ABSORPTION AND DESORPTION OF WATER ALONG THE LONGITUDINAL AXIS ABOVE AND BELOW THE FIBER SATURATION POINT - (SHORT-TIME OF ABSORPTION)

The process of absorption of liquid water along the longitudinal direction is studied by using short time of immersion (Shorter than 30 min). The water is then transported below the fiber saturation point at the beginning of the process and above this fiber saturation during the greater part of the process. The following step of desorption is also studied for the presaturated sample, by exposing it in air. A one dimensional transport is studied in all cases through the thickness of parallelepipedic sample whose other faces are protected from water. Transient diffusion with a constant diffusivita is found to describe the process of absorption, and diffusion-evaporation explains the process of desorption. Analytical solutions when the initial moisture content in the sample is uniform, and numerical models in other cases, have been successfully tested to describe the process of absorption and desorption.