Experimental and numerical investigation of the effect of phase change materials on clothing during periodic ventilation

A numerical and experimental investigation is conducted of periodic ventilation processes in fabric containing microcapsules of phase change materials (PCM). When PCMs are added to textiles, they release heat as the liquid changes to a solid state and absorb heat as the solid returns to a liquid state. In this work, PCMs are incorporated in a numerical three-node fabric ventilation model to study their transient effect on body heat loss during exercise when subjected to sudden changes in environmental conditions from warm indoor air to cold outdoor air. The results indicate that the heating effect lasts approximately 12.5 minutes depending on PCM percentage and cold outdoor conditions. Heat released by PCMs decreases the clothed-body heat loss by an average of 40-55 W/m(2) for a one-layer suit depending on the frequency of oscillation and crystallization temperature of the PCM. The experimental results reveal that under steady-state environmental conditions, the oscillating PCM fabric has no effect on dry resistance, even though the measured sensible heat loss increases with decreasing air temperature of the chamber. When a sudden change in ambient conditions occurs, the PCM fabric delays the transient response and decreases body heat loss.