Influence of air flow direction on thermal resistance and water vapor permeability of RIB knit fabrics

Thermal resistance and water vapor permeability play a critical role in thermo-physiological comfort. there are many factors,which can have influence on the thermal resistance and the water vapor permeability; one of them is airflow direction. this study is aimed to effort to identify the impact of airflow direction on thermal resistance and the water vapor permeability when forced convection heat transfer is used. 18 samples of rib knit fabrics made from the same polyester yarn were prepared. rib direction on the surface of rib knit fabrics provides a channel for airflow. the thermal resistance and the water vapor permeability in two directions of ribs against the airflow,perpendicular and parallel,was measured. it was found that there is the impact of rib directions on the thermal resistance and on the water vapor permeability. results indicates that the thermal resistance increases when the ribs lies parallel with the direction of airflow and the water vapor permeability has the tendency to decrease when the ribs lies parallel with the direction of airflow.