Building Physics Section, Kasteelpark Arenberg 40, 3001 Leuven, Belgium
² University of Innsbruck, Unit for Energy Efficient Buildings, Technikerstrasse 13, 6020 Innsbruck, Austria

^* Corresponding author: michele.janetti@uibk.ac.at

Abstract

This study explores the applicability of the phase field method for modelling moisture storage and transport in porous materials. Accordingly, the system is treated as a continuum where the phases (liquid and humid air) are separated through a diffuse interface, which evolves in the pores until the equilibrium state is reached. The interface thickness is related to the surface tension, while the contact angle is defined as a boundary condition. The mass transfer in the porous matrix is driven by the Cahn-Hilliard equation and the phase transition is controlled by an equation of state. The above method is tested for a simple geometry (infinitely extended parallel plates), by comparing the numerical outcomes against available measured data and analytical solutions. The challenges arising for a further application to complex pore structures and real building materials are discussed.