Water vapour permeability resistance through clothing material at combinations of temperature and pressure that simulate elevated altitudes

Abstract

Abstract Combinations of temperature and pressure at a simulated high altitude upon the water vapour permeability resistance of textile materials was investigated through a series of experiments. We developed a new apparatus in order to measure the water vapour resistance with and without temperature differences either side of the specimens. Although the effect of temperature on the water vapour resistance was found to be small, that of atmospheric pressure was significant. That is, the water vapour resistance decreases with the increasing altitude because the water vapour diffusion coefficient in the air increases with the increasing altitude due to the decrease in the atmospheric pressure. It was found that the condensation flux in the specimens increases with the increase in simulated altitude. Furthermore, the water vapour resistance decreases remarkably as the amount of condensation increases. This means that condensation is enhanced at high altitude because of a decrease in the water vapour resistance and of the reduced saturated water vapour concentration at lower temperatures. This may cause discomfort or coldness and a decrease in body temperature.