Surface Evaporation
Physical transport mechanisms describe the movement of vapor molecules across the stagnant air film adjacent to a wet textile surface during drying or degasification. In industrial fabric processing, boundary layer mass transfer governs how rapidly moisture and volatile solvents escape from woven structures into surrounding air streams. The thickness of this stagnant fluid layer controls the resistance to vapor migration.
Fluid Dynamics
Air velocity across the fabric surface reduces fluid film thickness, accelerating phase change rates during stenter drying cycles. Laminar flow creates thicker boundary layers with higher diffusion resistance, whereas turbulent flow disrupts stagnant air and enhances vapor removal. Textile construction features, including pile height and yarn roughness, alter local micro-turbulence near the surface boundary.
Heat transfer from heated air jets works simultaneously with mass movement, providing latent heat required for liquid vaporization.
Drying Kinetic
Relative humidity of the bulk air stream dictates the driving force for mass migration across the boundary layer. Saturated air reduces concentration gradients, stalling chemical evaporation regardless of surface temperature. Dryer exhaust dampers adjust ambient humidity levels to maintain steady mass flux.
Process Limit
Mass transfer principles govern surface evaporation exclusively when free moisture or volatile liquid resides on fiber exteriors. Internal capillary flow and bound water desorption inside core fibers operate under distinct physical diffusion equations.
