Numerical evaluation of a dual phase change material-integrated cap for prolonged thermal protection in extreme heat

• PCM caps enhance thermal comfort in extreme heat conditions. • RT-27 melts faster, while Capric Acid ensures prolonged cooling. • Numerical model validated with strong agreement to prior studies. • Wool-cotton insulation boosts heat retention and user comfort. • Study bridges gap in wearable PCM-based thermal solutions. With the increasing frequency of extreme heat events, effective thermal regulation in wearable caps is essential. This study presents a numerical investigation of a PCM-integrated wearable cap designed for prolonged outdoor exposure. Two PCMs—Rubitherm RT-27 and Capric Acid—were analyzed under natural convection for their temperature control, melting behavior, and energy storage capacity. At an ambient temperature of 40 °C, RT-27 achieved full melting in 155 minutes, while Capric Acid required 230 minutes, offering extended thermal protection. At 50 °C, melting times reduced to 108 minutes for RT-27 and 133 minutes for Capric Acid. The dual-PCM system maintained inner cap temperatures between 6–14 °C lower than ambient, depending on the PCM and external conditions. RT-27 provided rapid initial cooling, whereas Capric Acid ensured sustained thermal regulation. The cap’s layered design, including wool-cotton insulation, further delayed heat transfer and enhanced comfort. Compared to conventional fabric-based caps, the PCM-integrated cap significantly prolonged thermal relief duration. This study demonstrates the practical potential of multi-PCM systems for wearable passive cooling applications in extreme environments.