Abstract
Heat transfer accompanied with mass transfer of water vapor is one of the most important issues concerning the thermal comfort of the human body. A simple theoretical model is employed which makes use of an analogy between heat transfer and mass transfer. At the same time an experiment is carried out to examine the theoretical model using a vertical hot-plate with constant evaporation. Through perspiration at least 80% of the heat supply is dissipated as latent heat. In the case of a constant simulated skin temperature, the buoyancy under a wet condition is about 50% larger than that under a dry condition. Nevertheless, the convective heat transfer coefficient increases only 10%, because the coefficient is proportional to the one-fourth power of buoyancy. When an experiment is conducted using a thermal manikin, the heat transfer coefficient under a dry condition is sometimes substituted for the coefficient under a wet condition. This is because it is difficult to maintain a constant skin temperature under the wet condition due to the large heat dssipation of the manikin. The above result suggests an error factor of about 10%.
