Empirical evaluation of convective heat and moisture transport coefficients in porous cotton medium

The air penetration within a porous clothing system oil a moving human being is all important physical process that considerably affects the heat and moisture resistance Of the textile material. This effect of the coupled convection heat and mass exchange within the clothing system is experimentally investigated and theoretically modeled to determine the heat and mass transfer coefficients between the air penetrating the void space and the solid fiber as a function of the velocitly of penetrating air Experiments were conducted inside environinentally controlled chambers to measure the transient moisture uptake of untreated Cotton fabric samples as well as the outer fabric temperature using an infrared pyrometer. The moisture uptake was conducted at three different volumetric flow rates Of 0.0067, 0.018 and 0.045 m(3)/sec/m(2) of fabric area to represent airflow penetrations that could result from slow, medium, and vigorous walking, respectively. The theoretical analysis is based oil a two-node adsorption model of the fibrous medium. A set of four coupled differential equations were derived describing time-dependent convective heat and mass transfer between the penetrating air and the solid fiber in terms of relevant unknown transport coefficients. The unknown model parameters were adjusted to fit the experimental data. The outer heat and mass transfer coefficients were found to increase with the air penetration flow rate.