The Effect of Moisture Absorption in Clothing on the Human Heat Balance (Het Effect van Vochtabsorptie in Kleding op de Warmtebalans)

A theory of moisture absorption in clothing, with the associated effects of heat transfer, was developed based on the assumption that clothing can be regarded as a moisture buffering capacitor enclosed between heat and vapour resistances, and covered with the adjacent air layer. The theory was checked with an experiment involving four subjects. They wore heavy woolen clothing, which was either initially dried or wetted, in both a warm and a cool environment. The experimental results confirmed satisfactorily the theoretical predictions that (1) the dry and evaporative heat loss will change in time and will both converge for the dry and moist garments to the equilibrium condition, (2) the clothing surface temperature and humidity are bound to a straight line on the psychrometric chart, (3) dry garments cause higher heat strain than wet garments, (4) the time course is predictable from the buffering capacity of the clothing and the heat transfer coefficient, and (5) the apparent heat and moisture transfer coefficients are bound to a linear relationship, revealing the true values only during equilibrium. Contrary to the expectation the observed vapour resistance is lower in the heat than in the cold, probably due to differences in sweat distribution. Summary in Dutch and English.