Investigation of phase change material based cool pack performance in vests for personalized thermal comfort in extremely hot climatic conditions: Model development and case studies

Vests with provisions for carrying multiple phase change material (PCM) based cool packs are one of the possible ways to provide personalized thermal comfort in extremely hot climatic conditions. Although this passive cooling mechanism is simple to implement, there are several challenges associated with the design of these heat packs. For instance, the heat packs must maintain the skin temperature within the comfortable range of $33\pm 2$ ${}^{o}C$ (87.8-95 ${}^{o}F$) for the desired duration while also being as lightweight as possible. For the heat pack design, it is important to consider not only the hot climatic condition that causes heat to flow from ambient to body surface but also the heat generation from the body itself for different activity levels, such as reclining, standing, walking, jogging, running, and so on. In the present work, a numerical framework has been developed and experimental validation performed to investigate the performance of cool packs when it is loaded with any one of the following five PCMs, namely Ice, savE OM 21, Coconut oil, C18 paraffin, and Octadecane. The comparative performance of these cool packs is assessed based on the comfort duration for which they can maintain the body surface temperature within the specified range of $33\pm 2$ ${}^{o}C$. SavE OM21 PCM exhibited excellent performance in terms of providing thermal comfort more precisely. However, thermal conductivity must be enhanced from 0.14-0.21 $W/mK$ to 1.0 $W/mK$. The lower masses of C18 paraffin and Octadecane PCM were deemed suitable for practical use in real-world scenarios.