Eleven phase change materials (PCMs) for cooling humans in heat-stressed conditions were evaluated for their cooling characteristics. Effects of packaging material and segmentation were also investigated. Sample packs with a different type PCM (water- and oil-based PCMs, cooling gels, inorganic salts) or different packaging (aluminum, TPU, TPU + neoprene) were investigated on a hotplate. Cooling capacity, duration, and power were determined. Secondly, a PCM pack with hexagon compartments was compared to an unsegmented version with similar content. Cooling power decreased whereas cooling duration increased with increasing melting temperature. The water-based PCMs showed a >2x higher cooling power than other PCMs, but were relatively short-lived. The flexible gels and salts did not demonstrate a phase change plateau in cooling power, compromising their cooling potential. Using a TPU or aluminum packaging was indifferent. Adding neoprene considerably extended cooling duration, while decreasing power. Segmentation has practical benefits, but substantially lowered contact area and therefore cooling power.
Classical Analogue of Electromagnetically Induced Transparency with a Metal-Superconductor Hybrid Metamaterial
