Abstract
A new method is developed to measure the moisture transmission resistance (MTR) of fabrics. Hitherto the apparent MTR, whose physical meaning is indefinite, has reluctantly been introduced under the cup method, because the humidity inside the cup covered by fabrics is assumed to be constant. In order to investigate the spatial variation of humidity, the diffusion equation is numerically solved in the case of the cup uncovered by fabrics. The humidity changes rapidly and regularly inside the cup, while its variation is quite small outside the cup. The reciprocal of the evaporation rate is also found to be linearly dependent on the thickness of the air layer inside the cup. This relation suggests that the MTR can be correctly evaluated by using the difference between the evaporation rates for the cups covered and uncovered by fabrics. It has been confirmed by experiment that this simple method works quite well.
