Design and performance of personal cooling garments based on three-layer laminates

Personal cooling systems are mainly based on cold air or liquids circulating through a tubing system. They are weighty, bulky and depend on an external power source. In contrast, the laminate-based technology presented here offers new flexible and light weight cooling garments integrated into textiles. It is based on a three-layer composite assembled from two waterproof, but water vapor permeable membranes and a hydrophilic fabric in between. Water absorbed in the fabric will be evaporated by the body temperature resulting in cooling energy. The laminate's high adaptiveness makes it possible to produce cooling garments even for difficult anatomic topologies. The determined cooling energy of the laminate depends mainly on the environmental conditions (temperature, relative humidity, wind): heat flux at standard climatic conditions (20 degrees C, 65% R. H., wind 5 km/h) has measured 423.2 +/- 52.6 W/m(2), water vapor transmission resistance, R(et), 10.83 +/- 0.38 m 2 Pa/W and thermal resistance, R(ct), 0.010 +/- 0.002 m(2) K/W. Thermal conductivity, k, changed from 0.048 +/- 0.003 ( dry) to 0.244 +/- 0.018 W/m K ( water added). The maximum fall in skin temperature, Delta T(max), under the laminate was 5.7 +/- 1.2 degrees C, taken from a 12 subject study with a thigh cooling garment during treadmill walking (23 degrees C, 50% R.H., no wind) and a significant linear correlation (R = 0.85, P = 0.01) between body mass index and time to reach 67% of Delta T(max) could be determined.