MEASUREMENTS OF WATER-VAPOR CONCENTRATION DEPENDENCY OF APPARENT DIFFUSION COEFFICIENT OF FIBER ASSEMBLY USING A SIXTEEN-FOLD BEAM INFRARED HYGROMETER

摘要

We have proposed a simple method for measuring water-vapor permeability of fiber assembly using water-vapor counter diffusion in a sample between the upper moist air layer and the lower dry-air layer. Comparing the measured humidity change by optical fiber infrared hygrometer with the numerical ones the water-vapor permeability is to determine as apparent diffusion coefficient. In the present paper, a new sixteen-fold beam infrared hygrometer is developed and is installed in a new measurement apparatus to make the system more compact and to measure the water-vapor concentration change more precisely. Three types of thickness of fiber assembly (15TH-145) are tested with a new system under the condition of the moist air in the upper chamber 3, of which is changed at the dew-point of 20℃, 22.5℃, 25℃ and 27.5℃, respectively. From these measured results the apparent diffusion coefficients are estimated, respectively. These show that the water-vapor concentration dependency of apparent diffusion coefficient is also confirmed but these values are slightly low and weak dependency. Using a rough liner model of the water-vapor concentration dependency, new numerical calculations are attempted for some examples case and these results are nearly agreed with both the measured and the previous numerical ones.