In walking conditions, the air spacing between the fabric layer of a porous clothing system and the human skin changes with the walking frequency. This change will cause air penetration in and out of the clothing system depending on the fabric air permeability. The air passing through the fabric can considerably reduce the heat and moisture transfer resistance of the clothing system and its suitability for a given thermal environment. In this work, the coupled convection heat and moisture exchange within the clothing system subject to sinusoidal air layer thickness variation about a fixed mean is experimentally investigated and theoretically modeled to predict the periodic fabric regain, the fabric temperature and the transient conditions of the air layer located between the fabric and the skin. Experiments were conducted in an environmental chamber under controlled conditions of 25 °C and 50% relative humidity using a sweating hotplate at 35 °C that represents the human skin and a gear motor was used to generate the oscillating fabric motion. The mean air spacing was 38.1 mm with amplitude of 6.35 mm. The first set of experiments was done using a dry isothermal hot plate where the sensible heat transfer was measured through the heat controller to the plate. The second set of experiments was conducted with an isothermal sweating hot plate and the total heat (sensible and latent) transport from the plate was recorded. A mathematical model was developed for the heat and mass transport through the air spacing layer and the fiber clothing system. In the fabric, a three-node adsorption model was used to describe the effect of fabric motion (ventilation) on the sensible and latent heat flows from the human skin under different environmental conditions to the air layer and through the fabric clothing system. The fiber model was linked to the transport model of the oscillating air spacing layer that falls between the fiber and the fixed boundary (human skin). The transport equations were solved numerically, for the steady periodic regain and fabric temperature, the air spacing layer temperature and humidity ratio. The sensible and latent heat transport quantities at the moist solid boundary were also calculated. Good agreement was observed between the model predictions of heat loss or gain from the hot plate and the experimentally measured results.
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