Development in the textile industry expands executive boundaries to produce industrial clothing and textiles. Better understanding of traort phenomena in textiles could help in optimizing aspects of the making textiles process and development of new textile with special applications. The coupled heat and mass transfer mechanism in porous textiles is complicated. Heat and moisture transfer in textile is coupled with the sorption of water vapor in the fibers and the associated energy change within. The heat transfer mechanism in porous textiles includes conduction by the solid material of the fibers, conduction by intervening air, radiation, and convection. Meanwhile, the moisture transfer mechanisms include vapor diffusion in the void spaces, moisture sorption by the fibers, capillary effects and evaporation/condensation. The water vapor diffuses in the void spaces of porous fibrous media due to the difference in the water vapor concentration. The moisture sorption by the fibers takes place because of the water vapor’s internal chemical compositions and structures. Until now, the study of traort phenomena spent much time and energy, but nowadays with the advancement of numerical methods, and tools like Computational Fluid Dynamics (CFD), accurate simulation of textiles and fibers and adsorption in fibers is possible. In the present study, using these tools, the fabric will be simulated with two methods. The first approach is to consider fabric as a porous media. The second approach is to simulate fabric as a structure composed from large number of fibers. Textiles ability in the excess heat and moisture transfer from the body are studied in this project. For this purpose, the diffusion of heat and mass from the body skin into the fabric and its surrounding media is simulated. The moisture of the skin by diffusion through the fabric is transferred from lower layers of fabric, adjacent to the skin, to the fabric surface and then to the surrounding environment. Therefore, in this study, the governing heat and mass transfer equations and structural relationships are presented and solved, using CFD. The first approach modeling is performed to model a fabric as a porous media for two cases of PAN fibers and wool fibers. The effect of physical variables is considered on transfer properties of textiles. To verify the results, the experimental data is used for comparing the predictions of PAN fibers. The second approach, which takes into account the water vapor sorption mechanisms in fibers, is developed to describe and predict the coupled heat and moisture diffusion in porous textile. The model is based on the energy and moisture conservation equations during the traortation for textiles made from PAN fibers. This model takes the geometrical characters of the fiber into account. It allows the study of the direct sorption in fibers and the influence between the fibers. The presence of moisture in textiles heavily affects its performance. In this model, absorption of water vapor in the air within the fibers by suitable boundary conditions is simulated. In order to determine the boundary conditions on the fibers surface, appropriate subprograms are developed and implemented into the present CFD code. The processes of water vapor transfer in the void space between fibers, sorption in fibers and their interaction with heat transfer are illustrated. The effects of porosity of the fabric on heat and mass transfer are also discussed. Key Words : Coupled Heat and Moisture Transfer, Moisture Sorption, Porous Textiles.
