NUMERICAL SIMULATION OF COUPLED HEAT AND MASS TRANSFER IN HYGROSCOPIC POROUS MATERIALS CONSIDERING THE INFLUENCE OF ATMOSPHERIC PRESSURE

Abstract

A model of simultaneous transport in hygroscopic porous materials was developed. Water in fabrics is considered to be present in three forms: liquid water in the void space between fibers, bound water in the fibers, and vapor. It is assumed that the heat and mass transport mechanisms include movement of liquid water due to the capillarity and atmospheric pressure gradient, diffusion of vapor within interfibers due to the partial pressure gradient of vapor and total gas pressure gradient, diffusion of vapor into fiber, evaporation, and condensation of water. The moisture diffusion process into hygroscopic porous materials such as wool fabrics was simulated. At normal atmospheric pressure, the results were compared with experimental data on the temperature and water content changes reported in the literature. The distribution of temperature, moisture concentration, liquid water saturation, and atmospheric pressure in the void space between fibers at different boundary conditions are numerically computed and compared. The conclusion is that atmospheric pressure gradient has significant impact on heat and mass transport processes in hygroscopic porous materials.