Model for simulation of freezing and thawing processes in building materials

This paper presents a mathematical model for simultaneous heat and moisture transfer under freezing–thawing in porous hygroscopic material. Even below 0°C, unfrozen liquid water exists in the material which plays an important role in the processes. The model takes into account the existence of unfrozen liquid water. The system is treated as a three-(gas, liquid and solid) phase system of water. Moisture chemical potential is used as a moisture potential. Under freezing, moisture chemical potential is a unique function of local temperature. So, during freezing, two unknown variables to be solved are solid water content and moisture potential or temperature. A simple example of simulation for freezing processes is shown.