Alternate Basic l/b-model of Effective Porosity Created for Hydrophilic (l) and/or Hydrophobic (b) Moist Textile Materials

Abstract

There are several standard test methods (based on different construction mechanisms) and the respective experimental conditions (relative humidity, air velocity, test temperature) which lead to essentially different estimates of water vapour permeability as well as the effective transport coefficients for the same textile materials. To develop objective comparative methodology within a set of similar materials, one needs either to eliminate completely the effect of both factors above or to take into consideration their combined influence on the textile transport characteristics in a self-consistent manner. The latter, a more promising strategy of comparison, requires, first of all, a correct definition of properties related just to the textile materials, but not to the specific test-methods or to their experimental conditions and peculiarities. This work is an attempt to create a physically-plausible alternate model of hydrophilic (l) and/or hydrophobic (b) textile materials by the special concept of effective porosity dependent on the moisture content and, as a result, on the bulk density of fabric. We consider the permeability in the generalized Darcy's-Fick's law as the function of effective porosity, which controls all main transport coefficients of textile material. Any adjustable coefficients are absent in the alternate basic l/b-model proposed.

New Non-Stationary Gradient Model of Heat-Mass-Electric Charge Transfer in Thin Porous Media

“…We refer now the readers of present work to our previous results reported not only in [1] but also in [4][5][6] where the foundation of fluctuational thermodynamics model (FT-model) has been in detail represented. The main idea of latter was the extension of macroscopic nonequilibrium thermodynamics [2,3] on the spatial mesoscopic, nano-and, even, microscopic (i.e.…”

“…The conjectural replacement of the ( 2 8 R/ )-quantity in a medium by the effective quantity termed permeability of PM K [m 2 ] leads, often, to the confusions at its experimental determination and interpretation [1]. The additional, rather crude, from our viewpoint, approximations of the supposed convective velocity D u (termed the D'Arcy's velocity) and the conjectural Reynold's number for PM:…”

“…The fluctuation i-phase interpretation of thermal pressure (32,49,50) become the important indicative factors to control, for example, the given optimal conditions for the comfortable wear of TPM-fabrics. We have argued in our previous work [1] that the interrelation between the volume densities of matrix MM m / V , moist air ma ma m / V and water content (liquid) ll m / V is essential to specify the following factor of difference between the hydrophobic (hb) and hydrophilic (hl) TPMs: . In other words, the very small δ-thickness of TPM can become in a combination with the given asymptotic parameter 0   the determinative factors for its changeable properties and, first of all, permeability in accordance with the proposed in [1] alternate basis l/b-model of the moist permeable media (see, in particular, Eq.…”

“…It was recently shown [1] that all above-mentioned characteristics of a realistic PM can manifest their cumulative effect by the rather simple experimental observation, at least, for the particular case of TPMs (see below). The specific feature of latters is the very small actual magnitude of thickness ( L   ) which becomes much less than two other linear TPM-sizes.…”