In order to understand the drying process of fabrics, drying experiment in household manner was conducted at five atomospheric conditions. (10 and 20°C at 65% RH, and 30°C at 40, 65 and 90% RH)
Other experiments on 18 samples of different fabrics were conducted in a condition of 30°C at 40% RH.
The following conclusions were obtained.
1. Evaporation rate of water (K₁ [g/cm²•min]) in the constant rate period is mainly determined by the difference between the temperatures of air and wet bulb (t_a and t_w), although it changes somewhat by the difference between fabrics.
In the constant rate period, the water in the fabric comes to the surface so rapidly by capillary migration, that the fabric surface is almost saturated with water vapor, and evaporation of water continues in each constant rate of each fabrics.
Hygroscopic, roughly wovened, napped fabric has a wide surface for evaporation, and water evaporates rapidly from these fabrics than from other hydrohobic smooth surfaced fabrics in the constant rate period.
2. The end of the constant rate period where the critical moisture content (C. M. C.) is defined, appeared to be the final point where the fabric surface is still saturated with water vapor.
Higher rate of water transfer from the fabric to the air in the constant rate period, and slower capillary migration in the fabric are main factors for higher C. M. C.
3. The drying rate constant (K₂ [1/min]) in the falling rate period is greater for hydrohobic fabrics, and for thinner fabrics. Also, for hygroscopic fabrics with smaller volume fraction of fiber, the rate constant K₂ is greater.