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ABSTRACT
A dynamic model of liquid water transfer coupled with moisture sorption, condensation, and heat transfer in porous textiles is developed by incorporating the physical mechanism of liquid diffusion in porous textiles into a coupled heat and moisture transfer model developed previously. An equation describing liquid diffusion behavior is developed in the form of the diffusion coefficient, and a numerical computational scheme to solve the coupled equations involves a fractional volume of fluid method. Experiments measuring fabric surface temperature are conducted to validate the model, and there is reasonable agreement between the predictions and the measurements.
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Numerical simulations of the coupled heat-liquid moisture transport of porous materials have wide industrial applications in textile engineering and functional designs for apparel. Heat transfer changes in porous media are influenced by the dispersion of fluid and the large contact surface area between the solid matrix and the fluid.
The heat transfer mechanisms in porous textiles include conduction by the solid material of the fibers, conduction by intervening air, radiation, and convection. Liquid and moisture transfer mechanisms include vapor diffusion in the void spaces and moisture sorption by the fibers, evaporation, and capillary effects. Water vapor moves through the textiles as a result of its concentration difference. Fibers absorb water vapor due to their internal chemical compositions and structures. The flow of liquid moisture through the textiles is caused by the fiber-liquid molecular attraction at the surface of fiber materials, which is determined mainly by the surface tension and effective capillary pore distribution and pathways. Evaporation and/or condensation take place, depending on the temperature and moisture distribution. The heat transfer process is coupled with moisture transfer processes with phase changes such as moisture sorption/desorption and evaporation/condensation.
Extensive research has been published on the diverse aspects of simultaneous heat and moisture transfer in the literature, both theoretically and experimentally. Henry [4] was the first researcher to begin the theoretical investigation of this phenomenon. He proposed a mathematical model to describe coupled heat and moisture transfer processes in textiles by considering moisture sorption/desorption in wool fibers. By assuming a linear relationship between the moisture content and temperature, he derived an analytical solution to the model. In 1969, David and Nordon [2] improved...