ABSTRACT
Drying wet nano-porous media are coupled in a complicated way. The structure of the solid matrix varies widely in shape. There is, in general, a distribution of void sizes, and the structures may also be locally irregular. Energy transport in such a medium occurs by conduction in all of the phases. Mass transport occurs within voids of the medium. In an unsaturated state these voids are partially filled with a liquid, whereas the rest of the voids contain some gas. It is a common misapprehension that non-hygroscopic fibers (i.e., those of low intrinsic for moisture vapor) will automatically produce a hydrophobic fabric. The major significance of the fine geometry of a textile structure in contributing to resistance to water penetration can be stated in the following manner:
The requirements of a water repellent fabric are (a) that the fi bers shall be spaced uniformly and as far apart as possible and (b) that they should be held so as to prevent their ends drawing together. In the meantime, wetting takes place more readily on surfaces of high fi ber density and in a fabric where there are regions of high fi ber density such as yarns, the peripheries of the yarns will be the fi rst areas to wet out and when the peripheries are wetted, water can pass unhindered through the fabric.
