This study examines how yarn microstructure influences isothermal water-vapor transport and the associated evaporative heat loss under ISO 11092 skin-model conditions. Sweating guarded hotplate experiments were performed on PET yarn-array specimens to measure evaporative heat flux and moisture resistance. A fiber-level two-dimensional finite element model was then developed to reproduce the same boundary conditions and simulate transport through a PET fiber/air matrix. Using a full-factorial design, denier per filament, the number of filaments, and packing factor were varied independently, with multiple random filament arrangements used for each parameter combination to account for microstructural variability. The model reproduced the main experimental trends and gave predictions consistent with measured heat flux and moisture resistance for representative yarn configurations. Over the investigated design space, packing factor had the strongest influence: higher packing reduced heat and moisture flux and increased moisture resistance. Denier per filament and the number of filaments showed smaller but systematic effects, mainly through changes in pore connectivity and tortuosity. Statistical analysis indicated that main effects accounted for most response variation, while interaction effects were limited within the studied ranges. Flow-field results further showed a shift from internal flow penetration at low packing to bypass-dominated transport at high packing. These findings provide a validated framework for linking yarn-level structural parameters with heat–moisture transport performance in fibrous assemblies.
Xu et al. (Wed,) studied this question.