Multiphase Heat and Mass Transfer Through Hygroscopic Porous Media with Applications to Clothing Materials

A set of partial differential equations describing time-dependent heat and mass transfer through porous hygroscopic materials was developed which includes factors such as the swelling of the solid due to water inhibition, and the heat of sorption evolved when the water is absorbed by the polymeric matrix. A numerical code to solve the set of nonlinear coupled equations was developed, and applied to an experimental apparatus designed to simulate transient and steady-state convectiondiffusion conditions for textile materials. Results are shown for hygroscopic porous textiles under conditions of pure diffusion, combined diffusion and convection, and pure forced convective flow. The numerical model was integrated with an existing human thermal physiology model to provide appropriate boundary conditions for the clothing model. The human thermal control model provides skin temperature, core temperature, skin heat flux, and water vapor flux, along with liquid water accumulation at the skin surface. The integrated model couples the dynamic behavior of the clothing system to the human physiology of heat regulation. This provided the opportunity to systematically examine a number of clothing parameters which are traditionally not included in steady-state thermal physiology studies, and to determine their potential importance under various conditions of human work rates and environmental conditions.