Design and Experimental Research on Solar-Powered Casualty Rewarming Sleeping Bag Suitable for Extreme Cold Conditions

To address the casualties caused by hypothermia in cold environments, this study designed a solar-powered rewarming sleeping bag for casualties under extremely cold conditions using the phase change materials ODE@ CaF₂ MPCMs and Cu₂O@ n-C₂₀, which release heat during phase change at low temperatures. Hot-water simulations and human experiments were also conducted. The results of hot-water simulations at 0 ℃,4 ℃, and 8 ℃, with an initial phase-change-material temperature of 40 ℃, showed that warm water with an initial temperature of 37 ℃ could be maintained at approximately 36 ℃ for 3600 s, and the bilateral distribution of phase-change materials had a higher heating rate than that of a unilateral distribution. In human experiments, under -5 ℃,0 ℃, and 5 ℃ temperature conditions, the average temperature could be maintained at approximately 35 ℃ for 3600 s, and the unilateral distribution of phase-change materials had better insulation than the bilateral distribution, with an average temperature increase of 2 ℃. At -15 ℃, the average temperature could be maintained above 32 ℃ for 540 min. A temperature-distribution uniformity analysis showed that the maximum coefficient of variation for the unilateral distribution was 0.036 and that for the bilateral distribution was 0.053, indicating a relatively uniform temperature distribution inside the sleeping bag, with the unilateral distribution being more uniform than the bilateral distribution. Comprehensive performance assessments showed that the sleeping bag had excellent insulation but requires optimization for convenience; after 30 repetitions of an experiment at -5 ℃, the temperature effect remained almost unchanged, with only a 0.05 ℃ decrease in the average human body temperature after 30 uses. Moreover, the cost of the sleeping bag is only approximately 400 RMB, and a single heating to 40 ℃ consumes approximately 0.24 kW·h, which is low and shows good economic benefits.