A numerical and experimental investigation is conducted of periodic ventilation process in fabric with microcapsules of phase change materials (PCMs). When microcapsules of phase change materials (PCMs) are added to textiles, they release heat as the liquid changes to solid state and absorb heat as the solid returns to liquid state. In this work, PCMs are incorporated in the numerical three-node fabric ventilation model of Ghali et al. (2002a) to study the transient effect of PCM on body heat loss during exercise when subjected to sudden change in environmental conditions from warm indoor conditions to cold outdoor conditions. The results indicate that the heating effect last approximately 12.5 minutes depending on PCM percentage and cold outdoor conditions. Heat released by PCM decreases the clothed-body heat loss by an average of 2.7 W for a one-layer suit depending on the frequency of oscillation and crystallization temperature of PCM. The experimental results revealed that under steady state conditions of the environment the oscillating PCM fabric has no effect on fabric dry resistance even though the measured sensible heat loss increased with decreasing the air temperature of the chamber. When a sudden change in ambient conditions occurs, the PCM fabric delays and the transient response and decreases body heat loss.

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