Effects of Air Temperature, Relative Humidity, and Wind Speed on Water Vapor Transmission Rate of Fabrics

The primary environmental variables which influence the water vapor transmission rate of fabrics include air temperature, relative humidity, and wind speed. The combined quantitative effects of air temperature, relative humidity, and wind speed have been explored. The air temperature varied from 10 °C to 30 °C in 5 °C-intervals. The relative humidity ranged from 0% to 50%. The wind speed was from 0.1 m/s to 0.4 m/s. A new test method was employed to measure the water vapor transmission rate of four typical fabrics exposed under 120 conditions of combinations of relative humidity and wind speed with air temperature. The results showed that high air temperature, low relative humidity, and high wind speed led to high water vapor transmission rate. The exponential equations were obtained from the whole database based on the multiple nonlinear regression analysis, resulting in a generalized quantitative description of various effects on the water vapor permeability of fabrics. The prediction quality was good, as the regression equations provided high correlation coefficients and low standard errors of the estimate. The prediction values from the regression equations agreed well with the experimental results.