Application of Computational Fluid Dynamics to Protective Clothing System Evaluation

Abstract

Convection, diffusion, and phase change processes influence heat and mass transfer through textile materials used in clothing systems. For example, water in a hygroscopic porous textile may exist in vapor or liquid form in the pore spaces or in bound form when it has been absorbed by the solid phase, which is typically some kind of hydrophilic polymer. Phase changes associated with water include liquid evaporation/condensation in the pore spaces and sorption/desorption from hydrophilic polymer fibers. Certain materials such as encapsulated paraffins may also be added to textiles; these materials are designed to undergo a solid-liquid phase change over temperature ranges near human body temperature, which influences the perceived comfort of clothing. Additional factors such as the swelling of the solid polymer due to water imbibition, and the heat of sorption evolved when the water is absorbed by the polymeric matrix, can all be incorporated into the appropriate conservation and transport equations describing heat and mass transfer through clothing layers. These physical factors, nonlinear material properties, and complex multiphase flows make the task of modeling and predicting levels of protection and comfort of various clothing designs difficult and elusive. Computational fluid dynamics (CFD) has proven to be useful at several levels of material and system modeling to evaluate and design protective clothing systems and material components. This paper summarizes current and past work aimed at utilizing CFD techniques for protective clothing applications.